关键词： 教育部重点实验室   流体动力传输   重型机械   燕山大学   控制   工程技术研究中心   工程研究中心   成形技术  

摘要： 燕山大学重型机械流体动力传输与控制实验室的前身为东北重型机械学院液压教研室，始建于1977年。2005年实验室成为河北省重型机械流体动2007年成为机械工业流体动力传输技术重点实验室。实验室是燕山大学国家冷轧板带装备及工艺工程技术研究中心、先进制造成形技术及装备国家地方联合工程研究中心、极端条件下机械结构和材料科学国防重点学科实验室、先进锻压成形技术与科学教育部重点实验室的重要组成部分。

关键词： 急性心源性肺水肿   无创机械通气   血流动力学  

摘要： 目的探讨无创机械通气对急性心源性肺水肿患者血流动力学的影响。方法选取急性心源性肺水肿患者82例,随机分为对照组和研究组,各41例。对照组行常规治疗,研究组在常规治疗的基础上行无创双水平正压通气,对比2组治疗前后症状缓解时间、呼吸频率,动脉血气分析指标以及心率(HR)、平均动脉压(MAP)、心输出量(CO)、心脏指数(CI)、每搏输出量(SV)的变化。结果研究组显效率显著高于对照组(P<0.05),2组治疗后呼吸频率、血氧分压[p(O2)]、血氧饱和度(Sa O2)均有改善(P<0.01),且研究组p(O2)和症状缓解时间优于对照组(P<0.01)。研究组治疗后HR、MAP、SV、CO、CI均明显改善(P<0.01),对照组HR、MAP、SV均显著改善(P<0.01);组间比较,研究组各指标均显著优于对照组(P<0.01)。结论无创机械通气能迅速纠正低氧血症,改善血流动力学,是抢救急性心源性肺水肿的一种安全有效的手段。

关键词： co-axial   dual mechanical ports   stator permanent magnet   flux switching   brushless machines   continuously-variable transmission   hybrid electric vehicles   power splitter  

摘要： In this paper, a co-axial dual-mechanical ports flux-switching permanent magnet (CADMP-FSPM) machine for hybrid electric vehicles (HEVs) is proposed and investigated, which is comprised of two conventional co-axial FSPM machines, namely one high-speed inner rotor machine and one low-speed outer rotor machine and a non-magnetic ring sandwiched in between. Firstly, the topology and operation principle of the CADMP-FSPM machine are introduced;secondly, the control system of the proposed electronically-controlled continuously-variable transmission (E-CVT) system is given;thirdly, the key design specifications of the CADMP-FSPM machine are determined based on a conventional dual-mechanical ports (DMP) machine with a wound inner rotor. Fourthly, the performances of the CADMP-FSPM machine and the normal DMP machine under the same overall volume are compared, and the results indicate that the CADMP-FSPM machine has advantages over the conventional DMP machine in the elimination of brushes and slip rings, improved thermal dissipation conditions for the inner rotor, direct-driven operation, more flexible modes, lower cogging torque and torque ripple, lower total harmonic distortion (THD) values of phase PM flux linkage and phase electro-motive force (EMF), higher torque output capability and is suitable for the E-CVT systems. Finally, the pros and cons of the CADMP-FSPM machine are highlighted. This paper lays a theoretical foundation for further research on CADMP-FSPM machines used for HEVs.

