随机振动加速度响应谱及与冲击等效性分析

目的 获得随机振动的加速度响应谱,提升随机振动与冲击的等效性分析精度。方法 首先,基于维纳-辛钦定理,推导单自由度系统在随机振动基础激励作用下加速度响应均方值的通用表达式;其次,分别推导单自由度系统在理想白噪声和限带非均匀谱随机振动基础激励作用下的加速度响应均方值;再次,基于3σ准则,推导限带非均匀谱随机振动的3σ加速度响应谱;最后,基于加速度响应等效,通过将装备随机振动条件的3σ加速度响应谱与冲击条件的冲击响应谱进行等效性分析,对GJB 150.18A—2009中的冲击试验剪裁条件进行精细优化。结果 精细优化后,可有效改善冲击试验剪裁条件的工程实施精度。结论 获得了限带非均匀谱随机振动的3σ加速度响应谱,并基于此对GJB 150.18A—2009中的冲击试验剪裁条件进行了精细优化,对于装备合理剪裁冲击试验具有借鉴意义。     

重复碰撞载荷下加筋板结构的动态响应研究

目的 探究船体加筋板结构在受到重复碰撞载荷作用下塑性变形的累计趋势,分析加筋板主要参数对损伤演化过程的影响,揭示高速、重复冲击下船体加筋结构的变化机理。方法 以一纵三肋加筋板为研究对象,建立基于能量法的刚塑性加筋板动态变形计算方法,以及基于Johnson-Cook本构关系的数值模拟方法,开展不同板架厚度、冲击能量以及冲击尺寸等参数对加筋板变形演化影响的研究。结果 对比分析了理论模型和数值方法,获得了不同参数下的加筋板的结构损伤演化规律。结论 理论解和数值解较为吻合。冲击能量增加后,加筋板的塑性变形量、塑性变形累积速度也随之增加。载荷集中程度越大,对于碰撞边界的破坏效应越大。     

Comprehensive temperature monitoring in an in-vessel forced-aeration static-bed composting process

Comprehensive temperature monitoring was done in an in-vessel forced-aeration static-bed composting process using sewage sludge. The three layers that divided the compost pile horizontally showed different temperature distributions. The temperature of the top layer appeared not to be influenced by the ambient temperature. The temperature of the center area of the top layer was taken to be the representative temperature for evaluating composting start-up performance. The temperature of the bottom layer was strongly influenced by the ambient temperature, and the temperature of the center area of the bottom layer was taken to be the representative temperature for pathogen control as it was the minimum temperature in the reactor. Composting start-up performance was influenced by several factors when the ambient temperature was either below or above 20°C. When the ambient temperature was below 20°C, the time taken to reach 65°C (T ₆₅) was influenced by the temperature of inflowing air, but when the temperature was higher than 20°C, it was influenced by the ratio of sewage sludge to seed compost (F/S). T ₆₅ was least when F/S was 1–2. Received: January 9, 2001 / Accepted: October 10, 2001     

人工湿地污水处理系统脱氮研究进展

系统地介绍了人工湿地去除污水中氮污染物的机理及国内外研究进展，详细阐述了影响人工湿地污水处理系统脱氮的内、外界因素，对于人工湿地污水处理工艺的推广应用提供科学依据。     

集体林地使用权市场制度的建立与完善

集体林地使用权市场将是我国南方集体林区土地市场发展的主要内容,它的健康发展需要一套制度来保障.在介绍集体林地使用权市场类型的基础上,分析了我国集体林地使用权市场制度的建设状况,并提出了今后急待建立和完善的林地使用权市场制度的主要内容.     

