Development of an experimentally validated semi-empirical fully-coupled performance model of a PEM electrolysis cell with a 3-D structured porous transport layer

A semi-empirical non-isothermal model incorporating coupled momentum, heat and mass transport phenomena for predicting the performance of a proton exchange membrane (PEM) water electrolysis cell operating without flow channels is presented. Model input parameters such as electro-kinetics properties and mean pore size of the porous transport layer (PTL) were determined by rotating disc electrode and capillary flow porometry, respectively. This is the first report of a semi-empirical fully coupled model which allows one to quantify and investigate the effect of the gas phase and bubble coverage on PEM cell performance up to very high current densities of about 5 A/cm². The mass transport effects are discussed in terms of the operating conditions, design parameters and the microstructure of the PTL. The results show that, the operating temperature and pressure, and the inlet water flowrate and thickness of the PTL are the critical parameters for mitigating mass transport limitation at high current densities. The model presented here can serve as a tool for further development and scale-up effort in the area of PEM water electrolysis, and provide insight during the design stage.     

A tree-structured crash surrogate measure for freeways

In this paper, we propose a novel methodology to define and estimate a surrogate measure. By imposing a hypothetical disturbance to the leading vehicle, the following vehicle’s action is represented as a probabilistic causal model. After that, a tree is built to describe the eight possible conflict types under the model. The surrogate measure, named Aggregated Crash Index (ACI), is thus proposed to measure the crash risk. This index reflects the accommodability of freeway traffic state to a traffic disturbance. We further apply this measure to evaluate the crash risks in a freeway section of Pacific Motorway, Australia. The results show that the proposed indicator outperforms the three traditional crash surrogate measures (i.e., Time to Collision, Proportion of Stopping Distance, and Crash Potential Index) in representing rear-end crash risks. The applications of this measure are also discussed.     

Palm Oil: A New Ethics of Visibility for the Production Landscape

The explosion of the palm oil industry in recent decades has transformed vast swathes of the Malaysian and Indonesian countryside. Milica Topalovic , Assistant Professor of Architecture and Territorial Planning at ETH Zurich, asserts that the resulting agro-industrial landscapes challenge the very concept of what is rural, and considers how such areas should be conceptualised.     

The Hinterland Urbanised?

What defines the urban? And can the non-urban necessarily always be classified as rural? Neil Brenner , Director of the Urban Theory Lab at Harvard University Graduate School of Design, reflects on the lack of an overarching theory to describe these realms, and argues that what we call the countryside or the hinterland has become key to the process of capitalist urbanisation.     

基于人机交互的语言训练中微信小程序开发设计研究

以微信小程序开发过程为个案,研究一种基于人机交互的涉及到交际语言训练功能的微信小程序开发设计过程。对微信小程序开发工具包和开发平台进行分析,实现在交际语言训练过程和人机交互功能的加强开发。该开发过程在推送精度和用户满意度方面均获得较强的数据表现。认为该开发模式适用于该个案的开发需求。     

Selective Laser Melting process optimization of Ti–Mo–TiC metal matrix composites

Selective Laser Melting (SLM) was used to process a powder mixture of CP Ti, 6.5 wt% Mo and 3.5 wt% Mo₂C. The process parameters were optimized to obtain full-density, crack free parts. After the in situ decomposition of Mo₂C in favor of the formation of TiC, the material consisted of a homogeneous dispersion of submicrometer sized TiC platelets in a β-(Ti,Mo) matrix exhibiting a high hardness up to 550 HV and compressive yield stress of 1164 ± 37 MPa. The microstructure and mechanical properties could be tailored by variation of the process parameters within the high-density processing window, as well as through post-process heat treatments.     

美国水资源管理体制、全球战略及对中国启示

本文分析了美国水资源开发利用现状,并从管理历史、管理体制、管理经验等角度综述了美国水资源管理的具体办法,并指出美国水资源管理政策的未来方向,总结美国水资源管理经验与教训,同时从实施手段、优先实施区域、全球战略变化等方面分析了美国水资源治理全球战略,通过以上对美国水资源管理体制及全球战略分析,提出了我国水资源管理的改进建议。     

An analysis of cascade‐aerated facultative waste stabilisation ponds in the United Kingdom

This paper examines the performance of cascade‐aerated facultative ponds in a waste stabilisation pond (WSP) installation in the United Kingdom. The pond system is privately owned and treats wastewater from a conference centre with a population equivalent between 20 and 40. A snapshot analysis investigates the removal efficiency of BOD, COD, SS, FC and nutrients. Further, the oxygen supply through ‘flow form’ cascades is examined, and the DO concentrations, surface loads and retention times are discussed. The results show a very high removal of BOD, COD and SS; and nutrient removal is satisfactory. An unusual finding is that the FC removal efficiency is almost two log units better than for a common maturation pond. This is possibly attributable to the high cascade flow, where wastewater is exposed to the damaging effects of sunlight (photo‐oxidation).     

MELCOR/MACCS simulation of the TMI-2 severe accident and initial recovery phases, off-site fission product release and consequences

MELCOR has become the preferred code of the Swiss nuclear industry and of PSI for severe accident analysis, on account of its integrated systems-level approach and validation against experiments and more detailed codes, while MACCS is commonly used by safety authorities for independent assessment of off-site consequences, in particular health effects. The present work arises out of a programme to assess MELCOR independently using empirical data consistent with the recommendations of the OECD/CSNI validation matrix for core degradation codes. The MELCOR 1.8.5RD calculations are based on a model for phases 1 and 2 provided by the code developers but with a simplified thermal hydraulic noding in certain regions and the inclusion of a simple representation of the fission product release and transport pathways. The model has also been extended to simulate phases 3, 4, and the continuing initial period of core recovery and stabilisation. These calculations are a first attempt to demonstrate a MELCOR–MACCS capability to simulate the whole plant accident sequence beyond phase 4, including the containment response and off-site consequences arising from fission product release from the containment. Emphasis is placed on the overall accident evolution and whole plant response, rather than the detailed behaviour. Results are compared with observed and deduced data for the major accident signatures and rough estimates for exposure based on off-site monitoring. The results provide a good basis for the NPP analysis foreseen.     

对做好高校新时期统战工作的思考

党政一把手高度重视是搞好高校统战工作的关键，为教学，科研的改革和发展服务是高校统战工作的中心，加强和完善党外表人物队伍建设是高校统战工作的重点，积极开展海外统战工作是搞好高校统战工作的重要途径，加强统战工作规范化、制度化建设是搞好高校统战工作的重要保证。