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反应—膜分离耦合过程的传质特性 总被引:4,自引:0,他引:4
在中空纤维膜系统中用纯水及不同浓度的氢氧化钠溶液和二氧化碳混合气进行反应分离,研究了膜分离与化学反应耦合过程的特性,在低二氧化碳进口摩尔分率、低气速及办高氢氧化钠浓度时,化学反应对分离的增强因子非常大。在反应-膜分离耦合体系中,过程阻力与中空纤维膜自身的阻力及溶液中的反应速度有很大关系。由于增加了中空纤维膜阻力,使得二氧化碳的吸收率比较小,但是增加中空纤维数目可以使膜分离器具有巨大的传质表面积,从 相似文献
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介绍不同雷诺数下海水绕流深海扬矿管的流动情况,分析管面形成层流及湍流边界层的分离过程,比较二者分离点的位置及压差阻力情况,分析绕流阻力和举力的形成过程、计算方法、影响因素及相应的减阻措施。 相似文献
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分析了高铬复合辊中铬偏析形成的原因及对剥落的影响。铬偏析影响共晶碳化物的组成及形态,控制组织对裂纹扩展的阻力,对轧辊的使用性能有直接的影响。 相似文献
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海水绕流场矿管边界层分析 总被引:1,自引:0,他引:1
介绍不同雷诺数下海水绕深海扬矿管的流动情况,分析管面形成层流及湍流边界层的分离过程,比较二者分离点的位置及压差阻力情况,分析绕流阻力和举力的形成过程、计算方法、影响因素及相应的减阻措施。 相似文献
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使用载荷分离理论的延性断裂韧性单试样方法,选取汽轮机转子钢Cr2Ni2MoV对规则化法和SPb分离参数法进行了研究.结果表明,在规则化法中,钝化修正时的钝化线方程仅对裂纹扩展较小时的J阻力曲线产生影响.提出了改进SPb分离参数法,消除了参考钝裂纹试样的影响;同时采用钝化修正后的初始裂纹长度和试验终止裂纹长度进行标定,可获得合理的裂纹长度预测结果.由改进SPb分离参数法得到J阻力曲线在较小裂纹扩展范围内均略高于由规则化法得到的J阻力曲线,而当裂纹产生扩展较大时,两种方法得到的J阻力曲线几乎完全重合;由规则化法得到的条件启裂J积分JQ值偏于保守. 相似文献
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《Acta Metallurgica》1982,30(10):1901-1907
Plastic flol of an Fe-30Mn-1Si alloy single crystal has been examined belol and above the Md temperature. By conducting a tlo step deformation test, it has been found that pre-injected ϵ-plates produce extremely large resistance against motion of either perfect or partial dislocations crossing them, in contrast to the relatively small hardening observed in the identical test of an Fe-18Cr-14Ni alloy. This has been discussed in terms of the dislocation pile-up and the resistance to plastic deformation in the blocking ϵ plates. Collision to and penetration through pre-injected ϵ plates of a groling ϵ plate have been examined under an electron microscope. 相似文献
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S. Das T. K. Bandyopadhyay S. Ghosh A. B. Chattopadhyay P. P. Bandyopadhyay 《Metallurgical and Materials Transactions A》2003,34(9):1919-1930
This investigation envisages the performance evaluation of a series of plasma-sprayed coatings from a few inexpensive powders,
namely, alumina, plasma dissociated zircon (PDZ), zircon sand, and zircon-20 wt pct calcia. The hardness and adhesion (bond)
strength of the coatings have been evaluated. All coatings offer an attractive thermal fatigue property. An added layer of
yttria between the top and bond coats improves the thermal fatigue resistance appreciably. The wear performance of these coatings
has also been evaluated using a “pin-on-disc” type wear testing setup. The Indian alumina coating offers a superior wear resistance
and thermal fatigue property compared to an imported alumina coating. The coatings based on zirconia-silica offer an attractive
thermal fatigue resistance along with an acceptable wear resistance. The latter improves considerably upon annealing of the
coatings because of the removal of the residual stresses accumulated during deposition. Among these zirconia-silica-based
coatings, the zircon-20 wt pct calcia is the most promising. The finishability of these coatings has been studied using a
surface grinding setup equipped with a diamond wheel. The cutting forces and the surface roughness of the ground surface have
been measured. The coatings have been found to possess a reasonably good grindability. 相似文献
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S. A. Muboyadzhyan L. P. Egorova D. S. Gorlov E. E. Bulavintseva 《Russian Metallurgy (Metally)》2017,2017(1):1-9
The corrosion resistance of an Ni–Co–Cr–Al–Si–Y + SPh (SPh is silicophosphate impregnation) alloy coating on 30Kh13, 38Kh2MYuA, VKS5, and VKS7 structural steels with low tempering temperatures has been studied. The steel–coating compositions have been tested to determine the accelerated cyclic corrosion resistance, the corrosion resistance under tropic climate chamber conditions and in salt fog, the stress corrosion resistance, and the corrosion resistance in an industrial atmosphere. The heat stability of coated samples is studied, metallographic studies of the samples before and after the tests are performed, and the influence of the coating on the strength characteristics of the structural steels is studied. 相似文献
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Beutler Larry E.; Rocco Francisco; Moleiro Carla M.; Talebi Hani 《Canadian Metallurgical Quarterly》2001,38(4):431
This article reviews extant literature on how patient resistance has been defined and its effects on psychotherapy. Resistance has been considered as both a patient-in-treatment state and as an enduring trait. In either form, patient resistance seems to interfere with treatment outcome. Resistance also functions as a moderating variable in determining the effectiveness of different levels of therapist directiveness. The evidence that patients who enter treatment with high levels of trait like resistance will benefit most from nondirective interventions is moderately strong. Conversely, those who enter treatment with low levels of trait like resistance benefit most from therapist directed interventions. Therapeutic practices associated with the research evidence are advanced. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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《Acta Metallurgica Materialia》1993,41(2):505-511
