Introduction to Applications of Nuclear Physics

Introduction to Applications of Nuclear Physics tài liệu, giáo án, bài giảng , luận văn, luận án, đồ án, bài tập lớn về...

Copyright © 2000, Cisco Systems, Inc. 1 © 2000, Cisco Systems, Inc. Introduction to Quality of Service Introduction to Quality of Service Copyright © 2000, Cisco Systems, Inc. 2 © 2000, Cisco Systems, Inc. www.cisco.com Econ_0385_02_010.ppt Keep All Graphics Inside This Box Objectives Objectives Upon completion of this module, you will be able to perform the following tasks: • Explain the significance of Quality of Service (QoS) • Describe new Quality of Service (QoS) features in Cisco IOS 12.1 • Explain which problems QoS solves The purpose of this module is to quickly survey the new Quality of Service (QoS) features in Cisco IOS 12.1 and to describe the problems they solve Copyright © 2000, Cisco Systems, Inc. 3 © 2000, Cisco Systems, Inc. www.cisco.com Econ_0385_02_010.ppt Keep All Graphics Inside This Box Topics Topics QoS overview New QoS features Quick look at Diff Serv framework Copyright © 2000, Cisco Systems, Inc. 4 © 2000, Cisco Systems, Inc. www.cisco.com Econ_0385_02_010.ppt Keep All Graphics Inside This Box Why Is QoS So Important? Why Is QoS So Important? QoS: • Allows the integration of data, voice, and video over the network • Mission-critical traffic can be prioritized over non-critical traffic –Certain business applications –Voice, SNA traffic • Can prioritize different groups of users , such as finance, sales, or suppliers The Cisco IOS QoS features enable networks to control and predictably service a variety of networked applications and traffic types. Implementing Cisco IOS QoS in your network promotes the following: • Control over resources—You control which resources (bandwidth, equipment, wide-area facilities, and so on) are being used. For example, you can limit bandwidth consumed over a backbone link by File Transfer Protocol (FTP) transfers or give priority to an important database access. • Tailored services—If you are an Internet Service Provider (ISP), the control and visibility provided by QoS enables you to offer carefully tailored grades of service differentiation to your customers. • Coexistence of mission-critical applications. Cisco QoS features make certain of the following: • That your WAN is used efficiently by mission-critical applications that are most important to your business. • That bandwidth and minimum delays required by time-sensitive multimedia and voice applications are available. • That other applications using the link get their fair service without interfering with mission-critical traffic. Moreover, in implementing QoS features in your network, you put in place the foundation for a future fully integrated network. http://cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/qos_c/qcdintro.htm Copyright © 2000, Cisco Systems, Inc. 5 © 2000, Cisco Systems, Inc. www.cisco.com Econ_0385_02_010.ppt Keep All Graphics Inside This Box Where Do We Use QoS? Where Do We Use QoS? Low bandwidth links Managing bandwidth Application service levels • Voice • Mission-critical applications IP network replacing ATM infrastructure Differentiated levels of service Internet The slide lists some of the places where QoS is being applied today. QoS is important to those using low bandwidth links, to protect voice or mission-critical traffic on those links, especially in the event of congestion. Control and protection of voice and mission-critical traffic can also be important to the customer over higher speed links. Sometimes QoS is desired because IP networking is Introduction to Applications of Nuclear Physics Introduction to Applications of Nuclear Physics Bởi: OpenStaxCollege Tori Randall, Ph.D., curator for the Department of Physical Anthropology at the San Diego Museum of Man, prepares a 550-year-old Peruvian child mummy for a CT scan at Naval Medical Center San Diego (credit: U.S Navy photo by Mass Communication Specialist 3rd Class Samantha A Lewis) 1/2 Introduction to Applications of Nuclear Physics Applications of nuclear physics have become an integral part of modern life From the bone scan that detects a cancer to the radioiodine treatment that cures another, nuclear radiation has diagnostic and therapeutic effects on medicine From the fission power reactor to the hope of controlled fusion, nuclear energy is now commonplace and is a part of our plans for the future Yet, the destructive potential of nuclear weapons haunts us, as does the possibility of nuclear reactor accidents Certainly, several applications of nuclear physics escape our view, as seen in [link] Not only has nuclear physics revealed secrets of nature, it has an inevitable impact based on its applications, as they are intertwined with human values Because of its potential for alleviation of suffering, and its power as an ultimate destructor of life, nuclear physics is often viewed with ambivalence But it provides perhaps the best example that applications can be good or evil, while knowledge itself is neither Customs officers inspect vehicles using neutron irradiation Cars and trucks pass through portable x-ray machines that reveal their contents (credit: Gerald L Nino, CBP, U.S Dept of Homeland Security) This image shows two stowaways caught illegally entering the United States from Canada (credit: U.S Customs and Border Protection) 2/2 An Introduction to Letters of Credit Citigroup ® Global Transaction Services [...]