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半分析方法在地球卫星100yr尺度长期预报中的性能评估 被引量:4
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作者 王大为 汤靖师 +2 位作者 刘林 马朝伟 郝世锋 《天文学报》 CSCD 北大核心 2017年第1期20-45,共26页
为了能够充分掌握空间目标的长期演化规律和分布情况,对它们的轨道进行长期预报是一种常用的方法.相比于几天的短期预报,长期预报更加关心计算速度以及几个主要轨道根数的精度.这里的主要根数指的是决定轨道形状的半长径a和偏心率e以及... 为了能够充分掌握空间目标的长期演化规律和分布情况,对它们的轨道进行长期预报是一种常用的方法.相比于几天的短期预报,长期预报更加关心计算速度以及几个主要轨道根数的精度.这里的主要根数指的是决定轨道形状的半长径a和偏心率e以及决定轨道空间指向的轨道倾角i和升交点经度?.考虑到以上这些需求,半分析方法是一种十分合适的预报手段.它首先在一个轨道周期内消除短周期项,而后用数值方法计算剩下的平均系统.虽然半分析法不是一种新方法,但几乎找不到定量评估其性能的文献.定量给出了半分析法在常用地球卫星轨道中的精度和速度,通过这些结果可以帮助了解半分析法在长期预报中的适用性.对于半分析法在一些特殊算例中的异常表现,也讨论了原因和可能的解决方法.在半分析的实现方法和精度选择上,均采用了比较通用的方法,希望结果可以为相关半分析工作提供有价值的参考. 展开更多
关键词 天体力学 行星与卫星:动力学演化 方法:分析
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3C 345和3C 273的光变分析 被引量:6
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作者 王洪涛 杨俊英 《天文学报》 CSCD 北大核心 2010年第1期27-33,共7页
用结构函数法,对两个经典的blazar 3C 273和3C 345的22 GHz、37 GHz和光学波段的数据进行了周期分析.结果显示,3C 273的周期性比较明显,22 GHz经分析存在7.0年和14.7年的周期,37 GHz存在7.2年和14.5年的周期,同时它的光学波段可能存在0.... 用结构函数法,对两个经典的blazar 3C 273和3C 345的22 GHz、37 GHz和光学波段的数据进行了周期分析.结果显示,3C 273的周期性比较明显,22 GHz经分析存在7.0年和14.7年的周期,37 GHz存在7.2年和14.5年的周期,同时它的光学波段可能存在0.7年和8.7年的周期.3C 345的37 GHz存在比较明显的8.8年的周期,22 GHz和光学波段分别存在不太明显的9.3年和10.2年的周期. 展开更多
关键词 类星体:个别 星系:基本参数 方法:分析
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月球探测中转移轨道误差分析和中途修正计算 被引量:2
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作者 赵玉晖 侯锡云 刘林 《天文学报》 CSCD 北大核心 2013年第3期261-273,共13页
针对返回型月球探测器,基于月球探测中转移轨道的动力学特征和误差传递矩阵的性质,分别对地月转移轨道和月地转移轨道的误差传递特点进行了研究,并根据误差传递矩阵给出估算第1次中途轨道修正速度增量的线性公式.通过具体算例,给出在实... 针对返回型月球探测器,基于月球探测中转移轨道的动力学特征和误差传递矩阵的性质,分别对地月转移轨道和月地转移轨道的误差传递特点进行了研究,并根据误差传递矩阵给出估算第1次中途轨道修正速度增量的线性公式.通过具体算例,给出在实际力学模型下月球探测中转移轨道误差传递性质,讨论了目标点和目标轨道两种不同的轨道修正方法的特点和适用情形,并结合再入约束条件对月地转移轨道第2次中途修正进行了分析和计算. 展开更多
关键词 行星和卫星:探测 方法:分析 方法:数值
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Numerical investigation on MHD Jeffery-Hamel nanofluid flow with different nanoparticles using fuzzy extension of generalized dual parametric homotopy algorithm
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作者 LALCHAND Verma RAMAKANTA Meher 《Journal of Central South University》 SCIE EI CAS CSCD 2024年第6期1915-1930,共16页
This study considers an MHD Jeffery-Hamel nanofluid flow with distinct nanoparticles such as copper,Al_(2)O_(3)and SiO_(2)between two rigid non-parallel plane walls with the fuzzy extension of the generalized dual par... This study considers an MHD Jeffery-Hamel nanofluid flow with distinct nanoparticles such as copper,Al_(2)O_(3)and SiO_(2)between two rigid non-parallel plane walls with the fuzzy extension of the generalized dual parametric homotopy algorithm.The nanofluids have been formulated to enhance the thermophysical characteristics of fluids,including thermal diffusivity,conductivity,convective heat transfer coefficients and viscosity.Due to the presence of distinct nanofluids,a change in the value of volume fraction occurs that influences the velocity profiles of the flow.The short value of nanoparticles volume fraction is considered an uncertain parameter and represented in a triangular fuzzy number range among[0.0,0.1,0.2].A novel generalized dual parametric homotopy algorithm with fuzzy extension is used here to study the fuzzy velocities at various channel positions.Finally,the effectiveness of the proposed approach has been demonstrated through a comparison with the available results in the crisp case. 展开更多
