The document discusses two types of superconductors:
Type I superconductors strictly follow the Meissner effect and exhibit perfect diamagnetism below a critical field, above which superconductivity is lost abruptly. Type II superconductors do not follow the Meissner effect strictly and have higher critical fields, existing in a mixed state between lower and upper critical fields where magnetic flux partially penetrates. The document provides examples of the magnetic behavior of type I and type II superconductors.
Superconductivity is the ability of certain materials to conduct electric current with practically zero resistance. This capacity produces interesting and potentially useful effects. For a material to behave as a superconductor, low temperatures are required.
Basically i have tried giving every details about the phenomenon Superconductivity in the simplest way. This is my first upload.I'll be very glad if u all give your valuable feedback. Thank u.
An Overview of Superconductivity with Special Attention on Thermodynamic Aspe...Thomas Templin
Superconductors are special types of conductors that exhibit a variety of physical phenomena such as zero resistivity, the absence of thermoelectric effects, ideal diamagnetism, the existence of a Meissner effect, and flux quantization. The observed phenomena mean that superconductivity is a well-defined thermodynamic equilibrium state/phase that does not depend on a sample’s history. Changes of phase are entirely reversible, and once a substance has come to equilibrium with its surroundings, there is no memory of its past history.
A variety of theoretical approaches have been developed to explain superconductivity. These include the two-fluid model of superconductivity, the Ginzburg-Landau theory, and the BCS model. These models are most suitable to explain the phenomena associated with type-I superconductors, i.e., the types of superconductors that only exist when the external magnetic field is below a relatively low threshold value of Bc as well as below a transition temperature Tc close to 0 K. In the 1980s a new type of superconductors was discovered, called type-II superconductors. Type-II materials are characterized by the coexistence of normally conducting and superconducting states as well as relatively high values of the critical field and transition temperature. Type-II superconductors have been used in a variety of technological applications, such as superconducting electromagnets, MRI, particle accelerators, levitating trains, and superconducting quantum-interference devices (SQUIDs).
The superconducting state has a lower free energy than the normal state. The exclusion of the magnetic field from a superconductor leads to an increase in the free energy. The Meissner effect thus implies the existence of a thermodynamical critical field for which these two effects balance out. Knowing only the experimental temperature dependence of the critical field, the Gibbs free energy, the entropy, and the specific heat that characterize the superconducting phase can be determined.
Superconductivity is the ability of certain materials to conduct electric current with practically zero resistance. This capacity produces interesting and potentially useful effects. For a material to behave as a superconductor, low temperatures are required.
Basically i have tried giving every details about the phenomenon Superconductivity in the simplest way. This is my first upload.I'll be very glad if u all give your valuable feedback. Thank u.
An Overview of Superconductivity with Special Attention on Thermodynamic Aspe...Thomas Templin
Superconductors are special types of conductors that exhibit a variety of physical phenomena such as zero resistivity, the absence of thermoelectric effects, ideal diamagnetism, the existence of a Meissner effect, and flux quantization. The observed phenomena mean that superconductivity is a well-defined thermodynamic equilibrium state/phase that does not depend on a sample’s history. Changes of phase are entirely reversible, and once a substance has come to equilibrium with its surroundings, there is no memory of its past history.
A variety of theoretical approaches have been developed to explain superconductivity. These include the two-fluid model of superconductivity, the Ginzburg-Landau theory, and the BCS model. These models are most suitable to explain the phenomena associated with type-I superconductors, i.e., the types of superconductors that only exist when the external magnetic field is below a relatively low threshold value of Bc as well as below a transition temperature Tc close to 0 K. In the 1980s a new type of superconductors was discovered, called type-II superconductors. Type-II materials are characterized by the coexistence of normally conducting and superconducting states as well as relatively high values of the critical field and transition temperature. Type-II superconductors have been used in a variety of technological applications, such as superconducting electromagnets, MRI, particle accelerators, levitating trains, and superconducting quantum-interference devices (SQUIDs).
