The document outlines an overarching strategy for maintaining wind turbine blades proposed by Maya Nissim of EDP Renewables. It discusses developing a blade maintenance program that is cost-effective and leads to long-term savings. The strategy would involve annual visual inspections of blades to document any damage according to a uniform severity scale and prioritize repairs. It also recommends proactive lightning inspections. EDP Renewables' goals are to perform proactive and reactive maintenance as needed to improve blade life and reliability while avoiding catastrophic failures. Historical blade failure data and examples of common damage types are presented.
There is plenty of room for improvement in operations and maintenance activities. James Parle will tell how a team from Muir Data systems developed a system that lets wind tech report more thoroughly on their activities with easy-to-use portable devices.
And Grant Leaverton will report on how unmanned aerial vehicles can provides high resolution images of wind turbine inspections, especially blades, without rappelling from the nacelle.
Maximizing efficiency of wind turbines is a vital consideration for operators, and managing erosion is a vital method to achieve this. Studies have consistently shown that erosion can lead to a loss in annual energy production (AEP) of up to 20% on severe cases. This figure is hard to ignore, and highlights the ROI benefits that can be achieved from paying close attention to erosion. The heart of the issue is the fact that wind blades come into contact with various elements in the air at rotation speeds up to 250 mph, leading to erosion in the form of pitting, gouging and delamination of the edge of the blade. This erosion not only compromises the integrity of the blade, but also impacts its aerodynamic efficiency, causing a significant loss in AEP. This loss can be compounded by the downtime necessary to make repairs to turbines, so owners have important motivations for protecting blades against erosion and making repairs quickly. In severe cases of erosion can even lead up to blade replacement which can get very expensive.
3M™ Wind Energy has extensive experience managing erosion, understanding the causes and effects of leading edge erosion, and bringing education to the industry on this problem. We have had decades of experience in understanding erosions and how to effectively prevent this.
This presentation gives an overview of Lloyd’s Register’s services regarding wind farm operations. In particular Lloyd's Register has worked hard to develop the service for risk-based optimisation of maintenance strategies.
If you operate, own, finance or insure one or more wind farms, Lloyd's Register can add value to your O&M planning by monitoring, learning, retaining and optimising the O&M tasks to minimise downtime, spares count, unscheduled maintenance, unnecessary site visits and to ensure, through informed planning, maintenance technicians arrive at site with correct parts, correct tools, correct training and expertise to keep the wind turbines running throughout their design life for the least possible cost.
There is plenty of room for improvement in operations and maintenance activities. James Parle will tell how a team from Muir Data systems developed a system that lets wind tech report more thoroughly on their activities with easy-to-use portable devices.
And Grant Leaverton will report on how unmanned aerial vehicles can provides high resolution images of wind turbine inspections, especially blades, without rappelling from the nacelle.
Maximizing efficiency of wind turbines is a vital consideration for operators, and managing erosion is a vital method to achieve this. Studies have consistently shown that erosion can lead to a loss in annual energy production (AEP) of up to 20% on severe cases. This figure is hard to ignore, and highlights the ROI benefits that can be achieved from paying close attention to erosion. The heart of the issue is the fact that wind blades come into contact with various elements in the air at rotation speeds up to 250 mph, leading to erosion in the form of pitting, gouging and delamination of the edge of the blade. This erosion not only compromises the integrity of the blade, but also impacts its aerodynamic efficiency, causing a significant loss in AEP. This loss can be compounded by the downtime necessary to make repairs to turbines, so owners have important motivations for protecting blades against erosion and making repairs quickly. In severe cases of erosion can even lead up to blade replacement which can get very expensive.
3M™ Wind Energy has extensive experience managing erosion, understanding the causes and effects of leading edge erosion, and bringing education to the industry on this problem. We have had decades of experience in understanding erosions and how to effectively prevent this.
This presentation gives an overview of Lloyd’s Register’s services regarding wind farm operations. In particular Lloyd's Register has worked hard to develop the service for risk-based optimisation of maintenance strategies.
If you operate, own, finance or insure one or more wind farms, Lloyd's Register can add value to your O&M planning by monitoring, learning, retaining and optimising the O&M tasks to minimise downtime, spares count, unscheduled maintenance, unnecessary site visits and to ensure, through informed planning, maintenance technicians arrive at site with correct parts, correct tools, correct training and expertise to keep the wind turbines running throughout their design life for the least possible cost.