关键词 fuzzy number Jeffery-Hamel(J-H)flow NANOFLUID homotopy analysis method
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火星非球形引力位田谐项联合摄动分析解 被引量:4
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作者 周垂红 喻圣贤 刘林 《天文学报》 CSCD 北大核心 2012年第3期205-212,共8页
火星非球形引力场模型与地球有明显差别,其非球形引力位中的田谐项系数基本都要比地球的相应值大一个量级,尤其是J_(2,2)项(赤道椭率项)的大小接近它的动力学扁率项J_2.对于低轨探测器,若要使轨道外推1 d弧段的精度达到500 m(相当于标... 火星非球形引力场模型与地球有明显差别,其非球形引力位中的田谐项系数基本都要比地球的相应值大一个量级,尤其是J_(2,2)项(赤道椭率项)的大小接近它的动力学扁率项J_2.对于低轨探测器,若要使轨道外推1 d弧段的精度达到500 m(相当于标准单位10^(-4)量级),在构造环火探测器的轨道分析解时,田谐项与J_2项以及田谐项与田谐项之间的联合摄动不容忽视.根据摄动量级分析和构造的摄动分析解证实,上述联合摄动对轨道沿迹方向的影响可超过10^(-4),并给出了数值验证.结果表明,与地球低轨卫星不同,在类似的问题中,构造环火卫星摄动分析解时,必须考虑这些联合摄动项的影响. 展开更多
关键词 天体力学 摄动理论 方法:分析 方法:数值
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基于扇形子镜的12m光学红外望远镜拼接共相误差仿真分析
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作者 沈世东 崔向群 张勇 《天文学报》 CAS CSCD 北大核心 2022年第6期4-17,共14页
为满足国内对应用大型通用光学望远镜在光学红外波段进行天文观测的需求,中国计划建设一架12 m大口径光学红外望远镜(12-meter large aperture optical-infrared telescope,LOT).LOT对于中国天文界具有极其重要的意义,将会在近红外波段... 为满足国内对应用大型通用光学望远镜在光学红外波段进行天文观测的需求,中国计划建设一架12 m大口径光学红外望远镜(12-meter large aperture optical-infrared telescope,LOT).LOT对于中国天文界具有极其重要的意义,将会在近红外波段实现共相.LOT的主镜将采用子镜拼接的方案,由72块扇形子镜拼接而成,并且中央部分有一块直径4.5m的圆形镜.分析了采用扇形子镜拼接方案下LOT的共相误差,提供了详细的共相误差理论推导过程,并对包括3种子镜面外误差在内的误差源进行深入的单独模拟和综合模拟.在共相波长为1μm的条件下,当服从正态分布的倾斜误差的均方根值小于0.016″或服从正态分布的活塞误差的均方根值小于42.5nm时,LOT的斯特列尔比大于0.8.仿真结果对于采用共相拼接镜面主动光学的主镜在LOT中的应用具有重要意义. 展开更多
关键词 望远镜 方法:分析 方法:数据分析 技术:高角分辨率
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环焦天线口径面相位分析
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作者 胡伟 王锦清 +1 位作者 柳聪 卜朝晖 《天文学报》 CAS CSCD 北大核心 2022年第3期65-73,共9页
环焦天线具有特殊的电磁特性和应用领域.对环焦天线的口径面相位误差进行了理论和仿真分析,推导了馈源和副面位置偏差引起的相位误差、主副面之间的补偿关系以及全息测量中天线转动引起的光程差.研究结果将对环焦天线的精确面形测量和... 环焦天线具有特殊的电磁特性和应用领域.对环焦天线的口径面相位误差进行了理论和仿真分析,推导了馈源和副面位置偏差引起的相位误差、主副面之间的补偿关系以及全息测量中天线转动引起的光程差.研究结果将对环焦天线的精确面形测量和补偿提供理论依据和参考. 展开更多
关键词 望远镜 方法:分析 技术:图像处理
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任意倾角的共轨运动研究
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作者 鲁瑞 雷汉伦 周礼勇 《天文学报》 CAS CSCD 北大核心 2023年第5期10-21,共12页
共轨运动天体与摄动天体的半长径相同,处于1:1平运动共振中.太阳系内多个行星的特洛伊天体即为处于蝌蚪形轨道的共轨运动天体,其中一些高轨道倾角特洛伊天体的轨道运动与来源仍未被完全理解.利用一个新发展的适用于处理1:1平运动共振的... 共轨运动天体与摄动天体的半长径相同,处于1:1平运动共振中.太阳系内多个行星的特洛伊天体即为处于蝌蚪形轨道的共轨运动天体,其中一些高轨道倾角特洛伊天体的轨道运动与来源仍未被完全理解.利用一个新发展的适用于处理1:1平运动共振的摄动函数展开方式,对三维空间中的共轨运动进行考察,计算不同初始轨道根数情况下共轨轨道的共振中心、共振宽度,分析轨道类型与初始轨道根数的关系.并将分析方法所得结果与数值方法的结果相互比较验证,得到了广阔初始轨道根数空间内共轨运动的全局图景. 展开更多
关键词 天体力学:圆型限制性三体问题 方法:分析与数值 共轨
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Analysis of the Conditional Correlations from Different Genetic Systems Between the Protein Content and the Appearance Quality Traits of Indica Rice 被引量:4
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作者 葛国科 郑希 +2 位作者 吴建国 叶子弘 石春海 《Journal of Genetics and Genomics》 SCIE CAS CSCD 北大核心 2007年第2期129-137,共9页