The superconducting state has a lower free energy than the normal state. The exclusion of the magnetic field from a superconductor leads to an increase in the free energy. The Meissner effect thus implies the existence of a thermodynamical critical field for which these two effects balance out. Knowing only the experimental temperature dependence of the critical field, the Gibbs free energy, the entropy, and the specific heat that characterize the superconducting phase can be determined.
Superconducting material and Meissner effectMradul Saxena
The project report gives brief explanation of the phenomenon of superconductivity and also give introduction to superconducting materials and their types, properties and their applications.
Properties of superconductors, Effects of the magnetic field, variation of resistance with temperature, Meissner Effect, isotope effect, Energy Gap, Coherence Length, BCS Theory, Types of superconductors ,
The fascinating phenomenon of superconductivity and its potential applications have attracted the attention of scientists, engineers and businessmen.
Superconductivity was discovered in 1911 by Heike Kamerlingh Onnes, as he studied the properties of metals at low temperatures.
Superconducting material and Meissner effectMradul Saxena
The project report gives brief explanation of the phenomenon of superconductivity and also give introduction to superconducting materials and their types, properties and their applications.
Properties of superconductors, Effects of the magnetic field, variation of resistance with temperature, Meissner Effect, isotope effect, Energy Gap, Coherence Length, BCS Theory, Types of superconductors ,
The fascinating phenomenon of superconductivity and its potential applications have attracted the attention of scientists, engineers and businessmen.
Superconductivity was discovered in 1911 by Heike Kamerlingh Onnes, as he studied the properties of metals at low temperatures.
Toxic effects of heavy metals : Lead and Arsenicsanjana502982
Heavy metals are naturally occuring metallic chemical elements that have relatively high density, and are toxic at even low concentrations. All toxic metals are termed as heavy metals irrespective of their atomic mass and density, eg. arsenic, lead, mercury, cadmium, thallium, chromium, etc.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
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What is greenhouse gasses and how many gasses are there to affect the Earth.moosaasad1975
What are greenhouse gasses how they affect the earth and its environment what is the future of the environment and earth how the weather and the climate effects.
hematic appreciation test is a psychological assessment tool used to measure an individual's appreciation and understanding of specific themes or topics. This test helps to evaluate an individual's ability to connect different ideas and concepts within a given theme, as well as their overall comprehension and interpretation skills. The results of the test can provide valuable insights into an individual's cognitive abilities, creativity, and critical thinking skills
The use of Nauplii and metanauplii artemia in aquaculture (brine shrimp).pptxMAGOTI ERNEST
Although Artemia has been known to man for centuries, its use as a food for the culture of larval organisms apparently began only in the 1930s, when several investigators found that it made an excellent food for newly hatched fish larvae (Litvinenko et al., 2023). As aquaculture developed in the 1960s and ‘70s, the use of Artemia also became more widespread, due both to its convenience and to its nutritional value for larval organisms (Arenas-Pardo et al., 2024). The fact that Artemia dormant cysts can be stored for long periods in cans, and then used as an off-the-shelf food requiring only 24 h of incubation makes them the most convenient, least labor-intensive, live food available for aquaculture (Sorgeloos & Roubach, 2021). The nutritional value of Artemia, especially for marine organisms, is not constant, but varies both geographically and temporally. During the last decade, however, both the causes of Artemia nutritional variability and methods to improve poorquality Artemia have been identified (Loufi et al., 2024).
Brine shrimp (Artemia spp.) are used in marine aquaculture worldwide. Annually, more than 2,000 metric tons of dry cysts are used for cultivation of fish, crustacean, and shellfish larva. Brine shrimp are important to aquaculture because newly hatched brine shrimp nauplii (larvae) provide a food source for many fish fry (Mozanzadeh et al., 2021). Culture and harvesting of brine shrimp eggs represents another aspect of the aquaculture industry. Nauplii and metanauplii of Artemia, commonly known as brine shrimp, play a crucial role in aquaculture due to their nutritional value and suitability as live feed for many aquatic species, particularly in larval stages (Sorgeloos & Roubach, 2021).
