Numerical research for contaminant release from un-suspended bottom sediment under different hydrodynamic conditions

Contaminant release from bottom sediments in rivers is one of the main problems to study the environmental hydrodynamics. Contaminant will release into the overlying water column under different hydrodynamic conditions through pore-water in sediment, the release mechanism can be roughly divided into convection diffusion, molecular diffusion and adsorption/desorption. In this article, phosphorus was as a typical contaminant with sorption. Through theoretical analysis of the contaminant release, according to different particle-sized and hydraulic conditions, the mathematics model of contaminant release can be established by the coupled Navier-Stokes equation, Darcy equation, solute transport equation and adsorption/desorption equation. Then that model was verified by flume experiment. Numerical studies show that, under different velocity, the instantaneous concentration of convection diffusion is about 6 times to 50 times larger than that of molecular diffusion during initial stages. The concentration of molecular diffusion is about 1 times to 4 times larger than to that of convection diffusion during late stages. Through analysis, the diffusive boundary layer near the interface can be obtained. In addition, the release will increase with particle size decreasing, and the release will be influenced much more by the size change when the particle size is relatively big under different velocity.     

Dynamics of a Dual Power-split Transmission Based on Loaded Tooth Contact Analysis

In order to implement the dynamic characteristic of a dual power-split transmission,a dynamic mechanics model is built. Firstly,according to the method of theoretical analysis of the tooth contact analysis ( TCA) and loaded tooth contact analysis ( LTCA) ,the actual meshing process of each gear pairs is simulated, and the time-varying mesh stiffness excitations are obtained,which can improve the numerical precision. Secondly,by using the lumped mass method,the bending-torsional coupling three dimensional dynamic model of the dual power-split transmission is established,and the identical dimensionless equations are deduced by eliminating the effect of rigid displacement and the method of dimensional normalization. Finally,by the method of the fourth order Runge-Kutta algorithm with variable step lengths,the responses of this system in a frequency domain and time domain are obtained,and the dynamic load change characteristics of each gear pairs are analyzed. The results show that the establishment,solution and analysis of the system dynamics model could provide a basis for the dynamic design,and have an important significance for the dynamic efficiency analysis and dynamic performance optimization design of the dual power-split transmission.     

基于MC2833和MC3362的RFID系统设计

RFID系统主要由阅读器和应答器组成。阅读器包含高频接收模块、控制单元及与应答器连接的耦合元件。高频接收模块以单片集成接收芯片MC3362为核心,结合MC145151构成锁相回路,接收应答器发送的信息。应答器由耦合元件以及高频发射模块组成,其工作所需能量全部由耦合线圈提供,采用自动开关控制应答器与电源的通断以降低功耗。     

多场耦合下微波碳热氯化回收铟的动态仿真

以实验室微波反应器为研究对象,基于有限元软件COMSOL Multiphysics,采用多场耦合方法对微波强化碳热氯化回收In Cl3的反应过程进行了动态仿真,并分析了其影响因素。结合微波加热过程、计算流体力学和物质传输过程,建立了由射频、传热、传质和流场4个物理场耦合的数学物理模型。通过考察腔室内的电场强度,得到微波加热过程的热源项与样品体的温度分布。结果表明,本研究模型能够准确描述微波输入功率、HCl通入浓度等多因素对铟化物回收过程的影响,为微波碳热氯化提铟过程的分析提供新的方法与依据。     

Interpolymer radical coupling: A toolbox complementary to controlled radical polymerization

The current review focuses on the relevance and practical benefit of interpolymer radical coupling methods. The latter are developing rapidly and constitute a perfectly complementary macromolecular engineering toolbox to the controlled radical polymerization techniques (CRP). Indeed, all structures formed by CRP are likely to be prone to radical coupling reactions, which multiply the available synthetic possibilities. Basically, the coupling systems can be divided in two main categories. The first one, including the atom transfer radical coupling (ATRC), silane radical atom abstraction (SRAA) and cobalt-mediated radical coupling (CMRC), relies on the recombination of macroradicals produced from a dormant species. The second one, including atom transfer nitroxide radical coupling (ATNRC), single electron transfer nitroxide radical coupling (SETNRC), enhanced spin capturing polymerization (ESCP) and nitrone/nitroso mediated radical coupling (NMRC), makes use of a radical scavenger in order to promote the conjugation of the polymer chains. More than a compilation of macromolecular engineering achievements, the present review additionally aims to emphasize the particularities, synthetic potential and present limitations of each system.     

