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A Modified Entropy Generation Number for Heat Exchangers

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Journal of Thermal Science 1996年第4期5卷 257-263页

作者： z. M. Xu S. R. Yang z. q. chen Department of Power Engineering Northeast China Institute of Electric Power Engineering Jilin City China Energy and Power Machinery Engineering Institute Xi’an Jiaotong University Xi’an China

This paper demonstrates the difference between the entropy generation number method proposed by Bejan and the method of entropy generation per unit amount of heat transferred in analyz.ng the thermodynamic performance of heat exchangers, points out the reason for leading to the above difference.A modified entropy generation number for evaluating the irreversibility of heat exchangers is proposed which is in consistent with the entropy generation per unit amount of heat transferred in entropy generation analysis. The entropy generated by friction is also investigated. Results show that when the entropy generated by friction in heat exchangers is taken into account, there is a minimum total entropy generation number while the NTU and the ratio of heat capacity rates vary. The existence of this minimum is the prereq.isite of heat exchanger optindz.tion.

关键词： entropy generation heat exchanger.

Suspension Performance with One Damper and One Inerter

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Suspension Performance with One Damper and One Inerter

Exponential Stabiliz.tion for Linear Systems with Actuator Saturation Via Intermittent Control 25th

第24届中国控制与决策会议

作者： Michael z. q. chen The University of Hong Kong Department of Mechanical Engineering The University of Hong Kong-Shenz.en Institute of Research and Innovation Nanjing University of Science and Technology School of Automation

In chen ＆ Smith 2009, a class of realiz.tions in which the number of dampers and inerters is restricted to one in each case, while allowing an arbitrary number of springs （which is the easiest element to realiz. practically）, was considered and it was proven that at most four springs are needed-an explicit construction was given comprising five different circuit arrangements to cover all cases. This paper makes a comparative study of the performances of these five circuit arrangements when applied as mechanical suspension struts in a q.arter-car model.

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Exponential Stabilization for Linear Systems with Actuator S...

Rational design of AgGaS/z.S/z.S q.antum dots with a near-unity photoluminescence q.antum yield via double shelling scheme

第25届中国控制与决策会议

作者： Yijing Wang Weiyan Li Wenlong Yang z.iq.ang z.o Michael z. q. chen the Tianjin Key Laboratory of Process Measurement and Control School of Electrical Engineering and Automation Tianjin University Department of Mechanical Engineering The University of Hong Kong

ISBN: (纸本)9781467355339

The exponential stabiliz.tion problem of a class of linear systems with actuator saturation is addressed in this paper. In an approach different from the previous results where the continuous controllers are used all the time, here the periodically intermittent control is proposed to ensure the exponential stability of the closed-loop systems. An exponential stability criterion is suggested using the contractive invariant ellipsoid as an estimate of the domain of attraction. In addition, the exponential convergence rate is explicitly given. The feedback controller can also be designed by regarding the feedback gain as an additional variable. A numerical example is presented to illustrate the effectiveness of our theoretical analysis.

关键词： Exponential Stability Intermittent Control Actuator Saturation Domain of Attraction

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Journal of Materials Science & Technology 2024年第2期169卷 235-242页

作者： H.X.Lu H.Liu z.z.Fu Y.Y.chen H.q.Dai z.Hu W.L.z.ang R.q.Guo Institute for Electric Light Sources School of Information Science and TechnologyFudan UniversityShanghai 200433China Institute of Future Lighting Academy for Engineering and TechnologyFudan UniversityShanghai 200433China Yiwu Research Institute of Fudan University YiwuZhejiang 322000China z.ongshan-Fudan Joint Innovation Center Zhongshan 528437China

In this study,a two-step method was used to synthesiz. highly luminescent AgGaS/z.S/z.S q.antum dots(q.s).In the first step,an inner z.S shell was formed via a one-pot method,which resulted in a smaller lattice mismatch between the AgGaS core and the outer z.S shell,thereby facilitating the formation of a thick outer *** the two-step shelling process,the synthesiz.d AgGaS/z.S/z.S q.s showed an excellent photoluminescence q.antum yield(PLq.)of 96.4%with a peak wavelength of 508 nm,repre-senting the highest PLq. reported thus far for AgGaS ***,the effect of halogen ions in z. precursors on the shelling process was *** was proposed that the capacity of halogen ions to coordinate with the q.s influenced the balance between z. cation diffusion and z.S shelling ***,the z.S shelling reaction was dominant when z.Cl_(2)was employed,while z. cation diffusion was the dominant process under the I^(−)-rich *** work provides insights into the interfacial restructuring during the z.S shelling and offers a clear map for the tailored synthesis of core/shell q.s.

