基于PLC的冷却系统自整定模糊控制研究

在机载产品地面试验过程中需要为其提供相应的冷却环境,可在受试产品发生改变时,制冷设备在传统控制算法下往往无法维持较为理想的控制结果,需要重新人工整定控制参数。为解决此问题,研究了基于PLC的冷却系统自整定模糊控制方法,该方法可在PLC内编写系统参数累加辨识程序,从而计算得到系统的模型参数以及初始控制参数,再通过模糊控制器对该参数进行实时整定。试验表明该控制方法可以对系统参数进行自动辨识,辨识结果能够反映模拟负载的功率变化趋势,控制结果无明显超调及稳态误差。将该方法应用于液冷机组,可以在被冷却对象发生较大变化时重新辨识控制器参数,免去人工进行参数调试的工序,加强了设备的通用性,获得良好的控制结果。     

关于环境试验设备期间核查方法的探讨

环境试验设备期间核查是内部质量控制的重要方式之一,可有效掌握在设备在2次校准/检定周期内的置信度,本文针对不同的环境试验设备,运用不同的方法,建立环境设备核查系统,明确依据、方法及判据等。分析各种方法的利弊,为各实验室的设备核查提供参考或依据。     

接地引下线导通电阻测试仪校准方法

本文介绍了接地引下线导通电阻测试仪的用途、原理及其技术指标,参考DL/T845.6-2022《电阻测量装置通用技术条件第6部分接地引下线导通电阻测试仪》中对接地引下线导通电阻测试仪的性能要求,提出了接地引下线导通电阻测试仪的计量性能要求、测量标准、校准项目和校准方法,并对电阻参数的测量不确定度进行了评定,可做为接地引下线导通电阻测试仪校准的方法参考和技术依据。     

新闻资讯

碰撞试验用假人多轴力传感器校准系统能力建设为弥补我国目前汽车碰撞试验用假人多轴力传感器校准能力上的不足,上海机动车检测中心计量所引进两台0.1级(0～50)kN和(0～500)kN标准力源加载机,该项目已获得国家CNAS认可,填补了国内的空白。升级后的校准系统,采用带新型数字平衡控制技术的工业级CPU,可实现在任意点保持、超低速平稳运行,     

冲击响应谱时域合成算法研究

为利用电动振动台进行模拟冲击环境试验给出了一种时域冲击波形合成方法.依据冲击响应谱时域合成的一般原则,选择合成小波中的正弦窗波作为基本波形,给出了确定各基本波形的波形参数的方法.计算结果表明本文所提算法是有效的,所合成的时域冲击波形能够满足参考冲击响应谱的精度要求,为开发冲击谱试验的控制软件研究者提供了一种思路.     

油气管道量化风险控制技术研究

针对风险控制无法有效量化问题,应用因果分析和保护层分析方法各自的特点,建立了基于因果分析-保护层方法的风险控制技术。通过应用因果分析技术对特定风险场景进行系统原因分析,查找出风险控制的关键致因,利用保护层方法辨识出关键致因的独立保护层,依据系统可靠性理论计算特定场景中独立保护层的失效频率,结合企业的风险标准和风险可接受水平,确定是否需要增加新的独立保护层或提高已有独立保护层的可靠性来达到企业理想的风险水平。以中石油西部管道公司典型管道系统为例,验证了该技术的可行性。     

车载巡测谱仪实源实装校准测试方法研究

为解决车载Na I(Tl)大晶体γ巡测谱仪系统探测效率的刻度问题。利用"计量标准器具",使用不同γ射线能量、不同活度的γ放射源;以固定安装车载大晶体的巡测车整体作为校准测试对象,在同一环境下,用"计量标准器具"环境辐射监测仪和车载大晶体γ辐射剂量率仪实源实装进行测试。以计量标准器具γ辐射剂量率仪测量数据为准,获得两种设备数据的相对标准偏差和校准因子,得到的校准因子可用于被测对象开展辐射环境监测和应急监测。该测试方法可行、可靠。     