Improved Viscoelastic Damping for Earthquake-Resistant Wood Structures

In this work viscoelastic polymeric damping material was studied for its ability to damp out vibrations in wood structures (houses). This is accomplished by placing a thin layer of the material between wood stud and sheathing material. Damping performance of three individual polymers was obtained and compared to two types of blends of the materials. Placing the strips of material next to each other (parallel arrangement for shear) rather than on top of each other (series arrangement for shear), gave improved damping results over a wider temperature range relative to the single polymers. This is attributed to the widening of the damping peak by combining the materials. This is expected to be useful in earthquake-resistant wooden structures, such as housing, by delaying collapse and by absorbing energy, thereby increasing likelihood of saving the lives of the inhabitants.     

Minor Role of Mitochondrial Respiration for Fatty-Acid Induced Insulin Secretion

An appropriate insulin secretion by pancreatic beta-cells is necessary to maintain glucose homeostasis. A rise in plasma glucose leads to increased metabolism and an elevated cytoplasmic ATP/ADP ratio that finally triggers insulin granule exocytosis. In addition to this triggering pathway, one or more amplifying pathways—activated by amino acids or fatty acid—enhance secretion by promoting insulin granule recruitment to, and priming at, the plasma membrane. The aim of this study was to clarify the impact of the mitochondrial respiratory activity on fatty acid-induced insulin secretion that was assessed by an extracellular flux analyzer. Treatment of isolated mouse islets with glucose (20 mM) increased insulin secretion 18-fold and correlated with ATP-synthesizing respiration. Furthermore, oxygen consumption rate (OCR) significantly increased by 62% in response to glucose, whereas the addition of palmitate resulted only in a minor increase of OCR at both 2.8 mM (11%) and 20 mM glucose (21%). The addition of palmitate showed a pronounced increase of coupling efficiency (CE) at 2.8 mM glucose but no further insulin secretion. However, treatment with palmitate at 20 mM glucose increased insulin secretion about 32-fold accompanied by a small increase in CE. Thus, fatty acid induced respiration has a minor impact on insulin secretion. Our data clearly demonstrate that fatty acids in contrast to glucose play a minor role for respiration-mediated insulin secretion. In the presence of high glucose, fatty acids contribute partially to amplifying pathways of insulin secretion by further increasing mitochondrial activity in the islets of Langerhans.     

通海系统管路阻尼处理降噪技术研究

机械设备通过管路系统产生的辐射噪声是合成潜艇总噪声的重要来源之一,随着浮筏装置的广泛应用,机械设备通过机脚、基座引起的振动噪声已得到较好的控制,同时原来被掩盖的管路系统引起的振动噪声逐渐突出。通过在管壁外敷设阻尼结构吸收并耗散振动能量是降低管路系统振动噪声的有效方法之一。通过对通海系统管路敷设阻尼胶带的插入损失进行了理论分析和试验研究,结果表明,管路表面敷设阻尼胶带能有效降低沿管路传递的振动,对于降低沿管路传播的振动噪声从而增强舰船的隐蔽性具有重要意义。     

Cooperative Effects in the Photoluminescence of (In,Ga)As/GaAs Quantum Dot Chain Structures

Multilayer In_0.4Ga_0.6As/GaAs quantum dot (QD) chain samples are investigated by means of cw and time-resolved photoluminescence (PL) spectroscopy in order to study the peculiarities of interdot coupling in such nanostructures. The temperature dependence of the PL has revealed details of the confinement. Non-thermal carrier distribution through in-chain, interdot wave function coupling is found. The peculiar dependences of the PL decay time on the excitation and detection energies are ascribed to the electronic interdot coupling and the long-range coupling through the radiation field. It is shown that the dependence of the PL decay time on the excitation wavelength is a result of the superradiance effect.     

钢管穿轧过程的三维热力耦合模拟

描述了使用有限元方法(FEM)模拟钢管在曼内斯曼式穿轧机上的穿孔过程,建立了三维有限元模型,并考虑了在金属成形过程中出现的热力学现象。模拟的结果动态地显示了在工件内部等效应变、等效应变率和温度的分布。基于这些参数,分析了钢管的穿孔过程,同时通过实验测试与有限元模拟的结果进行对比。结果表明,测试的结果与有限元模拟的结果比较吻合。