A factorial mating design in two environments was conducted using 7 cytoplasmic male sterile lines (A) and 5 restorer lines (R) along with their F1 (A × R) and F2 populations. The unconditional and conditio... A factorial mating design in two environments was conducted using 7 cytoplasmic male sterile lines (A) and 5 restorer lines (R) along with their F1 (A × R) and F2 populations. The unconditional and conditional analyses of genetic models and the corresponding statistic methods, including endospermic, cytoplasmic, and maternal plant genetic systems, were used to analyze the genetic relationships between protein content (PC) and the appearance quality traits of indica rice (Oryza sativa L.). The results from unconditional analysis indicated that PC was significantly correlated with the appearance quality traits of rice, except for the brown rice thickness (BRT). Only the genetic covariance between PC and the brown rice width (BRW) was positively correlative, whereas all the other pairwise traits were negatively correlative. The results from conditional analysis revealed that the weight of brown rice (WBR) or the amylose content (AC) could significantly affect the relationships between PC and the appearance quality traits of indica rice. The conditional analysis showed that WBR might negatively affect the relationships between PC and the brown rice length (BRL), BRW, or BRT through the geuotype x environmental (GE) interaction effects, but positively affected the relationships between PC and the ratio of brown rice length to width (RLW) or the ratio of brown rice length to thickness (RLT). The amylase content could positively affect the relationships between PC and BRL, RLW, RLT through the cytoplasmic effects and maternal additive effects, but negatively affected the relationships between PC and BRW. 展开更多
关键词 indica rice (Oryza sativa L.) COVARIANCE unconditional and conditional analysis methods protein content amylose content appearance quality
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30m级光学/红外望远镜的宽视场多目标光谱仪 被引量:2
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作者 季杭馨 胡中文 +5 位作者 朱永田 许明明 戴松新 章华涛 汤振 王晋峰 《天文学报》 CSCD 北大核心 2019年第4期69-88,共20页
宽视场多目标光谱仪具有宽波段、多分辨率模式和高通光效率的特点,是极大望远镜终端仪器使用率最高的通用型仪器. 30 m级望远镜的宽视场多目标光谱仪因体量和成本急剧增加而面临重要挑战,同时天文学的不断发展对天文新技术的发展提出了... 宽视场多目标光谱仪具有宽波段、多分辨率模式和高通光效率的特点,是极大望远镜终端仪器使用率最高的通用型仪器. 30 m级望远镜的宽视场多目标光谱仪因体量和成本急剧增加而面临重要挑战,同时天文学的不断发展对天文新技术的发展提出了更高的要求,尤其是多个巡天项目对于多目标光谱后随观测的迫切需求.综述了几类宽视场多目标光谱仪的发展现状,介绍了国际3架30 m望远镜宽视场多目标光谱仪概念设计的最新进展和仪器特点,着重介绍了中国参与研制的30 m望远镜(TMT)中的宽视场多目标光谱仪的相关进展. 展开更多
关键词 仪器:光谱仪 望远镜 技术:成像光谱技术 技术:光谱学 方法:分析
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近地卫星运动的坐标系附加摄动在拟平均根数法中的处理 被引量:5
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作者 汤靖师 刘林 《天文学报》 CSCD 北大核心 2010年第1期75-84,共10页
在常用的历元地心天球坐标系中研究和处理近地卫星的轨道问题,就必须考虑由于地球赤道面摆动所引起的坐标系附加摄动,正因为如此,给实际工作带来一些麻烦.关于这一问题,曾提出了一种针对瞬根数和平根数之间的转换(仅与坐标系附加摄动的... 在常用的历元地心天球坐标系中研究和处理近地卫星的轨道问题,就必须考虑由于地球赤道面摆动所引起的坐标系附加摄动,正因为如此,给实际工作带来一些麻烦.关于这一问题,曾提出了一种针对瞬根数和平根数之间的转换(仅与坐标系附加摄动的短周期项有关)的解决途径,但并未涉及采用分析法进行轨道外推的有关问题(这与坐标系附加摄动的长期和长周期项有关),这对处理近地卫星的轨道问题而言显然是不完整的.这里结合拟平均根数法进一步改进原提出的方法,较完善地解决这一坐标系附加摄动的计算问题.在此前提下,对于卫星定轨和预报及其相关工作,无论是采用数值法还是分析法,均可采用同一坐标系,即历元(目前是J2000.0)地心天球坐标系. 展开更多
关键词 天体力学 参考系 方法:分析
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基于图像的天体搜索研究与自动化集成软件开发 被引量:2
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作者 陆扬 安涛 +1 位作者 郭绍光 劳保强 《天文学报》 CSCD 北大核心 2019年第6期1-16,共16页
