基于地形网格剖分的射线追踪法的时间优化

地形的网格剖分程度直接影响着电磁仿真的计算精度及其计算量。以同一块地理模型为例,分析不同精度网格对电磁环境仿真精度和计算量的影响。正向算法中,辐射源的剖分精细情况也直接影响着电磁环境仿真精度和计算时间。结合电磁环境中辐射源和接收机的分布特点,提出了在保证仿真精度前提下减少仿真时间的网格剖分方法。     

广播电塔电磁环境仿真研究

介绍了一种广播电视发射塔电磁环境预测的方法,利用了广播电视发射塔天线的远场方向图,结合周边的实际地理环境状况,通过CEMS（复杂电磁环境方针系统）软件实现快速仿真。文中的广播电塔的天线使用了最常用的单极板天线,在CEMS软件中,用发射机代替广播电视电塔,在天线的辐射范围内按照一定的规律放置接收机并进行仿真分析。通过仿真分析,对以后广播电视电塔的选址和改进提供一定的依据。     

基于Daubechies4小波变换地形滤波的复杂电磁环境仿真加速方法

本文提出了一种基于射线追踪算法的复杂电磁环境仿真计算的加速方法,同时结合并行系统来共同加速仿真计算。对地形DEM数据进行Daubechies4二维离散小波变换,地形滤波在一定范围内有效降低了其复杂度。继而搭建并行计算系统,将滤波后的地形应用到多个辐射源的仿真建模并行计算,提高复杂电磁环境仿真计算速度。经过对该方法进行多次实验,验证了该方法可以在一定精度范围内提高复杂电磁环境计算速度。     

基于射线追踪法的态势计算的优化

区域态势仿真通常会采用在既定区域内放置大量的点状接收机来接收电磁信号,分析计算信号功率与场强,从而达到模拟态势区域的目的。这就要求每个点状接收机都需要进行信号的处理与计算,计算上的重复性很大。采用n米采点投影的方法,假定接收区域投影为长方形,将其划分成n*n米2的小正方形。发出射线后,从射线进入接收区域的位置开始,每隔n米对射线信号进行取样。该方法可以大幅度提高计算效率,且在仿真应用中得到了较好的效果。     

复杂电磁环境仿真软件中的大地形文件传输技术研究

为了提高仿真速度,仿真软件一般采用多台计算机进行协同工作,首先搭建一套电波传播仿真并行系统,该系统能够导入地理信息,并在导入的地图上进行电磁辐射源建模及电磁环境仿真工作。但是,对于一些很大的地形,其海量的三维地形数据的传输时间过长,这加大了总的仿真等待时间。所以为了综合利用多台计算机的资源优势,提出使用BitTorrent方式,使得服务端与客户端的计算机均可以为地形文件的传输做贡献,极大减少了地形文件传输时间,可以从侧面提高仿真工作的效率。     

小波处理下的电磁环境仿真加速方法效果对比

为了减少复杂电磁环境的仿真时间,在一定的精度允许的范围内,可对地形做适当的处理,以减少射线条数,换取仿真时间的缩短。本文通过小波分解,再进行中值滤波处理,以完成地形的平滑去噪处理。且为了选取最优小波基,本文采用不同小波基,对地形高程值进行小波变换和滤波处理,比较处理后的地形仿真效果,进而找出对地形做小波变换的最优小波基。     

基于地形分区的射线跟踪法加速方法的研究

通过分析影响射线跟踪法计算效率的因素,提出一种基于多线程的用于开放地理环境中的射线跟踪加速方法,以提高射线跟踪法在计算机仿真中的计算效率。该方法应用于特定复杂战场电磁环境,根据电磁波射线传播特性,采用对地形分区的途径减少射线与规则三角面地形面的求交次数,同时使用多线程追踪单个辐射源的射线路径。经过对方法进行仿真计算,验证该方法的有效性。     

