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Some Dichotomy Results for the Quenching Problem

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Acta Mathematica Sinica,English Series 2012年第7期28卷 1491-1506页

作者： gao Feng zheng Department of Mathematics Central China Normal University

It is shown that any solution to the semilinear problem{u（x,0=）u0（x）〈1,x∈[-1,1] u（±1,t）=0,t∈（0,T）, ut=uxx＋δ（1-u）^-p（x,t）∈（-1,1） ×（0,T）either touches 1 in finite time or converges smoothly to a ... 详细信息

关键词： Semilinear heat equation quenching in finite time finite energy steady state dichotomyproperty

Theoretical Analysis and Numerical Simulation of the Static and Dynamic Characteristics of Hydrostatic Guides Based on Progressive Mengen Flow Controller

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Chinese Journal of Mechanical Engineering 2010年第6期23卷 709-716页

作者： gao Dianrong zheng Dan ZHANG Zuochao Key Laboratory of Heavy Machinery Fluid Power Transmission and Control of Hebei Province Yanshan University Qinhuangdao 066004 China

The oil film thickness of oil hydrostatic guide with constant pressure supply based on capillary restrictor is greatly affected by load, and this kind of hydrostatic guide is usually applied to the machine tools with moderate load. The static and dynamic characteristics of the guide have been studied by using some theoretical, numerical and experimental approaches, and some methods and measures have been proposed to improve its performances. The hydrostatic guide based on progressive mengen（PM） flow controller is especially suitable for the heavy numerical control（NC） machine tools. However, few literatures about the research on the static and dynamic characteristics of the hydrostatic guides based on PM flow controller are reported. In this paper, the formulae are derived for analyzing the static and dynamic characteristics of hydrostatic guides with rectangle pockets and PM flow controller according to the theory of hydrostatic bearing. On the basis of the analysis of hydrostatic bearing with circular pocket, some equations are derived for solving the static pressure, volume pressure and squeezing pressure which influence the dynamic characteristics of hydrostatic guides with rectangle pocket. The function and the influencing factors of three pressures are clarified. The formulae of amplitude-frequency characteristics and dynamic stiffness of the hydrostatic guide system are derived. With the help of software MATLAB, programs are coded with C＋＋ language to simulate numerically the static and dynamic characteristics of the hydrostatic guide based on PM flow controller. The simulation results indicate that the sensitive oil volume between the outlet of the PM flow controller and the guide pocket has the greatest influence on the characteristics of the guide, and it should be reduced as small as possible when the field working condition is met. Choosing the oil with a greater viscosity is also helpful in improving the dynamic performance of hydrostatic guides. The re

关键词： PM flow controller rectangle pocket static characteristics dynamic characteristics hydrostatic guides

Phytoremediation and its models for organic contaminated soils

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Journal of Environmental Sciences 2003年第3期15卷 302-310页

作者： gao Yan-zheng ZHU Li-zhong Department of Environment Science Zhejiang UniversityHangzhou 310028China.

Soil pollution has been attracting considerable public attentions over the last decades. Sorts of traditional physiochemical methods have been used to remove the organic pollutants from soils. However, the enormous costs and low efficiencies associated with these remediation technologies limit their availabilities. Phytoremediation is an emerging technology that uses plants to cleanup pollutants in soils. As overwhelmingly positive results have been shown, phytoremediation is a most economical and effective remediation technique for organic contaminated soils. In this paper phytoremediation and its models for organic contaminated soils are viewed. The mechanisms of phytoremediation mainly include the direct plant uptake of organic pollutants, degradation by plant-derived degradative enzymes, and stimulated biodegradation in plant rhizosphere. Phytoremediation efficiency is close related to physicochemical properties of organic pollutants, environmental characteristics, and plant types. It is no doubt that soil amendments such as surfactants improve the solubilities and availabilities of organic pollutants in soils. However, little information is available about effects of soil amendments on phytoremediation efficiencies. Phytoremediation models have been developed to simulate and predict the environmental behavior of organic pollutants, and progress of models is illustrated. In many ways phytoremediation is still in its initial stage, and recommendations for the future research on phytoremediation are presented.

