3,513 research outputs found
Modelling Thermal Stratification in Atrium Using TAS Program and Verification of Prediction Results
This paper reports the TAS computer simulation of the three-storey atrium in Southern China. It was an attempt to correctly model thermal stratification of a large multi-level space within the atrium using TAS program. The prediction results of modelling with blinds and without water spray, particularly indoor air and mean radiant temperatures, and roof blind surface temperature, were compared and verified with the results from the site measurement to evaluate the capability and accuracy of the developed TAS model in simulating atrium’s indoor thermal environmental performance. The simulation results have shown that TAS program tends to overestimate its prediction results. For hot and overcast day simulation, the difference in air temperature over the 24 hours between measured and predicted is in the range of 0.1 K to 1.8 K on the first floor and 0.2 K to 4.3 K on the second floor respectively. Whereas for hot and clear day simulation, the difference is in the range of 0.1 K to 1.5 K on the first floor and 0.1 K to 2.7 K on the second floor respectively. Despite moderate discrepancies between the measured and predicted results, it is evident from the study that the created TAS model is capable to model thermal stratification within multi-level atrium, with reasonably accurate results
Modelling Thermal Environmental Performance In Top-lit Malaysian Atrium Using Computational Fluid Dynamics (CFD)
Computational Fluid Dynamics (CFD) programs are powerful design tools that can predict detailed flow movement, temperature distribution, and contaminant dispersion. This paper reports the steady-state 3-D CFD modelling of air movement and temperature distribution due to thermal buoyancy within top-lit three-storey representative Malaysian atrium forms using the computer code PHOENICS. Details of temperature distribution, airflow patterns and other comfort parameters would provide a better picture of the resultant thermal performance within the atrium in response to the changes of design variables. The CFD modelling studies were to investigate quantitatively the effects of varying inlet to outlet opening area ratios and also the outlet’s arrangement on the atrium’s thermal environmental performance in relation to occupants’ thermal comfort. The simulation results have revealed that sufficiently higher inlet to outlet opening area ratio (i.e. n>1) can improve the thermal performance on the occupied levels; while with an equal inlet to outlet opening area ratio (i.e. n=1), changing the outlet’s arrangement (i.e. location and configuration) has not significantly affected the atrium’s thermal performance
A genome-based study of the Muslim Hui community and the Han population of Liaoning province, PR China
To investigate the proposed historical origins of the Hui, a Chinese Muslim minority resident in Liaoning Province, PR China, DNA samples obtained from 53 individuals were analyzed at ten autosomal and six Y-chromosome microsatellite loci. As reference sources, equivalent samples were investigated from the coresident Han majority population. Both the Hui and the Han exhibited appreciable genetic heterogeneity in terms of the size, number, and size range of alleles, suggestive of population substructure resulting from their particular cultural and historical backgrounds. The contrast in the patterns of autosomal and Y-chromosome diversity of the two communities was obvious. Analysis of molecular variance showed that only 4.6% of total autosomal molecular variance was due to differences between the Hui and Han. The comparable value for Y-chromosome haplotype distributions of 14.0% indicated that the Hui and Han of Liaoning have separate paternal genetic histories
Very fast formation of superconducting MgB2/Fe wires with high Jc
In this paper we have investigated the effects of sintering time and
temperature on the formation and critical current densities of Fe-clad MgB2
wires. MgB2 wires were fabricated using the powder-in-tube process and sintered
for different periods of time at predetermined temperatures. All the samples
were examined using XRD, SEM and magnetisation measurements. In contrast to the
common practice of sintering for several hours, the present results show that
there is no need for prolonged heat treatment in the fabrication of Fe-clad
MgB2 wires. A total time in the furnace of several minutes is more than enough
to form nearly pure MgB2 with high performance characteristics. The results
from Tc, Jc and Hirr show convincingly that the samples which were sintered for
3 minutes above 800 oC are as good as those sintered for longer times. In fact,
the Jc field performance for the most rapidly sintered sample is slightly
better than for all other samples. Jc of 4.5 times 10 ^5 A/cm2 in zero field
