Nutrient removal performance of an anaerobic–anoxic–aerobic process as a function of influent C/P ratio

The laboratory scale anaerobic–anoxic–aerobic (A²O) process fed with synthetic brewage wastewater was designed to investigate the effects of changing feed C/P ratio on the performance of biological nutrient removal (BNR) processes. In the experiment, the influent chemical oxygen demand (COD) concentration was kept at approximately 300 mg L^?1 while the total phosphorus concentration was varied to obtain the desired C/P ratio. Results showed that when the C/P ratio was lower than 32, phosphorus removal efficiency increased as C/P ratio increased linearly, while when the C/P ratio was higher than 32, the P removal efficiency was maintained at 90–98%, and effluent P concentration was lower than 0.5 mg L^?1. However, regardless of the C/P ratio, excellent COD removal (90% or higher) and good total nitrogen removal (75–84%) were maintained throughout the experiments. It was also found that very good linear correlation was obtained between COD uptake per unit P released in the anaerobic zone and C/P ratio. In addition, the P content in the wasted activated sludge increased with the decrease in the C/P ratio. Based on the results, it was recommended that the wastewater C/P ratio and its effects be incorporated into BNR design and operational procedures, appropriate C/P ratios were used to achieve the effluent treatment goals. Copyright © 2005 Society of Chemical Industry     

Analysis of supersaturation and nucleation in a moving solution droplet with flowing supercritical carbon dioxide

A supercritical antisolvent (SAS) process is employed for production of solid nanoparticles from atomized droplets of dilute solution in a flowing supercritical carbon dioxide (SC CO₂) stream by attaining extremely high, very rapid, and uniform supersaturation. This is facilitated by a two‐way mass transfer of CO₂ and solvent, to and from the droplet respectively, rendering rapid reduction in equilibrium solubility of the solid solute in the ternary solution. The present work analyses the degree of supersaturation and nucleation kinetics in a single droplet of cholesterol solution in acetone during its flight in a flowing SC CO₂ stream. Both temperature and composition are assumed to be uniform within the droplet, and their variations with time are calculated by balancing the heat and mass transfer fluxes to and from the droplet. The equilibrium solubility of cholesterol with CO₂ dissolution has been predicted as being directly proportional to the Partial Molar Volume Fraction (PMVF) of acetone in the binary (CO₂–acetone) system. The degree of supersaturation has been simulated up to the time required to attain almost zero cholesterol solubility in the droplet for evaluating the rate of nucleation and the size of the stable critical nuclei formed. The effects of process parameters have been analysed in the pressure range of 7.1–35.0 MPa, temperature range of 313–333 K, SC CO₂ flow rate of 0.1136–1.136 mol s^?1, the ratio of the volumetric flow rates of CO₂‐to‐solution in the range of 100–1000, and the initial mole fraction of cholesterol in acetone solution in the range of 0.0025–0.010. The results confirm an extremely high and rapid increase in degree of supersaturation, very high nucleation rates and stable critical nucleus diameter of the order of a nanometre. Copyright © 2005 Society of Chemical Industry     

Rheological properties of polypropylene modified by high‐intensity ultrasonic waves

A new method using high‐intensity ultrasonic waves, instead of peroxide‐aided reactive extrusion, was applied to modify a linear polypropylene into a branched structure. The ultrasonic waves induced chain scission and created reactive macromolecules of polypropylene successfully in the melt state without any peroxide. To enhance and control the recombination reaction during sonication, a multifunctional agent and an antioxidant were used. The rheological property measurements clearly confirmed that the modified polypropylene had a nonlinear branched structure. It showed shear‐thinning behaviors in its viscosities at low frequencies, high elastic behaviors in Cole–Cole plots, and a high rheological polydispersity index in comparison with a linear polypropylene. The degradation or recombination of polypropylene was adequately controlled by an antioxidant, which stabilized the structure during sonication. Also, the use of an antioxidant was quite effective in improving the extrusion processability by delaying the instability of the extrudate to a higher shear rate. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

虚拟专用网的体系结构及实现

提出VPN接入设备的体系结构 ,包括系统的应用模型、层次划分和内部详细结构 ,阐述实现VPN的关键技术。     

Mechanical and microstructure studies on the modification of CA film by blending with PS

DriedMusa paradiciaca (banana) stem and veins of the leaves, which were hitherto discarded as a waste, were collected and used as starting material for the preparation of cellulose and cellulose acetate. This cellulose acetate was mixed with polystyrene to form blend of cellulose acetate-polystyrene in order to provide enhanced stability and extended utility to the end products. The films of these composites or their individual partners were made separately and studied for their mechanical properties, chemical modification and morphological changes. We report here that banana stem is good source of cellulose and that cellulose completely undergoes modification upon esterification.     

