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THE OPTIMAL TRUNCATED LOW-DIMENSIONAL DYNAMICAL SYSTEMS BASED ON FLOW DATABASES

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Acta Mechanica Sinica 1996年第2期12卷 104-116页

作者：吴锤结史汉生 Air Force Institute of Meteorology Nanjing 211101China

A new theory on the construction of optimal truncated Low-Dimensional Dynamical Systems (LDDSs) with different physical meanings has been developed, The physical properties of the optimal bases are reflected in the user-defined optimal conditions, Through the analysis of linear and nonlinear examples, it is shown that the LDDSs constructed by using the Proper Orthogonal Decomposition (POD) method are not the optimum. After comparing the errors of LDDSs based on the new theory POD and Fourier methods, it is concluded that the LDDSs based on the new theory are optimally truncated and catch the desired physical properties of the systems.

关键词： partial differential equation flow database optimization dynamical system

Calculation of Probability of Cloud-Free Lines-of-Sightat Given Heights in Foshan, China

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Advances in Atmospheric Sciences 1999年第2期16卷 297-303页

作者：李昀英孙立潭 Air Force Institute of Meteorology 211101 Nanjing

Based on Lund and Shanklin’s work (1972), methods of calculating Probability of Cloud-Free Lines-of-Sight (PCFLOS), Persistence Probability of Cloud-Free Lines-of-Sight (PPCFLOS) and Recurrence Probability of Cloud-free Lines-of-Sight (RPCFLOS) at given heights are presented. PCFLOS, PPCFLOS and RPCFLOS are calculated in Foshan, China by conventional observation data from 1961 to 1990. The conclusions are: (1) The higher the elevations, the smaller the PCFLOS and the larger the view angles, the larger the PCFLOS. (2) PPCFLOS and RPCFLOS decrease with the increase of elevation and the delay of time. (3) RPCFLOS is always equal to or larger than PPCFLOS at lag times.

关键词： Probability of cloud-free lines-of-sight Persistence probability of cloud-free lines-of-sight Recurrence probability of cloud-free lines-of-sight Cloud climate

SENSITIVE NUMERICAL SIMULATION AND ANALYSIS OF RAINSTORM USING NESTED WRF MODEL

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Journal of Hydrodynamics 2006年第5期18卷 578-586页

作者： WANG Shu-chang HUANG Si-xun LI Yi Institute of Meteorology PLA University of Science and Technology Nanjing 211101 China

Nowadays, the nested grid model is widely used to increase the resolution of numerical model. An attempt to investigate the influence of the newly developed nesting technique of WRF model on the mesoscale numerical simulation of severe storm is described in this article. The results of sensitivity tests infer that the WRF model give more accurate and vivid prediction of severe storm with nesting scheme. As is shown in the tests, simulating value of the precipitation centers using nesting scheme are larger than those without using nesting scheme, which indicates that the simulating precipitation of nested storm is closer to the real rainfall. And there is obvious improvement of distribution of rain area and position of precipitation centers. According to the high resolution output data of the WRF model, deep and detailed analysis of characters of the mesoscale system that triggers the rainstorm is reported in this article, and the thermal and dynamical characters of this Meiyu front severe storm are also discussed.

关键词： WRF nesting numerical simulation mesoscale analysis

EFFECT OF INSTABILITIES OF FLOW ON MESOSCALE PREDICTABILITY OF WEATHER SYSTEMS

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Journal of Hydrodynamics 2011年第2期23卷 193-203页

作者： LUO Yu ZHANG Li-feng Institute of Meteorology PLA University of Science and Technology Nanjing 211101

The numerical solution of Boussinesq equations is worked out as an initial-value problem to study the effect of the instabilities of flow on the initial error growth and mesoscale predictability. The development of weather systems depends on different dynamic instability mechanisms according to the spatial scales of the system and the development of mesoscale systems is determined by symmetric instability. Since symmetric instability dominates among the three types of dynamic instability, it makes the prediction of the associated mesoscale systems more sensitive to initial uncertainties. This indicates that the stronger instability leads to faster initial error growth and thus limits the mesoscale predictability. Besides dynamic instability, the impact of thermodynamic instability is also explored. The evolvement of convective instability manifests as dramatic variation in small spatial scale and short temporal scale, and furthermore, it exhibits the upscale growth. Since these features determine the initial error growth, the mesoscale systems arising from convective instability are less predictable and the upscale error growth limits the predictability of larger scales. The latent heating is responsible for changing the stability of flow and subsequently influencing the error growth and the predictability.

关键词： instabilities of flow mesoscale system predictability initial errors

Effect of Spin-Orbit Interaction and Input State on Quantum Discord and Teleportation of Two-Qubit Heisenberg Systems

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Chinese Physics Letters 2012年第3期29卷 25-28页

作者： QIN Meng ZHAI Xiao-Yue CHEN Xuan LI Yan-Biao WANG Xiao BAI Zhong Institute of Science PLA University of Science and TechnologyNanjing 211101

We study the *** discord and teleportation of a two-qubit Heisenberg XXX chain with spin-orbit *** analytical expressions of quantum discord,output state quantum discord and fidelity are obtained for this model The classical correlation,quantum correlation and entanglement of this system depending on coupling interaction,spin-orbit interaction and temperature are investigated in detail It is found that the quantum discord exists for the ferromagnetic case,but entanglement is zero under the same *** can obtain fidelity better than any classical communication protocol for the antiferromagnetic *** robustness of quantum discordagainst the temperature is helpful for the realization of quantum computation.