... bank on both sides of the transaction 5 LETTERS OF CREDIT The Language C H 2 A P T E R This chapter will familiarize you with the language used in Letters of Credit This language has evolved over many years and some of the terms are unique to Letters of Credit This section will help you understand the words which may later become a standard part of your vocabulary 8 Types of Letters of Credit All Letters. .. presentation of documents to the Confirming Bank Recognizing Letters of Credit In addition to learning the formal language of Letters of Credit, it is equally important to recognize variations in the types of instruments used The illustrations that follow resemble the standard forms used by Citibank and illustrate the distinctions among Letters of Credit Straight Letters of Credit Irrevocable Letters of Credit, ... of Credit and a typical import Letter of Credit In international trade every Commercial Letter of Credit facilitates both an import and an export since it operates on both sides of the transaction In this chapter, for ease of illustration, an export Letter of Credit refers to a Letter of Credit covering the export of goods and/or services from the U.S (payable in U.S dollars) and an import Letter of. .. undertaking to that of the Issuing Bank If an overseas bank (buyer ’s bank) issues its Irrevocable Letter of Credit and requests that Citibank, New York, add its confirmation and advise the Beneficiary, then Citibank, as Advising and Confirming Bank, could use its own form of advice and confirmation An example of Advice and Confirmation of Correspondent Illustration 2 – Revocable Letter of Credit 9 Citibank,... its bank to issue the Letter of Credit in either a revocable or irrevocable form A Revocable Letter of Credit may be amended or canceled by the Issuing Bank at any time with or without prior notice to, or agreement of, the Beneficiary An Irrevocable Letter of Credit cannot be amended or canceled without the agreement of the Issuing Bank, the Confirming Bank (if the Letter of Credit is confirmed), and... working day of our being in a position to provide our formal advice The enclosed Letter of Credit, together with any subsequent amendments thereto, and Advice of Credit must accompany all presentations made under the Letter of Credit Our examination of the documents will be in accordance with the terms of the Letter of Credit and the appropriate provisions of UCP 500 In accordance with our service standards,... (seller) While both Applicants and Beneficiaries benefit from the unique characteristics of a Letter of Credit, it is important for Applicants and Beneficiaries to recognize what a Letter of Credit is not: 1 It is not an unconditional guarantee of payment to anyone A Letter of Credit assures payment to a Beneficiary only if its terms and conditions are fulfilled through the presentation of strictly complying... type of Letter of Credit meets a different need, it is important Introduction to Modern Solid State Physics Yuri M. Galperin FYS 448 Department of Physics, P.O. Box 1048 Blindern, 0316 Oslo, Room 427A Phone: +47 22 85 64 95, E-mail: iouri.galperinefys.uio.no Contents I Basic concepts 1 1 Geometry of Lattices 3 1.1 Periodicity: Crystal Structures . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 The Reciprocal Lattice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.3 X-Ray Diffraction in Periodic Structures . . . . . . . . . . . . . . . . . . . 10 1.4 Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2 Lattice Vibrations: Phonons 21 2.1 Interactions Between Atoms . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.2 Lattice Vibrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 2.3 Quantum Mechanics of Atomic Vibrations . . . . . . . . . . . . . . . . . . 38 2.4 Phonon Dispersion Measurement . . . . . . . . . . . . . . . . . . . . . . . 43 2.5 Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 3 Electrons in a Lattice. 45 3.1 Electron in a Periodic Field . . . . . . . . . . . . . . . . . . . . . . . . . . 45 3.1.1 Electron in a Periodic Potential . . . . . . . . . . . . . . . . . . . . 46 3.2 Tight Binding Approximation . . . . . . . . . . . . . . . . . . . . . . . . . 47 3.3 The Model of Near Free Electrons . . . . . . . . . . . . . . . . . . . . . . . 50 3.4 Main Properties of Bloch Electrons . . . . . . . . . . . . . . . . . . . . . . 52 3.4.1 Effective Mass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 3.4.2 Wannier Theorem → Effective Mass Approach . . . . . . . . . . . . 53 3.5 Electron Velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 3.5.1 Electric current in a Bloch State. Concept of Holes. . . . . . . . . . 