天体搜索是天文数据处理流程的一个重要环节,也是以平方公里阵列射电望远镜(Square Kilometre Array,SKA)为代表的下一代射电望远镜在面向海量数据处理中的挑战之一.现今天体自动搜索算法、软件已日趋成熟并投入应用,不过在自动化、兼... 天体搜索是天文数据处理流程的一个重要环节,也是以平方公里阵列射电望远镜(Square Kilometre Array,SKA)为代表的下一代射电望远镜在面向海量数据处理中的挑战之一.现今天体自动搜索算法、软件已日趋成熟并投入应用,不过在自动化、兼容性等方面仍具有提升空间.以更自动化、更适应海量数据需求的天体搜索算法研究为宗旨,以现有算法为研究基础,天体自动搜索软件系统得到设计和开发.该系统包含友好的交互式用户操作界面,具备可视化输出数据显示、兼容不同数据输入和输出并包含为实际应用服务的文件管理功能.该系统对于大天区图以及图像集,均能够很好地进行自动化处理.测试结果显示,上述方法对于天体搜索的改进有一定成效.后续将在此基础上对该集成系统做进一步的改进开发,以适应更多的需求. 展开更多
关键词 技术:图像处理 方法:分析 星表
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环火卫星运动的坐标系附加摄动及相应坐标系的选择 被引量:6
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作者 刘林 赵玉晖 +2 位作者 张巍 王彦荣 王家松 《天文学报》 CSCD 北大核心 2010年第4期412-421,共10页
与处理地球卫星相关问题类似,在研究和处理环火卫星(尤其是低轨卫星)的轨道问题时,宜采用火心历元平赤道坐标系,即火心天球坐标系,其xy坐标面和x轴方向就是相应的平赤道面和平春分点方向.与地球的岁差章动现象类似,在该坐标系中,火星赤... 与处理地球卫星相关问题类似,在研究和处理环火卫星(尤其是低轨卫星)的轨道问题时,宜采用火心历元平赤道坐标系,即火心天球坐标系,其xy坐标面和x轴方向就是相应的平赤道面和平春分点方向.与地球的岁差章动现象类似,在该坐标系中,火星赤道面在空间的摆动同样会引起坐标系附加摄动.采用类似对地球岁差章动的处理方法,在一定精度前提下,基于IAU2000火星定向模型,处理了火星赤道面摆动中的岁差效应,并在此基础上,研究岁差对环火卫星轨道的影响,给出了相应的火星非球形引力位的变化及其导致的卫星轨道的坐标系附加摄动解,其表达形式简单,引用方便.与高精度数值解的比对表明,该分析解能够满足通常的精度要求.因此,在处理环火卫星(即使是低轨卫星)轨道及其相关问题时,可以采用统一坐标系:火心天球坐标系.而不必像当初处理地球卫星那样,为了避免计算坐标系附加摄动而引进一种混合型赤道坐标系,即采用瞬时真赤道面和历元平春分点方向作为其xy坐标面和x轴方向.在统一坐标系的选择下,实际工作中就不会存在坐标系转换的麻烦. 展开更多
关键词 天体力学 参考系 方法:分析 方法:数值
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Analysis of rock physics response of gas-bearing volcanic reservoir based on three-phase poroelastic theory 被引量:3
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作者 吴清岭 赵海波 +1 位作者 李来林 范兴才 《Applied Geophysics》 SCIE CSCD 2008年第4期277-283,共7页
Unlike previous theories with velocity and/or elastic modulus averaging, we use a three-phase porous rock physics model developed by Santos for analyzing the seismic response of two immiscible fluids in saturated poro... Unlike previous theories with velocity and/or elastic modulus averaging, we use a three-phase porous rock physics model developed by Santos for analyzing the seismic response of two immiscible fluids in saturated porous media. Considering reservoir reference pressure and coupling drag of two fluids in pores, the effects of frequency, porosity, and gas saturation on the phase velocities of the P-and S-waves are discussed in detail under field conditions. The effects of porosity and gas saturation on Vp/Vs are also provided. The data for our numerical experiments are from a sample of deep volcanic rock from Daqing. The numerical results show that the frequency dispersion effect can be ignored for deep volcanic rocks with low porosity and low permeability. It is concluded that for deep volcanic rocks the effect of gas content in pores on Vp/Vs is negligible but the effect of porosity is significant when there is a certain amount of water contained in the pores. The accurate estimate of lithology and porosity in this case is relatively more important. 展开更多
关键词 rock physics three-phase porous media seismic response and volcanic rock
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Prediction method of highway pavement rutting based on the grey theory 被引量:6
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作者 周岚 倪富健 赵岩荆 《Journal of Southeast University(English Edition)》 EI CAS 2015年第3期396-400,共5页
