Showing papers in "American Journal of Physics in 1968"
TL;DR: In this paper, the two-fluid model is used to describe the behavior of a superfluid in response to a transverse probe in a two-fluid model.
Abstract: Special Preface -- Preface -- Special Preface -- Preface -- Introduction -- Neutral Fermi Liquids -- Response and Correlation in Neutral Systems -- Charged Fermi Liquids -- Response and Correlation in Homogeneous Electron Systems -- Microscopic Theories of the Electron Liquid -- Introduction -- Experimental And Theoretical Background On He II -- Elementary Excitations -- Elementary Excitations in He II -- Superfluid Behavior: Response To A Transverse Probe. Qualitative Behavior Of A Superfluid -- Superfluid Flow: Macroscopic Limit -- Basis for the Two-Fluid Model -- First, Second, And Quasi-Particle Sound -- Vortex Lines -- Microscopic Theory: Uniform Condensate -- Microscopic Theory: Non-Uniform Condensate -- Conclusion -- * Second Quantization
2,494 citations
TL;DR: In this paper, a few more concepts that are important to the study of electron spin resonance have been introduced, but which are not encountered in the field of nuclear magnetic resonance, such as the quenching of orbital angular momentum and the magnetic coupling of the nuclear spin to that of the electron.
Abstract: So far we have confined our attention to nuclear magnetic resonance, although many of the basic principles apply to electron spin resonance. We have also considered questions concerning the electrons, such as the quenching of orbital angular momentum and the magnetic coupling of the nuclear spin to that of the electron. In this chapter we shall add a few more concepts that are important to the study of electron spin resonance1 but which are not encountered in the study of nuclear resonance.
1,726 citations
1,460 citations
1,014 citations
937 citations
750 citations
687 citations
646 citations
354 citations
293 citations
TL;DR: In this article, the statistical predictions of quantum mechanics for infinite ensembles are derived from its assertions for individual systems, and a discussion of the meaning of the state of an individual quantum mechanical system is given, and an application is made to clarify some of the paradoxical features of the theory.
Abstract: A formulation of quantum mechanics, which begins by postulating assertions for individual physical systems, is given. The statistical predictions of quantum mechanics for infinite ensembles are then derived from its assertions for individual systems. A discussion of the meaning of the “state” of an individual quantum mechanical system is given, and an application is made to the clarification of some of the paradoxical features of the theory.
TL;DR: In this article, the authors present an overview of dislocations in materials science and present a detailed discussion of the mechanisms of the dislocation and the mechanical strength of crystalline solids.
Abstract: In materials science, dislocations are irregularities within the crystal structure or atomic scale of engineering materials, such as metals, semi-conductors, polymers, and composites. Discussing this specific aspect of materials science and engineering, Introduction to Dislocations is a key resource for students. The book provides students and practitioners with the fundamental principles required to understand dislocations. Comprised of 10 chapters, the text includes advanced computer modeling and very high-resolution electron microscopy to help readers better understand the structure of atoms close to the core of dislocations. It shows that atomic arrangement has a significant effect on the formation of dislocations and thereby on the properties of solids. The first two chapters of the book present an overview of dislocations. The crystal structures and the various defects and dislocations are discussed, and methods of observation and diagnosis of dislocations are covered. Chapters 3 to 5 discuss the behavior of dislocations and explain how changes in the structure and arrangement of atoms can affect the behavior of dislocations. The three chapters also discuss the mechanical properties of dislocations. The remaining chapters offer a detailed discussion of the mechanisms of dislocations and the mechanical strength of crystalline solids. The book is written for undergraduate- and graduate-level students in both materials science and mechanical engineering. Non-experts and novices working on mechanical properties, mechanisms of deformation and fracture, and properties of materials, as well as industrial and academic researchers, will find this book invaluable. * Long-established academic reference by an expert author team, highly regarded for their contributions to the field.* Uses minimal mathematics to present theory and applications in a detailed yet easy-to-read manner, making this an understandable introduction to a complex topic.* Unlike the main competition, this new edition includes recent developments in the subject and up-to-date references to further reading and research sources.
[...]
TL;DR: In this article, it was shown that a baseball fielder will reach the right place at the right time to catch a fly ball if he runs at the only constant velocity for which the rate of change of tangent of the elevation angle and the bearing angle of the ball both remain constant.