54 3.6 Classification of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 3.7 Dynamics of Bloch Electrons . . . . . . . . . . . . . . . . . . . . . . . . . . 57 3.7.1 Classical Mechanics . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 3.7.2 Quantum Mechanics of Bloch Electron . . . . . . . . . . . . . . . . 63 3.8 Second Quantization of Bosons and Electrons . . . . . . . . . . . . . . . . 65 3.9 Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 i ii CONTENTS II Normal metals and semiconductors 69 4 Statistics and Thermodynamics 71 4.1 Specific Heat of Crystal Lattice . . . . . . . . . . . . . . . . . . . . . . . . 71 4.2 Statistics of Electrons in Solids . . . . . . . . . . . . . . . . . . . . . . . . 75 4.3 Specific Heat of the Electron System . . . . . . . . . . . . . . . . . . . . . 80 4.4 Magnetic Properties of Electron Gas. . . . . . . . . . . . . . . . . . . . . . 81 4.5 Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 5 Summary of basic concepts 93 6 Classical dc Transport 97 6.1 The Boltzmann Equation for Electrons . . . . . . . . . . . . . . . . . . . . 97 6.2 Conductivity and Thermoelectric Phenomena. . . . . . . . . . . . . . . . . 101 6.3 Energy Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 6.4 Neutral and Ionized Impurities . . . . . . . . . . . . . . . . . . . . . . . . . 109 6.5 Electron-Electron Scattering . . . . . . . . . . . . . . . . . . . . . . . . . . 112 6.6 Scattering by Lattice Vibrations . . . . . . . . . . . . . . . . . . . . . . . . 114 6.7 Electron-Phonon Interaction in Semiconductors . . . . . . . . . . . . . . . 125 6.8 Galvano- and Thermomagnetic . . . . . . . . . . . . . . . . . . . . . . . 130 6.9 Shubnikov-de Haas effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 6.10 Response to “slow” perturbations . . . . . . . . . . . . . . . . . . . . . . . 142 6.11 “Hot” electrons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 6.12 Impact ionization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Contents Introduction 1 Part 1. Singularities of solutions to equations of mathematical physics 7 Chapter 1. Prerequisites on operator pencils 9 1.1. Operator pencils 10 1.2. Operator pencils corresponding to sesquilinear forms 15 1.3. A variational principle for operator pencils 21 1.4. Elliptic boundary value problems in domains with conic points: some basic results 26 1.5. Notes 31 Chapter 2. Angle and conic singularities of harmonic functions 35 2.1. Boundary value problems for the Laplace operator in an angle 36 2.2. The Dirichlet problem for the Laplace operator in a cone 40 2.3. The Neumann problem for the Laplace operator in a cone 45 2.4. The problem with oblique derivative 49 2.5. Further results 52 2.6. Applications to boundary value problems for the Laplace equation 54 2.7. Notes 57 Chapter 3. The Dirichlet problem for the Lam´e system 61 3.1. The Dirichlet problem for the Lam´e system in a plane angle 64 3.2. The operator pencil generated by the Dirichlet problem in a cone 74 3.3. Properties of real eigenvalues 83 3.4. The set functions Γ and F ν 88 3.5. A variational principle for real eigenvalues 91 3.6. Estimates for the width of the energy strip 93 3.7. Eigenvalues for circular cones 97 3.8. Applications 100 3.9. Notes 105 Chapter 4. Other boundary value problems for the Lam´e system 107 4.1. A mixed boundary value problem for the Lam´e system 108 4.2. The Neumann problem for the Lam´e system in a plane angle 120 4.3. The Neumann problem for the Lam´e system in a cone 125 4.4. Angular crack in an anisotropic elastic space 133 4.5. Notes 138 Chapter 5. The Dirichlet problem for the Stokes system 139 i ii CONTENTS 5.1. The Dirichlet problem for the Stokes system in an angle 142 5.2. The operator pencil generated by the Dirichlet problem in a cone 148 5.3. Properties of real eigenvalues 155 5.4. The eigenvalues λ=1 and λ =–2 159 5.5. A variational principle for real eigenvalues 168 5.6. Eigenvalues in the case of right circular cones 175 5.7. The Dirichlet problem for the Stokes system in a dihedron 178 5.8. Stokes and Navier–Stokes systems in domains with piecewise smooth boundaries 192 5.9. Notes 196 Chapter 6. Other boundary value problems for the Stokes system in a cone 199 6.1. A mixed boundary value problem for the Stokes system 200 6.2. Real eigenvalues of the pencil to the mixed problem 212 6.3. The Neumann problem for the Stokes system 223 6.4. Notes 225 Chapter 7. The Dirichlet problem for the biharmonic and polyharmonic equations 227 7.1. The Dirichlet problem for the biharmonic equation in an angle 229 7.2. The Dirichlet problem for the biharmonic equation in a cone 233 7.3. The polyharmonic operator 239 7.4. The Dirichlet problem for ∆ 2 in domains with piecewise smooth boundaries 246 7.5. Notes 248 Part 2. Singularities of solutions to general elliptic equations and systems 251 Chapter 8. The Dirichlet problem for elliptic equations and systems in an angle 253 8.1. The operator pencil generated by the Dirichlet