26/10/2018
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1
Magnetism
Not only permanent ferromagnets,
many applications
motors, transformers, imaging,
data storage (probably just as
important as semiconductors for
modern computers)
FeCo/Pt superlattices high saturation
magnetism promising for magnetic
data storage
2
• How do solids react to an external field?
• What is the cause of spontaneous magnetic ordering?
Magnetism
Magnetism is an extremely active area of research with many
still unanswered questions
Condensed matter physics uses magnetism as a testing ground
for understanding complex quantum and statistical physics
Most magnetic phenomena caused by quantum mechanical
behaviour of the electrons
26/10/2018
2
3
• Magnetic moments in atoms
• Weak magnetism in solids
• Magnetic ordering
Magnetic properties
Weak magnetism in solids can largely be understood by atomic properties
magnetic ordering cannot - cannot describe it as
ordering of totally localised moments on atoms because these have
to “talk” to each other, otherwise there is no ordering in the first place
Ashcroft and Mermin Ch 31, 32; Oxford Basics Ch 19
4
Macroscopic description of magnetism:
Fundamental quantities
In vacuum we have:
magnetic field intensity
magnetic induction
When a material medium is placed in a magnetic field,
the medium is magnetized. This is described by the
magnetization vector M – the dipole moment per unit volume
we interpret as the “external field”
permeability of free space 4πx107 (SI units: N.A-2)
Magnetization induced by the field assume M is proportional to H
or
- magnetic susceptibility of the medium
(Real crystals anisotropic, and susceptibility is a second-rank tensor (ignore such effects)
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5
Units
• Both, and are measured in Tesla (T)
• 1 T is a strong field. The magnetic field of the earth is only
of the order of 10-5 T.
potential energy of one dipole in the external field:
Classification of materials
6
All magnetic materials may be grouped into three magnetic classes
depending on the magnetic ordering and the sign and magnitude of the
magnetic susceptibility:
(more later)
26/10/2018
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7
Diamagnetism
• Diamagnetism is caused by “currents” induced by the
external field. According to Lenz’ law, these currents always
lead to a field opposing the external field.
Potential energy U
increase in potential energy for higher field, unfavourable.
Paramagnetism
Potential energy U
the potential energy is lowered when moving the magnetized bodies to a
higher field strength
. • Paramagnetism is caused by aligning some dipoles, which
are already present, with the magnetic field
8
Ferromagnetism
A ferromagnet is a material where M can be nonzero
even in the absence of an applied magnetic field
Magnetism is said to be Spontaneous when it occurs even in the
absence of an externally applied magnetic field, as in the
case of a ferromagnet
26/10/2018
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9
Ferromagnet.
In your previous class you have already studies about the structure of an atom but some of the exception you can learn here in this chapter how the structure of an atom is fully defined
In your previous class you have already studies about the structure of an atom but some of the exception you can learn here in this chapter how the structure of an atom is fully defined
3.1 Discovery of the X Ray and the Electron
3.2 Determination of Electron Charge
3.3 Line Spectra
3.4 Quantization
3.5 Blackbody Radiation
3.6 Photoelectric Effect
3.7 X-Ray Production
3.8 Compton Effect
3.9 Pair Production and Annihilation
a branch of nano electronics that will improve technology by adding new freedom degrees to electronic for transfer and store information better than electronic devices :)
STRUCTURE OF ATOM
Sub atomic Particles
Atomic Models
Atomic spectrum of hydrogen atom:
Photoelectric effect
Planck’s quantum theory
Heisenberg’s uncertainty principle
Quantum Numbers
Rules for filling of electrons in various orbitals
3 templates are due based on the focus review. Attached are the temp.docxjesusamckone
3 templates are due based on the focus review. Attached are the templates .
the following need to be completed:
1-system disorder -cardiovascular disorder.
2-basic concept-legal responsibilities -obtaining informed consent for an adolescent.
3-system disorder-skin infection tinea pedis.
.
3.1 Discovery of the X Ray and the Electron
3.2 Determination of Electron Charge
3.3 Line Spectra
3.4 Quantization
3.5 Blackbody Radiation
3.6 Photoelectric Effect
3.7 X-Ray Production
3.8 Compton Effect
3.9 Pair Production and Annihilation
a branch of nano electronics that will improve technology by adding new freedom degrees to electronic for transfer and store information better than electronic devices :)
STRUCTURE OF ATOM
Sub atomic Particles
Atomic Models
Atomic spectrum of hydrogen atom:
Photoelectric effect
Planck’s quantum theory
Heisenberg’s uncertainty principle
Quantum Numbers
Rules for filling of electrons in various orbitals
3 templates are due based on the focus review. Attached are the temp.docxjesusamckone
3 templates are due based on the focus review. Attached are the templates .
the following need to be completed:
1-system disorder -cardiovascular disorder.
2-basic concept-legal responsibilities -obtaining informed consent for an adolescent.
3-system disorder-skin infection tinea pedis.
.
3-4 page essayInequality of income is greater in the United Sta.docxjesusamckone
3-4 page essay:
Inequality of income is greater in the United States than in other capitalistic countries. Taking this fact into consideration, what moral obligation, if any, do we have individually and as a society to narrow the gap? What role should the business community play? Defend your answer with ethical argumentation.
.
3 Vision Visioning is relatively easy. Casting a shared and clea.docxjesusamckone
3 Vision V
isioning is relatively easy. Casting a shared and clear vision, then holding one another accountable for its pursuit is what’s tough.
A vision is an expression of what a person or an organization cares about.
The insight to see new paths, the courage to try them, and judgment to measure results—these are the qualities of a leader. —MARY PARKER FOLLETT
WHY POLICE MANAGERS GET INTO TROUBLE!
The future isn’t what it used to be. —Yogi Berra Obviously police managers can get into trouble for a lot of reasons. The seven reasons I most often see follow. First, they choose to forfeit their integrity for the slick, fast, questionable shortcuts to success. Second, their vision isn’t shared by others. Third, the vision lacks clarity. Four, the vision may be great, but it is sorely void of a strategy for making it happen. Five, worse yet, it may contain a viable strategy, but there’s no built-in accountability. Six, some managers fail to recognize and deal with the existing culture.
We’ll tackle these issues in the following four sections:
• Vision
• Strategy
• Culture
• Prospection
VISION
If you have built castles in the air, your work need not be lost; that is where they should be. Now put the foundations under them. —Henry David Thoreau
A vision is stable; it doesn’t change often or much. After all, what we truly value does not flip-flop daily. Values are enduring and therefore visions are, too. A vision is a compass for maintaining a steady point toward a destination that we really care about. Strategy serves as a rudder for altering direction, speed, and tactics to successfully navigate the incoming tempest to change. Visions are constant while strategies vary.
The twentieth century began by changing the old constancies, while the twenty-first century began with change as the only constant.
The remainder of this section covers (1) the ingredients or “recipe” for a vision, (2) building a shared vision or not, and (3) accountability. (The foundational need for a clear vision is a part of strategy.)
Recipe
Here are the key characteristics of vision:
Purpose/Mission. Whether you call it a mission or a purpose, a vision statement must articulate the fundamental reason for the organization’s existence. It explains exactly why you exist and why you’re important.
Future. It paints an inspiring future that is not out of sight, but slightly out of reach. It is not an idle dream, but rather a compelling picture of the way it ought to look.
Values. A vision statement is loaded with values. It tells the reader precisely what the organization stands for and is prepared to be measured on.
Principled Decision Making. A shared vision should be judged on its ability to encourage principled decisions. Here’s the question: “Does my vision statement help me to know the wrong path while pointing to the right one?” When you study your shared vision, are you comfortable that it propels you toward moral high ground?
Change Agent. A shared vi.
3 Power points on nutrition while home schooling1 for elementary.docxjesusamckone
3 Power points on nutrition while home schooling
1 for elementary kids
1 for middle school kids
1 for parents
Must be 10 slide minimum
Must have pictures appropriate for school aged kids
Bullet points
Must include (only) one youtube video
.
3 paragraph minimum, in text references, and scholarly references. .docxjesusamckone
3 paragraph minimum, in text references, and scholarly references.
Post an explanation of the differences between the public and private health insurances as well as the difference in access to care based on one’s insurance.
Explain the differences between Medicare and Medicaid in terms of eligibility, cost, benefits, services provided, and limitations in services.
Finally, describe special programs that your state’s Medicaid program offers to increase access to care for vulnerable populations, such as pregnant women, children, single mothers, or immigrants.
.
2HOW THANKSGIVING AND SUPER BOWL TRAFFIC CONTRIBUTE TO FLIGH.docxjesusamckone
2
HOW THANKSGIVING AND SUPER BOWL TRAFFIC CONTRIBUTE TO FLIGHT DELAYS Comment by Jeremy Hodges: You should have a meaningful title that describes what your study is about. Start with a word like “examine” or “explore” to identify the type of study you conducted.
by
XXXXX
A Graduate Capstone Project Submitted to the College of Aeronautics,
Department of Graduate Studies, in Partial Fulfillment
of the Requirements for the Degree of
Master of Science in Aeronautics
Embry-Riddle Aeronautical University
Worldwide Campus
May 2018
HOW THANKSGIVING AND SUPER BOWL TRAFFIC CONTRIBUTE TO FLIGHT DELAYS
by
XXXXX
This Graduate Capstone Project was prepared under the direction of the candidate’s Graduate Capstone Project Chair, XXXXX, Comment by Jeremy Hodges: Dr. Jeremy Hodges
Worldwide Campus, and has been approved. It was submitted to the
Department of Graduate Studies in partial fulfillment
of the requirements for the degree of
Master of Science in Aeronautics
Graduate Capstone Project:
___________________________________________
XXXXXXXX. Comment by Jeremy Hodges: Jeremy Hodges, PhD
Graduate Capstone Project Chair
________________
xxii
Date
xxii
ii
xxii
xxii
ixAcknowledgements Comment by Jeremy Hodges: Add any acknowledgments here. You may use first person in this section, but avoid it everywhere else.
I'd like to thank my legs, for always supporting me; my arms, who are always by my side; and lastly my fingers, I can always count on them.