Improving Rotating Equipment Reliability and Machinery HealthMexxusts
Course Overview:
According to industry reports more than 60% of maintenance costs are spent on equipment wear, tear and failure. This year the Witbank Institute of Technology will be providing training on Improving Rotating Equipment Reliability and Machinery Health to make sure all rotating Equipment functions at its best. Predictably, continuous improvement of reliability by optimizing predictive maintenance for rotating equipment is one of the most important challenges maintenance professionals face today. This three day session course explains The Causes of Rotating Machinery Failures, Precision Maintenance for Rotating Equipment and Machines, Condition Monitoring and Predictive Maintenance, Design of Rotating Equipment and Machines and Root Cause Failure Analysis Procedure.
The aims of the O&M of Gas Turbines Workshop is to share the experiences of our internationally renowned expert with an aim to prevent such incidents and also to examine the factors and opportunities to increase plant safety, environmental performance. And improve uptime and availability all factors contributing to higher profitability.
The workshop will also examine scheduled maintenance and turnarounds which are opportunities to increase plant safety and environmental performance. By enhancing the mechanical integrity of HPI facilities, operating companies can achieve and maintain higher uptime and equipment availability; all are factors that contribute to higher profitability. Best-of-class companies hold the mindset that reliability programs provide great benefits. Investing in new monitoring and conditioning systems, along with preventive maintenance and inspection programs, can optimize unit and total facility performance.
The development of dry low NOx (DLN) combustors for gas turbines has cut the industry's consumption of water, while dramatically slashing air emissions. Unfortunately, this environmental enhancement has created an engineering challenge: The lean-burning DLN combustors are prone to flame instability, which can cause pressure pulsations large enough to destroy the combustor, launching debris downstream where it annihilates other hot-gas-path components. To detect and correct flame instability before it causes millions of dollars of turbine damage, savvy users have begun to install advanced sensors and robust software that monitor the combustor dynamics in real time.
High dynamics can limit hardware life and/or system operability. Thus, there have been various attempts to control combustion dynamics, to prevent degradation of system performance. There are two basic methods for controlling combustion dynamics in an industrial gas turbine combustion system: passive control and active control. As the name suggests, passive control refers to a system that incorporates certain design features and characteristics to reduce dynamic pressure oscillations. Active control, on the other hand, incorporates a sensor to detect, e.g., pressure fluctuations and to provide a feedback signal.
Which, When suitably processed by a controller, provides an input signal to a control device. The control device in turn operates to reduce the dynamic pressure oscillations. The workshop will examine the factors and the issues associated with combustor dynamics, and technologies like AMFM/CFM.
Benefits ofAttending
• LEARN best and effective practices in operations and maintenance of Gas Turbine Based Power Plants
• LEARN how to write and use SOPs
• IMPROVE your plants’ energy efficiency and availability
• ACHIEVE productive and safe operation
• NETWORK with other power plant professionals
• RECEIVE practical information for your CAPEX and OPEX expenditure budget planning
• LEARN about strategic procurement of High Value Spares and insurance
Optimizing Gas Turbines and Life ManagementWalter Lee
A practical and comprehensive course on condition & life
assessments for gas turbines with the aim of improving gas
turbine operational & maintenance practices, minimizing
the likelihood of failures, prolonging asset life & reducing
maintenance costs.
Best Practices for Maintenance
Properly selected and installed motors can operate for many years with minimal maintenance. Nonetheless, regular care will extend their life and maximize their energy efficiency.
Planned Maintenance is a proactive approach to maintenance that focuses on minimizing the downtime and costs associated with machine breakdowns. As one of the key pillars of the TPM Excellence framework, the goal of Planned Maintenance is to have trouble-free equipment that produce defect-free products.
Planned Maintenance achieves and sustains availability of machines at an optimum maintenance cost, reduces spares inventory, and improves reliability and maintainability of machines.
In this presentation developed by our JIPM-certified TPM Instructor, you will learn how to plan and organize the Plan Maintenance activities to strengthen the capabilities of your Maintenance department. It clarifies the roles of the Operations and Maintenance departments in supporting the TPM initiative and provides step-by-step guidance on the implementation of the Planned Maintenance pillar.
