An analytical poroelastic model for laboratorial mechanical testing of the articular cartilage (AC)

The articular cartilage (AC) can be seen as a biphasic poroelastic material. The cartilage deformation under compression mainly leads to an interstitial fluid flow in the porous solid phase. In this paper, an analytical poroelastic model for the AC under laboratorial mechanical testing is developed. The solutions of interstitial fluid pressure and velocity are obtained. The results show the following facts. (i) Both the pressure and fluid velocity amplitudes are proportional to the strain loading amplitude. (ii) Both the amplitudes of pore fluid pressure and velocity in the AC depend more on the loading amplitude than on the frequency. Thus, in order to obtain the considerable fluid stimulus for the AC cell responses, the most effective way is to increase the loading amplitude rather than the frequency. (iii) Both the interstitial fluid pressure and velocity are strongly affected by permeability variations. This model can be used in experimental tests of the parameters of AC or other poroelastic materials, and in research of mechanotransduction and injury mechanism involved interstitial fluid flow.     

亚微米颗粒在汇作用下运动机理的实验研究

当前,城市空气质量的不断恶化,引起了公众的普遍性关注.空气中的悬浮颗粒物,是城市大气环境重要污染源之一,其分布、运动及扩散规律已成为科学领域的研究热点.与连续流体不同,大气中的悬浮颗粒物是离散的,确定颗粒运动的模型是研究大气细微颗粒污染问题的关键.本文拟研究小空间静稳空气中亚微米级颗粒在汇作用下的运动规律,并构建其运动模型.在密闭实验空间中通过燃烧生成亚微米颗粒,利用静电吸附装置模拟颗粒汇,并通过粒子图像测速(particle image velocimetry,PIV)实验和激光多普勒测速仪(lasser Doppler velocimeter,LDV)实验技术测量分析不同空间内亚微米颗粒在大气中的热运动速度和在汇作用下的运动规律,并推导出颗粒物的速度分布经验公式.结果显示:粒子在汇作用下的运动与连续流体汇运动规律类似,但在小空间内颗粒的运动不满足流体连续方程;说明在无气流夹带输运情况下,利用汇作用及颗粒的扩散而发展的颗粒净化技术是可行的.     

Development and validation of stir bar sorptive extraction of polar phenols in water followed by HPLC separation in poly(vinylpyrrolididone‐divinylbenzene) monolith

An effective and simple method for polar phenols in water matrix was developed by using stir bar sorptive extraction (SBSE) based on a hydrophilic poly(vinylpyrrolididone‐divinylbenzene) (VPDB) monolithic material and HPLC analysis. To achieve optimum extraction performance for phenols, several parameters, including extraction and desorption time, desorption solvent, pH value, and ionic strength of sample matrix, were investigated. Under the optimized experimental conditions, eight phenols were directly enriched from water samples and analyzed by HPLC‐DAD. The detection limits (S/N = 3) and quantification limits (S/N = 10) of the proposed method for the target compounds were achieved within the range of 0.72–1.37 and 2.40–4.27 ng/mL from spiked water, respectively. Recoveries of eight phenolic compounds were found in the range of 55.2–95.9%. The calibration curves showed the linearity ranging from 5 to 150 ng/mL with linear regression coefficient R² values above 0.98. Method repeatability presented as intra‐ and interday precisions were also found with the RSDs less than 4.10 and 7.61%, respectively. The distribution coefficients between VPDB and water (K_VPDB/W) for phenolic compounds were also calculated and compared with K_O/W. Finally, the proposed method was successfully applied to the determination of the target compounds in tap water, sea water and wastewater samples.     

A priori and a posteriori error analysis of edge stabilization Galerkin method for the optimal control problem governed by convection-dominated diffusion equation

In this paper, we study an edge-stabilization Galerkin approximation scheme for the constrained optimal-control problem governed by convection-dominated diffusion equation. The method uses least-square stabilization of the gradient jumps across element edges. A priori and a posteriori error estimates are derived for both the state, co-state and the control. The theoretical results are illustrated by two numerical experiments.     

