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1.
热交换器是将不同温度介质之间的热量通过热传导的形式,由高温介质传递给低温介质,使介质达到生产所需温度的工艺设备,也可作为一种节能设备使用.通过对不同热交换器的结构分析,总结不同热交换器的优缺点、适用环境,为生产工艺设计人员及设备制造单位在选择可降低能耗、提高效率的设备上提供参考. 相似文献
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通过化学氧化法分别制备盐酸,盐酸和十二烷基苯磺酸,碳纳米管(MWNTs-COOH)掺杂的聚苯胺,利用红外光谱,紫外光谱,扫描电子显微镜和透射电子显微镜对所制备聚苯胺的结构和形貌进行分析。分析不同掺杂物对聚苯胺的结构和形貌的影响;同时研究了超声波作用对聚苯胺形貌以及聚苯胺包裹MWNTs-COOH情况的影响。 相似文献
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The curing of thermosets is a complex process involving the transition from a fluid into a (visco-) elastic solid. This phase transition comes along with an increase in stiffness and a volume shrinkage of the polymer. The latter may lead to severe residual strains and stresses, which in turn can cause damage in the final, usually quasi-brittle material. In this contribution a constitutive model is developed which takes into account the curing of a thermosetting material together with the process-induced damage as resulting from curing shrinkage. The curing of the material is governed by a phenomenological hypoelastic constitutive equation which includes temporal evolutions for stiffness and volume shrinkage. Thermal and viscous effects are neglected in the present study. An isotropic gradient-enhanced damage model is adapted to describe the damage evolution. The curing-damage model is implemented into a finite element code and numerical examples for thermosetting materials demonstrate that the proposed model is capable to predict cure-induced damage in thermosets. 相似文献
4.
I. I. Novikov 《Journal of Engineering Physics and Thermophysics》1987,53(5):1227-1232
Principles of the theory of thermodynamic similarity are considered in application to all aggregate states of a substance, including phase transitions, and to the change in dissipative structures in open systems.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 5, pp. 709–716, November, 1987. 相似文献
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A Wolfenden 《Journal of Materials Science》1997,32(9):2275-2282
Measurements of dynamic Young's modulus, E, and damping as a function of temperature, T, were made for alumina and silicon
carbide. The Young's modulus data were compared with some from the literature, and analysed in terms of a theoretical framework
relating the Debye temperature, θD, with the elastic constants. For both materials this analysis yielded a ratio T0/θD which was near 0.4, where T0 is an empirical fitting constant for the plot of (E(0)−E)/T versus 1/T (E(0) is the value of E at 0 K). The analysis of the
damping data in terms of an Arrhenius type dependence led to effective activation energies near kT, where k is Boltzmann's
constant.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
7.
A. Galerie Y. Wouters M. Pijolat F. Valdivieso M. Soustelle T. Magnin D. Delafosse C. Bosch B. Bayle 《Advanced Engineering Materials》2001,3(8):555-561
Selected topics in field of the study of the mechanisms of corrosion and of oxidation of metals or alloys are presented. The first part reports a new model for the mechanism of the breakaway oxidation of ferritic stainless steels in water vapour. The second part is devoted to the physico‐chemical aspects of oxidation and presents experimental methods useful in the kinetic modelling applied to two alloys, the zircalloy‐4 and an AlMg5 % in the liquid state. In the third part the physical and numerical modelling of the stress corrosion cracking behaviour in face‐centered cubic (fcc) alloys is detailed, which enables the study of the influence of macroscopic parameters (such as the temperature or hydrogen activity) on the fracture process. 相似文献
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Grace George S. K. Gupta P. V. R. Rao T. S. B. Narasaraju 《Journal of Materials Science》1987,22(6):2274-2276
Samples of phosphate and arsenate apatites of strontium and six of their solid solutions, spread over the entire compositional range, were prepared by a wet method. They were characterized by chemical, X-ray, electron microscopic and infrared analyses. The validity of Vegard's law established the homogeneity of the solid solutions. 相似文献
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Surface-charge density and potential of coal-liquid mixtures and control of their stability and fluidity 总被引:1,自引:0,他引:1
T. Hamieh 《Journal of Materials Science》1996,31(21):5665-5669
The preparation conditions of concentrated (>70%) aqueous suspensions of coal were optimized, as were the surface charge density and the surface potential of the coal-water suspensions. The theoretical study showed that (1–3) or (2–3) electrolytes such as Na2SO4 or Na5P3O10, greatly increase the surface charge density and the surface potential of the coal particles in water. This study has led to the interesting result that thinners and stabilizing agents of concentrated clay suspensions, such as lignosulphonates, tripolyphosphates, polynaphtalene sulphonates, etc., must also be good thinners and stabilizing agents for ground coal-water suspensions. Two parameters were controlled: the stability and the fluidity of the suspensions. A penetrometry technique revealed the importance of the resistance coefficient,C
