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101.
针对3^n阶矩阵的乘法运行,给出了一种分块算法,其乘法运行量比常规的矩阵乘法计算方法和补零的基-2算法都有所减少。 相似文献
102.
GC Borgia P Fantazzini C Palmonari G Timellini 《Canadian Metallurgical Quarterly》1996,14(7-8):899-901
NMR Relaxation and Imaging have been applied to study preparation processes of ceramic porous samples. Relaxation analysis gives a clear characterization of the materials, with high sensitivity. Differences in the method of preparation and steps as low as 25 degrees C in the firing temperatures are well detectable. Furthermore, the images permit distinguishing the different samples. The effects of the contrast in relaxation times dominate those due to the different porosities of the samples. Scanning Electron Microscopy confirms the interpretation that the changes in relaxation times are due to different pore space structures associated with the different firing temperatures. The higher the firing temperature, the larger are the pores and the higher is the amount of compact, sintered matrix, leading to higher relaxation times. 相似文献
103.
采用表面效应集总模型综合考虑表面费米能级钉扎和表面复合效应,对AlGaAs/GaAsHBT表面效应的影响进行了二维数值模拟。结果表明,表面态的存在对集电极电流几乎不产生影响,但显著增加基极电流,使得电流增益明显下降。同时还发现在台面结构AIGaAs/GaAsHBT中外基区表面复合的集边效应,即外基区表面复合主要发生在发射极台面与外基区的交界处附近,与外基区长度基本无关。模拟还表明基区缓变结构可以减少表面复合,提高电流增益。 相似文献
104.
The coal filter cake is a product of fine coal after floatation which has an ash content of 7-13%, water content of 30±2%, and a particle size of less than 1 mm. The ash content was measured by the intensity of the single backscattered gamma-ray, and its accuracy is mainly dependent on the energy of the gamma-ray. The 238Pu low energy photon source is selected in this work. The energy of its gamma-ray is 15 keV, which can result not only in the best sensitivity, but also in the lowest contribution to the environment radiation. The root mean square deviation of the ash measurement is±0.33% (±1σ). 相似文献
105.
106.
几种火焰喷焊自熔性合金层的耐磨性能 总被引:7,自引:0,他引:7
研究了不同自熔性合金粉末火焰喷焊层的显微组织与抗磨粒磨损性能,并对其磨面形貌进行了SEM观察分析。结果表明,在Ni60自熔性合金中加入适量的镍包WC粉末可明显提高其喷焊层的抗磨粒磨损性能。当WC的加入量为35%(wt)左右时,该喷焊层与60Si2Mn调质钢相比,相对的耐磨性可提高6倍以上。 相似文献
107.
GC Viscomi 《Canadian Metallurgical Quarterly》1997,10(1):59-86
Type I IFNs constitute a family of proteins exhibiting high homology in primary, secondary, and tertiary structures. They interact with the same receptor and transmit signals to cellular nucleus through a similar mechanism, eliciting roughly homogeneous biological activity. Nevertheless, the members of that family, IFN alpha species, IFN beta and IFN omega, due to local differences in the structure sometime show distinct properties. From the reported data it results that even minute changes or differences in the primary sequences could be responsible for a significant variety of biological actions, thus inducing to the hypothesis that Type I IFNs, rather than to be the result of a redundant replication during the evolution play definite roles in the defense of living organisms to foreign agents. 相似文献
108.
The production of the cognitive internal state word know by four 2- to 5-year-old children and their parents was examined. The levels of meaning of cognitive words can be categorized hierarchically along the dimensions of conceptual difficulty and abstractness (see Booth & Hall, 1995). The present study found that children and their parents expressed low levels of meaning less frequently, whereas they expressed high levels of meaning more frequently as a function of age. The children's use of know was also correlated positively with (1) their number of different words produced suggesting that cognitive words are related to more general semantic processes, and (2) with parental use of those same cognitive words suggesting that parental linguistic input may be an important mechanism in cognitive word acquisition. Finally, young children tended to use know more to refer to themselves than to refer to others, whereas their parents tended to use know equally to refer to self and others. The importance of cognitive words in a theory of language acquisition is discussed. 相似文献
109.
Although long-term clinical studies have shown no excessive risk of lymphoma in rheumatoid arthritis (RA) patients treated with methotrexate (MTX), an increasing number of reports of this association continue to appear. We describe two cases, review the cases in the world's literature, and summarize their important characteristics. Possible oncogenic mechanisms are discussed. Most lymphoproliferation cases presented here have features of immunosuppression-associated lymphoma. The immunosuppressed state is attributable to a combination of factors, such as RA itself and the actions of MTX. The risk factors for RA patients to develop lymphoma while on MTX include severe disease, intense immunosuppression, genetic predisposition, and an increased frequency of latent infection with prooncogenic viruses such as Epstein-Barr virus (EBV). The spontaneous remission of lymphomas in eight RA patients after MTX was stopped highlights the likely causative role of the drug in the development of these malignancies. If the clinical situation permits, a period of observation for spontaneous remission after MTX is stopped is advisable. The physicians caring for RA patients on MTX should maintain a high surveillance for signs and symptoms suggestive of lymphoma. 相似文献
110.