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.

A simplified approach for fire-resistance design of steel-concrete composite beams

Guo-Qiang Li,Wei-Yong Wang 국제구조공학회 2013 Steel and Composite Structures, An International J Vol.14 No.3

In this paper, a simplified approach based on critical temperature for fire resistance design of steel-concrete composite beams is proposed. The method for determining the critical temperature and fire protection of the composite beams is developed on the basis of load-bearing limit state method employed in current Chinese Technical Code for Fire safety of Steel Structure in Buildings. Parameters affecting the critical temperature of the composite beams are analysed. The results show that at a definite load level, section shape of steel beams, material properties, effective width of concrete slab and concrete property model have little influence on the critical temperature of composite beams. However, the fire duration and depth of concrete slab have significant influence on the critical temperature. The critical temperatures for commonly used composite beams, at various depth of concrete and fire duration, are given to provide a reference for engineers. The validity of the practical approach for predicting the critical temperature of the composite beams is conducted by comparing the prediction of a composite beam with the results from some fire design codes and full scale fire resistance tests on the composite beam.

Experimental Study on the Bend and Shear Behaviors of Steel-concrete Composite Beams with Notched Web of Inverted T-shaped Steel Section

Guo-Qiang Li,Xianhui Li,Liang Li 한국강구조학회 2012 International Journal of Steel Structures Vol.12 No.3

A new steel-concrete composite beam with notched web of inverted T-shaped steel section is proposed in this paper. This composite beam is composed of concrete slab and inverted T-shaped steel beam. Experimental studies on the bend and shear behavior of the composite beam are conducted. Four specimens are tested to investigate the bend behavior of the novel composite beam, and the formula for predicting the bend capacity is proposed and verified by comparing the results between predicted with the formula and the measured from the tests. Six specimens are also tested to study the shear behavior and the formula for estimating the shear capacity of the novel composite beam is recommended on the base of the test results. The formulas proposed in this paper may be employed to estimate the bend and shear capacity of the composite beam with notched web of inverted T-shaped steel section for application in practice.

A MODIFIED BFGS BUNDLE ALGORITHM BASED ON APPROXIMATE SUBGRADIENTS

Qiang Guo,Jian-Guo Liu 한국전산응용수학회 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.

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.

A simple approach to the elasto-plastic coupling analyses of circular tunnels in confining pressure-dependent strain-softening rock masses

Qiang Zhang,Cheng Li,Qiang Guo,Ming Min,Yanning Wang,Binsong Jiang 한국자원공학회 2017 Geosystem engineering Vol.20 No.5

The conventional strain-softening behaviors which assume the strength parameters as the functions of the plastic strain have been studied using various methods. However, rock-like materials have also been found to manifest pressure-dependent behavior for both elastic and plastic rock masses. The realization of the radial stress was found to be continuous, and gradually increased from supporting stress to in situ stress for the circular openings under hydrostatic pressure. The radial stress was spaced as numbers of sections, and each annulus was considered as an ideal plastic rock mass. The close-formed analytical solutions of each annulus can be easily obtained. Therefore, using the displacement continuum and stress boundary conditions, the dimensionless radius corresponding to the spaced radius could be derived. The radial stress and plastic shear strain at the inner radius of the outer adjacent annulus were employed to describe the material property evolution law. Then, the radii could be recursively obtained. Finally, for the conventional strain-softening rock masses, the pressure-dependent elastic rock and elasto-plastic coupling strain-softening rock masses were employed to validate the proposed approach. In this study, having completed the above steps, it was concluded that the results were in accordance with the numerical methods.

Anti-proliferative Effects of Atractylis lancea (Thunb.) DC. via Down-regulation of the c-myc/hTERT/Telomerase Pathway in Hep-G2 Cells

Guo, Wei-Qiang,Li, Liang-Zhi,He, Zhuo-Yang,Zhang, Qi,Liu, Jia,Hu, Cui-Ying,Qin, Fen-Ju,Wang, Tao-Yun Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.11

