抽油机液压刹车制动装置的研究与应用

抽油机刹车系统是作业及维护、保养、检修工作时,确保员工人身安全的重要安全制动装置。目前,刹车系统存在较大安全隐患。文章研究了抽油机刹车安全制动系统的分类及工作原理,分析了存在的安全隐患,提出了采用抽油机液压刹车制动保险销装置。该技术解决了抽油机传统刹车装置存在的问题,并获得了国家专利。应用效果表明:新设计提高了刹车系统安全制动性能。     

轿车前制动噪声降噪方案研究

本文针对轿车出现的前制动噪声问题进行了研究和改进,以及采取改进方案后是否会对制动性能造成影响进行了系统的阐述。     

太阳翼驱动机构的扰振力矩测试与分析

为了研究太阳翼驱动机构(solar array drive assembly,SADA)驱动太阳翼运行期间所产生的扰振力矩特性,设计了一套地面测试系统,包括应变式微振动测试平台、柔性负载以及模拟SADA在轨无重力工作环境的重力卸载装置。阐述了所设计测试系统的工作原理,并利用该测试系统进行了试验测试。测试结果表明:SADA驱动柔性负载运行期间所产生扰振力矩的扰振频率成分主要包含两部分,即:1)SADA驱动柔性负载耦合系统的低阶扭转固有频率;2)SADA电脉冲信号的输入频率及其高阶谐波。     

基于复数矢量分析的汽车起重机液压变幅机构优化设计

当前液压变幅机构设计方法采用手工绘图的方式来确定铰点位置,导致液压变幅机构运动性能较差,无法满足现代汽车起重机重要部件设计标准。为了解决上述问题,提出了基于复数矢量分析的汽车起重机液压变幅机构优化设计。首先依据汽车起重机液压变幅机构模型,对主臂、转台以及液压变幅三铰点进行优化。然后利用复数矢量分析原理,对液压变幅机构受力展开分析,通过调用不同矢量下的编制子程序,对机构位置、速度、加速度进行优化,保证其在质量、质心和转动惯量矩方面一致性,由此完成汽车起重机液压变幅机构优化设计。最后通过联合仿真及运动学实验分析可知,所提方法无论是角位置、角速度,还是角加速度均比传统方法更贴近联合仿真运动规律,能够有效保证液压变幅机构运动良好性能。     

多功能抑尘车用永磁同步电机控制器的开发

本系统选用32bit处理器TMS320F28035,设计开发了用于多功能抑尘车喷雾系统的电机控制器。电机控制器设计包含硬件和软件平台两个部分。其中硬件平台包括：故障检测模块、MOS驱动模块、电机相电流角度采样模块、主控模块。软件部分采用分层设计,其主要分为驱动层、应用层和算法层;其中应用层和算法层采用基于MBD开发模式,通过建立Simulink模型进行仿真,同时编写M语言脚本程序用于模型的C代码生成。该控制器和一台3.5kW内置式永磁同步电机进行匹配,并进行扭矩响应测试和全速域效率MAP测试,实验结果显示该控制器达到预期设计目标。     

汽车制动系统的匹配设计

通过对汽车制动系统的原理及结构性能的探讨,进一步掌握整车新产品开发设计中制动系统的匹配计算.     

汽车制动系统的匹配设计

通过对汽车制动系统的原理及结构性能的探讨,进一步掌握整车新产品开发设计中制动系统的匹配计算.     

基于虚拟源二叉树射线跟踪算法的改进

文章基于虚拟源二叉树射线跟踪算法,针对目前射线跟踪技术在遮挡测试和路径有效性检测过程中,由于部分遮挡等相交计算导致效率低的问题,使用新的判据代替求交运算,提高了算法效率。采用文章所提算法模型对某微小区的相关场景进行了仿真,并与基于GO(Geometrical Optics,几何光学原理)/UTD(Uniform Theory of Diffraction,一致性绕射理论)混合理论的三维仿真结果进行了比较,结果表明使用该判据可以提高二维射线跟踪算法的效率。在精度要求不高的情况下,文章所提出的二维射线跟踪算法在计算时间上具有较大的优势。     

乡镇生活污水溶解氧浓度模糊神经网络PID控制系统研究

在乡镇生活污水处理的好氧阶段,溶解氧浓度控制是非常重要的过程,具有滞后性和多干扰等特点,传统控制策略因控制精度较低和自适应能力差而难以满足要求。设计了基于模糊神经网络PID算法的溶解氧浓度控制方案,并在MATLAB中进行仿真。仿真结果表明,该控制方案具有响应速度快、超调量小和抗干扰能力强等优点。     

基于CAN通讯的新能源汽车驱动电机检测技术研究

基于CAN通讯的新能源汽车驱动电机检测技术，已成为当下工业研究的关键方向。本文探讨了CAN通讯在驱动电机中的特点，如高实时性、可靠性和扩展性等，深入分析了新能源汽车驱动电机的主要性能指标，包括效率、扭矩和响应时间等。通过现行的驱动电机国家标准，本文详细研究了基于CAN通讯驱动电机典型项目的检测技术和方法，介绍了CAN通讯的物理连接和通讯配置。最后，本文提出了新能源汽车驱动电机领域的未来发展趋势，强调了技术创新、行业应用前景及其面临的挑战和解决方案。本文为新能源汽车驱动电机的检测技术提供了一些见解和方向，有助于推动相关领域的技术进展和产业发展。     

AN APPLICATION RUNOFF MODEL STRATEGY FOR UNGAGED WATERSHEDS1

ABSTRACT: Mathematical models for predicting watershed surface flow responses are available, most of which are elaborate nonlinear numerical surface and channel flow models linked with infiltration models. Such models may be used to make predictions for ungaged areas, assuming an acceptable fitting of the model to the topography and roughness of the real system. For some application purposes, these models are impractical because of their complexity and expensive computer solutions. A procedure is developed that uses a complex model of an ungaged area to derive a simpler parametric nonlinear system model for repetitious simulation with input sequences. The predicted flow outputs are obtained with the simpler model at significant savings of money and time. The procedures for constructing a complex kinematic model of a 40 acre (161,880 m²) reference watershed and deriving the simpler system model are outlined. The results of predictions from both models are compared with a selected set of measured events, all having essentially the same initial conditions. Peak discharges ranged from 3 to 118 ft³/sec (0.085 to 3.34 m³/sec), which includes the largest event of record. The inherent limitations of lumped systems models are demonstrated, including the bias caused by their inability to model infiltration losses after rainfall ceases. Computer costs and times for the models were compared. The derived simple model has a cost advantage when repeated use of a model is required. Such an applications hydrologic model has an engineering tradeoff of reduced accuracy, and lumping bias, but is more economical for certain design purposes.     

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.     

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.     

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.     

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.     

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.     

Biodiversity and biotechnology

The maintenance of biodiversity is urged from many quarters and on grounds ranging from aesthetic considerations to its usefulness, particularly for biotechnology. But regardless of the grounds for preserving biodiversity, writers are generally in agreement that it should be preserved. But, in examining the various references biodiversity, such as species diversity, genetic diversity, and habitat diversity, it is apparent that we cannot aim to preserve biodiversityas such, since there are a number of conflicts in any such undertaking. In preserving one aspect of biodiversity, we damage another aspect. Five arguments which attempt to ground our moral concern for biodiversity are reviewed and critiqued, not only for their consistency but also for their power to move us to action. The final section of the paper shows how conflicts in the values of personal and environmental health can impair ethical action and especially policy formation.An earlier version of this paper was read at the conference on Agriculture, Food, and Human Values: Tradition and Change, Orlando, Florida, October 7–9, 1987.