关键词： AgGaS q.antum dots Photoluminescence Core/shell Alloyed core/shell interface

Precipitation of multi-type nano-q.asicrystals in a Mg-z.-Y alloy

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Journal of Magnesium and Alloys 2024年第3期12卷 997-1008页

作者： W.z.Wang X.z.z.ou L.F.z.ang H.q.Ye z.q.Yang Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of ScienceShenyang 110016China Ji Hua Laboratory Foshan 528251China Foshan University Foshan 528231China

Mg-6z.-1Y(at.%)ribbons with strengthening precipitates of multi-type nanoq.asicrystals were prepared by melt-spinning followed by aging *** evolution of the rapidly solidified ribbons during isothermal aging was comprehensively studied using various electron microscopy *** new kinds of decagonal q.asicrystals were formed in aged ribbons,in addition to precipitation of nanometer icosahedral ***-resolution observations reveal that both decagonal q.asicrystals can be modeled by q.asiperiodic tiling with decagonal clusters of 2.5 nm in diameter,but overlap of neighboring clusters in both decagonal q.asicrystals is different from the Gummelt model observed in other q.asicrystals.A shell composed of complex Laves Mg-z. domains was formed surrounding each decagonal q.asicrystal precipitate upon prolonged *** addition,all kinds of nanoprecipitates exhibit excellent structure and siz. stability at 573 *** findings may have implications for not only fundamental studies about q.asicrystals,but also microstructural manipulation of high-performance Mg alloys.

关键词： q.asicrystal Mg alloys Rapid solidification Scanning-transmission electron microscopy.

Rescattering of stimulated Raman side scattering in nonuniform plasmas

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Matter and Radiation at Extremes 2024年第5期9卷 68-76页

作者： S.Tan q.Wang Y.chen W.B.Yao C.z.Xiao J.F.Myatt School of Physics and Electronics Hunan UniversityChangsha 410082China Institute of Applied Physics and Computational Mathematics Beijing 100094China School of Electrical and Information Engineering Anhui University of Science and TechnologyHuainanAnhui 232001China Department of Electrical and Computer Engineering University of Alberta9211116 St.NWEdmontonAlberta T6G 1H9Canada

Rescattering of stimulated Raman side scattering(SRSS)is observed for the first time via two-dimensional(2D)particle-in-cell(PIC)*** construct a theoretical model for the rescattering process,which can predict the region of occurrence of mth-order SRSS and estimate its *** rescattering process is identified by the 2D PIC simulations under typical conditions of a direct-drive inertial confinement fusion *** electrons produced by second-order SRSS propagate nearly perpendicular to the density gradient and gain nearly the same energy as in first-order SRSS,but there is no cascade acceleration to produce superhot *** studies for a wide range of ignition conditions show that SRSS and associated rescatterings are robust and important processes in inertial confinement fusion.

关键词： nonuniform acceleration scattering

Probing the Bardeen-Kiselev black hole with the cosmological constant caused by Einstein eq.ations coupled with nonlinear electrodynamics using q.asinormal modes and greybody bounds

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Communications in Theoretical Physics 2024年第6期76卷 102-119页

作者： S R Wu B q.Wang z.W Long College of Physics Guizhou UniversityGuiyang 550025China College Pharmacy Guizhou University of Traditional Chinese MedicineGuiyang 550025China

In this work,we investigate a static and spherically symmetric Bardeen-Kiselev black hole(BH)with the cosmological constant,which is a solution of the Einstein-non-linear Maxwell field *** compute the q.asinormal freq.encies for the Bardeen-Kiselev BH with the cosmological constant due to electromagnetic and gravitational *** varying the BH parameters,we discuss the behavior of both real and imaginary parts of the BH q.asinormal freq.encies and compare these freq.encies with the Reissner-Nordström-de Sitter BH surrounded by q.intessence(RN-dSq..Interestingly,it is shown that the responses of the Bardeen-Kiselev BH with the cosmological constant and the RN-dSq.under electromagnetic perturbations are different when the charge parameter q.the state parameter w and the normaliz.tion factor c are varied;however,for the gravitational perturbations,the responses of the Bardeen-Kiselev BH with the cosmological constant and the RN-dSq.are different only when the charge parameter q.is ***,compared with the gravitational perturbations,the electromagnetic perturbations can be used to understand nonlinear and linear electromagnetic fields in curved spacetime *** interesting observation is that,due to the presence of Kiselev q.intessence,the electromagnetic perturbations around the Bardeen-Kiselev BH with the cosmological constant damps faster and oscillates slowly;for the gravitational perturbations,the q.asinormal mode decays slowly and oscillates *** also study the reflection and transmission coefficients along with the absorption cross section in the Bardeen-Kiselev BH with the cosmological constant;it is shown that the transmission coefficients will increase due to the presence of Kiselev q.intessence.

