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981.
Yeon-Pun Chang Bing-Chwen Yang Jiin-Wen Hwang 《Experimental Thermal and Fluid Science》1998,16(4):299-304
The influence of grooves in the U-turn areas for the multi-channel-plate heat exchangers (MCPHEs) is significant due to the friction and flow phenomena in this region. In this study, two types of MCPHE made of acrylic plates were tested: one with grooves in the U-turn area, one without. During this series of experiments, heat transfer rate, overall volumetric heat transfer coefficient, Nusselt number and overall pressure drop (i.e., including the entrance and exit losses) were measured and calculated in order to understand the overall performance of these two different constructions of MCPHE. The experimental results show that the heat exchanger without grooves in the U-turn area possessed higher heat transfer performance and lower overall pressure drop. 相似文献
982.
A constitutive relation to describe pseudo-elastic deformation in shape memory alloys is presented in this paper. It is capable
of describing deformation behaviour of polycrystalline materials under triaxial stress state as well as of monocrystalline
materials under one-dimensional condition. Total strain rate is supposed to be composed of elastic strain rate and transformation
strain rate. Deformation behaviour of Cu−Zn−Sn alloy and Ti−ni alloy is simulated by use of the proposed constitutive relation.
it is shown that simulated results are in a good agreement with experimental data.
The project supported by National Natural Science Foundation of China. 相似文献
983.
Coherent gradient sensing (CGS) method, a real time, full-field optical technique, is insensitive to vibrations and able to provide slope and curvature maps and surface topographies, to investigate non-uniform deformations. In this paper, we analyze the thermal effects on the optical path in CGS due to air convection, and the influence of grating thickness and refractive index on the measurement accuracy. A modified governing equation is derived considering the grating thickness, which is demonstrated by testing a standard sample. Finally, we apply CGS method to measure the full-field deformation of a specimen at high temperature. 相似文献
984.
Carbon nanomaterials, including herringbone graphite carbon nanofibers (GNFH), multiwalled carbon nanotubes (MWCNT), and carbon black, were surface-modified by a new poly(vinylpyrrolidone) (PVP) grafting process as well as by the conventional acid-oxidation (AO) process, and characterized by FTIR, TGA, Raman, HRTEM, XRD, and XPS measurements. Pt nanoparticles of 1.8 nm were evenly deposited on all PVP-grafted carbon nanomaterials. The effects of the two surface modification processes on the dispersion, average Pt nanoparticle sizes, the electrocatalytic performance, and electrical conductivities of Pt-carbon nanocomposites in direct methanol oxidation were systematically studied and compared. It was found that the PVP-grafted carbon nanomaterials have much less loss in the electric conductivity and thus better electrocatalytic performance, 17-463% higher, than their corresponding acid oxidation-treated nanocomposites. The electrocatalytic performance of the Pt-carbon nanocomposites decreases in the following order: Pt-PVP-GNFH > Pt-PVP-MWCNTarc > Pt-AO-MWCNTarc > Pt-PVP-MWCNTCVD > Pt-AO-MWCNTCVD > Pt-XC-72R > Pt-AO-GNFH, with the Pt-PVP-GNFH nanocomposite having approximately 270% higher performance than that of the Pt-Vulcan XC-72R nanocomposite. In addition, PtRu-PVP-GNFH shows even better (50% higher) electrocatalytic activity than the Pt-PVP-GNFH nanocomposite at a 0.6 V applied voltage. 相似文献
985.
Branched poly(1,4‐butylene carbonate‐co‐terephthalate)s: LDPE‐like semicrystalline thermoplastics 下载免费PDF全文
Seong Yeon Park Jiseul Chun Jong Yeob Jeon Pyung Cheon Lee Yongtaek Hwang Bo Geun Song Rafael Ramos Chang Y. Ryu Bun Yeoul Lee 《Journal of polymer science. Part A, Polymer chemistry》2015,53(7):914-923
Branched poly[1,4‐butylene carbonate‐co‐terephthalate]s (PBCTs) have been synthesized by the addition of a small amount of glycerol propoxylate ( 1 ) or pentaerythritol ( 2 ) in the polycondensation of 1,4‐butanediol, dimethyl carbonate, and dimethyl terephthalate. To avoid gel formation, the feed amount of 1 or 2 was carefully controlled at below 0.5 mol % for 1 and below 0.3 mol % for 2 . When feed of 1 or 2 was used, a high‐molecular weight melt state (Mw ~180,000 g/mol) was reached in a total reaction time of 5.5 to 6.5 h with a yield higher than 90%. The generated PBCTs were a semicrystalline polymer (Tg ~5 °C and Tm ~120 °C) when the terephthalate content (F[TPA]) was 45 to 50 mol %. The crystallization rate increased with increasing F[TPA] and branch content (F[ 1 or 2 ]); PBCT composed of F[TPA] = 49 mol % and F[ 1 ] = 0.44 mol % was crystallized completely in a short time, ~3 min, at a crystallization temperature of 50 °C. The branched PBCT exhibited more pronounced toughness in tensile test while providing the advantage of processibility at high shear rates due to the pronounced shear thinning in melt. It was also found that the branched PBCTs were biodegradable. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 914–923 相似文献
986.
987.
988.
A unified energy approach to a class of micromechanics models for composite materials 总被引:4,自引:0,他引:4
Several micromechanics models for the determination of composite moduli are investigated in this paper, including the dilute
solution, self-consistent method, generalized self-consistent method, and Mori-Tanaka's method. These micromechanical models
have been developed by following quite different approaches and physical interpretations. It is shown that all the micromechanics
models share a common ground, the generalized Budiansky's energy-equivalence framework. The difference among the various models
is shown to be the way in which the average strain of the inclusion phase is evaluated. As a bonus of this theoretical development,
the asymmetry suffered in Mori-Tanaka's method can be circumvented and the applicability of the generalized self-consistent
method can be extended to materials containing microcracks, multiphase inclusions, non-spherical inclusions, or non-cylindrical
inclusions. The relevance to the differential method, double-inclusion model, and Hashin-Shtrikman bounds is also discussed.
The application of these micromechanics models to particulate-reinforced composites and microcracked solids is reviewed and
some new results are presented. 相似文献
989.
990.
Zheng Yan LIN Wen Sheng WANG Kyo Shin HWANG 《数学学报(英文版)》2006,22(6):1767-1780
In this paper, we obtain functional limit theorems for d-dimensional FBM in HSlder norm via estimating large deviation probabilities for d-dimensional FBM in HSlder norm. 相似文献