In order to make a scientific pavement maintenance decision, a grey-theory-based prediction methodological framework is proposed to predict pavement performance. Based on the field pavement rutting data,analysis of va... In order to make a scientific pavement maintenance decision, a grey-theory-based prediction methodological framework is proposed to predict pavement performance. Based on the field pavement rutting data,analysis of variance (ANOVA)was first used to study the influence of different factors on pavement rutting. Cluster analysis was then employed to investigate the rutting development trend.Based on the clustering results,the grey theory was applied to build pavement rutting models for each cluster, which can effectively reduce the complexity of the predictive model.The results show that axial load and asphalt binder type play important roles in rutting development.The prediction model is capable of capturing the uncertainty in the pavement performance prediction process and can meet the requirements of highway pavement maintenance,and,therefore,has a wide application prospects. 展开更多
关键词 prediction method grey theory cluster analysis analysis of variance pavement rutting
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DECISION-MAKING OF SLICING SCHEME IN FUSED DEPOSITION MODELING PROCESS BASED ON ANALYTICAL HIERARCHICAL PROCESS 被引量:6
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作者 张剑峰 彭安华 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2010年第2期125-130,共6页
Based on analyzing the influences of a slicing scheme on stair-stepping effect, supporting structure, efficiency and deformation, etc. , analytical hierarchical process (AHP) combining with fuzzy synthetic evaluatio... Based on analyzing the influences of a slicing scheme on stair-stepping effect, supporting structure, efficiency and deformation, etc. , analytical hierarchical process (AHP) combining with fuzzy synthetic evaluation is introduced to make decision in slicing schemes for a processing part. The application in determining the slicing scheme for a computer mouse during prototyping shows that the method increases the rationality during decision- making and improves quality and efficiency for the prototyping part. 展开更多
关键词 DECISION-MAKING fused deposition modeling (FDM) analytical hierarchical process (AHP) slicing scheme
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Dynamic analysis and experimental study of vibro-acoustic system with uncertainties at middle frequencies 被引量:2
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作者 焦仁强 张建润 薛飞 《Journal of Southeast University(English Edition)》 EI CAS 2017年第2期166-170,共5页
To take into account the influence of uncetainties on the dynamic response of the vibro-acousitc structure, a hybrid modeling technique combining the finite element method(FE)and the statistic energy analysis(SEA)... To take into account the influence of uncetainties on the dynamic response of the vibro-acousitc structure, a hybrid modeling technique combining the finite element method(FE)and the statistic energy analysis(SEA) is proposed to analyze vibro-acoustics responses with uncertainties at middle frequencies. The mid-frequency dynamic response of the framework-plate structure with uncertainties is studied based on the hybrid FE-SEA method and the Monte Carlo(MC)simulation is performed so as to provide a benchmark comparison with the hybrid method. The energy response of the framework-plate structure matches well with the MC simulation results, which validates the effectiveness of the hybrid FE-SEA method considering both the