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STABILITY OF 3-D DISTURBANCE WAVES ON BOUNDARY LAYER WITH DISTRIBUTED LOCAL ROUGHNESS
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作者 曹卫东 陆昌根 胡庆喜 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2007年第3期225-231,共7页
The numerical solution of the stable basic flow on a 3-D boundary layer is obtained by using local ejection, local suction, and combination of local ejection and suction to simulate the local rough wall. The evolution... The numerical solution of the stable basic flow on a 3-D boundary layer is obtained by using local ejection, local suction, and combination of local ejection and suction to simulate the local rough wall. The evolution of 3-D disturbance T-S wave is studied in the spatial processes, and the effects of form and distribution structure of local roughness on the growth rate of the 3-D disturbance wave and the flow stability are discussed. Numerical results show that the growth of the disturbance wave and the form of vortices are accelerated by the 3-D local roughness. The modification of basic flow owing to the evolvement of the finite amplitude disturbance wave and the existence of spanwise velocity induced by the 3-D local roughness affects the stability of boundary layer. Propagation direction and phase of the disturbance wave shift obviously for the 3-D local roughness of the wall. The flow stability characteristics change if the form of the 2-D local roughness varies. 展开更多
关键词 local roughness boundary layer 3-d disturbance T-S wave STABILITY
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3-D Reconstruction and Visualization of Laser-Scanned Trees by Weighted Locally Optimal Projection and Accurate Modeling Method
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作者 TAMAYO Alexis LI Minglei +1 位作者 LIU Qin ZHANG Meng 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI CSCD 2022年第S01期135-142,共8页
This paper presents a method to reconstruct 3-D models of trees from terrestrial laser scan(TLS)point clouds.This method uses the weighted locally optimal projection(WLOP)and the AdTree method to reconstruct detailed ... This paper presents a method to reconstruct 3-D models of trees from terrestrial laser scan(TLS)point clouds.This method uses the weighted locally optimal projection(WLOP)and the AdTree method to reconstruct detailed 3-D tree models.To improve its representation accuracy,the WLOP algorithm is introduced to consolidate the point cloud.Its reconstruction accuracy is tested using a dataset of ten trees,and the one-sided Hausdorff distances between the input point clouds and the resulting 3-D models are measured.The experimental results show that the optimal projection modeling method has an average one-sided Hausdorff distance(mean)lower by 30.74%and 6.43%compared with AdTree and AdQSM methods,respectively.Furthermore,it has an average one-sided Hausdorff distance(RMS)lower by 29.95%and 12.28%compared with AdTree and AdQSM methods.Results show that the 3-D model generated fits closely to the input point cloud data and ensures a high geometrical accuracy. 展开更多
关键词 light detection and ranging(LiDAR) point cloud weighted locally optimal projection(WLOP) 3-d reconstruction AdTree
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THREE-DIMENSIONAL CONFORMAL RADIATION THERAPY FOR LOCALLY RECURRENT NASOPHARYNGEAL CARCINOMA
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作者 郑小康 马骏 +1 位作者 夏云飞 陈龙华 《Chinese Journal of Cancer Research》 SCIE CAS CSCD 2001年第3期221-225,共5页
Objective: To investigate the safety and effectiveness of three-dimensional conformal radiation therapy (3-D CRT) for locally recurrent nasopharyngeal carcinoma (NPC). Methods: From April 1998 to March 2000, 34 patien... Objective: To investigate the safety and effectiveness of three-dimensional conformal radiation therapy (3-D CRT) for locally recurrent nasopharyngeal carcinoma (NPC). Methods: From April 1998 to March 2000, 34 patients who had undergone previous external beam radiation therapy were retreated with 3-D CRT for locally recurrent NPC (33 poorly differentiated squamous cell carcinomas, 1 adenoma). The patients were re-staged according to Huaqing staging system with the following distribution: T1N0M0 in 5 cases, T2N0M0 in 11 cases, T3N0M0 in 12 cases, T4N0M0 in 6 cases. The maximal dimension of the gross tumor volume (GTV) ranged from 1.0 cm to 5.0 cm (median: 2.9 cm). CT simulation and 3-D planning were used to ensure full and conformal coverage of the planning target volume (PTV) by treated volume, while minimizing the absorbed dose of the adjacent normal tissue. 