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91.
T. Jovanovic Dj. Koruga B. Jovancicevic J. Simic-Krstic 《Fullerenes, Nanotubes and Carbon Nanostructures》2003,11(4):383-394
In the Bucky System II, based on electrical arc method, carbon soot was produced. Fullerenes C60 and C70 were Soxhlet extracted from the collected soot samples with toluene, chlorobenzene and with both of them successively, modifying the original methods. The yields of the both obtained toluene extracts were 5.4%. Chlorobenzene extract yield was 5.8%. After extraction of toluene insoluble soot with chlorobenzene, the entire extract yield was increased from 5.4% to 5.8%, due to modification of the existing methods. The difference of fullerenes solubilities in these solvents has been concluded. In the second part of our work toluene and chlorobenzene fullerenes extracts were separated by column chromatographies on active Al2O3, modifying the existing methods, by elution with hexane and mixtures of benzene, toluene, or xylene with hexane in determined ratios and orders. Identifications of buckminsterfullerene C60 in the first chromatographically purified fractions were achieved by electron impact ionization (EI) mass, IR, and UV/VIS spectroscopy. The second and the third purified fullerene fractions, toluene and chlorobenzene soot extracts were characterized by IR and UV/VIS methods. 相似文献
92.
93.
This paper presents two algorithms for determining the most reliable paths of a communication network, taking into account both the reliabilities of nodes and links. A network is modeled by a linear graph. The first algorithm adapts a node labeling scheme; second is based on the shortest-path matrix algorithm. Both algorithms can be applied to oriented and nonoriented nonsymetric networks. The numerical examples confirm that both algorithms efficiently handle networks with hundreds of nodes and edges. The total amount of computation, expressed by the number of multiplications and comparisons, increases in the labeling procedure with the square of the number of nodes, and in the matrix method with the cube of the number of nodes. 相似文献
94.
The topology selection, design, and performance evaluation of an on-board DC/DC converter, which delivers power from a 48 V input to a 1.2-1.65 V/70 A microprocessor load, are presented. It was shown that the symmetrical half-bridge topology with the current doubler and synchronous rectifiers is a suitable approach for this application. The measured full-load efficiency of a 200 kHz experimental half-bridge converter was higher than 82% in the entire output and input voltage range 相似文献
95.
The paper presents design considerations for a 12-V/1.5-V, 50-A voltage regulator module (VRM) for the next generation of microprocessors. The module has stringent power-density and transient-response specifications, which are hard to meet with traditional design techniques. The proposed design solutions increase the VRM efficiency, as well as achieve the desired transient response with a minimum amount of the output capacitance 相似文献
96.
Viseslava Rajkovic Dusan Bozic Milan T. Jovanovic 《Journal of Materials Processing Technology》2008,200(1-3):106-114
Copper matrix was reinforced with Al2O3 particles of different size and amount by internal oxidation and mechanical alloying accomplished using high-energy ball milling in air. The inert gas-atomised prealloyed copper powder containing 1 wt.% Al as well as a mixture of electrolytic copper powder and 3 wt.% commercial Al2O3 powder served as starting materials. Milling of Cu-1 wt.% Al prealloyed powder promoted formation of fine dispersed particles (1.9 wt.% Al2O3, approximately 100 nm in size) by internal oxidation. During milling of Cu-3 wt.% Al2O3 powder mixture the uniform distribution of commercial Al2O3 particles has been obtained. Following milling, powders were treated in hydrogen at 400 °C for 1 h in order to eliminate copper oxides formed at the surface during milling. Compaction was executed by hot-pressing. Compacts processed from 5 to 20 h-milled powders were additionally subjected to high-temperature exposure at 800 °C in order to examine their thermal stability and electrical conductivity. Compacts of Cu-1 wt.% Al prealloyed powders with finer Al2O3 particles and smaller grain size exhibited higher microhardness than compacts of Cu-3 wt.% Al2O3 powder mixture. This indicates that nano-sized Al2O3 particles act as a stronger reinforcing parameter of the copper matrix than micro-sized commercial Al2O3 particles. Improved thermal stability of Cu-1 wt.% Al compacts compared to Cu-3 wt.% Al2O3 compacts implies that nano-sized Al2O3 particles act more efficiently as barriers obstructing grain growth than micro-sized particles. Contrary, the lower electrical conductivity of Cu-1 wt.% Al compacts is the result of higher electron scatter caused by nano-sized Al2O3 particles. 相似文献
97.
Design considerations for a single-stage single-switch input-current shaper (S4ICS) which combines the boost-like front end with a continuous-conduction-mode DC/DC output stage are provided. A complete design-oriented mathematical model is derived for both discontinuous and continuous conduction modes of operation of the boost inductor. The design procedure is illustrated with the example of a 5-V/20-A universal line-voltage range S4ICS forward converter 相似文献
98.
Gordana Kocic Dusan Sokolovic Tatjana Jevtovic Tatjana Cvetkovic Andrej Veljkovic Hristina Kocic Svetlana Stojanovic Aneta Jovanovic Jelena Jovanovic Petar Zivkovic 《Journal of dairy science》2014
Cardiovascular repair and myocardial contractility may be improved by migration of bone marrow stem cells (BMSC) and their delivery to the site of injury, a process known as BMSC homing. The aim of our study was to examine the dietary effect of a newly patented depurinized milk (DP) that is almost free of uric acid and purine and pyrimidine compounds compared with a standard commercial 1.5% fat UHT milk diet or allopurinol therapy in rat experimental hyperuricemia. Bone marrow stem cell potential (BMCD34+, CD34-postive bone marrow cells), plasma oxidative stress parameters [advanced oxidation protein products, AOPP) and thiobarbituric acid reactive substances (TBARS)], myocardial damage markers [creatine phosphokinase (CPK), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH)], plasma cholesterol, and high-density lipoprotein cholesterol were investigated. The DP milk diet significantly increased the number of BMCD34+ stem cells compared with commercial UHT milk. Allopurinol given alone also increased the number of BMCD34+. Hyperuricemia caused a significant increase in all plasma enzyme markers for myocardial damage (CPK, LDH, and AST). A cardioprotective effect was achieved with allopurinol but almost equally with DP milk and more than with commercial milk. Regarding plasma AOPP, TBARS, and cholesterol levels, the most effective treatment was DP milk. In conclusion, the protective role of a milk diet on cardiovascular function may be enhanced through the new depurinized milk diet, which may improve cardiovascular system function via increased bone marrow stem cell regenerative potential, decreased plasma oxidative stress parameters, and decreased levels of myocardial damage markers and cholesterol. New dairy technology strategies focused on eliminating harmful milk compounds should be completely nontoxic. Novel milk products should be tested for their ability to improve tissue repair and function. 相似文献
99.
A novel, low-cost implementation of “democratic”load-current sharing of paralleled converter modules
A simple, low-cost, and robust “democratic” (autonomous) current-sharing (CS) circuit is proposed and analyzed. The circuit maintains good CS among the modules by properly adjusting the voltage references of the modules based on the differences between the average current of the paralleled modules and the currents of the individual modules. Design guidelines for achieving a desired CS performance are given and verified on a number of DC/DC modules operating in parallel 相似文献
100.
Betz R.E. Lagerquist R. Jovanovic M. Miller T.J.E. Middleton R.H. 《Industry Applications, IEEE Transactions on》1993,29(6):1110-1122
This work develops a comprehensive approach to the control of inverter-fed synchronous reluctance machines (SYNCREL), based on the machine's ideal model. From the theory a control simulation is designed. Simulation and experimental results are presented. The effects of saturation and iron losses are briefly considered 相似文献