微生物絮凝剂在重金属废水处理方面的研究进展

微生物絮凝剂是一种具有广阔应用前景的天然高分子絮凝剂,因其无毒、可生物降解、无二次污染等独特的性质受到人们的广泛关注。概述了微生物絮凝剂的种类和在重金属废水处理方面的研究进展,包括微生物絮凝剂的种类和结构特性,微生物絮凝剂在重金属废水处理方面的发展与特点等。     

一步法柠檬酸钠生产中钙盐条件的优化研究

研究了在使用不同钙盐条件下和柠檬酸的发酵液与钙盐中和反应生产柠檬酸钙的工艺条件,提出了采用不同钙盐条件下,柠檬酸与钙盐的比例关系,以及相应的pH值与柠檬酸根的残留量,为一步法生产柠檬酸钠在中和工序提供了良好的工艺条件,减少了后工序的生产难度,提高了中和工序的收率和最终的产品质量。     

商用车气压制动系统快放阀优化设计

针对商用车气压制动系统快放阀排气气压延迟问题,对快放阀进行优化设计以降低延迟气压与时间。应用系统仿真软件AMESim对快放阀进行模拟仿真,获得对排气延迟影响较大的变量,利用正交试验法研究了快放阀膜片厚度、排气口流通面积、排气口气隙宽度对快放阀排气延迟的影响。结果表明:最优快放阀结构的排气口气隙宽度为3 mm,膜片厚度为2 mm,下阀口支撑筋面积为70 mm²;通过快放阀结构的参数优化,可有效降低排气延迟气压与时间,压差同比降低约110 kPa,时间缩短0.65 s,同时提升了制动系统的稳定性。     

Investigation on compressive behavior of Cu-35Ni-15Al alloy at high temperatures

Microstructures and mechanical properties of Cu-35Ni-15Al alloy in cast and porous states were studied by scanning electron microscopy and compression tests. The influence of porosity, deformation temperature and loading rate on mechanical properties of the two kinds of alloys was investigated. The results show that the as cast alloy and porous alloys have almost the same phase constitution: Cu rich phase, Ni rich phase and K intermetallics. The yield strength of porous alloys increases continuously with decreasing porosity, the relationship between porosity and yield stress follows Gibson-Ashby equation. With decreasing deformation temperature, the yield strength of as cast alloy and porous alloy increase. With the increase of loading rate, the yield strength of these alloys shows an increasing trend. After compression, the microstructure of as cast alloy is more uniform, and porous alloys are more prone to have localized deformations.     

Role of dual SiOx: H based buffer at the p/i interface on the performance of single junction microcrystalline solar cells

In p-i-n structure a-Si solar cell a buffer layer with proper characteristics plays important role in improving the p/i interface of the cell, reducing mismatch of band gaps and number of recombination centres. However for p-i-n structure microcrystalline ( µc-Si: H) cell which has much less light induced degradation than a-Si:H cell, not much work has been done on development of proper buffer layer and its application to µc-Si:H cell. In this paper we have reported the development of two intrinsic oxide based microcrystalline layer having different characteristics for use as buffer layers at the p/i interface of µc-Si:H cell. Previously SiO_x:H buffer layer has been used at the p/i interface which showed positive effects. To explore the possibility of improving the performance of p-i-n structure µc-Si:H cell further we have thought it interesting to use two buffer layers with different characteristics at the p/i interface. The two buffer layers have been characterized in detail and applied at the p/i interface of the µc-Si:H cell with positive effects on all the PV parameters mainly improves the open circuit voltage (V_oc) and enhances short circuit current (I_sc). The maximum initial efficiency obtained is 8.97% with dual buffer which is 6.7% higher than that obtained by using conventional single buffer layer at the p/i interface. Stabilized efficiency of the cell with dual buffer is found to be ~9.5% higher than that with single buffer after 600 h of light soakings.     

