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Painlevé Property and Integrability of Polynomial Dynamical Systems

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Communications in Mathematical Research 2014年第4期30卷 358-368页

作者： Li Wen-lei shi shao-yun School of Mathematics Jilin University Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education Jilin University

The main purpose of this paper is to investigate the connection between the Painlev′e property and the integrability of polynomial dynamical systems. We show that if a polynomial dynamical system has Painlev′e property, then it admits certain class of first integrals. We also present some relationships between the Painlev′e property and the structure of the differential Galois group of the corresponding variational equations along some complex integral curve.

关键词： Painlev′e property integrability differential Galois group

Lyapunov-type Inequalities for a System of Nonlinear Differential Equations

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Communications in Mathematical Research 2017年第3期33卷 205-214页

作者： wei geng-ping shi shao-yun Department of Mathematics Huaihua University Huaihua Hunan 418008 不详

This paper presents several new Lyapunov-type inequalities for a system of first-order nonlinear differential equations. Our results generalize and improve some existing ones.

关键词： Lyapunov-type inequality nonlinear differential equation Hamiltonian system

A(k,n-k) Conjugate Boundary Value Problem with Semipositone Nonlinearity

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Communications in Mathematical Research 2015年第1期31卷 51-61页

作者： YAO QING-LIU shi shao-yun Department of Applied Mathematics Nanjing University of Finance and Economics

The existence of positive solution is proved for a （k, n - k） conjugate boundary value problem in which the nonlinearity may make negative values and may be singular with respect to the time variable. The main results of Agarwal et al. （Agarwal R P, Grace S R, O＇Regan D. Semipositive higher-order differential equations. Appl. Math. Letters, 2004, 14： 201-207） are extended. The basic tools are the Hammerstein integral equation and the Krasnosel＇skii＇s cone expansion-compression technique.

关键词： higher order ordinary differential equation boundary value problem semipositone nonlinearity positive solution

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 proposed.The authors consider nonnegativity,boundedness,global asymptotic stability of the solutions and bifurcation properties of the steady states.It is proved that the virus is cleared from the host under some conditions if the basic reproduction number R0 is less than unity.Meanwhile,the model exhibits the phenomenon of backward bifurcation.We also obtain one equilibrium is semi-stable by using center manifold theory.It is proved that the endemic equilibrium is globally asymptotically stable under some conditions if R0 is greater than unity.It also is proved that the model undergoes Hopf bifurcation from the endemic equilibrium under some conditions.It is novelty that the model exhibits two famous bifurcations,backward bifurcation and Hopf bifurcation.The model is extended to incorporate the specific Cytotoxic T Lymphocytes(CTLs)immune response.Stabilities of equilibria and Hopf bifurcation are considered accordingly.In 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

Understanding the Thermal Impedance of Silicone Rubber/Hexagonal Boron Nitride Composites as Thermal Interface Materials

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Chinese Journal of Polymer Science 2024年第3期42卷 352-363,I0008页

作者： Yuan Ji shi-Da Han Hong Wu shao-yun Guo Feng-Shun Zhang Jian-Hui Qiu The State Key Laboratory of Polymer Materials Engineering Sichuan Provincial Engineering Laboratory of Plastic/Rubber Complex Processing TechnologyPolymer Research InstituteSichuan UniversityChengdu 610065China Institute of Chemical Materials China Academy of Engineering PhysicsMianyang 621900China Department of Mechanical Engineering Faculty of Systems Science and TechnologyAkita Prefectural UniversityAkita 015-0055Japan

Silicone rubber(SR) composites are most widely used as thermal interface materials(TIMs) for electronics heat dissipation. Thermal impedance as the main bottleneck limiting the performance of TIMs is usually neglected. Herein, the thermal impedance of SR composites loaded with different levels of hexagonal boron nitride(h-BN) as TIMs was elaborated for the first time by the ASTM D 5470 standard test and finite element analysis. It was found that elastic modulus and surface roughness of SR composites increased with the increase of h-BN content, indicating that the conformity was reduced. When the assembly pressure was 0.69 MPa, there existed an optimal h-BN content at which the contact resistance was minimum(0.39 K·cm^(2)·W^(-1)). Although the decreased bond line thickness(BLT) by increasing the assembly pressure was beneficial to reduce the thermal impedance, the proper assembly pressure should be selected to prevent the warpage of the contact surfaces and the increase in contact resistance, according to the compression properties of the SR composites. This study provides valuable insights into fabrication of high-performance TIMs for modern electronic device applications.

