459 research outputs found
Intrinsic thermal interfacial resistance measurement in bonded metal-polymer foils
Heat conduction through bonded metalâpolymer interfaces often limits the overall heat transfer in electronic packaging, batteries, and heat recovery systems. To design the thermal circuit in such systems, it is essential to measure the thermal interfacial resistance (TIR) across âŒ1 ”m to 100 ”m junctions. Previously reported TIR of metalâpolymer junctions utilize ASTM E1530-based two-block systems that measure the TIR by applying pressure across the interface through external heating and cooling blocks. Here, we report a novel modification of the ASTM-E1530 technique that employs integrated heaters and sensors to provide an intrinsic TIR measurement of an adhesively bonded metalâpolymer junction. We design the measurement technique using finite element simulations to either passively suppress or actively compensate the lateral heat diffusion through the polymer, which can minimize the systematic error to âČ5%. Through proof-of-concept experiments, we report the TIR of metalâpolymer interfaces made from DuPontâs Pyralux double-side copper-clad laminates, commonly used in flexible printed circuit boards. Our TIR measurement errors are <10%. We highlight additional sources of errors due to non-idealities in the experiment and discuss possible ways to overcome them. Our measurement technique is also applicable to interfaces that are electrically insulating such as adhesively joined metalâmetal junctions and sputter-coated or welded metalâpolymer junctions. Overall, the technique is capable of measuring TIR âł10â5 m2 KWâ1 in bonded metalâpolymer foils and can be tailored for in situ measurements in flexible electronics, circuit packaging, and other hybrid metalâpolymer systems.DE-EE0008312Ope
Neutrino hierarchy from CP-blind observables with high density magnetized detectors
High density magnetized detectors are well suited to exploit the outstanding
purity and intensities of novel neutrino sources like Neutrino Factories and
Beta Beams. They can also provide independent measurements of leptonic mixing
parameters through the observation of atmospheric muon-neutrinos. In this
paper, we discuss the combination of these observables from a multi-kton iron
detector and a high energy Beta Beam; in particular, we demonstrate that even
with moderate detector granularities the neutrino mass hierarchy can be
determined for values greater than 4.Comment: 16 pages, 7 figures. Added a new section discussing systematic errors
(sec 5.2); sec.5.1 and 4 have been extended. Version to appear in EPJ
A framework for digital sunken relief generation based on 3D geometric models
Sunken relief is a special art form of sculpture whereby the depicted shapes are sunk into a given surface. This is traditionally created by laboriously carving materials such as stone. Sunken reliefs often utilize the engraved lines or strokes to strengthen the impressions of a 3D presence and to highlight the features which otherwise are unrevealed. In other types of reliefs, smooth surfaces and their shadows convey such information in a coherent manner. Existing methods for relief generation are focused on forming a smooth surface with a shallow depth which provides the presence of 3D figures. Such methods unfortunately do not help the art form of sunken reliefs as they omit the presence of feature lines. We propose a framework to produce sunken reliefs from a known 3D geometry, which transforms the 3D objects into three layers of input to incorporate the contour lines seamlessly with the smooth surfaces. The three input layers take the advantages of the geometric information and the visual cues to assist the relief generation. This framework alters existing techniques in line drawings and relief generation, and then combines them organically for this particular purpose
An Updated Analysis on Atmospheric Neutrinos
We have reanalysed the atmospheric neutrino data including new results from
Super-Kamiokande and Soudan-II experiments, under the assumption of two-flavor
neutrino oscillation. We present the allowed region of oscillation parameters
for the channel. In performing this re-analysis we also
take into account some recent theoretical improvements in the flux
calculations.Comment: Latex file, 2 pages including 2 ps figures, Talk presented by H.