Abstract
Scholar: XXXXX
Title: How Thanksgiving and Super Bowl Traffic Contribute to Flight Delays
Institution: Embry-Riddle Aeronautical University
Degree: Master of Science in Aeronautics
Year: 2017
This study explores the effects of non-scheduled flights on scheduled flight delays during Thanksgiving and Super Bowl across 5 years. Flight delay data were collected from the Bureau of Transport Statistics and the Federal Aviation Administration. Super Bowl and Thanksgiving were chosen as the special events of interest for this study as they provided complementary datasets. Super Bowl showed an increase in non-scheduled flights whereas Thanksgiving showed greater scheduled flight operations. The results of this study concluded that scheduled flights showed greater delays during Super Bowl when compared to Thanksgiving. A significant interaction was also found to exist between scheduled and non-scheduled flights operating during the two special events. Both scheduled flight delays and non-scheduled flight delays increased during Super Bowl. However, during Thanksgiving this relationship did not exist – scheduled flights had much fewer delays than non-scheduled flights. Due to the increase in the number of non-scheduled flight operations during Super Bowl, delays increased thereby increasing operating costs for flights. The outcomes of this study shed light on another aspect of airspace efficiency that could be researched to reduce costs and improv.
3 page essay In-text scholar references in APA formatI.docxjesusamckone
**3 page essay In-text scholar references in APA format**
Introduction
Briefly explain Corrigan’s model of the stages of stigma and his recommendations and hierarchy about recovery.
Explain whether Delle’s experience follows that model. Use specific examples to argue your perspective. If you agree, identify which stage of recovery Delle is in.
Analyze Delle’s reports about his own experiences with both types of stigma. Provide specific examples, and in your analysis consider the following questions:
Does one type of stigma predominate in his talk?
Which of Delle’s personal values or beliefs were challenged by his internalizations about his own illness and help-seeking?
What strengths does he exhibit?
What was the primary benefit of his diagnosis?
Do you think his experience would be different if his culture was different? Explain why or why not?
Conclusion
.
3 Law peer reviewed references needed.Answer the Discussion Board bo.docxjesusamckone
3 Law peer reviewed references needed.Answer the Discussion Board board questions in paragraph form.
1. A premature infant was delivered at Woman’s Hospital by the plaintiff. The child died shortly after birth, and the plaintiff was assured by the floor nurse that the hospital would take care of the infant’s burial. When the mother went to the obstetrician for an examination six weeks later, she was given her folder to hold while waiting for the physician. She found in it a note from the pathologist about disposal of the baby’s body. When the plaintiff asked the physician about the disposal of the body, he instructed his nurse to take her to the hospital across the street to see someone who would tell her what had been done with the baby. When the woman and the nurse found the person, the plaintiff was handed a large jar with the baby’s body inside. As a result, the plaintiff suffered nightmares, could not sleep, was depressed when she was around children, had surgery for a pseudopregnancy, and required psychiatric treatment. Should a patient–physician relationship include the contract to dispose of a dead body?
2. The plaintiff’s 18-year-old son died suddenly at home. His body was taken to the hospital, where the cause of death could not be found without an autopsy. The deputy medical examiner ordered a postmortem examination. The plaintiff was a member of the Jewish Orthodox faith and refused the postmortem examination of his son on the basis that religious conviction prohibited any molestation of the body after death. Is freedom of religion curtailed by a law that has a compelling state interest?
.
2To ADD names From ADD name Date ADD date Subject ADD ti.docxjesusamckone
2
To: ADD names From: ADD name Date: ADD date Subject: ADD title
Introduction
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum et nisl ante. Etiam pulvinar fringilla ipsum facilisis efficitur. Maecenas volutpat risus dignissim dui euismod auctor. Nulla facilisi. Mauris euismod tellus malesuada dolor egestas, ac vulputate odio suscipit.
Sed pellentesque sagittis diam, sit amet faucibus diam lobortis quis. Sed mattis turpis ligula, in accumsan ante pellentesque eu. Quisque ut nisl leo. Nullam ipsum odio, eleifend non orcinon, volutpat sollicitudin lacus (Cuddy, 2002). Identify Changes
Donec tincidunt ligula eget sollicitudin vehicula. Proin pharetra tellus id lectus mollis sollicitudin. Etiam auctor ligula a nulla posuere, consequat feugiat ex lobortis. Duis eu cursus arcu, congue luctus turpis. Sed dapibus turpis ac diam viverra consectetur. Aliquam placerat molestie eros vel posuere.
This Photo by Unknown Author is licensed under CC BY-SA
Figure 1. Title (Source: www.source-of-graphic.edu )Product Offerings
Sed facilisis, lacus vel accumsan convallis, massa est ullamcorper mauris, quis feugiat eros ligula eget est. Vivamus nunc turpis, lobortis et magna a, convallis aliquam diam. Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Figure 2. Title (Source of data citation)
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum et nisl ante. Etiam pulvinar fringilla ipsum facilisis efficitur. Maecenas volutpat risus dignissim dui euismod auctor. Nulla facilisi. Mauris euismod tellus malesuada dolor egestas, ac vulputate odio suscipit. Capabilities
Donec tincidunt ligula eget sollicitudin vehicula. Proin pharetra tellus id lectus mollis sollicitudin. Etiam auctor ligula a nulla posuere, consequat feugiat ex lobortis. Duis eu cursus arcu, congue luctus turpis. Sed dapibus turpis ac diam viverra consectetur.
References
Basu, K. K. (2015). The Leader's Role in Managing Change: Five Cases of Technology-Enabled Business Transformation. Global Business & Organizational Excellence, 34(3), 28-42. doi:10.1002/joe.21602.
Connelly, B., Dalton, T., Murphy, D., Rosales, D., Sudlow, D., & Havelka, D. (2016). Too Much of a Good Thing: User Leadership at TPAC. Information Systems Education Journal, 14(2), 34-42.
Rouse, M. (2018). Changed Block Tracking. Retrieved from Techtarget Network: https://searchvmware.techtarget.com/definition/Changed-Block-Tracking-CBT
Change the Chart Title to Fit Your Needs
Series 1 Category 1 Category 2 Category 3 Category 4 4.3 2.5 3.5 4.5 Series 2 Category 1 Category 2 Category 3 Category 4 2.4 4.4000000000000004 1.8 2.8 Series 3 Category 1 Category 2 Category 3 Category 4 2 2 3 5
Assessing Similarities and Differences in Self-Control
between Police Officers and Offenders
Ryan C. Meldrum1 & Christopher M. Donner2 & Shawna Cleary3 &
Andy Hochstetler4 & Matt DeLisi4
Received: 2 August 2019 /Accepted: 21 October 2019 /
Published online: 2 December 2019
# Southern Criminal.
3 page essay regarding civil liberties, civil rights, and the presid.docxjesusamckone
3 page essay regarding civil liberties, civil rights, and the presidency.
(intro) Must briefly discuss each topic then make a statement about a contemporary political problem related to one of the topics.
(Body) identify, discuss and describe a contemporary problem related to one of the topics.
(conclusion) construct and communicate a solution to the problem.
.
2TITLE OF PAPERDavid B. JonesColumbia Southe.docxjesusamckone
2
TITLE OF PAPER
David B. Jones
Columbia Southern University
BBA: 3201 Principles of Marketing
Nancy Ely Mount
Month/Date/ 2020
Marketing is
Four Elements of Marketing:
Creating
Communicating
Delivering
Exchanging
Holistic Marketing Concept is a people oriented approach utilizing the four principles of :
Relationship
Integrated
Internal
Performance marketing
.
2Running head THE JONES ACTThe Jones Act 2.docxjesusamckone
2
Running head: THE JONES ACT
The Jones Act 2
The Jones Act of the Merchant Marine Act of 1920
Latissa Butler
American Public University
Dr. Wallace Burns
February 23, 2020
The Jones Act of the Merchant Marine Act of 1920
The century-old Merchant Marine law of 1920, also known as "Jones Act" has been part of a contentious topic in the U.S for a long time. Jones Act has seen an excessive strain in the economy with prices of goods in many states hiking due to the restriction of foreign ships into U.S water territorials. There has also been a tremendous impact on the environment and internal revenue. The limits have impacted heavily on people living in the coasts of Hawaii, Alaska the island of Puerto Rico and Guam as a result of the Section 27 act which only allows "cabotage".
Conversely, the federal law has fostered domestic shipbuilding leading to increased employment and a boost to national security. Jones Act also allows the compensation of sailors who might experience accidents in the line of duty. If this were to happen, I am in support of the repealing part of the law that acts as a burden to the American citizen.
Since its enactment to law, the Jones Act, has hit hardest on the economy of U.S. despite the reforms done on Section 28. The restrictions on vessels made and operated by Americans has led to the variability in the shipping rates. The cost of transporting commodities has risen drastically due to the lack of competition from foreign markets, ultimately leading to an increase in prices of goods (Washington Post, 2010). Shipping industries locally, on the other hand, have increased the costs of the services they offer. The move to raise the prices of the available commodities has seen many citizens seeking for alternative means of importing and transporting their produce from the neighboring countries. The lack of a free market that has move to the states, must settle for higher prices than others due to the difference in the shipping cost. According to The International Trade Commission's 1995 Analysis, the cost incurred during the transportation of goods by these means apart from the sea is also high and impact on the economy of the country. The amount of fuel consumption during transporting goods through road is too expensive when evaluated.
The effect of the Jones Act on the environment has also been felt across the state. The smoke and gases released as a result of traffic have led to the rise in temperatures in a different part of America. Carbon emission has, in the past, contributed to high cost incurred when managing. Additionally, the restriction has led to a loss in the amount of foreign revenue in the U.S. Due to this fact, a lot of bilateral agreements have failed as a result of the Jones Act law which has consequently had an effect on the economy of the U.S (Hoxie, Phillip, Smith & Vincent, 2019). In my opinion, based on the impact the law has on the economy of the co.
2958 IEEE TRANSACTIONS ON INFORMATION FORENSICS AND SECURITY, .docxjesusamckone
2958 IEEE TRANSACTIONS ON INFORMATION FORENSICS AND SECURITY, VOL. 14, NO. 11, NOVEMBER 2019
Interdependent Strategic Security Risk Management
With Bounded Rationality in the Internet of Things
Juntao Chen , Student Member, IEEE, and Quanyan Zhu, Member, IEEE
Abstract— With the increasing connectivity enabled by the
Internet of Things (IoT), security becomes a critical concern,
and users should invest to secure their IoT applications. Due to
the massive devices in the IoT network, users cannot be aware
of the security policies taken by all its connected neighbors.