关键词： Thermal interface materials Hexagonal boron nitride Thermal impedance Surfaces

Identification of reservoir types in deep carbonates based on mixedkernel machine learning using geophysical logging data

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Petroleum Science 2024年第3期21卷 1632-1648页

作者： Jin-Xiong shi Xiang-Yuan Zhao Lian-Bo Zeng yun-Zhao Zhang Zheng-Ping Zhu shao-Qun Dong Key Laboratory of Exploration Technologies for Oil and Gas Resources of the Ministry of Education Yangtze University School of Geosciences Yangtze University College of Geosciences China University of Petroleum (Beijing) Petroleum Exploration and Production Research Institute of SINOPEC School of Earth Sciences and Engineering Xi'an Shiyou University

Identification of reservoir types in deep carbonates has always been a great challenge due to complex logging responses caused by the heterogeneous scale and distribution of storage spaces. Traditional cross-plot analysis and empirical formula methods for identifying reservoir types using geophysical logging data have high uncertainty and low efficiency, which cannot accurately reflect the nonlinear relationship between reservoir types and logging data. Recently, the kernel Fisher discriminant analysis(KFD), a kernel-based machine learning technique, attracts attention in many fields because of its strong nonlinear processing ability. However, the overall performance of KFD model may be limited as a single kernel function cannot simultaneously extrapolate and interpolate well, especially for highly complex data cases. To address this issue, in this study, a mixed kernel Fisher discriminant analysis(MKFD) model was established and applied to identify reservoir types of the deep Sinian carbonates in central Sichuan Basin, China. The MKFD model was trained and tested with 453 datasets from 7 coring wells, utilizing GR,CAL, DEN, AC, CNL and RT logs as input variables. The particle swarm optimization(PSO) was adopted for hyper-parameter optimization of MKFD model. To evaluate the model performance, prediction results of MKFD were compared with those of basic-kernel based KFD, RF and SVM models. Subsequently, the built MKFD model was applied in a blind well test, and a variable importance analysis was conducted. The comparison and blind test results demonstrated that MKFD outperformed traditional KFD, RF and SVM in the identification of reservoir types, which provided higher accuracy and stronger generalization. The MKFD can therefore be a reliable method for identifying reservoir types of deep carbonates.

关键词： Reservoir type identification Geophysical logging data Kernel Fisher discriminant analysis Mixed kernel function Deep carbonates

Supercritical CO_(2) Cycles for Nuclear-Powered Marine Propulsion:Preliminary Conceptual Design and Off-Design Performance Assessment

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Journal of Thermal Science 2024年第1期33卷 328-347页

作者： LI Zhaozhi shi Mingzhu shao Yingjuan ZHONG Wenqi Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education School of Energy and EnvironmentSoutheast UniversityNanjing 210096China

Using the efficient,space-saving,and flexible supercritical carbon dioxide(sCO_(2)) Brayton cycle is a promising approach for improving the performance of nuclear-powered ships.The purpose of this paper is to design and compare sCO_(2) cycle power systems suitable for nuclear-powered ships.Considering the characteristics of nuclear-powered ships,this paper uses different indicators to comprehensively evaluate the efficiency,cost,volume,and partial load performance of several nuclear-powered sCO_(2) cycles.Four load-following strategies are also designed and compared.The results show that the partial cooling cycle is most suitable for nuclear-powered ships because it offers both high thermal efficiency and low volume and cost,and can maintain relatively high thermal efficiency at partial loads.Additionally,the new load-following strategy that adjusts the turbine speed can keep the compressor away from the surge line,making the cycle more flexible and efficient compared to traditional inventory and turbine bypass strategies.

