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Institution

University of Wisconsin–Milwaukee

EducationMilwaukee, Wisconsin, United States
About: University of Wisconsin–Milwaukee is a education organization based out in Milwaukee, Wisconsin, United States. It is known for research contribution in the topics: Population & Gravitational wave. The organization has 11839 authors who have published 28034 publications receiving 936438 citations. The organization is also known as: UWM & University of Wisconsin-Milwaukee.


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Journal ArticleDOI
TL;DR: The conclusion of this paper is that CTC’s may not be as nasty as people have assumed, and is reinforced by the fact that they do not affect Gauss’'s theorem and thus do not affected the derivation of global conservation laws from differential ones.
Abstract: The laws of physics might permit the existence, in the real Universe, of closed timelike curves (CTC’s). Macroscopic CTC’s might be a semiclassical consequence of Planck-scale, quantum gravitational, Lorentzian foam, if such foam exists. If CTC’s are permitted, then the semiclassical laws of physics (the laws with gravity classical and other fields quantized or classical) should be augmented by a principle of self-consistency, which states that a local solution to the equations of physics can occur in the real Universe only if it can be extended to be part of a global solution, one which is well defined throughout the (nonsingular regions of) classical spacetime. The consequences of this principle are explored for the Cauchy problem of the evolution of a classical, massless scalar field Φ (satisfying □Φ=0) in several model spacetimes with CTC’s. In general, self-consistency constrains the initial data for the field Φ. For a family of spacetimes with traversible wormholes, which initially possess no CTC’s and then evolve them to the future of a stable Cauchy horizon scrH, self-consistency seems to place no constraints on initial data for Φ that are posed on past null infinity, and none on data posed on spacelike slices which precede scrH. By contrast, initial data posed in the future of scrH, where the CTC’s reside, are constrained; but the constraints appear to be mild in the sense that in some neighborhood of every event one is free to specify initial data arbitrarily, with the initial data elsewhere being adjusted to guarantee self-consistent evolution. A spacetime whose self-consistency constraints have this property is defined to be ‘‘benign with respect to the scalar field Φ.’’ The question is posed as to whether benign spacetimes in some sense form a generic subset of all spacetimes with CTC’s. It is shown that in the set of flat, spatially and temporally closed, 2-dimensional spacetimes the benign ones are not generic. However, it seems likely that every 4-dimensional, asymptotically flat space-time that is stable and has a topology of the form R×(S-one point), where S is a closed 3-manifold, is benign. Wormhole spacetimes are of this type, with S=S^1×S^2. We suspect that these types of self-consistency behavior of the scalar field Φ are typical for noninteracting (linearly superposing), classical fields. However, interacting classical systems can behave quite differently, as is demonstrated by a study of the motion of a hard-sphere billiard ball in a wormhole spacetime with closed timelike curves: If the ball is classical, then some choices of initial data (some values of the ball’s initial position and velocity) give rise to unique, self-consistent motions of the ball; other choices produce two different self-consistent motions; and others might (but we are not yet sure) produce no self-consistent motions whatsoever. By contrast, in a path-integral formulation of the nonrelativistic quantum mechanics of such a billiard ball, there appears to be a unique, self-consistent set of probabilities for the outcomes of all measurements. This paper’s conclusion, that CTC’s may not be as nasty as people have assumed, is reinforced by the fact that they do not affect Gauss’s theorem and thus do not affect the derivation of global conservation laws from differential ones. The standard conservation laws remain valid globally, and in asymptotically flat, wormhole spacetimes they retain a natural, quasilocal interpretation.

204 citations

Journal ArticleDOI
09 Jun 1972-Science
TL;DR: Phonemic restorations appear to be a specialized application to speech of the much broader phenomenon of auditory induction, which helps maintain stable auditory perception in the authors' frequently noisy environment.
Abstract: Within certain auditory patterns, fainter sounds may be "heard" clearly when replaced by louder sounds having appropriate spectral compositions. This auditory induction of fainter by louder sounds can cancel the perceptual effects of masking. Phonemic restorations, which have been reported previously, appear to be a specialized application to speech of the much broader phenomenon of auditory induction. The rules governing auditory induction indicate that it helps maintain stable auditory perception in our frequently noisy environment.

