Here is a book that takes the sting out of learning object-oriented design patterns! Using vignettes from the fictional world of Harry Potter, author Avinash C. Kak provides a refreshing alternative to the typically abstract and dry object-oriented design literature. Designing with Objects is unique. It explains design patterns using the short-story medium instead of sterile examples. It is the third volume in a trilogy by Avinash C. Kak, following Programming with Objects (Wiley, 2003) and Scripting with Objects (Wiley, 2008). Designing with Objects confronts how difficult it is for students to learn complex patterns based on conventional scenarios that they may not be able to relate to. In contrast, it shows that stories from the fictional world of Harry Potter provide highly relatable and engaging models. After explaining core notions in a pattern and its typical use in real-world applications, each chapter shows how a pattern can be mapped to a Harry Potter story. The next step is an explanation of the pattern through its Java implementation. The following patterns appear in three sections: Abstract Factory, Builder, Factory Method, Prototype, and Singleton; Adapter, Bridge, Composite, Decorator, Facade, Flyweight, and Proxy; and the Chain of Responsibility, Command, Interpreter, Iterator, Mediator, Memento, Observer, State, Strategy, Template Method, and Visitor. For readers use, Java code for each pattern is included in the book s companion website. * All code examples in the book are available for download on a companion website with resources for readers and instructors. * A refreshing alternative to the abstract and dry explanations of the object-oriented design patterns in much of the existing literature on the subject. * In 24 chapters, Designing with Objects explains well-known design patterns by relating them to stories from the fictional Harry Potter series

Computer Architectures is a collection of multidisciplinary historical works unearthing sites, concepts, and concerns that catalyzed the cross-contamination of computers and architecture in the mid-20th century. Weaving together intellectual, social, cultural, and material histories, this book paints the landscape that brought computing into the imagination, production, and management of the built environment, whilst foregrounding the impact of architecture in shaping technological development. The book is organized into sections corresponding to the classic von Neumann diagram for computer architecture: program (control unit), storage (memory), input/output and computation (arithmetic/logic unit), each acting as a quasi-material category for parsing debates among architects, engineers, mathematicians, and technologists. Collectively, authors bring forth the striking homologies between a computer program and an architectural program, a wall and an interface, computer memory and storage architectures, structures of mathematics and structures of things. The collection initiates new histories of knowledge and technology production that turn an eye toward disciplinary fusions and their institutional and intellectual drives. Constructing the common ground between design and computing, this collection addresses audiences working at the nexus of design, technology, and society, including historians and practitioners of design and architecture, science and technology scholars, and media studies scholars.

This textbook offers theoretical and practical knowledge of the finite element method. The book equips readers with the skills required to analyze engineering problems using ANSYS (R), a commercially available FEA program. Revised and updated, this new edition presents the most current ANSYS (R) commands and ANSYS (R) screen shots, as well as modeling steps for each example problem. This self-contained, introductory text minimizes the need for additional reference material by covering both the fundamental topics in finite element methods and advanced topics concerning modeling and analysis. It focuses on the use of ANSYS (R) through both the Graphics User Interface (GUI) and the ANSYS (R) Parametric Design Language (APDL). Extensive examples from a range of engineering disciplines are presented in a straightforward, step-by-step fashion. Key topics include: * An introduction to FEM * Fundamentals and analysis capabilities of ANSYS (R) * Fundamentals of discretization and approximation functions * Modeling techniques and mesh generation in ANSYS (R) * Weighted residuals and minimum potential energy * Development of macro files * Linear structural analysis * Heat transfer and moisture diffusion * Nonlinear structural problems * Advanced subjects such as submodeling, substructuring, interaction with external files, and modification of ANSYS (R)-GUI Electronic supplementary material for using ANSYS (R) can be found at http://link.springer.com/book/10.1007/978-1-4899-7550-8. This convenient online feature, which includes color figures, screen shots and input files for sample problems, allows for regeneration on the reader's own computer. Students, researchers, and practitioners alike will find this an essential guide to predicting and simulating the physical behavior of complex engineering systems."

