检索结果-南通市图书馆

Constructal entransy dissipation rate minimization for a heat generating volume cooled by forced convection

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2011年第27期56卷 2966-2973页

作者： xiao QingHua chen LinGen sun FengRui College of Naval Architecture and Power Naval University of Engineering Wuhan 430033 China

The geometry of a heat generating volume cooled by forced convection is optimized by applying the entransy dissipation extremum principle and constructal theory, while the optimal spacing between the adjacent tubes and the optimal diameter of each tube are obtained based on entransy dissipation rate minimization. The results of this work show that the optimal constructs based on entransy dissipation rate minimization and maximum temperature difference minimization, respectively, are clearly different. For the former, the porosity of the volume of channels allocated to the heat generating volume is 1/2; while for the latter, the larger the porosity is, the better the performance will be. The optimal construct of the former greatly decreases the mean thermal resistance and improves the global heat transfer performance of the system compared with the optimal construct of the latter. This is identical to the essential requirement of the entransy dissipation extremum principle that the required heat transfer temperature difference is minimal with the same heat transfer rate (the given amount of heat generated in the heat generating volume) based on the entransy dissipation extremum principle.

关键词：对流冷却构形理论耗散率最小化发电量极值原理结构优化传输性能

Constructal entransy dissipation rate minimization for heat conduction based on a tapered element

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2011年第22期56卷 2400-2410页

作者： xiao QingHua chen LinGen sun FengRui College of Naval Architecture and Power Naval University of Engineering Wuhan 430033 China

Based on constructal theory,the structure of a tapered element and high-conductivity link is optimized by taking the minimization of the entransy dissipation rate as the optimization *** results show that the mean temperature difference of the heat transfer cannot always decrease when the internal complexity of the control-volume *** exists an optimal constructal order leading to the minimum mean temperature difference for heat *** thermal current density in high-conductivity links with variable shapes does not linearly depend on the ***,the optimized constructs based on the minimization of the entransy dissipation rate are different from those based on the minimization of the maximum temperature *** with the construct based on the minimization of the maximum temperature difference,the construct based on the minimization of the entransy dissipation rate can reduce the mean temperature difference,and improve the heat transfer performance *** entransy describes the heat transfer ability more suitably,various constructal problems in heat conduction may be addressed more effectively using this basis.

关键词：构形理论耗散率最小化热传导元素锥形优化目标平均温差

STRUCTURE AND PROPERTIES OF PHOSPHROUS-CONTAINING POLY(ARYLETHER KETONE)WITH BISPHENOL-A MOIETY

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2007年第6期25卷 651-655页

作者： Kai-jun Li xiao-ting chen Hao sun Xu-dong Tang College of Material Science ＆ Chemical Engineering Tianjin University of Science ＆ Techology Tianjin 300457 China

A phosphrous-containing poly（aryl ether ketone） was synthesized derived from bisphenol-A and bis[4-（4- fluorobenzoyl）phenyl] phenyl phosphine oxide （FPPPO） by nucleophilic substitution reaction. The structure of the polymer was characterized by FT-IR, ^1H-NMR and ^31p-NMR. The thermal property of the PAEK was measured by DSC and TGA. The glass transition temperature （Tg） of the polymer was 205℃, and the 5% weight loss temperature under nitrogen was 475℃. Good solubility of the polymer in organic solvents, such as N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide and chloroalkanes was observed, flexible film was obtained from the polymer＇s CH2Cl2 solution. The limiting oxygen index （LOI） of the PAEK was 40, which indicated that organic phosphorus moiety can offer good flame retardant property to the polymer.

关键词： Poly(aryl ether ketone) Bis[4-(4-fluorobenzoyl)phenyl] phenyl phosphine oxide (FPPPO) Nucleophilic substitution reaction Bisphenol-A.

Resin Matrix Shear Band and Its Special Effect on Stress Concentration of Fiber Composites

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2014年第6期32卷 703-710页

作者： Guo-wei Zhu Feng-de Ma 贾玉玺 Peng Qu Yun-li Guo xiao-chen sun Key Laboratory for Liquid-Solid Structural Evolution & Processing of Materials (Ministry of Education) Shandong University

A constitutive model is constructed to consider the resin matrix post-yield softening and progressive hardening behaviors. A user-defined material mechanical behavior （UMAT） subroutine is created, then the non-linear three-dimensional finite element analysis on the tensile processes of multi-fiber composites is conducted. The approximate 45° shear bands emanating from the matrix crack tip are found, being coincided with the experimental observations. The shear stress on the adjacent intact fiber/matrix interface is strongly influenced by the shear band and thus the stress concentration factor （SCF） changes obviously in the adjacent fibers. The distinct stress redistribution in the adjacent intact fibers implies the significant effect of the shear bands on the progressive fiber fracture initiation. As the inter-fiber spacing increases, the peak value of the SCF in the adjacent intact fiber decreases, whereas the overload zone becomes wider. The research has provided a helpful tool to evaluate the failure of fiber composites and optimize the composite performance through the proper selection of resin matrix properties and fiber volume fraction.