Nunokawa at the Erice School on Nuclear Physics, 19th course "Neutrinos in
Astro, Particle and Nuclear Physics", Erice, Italy, 16-24 September 1997, to
appear in the proceeding
Active-active and active-sterile neutrino oscillation solutions to the atmospheric neutrino anomaly
We perform a fit to the full data set corresponding to 33.3 kt-yr of data of
the Super-Kamiokande experiment as well as to all other experiments in order to
compare the two most likely solutions to the atmospheric neutrino anomaly in
terms of oscillations in the and
channels. Using state-of-the-art atmospheric neutrino fluxes we have determined
the allowed regions of oscillation parameters for both channels. We find that
the values for the active-sterile oscillations (both for positive
and negative ) are higher than for the case,
and that the increased Super-Kamiokande sample slightly favours oscillations over oscillations into a sterile species ,
, and disfavours . We also give the
zenith angle distributions predicted for the best fit points in each of the
possible oscillation channels. Finally we compare our determinations of the
atmospheric neutrino oscillation parameters with the expected sensitivities of
future long-baseline experiments K2K, MINOS, ICARUS, OPERA and NOE.Comment: Updated to 535 days of Super-Kamiokande and corresponding
modifications in the discussion and figures. Some References adde
Associated Production of a KK-Graviton with a Higgs Boson via Gluon Fusion at the LHC
In order to solve the hierarchy problem, several extra-dimensional models
have received considerable attention. We have considered a process where a
Higgs boson is produced in association with a KK-graviton () at the
LHC. At the leading order, this process occurs through gluon fusion mechanism
via a quark loop. We compute the cross section and
examine some features of this process in the ADD model. We find that the quark
in the loop does not decouple in the large quark-mass limit just as in the case
of process. We compute the cross section of this process for the case
of the RS model also. We examine the feasibility of this process being observed
at the LHC.Comment: 18 pages, 11 figures. Calculation in the Higgs effective theory
framework adde
Neutrino masses: From fantasy to facts
Theory suggests the existence of neutrino masses, but little more. Facts are
coming close to reveal our fantasy: solar and atmospheric neutrino data
strongly indicate the need for neutrino conversions, while LSND provides an
intriguing hint. The simplest ways to reconcile these data in terms of neutrino
oscillations invoke a light sterile neutrino in addition to the three active
ones. Out of the four neutrinos, two are maximally-mixed and lie at the LSND
scale, while the others are at the solar mass scale. These schemes can be
distinguished at neutral-current-sensitive solar & atmospheric neutrino
experiments. I discuss the simplest theoretical scenarios, where the lightness
of the sterile neutrino, the nearly maximal atmospheric neutrino mixing, and
the generation of & all follow
naturally from the assumed lepton-number symmetry and its breaking. Although
the most likely interpretation of the present data is in terms of
neutrino-mass-induced oscillations, one still has room for alternative
explanations, such as flavour changing neutrino interactions, with no need for
neutrino mass or mixing. Such flavour violating transitions arise in theories
with strictly massless neutrinos, and may lead to other sizeable flavour
non-conservation effects, such as , conversion in
nuclei, unaccompanied by neutrino-less double beta decay.Comment: 33 pages, latex, 16 figures. Invited Talk at Ioannina Conference,
Symmetries in Intermediate High Energy Physics and its Applications, Oct.
1998, to be published by Springer Tracts in Modern Physics. Festschrift in
Honour of John Vergados' 60th Birthda
Optical properties of structurally-relaxed Si/SiO superlattices: the role of bonding at interfaces
We have constructed microscopic, structurally-relaxed atomistic models of
Si/SiO superlattices. The structural distortion and oxidation-state
characteristics of the interface Si atoms are examined in detail. The role
played by the interface Si suboxides in raising the band gap and producing
dispersionless energy bands is established. The suboxide atoms are shown to
generate an abrupt interface layer about 1.60 \AA thick. Bandstructure and
optical-absorption calculations at the Fermi Golden rule level are used to
demonstrate that increasing confinement leads to (a) direct bandgaps (b) a blue
shift in the spectrum, and (c) an enhancement of the absorption intensity in
the threshold-energy region. Some aspects of this behaviour appear not only in
the symmetry direction associated with the superlattice axis, but also in the
orthogonal plane directions. We conclude that, in contrast to Si/Ge, Si/SiO
superlattices show clear optical enhancement and a shift of the optical
spectrum into the region useful for many opto-electronic applications.Comment: 11 pages, 10 figures (submitted to Phys. Rev. B
Predicting User-Cell Association in Cellular Networks from Tracked Data
We consider the problem of predicting user location in the form of user-cell association in a cellular wireless network. This is motivated by resource optimization, for example switching base transceiver stations on or off to save on network energy consumption. We use GSM traces obtained from an operator, and compare several prediction methods. First, we find that, on our trace data, user cell sector association can be correctly predicted in ca. 80% of the cases. Second, we propose a new method, called âMARPLâ, which uses Market Basket Analysis to separate patterns where prediction by partial match (PPM) works well from those where repetition of the last known location (LAST) is best. Third, we propose that for network resource optimization, predicting the aggregate location of a user ensemble may be of more interest than separate predictions for all users; this motivates us to develop soft prediction methods, where the prediction is a spatial probability distribution rather than the most likely location. Last, we compare soft predictions methods to a classical time and space analysis (ISTAR). In terms of relative mean square error, MARPL with soft prediction and ISTAR perform better than all other methods, with a slight advantage to MARPL (but the numerical complexity of MARPL is much less than ISTAR)
Solutions to the Atmospheric Neutrino Problem
I summarize here the results of a global fit to the full data set
corresponding to 535 days of data of the Super-Kamiokande experiment as well as
to all other atmosferic neutrino experiments in order to compare the most
likely solutions to the atmospheric neutrino anomaly in terms of oscillations
in the , , and
channels.Comment: 6 pages latex file using ltwol.sty. 4 postscript figures. To Appear
in Proceeding of "International High Energy Physics Conference", Vancouver,
Canada, July 199
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