This book constitutes the refereed post-proceedings of the 11th IFIP WG 5.1 International Conference on Product Lifecycle Management, PLM 2014, held in Yokohama, Japan, in July 2014. The 51 full papers presented were carefully reviewed and selected from 77 submissions. They are organized in the following topical sections: BIM operations, maintenance, and renovation; BIM concepts and lifecycle management; design and education; naval engineering and shipbuilding; aeronautical and automotive engineering; industry and consumer products; interoperability, integration, configuration, systems engineering; change management and maturity; knowledge engineering; knowledge management; service and manufacturing; and new PLM.

How can we optimize a bedridden patient's mattress? How can we make a passenger seat on a long distance flight or ride more comfortable? What qualities should a runner's shoes have? To objectively address such questions using engineering and scientific methods, adequate virtual human body models for use in computer simulation of loading scenarios are required. The authors have developed a novel method incorporating subject studies, magnetic resonance imaging, 3D-CAD-reconstruction, continuum mechanics, material theory and the finite element method. The focus is laid upon the mechanical in vivo-characterization of human soft tissue, which is indispensable for simulating its mechanical interaction with, for example, medical bedding or automotive and airplane seating systems. Using the examples of arbitrary body support systems, the presented approach provides visual insight into simulated internal mechanical body tissue stress and strain, with the goal of biomechanical optimization of body support systems. This book is intended for engineers, manufacturers and physicians and also provides students with guidance in solving problems related to support system optimization.

Based on the competition of international production networks, the pressure to - crease the efficiency of production systems has increased significantly. In ad- tion, the number of technical components in many products and as a consequence also the requirements for corresponding assembly processes and logistics pr- esses increases. International logistics networks require corresponding logistics concepts. These requirements can be managed only by using appropriate Digital Factory tools in the context of a product lifecycle management environment, which allows reusing data, supports an effective cooperation between different departments, and provides up-to-date and relevant data to every user who needs it. Simulating the complete material flow including all relevant production, st- age, and transport activities is recognized as a key component of the Digital F- tory in the industry and as of today widely used and accepted. Cutting inventory and throughput time by 20-60% and enhancing the productivity of existing p- duction facilities by 15-20% can be achieved in real-life projects.

For modeling the transport of carriers in nanoscale devices, a Green-function formalism is the most accurate approach. Due to the complexity of the formalism, one should have a deep understanding of the underlying principles and use smart approximations and numerical methods for solving the kinetic equations at a reasonable computational time. In this book the required concepts from quantum and statistical mechanics and numerical methods for calculating Green functions are presented. The Green function is studied in detail for systems both under equilibrium and under nonequilibrium conditions. Because the formalism enables rigorous modeling of different scattering mechanisms in terms of self-energies, but an exact evaluation of self-energies for realistic systems is not possible, their approximation and inclusion in the quantum kinetic equations of the Green functions are elaborated. All the elements of the kinetic equations, which are the device Hamiltonian, contact self-energies and scattering self-energies, are examined and efficient methods for their evaluation are explained. Finally, the application of these methods to study novel electronic devices such as nanotubes, graphene, Si-nanowires and low-dimensional thermoelectric devices and photodetectors are discussed.

Manufacturing industry has been one of the key drivers for recent rapid global economic development. Globalisation of manufacturing industries due to distributed design and labour advantage leads to a drive and thirst for technological advancements and expertise in the fields of advanced design and manufacturing. This development results in many economical benefits to and improvement of quality of life for many people all over the world. This rapid development also creates many opportunities and challenges for both industrialists and academics, as the design requirements and constraints have completely changed in this global design and manufacture environment. Consequently the way to design, manufacture and realise products have changed as well. More and more design and manufacture tasks can now be undertaken within computer environment using simulation and virtual reality technologies. These technological advancements hence support more advanced product development and manufacturing operations in such a global design and manufacturing environment. In this global context and scenario, both industry and the academia have an urgent need to equip themselves with the latest knowledge, technology and methods developed for engineering design and manufacture.

Designed to provide tools for independent study, this book contains student-tested mathematical exercises joined with MATLAB programming exercises. Most chapters open with a review followed by theoretical and programming exercises, with detailed solutions provided for all problems including programs. Many of the MATLAB exercises are presented as Russian dolls: each question improves and completes the previous program and results are provided to validate the intermediate programs. The book offers useful MATLAB commands, advice on tables, vectors, matrices and basic commands for plotting. It contains material on eigenvalues and eigenvectors and important norms of vectors and matrices including perturbation theory; iterative methods for solving nonlinear and linear equations; polynomial and piecewise polynomial interpolation; Bezier curves; approximations of functions and integrals and more. The last two chapters considers ordinary differential equations including two point boundary value problems, and deal with finite difference methods for some partial differential equations. The format is designed to assist students working alone, with concise Review paragraphs, Math Hint footnotes on the mathematical aspects of a problem and MATLAB Hint footnotes with tips on programming.

