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GLOBAL CONVERGENCE PROPERTIES OF TWO MODIFIED BFGS-TYPE METHODS
Guo, Qiang,Liu, Jian-Guo 한국전산응용수학회 2007 Journal of applied mathematics & informatics Vol.23 No.1
This article studies a modified BFGS algorithm for solving smooth unconstrained strongly convex minimization problem. The modified BFGS method is based on the new quasi-Newton equation $B_k+1{^s}_k=yk\;where\;y_k^*=yk+A_ks_k\;and\;A_k$ is a matrix. Wei, Li and Qi [WLQ] have proven that the average performance of two of those algorithms is better than that of the classical one. In this paper, we prove the global convergence of these algorithms associated to a general line search rule.
GLOBAL CONVERGENCE OF A MODIFIED BFGS-TYPE METHOD FOR UNCONSTRAINED NON-CONVEX MINIMIZATION
Guo, Qiang,Liu, Jian-Guo 한국전산응용수학회 2007 Journal of applied mathematics & informatics Vol.24 No.1
To the unconstrained programme of non-convex function, this article give a modified BFGS algorithm associated with the general line search model. The idea of the algorithm is to modify the approximate Hessian matrix for obtaining the descent direction and guaranteeing the efficacious of the new quasi-Newton iteration equation $B_{k+1}s_k=y^*_k,\;where\;y^*_k$ is the sum of $y_k\;and\;A_ks_k,\;and\;A_k$ is some matrix. The global convergence properties of the algorithm associating with the general form of line search is proved.
Method for Feature Extraction of Radar Full Pulses Based on EMD and Chaos Detection
Guo, Qiang,Nan, Pulong The Korea Institute of Information and Commucation 2014 Journal of communications and networks Vol.16 No.1
A novel method for extracting frequency slippage signal from radar full pulse sequence is presented. For the radar full pulse sequence received by radar interception receiver, radio frequency (RF) and time of arrival (TOA) of all pulses constitute a two-dimensional information sequence. In a complex and intensive electromagnetic environment, the TOA of pulses is distributed unevenly, randomly, and in a nonstationary manner, preventing existing methods from directly analyzing such time series and effectively extracting certain signal features. This work applies Gaussian noise insertion and structure function to the TOA-RF information sequence respectively such that the equalization of time intervals and correlation processing are accomplished. The components with different frequencies in structure function series are separated using empirical mode decomposition. Additionally, a chaos detection model based on the Duffing equation is introduced to determine the useful component and extract the changing features of RF. Experimental results indicate that the proposed methodology can successfully extract the slippage signal effectively in the case that multiple radar pulse sequences overlap.
A New Control Strategy for a Three-Phase PWM Current-Source Rectifier in the Stationary Frame
Guo, Qiang,Liu, Heping,Zhang, Yi The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.4
This paper presents a novel power control strategy for PWM current-source rectifiers (CSRs) in the stationary frame based on the instantaneous power theory. In the proposed control strategy, a virtual resistance based on the capacitor voltage feedback is used to realize the active damping. In addition, the proportional resonant (PR) controller under the two-phase stationary coordinate is designed to track the ac reference current and to avoid the strong coupling brought about by the coordinate transformation. The limitations on improving steady-state performance of the PR controller is investigated and mitigated using a cascaded lead-lag compensator. In the z-domain, a straightforward procedure is developed to analyze and design the control-loop with the help of MATLAB/SISO software tools. In addition, robustness against parameter variations is analyzed. Finally, simulation and experimental results verify the proposed control scheme and design method.