Instead, a user makes security decisions based on the cyber
risks that he perceives by observing a selected number of
nodes. To this end, we propose a model which incorporates
the limited attention or bounded rationality nature of players
in the IoT. Specifically, each individual builds a sparse cognitive
network of nodes to respond to. Based on this simplified cognitive
network representation, each user then determines his security
management policy by minimizing his own real-world security
cost. The bounded rational decision-makings of players and their
cognitive network formations are interdependent and thus should
be addressed in a holistic manner. We establish a games-in-
games framework and propose a Gestalt Nash equilibrium (GNE)
solution concept to characterize the decisions of agents and
quantify their risk of bounded perception due to the limited
attention. In addition, we design a proximal-based iterative
algorithm to compute the GNE. With case studies of smart
communities, the designed algorithm can successfully identify
the critical users whose decisions need to be taken into account
by the other users during the security management.
Index Terms— Risk management, bounded rationality, cogni-
tive networks, Internet of Things, smart community.
I. INTRODUCTION
RECENT years have witnessed a significant growthof urban population. As the growth continues, cities
need to become more efficient to serve the surging pop-
ulation. To achieve this objective, cities need to become
smarter with the integration of information and communication
techniques (ICTs) and urban infrastructures. Driven by the
advances in sensing, computing, storage and cloud technolo-
gies, the Internet of Things (IoT) plays a central role in
supporting the development of smart city. Though IoT enables
a highly connected world, the security of IoT becomes a
critical concern. There are 5.5 million new things connected
Manuscript received May 21, 2018; revised March 4, 2019; accepted
April 9, 2019. Date of publication April 15, 2019; date of current ver-
sion July 2, 2019. This work was supported in part by the National Sci-
ence Foundation under Award SES-1541164 and Award ECCS-1847056,
in part by the Army Research Office (ARO) under Grant W911NF1910041,
and in part by a grant through the Critical Infrastructure Resilience
Institute (CIRI). The associate editor coordinating the review of this
manuscript.
2
BUS 503 JOURNAL
BUS 503 SAMPLE Journal
Student NAME
Professor Name
1
Running head: BUS 503 JOURNAL
Due Date: May 12, 2019
Course Quotes
“What does it mean for our writing productivity and writing quality? Simply put, it means this: if we commit to practice our academic writing, and obtain continual feedback, our writing and productivity levels will improve” (Goodson, 2017, p. 9).
Example of a Comment:
I have found that writing requires practice. Technology such as texting and social media has hindered my academic writing, so I must be deliberate in practicing academic writing.
“Every dimension of their future success as academics (grades, promotions, presentations, to professional groups, funding for research projects) will depend on how well and how much they write” (Goodson, 2017, p. 22).
Example of an Aha Moment:
This quote reminded of an inspirational leader who is able to eloquently present information based on research and facts. Research indicates that academic writing is part of our personal and professional daily life, yet, we do not align with the concept.
“Even if you don’t see yourself as a writer, yet, practicing new habits and strategies will help you develop this new perspective…” (Goodson, 2017, p. 23).
Example of a questions:
What steps do I need take to develop new habits and strategies? Goodson (2017) outlines steps that I will need to learn and embrace to embark on my academic writing development.
References:
In this area add ALL references you are using for your journal – for example you could immediately add our two course texts. The advantage of having this added is when you compose your paper/project – you will already have your reference page completed per APA formatting:
Goodson, P. (2017). Becoming an academic writer: 50 exercises for paced, productive, and powerful writing. Sage Publications.
REFLECTIVE JOURNAL
1
REFLECTIVE JOURNAL
Reflective Journal
Edina Purser
University of Mary Business Research and Writing
Karmen P. Sorenson
01 Jun 2020
Reflective Journal
Exercise 7
"I have, therefore, learned to keep writing diaries as a mechanism and a place for documenting my progress" (Goodson, 2013, p.36). Goodson's advice of constant writing of diaries reminds me of Project Diaries' (2011, p.1) quote that "Keeping project records, including the preparation, assembly, and preservation of such records is considered one of the most important duties and responsibilities that the Engineer delegates to the Inspector." Thus, I am aware that diaries are evaluation tools for recording data over a particular period. Diaries depend on adequate documentation of a continuing process. Therefore, I ensure that I complete with my entries when I am close to a specific event since logs are not suitable for evaluation after the implementation of any event.
However, I still have the option of using journals to reconstruct events. I ensure that I writ.
26.5Albert Beveridge, Defense of Imperialism”Albert Beveridge (.docxjesusamckone
26.5Albert Beveridge, “Defense of Imperialism”
Albert Beveridge (1862-1927) was a Republican Senator from Indiana, historian, and imperialist. A supporter of President Theodore Roosevelt (in office from 1901-1909), Beveridge supported American expansion in the Philippines, Cuba, and Puerto Rico after the American victory in the Spanish-American War (1898). In “Defense of Imperialism,” Beveridge portrays Americans as a people favored by God who are destined to rule over additional lands and achieve commercial supremacy. He did not believe that the people of the Philippines, Cuba, and Puerto Rico were mature or capable of self-government, which justified American rule. In addition, Beveridge acknowledges the importance of imperial adventures to justifying national greatness in the early twentieth-century. Beveridge’s ideas represent, in sum, two primary justifications for the New Imperialism of the late nineteenth and early twentieth-centuries. On the one hand, imperialists argued that foreign control was necessary for peoples not yet ready to govern themselves. On the other hand, they recognized that imperialism served the interests of the metropole insofar as it justified “Great Power” status among the community of nations.
It is a noble land that God has given us; a land that can feed and clothe the world; a land whose coastlines would enclose half the countries of Europe; a land set like a sentinel between the two imperial oceans of the globe, a greater England with a nobler destiny.
It is a mighty people that He has planted on this soil; a people sprung from the most masterful blood of history, a people perpetually revitalized by the virile, man-producing working-folk of all the earth; a people imperial by virtue of their power, by right of their institutions, by authority of their Heaven-directed purposes— the propagandists and not the misers of liberty.
It is a glorious history our God has bestowed upon His chosen people; a history heroic with faith in our mission and our future; a history of statesmen who flung the boundaries of the Republic out into unexplored lands and savage wilderness; a history of soldiers who carried the flag across blazing deserts and through the ranks of hostile mountains, even to the gates of sunset; a history of a multiplying people who overran a continent in half a century; a history of prophets who saw the consequences of evils inherited from the past and of martyrs who died to save us from them; a history divinely logical, in the process of whose tremendous reasoning we find ourselves today.
Therefore, in this campaign, the question is larger than a party question. It is an American question. It is a world question. Shall the American people continue their march toward the commercial supremacy of the world? Shall free institutions broaden their blessed reign as the children of liberty wax in strength, until the empire of our principles is established over the hearts of all mankind?
Have we no mission to per.
2Evaluating StocksEvaluating StocksLearning Team BFIN402.docxjesusamckone
2
Evaluating Stocks
Evaluating Stocks
Learning Team B
FIN/402
03/16/2020
Troy Mahone
The stocks in this portfolio are the following: PepsiCo, Apple, Microsoft, Aritzia, and Amazon. An assessment was conducted to establish if the stocks should remain in the portfolio.
Stock Reviews and Discussion
If I review the investment in PepsiCo., the business has reflected a slight decrease in the stock price, as being traded daily on the floor, the reason which we can assume is the over all market turbulence, being caused by the Oil market, and it is directly impacting US economy, and hence reflecting the same on the stocks trade in the market.
Apple Inc., stock has also reflected a bit decline as directly related to activities being performed in the market, more over the share is constantly moving the range of $30 up/down, being range bound, hence reflects that the business is performing well, and keeping at the place in the market. Citing Chinese government data, Reuters recently reported that Apple sold just 494,000 iPhones in the country in February. That was a steep decline from the 1.27 million units the company had shipped in the prior-year period and the two million units sold in January. The situation was bad across the board, as overall smartphone shipments fell 54.7% annually during the month, according to the China Academy of Information and Communications Technology.
Microsoft has reflected a steady decline, although it is not much material, and market expectancy is to correct it, I believe the more effect on Microsoft stock price down fall is related to news spread in the market, that Bill Gates is resigning himself, from the position of the President and leaving the board, market sentiments are attached to this news, but I believe in coming few months, business is going to show tremendous growth in the shares value. I feel that Microsoft offers many types of shares like mutual funds holders, individuals, stakeholders and other institutional shares. With these shares they are often bought and sold. The rates of shares range 42.14% to 6.18%.
Aritizia has shown some of the great moment during the last tenure, touching up the higher side and then again the lower side, is a mixed up reaction, as it moved between range of $200-250 in few days, the reason of such movement is overall market performance, the oil war, and the Corona virus worldwide economic impact. The current state of our society has resulted in a very volatile market. In times like these investors may be cautious towards putting their savings into stocks. However, this is also a good time to buy at low prices. ATZAF has seen a decline in market price over the past month, however a significant amount of that decline can be attributed to nation-wide panic. Most of the clothing inventory held by Aritzia comes from Vietnam. Countries in Asia are being hit especially hard by the virus and as a result North American companies are seeing experiencing breaks in their sup.
Biological screening of herbal drugs: Introduction and Need for
Phyto-Pharmacological Screening, New Strategies for evaluating
Natural Products, In vitro evaluation techniques for Antioxidants, Antimicrobial and Anticancer drugs. In vivo evaluation techniques
for Anti-inflammatory, Antiulcer, Anticancer, Wound healing, Antidiabetic, Hepatoprotective, Cardio protective, Diuretics and
Antifertility, Toxicity studies as per OECD guidelines
Acetabularia Information For Class 9 .docxvaibhavrinwa19
Acetabularia acetabulum is a single-celled green alga that in its vegetative state is morphologically differentiated into a basal rhizoid and an axially elongated stalk, which bears whorls of branching hairs. The single diploid nucleus resides in the rhizoid.
This slide is special for master students (MIBS & MIFB) in UUM. Also useful for readers who are interested in the topic of contemporary Islamic banking.
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
A Strategic Approach: GenAI in EducationPeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
How to Make a Field invisible in Odoo 17Celine George
It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
Introduction to AI for Nonprofits with Tapp NetworkTechSoup
Dive into the world of AI! Experts Jon Hill and Tareq Monaur will guide you through AI's role in enhancing nonprofit websites and basic marketing strategies, making it easy to understand and apply.
