首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 78 毫秒
1.
设计了以烧结法制备铜表面多孔层的工艺过程,并以丙酮作为介质,测试了所制备的多孔表面强化管的传热性能.结果表明,表面多孔管显著地强化了沸腾给热.以0.074~0.046mm紫铜粉和R粉的复合粉烧结多孔管为例,当热通量为2.00×104~6.85×104kJ/(m2·h),沸腾给热系数可达2.23×104~5.28×104kJ/(m2·h·℃),比普通光滑管提高8~24倍;总传热系数可达3800~6236kJ/(m2·h·℃),比普通光滑管提高0.7~6倍  相似文献   

2.
利用脉冲法研究了间二甲苯在HZSM-5沸石上催化异构化动力学行为,在485-528℃温度范围内,载气流量25-60毫升/分,压力0.2-0.3MPa,反应是表观一级反应,表观活化能113.5kJ/mol。气相色谱保留体积法测得间二甲苯的吸附热国54kJ/mol,故得到表面反应活化能为59.5kJ/mol。  相似文献   

3.
磺化三聚氰胺甲醛树脂磺化阶段化学结构变化   总被引:8,自引:0,他引:8  
研究了羟甲基三聚氰胺磺化阶段体系化学结构的变化、产物的组成及pH值、温度和时间对磺化反应的影响。用13C—NMRMIJ定发现,在摩尔比F/M=4.0和S/M=1.0的反应体系中,磺化可同时发生在仲氮和叔氮原子上,两种结构之比约为2/1。在pH>11.0,温度为80-90℃和合适的时间内可以获得高磺化程度的三聚氰胺磷酸盐。  相似文献   

4.
用化学共沉淀法制得掺有一定量锑离子的α-Fe2O3,超微粉料.TG-DTA、XRD及SEM等分析表明,掺锑量(Sb/Fe原子比)小于0.2时,材料仍保持α-Fe2O3的晶体结构,但其晶化温度随Sb含量的增加向高温区移动;在低温段纯α-Fe2O3的晶粒生长活化能(Q=10.3kJ/mol)远小于Sb/Fe=0.1(Q=35.3kJ/mol)粉料的活化能;Sb5+取代α-Fe2O3晶粒中Fe3+格位与在450℃下长期工作粉料颗粒不易长大,是造成掺锑α-Fe2O3元件电阻降低一个多数量级及气敏性能显著改善的主要原因.  相似文献   

5.
葡萄糖-BrO3--Mn2+-H2SO4-丙酮体系的振荡反应   总被引:1,自引:0,他引:1       下载免费PDF全文
以葡萄糖为有机底物,与-BrO3--Mn2+-H2SO4-丙酮组成振荡反应体系,在恒温条件下进行振荡反应。结果表明:反应有诱导期,体系电导(L)不随时间(t)变化;振荡周期,L随t发生周期变化,溶液颜色在粉红色与无色之间交替变化,有典型的振荡波型。诱导期及振荡周期反应的表观活化能分别为84.275kJ/mol和98.153kJ/mol。体系振荡反应物浓度范围[葡萄糖]0.01~0.02mol/L,[BrO3-]0.03~0.045mol/L,[Mn2+]0.06~0.08mol/L,[丙酮]0.27~0.30mol/L,[H2SO4]0.8~1.2mol/L。振荡反应有Br2产生,Br2准一级消耗速率常数kBr2=1.6×10-5S-。对温度、反应物浓度、丙酮、Mn2+、Cl-、底物对振荡反应的影响作了探讨。  相似文献   

6.
用真空葛氏摆研究了CuZnAl形状记忆合金平衡状态下的内耗。在室温至500℃ 温度范围内,观测到两个弛豫型内耗峰,峰温分别为240℃和340℃(J≈1,7Hz). 通过改变频率测得240℃峰的弛豫激活能为113kJ/mol,345℃峰的弛豫激活能 为176kJ/mol.计算了两个峰的τ0值,确定345℃峰为α相中Zener弛豫 峰,240℃峰则是由β有序相内反向畴界处某种点缺陷运动所产生。  相似文献   

7.
钠快离子导体Na2.5Zr2-xTiSi1.51.512.0系统x=0-2.0的化合物,由NaPO-ZrO-ZrP-SiO-TiO为反应的起始原料,在900℃-1200℃的高温下反应数小时至二十小时制得。系统化合物的相变关系已探明,并测定了有关的单纯相在不同温度下的导电率以及电导激活能。相当于起始组成为Na2.5Zr1.0Ti1.0Si1.51.512.0的单纯相(标为2.51相)在300℃时的导电率σ300=1.85×10-2(Ω·cm)-1,其电导激活能为23.64kJ/mole,相当于起始组成为Na2.5Ti2.0Si1.51.512.0的单纯相(标为2.52相)在300℃时的导电率σ300=0.46×10-2(Ω·cm)-1,其电导激活能为28.89kJ/mole.  相似文献   

8.
以热重量法研究了Ce1-xTbxO2-δ(x=0.3,0.4,0.5)的缺氧分数6值.发现δ值随组成、环境氧分压和温度的不同在0.06—0.4范围内变化.样品CT30和CT50于650℃以上温度在空气中失氧形成氧空位的反应热熔经估算分别为36.0和40.6kJ/mol.研究表明,该数值主要由Tb离子的反应性决定,该复合氧化物中Ce离子的还原反应热焓显著小于它在纯CeO2-δ中的数值.  相似文献   

9.
长毛对虾酸性磷酸酶的纯化与性质   总被引:32,自引:2,他引:32  
分别从健康和患病长毛对虾(Penaeuspenicilatus)肌肉提取一种酸性磷酸酶(AC-Pae,EC.3.1.3.2.),进一步用硫酸铵分级分离,SephadexG-200柱纯化,经聚丙烯酰胺凝胶电泳,并于BeckmanDU-8B紫外分光光度计扫描为单一区带酶液。该酶紫外吸峰在280nm处,荧光激发峰在284nm处,发射峰在347nm处。酶的分子量为73000道尔顿,等电点为4.7酶水解对硝基苯磷酸二钠(PUPP)最适pH为4.5,最适温度40℃。健康虾与病虾酶的活化能分别为41.03kJ/mol·L和45.78kJ/mol·L,米多常数km值分别为0.80×10-4mol/L和1.43×10-4mol/L。重金属离子Cu2+,Hg2+,有机溶剂甲醇,乙醇,乙二醇等对ACPase有明显的抑制作用。  相似文献   

10.
研究了形如Ex(k)=Ax(k)+f(k,X(k))的非线性差分方程解的极限性质.Ex(k)=x(k+1).A是n×n(n≥2)阶常数矩阵.x(k)∈Rn.f:J×G→Rn,J={j0+k|k=1,2,….j0∈R},G.Rn.f满足对任一紧集中的x(k)一致有f(k,x(k))→0,当k→∞.利用差分不等式及比较原理得到:当A的谱半径小于1时,方程的有界解均趋于零解.当A的话半径大于1时,方程有无界解.并研究了所有解均趋于零解的充分条件.  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   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号