Study of mechanical aspects of leak tightness in a pressure relief valve using advanced FE-analysis

This paper presents a numerical study involving the deformation of contact faces in the metal-to-metal seal in a typical pressure relief valve. The valve geometry is simplified to an axisymmetric problem, which comprises a simple geometry consisting of only 3 components. A cylindrical nozzle, which has a valve seat on top, contacts with a disk, which is preloaded by a compressed linear spring. All the components are made of AISI type 316N(L) steel defined using the multilinear kinematic hardening model based on monotonic and cyclic tests at 20° C. In-service observations show that there is a limited fluid leakage through the valve seat at operational pressures about 90% of the set pressure, which is caused by the fluid penetrating into surface asperities at the microscale. Nonlinear FEA in ANSYS using the fluid pressure penetration (FPP) technique revealed that there is a limited amount of fluid penetrating into gap, which is caused by the plastic deformation of the valve seat at the macroscale. Prediction of the fluid pressure distribution over the valve seat just before the valve lift is addressed in this study considering the FPP interaction on multiscale. This is the principal scope, since it allows adjustment of the valve spring force in order to improve the leak tightness.     

农村沼气推广现状及发展对策

沼气能源是一种生物质能，属于可再生能源，在自然界中可以不断再生、永续利用的资源。本文通过查阅文献、问卷调查及访谈相结合的方法收集资料，客观地描述了疏勒县农村沼气推广现状，并从农民自身情况、政府推进影响、环境保护三方面来考察。结果表明：沼气推广进展缓慢主要原因是日常维护难。     

Bicriteria decision model for farm management of the Colorado potato beetle: development and validation

This paper describes the development and testing of a deterministic simulation model for pest and resistance management of the Colorado potato beetle (CPB). Historically, CPB have developed resistance to new pesticides quickly. A potato farmer's pesticide application decisions trade off current crop yields and resistance development. The simulation incorporates major aspects of beetle life processes, pesticide resistance, and potato growth in order to predict the consequences of a pesticide application strategy over a ten-year planning horizon.     

产业结构变化及其生态环境效应——以新疆喀什地区为例

摘要：产业结构是人类作用于生态环境系统的主要环节,产业结构是否合理很大程度上决定了经济效益、资源利用效率和对环境的胁迫。以喀什地区为例,通过计算产业结构的生态环境影响指数,定量评价了20年来喀什地区产业结构变化的生态环境效应。研究结果表明：研究时段内全区的第一产业产值比重持续下降,区域工业化、城市化进程缓慢。20余年来,产业结构变化对生态环境的影响属于中等,且有所降低,产业结构的调整限制了人类活动对自然生态环境的干扰。研究结果对喀什地区经济的发展具有一定的指导意义。     

新疆喀什地区农业水安全初步研究

虚拟水是指生产商品和服务过程中所使用的所有水资源水量。本文在虚拟水理论的基础上,通过查阅2003—2009年《新疆统计年鉴》中的相关数据,计算并分析了喀什地区主要农产品的虚拟水含量。结果表明：喀什地区农业生产用水远远大于区域可提供的水资源总量,农业用水和农业生产处于不安全状态。     

利用水泥回转窑协同处置废弃农药及包装物的监测分析

在不同工况条件下,对某水泥厂协同处置废弃农药及包装物的污染物排放进行监测。结果表明:该处置过程的污染物排放符合相关排放标准要求。     

唐古拉冬克玛底冰川流域pH值和电导率分析

2005-05-11～2005-09-27,在青藏高原唐古拉段冬克玛底冰川流域对融水径流和草地径流分别进行采样.对样品的pH值和电导率进行了分析.结果表明,研究区环境受人类活动影响很小.借助电导率水量来源模型对冬克玛底河流量进行划分,暖季径流主要以冰川冰融水补给为主,占总流量的62%以上,其次是积雪融水和降雨补给,其中,第1、3阶段的积雪融水补给分别占31%和37%,第2阶段的降雨补给占17%左右;土壤冻结水消融对径流贡献很小,占2%以下.     

喀什市2022年环境空气质量特征分析

为摸清喀什市环境空气质量变化特征,为管理部门进行污染精准管控提供科学参考,基于喀什市2022年环境空气自动监测数据开展分析研究。结果表明:2022年喀什市二氧化硫、二氧化氮、臭氧、一氧化碳年均质量浓度均优于国家二级标准。超标污染物主要为可吸入颗粒物和细颗粒物。喀什市细颗粒物、可吸入颗粒物浓度呈春、秋、冬季高,夏季低的季节特征。