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836 results on '"Yang, Jiashi"'

164. Switching considerations to combat spectral pollution in TDMA for satellite broadcasting

Author

Qi, Yusheng, Wu, Gene, Yang, Jiashi, and Feher, Kamilo

Subjects
Digital communications -- Research, Switching theory -- Research, Time division multiplexing -- Research, Business, Electronics, Mass communications
Abstract

A better switching technique to combat spectral pollution, i.e., spectral spreading of burst TDMA digital FM and Pi/4-QPSK systems is proposed. The effects of rectangular, linear and raised cosine ramp on/off switching are examined on two prototypes both in hardware experimental methods and computer simulation for different gating rates, duty cycles, roll-off factors of transmitter filter and ramp on/off times. The measured results agree with the computer simulation and indicate that the adjacent channel interference (ACI) caused by the burst operating in TDMA Pi/4-QPSK is significantly reduced by raised cosine switching in comparison with other switchings. Raised cosine switching is a promising method to improve the spectral pollution performance.

Published
1993

174. An improved pi/4-QPSK with nonredundant error correction for satellite mobile broadcasting

Author

Feher, Kamilo and Yang, Jiashi

Subjects
Communications And Radar
Abstract

An improved pi/4-quadrature phase-shift keying (QPSK) receiver that incorporates a simple nonredundant error correction (NEC) structure is proposed for satellite and land-mobile digital broadcasting. The bit-error-rate (BER) performance of the pi/4-QPSK with NEC is analyzed and evaluated in a fast Rician fading and additive white Gaussian noise (AWGN) environment using computer simulation. It is demonstrated that with simple electronics the performance of a noncoherently detected pi/4-QPSK signal in both AWGN and fast Rician fading can be improved. When the K-factor (a ratio of average power of multipath signal to direct path power) of the Rician channel decreases, the improvement increases. An improvement of 1.2 dB could be obtained at a BER of 0.0001 in the AWGN channel. This performance gain is achieved without requiring any signal redundancy and additional bandwidth. Three types of noncoherent detection schemes of pi/4-QPSK with NEC structure, such as IF band differential detection, baseband differential detection, and FM discriminator, are discussed. It is concluded that the pi/4-QPSK with NEC is an attractive scheme for power-limited satellite land-mobile broadcasting systems.

Published
1991
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175. Flexural vibration of a lithium niobate piezoelectric plate with a ferroelectric inversion layer.

Author

Huang, Dejin and Yang, Jiashi

Subjects
*LITHIUM niobate, *LAMB waves, *EQUATIONS of motion, *IRON & steel plates, *ORTHOTROPIC plates, *ELECTRIC fields
Abstract

Two-dimensional equations for flexural motions of a lithium niobate piezoelectric plate are derived from three-dimensional equations. The plate has a ferroelectric inversion layer where the piezoelectric constants reverse signs. The equations show an unconventional behavior that a uniform electric field along the plate thickness can produce bending. This offers many possibilities for new designs of devices. Waves in unbounded plates are examined for the accuracy of the equations. A piezoelectric energy harvester based on such a plate is analyzed as an example of the application of the equations derived in vibrations of finite plates. [ABSTRACT FROM AUTHOR]

Published
2020
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188. Thickness-stretch vibration of a crystal plate carrying a micro-rod array

Author

Yang Jiashi, Wang Ji, and Liu Nan

Subjects
Surface (mathematics), Materials science, genetic structures, General Physics and Astronomy, Bending of plates, Fundamental frequency, Rod, Physics::Fluid Dynamics, Crystal, Vibration, Plate theory, sense organs, Composite material, Anisotropy
Abstract

We analyze thickness-stretch vibrations of a plate of hexagonal crystal carrying an array of micro-rods with their bottoms fixed to the top surface of the plate.The rods undergo longitudinal vibrations when the crystal plate is in thickness-stretch motion.The plate is modeled by the theory of anisotropic elasticity.The rods are modeled by the one-dimensional structural theory for extensional vibration of rods.A frequency equation is obtained and solved using perturbation method.The effect of the rod array on the resonant frequencies of the crystal plate is examined.The results are potentially useful for using thickness-stretch modes of crystal plates to measure the mechanical properties of microrod arrays.

Published
2012

196. An exact analysis of forced thickness-twist vibrations of multi-layered piezoelectric plates

Author

Yang Jiashi, Chen Ziguang, Hu Yuantai, and Hu Hongping

Subjects
Physics, Piezoelectric coefficient, business.industry, Piezoelectric sensor, Mechanical Engineering, Computational Mechanics, Structural engineering, Piezoelectricity, Computer Science::Other, law.invention, Vibration, Condensed Matter::Materials Science, Resonator, Exact solutions in general relativity, Computer Science::Sound, Mechanics of Materials, law, PMUT, Composite material, business, Transformer
Abstract

This paper deals with the thickness-twist vibration of a multi-layered rectangular piezoelectric plate of crystals of 6 mm symmetry or polarized ceramics. An exact solution is obtained from the three-dimensional equations of linear piezoelectricity. The solution is useful to the understanding and design of composite piezoelectric devices. A piezoelectric resonator, a piezoelectric transformer, and a piezoelectric generator are analyzed as examples.

Published
2007

197. Electrically forced vibration of a thickness-twist mode piezoelectric resonator with non-uniform electrodes

Author

Yang Jiashi, Hu Hongping, and Chen Ziguang

Subjects
Materials science, Physics::Instrumentation and Detectors, Mechanical Engineering, Computational Mechanics, Mode (statistics), Piezoelectricity, Symmetry (physics), Vibration, Resonator, Physics::Plasma Physics, Mechanics of Materials, Normal mode, Control theory, Electrode, Twist, Composite material
Abstract

We study the effect of electrodes with varying thickness on thickness-twist vibration of a piezoelectric plate resonator of crystals of 6 mm symmetry. An exact theoretical analysis is performed. Results show that non-uniform electrodes have a strong effect on mode shapes, and suggest the possibility of using nonuniform electrodes for strong energy trapping.

Published
2007

200. Two-dimensional equations for electroelastic plates with relatively large shear deformations

Author

Yang, Jiashi, yang, Xiaomeng, Turner, Joseph A., Kosinski, John A., and Pastore, Robert A.

Subjects
Ultrasonics -- Research, Piezoelectric devices -- Research, Business, Electronics, Electronics and electrical industries
Abstract

Two-dimensional nonlinear equations for electroelastic plates in large thickness-shear deformations are described and discussed.

Published
2003

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