14,883 research outputs found
Quantization effects in Viterbi decoding rate 1/n convolutional codes
A Viterbi decoder's performance loss due to quantizing data from the additive white Gaussian noise (AWGN) channel is studied. An optimal quantization scheme and branch metric calculation method are presented. The uniformly quantized channel capacity C(sub u)(q) is used to determine the smallest number of quantization bits q that does not cause a significant loss. The quantizer stepsize which maximizes C(sub u)(q) almost minimizes the decoder bit error rate (BER). However, a slightly larger stepsize is better, like the value that minimizes the Bhattacharyya bound. The range and renormalization of state metrics is analyzed, in particular for K = 15 decoders such as the Big Viterbi Decoder (BVD) for the Galileo mission. These results are required to design reduced hardware complexity Viterbi decoders with a negligible quantization loss
A simplified model of the source channel of the Leksell Gamma Knife: testing multisource configurations with PENELOPE
A simplification of the source channel geometry of the Leksell Gamma
Knife, recently proposed by the authors and checked for a single
source configuration (Al-Dweri et al 2004), has been used to calculate the dose
distributions along the , and axes in a water phantom with a
diameter of 160~mm, for different configurations of the Gamma Knife including
201, 150 and 102 unplugged sources. The code PENELOPE (v. 2001) has been used
to perform the Monte Carlo simulations. In addition, the output factors for the
14, 8 and 4~mm helmets have been calculated. The results found for the dose
profiles show a qualitatively good agreement with previous ones obtained with
EGS4 and PENELOPE (v. 2000) codes and with the predictions of
GammaPlan. The output factors obtained with our model agree
within the statistical uncertainties with those calculated with the same Monte
Carlo codes and with those measured with different techniques. Owing to the
accuracy of the results obtained and to the reduction in the computational time
with respect to full geometry simulations (larger than a factor 15), this
simplified model opens the possibility to use Monte Carlo tools for planning
purposes in the Gamma Knife.Comment: 13 pages, 8 figures, 5 table
Research Framework for Consumer Satisfaction with Internet Shopping
Consumer satisfaction with Internet shopping has been conceptualized in a variety of ways. Studies in this area remain broad and appear relatively fragmented. In view of this, the purpose of this study is to propose a research framework that integrates both end-user computing satisfaction literature and service quality literature. This framework explicitly considers information quality, system quality, and service quality as the key dimensions of consumer satisfaction with Internet shopping. We believe the research framework and propositions serve as salient guidelines for researchers
Identifying the Higgs Boson in Electron--Photon Collisions
We analyze the production and detection of the Higgs boson in the next
generation of linear colliders operating in the mode. In
particular, we study the production mechanism , where one photon is generated via the laser
backscattering mechanism, while the other is radiated via the usual
bremsstrahlung process. We show that this is the most important mechanism for
Higgs boson production in a GeV collider for
M_H\raisebox{-.4ex}{\rlap{\sim}} \raisebox{.4ex}{>}140 GeV. We also study
the signals and backgrounds for detection of the Higgs in the different decay
channels, , , and , and suggest kinematical cuts to
improve the signature of an intermediate mass Higgs boson.Comment: (REVTEX 2.0, 12 pages and 9 figures available upon request, Preprint
MAD/PH/753
The Plasma Puddle as a Perturbative Black Hole
We argue that the weak coupling regime of a large N gauge theory in the Higgs
phase contains black hole-like objects. These so-called ``plasma puddles'' are
meta-stable lumps of hot plasma lying in locally un-Higgsed regions of space.
