35,497 research outputs found
Observation of coasting beam at the HERA Proton--Ring
We present data collected with the HERA-B wire target which prove the
existence of coasting beam at the HERA proton storage ring. The coasting beam
is inherently produced by the proton machine operation and is not dominated by
target effects.Comment: 17 pages (Latex), 12 figures (Enc. Postscript
Potentials for Generating Alternative Fuels from Empty Palm Fruit Bunches by Pyrolysis
The threat that the disposal of empty palm fruit bunches constitute to communities in oil palm
processing areas in Nigeria coupled with the current global focus on alternative energy is the trigger
for this work. An existing pyrolytic reactor consisting of a reactor unit, condensate receiver, copper
pipe connectors and gas receiver was modified and adapted for converting empty palm fruit bunches
to alternative fuels. The average char yield was 44.9%, and the percentage of feedstock converted
into pyrogas and tar oil was 55.1%. The char yield decreased gradually as temperature was increased
from 300-700°C. Char yield was highest (39.78%) when the temperature was 300°C and the lowest
char yield was 25.05% at 700°C The calorific values of char ranged between 21.12 and 23.76 MJ/kg.
Apart from the potential of generating energy from pyrolysed EFB, it abates the disposal problem that
EFB constitutes in the oil palm industry
Kerncraft: A Tool for Analytic Performance Modeling of Loop Kernels
Achieving optimal program performance requires deep insight into the
interaction between hardware and software. For software developers without an
in-depth background in computer architecture, understanding and fully utilizing
modern architectures is close to impossible. Analytic loop performance modeling
is a useful way to understand the relevant bottlenecks of code execution based
on simple machine models. The Roofline Model and the Execution-Cache-Memory
(ECM) model are proven approaches to performance modeling of loop nests. In
comparison to the Roofline model, the ECM model can also describes the
single-core performance and saturation behavior on a multicore chip. We give an
introduction to the Roofline and ECM models, and to stencil performance
modeling using layer conditions (LC). We then present Kerncraft, a tool that
can automatically construct Roofline and ECM models for loop nests by
performing the required code, data transfer, and LC analysis. The layer
condition analysis allows to predict optimal spatial blocking factors for loop
nests. Together with the models it enables an ab-initio estimate of the
potential benefits of loop blocking optimizations and of useful block sizes. In
cases where LC analysis is not easily possible, Kerncraft supports a cache
simulator as a fallback option. Using a 25-point long-range stencil we
demonstrate the usefulness and predictive power of the Kerncraft tool.Comment: 22 pages, 5 figure
The 3-D viscous flow CFD analysis of the propeller effect on an advanced ducted propeller subsonic inlet
A time marching Navier-Stokes code called PARC3D was used to study the 3-D viscous flow associated with an advanced ducted propeller (ADP) subsonic inlet at take-off operating conditions. At a free stream Mach number of 0.2, experimental data for the inlet-with-propeller test model indicated that the airflow was attached on the cowl windward lip at an angle of attack of 25 degrees became unstable at 29 degrees, and separated at 30 degrees. An experimental study with a similar inlet and with no propeller (through-flow) indicated that flow separation occurred at an angle of attack a few degrees below the value observed when the inlet was tested with the propeller. This tends to indicate that the propeller exerts a favorable effect on the inlet performance. During the through-flow experiment a stationary blockage device was used to successfully simulate the propeller effect on the inlet flow field at angles of attack. In the present numerical study, this flow blockage was modeled via a PARC3D computational boundary condition (BC) called the screen BC. The principle formulation of this BC was based on the one-and-half dimension actuator disk theory. This screen BC was applied at the inlet propeller face station of the computational grid. Numerical results were obtained with and without the screen BC. The application of the screen BC in this numerical study provided results which are similar to the results of past experimental efforts in which either the blockage device or the propeller was used
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An incremental approach to MSE-based feature selection
