155 research outputs found
Granular Materials, Contact Problems, DVI, MPRGP
Active-set algorithm for solving inner optimization problem in multi-body dynamics is presented. The efficiency of our algorithm is demonstrated on the solution of simple simulation with thousands of moving spherical particles and static box obstacles. We discuss the solvability and the uniqueness of solution of the problem and the influence of solution to resulting velocity during time-stepping schema
QuadStack: An Efficient Representation and Direct Rendering of Layered Datasets
We introduce QuadStack, a novel algorithm for volumetric data compression and direct rendering. Our algorithm exploits the data redundancy often found in layered datasets which are common in science and engineering fields such as geology, biology, mechanical engineering, medicine, etc. QuadStack first compresses the volumetric data into vertical stacks which are then compressed into a quadtree that identifies and represents the layered structures at the internal nodes. The associated data (color, material, density, etc.) and shape of these layer structures are decoupled and encoded independently, leading to high compression rates (4× to 54× of the original voxel model memory footprint in our experiments). We also introduce an algorithm for value retrieving from the QuadStack representation and we show that the access has logarithmic complexity. Because of the fast access, QuadStack is suitable for efficient data representation and direct rendering. We show that our GPU implementation performs comparably in speed with the state-of-the-art algorithms (18-79 MRays/s in our implementation), while maintaining a significantly smaller memory footprint
On the representation of solutions of delayed differential equations via Laplace transform
In this paper, the unilateral Laplace transform is used to derive a closed-form formula for a solution of a system of nonhomogeneous linear differential equations with any finite number of constant delays and linear parts given by pairwise permutable matrices. This unifies the recent results on the representation of such solutions
Типовая учебная программа по учебной дисциплине для специальности 1-23 01 07 Информация и коммуникация
ZnS nanoparticles stabilized by cetyltrimethylammonium bromide (CTAB) were modelled in the Materials Studio environment. Four types of models with different distances between ZnS nanoparticles and different amounts of CTA cations without water and in water environment were built and characterized by calculated sublimation energies. The results of molecular modelling without water showed that the most favourable model consisted of two ZnS nanoparticles with a distance of 8-9 nm separated without immersing of CTAs. On the contrary, the most favourable model in water environment was composed of ZnS nanoparticles that nearly touched each other. CTA cations exhibited tendency to be located on the ZnS surface forming sparse covers. Size distributions of ZnS-CTA particles obtained by TEM measurements well agreed with molecular modelling results.Web of Science79121559154
Experimental Tests of Neutron Shielding for the ATLAS Forward Region
Experimental tests devoted to the optimization of the neutron shielding for the ATLAS forward region were performed at the CERN-PS with a 4 GeV/c proton beam. Spectra of fast neutrons, slow neutrons and gamma rays escaping a block of iron (404080 cm) shielded with different types of neutron and gamma shields (pure polyethylene - PE, borated polyethylene - BPE, lithium filled polyethylene - LiPE, lead, iron) were measured by means of plastic scintillators, a Bonner spectrometer, a HPGe detector and a slow neutron detector. Effectiveness of different types of shielding agaisnt neutrons and -rays were compared. The idea of a segmented outer layer shielding (iron, BPE, iron, LiPE) for the ATLAS Forward Region was also tested
Study of dielectron production in C+C collisions at 1 AGeV
The emission of e+e- pairs from C+C collisions at an incident energy of 1 GeV
per nucleon has been investigated. The measured production probabilities,
spanning from the pi0-Dalitz to the rho/omega! invariant-mass region, display a
strong excess above the cocktail of standard hadronic sources. The
bombarding-energy dependence of this excess is found to scale like pion
production, rather than like eta production. The data are in good agreement
with results obtained in the former DLS experiment.Comment: submitted to Physics Letters
The High-Acceptance Dielectron Spectrometer HADES
HADES is a versatile magnetic spectrometer aimed at studying dielectron
production in pion, proton and heavy-ion induced collisions. Its main features
include a ring imaging gas Cherenkov detector for electron-hadron
discrimination, a tracking system consisting of a set of 6 superconducting
coils producing a toroidal field and drift chambers and a multiplicity and
electron trigger array for additional electron-hadron discrimination and event
characterization. A two-stage trigger system enhances events containing
electrons. The physics program is focused on the investigation of hadron
properties in nuclei and in the hot and dense hadronic matter. The detector
system is characterized by an 85% azimuthal coverage over a polar angle
interval from 18 to 85 degree, a single electron efficiency of 50% and a vector
meson mass resolution of 2.5%. Identification of pions, kaons and protons is
achieved combining time-of-flight and energy loss measurements over a large
momentum range. This paper describes the main features and the performance of
the detector system
Scanning of irradiated silicon detectors using particles and low energy protons
In a spectroscopic study of non-irradiated and proton-irradiated silicon diodes, the detectors were illuminated from the front side and from the rear side by various alpha particle sources (mainly ThC') and by monoenergetic protons with energies from 1.0 to 2.5~MeV. Their response characteristics have been studied as a function of the incoming particle energy and the applied bias voltage. The charge collection efficiency was determined as a function of fluenc
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