基于存储示波器的PS/2键盘电磁截获研究

计算机键盘有用信号电磁截获的传统方法是基于宽带接收机完成的,这种方法较复杂且需要较多的设备和空间。为使键盘截获技术向小型化和实用化过渡,提出了使用基于软件无线电的解码技术及基于存储示波器全频谱远场截获。首先,基于频谱对比的方法对有用信号的频段进行初判,然后对截获的全频域信号中包含有敏感信息的频段基于软件无线电的方法进行带通滤波和解调。最后,使用一种能够精确判别按键信息的解码方法,通过预先设计的程序来实现信息的截获。实验结果表明计算机键盘有用信号电磁截获实现实用化和小型化是有一定可行性的,并且能够得到比较精确的结果。     

新一代多普勒气象雷达电磁环境影响评价方法探讨

新一代多普勒气象雷达对电磁环境的影响主要取决于发射机、天线的运行参数和扫描方式。本文结合实际工程项目,对雷达运行的电磁环境影响评价内容和方法进行了研究,明确了电磁环境影响控制范围及建筑限高,提出了电磁辐射防护措施。     

复杂电磁环境仿真软件中的电磁态势显示计算技术研究

在复杂电磁环境仿真软件中，电磁态势显示是一个重要的功能，而传统的单PC机仿真软件很难满足电磁态势显示大数据量和高计算精度的要求。从分布式计算以及接收区域模型化两个方面对传统的射线追踪算法加以改进，使其更加适合电磁态势仿真场景，以达到提升仿真效率的目的。     

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.     

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.     

Surface applied water treatment residuals affect bioavailable phosphorus losses in Florida sands

Water treatment residuals (WTR) can reduce runoff P loss and surface co-application of P-sources and WTR is a practical way of land applying the residuals. In a rainfall simulation study, we evaluated the effects of surface co-applied P-sources and an Al-WTR on runoff and leacheate bioavailable P (BAP) losses from a Florida sand. Four P-sources, namely poultry manure, Boca Raton biosolids (high water-soluble P), Pompano biosolids (moderate water-soluble P), and triple super phosphate (TSP) were surface applied at 56 and 224kgPha(-1) (by weight) to represent low and high soil P loads typical of P- and N-based amendments rates. The treatments further received surface applied WTR at 0 or 10gWTRkg(-1) soil. BAP loss masses were greater in leachate (16.4-536mg) than in runoff (0.91-46mg), but were reduced in runoff and leachate by surface applied WTR. Masses of total BAP lost in the presence of surface applied WTR were less than approximately 75% of BAP losses in the absence of WTR. Total BAP losses from each of the organic sources applied at N-based rates were not greater than P loss from TSP applied at a P-based rate. The BAP loss at the N-based rate of moderate water-soluble P-source (Pompano biosolids) was not greater than BAP losses at the P-based rates of other organic sources tested. The hazards of excess P from applying organic P-sources at N-based rates are not greater than observed at P-based rates of mineral fertilizer. Results suggest that management of the environmental P hazards associated with N-based rates of organic materials in Florida sands is possible by either applying P-sources with WTR or using a moderate water-soluble P-source.     

Animal Consciousness and Ethics in Asia and the Pacific

The interactions between humans, animals and the environment have shaped human values and ethics, not only the genes that we are made of. The animal rights movement challenges human beings to reconsider interactions between humans and other animals, and maybe connected to the environmental movement that begs us to recognize the fact that there are symbiotic relationships between humans and all other organisms. The first part of this paper looks at types of bioethics, the implications of autonomy and the value of being alive. Then the level of consciousness of these relationships are explored in survey results from Asia and the Pacific, especially in the 1993 International Bioethics Survey conducted in Australia, Hong Kong, India, Israel, Japan, New Zealand, The Philippines, Russia, Singapore and Thailand. Very few mentioned animal consciousness in the survey, but there were more biocentric comments in Australia and Japan; and more comments with the idea of harmony including humans in Thailand. Comparisons between questions and surveys will also be made, in an attempt to describe what people imagine animal consciousness to be, and whether this relates to human ethics of the relationships. This revised version was published online in July 2006 with corrections to the Cover Date.     

