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Exponential Stability of the Euler-Bernoulli Beam Equation with external Disturbance and Output Feedback Time-Delay

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Journal of Systems Science & Complexity 2019年第2期32卷 542-556页

作者： WU Jilong SHANG Yingfeng Department of Mathematics Tianjin University

This paper concerns the stability of a one-dimensional Euler-Bernoulli beam equation with external disturbance and output feedback time-delay, in which the disturbance is bounded by an exponential function. In order to estimate disturbance, the authors design an estimator of disturbance,which is composed of two parts: One is the system measurement that is called the eigen-measurement,another is a time-variant estimator of disturbance. Thus, the feedback controller which is based on the estimate of the disturbance is designed to stabilize the system. The finite-time stability of the system under this control law is proved by Lyapunov function method. Finally, some numerical simulations on the dynamical behavior of the closed-loop system is presented to show the correctness of the result.

关键词： Eigenfunction measurement exponential stability external disturbance feedback control

Buckling of Cassini Oval Pressure Hulls Subjected to external Pressure

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China Ocean Engineering 2019年第4期33卷 503-508页

作者： TANG Wen-xian WANG Wei-min ZHANG Jian WANG Shu-yan Jiangsu Provincial Key Laboratory of Advanced Manufacturing for Marine Mechanical Equipment Jiangsu University of Science and Technology Zhenjiang 212003 China School of Mechanical Engineering Jiangsu University of Science and Technology Zhenjiang 212003 China

The paper focuses on Cassini oval pressure hulls under uniform external pressure. The Cassini oval pressure hull is proposed based on the shape index of Cassini oval. The buckling of a series of Cassini oval pressure hulls with the shape index of 0.09–0.30 and one spherical pressure hull with the diameter of 2 m is devoted. Such hulls are numerically studied in the case of constant volume, material properties, and wall thickness. The results show that Cassini oval pressure hulls with the shape index of 0.10–0.11 can resist about 4% more external pressure than the spherical one. This deviates from the classical mechanics conclusion that spherical shell is the optimal shape for underwater pressure resistant structures.

关键词： pressure hull Cassini oval shell shape index buckling behaviour external pressure

Optical simulation of external quantum efficiency spectra of CuIn_(1-x)Ga_xSe_2 solar cells from spectroscopic ellipsometry inputs

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Journal of Energy Chemistry 2018年第4期27卷 1151-1169页

作者： Abdel-Rahman A.Ibdah Prakash Koirala Puruswottam Aryal Puja Pradhan Michael J.Heben Nikolas J.Podraza Sylvain Marsillac Robert W.Collins Department of Physics & Astronomy and Center for Photovoltaics Innovation & Commercialization University of Toledo Virginia Institute of Photovoltaics Old Dominion University

Applications of in-situ and ex-situ spectroscopic ellipsometry （SE） are presented for the development of parametric expressions that define the real and imaginary parts （ε1, ε2） of the complex dielectric function spectra of thin film solar cell components. These spectra can then be utilized to analyze the structure of complete thin film solar cells. Optical and structural/compositional models of complete solar cells developed through least squares regression analysis of the SE data acquired for the complete cells enable simulations of external quantum efficiency （EQE） without the need for variable parameters. Such simulations can be compared directly with EQE measurements. From these comparisons, it becomes possible to understand in detail the origins of optical and electronic gains and losses in thin film photovoltaics （PC） technologies and, as a result, the underlying performance limitations. In fact, optical losses that occur when above-bandgap photons are not absorbed in the active layers can be distinguished from electronic losses when electron-hole pairs generated in the active layers are not collected. This overall methodology has been applied to copper indium-gallium diselenide （Culn1-xGaxSe2; CIGS） solar cells, a key commercialized thin film PV technology. CIGS solar cells with both standard thickness （〉2 μm） and thin （〈1 μm） absorber layers are studied by applying SE to obtain inputs for EQE simulations and enabling comparisons of simulated and measured EQE spectra. SE data analysis is challenging for CIGS material components and solar cells because of the need to develop an appropriate （ε1, ε2） database for the CIGS alloys and to extract absorber layer Ga profiles for accurate structural/compositional models. For cells with standard thickness absorbers, excellent agreement is found between the simulated and measured EQE, the latter under the assumption of 100% collection from the active layers, which include the CIGS bulk and CIGS/CdS heterojunction inter

关键词： Solar cells Thin-film Ellipsometry Spectroscopic Culn1-xGaxSe2(CIGS) Optical properties Quantum efficiency external Simulation Solar-cell

