检索结果-内蒙古大学图书馆

作者： Xu, Zexiang Wu, Hsiang-Tao Wang, Lvdi Zheng, Changxi Tong, Xin Qi, Yue State Key Lab. of Virtual Reality Technology and Systems Beihang University China Microsoft Research United States Columbia University United States

(Figure Presented) Dynamic hair strands have complex structures and experience intricate collisions and occlusion, posing significant challenges for high-quality reconstruction of their motions. We present a comprehensive dynamic hair capture system for reconstructing realistic hair motions from multiple synchronized video sequences. To recover hair strands' temporal correspondence, we propose a motion-path analysis algorithm that can robustly track local hair motions in input videos. To ensure the spatial and temporal coherence of the dynamic capture, we formulate the global hair reconstruction as a spacetime optimization problem solved iteratively. Demonstrated using a range of real-world hairstyles driven by different wind conditions and head motions, our approach is able to reconstruct complex hair dynamics matching closely with video recordings both in terms of geometry and motion details. Copyright © ACM.

关键词： Video recording

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The effect of anatomic variations of circle of Willis on cerebral blood distribution during posture change from supination to standing: A model study

The effect of anatomic variations of circle of Willis on cer...

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作者： Zhang, Chi Li, Shuyu Pu, Fang Fan, Yubo Li, Deyu Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education School of Biological Science and Medical Engineering Beihang University No. 37 Xueyuan Road Beijing100191 China State Key Lab of Virtual Reality of Technology and Systems Beihang University Beijing100191 China

The anatomic variation of Circle of Willis (CoW) has great impact on its compensatory capacity during stroke and cerebral ischemia. In the present study, a series of lumped parameter models were developed and used to simulate the effect of postural changes on the cerebral blood flow in ICA stenosis patients with different anatomic variants of the CoW. The results showed that the asymmetric distribution of cerebral blood flow caused by stenosis was attenuated in standing position in complete and half-complete CoW. However, in incomplete CoW, the decrease in blood flow in the ipsilateral cerebral arteries caused by unilateral ICA stenosis was dramatic in both supine and standing positions, a likely result of inadequate collateral circulation within the CoW. In conclusion, the anatomic variation of CoW plays a significant role in maintaining the balance of cerebral blood supply in patients with ICA stenosis, especially during postural change. © 2014 - IOS Press and the authors.

关键词： Blood

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Multiple-echo suppression modeling and experimental verification for acoustic transmission along periodic drillstring using dual receivers

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Shock and Vibration 2014年第1期2014卷

作者： Cheng, Li Jinfeng, Chang Zhao, Liu Shangchun, Fan State Key Laboratory of Virtual Reality Technology and System Beihang University Beijing100191 China Science and Technology on Inertial Laboratory Beihang University Beijing100191 China

In the oil industry, the accompanied reverberation is a major constraint in the transmission rate and distance because the drillstring is a heterogeneous assembly. Based on the transient impulse responses in uplink and downlink channels, an improved simplified echo suppression model with two acoustic receivers is presented in consideration of position optimization of single acoustic receiver. Then the acoustic receiving characteristics of transmitted signals in a length-limited periodic drillstring channel are obtained in single- and dual-receiver modes. An additive downward white Gaussian noise is also introduced in the channel. Moreover, an experimental rig is established by using a rotatable electromagnetic vibration exciter and two piezoelectric accelerometers, which are spaced one-quarter wavelength apart along a 6.3-meter simulated periodic drillstring. The ASK-, FSK-, and PSK-modulated square-wave pulse sequences at a transmission rate of 200 bit/s are applied to the simulated drillstring at a rotation speed of 0, 80, and 140 r/min, respectively. The experimental results show that the dual-receiver mode can exhibit a significantly improved average error bit ratio, which is approximately 2.5 to 3 times lower than that of the single-receiver mode, especially under the conditions of higher rotation speeds. © 2014 Li Cheng et al.