They decay via O(1/N) thermal radiation and, perhaps surprisingly, absorb all
incident matter. We show that an incident particle of energy E striking the
plasma puddle will shower into an enormous number of decay products whose
multiplicity grows linearly with E, and whose average energy is independent of
E. Once these ultra-soft particles reach the interior they are thermalized by
the plasma within, and so the object appears ``black.'' We determine some gross
properties like the size and temperature of the the plasma puddle in terms of
fundamental parameters in the gauge theory. Interestingly, demanding that the
plasma puddle emit thermal Hawking radiation implies that the object is black
(i.e. absorbs all incident particles), which implies classical stability, which
implies satisfaction of the Bekenstein entropy bound. Because of the AdS/CFT
duality and the many similarities between plasma puddles and black holes, we
conjecture that black objects are a robust feature of quantum gravity.Comment: 23 pages, 3 figures, V2: minor changes, ref added, appendix A.5 moved
to body of pape
Persistent Currents in the Presence of a Transport Current
We have considered a system of a metallic ring coupled to two electron
reservoirs. We show that in the presence of a transport current, the persistent
current can flow in a ring, even in the absence of magnetic field. This is
purely a quantum effect and is related to the current magnification in the
loop. These persistent currents can be observed if one tunes the Fermi energy
near the antiresonances of the total transmission coefficient or the two port
conductance.Comment: To appear in Phys. Rev. B. Three figures available on reques
Persistent currents in coupled mesoscopic rings
We have analysed the nature of persistent currents in open coupled mesoscopic
rings. Our system is comprised of two ideal loops connected to an electron
reservoir. We have obtained analytical expressions for the persistent current
densities in two rings in the presence of a magnetic field. We show that the
known even-odd parity effects in isolated single loops have to be generalised
for the case of coupled rings. We also show that when the two rings have
unequal circumferences, it is possible to observe opposite currents
(diamagnetic or paramagnetic) in the two rings for a given Fermi level.Comment: Submitted to PRB. 9 figures availabel on reques
Western Australian Radiology Departments’ Views on Australian Personally Controlled Electronic Health Record
Introduction: Since the last decade, many countries have started developing a national electronic health record (EHR). The national EHR in Australia is called Personally Controlled Electronic Health Record (PCEHR). It has been available for use since 1 July 2012. A federal government’s review of its implementation was conducted in late 2013 because it failed to meet the set targets. The purpose of this study was to investigate Western Australian radiology departments’ views on the PCEHR complementary to the government’s review report. Methods: Chief medical imaging technologists (n=18) and picture archiving and communication system (PACS) administrators (n=18) from public and private hospitals in Western Australian were invited to participate in this study in May 2014. The response rate for participation was 22.2 percent (8/36). Semi-structured interviews were conducted with the participants to obtain their perceptions of PCEHR. The interviews were analysed inductively and thematically. Results: There were eight people (n=8) who agreed to participate. They believed the PCEHR would enhance efficiency and effectiveness of healthcare services if barriers to its implementation were addressed. The major barriers identified were concern of individual privacy, increase of staff workload, inadequate system functionalities and training, lack of involvement of stakeholders and money. The use of Medicare to provide both positive and negative incentives to the stakeholders was suggested as a viable solution to address the current barriers. Conclusion: This study investigated four Western Australian radiology departments’ perceptions of PCEHR. Although their perceptions were similar to the ideas in the government’s review report in general, new insights were also provided by the participants. These findings could potentially complement the government’s review
Detection of the heavy Higgs boson at colliders
We consider the possibility of detecting a heavy Higgs boson () in
proposed colliders through the semi-leptonic mode . We show that
due to the non-monochromatic nature of the photon beams produced by the
laser-backscattering method, the resultant cross section for Higgs production
is much smaller than the on-resonance cross section and generally {\it
decreases} with increasing collider energy. Although continuum production
is expected to be negligible, we demonstrate the presence of and calculate
sizeable backgrounds from ,
with , respectively, and
.
This channel may be used to detect a Higgs of mass up to around 350~GeV
at a 0.5~TeV collider, assuming a nominal yearly luminosity of
10--20~fb.Comment: 18 pages (in RevTeX) plus Postscript figures (available by email or
FAX), NUHEP-TH-92-29 and DOE-309-CPP-47. (Revised version: NO CHANGES to the
manuscript, simply removed corrupted figure files
The Boson Loop Background to H -> ZZ at Photon-photon Colliders
We have performed a complete one-loop calculation of in the Standard Model, including both gauge bosons and fermions
in the loop. We confirm the large irreducible continuum background from the
-boson loop found by Jikia. We have included the photon-photon luminosity,
and find that the continuum background of transverse boson pairs prohibits
finding a heavy Higgs with mass \gtap 350 GeV in this decay mode.Comment: 16 pages + 4 PS figures included (uuencoded), MAD/PH/77
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