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排序方式: 共有270条查询结果,搜索用时 15 毫秒
1.
Alexandre Szklo Giovani Machado Roberto Schaeffer Jacqueline Mariano Janaí na Sala Marina Tavares 《Catalysis Today》2005,106(1-4):123-128
This paper assesses the impacts of a GTL plant on the expansion of Brazil's oil refining segment. The GTL plant (50,000 bpd) was sized to start up operations in 2015, producing diesel and naphtha through the indirect route (FT-synthesis). This plant will consume the non-associated natural gas production from the recent discoveries at the Santos Basin (around 419 Bm3), and the associated gas production from the Campos Basin. Both basins are located in the Southeast of Brazil, the most populated, rich and industrialized region of the country. Two different criteria for refinery expansion were simulated in order to meet oil product demand scenarios. Findings show that depending on the refinery expansion criteria considered GTL will play a fundamental hole to meet the oil product demand forecast to Brazil in the next 10 years. 相似文献
2.
We propose that chronically denervated Schwann cells may be less able to respond to axonal signals than their acutely denervated counterparts, and that this lack of sensitivity may be one reason why axons fail to regenerate into chronically denervated nerve stumps. To test this proposal we have used in situ hybridization, and quantitative and qualitative immunohistochemistry to compare the expression of c-erbB2 and c-erbB4 receptors in Schwann cells denervated for up to 6 months in vivo, with that seen in Schwann cells denervated for similar periods of time but then exposed to regenerating axons. The results were correlated with the extent of axonal regeneration in each experimental group as assessed from transverse sections which had been double-immunolabelled using anti S-100 and anti-beta tubulin III antibodies. Since c-erbBs are receptors for neuronally derived neuregulins we probed the appropriate axotomised DRG neurons for expression of GGF2 mRNA. When the denervated distal stumps were anastomosed to acutely transected proximal stumps, GGF expression in DRGs increased transiently during the first week: we assume that secreted GGF2 derived from regrowing axon sprouts would have been available to Schwann cells in all distal stumps. Endoneurial cell proliferation (predominantly Schwann cell proliferation); levels of expression of c-erbB receptors by Schwann cells, and the degree to which axons regenerated into the distal stumps all decreased as the period of prior denervation increased: the longer the time of denervation, the lower the expression of c-erbBs in Schwann cells, and the smaller the percentage of bands of Bungner which were re-innervated. 相似文献
3.
B Godeau E Oksenhendler Y Brossard J Bartholeyns JB Leaute N Duedari A Schaeffer P Bierling 《Canadian Metallurgical Quarterly》1996,36(4):328-330
BACKGROUND: The platelet count increases transiently after treatment with polyclonal anti-D in about 50 percent of D+ patients with autoimmune thrombocytopenic purpura (AITP). The effect is usually attributed to macrophage Fc-receptor blockade by antibody-coated red cells. As polyclonal anti-D is in limited supply, prospective testing was performed on a monoclonal anti-D (MoAb D) in such patients. STUDY DESIGN AND METHODS: Seven D+ patients with chronic AITP received MoAb D intravenously at doses of 47 to 95 microg per kg of body weight. Response was assessed by studying platelet count increment. Hemolysis and red cell-bound MoAb D were measured before and after MoAb D administration. RESULTS: MoAb D red cell binding was demonstrated in all patients at a ratio higher than that observed in AITP patients successfully treated with polyclonal anti-D. However, little or no platelet count increment was observed in six patients, while a transient response was observed in only one (platelet count 97 x 10(9)/L before MoAb D infusion and 163 x 10(9)/L 4 days later). Furthermore, because five patients showed signs of hemolysis and two became anemic, higher doses of MoAb D should be used only with caution in patients with AITP. CONCLUSION: The MoAb D used in this study cannot be proposed as an alternative treatment for patients with AITP. 相似文献
4.
5.
