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51.
In this paper we assume, like in Balint et al. [Mater. Sci. Semiconductor Process. V3/3 (2000) 115–121], that the melt/solid interface in the case of vertically stabilized Bridgman–Stockbarger semiconductor growth system is a thin layer, masking the crystal, where a weak form of the periodical structure of the crystal exists. In these conditions, using a new diffusion coefficient in the equation of the dopant transport in the interface region, we compute the axial and radial variation of the dopant field in this region for crystal and melt with thermophysical properties similar to the gallium-doped germanium. We compare the results to those obtained in Mater. Sci. Semiconductor Process. V3/3 (2000) 115–121 [1], where we have changed the diffusion coefficient only in the boundary condition for the dopant concentration at the melt/solid interface. 相似文献
52.
The catalytic behavior of the cubic (≈70%) Pt nanoparticles supported on alumina, with an average diameter of 132 nm, was investigated for NO/CH4 reaction. It was observed that the formation of reaction products (N2O, CO and NH3) is related to the size as well to the shape (facet) of the Pt nanoparticles.
相似文献53.
Vanda De Angelis Mariagrazia Mecoli Chris Nikoi Giovanni Storchi 《Computers & Operations Research》2007
This paper deals with the weekly planning of WFP emergency deliveries of food aid by air in Angola, where planes are required to travel back and forth between depots and clients, deliver entire loads to the client reached every time and, at night, park at a depot, subject to parking space availability. An ILP model has been formulated, called the VRVDFL model, tailored for the real problem, and has been solved. The computational experience is reported. 相似文献
54.
Spectral clustering in multi-agent systems 总被引:2,自引:2,他引:0
We examine the application of spectral clustering for breaking up the behavior of a multi-agent system in space and time into
smaller, independent elements. We propose clustering observations of individual entities in order to identify significant
changes in the parameter space (like spatial position) and detect temporal alterations of behavior within the same framework.
Available knowledge of important interactions (events) between entities is also considered. We describe a novel algorithm
utilizing iterative subdivisions where clusters are pre-processed at each step to counter spatial scaling, rotation, replay
speed, and varying sampling frequency. A method is presented to balance spatial and temporal segmentation based on the expected
group size, and a validity measure is introduced to determine the optimal number of clusters. We demonstrate our results by
analyzing the outcomes of computer games and compare our algorithm to K-means and traditional spectral clustering. 相似文献
55.
F. Sacconi M. P. Persson M. Povolotskyi L. Latessa A. Pecchia A. Gagliardi A. Balint T. Fraunheim A. Di Carlo 《Journal of Computational Electronics》2007,6(1-3):329-333
The electronic, structural and transport properties of silicon nanowires have been investigated with different approaches.
The Empirical Tight-Binding model (ETB) and Linear Combination of Bulk Bands (LCBB) method are used to calculate effect of
quantum confinement on electronic energies, bandgap and effective masses in silicon nanowires in function of Si cell size.
Both hydrogenated and SiO2 terminated silicon surfaces are studied. Transport properties of nanowires are obtained by applying the Non-Equilibrium Green
Function (NEGF) method. NEGF approach has been used to describe nanoMOSFET devices based on Silicon nanowires. 相似文献
56.
Lazar Balint Irena Vedrina-Dragojevi Marija Horvati Ivo Murati 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1994,198(1):29-32
A simple and highly selective spectrofluorometric method for the determination of the total mercury (Hg) in natural waters is described. Fluorescence quenching of rhodamine B with Hg(II) in the presence of iodide, after a concentration step, has been made the basis of this sensitive method. Organic and inorganic Hg compounds in water samples were decomposed with sulphuric acid and potassium permanganate. Precipitated manganese dioxide and excess oxidants (permanganate) were destroyed with hydroxylammonium chloride. Hg(II) was reduced by tin(II) chloride and Hg vapour driven by an air stream into an absorption solution containing potassium permanganate and sulphuric acid, using a closed, recirculating air stream. In this solution fluorescence quenching of rhodamine B at an excitation wavelength of 485 nm and emission wavelength of 586 nm was measured. This method is suitable for the determination of total Hg in drinking and surface waters. The method gives reliable results down to a concentration of 0.5 g Hg per litre of water. The water samples analysed by this method gave a mean recovery and standard error of 97.3±2.39 for added Hg.
