基于相似系数法的冷源供水温度研究

针对中华鲟保育池冷冻水系统冷源设备选型采用经济性或生态因子进行单因素比选的不足,通过相似系数法对保育池不同水温工况下的经济性和生长影响因子赋予权重,提出了统筹经济指标和生长影响因子指标的综合评价指标。分析结果表明,21℃为保育池冷冻水系统最佳供水温度,不仅满足中华鲟生长对水温的要求,经济性也较好。将基于相似系数法的权重确定方法应用于保育池冷源供水温度的比选,提高了比选的客观性,对其他涉及主观性评价指标的方案比选具有一定的借鉴意义。     

Reliability Allocation for Series-Parallel Systems subject to Potential Propagated Failures

To analyze the dependent failures in the early stage of system development, this paper considers the potential propagated failures in the reliability allocation process. Factors which can be used to not only measure the component importance but also to reflect the influence brought by propagated failures are proposed. Specifically, cooperative game theory is introduced to explore how the propagated failures affect the failure severity level. Failure rates are obtained by using the Alpha Factor Model with the consideration of dependence among components. Reliability improvement rate is also developed to proportionally assign the target improvement of system reliability to the corresponding components. Furthermore, reliability allocation frameworks for series, parallel and series-parallel systems are designed respectively to make the proposed model meet a wide range of applications. An illustrative example of a hydraulic cooling system is presented to show how the proposed approach is applied. The allocation results demonstrate that the proposed method can achieve a valid reliability improvement with the minimum error.     

High coverage H2 adsorption and dissociation on fcc Co surfaces from DFT and thermodynamics

Hydrogen adsorption, desorption and dissociation on the Co(100), (311), (111) and (110) surfaces at different coverage have been systematically studied using density functional theory and ab initio atomistic thermodynamics. On the basis of the computed stepwise H₂ adsorption energies, the saturated coverage on the Co(311), (111), (110) surfaces are 8/18, 3/9 and 6/18 ML, respectively, revealing that these surfaces have different potential hydro-treating abilities and activity. The lateral repulsive interactions can affect the adsorption structures and become stronger with the increasing of H₂ coverage, which lead to H₂ migration over Co surfaces. Comparison of dissociation energies and corresponding desorption energies, it can be concluded that H₂ molecules prefer dissociation rather than desorption both kinetically and thermodynamically at different coverage. Hydrogen stable coverage on the surfaces highly depends on temperatures and H₂ partial pressure. These results should provide important information about morphology of Co-catalysts under Fischer-Tropsch synthesis reduction conditions.     

Amorphizing of Cu Nanoparticles toward Highly Efficient and Robust Electrocatalyst for CO2 Reduction to Liquid Fuels with High Faradaic Efficiencies

Conversion of carbon dioxide (CO₂) into valuable chemicals, especially liquid fuels, through electrochemical reduction driven by sustainable energy sources, is a promising way to get rid of dependence on fossil fuels, wherein developing of highly efficient catalyst is still of paramount importance. In this study, as a proof‐of‐concept experiment, first a facile while very effective protocol is proposed to synthesize amorphous Cu NPs. Unexpectedly, superior electrochemical performances, including high catalytic activity and selectivity of CO₂ reduction to liquid fuels are achieved, that is, a total Faradaic efficiency of liquid fuels can sum up to the maximum value of 59% at ?1.4 V, with formic acid (HCOOH) and ethanol (C₂H₆O) account for 37% and 22%, respectively, as well as a desirable long‐term stability even up to 12 h. More importantly, this work opens a new avenue for improved electroreduction of CO₂ based on amorphous metal catalysts.     

移动边缘计算中资源分配和定价方法综述

移动边缘计算（mobile edge computing,MEC）通过将计算任务卸载至边缘服务器，降低网络负荷，减少传输时延，提升用户服务体验。因此，MEC受到了广泛关注，并成为5G的关键技术。资源分配作为MEC的主要问题，在提升能量效率、缩短任务时延和节约成本方面具有非常重大的研究意义。首先，介绍了MEC的基本概念、参考架构和技术优势；然后，从技术层面和经济层面归纳总结了MEC中最新的资源分配和定价策略；最后，讨论了MEC资源分配和定价策略中可能存在的问题与挑战，并提出了一些可行的解决方案，为后续研究发展提供参考。     

A strategy to reduce the impact of tar on a Ni‐YSZ anode of solid oxide fuel cells

High‐temperature raw coke oven gas (COG) is a promising fuel for use in solid oxide fuel cells (SOFCs) because it is rich in both hydrogen (55%‐60%) and methane (23%‐27%). However, the tar present in COG limits its ability to directly generate power using state‐of‐art SOFCs because the presence of tar limits the cell's performance and stability. In this work, a strategy is presented in the attempt to reduce the influence of tar on SOFCs by applying a La_0.7Sr_0.3MnO₃ catalyst as a protective layer for the cell. The results showed that 44‐g Nm^?3 toluene had a profoundly negative effect on the performance of a conventional cell, which showed severely reduced performance after only 1.4 hours of exposure to toluene‐contaminated hydrogen. In contrast, the catalyst‐modified cell showed good stability for at least 110 hours under the same conditions. This work provides a promising route to directly utilize raw COG as an SOFC fuel that is also suitable for biosyngas.