Ariel Felner Uzi Zahavi Robert Holte Jonathan Schaeffer Nathan Sturtevant Zhifu Zhang 《Artificial Intelligence》2011,175(9-10):1570-1603
In the field of heuristic search it is usually assumed that admissible heuristics are consistent, implying that consistency is a desirable attribute. The term “inconsistent heuristic” has, at times, been portrayed negatively, as something to be avoided. Part of this is historical: early research discovered that inconsistency can lead to poor performance for A? (nodes might be re-expanded many times). However, the issue has never been fully investigated, and was not re-considered after the invention of IDA?.This paper shows that many of the preconceived notions about inconsistent heuristics are outdated. The worst-case exponential time of inconsistent heuristics is shown to only occur on contrived graphs with edge weights that are exponential in the size of the graph. Furthermore, the paper shows that rather than being something to be avoided, inconsistent heuristics often add a diversity of heuristic values into a search which can lead to a reduction in the number of node expansions. Inconsistent heuristics are easy to create, contrary to the common perception in the AI literature. To demonstrate this, a number of methods for achieving effective inconsistent heuristics are presented.Pathmax is a way of propagating inconsistent heuristic values in the search from parent to children. This technique is generalized into bidirectional pathmax (BPMX) which propagates values from a parent to a child node, and vice versa. BPMX can be integrated into IDA? and A?. When inconsistent heuristics are used with BPMX, experimental results show a large reduction in the search effort required by IDA?. Positive results are also presented for A? searches. 相似文献
6.
A VLSI design of a multiprecision matrix multiplier and polynomial evaluator that addresses the issues of implementation is described. The design consists of a two-dimensional array of bit-serial multiply and accumulate cells, each implemented as an accumulator and a pair of registers. A configuration of N2 cells can perform N-width band-matrix multiplication, N × N full-matrix multiplication, and evaluate N polynomials of N coefficients at N points for two's complement numbers, each in linear time. The cell design allows the precision of the calculations to be arbitrarily increased easily, either linearly in space or time. Using current technology, 32-bit multiplication of 100 × 100 matrices can be performed in an estimated quarter of a millisecond. 相似文献
7.
G.A. Oliveira Junior L.R. Schaeffer F. Schenkel F. Tiezzi C.F. Baes 《Journal of dairy science》2021,104(4):4404-4412
About 30% of producers use hormone protocols to synchronize ovulation and perform timed artificial insemination (AI) in Canada. Days from calving to first service (CTFS) and first service to conception (FSTC) become masked phenotypes leading to biased genetic evaluations of cows for these fertility traits. The objectives of this study were to (1) demonstrate and quantify the potential amount of bias in genetic evaluations, and (2) find a procedure that could remove the bias. Simulation was used for both objectives. The proposed solution was to identify cows that have been treated by hormone protocols, make their CTFS and FSTC missing, and perform a multiple trait analysis including traits that have high genetic correlations with CTFS and FSTC, and which are not affected by the hormone protocols themselves. A total of 12 scenarios (S1–S12) were tested, changing the percentage of herds and cows that were randomly selected to be under timed AI. Cows that were given hormone protocols had CTFS of 86 d and FSTC of 0, which were used in genetic evaluation. Four criteria were used to indirectly measure the presence of bias: (1) the correlation between true (TBV) and estimated (EBV) breeding values (accuracy); (2) the differences in the mean EBV of top 25, 50, and 75 sires; (3) changes in correlation between TBV and EBV rankings; and (4) the changes in mean EBV over the simulated generations. All criteria changed unfavorably and proportionally to the increased use of timed AI. The accuracy within each class of animals (cows, dams, or sires) decreased proportionally with increased use of timed AI, varying from 0.32 (S12) to 0.52 (S1) for bull EBV for CTFS. The average EBV of the top sires (best 25, 50, 75, or 100 sires) approached population average EBV values when increasing the number of treated animals. The sire rank correlation between EBV and TBV within simulated scenarios was smaller for scenarios with more synchronized animals, going from 0.38 (S12) to 0.67 (S1). The long-term use of hormonal synchronized cows clearly decreased the mean EBV over generations in the population for CTFS and FSTC. The inclusion of genetically correlated traits in a multiple trait model was effective in removing the bias due to the presence of hormonal synchronized cows. However, given the constraints within the simulation, it is important that further investigation with real data is conducted to determine the true effect of including timed AI records within genetic evaluations of fertility traits in dairy cattle. 相似文献
8.
