检索结果-南通市图书馆

Influence of Water Pollution on mIC of Stainless Steel 304L

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2002年第2期9卷 45-48页

作者： LING Yun CHEN z G GUEmPL P KAESSER m Jiangsu University of Science and Technology Zhenjiang 212013 China Jiangsu University of Science and Technology Zhenjiang 212013 China Industrial University of Konstance Konstance Germany Industrial University of Konstance Konstance Germany

Crystallization kinetics of Pr 8Fe 86 x zr x B 6 ( x =0, 1, 2) amorphous alloys was studied by DTA and XRD methods. The experimental results showed that the crystalline phases of Pr 8Fe 86 B 6 alloy are composed of α Fe phase, Pr 2Fe 23 B 3 and Pr 2Fe 14 B, when crystallization temperature is below 900 ℃. The activation energy of α Fe phase remains relatively constant about 306.09 kJ/mol, as the crystalline fraction of α Fe phase is below 8 %. At the beginning of crystallization, the activation energy of Pr 2Fe 23 B 3 and Pr 2Fe 14 B phases are 510.85 kJ/mol and 725.97 kJ/mol, respectively, and then the activation energy of three phases declines with increasing the crystalline fraction. The crystallization behavior of α Fe and Pr 2Fe 14 B essentially results in the formation of a α Fe/Pr 2Fe 14 B composite microstructure with a coarse grain size in annealed Pr 8Fe 86 B 6 alloy, which is attributed to a difficult nucleation and an easy growth for both the α Fe and Pr 2Fe 14 B in the alloy. zr can be used to change the crystallization behavior of the α Fe phase in Pr Fe B amorphous alloy, which is helpful to the formation of the α Fe/Pr 2Fe 14 B nanocomposite microstructure with a fine grain size for the α Fe phase in the alloy.

关键词： Pr 8Fe86-x zr xB 6 amorphous alloy crystallization kinetics activation energy

文献快报(3):童年早期食欲特征可预测青春期进食障碍风险

在线全文

学校读者我要写书评

暂无评论

中国学校卫生 2024年第4期45卷 508-508页

作者：左敏(编译) 孙莹(审校) 安徽医科大学公共卫生学院儿少卫生与妇幼保健学系合肥230032

进食障碍是一种严重的精神疾病,近年来在全球的发病率迅速上升。进食障碍经常与其他精神疾病并存,且死亡率较高。英国伦敦大学Llewellyn教授领衔的团队使用了荷兰R世代研究(Generation R Study)和英国Gemini研究的数据,对2801名荷兰儿童... 详细信息

进食障碍是一种严重的精神疾病,近年来在全球的发病率迅速上升。进食障碍经常与其他精神疾病并存,且死亡率较高。英国伦敦大学Llewellyn教授领衔的团队使用了荷兰R世代研究(Generation R Study)和英国Gemini研究的数据,对2801名荷兰儿童和869名英国儿童开展了为期10年的随访研究。儿童4~5岁时,父母报告儿童食欲特征;12~14岁时,青少年自我报告暴饮暴食和限制性进食等多种进食障碍症状。结果显示,童年早期对食物反应性较高(看到、闻到或尝到美味食物时有进食的冲动)会增加青少年期出现暴饮暴食、失控性进食(感到失控,吃得比平时多)、限制性饮食(限制食物摄入以控制或减轻体重)和补偿性行为(抵消暴食后体重增加的行为,如催吐、禁食、多运动等)的概率。

关键词：进食障碍食物摄入英国伦敦大学精神疾病随访研究自我报告青春期青少年期

male reproductive suppression： not a social affair

在线全文

学校读者我要写书评

暂无评论

Current zoology 2017年第5期63卷 573-579页

作者： z. Valentina zlzzRI Andrea JESSEN Joris m. KOENE Department of Ecological Science--Animal Ecology VU University Amsterdam De Boelelaan 1085 1081 HVAmsterdam The Netherlands

