Fixed Number and Quantum Size Effects in Nanoscale Superconductors

In recent experiments on nanoscale Al particles, whose electron number was fixed by charging effects, a ``negative gap'' was observed in particles with an odd number of electrons. This observation has called into question the use of a grand canonical ensemble in describing superconductivity in such ultrasmall particles. We have studied the effects of fixed electron number and finite size in nanoscale superconductors, by applying the canonical BCS theory for the attractive Hubbard model. The ground state energy and the energy gap are compared with the conventional and parity-projected grand canonical BCS results, and in one dimension also with the exact solutions by the Bethe ansatz. The crossover from the bulk to quantum limit is studied for various regimes of electron density and coupling strength. The effects of boundary conditions and different lattice structures are also examined. A ``negative gap'' for odd electron number emerges most naturally in the canonical scheme. For even electron number, the gap is particularly large for ``magic numbers'' of electrons for a given system size or of atoms for a fixed electron density. These features are in accordance with the exact solutions, but are essentially missed in the grand canonical results.Comment: 2 pages, 4 figures, submitted to Physica C for M2S-HTSC-VI Proceeding

Vortex generator design for aircraft inlet distortion as a numerical optimization problem

Aerodynamic compatibility of aircraft/inlet/engine systems is a difficult design problem for aircraft that must operate in many different flight regimes. Takeoff, subsonic cruise, supersonic cruise, transonic maneuvering, and high altitude loiter each place different constraints on inlet design. Vortex generators, small wing like sections mounted on the inside surfaces of the inlet duct, are used to control flow separation and engine face distortion. The design of vortex generator installations in an inlet is defined as a problem addressable by numerical optimization techniques. A performance parameter is suggested to account for both inlet distortion and total pressure loss at a series of design flight conditions. The resulting optimization problem is difficult since some of the design parameters take on integer values. If numerical procedures could be used to reduce multimillion dollar development test programs to a small set of verification tests, numerical optimization could have a significant impact on both cost and elapsed time to design new aircraft

DEVELOPMENT AT THE URBAN FRINGE AND BEYOND: IMPACTS ON AGRICULTURE AND RURAL LAND

Land development in the United States is following two routes: expansion of urban areas and large-lot development (greater than 1 acre per house) in rural areas. Urban expansion claimed more than 1 million acres per year between 1960 and 1990, yet is not seen as a threat to most farming, although it may reduce production of some high-value or specialty crops. The consequences of continued largelot development may be less sanguine, since it consumes much more land per unit of housing than the typical suburb. Controlling growth and planning for it are the domains of State and local governments. The Federal Government may be able to help them in such areas as building capacity to plan and control growth, providing financial incentives for channeling growth in desirable directions, or coordinating local, regional, and State efforts.land development, sprawl, large-lot housing, land zoning, population growth, housing, specialty agriculture, high-value agriculture, rural amenities, smart growth, Land Economics/Use,

Electronic Shell Structure of Nanoscale Superconductors

Motivated by recent experiments on Al nanoparticles, we have studied the effects of fixed electron number and small size in nanoscale superconductors, by applying the canonical BCS theory for the attractive Hubbard model in two and three dimensions. A negative ``gap'' in particles with an odd number of electrons as observed in the experiments is obtained in our canonical scheme. For particles with an even number of electrons, the energy gap exhibits shell structure as a function of electron density or system size in the weak-coupling regime: the gap is particularly large for ``magic numbers'' of electrons for a given system size or of atoms for a fixed electron density. The grand canonical BCS method essentially misses this feature. Possible experimental methods for observing such shell effects are discussed.Comment: 5 pages, 5 figure

Single Source of Error State Space Approach to the Beveridge Nelson Decomposition

A well known property of the Beveridge Nelson decomposition is that the innovations in the permanent and transitory components are perfectly correlated. We use a single source of error state space model to exploit this property and perform a Beveridge Nelson decomposition. The single source of error state space approach to the decomposition is computationally simple, and in contrast to other methods of performing the Beveridge-Nelson decomposition, it incorporates the direct estimation of the long-run multiplier.Beveridge Nelson decomposition; Long-run multiplier; Single source of error; State-space models.

Philosophy of Human Nature as a Function of Political Preference, Political Involvement, and Age

The present study used the Philosophy of Human Nature (PHN) Scale and a 2X2X2 factorial design with party preference, level of political involvement, and age as the three main effects to test twelve specific hypotheses. One hundred twenty subjects were randomly selected from among the Democratic and Republican parties of Kittitas County and students from Central Washington State College, and the PHN Scale was administered to them

Direct costing

Thesis (M.B.A.)--Boston UniversityAccounting as a profession has made outstanding progress up through the mid-years of the century. Notwithstanding that it has grown from historical record-keeping to a functional position indispensable in the conduct of business, today1s era of accelerated technological achievement and industrial expansion places continued challenging demands for accounting research leading to still more valuable contributions. An examination of accounting association, publications provides ample evidence of professional interest in such research. From the matrix of accounting self appraisal, dissatisfaction, investigation and trial, there have been many business oriented concepts or techniques generated which have found their way into acceptable accounting procedure. One that is in such transition today is direct costing. In past years accounting techniques have become increasingly complex, obscuring simple cost, volume, and profit relationships. Meanwhile, the tremendous technological strides in industry have resulted in the placement of many engineers, scientists, and other non-financially trained persons in top management positions. As a result of these trends, many of today 1s executives do not fully understand accounting methods and the resultant information which comprise some of their tools for decision-making. The need exists for accounting systems which are simple and show fundamental relationships readily. Direct costing fulfills these requirements

A theory of interpersonal trust in the communication of small task-oriented groups

Thesis (M.A.)--University of Kansas, Speech and Drama, 1968