重庆境内07.7泥石流灾害形成机理及启示

2007年7月在暴雨激发下,重庆境内多处暴发泥石流,本次泥石流的集中暴发是地形地貌、物源和暴雨等多因子耦合异变的必然结果,打破115年记录的降雨是泥石流暴发的客观因素,但人类工程活动,如山区城镇建设、采矿、交通建设等造成的弃渣、毁林,是引发泥石流灾害的重要原因。对本次泥石流形成条件、形成机理进行了分析,并综合历史泥石流事例、山洪、水土流失分区、地形地貌、物源、气候等因素,对重庆境内泥石流发育趋势进行了初步分区;并基于成因分析、机理研究和泥石流分区,提出了重庆境内泥石流灾害有关防治对策建议。     

金川县沙耳干河坝泥石流治理工程研究

金川县境内的沙耳干河坝泥石流沟泥石流活动频繁,暴发频率属于中等。为了减少泥石流灾害的威胁和危害,进行现场踏勘,开展泥石流的治理工程研究,具有重要意义。拦砂坝、谷坊坝、单侧防护堤、排导槽和导流堤等工程对泥石流的预防与治理具有显著作用,采用多种措施相结合的方式相对于单一措施更为有效。在治理工程的建设过程中可能引发相应的环境问题,对其中影响较大的水土流失问题提出防治措施,并进行可行性研究,同时提出实施建议。     

Phragmites australis and Typha orientalis in removal of pollutant in Taihu Lake, China

Two plant populations of Phragmites australis and Typha orientalis grown in gravel and sediment substrate were studied to assess their capabilities for purifying polluted water in Taihu Lake, China. The substrate displayed most significant effects on the suspended matter (P < 0.01), with the reduction of 76%-87% and 52%-63% for P. australis, and 83%-86% and 45%-62% for T. orientalis in gravel substrate and sediment substrate, respectively. Both species and substrates significantly decreased the N and P conc...     

我国物质流研究述评

在分析我国近年来物质流研究成果的基础上,探讨目前研究存在的问题,并提出今后物质流研究应在以下几方面作出努力:建立学术平台、研究基地,加强学术交流;建立统一的分析和计算的框架和具体系数的估算方法;把物质流分析的成果与具有社会价值的经济、人口、土地等因素结合分析,与国外进行对比,找出我国的问题所在;建立我国或者特定区域的隐藏流系数的实时分析模型;物质投入产出表的编撰与研究;对我国未开展物质流研究的典型区域进行物质流分析。     

反相流动注射催化动力学分光光度法测定海水中的痕量Cu

在弱碱性的介质中,Cu能够对H2O2氧化对苯二酚的反应起到明显的催化作用,反应产物在500 nm波长处有最大吸收峰.据此,发展了一种反相流动注射催化动力学分光光度法测定海水痕量Cu的新方法.在最佳条件下,Cu2+的浓度在0～40 μg/L具有良好的线性关系,相关系数0.9993,检出限为0.2 μg/L,回收率为98.7%～104.2%,用5 μg/L标准溶液进样的相对标准偏差为1.03%(n=10).     

Simulation of the flow of an explosive atmosphere exposed to a hot surface

The accidental ignition of combustible atmospheres by hot surfaces is of great concern for chemical and process plant safety. In this paper, we present our research regarding the evolution of thermal plumes originating from hot hemispheres and discs. In particular, we focus on the effect of the orientation of the surface on the ignition process. The auto-ignition temperatures and ignition locations were studied experimentally. To get further insight, we conducted detailed numerical simulations and validated them with measurements. Three-dimensional simulations were performed on hot hemispheres and hot discs for different orientations ranging from 0° to 180°. The solver employs a transient, implicit scheme which is based on the coupled heat transfer and flow equations. The mesh in the vicinity of the hot surfaces is refined to resolve the steep temperature gradients and to capture the boundary layer separation. The influence of the orientation on critical hot spots in the gas mixture is analysed by examining the flow structures and the temperature evolution of the buoyancy-driven flow. Using the obtained results, we discuss the change of the onset and location of the ignition.     

