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GLOBAL DISCONTINUOUS SOLUTIONS TO A CLASS OF DISCONTINUOUS INITIAL VALUE PROBLEMS FOR THE SYSTEM OF ISENTROPIC FLOW AND APPLICATIONS^(***)

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Chinese Annals of Mathematics,Series B 1989年第1期10卷 1-18页

作者：李大潜赵彦淳 Department of Mathematics and Institute of Mathematics Fudan University Shanghai China Institute of Mathematics Fudan University Shanghai China

In this paper, the authors discuss a kind of discontinuous initial value problems for the system of one-dimensional isentropic flow and prove the existence or nonexistence of global discontinuous solutions only containing one shock in a class of piecewise continuous and piecewise smooth functions. As applications, various interaction problems of a typical shock with a rarefaction wave are considered.

关键词： discontinuous CLASS piecewise determ backward Riemann holds Rankine hence simply

A New Semi-Lagrangian Finite Volume Advection Scheme Combines the Best of Both Worlds

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Advances in Atmospheric Sciences 2021年第9期38卷 1608-1609页

作者： Lucas HARRIS NOAA/Geophysical Fluid Dynamics Laboratory Princeton University Forrestal Campus201 Forrestal RoadPrincetonNJ 08540-6649USA

Advection,or transport by wind,is fundamental to numerical weather and climate *** is especially important to solve the equations governing the distribution of heat,moisture,pollutants,and so *** classes of advection schemes have become dominant in recent ***-Lagrangian (SL;Diamantakis,2013) methods form the advection equation in its"Lagrangian"or flow-following form and use the winds (either prescribed or predicted) to trace trajectories backwards from a grid point to their original location on the previous time step.

关键词： prescribed backward Finite

AN ANALYTIC METHOD OF FRACTIONAL STEPS FOR THE NUMERICAL SOLUTION TO CONVECTION-DOMINATED PROBLEMS

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Science China Mathematics 1990年第8期33卷 944-954页

作者：吴江航孙毓平 Department of Mechanics Peking University Beijing 100871 PRC

An analytic method of fractional steps, which is unconditionally L_∞-stable, is proposed for the numerical solution to convection-dominated problems. In this paper the stability and convergence of the analytic soluti... 详细信息

关键词： convection-dominated problems method of fractional steps backward characteristics technique finite analytic method maximum and minimum principles.

The Sum and Difference of Two Constant Elasticity of Variance Stochastic Variables

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Applied Mathematics 2013年第11期4卷 1503-1511页

作者： Chi-Fai Lo Department of Physics Institute of Theoretical Physics The Chinese University of Hong Kong Hong Kong China

We have applied the Lie-Trotter operator splitting method to model the dynamics of both the sum and difference of two correlated constant elasticity of variance (CEV) stochastic variables. Within the Lie-Trotter splitting approximation, both the sum and difference are shown to follow a shifted CEV stochastic process, and approximate probability distributions are determined in closed form. Illustrative numerical examples are presented to demonstrate the validity and accuracy of these approximate distributions. These approximate probability distributions can be used to valuate two-asset options, e.g. spread options and basket options, where the CEV variables represent the forward prices of the underlying assets. Moreover, we believe that this new approach can be extended to study the algebraic sum of N CEV variables with potential applications in pricing multi-asset options.

关键词： Constant Elasticity of Variance Stochastic Variables Probability Distribution Functions backward Kolmogorov Equation Lie-Trotter Splitting Approximation

THE TRANSFORMATION AND DETECTION OF ACOUSTIC ECHO SIGNALS WITH SWTTYPE SODAR PROBING SYSTEM

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Chinese Science Bulletin 1989年第22期34卷 1891-1895页

作者：赵松年熊小芸 Institute of Atmospheric Physics Academia Sinica. Beijing 100011. PRC

The Acoustic Sodar is widely used in the probe of the atmospheric boundary layer. We will use the Phase Locked Tracking Filter (PLTF) as the total program to measure the Doppler frequency deviation signal f_d of random weak signal under the condition of an interference of strong noise and also we will use the transformation method of

关键词： Phase Locked Tracking Filter fading channel backward scatter

The secrets to running economy

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Journal of Sport and Health Science 2022年第3期11卷 273-274页

作者： Walter Herzog Human Performance Laboratory Faculty of KinesiologyUniversity of CalgaryCalgaryAB T2N 1N4Canada

Every once in a while,a sport is revolutionized by a discovery or a new *** the mid-1980s,cross-country skiing was changed forever by the introduction of the skating *** Fosbury revolutionized high-jumping when he won the Olympic Games by crossing the bar“backwards”,and the development of the“klapp-skate”led to vast improvements of world records in speed skating.

