1,752 research outputs found
The Impact of Galactic Disc Environment on Star-Forming Clouds
We explore the effect of different galactic disc environments on the
properties of star-forming clouds through variations in the background
potential in a set of isolated galaxy simulations. Rising, falling and flat
rotation curves expected in halo dominated, disc dominated and Milky Way-like
galaxies were considered, with and without an additional two-arm spiral
potential. The evolution of each disc displayed notable variations that are
attributed to different regimes of stability, determined by shear and
gravitational collapse. The properties of a typical cloud were largely
unaffected by the changes in rotation curve, but the production of small and
large cloud associations was strongly dependent on this environment. This
suggests that while differing rotation curves can influence where clouds are
initially formed, the average bulk properties are effectively independent of
the global environment. The addition of a spiral perturbation made the greatest
difference to cloud properties, successfully sweeping the gas into larger,
seemingly unbound, extended structures and creating large arm-interarm
contrasts.Comment: Accepted to MNRAS on 3rd December, 201
Picture coding in viewdata systems
Viewdata systems in commercial use at present offer the facility
for transmitting alphanumeric text and graphic displays via the public
switched telephone network. An enhancement to the system would be to
transmit true video images instead of graphics. Such a system, under
development in Britain at present uses Differential Pulse Code Modulation
(DPCM) and a transmission rate of 1200 bits/sec. Error protection
is achieved by the use of error protection codes, which increases
the channel requirement.
In this thesis, error detection and correction of DPCM coded
video signals without the use of channel error protection is studied.
The scheme operates entirely at the receiver by examining the local
statistics of the received data to determine the presence of errors.
Error correction is then undertaken by interpolation from adjacent
correct or previousiy corrected data.
DPCM coding of pictures has the inherent disadvantage of a slow
build-up of the displayed picture at the receiver and difficulties with
image size manipulation. In order to fit the pictorial information
into a viewdata page, its size has to be reduced. Unitary transforms,
typically the discrete Fourier transform (DFT), the discrete cosine
transform (DCT) and the Hadamard transform (HT) enable lowpass filtering and decimation to be carried out in a single operation in the transform
domain. Size reductions of different orders are considered and the merits
of the DFT, DCT and HT are investigated.
With limited channel capacity, it is desirable to remove the
redundancy present in the source picture in order to reduce the bit
rate. Orthogonal transformation decorrelates the spatial sample
distribution and packs most of the image energy in the low order
coefficients. This property is exploited in bit-reduction schemes
which are adaptive to the local statistics of the different source
pictures used. In some cases, bit rates of less than 1.0 bit/pel
are achieved with satisfactory received picture quality.
Unlike DPCM systems, transform coding has the advantage of being
able to display rapidly a picture of low resolution by initial inverse
transformation of the low order coefficients only. Picture resolution
is then progressively built up as more coefficients are received and
decoded. Different sequences of picture update are investigated to
find that which achieves the best subjective quality with the fewest
possible coefficients transmitted
Probing neutrino and Higgs sectors in model with lepton-flavor non-universality
The neutrino and Higgs sectors in the \mbox{SU(2)}_1 \times \mbox{SU(2)}_2
\times \mbox{U(1)}_Y model with lepton-flavor non-universality are discussed.
We show that active neutrinos can get Majorana masses from radiative
corrections, after adding only new singly charged Higgs bosons. The mechanism
for generation of neutrino masses is the same as in the Zee models. This also
gives a hint to solving the dark matter problem based on similar ways discussed
recently in many radiative neutrino mass models with dark matter. Except the
active neutrinos, the appearance of singly charged Higgs bosons and dark matter
does not affect significantly the physical spectrum of all particles in the
original model. We indicate this point by investigating the Higgs sector in
both cases before and after singly charged scalars are added into it. Many
interesting properties of physical Higgs bosons, which were not shown
previously, are explored. In particular, the mass matrices of charged and
CP-odd Higgs fields are proportional to the coefficient of triple Higgs
coupling . The mass eigenstates and eigenvalues in the CP-even Higgs
sector are also presented. All couplings of the SM-like Higgs boson to normal
fermions and gauge bosons are different from the SM predictions by a factor
, which must satisfy the recent global fit of experimental data, namely
. We have analyzed a more general diagonalization of gauge boson
mass matrices, then we show that the ratio of the tangents of the and
mixing angles is exactly the cosine of the Weinberg angle, implying that
number of parameters is reduced by 1. Signals of new physics from decays of new
heavy fermions and Higgs bosons at LHC and constraints of their masses are also
discussed.Comment: 40 pages, 1 figure; Journal vesio
Validating foundry technologies for extended mission profiles
This paper presents a process qualification and characterization strategy that can extend the foundry process reliability potential to meet specific automotive mission profile requirements. In this case study, data and analyses are provided that lead to sufficient confidence for pushing the allowed mission profile envelope of a process towards more aggressive (automotive) applications.\ud
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Evaluation of human epididymal secretory protein E4 (HE4) for monitoring for ovarian cancer recurrence
INTRODUCTION: Serum HE4, a new biomarker for ovarian cancer, was shown to have a better sensitivity for detecting ovarian cancer compared to Ca 125, especially in early disease. In this study, we measured the HE4 levels in patients who had relapsed ovarian cancer in an attempt to elucidate its role in disease monitoring and recurrence detection. METHODS: HE4 levels were measured at pre-treatment, immediately post ...postprin
The influences of cleanliness and employee attributes on perceived service quality in restaurants in a developing country
© 2017, © Emerald Publishing Limited. Purpose: The purpose of this paper is to investigate the service quality of full-service restaurants in Vietnam to explore possible factors that may impact customer perception, which subsequently influences customer satisfaction and behavioural intentions. Based on the DINESERV model and service clues, the possible dimensions to construct customer perception were realised, and four key dimensions were suggested. Design/methodology/approach: Data were collected from four urban local full-service restaurants in Vietnam, and factor analysis and SEM-PLS were then performed to uncover the relationship between customer perception, satisfaction and behavioural intentions. Findings: The results suggest that customer perception significantly influences customer satisfaction and behavioural intentions, and customer satisfaction itself is also found to have influence on behavioural intentions. Originality/value: This is an original piece of work which contributes to the exploration of service quality in developing countries and to the incorporation of cleanliness into analyses of restaurant service quality in particular
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