Optimization in Science and Engineering is dedicated in honor of the 60th birthday of Distinguished Professor Panos M. Pardalos. Pardalos's past and ongoing work has made a significant impact on several theoretical and applied areas in modern optimization. As tribute to the diversity of Dr. Pardalos's work in Optimization, this book comprises a collection of contributions from experts in various fields of this rich and diverse area of science. Topics highlight recent developments and include: Deterministic global optimization Variational inequalities and equilibrium problems Approximation and complexity in numerical optimization Non-smooth optimization Statistical models and data mining Applications of optimization in medicine, energy systems, and complex network analysis This volume will be of great interest to graduate students, researchers, and practitioners, in the fields of optimization and engineering.

Timely, authoritative, application-oriented… an in-depth exploration of current and future uses of FPGAs in digital systems The development of field-programmable gate arrays (FPGAs) may well be the most important breakthrough for the microelectronics industry since the invention of the microprocessor. Using FPGAs, a system designer working on a PC can now develop a working prototype in a few hours and change it at will in just a few minutes, rather than waiting weeks or months for a printed-circuit assembly or a custom integrated circuit to be built. This newfound ability to change a system by simply altering its configuration memory is also leading to exciting new forms of computing, such as array applications that exploit parallelism. Now in a book that functions equally well as a working professional reference and a pedagogically consistent computer engineering text, John V. Oldfield and Richard C. Dorf:

• Provide a detailed overview of FPGAs in digital systems design
• Explain the underlying principles, strengths, and limitations of most FPGA architectures
• Supply many real-life case studies, from elementary to advanced applications—including examples of "custom computing machines"
• Review cutting-edge developments, including new architectures and a new field-programmable interconnect chip
• Discuss key economic and business aspects of FPGA manufacture and applications and their role in intellectual property protection
• Demonstrate ways in which FPGAs offer plausible solutions to some of the major computing problems of our day

The Virtual and the Real in Planning and Urban Design: Perspectives, Practices and Applicationsexplores the merging relationship between physical and virtual spaces in planning and urban design. Technological advances such as smart sensors, interactive screens, locative media and evolving computation software have impacted the ways in which people experience, explore, interact with and create these complex spaces. This book draws together a broad range of interdisciplinary researchers in areas such as architecture, urban design, spatial planning, geoinformation science, computer science and psychology to introduce the theories, models, opportunities and uncertainties involved in the interplay between virtual and physical spaces. Using a wide range of international contributors, from the UK, USA, Germany, France, Switzerland, Netherlands and Japan, it provides a framework for assessing how new technology alters our perception of physical space.

Describing a new optimization algorithm, the "Teaching-Learning-Based Optimization (TLBO)," in a clear and lucid style, this book maximizes reader insights into how the TLBO algorithm can be used to solve continuous and discrete optimization problems involving single or multiple objectives. As the algorithm operates on the principle of teaching and learning, where teachers influence the quality of learners' results, the elitist version of TLBO algorithm (ETLBO) is described along with applications of the TLBO algorithm in the fields of electrical engineering, mechanical design, thermal engineering, manufacturing engineering, civil engineering, structural engineering, computer engineering, electronics engineering, physics and biotechnology. The book offers a valuable resource for scientists, engineers and practitioners involved in the development and usage of advanced optimization algorithms.

Recent rapid globalisation of manufacturing industries leads to a drive and thirst for rapid advancements in technological development and expertise in the fields of advanced design and manufacturing, especially at their interfaces. This development results in many economical benefits to and improvement of quality of life for many people all over the world. Technically speaking, this rapid development also create many opportunities and challenges for both industrialists and academics, as the design requirements and constraints have completely changed in this global design and manufacture environment. Consequently the way to design, manufacture and realise products have changed as well. The days of designing for a local market and using local suppliers in manufacturing have gone, if enterprises aim to maintain their competitiveness and global expansion leading to further success. In this global context and scenario, both industry and the academia have an urgent need to equip themselves with the latest knowledge, technology and methods developed for engineering design and manufacture. To address this shift in engineering design and manufacture, supported by the European Commission under the Asia Link Programme with a project title FASTAHEAD (A Framework Approach to Strengthening Asian Higher Education in Advanced Design and Manufacture), three key project partners, namely the University of Strathclyde of the United Kingdom, Northwestern Polytechncial University of China, and the Troyes University of Technology of France organised a third international conference.