铝电解槽磁流体稳定性有限元分析

本文采用有限元法求解分层磁流体小扰动方程系统特征值，研究铝电解槽稳定性。研究结果表明，在没有电磁力时，铝液表面波动（内波）是稳定的。存在电磁力时，它会激发铝液表面波动的某些低频长波分量不稳定性，高频短波不受影响。被激发的不稳定波动频率和扰动增长率与电流密度，磁感应强度垂直分量，铝电解槽长宽比，电解质和铝液的密度差，厚度等因素密切相关。减少电流密度，磁感应强度，增加电极距离和铝液厚度可以提高铝电解槽的稳定性。这对铝电解槽优化设计和在线控制有重要意义。     

Hybrid gas-to-particle conversion and chemical vapor deposition for the production of porous alumina films

Porous alumina films can be found in a wide variety of materials, including filters, thermal insulation components, dielectrics, biomedical and catalyst supports, coatings and adsorbents. Production methods for these films are as equally diverse as their applications. In this work, a hybrid process based upon chemical vapor deposition and gas-to-particle conversion is presented as an alternative technique for producing porous alumina films, with the main advantages of solvent-free, low substrate-temperature operation. In this process, nanoparticles were produced in the vapor phase by reaction of aluminum acetylacetonate in the presence of oxygen. Downstream of this reaction zone, these nanoparticles were collected via thermophoresis onto a cooled substrate, forming a porous film. Some deposited films were subjected to post-processing in the form of annealing in air. Fourier-transform infrared spectra and X-ray energy-dispersive spectroscopy analysis confirmed the production of alumina at processing temperatures above 973 K. X-Ray diffraction revealed that the films were amorphous. Film thickness, ranging from 30 to 250 μm, and the average deposition rate were determined from scanning electron microscopy results. From transmission electron microscopy, the average primary particle size was determined to be approximately 18 nm and the formation of nanoparticle aggregates was evident. Annealing of the films at temperatures ranging from 523 to 1173 K in the presence of air did not have an effect on particle size. The specific surface area of the powder composing the films ranged from 10 to 185 m² g⁻¹, as determined from nitrogen gas adsorption by the Brunauer–Emmett–Teller method.     

Posttraumatic stress in children and adolescents exposed to family violence: I. Overview and issues.

Exposure to child physical abuse and parents' domestic violence can subject youth to pervasive traumatic stress and can lead to posttraumatic stress disorder (PTSD). This article presents evolving conceptualizations in the burgeoning field of trauma related to family violence exposure and describes how the often repeating and ongoing nature of family violence exposure can complicate a PTSD diagnosis. In addition, recent literature indicates that children exposed to family violence may experience problems in multiple domains of functioning and may meet criteria for multiple disorders in addition to PTSD. Considerations salient to the recognition of traumatic stress in this population and that inform assessment and treatment planning are presented. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

负载化非茂单活性中心催化剂乙烯聚合的研究

在硅胶上负载了双(N-环己基-3-叔丁基水杨醛亚胺基)二氯化锆配合物,得到负载化非茂单活性中心催化剂。该催化剂用于乙烯聚合,考察了配合物用量、共聚单体1-己烯用量、聚合温度、聚合压力、聚合时间、三乙基铝用量对乙烯聚合性能的影响及对聚合物的相对分子质量、相对分子质量分布、熔体流动指数和密度的影响。实验结果表明,负载化非茂单活性中心催化剂保持了原均相催化剂的乙烯聚合性能;该催化剂在淤浆聚合工艺中聚合平稳,所得聚合物的颗粒形态良好。     

线缆护套材料在我国西部环境中的试验研究

本文通过对线缆外护套材料在我国西部地区严酷环境试验站中土壤和大气1～5年的试验结果分析，总结了塑料护套材料的耐蚀性能。为线缆护套的防护设计、合理选材及制定标准提供科学依据。