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Symmetry and Period-Adding Windows in a Modified Optical Injection Semiconductor Laser Model

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Chinese Physics Letters 2012年第1期29卷 1-4页

作者： LI Xian-Feng andrew y-t.leung CHU yan-Dong Department of Mathematics Lanzhou Jiaotong UniversityLanzhou 730070 Department of Civil and Architectural Engineering City University of Hong KongHong Kong

Hierarchical structural symmetry of periodic islands embedded in the chaotic region of modified optical injection semiconductor lasers(MOISLs)is expounded upon in phase *** onset of the bifurcation cascade shows remarkable accumulation *** cascade follows a specific period-adding ***-similarities and infinite spiral nestings shrinking beyond a certain point of the periodic hub are revealed to affirm the existence of self-organized distribution of periodicity and chaos in phase diagrams.

关键词： periodic bifurcation symmetry

Dynamic stiffness for thin-walled structures by power series

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2006年第8期7卷 1351-1357页

作者： ZHU Bin leung A.y.t. Department of Civil Engineering Zhejiang University Hangzhou 310027 China Department of Building and Construction City University of Hong Kong Hong Kong China

the dynamic stiffness method is introduced to analyze thin-walled structures including thin-walled straight beams and spatial twisted helix beam. A dynamic stiffness matrix is formed by using frequency dependent shape functions which are exact solutions of the governing differential equations. With the obtained thin-walled beam dynamic stiffness matrices, the thin-walled frame dynamic stiffness matrix can also be formulated by satisfying the required displacements compatibility and forces equilib-rium, a method which is similar to the finite element method (FEM). then the thin-walled structure natural frequencies can be found by equating the determinant of the system dynamic stiffness matrix to zero. By this way, just one element and several elements can exactly predict many modes of a thin-walled beam and a spatial thin-walled frame, respectively. Several cases are studied and the results are compared with the existing solutions of other methods. the natural frequencies and buckling loads of these thin-walled structures are computed.

关键词： Dynamic stiffness method thin-wall structures Power series Buckling

Solution procedure of residue harmonic balance method and its applications

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Science China(Physics,Mechanics & Astronomy) 2014年第8期57卷 1581-1591页

作者： GUO ZhongJin leung A y t MA Xiaoyan School of Mathematics and Statistics Taishan University Department of Civil and Architectural Engineering City University of Hong Kong

this paper presents a simple and rigorous solution procedure of residue harmonic balance for predicting the accurate approximation of certain autonomous ordinary differential *** this solution procedure,no small parameter is *** harmonic residue of balance equation is separated in two parts at each *** first part has the same number of Fourier terms as the present order of approximation and the remaining part is used in the subsequent *** corrections are governed by linear ordinary differential equation so that they can be solved easily by means of harmonic balance method *** kinds of different differential equations involving general,fractional and delay ordinary differential systems are given as numerical examples *** accurate limited cycle frequency and amplitude are *** results match well with the exact solutions or numerical solutions for a wide range of control *** with those available shows that the residue harmonic balance solution procedure is very effective for these autonomous differential ***,the present method works not only in predicting the amplitude but also the frequency of bifurcated period solution for delay ordinary differential equation.

关键词： residue harmonic balance accurate approximation fractional ordinary differential system delay ordinary differential system

tHE EVALUAtION OF StRESS INtENSIty FACtORS OF PLANE CRACK FOR ORtHOtROPIC PLAtE WItH EQUAL PARAMEtER By F2LFEM

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Acta Mechanica Solida Sinica 2006年第2期19卷 128-134页

作者： Fan Jie Zhang Xiaochun A.y.t. leung Zhong Weifang Department of Mechanics Huazhong University of Science and Technology Wuhan 430074 China Department of Building and Construction City University of Hong Kong Hong Kong China

In this paper, the evaluation of stress intensity factor of plane crack problems for orthotropic plate of equal-parameter is investigated using a fractal two-level finite element method （F2LFEM）. the general solution of an orthotropic crack problem is obtained by assimilating the problem with isotropic crack problem, and is employed as the global interpolation function in F2LFEM. In the neighborhood of crack tip of the crack plate, the fractal geometry concept is introduced to achieve the similar meshes having similarity ratio less than one and generate an infinitesimal mesh so that the relationship between the stiffness matrices of two adjacent layers is equal. A large number of degrees of freedom around the crack tip are transformed to a small set of generalized coordinates. Numerical examples show that this method is efficient and accurate in evaluating the stress intensity factor （SIF）.

关键词： plane crack orthotropic plate fractal finite element stress intensity factor

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Advances in Atmospheric Sciences 2022年第1期39卷 67-79页

作者： Paxson K.y.CHEUNG Wen ZHOU Dongxiao WANG Marco y.t.leung Guy-Carpenter Asia-Pacific Climate Impact Centre School of Energy and EnvironmentCity University of Hong KongHong KongChina Department of Atmospheric and Oceanic Sciences&Institute of Atmospheric Sciences Fudan UniversityShanghai 200438China School of Marine Sciences Sun Yat-sen UniversityGuangdong 510275China

this study focuses on the temporal variation of dissimilarity in heat content(HC)anomalies in the upper 300 m of ocean(HC300A)in the equatorial Pacific(±10°N)and its response to the El Ni?o-Southern Oscillation(ENSO).the HC300A anomalies are derived from four ocean reanalyses that are commonly used in ENSO studies and are compared using a simple differencing *** dissimilarity in HC300A is found to vary closely with the magnitude of ENSO(regardless of phase),meaning that it tends to be greater during strong ENSO ***,the dissimilarity among ocean reanalyses persists after the event *** effect is more pronounced after strong *** persistence of the dissimilarity after ENSO events is a result of a late maturation of the ENSO signal,its persistence,and the interruption of the signal decay due to follow-up ENSO *** combined effect of these three factors slows down the decay of HC300A in the region and hence results in the slow decay of *** is also found that areas with a significant spread in vertical temperature profiles collocate with the ENSO signal during warm ENSO ***,differences in subsurface process reconstruction are a significant factor in the dissimilarity among ocean reanalyses during warm ENSO events.