质量块对动态力传感器校准的影响特性

校准质量块是动态力传感器校准中的关键部件,其加速度分布的均匀性直接影响动态力传感器的校准准确度,采用有限元分析方法结合实验对比方法,研究了质量块形状尺寸、密度、弹性模量及比模量等参数对质量块加速度分布均匀性的影响,给出了各因素的影响特性。实验结果表明,使用重质合金质量块可提高动态力传感器的校准准确度。     

激光位移传感器动态幅值校准研究

针对目前激光位移传感器校准所存在的精度低、校准局限性大等诸多问题,本文提出了一种激光位移传感器动态幅值校准的方法。本校准方法首先采用电磁振动台激励标准结构件进行量级放大,以产生特定高频的大位移振幅;然后基于多普勒效应的激光测振仪测得的位移作为标准量,对激光位移传感器的动态幅值进行校准;最后通过一系列不同共振频率的标准结构件对不同频率下的位移振幅校准进行试验研究。研究结果表明：与现有技术相比较,本文提出的激光位移传感器动态幅值校准方法可对激光位移传感器不同频率下的动态幅值进行精确校准,对工程实际应用具有重要价值。     

一种专用测试系统校准装置的设计与实现

针对某型专用测试系统缺乏相应校准装置的问题,设计了基于PXI和虚拟仪器的专用测试系统校准装置,根据不同任务需求,本装置可灵活搭配多种模块化子系统,组成具有重定义功能的特定系统,实现检测设备的快速量值传递。本装置的应用,能够解决目前军用计量保障所存在的测试速度慢、受检率低、成本高等问题,具有重要的实用价值和研究意义。     

Conversion of temperate forests into heaths: Role of ecosystem disturbance and ericaceous plants

Fire and logging in nutrient-poor temperate forests with certain ericaceous understory plants may convert the forests into heaths. The process of disturbance-induced heath formation is documented by using examples ofCalluna in western Europe,Kalmia in Newfoundland, andGaultheria (salal) in coastal British Columbia. In a cool, temperate climate, rapid vegetative growth ofCalluna, Kalmia, and salal following disturbance results in increasing organic accumulation (paludification), nutrient sequestration, soil acidification, and allelochemicals. These are thought to be the main reasons to conifer regeneration failure in disturbed habitats. If continuation in forest is a land-use objective, then temperate forests with an ericaceous understory should not be logged unless effective silvicultural methods are devised to control the ericaceous plants and restore forest regeneration. Preharvest vegetation control may be considered as an option. Failure to control the understory plants may lead to a long-term vegetation shift, from forest to heathland, particularly in nutrient-poor sites. Successful methods of controllingKalmia andGaultheria, however, have yet to be developed. While theKalmia- andGaultheria- dominated heathlands are undesirable in Canada and the Pacific Northwest, a wide range ofCalluna heathlands of western Europe are being conserved as natural and seminatural vegetation.     

Using Paleo Reconstructions to Improve Streamflow Forecast Lead Time in the Western United States

In water stressed regions, water managers are exploring new horizons that would help in long‐range streamflow forecasts. Oceanic‐atmospheric oscillations have been shown to influence streamflow variability. In this study, long‐lead time streamflow forecasts are made using a multiclass kernel‐based data‐driven support vector machine (SVM) model. The extended streamflow records based on tree ring reconstructions were used to provide a longer time series data. Reconstructed data were used from 1658 to 1952 and the instrumental record was used from 1953 to 2007. Reconstructions for oceanic‐atmospheric oscillations included the El Niño‐Southern Oscillation, Pacific Decadal Oscillation, Atlantic Multidecadal Oscillation, and North Atlantic Oscillation. Streamflow forecasts using all four oscillations were made with one‐year to five‐year lead times for 21 gages in the western United States. This is the first study that uses both instrumental and reconstructed data of oscillations in SVM model to improve streamflow forecast lead time. SVM model was able to provide “satisfactory” to “very good” forecasts with one‐ to five‐year lead time for the selected gages. The use of all the oscillation indices helped in achieving better predictability compared to using individual oscillations. The SVM modeling results are better when compared with multiple linear regression model forecasts. The findings are statistical in nature and are expected to be useful for long‐term water resources planning and management.     

