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Search Results: 1 - 10 of 520 matches for " Chunhua "
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Experiment Teaching Innovation of the Course Computer Hardware Fundamentals  [PDF]
Chunhua Fang, Zhendi Wu
Open Journal of Social Sciences (JSS) , 2014, DOI: 10.4236/jss.2014.25007
Abstract: The course Computer Hardware Fundamentals to non-electrical engineering students aims to teach the basic principles and applications of microcomputers so that the students could use computers to solve practical problems in professional or related fields. The teachers have to face the fact that the current experiment teaching cannot meet the demand of students because of less class hour. Based on the analysis of a questionnaire which focuses on the students’ expectation of the experiments as well as the problems existing in the current experiments, a new general elective experimental course “Computer hardware Technology Fundamental Application Experiments” is put forward, and some innovative experiment teaching content and methods are introduced in this paper.
Finite Element Analysis on a Square Canister Piezoelectric Energy Harvester in Asphalt Pavement  [PDF]
Hongbing Wang, Chunhua Sun
World Journal of Engineering and Technology (WJET) , 2016, DOI: 10.4236/wjet.2016.42035
Abstract: A novel square canister piezoelectric energy harvester was proposed for harvesting energy from asphalt pavement. The square of the harvester was of great advantage to compose the harvester array for harvesting energy from the asphalt pavement in a large scale. The open circuit voltage of the harvester was obtained by the piezoelectric constant d33 of the piezoelectric ceramic. The harvester is different from the cymbal harvester which works by the piezoelectric constant d31. The finite element model of the single harvester was constructed. The open circuit voltage increased with increase of the outer load. The finite element model of the single harvester buried in the asphalt pavement was built. The open circuit voltage, the deformation difference percent and the stress of the ceramic of the harvester were obtained with different buried depth. The open circuit voltage decreased when the buried depth was increased. The proper buried depth of the harvester should be selected as 30 - 50 mm. The effects of structure parameters on the open circuit voltage were gotten. The output voltage about 64.442 V could be obtained from a single harvester buried under 40 mm pavement at the vehicle load of 0.7 MPa. 0.047 mJ electric energy could be gotten in the harvester. The output power was about 0.705 mW at 15 Hz vehicle load frequency.
Finite Element Analysis and Test of an Ultrasonic Compound Horn  [PDF]
Hongbing Wang, Chunhua Sun
World Journal of Engineering and Technology (WJET) , 2017, DOI: 10.4236/wjet.2017.53029
Abstract: An?ultrasonic compound horn is designed and manufactured, and the horn is analyzed by wave equation, finite element method and test. The modal frequencies and frequencies of the first and second longitudinal vibration of the horn are obtained by the finite element analysis. The horn is made and modal testing is carried out. The modal frequencies of the first and second longitudinal vibration are obtained respectively. The test results are in good agreement with the theoretical calculation. Experimental results show the maximum amplitude of the horn can reach 9?nm with applied excitation voltage of amplitude 7?V and frequency 21,450?Hz, when the amplitude of voltage increases?to 80?V, the horn of maximum amplitude reaches?23 μm. The maximum amplitude of the horn is approximately proportional to the amplitude of excitation voltage. The horn has the characteristics of high sensitivity and large amplitude, and can be used in ultrasonic machining and other fields.
Research Status of Wind Energy Piezoelectric Generator  [PDF]
Chunhua Sun, Guangqing Shang
Energy and Power Engineering (EPE) , 2018, DOI: 10.4236/epe.2018.1012031
Abstract: It is of great significance for developing self-powered micro-devices to explore the research of piezoelectric effect in conversion of wind energy into electricity. Based on the different excitation modes, the existing wind energy piezoelectric generators are firstly classified. The research status of wind piezoelectric generators is further analyzed, and characteristics of various types of wind energy piezoelectric generators are summarized. Finally, the future research direction and emphasis of wind energy piezoelectric generators is proposed to carry out its miniaturization, lightweight and integration.