Spektrofluorometrische Methode zur Bestimmung des Gehalts an Gesamtquecksilber im Wasser
Zusammenfassung Es wurde eine einfache, schnelle und hochselektive spektrofluorometrische Methode zur quantitativen Bestimmung des Gehalts an Gesamtquecksilber in Wasser beschrieben. Diese empfindliche Methode begründet sich auf der Fluorescenzlöschung in Rodamin-B-Lösung mittels Hg(II) bei Anwesenheit von Jodid und nach einem Verfahren, das den Zweck einer Quecksilberanreicherung hat. In Wasserproben wurden die organischen als auch anorganischen Quecksilberverbindungen mit H2SO4 aufgeschlossen und mit KMnO4 oxydiert. Nach der Beseitigung des entstandenen MnO2-Niederschlags bzw. des überschüssigen Permanganats mit HONH3Cl wurde das Quecksilber mit SnCl2 reduziert. Dann wurde das flüchtige Quecksilber durch einen Luftstrom in wässerige Absorptionslösung mit H2SO4 und KMnO4 eingeleitet und damit angereichert. In dieser Meßlösung wurde die Fluorescenzlöschung des Rodamin-B bei der Anregungswellenlänge von 485 nm und Emissionswellenlänge von 586 nm ermittelt. Das entwickelte Untersuchungsverfahren ist für die Bestimmung des Gehalts an Gesamtquecksilber in Trinkwasser und Oberflächengewässern anwendbar. Die Nachweisgrenze liegt bei etwa 0,5 g Quecksilber/L Wasser. Zusätze von Quecksilber zu untersuchten Wasserproben ergaben eine Wiederfindungsrate und Standardfehler von im Durchschnitt 97,3±2,39.相似文献
57.
Daiane?TomacheskiEmail authorView authors OrcID profile Michele?Pittol Carlos?E.?Ermel Douglas?N.?Sim?es Vanda?F.?Ribeiro Ruth?M.?C.?Santana 《Polymer Bulletin》2017,74(12):4841-4855
A common type of thermoplastic elastomer is a blend of styrene-ethylene-butylene-styrene copolymer (SEBS) with polypropylene and mineral oil. The knowledge about the processing parameters that influence the blend of these components is important to achieve the best material properties. In this study, were evaluated the influence of screw configuration (low and high shear) and speed (200, 300, and 400 rpm), molding form (compression and injection) and SEBS type (high and low molecular weight). The specimens were characterized according to their morphology, crystallinity, thermomechanical and mechanical properties. Samples processed in a screw with more kneading zones had a lower modulus value. Compression molded specimens had lower mechanical performance than injected samples. Samples prepared with low molecular weight SEBS presented a loss of mechanical properties. It was possible to correlate processing form with all the properties evaluated. The analyzed variables influenced the morphology, crystallinity and thermomechanical properties, but had low influence on the tensile properties. 相似文献
58.
The catalytic behavior of the cubic (70%) Pt nanoparticles supported on alumina, with an average diameter of 132nm, was investigated for NO/CH4 reaction. It was observed that the formation of reaction products (N2O, CO and NH3) is related to the size as well to the shape (facet) of the Pt nanoparticles. 相似文献
59.
Nanoindentation was used to determine room temperature Young's modulus and hardness of the top surface and cross section of an electron beam physical vapor deposited yttrium-stabilized zirconia layer. In situ observations of indentations inside a scanning electron microscope (SEM) chamber were used along with normalized cross correlation (NCC) to evaluate the degree to which indentation of a columnar microstructure can be affected by elastic structural deformation. It was found that (i) the top surface Young's modulus is roughly twice that of the cross section. (ii) Upon isothermal heat treatment at 1100 °C for 80 h, an increase in Young's modulus and hardness occurred, to a greater degree in the bottom 20 μm of the cross section, and in the top surface, which was attributed to preferential sintering in these zones. (iii) NCC analysis of SEM observations of nanoindentation in the cross section gave an estimate of the extent to which elastic structural deformation is a constituent of the measured displacement. It was found that depending on the indenter location relative to the columnar microstructure, an underestimation of the Young's modulus by as much as a factor of four can occur. 相似文献
60.
DNA polymerase η (Polη) is a translesion synthesis polymerase that can bypass different DNA lesions with varying efficiency and fidelity. Its most well-known function is the error-free bypass of ultraviolet light-induced cyclobutane pyrimidine dimers. The lack of this unique ability in humans leads to the development of a cancer-predisposing disease, the variant form of xeroderma pigmentosum. Human Polη can insert rNTPs during DNA synthesis, though with much lower efficiency than dNTPs, and it can even extend an RNA chain with ribonucleotides. We have previously shown that Mn2+ is a specific activator of the RNA synthetic activity of yeast Polη that increases the efficiency of the reaction by several thousand-fold over Mg2+. In this study, our goal was to investigate the metal cofactor dependence of RNA synthesis by human Polη. We found that out of the investigated metal cations, only Mn2+ supported robust RNA synthesis. Steady state kinetic analysis showed that Mn2+ activated the reaction a thousand-fold compared to Mg2+, even during DNA damage bypass opposite 8-oxoG and TT dimer. Our results revealed a two order of magnitude higher affinity of human Polη towards ribonucleotides in the presence of Mn2+ compared to Mg2+. It is noteworthy that activation occurred without lowering the base selectivity of the enzyme on undamaged templates, whereas the fidelity decreased across a TT dimer. In summary, our data strongly suggest that, like with its yeast homolog, Mn2+ is the proper metal cofactor of hPolη during RNA chain extension, and selective metal cofactor utilization contributes to switching between its DNA and RNA synthetic activities. 相似文献