关键词： interaction computation quantum

Criteria for minimization of spectral abscissa of time-delay systems

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Applied Mathematics and Mechanics(English Edition) 2021年第7期42卷 969-980页

作者： Zaihua WANG Department of Basic Courses Army Engineering UniversityNanjing 211101China

Spectral abscissa(SA)is defined as the real part of the rightmost characteristic root(s)of a dynamical system,and it can be regarded as the decaying rate of the system,the smaller the better from the viewpoint of fast *** on the Puiseux series expansion of complex-valued functions,this paper shows that the SA can be minimized within a given delay interval at values where the characteristic equation has repeated roots with multiplicity 2 or *** sufficient conditions in terms of the partial derivatives of the characteristic function are established for testing whether the SA is minimized or not,and they can be tested directly and easily.

关键词： time delay stability parameter tuning spectral abscissa(SA) decaying speed

Multiplicity-induced optimal gains of an inverted pendulum system under a delayed proportional-derivative-acceleration feedback

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Applied Mathematics and Mechanics(English Edition) 2022年第11期43卷 1747-1762页

作者： Zisong MEI Zaihua WANG Department of Basic Courses Army Engineering UniversityNanjing 211101China

This paper studies the stabilization to an inverted pendulum under a delayed proportional-derivative-acceleration(PDA)feedback,which can be used to understand human balance in quiet *** closed-loop system is described by a neutral delay differential equation(NDDE).The optimal feedback gains(OFGs)that make the exponential decaying rate maximized are determined when the characteristic equation of the closed-loop has a repeated real root with multiplicity *** a property is called multiplicity-induced dominancy of time-delay systems,and has been discussed intensively by many authors for retarded delay differential equations(RDDEs).This paper shows that multiplicity-induced dominancy can be achieved in *** addition,the OFGs are delay-dependent,and decrease sharply to small numbers correspondingly as the delay increases from zero and varies slowly with respect to moderate ***,the inverted pendulum can be well-stabilized with moderate delays and relatively small feedback *** result might be understandable that the elderly with obvious response delays can be well-stabilized with a delayed PDA feedback controller.

关键词： human balance inverted pendulum proportional-derivative-acceleration(PDA)feedback neutral delay differential equation(NDDE) multiplicity-induced dominancy

A Study of the Environmental Influence on the Amplitude of Lee Waves

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Advances in Atmospheric Sciences 2008年第3期25卷 474-480页

作者：臧增亮张铭 Institute of Meteorology PLA University of Science & TechnologyNanjing 211101

A three-layer theoretical model is used to calculate the lee wave of a real example occurring over Blue Ridge in Pittsburgh, in which the maximum vertical velocity is 0.11 m s^-1. Based on this, the influence of changes in the thickness and values of the Scorer parameter in each layer are analyzed. It is shown that the influence of each layer parameters on the lee-wave amplitude is different, and the amplitude is more sensitive to the changes in the lower layer. Since the environment changes can affect the Scorer parameter profile, the influence of the environment on the amplitude is studied. The results show that the amplitude will decrease in the daytime because of solar heating, and increase at night because of radiational cooling, according to observational data. The case is also simulated by the Advanced Regional Prediction System （ARPS） model. The simulated amplitude is 0.089 m s^-1, which is close to the calculated result. Numerical sensitivity experiments are performed to test the former calculated experiments. The simulated results are consistent with the analytically calculated results.

关键词： lee waves Scorer parameter amplitude numerical simulation

Reconstruction of 3-D surface waves generated by moving submerged sphere based on stereo imaging principle

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Journal of Hydrodynamics 2020年第1期32卷 139-147页

作者： Xin-long Wang Gang Wei Hui Du Shao-dong Wang Department of Meteorology and Oceanography National University of Defense TechnologyNanjing 211101China

A sailing ship can produce significant disturbances on the water surface,but the perturbation generated by a moving submerged source is much smaller due to the physical property of the free surface,as represented by the rigid-lid assumption,with the geometric displacement barely observed or *** on the stereo imaging principle,an experimental system for the three-dimensional measurement of the surface perturbation is built by assembling two charge coupled device(CCD)sensors,to measure the surface waves generated by a small submerged sphere,including the small-scale vertical displacements and the flow field on the water *** obtained results are consistent with those obtained by the theoretical analysis,and the measurement accuracy for the vertical displacements is improved by 50%compared to that of the direct optical method based on the image grey ***,the present measurement technique can be efficiently and precisely applied to other measurements of small-scale disturbances on a free surface.

关键词： Surface wake stereo imaging geometric reconstruction particle image velocimetry(PIV)