A weighted average global process model based on two−stage kinetic scheme for biomass combustion

This research study combustion kinetics of four biomass samples in China, red pine (Pinus tabulaeformis), corn straw (hybrid corn Zheng Dan-958), Bermuda grass and bamboo (Phyllostachys heterocycla var), using thermogravimetric analysis (TGA). Three stages of combustion process are identified as water evaporation, removal and combustion of volatile matters and combustion of char. Thermal kinetic parameters of each sample are calculated by using 1st order Coats–Redfern method based on the TGA data. It is found that the activation energy of the global process is in the range of 53.6–65.2 kJ mol⁻¹ with a poor linear correlation. The experimental data are then used to develop a two−stage reaction kinetic scheme with low temperature region (2nd stage) and high temperature region (3rd stage). The activation energy of the second stage is in the range of 123.5–140.5 kJ mol⁻¹, and that of the third stage was in the range of 59.4–93.4 kJ mol⁻¹, both of which were based on the 1st order Coats–Redfern method. Because the global process of actual combustion is different from the TGA, a modified weighted average model is proposed based on the two−stage reaction kinetic scheme. According to the modified model, the kinetic parameters of the global process for actual combustion are calculated and are all found a little smaller than that of the 2nd stages. That will benefit for the combustion simulation and the design of facility of biomass fuel.     

Study of interfacial friction mechanism based on the coupled-oscillator model

A new coupled-oscillator model, in which the relationship of the lateral force and the normal force are considered, is proposed for the interfacial friction. The Maugis-Dugdal model is used to approximately substitute the Lennard-Jones potential of the interfacial friction in the new model. The mechanism of microscopic sliding and the energy dissipation mechanism of friction are discussed. The formulae for frictional force calculation are then deduced. Based on theoretical analysis, it is found that the frictional force increases approximately as 2/3 the power of the normal force for a tip-sample contact system, which is same as the classical conclusion of nano-tribology. A comparison between the theoretical results and the experimental data obtained with an atomic force microscope is presented at the end of the paper. The result has shown that the new coupled-oscillator model and the formulae deduced are feasible.     

Evaluating industry performance using extracted RGR rules based on feature selection and rough sets classifier

In strategy of investment, an important thing for investors is to correctly predict firm’s revenue growth rate (RGR), which is an effective evaluation indicator for them to see how big the potential power of future development is and measure how about the growth of future development for a target firm that may be selected to investment portfolios. However, conventional methods of forecasting RGR have some shortcomings such as statistical methods based on strict assumptions of linearity and/or normality limit applications in real world. Additionally, due to rapid changing of information technology (IT) today, some techniques (i.e. rough sets and data mining tools) have become important research trends to both practitioners and academicians. With these reasons above, a new procedure, using the feature selection method and rough sets classifier, is proposed to extract decision rules and improve accuracy rate for classifying RGR. In empirical study, an actual RGR dataset collected from publicly traded company of stock markets is employed to illustrate the proposed procedure. The experimental results of RGR dataset analyses indicate that the proposed procedure surpasses the listing methods in terms of both higher accuracy and fewer attributes, and the output of proposed procedure is to generate a set of easily understandable decision rules that are readily applied in knowledge-based investment systems by investors.     

纤维板目标厚度和目标密度对剖面密度分布的影响

剖面密度分布(VDP)是影响纤维板物理力学性能的重要因素之一.本文采用单因子试验法分析了目标厚度和目标密度对纤维板VDP的影响.结果表明,目标厚度增加,表层最高密度增加、芯层最低密度降低,VDP曲线形状更加陡峭;目标密度增大,表层最高密度和芯层最低密度均增大,但对VDP曲线的形状几乎没有影响.     

开放教学的相关理论及教学方法

本文介绍了开放教学的基本概念以及相关理论。然后对教学方法进行了梳理,提炼整理了几种符合开放教学理念的现代教学方法,并进行了分析,得到一些有益的结论。