关键词： Polyacrylamide   Agonists   Ligands   Modulators   Receptors  

摘要： Increasing attention has recently been devoted to allosteric modulators, as they can provide inherent advantages over classic receptor agonists. In the field of nicotinic receptors (nAChRs), the main advantage is that allosteric modulators can trigger pharmacological responses, limiting receptor desensitization. Most of the known allosteric ligands are "positive allosteric modulators" (PAMs), which increase both sensitivity to receptor agonists and current amplitude. Intriguingly, some allosteric modulators are also able to activate the alpha 7 receptor (alpha 7-nAChR) even in the absence of orthosteric agonists. These compounds have been: named "ago-allosteric modulators" and GAT107 has been studied in depth because of its unique mechanism of action. We here investigate by molecular dynamics simulations, metadynamics, and essential dynamics the activation mechanism of alpha 7-nAChR, in the presence of different nicotinic modulators. We determine the free energy profiles associated with the closed-to-open motion of the loop C, and we highlight mechanistic differences observed in the presence of different modulators. In particular, we demonstrate that GAT107 triggers conformational motions and cross-talk similar to those observed when the alpha 7-nACh receptor is in complex with both an agonist and an allosteric modulator.

关键词： YB4   Electronic structure   Chemical bonding   Anisotropic elastic stiffness   Lattice dynamics  

摘要： The electronic structure, mechanical properties and lattice dynamics of YB4 are investigated using first-principles calculations. The Y-B bonding is ionic-covalent, the Y-Y bonding is metallic, the B-B bonding within B-6 octahedron is weak tau-type covalent and that connecting the octahedra is strong sigma-type covalent. The chemical bonding anisotropy has also been confirmed by lattice dynamic properties, and is reflected by the anisotropic elastic stiffness. The maximum Young's modulus (427 GPa) is 1.5 times larger than its minimum (285 GPa). The lowest shear moduli are associated with the [1 1 01(1 0 0) and [1 1 01(1 1 0) systems. The linear compressibility of a (1.70 x 10(-3) GPa) is larger than that of c (1.47 x 10(-3) GPa). Based on the low c(44), c(66) and Pugh's ratio G/B, YB4 is predicted as a damage to lerant ceramic. YB4 also has a relatively low Young's modulus (339 GPa), which ensures it good thermal shock resistance. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Crystallization kinetics   Morphology   Mechanical properties   Poly(ethylene succinate-co-octamethylene succinate)  

摘要： The crystallization kinetics, morphology and mechanical properties of a novel poly(ethylene succinate-co-octamethylene succinate) (PEOS) copolyester with 82 mol% ethylene succinate (ES) units and 18 mol% octamethylene succinate (OS) units, and its homopolymer poly(ethylene succinate) (PBS) were extensively investigated. The glass transition temperature, cold crystallization peak temperature and melting point of PEOS are around 24, 47.5, and 80.5 degrees C, respectively. The Avrami equation was used to analyze the isothermal melt crystallization kinetics of PEOS and PES. They display the same crystallization mechanism, and PEOS crystallizes slower than PES at the same degree of supercooling. The spherulitic growth rates of PEOS and PBS exhibit a bell shape within the investigated crystallization temperature range, with the crystallization regime transition temperature of PEOS being lower than that of PES. In addition, PEOS has high thermal stability and good mechanical properties. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Crystal chemistry   Diffusion   Mechanical properties   Alloy design   Heat treatment   Phase transformations  

摘要： Pure Mg was diffusion bonded to pure Zn at 315 degrees C for 168 h to produce equilibrium intermetallic compounds of the Mg-Zn system. All equilibrium phases at 315 degrees C, Mg21Zn25, Mg4Zn7, MgZn2, Mg2Zn11, were observed to develop. Concentration profiles by electron probe microanalysis, electron diffraction patterns by transmission electron microscopy, and load-displacement curves by nano-indentation were examined to characterize the phase constituents, crystal structure, diffusion kinetics, and mechanical properties. Mg21Zn25 with trigonal, Mg4Zn7 with monoclinic, and Mg2Zn11 with cubic structures were found and their lattice parameters were reported herein. Mg4Zn7 and Mg2Zn11 were observed to have a range of solubility of approximately 2.4 at% and 1.6 at%, respectively. Interdiffusion in MgZn2 occurred most rapidly, was an order of magnitude slower in Mg4Zn7 and Mg2Zn11, and was the slowest in Mg21Zn25. Composition-dependence of interdiffusion within each intermetallic phase was negligible. The intermetallic phases exhibited insignificant creep, but evidence of discontinuous yielding was observed. The average hardness and reduced moduli were similar for Mg21Zn25, Mg4Zn7, and MgZn2 phases, similar to 5 GPa and similar to 90 GPa, respectively. However, the Mg2Zn11 phase had lower hardness of 3.76 GPa and higher modulus of 108.9 GPa. The mechanical properties in the characterized intermetallic phases, exclusive of Mg21Zn25, were strongly concentration-dependent. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： POLYLACTIC acid   CRYSTALLIZATION -- Kinetics   MICROFIBRILS   COMPOSITE materials   RHEOLOGY   MATERIALS -- Mechanical properties   SURFACE active agents  