In the animal kingdom there are countless strategies via which males optimize their reproductivesuccess when faced with male-male competition. These male strategies typically fall into two maincategories： pre- and post-copulatory competition. Within these 2 categories, a set of behaviors,referred to as reproductive suppression, is known to cause inhibition of reproductive physiologyand/or reproductive behavior in an otherwise fertile individual. What becomes evident when con-sidering examples of reproductive suppression is that these strategies conventionally encompassreproductive interference strategies that occur between members of a hierarchical social ***, mechanisms aimed at impairing a competitor＇s reproductive output are also present innon-social animals. Yet, current thinking emphasizes the importance of sociality as the primarydriving force of reproductive suppression. Therefore, the question arises as to whether there is anactual difference between reproductive suppression strategies in social animals and equivalentpre-copulatory competition strategies in non-social animals. In this perspective paper we explore abroad taxonomic range of species whose individuals do not repeatedly interact with the same indi-viduals in networks and yet, depress the fitness of rivals. Examples like alteration of male repro-ductive physiology, female mimicry, rival spermatophore destruction, and cementing the rival＇sgenital region in non-social animals, highlight that male pre-copulatory reproductive suppressionand male pre-copulatory competition overlap. Finally, we highlight that a distinction between malereproductive interference in animals with and without a social hierarchy might obscure importantsimilarities and does not help to elucidate why different proximate mechanisms evolved. We there-fore emphasize that male reproductive suppression need not be restricted to social animals.

关键词： indirect sperm transfer, offensive strategies, male pre-copulatory competition, male reproductive suppression, repro-ductive strategies.

Impact of reduced frequency on the time lag in pressure distribution over a supercritical airfoil in a pitch-pause-return motion

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2019年第2期32卷 243-252页

作者： Haghighat z.ESLAmI Ali R.DAVARI m.R.SOLTANI Aerospace Division Department of Engineering Science and Research Branch Islamic Azad University Department of Aerospace Engineering Sharif University of Technology

Effects of reduced frequency, stop angle, and pause duration have been studied on a thin supercritical airfoil undergoing a pitch-pause-return motion, which is one of the classic maneuvers introduced by the AIAA Fluid Dynamics Technical Committee. Experiments were conducted in a low-speed wind tunnel at both a constant mean angle of attack and an oscillation amplitude with a reduced frequency ranging from 0.01 to 0.12. The desired stop angles of the airfoil were set to occur during the upstroke motion. The unsteady pressure distribution on the airfoil was measured for below, near, and beyond static stall conditions. Results showed that the reduced frequency and stop angle were the dominant contributors to the time lag in the flowfield. For stop angles in both belowand post-stall regions, the time for the flowfield to reach its steady state conditions, known as the time lag, decreased as the reduced frequency was increased. However, in the static-stall region and for a certain value of reduced frequency, a resonance phenomenon was observed, and a minimum time lag was achieved. The pressure distribution in this condition was shown to be highly influenced by this phenomenon.

关键词： Dynamic stall Pitch pause return motion Reduced frequency Static stall Time lag

Seismic performance and comparison of three different I beam to box column joints

在线全文

学校读者我要写书评

暂无评论

Earthquake Engineering and Engineering Vibration 2014年第4期13卷 717-729页

作者： z.Saneei Nia A.mazroi m.Ghassemieh H.Pezeshki School of Civil Engineering College of Engineering University of Tehran Department of Civil Engineering Central Branch of Azad University Building and Housing Researching Center

Despite the inherently advantages of the box column, finding the best option for the I beam to the box column connection is the main challenge in using the box column as a structural member for special moment frames. In this paper, the seismic performance of urtreinforced connection, weakened connection and strengthened connection was evaluated through a comprehensive experimental program. The seismic comparisons were fabricated by assessing the strength, ductility and energy dissipation in each configuration. Three full scale tests with several connections were carried out. All the specimens were subjected to cyclic loading and prior to failure by forming a plastic hinge in the beam, all the connections managed to reach an inelastic rotation of more than 6.0% rad. The experimental and analytical results showed that the seismic performance of the strengthened connection with flange and shear plates turned out to be the most effective in the beam to the box column connection. moreover, the normalized stress distribution of the continuity plates revealed that the possibility of the weld fracture in unreinforced connection is more than other specimens.

