Working Materials Research Articles

Low hysteresis materials for magnetic refrigeration: Gd1−xErxAl2

The series of ferromagnetic intermetallics Gd1−x ErxAl2 are candidate working materials for magnetic refrigeration because of their large moment, small anisotropy, and their wide range of Curie temperatures (14 to 164 K). We have measured the magnitude of the magnetic hysteresis as a function of temperature from 4 K to TC for polycrystalline samples of these materials by ac magnetic susceptibility and magnetization hysteresis loops. We found, as expected, virtually no hysteresis in GdAl2, and, more surprisingly, less than 3000 A/m hysteresis in ErAl2 and 2×104 A/m in Gd0.5 Er0.5Al2. Moreover, the hysteresis in Gd0.5 Er0.5Al2 was <100 A/m for T−TC< 20 K.

Applied mechanics and the modern string instrument—Classical guitar

The design of string instruments is approached formally as a problem of three coupled oscillators: (a) the vibrating plate with appropriate boundary conditions, (b) the real string with characteristic anharmonicity and end-stiffness, and (c) the cavity resonance spectra with their body-form determined complexities. Instrument models are then constructed based on the fundamental approach, with all of the compromises required by classical dimension and form limitations, as well as the draftsman's working methods and materials. Acoustical measurements are made to demonstrate the effectiveness of the designs, and finally, concert musician acceptance in concert hall conditions is evaluated. The collaboration of Richard Schneider, luthier, and Dr. E. E. Watson, acoustician, is gratefully acknowledged.

Materials for magnetic refrigeration between 2 K and 20 K

As part of a research and development programme on magnetic refrigeration, paramagnetic materials suitable for magnetic refrigeration in the 2 to 20 K range have been studied. The bestgadolinium materials with known properties, as derived from a literature survey, are plotted. For one of those materials, gadolinium gallium garnet, we present the results of our field-dependent heat capacity measurements. Preparation and fabrication of gadolinium compounds are discussed briefly as well as the scope for further work for selecting and studying working materials for magnetic refrigeration.

Fabrication of liquid-metal working materials for radiation loops

Fabrication of liquid-metal working materials for radiation loops

Disintegration of plasmogenic dielectric working materials in pulsed plasma accelerators

The mechanism is studied by which dielectric (Teflon) inserts in pulsed plasma accelerators disintegrate. The local-bulk character of this disintegration, which is revealed here, indicates that thermal radiation fluxes play a predominant role in this process.

The Contamination of Liquid Nitrogen by Oxygen of the Air

THE explosion hazards involved in the use of liquid air probably are not as well appreciated as they might be. Such a simple material as cotton waste will burn almost explosively in the proper conditions when ignited and liquid air is poured over it. Almost any reducing reagent can form an explosive mixture with liquid air, and in general it is safe to say that most hydrocarbons when mixed with liquid air are potentially very hazardous. Naturally most people use liquid air around a metal or glass trap containing their particular working materials, and the only hazard here is the question of strength of the trap. Unfortunately too many times such traps have broken for one reason or another. Oxygen-free liquid nitrogen, which is available on the market and may be used instead is commonly believed to introduce a similar hazard due to contamination of the coolant with oxygen from the atmosphere during storage and ...

New Phases in the Study of Primitive Music

W HEN we attempt to study art, or especially to describe an art to those unfamiliar with it, we find that, while it is comparatively easy to discuss colors, materials, and subjects, a brief and satisfactory characterization of its style is exceedingly difficult of accomplishment. Yet it is this very style that so completely distinguishes the work of one artist or group from that of another, much more than employment of pigments or other materials, or subjects chosen for expression. Exactly the same condition exists in music. All the arts have certain features in common, in that they are supplied at the outset by nature with certain working materials and it is quite possible that over wide areas the same or very similar elements may be encountered. But it is the way in which the artists play with the material that is furnished that gives us the styles, and it seems to me that the most important of the plays is not the selection from the mass of materials of those which the artist favors, for usually all that are available are chosen at one time or another, but the patterns or designs that the artist creates from them. When local styles become sufficiently fashionable and fixed they form types. They may be the result of the acceptance by many of sudden departures from other types (and I think this fact is not often taken sufficiently into consideration), or they may mark the gradual accumulation of lesser divergences. This whole question of the growth of variants and the determinants of the beginnings of new styles, while recognized as important by many thoughtful students, has not, for lack of time and sufficient material from which to draw, been as yet adequately studied. Nor do we always detect the influence of religion upon artendeavor, which has too often resulted in its marked restraint or warping, a fact not only evident in primitive arts, but even in classical arts and in that of Christianity.

Analyzing, Grading and Valuing Operations in a Modern Manufacturing Organization

THE following is a description of the procedure followed by a Massachusetts corporation in wage determination. So much of the plan is dependent upon the company's policies and the conditions of work provided, that it is impossible to judge as to its merits without some portrayal of these two factors. The determination of wages of foremen and other members of the management involves special consideration, so this article will deal only with the plan followed in regard to factory and clerical employes. The factory itself is highly organized. By this is meant not so much that there is an extreme subdivision of labor, as that a clean-cut definition has been made of the responsibilities of the management, of its various members, and of the responsibilities and the nature of the work of each of its employes. For the most part production is planned by members of the organization who have been trained in this function of management, thus leaving the foremen and his assistants more free to attend to problems of personnel. As a consequence, working conditions are much more attractive than they are apt to be when the planning of work is left to the foreman and his assistants. In the majority of operations, methods of work have been most carefully analyzed and the details of the jobs are specified, as are also the working conditions and materials. The tools, equipment and materials described in the specifications are so far as possible the best obtainable for the task and the product, and it is somebody's to see that all these requirements are according to standard, and provided in the place and at the time they are needed. The practice of issuing job tickets with these specifications and instructions for all work done, is accepted as a principle, and is being xtended as rapidly as possible throughout the organization. There are limitations, of course,-in human ability, in the planning operations and in materials provided. There is the innate perversity of inanimate things-no one realizes this better than the engineer who makes it his work to reduce these limitations in some measure. But the extent to which work and working conditions may be improved by men trained in r search in various fields is far beyond the average practice of today. This company has built up its business on a reputation for a fine quality of product, and this tradition of quality has influenced general working conditions in the plant to a marked degree. The neatness and comfort of work rooms and the type of people in the company's employ are such as would be expected in consequence of this insistence upon quality during a great many years' operation.