METHODOLOGIES FOR CALIBRATION AND PREDICTIVE ANALYSIS OF A WATERSHED MODEL1

ABSTRACT: The use of a fitted parameter watershed model to address water quantity and quality management issues requires that it be calibrated under a wide range of hydrologic conditions. However, rarely does model calibration result in a unique parameter set. Parameter nonuniqueness can lead to predictive nonuniqueness. The extent of model predictive uncertainty should be investigated if management decisions are to be based on model projections. Using models built for four neighboring watersheds in the Neuse River Basin of North Carolina, the application of the automated parameter optimization software PEST in conjunction with the Hydrologic Simulation Program Fortran (HSPF) is demonstrated. Parameter nonuniqueness is illustrated, and a method is presented for calculating many different sets of parameters, all of which acceptably calibrate a watershed model. A regularization methodology is discussed in which models for similar watersheds can be calibrated simultaneously. Using this method, parameter differences between watershed models can be minimized while maintaining fit between model outputs and field observations. In recognition of the fact that parameter nonuniqueness and predictive uncertainty are inherent to the modeling process, PEST's nonlinear predictive analysis functionality is then used to explore the extent of model predictive uncertainty.     

THE VULNERABILITY OF WETLANDS TO CLIMATE CHANGE: A HYDROLOGIC LANDSCAPE PERSPECTIVE1

ABSTRACT: The vulnerability of wetlands to changes in climate depends on their position within hydrologic landscapes. Hydrologic landscapes are defined by the flow characteristics of ground water and surface water and by the interaction of atmospheric water, surface water, and ground water for any given locality or region. Six general hydrologic landscapes are defined; mountainous, plateau and high plain, broad basins of interior drainage, riverine, flat coastal, and hummocky glacial and dune. Assessment of these landscapes indicate that the vulnerability of all wetlands to climate change fall between two extremes: those dependent primarily on precipitation for their water supply are highly vulnerable, and those dependent primarily on discharge from regional ground water flow systems are the least vulnerable, because of the great buffering capacity of large ground water flow systems to climate change.     

湿地植物在城镇污水处理系统中的作用特性研究

将不同类型湿地植物如凤眼莲、荇菜、稗草、黑藻、皇竹草、美人蕉等,引入城镇污水处理系统,考察其对污染物的去除效果和在湿地组合系统中的作用特性。盆栽实验发现,虽然植物对污水N、P营养元素的直接去除率分别只有14.0%～59.4%和8.6%～55.2%,但植物通过过滤、截留及加强有机物降解转化的作用,对水体中污染物的去除具有协同效应,使水体N、P的总去除率分别达65.4%～83.8%和43.5%～69.5%。将植物引入组合处理系统,中试实验结果表明,水体TN、TP和COD月平均去除率分别高达80.4%、74.3%和81.3%。与常规生化处理系统相比,处理效果大为增强,生化反应的能耗相对减少,出水水质较稳定,使湿地组合系统成为一种去N除P,防止水体富营养化的有效处理方法。     

城市河流硬质护岸生态修复研究进展

针对硬质护岸给城市河流生态环境造成的影响,初步探讨了生态型河流护岸的概念与内涵;分类介绍了硬质护岸生态修复一些代表性的技术和方法,分析了这些技术的适用范围;并提出了目前关于硬质护岸生态修复技术研究的热点问题和发展方向。     

冬季浮萍放养体系对养猪场废水的处理效果

以经筛选得到的本地优势浮萍为供试材料,以经稀释的养猪场废水为供试污水,考察了模拟冬季气象条件下浮萍单种体系和浮萍-水花生、浮萍-水葫芦混养体系对污水氮、磷的净化效果及植物生长情况,并与年平均气象条件下的相关结果作对比分析。结果表明,相对于年平均气象条件下的试验结果,冬季气候条件下三种体系对供试废水COD、NH4+-N和TP的去除速率和总去除率均有所下降,最大降幅均出现在浮萍单种体系,而混养体系表现较为稳定,尤其是浮萍-水花生混养体系,其对上述污染物的总去除率均维持在80%左右。浮萍混养体系对废水污染物的去除受冬季气候影响较小,利用其处理废水可克服冬季气候对浮萍单种体系污水处理系统的不良影响,通过合理的工艺组合,可实现浮萍污水处理系统全年气候下的连续运行和对污水氮、磷的高效去除。