204 citations

Journal ArticleDOI
TL;DR: This article tested the validity of two implicational universals regarding consonant clusters regarding non-primary languages and found that they hold also for nonprimary languages such as Chinese, Japanese, or Korean.
Abstract: The validity of two implicational universals regarding consonant clusters was tested in an analysis of the interlanguage of 11 subjects who were native speakers of Chinese, Japanese, or Korean. The results were strongly supportive of the two universals, suggesting the possibility that primary language universals hold also for nonprimary languages.

204 citations

Journal ArticleDOI
TL;DR: In this paper, the morphology, composition and crystallinity of both precipitator and cenosphere fly ash particles of different sizes were studied with scanning electron microscopy (SEM), EDX, and X-ray diffraction (XRD).
Abstract: The morphology, composition and crystallinity of both precipitator (solid) and cenosphere (hollow) fly ash particles of different sizes were studied with scanning electron microscopy (SEM), EDX, and X-ray diffraction (XRD). Bulk density, tap density and real density of both precipitator and cenosphere particles of different sizes as well as the wall thickness to diameter ratio of cenosphere particles were measured. The microhardness of individual fly ash particles embedded in the matrix of aluminum alloy was also measured. The crystalline to amorphous ratio weight percentage in fly ash particles, and the weight or volume fraction of each crystalline component varies with the particle size. The crystallinity of precipitator particles increased as the particle size increases, whereas the crystallinity of cenosphere decreased as the particle size increases. The elastic modulus of fly ash was estimated from the crystallinity of fly ash and the volume fraction of each component, using the rule of mixtures. The calculated upper limits for Young's modulus of precipitator particles were 126 GPa for particles in the size range 150–250 μm and 98 GPa for particles in the size range 5–10 μm. Young's modulus of cenosphere particles was estimated to be approximately in the range of 13–17 GPa in all particle size ranges. The hardness of the larger precipitator fly ash particles (120 μm) exhibited a wide scatter in the range of 160–400 kg mm−2, while the hardness of the smaller size precipitator particles (20 μm) were in a narrow range from 250 to 270 kg mm−2.

203 citations

Journal ArticleDOI
TL;DR: In this paper, the authors discuss some recent progress in the research on nanocarbon-based electronic gas sensors, including carbon nanotubes (CNTs), graphene, and their composites (i.e., nanocarbons and nanocrystal hybrids), identify the technological barriers that impair their commercialization, and present an outlook of the challenges and opportunities for the use of carbon-based materials in next generation gas sensors.
Abstract: Novel materials based on nanocarbons (e.g., carbon nanotubes (CNTs) and graphene) have attracted much attention as sensing elements in miniaturized, low-power consumption, and ubiquitous electronic gas sensors due to their unique structural and electronic properties. This highlight discusses some recent progress in the research on nanocarbon-based electronic gas sensors, including CNTs, graphene, and their composites (i.e., nanocarbon–nanocrystal hybrids), identifies the technological barriers that impair their commercialization, and presents an outlook of the challenges and opportunities for the use of nanocarbon-based materials in next generation gas sensors.

203 citations


Authors

Showing all 11948 results

NameH-indexPapersCitations
Caroline S. Fox155599138951
Mark D. Griffiths124123861335
Benjamin William Allen12480787750
James A. Dumesic11861558935
Richard O'Shaughnessy11446277439
Patrick Brady11044273418
Laura Cadonati10945073356
Stephen Fairhurst10942671657
Benno Willke10950874673
Benjamin J. Owen10835170678
Kenneth H. Nealson10848351100
P. Ajith10737270245
Duncan A. Brown10756768823
I. A. Bilenko10539368801
F. Fidecaro10556974781
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202330
2022194
20211,150
20201,189
20191,085
20181,141