Rehabilitation and Flood Management Planning in a Steep,Boulder-Bedded Stream

This study demonstrates the integration of rehabilitation and flood management planning in a steep, boulder-bedded stream in a coastal urban catchment on the South Island of New Zealand. The Water of Leith, the primary stream flowing through the city of Dunedin, is used as a case study. The catchment is steep, with a short time of concentration and rapid hydrologic response, and the lower stream reaches are highly channelized with floodplain encroachment, a high potential for debris flows, significant flood risks, and severely degraded aquatic habitat. Because the objectives for rehabilitation and flood management in urban catchments are often conflicting, a number of types of analyses at both the catchment and the reach scales and careful planning with stakeholder consultation were needed for successful rehabilitation efforts. This included modeling and analysis of catchment hydrology, fluvial geomorphologic assessment, analysis of water quality and aquatic ecology, hydraulic modeling and flood risk evaluation, detailed feasibility studies, and preliminary design to optimize multiple rehabilitation and flood management objectives. The study showed that all of these analyses were needed for integrated rehabilitation and flood management and that some incremental improvements in stream ecological health, aesthetics, and public recreational opportunities could be achieved in this challenging environment. These methods should be considered in a range of types of stream rehabilitation projects.     

AN INDEX FOR MEASURING THE PERFORMANCE OF IRRIGATION MANAGEMENT SYSTEMS WITH AN APPLICATION1

ABSTRACT: This paper presents a statistically valid index for measuring the performance of irrigation systems. The index is applied to a sample of 39 farms on a watercourse under the warabandi system of irrigation management in India. It is found that while the farmers in fact irrigated almost exactly the total amount of irrigated area as designed, inter-farm variations were considerable. The index shows that the degree of error of managerial effectiveness of irrigation on this watercourse is 20 percent. Therefore it is concluded that the system is performing at 80 percent effectiveness.     

WATER LOSS EQUATIONS AND COEFFICIENTS TO ESTIMATE RUNOFF FROM RAINFALL1

Infiltration models are based on physical characteristics of the soil and initial soil moisture. For a given soil it is based on the initial soil moisture distribution. A computer simulation model for flood runoff systems (FH-Model) was used to analyze 39 sets of rainfall-runoff data on four small watersheds ranging in size from 17 to 342 square kilometers located in the Yamaska River basin in Quebec. From these analyses, parameters and coefficients have been determined for a water loss (infiltration) equation. A method for determining the loss parameters, using a nonlinear least square curve fitting technique, is presented. Expressions were made to relate the loss parameters to antecedent precipitation. The equations were tested on 11 storm rainfall and runoff events on a watershed located in the same region and close agreements were found.     

Vegetation dynamics in impounded marshes along the Indian River Lagoon,Florida, USA

Data are presented on the vegetation dynamics of two impounded marshes along the Indian River Lagoon, in east-central Florida, USA. Vegetation in one of the marshes (IRC 12) was totally eliminated by overflooding and by hypersaline conditions (salinities over 100 ppt) that developed there in 1979 after the culvert connecting the marsh with the lagoon was closed. Over 20% recovery of the herbaceous halophytesSalicornia virginica, S. bigelovii, andBatis maritima was observed at that site after the culvert was reopened in 1982, but total cover in the marsh remains well below the original 75%. No recovery of mangroves was observed at this site. The second site (SLC 24), while remaining isolated from the lagoon during much of the study, did not suffer the complete elimination of vegetation experienced at the first site. At this location, mangroves increased in cover and frequency with a concomitant decrease in herbaceous halophytes. Considerable damage to the vegetation was evident at IRC 12 when the impoundment was closed and flooded for mosquito control in 1986. Although the damage was temporary, its occurrence emphasizes the need of planning and constant monitoring and adjustment of management details as conditions within particular marshes change. Storms and hurricanes may be important in promoting a replacement of black mangroves by red mangroves in closed impoundments because the former cannot tolerate pneumatophore submergence for long periods of time. University of Florida-IFAS Journal Series R-00521.