4,256 research outputs found
Quantum graph as a quantum spectral filter
We study the transmission of a quantum particle along a straight
input--output line to which a graph is attached at a point. In the
point of contact we impose a singularity represented by a certain properly
chosen scale-invariant coupling with a coupling parameter . We show
that the probability of transmission along the line as a function of the
particle energy tends to the indicator function of the energy spectrum of
as . This effect can be used for a spectral analysis
of the given graph . Its applications include a control of a
transmission along the line and spectral filtering. The result is illustrated
with an example where is a loop exposed to a magnetic field. Two more
quantum devices are designed using other special scale-invariant vertex
couplings. They can serve as a band-stop filter and as a spectral separator,
respectively.Comment: 15 pages, 8 figures. Copyright (2013) American Institute of Physics.
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Blunder, Error, Mistake, Pitfall: Trawling the OED with the Help of the Historical Thesaurus
The paper considers the lexis of error and examines its use across time in relation to the writing and spelling of English, to grammar and pronunciation. Discussion focuses first on the earliest records of notions of correctness in English language usage, from Ælfric forwards to the emergence of standard English, from the sixteenth century’s growing worries about copiousness and purity of diction to eighteenth-century concerns to prescribe and rule the language. The historical overview is complemented by consideration of the data drawn together by the Glasgow Historical Thesaurus project, its evidence taken from the Oxford English Dictionary and the Dictionary of Old English Corpus. For earlier centuries, there are by far fewer relevant citations, often buried within words wide in reference. With the help of the Historical Thesaurus we drill down to view how views of language mistakes and errors have changed over the centuries of the recorded history of English
Geochemistry of volcanic rocks from the Wawa greenstone belt
The Wawa greenstone belt is located in the District of Algoma and extends east-northeast from Lake Superior to the western part of the Sudbury District in Ontario, Canada. Recent mapping by Attoh has shown that an unconformity at the base of the Dore' Formation and equivalent sedimentary rocks marks a significant stratigraphic break which can be traced throughout the volcanic belt. This break has been used to subdivide the volcanic-sedimentary into pre- and post-Dore' sequences. The pre-Dore' sequence includes at least two cycles of mafic-to-felsic volcanism, each capped by an iron-formation unit. The post-Dore' sequence includes an older mafic-to-felsic unit, which directly overlies sedimentary rocks correlated with the Dore' Formation, and a younger felsic breccia unit interpreted to have formed as debris flows from a felsic volcanic center. In the present study, samples of both the pre-and post-Dore' volcanic sequences were analyzed for major and trace elements, incuding rare earths (REE). This preliminary study is part of an ongoing program to assess the petrogenesis of the volcanic rocks of the Wawa greenstone belt
Rhyolitic components of the Michipicoten greenstone belt, Ontario: Evidence for late Archaen intracontinental rifts or convergent plate margins in the Canadian Shield?
Rhyolitic rocks often are the dominant felsic end member of the biomodal volcanic suites that characterize many late Archean greenstone belts of the Canadian Shield. The rhyolites primarily are pyroclastic flows (ash flow tuffs) emplaced following plinian eruptions, although deposits formed by laval flows and phreatomagmatic eruptions also are presented. Based both on measured tectono-stratigraphic sections and provenance studies of greenstone belt sedimentary sequences, the rhyolites are believed to have been equal in abundance to associated basaltic rocks. In many recent discussions of the tectonic setting of late Archean Canadian greenstone belts, rhyolites have been interpreted as products of intracontinental rifting . A study of the tectono-stratigraphic relationships, rock associations and chemical characteristics of the particularly ell-exposed late Archean rhyolites of the Michipicoten greenstone belt, suggests that convergent plate margin models are more appropriate
Geometric approach to non-relativistic Quantum Dynamics of mixed states
In this paper we propose a geometrization of the non-relativistic quantum
mechanics for mixed states. Our geometric approach makes use of the Uhlmann's
principal fibre bundle to describe the space of mixed states and as a novelty
tool, to define a dynamic-dependent metric tensor on the principal manifold,
such that the projection of the geodesic flow to the base manifold gives the
temporal evolution predicted by the von Neumann equation. Using that approach
we can describe every conserved quantum observable as a Killing vector field,
and provide a geometric proof for the Poincare quantum recurrence in a physical
