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1.
黑曲霉A3(AspergilusnigerA3)为高产木聚糖酶菌株。该菌所产生的木聚糖粗酶经硫酸铵、乙醇沉淀,SephadexG-100和DEAE-SephadexA-50分离纯化后,获得3个组分,分别称为X1、X2、X3。它们的最适反应温度和pH依次为40、50、50℃和35、45、50。  相似文献   

2.
实验研究CaO-MgO-SiO2熔块对Al2O3瓷烧结的作用结果表明:在20%wt%CaO,30wt%MgO,50wt%SiO2区域附近的熔块能很好地促进Al2O3瓷的低温烧结;除了第2相对晶界的钉扎作用以及固溶作用外,MgO在烧结中的作用能维持CaO/SiO2比,即维持烧结系统中的液相量;La2O3,Sm2O3能使Al2O3瓷的烧结温度下降大约30℃,其表面显微结构也有所改善。  相似文献   

3.
铅锶合金在硫酸溶液中的阳极腐蚀行为   总被引:1,自引:1,他引:1  
研究了可用作免维护铅蓄电池板栅材料的Pb-Sr及Pb-Sr-As-Sn合金的腐蚀性质。采用线性电位扫法,测上述合金在1.3V时恒电位生长的腐蚀膜中Pb(Ⅱ)化合物量随时间的变化率,并观察温度对此变化率的影响,计算了形成上述Pb(Ⅱ)化合物的反应在温度20°-50℃范围内的表观活化能。还比较了Pb-Sr合金和Pb-Ca合金的阳极腐蚀行为。  相似文献   

4.
合成渣对钢液吸氮的保护作用   总被引:6,自引:0,他引:6  
在真空感应炉中研究了1600℃渣层覆盖条件下气相中不同氮分压时,钢液中氮含量的变化。结果表明,钙基中性及氧化性渣,如CaO-Al2O3-SiO2和CaO-Al2O3-SiO2-FeO可作为绝缘层有效地防止氮在钢液和气相间的传质。因为在上述渣中,氮的溶解量约在30×10^-6 ̄80×10^-6之间。  相似文献   

5.
研究了磷对C4A3S单矿物及C3S-C2S-C4A3S-C4AF-CaSO4五元系统矿物形成及其水泥性能的影响。结果表明,少量的磷能改善系统的易烧性,降低烧成温度。当P2O5含量小于0.3%时,基本不影响C3S的形成,但降低水泥3d强度,而7d,28d强度增进幅度较大;磷阻碍C4A3S单矿物的形成,当P2O5达0.5%以上时,系统的C4A3S及C3S形成量明显减少,f-CaO升高,水泥各龄期强度均显著降低。  相似文献   

6.
Q相-CA-C_(12)A_7系列水泥烧成条件的研究   总被引:2,自引:2,他引:0  
在前人研究Q相合成基础上,研究了Q相-CA-C12A7系列水泥各矿物的烧成条件。研究结果表明:在Q相-CA-C12A7系统中,不同配比的生料在1260℃以下,熟料中形成CA,C12A7和C3A等铝酸盐化合物;在1260℃时,Q相开始形成,随着温度的升高,Q相的含量逐渐增大,CA、C12A7的含量逐渐减少;Q相的形成温度在1260~1300℃之间;在1300℃以上,试样开始熔化。  相似文献   

7.
喷射沉积Al-20Si-5Fe-3Cu-Mg   总被引:1,自引:0,他引:1  
利用喷射沉积技术制备了Al-20Si-5Fe-3Cu-1Mg合金,借助扫描电镜(SEM),X-射线衍射和拉伸试验等手段研究了喷射沉积合金的微观组织和力学性能,分析了Fe对合金挤压和热处理后的组织变化,拉伸试验结果表明,喷射沉积Al-20Si-5Fe-3Cu-1Mg合金具有比粉末冶金Al-20Si-3Cu-1Mg合金更高的高温(300℃)强度。  相似文献   

8.
用匀浆提取,90%硫酸铵沉淀和CM-纤维素、DEAE-SephabexA-50、SephadexG-100柱层析的方法从猪心肌中分离纯化了细胞质苹果酸脱氨酶。酶制品达到了IFCC规定的标准。  相似文献   

9.
研究了烧结温度对Fe-Cr-Mo-C系试样密度及性能的影响,探讨了实现烧结致密化的机理.结果表明,采用真空烧结工艺,在1160~1260℃范围内,Fe-(13~20)Cr-1.5Mo-(1.8~3.6)C粉末压块可实现液相烧结致密化,制得密度大于7.3g/cm3,硬度HRA70以上的高Cr烧结铁基材料.适宜的液相烧结温度随C含量增加而降低.  相似文献   

10.
ZA27合金熔炼     
1ZA27合金的化学成分及机械性能表1ZA27合金的化学成分主要成分%杂质含量<%AlCuMgZnFePbCdSn25-282.0-2.50.01-0.02余量0.100.0040.0030.002表2ZA27合金的物理性能σbMPaσaMPaδs%HB密度g/380-441365-3722.5-1190-1255.02材料准备表3炉料合金元素的标准名称牌号标准铝锭A1997或A1996GB1196-83锌锭Zn-0或Zn-1GB470-83镁锭Mg99.95GB3499-83铜Cu-1GB466-82中间合金AlCu-50GB87535-88ZnCl2二级以上GB1625-79变质剂自制3工装准备燃油坩埚炉一台;WRN-120EU-2测温仪一台;天平一架;其它炉炼工具自制。4熔炼及熔炼过程控制ZnAl27合金的熔炼与传统的有色合金熔炼过程无大的区别,其基本过程大致分为:准备(炉料、设备和工具)、加料、加热熔化、精炼变质、炉前检验和浇注六大步骤,较传统合金熔炼多了一道变质处理工序。其中熔炼过程温度的控制,精炼剂的脱水,合金的变质处理,回炉料的加入量等对合金的机械性能起着至关重要的作用。而整个熔炼过程则紧紧围绕...  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.
何延凌 《科技信息》2008,(4):258-258
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.
王慧 《科技信息》2008,(10):240-240
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.
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.
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.
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   

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