关键词： Acoustic receivers

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Verbally Assisting virtual-Environment Tactile Maps: A cross-linguistic and cross-cultural study

Advances in Intelligent Systems and Computing

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Advances in Intelligent systems and Computing 2014年 215卷 821-831页

作者： Lohmann, Kris Yu, Junlei Kerzel, Matthias Wang, Dangxiao Habel, Christopher Department of Informatics University of Hamburg Hamburg Germany State Key Lab of Virtual Reality Technology and Systems Beihang University Beijing China

The Verbally Assisting virtual-Environment Tactile Maps (VAVETaM) approach proposes to increase the effectiveness of tactile maps by realizing an intelligent multi-modal tactile map system that generates assisting utterances that generates assisting utterances acquiring survey knowledge from virtual tactile maps. Two experiments in German conducted with blindfolded sighted people and with blind and visually impaired people show that both types of participants benefit from verbal assistance. In this paper, we report an experiment testing the adaptation of the German prototype to be useable by Chinese native speakers. This study shows that the VAVETaM system can be adapted to Chinese language with comparable small effort. The Chinese participants' achievement in acquiring survey knowledge is comparable to those of the participants in the German study. This supports the view that human processing of representationally multi-modal information is comparable between different cultures and languages. © Springer-Verlag Berlin Heidelberg 2014.

关键词： Mergers and acquisitions

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Research on Garment Seam Simulation Method Based on Spring-Mass Model

Research on Garment Seam Simulation Method Based on Spring-M...

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2014年国际计算机科学与软件工程学术会议

作者： Yuan-Wei CHEN Bing HE Ran HU State Key Lab of Virtual Reality Technology and Systems Beihang University Xueyuan Road No.37Haidian DistrictBeijing CityChina

Garments are made by stitching cloth together which are cut as per the designed *** stitching method of seams has great influence on garment style and *** not only influences such cloth characteristics as bending rigidity,but also the formation and display of wrinkle at corresponding *** the influence of seam is taken into consideration in the modelbuilding in this *** article has made a detailed introduction about using mass-spring model to construct a seam model which can be inserted into the basic garment mass-spring model to emulate on a whole and simulate the wavy wrinkle effect at the seam.

关键词： Seam Simulation Cloth Simulation Mass-Spring Graphics Wrinkle Simulation

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3D path planning of a laser manipulation robotic system for tooth preparing

3D path planning of a laser manipulation robotic system for ...

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IEEE International Conference on Robotics and Automation (ICRA)

作者： Lei Ma Dangxiao Wang Yuru Zhang Lei Wang Peijun Lv Yuchun Sun State Key Lab of Virtual Reality Technology and Systems Beihang University Beijing China School and Hospital of Stomatology Peking University Beijing China

In this paper, we proposed a 3D path planning method for a miniature robotic system, which can manipulate a beam of ultra-short pulse laser to cut a decayed tooth to formulate an expected 3D shape. Using high resolution STereo Lithography (STL) models of the original decayed tooth and the target preparing shape as the input, our method consists of a fast slicing algorithm and an optimized path generating algorithm, which realized a high efficient layer-by-layer cutting for laser ablation. Theoretical analysis on the geometric distortion and surface roughness was carried out to model the influence of the path planning algorithms on the accuracy of the prepared tooth. Experimental results on a real tooth indicate that the path planning method can maintain the accuracy for the laser ablation process.

关键词： Teeth Laser beam cutting Rough surfaces Surface roughness Robots Mirrors Path planning

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Transparency enhanced multirate wave variable control scheme with energy reusage

Transparency enhanced multirate wave variable control scheme...

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IEEE International Conference on Robotics and Biomimetics

作者： Yong Liu Xulong Zhang Wusheng Chou The State Key Lab of Virtual Reality Technology and Systems of China Beihang University Beijing China The Robotic Research Institute Beihang University Beijing China

ISBN: (纸本)9781479973989

This paper presents a newly designed control scheme for haptic interaction with uniform sample rate virtual environment. In most practical application in haptic interaction, we lack the knowledge about the model of the sampling rate. Unfortunately, by using the conventional wave variable method, the impedance parameter should adjust accordingly to guarantee the passivity of the interaction. Considering the inconvenient of the wave variable method, a novel scheme, named multirate wave transformation with energy reusage, is introduced. The proposed control scheme re-harvests the energy leakage caused by sampling rate by an energy observer, and an energy reservoir is formed to accumulate the re-harvested energy. Then, an energy regulator reuses the energy to passify the haptic interaction. Furthermore, we also demonstrated by analysis that the proposed control scheme can achieve a better interactive transparency by comparison with the traditional wave variable method. Finally, the effectiveness and performance of the proposed control scheme are validated with a haptic rendering experimental platform.