关键词： phytoremediation organic pollutant soil

LARGE AMPLITUDE FREE VIBRATIONS OF LAMINATED COMPOSITE PLATES

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Acta Mechanica Solida Sinica 2000年第1期13卷 75-80页

作者： Wang Haowen gao zheng zheng Zhaochang Department of Aircraft Nanjing University of Aeronautics and AstronauticsNanjing 210016China Department of Engineering Mechanics Tsinghua UniversityBejing 100084China

This paper deals with large amplitude free flexural vibrations of laminated composite plates using a 9-node Heterosis degenerated isoparametric quadrilateral element, including the effects of transverse shear and rotary inertia. The nonlinear dynamic equations of the plates are formulated in von Karman's sense. Amplitude-frequency relationships are obtained through dynamic response history using; the Newmark numerical integration scheme. Detailed numerical results based on various parameters are presented for orthotropic laminated plates with different boundary conditions. The rectangular anti-symmetric cross-ply plates show the softening type of nonlinearity for initial small amplitudes. The displacement amplitudes decrease and nonlinear frequencies increase with the increment of time.

关键词： composite plate free vibration

Resistance of the diffusive boundary layer to salt release from saline sediments to freshwater

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Acta Oceanologica Sinica 2008年第1期27卷 23-28页

作者： gao Zengwen zheng Xilai XU Qinxuan Key Laboratory of Ministry of Education for Marine Environmental Science and Ecology Ocean University of China Qingdao 266003 China

The diffusive boundary layer （DBL） is the zone for matter exchange between surface water and aquatic sediments. To elucidate the influence of DBL on salt release from saline sediments to freshwater, two experiments with or without wind blowing were conducted. According to the experiments, a 3.5 cm DBL is formed above the smoothed sediments at a steady wind field and this thickness is greater than other studies. The observed flux of salt through the DBL is 6% larger than the calculated value from Fick＇ s first law. The results indicate that molecular diffusion is the dominant mechanism for salt transport through the DBL. The presence of DBL suppresses the hydrodynamic enhancement for matter exchange between sediments and overlying water. Therefore, salts in the sediments of a polder reservoir may influence the water quality chronically.

关键词： sediment-water interface diffusive boundary layer molecular diffusion salt transport resistance effect

Multi-frequency point supported LLRF front-end for CiADS wide-bandwidth application

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Nuclear Science and Techniques 2020年第3期31卷 66-73页

作者： Qi Chen zheng gao zheng-Long Zhu Zong-Heng Xue Yuan He Xian-Wu Wang Institute of Modern Physics Chinese Academy of SciencesLanzhou 730000China School of Nuclear Science and Technology University of Chinese Academy of SciencesBeijing 100049China

The China initiative Accelerator Driven System,CiADS,physics design adopts 162.5 MHz,325 MHz,and 650 MHz cavities,which are driven by the corresponding radio frequency(RF)power system,requiring frequency translation front-end for the RF *** that application,a general-purpose design front-end prototype has been developed to evaluate the multi-frequency point supported design *** difficult parts to achieve the requirements of the general-purpose design are reasonable device selection and balanced *** a carefully selected low-noise wide-band RF mixer and amplifier to balance the performance of multi-frequency supported down-conversion,specially designed LO distribution net to increase isolation between adjacent channels,and external band-pass filter to realize expected up-conversion frequencies,high maintenance and modular front-end generalpurpose design has been *** of standard parameters show an R2 value of at least 99.991%in the range of-60-10 dBm for linearity,up to 18 dBm for P1dB,and up to 89 dBc for cross talk between adjacent *** phase noise spectrum is lower than 80 dBc in the range of 0-1 MHz;cumulative phase noise is 0.006°;and amplitude and phase stability are 0.022%and 0.034°,respectively.

关键词： Frequency jump RF Front-end LLRF CiADS

Robustness Analysis of Discrete-time Indirect Model Reference Adaptive Control with Normalized Adaptive Laws

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International Journal of Automation and computing 2010年第3期7卷 381-388页

作者： Qing-zheng gao Xue-Jun Xie Department of Physics and Information Engineering Jining University Qufu 273155 PRC School of Electrical Engineering and Automation Xuzhou Normal University Xuzhou 221116 PRC

For a class of discrete-time systems with unmodeled dynamics and bounded disturbance, the design and analysis of robust indirect model reference adaptive control （MRAC） with normalized adaptive law are investigated. The main work includes three parts. Firstly, it is shown that the constructed parameter estimation algorithm not only possesses the same properties as those of traditional estimation algorithms, but also avoids the possibility of division by zero. Secondly, by establishing a relationship between the plant parameter estimate and the controller parameter estimate, some similar properties of the latter are also established. Thirdly, by using the relationship between the normalizing signal and all the signals of the closed-loop system, and some important mathematical tools on discrete-time systems, as in the continuous-time case, a systematic stability and robustness analysis approach to the discrete indirect robust MRAC scheme is developed rigorously.