system with finite energy levels.Comment: 19 pages, 1 figure. Minor corrections. Accepted to Journal of
Mathematical Physic
Sub 1GHz M2M communications standardization: The advancement in white space utilization for enhancing the energy efficiency
Energy efficiency of machine to machine (M2M) communications terminals is one of the major design goals of M2M networks, resulting from anticipated over 50 billion M2M communications devices to be deployed into the networks by 2020 [1]. The stakeholders in the M2M communications have observed that it will be environmental and economic catastrophic to deploy M2M communications devices without solving the energy inefficiencies associated with wireless devices that are expected to be used for M2M communications. In view of the aforementioned energy challenge, sub 1GHz spectra have provided enormous opportunities that can be energy efficient, cost effective and coverage efficiency which can be utilized for M2M communications. This work will evaluate the energy efficiency benefits of optimized Sub 1GHz spectra for M2M communications
Vector wind, horizontal divergence, wind stress and wind stress curl from SEASAT-SASS at one degree resolution
Conventional data obtained in 1983 are contrasted with SEASAT-A scatterometer and scanning multichannel microwave radiometer (SMMR) data to show how observations at a single station can be extended to an area of about 150,000 square km by means of remotely sensed data obtained in nine minutes. Superobservations at a one degree resolution for the vector winds were estimated along with their standard deviations. From these superobservations, the horizontal divergence, vector wind stress, and the curl of the wind stress can be found. Weather forecasting theory is discussed and meteorological charts of the North Pacific Ocean are presented. Synoptic meteorology as a technique is examined
Discovery of Reflection Nebulosity Around Five Vega-like Stars
Coronagraphic optical observations of six Vega-like stars reveal reflection
nebulosities, five of which were previously unknown. The nebulosities
illuminated by HD 4881, HD 23362, HD 23680, HD 26676, and HD 49662 resemble
that of the Pleiades, indicating an interstellar origin for dust grains. The
reflection nebulosity around HD 123160 has a double-arm morphology, but no
disk-like feature is seen as close as 2.5 arcsec from the star in K-band
adaptive optics data. We demonstrate that uniform density dust clouds
surrounding HD 23362, HD 23680 and HD 123160 can account for the observed
12-100 micron spectral energy distributions. For HD 4881, HD 26676, and HD
49662 an additional emission source, such as from a circumstellar disk or
non-equilibrium grain heating, is required to fit the 12-25 micron data. These
results indicate that in some cases, particularly for Vega-like stars located
beyond the Local Bubble (>100 pc), the dust responsible for excess thermal
emission may originate from the interstellar medium rather than from a
planetary debris system.Comment: The Astrophysical Journal, in press for March, 2002 (32 pages, 13
figures
The Shift to Hybrid Pensions by U.S. Employers: An Empirical Analysis of Actual Plan Conversions
For nearly two decades, employers have been restructuring traditional defined benefit pension plans to look and operate more like defined contribution plans from participants’ perspectives while retaining defined benefit funding characteristics. This shift to cash balance and pension equity plans has become controversial because some participants and outside analysts have concluded the shift to these new plan styles has been primarily motivated by the desire to cut pension costs and reduce benefits. This paper empirically documents the shift from traditional pension forms to these new hybrid forms for a sample of actual plan conversions. The analysis investigates the implications of the plan conversions on plan costs and the levels and distribution of benefits. If finds that some employers did indeed modify their plans to reduce costs but that, on average, cost savings from the shift to hybrid plans have been negligible. The paper documents that some workers will receive smaller benefits under the new plans than they would under the old but shows that most plan sponsors implemented substantial grandfathering or other transition protection to eliminate or limit the effect of the transitions on workers with substantial tenure or age at the time of conversion. The controversial “wear-away” is evaluated against provisions in the prior plans that provided subsidized benefits to early retirees and then reduced them if workers extended their career beyond early retirement eligibility. It finds that wear-away has actually been ameliorated in the shift to hybrid plans although shifted forward in the career in most cases. The paper shows that it is largely the elimination of these early retirement incentives that is at the heart of the shift to hybrid plans. This shift is resulting in new incentives to work beyond early retirement ages and is redistributing benefits more equitably across the total workforce than traditional pensions have done
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