Assessment of Building external Wall Thermal Performance Based on Temperature Deviation Impact Factor under Discontinuous Radiant Heating

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Journal of Thermal Science 2019年第6期28卷 1129-1140页

作者： YANG Jie WANG Jun XIONG Feng LIANG Hao LI Yunzhang College of Architecture and Environment Sichuan UniversityChengdu 610065China Center of Science and Technology Industrial Development Ministry of Housing and Urban-Rural DevelopmentBeijing 100835China

As the variation and timely meeting thermal environment requirement of indoor air temperature has a close relationship with the thermal performance of building external wall under discontinuous radiant heating condition, one appropriate assessment method or index for assessing the building external wall thermal performance is very necessary. In order to reasonably evaluate the thermal performance of external wall under discontinuous radiant heating condition and build the direct connections and interactions among the indoor air temperature, external wall inner surface temperature and outdoor air temperature, the first and second impact factors of temperature deviation were established, based on one mathematical model of room heat transfer. For one experimental room and four types of external walls under discontinuous radiant heating condition, both the influence of the external wall inner surface temperature deviation on the indoor air temperature and that of the outdoor air temperature deviation on the external wall inner surface temperature were determined effectively with the first and second impact factors of temperature deviation. In addition, favourable performance for the self-insulation and inner insulation walls were found, due to their superiority in effectively and timely improving the indoor thermal environment under discontinuous radiant heating condition.

关键词： temperature deviation impact factor building external wall thermal performance discontinuous radiant heating

Mixed mode oscillations as well as the bifurcation mechanism in a Duffing’s oscillator with two external periodic excitations

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Science China(Technological Sciences) 2019年第10期62卷 1816-1824页

作者： ZHANG XiaoFang ZHENG JianKang WU GuoQing BI QinSheng Faculty of Civil Engineering and Mechanics Jiangsu UniversityZhenjiang212013China School of Mechanical Engineering Nantong Institute of TechnologyNantong226002China

The main purpose of the paper is to present an approach to account for the mechanism of bursting oscillations occurring in the systems with multiple periodic excitations. Since the traditional slow-fast analysis method can be used only for the systems with two scales in time domain, when there exists an order gap between the exciting frequencies and the natural frequency, how to explore the mechanism of the complicated dynamics remains an open problem, especially for the case when two exciting terms exist. To explain our approach, a relative simple Duffing’s oscillator with two external periodic excitations is introduced as an example. For the case when one exciting frequency is integer times of the other exciting frequency, by employing Moivre’s equation, the two exciting terms can be transformed into the functions of one basic periodic exciting term. Regarding the basic periodic exciting term as a slow-varying parameter, the two exciting terms can be changed into the functions of the slow-varying parameter, based on which the whole model can be transformed into a generalized autonomous system with one slow-varying parameter. Equilibrium branches as well as the related bifurcations of the generalized autonomous system can be derived with the variations of the amplitudes of the two excitations, which describes the relationship between the state variables of the generalized autonomous system and the slow-varying parameter. Considering the slow-varying parameter as a generalized state variable, one may obtain the so-called transformed phase portraits, which present the relationship between the state variable and the slowvarying parameter. The bifurcation mechanism of the mixed oscillations can be obtained by overlapping the equilibrium branches and the transformed phase portraits. Upon the approach, different types of bursting oscillations are presented. It is pointed that when the trajectory moves almost strictly along the segments of the stable equilibrium branches

关键词： multiple external periodic excitations two scales in frequency domain bursting oscillations bifurcation mechanism

One-dimensional mass transport with dynamic external potentials

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Chinese Physics B 2019年第2期28卷 161-166页

作者： Xingxing Zhang Dongqin Zheng Weirong Zhong Siyuan Laboratory Department of PhysicsJinan University

Using non-equilibrium molecular dynamics and the Monte Carlo method, we simulated mass transport in a onedimensional channel with dynamic external potentials. This study focuses on the influence of the dynamic external potential field on the mass transport. Traveling wave and standing wave potential fields have been employed as our dynamic potential field. We found that mass transport can be promoted by the traveling wave field when the external potential moves along the direction of the mass current. When the standing wave field is exerted on the channel, the channel is found to work like a switch. The mass current can be "on" or "off" by adjusting the standing wave frequency. The effects of the period number,the amplitude and the velocity of the external potential on the mass transport are also discussed. Our research provides valuable advice for the control o particle transport through one-dimensional channels.