LEARNING OBJECTIVES
1. Understand what is Planned Maintenance and why it is important in TPM implementation
2. Acquire knowledge on how to plan and organize Planned Maintenance activities
3. Describe the seven implementation steps of Planned Maintenance
4. Gain knowledge on the JIPM TPM Excellence Criteria for Planned Maintenance
CONTENTS
1. Introduction to Planned Maintenance
2. What is Planned Maintenance?
3. Planning & Organizing for Planned Maintenance
4. The 7 Steps of Planned Maintenance
5. JIPM TPM Excellence Criteria for Planned Maintenance
To download this complete presentation, goto:
https://www.oeconsulting.com.sg/training-presentations
This webinar describes some of the challenges faced when monitoring a large fleet of wind turbines. Factors such as different turbine and gearbox types, different condition monitoring systems (CMS), geographically dispersed sites and variations in maintenance practice all make the job of a monitoring engineer a difficult task. Romax utilize in-house software called InSight Fleet Monitor to provide condition monitoring services for over 2 GW of assets globally. Using a single software platform enables the CMS engineers to effectively monitor a huge number of wind turbines efficiently.
This webinar uses some recent examples and case studies to demonstrate fleet-wide condition monitoring in practice. Examples focus on main bearing and gearbox fault detection and, most importantly for the operator, methods for predicting the remaining useful life or ‘time to repair’ for key components.
View this webinar to learn:
-How condition monitoring can be effectively rolled out for large, disparate fleets of wind turbines.
-Valuable insights from recent examples in the field, particularly relating to gearbox and main bearing faults.
-Predicting ‘time to repair’ for major components.
A Brief Presentation On Bearing Fault Detection Techniques .pdfHemanth Kumar Jawahar
Bearings are parts that assist the rotation of objects. They support the rotation of shafts in the machines. The machines include generators, aircrafts, automobiles and many others.Approximately,10 Billion bearings are manufactured annually worldwide. Nearly 50 million bearings fail annually worldwide. Here are some of the bearing failure causes⬇
1️⃣ One-third of bearing failures are due to fatigue
2️⃣ One-third of bearing failures are due to lubrication problems (incorrect lubricant choice, quantity, or interval).
3️⃣ A small percentage of bearing failures are due to contamination (ineffective seals).
4️⃣ A roughly equal small percentage of bearing failures occur for other reasons (improper handling and mounting, excessive loads, wrong fits, etc.).
Therefore, it's important for any industry/plant to use a suitable bearing fault detection technique to analyze the causes of bearing failures.
Generating a custom Ruby SDK for your web service or Rails API using Smithyg2nightmarescribd
Have you ever wanted a Ruby client API to communicate with your web service? Smithy is a protocol-agnostic language for defining services and SDKs. Smithy Ruby is an implementation of Smithy that generates a Ruby SDK using a Smithy model. In this talk, we will explore Smithy and Smithy Ruby to learn how to generate custom feature-rich SDKs that can communicate with any web service, such as a Rails JSON API.
Slack (or Teams) Automation for Bonterra Impact Management (fka Social Soluti...Jeffrey Haguewood
Sidekick Solutions uses Bonterra Impact Management (fka Social Solutions Apricot) and automation solutions to integrate data for business workflows.
We believe integration and automation are essential to user experience and the promise of efficient work through technology. Automation is the critical ingredient to realizing that full vision. We develop integration products and services for Bonterra Case Management software to support the deployment of automations for a variety of use cases.
This video focuses on the notifications, alerts, and approval requests using Slack for Bonterra Impact Management. The solutions covered in this webinar can also be deployed for Microsoft Teams.
Interested in deploying notification automations for Bonterra Impact Management? Contact us at sales@sidekicksolutionsllc.com to discuss next steps.
Essentials of Automations: Optimizing FME Workflows with ParametersSafe Software
Are you looking to streamline your workflows and boost your projects’ efficiency? Do you find yourself searching for ways to add flexibility and control over your FME workflows? If so, you’re in the right place.
Join us for an insightful dive into the world of FME parameters, a critical element in optimizing workflow efficiency. This webinar marks the beginning of our three-part “Essentials of Automation” series. This first webinar is designed to equip you with the knowledge and skills to utilize parameters effectively: enhancing the flexibility, maintainability, and user control of your FME projects.
