循环应力对储气库岩石微观结构及力学性质影响数值模拟

针对储气库循环注采过程中循环应力对储气库岩石产生疲劳损伤的问题。利用颗粒离散元法建立岩心真三轴数值模型,根据岩心室内试验标定数值模型参数,然后对数值模型进行多周期等幅值轴向循环应力加载,研究循环应力对储气库岩石微观结构及力学性质的影响。结果表明:循环应力加载过程中,模型内生成的无黏结接触数量和微裂缝数量逐渐增多,而生成位置受原始裂缝控制明显,模型孔隙度逐渐减小,且模型内无黏结接触数量、微裂缝数量和孔隙度的变化速率均呈递减趋势;相同应力水平下模型侧向应变和轴向应变均增大,但侧向应变占主导地位;模型弹性模量逐渐降低,而模型泊松比和损伤量逐渐增加,且模型弹性模量、泊松比和损伤量的变化速率均呈递减趋势。     

A357履带板的半固态触变成形工艺研究

采用半固态触变成形实验,对履带板件进行了模具设计、成形工艺参数制定,成功制得A357铝合金履带板件。并通过拉伸试验和微观组织观察,研究了T6热处理工艺对零件的力学性能和微观组织的影响。试验结果表明:经过T6热处理工艺,过饱和的基体中不断析出强化相Mg₂Si并高度弥散分布在晶粒内部与晶界处,零件的强度得到较大提高。     

基于改进遗传算法的自适应越区切换方案

针对列车通信在越区切换过程中切换触发率和切换成功率均较低的问题, 提出一种基于改进遗传算法的自适应联合判决切换算法. 首先, 以遗传算法为基础, 在高速特性下对切换判决过程中的相关参数进行优化, 针对列车的不同运行速度动态选择出满足快速切换需求的迟滞容限值； 其次, 引入满意通信概率（SCP), 当列车在小区之间移动时, SCP值达不到要求的将不能接入下一个小区, 以保障通信质量的优良. 仿真结果表明, 与传统切换方案相比, 该方案可实现提高切换触发率和切换成功率的目标, 具有较高的满意通信概率.     

基于双响应曲面的精密产品子集模拟可靠稳健优化设计

针对不确定性场景下小失效概率的精密产品可靠性问题,提出了基于双响应曲面法(dual response surface methodology,DRSM)与子集模拟的可靠稳健优化方法。首先,建立精密产品多失效模式极限状态的RSM模型和以质量特性均值-方差为优化目标的功能函数DRSM模型。其次,在此基础上运用子集模拟法进行可靠性分析,将精密产品小失效概率描述成一系列较大的条件失效概率之积。最后,将极值事件的优化问题视作稀有事件的可靠性问题的特例,基于该转换思想采用子集模拟法将优化问题在可靠性问题的框架内进行求解。案例分析及验证结果表明所提方法的有效性。     

Effect of Graphene Nanoplatelets addition on mechanical properties of pure aluminum using a semi-powder method

In recent years, graphene has attracted considerable research interest in all fields of science due to its unique properties. Its excellent mechanical properties lead it to be used in nano-composites for strength enhancement. This paper reports an Aluminum–Graphene Nanoplatelets(Al/GNPs)composite using a semi-powder method followed by hot extrusion. The effect of GNP nano-particle integration on tensile, compressive and hardness response of Al is investigated in this paper. It is demonstrated that 0.3 wt% Graphene Nanoplatelets distributed homogeneously in the matrix aluminum act as an effective reinforcing filler to prevent deformation. Compared to monolithic aluminum(in tension), Al–0.3 wt% GNPs composite exhibited higher 0.2% yield strength(+14.7%), ultimate tensile strength(+11.1%) and lower failure strain( -40.6%). Surprisingly, compared to monolithic Al(in compression), Al–0.3 wt% GNPs composite exhibited same 0.2% compressive yield strength and lower ultimate compression strength(- 7.8%),and lower failure strain(- 20.2%). The Al–0.3 wt% GNPs composite exhibited higher Vickers hardness compared to monolithic aluminum(+11.8%).Scanning electron microscopy(SEM), Energy-Dispersive X-ray Spectroscopy(EDS) and X-ray diffraction(XRD) were used to investigate the surface morphology, elemental percentage composition, and phase analysis, respectively.     

朝鲜崖柏生境及高生长规律分析

采用标准地调查法测定朝鲜崖柏的土壤特征、林下植被和高生长规律.结果表明:朝鲜崖柏生长于土层较薄且呈弱酸性的山地暗棕壤,不同标准地林下植被差异明显;不同标准地朝鲜崖柏树高的年生长量均呈逐年下降趋势.     

Preparation and Mechanical Properties of a Novel Textile Pad for Wound Debridement

Various types of wound debridement approaches are currently available in clinical practice such as autolytie, enzymatic. biodebridement, mechanical, and surgical debridemenl techniques. A critical look at these various options can explain their potential but also their limitations. In this study, a novel textile pad, which is composed of polyester filaments on the fleecy side and a bioeompatible coating on the opposite side, was made to provide a safe, inexpensive, easier and especially more efficient debridement process that can be used in all healthcare settings by all healthcare practitioners. Eighteen kinds of samples were prepared with different pile density, ground yarn count and coating amount. Dimensional morphology, stitch density, mass per unit area and mechanical properties were investigated to study the intrinsic relationship of structure and properties of textile pad for wound debridement. Results showed that tensile strength and suturing strength at piped site increased obviously with the increment of ground yarn count, while the amount of coating could also have a slight impact on these two properties. However, compressive load was mainly affected by pile density, with no obvious relation to ground yarn count and coating amount.     

一个具有Markov性的入圈问题

研究序列{Xn},{Xn}满足Xn=Yn(mod 2),其中Yn∈Z+,Y0≥2,Yn+1=Yn+[Yn/2],证明了{Xn}为一独立随机变量序列,并且是一时间齐次Markov链.最后,利用该Markov链{Xn}的性质,证明了入圈问题经过有限次插点,Cm的任意一边上都至少插入一个新点.     

水热法制备Li_(4-3x)Eu_x(WO_4)_2微晶及其发光性能

采用水热法制备了Li_(4-3x)Eu_x(WO_4)_2系列红色荧光粉.通过荧光分析(FL)、扫描电镜(SEM)和X射线衍射(XRD)对所得粉体的发光性能、颗粒大小及形貌和物相进行表征分析.XRD分析结果表明,制备的Li_(4-3x)Eu_x(WO_4)_2微晶均为白钨矿四方结构.SEM结果表明,Li_(4-3x)Eu_x(WO_4)_2颗粒度为2.0μm×0.2μm~12μm×1.0μm,且随x的增大而增大.荧光分析结果表明,该荧光粉可被近紫外光(395nm)有效激发,最大发射波长位于614nm,即为纯正的红光.随着x的增大,样品中Eu~(3+)的593nm和614nm两个特征发射峰的强度先增大后减小,当x=1.0时达到最大.     

离子液体[C2mim]NO3与[C2mim][MetSO4]的热力学性能研究

采用MDY-2型密度仪在常压、一定温度范围内对离子液体1-乙基-3-甲基咪唑硝酸盐(简写为[C2mim]NO3)和1-乙基-3-甲基咪唑硫酸甲酯盐(简写为[C2mim][MetSO4])的密度进行了测定.结果表明,离子液体的密度随温度升高呈线性下降的趋势.由离子液体的密度值计算得到离子液体[C2mim]NO3和[C2m...