生物质炭对气态挥发性有机污染物的吸附性能及机理

为探究生物质炭对气态有机污染物的吸附能力及作用机理,以核桃壳和椰子壳为原料制备生物质炭.采用元素分析仪、傅里叶红外光谱仪、Boehm滴定和比表面积及孔隙率分析仪分析生物质炭理化特征,并利用吸附柱实验考察生物质炭对气态挥发性有机污染物(苯和甲苯)的吸附行为.结果表明:相同制备条件下,椰壳生物质炭吸附性能高于核桃壳生物质炭.在实验温度范围内(400~700℃),随着制备温度的升高,生物质炭吸附性能增大.低温下制备的生物质炭(400℃)吸附行为符合准二级动力学模型,高温下制备的生物质炭(700℃)的吸附过程符合准一级动力学模型.在吸附温度30℃时,生物质炭对苯和甲苯的等温吸附过程符合Toth模型,计算得到生物质炭最大的理论饱和吸附量为18.98 mg/g苯和61.73 mg/g甲苯.生物质炭的表面酸性官能团和孔道结构在吸附过程中起关键作用,影响吸附质在生物质炭的表面吸附和粒内扩散吸附过程.     

高校朋辈辅导的差异化策略研究——基于北京本科院校大学生朋辈辅导员工作情况的调查分析

本文基于对北京本科院校大学生朋辈辅导员工作情况的问卷调查,发现在共性基础上存在着差异,211院校的学生以及各类院校中有过学生干部经历的学生对于学生工作以及朋辈辅导员工作更为积极乐观,所以学生工作需要结合院校类型,给予更多的学生以学生管理工作的锻炼成长机会.     

An ICPSO-RBFNN nonlinear inversion for electrical resistivity imaging

To improve the global search ability and imaging quality of electrical resistivity imaging(ERI) inversion, a two-stage learning ICPSO algorithm of radial basis function neural network(RBFNN) based on information criterion(IC) and particle swarm optimization(PSO) is presented. In the proposed method, IC is applied to obtain the hidden layer structure by calculating the optimal IC value automatically and PSO algorithm is used to optimize the centers and widths of the radial basis functions in the hidden layer. Meanwhile, impacts of different information criteria to the inversion results are compared, and an implementation of the proposed ICPSO algorithm is given. The optimized neural network has one hidden layer with 261 nodes selected by AKAIKE's information criterion(AIC) and it is trained on 32 data sets and tested on another 8 synthetic data sets. Two complex synthetic examples are used to verify the feasibility and effectiveness of the proposed method with two learning stages. The results show that the proposed method has better performance and higher imaging quality than three-layer and four-layer back propagation neural networks(BPNNs) and traditional least square(LS) inversion.     

“徽派”与“扬气” ——徽州与扬州传统建筑装饰差异性研究

装饰一直都作为建筑不可或缺的组成部分,它给予建筑美学特征,又赋予建筑文化、历史、社会、宗教等象征意义。本文针对徽州建筑,以及徽州文化、经济影响至深的扬州传统建筑,通过分析比较,挖掘不同的地域文化、不同的历史信息、不同的建筑文化。通过装饰对比,研究徽州与扬州传统建筑的互融与差异,揭示徽派建筑与江浙建筑的内在联系。     

地震计标定及特性分析应用研究

地震计的参数是进行地震波形反演、地震震级确定的基本资料,其性能指标影响着地震数据产出的质量。地震计标定时,初始点位置的选取直接影响对仪器性能好坏的判断。本文以某水库地震监测台网中1个台站标定为例,通过检验和测定地震计标定过程中通频带平坦程度、三分向幅度响应一致性、频带范围、周期阻尼等参数,详细讨论了标定过程中起始点位置的选择原则及影响周期、阻尼计算结果的因素。     

水下无线传感器网络自适应转发协议

针对水下传感器网络延时长、网络拓扑动态变化的问题,提出一种三维水下无线传感器网络自适应转发协议AFP(adaptive forwarding protocol)。AFP采用自适应方法获得转发概率与转发区域,让转发区域内与上一跳转发节点距离相对远,且与上一跳节点与目的节点的矢量方向相对近的节点以高概率转发分组,从而减少了转播冗余和冲突,提高了转播效率。应用NS-2仿真软件对协议的性能进行仿真,仿真结果表明:与VBF协议相比,AFP提高了分组投递率、减少了端对端延迟,证明了AFP在水下无线传感器网络环境下工作的可行性和有效性。     

散粒体的自组织临界性分析

基于二维模拟实验,研究竖向荷载下散粒体中的自组织临界性,揭示细观拱效应与宏观大崩塌的变化规律,以及拱效应与材料性质的关系.散粒体中每个小自组织的临界发展过程包括自组织搭拱、拱随遇平衡和拱崩塌的动力学演化.散粒体大坍塌是众多小自组织临界发生后的力学性质由量变到质变的过程.用随机理论细观探讨一个预期失败模式的理论模型,为研究散体材料结构自组织临界性系统的可预测性及灾害预测预报提供了科学依据.     

复合弯扭作用下预应力单箱组合梁的扭转承载能力分析

组合梁结构在实际工程中常处于弯扭复合受力状态,为探讨预应力单箱组合梁在复合弯扭作用下的扭转承载性能,引入了弯矩影响系数和预应力影响系数,提出了预应力单箱组合梁在弯扭作用下的开裂扭矩计算公式.并在大扭弯比条件下,基于空间桁架理论,推导了预应力单箱组合梁在弯扭作用下的极限扭矩计算公式.为了验证该理论的正确性,设计了4根模型梁试件进行弯扭加载试验.理论计算值与试验值的对比结果表明,由理论计算公式得出的结果与实际吻合良好,可为研究组合梁结构的复合弯扭问题提供一定的理论参考.     

Extended trajectory shaping guidance law considering a first-order autopilot lag

To satisfy the terminal position and impact angel constraints, an optimal guidance problem was discussed for homing missiles. For a stationary or a slowly moving target on the ground, an extended trajectory shaping guidance law considering a first-order autopilot lag (ETSGL-CFAL) was proposed. To derive the ETSGL-CFAL, a time-to-go-nth power weighted objection function was adopted and three different derivation methods were demonstrated while the Schwartz inequality method was mainly demonstrated. The performance of the ETSGL-CFAL and the ETSGL guidance laws was compared through simulation. Simulation results show that although a first-order autopilot is introduced into the ETSGL-CFAL guidance system, the position miss distance and terminal impact angle error induced by the impact angle is zero for different guidance time.     

Effect of tin addition on the microstructure and properties of ferritic stainless steel

This article reports the effects of Sn on the inclusions as well as the mechanical properties and hot workability of ferritic stainless steel. Precipitation phases and inclusions in Sn-bearing ferritic...