Popular matchings: structure and algorithms

An instance of the popular matching problem (POP-M) consists of a set of applicants and a set of posts. Each applicant has a preference list that strictly ranks a subset of the posts. A matching M of applicants to posts is popular if there is no other matching M' such that more applicants prefer M' to M than prefer M to M'. This paper provides a characterization of the set of popular matchings for an arbitrary POP-M instance in terms of a structure called the switching graph, a directed graph computable in linear time from the preference lists. We show that the switching graph can be exploited to yield efficient algorithms for a range of associated problems, including the counting and enumeration of the set of popular matchings and computing popular matchings that satisfy various additional optimality criteria. Our algorithms for computing such optimal popular matchings improve those described in a recent paper by Kavitha and Nasre

The effect of thermal diffusion on the formation of interface resistance on oxide-coated cathodes.

Thesis (M.A.)--Boston UniversityThe goal of this investigation is to determine many of the factors which contribute to cathode interface resistance formation in a commercial type twin triode and to analyze these factors quantitatively by well known chemical and physical methods, However, since the vacuum tube represents such a complex system it is necessary to introduce this problem by reference to early history and many of the parameters associated with vacuum tube manufacture. With reference to historical introduction, the electron theory of metals, with special emphasis on the role which work function plays, is discussed. [TRUNCATED

Analytical Investigation of Some Three-Dimensional Flow Problems in Turbomachines

One problem encountered in the theory of turbomachines is that of calculating the fluid velocity components when the inner and outer boundaries of the machine as well as the shape of or forces imparted by the blade row are given. The present paper discusses this problem under the restrictions that the fluid is inviscid and incompressible and that the blade rows consist of an infinite number of infinitely thin blades so that axially symmetric flow is assumed. It is shown, in general, that the velocity components in a plane through the turbomachine axis may be expressed in terms of the angular momentum and the leading-edge blade force normal to the stream surfaces. The relation is a nonlinear differential equation to which analytic solutions may be obtained conveniently only after the introduction of linearizing assumptions. A quite accurate linearization is effected through assuming an approximate shape of the stream surfaces in certain nonlinear terms. The complete linearized solution for the axial turbomachine is given in such form that blade loading, blade shape, distribution of angular momentum, or distribution of total head may be prescribed. Calculations for single blade rows of aspect ratio 2 and 2/3 are given for a radius ratio of 0.6. They indicate that the process of formation of the axial velocity profile may extend both upstream and downstream of a high-aspect-ratio blade row, while for low aspect ratios the major portion of the three-dimensional flow occurs within the blade row itself. When the through-flow velocity varies greatly from its mean value, the simple linearized solution does not describe the flow process adequately and a more accurate solution applicable to such conditions is suggested. The structure of the first-order linearized solution for the axial turbomachine suggested a further approximation employing a minimizing operation. The simplicity of this solution permits the discussion of three interesting problems: Mutual interference of neighboring blade rows in a multistage axial turbomachine, solution for a single blade row of given blade shape, and the solution for this blade row operating at a condition different from the design condition. It is found that the interference of adjacent blade rows in the multistage turbomachine may be neglected when the ratio of blade length to the distance between centers of successive blade rows is 1.0 or less. For values of this ratio in excess of 3.0, the interference may be an important influence. The solution for the single blade row indicated that, for the blade shape considered, the distortion of the axial velocity profile caused by off-design operation is appreciably less for low- than for high-aspect-ratio blades. To obtain some results for a mixed-flow turbomachine comparable with those for the axial turbomachine as well as to indicate the essential versatility of the method of linearizing the general equations, completely analogous theoretical treatment is given for a turbomachine whose inner and outer walls are concentric cones with common apex and whose flow is that of a three-dimensional source or sink. A particular example for a single rotating blade row is discussed where the angular momentum is prescribed similarly to that used in the examples for the axial turbomachine

U.S.-Owned Affiliates and Host-Country Exports

U.S.-owned manufacturing affiliates in foreign countries tended to become more export-oriented between 1966 and 1977. The shift toward exporting characterized affiliates in most industries and most countries.The bulk of U.S.-owned production abroad continues to be for local sale in most industries and areas. Exporting to the U.S. remains a small part of affiliate activities in almost all cases. The most export-oriented were subsidiaries in machinery industries in Southeast Asia which were also the only ones outside Canada that sold a substantial part of their production in the U.S. In most industries and most countries U.S.-owned companies led the rise in exports and increased their shares in the exports of their host countries. This role of U.S. subsidiaries was particularly notable in Southeast Asia,and in those countries was concentrated in the machinery industry. The increasing share of U.S. affiliates in host-country exports was quite a general phenomenon, however, and high rates of affiliate export growth were associated with rapid growth of host country GDP and exports.

Prices and Terms of Trade for Developed-Country Exports of Manufactured Goods

The purpose of this paper is to contribute some new measurements to t112 discussion of trends in the terms of trade between manufactured goods exports of developed countries and primary product exports of developing countries. The new measures are manufactured goods price indexes that are derived from price data rather than from unit value data and include some corrections for quality change. Our calculations indicate that the prices of manufactured goods exported by developed countries to developing countries have risen over twenty years or so by 75 per cent, as compared to the 140 per cent shown by the generally used UN unit value indexes. The decline in terms of trade for these goods relative to primary products has been almost 50 per cent over this period. Over tile last hundred years, fluctuations in the terms of trade of manufactured goods relative to primary products !lave been very wide, as far as we can tell from the inadequate measures we have. Impressions about trends have been highly dependent on choices of beginning and end years. There is very little evidence for a long-run trend in either direction.

The Effect of Multinational Firms' Operations on Their Domestic Employment

Given the level of its production in the U.S., a firm that produces more abroad tends to have fewer employees in the U.S. and to pay slightly higher salaries and wages to them. The most likely explanation seems to be that the larger a firm's foreign production, the greater its ability to allocate the more labor-intensive and less skill-intensive portions of its activity to locations outside the United States. This relationship is stronger among manufacturing firms than among service industry firms, probably because services are less tradable than manufactured goods or components, and service industries may therefore be less able to break up the production process to take advantage of differences in factor prices.