X-ray photoemission and the electronic structure of solids

The principles of X-ray photoelectron spectroscopy are outlined. The application of this technique to the study of the electronic structure of metals, alloys and compounds is illustrated using data in Ag, β-brass, ReO₃ and VO₂. In the latter a major change in the density of states is observed on passing through the metal-insulator transition.     

The magic angle and all that: probing the structure of solids using nuclear magnetic resonance

It has been known for some 25 years that much improved resolution of NMR spectra of solids can be achieved if the sample is rotated rapidly at a ‘magic’ angle of 54 °44′ to the magnetic field. However, the full potential of the method has been realised only within the past few years, largely because of the technical difficulties of establishing the correct conditions experimentally. It can now be applied to a wide range of problems in chemistry, materials science, and biology.     

The diffusion of moisture in sorbent solids part II. activated alumina

Ordinary and thermal diffusion of moisture in activated alumina are investigated using a new diffusion cell design and scheme of analysis reported earlier. The specific form of the mass flux equation has a pronounced effect on the magnitude of the associated thermal diffusion ratio. In the case of activated alumina-moist air, if a partial pressure gradient is used, then the thermal diffusion term is small if not zero.Free, Knudsen and surface diffusion all play a part in the diffusion through activated alumina. However, surface diffusion makes the major contribution and for this reason the model in this case can be simplified to a two parameter surface model.The activation energy for surface diffusion is constant and is approximately equal to the mean isosteric heat of absorption. In addition, mean pore radius, turtuosity, and other physical constants are computed from the least square fit of experimental data. Furthermore, the model is theoretically consistent over the entire concentration range (0≦ C_A ≦ C_Asat).A new fact about activated alumina (Grade F1) it that it does not transfer moisture in a nonisothermal condition so long as the partial pressures of moisture on the two sides of the pellet are the same. There appears to be no previous report of this fact in the periodical literature.     

The structure of invention

This paper explores the process by which radically novel technologies - ones such as radar, the turbojet, or the polymerase chain reaction - come into being. It shows that this process - “invention” - has a certain logical structure common to all cases. Invention is a process of linking some purpose or need with an effect that can be exploited to satisfy it. It may begin with a purpose or need for which existing methods are not satisfactory; this forces the seeking of a new principle (the idea of an effect in action). Or it may begin with a phenomenon or effect itself - usually a freshly discovered one - for which some associated principle of use suggests itself. Either way, translating this base principle into physical reality requires the creation of suitable working parts and supporting technologies. These raise their own challenges or problems, the solution of which may raise further challenges. As a result, invention is a recursive process: it repeats until each challenge or problem (and subproblem, and sub-subproblem) resolves itself into one that can be physically dealt with. It is challenging, usually lengthy, part-conceptual, and part-experimental.     

The coefficient of resistance as a function of Reynolds number for solids of various shapes

The purpose of the present article is twofold. First it is an attempt to show the usefulness of the degree of true sphericity as an expression for shape of rock particles. Second it is intended as a background for a new, analytical, sedimentographic method to be given in a forthcoming paper. Any radical variation in shape influences the numerical value of the degree of true sphericity and affects the size of the surface area, the size of the largest cross-sectional area and the degree of circularity of a great number of cross-sections of a solid. These factors determine to a large extent the settling velocity of that solid. The resistance of wholly submerged bodies, as a theoretical foundation for determining the coefficient of resistance as a function of Reynolds number for solids of different degree of sphericity, is discussed. The influence of the degree of circularity on the resistance is then shown by graphs constructed on the basis of available data. Formulæ for calculating the coefficient of resistance and Reynolds number are introduced and their practical value demonstrated by graphic illustrations. The sedimentological significance and usefulness of the results are discussed.     

The diffusion of moisture in sorbent solids—I. Diffusion cell and pore diffusion

A complete theory of diffusion of absorbing gases in porous solids is developed. Both ordinary and thermal diffusion are considered. The thermodynamics of irreversible processes is used to derive the general flux equations.A new theoretical model of surface diffusion is presented. Moreover, the proper method of combining surface and gas-phase fluxes is established. The total flux in the pores is represented by a 5 parameter model, which includes the effects of (1) free (gaseous) diffusion, (2) Knudsen diffusion, and (3) surface diffusion.The design of a new diffusion cell is presented along with a stagewise method for analyzing results. The cell is unique in that specimens mounted in copper clad circuit board material permits nonisothermal as well as isothermal operation. Earlier designs were confined to isothermal operation due to mounting specimens in metallic materials such as brass and aluminum.     

国外产业结构转型理论述评

产业结构与经济增长具有密切的双向因果关系。文章从需求和供给两个角度以及最新的进展方面对产业结构转型这一领域的研究进行了梳理。其中,需求角度的产业结构转型主要是收入增长和多样化、专业化的需求导致的;供给角度的产业转型则基于农业和工业生产率的提高。政策、制度以及人力资本的积累会影响到产业转型。该理论的最新进展是围绕着同时考虑供给和需求面对产业转型的影响以及考虑符合卡尔多Kaldor事实的产业结构转型两个方面展开的。