关键词： box column special moment frame unreinforced connection weakened connection strengthened connection seismic comparison

InGaN/GaN laser diode characterization and quantum well number effect

在线全文

学校读者我要写书评

暂无评论

Chinese Optics Letters 2009年第3期7卷 226-230页

作者： S.m.Thahab H.Abu Hassan z.Hassan Nano-Optoelectronics Research and Technology Laboratory School of PhysicsUniversiti Sains Malaysia

The effect of quantum well number on the quantum efficiency and temperature characteristics of In- GaN/GaN laser diodes （LDs） is determined and investigated. The 3-nm-thick In0.13Ca0.87N wells and two 6-am-thick GaN barriers are selected as an active region for Fabry-Perot （FP） cavity waveguide edge emitting LD. The internal quantum efficiency and internal optical loss coefficient are extracted through the simulation software for single, double, and triple InGaN/GaN quantum wells. The effects of device temperature on the laser threshold current, external differential quantum efficiency （DQE）, and output wavelength are also investigated. The external quantum efficiency and characteristic temperature are improved significantly when the quantum well number is two. It is indicated that the laser structures with many quantum wells will suffer from the inhomogeneity of the carrier density within the quantum well itself which affects the LD performance.

关键词： Computer software Efficiency Fabry Perot interferometers Quantum well lasers Semiconductor lasers Semiconductor quantum wells

Effect of Y Addition on microstructure and mechanical Properties of Friction Stir Welded zK60 Alloy

在线全文

学校读者我要写书评

暂无评论

Journal of materials Science & Technology 2009年第3期25卷 351-355页

作者： G.m. Xie z.Y. ma L. Geng School of materials Science and Engineering Harbin Institute of Technology Harbin 150001 China Shenyang National Laboratory for materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

6 mm thick zK60 and zK60-Y alloy plates were successfully friction stir welded （FSW） at a tool rotation rate of 1200 r/min and a traverse speed of 100 mm/min. FSW resulted in the dissolution of mgzn2 particles in the zK60 and the breakup and dispersion of W-phase （mg3zn3Y2） particles in the zK60-Y alloy, thereby leading; to a decrease in the hardness of the nugget zone （Nz） for the zK60 alloy and an increase in the hardness of the Nz for the zK60-Y alloy, respectively. While two FSW joints exhibited similar joint efficiency （87%-89% of ultimate tensile strengths of the parent materials）, the yield strength of the FSW zK60-Y joint was substantially higher than that of the FSW zK60 joint. The fracture occurred in the Nz and the heat affected zone for the zK60 and zK60-Y joints, respectively, which were consistent with the lowest hardness distribution of the welded joints.

关键词： Friction stir welding magnesium microstructure mechanical properties

Thermal Product of Type-E Fast Response Temperature Sensors

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2010年第4期19卷 364-371页

作者： H.A.mohammed H.Salleh m.z.Yusoff Antonio Campo Department of mechanical Engineering College of EngineeringUniversiti Tenaga NasionalKm 7Jalan Kajang-Puchong43009 KajangSelangorMalaysia Department of mechanical Engineering The University of Texas at San AntonioSan AntonioTX 78249USA

This paper provides practical data for thermal product values of different scratched temperature sensors that can be used for accurate transient heat transfer measurements under hypersonic flow *** effect of using different scratch techniques(abrasive papers and scalpel blades)to form the sensor's junction is *** was observed that the thermal product of a particular sensor depends on the mach number,junction scratch technique, junction location and enthalpy *** was demonstrated that using different scratched technique would produce different thermal product values.

关键词： thermal product fast response temperature sensor hypersonic flow.

Serrated Flow model for metallic Glasses under Compressive Loading

在线全文

学校读者我要写书评

暂无评论

Acta metallurgica Sinica(English Letters) 2013年第5期26卷 503-508页

作者： m.A.Yousfi K.Hajlaoui z.Tourki A.R.Yavari Laboratoire de mcanique de Sousse LMS ENISo Universit de Sousse SImaP-LTPCm Institut National Polytechnique de Grenoble

A rheological model is proposed that incorporates the serrated flow nature of metallic glasses. It involves the process of the nucleation, propagation and the arrest of a shear bands in the samples subjected to compressive deformation at room temperature. Numerical resolution of the constitutive equations resulting from the model is compared with the stress-strain curve obtained from in-situ nano-compression test in SEm of zrbased metallic glass. Parametric identification method was applied and enabled us to release the physical parameters of the model. The obtained results showed that the model is adequately valid to describe the experimental data and the almost adjustable model parameters are physically meaningful and comparable to literature.

关键词： metallic glasses Shear bands Serrated flow Rheological modelling Nanocrystallization