摘要： Melt blending is one of the most promising techniques for eliminating poly(lactic acid)'s (PLA) numerous drawbacks. However, success in a typical melt blending process is usually achieved through the inclusion of high concentrations of a second polymeric phase which can compromise PLA's green nature. In a pioneering study, we introduce the production of in situ microfibrillar PLA/polyamide-6 (PA6) blends as a cost-effective and efficient technique for improving PLA's properties while minimizing the required PA6 content. Predominantly biobased products, with only 3 wt % of in situ generated PA6 microfibrils (diameter approximate to 200 nm), were shown to have dramatically improved crystallization kinetics, mechanical properties, melt elasticity and strength, and foaming-ability compared with PLA. Crucially, the microfibrillar blends were produced using an environmentally friendly and cost-effective process. Both of these qualities are essential in guarantying the viability of the proposed technique for overcoming the obstacles associated with the vast commercialization of PLA.

关键词： Atomistic simulation   Mechanical properties   Silicon Carbide   Carbon enrichments  

摘要： Silicon Carbide (SiC) exhibits excellent mechanical, thermal and electrical properties. Low fracture toughness is one of the limiting properties of SiC that hinders its widespread applications. Recent studies suggest that controlled alteration of local micro-structure may lead to dislocation nucleation in certain SiC poly-types. Here, we report classical molecular dynamics simulations results to demonstrate mechanical behavior of a new type SiC-based "C enriched" ceramics where certain Si atoms are substituted by C atoms. We studied four different systems with different fraction of "C" enrichment, namely 10%, 20%, 30% and 40%. Thermodynamic viability of such novel micro-structures have been studied recently (Adnan and Ferdous, 2015). Significant effects of "C" enrichment on the tensile and shear properties of the new ceramic materials have been observed. Compared to pure SiC, the tensile strengths of enriched systems always increase but to a different extent depending on the amount of enrichment. Shear strengths, however, tend to decrease with increase in carbon enrichment until enrichment is 40%. The elastic constants C-11 and C-44 were measured and both increase significantly with carbon enrichment. The area under the stress-strain tensile and shear curves have been estimated to assess the tensile and shear toughness properties and it has been found that both types of toughness increase significantly with carbon enrichment. (C) 2015 Elsevier B.V. All rights reserved.

关键词： Radiation damage   Nanowires   Mechanical properties   Computer simulation  

摘要： In this work we study, by means of molecular dynamics simulation, the change in the mechanical properties of a gold nanowire with pre-existing radiation damage. The gold nanowire is used as a simple model for a nanofoam, made of connected nanowires. Radiation damage by keV ions leads to the formation of a stacking fault tetrahedron (SFT), and this defect leads to a reduced plastic threshold, as expected, when the nanowire is subjected to tension. We quantify dislocation and twin density during the deformation, and find that the early activation of the SFT as a dislocation source leads to reduced dislocation densities compared to the case without radiation damage. In addition, we observed a total destruction of the SFT, as opposed to a recent simulation study where it was postulated that SFTs might act as self-generating dislocation sources. The flow stress at large deformation is also found to be slightly larger for the irradiated case, in agreement with recent experiments. (C) 2015 Elsevier B.V. All rights reserved.