Dynamic temperature model for proton exchange membrane fuel cell using online variations in load current and ambient temperature

This paper presents a dynamic temperature model for a proton exchange membrane fuel cell (PEMFC) system. The proposed model overcomes the complexity of conventional models using first-order expressions consisting of load current and ambient temperature. The proposed model also incorporates a PEMFC cooling system, which depends upon the temperature difference between events. A dynamic algorithm is developed to detect load changing events and calculate instantaneous PEMFC temperature variations. The parameters of the model are extracted by employing the lightning search algorithm (LSA). The temperature characteristics of the NEXA 1.2 kW PEMFC system are experimentally studied to validate model performance. The results show that the proposed model output and the temperature data obtained from experiments for linear and abrupt changes in PEMFC load current are in agreement. The root-mean-square error between the model output and experimental results is less than 0.9. Moreover, the proposed model outperforms the conventional models and provides advantages such as simplicity and adaptability for low and high sampling data rates of input variables, namely, load current and ambient temperature. The model is not only helpful for simulations but also suitable for dynamic real-time controllers and emulators.     

Hydrodynamic Modeling Improves Green River Reconnection with Floodplain Wetlands for Endangered Fish Species Recovery

We performed two‐dimensional (2D) hydrodynamic modeling to aid recovery of the endangered razorback sucker (Xyrauchen texanus) by reconnecting the Green River with its historic bottomland floodplain wetlands at Ouray National Wildlife Refuge, Utah. Reconnection allows spring flood flows to overtop the river levee every two to three years, and passively transport razorback sucker larvae to the wetlands to grow in critical habitat. This study includes (1) river hydrologic analysis, (2) simulation of a levee breach/weir, overtopping of river flood flows, and 2D flow through the wetlands using Hydrologic Engineering Center River Analysis System 2D, and (3) modeling flow and restoration scenarios. Indicators of hydrologic alteration were used to evaluate river flow metrics, in particular flood magnitudes, frequency, and duration. Results showed a target spring flow of 16,000 cfs (453 m³/s) and a levee breach elevation of 4,663 ft (1,421 m) amsl would result in a median flow >6,000 acre‐feet (7.4 million m³) over five days into the wetlands, which is adequate for razorback sucker larvae transport and rearing. Modeling of flow/restoration scenarios showed using gated water control structures and passive low‐water crossings between wetland units can provide adequate control of flow movement into and storage in multiple units. Levee breaching can be a relatively simple, cost‐effective method to reconnect rivers and historic floodplains, and hydrodynamic modeling is an important tool for analyzing and designing wetland reconnection.     

北京市生态涵养区生态服务价值评估与生态补偿机制探讨

在分析北京市生态涵养区在生态补偿制度建设困境的基础上,本文将国内外区域生态系统价值评估模型相结合,运用修正的生态服务价值评估模型,对北京市生态涵养区2016年的生态服务价值进行了估算,并分析了2009-2016年生态服务价值的变动及其影响因素,从科学评估生态服务价值、完善生态补偿标准方法的制定、健全生态保护补偿制度、将绿色GDP纳入生态涵养区绩效考核指标评价体系几个方面探讨了完善生态补偿机制的政策措施。一方面更加直观地揭示了生态涵养区生态服务的重要经济价值,另一方面为建立更加科学的生态补偿机制提供了可参考的依据。     

甘肃白龙江流域水源涵养服务时空格局及其影响因素

白龙江流域是长江上游的主要生态屏障和水源涵养区,对维系流域生态和可持续发展至关重要。以甘肃白龙江流域为例,基于参数本地化的InVEST模型对1990—2016年水源涵养时空变化及其影响因素进行分析。结果表明:流域多年平均水源涵养深度为47.50 mm,呈现先减少后回升的趋势。空间上,其高值区主要集中于迭部、文县和舟曲的中高山阴陡坡林区（平均涵养深度在该三县2500~3500 m海拔段、阴坡和半阴坡、25°以上坡段和林地高于流域的平均涵养深度）;低值区主要位于宕昌和武都的中低山阳缓坡农牧区（平均涵养深度在该两县 2500 m以下海拔段、阳坡和半阳坡、25°以下坡段和耕、草地低于流域的平均涵养深度）。气候背景下,人类活动驱动的土地利用/覆被格局空间差异是影响水源涵养时空变化的重要因素,退耕还林对减缓气候变暖背景下水源涵养深度的下降具有重要意义。     