A workshop hosted by the South African Journal of Science aimed at postgraduate students and early career researchers with little or no experience in writing and publishing journal articles.
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
Advantages and Disadvantages of CMS from an SEO Perspective
2610201811MagnetismNot only permanent ferromag.docx
1. 26/10/2018
1
1
Magnetism
Not only permanent ferromagnets,
many applications
motors, transformers, imaging,
data storage (probably just as
important as semiconductors for
modern computers)
FeCo/Pt superlattices high saturation
magnetism promising for magnetic
data storage
2
• How do solids react to an external field?
• What is the cause of spontaneous magnetic ordering?
Magnetism
2. Magnetism is an extremely active area of research with many
still unanswered questions
Condensed matter physics uses magnetism as a testing ground
for understanding complex quantum and statistical physics
Most magnetic phenomena caused by quantum mechanical
behaviour of the electrons
26/10/2018
2
3
• Magnetic moments in atoms
• Weak magnetism in solids
• Magnetic ordering
Magnetic properties
Weak magnetism in solids can largely be understood by atomic
properties
magnetic ordering cannot - cannot describe it as
ordering of totally localised moments on atoms because these
have
to “talk” to each other, otherwise there is no ordering in the
first place
3. Ashcroft and Mermin Ch 31, 32; Oxford Basics Ch 19
4
Macroscopic description of magnetism:
Fundamental quantities
In vacuum we have:
magnetic field intensity
magnetic induction
When a material medium is placed in a magnetic field,
the medium is magnetized. This is described by the
magnetization vector M – the dipole moment per unit volume
we interpret as the “external field”
permeability of free space 4πx107 (SI units: N.A-2)
Magnetization induced by the field assume M is
proportional to H
or
- magnetic susceptibility of the medium
(Real crystals anisotropic, and susceptibility is a second-rank
tensor (ignore such effects)
4. 26/10/2018
3
5
Units
• Both, and are measured in Tesla (T)
• 1 T is a strong field. The magnetic field of the earth is only
of the order of 10-5 T.
potential energy of one dipole in the external field:
Classification of materials
6
All magnetic materials may be grouped into three magnetic
classes
depending on the magnetic ordering and the sign and magnitude
of the
magnetic susceptibility:
(more later)
26/10/2018
4
7
5. Diamagnetism
• Diamagnetism is caused by “currents” induced by the
external field. According to Lenz’ law, these currents always
lead to a field opposing the external field.
Potential energy U
increase in potential energy for higher field, unfavourable.
Paramagnetism
Potential energy U
the potential energy is lowered when moving the magnetized
bodies to a
higher field strength
. • Paramagnetism is caused by aligning some dipoles, which
are already present, with the magnetic field
8
Ferromagnetism
A ferromagnet is a material where M can be nonzero
even in the absence of an applied magnetic field
Magnetism is said to be Spontaneous when it occurs even in the
absence of an externally applied magnetic field, as in the
6. case of a ferromagnet
26/10/2018
5
9
Ferromagnetism
10
d-electron states/orbitals
26/10/2018
6
11
f-electron states/orbitals
Isolated Atoms
• The magnetic moment of a free atom has three main
sources
1. the spin of the electrons
2. the electron orbital angular momentum about the nucleus
7. 3. the change in orbital moment induced by an applied
magnetic field
• In classical picture, electrons orbit around nucleus
• Each orbit like a loop of electric current
• A loop of current produces a magnetic field, so electrons in
an atom generates a magnetic field
• Quantum numbers n,l,m l and ms label the electrons in an
atom (alternatively called n, l, lz, σz )12
26/10/2018
7
Hund’s Rules for Isolated Atoms
13
Set of Rules – Hund’s Rules that determines how electrons fill
orbitals
Recall from QM, an electron in an atomic orbital can be
labelled
by four quantum numbers:
Principle quantum number
Angular momentum
z-component of ang. mom.
8. z-component of spin
Sometimes the angular momentum shells
are known as and can accommodate
electrons, respectively.
Start with some fundamentals of electrons in isolated atoms
Hund’s Rules for Isolated Atoms
14
lz = 2
lz= 1
lz= 0
lz=-1
lz=-2
26/10/2018
8
15
Hund’s Rules for Isolated Atoms
Hund’s 0th Rule – (Aufbau Principle) shells filled starting
9. with lowest available energy state. An entire shell filled
before another started
Madelung Rule): energy ordering is from lowest value of n+l
to largest when two shells have the same n+l, fill one with
smallest n first
Two examples:
Nitrogen (N) 7 electrons, filled 1s shell with 2
electrons spin-up and spin-down, 2 electrons in
the 2s shell with 2 electrons spin-up and spin-down,
3 electrons in the 2p shell
Praseodymium (Pr) 59 electrons
or as
p
16
Hund’s Rules for Isolated Atoms
The shell filling sequence is the rule which defines the overall
structure of the periodic table.
When shells are partially filled need to describe which of the
orbitals
10. are filled in these shells and which spin states are filled
Hund’s Rules
(1) Electrons try to align their spins, i.e. the electrons
should occupy the orbitals such that the maximum
possible value of the total spin S is realized.
Consider Pr as example - the 3 valence electrons will
have spins that point in same direction giving S=3/2
26/10/2018
9
17
Hund’s Rules for Isolated Atoms
(2) The electrons should occupy the orbitals such that
the maximum of L, consistent with S, is realized.
For Pr, this means giving
so we have and
(3) The total angular momentum J is calculated
• If the sub-shell is less than half-full J=L-S
• If the sub-shell is more than half full J=L+S
11. • If the sub-shell is half full, L=0 and J=S
For Pr, since shell less than half-full we use J=L-S = 6 - 3/2 =
9/2
18
Preference for spins to align comes from the Coulomb
interaction
energy between the electron and nucleus
For spins anti-aligned, electrons
are closer and the nucleus is
partially screened by the
negative charge of the other
electron.
For spins aligned the electrons
repel each other and see the full
positive charge of the nucleus.
26/10/2018
10
19
12. • The first of Hund’s rules requires S=3/2.
• The possible l z values for the 3d shell are -2,-1,0,1,2.
Hund’s second rule requires to choose the largest possible
value of L, i.e. to choose l z =0,1,2, so L=3.
• Since the sub-band is less than half filled, J=L-S=3-3/2=3/2.
Another example: Cr 3+
Cr3+ has three electrons in the 3d sub-shell
20 Ashcroft & Mermin Ch31
26/10/2018
11
21
(2S+1) X J
22
Coupling of electrons in atoms to an external
field
Seen how electron orbital and spin can align with each other
Now consider how electrons couple to an external magnetic
field
13. A is the vector potential
particle in electromagnetic field
change the momentum (operator)
First recall -
for electrons q=-e
26/10/2018
12
23
Coupling of electrons in atoms to an external
field
In absence of a magnetic
field the Hamiltonian for an
electron in an atom is:
V is electrostatic
potential from the
nucleus
In presence of a magnetic field:
14. where is the electron spin, g is the electron g-factor (about
2)
and the Bohr magneton is
Zeeman term
24
Zeeman effect
(l z)
Splitting of spectral lines when atom is placed in an external
magnetic field
Predicted by Lorentz, first observed by Zeeman
Energy level splitting in the normal Zeeman effect for singlet
levels l=2 and
l=1
26/10/2018
13
25
Coupling of electrons in atoms to an external
field
For a uniform magnetic field, we can take and
15. and so
can be written as:
First two terms just Hamiltonian in absence of field,
Can rewrite 3rd term as:
where is the angular momentum of the
electron
is the Bohr magneton
26
Coupling of electrons in atoms to an external
field
With 3rd term as
Can combine with 5th term of below
To obtain final expression:
paramagnetic
term
Coupling of field to total
magnetic moment of electron
diamagnetic
term
16. These two terms are
responsible for the paramagnetic
and diamagnetic response of atoms
to external magnetic fields
26/10/2018
14
27
Coupling of electrons in atoms to an external
field
Free spin (Curie or Langevin) Paramagnetism
Consider the paramagnetic term in previous equation –
generalize to multiple
electrons in the atom:
L and S, orbital and spin components
of all electrons, and
Can write as:
where
(see Oxford Solid
17. State Basics for
derivation or
Ashcroft and Mermin
Appendix P)
The partition function is
And the corresponding free energy is
It describes the reorientation of free spins in an atom
28
Coupling of electrons in atoms to an external
field
Free spin (Curie or Langevin) Paramagnetism
Given the free energy
The magnetic moment per spin is
Assuming a density n of these atoms it can be shown that the
susceptibility is:
Curie Law
Called “Curie paramagnetism or Langevin paramagnetism”
Curie constant
Ashcroft & Mermin
18. Ch31
26/10/2018
15
29
Coupling of electrons in atoms to an external field
Curie paramagnetism dominant when
So can only observe diamagnetism when
For example, filled shell configurations like
noble gases
[Or if J=0, but L and S not equal to zero. This
occurs when shell has one electron fewer than
being half full ]
Larmor Diamagnetism
The expectation of the diamagnetic term for B in the z direction
is
The atom is rotationally symmetric:
Consider now diamagnetic term – coupling of the orbital motion
to the
19. magnetic field
30
Coupling of electrons in atoms to an external field
Larmor Diamagnetism
The atom is rotationally symmetric:
So we have
and the magnetic moment per electron is:
Assume density of electrons, can write:
Larmor Diamagnetism
(recall M=χ H = χ B/ μ0)
= χ B/ μ0
26/10/2018
16
31
32
26/10/2018
20. 17
Will be some amount of diamagnetism in all materials, above
good description
for core electrons – but for conduction electrons in a metal we
have
Landau-diamagnetism:
where is the susceptibility of the free
Fermi gas
33
Magnetism of atoms in solids
Diamagnetism in solids
In above, Larmor diamagnetism applied to isolated atoms with
At low temperatures, noble gas atoms form weak bonds in
crystal and
description still applies, where density of electrons is put equal
to the
atomic number Z times the density of atoms, n. the radius r is
the
atomic radius
34
Magnetism of atoms in solids
Curie Paramagnetism
21. Recall: Curie paramagnetism describes the reorientation of free
spins in an atom
Does it occur in solids?