关键词： Haptic interfaces virtual environments Force Impedance Reservoirs Regulators Rendering (computer graphics)

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Characteristics analysis of joint acoustic echo and noise suppression in periodic drillstring waveguide

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Shock and Vibration 2014年第1期2014卷

作者： Cheng, Li Jinfeng, Chang Zhao, Liu Shangchun, Fan Tianhuai, Ding State Key Laboratory of Virtual Reality Technology and System Beihang University Beijing 100191 China Science and Technology on Inertial Laboratory Beihang University Beijing 100191 China Department of Precision Instruments and Mechanology Tsinghua University Beijing 100086 China

A new method of wireless data telemetry used by oil industry uses compressional acoustic waves to transmit downhole information from the bottom hole to the surface. Unfortunately, acoustic echoes and drilling vibration noises in periodic drillstring are a major issue in transmission performance. A combined acoustic echo and noise suppression method based on wave motion characteristic in drillstring is adopted to enhance an upward-going transmitted acoustic signal. The presented scheme consists of a primary acoustic echo canceller using an array of two accelerometers for dealing with the downward-going noises and a secondary acoustic insulation structure for restraining the upward-going vibration noises. Furthermore, the secondary acoustic insulation structure exhibits a banded and dispersive spectral structure because of periodic groove configuration. By using a finite-differential algorithm for the one-dimensional propagation of longitudinal waves, acoustic receiving characteristics of transmitted signals are simulated with additive Gaussian noise in a periodic pipe structure of limited length to investigate the effects on transmission performance optimization. The results reveal that the proposed scheme can achieve a much lower error bit ratio over a specified acoustic isolation frequency range with a 30-40 dB reduction in the average noise level compared to traditional single-receiver scheme. © 2014 Li Cheng et al.

关键词： Periodic structures

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NECAS: Near field communication system for smartphones based on visible light

NECAS: Near field communication system for smartphones based...

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IEEE Conference on Wireless Communications and Networking

作者： Jianwei Niu Wenfang Song Chuang Liu Lei Shu Canfeng Chen State Key Laboratory of Virtual Reality Technology and Systems Beihang University Beijing China Guangdong Petrochemical Equipment Fault Diagnosis Key Lab Guangdong University of Petrochemical Technology China Nokia Research Center Beijing China

ISBN: (纸本)9781479930845

A novel near field communication system for s-martphones based on visible light (NECAS) is presented in this paper. NECAS encodes information using combinations of different colors (red, green and blue) and their intensity levels of a smartphone screen, while the receiver captures the light signal via color sensors. In our scheme, a smartphone screen is segmented into four sub-blocks, and each of them can be used to encode information independently. NECAS can be used in a range of Near Field Communication applications such as contactless payments, electronic ticket checking and device paring. We design the color encoding scheme by experimentally profiling the interference of three color channels and the refresh rate of smartphones. We implement a joint decoding algorithm to deal with the significant interference among color channels. With a feedback channel, the retransmission scheme is adopted to improve communication reliability, and the system can dynamically adjust the number of combinations of different colors and intensity levels to fit the communication environment. Our design is validated via extensive experiments using a hardware implementation on Android smartphones and an Arduino platform.

关键词： Image color analysis Receivers Smart phones Sensors Bit error rate Throughput Encoding

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A moving foreground expansion method based on the gaussian distribution

A moving foreground expansion method based on the gaussian d...

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2013 IEEE International Conference on Green Computing and Communications and IEEE Internet of Things and IEEE Cyber, Physical and Social Computing, GreenCom-iThings-CPSCom 2013

作者： Li, Yanhua Li, Wei Xiang, Qi State Key Laboratory of Virtual Reality Technology and System Key Lab. of Beijing Network Technology Beihang University Beijing China

ISBN: (纸本)9780769550466

With the development of computer science, intelligent video surveillance technology has been widely used, moving target detection becomes an important part in the field of intelligent video surveillance. Moving foreground extraction, which is the first step of moving target detection, decides the accuracy of moving target detection. Traditional frame difference, background subtraction and other moving foreground extraction algorithms do get the extracted results but still have some shortcomings, such as disabilities and holes. So a moving foreground expansion method based on Gaussian distribution is proposed in this paper. This method utilizes the theory of Gaussian distribution to establish the Gaussian kernel on the boundary of the moving foreground. Next, the mean and variance of the Gaussian kernel is calculated. And then the necessary probability can be obtained with the mean and variance. At last, we can determine whether to expand according to the contrast result of the probability and the stated threshold, making the missing parts get an effective supplement and expansion. The experiments show that the method can detect moving targets more accurately due to effectively complementing the moving foreground. © 2013 IEEE.

关键词： Gaussian distribution

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