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Kai Li,Sheng Li,De-you Zhao 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.3
The visualizing energy flow and control in vibrating stiffened plates with a cutout are studied using finite element method. The vibration intensity, vibration energy and strain energy distribution of stiffened plates with cutout at different excitation frequencies are calculated respectively and visualized for the various cases. The cases of different size and boundaries conditions of cutouts are also investigated. It is found that the cutout or opening completely changes the paths and distributions of the energy flow in stiffened plate. The magnitude of energy flow is significantly larger at the edges near the cutout boundary. The position of maximum strain energy distribution is not corresponding to the position of maximum vibrational energy. Furthermore, the energy-based control using constrained damping layer (CDL) for vibration suppression is also analyzed. According to the energy distribution maps, the CDL patches are applied to the locations that have higher energy distribution at the targeted mode of vibration. The energybased CDL treatments have produced significant attenuation of the vibration energy and strain energy. The present energy visualization technique and energy-based CDL treatments can be extended to the vibration control of vehicles structures.
An Iterative Algorithm for Solving the Least-Squares Problem of Matrix Equation AXB+CYD=E
Kai-juan Shen,Chuan-hua You,Yu-xia Du 한국전산응용수학회 2008 Journal of applied mathematics & informatics Vol.26 No.5
In this paper, an iterative method is proposed to solve the least-squares problem of matrix equation AXB + CY D = E over un-known matrix pair [X, Y ]. By this iterative method, for any initial matrix pair [X1, Y1], a solution pair or the least-norm least-squares solution pair of which can be obtained within finite iterative steps in the absence of roundoff errors. In addition, we also consider the optimal approximation problem for the given matrix pair [X0, Y0] in Frobenius norm. Given numerical examples show that the algorithm is efficient. In this paper, an iterative method is proposed to solve the least-squares problem of matrix equation AXB + CY D = E over un-known matrix pair [X, Y ]. By this iterative method, for any initial matrix pair [X1, Y1], a solution pair or the least-norm least-squares solution pair of which can be obtained within finite iterative steps in the absence of roundoff errors. In addition, we also consider the optimal approximation problem for the given matrix pair [X0, Y0] in Frobenius norm. Given numerical examples show that the algorithm is efficient.
You Zhou,Liwei Xue,Kai Yi,Li Zhang,Seung Kon Ryu,Ri Guang Jin 한국탄소학회 2012 Carbon Letters Vol.13 No.3
A new model and resultant equation for the coagulation of acrylonitrile monomers in precipitation polymerization are suggested in consideration of the surface tension (γ) and cohesive energy density (ECED). The equation was proven to be quite favorable by considering figure fittings from known surface tensions and cohesive energy densities of certain organic solvents. The relationship between scale value of surface tension (γ/M) and cohesive energy density of monomers can be obtained by changing the coagulation bath component for effective precipitation polymerization of acrylonitrile in wet spinning.
Experimental and numerical investigation on the pyrolysis of single coarse lignite particles
Kai Zhang,Changfu You,Yulei Li 한국화학공학회 2012 Korean Journal of Chemical Engineering Vol.29 No.4
This paper reports on the mathematical modeling of the pyrolysis of single coarse lignite particles using a kinetics model coupled with a heat transfer model. The parallel reaction kinetics model of the lignite pyrolysis makes no assumptions about the activation energy distribution and the conversion of sub-reactions. The pyrolysis kinetics parameters were obtained on the basis of experimental data from thermogravimetric analysis (TGA) tests. The heat transfer model includes diffusive, convective and radiative heat transfer modes. The experimental investigations were carried out for single lignite particles in an electrically heated reactor. Measurements of the temperature and mass loss were performed during the pyrolysis in a nitrogen atmosphere. The model predictions for the temperature and mass loss histories agree well with the experimental data, verifying that the mathematical model accurately evaluates the pyrolysis of lignite particles. The effects of temperature and particle size on the pyrolysis time and final residual mass fraction were evaluated using the numerical model.
