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Physical Concepts (physical + concept)
Selected AbstractsInterface Engineering of Inorganic Thin-Film Solar Cells , Materials-Science Challenges for Advanced Physical ConceptsADVANCED MATERIALS, Issue 42 2009Wolfram Jaegermann Abstract The challenges and research needs for the interface engineering of thin-film solar cells using inorganic-compound semiconductors are discussed from a materials-science point of view. It is, in principle, easily possible to define optimized device structures from physical considerations. However, to realize these structures, many materials' limitations must be overcome by complex processing strategies. In this paper, interface properties and growth morphology are discussed using CdTe solar cells as an example. The need for a better fundamental understanding of cause,effect relationships for improving thin-film solar cells is emphasized. [source] Electron correlation: The many-body problem at the heart of chemistryJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 8 2007David P. Tew Abstract The physical interactions among electrons and nuclei, responsible for the chemistry of atoms and molecules, is well described by quantum mechanics and chemistry is therefore fully described by the solutions of the Schrödinger equation. In all but the simplest systems we must be content with approximate solutions, the principal difficulty being the treatment of the correlation between the motions of the many electrons, arising from their mutual repulsion. This article aims to provide a clear understanding of the physical concept of electron correlation and the modern methods used for its approximation. Using helium as a simple case study and beginning with an uncorrelated orbital picture of electronic motion, we first introduce Fermi correlation, arising from the symmetry requirements of the exact wave function, and then consider the Coulomb correlation arising from the mutual Coulomb repulsion between the electrons. Finally, we briefly discuss the general treatment of electron correlation in modern electronic-structure theory, focussing on the Hartree-Fock and coupled-cluster methods and addressing static and dynamical Coulomb correlation. © 2007 Wiley Periodicals, Inc. J Comput Chem 28: 1307,1320, 2007 [source] Sedimentation behaviour and turbidity of carrot juices in relation to the characteristics of their cloud particlesJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 8 2003Martin Reiter Abstract The cloud stability of carrot juices was investigated using physical methods. In contrast to cloudy juices from fruits or other vegetables described so far, complete clarification of juice samples could not be achieved even after ultracentrifugation. Since the density of one particle fraction was almost equal to that of the continuous phase, this fraction was resistant to sedimentation by centrifugal forces up to 60 600 × g in an 8° Brix carrot juice. Cloud stability problems of carrot juices, therefore, are usually associated with bottom sediment formation, but not with visible loss of turbidity. Particle size and density were shown to be decisive for suspension stability, whilst both particle charge and serum viscosity did not show any effect on cloud stability. The reasons for the exceptional stability of the suspended particles are discussed. Based on three particle fractions, a new physical concept could be deduced according to particle size and density explaining the extraordinary suspension stability of carrot juices. Copyright © 2003 Society of Chemical Industry [source] Thin Film Solar Cells: Materials Science at InterfacesADVANCED ENGINEERING MATERIALS, Issue 10 2005J. Fritsche Abstract Interfaces are important for the efficiencies of thin film solar cells. In particular for polycrystalline chalcogenide semiconductors as Cu(In,Ga)(S,Se)2 and CdTe the existing physical concepts, which describe the electronic properties of semiconductor interfaces, are not sufficient. The increased complexity is mostly due to the non-abruptness of the interfaces and the strong tendency for the formation of defects. For the CdTe thin film solar cell a very relevant interface for their operation and efficiency is the CdTe/CdS semiconductor hetero junction. The properties of the semiconductor interfaces have been characterised systematically with photoelectron spectroscopy (XPS/UPS) in integrated ultra high vacuum (UHV) systems for sample preparation and analysis. Withal the key topic is the experimental determination of the band alignment at the semiconductor interfaces. For high efficiency CdTe solar cell production CdCl2 activation is of major importance. The effects of the CdCl2 treatment step on CdTe solar cells had been not completely understood so far. To investigate its influence the activation process has been transferred into the integrated UHV system. We will report about chemical and electronic modifications of the CdTe/CdS hetero interface due to in-situ CdCl2 activation performing sputter depth profiles in combination with X-ray photoelectron spectroscopy (XPS). [source] Is Conceptual Analysis Needed for the Reduction of Qualitative States?PHILOSOPHY AND PHENOMENOLOGICAL RESEARCH, Issue 3 2002JANET LEVIN In this paper I discuss the claim (advanced in various ways by Joseph Levine, Frank Jackson and David Chalmers) that the successful reduction of qualitative to physical states requires some sort of intelligible connection between our qualitative and physical concepts, which in turn requires a conceptual analysis of our qualitative concepts in causal-functional terms. While I defend this claim against some of its recent critics, I ultimately dispute it, and propose a different way to get the requisite intelligible connection between qualitative and physical concepts. [source] Optical characterization of concentrated dispersions: applications to laboratory analyses and on-line process monitoring and control,POLYMER INTERNATIONAL, Issue 9 2004H Buron Abstract Light scattering methods are often used to study the stability of suspensions or emulsions and to estimate the dispersed phase properties such as particle size and volume fraction. However, such optical methods often require a previous dilution of the dispersion because of a limited measurement range, and are then unable to give information about the real physical state of dense heterogeneous media. A new technology based on multiple light scattering analysis and called Turbiscan has been recently developed by a French company, Formulaction, to fill this gap and to characterize both diluted and concentrated dispersions. In the first part, we review the physical concepts of multiple light scattering by dispersions. In relation to the optical analyser Turbiscan, we present physical and statistical models for the radiative transfer in dense suspensions. In the second part, we investigate the influence of particle volume fraction and particle size (polystyrene latex bead suspensions) on the backscattered and transmitted light fluxes measured by Turbiscan. The experimental data are compared with results from the physical models. In the last section, we use the optical analyser Turbiscan Lab to detect and characterize various concentrated dispersions destabilization (coalescence, flocculation, creaming and sedimentation), and then the Turbiscan On Line to monitor and characterize an emulsification process under ultrasonic agitation. Copyright © 2004 Society of Chemical Industry [source] The Analogy between Light and Sound in the History of Optics from the ancient Greeks to Isaac Newton.CENTAURUS, Issue 3 2010Part Analogies between hearing and seeing already existed in ancient Greek theories of perception. The present paper follows the evolution of such analogies until the rise of 17th century optics, with due regard to the diversity of their origins and nature but with particular emphasis on their bearing on the physical concepts of light and sound. Whereas the old Greek analogies were only side effects of the unifying concepts of perception, the analogies of the 17th century played an important role in constructing optical theories by imitation of acoustic theories, or vice versa. This transition depended on several factors including the changing relations between optics, music, mathematics, and physics, the diversity of early modern concepts of sound, and the rise of a new physics based on experimentation and mechanical explanation. [source] The Analogy between Light and Sound in the History of Optics from the Ancient Greeks to Isaac Newton.CENTAURUS, Issue 2 2010Part Analogies between hearing and seeing already existed in ancient Greek theories of perception. The present paper follows the evolution of such analogies until the rise of 17th century optics, with due regard to the diversity of their origins and nature but with particular emphasis on their bearing on the physical concepts of light and sound. Whereas the old Greek analogies were only side effects of the unifying concepts of perception, the analogies of the 17th century played an important role in constructing optical theories by imitation of acoustic theories, or vice versa. This transition depended on several factors including the changing relations between optics, music, mathematics, and physics, the diversity of early modern concepts of sound, and the rise of a new physics based on experimentation and mechanical explanation. [source] | ||||||||||||||||