Comparing Evolved Extractive Text Summary Scores of Bidirectional Encoder Rep...University of Maribor
Slides from:
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Track: Artificial Intelligence
https://www.etran.rs/2024/en/home-english/
The ability to recreate computational results with minimal effort and actionable metrics provides a solid foundation for scientific research and software development. When people can replicate an analysis at the touch of a button using open-source software, open data, and methods to assess and compare proposals, it significantly eases verification of results, engagement with a diverse range of contributors, and progress. However, we have yet to fully achieve this; there are still many sociotechnical frictions.
Inspired by David Donoho's vision, this talk aims to revisit the three crucial pillars of frictionless reproducibility (data sharing, code sharing, and competitive challenges) with the perspective of deep software variability.
Our observation is that multiple layers — hardware, operating systems, third-party libraries, software versions, input data, compile-time options, and parameters — are subject to variability that exacerbates frictions but is also essential for achieving robust, generalizable results and fostering innovation. I will first review the literature, providing evidence of how the complex variability interactions across these layers affect qualitative and quantitative software properties, thereby complicating the reproduction and replication of scientific studies in various fields.
I will then present some software engineering and AI techniques that can support the strategic exploration of variability spaces. These include the use of abstractions and models (e.g., feature models), sampling strategies (e.g., uniform, random), cost-effective measurements (e.g., incremental build of software configurations), and dimensionality reduction methods (e.g., transfer learning, feature selection, software debloating).
I will finally argue that deep variability is both the problem and solution of frictionless reproducibility, calling the software science community to develop new methods and tools to manage variability and foster reproducibility in software systems.
Exposé invité Journées Nationales du GDR GPL 2024
BREEDING METHODS FOR DISEASE RESISTANCE.pptxRASHMI M G
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Deep Behavioral Phenotyping in Systems Neuroscience for Functional Atlasing a...Ana Luísa Pinho
Functional Magnetic Resonance Imaging (fMRI) provides means to characterize brain activations in response to behavior. However, cognitive neuroscience has been limited to group-level effects referring to the performance of specific tasks. To obtain the functional profile of elementary cognitive mechanisms, the combination of brain responses to many tasks is required. Yet, to date, both structural atlases and parcellation-based activations do not fully account for cognitive function and still present several limitations. Further, they do not adapt overall to individual characteristics. In this talk, I will give an account of deep-behavioral phenotyping strategies, namely data-driven methods in large task-fMRI datasets, to optimize functional brain-data collection and improve inference of effects-of-interest related to mental processes. Key to this approach is the employment of fast multi-functional paradigms rich on features that can be well parametrized and, consequently, facilitate the creation of psycho-physiological constructs to be modelled with imaging data. Particular emphasis will be given to music stimuli when studying high-order cognitive mechanisms, due to their ecological nature and quality to enable complex behavior compounded by discrete entities. I will also discuss how deep-behavioral phenotyping and individualized models applied to neuroimaging data can better account for the subject-specific organization of domain-general cognitive systems in the human brain. Finally, the accumulation of functional brain signatures brings the possibility to clarify relationships among tasks and create a univocal link between brain systems and mental functions through: (1) the development of ontologies proposing an organization of cognitive processes; and (2) brain-network taxonomies describing functional specialization. To this end, tools to improve commensurability in cognitive science are necessary, such as public repositories, ontology-based platforms and automated meta-analysis tools. I will thus discuss some brain-atlasing resources currently under development, and their applicability in cognitive as well as clinical neuroscience.
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Abnormal or anomalous secondary growth in plants. It defines secondary growth as an increase in plant girth due to vascular cambium or cork cambium. Anomalous secondary growth does not follow the normal pattern of a single vascular cambium producing xylem internally and phloem externally.
1. 4.5 CRITICAL FIELD AND CRITICAL TEMPERATURE
In 1913, Kamerlingh Onnes observed that a
superconductor regains its normal state below the critical
temperature if it is placed in a sufficiently strong magnetic
field. The value of the magnetic field at which the
superconductivity vanishes is called the threshold or the
critical field, Hc, and is of the order of a few hundred
oersteds for most of the pure superconductors. This field
changes with temperature. Thus we find that the
superconducting state is stable only in some definite
ranges of magnetic fields and higher temperature.