r that can be used as a criterion for the evaluation of coal-water mixture stability and fluidity. Concentrated coal suspensions (about 75% of solid by weight) were prepared in water by using different additives, for instance sodium tripolyphosphate (NaTPP) and surfactants like lignosulphonates (by coupling of the dispersion and stabilizing effects) with the optimum concentration ratio of these two products equal to 1.9. The stability of the suspensions was then greater than 2 months and the viscosity was 1900 cP. 相似文献
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Synthesis of polymeric titanium and zirconium precursors and preparation of carbide fibres and films 总被引:2,自引:0,他引:2
Polymeric precursors for carbothermal reactions were prepared from the chelate derivatives of titanium and zirconium alkoxides L2M(OR)2 (L is an acetylacetonato or ethyl acetoacetato group) in alcohols by reaction with organic compounds having two or more reactive OH groups, such as ethylene glycol, saccharose, tartaric acid or dihydroxybenzenes. These organic groups act as bridging ligands in transesterification and condensation polymerization yielding either spinnable viscous solutions or elastic gels. The rheological properties of the concentrated solutions allowed for the preparation of polymer fibres and films. At temperatures up to 1600 °C, bulk precursors as well as fibres and films were thermally converted into carbide powders, films or coatings. The structural transformations of the polymeric materials into the carbides were investigated using thermogravimetric–differential thermal analyses (TGA–DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infra-red (FTIR) analysis and Raman spectroscopy. 相似文献
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A. Zmitrowicz 《Acta Mechanica》2003,166(1-4):185-206
Summary. Glaciers slide at their base. A deeper understanding of the frictional behaviour and sliding between an ice mass and a rock bed is an important problem in glacier physics. In this study we investigate two approaches to the problem of glacier sliding. The first approach models friction forces between the ice and the bed. The second approach considers various proposals of a sliding velocity. Anisotropy of rock bed topographies is a source of anisotropic tribological phenomena. Therefore, anisotropic and inhomogeneous friction and anisotropic sliding are discussed in detail. Various types of friction anisotropy are distinguished with the aid of linear and nonlinear friction models. Next, anisotropic friction and sliding rules are derived using an elasto-plastic analogy. A sliding law proposed by Hindmarsh is applied in the analysis of anisotropic sliding. Extended forms of the sliding law are given with the aid of anisotropic friction models. Furthermore, stick-slip motions are identified as important in the dynamics of glacier sliding. 相似文献
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HRP引发酚类与淀粉接枝共聚物的制备及结构性能表征 总被引:2,自引:0,他引:2
降解淀粉和酚类在辣根过氧化物酶(HRP)/H2O2的催化作用下进行自由基接枝共聚反应,制备了淀粉和酚类接枝共聚物。研究了淀粉降解程度、酚类单体配比、HRP用量、反应温度和pH对接枝改性淀粉结构与性能的影响。研究结果表明,用α-淀粉酶降解后的淀粉15与12g间苯三酚(PG)和20g对羟基苯磺酸钠(HBS)在5mg HRP/H2O2引发体系下,在30℃及pH值为7.0时反应5h制备的酚类与淀粉接枝共聚物具有较好的性能,其水溶液的表面张力为26.6mN/m,所鞣制皮革收缩温度(Ts)达到了78℃。用FT-IR、1 H NMR、UV-Vis和GPC等方法对产物的化学结构进行了表征。 相似文献
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SiH4,Si2H6的制备与分离 总被引:1,自引:0,他引:1
用Mg2Si制备SiH4必然伴随产生Si2H6.经二级低温冷凝 ,分子筛吸附和恒温恒压汽化等工艺技术过程,能够对两种气体进行最有效的分离 .并且可以制备Si2H6和总杂质含量≤10×10-6,基磷<0.2×10-9, 基硼<0.05×10-9的高纯SiH4. 相似文献
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Agbo SO Küster E Georgi A Akkanen J Leppänen MT Kukkonen JV 《Journal of hazardous materials》2011,189(1-2):235-240
Fate of organic contaminants under UV irradiation as environmental variable was studied. Aqueous solutions of pentachlorophenol and phenanthrene were subjected to simulated solar radiation and monitored during ≤ 93 h. Immobilization tests were conducted using Daphnia magna neonates in pre-irradiated water for the assessment of photoproduct-mediated toxicity. We observed a time-dependent decrease in exposure concentrations following irradiation, which correlated positively with reduced immobilization of the animals. A complete disappearance of the lowest and highest concentrations of pentachlorophenol was noted after 25 h and 75 h, respectively. Survivorship of the animals increased until 100% and correlated positively with irradiation time. However, phenanthrene was rather persistent under irradiation, with less than 25% decline in exposure concentrations after 93 h. Neonates were not immobilized at maximum aqueous solubility of phenanthrene. Rate constants (k) for the photodegradation of pentachlorophenol at 0.41, 0.59, 1.1, and 2.1 mg l(-1) were in the range of 7.2 × 10(-2) and 4.9 × 10(-2)h(-1), showing a slight decrease with increasing initial pentachlorophenol concentration. Nonetheless, pentachlorophenol degradation in the studied concentration range could still be described by the pseudo-first-order kinetics. K values for phenanthrene at 0.12 and 0.22 mg l(-1) were 2.9 × 10(-3)h(-1) and 4.2 × 10(-3)h(-1), respectively. 相似文献
20.
Charles W. Bert 《Dynamical Systems: An International Journal》1990,5(1):30-35
Single-wheel vehicles include the monocycle proposed by Leonardo da Vinci and the more familiar unicycle. Although these vehicles are very simple mechanically, their stability characteristics are complicated and it is believed that they have not been investigated analytically previously. In this paper, a unified analysis applicable to both types of vehicles is presented along with typical calculations and a discussion of their implications 相似文献