非线性弹性大变形材料梁的抗爆特性

从理论上探讨了非线性弹性大变形材料应用于抗爆结构的可行性,为此,基于等效结构体系的分析原理,将两端固定铰支梁的横向和纵向位移表示为三角级数形式,应用第二类Lagrange方程建立了非线性大变形材料梁的非线性分析方法,并且用ABAQUS有限元软件中的超弹性材料模型验证了所提出的方法的有效性。对典型的爆炸荷载作用下非线性弹性大变形材料梁的抗爆特性进行了分析,讨论了动力放大系数和材料性质及动荷载之间的关系。结果表明:与线弹性小变形材料相比,非线性弹性大变形材料具有优良的抗爆特性,结构的抗爆能力随结构变形的增大而显著提高。     

网络编码在高质量应用层组播中的应用

在面向节点群的混合网状应用层组播模型(Hybrid Mesh Application Multicast Model,HM-ALM)中设计并实现了确定性线性网络编码,探讨了网络编码对提高组播性能的作用.实验表明,网络编码能减少传输延迟和增强系统健壮性.使用网络编码后系统传输延迟减少了约50%;在系统动态变化时,正确接收数据的节点数可以达到最大值,系统能更快恢复稳定.     

直流电弧等离子体法制备纳米粒子实验装置研究

研制了一种实验室用直流电弧等离子体法制备纳米粒子的实验装置,该装置由纳米粒子生成室、阴极、阳极、真空泵和直流电源等组成。其特点是：结构简单、操作方便、成本低。该实验装置可用于制备金属纳米粒子、合金纳米粒子及金属一陶瓷复合纳米粒子。     

疏水缔合聚合物在石英砂表面的吸附——疏水基含量和微嵌段长度对吸附的影响

研究了不同分子结构的疏水缔合聚合物和部分水解聚丙烯酰胺在45、55和65 ℃下的静态吸附特征。 实验结果表明,疏水缔合聚合物的疏水基含量和微嵌段长度可以改变聚合物在石英砂表面的最大吸附量,而其中疏水基含量是主要影响因素,等温吸附曲线出现2个平台区。 随着温度的升高, 部分水解聚丙烯酰胺吸附量增大,而缔合聚合物则表现出相反的规律;缔合聚合物通过改变疏水基含量和微嵌段长度来影响其吸附性能。     

Solubility of nano-sized metal oxides evaluated by using in vitro simulated lung and gastrointestinal fluids: implication for health risks

The solubility of nano-sized metal oxides (nZnO, nCuO, nTiO₂, nCeO₂, and nFe₃O₄, 17–42 nm) and some non-nano-mineral powders (ZnO, ZnSiO₃, ZnS, and CuO) were evaluated by using gastrointestinal solubility bioavailability research consortium (SBRC), in vitro gastrointestinal (IVG) method, pulmonary artificial lysosomal fluid (ALF), and Gamble solution method, respectively. It is found that these nano-sized metal oxides aggregated more or less when suspending in the simulated biological fluids analyzed by dynamic light scattering (2 mg L^?1) and UV-Vis spectrometry (100 mg L^?1). The aggregation and sedimentation of nano-metal oxides in a simulated biofluid are influenced by its surface property and the ingredient of the liquid. The dissolution in fluids may decrease the aggregating radius of a nano-metal oxide. In return, the aggregative effect can influence the solubility of metal elements and result in their weakened bioaccessibility. The suspending stability was consistent in the order of nFe₃O₄ < nCuO < nTiO₂ < nCeO₂ < nZnO in all the simulated biological fluids. Nano-ZnO and nCuO showed higher gastrointestinal and pulmonary bioaccessibility than nFe₃O₄, nTiO₂, and nCeO₂. The further comparisons on the bioaccessibility for nCuO and nZnO with non-nano-powder CuO and ZnO indicated that the aggregating size in suspension could play more important role in influencing the bioaccessibility than single particle size does. The present study reveals that aggregation of all studied nano-sized metal oxides occurred in body physiologic fluids and that nZnO and nCuO were easily dissolved in simulated physiologic fluids, suggesting more potential health risks from nZnO and nCuO’s exposure.

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Graphical abstract Aggregation and sedimentation of nano-sized metal oxides with its bioaccessibility: a hint to health risks

     

Impurity effects on ionic-liquid-based supercapacitors

Small amounts of an impurity may affect the key properties of an ionic liquid and such effects can be dramatically amplified when the electrolyte is under confinement. Here the classical density functional theory is employed to investigate the impurity effects on the microscopic structure and the performance of ionic-liquid-based electrical double-layer capacitors, also known as supercapacitors. Using a primitive model for ionic species, we study the effects of an impurity on the double layer structure and the integral capacitance of a room temperature ionic liquid in model electrode pores and find that an impurity strongly binding to the surface of a porous electrode can significantly alter the electric double layer structure and dampen the oscillatory dependence of the capacitance with the pore size of the electrode. Meanwhile, a strong affinity of the impurity with the ionic species affects the dependence of the integral capacitance on the pore size. Up to 30% increase in the integral capacitance can be achieved even at a very low impurity bulk concentration. By comparing with an ionic liquid mixture containing modified ionic species, we find that the cooperative effect of the bounded impurities is mainly responsible for the significant enhancement of the supercapacitor performance.     

Sliding-mode control of switched delay systems with nonlinear perturbations: average dwell time approach

This paper investigates the robust sliding-mode control (SMC) problem for a class of uncertain switched systems with a time delay. The design process of sliding-mode control is divided into two steps. First, a sliding surface is constructed such that the reduced-order equivalent sliding mode restricted to the sliding surface is completely invariant to all admissible uncertainties under switching laws with an average dwell-time property. Second, variable structure controllers are developed to drive the states of the switched delay system to reach the sliding surface in finite time and remain on it thereafter. Finally, a numerical example is given to illustrate the effectiveness of the proposed method.     

The hysteresis loops of a ferroelectric bilayer film with surface transition layers

Based on the transverse Ising model in the framework of the mean field approximation,this paper discusses a ferroelectric bilayer film with the surface transition layers within each constituent slab and an antiferroelectric interfacial coupling between two slabs.The hysteresis loop of a bilayer film is investigated.The results show that the surface transition layer in a ferroelectric bilayer film plays a significant role in realizing the multiple-state memory.     

Particles in composite polymer electrolyte for solid-state lithium batteries:A review

Solid-state lithium batteries(SSLBs)have been identified as one kind of the most promising energy conversion and storage devices because of their safety,high en...     

Effect of Co on the thermal stability and impact toughness of sintered Nd–Fe–B magnets

The effect of Co on the thermal stability and impact toughness of sintered Nd–Fe–B magnets has been investigated. The results showed that the addition of Co decreased the intrinsic coercivity and the temperature coefficient of remanence (α), and increased the temperature coefficient of coercivity (β) for sintered Nd–Fe–B magnets. The impact toughness of sintered Nd–Fe–B magnets with the addition of Co first decreases, reaches a minimum, and then starts to increase. The possible reasons for increasing the temperature coefficients of coercivity (β) for sintered Nd–Fe–B magnets were analyzed, and the relations between the microstructure and impact toughness of sintered Nd–Fe–B magnets were studied.