Fig. 4.3. Variation of penetration depth with temperatures
for Tin.
2. For higher temperature fields and temperatures, the
normal state is more stable. A typical plot of critical
magnetic field versus temperature for lead is shown in Fig.
4.4. Such a plot is also referred to as the magnetic phase
diagram. These types of curves are almost parabolic and
can be expressed by the relation
Hc = Hc(0)[1 −
T2
Tc
2]
where Hc(0) is the critical field at 0 K. Thus, at the critical
temperature, the critical field becomes zero,
i.e.𝐻𝑐( 𝑇𝑐) = 0
Fig. 4.4. Variation of I Hc with T for Pb.
4.6 TYPE I AND TYPE II SUPERCONDUCTORS
3. The London electromagnetic theory, theory proposed
by Gorter, Casimir and BCS showed that, more than 24
elements and many alloys and compounds possess the
superconducting properties, and now new
superconductors are being discovered continually, as new
structures and degree of purity of crystalline material
becomes available. No particular type of crystal lattice
seems to be necessary for superconductivity, since nearly
all types of metals containing tight but not very tight
packing of atoms, can possess the property of
superconductivity. The exception for this is, silver, gold
and copper metals which are good conductors at normal
temperature. The only difference in respect of this is that,
different metals will possess the property of
superconductivity at different critical temperatures. The
critical temperature is that temperature at which the
resistivity of the metal drops to zero. It is denoted by Tc.
It is also called as a "transition temperature", since at this
temperature the transition of the metal takes place from
normal to superconducting state Transition or critical
temperature is different for different metals. It depends
upon the lattice structure of the metal. viz. Tc = 7.22° K for
4. Lead, Tc =4.152°K for Mercury, Tc = 2.38°K for Thallium,
Tc= 14.7°K for Niobium nitrate and Tc = 8.0°K for Niobium.
The superconducting properties of the metals can be
changed by varying (i) temperature, (ii) magnetic field, (iii)
magnetic stress, (iv) impurity, (v) atomic structure, (vi)
size, (vii) frequency of excitation of applied electric field
and (viii) isotopic mass.
Superconductors have been classified as type I and
type II depending upon their behaviour in an external
magnetic field, i.e., how strictly they follow the Meissner
effect. We describe below these two types of
superconductors.
4.6.1. TYPE I OR SOFT SUPERCONDUCTORS
In the superconducting state, the complete and abrupt
loss of resistance must be a consequence of some
fundamental change in the electronic or atomic structure
of the metal. Because of this change some other physical
properties may also change. Depending upon the nature
of these changes, there are two types of superconductors.
Type I : The superconductors in which only loss of
5. resistance takes place at transition temperature while
other following physical properties remain unchanged.
(i)The x-ray diffraction pattern is the same both above and
below the transition temperature Tc which shows that no
change of crystal (metal) lattice is involved. The absence
of any appreciable change in the intensity distribution also
shows that the change in electronic structure must be very
slight.
(ii) There is no appreciable change in reflectivity of the
metal either in visible or in the infrared region, although
the optical properties are usually closely connected with
the electrical conductivity.
(iii) There is no change in the absorption of fast or slow
electrons. The photoelectric properties are also
unchanged.
(iv) In the absence of the magnetic field there is no latent
heat and no change of volume at the transition.
(v) The elastic properties and thermal expansion do not
change in the transition. This is probably due to
inadequate sensitivity of the experimental methods
6. Fig. 4.5. Magnetization curve of pure lead at 4.2 K.
The superconductors which strictly follow the
Meissner effect are called type I superconductors. The
typical magnetic behaviour of lead, a type I
superconductor, is shown in Fig. 4.5. These superconduc-
tors exhibit perfect diamagnetism below a critical field He
which, for most of the cases, is of the order of 0.1 testa.
As the applied magnetic field is increased beyond He, the
field penetrates the material com-pletely and the latter
abruptly reverts to its normal resistive state. These
materials give away their superconductivity at lower field
strengths and are referred to as the soft superconductors.
Pure specimens of various metals exhibit this type of
7. behaviour. These materials have very limited technical
applications owing to the very low values of Hc.
