液压油管钳卡紧系统的改进

在油管钳的卡紧系统中.增加杠杆机构.并且对坡板的结构进行科学的设计.能够使该系统主要零部件的受力大为改善.通过对新的卡紧系统进行受力分析,建立了13元方程组.进行了编程求解.给出了精确的解题方法,同时从理论上进一步证明.本钳口卡紧系统的强度安全可靠.而且牙板不易打滑.     

有机玻璃增韧改性的研究

采用了丙烯酸、丙烯酸丁酯、甲基丙烯酸甲酯三元共聚的方法,制备了增韧透明的有机玻璃,讨论了各组分对材料的冲击强度、维卡软化点、透光率的影响,以及出现此结果的原因。     

A multi-axial constitutive model for metal matrix composites

Metal matrix composites (MMCs) generally do not follow the classical plasticity theory, even though the matrix metals do deform plastically. A tension-compression yield asymmetry is typically observed in MMCs. For particulate-reinforced MMCs, this non-classical response is mainly due to the variation of damage evolution with loading modes. In this paper, a viscoplastic multi-axial constitutive model for plastic deformation of MMCs is constructed using the Mises-Schleicher yield criterion. The subsequent plastic flow is characterized by an associated and decomposed flow rule considering effects from both deviatoric and hydrostatic stresses. This model is capable of describing the multi-axial yield and flow behavior of MMCs by using simulated or measured asymmetric tensile and compressive stress-strain responses as input. As an example, the influence of damage evolution in terms of interfacial debonding in MMCs (obtained from FEM simulations) is incorporated through the different tensile and compressive stress-strain behaviors. Applying this model to predict the torsion and the pressure-dependant tensile responses of some commonly used MMCs provides good agreement with experimental data.     

Study on the cesium Tutton compounds,Cs2M(XO4)2∙6H2O (M = Mg,Co, Zn; X = S,Se): Preparation,X-ray powder diffraction and infrared spectra

The crystallization processes in the three-component systems Cs₂SO₄–MSO₄–H₂O (M = Mg, Co, Zn) have been studied at 25 °C. It has been established that cesium Tutton compounds, Cs₂M(SO₄)₂·6H₂O (M = Mg, Co, Zn; X = S, Se), crystallize from the ternary solutions within large concentration ranges. The double salts were identified by means of X-ray powder diffraction and infrared spectroscopy. Infrared spectra of the cesium compounds are presented and discussed with respect to both the normal modes of the tetrahedral ions and the water molecules. The water librations are also discussed. The strength of the hydrogen bonds formed in the cesium salts as deduced from the frequencies of ν_OH is commented. The analysis of the spectra reveals that stronger hydrogen bonds are formed in the cesium selenates as compared to those in the respective sulfates due to the stronger proton acceptor ability of the selenate ions.     

Optimization design of strong and tough nacreous nanocomposites through tuning characteristic lengths

How nacreous nanocomposites with optimal combinations of stiffness, strength and toughness depend on constituent property and microstructure parameters is studied using a nonlinear shear-lag model. We show that the interfacial elasto-plasticity and the overlapping length between bricks dependent on the brick size and brick staggering mode significantly affect the nonuniformity of the shear stress, the stress-transfer efficiency and thus the failure path. There are two characteristic lengths at which the strength and toughness are optimized respectively. Simultaneous optimization of the strength and toughness is achieved by matching these lengths as close as possible in the nacreous nanocomposite with regularly staggered brick-and-mortar (BM) structure where simultaneous uniform failures of the brick and interface occur. In the randomly staggered BM structure, as the overlapping length is distributed, the nacreous nanocomposite turns the simultaneous uniform failure into progressive interface or brick failure with moderate decrease of the strength and toughness. Specifically there is a parametric range at which the strength and toughness are insensitive to the brick staggering randomness. The obtained results propose a parametric selection guideline based on the length matching for rational design of nacreous nanocomposites. Such guideline explains why nacre is strong and tough while most artificial nacreous nanocomposites aere not.     

基于SCI-E和ESI的河北医科大学与华北地区4所医学高校科研实力对比分析

采用文献计量学方法,以科学引文索引为信息源,检索2004—2013年河北医科大学以及首都医科大学、天津医科大学、山西医科大学和内蒙古医科大学等4所华北地区医学高校的SCI论文,通过与4所医学高校的SCI论文之间的对比,展示了河北医科大学的科研论文现状,同时提出了一些建议.     

下肢运动方式对COPD有创机械通气患者肌力的影响

为了比较运动方式对COPD有创机械通气患者肌力的影响，对入住ICU的112例COPD有创机械通气患者进行分组对照实验.按预设的早期运动方案，两组患者下肢运动方式不一样，干预组采用床上脚踏车进行下肢运动，对照组采用手动下肢运动.结果表明，脱离ICU监护时下肢主、客观肌力指标、ICU活动水平和Barthel指数评分以及出院时Barthel指数评分，两组患者之间差异有统计学意义(P<0.05)， 脱离ICU监护时上肢主、客观肌力指标和出院6个月Barthel指数，两组患者之间差异无统计学意义(P>0.05)，说明COPD有创机械通气患者实施床上脚踏车运动安全可行，且可以改善下肢肌力和运动水平，促进日常生活功能的恢复.     

人造地震动合成中的位移误差分析

三角函数级数法是合成人工地震动常用算法之一,但是通过对加速度积分求取位移时,却存在与零线漂移相类似的位移漂移现象。     

金川露天矿F1、F2断层深力学特性的实验研究

本文以室内力学实验结果为依据, 探讨了断层泥常规力学特性及与时间有关的蠕变特性, 并从瞬时变形、蠕变变形、强度、破坏等方面探讨了水岩相互作用结果。     

有限元强度折减系数法在北门沟坡滑坡稳定性评价中的应用

利用有限元强度折减系数法求得的滑坡安全稳定性系数进行北门沟滑坡稳定性评价。通过强度折减,当滑坡达到不稳定状态时,有限元计算不再收敛,此时的折减系数就是滑坡的安全稳定性系数。经计算,可以得到滑坡体破坏形式和破坏扩张趋势,有助于对滑体破坏机制的理解。计算表明,有限元强度折减法与传统刚体极限平衡法计算的稳定性系数很接近,这为滑坡稳定性评价提供了另一条途径。