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1.
对HFC134a和CFC12水平管内流动沸腾换热进行了实验研究.在实验工况范围内,HFC134a比CFC12的沸腾换热系数高32%~43%;流量对HFC134a与CFC12水平管内流动沸腾换热系数之比的影响较大,干度和热流密度对其影响相对较小 相似文献
2.
5种新分离细菌的分子鉴定及分类 总被引:5,自引:0,他引:5
测定和比较了5种新分离细菌的16SrDNA序列,并对其进行分子鉴定和分类.结果表明:F5771和A5608为棒杆菌属(Corynebacterium)的2个新种;LCDC89055是1种放线菌,与Actinomycespyogenes遗传距离较近;而LCDC87080和CDCgroupANF1like则分别为Aneui和Turicelaotitidis菌的不同菌株. 相似文献
3.
HFC的MAC协议中随机访问机制性能分析 总被引:2,自引:0,他引:2
为了在HFC网络上实现交互式业务,人们对基于HFC网络的介质访问协议进行了广泛的研究,已出现了几种基于HFC的MAC协议.这些MAC协议基本上都采用了基于竞争的随机访问与预约相结合的协议,因此,基于竞争的随机访问机制的性能对整个协议的性能有非常大的影响.对基于HFC网络的MAC协议中竞争时隙所采用的随机访问机制的性能进行分析.首先给出随机访问机制的分析模型,然后求出了吞吐量通信量以及平均延时吞吐量的表达式. 相似文献
4.
比较研究了β环糊精(βCD)和阴离子表面活性剂(ASF)对Cu(Ⅱ)3,5diBrPADAB和Ni(Ⅱ)3,5diBrPADAB显色反应的协同作用.结果表明:βCD和ASF对显色反应能否起协同作用,主要决定于ASF的结构和疏水性的大小,以及显色配合物的结构和共轭体系的长短 相似文献
5.
用DMFSOCl2和DMFPOCl3均能使莰烯甲酰化,所得ω甲酰基莰烯中均以E型异构体为主.随着甲酰化反应温度降低,Z型ω甲酰基莰烯的得率有所增加. 相似文献
6.
Automatic Fixture Planning 总被引:1,自引:0,他引:1
IntroductionWiththerapiddevelopmentofCIMStechnology,computeraidedfixturedesign(CAFD)isbecomingahighlightresearchfield.CAFD,... 相似文献
7.
分析了Fe基与TiC直接反应制备FeTiCp复合材料的工艺及复合强化机制,初步优化了工艺参数。结果表明,一定的TiCp含量有其对应的最佳烧结温度;而烧结保温时间对材料的性能无显著影响。淬火处理后能显著提高Fe基TiCp复合材料的硬度及耐磨性。 相似文献
8.
对现有FeMnSi、FeMnSiCrNi系形状记忆合金的成份和γε马氏体相变温度的实验测定数据进行了多元线性回归处理,建立了马氏体相变温度Mεs、Aεs以及相变热滞(Aεs-Mεs)与合金成份之间的定量经验关系.结果表明:Mn、Cr、Ni元素均降低相变温度Mεs和Aεs;但Si明显使其升高.同时表明此类合金中的Si、Cr含量增加,合金的相变热滞增大.这一结果为此类合金的成份设计提供了依据. 相似文献
9.
以玉米离体根和根细胞质膜(PM)为材料,研究了加铁培养和缺铁条件下EDTAFe3+还原酶和硝酸还原酶(NR)各自的活性差异,并比较了加入EDTAFe3+和铁氰化物对缺铁和加铁培养的根细胞质膜上NR活性的影响.发现缺铁条件下根细胞PMEDTAFe3+还原酶活性比对照高约15~23%,NR活性比对照下降了约17~43%,离体根实验也证明缺铁条件下EDTAFe3+还原酶活性高于加铁培养.EDTAFe3+促进质膜NR活性,而铁氰化物抑制质膜NR活性.加入不同离子对EDTAFe3+还原酶和铁氰化物还原酶(FCR)活性均有一定影响. 相似文献
10.
将荧光活性物质2(4二苯基)6苯基苯并恶唑(PBBO)固定在增塑的PVC膜中,研究水溶液中黄连素对PBBO的猝灭机理.结果表明,该体系存在静态猝灭和内滤效应两种猝灭机理.推导了黄连素浓度与F0/F(膜荧光强度/猝灭剂存在下膜荧光强度)之间的数学表达式,实验结果与推导的理论公式相符. 相似文献
11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness. 相似文献
12.
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly. 相似文献
13.
Wuthering Heights, Emily Bronte's only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well. 相似文献
14.
The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation. 相似文献
15.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。 相似文献
16.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death. 相似文献
17.
Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system. 相似文献
18.
Miao Maosheng 《华南师范大学学报(自然科学版)》2014,(6)
正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula- 相似文献
19.
Yang Weitao 《华南师范大学学报(自然科学版)》2014,46(6):137-138
We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re- 相似文献
20.
Bernard Kirtman 《华南师范大学学报(自然科学版)》2014,(6)
正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that 相似文献