锯末对Cu~(2+)的吸附特性研究

以工业废弃物锯末为吸附剂,研究其对水中Cu2+的吸附特性.结果表明,锯末对Cu2+的吸附速度较快,1 h后基本达到平衡.准二级速率方程很好地模拟了吸附反应的动力学方程(R20.99).锯末对Cu2+吸附主要机制是离子交换,吸附量随pH升高而升高.离子强度对吸附反应有一定影响:Cu2+和锯末一部分是内层结合,一部分是外层结合.经过酸碱处理的锯末在吸附能力上有了一定程度的提高.Langmuir模型对原始锯末的吸附等温线拟合最好,Langmuir-Freundlich模型对经过酸碱处理的锯末拟合最好.热力学分析显示吸附反应具有自发性、放热、熵增特性.     

pH对Cd~(2+)离子在δ-MnO_2上的吸附与解吸的影响

研究了pH值对δ-MnO2对模拟废水中Cd2+的吸附作用的影响,当pH<2.3时,吸附率仅为20%,pH>5时Cd2+的吸附率在96%以上;吸附过程为非特性吸附,可以用Elovich方程和双速率方程来描述。吸附后δ-MnO2在pH<2.05时可以有效的解吸,解吸率约为75%。     

Impact of safety attitude,safety knowledge and safety leadership on chemical industry workers’ risk perception based on Structural Equation Modelling and System Dynamics

In chemical industry, major accidents occur occasionally. Past research has demonstrated that risk perception was relevant to safety as it might affect the behavior, which could exert influence on the probability of accidents. It is important to adjust workers' risk perception to reduce accidents in chemical industry. To achieve this goal, some key influencing factors of workers’ risk perception of were identified from 3 aspects including safety attitude, safety knowledge and safety leadership. This was accomplished by gathering empirical data from 287 workers employed in 6 Chemical plants in Jiangsu, China. The model of influencing factors of risk perception for workers was established based on Structural Equation Modelling (SEM), and the path coefficients and weights were analyzed by the SEM. On that basis, the System Dynamics (SD) model of risk perception for workers was established. The study findings revealed safety attitude and safety leadership have a direct positive impact on perception of risk probability and perception of risk severity, safety knowledge has a direct positive impact on perception of risk severity, while safety knowledge has no direct positive impact on perception of risk probability. The findings of the study can provide theoretical supports and method guidance for adjusting the risk perception of workers in chemical industry.     

吸附质污染物输运研究

对含沙水体中的吸附质污染物输运过程进行分析,从单元体出发推导考虑泥沙影响的污染物输运方程。导出的方程考虑了冲刷沉降、孔隙水扩散和孔隙水混合作用的影响,并应用于灌河口的TP浓度计算,验证结果较好。     

Identifying the factors influencing the performance of reverse supply chains (RSC)

This paper aims to extract the factors influencing the performance of reverse supply chains (RSCs) based on the structure equation model (SEM). We first introduce the definition of RSC and describe its current status and follow this with a literature review of previous RSC studies and the technology acceptance model . We next develop our research model and 11 hypotheses and then use SEM to test our model and identify those factors that actually influence the success of RSC. Next, we use both questionnaire and web‐based methods to survey five companies which have RSC operation experience in China and Korea. Using the 168 responses, we used measurement modeling test and SEM to validate our proposed hypotheses. As a result, nine hypotheses were accepted while two were rejected. We found that ease of use, perceived usefulness, service quality, channel relationship and RSC cost were the five most important factors which influence the success of RSC. Finally, we conclude by highlighting our research contribution and propose future research.     