problem 254 8.2. An asymptotic formula for the eigenvalue close to m 263 8.3. Asymptotic formulas for the eigenvalues close to m − 1/2 265 8.4. The case of a convex angle 272 8.5. The case of a nonconvex angle 275 8.6. The Dirichlet problem for a second order system 283 8.7. Applications 286 8.8. Notes 291 Chapter 9. Asymptotics of the spectrum of operator pencils generated by general boundary value problems in an angle 293 9.1. The operator pencil generated by a regular boundary value problem 293 9.2. Distribution of the eigenvalues 299 9.3. Notes 305 Chapter 10. The Dirichlet problem for strongly elliptic systems in particular cones 307 10.1. Basic properties of the operator pencil generated by the Dirichlet problem 308 CONTENTS iii 10.2. Elliptic systems in R n 313 10.3. The Copyright © 2000, Cisco Systems, Inc. 1 © 2000, Cisco Systems, Inc. Introduction to Quality of Service Introduction to Quality of Service Copyright © 2000, Cisco Systems, Inc. 2 © 2000, Cisco Systems, Inc. www.cisco.com Econ_0385_02_010.ppt Keep All Graphics Inside This Box Objectives Objectives Upon completion of this module, you will be able to perform the following tasks: • Explain the significance of Quality of Service (QoS) • Describe new Quality of Service (QoS) features in Cisco IOS 12.1 • Explain which problems QoS solves The purpose of this module is to quickly survey the new Quality of Service (QoS) features in Cisco IOS 12.1 and to describe the problems they solve Copyright © 2000, Cisco Systems, Inc. 3 © 2000, Cisco Systems, Inc. www.cisco.com Econ_0385_02_010.ppt Keep All Graphics Inside This Box Topics Topics QoS overview New QoS features Quick look at Diff Serv framework Copyright © 2000, Cisco Systems, Inc. 4 © 2000, Cisco Systems, Inc. www.cisco.com Econ_0385_02_010.ppt Keep All Graphics Inside This Box Why Is QoS So Important? Why Is QoS So Important? QoS: • Allows the integration of data, voice, and video over the network • Mission-critical traffic can be prioritized over non-critical traffic –Certain business applications –Voice, SNA traffic • Can prioritize different groups of users , such as finance, sales, or suppliers The Cisco IOS QoS features enable networks to control and predictably service a variety of networked applications and traffic types. Implementing Cisco IOS QoS in your network promotes the following: • Control over resources—You control which resources (bandwidth, equipment, wide-area facilities, and so on) are being used. For example, you can limit bandwidth consumed over a backbone link by File Transfer Protocol (FTP) transfers or give priority to an important database access. • Tailored services—If you are an Internet Service Provider (ISP), the control and visibility provided by QoS enables you to offer carefully tailored grades of service differentiation to your customers. • Coexistence of mission-critical applications. Cisco QoS features make certain of the following: • That your WAN is used efficiently by mission-critical applications that are most important to your business. • That bandwidth and minimum delays required by time-sensitive multimedia and voice applications are available. • That other applications using the link get their fair service without interfering with mission-critical traffic. Moreover, in implementing QoS features in your network, you put in place the foundation for a future fully integrated network. http://cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/qos_c/qcdintro.htm Copyright © 2000, Cisco Systems, Inc. 5 © 2000, Cisco Systems, Inc. www.cisco.com Econ_0385_02_010.ppt Keep All Graphics Inside This Box Where Do We Use QoS? Where Do We Use QoS? Low bandwidth links Managing bandwidth Application service levels • Voice • Mission-critical applications IP network replacing ATM infrastructure Differentiated levels of service Internet The slide lists some of the places where QoS is being applied today. QoS is important to those using low bandwidth links, to protect voice or mission-critical traffic on those links, especially in the event of congestion. Control and protection of voice and mission-critical traffic can also be important to the customer over higher speed links. Sometimes QoS is desired because IP networking is Introduction to Frontiers of Physics Introduction to Frontiers of Physics Bởi: OpenStaxCollege This galaxy is ejecting huge jets of matter, powered by an immensely massive black hole at its center (credit: X-ray: .. .Introduction to Applications of Nuclear Physics Applications of nuclear physics have become an integral part of modern life From the bone scan that detects a cancer to the radioiodine... of nuclear weapons haunts us, as does the possibility of nuclear reactor accidents Certainly, several applications of nuclear physics escape our view, as seen in [link] Not only has nuclear physics. .. destructor of life, nuclear physics is often viewed with ambivalence But it provides perhaps the best example that applications can be good or evil, while knowledge itself is neither Customs officers