Urban ecological systems: scientific foundations and a decade of progress

Urban ecological studies, including focus on cities, suburbs, and exurbs, while having deep roots in the early to mid 20th century, have burgeoned in the last several decades. We use the state factor approach to highlight the role of important aspects of climate, substrate, organisms, relief, and time in differentiating urban from non-urban areas, and for determining heterogeneity within spatially extensive metropolitan areas. In addition to reviewing key findings relevant to each state factor, we note the emergence of tentative "urban syndromes" concerning soils, streams, wildlife and plants, and homogenization of certain ecosystem functions, such as soil organic carbon dynamics. We note the utility of the ecosystem approach, the human ecosystem framework, and watersheds as integrative tools to tie information about multiple state factors together. The organismal component of urban complexes includes the social organization of the human population, and we review key modes by which human populations within urban areas are differentiated, and how such differentiation affects environmentally relevant actions. Emerging syntheses in land change science and ecological urban design are also summarized. The multifaceted frameworks and the growing urban knowledge base do however identify some pressing research needs.     

Neighbourhood characteristics and urban gardens in the Toledo metropolitan area: staffing and voluntarism,food production,infrastructure, and sustainability practices

Urban gardens are important sources of sustenance for communities with limited access to food. Hence, this study focuses on food production in gardens in the Toledo metropolitan area in Northwest Ohio. We administered surveys to 150 garden managers from November 2014 to February 2015 in our attempt to better understand how neighbourhood racial composition and poverty levels are related to staffing and voluntarism, food production and distribution, the development of infrastructure, and the adoption of sustainability practices in urban gardens. The results from 30 gardens are presented in this paper. We used Geographic Information Systems to map the gardens and overlay the map with 2010 census data so that we could conduct demographic analyses of the neighbourhoods in which the gardens were located. Though the gardens were small – two acres or less – up to 46 varieties of food were grown in a single garden. Gardens also operated on small budgets. Food from the gardens was gifted or shared with friends, family, and neighbourhood residents. Gardens in predominantly minority neighbourhoods tended to have fewer institutional partners, less garden infrastructure, and had adopted fewer sustainable practices than gardens in predominantly White neighbourhoods. Nonetheless, residents of predominantly minority and high-poverty neighbourhoods participated in garden activities and influenced garden operations. Volunteering and staffing were racialised and gendered.     

Predicting deer-vehicle collisions in an urban area

Collisions with deer and other large animals are increasing, and the resulting economic costs and risks to public safety have made mitigation measures a priority for both city and wildlife managers. We created landscape models to describe and predict deer-vehicle collision (DVCs) within the City of Edmonton, Alberta. Models based on roadside characteristics revealed that DVCs occurred frequently where roadside vegetation was both denser and more diverse, and that DVCs were more likely to occur when the groomed width of roadside right-of-ways was smaller. No DVCs occurred where the width of the vegetation-free or manicured roadside buffer was greater than 40 m. Landscape-based models showed that DVCs were more likely in more heterogeneous landscapes where road densities were lower and speed limits were higher, and where non-forested vegetation such as farmland was in closer proximity to larger tracts of forest. These models can help wildlife and transportation managers to identify locations of high collision frequency for mitigation. Modifying certain landscape and roadside habitats can be an effective way to reduce deer-vehicle collisions.     

BIOLOGICAL INDICATORS AND BIOLOGICAL EFFECTS OF ESTUARINE/COASTAL POLLUTION1

ABSTRACT: Sustained interest in and concern about the health status of the aquatic environment has resulted in extensive research focused on (1) effects of pollution on survival, growth, and reproduction of resource species at all life stages; (2) diseases of fish and shellfish, as they may be related to pollution and as they may serve as indicators of environmental stress; and (3) contaminant body burdens in fish and shellfish - their effects on the aquatic animals and their potential effects on humans. Effects, lethal and sublethal, of pollutants on life history stages of fish and shellfish have been documented, as have impacts on local stocks in badly degraded habitats, but as yet there has been no adequate quantitative demonstration of effects on entire aquatic species - probably because of the difficulty in sorting out relative effects of the many environmental factors that influence abundance. Sublethal effects, especially those that result in disease, have been examined intensively, and some diseases and disease syndromes have been associated statistically with pollution. Other pollution indicators (biochemical, physiological, genetic, behavioral, and ecological) have also received some attention, as have body burdens of contaminants in aquatic species. Research, especially that conducted during the past decade, has done much to clarify the many pathways and toxic effects of contaminants on aquatic animals, and has also helped to identify mechanisms for survival of fish and shellfish in the presence of environmental changes caused by human activities.     