5–7 static conformal coplanar or noncoplanar portals were delivered for each fraction irradiation. The total dose delivered ranged from 65–70 Gy, with 2.5 Gy per fractionation, one fractionation per day, 5 days a week. Median follow-up time from 3-D CRT was 25 months (range: 12–36 months). Results: Over the follow-up period, local recurrence was observed in 3 patients, regional failure in 3, distant metastasis in 3, and six patients died; 88.2% (30/34) of the patient maintained local control, 82.4% (28/34) survived, and 76.5% (26/34) survived with no evidence of tumor. Acute complications were minor and few. The overall incidence of late complication was 20.6% (7/34), and severe complication was 14.7% (5/34), after re-irradiation with 3-D CRT. Conclusion: 3-D CRT is safety and effectiveness for most of the patients with locally recurrent NPC. Our preliminary results indicate a high local control rate and a low complication rate. The long-term curative effect and sequelae await further study. 展开更多
关键词 Nasopharyngeal neoplasms RADIOTHERAPY local failure 3-d conformal
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Exponential Convergence Theory of the Multipole and Local Expansions for the 3-D Laplace Equation in Layered Media
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作者 Wenzhong Zhang Bo Wang Wei Cai 《Annals of Applied Mathematics》 2023年第2期99-148,共50页
In this paper,we establish the exponential convergence theory for the multipole and local expansions,shifting and translation operators for the Green's function of 3-dimensional Laplace equation in layered media.A... In this paper,we establish the exponential convergence theory for the multipole and local expansions,shifting and translation operators for the Green's function of 3-dimensional Laplace equation in layered media.An immediate application of the theory is to ensure the exponential convergence of the FMM which has been shown by the numerical results reported in[27].As the Green's function in layered media consists of free space and reaction field components and the theory for the free space components is well known,this paper will focus on the analysis for the reaction components.We first prove that the density functions in the integral representations of the reaction components are analytic and bounded in the right half complex wave number plane.Then,by using the Cagniard-de Hoop transform and contour deformations,estimates for the remainder terms of the truncated expansions are given,and,as a result,the exponential convergence for the expansions and translation operators is proven. 展开更多
关键词 Fast multipole method layered media multipole expansions local expansions 3-d Laplace equation Cagniard–de Hoop transform equivalent polarization sources
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Deep seismic sounding investigation into the deep structure of the magma system in Changbaishan-Tianchi volcanic region 被引量:6
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作者 张先康 张成科 +7 位作者 赵金仁 杨卓欣 李松林 张建狮 刘宝峰 成双喜 孙国伟 潘素珍 《Acta Seismologica Sinica(English Edition)》 CSCD 2002年第2期143-151,共9页
The magma system of Changbaishan-Tianchi Volcanic region is studied with three-dimensional deep seismic sounding (DSS) technique. The results show that the magma system of Changbaishan-Tianchi volcanic region, mainly ... The magma system of Changbaishan-Tianchi Volcanic region is studied with three-dimensional deep seismic sounding (DSS) technique. The results show that the magma system of Changbaishan-Tianchi volcanic region, mainly characterized by low velocity of P wave, can be divided into three parts in terms of depth. At the depth range of 9-15 km, the distribution of the magma system is characterized by extensiveness, large scale and near-SN orientation. This layer is the major place for magma storage. From the depth of 15 km down to the lower crust, it is characterized by small lateral scale, which indicates the 'trace' of magma intrusion from the upper mantle into the crust and also implies that the magma system most probably extends to the upper mantle, or even deeper.