173 research outputs found
Solar walls for high-performance buildings
Passive solar design can reduce building energy demand for heating, cooling and ventilation, while also contributing to the comfort, well-being and productivity of the building’s occupants. The successful application of passive solar features, such as solar walls, requires a good understanding of the factors influencing their energy performance and a correct assessment of this performance during the design process. This paper discusses some basic design strategies for successful application of solar walls and the factors with the most significant impact on their efficiency. It summarizes the principle results and findings of an experimental study, based on dynamic simulations and test site measurements. The energy performance of various configurations of unvented solar walls was investigated in different climatic conditions. The outcomes of the dynamic simulations were used to develop a simplified quasisteady-state model, which can be used for approximate evaluation of the heat gains and heat losses through an unvented solar wall on a monthly basis. The model is compatible with the monthly method of EN ISO 13790.This work has been supported by The National Science Fund of Bulgaria under projects number ДУНК-01/3 (DUNK-01/3) and ДФНИ Е 02/17 (DFNI E 02/17)
Discovery of a bipolar and highly variable mass outflow from the symbiotic binary StHa 190
A highly and rapidly variable bipolar mass outflow from StHa 190 has been
discovered, the first time in a yellow symbiotic star. Permitted emission lines
are flanked by symmetrical jet features and multi-component P-Cyg profiles,
with velocities up to 300 km/sec. Given the high orbital inclination of the
binary, if the jets leave the system nearly perpendicular to the orbital plane,
the de-projected velocity equals or exceeds the escape velocity (1000 km/sec).
StHa190 looks quite peculiar in many other respects: the hot component is an
O-type sub-dwarf without an accretion disk or a veiling nebular continuum and
the cool component is a G7 III star rotating at a spectacular 105 km/sec unseen
by a large margin in field G giants.Comment: Letter to the Editor, Astron.Astrophys, in pres
The large-scale ionised outflow of CH Cygni
HST and ground-based [OII} and [NII] images obtained from 1996 to 1999 reveal
the existence of a ionised optical nebula around the symbiotic binary CH Cyg
extending out to 5000 A.U. from the central stars. The observed velocity range
of the nebula, derived from long-slit echelle spectra, is of 130 km/s. In spite
of its complex appearence, the velocity data show that the basic morphology of
the inner regions of the optical nebula is that of a bipolar (or conical)
outflow extending nearly along the plane of the sky out to some 2000 A.U. from
the centre. Even if the extension of this bipolar outflow and its position
angle are consistent with those of the radio jet produced in 1984 (extrapolated
to the time of our optical imagery), no obvious counterpart is visible of the
original, dense radio bullets ejected by the system. We speculate that the
optical bipolar outflow might be the remannt of the interaction of the bullets
with a relatively dense circumstellar medium.Comment: 8 text pages + 3 figures (jpeg). ApJ in press. For a full PostScript
version with figures inline see
ftp://ftp.ll.iac.es/pub/research/preprints/PP252001.ps.g
Merging Galaxies in the SDSS EDR
We present a new catalog of merging galaxies obtained through an automated
systematic search routine. The 1479 new pairs of merging galaxies were found in
approximately 462 sq deg of the Sloan Digital Sky Survey Early Data Release
(SDSS EDR; Stoughton et al. 2002) photometric data, and the pair catalog is
complete for galaxies in the magnitude range 16.0 <= g* <= 20.
The selection algorithm, implementing a variation on the original
Karachentsev (1972) criteria, proved to be very efficient and fast. Merging
galaxies were selected such that the inter-galaxy separations were less than
the sum of the component galaxies' radii.
We discuss the characteristics of the sample in terms of completeness, pair
separation, and the Holmberg effect. We also present an online atlas of images
for the SDSS EDR pairs obtained using the corrected frames from the SDSS EDR
database. The atlas images also include the relevant data for each pair member.