Abstract: A baseball fielder will arrive at the right place at the right time to catch a fly ball if he runs at the only constant velocity for which the rate of change of tangent of the elevation angle of the ball and the bearing angle of the ball both remain constant. Remarks are made concerning curve balls. Baseball is not a scientific game—although, unknown to the players, many principles of physics can be applied to it.
TL;DR: In this paper, the principal theoretical and experimental results concerning the lattice properties of ideal inert-gas crystals are presented and discussed, and it is shown that there are no qualitative disagreements between theory and experiment.
Abstract: In this review-tutorial article, the principal theoretical and experimentals results concerning the lattice properties of ideal inert-gas crystals are presented and discussed. The work published since Pollack's article is emphasized. It is shown that there are no qualitative disagreements between theory and experiment. Where theory and experiment are reliable, quantitative agreement is found between the measurements and the predictions based on simple two-body central potentials.
TL;DR: In this article, the Hartree-Fock approximation is compared with the exact solution for the problem of two particles in a common harmonic oscillator potential interacting through harmonic oscillators forces.
Abstract: The problem of two particles in a common harmonic oscillator potential interacting through harmonic oscillator forces is discussed from the standpoint of the Hartree-Fock approximation and compared with the exact solution.
TL;DR: In this article, the concepts of radiation transfer were introduced in terms of the more familiar units of radiometry, and the conversion to photometric units can then be accomplished by a straightforward integration.
Abstract: In order to reduce the confusion associated with many of the introductory treatments of photometry, it is suggested that initially the concepts of radiation transfer be introduced in terms of the more familiar units of radiometry. The conversion to photometric units can then be accomplished by a straightforward integration. The approach is illustrated with five of the basic quantities of radiometry.
TL;DR: A complete English translation of the classic Enrico Fermi paper on beta decay published in Zeitschrift fur Physik in 1934 is given in this paper, where the authors also present a complete English version of the paper.
Abstract: A complete English translation is given of the classic Enrico Fermi paper on beta decay published in Zeitschrift fur Physik in 1934.
TL;DR: In this paper, the relations among the statistical ensembles, systems, and states (pure and mixed) of quantum theory are explored. But the conceptual gulf between classical states and quantum states is wider than commonly assumed.
Abstract: This paper carefully explores the relations among the statistical ensembles, systems, and states (pure and mixed) of quantum theory. By systematically contrasting the classical and quantal realizations of a general paradigm for a probabilistic physics, important distinctions are exposed both in statics and dynamics. Included are observations concerning the intrinsic ambiguity of the quantum-state concept and the peculiarly quantum property of dynamic indivisibility. It is concluded that the conceptual gulf between classical states and quantum “states” is wider than commonly assumed.
TL;DR: In this article, a comprehensive review of the properties of dilute solutions is not given Rather, the simple physical notions underlying an understanding of their properties are discussed, and special emphasis is placed on those phenomena which are of importance in understanding the dilution refrigerator.
Abstract: Properties of dilute solutions of 3He in 4He at low temperatures and their application to dilution refrigeration are discussed from a review—tutorial point of view A comprehensive review of the properties of dilute solutions is not given Rather, the simple physical notions underlying an understanding of their properties are discussed Special emphasis is placed on those phenomena which are of importance in understanding the dilution refrigerator After a review of the phase-separation phenomenon in 3He-4He solutions, the experimental and theoretical basis for the effective interaction between 3He quasiparticles is discussed Then the energy of the 3He quasiparticles, their chemical potential, and their dependence on the local density and velocity of the superfluid are treated A few brief remarks on a possible superfluid transition are made A discussion is given of the qualitative aspects of different types of dilution refrigerators: the “evaporation”-like continuous and single-cycle refrigerators and
TL;DR: In this article, a diagrammatic procedure is described by which the time dependence of the population of any level in a decay scheme of arbitrary complexity can be prescribed directly in terms of transition probabilities and initial populations without specifically solving the determining differential equations.
Abstract: A diagrammatic procedure is described, by which the time dependence of the population of any level in a decay scheme of arbitrary complexity can be prescribed directly in terms of transition probabilities and initial populations, without specifically solving the determining differential equations.