基于生态供受体理论的全国水土保持重要区识别

科学评估土壤保持功能是生态保护红线划定的基础.依据生态供受体理论,针对土壤保持服务对应的水土流失这一生态问题,从水土流失的供体（水土流失量）、受体（人口密度）、辐射传输（距离水体距离）三个方面构建模型,分析土壤保持功能的重要性.结果表明全国潜在侵蚀量577.34×10¹⁰t/a,潜在土壤侵蚀随着坡度和降水量的增加而增加.土壤保持功能极重要区面积98.98×10⁴km²,主要分布在西南地区的无量山和哀牢山,黄土高原东部,东南地区的浙闽丘陵,东部地区的鲁中山区、鲁东半岛,以及辽东半岛.西南地区山高、谷深、坡陡、流急、地形稳定性差等因素造成水土流失严重,维持该地区的水土保持功能极为重要;西北地区的黄土高原土质疏松且多暴雨导致水土流失比较严重,维持该地区土壤保持功能非常重要.对比常用的生态保护功能模型,供受体理论模型除考虑自然影响因素之外,突出了人类活动的因素,对评估生态保护功能与水土保持生态风险更客观.依据供受体理论构建的土壤保持模型适用于土壤保持功能和土壤潜在侵蚀风险的评估,可作为评估生态系统安全和划定生态保护红线的重要依据.     

飞机典型液压管路系统减振优化计算方法研究

目的研究管道走向和卡箍位置对管道应力的影响。方法以飞机典型液压管路系统为优化对象,对管路系统及支持结构进行动力学参数化建模,使用MATLAB和MSC.NASTRAN构筑基于遗传算法的自动减振优化计算平台,以管壁结构和飞机支持结构的动态应力响应最小为优化目标,对管路走向(包括拐折位置、曲率半径)、卡箍位置进行优化计算,从而建立一种飞机管路系统设计中的自动减振优化计算方法。结果使用建立的减振优化计算平台优化计算设计后,飞机典型液压管路系统最大动态应力值降低了50%。结论提供的优化方法能够有效地通过优化管道布置参数降低应力水平。     

基于改进FWA-NN的污水处理过程溶解氧浓度预测

为实现对污水处理过程溶解氧质量浓度的实时准确预测,提出了一种改进的混沌烟花混合优化算法并构建了基于改进算法的神经网络在线软测量模型.结合污水处理过程的数据特征,定义了一项新的样本相似度衡量指标用于提取更具代表性的建模数据.在改进算法中,为提高基本烟花算法初始成员的质量,定义了一种改进的两级正弦混沌映射并利用混沌运动的遍历性精选烟花算法的初始群成员;通过融合混沌算法改进了基本烟花算法的搜索机制,基于设定准则将寻优过程分为两阶段并采用两分群同时进行.测试结果表明改进算法的收敛速度和收敛精度有较大程度提高.将改进的软测量建模方法和样本数据提取方法用于污水处理过程溶解氧质量浓度软测量建模,应用结果表明该模型的均方根误差和平均泛化误差分别为0.0175和0.0118,具有较强的泛化性能.     

Transient modeling of trickling filters for biological ammonia removal

A dynamic model for nitrifying trickling filters is developed, based on material balances in the biofilm and the bulk liquid. The model predicts the profile of ammonia as a function of the operating parameters (volumetric flow rate and feed ammonia concentration) and the biofilm thickness as a function of filter depth and time. This revised version was published online in July 2006 with corrections to the Cover Date.     

基于ABMS的矿山监管Agent工作倦怠现象的仿真研究

基于Agent的仿真建模方法（Agent based modeling and simulation,ABMS）和资源保存理论(conservation of resource theory,COR),构建了多Agent仿真模型,通过确定监管Agent、决策支持Agent、职能配合Agent和矿工Agent及其属性,借助Netlogo仿真平台模拟决策支持力度、职能配合程度以及矿工行为选择对监管Agent工作倦怠的影响,可以输出情感耗竭、人格解体和个人成就3个维度下监管Agent的数量。研究表明:决策支持系数Sc对监管Agent工作倦怠现象影响最大、处理有效性系数Ec影响次之、职能配合系数Fc影响最小,多Agent仿真模型促进了矿山监管Agnet工作倦怠现象的量化分析研究,为矿山安全治理提供了有效的决策依据。     

基于API极限工况下修井机井架强度计算研究

为研究井架在复杂工况下的强度与安全问题,以现场使用的350型修井机井架为研究对象,采用数值模拟对井架进行参数化建模;按照极限作业工况下24种组合载荷对井架进行强度分析,得出操作工况、非预期工况和可预期工况下井架的最大变形和应力云图;提取计算井架构件UC值的相关数据,对井架进行强度、刚度和整体安全性校核。结果表明:井架在常规风力作用下,最大钩载作业工况为其主要受力工况,此时井架最大等效应力小于许用应力,可满足安全需求;在相关工况中,井架的最大等效应力集中出现在上下体连接处、二层台和底部大腿处,计算井架构件各工况下的UC值均小于许用最大UC值,表明井架结构综合强度足够,满足API标准使用要求。