This catalog will be useful for conducting studies of the general
characteristics of merging galaxies, their environments, and their component
galaxies. The redshifts for a subset of the interacting and merging galaxies
and the distribution of angular sizes for these systems indicate the SDSS
provides a much deeper sample than almost any other wide-area catalog to date.Comment: 58 pages, which includes 15 figures and 6 tables. Figures 2, 8, 9,
10, 11, 13, and 14 are provided as JPEG files. For online atlas, see
http://home.fnal.gov/~sallam/MergePair/ . Accepted for publication in A
UVSat: a concept of an ultraviolet/optical photometric satellite
Time-series photometry from space in the ultraviolet can be presently done
with only a few platforms, none of which is able to provide wide-field
long-term high-cadence photometry. We present a concept of UVSat, a twin space
telescope which will be capable to perform this kind of photometry, filling an
observational niche. The satellite will host two telescopes, one for
observations in the ultraviolet, the other for observations in the optical
band. We also briefly show what science can be done with UVSat.Comment: 6 pages, 2 figures, accepted for publication in the Proceedings of
the PAS (Proc. of the 2nd BRITE Science conference, Innsbruck
Accelerating Computation of Eigenvectors in the Dense Nonsymmetric Eigenvalue Problem
Abstract. In the dense nonsymmetric eigenvalue problem, work has focused on the Hessenberg reduction and QR iteration, using efficient al-gorithms and fast, Level 3 BLAS. Comparatively, computation of eigen-vectors performs poorly, limited to slow, Level 2 BLAS performance with little speedup on multi-core systems. It has thus become a dominant cost in the solution of the eigenvalue problem. To address this, we present im-provements for the eigenvector computation to use Level 3 BLAS and parallelize the triangular solves, achieving good parallel scaling and ac-celerating the overall eigenvalue problem more than three-fold.
Orbifold projection in supersymmetric QCD at N_f\leq N_c
Supersymmetric orbifold projection of N=1 SQCD with relatively small number
of flavors (not larger than the number of colors) is considered. The purpose is
to check whether orbifolding commutes with the infrared limit. On the one hand,
one considers the orbifold projection of SQCD and obtains the low-energy
description of the resulting theory. On the other hand, one starts with the
low-energy effective theory of the original SQCD, and only then perfoms
orbifolding. It is shown that at finite N_c the two low-energy theories
obtained in these ways are different. However, in the case of stabilized
run-away vacuum these two theories are shown to coincide in the large N_c
limit. In the case of quantum modified moduli space, topological solitons
carrying baryonic charges are present in the orbifolded low-energy theory.
These solitons may restore the correspondence between the two theories provided
that the soliton mass tends to zero in the large N_c limit.Comment: 10 pages; misprint corrected, reference adde
CPU, GPU i FPGA implementacija MALD algoritma za otkrivanje nepravilnosti na površini keramičkih pločica
This paper addresses adjustments, implementation and performance comparison of the Moving Average with Local Difference (MALD) method for ceramic tile surface defects detection. Ceramic tile production process is completely autonomous, except the final stage where human eye is required for defects detection. Recent computational platform development and advances in machine vision provides us with several options for MALD algorithm implementation. In order to exploit the shortest execution time for ceramic tile production process, the MALD method is implemented on three different platforms: CPU, GPU and FPGA, and it is implemented on each platform in at least two ways. Implementations are done in MATLAB’s MEX/C++, C++, CUDA/C++, VHDL and Assembly programming languages. Execution times are measured and compared for different algorithms and their implementations on different computational platforms.U ovom radu razmatra se prilagodba, implementacija i usporedba performansi metode pomičnog usrednjavanja s lokalnom diferencijom (MALD) s primjenom u otkrivanju površinskih nedostataka na keramičkim pločicama. Proizvodna linija keramičkih pločica je autonomna sve do zadnje faze u kojoj je potreban ljudski vid kako bi se otkrili eventualni nedostaci na keramičkim pločicama. Nedavnim razvojem računalnih platformi i razvojem metoda računalnog vida omogućena je implementacija MALD metode na nekoliko načina. U nastojanju skraćenja vremena potrebnog za proizvodnju keramičkih pločica, MALD metoda je implementirana u trima različitim platformama: CPU (central processing unit), GPU (graphic processing unit) i FPGA (field programmable gate array), te s barem dva različita algoritma. Implementacija je izvršena sa MATLAB MEX/C++, C++, CUDA/C++, VHDL te Asembler programskim jezicima. Izmjerena vremena obrade su me.usobno uspore.ena za različite algoritme i njihove implementacije na različitim računalnim platformama
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