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41.
由于无线通信环境中存在的诸多不确定因素以及其在现代无线通信系统中的重要作用,合理的无线信道成为通信系统仿真研究的重要目的。确立信道仿真模型的目的就是为了尽可能的得到实际信道的统计特性,该文针对Jakes提出的信道模型,通过仿真来分析其局限性,并参考其中的谐波叠加(sum of sinusoids,SOS)法,来建立一种采用了随机分支增益、随机初始相位和有条件的随机多普勒频率改进的信道模型。 相似文献
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The responsibility for managing coral reefs and other coastal resources was largely devolved to coastal municipalities and cities in the Philippines in 1991 with the passage of the Local Government Code. Devolution of powers and responsibilities to local government has paved the way for mainstreaming coastal resource management at the local level. However, the capacity to carry out this mandate has only recently begun to mature as municipalities and cities gain an increased awareness of the importance of coastal resources to communities and economic development. Approaches and strategies to increase local government capacity for coastal resource management are described based on the experiences of the Coastal Resource Management Project of the United States Agency for International Development. Qualitative and quantitative data are used to illustrate the possible impact of these capacity building efforts and to describe the current capacity of local government to undertake coastal resource management. After five years of project implementation, coastal municipalities have increased technical capacity, have allotted financial resources, and have achieved key performance benchmarks in the delivery of coastal resource management as a basic service. 相似文献
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大粒径沥青混合料基层施工压实控制研究 总被引:1,自引:0,他引:1
结合沪蓉西高速公路宜长试验段采用大粒径沥青混合料(LSAM)作为柔性基层的实例,采用核子密度仪进行施工压实度跟踪检测。检测结果表明:胶轮压路机对LSAM压实度的提高作用不明显;LSAM-30一次性铺筑13.5cm仍能保证其具有较好的压实性能;核子密度仪测得LSAM压实度有较高水平且有减小趋势时,应立即停止碾压。另外,对LSAM压实度"超百"现象进行了研究,指出对于LSAM基于旋转压实仪的标准密度能更好地指导现场施工。 相似文献
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利用汕梅高速公路混凝土路面标的施工试验数据,提炼出了一种新的非正态概率密度函数,并对施工结果进行了检验,得出了可靠的结果。 相似文献
45.
基于ADAMS/Car Ride车辆平顺性仿真研究 总被引:1,自引:0,他引:1
以虚拟样机技术进行车辆平顺性仿真研究.建立了基于ADAMS/Car Ride的多体动理学模型,通过虚拟四柱试验台对模型进行仿真试验。仿真结果表明,ADAMS/Car Ride可方便地进行路面功率谱密度响应仿真试验,所建立的包含虚拟四柱试验台的整车模型可深入进行车辆平顺性研究。 相似文献
46.
Asha Weinstein Agrawal Paul Schimek 《Transportation Research Part D: Transport and Environment》2007,12(8):548-563
This paper examines data about walking trips in the US Department of Transportation’s 2001 National Household Travel Survey. The paper describes and critiques the methods used in the survey to collect data on walking. Using these data, we summarize the extent of walking, the duration and distance of walk trips, and variations in walking behavior according to geographic and socio-demographic factors. The results show that most Americans do not walk at all, but those who do average close to thirty minutes of walking a day. Walk trips averaged about a half-mile, but the median trip distance was a quarter of a mile. A significant percentage of the time Americans’ walk was spent traveling to and from transit trips. Binary logit models are used for examining utility and recreational walk trips and show a positive relationship between walking and population density for both. For recreational trips, this effect shows up at the extreme low and high ends of density. For utility trips, the odds of reporting a walk trip increase with each density category, but the effect is most pronounced at the highest density categories. At the highest densities, a large portion of the effect of density occurs via the intermediary of car ownership. Educational attainment has a strong effect on propensity to take walk trips, for both for utility and recreation. Higher income was associated with fewer utility walk trips but more recreational trips. Asians, Latinos, and blacks were less likely to take utility walk trips than whites, after controlling for income, education, density, and car ownership. The ethnic differences in walking are even larger for recreational trips. 相似文献
47.
文章通过对美国产PQI-301路面无核密度仪的应用,介绍了其标定的具体方法及其对沥青路面施工过程中的碾压工艺的确定、压实度的测定及在路面离析情况分析中的作用。 相似文献
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用一维不可压缩、非稳态管内流动模型描述公路隧道气流流动与浓度分布,并结合实际的越江隧道,对各种工况下隧道内空气流动状况和污染物浓度分布进行了模拟计算。 相似文献