(less than 8-9 km deep), the range of magma distribution is even smaller, centering on an SN-oriented area just north of the Tianchi crater. If low velocity of P wave is related to the magma system, it then reflects that the magma here is still in a state of relatively high temperature. In this sense, the magma system of Changbaishan-Tianchi volcanic region is at least not 'remains', in other words, it is in an 'active' state. 展开更多
关键词 Changbaishan-Tianchi volcanic region 3-d deep seismic sounding magma system
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Atmospheric Pressure-Aware Seamless 3-D Localization and Navigation for Mobile Internet Devices
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作者 Nengqiang He Jinhai Huo +3 位作者 Yuhan Dong Yipeng Li Yang Yu Yong Ren 《Tsinghua Science and Technology》 EI CAS 2012年第2期172-178,共7页
This paper describes a seamless three-dimensional (3-D) localization and navigation system for smartphones. The smartphone includes an atmospheric pressure sensor to measure the user's altitude that is combined wit... This paper describes a seamless three-dimensional (3-D) localization and navigation system for smartphones. The smartphone includes an atmospheric pressure sensor to measure the user's altitude that is combined with the outdoor Global Positioning System (GPS) and indoor WiFi-APs localization systems in a seamless 3-D localization system. The smartphone software also provides seamless navigation services by updating map information for both indoor and outdoor locations through the mobile Internet. The indoor floor information calculated from the altitude information is used to project localization anchor nodes, e.g., WiFi-AP, on different floors onto the user's floor with an indoor 3-D localization algorithm using projection distances based on a Received Signal Strength (RSS) algorithm. Tests show that the 3-D method reduces systematic errors and achieves much higher accuracy than the traditional two-dimensional localization method. 展开更多
关键词 3-d localization and navigation atmospheric pressure mobile smartphone mobile Internet
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Numerical analysis of 3-D sound propagation in lined ducts with circumferential mode sound sources at inlet
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作者 ZHU Zhichi and WU Jinlong( Tsinghua University ) 《Chinese Journal of Acoustics》 1991年第2期111-118,共8页
Numerical analysis of three-dimensional sound propagation in soft-soft or soft-hard circular ducts with circumferential and axial modes of sound sources at the inlet has been carried out. In this paper , the numerical... Numerical analysis of three-dimensional sound propagation in soft-soft or soft-hard circular ducts with circumferential and axial modes of sound sources at the inlet has been carried out. In this paper , the numerical method and the samples are offered and the effects of circumferential and axial modes on numerical results are discussed in detail . 展开更多
关键词 Numerical analysis of 3-d sound propagation in lined ducts with circumferential mode sound sources at inlet MODE
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基于奥米亚寄生蝇的三维声定位MEMS器件设计 被引量:4
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作者 王瑞荣 《电子器件》 CAS 北大核心 2014年第2期171-176,共6页
为进一步减小声定位器件尺寸、提高测量精度,我们提出了一种微型仿生三维声定位传感器,利用MALAB对该听觉模型进行了分析,结合ANSYS进行了器件的设计与仿真。仿真结果表明:该传感器很好的实现了耦合放大机制,对于244 Hz的声波,入射角度... 为进一步减小声定位器件尺寸、提高测量精度,我们提出了一种微型仿生三维声定位传感器,利用MALAB对该听觉模型进行了分析,结合ANSYS进行了器件的设计与仿真。仿真结果表明:该传感器很好的实现了耦合放大机制,对于244 Hz的声波,入射角度在XZ平面内从90゜变化至0゜时,振幅值比从1变化至3.11,时延从0变化至45μs,YZ平面内,振幅值比从1变化至2.85,时延从0变化至43μs。 展开更多
关键词 微型传感器 三维声定位 奥米亚寄生蝇 有限元分析
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基于波束形成的三维传声器阵列仿真 被引量:1
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作者 崔丽兰 田杨萌 +2 位作者 王彩霞 刘琳 张潇艺 《科学技术与工程》 北大核心 2022年第31期13801-13809,共9页