Yes, possible,
e.g. through “crystal field splitting” where atoms are no longer
in a rotationally
symmetric environment
Also, the number of electrons on an atom can become modified
in a material,
e.g. Pr, we had 3 free electrons in valence (4f) shell (J=9/2), but
in many
compounds Pr donates two of its 6s electrons and one f electron
(J=4).
Paramagnets can have many different effective values of J –
need to know
microscopic details of bonding in system!
(in this case, L=5, S=2/2 and J=L-S = 5 -1=4)
e.g Fe iron
d 6
4μB
22. Module 2 - Background
SOCIAL MEDIA AND HR; BEHAVIORAL ANCHORED
RATING SCALES; SIMULATION TRAINING
Staffing
Required Material
Davenport, T. H. (2012). Case study: Social media engages
employees. FT.Com, Retrieved from the Trident Online Library.
Facebook, Blogs & the Boss: The intersection of social media &
the workplace. (2013). Retrieved
from https://www.youtube.com/watch?v=PRrJ9eINYZI
Wild About Trial (2015). Legal Smart with Alison Triessl—
Social Media & Employment. Retrieved
from https://www.youtube.com/watch?v=d26eEzr5KuI.
Wilkie, D., & Wright, A. (2014). Balance risks of screening
social media activity. HR Magazine, 59(5), 14. Retrieved from
ProQuest in the Trident Online Library.
Wright, A. Nov., 2014). How Facebook recruits. Retrieved
from http://www.shrm.org/hrdisciplines/technology/articles/pag
es/how-facebook-recruits.aspx
Optional Material
Segal, J. A. (2014). The law and social media in hiring. HR
Magazine, 59(9), 70-72. Retrieved from ProQuest in the Trident
Online Library.
Segal, J. A., & LeMay, J., S.P.H.R. (2014). Should employers
use social media to screen job applicants? HR Magazine,
59(11), 20-21. Retrieved from ProQuest in the Trident Online
Library.
Skill Boosters (2015). Top 5—Social media fails at work.
Retrieved
from https://www.youtube.com/watch?v=6TXjQt3qYwk.
Swain, K. (2017). The impact of social media in the workplace
pros and cons. Retrieved from http://work.chron.com/impact-
social-media-workplace-pros-cons-22611.html.
Walden, J. A. (2016). Integrating Social Media Into the
Workplace: A Study of Shifting Technology Use
Repertoires. Journal Of Broadcasting & Electronic
23. Media, 60(2), 347-363. Available in the Trident Online Library.
Wright, A. D. (2014). More states prohibit social media
snooping. HR Magazine, 59(10), 14. Retrieved from ProQuest in
the Trident Online Library.
Behaviorally Anchored Rating Scales
Required Material
Behaviorally Anchored Rating Systems—BARS. Retrieved
from http://performance-appraisals.org/appraisal-
library/Behaviorally_Anchored_Rating_Systems_-_BARS/
Govekar, P. & Christopher, J. Assessing academic advising
using behaviorally anchored rating scales (BARS). Example.
Retrieved
from http://www.westga.edu/~bquest/2007/BARS7.pdf
Optional Material
Behaviorally Anchored Rating Scale (BARS) Guide. Retrieved
from www.in.gov/spd/files/bars.doc
Simulation Training
Required Material
Abernathy, D., Allerton, H., Barron, T., & Salopek, J. (1999).
Everyday simulation. Training & Development, 53(11), 37.
Available in the Trident Online Library.
AusBusiness Traveller (2011). Inside REAL Qantas 747 Flight
Simulator HD. Retrieved
from https://www.youtube.com/watch?v=L8JUWUKXV08. (for
Discussion Forum)
(AusBusiness Traveller, 2011)
Hiringsimulation.com (2017). Why Job Simulation Works.
Optional Material
Catling, C., Hogan, R., Fox, D., Cummins, A., Kelly, M., &
Sheehan, A. (2016). Simulation workshops with first year
midwifery students. Nurse Education in Practice, 17, 109-115.
Available in the Trident Online Library.
Lambert, C., and Lloyd-Jones, H. (2014). Run simulation in
your workplace. Education for Primary Care. 25(6), 357-359.
Retrieved from BBSCOHost in the Trident Online Library.
McMaster, S., Ledrick, D., Stausmire, J., & Burgard, K. (2014).
24. Evaluation of a simulation training program for uncomplicated
fishhook removal. Wilderness & Environmental Medicine, 25,
416-424. Available in the Trident Online Library.
Uptick in simulation training. (2013). Air Force Time, 3.
Available in the Trident Online Library.
Discussion: Simulation Training/Development
Deidriaunna Priest posted Apr 22, 2020 1:57 PM
Hello Class,
Simulation training is considered to be one of the most effective
ways of learning. It provides a realistic, immersive experience
in the context of the learning job (Srivastava & Srivastava
2019). Simulation training offers visuals and scenarios that
occur in real life. Most training occurs online without hands-on
training. Having practical exercises will help all types of
learners. Companies can save money, being that there able to
assess how well their trainees are doing.
HRM professionals can objectively determine the value of
simulation training by getting real experiences, feedback, and
retention. Providing authentic experiences allows individuals to
get an idea of work functions. Reading guides and watching
webinars are not beneficial to all employees. Getting feedback
will enable employers to get a better understanding of needs and
concerns. Being that employees are training in real-life
situations, they're able to retain more information.
Simulation training has significant benefits, but it also has
disadvantages. Simulators can be costly due to updates and
maintenance. Also, training all employees should be trained
adequately on software and hardware.
Having simulation training allows trainees to participate in
activities within a safe environment. Learners are capable of
learning things from errors. Also, getting hands-on thinking
skills and effective communication will enhance real-life
25. situations.
References
Arias, Raphael Gonçalves. "5 Secrets to Master the Risk
Assessment Matrix." SoftExpert Excellence Blog,
31 Jan. 2020, blog.softexpert.com/en/risk-assessment-matrix-
secrets/.
Srivastava, Av, and Av Srivastava. “Simulation Training -
Definition, Learning Benefits & Top
Companies.” Learning Light, 25 Nov.
2019, www.learninglight.com/simulation-based-training-
providers/.
“The Major Benefits of Using Simulation Training in Corporate
Learning.” Designing Digitally, Inc.,
www.designingdigitally.com/blog/2018/11/major-benefits-
using-simulation-training-corporate-
learning.
23/10/2017
1
Semiconductors
Semiconductors
One shouldn’t work on semiconductors, that is a
filthy mess; who knows whether any
semiconductors exist.
(Über Halbleiter soll man nicht arbeiten, das ist
26. eine Schweinerei; wer weiss, ob es überhaupt
Halbleiter gibt.)
Wofgang Pauli, 1931
23/10/2017
2
Why semiconductors?
• SEMICONDUCTORS: They are here, there, and everywhere
• Computers Silicon (Si) MOSFETs, ICs, CMOS
laptops, anything “intelligent”
• Cell phones, pagers Si ICs, GaAs FETs, BJTs
• CD players AlGaAs and InGaP laser diodes, Si
photodiodes
• TV remotes, mobile terminals Light emitting diodes (LEDs)
• Satellite dishes InGaAs MMICs (Monolithic Microwave
ICs)
• Fiber networks InGaAsP laser diodes, pin photodiodes
27. • Traffic signals, car GaN LEDs (green, blue)
taillights InGaAsP LEDs (red, amber)
• Air bags Si MEMs, Si ICs
• and, they are important, especially to Elec.Eng.& Computer
Sciences
Introduction
Semiconductors are materials whose electrical
properties lie between Conductors and Insulators.
Ex : Silicon and Germanium
Difference in conductivity
23/10/2017
3
Semiconductor Materials
• Elemental semiconductors – Si and Ge (column IV of periodic
table) –compose of single species of atoms
• Compound semiconductors – combinations of atoms of column
III and column V and some atoms from column II and VI.
(combination of two atoms results in binary compounds)
• There are also three-element (ternary) compounds (GaAsP)
and
28. four-elements (quaternary) compounds such as InGaAsP.
gap size
(eV)
InSb 0.18
InAs 0.36
Ge 0.67
Si 1.11
GaAs 1.43
SiC 2.3
diamond 5.5
MgF2 11
valence
band
conduction
band
Can a material with
μ in a band gap
conduct?
29. 23/10/2017
4
Semiconductor
materials
Semiconductor Materials
• The wide variety of electronic and optical properties of these
semiconductors provides the device engineer with great
flexibility in the design of electronic and opto-electronic
functions.
• Ge was widely used in the early days of semiconductor
development for transistors and diods.
• Si is now used for the majority of rectifiers, transistors and
integrated circuits.
• Compounds are widely used in high-speed devices and
devices
requiring the emission or absorption of light.
• The electronic and optical properties of semiconductors are
strongly affected by impurities, which may be added in
precisely
controlled amounts (e.g. an impurity concentration of one part
per million can change a sample of Si from a poor conductor to
a
good conductor of electric current). This process called doping.
30. 23/10/2017
5
Intrinsic semiconductors
• Pure, i.e. not doped, semiconductors are called intrinsic.
• For the electronic properties of a semiconductor, “pure”
means pure within 1 ppm to 1 ppb.
Intrinsic Material
A perfect semiconductor crystal with no impurities or lattice
defects is called an
intrinsic semiconductor.
At T=0 K –
No charge carriers
Valence band is filled with electrons
Conduction band is empty
At T>0
Electron-hole pairs are generated
EHPs are the only charge carriers in
intrinsic material
Since electron and holes are created in
31. pairs – the electron concentration in
conduction band, n (electron/cm3) is
equal to the concentration of holes in the
valence band, p (holes/cm3).
Each of these intrinsic carrier
concentrations is denoted ni.
Thus for intrinsic materials n=p=ni
Electron-hole pairs in the covalent bonding
model in the Si crystal.
23/10/2017
6
Doped semiconductors
• A very small amount of impurities can have a big
influence on the conductivity of a semiconductor.
• Controlled addition of impurities is called doping.
• There are two types of doping: n doping
(impurities increasing #electrons) and p doping
32. (impurities increasing #of holes).
• Typical doping levels are in the order of 1019 to
1023 impurity atoms per m3. Remember: Si has a
concentration of 5*1028 atoms per m3 and an
intrinsic carrier concentration of 1016
electrons/holes per m3 at room temperature.