Here’s what you’ll gain:
- Essentials of FME Parameters: Understand the pivotal role of parameters, including Reader/Writer, Transformer, User, and FME Flow categories. Discover how they are the key to unlocking automation and optimization within your workflows.
- Practical Applications in FME Form: Delve into key user parameter types including choice, connections, and file URLs. Allow users to control how a workflow runs, making your workflows more reusable. Learn to import values and deliver the best user experience for your workflows while enhancing accuracy.
- Optimization Strategies in FME Flow: Explore the creation and strategic deployment of parameters in FME Flow, including the use of deployment and geometry parameters, to maximize workflow efficiency.
- Pro Tips for Success: Gain insights on parameterizing connections and leveraging new features like Conditional Visibility for clarity and simplicity.
We’ll wrap up with a glimpse into future webinars, followed by a Q&A session to address your specific questions surrounding this topic.
Don’t miss this opportunity to elevate your FME expertise and drive your projects to new heights of efficiency.
GraphRAG is All You need? LLM & Knowledge GraphGuy Korland
Guy Korland, CEO and Co-founder of FalkorDB, will review two articles on the integration of language models with knowledge graphs.
1. Unifying Large Language Models and Knowledge Graphs: A Roadmap.
https://arxiv.org/abs/2306.08302
2. Microsoft Research's GraphRAG paper and a review paper on various uses of knowledge graphs:
https://www.microsoft.com/en-us/research/blog/graphrag-unlocking-llm-discovery-on-narrative-private-data/
Securing your Kubernetes cluster_ a step-by-step guide to success !KatiaHIMEUR1
Today, after several years of existence, an extremely active community and an ultra-dynamic ecosystem, Kubernetes has established itself as the de facto standard in container orchestration. Thanks to a wide range of managed services, it has never been so easy to set up a ready-to-use Kubernetes cluster.
However, this ease of use means that the subject of security in Kubernetes is often left for later, or even neglected. This exposes companies to significant risks.
In this talk, I'll show you step-by-step how to secure your Kubernetes cluster for greater peace of mind and reliability.
Accelerate your Kubernetes clusters with Varnish CachingThijs Feryn
A presentation about the usage and availability of Varnish on Kubernetes. This talk explores the capabilities of Varnish caching and shows how to use the Varnish Helm chart to deploy it to Kubernetes.
This presentation was delivered at K8SUG Singapore. See https://feryn.eu/presentations/accelerate-your-kubernetes-clusters-with-varnish-caching-k8sug-singapore-28-2024 for more details.
State of ICS and IoT Cyber Threat Landscape Report 2024 previewPrayukth K V
The IoT and OT threat landscape report has been prepared by the Threat Research Team at Sectrio using data from Sectrio, cyber threat intelligence farming facilities spread across over 85 cities around the world. In addition, Sectrio also runs AI-based advanced threat and payload engagement facilities that serve as sinks to attract and engage sophisticated threat actors, and newer malware including new variants and latent threats that are at an earlier stage of development.
The latest edition of the OT/ICS and IoT security Threat Landscape Report 2024 also covers:
State of global ICS asset and network exposure
Sectoral targets and attacks as well as the cost of ransom
Global APT activity, AI usage, actor and tactic profiles, and implications
Rise in volumes of AI-powered cyberattacks
Major cyber events in 2024
Malware and malicious payload trends
Cyberattack types and targets
Vulnerability exploit attempts on CVEs
Attacks on counties – USA
Expansion of bot farms – how, where, and why
In-depth analysis of the cyber threat landscape across North America, South America, Europe, APAC, and the Middle East
Why are attacks on smart factories rising?
Cyber risk predictions
Axis of attacks – Europe
Systemic attacks in the Middle East
Download the full report from here:
https://sectrio.com/resources/ot-threat-landscape-reports/sectrio-releases-ot-ics-and-iot-security-threat-landscape-report-2024/
Neuro-symbolic is not enough, we need neuro-*semantic*Frank van Harmelen
Neuro-symbolic (NeSy) AI is on the rise. However, simply machine learning on just any symbolic structure is not sufficient to really harvest the gains of NeSy. These will only be gained when the symbolic structures have an actual semantics. I give an operational definition of semantics as “predictable inference”.
All of this illustrated with link prediction over knowledge graphs, but the argument is general.