Modeling Flow,Nutrient, and Sediment Delivery from a Large International Watershed Using a Field‐Scale SWAT Model

A large international watershed, the St. Clair‐Detroit River System, containing both extensive urban and agricultural areas, was modeled using the Soil and Water Assessment Tool (SWAT) model. The watershed, located in southeastern Michigan, United States, and southwestern Ontario, Canada, encompasses the St. Clair, Clinton, Detroit (DT), Sydenham (SY), Upper, and Lower Thames subwatersheds. The SWAT input data and model resolution (i.e., hydrologic response units, HRUs), were established to mimic farm boundaries, the first time this has been done for a watershed of this size. The model was calibrated (2007–2015) and validated (2001–2006) with a mix of manual and automatic methods at six locations for flow and water quality at various time scales. The model was evaluated using Nash–Sutcliffe efficiency and percent bias and was used to explore major water quality issues. We showed the importance of allowing key parameters to vary among subwatersheds to improve goodness of fit, and the resulting parameters were consistent with subwatershed characteristics. Agricultural sources in the Thames and SY subwatersheds and point sources from DT subwatershed were major contributors of phosphorus. Spatial distribution of phosphorus yields at HRU and subbasin levels identified locations for potential management targeting for both point and nonpoint sources and revealed that in some subwatersheds nonpoint sources are dominated by urban sources.     

Dynamic contact angle effects on gas-liquid behaviors in the cathode of proton exchange membrane fuel cell with stirred tank reactor design

Liquid water management is still a critical issue in the improvement of proton exchange membrane fuel cell (PEMFC) performance. In this work, for the first time, the liquid water behavior and transport inside the cathode of a PEMFC with a stirred tank reactor (STR) design, rather than the conventional PEMFC flow channel design, are numerically studied. The dynamic contact angle (DCA) is applied to multiple wall boundaries in the numerical model through a user-defined-function (UDF) code, i.e., STR-DCA model. Another numerical model with the static contact angle (SCA) and same operating conditions, i.e., STR-SCA model, is also developed for comparison. The volume of fluid (VOF) method is employed in the simulation to track the gas-liquid interface. The results show that the liquid water distribution and transport are significantly different between these two models, indicating the remarkable effects of DCA on the simulation results. It is also verified the capability of STR-PEMFC to reduce the liquid water flooding, showing the potential of this channel-less type fuel cell in the further development.     

A new look at the psychological contract during organizational socialization: The role of newcomers' obligations at entry

Previous studies have demonstrated that the psychological contract is largely shaped during socialization. This study adopts a complementary perspective and analyzes how the psychological contract at the start of employment shapes the subsequent socialization process. Drawing upon social exchange theory, we propose that newcomers with a higher sense of their personal obligations at entry will perceive orientation training as more useful and develop better relationships with their supervisors and peers, which in turn will facilitate their work adjustment. Results of a longitudinal survey on a sample of 144 recruits from a European Army show that newcomers with a higher initial sense of their employee obligations toward their employer report higher perceived training utility, higher leader–member exchange (LMX) with their instructors, and higher team–member exchange (TMX) with their platoon peers. Moreover, perceived training utility and LMX predict the fulfillment of employers' obligations; and training utility predicts the level of newcomers' employee obligations. Finally, training utility, LMX, and TMX predict some of three indicators of newcomers' adjustment, namely, role clarity (training utility and LMX), group integration (TMX), and organizational values understanding (training utility). These results highlight how newcomers' obligations at the start of employment contribute to the social exchange dynamic underlying organizational socialization. Copyright © 2015 John Wiley & Sons, Ltd.     

石英灯辐射式瞬态热环境试验关键技术分析

结合石英灯辐射式加热器的特性,从传感器弱信号传输、无功补偿、智能控制、仿形加热器、开环试验技术等角度出发,分析了对型号瞬态热试验性能的影响。结合瞬态热试验的实施,给出了上述几个角度制约热试验实施的改进措施,以期提高试验系统瞬态热试验的有效性。