The application of CMOS circuits and ASIC VLSI systems to problems in medicine and system biology has led to the emergence of Bio/CMOS Interfaces and Co-Design as an exciting and rapidly growing area of research. The mutual inter-relationships between VLSI-CMOS design and the biophysics of molecules interfacing with silicon and/or onto metals has led to the emergence of the interdisciplinary engineering approach to Bio/CMOS interfaces. This new approach, facilitated by 3D circuit design and nanotechnology, has resulted in new concepts and applications for VLSI systems in the bio-world. This book offers an invaluable reference to the state-of-the-art in Bio/CMOS interfaces. It describes leading-edge research in the field of CMOS design and VLSI development for applications requiring integration of biological molecules onto the chip. It provides multidisciplinary content ranging from biochemistry to CMOS design in order to address Bio/CMOS interface co-design in bio-sensing applications.

The aim of the book is to provide engineers with a practical guide to Finite Element Modelling (FEM) in Abaqus CAE software. The guide is in the form of step-by-step procedures concerning yarns, woven fabric and knitted fabrics modelling, as well as their contact with skin so that the simulation of haptic perception between textiles and skin can be provided. The specific modelling procedure will be proceeded by a theoretical background concerning mechanical characteristics of the modelled elements or phenomena. Models will be validated and discussed. In addition, virtual object tests results will be presented and compared to the outcome of the modelling process.

A definitive user's guide to the U.S. National CAD Standard
The Architect's Guide to the U.S. National CAD Standard helps make the National CAD Standard (NCS) more accessible to architects by presenting:
* Clear and succinct explanations of concepts and options in the NCS
* A step-by-step approach to seamlessly implement standardized drawings in any size firm
* Successful strategies design firms can use to best take advantage of the NCS requirements

The Architect's Guide to the U.S. National CAD Standard presents an informative overview of the NCS, including illustrations and frequently asked questions. It shows architects how to minimize immediate costs and downtime, how to reap immediate benefits, and how best to learn the system at an individualized pace. Used side by side with the Standard, this authoritative guide offers helpful insight into how the NCS is likely to be interpreted and presents a variety of available options for meeting the standardization requirements.
Interior designers, construction managers, urban planners, as well as owners, engineers, and facility managers will also find this authoritative reference to be invaluable

Technology computer-aided design, or TCAD, is critical to today's semiconductor technology and anybody working in this industry needs to know something about TCAD. This book is about how to use computer software to manufacture and test virtually semiconductor devices in 3D. It brings to life the topic of semiconductor device physics, with a hands-on, tutorial approach that de-emphasizes abstract physics and equations and emphasizes real practice and extensive illustrations. Coverage includes a comprehensive library of devices, representing the state of the art technology, such as SuperJunction LDMOS, GaN LED devices, etc.

* Provides simple, conceptual descriptions of everyday technologies * Includes clear examples and diagrams that demonstrate the principles and techniques, not just a "how-to" punch list * Covers advanced topics for readers who want to dive into the deep end of the technology pool * Avoids jargon-where terminology does appear, the text will provide clear, concise definitions

The two volumes of this book collect high-quality peer-reviewed research papers presented in the International Conference on ICT for Sustainable Development (ICT4SD 2015) held at Ahmedabad, India during 3 - 4 July 2015. The book discusses all areas of Information and Communication Technologies and its applications in field for engineering and management. The main focus of the volumes are on applications of ICT for Infrastructure, e-Governance, and contemporary technologies advancements on Data Mining, Security, Computer Graphics, etc. The objective of this International Conference is to provide an opportunity for the researchers, academicians, industry persons and students to interact and exchange ideas, experience and expertise in the current trend and strategies for Information and Communication Technologies.