Journalists' views of advertiser pressures on agricultural news

All major journalism ethical codes explicitly state that journalists should protect editorial copy from undue influence by outside sources. However, much of the previous research on agricultural information has concentrated on what information various media communicate (gatekeeping studies) or communication's role in increasing innovation adoption (diffusion studies). Few studies have concentrated specifically on organizational and structural constraints that might adversely affect agricultural journalists' ethical standards; those that have, focus largely on farm magazines. A study of newspaper reporters who cover agricultural news found that the most pressing ethical concern is the effect of advertiser (agri-business) pressure on editorial copy, and that their concerns in general parallel those of farm magazine writers and editors. The majority reported being in situations in which they might be exposed to advertiser pressure, including pressures to change or withhold editorial copy. Large minorities suggested that advertising pressures affect the overall environment in which agricultural journalists work, and more than one in ten said they allow advertiser pressures to influence editorial decisions. The newspaper reporters who cover agricultural beats showed slightly more resistance to advertiser pressure than did farm magazine editors in a parallel study.     

Definition Procedures Have Little Effect on Performance of Environmental Classifications of Streams and Rivers

Mapped environmental classifications are defined using various procedures, but there has been little evaluation of the differences in their ability to discriminate variation in independent ecological characteristics. We tested the performance of environmental classifications of the streams and rivers of France that had been defined from the same environmental data using geographic regionalization and numerical classification of individual river valley segments. Test data comprised invertebrate assemblages, water chemistry, and hydrological indexes obtained from sites throughout France. Classification performance was measured by analysis of similarity (ANOSIM). Geometric regions defined by a regular grid and without regard to environmental variables and a posteriori classifications based on clustering the test datasets defined lower and upper bounds of performance for a given number of classes. Differences in classification performances were generally small. The ANOSIM statistics for the a posteriori classifications were around twice that of all environmental classifications, including geometrically defined regions. The hydro-ecoregions performed slightly better for the invertebrate data and the network classification performed slightly better for the chemistry and hydrological data. Our results indicate that environmental classifications that are defined using different procedures can be comparable in terms of their ability to discriminate variation of ecological characteristics and that alleged differences in performance arising from different classification procedures can be small relative to unexplained variation. We conclude that definition procedures might have little effect on the performance of large-scale environmental classifications and decisions over which procedures to use should be based primarily on pragmatic considerations.     

MANGANESE CYCLE IN IMPOUNDMENT WATER

Manganese entering impounded water will undergo a cyclic transformation. Oxidation precipitates manganese from top waters. At the bottom of the lake, biological activity will render manganese soluble by both intracellular as well as extracellular activity. The study was made to demonstrate that biological reduction and transformation, organometallic complexation, together with the presence of carbon dioxide and the lowering of pH all have some effect on the solubility of manganese. Dissolved manganese may be brought back to top waters during the lake overturn and therefore deteriorates the water quality.     

Provincial development plans in Zimbabwe: an analysis of their content,structure and methodology

Zimbabwean provincial plans were instituted to help in the achievement of the national goal of the creation of an egalitarian, socialist and integrated society. The national goal itself was adopted as an antithesis to the dualist society characterised by spatial, economic, social, politican and technological inequalities that Zimbabwe inherited from colonialism. This meant that provincial plans had to play both a functional (or growth allocating/distribution) and a territorial (or redistribution) role.

This paper reviews their role in achieving the national goal by examining their functions, content, structure and methodology. The paper concludes that because of their nature, provincial plans are not suitable tools for the achievement of the national goal.