基于交变电场的月表除尘方法研究进展

实施月球表面探测时, 月表尘埃物质容易在探测设备表面沉积并造成严重不利影响. 近年来交变电场 除尘方法被认为是在月表进行尘埃防护的有效手段, 但要使该方法实用化, 仍需要弄清除尘的机理, 确定相关 影响的因素, 以便进行优化设计. 本文从实现交变电场的电帘出发, 分别介绍电帘表面的交变电场分布、颗粒 在电帘表面的受力状态、颗粒群运动过程中的摩擦电荷分布、颗粒运动的模拟方法、颗粒运动过程、除尘效 率和能耗的理论和实验研究, 并对自清洁太阳能电池板系统的设计与制备进行了总结. 对颗粒的起跳过程、静 电的生成和除尘效率影响因素等普遍关注的问题进行了细致的讨论和总结, 指出了颗粒的带电量对起跳过程 的关键作用. 最后, 对该除尘防尘存在的问题进行了归纳, 并展望了该领域的发展趋势.      

Synthesis of Unsymmetrical 1,3‐Diynes via Pd/Cu‐Catalyzed Cross‐Coupling of Terminal Alkynes at Room Temperature

A facile and practical synthetic route of unsymmetrical 1,3‐diynes via the PdCl/CuI catalyzed oxidative coupling of two different terminal alkynes has been developed by using 3‐(diphenylphosphino)propanoic acid as a ligand in the presence of oxygen. This system is suitable for not only aromatic alkynes but also heteroaromatic and aliphatic alkynes which were transformed into the corresponding unsymmetrical 1,3‐diynes in moderate to good yields at room temperature. Moreover, the unsymmetrical 1,3‐diynes were also obtained on a multi‐gram scale. Mechanistic studies suggest that oxygen plays a key role in the catalytic cycles.     

Three‐photon absorption properties of a novel symmetrical Carbazole derivative having terminal 1,10‐phenanthroline rings via carbon–nitrogen (C = N) double bond

Three‐photon absorption (3PA) properties of symmetric‐type carbazole derivatives show great potential for application in light‐activated therapy and optical limiting. A novel symmetrical carbazole derivative (abbreviated as POCP) with end‐groups of 1,10‐phenanthroline rings as the donor moieties, chained via carbon–nitrogen (C = N) double bond, has been synthetized and its three photon absorption properties has been also determined by using a Q‐switched Nd: YAG laser pumped with 30 ps pulses at 1064 nm in dimethylformamide. The measurement of 3PA cross‐section of this compound is performed by open aperture Z‐scan and σ_3PA is 481 × 10^–78 cm⁶ ? s²/photon² for the transition S₀ → S₁. The influence of the molecular structure of this compound on three‐photon absorption cross‐sections is discussed micromechanically by Austin model 1 and Zerner's Intermediate Neglect of Differential Overlap/S method. Copyright © 2012 John Wiley & Sons, Ltd.     

双功能WC/HZSM-5催化剂上正己烷芳构化反应性能

以HZSM-5(SiO2/Al2O3=38)为载体,偏钨酸铵为钨源制备了双功能催化剂WC/HZSM-5,考察了其催化正己烷芳构化反应性能,并采用X射线衍射、扫描电子显微镜、X射线能量散射谱和程序升温氨脱附等手段对催化剂进行了表征,探讨了制备方法和WC含量对WC/HZSM-5催化剂性能的影响.结果表明,采用原位还原碳化法制备的WC/HZSM-5(RC)催化剂上正己烷芳构化反应性能优于浸渍法制备的WC/HZSM-5(IP).5%WC/HZSM-5(RC)样品在反应初始阶段芳烃选择性为10.28%,而HZSM-5上的仅为2.56%.WC/HZSM-5(RC)催化剂上反应产物中轻质芳烃(苯、甲苯和二甲苯)含量增加,重质芳烃C9+含量降低,其催化性能优于Pt/HZSM-5催化剂.产物分布的变化可能是由于WC与分子筛间的协同作用所致.     

A Posteriori Error Estimators of Gradient Recovery Type for Elliptic Obstacle Problems

In this paper, we present a posteriori error estimates of gradient recovery type for elliptic obstacle problems. The a posteriori error estimates provide both lower and upper error bounds. It is shown to be equivalent to the discretization error in an energy type norm for general meshes. Furthermore, when the solution is smooth and the mesh is uniform, it is shown to be asymptotically exact. Some numerical results which demonstrate the theoretical results are also reported in this paper.