关键词： dynamic external potentials traveling wave standing wave mass transport

Numerical study on variation characteristics of the unsteady bearing forces of a propeller with an external transverse excitation

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Journal of Hydrodynamics 2019年第2期31卷 400-412页

作者： Min-hua Shu Ke Chen Yun-xiang You Tian-qun Hu Remfeng Wang State Key Laboratory of Ocean Engineering Collaboration Innovation Center for Advanced Ship and Deep-Sea Exploitation EquipmentShanghai JiaoTong UniversityShanghai 200240China

The unsteady bearing forces of a propeller can be significantly affected by external transverse *** paper numerically studies the unsteady variation characteristics of the bearing forces of a three-blade conventional propeller with external transverse excitations or without *** dynamic mesh method combined with the RANS turbulence model is *** numerical simulation shows the frequency response in the frequency domain of KT,Kq under external transverse *** frequency of the response is found always equal to twice of the excitation *** the amplitude of the external transverse excitation keeps constant,the amplitude of the response increases with the in crease of the excitation *** the excitation frequency keeps constant,the amplitude of the response increases with the increase of the excitation amplitude,in a power-law *** pressure distribution can be significantly affected by the external transverse excitation,leading to a high irregularity of the flow field.

关键词： external transverse excitation unsteady bearing forces excitation frequency propeller dynamic mesh method

Introducing an external Terminal Operator or Not? The Decision of Ports in a Duopoly Market

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Journal of Systems Science & Complexity 2020年第1期33卷 146-166页

作者： GUO Libin LI Jian LIU Qing XING Wei College of Information Science and Technology Beijing University of Chemical TechnologyBeijing 100029China School of Management Qufu Normal UniversityRizhao 276826China Research Base of Beijing Modern Manufacturing Development College of Economics and ManagementBeijing University of TechnologyBeijing 100124China Hamburg Business School University of HamburgHamburg 20148Germany School of Economics and Management China University of PetroleumQingdao 266580China

Facing with increasing competition,many ports are taking innovative approaches to improve productivity and *** a variety of methods,introducing external terminal operators(ETOs)while the port acts as a landlord to collect"rents"from those operators for conducting terminal activities inside the port is regarded as an effective way and is commonly observed in *** paper analyzes the decisions of two competing ports about whether to introduce their respective ETOs using a three-stage non-cooperative game model when there already exists a port’s self-operation terminal operator(STO).At the first stage,the two ports simultaneously decide whether to introduce an *** a port decided to introduce an ETO,at the second stage,it will further decide the unit fee to charge from the *** the third stage,the two ports and the introduced ETO(s)simultaneously decide their respective profit-maximizing output *** findings indicate the equilibrium is both ports will introduce their respective ETOs,but when the ports and ETOs are substitutable in the sense of having the same level of productivity,the equilibrium solution is only one port should introduce an *** simulation results show that even if one of ETOs is inefficient this still hold true.

关键词： external terminal operator intra-port competition landlord port mode port authority self-operation terminal operator

Quantifying the thermal damping effect in underground vertical shafts using the nonlinear autoregressive with external input(NARX) algorithm

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International Journal of Mining Science and Technology 2019年第2期29卷 255-262页

作者： Pedram Roghanchi Karoly C.Kocsis Mineral Engineering Derpartment New Mexico Institute of Mining and Technology Mining Engineering Derpartment University of Nevada

As air descends the intake shaft, its infrastructure, lining and the strata will emit heat during the night when the intake air is cool and, on the contrary, will absorb heat during the day when the temperature of the air becomes greater than that of the strata. This cyclic phenomenon, also known as the "thermal damping effect" will continue throughout the year reducing the effect of surface air temperature variation. The objective of this paper is to quantify the thermal damping effect in vertical underground airways. A nonlinear autoregressive time series with external input(NARX) algorithm was used as a novel method to predict the dry-bulb temperature(Td) at the bottom of intake shafts as a function of surface air temperature. Analyses demonstrated that the artificial neural network(ANN) model could accurately predict the temperature at the bottom of a shaft. Furthermore, an attempt was made to quantify typical "damping coefficient" for both production and ventilation shafts through simple linear regression models. Comparisons between the collected climatic data and the regression-based predictions show that a simple linear regression model provides an acceptable accuracy when predicting the Tdat the bottom of intake shafts.

关键词： Underground mining Vertical openings Thermal damping effect Artificial neural network Nonlinear autoregressive with external input(NARX)