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961.
A practical antenna has been designed and developed for INMARSAT mobile satellite communications. The design uses low cost materials such as foam and copper foil to create a stacked microstrip antenna array. Several techniques were adopted to enhance the impedance bandwidth and axial ratio bandwidth. The final design parameters were optimized by EM simulation. Finally, the L-strip fed six-element stacked microstrip antenna array was constructed and tested. Simulated and measured results show that in the whole INMARSAT work band, the VSWR of the antenna is less than 1.6, its antenna gain is higher than 15dB and wide-angle axial ratio (AR) 3dB is more than 21°. The antenna has been successfully used with a HNS 9201 terminal. 相似文献
962.
The Asian region is considered as the most thriving region in terms of economic integration at present. Given the fact that most of the Asian countries’ commodity trade relies on maritime transport, its economic integration is expected to affect the shipping activities and consequently maritime CO2 emissions. This study develops a novel and systematic analysis on the key driving factors through which trade liberalization can influence maritime CO2 emissions. Our simulation results suggest that, depending on the level of Asian integration, global CO2 emissions may slightly fall (ASEAN+3 FTA) or even rise (ASEAN+6 FTA). The reason for the latter is that the “trade scale effect” (higher emissions due to a significant increase in trade among participating countries) outweighs the “trade structure effect” and “shipment type effect” (lower emissions as a result of an increase in intra-Asia trade and a change in commodity composition). Finally, all countries involved in the Asian integration, except Japan, will experience an increase in maritime CO2 emissions. In particular, a relatively significant increase in the maritime CO2 emissions occurs in the developing Asian countries owing to substantial trade scale effect after removing their relatively high trade barriers. 相似文献
963.
Particular safety problems relate to traffic on local streets. Local Area Traffic Management (LATM) schemes are often implemented with the objective of counteracting these safety problems. One analytical difficulty in appraising the effectiveness of LATM in dealing with safety problems has been the ‘footloose’ nature of accident locations in a local street network. Seldom are there distinct ‘blackspot’ locations. An area‐wide approach is needed and the interaction between the system and arterial road network must be considered. The paper describes the development of a Safety Evaluation Method for Local Area Traffic Management (termed SELATM). It is a GIS‐based program for analysing accident patterns over time and the evaluation of the safety benefits of LATM schemes. The evaluation is perform at different network levels for various accident variables. The thrust of the program involved the integration of network data with data on accidents and the installed devices to generate summary accident statistics for the various network levels allowing for before and after comparison with a control area. This program as developed is applied to a LATM scheme at Enfield, a suburb in metropolitan Adelaide. 相似文献
964.
王文平 《武汉船舶职业技术学院学报》2014,(5):65-66
本文应用Laplace变换推导了形如∫+∞0tnf(t)dt、∫+∞0f(t,x)dx的广义积分的相对简便新颖的计算方法。 相似文献
965.
闹加才让 《铁道标准设计通讯》2019,(4)
铁路机务段设计具有涉及专业多、专业接口复杂的特点,传统二维设计容易出现管线碰撞及设计缺陷。为提高设计质量,以迁建西安机务段项目为依托,对BIM技术在大型铁路工程中的应用进行探索。本项目运用Inventor、Revit、Navisworks等设计软件作为BIM设计工具,将所涉及的14个专业工程内容全部进行BIM设计。通过建立族库、各专业BIM设计、模型整合的流程,构建一个覆盖全专业的数字化仿真模型,并总结出一套机务段BIM设计流程。实现了模型可视化展示、二维出图、属性信息添加、工程量统计、碰撞检测等应用。机务段工程设计复杂,专业接口众多,运用BIM技术可直观展示设计意图,并能轻易发现各专业设计中的错、漏、碰、缺问题,为提高设计质量提供有力保障。 相似文献
966.
将竞赛与日常教学结合起来,实现赛教融合是当代职业院校培养优秀学生的重要途径之一,该方法不仅能大幅度提升学生成绩和职业能力,同时对学生融会贯通理论知识和实践技能也大有裨益。本文通过对“赛教融合、以赛促教”对学生职业能力提升的意义阐述,分析其发展现状,继而提出解决策略,希望能帮助职校学生实现理论向职业技能的有效转化,提高其职业能力,推动其向高素质、创新型技能人才目标发展。 相似文献
967.
968.
969.
目的 为系统完善地评估我国儿童视觉运动整合的发育提供有效工具。方法 引入VMI 4R测验 ,分层随机整群抽取西安城市健康儿童 1 798人 ,组成标准化人群 ,进行VMI 4R测验。并于标准人群中随机抽取儿童进行信度和效度检验。结果 编制了西安城市儿童VMI 4R测验的年龄等值、标准分和百分位常模 ;分半信度、KR2 0 系数、复测信度、评定者间信度检验的r值于 0 90~ 0 96之间 (P <0 0 1 )。效度检验中 ,VMI 4R与WISC R、WPPSI R、CRT、FQS、绘人测验呈中 高度相关 (P <0 0 5)。结论 调查结果显示VMI 4R测验结构稳定 ,信度良好 ,能有效反映儿童的视觉运动整合水平和特点 ,是值得推广的儿童智能筛查和认知发育评估的工具。 相似文献
970.
物流系统绩效综合评价方法的研究 总被引:1,自引:0,他引:1
在分析常用物流系统绩效综合评价方法的基础上,根据各种方法的不同特点和物流系统的实际应用,提出一种新的集成评价方法,与目前广泛应用的综合评价方法相比,具有一定的优越性。 相似文献