complexity of the vibro-acoustic structure and the uncertainties in mid-frequency vibro-acousitc analysis. Based on the hybrid method, a vibroacoustic model of a construction machinery cab with random properties is established, and the excitations of the model are measured by experiments. The responses of the sound pressure level of the cab and the vibration power spectrum density of the front windscreen are calculated and compared with those of the experiment. At middle frequencies, the results have a good consistency with the tests and the prediction error is less than 3. 5dB. 展开更多
关键词 hybrid finite element method and statistic energy analysis(FE-SEA) method dynamic analysis vibroacoustic system UNCERTAINTIES mid-frequency range
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Study on the evaluation index system and evaluation method for self-elevating drilling unit design 被引量:1
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作者 王运龙 纪卓尚 《Journal of Marine Science and Application》 2009年第1期46-52,共7页
In the process of designing self-elevating drilling unit, it is important, yet complicated, to use comparison and filtering to select the optimum scheme from the feasible ones. In this research, an index system and me... In the process of designing self-elevating drilling unit, it is important, yet complicated, to use comparison and filtering to select the optimum scheme from the feasible ones. In this research, an index system and methodology for the evaluation of self-elevating drilling unit was proposed. Based on this, a multi-objective combinatorial optimization model was developed, using the improved grey relation Analysis (GRA), in which the analytic hierarchy process (AHP) was used to determine the weights of the evaluating indices. It considered the connections within the indices, reflecting the objective nature of things, and also considered the subjective interests of ship owners and the needs of designers. The evaluation index system and evaluation method can be used in the selection of an optimal scheme and advanced assessment. A case study shows the index system and evaluation method are scientific, reasonable, and easy to put into practice. At the same time, such an evaluation index system and evaluation method will be helpful for making decisions for other mobile platforms. 展开更多
关键词 self-elevating drilling unit evaluation index system evaluation method grey relation analysis (GRA) analytic hierarchy process (AHP)
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Numerical modeling of the 2D time-domain transient electromagnetic secondary field of the line source of the current excitation 被引量:4
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作者 刘云 王绪本 王贇 《Applied Geophysics》 SCIE CSCD 2013年第2期134-144,235,共12页
To effectively minimize the electromagnetic field response in the total field solution, we propose a numerical modeling method for the two-dimensional (2D) time- domain transient electromagnetic secondary field of t... To effectively minimize the electromagnetic field response in the total field solution, we propose a numerical modeling method for the two-dimensional (2D) time- domain transient electromagnetic secondary field of the line source based on the DuFort- Frankel finite-difference method. In the proposed