Si
14
-
-
-
-
-
-
-
-
-
-
-
- -
-
33. However, like all
other elements it
would prefer to have
8 electrons in its
outer shell
The Silicon Atomic Structure
Silicon: our primary example and
focus
Atomic no. 14
14 electrons in three shells: 2 ) 8 ) 4
i.e., 4 electrons in the outer "bonding"
shell
Silicon forms strong covalent bonds with
4 neighbors
3s2 3p2 2s2 2p6 1s2
Si
23/10/2017
7
Si and Ge are tetravalent elements – each atom of Si (Ge) has 4
34. valence
electrons in crystal matrix
T=0 all electrons are bound in
covalent bonds
no carriers available for
conduction.
For T> 0 thermal fluctuations can
break electrons free creating
electron-hole pairs
Both can move throughout the lattice
and therefore conduct current.
Electrons and Holes
Excite electron from valance
band to conduction band, e.g.,
absorbing a photon or thermal
excitation.
35. Absence of electron in
valence
band called a “hole” – treat
holes as elementary particles.
To conserve charge, if electron
is negative, hole is positive
charged.
Electron can fall back into
hole, releasing energy ,e.g.
emitting photon, and
annihilating
electron and hole.
Holes
23/10/2017
8
Effective Mass of Electrons
As before, describe curvature at
36. bottom of band in terms of effective
mass.
Near bottom of conduction band,
where k=k min
And the corresponding group
velocity is
The effective mass is defined as,
Recall, for free electron
Effective Mass of Holes
valence band
convension is:
“hole”
For the top of the valence band, can
write:
And define effective mass for holes,
Energy to move hole away from top of
band is:
And corresponding hole velocity is:
37. 23/10/2017
9
Alternative definition is to define effective mass as being the
quantity that satisfies Newton’s second law
Effective Mass
A force is applied to an electron, then work done on electron
equal to its change in energy – consider work done per unit
time
Change in energy per unit time:
Equating:
used
(chain rule)
(since )
Then:
Effective mass
as a function of
momentum
39. Electrons and Holes
Electron-hole pairs in a semiconductor.
The bottom of the conduction band
denotes as Ec and the top of the valence
band denotes as Ev.
For T>0
some electrons in the valence band receive
enough thermal energy to be excited
across the band gap to the conduction
band.
The result is a material with some electrons
in an otherwise empty conduction band and
some unoccupied states in an otherwise
filled valence band.
An empty state in the valence band is
referred to as a hole.
If the conduction band electron and the
hole are created by the excitation of a
40. valence band electron to the conduction
band, they are called an electron-hole
pair (EHP).
Increasing conductivity by temperature
15 0 20 0 25 0 30 0 35 0 40 0 45 0 50 0
10 0
1 10
3
1 10
4
1 10
5
1 10
6
1 10
7
1 10
8
1 10
9
1 10
10
41. 1 10
11
1 10
12
1 10
13
1 10
14
1 10
15
1 10
16
1 10
17
Carrier Concentration vs T emp (in Si)
T em p erature (K )
In
tr
in
si
c
C
o
n
42. ce
n
tr
at
io
n
(
cm
^
-3
)
ni
T
T
Therefore the conductivity of a semiconductor is influenced by
temperature
As temperature increases, the number of free electrons and
holes created increases exponentially.
23/10/2017
11
Adding Electrons or Holes with Impurities: Doping
43. A phosphorous atom P replaces a silicon atom. The
P atom is like an Si atom plus an extra electron.
Extra electron goes in conduction band
P is an electron donor in silicon – also called an
n-type dopant. n is symbol for electron density
n- and p-doping
donor atom acceptor atom
Analogously, an Al replacing a silicon atom. The
Al atom has one fewer electrons than Si. Gives rise to a
hole. Al is an electron acceptor in silicon – also called an
p-type dopant. p is symbol for hole density.
23/10/2017
12
Adding Electrons of Holes with Impurities: Doping
All electrons
in covalent
bond with 2
44. electrons
Extra
electron
Extra hole
Donor and acceptors in covalent bonding model
In the covalent bonding
model, donor and acceptor
atoms can be visualized as
shown in the Figure. An Sb
atom (column V) in the Si
lattice has the four necessary
valence electrons to complete
the covalent bonds with the
neighboring Si atoms, plus one
extra electron. This fifth
electron does not fit into the
bonding structure of the
lattice and is therefore
loosely bound to the Sb atom.
Donor and acceptor atoms
in the covalent bonding
model of a Si crystal.
23/10/2017
45. 13
Donor and acceptors in covalent bonding model
A small amount of thermal energy
enables this extra electron to
overcome its coulombic binding to
the impurity atom and be donated
to the lattice as a whole. Thus it is
free to participate in current
conduction. This process is a
qualitative model of the excitation
of electrons out of a donor level and
into the conduction band.
Similarly, the column III impurity
Al has only three valence electrons
to contribute to the covalent
bonding, thereby leaving one bond
incomplete. With a small amount of
thermal energy, this incomplete
bond can be transferred to other
atoms as the bonding electrons
exchange positions.
Donor and acceptor atoms
in the covalent bonding
model of a Si crystal.
Adding Electrons or Holes with Impurities: Doping
Consider n-type dopant, e.g. P in Si
Extra electron in conduction band acts like
46. a free electron with mass, m*
but also have positive charge in nucleus of P
Forms a bound state like a H atom –
Attract with potential:
Energy eigenstates of H atom
Rydberg constant
Radius of wave function
mass of electron
Analogously, for a hydrogenic
Impurity state we have:
4
23/10/2017
14
n-doping Estimate binding energy
with Bohr model:
using the modifications
phosphorus
penta-valent,
47. one electron too many
order of magnitude
The radius of this is quite big, 30 times the
Bohr radius
Adding Electrons or Holes with Impurities: Doping
23/10/2017
15
Extrinsic Material
By doping, a crystal can be altered so that it has a predominance
of either
electrons or holes. Thus there are two types of doped
semiconductors, n-type
(mostly electrons) and p-type (mostly holes). When a crystal is
doped such that
the equilibrium carrier concentrations n0 and po are different
from the intrinsic
carrier concentration ni, the material is said to be extrinsic.
Donor impurities (elements
of group V): P, Sb, As
Acceptor elements (group
III): B, Al, Ga, In
48. The valence and conduction bands of
silicon with additional impurity energy
levels within the energy gap.
When impurities or lattice
defects are introduced,
additional levels are created
in the energy bands
structure, usually within the
band gap.
Total number of electrons
III – Al – 13
IV – Si – 14
V - P - 15
Extrinsic Material – donation of electrons
An impurity from column V
introduces an energy level very
near the conduction band in Ge
or Si. This level is filled with
electrons at 0 K, and very little
thermal energy is required to
excite these electrons to the
conduction band. Thus, at about
50-100 K nearly all of the
electrons in the impurity level
are "donated" to the conduction
band. Such an impurity level is
called a donor level, and the
49. column V impurities in Ge or Si
are called donor impurities.
Donation of electrons from
a donor level to the
conduction band
n-type material
23/10/2017
16
Extrinsic Material – donation of electrons
From figure we note that the
material doped with donor
impurities can have a
considerable concentration of
electrons in the conduction band,
even when the temperature is
too low for the intrinsic EHP
concentration to be appreciable.
Thus semiconductors doped with
a significant number of donor
atoms will have n0>>(ni,p0) at
room temperature. This is n-type
material.
Donation of electrons from
a donor level to the
50. conduction band
n-type material
Extrinsic Material – acceptance of electrons
Acceptance of valence band
electrons by an acceptor level,
and the resulting creation of
holes.
Atoms from column III (B,
Al, Ga, and In) introduce
impurity levels in Ge or Si
near the valence band. These
levels are empty of electrons
at 0 K. At low temperatures,
enough thermal energy is
available to excite
electrons from the valence
band into the impurity level,
leaving behind holes in the
valence band.
P-type material
23/10/2017
17
51. Extrinsic Material – acceptance of electrons
Acceptance of valence band
electrons by an acceptor level,
and the resulting creation of
holes.
Since this type of impurity
level "accepts" electrons
from the valence band, it is
called an acceptor level, and
the column III impurities are
acceptor impurities in Ge and
Si. As figure indicates,
doping with acceptor
impurities can create a
semiconductor with a hole
concentration p0 much
greater than the conduction
band electron concentration
n0 (this is p-type material).
P-type material
Statistical Mechanics of Semiconductors
Recall from Lecture 3 – density of states for free electrons
per unit volume
Electrons in conduction band like
free electrons but with mass m*, can write:
52. Similarly the density of states for holes
near the top of the valence band are:
2/11/2017
1
Magnetism 2
where is the g-factor. The spin is and the Bohr
magneton is
Then the energy of an electron with spin up (same direction as
Magnetic field is:
And that with spin down is
where
Magnetic Spin Susceptibility – Pauli
Paramagnetism
Consider the response of free electrons to an externally applied
53. magnetic field. The electron’s motion can be curved due to the
Lorentz force, but also the spins can flip. Looking at latter
effect.
The Hamiltonian becomes:
2/11/2017
2
The spin magnetization of the system (magnetic moment per
unit volume) in direction of the field is:
With applied magnetic field the energy is lower when the spins
point down, so more of them will point down and a
magnetisation
develops in the direction of applied field – known as
Pauli paramagnetism (spin magnetization of free electron gas)
Magnetic Spin Susceptibility – Pauli
Paramagnetism
4
54. Magnetic Spin Susceptibility – Pauli
Paramagnetism
Find Pauli paramagnetism for T=0
For no magnetic field, electrons
are filled up to the Fermi energy with
With magnetic field, up electrons
more energetically unfavorable by
therefore will have
fewer spin up electrons
2/11/2017
3
5
Magnetic Spin Susceptibility – Pauli
Paramagnetism
That is, with the magnetic field that states with up and down
spin are
shifted in energy by and , respectively.
Hence, spin up electrons that are pushed above the Fermi energy
can lower their energies by flipping their spins to become spin
55. down
electrons. The total number of spins that flip (the area of the
approximately rectangular shape) is roughly
Then from:
we obtain:
and
so
6
Spontaneous magnetic order in solids
Heisenberg Hamiltonian
Model description of how spins align – assume an interaction
between
neighbouring spins – so-called “exchange interaction”
Assume an insulator, so electrons don’t hop from site to site.
