Viscous pressure behaviour in shear-induced concentration banding

The behaviour of the viscous pressure as a function of the shear rate is studied for a non-Newtonian polymer solution in a cone-and-plate device, in the presence of a shear-induced concentration banding transition. In this transition, where the system splits into two bands with different polymer concentrations, the slope of the viscous pressure is shown to have a clear discontinuity. This behaviour is rather different from the one observed in shear banding in liquid crystals, where concentration remains homogeneous but the system splits into two bands with different orientations and shear rates.     

宽粒度分布的细颗粒沉降

针对浆态床ＦＴ合成中液体蜡与细颗粒催化剂的分离，对与其粒径分布相似的细石英砂与水的体系的沉降分离进行了考察，用超声波浓度仪测定沉降过程中的颗粒浓度。由此得出了沉降过程的浓度场，并从沉降曲线可以看出宽粒度分布的沉降不同于相同或相近粒径的沉降，而且可得出颗粒浓度、悬浮液高度对沉降的影响情况     

新疆哈密、托里两地花岗岩建筑石材天然放射性水平初步调查

以新疆哈密、托里两地的大型石材企业为研究对象,初步调查了新疆石材资源花岗岩的天然放射性水平,包括矿坑、原料和产品、废品堆场的表面吸收剂量率、氡浓度以及固体样品及加工废水中的天然放射性核素浓度,监测了建材生产企业相关区域的γ辐射剂量率。结果表明,约有20%～25%的花岗岩样品超过国家环保部关于伴生矿的γ辐射剂量率认定值,其余基本上处于当地本底范围。     

MODELING FINES ELUTRIATION FROM A SPOUTED BED OF PULP FIBERS

A model was developed to describe the elutriation of fines from a spouted bed of pulp fibers, which is a new method to separate fines from fibers. During spouting the pulp fibers are aggregated in fiber floes, which we model as coarse porous spheres. In general, we can distinguish three liquid regions inside and around a coarse particle in a shear flow: bulk liquid, liquid passing through the sphere, and liquid circulating inside it. A system of three ordinary differential equations describing the balance of fines in these regions was solved numerically. A source term was included to account for the release of fines during the dynamic equilibrium between formation and break-up of fiber floes. Comparison between theory and experiment showed that a simplified two-region model, which contains two adjustable parameters, is adequate to describe the elutriation data.     

THE DEPOSITION OF REJECTED MATTER IN MEMBRANE SEPARATION PROCESSES

The mechanism by which particles rejected at a membrane filter that is operated in cross-flow are returned to the feed stream has remained unclear. Comparisons with concentration polarization during molecular rejection raise difficulties because molecular diffusivities are much larger than those considered plausible for particles. In the present work particles are postulated not to return to the bulk but rather to flow along the surface of the membrane in a layer whose thickness increases in the direction of feed flow. A model for both the steady and transient case is solved using the method of characteristics. The role of the rheology of the close-packed layer is emphasized.     

环境陆地γ辐射水平的间接测量

本文介绍了由土壤样品中天然放射性核素浓度间接测量环境陆地γ辐射照射量率值的方法和结果。对514个测点与用闪烁剂量率仪直接测量结果比较,83.7%测点在±30%误差范围内一致。对本省514个测点土壤样品的核素浓度和陆地γ辐射直接测量值,采用多元回归拟合的单位比活度-1m 高处陆地γ照射量率系数,测得的陆地γ照射量率与用 Harold.L.Beck 提供的该系数所得结果相一致。     

High-voltage electrochemical performance of LiNi0.5Co0.2Mn0.3O2 cathode materials via Al concentration gradient modification

Al₂O₃-modified LiNi_0.5Co_0.2Mn_0.3O₂ cathode material is successfully synthesized via a facile carboxymethyl cellulose (CMC)-assisted wet method followed by a high-temperature calcination process. Al concentration gradient doping and accompanying formation of Al-coating are simultaneously accomplished in the modified samples. XRD and EDS analysis demonstrate that Al element is successfully doped into the crystal lattice with concentration gradient distribution inside the particles, reducing the Li/Ni cation mixing and stabilizing the layered structure. The compact distribution of Al on the surface forms a protective layer between the electrodes and the electrolyte, prohibiting the harmful side reactions and phase transition on the interphase. Compared with the pristine, the modified material with 2000?ppm Al₂O₃ (Al-2000) shows the best high-voltage performance with the capacity retention increased by ~13.3% from 138.3 to 163.0 mAh g^?1 at 1?C in 3.0–4.6?V after 100 cycles. Even under the high current rate of 8?C (1240 mAh g^?1) after 200 cycles, the Al-2000 still exhibits a capacity retention of 88.6%, greater than 80.3% for the pristine. Furthermore, results from the cyclic voltammetry (CV) and the electrochemical impedance spectroscopy (EIS) measurements confirm the roles of the Al₂O₃ modification in decreasing polarization and electrochemical resistances, contributing to the kinetic process of electrodes.     

Modeling and Parameter Identification for a Biofilm in a Microbial Fuel Cell

A dynamic physical model of a microbial fuel cell (MFC) anode is presented and parameterized. It describes the evolution of current density and biofilm mass over time as a function of substrate concentration. The model is particularly useful for process monitoring or control purposes because it reproduces the dynamics of the MFC anode and contains comparatively few parameters. Parameters are identified using data from the response of the MFC to a substrate concentration pulse. Theoretical and practical identifiability of the parameters is evaluated, and parameter confidence intervals are determined.     

烟道气烟色监测仪的研制

烟尘浓度检测是环境监测的一项重要内容。本文论述了光电传感器的关系特性,介绍了烟道气烟色监测仪的工作原理,硬件结构设计,软件编程和使用情况。     

μ-ICC2.45在线微波浓度测量仪服务于沼气加工和污水污泥的处理

本文介绍proMtec在线实时微波浓度测量仪在沼气生产中对填料的浓度、污水污泥处理过程中对污泥浓度密度进行测量的应用。以其新颖的测量手段和独特的结构设计,对进入发酵罐物料和其卸料的在线TS-含量进行监控,以达到最理想的物料平衡,提高细菌的活性,使沼气收益最大化。在线式实时监控,有利于对生产过程的即时掌控,帮助实现节能减排。相比较传统测量方法,μ-ICC 2.45测量设备探头不受结垢、堵塞的影响,可直接安装于大口径的管路或是箱体上。