method, we included the treatment of the earth-air boundary conductivity, calculated the normalized partial derivative of the induced electromotive force (Emf), and determined the forward time step. By extending upward the earth-air interface to the air grid nodes and the zero-value boundary conditions, not only we have a method that is more efficient but also simpler than the total field solution. We computed and analyzed the homogeneous half-space model and the fiat layered model with high precision--the maximum relative error is less than 0.01% between our method and the analytical method--and the solution speed is roughly three times faster than the total-field solution. Lastly, we used the model of a thin body embedded in a homogeneous half-space at different delay times to depict the downward and upward spreading characteristics of the induced eddy current, and the physical interaction processes between the electromagnetic field and the underground low-resistivity body. 展开更多
关键词 Time-domain transient electromagnetics secondary field DuFort-Frankel finite-difference method numerical modeling.
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Primary Lymphoma of Respiratory System (A Report of 11 Cases)
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作者 周立强 谭文勇 +4 位作者 鲁海珍 王金万 冯奉仪 储大同 孙燕 《The Chinese-German Journal of Clinical Oncology》 CAS 2005年第1期43-46,68,共5页
Objective: To analyze the clinical and pathologic features and the treatmentoutcomes of primary lymphoma of respiratory system (PLRS). Methods: The clinical manifestation,imaging changes, pathologic subtypes, treatmen... Objective: To analyze the clinical and pathologic features and the treatmentoutcomes of primary lymphoma of respiratory system (PLRS). Methods: The clinical manifestation,imaging changes, pathologic subtypes, treatment and overall survival of 11 patients with PLRS wereanalyzed retrospectively. Results: Of the 11 patients diagnosed with PLRS by histopathology, thetumor of 2 patients occurred in trachea and the other 9 in lung. Cough, dyspnea and fever were themost frequent symptoms. Mass or infiltrative changes could be found on the chest X-ray and/or CTscan. Two patients were diagnosed as having Hodgkin's Lymphoma (HL) and 9 having non-Hodgkin'sLymphoma (NHL), including 7 patients with low degree NHL [5 of them (55.6%) were mucosa-associatedlymphoid tissue (MALT) lymphoma] and 2 with intermediate degree NHL. Of 10 patients undergoingexploratory thoracotomy and surgical treatment, 8 received adjuvant chemotherapy and 2 adjuvant ofradiotherapy. The remaining patient was subjected to combined chemotherapy. Both of HL patientssurvived more than 5 years without clinical disease. The median survival of MALT lymphoma and othertype of NHL was 39 months and 34 months respectively. Conclusion: Both the clinical manifestationand imaging changes are non-specific. The diagnosis was made through exploratory thoracotomy (10cases) and fiber-optical bronchoscopy (1 case). MALT lymphoma is the most frequent pathologicsubtype. Majority of patients are diagnosed and treated by surgical resection. The prognosis isacceptable. 展开更多
关键词 LYMPHOMA non-Hodgkin's/pathology non-hodgkin's/drug therapy hodgkin'slymphoma respiratory system
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