关键词： supercritical CO_(2)cycle nuclear marine propulsion off-design performance

The risk factors and threshold level of subchronic inhalation exposure of reclaimed water

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Journal of Environmental Sciences 2024年第3期137卷 639-650页

作者： Jiayang Kong yun Lu yunru Ren Menghao Chen Gang Liu Liangliang shi State Key Joint Laboratory of Environment Simulation and Pollution Control State Environment Protection Key Laboratory of Microorganism Application and Risk ControlSchool of EnvironmentTsinghua UniversityBeijing 100084China

Inhalation of reclaimed water is known to cause lung infammation,and free endotoxins have been shown to be a major risk factor for acute exposure.Subchronic exposure has also been shown to induce infammatory responses with visible tissue damage.However,subchronic risk factors have yet to be identified,and a threshold for the protection of occupational populations during urban reuse is necessary.In this study,potential risk factors in reclaimed water were examined by subchronic exposure with fractionated reclaimed water,and the health risk threshold was tested with a series of diluted reclaimed water.Accordingly,following a 12-week exposure,macromolecules and microorganisms were found to be two major risk factors in reclaimed water that could cause pulmonary infammation,including increased proportion of polymorphonuclear leukocytes in bronchoalveolar fuid,formation of inducible bronchus-associated lymphoid tissue,and elevation of Immunoglobulin A levels.Moreover,infammation persisted after a 4-week recovery period.The calculated threshold of reclaimed water exposure for mice was 31.8 Endotoxin Unit(EU)/(kg·day)under when exposed to 50%additional relative humidity from reclaimed water at 25℃ for 2 hr/day.Meanwhile,the subchronic threshold estimate for humans under the same exposure conditions was found to be 12.2 EU/(kg·day),corresponding to endotoxin levels of 61.7 EU/mL in reclaimed water.The threshold level of endotoxin was lower than that in most non-potable reclaimed water.The findings of this study suggest that occupational exposure of reclaimed water can serve as a potential risk to workers.

关键词： Reclaimed water Inhalation exposure Risk factor Threshold Infammation Endotoxin

GNSS gyroscopes:determination of angular velocity and acceleration with very high-rate GNSS

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Satellite Navigation 2024年第1期5卷 74-90页

作者： yun shi Peiliang Xu Yuanming Shu Xiaolin Meng School of Geomatics Xi’an University of Science and TechnologyXi’an710054People’s Republic of China Disaster Prevention Research Institute Kyoto UniversityUjiKyoto611-0011Japan College of Marine Geosciences Ocean University of ChinaQingdaoPeople’s Republic of China School of Instrument Science and Engineering Southeast UniversityNanjing210096People’s Republic of China

Although global navigation satellite systems(GNSS)have been routinely applied to determine attitudes,there exists no literature on determining angular velocity and/or angular acceleration from GNSS.Motivated by the invention of computerized accelerometers of the correspondence author and following the success of accurately recovering translational velocity and acceleration waveforms from very high-rate GNSS precise positioning by Xu and his collaborators in 2021,we propose the concept of GNSS gyroscopes and reconstruct angular velocity and acceleration from very high-rate GNSS attitudes by applying regularization under the criterion of minimum mean squared errors.The major results from the experiments can be summarized in the following:(i)angular velocity and acceleration waveforms computed by applying the difference methods to high-rate GNSS attitudes are too noisy and can be physically not meaningful and numerically incorrect.The same can be said about inertial measurement unit(IMU)attitudes,if IMU gyros are not of very high accuracy;(ii)regularization is successfully applied to reconstruct the high-rate angular velocity and acceleration waveforms from 50 Hz GNSS attitudes and significantly outperforms the difference methods,validating the proposed concept of GNSS gyroscopes.By comparing the angular velocity and acceleration results by using the difference methods and regularization,we find that the peak values of angular velocity and acceleration by regularization are much smaller by a maximum factor of 1.57 in the angular velocity to a maximum factor of 8662.53 times in the angular acceleration in the case of high-rate GNSS,and by a maximum factor of 1.26 in the angular velocity to a maximum factor of 2819.85 times in the angular acceleration in the case of IMU,respectively;and(iii)the IMU attitudes apparently lead to better regularized angular velocity and acceleration waveforms than the high-rate GNSS attitudes,which can well be explained by the fact that the former is of better accuracy than the latter.As

关键词： Angular velocity Angular acceleration High-rate GNSS GNSS attitudes GNSS gyroscopes Regularization