Model Hamiltonian is:
is the spin on site i and B is the magnetic field experience by
the spins
56. is the interaction energy. Neglecting the magnetic field, and
assume each spin coupled to its neighbour with the same
strength, can
drop i,j
is the interaction energy
Factor of ½ avoids over-counting in sum
If lower energy when spins aligned; whereas if
it is lower energy
when spins are anti-aligned
2/11/2017
4
7
Spontaneous magnetic order in solids
The Hamiltonian doesn’t indicate a
preferred spin direction.
In a real system, atoms are often in an asymmetric environment
due to the
lattice and will be directions that the spin would rather point.
57. Add term to the Heisenberg Hamiltonian:
called anisotropy energy as gives system a preferred direction,
here in the
or directions.
Or, for spin pointing along the orthogonal axis directions:
8
Spontaneous magnetic order in solids
If the anisotropy term is very large in
It will force the spin to be either or
This gives the Ising Model
where only (and reintroducing the magnetic
field B)
2/11/2017
5
58. Experiments: MExFM
9
(a) Atomic-resolution image of an antiferromagnetic NiO(001)
surface
obtained by Non-Contact Atomic Force Microscopy (NC-AFM).
The line
section reveals an apparent height difference of 4.5 pm between
nickel
(dark) and oxygen (bright) sites.
(b) Spin-resolved image of NiO(001) with atomic resolution as
obtained
by Magnetic Exchange Force Microscopy (MExFM)
Imaging & Microscopy, Jun. 01, 2008 R. Wiesendanger,
Experiments: Spin-polarized STM
10
Differential conductance asymmetry A dI/dV. a Two magnetic
configurations in spin-STM measurements, AP and P,
corresponding to two distinct magnetic states of a bilayer Co
nanoisland, pointing up and down, respectively. b, c dI/dV
images of the Co nanoisland ‘A’ in Fig. 5 a measured at μ0 H
ext = −1 T and V b = + 0.03 V for AP (b) and P (c) states. d A
59. dI/dV map calculated from the dI/dV images of b and c. e Two
relative magnetization configurations of spin-STM
measurements, corresponding to two distinct magnetic states of
a bilayer Fe nanoisland, α and β. f, g dI/dV images of a Fe
nanoisland, measured at external fields of (b) 0 T and (c) a
value ≥ H sat. h A dI/dV map calculated from the dI/dV images
of f
and g.b–d
Nano Convergence 2017 4:8 Soo-hyon Pharj and Dirk Sander,
https://nanoconvergencejournal.springeropen.com/articles/10.11
86/s40580-017-0102-5#Fig5
2/11/2017
6
11
Domains and Hysteresis
In real materials there are regions “domains” with different spin
orientation.
Reduces the dipolar energy (resulting from the sum of the
individual dipole-
dipole interactions on the atoms).
Can understand like since if view as magnets; two like ends
(North/South) will
60. repel; lower energy by flipping one.
Boundary between domains,
call “domain wall”
Applying magnetic field
increases domain size
of that pointing in same
direction
Ising type ferromagnet
moments only up or down
12
Domains and Hysteresis
Another way of understanding why magnetic domains are
energetically
preferred is to consider the magnetic field they induce:
The magnetic field will be much lower if they are anti-aligned
as can be seen.
The magnetic field has associated energy .
Thus, minimizing the field lowers the energy of the “two
61. dipoles”
2/11/2017
7
13
Ferromagnetic domains: Disorder Pinning
Above: both domain walls (red) start and end at same place.
But, one on right, passes through vacancy. It therefore
has one less anti-aligned spins, so overall energy lower
(more favourable) – say, domain wall is “pinned” to the
disorder
An Ising ferromagnet
The length of the domain wall
depends on balance between J and
If large, small wall
If small, wide wall
Consider scaling of wall: if length is then each spin
twists and angle:
. Then the first term in Eq(1) can be written as:
62. The spin do not need, however, to only point up or down,
corresponding to
large in
The domain wall may be more like a gradual rotation of up
pointing spins
to down pointing spins like below:
14
Ferromagnetic domains: Bloch/Neel Wall
Called a Bloch Wall or Neel Wall
(1)
Small angle expansion
2/11/2017
8
15
Ferromagnetic domains: Bloch/Neel Wall
Can see has lowest energy if so can think of the
second term being
an “energy cost”
63. Then for the N unit cells in the domain wall (the “energy
stiffness”), given
per unit area A (per lattice constant a):
Recall from Eq(1)
We also have 2nd term. When spins not exactly up or down, will
be energy
cost proportional to per spin, so for the N unit cells in
the domain wall:
16
Ferromagnetic domains: Bloch/Neel Wall
Total energy cost due to anisotropy:
So with these two energy costs (penalties) we have the total
energy cost:
64. Minimizing this energy with respect to length L we find:
and therefore
Energy balance between cost
of domain wall formation versus
gain due to having domains
2/11/2017
9
17
Hysteresis curve
coercive
field
remanent
magnetization
saturation
magnetisation
65. note that here
We know from electromagnetism that ferromagnets
exhibit a hysteresis loop with applied external field.
When field is returned to zero after being applied, there
is a remanent magnetization
This is because
there is a large
activation energy for
changing the
magnetization
How to understand the activation energy barrier – consider
small crystallite with all spins aligned. The energy per volume
in an external field is:
Where M is the magnetization and is the component in the
-direction.
19
66. Single Domain Crystallites
=
Zeeman energy per
unit volume
Number of spins per unit volume
angle of magnetization with respect to axis
Plotting Eq(1) vs gives
parabola -
2/11/2017
10
20
Single Domain Crystallites
- minimum of energy when magnetization in plus or minus z-
direction,
corresponding to , and energy barrier in between.
For increasing
B field, there are stable and metastable states. If B field large
enough, spins
will flip – this behaviour can result in the observed hysteresis
67. 24/10/2017
1
Semiconductors 2
Statistical Mechanics of Semiconductors
Recall from Lecture 3 – density of states for free electrons
per unit volume
Electrons in conduction band like
free electrons but with mass m*, can write:
Similarly the density of states for holes
near the top of the valence band are:
24/10/2017
2
The Fermi-Dirac distribution for a semiconductor
• For a metal, the Fermi energy is the highest occupied
energy at 0 K. The chemical potential is temperature-
dependent (but not much) and so the two are essentially
the same.
68. • For a semiconductor, the definition of the Fermi energy
is not so clear. We better use the chemical potential.
• Some (many) people also use the term “Fermi energy” for
semiconductors but then it is temperature-dependent.
Earlier (Lecture 3) we wrote it as:
In this Section, we call it the Fermi-Dirac function to
reflect relates to
electrons – recall it gives the probability that an available
energy state E will
be occupied by an electron at absolute temperature T.
Statistical Mechanics of Semiconductors
For a given chemical potential, the total number of electrons in
the conduction band as a function of temperature is:
where
For
We have
And then,
Boltzman distribution
24/10/2017
69. 3
Statistical Mechanics of Semiconductors
Want to solve integral: multiply Eq (1) by
(1)
Standard Equation for density of electrons
Statistical Mechanics of Semiconductors
Similarly can get the number of holes in the valence band p as:
When substantially above the top of the valence
band we have:
and
Standard Equation for density of holes
24/10/2017
4
Number of electrons excited into conduction band must equal
number
of holes left behind in valance band so
Law of Mass Action
Intrinsic Semiconductors
70. Forming product of density of electrons in conduction band,
and holes in the
valence band we obtain important relation:
Depends only on band gap
Dividing the density of electrons in conduction band n(T), and
holes in the valence
band p(T) we obtain:
Intrinsic Semiconductors
Taking the log of both sides of the below
and solving for gives:
That is, an expression for the chemical potential – at T=0 gives
exactly in
the middle of the band-gap
Using the law of Mass Action above with n=p we obtain:
24/10/2017
5
Extrinsic/Doped Semiconductors
Law of Mass Action also holds for doping when we have
Concentrations n and p
71. From the law of mass action we have
Consider intrinsic case:
np =
Example
gap size (eV) n in m
-3
at 150 K
n in m
-3
at 300 K
InSb 0.18 2x10
22
6x10
23
Si 1.11 4x10
6
2x10
16
diamond 5.5 6x10
-68
72. 1x10
-21
Using prefactor
24/10/2017
6
Dopants, n- and p-type
Majority and minority carriers
equal number of
electrons and holes
majority: electrons
minority: holes
24/10/2017
7
Band diagram, density of states, Fermi-Dirac distribution,
and the carrier concentrations at thermal equilibrium
Intrinsic
semiconductor
73. n-type
semiconductor
p-type
semiconductor
Consider a Si sample maintained at T = 300K under
equilibrium conditions, doped with Boron to a
concentration 2×1016 cm-3 : Given the intrinsic
concentration n i = p i is 1x10
10 cm-3
• What are the electron and hole concentrations (n
and p) in this sample? Is it n-type or p-type?
Example
Suppose the sample is doped additionally with Phosphorus
to a concentration 6×1016 cm-3.
• Is the material now n-type or p-type?
What are the n and p concentrations now?
21/10/2018
74. 1
1
Dispersion of one-dimensional chain
We expect periodicity since:
In general for integer p,
The set of points in k-space which are equivalent to k=0 is
known
as the reciprocal lattice (seen this before!)
belongs to the reciprocal lattice if:
2
Dispersion of one-dimensional chain
At shorter wavelength (larger k) we define:
speed at which a wave packet moves
speed at which maxima and minima move
21/10/2018
2
3
75. examples of dispersion relations
vibrations in a 1D chain
a quantum mechanical particle
k
4
examples of dispersion relations
light in vaccum
k
in vacuum the dispersion relation of light is linear.
Light travels with c independent of the frequency.
light in matter
21/10/2018
3
Dispersion of one-dimensional chain
5
Recall dispersion relation for 1-D chain below:
Doesn’t hold for all k – only particular k,
76. k is quantized
Ashcroft & Mermin Ch 22
6
Periodic boundary conditions
Max Born and Theodore von Karman (1912)
chain with N atoms:
1
N
A finite chain with no end!
