Gas flows through shallow T-junctions and parallel microchannel networks

We apply a recent extension of the Hele-Shaw scheme to analyze steady compressible viscous flows through micro T-junctions. The linearity of the problem in terms of an appropriately defined quadratic form of the pressure facilitates the definition of the viscous resistance of the configuration, relating the gas mass-flow rate to entrance and exit conditions. Furthermore, under rather mild restrictions, the performance of complex microchannel networks may be estimated through superposition of the contributions of multiple basic junction elements. This procedure is applied to an optimization model problem of a parallel microchannel network. The analysis and results are readily adaptable to incompressible flows

The microstructure and microtexture of zirconium oxide films studied by transmission electron backscatter diffraction and automated crystal orientation mapping with transmission electron microscopy

A detailed characterization of nanostructured thin zirconium oxide films formed during aqueous corrosion of a nuclear-grade zirconium alloy (Zircaloy-4) has been carried out by means of two novel, ultra-high-spatial-resolution grain mapping techniques, namely automated crystal orientation mapping in the transmission electron microscope (TEM) and transmission electron backscatter diffraction (t-EBSD). While the former provided excellent spatial resolution with the ability to identify tetragonal ZrO<sub>2</sub> grains as small as ∼5 nm, the superior angular resolution and unambiguous indexing with t-EBSD enabled verification of the TEM observations. Both techniques revealed that in a stress-free condition (TEM foil prepared by focused ion beam milling), the oxide consists mainly of well-oriented columnar monoclinic grains with a high fraction of transformation twin boundaries, which indicates that the transformation from tetragonal to monoclinic ZrO<sub>2</sub> is a continuous process, and that a significant fraction of the columnar grains transformed from stress-stabilized tetragonal grains with (0 0 1) planes parallel to the metal–oxide interface. The TEM analysis also revealed a small fraction of size-stabilized, equiaxed tetragonal grains throughout the oxide. Those grains were found to show significant misalignment from the expected (0 0 1) growth direction, which explains the limited growth of those grains. The observations are discussed in the context of providing new insights into corrosion mechanisms of zirconium alloys, which is of particular importance for improving service life of fuel assemblies used in water-cooled reactors

The challenge of remanufactured products: the role of returns policy and channel structure to reduce consumers' perceived risk

While remanufactured products represent an increasingly researched phenomenon in the literature, not much is known about consumers' understanding and acceptance of such products. This study explores this issue in the context of the theory of perceived risk (TPR), investigating return policy leniency and distribution channel choice as potential factors to foster remanufactured products' sales

Previously Taxed Property and the Federal Estate Tax

In 1918 Congress added to the then simple but rapidly proliferatingestate tax law a deduction for property previously taxed, the prototypeof today\u27s section 812(c).1 In recommending the new provision, theHouse Committee on Ways and Means said: It has come to the attention of the committee that persons closely related have died within such a short space of time that the same estate passing within a short period of time has been subjected to the estate tax, and thereby diminished unreasonably because of the short period within which the two levies have been made. For example, a husband dies leaving a large amount of property to his wife, an elderly woman, who dies within a few weeks after her husband\u27s death. Under existing law the entire estate is taxed on the transfer from husband to wife and on the transfer from wife to other beneficiaries. To alter this result the Committee recommended and Congress adopteda provision allowing the executor to deduct from the decedent\u27s grossestate any part thereof that was received by the decedent, directly or byexchange, from the taxable estate of any other person who had died withinthe previous five years. The provision was simple and straightforwar

Massive spinor fields in flat spacetimes with non-trivial topology

The vacuum expectation value of the stress-energy tensor is calculated for spin $1\over 2$ massive fields in several multiply connected flat spacetimes. We examine the physical effects of topology on manifolds such as $R^3 \times S^1$, $R^2\times T^2$, $R^1 \times T^3$, the Mobius strip and the Klein bottle. We find that the spinor vacuum stress tensor has the opposite sign to, and twice the magnitude of, the scalar tensor in orientable manifolds. Extending the above considerations to the case of Misner spacetime, we calculate the vacuum expectation value of spinor stress-energy tensor in this space and discuss its implications for the chronology protection conjecture.Comment: 18 pages, Some of the equations in section VI as well as typographical errors corrected, 5 figures, Revtex

We Could, but Should We? Ethical Considerations for Providing Access to GeoCities and Other Historical Digital Collections

We live in an era in which the ways that we can make sense of our past are evolving as more artifacts from that past become digital. At the same time, the responsibilities of traditional gatekeepers who have negotiated the ethics of historical data collection and use, such as librarians and archivists, are increasingly being sidelined by the system builders who decide whether and how to provide access to historical digital collections, often without sufficient reflection on the ethical issues at hand. It is our aim to better prepare system builders to grapple with these issues. This paper focuses discussions around one such digital collection from the dawn of the web, asking what sorts of analyses can and should be conducted on archival copies of the GeoCities web hosting platform that dates to 1994.This research was supported by the Natural Sciences and Engineering Research Council of Canada, the Social Sciences and Humanities Research Council of Canada, the US National Science Foundation (grants 1618695 and 1704369), the Andrew W. Mellon Foundation, Start Smart Labs, and Compute Canada

Analytic solutions of the 1D finite coupling delta function Bose gas

An intensive study for both the weak coupling and strong coupling limits of the ground state properties of this classic system is presented. Detailed results for specific values of finite $N$ are given and from them results for general $N$ are determined. We focus on the density matrix and concomitantly its Fourier transform, the occupation numbers, along with the pair correlation function and concomitantly its Fourier transform, the structure factor. These are the signature quantities of the Bose gas. One specific result is that for weak coupling a rational polynomial structure holds despite the transcendental nature of the Bethe equations. All these new results are predicated on the Bethe ansatz and are built upon the seminal works of the past.Comment: 23 pages, 0 figures, uses rotate.sty. A few lines added. Accepted by Phys. Rev.

Eigenvalue Separation in Some Random Matrix Models

The eigenvalue density for members of the Gaussian orthogonal and unitary ensembles follows the Wigner semi-circle law. If the Gaussian entries are all shifted by a constant amount c/Sqrt(2N), where N is the size of the matrix, in the large N limit a single eigenvalue will separate from the support of the Wigner semi-circle provided c > 1. In this study, using an asymptotic analysis of the secular equation for the eigenvalue condition, we compare this effect to analogous effects occurring in general variance Wishart matrices and matrices from the shifted mean chiral ensemble. We undertake an analogous comparative study of eigenvalue separation properties when the size of the matrices are fixed and c goes to infinity, and higher rank analogues of this setting. This is done using exact expressions for eigenvalue probability densities in terms of generalized hypergeometric functions, and using the interpretation of the latter as a Green function in the Dyson Brownian motion model. For the shifted mean Gaussian unitary ensemble and its analogues an alternative approach is to use exact expressions for the correlation functions in terms of classical orthogonal polynomials and associated multiple generalizations. By using these exact expressions to compute and plot the eigenvalue density, illustrations of the various eigenvalue separation effects are obtained.Comment: 25 pages, 9 figures include