Use design to transform your ideas into powerful visuals that connect with the right audience, define your brand, or take your project to the next level. Students, entrepreneurs, community groups, social media influencers, bloggers or campaigners: this practical guide is for you, and everyone else who wants to learn how to communicate visually, combining the building blocks of type, photography, illustration, and colour to create designs that inform, influence, and enthral. All the key principles of graphic design are explained via a series of specially created, beautifully streamlined graphics that show, rather than tell, you what you need to know. In addition, detailed how-to demonstrations, hands-on workshops, and inspirational galleries of the best design will help you to achieve your aims, from creating a brand identity or setting the right mood by choosing the best typeface, to organizing the elements of a layout to boost your message and meaning. Ten step-by-step projects help you create your own bespoke designs - for websites, digital newsletters, e-commerce, invitations, posters, sales materials, and more. There's also plenty of practical advice, including tips on publishing online, dealing with printers, commissioning professionals, and finding free design tools. If you're ready to use the power of design to take your personal project or burgeoning business to the next level, Graphic Design for Everyone is a one-stop resource to becoming an effective, inspirational visual communicator.

This book gathers selected contributions presented at the INdAM Workshop "DREAMS", held in Rome, Italy on January 22 26, 2018. Addressing cutting-edge research topics and advances in computer aided geometric design and isogeometric analysis, it covers distinguishing curve/surface constructions and spline models, with a special focus on emerging adaptive spline constructions, fundamental spline theory and related algorithms, as well as various aspects of isogeometric methods, e.g. efficient quadrature rules and spectral analysis for isogeometric B-spline discretizations. Applications in finite element and boundary element methods are also discussed. Given its scope, the book will be of interest to both researchers and graduate students working in these areas.

This book is primarily intended as a research monograph that could also be used in graduate courses for the design of parallel algorithms in matrix computations. It assumes general but not extensive knowledge of numerical linear algebra, parallel architectures, and parallel programming paradigms. The book consists of four parts: (I) Basics; (II) Dense and Special Matrix Computations; (III) Sparse Matrix Computations; and (IV) Matrix functions and characteristics. Part I deals with parallel programming paradigms and fundamental kernels, including reordering schemes for sparse matrices. Part II is devoted to dense matrix computations such as parallel algorithms for solving linear systems, linear least squares, the symmetric algebraic eigenvalue problem, and the singular-value decomposition. It also deals with the development of parallel algorithms for special linear systems such as banded ,Vandermonde ,Toeplitz ,and block Toeplitz systems. Part III addresses sparse matrix computations: (a) the development of parallel iterative linear system solvers with emphasis on scalable preconditioners, (b) parallel schemes for obtaining a few of the extreme eigenpairs or those contained in a given interval in the spectrum of a standard or generalized symmetric eigenvalue problem, and (c) parallel methods for computing a few of the extreme singular triplets. Part IV focuses on the development of parallel algorithms for matrix functions and special characteristics such as the matrix pseudospectrum and the determinant. The book also reviews the theoretical and practical background necessary when designing these algorithms and includes an extensive bibliography that will be useful to researchers and students alike. The book brings together many existing algorithms for the fundamental matrix computations that have a proven track record of efficient implementation in terms of data locality and data transfer on state-of-the-art systems, as well as several algorithms that are presented for the first time, focusing on the opportunities for parallelism and algorithm robustness.

