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991.
992.
塑料挤出成型模具流道优化设计 总被引:3,自引:0,他引:3
本文依据流变学理论,采用优化方法进行挤出成型模具(即机头)流道设计,探讨了建立流道优化数学模型的有关问题。 相似文献
993.
994.
By analyzing the extended X-ray absorption fine structure (EXAFS) of the Mo K-absorption edge, structural information for both oxidic and sulfided K-MoO3/-Al2O3 catalysts with different potassium content was obtained. The oxidic samples show two backscatterer peaks in the radial distribution function (RDF), which correspond to the Mo-O coordinations in the nearest Mo-O shell. The nearest oxygen atoms are present with large configurational disorder. The RDF for the K/Mo = 0 sample is significantly different from that for crystalline MoO3 and ammonium heptamolybdate. The RDFs for potassium promoted samples are, in some extent, similar to that for ammonium heptamolybdate. The sample with K/Mo = 0.8 and that with K/Mo=1.5 do not show obvious difference in their local Mo-O structures. The EXAFS results support the earlier conclusions from Raman spectroscopy studies on identical samples [7]. When the samples are sulfided, a rearrangement of the local neighbors around Mo atoms takes place, to form small MoS2-like crystallites. The Mo-S and Mo-Mo coordination distances on these catalysts are the same as those in crystalline MoS2, but the coordination numbers are significantly lower than in MoS2. The EXAFS results indicate that Mo species on the K/Mo=0 catalyst mainly consist of Mo-S-Mo units (the basic building units of MoS2), which are highly dispersed and show a higher level of disorder than in MoS2. With the modification by the potassium promoter, Mo species are significantly aggregated and their local neighbors are more similar to those in MoS2, but the Mo species still exist in a state of high dispersion. 相似文献
995.
Modification of silk with aminated polyepichlorohydrin to improve dyeability with reactive dyes 总被引:1,自引:0,他引:1
Xie Weibin He Jinxin Chen Shuilin Chen Guoqiang Peng Taozhi 《Coloration Technology》2007,123(2):74-79
Reactive dyes have almost complete exhaustion and ideal fixation on aminated polyepichlorohydrin pretreated silk without addition of salt or alkali. The effects of varying pretreatments and dyeing conditions were studied. The dyeing behaviour of CI Reactive Red 15 on modified silk under pH 6 was investigated. Dyeings of modified silk showed good wash fastness, dry and wet rub fastnesses as well as light fastness. The quality of the dyed silks obtained after pretreatment was shown to be satisfactory and the dyeing effluent was less polluted. 相似文献
996.
997.
Yang Qin Frieder Jäkle 《Journal of Inorganic and Organometallic Polymers and Materials》2007,17(1):149-157
The binding of Lewis bases to organoboron polymeric Lewis acids has been studied and the parameters that determine the complexation
equilibrium have been investigated, which include (i) the strength of the individual Lewis acids and Lewis bases, (ii) concentration,
and (iii) temperature. While the strongly Lewis acidic borane polymers poly(4-bis(pentafluorophenyl)borylstyrene) (PS-BPf) and poly(4-(di-2-thienylboryl)styrene) (PS-BTh) form isolable complexes with strong Lewis bases such as 4-t-butylpyridine (tPy), a temperature dependent equilibrium is established with weaker bases such as THF. Similarly, the weakly Lewis acidic
boronate polymer poly(4-diethoxyborylstyrene) (PS-BOEt) undergoes a temperature dependent equilibrium with the strong Lewis base 4-dimethylaminopyridine (DMAP), while poly(4-pinacolatoborylstyrene)
(PS-BPin) does not significantly bind to pyridine bases. Decomplexation of PS-BTh·
t
Py is achieved by treatment with the stronger Lewis acid, B(C6F5)3, thereby confirming the reversible nature of the polymeric Lewis acid–base adducts.
This paper is dedicated to Professor Ian Manners in gratitude of his guidance throughout the years and recognition of his
scientific accomplishments 相似文献
998.
介绍了我国石化企业近年来压力管道专用树脂的研发生产状况,以及相关标准对聚乙烯(PE)压力管道树脂的要求。我国已有7家石化企业生产的PE压力管道专用树脂通过了PE 80级或PE 100级认证。随着我国石化企业对高等级管道专用树脂的开发,逐步改变了我国PE 100级管道专用树脂长期依赖进口的局面。 相似文献
999.
Kaneshiro ES 《Lipids》2004,39(8):753-761
Pneumocystis can transiently colonize healthy individuals without causing adverse symptoms, and most people test positive for exposure
to this organism early in life. However, it can cause Pneumocystis pneumonia (PcP) in people with impaired immune systems and is a major cause of death in HIV/AIDS. Although it has close affinities
to the Ascomycetes, Pneumocystis has features unlike those of any single group of fungi. For example, Pneumocystis does not synthesize ergosterol, which is consistent with the inefficacy of amphotericin B and some triazoles in clearing
PcP. Pneumocystis sterols include distinct Δ7 24-alkylsterols. Metabolic radiolabeling experiments demonstrated that P. carinii synthesizes sterols de novo. Cholesterol is the most abundant sterol in Pneumocystis; most, if not all, is scavenged from the mammalian host lung by the pathogen. The P. carinii erg7, erg6, and erg11 genes have been cloned, sequenced, and expressed in heterologous systems. The recombinant P. carinii S-adenosyl-l-methionine:C-24 sterol methyl transferase (SAM:SMT) has a preference for lanosterol over zymosterol as substrate, and the
enzyme can catalyze the transfer of either one or two methyl groups to the C-24 position of the sterol side chain. Two different
sterol compositions were detected among human-derived P. jirovecii; one was dominated by C28 and C29 sterols, and the other had high proportions of higher molecular mass components, notably the C32 sterol pneumocysterol. The latter phenotype apparently represents organisms blocked at 14α-demethylation of the sterol nucleus.
These studies suggest that SAM:SMT is an attractive drug target for developing new chemotherapy for PcP. 相似文献
1000.
We propose a fast method for 3D shape segmentation and labeling via Extreme Learning Machine (ELM). Given a set of example shapes with labeled segmentation, we train an ELM classifier and use it to produce initial segmentation for test shapes. Based on the initial segmentation, we compute the final smooth segmentation through a graph‐cut optimization constrained by the super‐face boundaries obtained by over‐segmentation and the active contours computed from ELM segmentation. Experimental results show that our method achieves comparable results against the state‐of‐the‐arts, but reduces the training time by approximately two orders of magnitude, both for face‐level and super‐face‐level, making it scale well for large datasets. Based on such notable improvement, we demonstrate the application of our method for fast online sequential learning for 3D shape segmentation at face level, as well as realtime sequential learning at super‐face level. 相似文献