关键词： ocean reanalysis ocean heat content intercomparison ENSO equatorial Pacific

Extended Impact of Cold Air Invasions in East Asia in Response to a Warm South China Sea and Philippine Sea

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Advances in Atmospheric Sciences 2023年第3期40卷 531-540页

作者： Marco y.-t.leung Dongxiao WANG Wen ZHOU yuntao JIAN School of Marine Sciences Sun Yat-Sen UniversityZhuhai 519082China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai 519000China Department of Atmospheric and Oceanic Sciences&Institute of Atmospheric Sciences Fudan UniversityShanghai 200438China Guy Carpenter Asia-Pacific Climate Impact Centre Center for Ocean Research in Hong Kong and Macao(CORE)School of Energy and EnvironmentCity University of Hong KongHong KongChina

During boreal winter,the invasion of cold air can lead to remarkable temperature drops in East Asia which can result in serious socioeconomic ***,we find that the intensity of strong synoptic cold days in the East China Sea and Indochina Peninsula are *** enhanced synoptic cold days in these two regions are attributed to surface warming over the South China Sea and Philippine Sea(SCSPS).the oceanic forcing of the SCSPS on the synoptic cold days in the two regions is verified by numerical *** warming of the SCSPS enhances the baroclinicity,which intensifies meridional wind and cold advection on synoptic *** leads to a more extended region that is subject to the influence of cold invasion.

关键词： ocean warming extra-tropical cyclones baroclinicity temperature whiplash

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新型p型板单元及其在结构振动分析中的应用

计算力学学报 2008年第4期25卷 447-453页

作者：朱斌 leung A y t 浙江大学土木系杭州310027 香港城市大学建筑工程系

利用Legendre正交多项式作为形函数基底函数,开发了两种新型的通用p型板单元。单元矩阵的解析积分保证了p型有限单元解的精确性及单调收敛性。计算实例表明所开发的p型有限单元计算结果随基底函数中附加项数量的增加而快速收敛,且它们... 详细信息

利用Legendre正交多项式作为形函数基底函数,开发了两种新型的通用p型板单元。单元矩阵的解析积分保证了p型有限单元解的精确性及单调收敛性。计算实例表明所开发的p型有限单元计算结果随基底函数中附加项数量的增加而快速收敛,且它们的计算精度远高于一般线性单元。另外,p型板单元不使用缩减积分也能分析薄板的振动问题。利用它们收敛率高的特点,分析了结构破坏的时频特性。p型有限单元仿真结果与实测结果良好的吻合证明了它们用于结构振动响应分析的有效性。

关键词： p型有限单元板振动响应小波变换

LOCALLy NONLINEAR StOCHAStIC ANALySIS OF OFFSHORE StRUCtURES

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China Ocean Engineering 1988年第3期2卷 1-10页

作者： y.t.leung y.K.Cheung Department of Civil Engineering University of Hong Kong Hong Kong Professor Hong Kong Senior Lecturer

this paper’ presents a simple method for the stochastic dynamic analysis of some offshore platforms with localized nonlinearity. the transfer function of the platform with initial linear stiffness is first determined, and the nonlinear iteration is performed on the condensed stiffness matrix only. Computational efforts are reduced. this method can be used to analyze a fixed platform on nonlinear foundation and a guyed tower platform having nonlinear guylines.

关键词： LOCALLy NONLINEAR StOCHAStIC ANALySIS OF OFFSHORE StRUCtURES

An Extreme Drought over South China in 2020/21 Concurrent with an Unprecedented Warm Northwest Pacific and La Niña

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Advances in Atmospheric Sciences 2022年第10期39卷 1637-1649页

作者： Weijie FENG Marco y.-t.leung Dongxiao WANG Wen ZHOU Oscar y.W.ZHANG School of Marine Sciences Sun Yat-Sen UniversityZhuhai 519082China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai 519082China Department of Atmospheric and Oceanic Sciences&Institute of Atmospheric Sciences Fudan UniversityShanghai 200433China Guy Carpenter Asia-Pacific Climate Impact Centre School of Energy and EnvironmentCity University of Hong KongHong KongChina

An extreme drought appeared in South China from October 2020 to March *** that time,sea surface temperatures exhibited an unprecedented warm center over the northwest Pacific(NWP)and a cold center over the tropical eastern Pacific(La Niña).this study demonstrates the combined effects of an exceptionally warm NWP and a moderate La Niña are closely linked to the anomalous drought in South *** sea surface temperature anomaly in these two regions induced a steeper horizontal geopotential height gradient over South *** a result,anomalous northeasterly winds prevailed over South China,altering water vapor transport and moisture convergence.A simplified atmospheric general circulation model also verifies the influence of the NWP warm anomaly on South China *** study points out that the sea surface temperature variation in the NWP was important to the occurrence of extreme drought in South China from October 2020 to March 2021.

关键词： drought in South China ENSO northwest Pacific warming