JMeter webinar - integration with InfluxDB and GrafanaRTTS
Watch this recorded webinar about real-time monitoring of application performance. See how to integrate Apache JMeter, the open-source leader in performance testing, with InfluxDB, the open-source time-series database, and Grafana, the open-source analytics and visualization application.
In this webinar, we will review the benefits of leveraging InfluxDB and Grafana when executing load tests and demonstrate how these tools are used to visualize performance metrics.
Length: 30 minutes
Session Overview
-------------------------------------------
During this webinar, we will cover the following topics while demonstrating the integrations of JMeter, InfluxDB and Grafana:
- What out-of-the-box solutions are available for real-time monitoring JMeter tests?
- What are the benefits of integrating InfluxDB and Grafana into the load testing stack?
- Which features are provided by Grafana?
- Demonstration of InfluxDB and Grafana using a practice web application
To view the webinar recording, go to:
https://www.rttsweb.com/jmeter-integration-webinar
Transcript: Selling digital books in 2024: Insights from industry leaders - T...BookNet Canada
The publishing industry has been selling digital audiobooks and ebooks for over a decade and has found its groove. What’s changed? What has stayed the same? Where do we go from here? Join a group of leading sales peers from across the industry for a conversation about the lessons learned since the popularization of digital books, best practices, digital book supply chain management, and more.
Link to video recording: https://bnctechforum.ca/sessions/selling-digital-books-in-2024-insights-from-industry-leaders/
Presented by BookNet Canada on May 28, 2024, with support from the Department of Canadian Heritage.
Builder.ai Founder Sachin Dev Duggal's Strategic Approach to Create an Innova...Ramesh Iyer
In today's fast-changing business world, Companies that adapt and embrace new ideas often need help to keep up with the competition. However, fostering a culture of innovation takes much work. It takes vision, leadership and willingness to take risks in the right proportion. Sachin Dev Duggal, co-founder of Builder.ai, has perfected the art of this balance, creating a company culture where creativity and growth are nurtured at each stage.
1. Blade Maintenance for Reliability, an
Owner/Operator Perspective
An overarching strategy for maintaining blades including suggested timelines,
methods, procedures, and tools to inspect, document, maintain, and repair blades.
Maya Nissim
Turbine Performance Engineer, EDP Renewables
August 13, 2013
2. Blade Maintenance for Reliability, an Owner/Operator Perspective
2
• EDP Renewables North America LLC develops, constructs, owns, and operates wind farms
throughout North America
• 3rd largest renewable operator in the US and ranked 4th in net installed capacity
• Currently operating over 3,800 MW at 29 wind farms in 11 states with more than 2,100 turbines in
operation and approximately 66 million hours of operational history
• Headquartered in Houston, Texas
• Performance Engineering group part of Asset Operations & responsible for:
• Continuous improvement of turbine & main component performance & reliability
• Fault reduction
• Predictive maintenance
• Root cause analysis
• Failure trending and projections
• Component repair specifications
About EDP Renewables North America 1
3. Blade Maintenance for Reliability, an Owner/Operator Perspective
3
Blade Maintenance 2
4. Blade Maintenance for Reliability, an Owner/Operator Perspective
4
Problem Statement:
WTG blades are a vital main component whose role is to extract energy from the wind in order to
ultimately generate electricity. It is a valid assumption that blade damage has major impact on
our fleet performance and ability to achieve its production potential in forms of turbine efficiency,
downtime and cost of the major component repairs and replacements.
Objective:
Develop an overarching Asset Operations strategy for maintaining blades in EDPR’s fleet, including
suggested timelines, methods, procedures and tools to inspect, document, maintain, and repair
blades
Criteria:
The recommended strategy must be cost-effective and lead to long-term savings.
Motivation
Blade Maintenance Program Development 2
5. Blade Maintenance for Reliability, an Owner/Operator Perspective
5
Why?
When?
How?
Need to answer 3 basic Questions
Blade Maintenance Program Considerations 2
6. Blade Maintenance for Reliability, an Owner/Operator Perspective
6
Why?
Explore the assumption that preventative & proactive maintenance of blades will benefit the
company
•Economics of blade maintenance
•Historic blade failure rates & cost analysis
•Summary of known blade damage to-date
Considerations, Why? 2
When?
•Inspection/maintenance timeframe & frequency
How?