Nanocarbon-reinforced metal-matrix composites for structural applications
Guo, Qiang,Kondoh, Katsuyoshi,Han, Seung Min Cambridge University Press (Materials Research Soc 2019 MRS bulletin Vol.44 No.1
<▼1><B>Abstract</B><P/></▼1><▼2><P>Nanocarbon materials, such as carbon nanotubes, graphene, and their derivatives, are regarded as promising reinforcing agents in metal matrix composites (MMCs) because of their excellent intrinsic mechanical properties. Considering the various types of nanocarbons with different defect states and intrinsic properties, there is a potential for tailoring the mechanical behavior of nanocarbon-reinforced MMCs. This article reviews recent developments in both the processing and the structure-property correlations of these composites. Particular emphasis is given to the structure and properties of the nanocarbon-metal interfaces, as the external mechanical load is transferred between the nanocarbon and the metal matrix across their interfaces. Moreover, in addition to the intuitive load-bearing effect of the nanocarbon reinforcements, a copious interplay between nanocarbons and dislocations in the metal matrix has been found, which alters the deformation behavior that leads to additional strengthening. For structural applications, scalable fabrication routes for the nanocarbon-metal composites need to be developed, and studies on the mechanical behavior under real service conditions are needed.</P></▼2>
A MODIFIED BFGS BUNDLE ALGORITHM BASED ON APPROXIMATE SUBGRADIENTS
Guo, Qiang,Liu, Jian-Guo The Korean Society for Computational and Applied M 2010 Journal of applied mathematics & informatics Vol.28 No.5
In this paper, an implementable BFGS bundle algorithm for solving a nonsmooth convex optimization problem is presented. The typical method minimizes an approximate Moreau-Yosida regularization using a BFGS algorithm with inexact function and the approximate gradient values which are generated by a finite inner bundle algorithm. The approximate subgradient of the objective function is used in the algorithm, which can make the algorithm easier to implement. The convergence property of the algorithm is proved under some additional assumptions.
Guoqiang Xie,Liejia Qian,Heyuan Zhu,Hua Yang 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.4
We demonstrate a diode-pumped femtosecond Nd:glass laser with an enhanced repetition rate for the first time. A coupled cavity is employed to initiate the generation of multiple pulses with equal temporal intervals inside the main cavity. Stable pulse trains with a doubled repetition rate have been obtained successfully. Extension of the approach to a higher repetition rate is quite feasible, and a tripled repetition rate, i.e., 300 MHz, has been observed experimentally.
Reservoir bank slope stability prediction model based on BP neural network
Guoqiang Zhang,Wenkai Feng,Mingtang Wu,Hai Shao,Feng Ma 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.41 No.2
Safety monitoring and stability analysis of high slopes are essential for construction of concrete dam in precipitous gorges or mountainous areas. The estimate of slope stability is a difficult engineering shortcoming with a number of variables. Thereafter, a hybrid model of Support Vector Regression (SVR) and Teaching–learning-based optimization technique (TLBO) is proposed to develop the predicting function. TLBO was used in obtaining the best SRV factors to improve the prediction accuracy. Few essential factors, such as the installation height of instruments, classification of rock masses, modulus of elasticity, the complete measuring time cycle, the excavation height of slope, the start measuring time, and the actual excavation height after measurement are considered as the input parameter, but the slope displacement is regarded as output. The outcomes showed SRV-TLBO a reliable hybrid accurate prediction of slope stability, then it was effectively used to the left abutment slope of Jinping I hydropower station located in Yalongjiang concrete dam reservoir as a novel method for this purpose.
Flow between eccentric cylinders: a shear-extensional controllable flow
Guoqiang Tian,Mengmeng Wang,Xiaolin Wang,Gang Jin 한국유변학회 2016 Korea-Australia rheology journal Vol.28 No.2
In this work the non-Newtonian fluid between eccentric cylinders is simulated with finite element method. The flow in the annular gap between the eccentric rotating cylinders was found to be a shear-extensional controllable flow. The influence of rotating speed, eccentricity as well as the radius ratio on the extensional flow in the vicinity of the minimum gap between the inner and outer cylinder was quantitatively investigated. It was found that both the strengths of shear flow and extensional flow could be adjusted by changing the rotating speed. In respect to extensional flow, it was also observed that the eccentricity and radius ratio exert significant influences on the ratio of extensional flow. And it should be noted that the ratio of extensional flow in the mix flow could be increased when increasing the eccentricity and the ratio of shear flow in the mix flow could be increased when increasing the radius ratio.