We present a scalable approach for the fabrication of large-area arrays of carbon nanotube (CNT) structures using focused laser beams in the 0.05–10 W range. We show that CNT films can easily be micromachined into arrays of columns using a wide variety of commercially available pulsed lasers – Excimer, diode-pumped solid-state (DPSS), and CO2 – operating at wavelengths from 248 nm to 9300 nm. We demonstrate that vertically aligned carbon nanotube (VACNT) arrays with pitches from 20 to 500 μm can be produced with aspect ratios greater than 20:1. Machining speeds up to 425 mm/s were demonstrated and trenches were produced from 10 to 200 μm wide depending on the laser method and beam size. The CO2 laser had the largest beam diameter of 175 μm and produced the widest columns with the most taper. The remaining lasers, having beam diameters between 10 and 100 μm, produced smaller columns and finer pitch arrays. The VACNT arrays were shown to have high surface quality with no observable residue left behind, demonstrating focused laser micromachining as a readily available soft tooling means for direct manufacturing of VACNT devices. Laser micromachining methods are compared to evaluate the tradeoffs between quality and manufacturing costs. 相似文献
9.
Kamenova L. Avenas Y. Schaeffer C. Tzanova S. Kapelski G. Schulz-Harder J. 《Industry Applications, IEEE Transactions on》2009,45(5):1763-1769
This paper presents the concept and experimental demonstration of flat copper heat pipe (HP) embedded in extremely thin 3-D packaging substrates. Since conventional machining for this application is very complicated and expensive, the direct bonded copper (DBC) technology proved to be interesting for mass production. The experimental results demonstrated that the DBC HP is an excellent solution to enhance the heat transfer within the 3-D packaging. 相似文献
10.
B. Viehweger A. Karabet M. Düring L. Schaeffer 《Materialwissenschaft und Werkstofftechnik》2005,36(5):211-217
Mg‐wrought alloys recently became an engineer material of constantly increasing interest. The mechanical properties of extruded Mg‐feedstock of the alloys AZ80 and AZ31 indicate their suitability for automotive applications in form of high‐quality forgings. Therefore a detailed knowledge about the forming behaviour is of particular importance. In order to compare mechanical properties of available Mg‐feedstock qualities compression tests at room temperature have been carried out by applying batches of AZ31‐ and AZ80‐feedstock. Cylindrical specimens were made out of received continuously casted as well as extruded AZ31‐ and AZ80 ‐ rods. A quantitative analysis of Mg‐feedstock’s microstructure has been carried out. The characterization of the deformability of applied Mg‐feedstock under hot working conditions could be performed by means of uniaxial plain strain upsetting tests at temperatures between 300 and 450 °C as well as logarithmic strain rates of 10‐1, 1 and 10s‐1. It is shown that the chosen parameter range ensures an enhanced deformability of continuously as well as extruded Mg‐feedstock. The subsequently carried out determination of microstructural evolution could be related to obtained flow stress curves of applied batches of Mg‐feedstock. Furthermore, FVM/FEM‐systems have been employed in order to design a simplified geometry of heated forging dies suitable for forging tests. The tests have been carried out by means of a hydraulic press. During the tests their punch velocity has been varied between 1 and 40 mm/s. Hence numerically simulated results could be confirmed by practical tests. Exemplary forgings of a simplified shape were made out of all applied batches of Mg‐feedstock. No remarkable failures have been detected. 相似文献