The fracture resistance of two directionally-solidified, NiAl refractory metal systems has been measured and analyzed. One system, NiAl/Mo, has a microstructure consisting of Mo rods. The second system, NiAl/Cr(Mo), has a layered microstructure. Both materials are found to have an appreciably higher initiation toughness than NiAl, followed by a rising resistance, with the layered microstructure giving the superior properties. The results have been rationalized by available models based on the following three mechanisms: crack trapping, crack renucleation and ductile phase bridging. 相似文献
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PA Meier DP Dooley JH Jorgensen CC Sanders WM Huang JE Patterson 《Canadian Metallurgical Quarterly》1998,177(4):951-954
Campylobacter fetus subspecies fetus has been recognized as a cause of systemic illness in immunocompromised hosts, including relapsing bacteremia in human immunodeficiency virus (HIV)-infected patients. Acquired resistance to quinolone therapy, while reported for a variety of bacteria, including Campylobacter jejuni, has not been previously documented for C. fetus. Two cases of quinolone-resistant C. fetus bacteremia were detected in HIV-infected patients. Cloning and nucleotide sequencing of the C. fetus gyrA gene in the 2 resistant isolates demonstrated a G-to-T change that led to an Asp-to-Tyr amino acid substitution at a critical residue frequently associated with quinolone resistance. In addition, comparison of the pre- and posttreatment isolates from 1 patient documented outer membrane protein changes temporally linked with the development of resistance. Relapsing C. fetus infections in quinolone-treated HIV-infected patients may be associated with the acquisition of resistance to these agents, and this resistance may be multifactorial. 相似文献
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ML Zeckel 《Canadian Metallurgical Quarterly》1997,9(5):311-31; discussion 332-5
The worldwide increase in the incidence of resistant Gram-positive infections has renewed interest in the glycopeptide class of antimicrobial agents. Two glycopeptides are available in many parts of the world--vancomycin and teicoplanin. These two agents appear to differ in several respects, including: potential for selecting microbial resistance, dosing convenience, safety, and efficacy in severe infection. Teicoplanin appears to have lower toxicity and greater convenience; however, its widespread acceptance has been plagued by concerns over antimicrobial resistance, efficacy, and appropriate dosing. A review of available studies suggests that teicoplanin, when dosed at 6 mg/kg/day, is better tolerated than vancomycin 15 mg/kg/q12h; however, at these doses, it appears to be somewhat less effective than vancomycin in serious Staphylococcus aureus infection, such as endocarditis. Although higher doses of teicoplanin, 12 mg/kg/day to 30 mg/kg/day, have been associated with efficacy comparable to that of vancomycin in serious S. aureus infections, such doses may eliminate some of the safety advantages conferred by lower teicoplanin doses. Teicoplanin has been associated with resistance among coagulase-negative staphylococci and the selection of resistance in S. aureus. There is some evidence that widespread use of teicoplanin might accelerate the development of S. aureus resistance to both teicoplanin and vancomycin. The selection of an appropriate glycopeptide in an individual patient should be based not only on convenience, but also on a determination of optimal efficacy, safety at an efficacious dose, and the potential for resistance. 相似文献
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Solubility of nanopowders of vanadium, titanium, chromium, and zirconium borides and carbides and of silicon carbide has been studied in standard electrolytes used for nickel plating. As the objects of the investigation, nanopowders with the contents of the main phase of 92.6–95.3% and an average particle size of 35–62 nm have been used. Their corrosion resistance was estimated depending on the electrolyte acidity, temperature, and duration of the interaction. It has been established that within each group of compounds the nanopowders are close in terms of their corrosion resistance in the electrolytic solutions and are characterized by an unlimited induction period in alkaline media, except for the silicon-carbide nanopowder, which is stable in solutions of any acidity. 相似文献
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Enterococcus faecium, which was highly resistant to vancomycin (MIC 256 mg/liter), but susceptible to teicoplanin (MIC 2 mg/liter), caused two distinct episodes of infection on a renal unit in the United Kingdom. Pulsed field gel electrophoresis (PFGE) indicated that a single strain caused the first episode, while the second episode, which occurred 1 year later, involved multiple strains, all of which were distinct from the original strain. Vancomycin resistance in all but one of these strains was mediated by transferable plasmids that carried the vanB glycopeptide resistance gene. Transfer either of resistance plasmids or the vanB resistance determinant itself to different strains occurred during the second episode. Plasmid-mediated vanB resistance has not been widely documented. A retrospective study of a reference collection revealed two other vanB-encoding plasmids from an E. faecalis and an E. faecium referred from two further UK centers. Although restriction analysis indicated no similarity between the plasmids from the three different centers, all contained a 2.1-kb EcoRV fragment that hybridized with a probe for the vanB gene. This suggests that there has been dissemination of a conserved glycopeptide resistance determinant, of which vanB is a part. 相似文献