4.6.2. TYPE II OR HARD SUPERCONDUCTORS
Type II : The superconductors in which, along with the loss
of resistance, the following physical properties also
change at transition temperature.
(i)In superconducting metals, magnetic properties
remarkably change in comparison to electrical properties.
In the superconducting state, practically no magnetic flux
is able to penetrate the metal, which thus, behaves as if it
had zero permeability or a strong diamagnetic
susceptibility. Due to this property, the shape of the
specimen plays an important role and when
superconductivity is destroyed by a magnetic field, the
magnetic behaviour becomes complicated for any shape
except that of the long cylinder parallel to the field. In such
circumstances, the specimen breaks up into a mixture of
superconducting and normal regions known as the
"Intermediate State".
8. Fig. 4.6 : Temperature Variation of Sp. heat
(ii) The specific heat of a superconductor is
discontinuously higher just below the critical temperature
as shown in Fig. 4.9 viz. For tin the sp. heat is 1.9. x 10- 4
watt.sec / (g) (°k) just above the critical temperature and
is equal to 2.79 x 10-4 Watt-sec / (g) (°k) just below the
critical temperature. In the intermediate state, the sp.
heat may be several times higher than these values. If the
superconducting transition takes place in the presence of
magnetic field, transition in latent heat and small change
in volume takes place.
(iii) All thermo-electric effects disappear in the
superconducting state.
9. (iv) The thermal conductivity changes discontinuously
when superconductivity is destroyed in a magnetic field.
The thermal conductivity of superconductors undergoes a
continuous change between two phases in the absence of
magnetic field and is usually lower in the superconducting
phase for pure metal as shown in the Fig. 4.7 viz. The
thermal conductivity of
Fig. 4.7. Magnetization curve of a lead-exceeds Ha,
I : Superconducting state
II: Vortex or mixed or intermediate state
III: Normal state
10. These superconductors do not follow the Meissner
effect strictly, i.e., the magnetic field does not penetrate
these materials abruptly at the critical-field. The typical
magnetization curve for Pb-Bi alloy shown in Fig. 4.7
illustrates the magnetic behaviour of such a
superconductor. It follows from this curve that for fields
less than Ha, the material exhibits perfect diamagetism
and no flux penetration takes place. Thus for H <Hc1, the
material exists in the super-conducting state. As the field
-exceeds Hc1,the flux begins to bismuth alloy at 4.2 K.
penetrate the specimen and, for H = Hc2 the complete
penetration occurs and the material becomes a normal
conductor. The fields Hc1 and Hc2 are called the lower and
upper critical fields respectively. In the region between
the fields Hc1and Hc2, the diamagnetic behaviour of the
material vanishes gradually and the flux density B inside
the specimen remains non-zero, i.e., the Meissner effect
is not strictly followed. The specimen in this region is said
to be existing in the vortex or intermediate state which
has a complicated distribution of superconducting and
non-superconducting regions and may be regarded as a
mixture of superconducting and normal states. The type II
superconductors are also called the hard superconductors
11. because relatively large fields are needed to bring them
back to the normal state. Also, large magnetic hysteresis
can be induced in these materials by appropriate
mechanical treatment. Hence these materials can be used
to manufacture superconducting wires which can be used
to produce high magnetic fields of the order of 10 tesla.
Apart from some metals and alloys, the newly developed
copper oxide superconductors belong to this category and
have Ho of about 150 tesla.
Fig. 4.8. Entropy versus temperature for aluminium.
7. : Conclusions from the BCS theory
12. 1. The electron-lattice-electron interaction is attractive
and can overcome the Coulomb repulsion between
electrons.
2. An attractive interaction between electrons can also
lead to a ground state of the entire electronic system
which is separated from excited states by an energy gap.
The critical field, thermal properties and most of the
electromagnetic properties are the consequences of
energy gap.
3. It gives the isotope effect.
4. The London penetration depth and the Pippard
coherence length are natural consequences of the BCS
ground state.
5. Several specialized effects, such as quantization of
magnetic flux through superconducting ring, have given
impressive evidence for the BCS theory.