There's simply no better resource for anyone learning about and/or teaching CAD software than the Beginning AutoCAD Exercise Workbook. Veteran AutoCAD experts and former instructors Shrock and Heather have packed the 2021 version with a vastly improved interior design layout, 30 in-depth lessons with hundreds of useful practice exercises, all new screenshots, along with tried and true features such as "CAD tips" and side-by-side metric/inch measurements. The detailed, step-by-step format makes mastering AutoCAD much easier, in or out of a formal classroom. Readers can download the provided templates used for drawings in the book from the Industrial Press website. New and/or Improved Features in Beginning AutoCAD 2021 Streamlined Trim and Extend command-Boundary edges are now selected automatically, making trimming or extending objects far more efficient. Revision Cloud enhancements-Users can use one value that measures the chord distance between the end points of each cloud arc to create more consistent revision clouds. Measure Geometry: Quick Measure-The area and perimeter of closed objects (and even multiple objects) can be measured with a simple click, all in one go. Beginning AutoCAD 2021 contains more content than ever before, yet has been redesigned and reduced by more than 100 pages, making it more manageable to read and carry. There's simply no better resource for anyone learning about and/or teaching CAD software than the Beginning AutoCAD Exercise Workbook. Veteran AutoCAD experts and former instructors Shrock and Heather have packed the 2021 version with a vastly improved interior design layout, 30 in-depth lessons with hundreds of useful practice exercises, all new screenshots, along with tried and true features such as "CAD tips" and side-by-side metric/inch measurements. The detailed, step-by-step format makes mastering AutoCAD much easier, in or out of a formal classroom. Readers can download the provided templates used for drawings in the book from the Industrial Press website. New and/or Improved Features in Beginning AutoCAD 2021 Streamlined Trim and Extend command-Boundary edges are now selected automatically, making trimming or extending objects far more efficient. Revision Cloud enhancements-Users can use one value that measures the chord distance between the end points of each cloud arc to create more consistent revision clouds. Measure Geometry: Quick Measure-The area and perimeter of closed objects (and even multiple objects) can be measured with a simple click, all in one go. Beginning AutoCAD 2021 contains more content than ever before, yet has been redesigned and reduced by more than 100 pages, making it more manageable to read and carry. Cheryl Shrock is a retired Professor and Chairperson of Computer Aided Design at Orange Coast College in California. The AutoCAD ExerciseWorkbooks are the result of both her teaching skills and her industry experience. She is an Autodesk (R) registered author. Steve Heather has more than 30 years of experience as a practicing mechanical engineer, and has taught AutoCAD to engineering and architectural students at the college level. He is a Beta Tester for Autodesk (R), testing the latest AutoCAD software, and a member of the AutoCAD (R) Customer Council.* Starting AutoCAD * Creating & Using a Template * Selecting a Command * Drawing Lines * Erase * Undo and Redo * Starting a New Drawing * Opening Multiple Files * Automatic Save * Circle * Rectangle * Grid and Increment Snap * Transparency * Object Snap * Zoom * Drawing Setup * Polygon * Ellipse * Point * Break * Trim * Extend * Move * Drag * Explode * Copy * Mirror * Fillet * Chamfer * Single & Multiline Text * Tabs & Indents * Columns * Paragraph & Line Spacing * Editing * Coordinate Input * Absolute Coordinates * Direct Distance Entry (DDE) * Measure Tools * Moving the Origin * Displaying the UCS Icon * Polar Coordinate Input * Dynamic Input* Polar Tracking * Using Polar Tracking & DDE * Polar Snap * Offset * Properties Palette * Quick Properties Panel * Array * Scale: Stretch: Rotate * Hatch Types * Editing Hatch Set Properties * Linear, Continue, & Baseline Dimensioning * Ignoring Hatch Objects * Editing Dimension Text Values * Modifying a Dimension Style * Dimension Breaks * Jogging a Dimension Line * Adjusting the Distance Between Dimensions * Dimensioning Diameters & Radii * Angular Dimensioning * Center Mark-Automatic & Manual * Centerline * Flip Arrow * Creating a Multileader Style * Special Text Characters * Dim Command... and much more!

'Inclusive Designing' presents the proceedings of the seventh Cambridge Workshop on Universal Access and Assistive Technology (CWUAAT '14). It represents a unique multi-disciplinary workshop for the Inclusive Design Research community where designers, computer scientists, engineers, architects, ergonomists, policymakers and user communities can exchange ideas. The research presented at CWUAAT '14 develops methods, technologies, tools and guidance that support product designers and architects to design for the widest possible population for a given range of capabilities, within a contemporary social and economic context. In the context of developing demographic changes leading to greater numbers of older people and people with disabilities, the general field of Inclusive Design Research strives to relate the capabilities of the population to the design of products. Inclusive populations of older people contain a greater variation in sensory, cognitive and physical user capabilities. These variations may be co-occurring and rapidly changing leading to a demanding design environment. Recent research developments have addressed these issues in the context of: governance and policy; daily living activities; the workplace; the built environment, Interactive Digital TV and Mobile communications. Increasingly, a need has been identified for a multidisciplinary approach that reconciles the diverse and sometimes conflicting demands of Design for Ageing and Impairment, Usability and Accessibility and Universal Access. CWUAAT provides a platform for such a need. This book is intended for researchers, postgraduates, design practitioners, clinical practitioners, and design teachers.