•Possible Resources
•Up-tower vs. down-tower; visual vs. physical
•SOP & Change Management Process
•Measure Success
7. Blade Maintenance for Reliability, an Owner/Operator Perspective
7
Why?
Explore the assumption that preventative & proactive maintenance of blades will benefit the company
•Economics of blade maintenance
•Historic blade failure rates & cost analysis
•Summary of known blade damage to-date
Considerations, When? 2
When?
•Inspection/maintenance timeframe & frequency
How?
•Possible Resources
•Up-tower vs. down-tower; visual vs. physical
•SOP & Change Management Process
•Measure Success
8. Blade Maintenance for Reliability, an Owner/Operator Perspective
8
Why?
Explore the assumption that preventative & proactive maintenance of blades will benefit the company
•Economics of blade maintenance
•Historic blade failure rates & cost analysis
•Summary of known blade damage to-date
Considerations, How? 2
When?
•Inspection/maintenance timeframe & frequency
How?
•Possible Resources
•Up-tower vs. down-tower; visual vs. physical
•SOP & Change Management Process
•Measure Success
9. Blade Maintenance for Reliability, an Owner/Operator Perspective
9
Blade Data Inputs 3
Blade Maintenance
Program
Independent
Observations
EOW Inspections Lightning Events
Database
Determine
blades to
inspect
Determine
blades to
inspect
Vaisala
lightning
data
Generate
inspection
report and
email request
Site inspects
all blades on
specified
turbine
3rd party
inspects
specified blades
3rd party
inspects
specified blades
3rd party
creates
inspection
report
3rd party
creates
inspection
report Site inspection
report
generated
Sites inspect
blades of
specified
turbine
Site
inspection
report
generated
10. Blade Maintenance for Reliability, an Owner/Operator Perspective
10
Goal is to maintain uniform & consistent categorization
Blade Damage Severity Rating 3
Cat 5
Cat 4
Cat 3Cat 2
11. Blade Maintenance for Reliability, an Owner/Operator Perspective
11
Overview of blade failure downtime data & typical blade damage types*
Historical Blade Data 3
Blade Failure Mode Frequency
Trailing Edge
Blade Shell (general)
Spar
Blade Root
Leading Edge
*Data taken from EDPR’s offline turbine database so only captures turbines that were taken offline for the
respective blade issues and thus does not necessarily capture all issues present on running turbines.
12. Blade Maintenance for Reliability, an Owner/Operator Perspective
12
Trailing Edge
Split tip, lightning damage, impact,
damage during transport, de-bonding
Trailing Edge Examples
Historical Blade Damage 3
1135%
13. Blade Maintenance for Reliability, an Owner/Operator Perspective
13
Blade Shell (general)
Delamination (impact), de-bonding, EWV,
lightning to shell
Blade Shell (general) Examples
Historical Blade Damage 3
1327%
14. Blade Maintenance for Reliability, an Owner/Operator Perspective
14
Other/Unknown
Most due to ice/storm conditions on
blades, rest due to large corrective actions
Other/Unknown Examples
Historical Blade Damage 3
3215%
15. Blade Maintenance for Reliability, an Owner/Operator Perspective
15
Spar
Carbon fiber damage due to lightning &/or
manufacturing defect
Spar Examples
Historical Blade Damage 3
249%
16. Blade Maintenance for Reliability, an Owner/Operator Perspective
16
LPS
Blown receptors, burnt cable, missing or
crooked receptors
LPS Examples
Historical Blade Damage 3
66%
18. Blade Maintenance for Reliability, an Owner/Operator Perspective
18
Leading Edge
LE bond line cracks, LE erosion
Leading Edge Examples
Historical Blade Damage 3
192%
19. Blade Maintenance for Reliability, an Owner/Operator Perspective
19
Concluding Remarks 4
EDPR’s goals for the long term performance and care of our rotor blades:
• Proactive annual visual inspection of a percentage of blades
• Uniform & consistent damage categorization scale
• Documentation of all findings
• Prioritize repair of blades found to have damage and conduct at optimal time to avoid
catastrophic failure
• Proactive lightning inspections
• Prescription of “next steps” (i.e. re-inspection interval, repair)
• Continuously seek to improve the life of our blades by performing maintenance as needed
as well as proactively seek new methods for protecting them from excessive wear