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风帆助航与天帆系统 被引量:1
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作者 李斌 《世界海运》 2011年第8期19-21,共3页
介绍风帆助航的特点与应用,分析其在节能、安全和航行性能方面可能存在的问题,阐述一种新型的高科技风帆系统——天帆系统的原理、航线优化设计和安全措施。
关键词 船舶推进 助航 天帆系统 节能
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天网千帆——一种新型文件搜索引擎 被引量:4
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作者 谢欣 刘菲菲 李晓明 《华南理工大学学报(自然科学版)》 EI CAS CSCD 北大核心 2004年第z1期58-62,共5页
为解决因网络中共享文件大量增加而造成的现有文件搜索引擎查准率和查全率低、查询结果可用性不强的问题,在分析用户查询日志的特征和统计文件服务器文件特点的基础上,提出了一种新的文件搜索引擎实现方案,在查询中使用基于资源的匹配... 为解决因网络中共享文件大量增加而造成的现有文件搜索引擎查准率和查全率低、查询结果可用性不强的问题,在分析用户查询日志的特征和统计文件服务器文件特点的基础上,提出了一种新的文件搜索引擎实现方案,在查询中使用基于资源的匹配来替代传统的字符串匹配,并对查询结果进行个性化排序,从而有效地提高了查询结果的质量,并提供了自动纠错等功能.在天网千帆文件搜索引擎上通过了该方案的系统实现,实验结果证明了该设计的有效性. 展开更多
关键词 网千 文件搜索引擎 自动纠错
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塑料大棚内太阳能贮热系统
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作者 谢毓琦 周建明 《山东农机化》 1998年第7期12-12,共1页
一、太阳能贮热系统的原理 塑料大棚内由于温室效应,在早春和晚秋季节,白天棚内的气温往往高于作物所需温度,即有多余的太阳能;而在夜晚,棚内气温往往低于作物所需温度,需要补充热量。太阳能贮热系统,就是利用风机把白天棚内的热空气经... 一、太阳能贮热系统的原理 塑料大棚内由于温室效应,在早春和晚秋季节,白天棚内的气温往往高于作物所需温度,即有多余的太阳能;而在夜晚,棚内气温往往低于作物所需温度,需要补充热量。太阳能贮热系统,就是利用风机把白天棚内的热空气经管道送入地下。 展开更多
关键词 贮热 太阳能 塑料大棚 子管道 补充热 贮热过程 天帆 贮热量 热空气
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Optimal control of a spacecraft with deployable solar arrays using particle swarm optimization algorithm 被引量:5
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作者 GE XinSheng SUN Kai 《Science China(Technological Sciences)》 SCIE EI CAS 2011年第5期1107-1112,共6页
The optimal control problem of the multibody dynamics of a spacecraft in space, modeled as a central body with one-sided connected deployable solar arrays, is investigated. The dynamical equations of motion of the spa... The optimal control problem of the multibody dynamics of a spacecraft in space, modeled as a central body with one-sided connected deployable solar arrays, is investigated. The dynamical equations of motion of the spacecraft with solar arrays are derived using the multibody dynamics method. The control of the attitude motion of a spacecraft system can be transformed into the motion planning problem of nonholonomic system when the initial angular momentum is zero. These are then used to investigate the motion planning of the spacecraft during solar arrays deployment via particle swarm optimization (PSO) and results are obtained with the optimal control input and the optimal trajectory. The results of numerical simulation show that this approach is effective for the control problem of the attitude of a spacecraft during the deployment process of its solar arrays. 展开更多
关键词 multibody spacecraft attitude dynamics optimal control particle swarm optimization
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Venus round trip using solar sail 被引量:1
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作者 ZHU KaiJian ZHANG RongZhi +2 位作者 XU Dong WANG JiaSong LI ShaoMin 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2012年第8期1485-1499,共15页
Trajectory optimization and simulation is performed for Venus round trip (VeRT) mission using solar sail propulsion. Solar gravity is included but atmospheric drag and shadowing effects are neglected in the planet-cen... Trajectory optimization and simulation is performed for Venus round trip (VeRT) mission using solar sail propulsion. Solar gravity is included but atmospheric drag and shadowing effects are neglected in the planet-centered escape and capture stages. The spacecraft starts from the Geostationary orbit (GEt) at a predetermined time to prepare a good initial condition for the Earth-Venus transfer, although the launch window is not an issue for spacecraft with solar sails. The Earth-Venus phase and the return trip are divided into three segments. Two methods are adopted to maintain the mission trajectory for the VeRT mis- sion and then compared through a numerical simulation. According to the first approach, Planet-centered and heliocentric ma- neuvers are modeled using a set of blended analytical control laws instead of the optimal control techniques. The second pro- cedure is the Direct Attitude Angle Optimization in which the attitude angles of the solar sail are adopted as the optimization variables during the heliocentric transfer. Although neither of the two methods guarantees a globally optimal trajectory, they are more efficient and will produce a near-optimal solution if employed properly. The second method has produced a better result for the minimum-time transfer of the VeRT mission demonstrating the effectiveness of the methods in the preliminary design of the complex optimal interplanetary orbit transfers. 展开更多
关键词 venus round trip solar sail analytical control laws direct attitude angle optimization
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