Feature selection plays an important role in classification systems. Using classifier error rate as the evaluation function, feature selection is integrated with incremental training. A neural network classifier is implemented with an incremental training approach to detect and discard irrelevant features. By learning attributes one after another, our classifier can find directly the attributes that make no contribution to classification. These attributes are marked and considered for removal. Incorporated with a Minimum Squared Error (MSE) based feature ranking scheme, four batch removal methods based on classifier error rate have been developed to discard irrelevant features. These feature selection methods reduce the computational complexity involved in searching among a large number of possible solutions significantly. Experimental results show that our feature selection methods work well on several benchmark problems compared with other feature selection methods. The selected subsets are further validated by a Constructive Backpropagation (CBP) classifier, which confirms increased classification accuracy and reduced training cost
Supernovae in isolated galaxies, in pairs and in groups of galaxies
In order to investigate the influence of the environment on the supernova
(SN) production we have performed a statistical investigation of the SNe
discovered in isolated galaxies, in pairs and in groups of galaxies. 22 SNe in
18 isolated galaxies, 48 SNe in 40 galaxies members of 37 pairs and 211 SNe in
170 galaxies members of 116 groups have been selected and studied. We found
that the radial distributions of core-collapse SNe in galaxies located in
different environments are similar, and consistent with that reported by
Bartunov, Makarova & Tsvetkov (1992). SNe discovered in pairs do not privilege
a particular direction with respect to the companion galaxy. Also the azimuthal
distributions inside the hosts members of galaxy groups are consistent with
being isotropics. The fact that SNe are more frequent in the brighter
components of the pairs and groups is expected from the dependence of the SN
rates on the galaxy luminosity. There is an indication that the SN rate is
higher in galaxy pairs compared with that in groups. This can be related to the
enhanced star formation rate in strongly interacting systems. It is concluded
that, with the possible exception of strongly interacting system, the parent
galaxy environment has no direct influence on the SN productionComment: 10 pages, accepted for publication to MNRA
Fabrication and test of a space power boiler feed electromagnetic pump. 3: Endurance and final performance tests
A three-phase helical induction electromagnetic pump designed for the boiler feed pump of a potassium Rankine cycle space power system was developed and built. It was mounted in a liquid metal test loop and successfully tested over a range of potassium temperatures from 900 to 1400 F, flow rates from 0.75 to 4.85 lb/sec, developed pressures up to 340 psi, net positive suction head from 1 to 22 psi, and NaK coolant temperatures from 800 to 950 F. Maximum efficiency at design point conditions of 3.25 lb/sec flow rate, 240 psi developed head, 1000 F potassium inlet temperature, and 800 F NaK coolant inlet temperature was 16.3 percent. After the performance tests the pump was operated without any difficulty at design point for 10,000 hours, and then a limited number of repeat performance tests were made. There was no appreciable change in pump performance after 10,000 hours of operation. A supplementary series of tests using the quasi-square wave power output of a dc to three-phase ac inverter showed that the pump would operate without difficulty at a frequency as low as 25 Hz, with little loss in efficiency
Clues to AGN Growth from Optically Variable Objects in the Hubble Ultra Deep Field
We present a photometric search for objects with point-source components that
are optically variable on timescales of weeks--months in the Hubble Ultra Deep
Field (HUDF) to i'(AB)=28.0 mag. The data are split into four sub-stacks of
approximately equal exposure times. Objects exhibiting the signature of optical
variability are selected by studying the photometric error distribution between
the four different epochs, and selecting 622 candidates as 3.0 sigma outliers
from the original catalog of 4644 objects. Of these, 45 are visually confirmed
as free of contamination from close neighbors or various types of image
defects. Four lie within the positional error boxes of Chandra X-ray sources,
and two of these are spectroscopically confirmed AGN. The photometric redshift
distribution of the selected variable sample is compared to that of field
galaxies, and we find that a constant fraction of ~1% of all field objects show
variability over the range of 0.1<z<4.5. Combined with other recent HUDF
results, as well as those of recent state-of-the-art numerical simulations, we
discuss a potential link between the hierarchical merging of galaxies and the
growth of AGN.Comment: 9 pages, 6 figures, accepted for publication in Astrophysical
Journal, minor changes to reference
Marine cage farming of Asian seabass under participatory mode - A success story
Karwar Research Centre of ICAR-CMFRI in
association with the Directorate of fisheries, Govt.
of Goa identified Polem village ( 14° 54' 21.12" N ;
74° 04' 32.20" E) in south Goa for the cage culture
demonstration under the proejct 'National
Innovations on Climate Resilient Agriculture
(NICRA)'. Awareness programmes were conducted
for the fishermen communities in the village
regarding the present status of marine fisheries
resources of India and future prospects
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