Kai Yang,Cheng FangWang,Chun Xue You,Zhu Feng Geng,Rui Qi Sun,Shan Shan Guo,Shu Shan Du,Zhi Long Liu,Zhi Wei Deng 한국응용곤충학회 2014 Journal of Asia-Pacific Entomology Vol.17 No.3
During our screening program for agrochemicals from Chinese medicinal herbs and wild plants, the essential oilof Litsea cubeba fruits was found to possess strong contact toxicity against the cigarette beetle Lasiodermaserricorne adults and the booklouse Liposcelis bostrychophila, with LD50 values of 27.33 μg/adult and71.56 μg/cm2, respectively, and also showed strong fumigant toxicity against the two stored product insectswith LC50 values of 22.97 and 0.73 mg/L, respectively. The essential oil obtained by hydrodistillation wasinvestigated by GC MS. The main components of the essential oil were identified to be E-citral (geranial)(27.49%), Z-citral (neral) (23.57%) and D-limonene (18.82%) followed by β-thujene (3.34%), β-pinene (2.85%), α-pinene (2.57%), 6-methyl-5-hepten-2-one (2.40%) and linalool (2.36%). Citral (Z/E-citral), D-limonene, β-pinene,α-pinene and linalool were separated and purified by silica gel column chromatography and preparative thinlayer chromatography, and further identified by means of physicochemical and spectrometric analysis. Citral andlinalool showed strong contact toxicity against L. serricorne and L. bostrychophila (LD50 = 11.76, 12.74 μg/adultand 20.15, 99.97 μg/cm2, respectively) and fumigant toxicity against L. serricorne and L. bostrychophila (16.54,18.04 mg/L air and 0.14, 0.71 mg/L air, respectively). Otherwise, citral, D-limonene and linalool were strongly repellentagainst the cigarette beetle L. serricorne as the essential oil whereas β-pinene and α-pinene exhibited weakerrepellency against the cigarette beetle compared with the positive control, DEET. Moreover, except α-pinene andlinalool, the other three compounds as well as the essential oil exhibited comparable repellency against thebooklouse relative to DEET.
Sensorless Assistive Torque Design for a Lower Extremity Exoskeleton
Kai-Tai Song,Yun-Chih Liao,You-Lin Jian 제어로봇시스템학회 2014 제어로봇시스템학회 국제학술대회 논문집 Vol.2014 No.10
For improving mobility of the elderly, it is desirable to use a lower limb exoskeleton to enhance strength and endurance for their daily life activities. This paper presents a novel design of assist torque generation and compliant motion of a knee joint for an exoskeleton robot. Based on a sensorless approach, a method is suggested to estimate the external torque and generate the assistance torque of the attached DC motor. The developed lower limb exoskeleton joint provides assistive torque in order to comply with motion of the user. In comparison with existing lower limb exoskeletons, the proposed exoskeleton robot can execute various training programs by adjusting the assisting torque with less sensors and reduced hardware complexity. Experimental results on a knee exoskeleton validate the proposed method. Desirable assistive torque can be generated to be compliant with a swing motion.
You Xu,Qingjie Zhang,Kai Deng 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.1
In this paper, a dual-converter three-phase pulse width modulation (PWM) rectifier based on unbalanced one-cycle control (OCC) strategy is proposed. The proposed rectifier is used to eliminate the second harmonic waves of DC voltage and distortion of line currents under unbalanced input grid voltage conditions. The dual-converter PWM rectifier employs two converters, which are called positive-sequence converter and negative-sequence converter. The unbalanced OCC system compensates feedback currents of positive-sequence converter via grid negative-sequence voltages, as well as compensates feedback currents of negative-sequence converter via grid positive-sequence voltages. The AC currents of positive- and negative-sequence converter are controlled to be symmetrical. Thus, the workload of every switching device of converter is balanced. Only one conventional PI controller is adopted to achieve invariant power control. Then, the parameter tuning is simplified, and the extraction for positive- and negative-sequence currents is not needed anymore. The effectiveness and the viability of the control strategy are demonstrated through detailed experimental verification.
AN ITERATIVE ALGORITHM FOR SOLVING THE LEAST-SQUARES PROBLEM OF MATRIX EQUATION AXB+CYD=E
Shen, Kai-Juan,You, Chuan-Hua,Du, Yu-Xia Korean Society of Computational and Applied Mathem 2008 Journal of applied mathematics & informatics Vol.26 No.5
In this paper, an iterative method is proposed to solve the least-squares problem of matrix equation AXB+CYD=E over unknown matrix pair [X, Y]. By this iterative method, for any initial matrix pair [$X_1,\;Y_1$], a solution pair or the least-norm least-squares solution pair of which can be obtained within finite iterative steps in the absence of roundoff errors. In addition, we also consider the optimal approximation problem for the given matrix pair [$X_0,\;Y_0$] in Frobenius norm. Given numerical examples show that the algorithm is efficient.