关键词： technique. backward revolution

Variable selection strategies and its importance in clinical prediction modelling

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Family Medicine and Community Health 2020年第1期8卷 37-43页

作者： Mohammad Ziaul Islam Chowdhury Tanvir C Turin Department of Community Health Sciences Cumming School of MedicineUniversity of CalgaryCalgaryAlbertaCanada Department of Family Medicine Cumming School of MedicineUniversity of CalgaryCalgaryAlbertaCanada

Clinical prediction models are used frequently in clinical practice to identify patients who are at risk of developing an adverse outcome so that preventive measures can be initiated.A prediction model can be developed in a number of ways;however,an appropriate variable selection strategy needs to be followed in all *** purpose is to introduce readers to the concept of variable selection in prediction modelling,including the importance of variable selection and variable reduction *** will discuss the various variable selection techniques that can be applied during prediction model building(backward elimination,forward selection,stepwise selection and all possible subset selection),and the stopping rule/selection criteria in variable selection(p values,Akaike information criterion,Bayesian information criterion and Mallows’Cp statistic).This paper focuses on the importance of including appropriate variables,following the proper steps,and adopting the proper methods when selecting variables for prediction models.

关键词： criterion backward subset

Global and Bifurcation Analysis of an HIV Pathogenesis Model with Saturated Reverse Function

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Communications in Mathematical Research 2019年第4期35卷 301-317页

作者： Liu Yong-qi Meng Xiao-ying Shi Shao-yun College of Applied Mathematics Beijing Normal UniversityZhuhaiGuangdong519087 School of Statistics and Mathematics Zhongnan University of Economics and LawWuhan430073 不详

In this paper,an HIV dynamics model with the proliferation of CD4 T cells is *** authors consider nonnegativity,boundedness,global asymptotic stability of the solutions and bifurcation properties of the steady *** is proved that the virus is cleared from the host under some conditions if the basic reproduction number R0 is less than ***,the model exhibits the phenomenon of backward *** also obtain one equilibrium is semi-stable by using center manifold *** is proved that the endemic equilibrium is globally asymptotically stable under some conditions if R0 is greater than *** also is proved that the model undergoes Hopf bifurcation from the endemic equilibrium under some *** is novelty that the model exhibits two famous bifurcations,backward bifurcation and Hopf *** model is extended to incorporate the specific Cytotoxic T Lymphocytes(CTLs)immune *** of equilibria and Hopf bifurcation are considered *** addition,some numerical simulations for justifying the theoretical analysis results are also given in paper.

关键词： HIV model global asymptotical stability center manifold theory Hopf bifurcation backward bifurcation

Noise-robust voice conversion based on joint dictionary optimization

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Chinese Journal of Acoustics 2020年第2期39卷 259-272页

作者： ZHANG Shilei JIAN Zhihua SUN Minhong ZHONG Hua LIU Erxiao School of Communication Engineering Hangzhou Dianzi UniversityHangzhou 310018

A noise robust voice conversion algorithm based on joint dictionary optimization is proposed to effectively convert noisy source speech into the target one. In composition of the joint dictionary, speech dictionary is optimized using backward elimination algorithm. At the same time, a noise dictionary is introduced to match the noisy speech. The experimental results show that the backward elimination algorithm can reduce the number of dictionary frames and reduce the amount of calculation while ensuring the conversion effect. In low SNR and multiple noise environments, the algorithm has better conversion effect than both the traditional NMF algorithm and the NMF conversion algorithm plus spectral subtraction de-noising. The proposed algorithm improves the robustness of voice conversion system.

关键词： optimization noise backward