6. Thus, superconductivity is the special state of the solid-
metal or element, which occurs in low temperature
region. When metal acquires this state, its electrical
resistance becomes zero and hence it can conduct very
large amount of electric current without any loss of
13. electrical power. Because of this property, in the
beginning it was known as "perfect conductor".
Uses of Superconductors
There are wide applications of superconductors in the
field of engineering including radioelectronics. This new
branch of electronics based on superconductivity is
known as low temperature electronics, which is
commonly known as cryogenic electronics or simply
"Cryoelectronics". In this branch of electronics, by using
superconductors, "supersensitive miniature receivers"
capable of detecting extremely weak radio signals to which
common receivers are insensitive, are manufactured.
Large scale (LSI) and Very Large Scale (VLSI) integrated
circuits are designed for a new class of electronic
computers. The superconductors are also used to
increase the frequency stability and frequency
selectivity in microwave appliances. They are also used
for the extension of radiowave bands into microwave
region.
Further, the superconductors are used in the
construction of
following equipments.
1.Microwave and far infrared frequency oscillators.
14. 2.Superconducting magnetometers capable of measuring
magnetic fields whose induction B is smaller than 10-
"
Tesla.
3.Superconducting galvanometer of extremely low
resistance and hence very high voltage sensitivity, down
to 10-11 V.
4.High-responsivity photodetectors ( bolometers) with a
threshold
response of about 10 i
's
W per hertz of the transmission
band of the detecting system.
5.Cryotron switches - the basic elements of amplifiers and
modulators. Superconductivity
6.At low frequencies, cryotron based amplifiers can
detect signals lower than 10-1
'V at a time constant of 1
second, and input resistance below 10-5
Ohm.
7.Resonators with a quality factor of about 1011
in the
microwave band. Superconducting resonators can
improve the frequency stability of common klystrons by a
factor 105
or 106
.
8.Superconducting filters - These filters offer the
possibility of increasing the selectivity in the rejection
band by a factor of 103
to 106
in comparison with
common filters.
9.Superconductivity enables to decrease the diameter of
'h f' cables from 10 cm and over to a few millimeters.
15. 10.High-current high-magnetic field solenoids. Wire
solenoids made of certain alloy superconductors can
produce magnetic fields larger than 10 Webers/m2, with
no power dissipation.
11.Electromagnets - The strong diamagnetism of
superconductors offers the possibility of supporting
heavy loads by a magnetic field.
12.Frictionless bearings for rotating equipments.
13.Computer memory cells - These are utilised in the form
of a closed superconducting circuit in which a persistence
current can be induced for the purpose of writing and
storage of information in computers.
14.By using Meissner effect, it is possible to design the
railway track on which the train can run with high speed
without friction with the railway track.
There are wide applications of superconductors in the
field of engineering including radioelectronics.
i)The superconductors are used to increase the frequency
stability and frequency selectivity in microwave appliances.
ii)They are also used for the extension of radiowave bands
into microwave region.
iii)At low frequencies, cryotron based amplifiers can detect
signals lower than 10-1'V at a time constant of 1 second,
and input resistance below 10-5
Ohm.
(vi) Resonators with a quality factor of about 1011
in the
microwave band. Superconducting resonators can
16. improve the frequency stability of common klystrons by a
factor 105
or 106
.
(vii) Superconducting filters - These filters offer the
possibility of increasing the selectivity in the rejection
band by a factor of 103
to 106
in comparison with
common filters.
(viii) Superconductivity enables to decrease the diameter of 'h
f' cables from 10 cm and over to a few millimeters.
(ix) High-current high-magnetic field solenoids. Wire
solenoids made of certain alloy superconductors can
produce magnetic fields larger than 10 Webers/m2
, with
no power dissipation.
(x) Electromagnets - The strong diamagnetism of
superconductors offers the possibility of supporting
heavy loads by a magnetic field.
(xi) Frictionless bearings for rotating equipments.
(xii) Computer memory cells - These are utilised in the form of
a closed superconducting circuit in which a persistence
current can be induced for the purpose of writing and
storage of information in computers.
By using Meissner effect, it is possible to design