312 research outputs found

    Active noise control in a three-dimensional space

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    In this research, a new approach is presented for optimizing the performance of active noise control in three-dimensional space. The work focuses on the critical role of determining the locations for secondary sources in active noise suppression. A systematic technique is proposed for estimating optimal locations of secondary sources on the boundary of a three-dimensional domain for both local and global active control of harmonic sound fields. The theoretical foundation of this work is Huygen\u27s principle. The indirect boundary element method (IBEM) which is a numerical implementation of Huygen\u27s principle is employed as a basis for the numerical analysis. The fictitious source distribution used to represent the boundary in the indirect boundary element method is the focus of this investigation. Using numerical predictions of the fictitious source strength distribution on the boundary, it is found that the optimal locations for secondary sources are the boundary node locations with high fictitious source strengths. The strengths of the secondary sources, normal velocities in this research, can then be optimized using a minimum squared pressure criterion at selected observation points;Examples are presented to verify both the validity of the computer implementation and the conception of this approach. These examples include active cancellation of an interior sound field with rigid wall boundary conditions and normal acoustic impedance boundary conditions, as well as reduction of sound radiation. Selected numerical predictions are compared with published experimental results and numerical predictions obtained by other researchers using alternative numerical techniques. Numerical predictions using the proposed method are found to be impressive and promising. The results demonstrate that significant attenuation can be achieved by locating secondary sources using the method presented in this work. It can be concluded from these results that the fictitious source strength on the boundary of the domain provides a powerful method for estimating optimal locations for secondary sources in active cancellation of three-dimensional sound fields. The results also suggest promising potential applications of the approach in active control design for vehicle and aircraft passenger compartment. A particularly useful feature of the approach in the design of active noise control systems is that the fictitious source distribution for a given situation is determined as an intermediate step in characterizing the primary sound field. The proposed process for source location is thus computationally efficient because it builds directly upon other essential intermediate results

    VIRTUAL RECONSTRUCTION KINEMATICS ON THE START ACTION OF ELITE MALE SHORT TRACK SPEED SKATERS UNDER NEW RULES:A COMPARISON ANALYSIS

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    The gradual improvement of athletic performance and ability of sports has put forward higher requirements for the scientific level of training, among which the simulation of athlete \u27s action is an important research method and means.Short track speed skating has always been a traditional advantage project of our country. In the 500m competition of short track speed skating, occupy a good position in the starting phase has an important influence on the whole process of the competition,which can make the athlete enter the corner in advance and thus successfully complete the acceleration phase.The International Skating Union (ISU)changed the rules of start action,and various starting actions emerged.The athlete of National Short Track Speed Skating Team named Wu Dajing(Champion of Men’s 500m in 2016/17 Season)changed his technique of start action, he is the only one who use lateral type start action in National Team.This paper uses the three-dimensional video analysis method to analyze the kinematics parameters of start action of Wu Dajing and Canadian athlete Charles Hamelin (who has been using the lateral starting action) at the 500m competition of 2016/17 ISU World Cup in Shanghai. Indicating that technical parameter of the start action of Wu Dajing (center of gravity, trunk angle, pedal ice angle, lower limb joint angle, etc.) are better than Charles, the pedal effect is better than Charles, which shows that he has a good learning ability of the new technology , it is recommended in the training he should focus on improving the stability of start action

    Case Report -Acupuncture Treatment for Hypothyroidism

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    The main purpose of doing this work is to show the most effective acupoints used in the acupuncture treatment of hypothyroidism in our practice and the results after the treatment

    STUDIES ON THE KINEMATICS OF CHINESE ELITE MAN HAMMER ATHLETE THROWING TECHNOLOGY

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    The purpose of this study is to provide the theoretical basis for the teaching and training of the hammer throwing and improve Chinese man hammer to reach world-class as soon as possible.This paper made a 3D camera resolution on the top three men's hammer throwers in 2012 China Long Throw Open (Shizhu Wang, kun Guo and xiao Feng). With the comparative analysis on the related kinematic parameters of the world elite men's hammer throwers, it presents the main problems and gaps in China men's hammer throwers motion technology