为研究基于传声器阵列的声源定位技术在户外环境下实现全方位、高效、便捷的声源信号定位,通过使用波束形成声源定位算法,在考虑传声器阵列的拓扑结构特性下,对各个三维阵列进行声源定位数值仿真。为验证不同阵列的传声器阵列定位效果,... 为研究基于传声器阵列的声源定位技术在户外环境下实现全方位、高效、便捷的声源信号定位,通过使用波束形成声源定位算法,在考虑传声器阵列的拓扑结构特性下,对各个三维阵列进行声源定位数值仿真。为验证不同阵列的传声器阵列定位效果,基于波束形成算法使用MATLAB对相同阵元数不同分布阵型的三维传声器阵列声源定位进行仿真。结果表明:相同阵元数不同分布阵型的三维传声器阵列定位声源点的定位精度存在不同的差异,且基于波束形成的三维旋排球阵列传声器阵列在全方位声源定位中结果精确度最高。可见设计传声器阵列时,应该要充分考虑到阵元个数、阵列孔径的大小及阵元间距对阵列声源定位的影响。 展开更多
关键词 波束形成算法 传声器阵列 声源定位 三维阵列 栅瓣
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A new navigation approach of terrain contour matching based on 3-D terrain reconstruction from onboard image sequence 被引量:5
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作者 LI LiChun1,2,YU QiFeng2,SHANG Yang2,YUAN Yun2,LU HongWei3 & LIU XiaoLin4 1 Beijing Aerospace Control Center,Beijing 100094,China 2 College of Aerospace and Material Engineering,National University of Defense Technology,Changsha 410073,China +1 位作者 3 Equipment Research Institute of PLA’s Second Artillery,Beijing 100085,China 4 College of Mechatronic Engineering and Automation,National University of Defense Technology,Changsha 410073,China 《Science China(Technological Sciences)》 SCIE EI CAS 2010年第5期1176-1183,共8页
This article presents a passive navigation method of terrain contour matching by reconstructing the 3-D terrain from the image sequence(acquired by the onboard camera).To achieve automation and simultaneity of the ima... This article presents a passive navigation method of terrain contour matching by reconstructing the 3-D terrain from the image sequence(acquired by the onboard camera).To achieve automation and simultaneity of the image sequence processing for navigation,a correspondence registration method based on control points tracking is proposed which tracks the sparse control points through the whole image sequence and uses them as correspondence in the relation geometry solution.Besides,a key frame selection method based on the images overlapping ratio and intersecting angles is explored,thereafter the requirement for the camera system configuration is provided.The proposed method also includes an optimal local homography estimating algorithm according to the control points,which helps correctly predict points to be matched and their speed corresponding.Consequently,the real-time 3-D terrain of the trajectory thus reconstructed is matched with the referenced terrain map,and the result of which provides navigating information.The digital simulation experiment and the real image based experiment have verified the proposed method. 展开更多
关键词 TERRAIN CONTOUR matching VISION-BASED NAVIGATION 3-d reconstruction control points key frame registration optimal local HOMOGRAPHY
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Sound image externalization for headphone based real-time 3D audio
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作者 Yougen YUAN Lei XIE +2 位作者 Zhong-Hua FU Ming XU Qi CONG 《Frontiers of Computer Science》 SCIE EI CSCD 2017年第3期419-428,共10页
3D audio effects can provide immersive auditory experience, but we often face the so-called in-head localization (IHL) problem in headphone sound reproduction. To ad- dress this problem, we propose an effective soun... 3D audio effects can provide immersive auditory experience, but we often face the so-called in-head localization (IHL) problem in headphone sound reproduction. To ad- dress this problem, we propose an effective sound image externalization approach. Specifically, we consider several important factors related to sound propagation, which include image-source model based early reflections with distance decay, wall absorption and air absorption, late reverberation and other dynamic factors like head movement. We apply our sound image externalization approach to a headphone based real-time 3D audio system. Subjective listening tests show that the sound image externalization performance is significantly improved and the sound source direction is preserved as well. A/B preference test further shows that, as compared with a recent popular approach, the proposed approach is mostly preferred by the listeners. 展开更多
关键词 3D audio in-head localization (IHL) headphone reproduction sound image externalization REFLECTIONS
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