Atractylis lancea (Thunb.) DC. (AL), an important medicinal herb in Asia, has been shown to have anti-tumor effects on cancer cells, but the involved mechanisms are poorly understood. This study focused on potential effects and molecular mechanisms of AL on the proliferation of the Hep-G2 liver cancer cell line in vitro. Cell viability was assessed by MTT test in Hep-G2 cells incubated with an ethanol extract of AL. Then, the effects of AL on apoptosis and cell cycle progression were determined by flow cytometry. Telomeric repeat amplification protocol (TRAP) assays was performed to investigate telomerase activity. The mRNA and protein expression of human telomerase reverse transcriptase (hTERT) and c-myc were determined by real-time RT-PCR and Western blotting. Our results show that AL effectively inhibits proliferation in Hep-G2 cells in a concentrationand time-dependent manner. When Hep-G2 cells were treated with AL after 48h,the $IC_{50}$ was about 72.1 ${\mu}g/mL$. Apoptosis was induced by AL via arresting the cells in the G1 phase. Furthermore, AL effectively reduced telomerase activity through inhibition of mRNA and protein expression of hTERT and c-myc. Hence, these data demonstrate that AL exerts anti-proliferative effects in Hep-G2 cells via down-regulation of the c-myc/hTERT/telomerase pathway.

Study of Synthesis and Electrochemical Properties of Spinel LiNi0.5Mn1.2Ti0.3O4 by Different Methods

Guo-Qiang Liu 대한금속·재료학회 2010 METALS AND MATERIALS International Vol.16 No.5

Two spinel LiNi0.5Mn1.2Ti0.3O4 samples were successfully synthesized by the sol–gel method using chemicals LiAc·2H2O, Mn(Ac)2·2H2O, Ni(Ac)2·4H2O and Ti(OCH3)4 as reactants. When reactants are calcined in air,a sample of LiNi0.5Mn1.2Ti0.3O4 (1), which contains Mn 3+and Mn 4+ions, is obtained. The sample of LiNi0.5Mn1.2Ti0.3O4 (2), which contains only Mn 4+ions, is obtained when reactants are calcined in an oxygen atmosphere. X-ray diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge-discharge test and cyclic voltammogram test were employed to investigate the two samples. XRD results show that there is a small shift towards a larger diffraction angle for peaks of the LiNi0.5Mn1.2Ti0.3O4 (2) sample. SEM indicates that the two samples exhibit polyhedral shapes. The cyclic voltammogram test demonstrates that reduction-oxidation reactions take place at different voltages for the two samples. The prepared sample of LiNi0.5Mn1.2Ti0.3O4with Mn 3+ions exhibits excellent cycle performance at different current rates. Its discharge capacity is 133.9mAh/g at 0.1C.

Experimental Research on Steel Beam to Concrete Wall Joints under Cyclic Loading

Guo Qiang Li,Bing Qu,Fei Fei Sun,Goman W. M. Ho,Michael K. Y. Kwok 한국강구조학회 2003 韓國鋼構造學會誌 Vol.15 No.3

Analysis of restrained heated steel beams during cooling phase

Guo-Qiang Li,Shi-Xiong Guo 국제구조공학회 2009 Steel and Composite Structures, An International J Vol.9 No.3

Observations from experiments and real fire indicate that restrained steel beams have better fireresistant capability than isolated beams. Due to the effects of restraints, a steel beam in fire condition can undergo very large deflections and the run away damage may be avoided. However disgusting damages may occur in the beam-to-column connections, which is considered to be mainly caused by the enormous axial tensile forces in steel beams resulted from temperature decreasing after fire dies out. Over the past ten years, the behaviour of restrained steel beams subjected to fire during heating has been experimentally and theoretically investigated in detail, and some simplified analytical approaches have been proposed. While the performance of restrained steel beams during cooling has not been so deeply studied. For the safety evaluation and repair of steel structures against fire, more detailed investigation on the behaviour of restrained steel beams subjected to fire during cooling is necessary. When the temperature decreases, the elastic modulus and yield strength of steel recover, and the contraction force in restrained steel beams will be produced. In this paper, an incremental method is proposed for analyzing the behaviour of restrained steel beams subjected to cooling. In each temperature decrement, the development of deformation and internal forces of a restrained beam is divided into four steps, in order to consider the effect of the recovery of the elastic modulus and strength of steel and the contraction force generated by temperature decrease in the beam respectively. At last, the proposed approach is validated by FE method.