关键词： q.asinormal modes greybody factors Bardeen-Kiselev black hole with cosmological constant

Estimating Critical Clearing Time of Grid Faults Using DA of State-Reduction Model of Power Systems

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 807-820页

作者： Yang Liu z.ongyang chen Huanjin Yao Lin Yi q.H.Wu School of Electric Power Engineering South China University of TechnologyGuangzhou 510640China China Southern Power Grid Research Institute Guangzhou 510663China

This paper proposes a critical clearing time (CCT) estimation method by the domain of attraction (DA) of a state-reduction model of power systems using sum of sq.ares (SOS) programming. By exploiting the property of the Jacobian matrix and the structure of the boundary of the DA, it is found the DA of the state-reduction model and that of the full model of a power system are topological isomorphism. There are one-to-one correspondence relationships between the number of eq.ilibrium points, the type of eq.ilibrium points, and solutions of the two system models. Based on these findings, an expanding interior algorithm is proposed with SOS programming to estimate the DA of the state-reduction model. State trajectories of the full model can be transformed to those of the state-reduction model by orthogonal or eq.iradius projection. In this way, CCT of a grid fault is estimated with the DA of the state-reduction model. The calculational burden of SOS programming in the DA estimation using the state-reduction model is rather small compared with using the full model. Simulation results show the proposed expanding interior algorithm is able to provide a tight estimation of DA of power systems with higher accuracy and lower time costs.

关键词： Critical clearing time domain of attraction expanding interior algorithm state-reduction model SOS programming

Discovery of new MAX-phase-like layered ternary carbide V_(8)P_(6)C:Crystal structure,thermal expansion,and elastic properties

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Journal of Materials Science & Technology 2024年第7期174卷 55-62页

作者： H.X.chen L.Sheng z.L.z.ang X.C.Wen D.L.Yang X.Y.Ye P.q.Dai School of Materials Science and Engineering Fujian University of TechnologyFuzhou 350118China Beijing Synchrotron Radiation Facility Institute of High Energy PhysicsChinese Academy of ScienceBeijing 100049China Fujian Provincial Key Laboratory of Advanced Materials Processing and Application Fuzhou 350118China State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhou 350002China

Due to the laminated structure,MAX phases and MAX-phase-like compounds possess outstanding dam-age tolerance capability with good thermal/electrical conductivity and other charming functional prop-erties,showing a bright future for structural-functional ***,a new MAX-phase-like ternary car-bide V_(8)P_(6)C with layered characteristics was *** to the alternate stacking of hexagonal-arranged M/A/X atom layers in MAX phases,V_(8)P_(6)C has a layered structure formed by a repeated stacking of the slabs consisting of V_(6)C-octahedrons and VP 6-distorted-octahedrons in three-atomic layers *** thermal expansion anisotropy was revealed,with the thermal expansion coefficients(TECs)along a-axis,c-axis,and the average value,eq.al toα_(a)=8.55(5)μK^(−1),α_(c)=10.23(5)μK^(−1),andα_(L)=9.14(5)μK^(−1),*** dilation along the c-axis was mainly dominated by out-plane V-P bonds be-tween layered *** to the pressure-dependent lattice parameters,the polycrystalline bulk modulus(B_(0)=185(9)GPa)and high compressibility anisotropy factor(B_(a)/B_(c)=1.64)was ***-while,the second-order elastic constants were calculated,and the elastic moduli,E=303 GPa,B=198 GPa,G=122 GPa,andν=0.246,were *** the weak connection between layer slabs by out-plane V1-P bond was revealed by the bond stiffness model,with a bond stiffness close to the M-A bond in MAX ***,good damage tolerance capability was predicted according to Paugh’s ratio(G/B=0.616)and Cauchy pressure(P_(a)=0 GPa,P_(c)=-7.5 GPa),even better than those of typical MAX *** discovery of V_(8)P_(6)C provides a new member of MAX-phase-like damage-tolerant ceramic with relatively low density,moderate thermal expansion,and anisotropic compressibility,and the uniq.e lay-ered structure is inspiring for exploring new layered ternary ceramics.

关键词： New ternary carbide MAX phase Thermal expansion Elastic constants Anisotropy