    KINEMATIC ANALYSIS OF BASKET WITH 1/2 TURN TO HANDSTAND OF HAIBIN TENG ON PARALLEL BARS

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    The basket with 1/2 turn to handstand has become a powerful weapon of world famous competition for the gold medal of parallel bars. Therefore, we make movement analysis on Haibin Teng, who won the champion in Athens Olympic, over the movement in qualification trial, and obtained kinematics references, which provides theoretical and technical basis for the development and improvement of the skill of Chinese athletes

    KINEMATIC ANALYSIS OF LI YA SALTO CONNECTING STRADDLED JAEGER SALTO ON THE UNEVEN BARS

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    He Kexin, called the “UB princess”, is the only individual event grand slam winner on uneven bars of the Chinese Women's Gymnastics Team. Her special skill “Straddled Jaeger Salto with a 1/2 Turn to re-grasp HB (also called Li Ya Salto) connecting the Straddled Jaeger Salto” was videotaped and 3-D analyzed. The conclusive kinematic characteristics of this high skilled element can provide useful information for the technical training of coaches and athletes, and enrich gymnastic theories

    KINEMATICS ANALYSIS ON HANDSPRING SIDEWAYS STRETCHED SIDEWARD SOMERSAULT WITH 1 3/4 TURNS IN HORSE-VAULTING OF ZEPENG LUO

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    By using the 3D video analysis method, we have tested on the handspring sideways stretched side-ward somersault with 1 3/4 turns in Horse-vaulting (also known as Kasamatsu 360°) of Chinese elite athletes Zepeng Luo at the game site; obtain the relevant kinematics’ parameters through analysis on the complete movement. The results show that: Zepeng Luo completed this action with high quality and advanced technology, but at the first flight, his legs were not fully close together

    WEIGHT LIFTING TECHNOLOGY BIOMECHANICS RAPID FEED BACK SYSTEM STUDY

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    Weightlifting is one of the important part of the Olympic. For a variety of reasons, the coach is by observation and experience qualitative methods on, the athletes technical action guide to further reveal the characteristics of technical action. The hope to be able to the test the qualitative and quantitative test of real combination more looking forward to the kinematics and dynamics of the key indicators. So after consulting a large number of literature and coaches discussion, we make the sports biomechanics research weight lifting technology rapid diagnosis system, the use of 3rd load station acquisition lower limb legal date, combining synchronous acquisition. Barbell center kinematics parameters to rapid analysis weightlifting action techniques. Help improve weightlifting athletes technical effect

    STUDY ON KNEE JOINT ISOKINETIC STRENGTH OF MALE VOLLEYBALLPLAYERS

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    The purpose of this study is to measure the knee joint mechanics of eight elite volleyball players using isokinetic system and to discuss the possible diagnosis of injury risk of the results. Isokinetic-concentric contraction peak torque of the knee flexors and extensors decreased when angular velocity increased. With the same angular velocity, extension peak torque became higher than flexion peak torque. There was also a significant difference between the left and right knees in each flexion and extension peak torques. As the angular velocity increased, the flexion to extension peak torque ratios decreased; at the same time, average power increased while the work done decreased. The extensors showed greater work done than the flexors. The knee torque curves could be used as evidence for diagnosis of possible knee injury risks among volleyball players

    KINEMATIC ANALYSIS ON SERVE TECHNIQUE OF WORLD’S ELITE FEMALE TENNIS PLAYER

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    The purpose of this study was to obtain the kinematic parameters on serve technique of WTA (Women's Tennis Association) top two Serena Williams and Simona Halep. The study selected WTA top two players’ first serve in 2014 China Open, which was held in Beijing, China. This paper makes analysis on serve technique between two elite players through the method of three-dimensional video analysis. The kinematic technical feature has been obtained through this study, resulting in not only providing referential statistics for the technical training of the players, but also enriching the technical theory of tennis
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