and above 10 ^5 A/cm2 in 2T at 15 K has been achieved for the best Fe-clad MgB2
wires. As a result of such a short sintering there is no need for using high
purity argon protection and it is possible to carry out the heat treatment in a
much less protective atmosphere or in air. These findings substantially
simplify the fabrication process, making it possible to have a continuous
process for fabrication and reducing the costs for large-scale production of
MgB2 wires.Comment: 15 pages, one table, 9 figures, submitted to Physica C on June 8,
200
Evolution of Parton Fragmentation Functions at Finite Temperature
The first order correction to the parton fragmentation functions in a thermal
medium is derived in the leading logarithmic approximation in the framework of
thermal field theory. The medium-modified evolution equations of the parton
fragmentation functions are also derived. It is shown that all infrared
divergences, both linear and logarithmic, in the real processes are canceled
among themselves and by corresponding virtual corrections. The evolution of the
quark number and the energy loss (or gain) induced by the thermal medium are
investigated.Comment: 21 pages in RevTex, 10 figure
Exact solutions of noncommutative vacuum Einstein field equations and plane-fronted gravitational waves
We construct a class of exact solutions of the noncommutative vacuum Einstein
field equations, which are noncommutative analogues of the plane-fronted
gravitational waves in classical gravity.Comment: 10 pages, comments adde
A dynamical dark energy model with a given luminosity distance
It is assumed that the current cosmic acceleration is driven by a scalar
field, the Lagrangian of which is a function of the kinetic term only, and that
the luminosity distance is a given function of the red-shift. Upon comparison
with Baryon Acoustic Oscillations (BAOs) and Cosmic Microwave Background (CMB)
data the parameters of the models are determined, and then the time evolution
of the scalar field is determined by the dynamics using the cosmological
equations. We find that the solution is very different than the corresponding
solution when the non-relativistic matter is ignored, and that the universe
enters the acceleration era at larger red-shift compared to the standard
model.Comment: 4 pages, 3 figures, accepted for publication in GER
Quantum Isometries of the finite noncommutative geometry of the Standard Model
We compute the quantum isometry group of the finite noncommutative geometry F
describing the internal degrees of freedom in the Standard Model of particle
physics. We show that this provides genuine quantum symmetries of the spectral
triple corresponding to M x F where M is a compact spin manifold. We also prove
that the bosonic and fermionic part of the spectral action are preserved by
these symmetries.Comment: 29 pages, no figures v3: minor change
Flux Jumping and a Bulk-to-Granular Transition in the Magnetization of a Compacted and Sintered MgB2 Superconductor
The recent discovery of intermediate-temperature superconductivity (ITC) in
MgB2 by Akimitsu et al. and its almost simultaneous explanation in terms of a
hole-carrier-based pairing mechanism by Hirsch, has triggered an avalanche of
studies of its structural, magnetic and transport properties. As a further
contribution to the field we report the results of field (H) and temperature
(T) dependent magnetization (M) measurements of a pellet of uniform,
large-grain sintered MgB2. We show that at low temperatures the size of the
pellet and its critical current density, Jc(H) - i.e. its M(H) - ensure low
field flux jumping, which of course ceases when M(H) drops below a critical
value. With further increase of H and T the individual grains decouple and the
M(H) loops drop to lower lying branches, unresolved in the usual full M(H)
representation. After taking into account the sample size and grain size,
respectively, the bulk sample and the grains were deduced to exhibit the same
magnetically determined Jc s (e.g. 105 A/cm2, 20 K, 0T) and hence that for each
temperature of measurement Jc(H) decreased monotonically with H over the entire
field range, except for a gap within the grain-decoupling zone.Comment: 7 pages, 6 figures, Changes: Fig 6 Vertical scale an order of
magnitude out (changed figure and associated text). Also corrected typo in
last sectio
Molecular Modeling of Nucleic Acid Structure: Energy and Sampling
An overview of computer simulation techniques as applied to nucleic acid systems is presented. This unit expands an accompanying overview unit (UNIT ) by discussing methods used to treat the energy and sample representative configurations. Emphasis is placed on molecular mechanics and empirical force fields.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143698/1/cpnc0708.pd
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