21/10/2018
4
Counting normal modes
7
Periodic boundary conditions
1
N
Max Born and Theodore von Karman (1912)
chain with N atoms:
77. =
Must have wave ansatz satisfied
Recall:
that is, make satisfied for n n+N
must have to hold true
must then have
Length of first
Brillouin zone
a
8
Finite chain with 10 unit cells and
one atom per unit cell
• N atoms give N so-called normal modes of vibration.
• For long but finite chains, the points are very dense.
Example:
is spacing between
k values1
21/10/2018
78. 5
9
counting normal modes.....
From boundary conditions
chain with 1 atom / unit cell and
N unit cells
N x 1 modes
(since we have N degrees of freedom)
# k-points
# eigenvalues per k-point
# k-points
# eigenvalues per k-point
chain with 2 atom / unit cell and
N unit cells
N x 2 modes
(since we have 2xN degrees of freedom)
Will look at 2
atom chain later
10
79. Single harmonic oscillator: quantum model
The energy levels are
quantized
image source: wikimedia, author AllenMcC.
Quantum Modes: Phonons
In our chain, harmonic oscillator can be a collective normal
mode,
not just motion of a single particle
Correspondence: for classical harmonic system with normal
oscillation mode at frequency , corresponding quantum
system
will have eigenstates with energy:
n is an integer
http://commons.wikimedia.org/wiki/User:AllenMcC.
21/10/2018
6
11
Quantum Modes: Phonons
The ground state being n=0 eigenstate, and has zero-point
80. energy
The lowest energy excitation is of energy greater than
the
ground state, corresponding to n=1 eigenstate.
Each excitation of this normal mode by a step up
(increasing quantum number n) is known as a phonon
A phonon is a discrete quantum of vibration
12
long chain: quantum model
• The excitations of these oscillators (normal modes) are
called phonons.
• The dispersion is often called a phonon dispersion curve.
l is an integer
21/10/2018
7
Vibrations of a 1-D Diatomic Chain
13
Assume:
81. or
Vibrations of a1-D Diatomic Chain
14
is quantised in units of
As for the 1-D chain with one mass
write down Newton’s equations
of motion for deviation
of the equilibrium position
Similarly, to before, propose Ansatz:
If system has N unit cells, L=Na, and using boundary conditions
as before:
As before, dividing range of k by spacing between k’s, we get N
different values of k;
one k per unit cell
21/10/2018
8
15
Vibrations of a 1-D Diatomic Chain
82. Substitute Ansatz into the
equation of motion:
gives:
or as an eigenvalue equation:
16
Vibrations of a1-D Diatomic Chain
Find solutions by finding zero’s of the secular determinant
so
and the second term becomes:
21/10/2018
9
17
Vibrations of a 1-D Diatomic Chain
When phonons interact with light
(photons) it is the upper “optical”
branch, hence name
Group velocity
83. goes to zero at zone boundary
and for optical, at k=0
Finally, the dispersion relation is:
18
Vibrations of a 1-D Diatomic Chain
Effective spring constant
Density of chain
Expanding for small k,
can show:
Could have derived this sound velocity – recall, we had earlier:
=
21/10/2018
10
19
Vibrations of a 1-D Diatomic Chain
Acoustic mode, which has =0 is solved by,
Consider acoustic and optical phonon as , we had:
84. which becomes,
Says the two atoms move together for the acoustic mode in the
long
wavelength limit
20
Vibrations of a 1-D Diatomic Chain
Tells the two atoms move in opposite directions
The optical mode, at
has frequency:
As , we had
and eigenvector
21/10/2018
11
21
Vibrations of a1-D Diatomic Chain
As for electronic states,
can unfold into the “extended zone scheme”
22
85. Vibrations of a 1-D Diatomic Chain
Can show that as the two atoms in cell become
identical and
dispersion becomes that of monatomic dispersion
21/10/2018
12
Vibrations/Phonons
23
Had one mass per cell, one mode per distinct value of k
(acoustic, go to zero at
k=0)
For two masses per cell, two modes per distinct value of k
(acoustic, optical)
For M atoms per cell, get M modes per distinct value of k – one
will be acoustic,
others optical.
For 1-D chain atoms only move in line, one degree of freedom
For 3-D solid atoms have three degrees of freedom
Three different acoustic modes at each k at long wavelength –
one “longitudinal
86. acoustic” and two “transverse acoustic”
For N atoms per cell, 3(N-1) optical modes, always 3 acoustic
modes – 3N
degrees of freedom per cell
24
Phonons in 3D crystals: Aluminium
One atom per cell, just 3 acoustic modes
21/10/2018
13
25
Phonons in 3D crystals: diamond
• We see acoustic and optical phonons. 3 branches for every
atom per unit
cell. Here two atoms, six branches, three ac, three opt (3(N-1) =
3(2-1)=3)
• important to identify Bravais lattice and basis if we want to
make
predictions as to vibrational properties
State of the art calculation + expt
26
87. Phonon dispersion and phonon density of states of TiC2 as
determined
by DFT calculations.
Like for the electron energy
dispersion and density of states
6 atoms per unit cell – 3(N-1)=3(6-1)=15 opt, 3 acoustic
Density of phonon
states, g(ω),
21/10/2018
14
Revision
27
28
17/10/2017
1
1
88. Lattice vibrations – 1D
Consider one dimensional system of atoms in a line
Recall: The potential between two neighbouring atoms has the
form above
2
In region of minimum, Taylor expansion:
Lattice vibrations – 1D
At finite temperature T the atoms can oscillate between
and
Since potential is asymmetric away from minimum, this leads to
an
Average position greater than
- Thermal Expansion (though not all systems behave like this)
Handout 6
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2
3
Lattice vibrations – 1D
89. Compressibility/elasticity
Hooke’s Law – quadratic potential about minimum
Applying a force to compress system
- reduces distance between atoms
Compressibility: (assuming )
In one-dimension, with L the length:
(taking = )
4
Lattice vibrations – 1D
In an isotropic compressible fluid
sound waves with velocity:
For the 1-D solid take the density as where is
the mass of atom
then
bulk modulus
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90. 5
Lattice vibrations -1D chain
Handout 6
Ch 22
Ashcroft &
Mermin
Let the position of the atom be
And the equilibrium position be
Allowing motion of atoms:
Can write total potential energy as:
6
Lattice vibrations -1D chain
The force on the mass
Ansatz
Solution
:
91. Substitute solution into (1)
(1)
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Dispersion of one-dimensional chain
7
in general we have that ω depends on k.
ω(k) is called the dispersion relation. Periodic in
8
The first Brillouin zone
Recall: The first Brillouin zone is the region of reciprocal
space which is closer to one reciprocal lattice point than to
92. any other (Wigner-Seitz cell in reciprocal space).
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Dispersion of one-dimensional chain
9
10
sound
wave
dispersion relation
For small k the sin is equal to its argument
but for k very small (lambda very long) the crystalline structure
is
93. unimportant and we get sound waves.
.
Dispersion of one-dimensional chain
sound
velocity
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11
Dispersion of one-dimensional chain
We expect periodicity since:
94. In general for integer p,
The set of points in k-space which are equivalent to k=0 is
known
as the reciprocal lattice (seen this before!)
belongs to the reciprocal lattice if:
12
Dispersion of one-dimensional chain
At shorter wavelength (larger k) we define:
speed at which a wave packet moves
speed at which maxima and minima move
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95. 13
examples of dispersion relations
vibrations in a 1D chain
a quantum mechanical particle
k
14
examples of dispersion relations
light in vaccum
k
in vacuum the dispersion relation of light is linear.
Light travels with c independent of the frequency.
light in matter
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Counting normal modes
15
Periodic boundary conditions
1
N
A finite chain with no end!
Max Born and Theodore von Karman (1912)
chain with N atoms:
16
Finite chain with 10 unit cells and
97. one atom per unit cell
• N atoms give N so-called normal modes of vibration.
• For long but finite chains, the points are very dense.
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17
counting normal modes.....
boundary conditions
chain with 1 atom / unit cell and
N unit cells
N x 1 modes
(since we have N degrees of freedom)
# k-points
98. # eigenvalues per k-point
# k-points
# eigenvalues per k-point
chain with 2 atom / unit cell and
N unit cells
N x 2 modes
(since we have 2xN degrees of freedom)
18
Single harmonic oscillator: quantum model
The energy levels are
quantized
image source: wikimedia, author AllenMcC.
99. Quantum Modes: Phonons
In our chain, harmonic oscillator can be a collective normal
mode,
not just motion of a single particle
Correspondence: for classical harmonic system with normal
oscillation mode at frequency , corresponding quantum
system
will have eigenstates with energy:
http://commons.wikimedia.org/wiki/User:AllenMcC.
http://commons.wikimedia.org/wiki/User:AllenMcC.
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19
Quantum Modes: Phonons
100. The ground state being n=0 eigenstate, and has zero-point
energy
The lowest energy excitation is of energy greater than
the
ground state, corresponding to n=1 eigenstate.
Each excitation of this normal mode by a step up
(increasing quantum number n) is known as a phonon
A phonon is a discrete quantum of vibration
Adv.: In Handout 6, read on about effect of temperature
(Bose occupation factor) and how the heat capacity can be
obtained.
101. 17/10/2017
1
1
Lattice vibrations – 1D
Consider one dimensional system of atoms in a line
Recall: The potential between two neighbouring atoms has the
form above
2
In region of minimum, Taylor expansion:
Lattice vibrations – 1D
At finite temperature T the atoms can oscillate between
102. and
Since potential is asymmetric away from minimum, this leads to
an
Average position greater than
- Thermal Expansion (though not all systems behave like this)
Handout 6
17/10/2017
2
3
Lattice vibrations – 1D
Compressibility/elasticity
Hooke’s Law – quadratic potential about minimum
103. Applying a force to compress system
- reduces distance between atoms
Compressibility: (assuming )
In one-dimension, with L the length:
(taking = )
4
Lattice vibrations – 1D
In an isotropic compressible fluid
sound waves with velocity:
For the 1-D solid take the density as where is
the mass of atom
then
bulk modulus
104. 17/10/2017
3
5
Lattice vibrations -1D chain
Handout 6
Ch 22
Ashcroft &
Mermin
Let the position of the atom be
And the equilibrium position be
Allowing motion of atoms:
105. Can write total potential energy as:
6
Lattice vibrations -1D chain
The force on the mass
Ansatz