关键词： Discrete-time systems model reference adaptive control (MRAC) swapping lemmas stability robustness

Selection and thermal physical characteristics analysis of in-situ condition preserved coring lunar rock simulant in extreme environment

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International Journal of Mining Science and Technology 2023年第11期33卷 1411-1424页

作者： Haichun Hao Mingzhong gao Cunbao Li Xuan Wang Yan Wu zheng gao Wen Yu Xuemin Zhou Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization Institute of Deep Earth Sciences and Green EnergyCollege of Civil and Transportation EngineeringShenzhen UniversityShenzhen 518060China Shenzhen Key Laboratory of Deep Underground Engineering Sciences and Green Energy Shenzhen UniversityShenzhen 518060China Center for Lunar and Planetary Sciences Institute of GeochemistryChinese Academy of SciencesGuiyang 550081China

With the increasing scarcity of Earth’s resources and the development of space science and technology,the exploration, development, and utilization of deep space-specific material resources(minerals, water ice, volatile compounds, etc.) are not only important to supplement the resources and reserves on Earth but also provide a material foundation for establishing extraterrestrial research bases. To achieve large depth in-situ condition-preserved coring(ICP-Coring) in the extreme lunar environment, first, lunar rock simulant was selected(SZU-1), which has a material composition, element distribution, and physical and mechanical properties that are approximately equivalent to those of lunar mare basalt. Second, the influence of the lunar-based in-situ environment on the phase, microstructure, and thermal physical properties(specific heat capacity, thermal conductivity, thermal diffusivity, and thermal expansion coefficient)of SZU-1 was explored and compared with the measured lunar rock data. It was found that in an air atmosphere, low temperature has a more pronounced effect on the relative content of olivine than other temperatures, while in a vacuum atmosphere, the relative contents of olivine and anorthite are significantly affected only at temperatures of approximately-20 and 200 ℃. When the vacuum level is less than100 Pa, the contribution of air conduction can be almost neglected, whereas it becomes dominant above this threshold. Additionally, as the testing temperature increases, the surface of SZU-1 exhibits increased microcracking, fracture opening, and unevenness, while the specific heat capacity, thermal conductivity,and thermal expansion coefficient show nonlinear increases. Conversely, the thermal diffusivity exhibits a nonlinear decreasing trend. The relationship between thermal conductivity, thermal diffusivity, and temperature can be effectively described by an exponential function(R^(2)>0.98). The research results are consistent with previous studies

关键词： Lunar-based Lunar rock simulant Extreme environment Thermal physical properties

Characterization of the fracture compressibility and its permeability for shale under the effects of proppant embedment and compaction:A preliminary study

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Petroleum Science 2022年第3期19卷 1125-1138页

作者： Jian-Hua Li Bo-Bo Li Qiao-Yun Cheng zheng gao Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization Institute of Deep Earth Sciences and Green EnergyCollege of Civil and Transportation EngineeringShenzhen UniversityShenzhen518060GuangdongChina Shenzhen Key Laboratory of Deep Underground Engineering Sciences and Green Energy Shenzhen UniversityShenzhen518060GuangdongChina College of Mining Guizhou UniversityGuiyang550025GuizhouChina Guizhou Key Laboratory of Comprehensive Utilization of Non-metallic Mineral Resources Guiyang550025GuizhouChina National&Local Joint Laboratory of Engineering for Effective Utilization of Regional Mineral Resources from Karst Areas Guizhou UniversityGuiyang550025GuizhouChina

Hydraulic fracturing technology plays a key role in improving the recovery rate of shale *** improvement of permeability in relation to hydraulic fracturing depends on changes brought about by the proppant on the fracture structure in *** it is of great significance to describe the microscopic changes during this process by means of an accurate theoretical *** this study,based on the heterogeneity of shale fracture and the compaction and embedment of a proppant,we proposed a permeability model to examine the combined effects of a proppant and stress to describe the change mechanism in ***,changes in fracture width and porosity were considered,and a calculation model of fracture compressibility under proppant compaction and embedment was *** difference from previous studies is that the compressibility and permeability of supported fractures can be further quantified and analyzed by this ***,its rationality was verified by publicly released test *** results show that,the compressive effect of stress and the embedding of proppant both have a negative impact on shale permeability.

关键词： Shale Fracture compressibility Permeability Hydraulic fracturing Proppant embedment