商场工作人员自我效能感与火灾时行为的结构方程模型分析*

为充分发挥商场工作人员在火灾风险下的疏导作用,提高疏散效率。引入火灾安全意识、行为选择动机、火灾认知能力为中介变量,研究商场工作人员自我效能感与火灾时的有利行为、不利行为之间的关系,构建结构方程模型;对西安市某大型商场212名工作人员进行问卷调查,运用Amos24.0软件进行分析。研究结果表明:自我效能感主要通过火灾安全意识、行为选择动机、火灾认知能力对商场工作人员发生火灾时的行为产生影响,这3个中介变量对商场工作人员发生火灾时的有利行为呈显著正相关,对不利行为呈显著负相关;火灾认知能力对商场工作人员发生火灾时的有利行为影响最大,行为选择动机对商场工作人员发生火灾时的不利行为影响最大。研究结果可为商场火灾安全疏散管理提供有效依据,对商场火灾疏散具有重要意义。     

BOD_5快速测定法

寻求BOD生化过程动力学方程,依据广泛性的、相关性很好的多组实验数据(X,Y),建立回归方程用于计算BOD5。本法仍以国标GB/T7488-1987为依据,仅以较少培养时间的BOD值推算得BOD5值。BOD5的计算值与其实测值间的相对误差<5%。     

Biogeographic distribution patterns of algal community in different urban lakes in China: Insights into the dynamics and co-existence

Urban lake ecosystems are significant for social development, but currently we know little about the geographical distribution of algal community in urban lakes at a large-scale. In this study, we investigated the algal community structure in different areas of urban lakes in China and evaluated the influence of water quality parameters and geographical location on the algal community. The results showed that obvious differences in water quality and algal communities were observed among urban lakes in different geographical areas. Chlorophyta was the dominant phylum, followed by cyanobacteria in all areas. The network analysis indicated that algal community composition in urban lakes of the western and southern area showed more variations than the eastern and northern areas, respectively. Redundancy analysis and structural equation model revealed that nutrients and pH were dominant environmental factors that affected the algal community, and they showed higher influence than that of iron, manganese and COD _Mn concentration. Importantly, algal community and density exhibited longitude and latitude relationship. In general, these results provided an ecological insight into large-scale geographical distributions of algal community in urban lakes, thereby having potential applications for management of the lakes.     

Do Energy‐Based PET Models Require More Input Data than Temperature‐Based Models? — An Evaluation at Four Humid FluxNet Sites

It is well established that wet environment potential evapotranspiration (PET) can be reliably estimated using the energy budget at the canopy or land surface. However, in most cases the necessary radiation measurements are not available and, thus, empirical temperature‐based PET models are still widely used, especially in watershed models. Here we question the presumption that empirical PET models require fewer input data than more physically based models. Specifically, we test whether the energy‐budget‐based Priestley‐Taylor (P‐T) model can reliably predict daily PET using primarily air temperature to estimate the radiation fluxes and associated parameters. This method of calculating PET requires only daily minimum and maximum temperature, day of the year, and latitude. We compared PET estimates using directly measured radiation fluxes to PET calculated from temperature‐based radiation estimates at four humid AmeriFlux sites. We found good agreement between P‐T PET calculated from measured radiation fluxes and P‐T PET determined via air temperature. In addition, in three of the four sites, the temperature‐based radiation approximations had a stronger correlation with measured evapotranspiration (ET) during periods of maximal ET than fully empirical Hargreaves, Hamon and Oudin methods. Of the three fully empirical models, the Hargreaves performed the best. Overall, the results suggest that daily PET estimates can be made using a physically based approach even when radiation measurements are unavailable.     

基于边界定位法的填埋场渗漏检测

提出了以传输线模型为基础的新型填埋场渗漏检测方法,并且建立了填埋场渗漏检测的非均匀传输线模型.利用模型中边界电气量以及渗漏区域2个分界面电压连续的基本原理推导出测距方程,通过线路两端电气量的采样值,计算模型的特性阻抗和传播系数.结果表明:检测频率为30 MHz时,渗漏和未渗漏区域的衰减常数和相位常数差异性最大;同一频率下,渗漏区域的值高于未渗漏区域;特性阻抗的模值随频率增加而减小,辐角则随频率的增加而增大;测量中不同步采样对测距精度有一定影响.为提高测距精度,应选用较高的检测频率并保证两端电气量同步采样.