Research Status and Development Direction of Piezoelectric Wind Energy Harvesting Technology  [PDF]
Hongbing Wang, Chunhua Sun
Journal of Power and Energy Engineering (JPEE) , 2019, DOI: 10.4236/jpee.2019.73001
Abstract: In recent years, with the rapid development of large-scale distributed wireless sensor systems and micro-power devices, the disadvantages of traditional chemical battery power supply mode are becoming more and more obvious. Piezoelectric energy collector has attracted wide attention because of its simple structure, no heating, no electromagnetic interference, environmental protection and easy miniaturization. Wind energy is a reproducible resource. Wind energy harvester based on piezoelectric intelligent material can be named piezoelectric wind energy harvesting which converts wind energy into electric power and will have great application prospect. To promote the development of piezoelectric wind energy harvesting technology, research statuses on piezoelectric wind energy harvesting technology are reviewed. The existing problem and development direction about piezoelectric wind energy harvester in the future are discussed. The study will be helpful for researchers engaged in piezoelectric wind energy harvesting.
Time Delay Induced Oscillation: An Example on a Class of n Coupled Van Der Pol Oscillators Model with Delays  [PDF]
Chunhua Feng, Carl S. Pettis
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.36087
Abstract: In this paper, a class of n coupled van der Pol oscillator model with delays is considered. By employing an analysis approach, some sufficient conditions to guarantee the existence of stability and oscillations for themodel are obtained. Examples are provided to demonstrate the results.
Oscillatory Behavior of a Network Epidemic SIS Model with Nonlinear Infectivity  [PDF]
Chunhua Feng, Carl S. Pettis
Applied Mathematics (AM) , 2014, DOI: 10.4236/am.2014.51021
Abstract:

In this paper, an epidemic SIS model with nonlinear infectivity on heterogeneous networks and time delays is investigated. The oscillatory behavior of the solutions is studied. Two sufficient conditions are provided to guarantee the oscillatory behavior for the solutions. Some computer simulations are demonstrated.

A Preconditioned Method for Rotating Flows at Arbitrary Mach Number
Chunhua Sheng
Modelling and Simulation in Engineering , 2011, DOI: 10.1155/2011/537464
Abstract: An improved preconditioning is proposed for viscous flow computations in rotating and nonrotating frames at arbitrary Mach numbers. The key to the current method is the use of both free stream Mach number and rotating Mach number to construct a preconditioning matrix, which is applied to the compressible governing equations written in terms of primitive variables. A Fourier analysis is conducted that reveals the efficacy of the modified preconditioning. Numerical approximations for the convective and diffusive fluxes are detailed based on the preconditioned system of equations. A set of boundary conditions using characteristic variables are described for internal and external flow computations. Numerical validations are performed on four realistic viscous flows in both fixed and rotating frames. The results indicated that the modified preconditioning has a superior performance compared to the original method to predict flows from extremely low to supersonic Mach numbers.
CRMS: An Algorithm of Classification Rule Mining Based on Multiple Supports
Chunhua Ju
Computer and Information Science , 2009, DOI: 10.5539/cis.v2n2p131
Abstract: The paper presents an algorithm CRMS of classification rule mining based on multi-support, in which the frequent classification item-set tree is adopted to organize the frequent pattern sets, and array to figure the classification projected transaction subsets. The multi-support method is applied in CRMS due to the unevenly distributed classification patterns. The CRMS uses the breath first strategy assisted by the depth first strategy, and adopts pseudo projection, which makes it unnecessary to scan the database and construct the projected transaction subsets repeatedly, therefore the memory and time cost is very low, and the projecting-efficiency and scalability are higher. The CRMS algorithm can be used in the basket analysis, association rule mining for consumption behavior in the retailing industry, which supports the product layout, buying recommendation and the sale promotion.
A Fluctuation Limit Theorem of Branching Processes with Immigration and Statistical Applications
Chunhua Ma
Mathematics , 2009,
Abstract: We prove a general fluctuation limit theorem for Galton-Watson branching processes with immigration. The limit is a time-inhomogeneous OU type process driven by a spectrally positive Levy process. As applications of this result, we obtain some asymptotic estimates for the conditional least-squares estimator of the offspring means and variances of the offspring and immigration distributions.
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