关键词： Fiber composite Stress concentration Shear band Fiber volume fraction Theory and modeling.

Boosting the water gas shift reaction on Pt/CeO_(2)-based nanocatalysts by compositional modification: Support doping versus bimetallic alloying

在线全文

学校读者我要写书评

暂无评论

Journal of Energy Chemistry 2022年第4期31卷 241-249页

作者： Kun Yuan xiao-chen sun Hai-Jing Yin Liang Zhou Hai-Chao Liu Chun-Hua Yan Ya-Wen Zhang Beijing National Laboratory for Molecular Sciences(BNLMS) State Key Laboratory of Rare Earth Materials Chemistry and ApplicationsPKU-HKU Joint Laboratory in Rare Earth Materials and Bioinorganic ChemistryCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China Beijing National Laboratory for Molecular Sciences(BNLMS) State Key Laboratory for Structural Chemistry of Stable and Unstable SpeciesCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China

The water gas shift reaction is of vital significance for the generation and transition of energy due to the application in hydrogen production and industries such as ammonia synthesis and fuel *** influence of support doping and bimetallic alloying on the catalytic performance of Pt/Ce O_(2)-based nanocatalysts in water gas shift reaction was reported in this *** lanthanide ions and 3d transition metals were respectively introduced into the Ce O_(2)support or Pt to form Pt/Ce O_(2):Ln(Ln=La,Nd,Gd,Tb,Yb)and Pt M/Ce O_(2)(M=Fe,Co,Ni)*** sample of Pt/Ce O_(2):Tb showed the highest activity(TOF at 200℃=0.051 s^(-1))among the Pt/Ce O_(2):Ln and the undoped Pt/Ce O_(2)***,the sample of Pt Fe/Ce O_(2)exhibited the highest activity(TOF at 200℃=0.12 s^(-1))among Pt M/Ce O_(2)*** results of the multiple characterizations indicated that the catalytic activity of Pt/Ce O_(2):Ln catalysts was closely correlated with the amount of oxygen vacancies in doped ceria ***,the different activity of Pt M/Ce O_(2)bimetallic catalysts was owing to the various Pt oxidation states of the bimetals dispersed on *** study of the reaction pathway indicated that both the samples of Pt/Ce O_(2)and Pt/Ce O_(2):Tb catalyzed the reaction through the formate pathway,and the enhanced activity of the latter derived from the increased concentration of oxygen vacancies along with promoted water *** for the sample of Pt Fe/Ce O_(2),its catalytic mechanism was the carboxyl route with a higher reaction rate due to the moderate valence of Pt along with improved CO activation.

关键词： Pt/CeO_(2)catalysts Water–gas shift reaction Support doping Bimetallic alloying

Strong metal-support interactions between highly dispersed Cu^(+) species and ceria via mix-MOF pyrolysis toward promoted water-gas shift reaction

在线全文

学校读者我要写书评

暂无评论

Journal of Energy Chemistry 2024年第4期91卷 475-483页

作者： xiao-chen sun Xing-Chi Li Ze-Wei Xie chen-Yue Yuan De-Jiu Wang Qian Zhang xiao-Yu Guo Hao Dong Hai-Chao Liu Ya-Wen Zhang Beijing National Laboratory for Molecular Sciences(BNLMS) State Key Laboratory of Rare Earth Materials Chemistry and ApplicationsPKU-HKU Joint Laboratory in Rare Earth Materials and Bioinorganic ChemistryCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China Beijing National Laboratory for Molecular Sciences(BNLMS) College of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China Beijing National Laboratory for Molecular Sciences(BNLMS) State Key Laboratory for Structural Chemistry of Stable and Unstable SpeciesCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China

The modulation of metal-support interfacial interaction is significant but challenging in the design of high-efficiency and high-stability supported ***,we report a synthetic strategy to upgrade Cu-CeO_(2)interfacial interaction by the pyrolysis of mixed metal-organic framework(MOF)*** obtained highly dispersed Cu/CeO_(2)-MOF catalyst via this strategy was used to catalyze water-gas shift reaction(WGSR),which exhibited high activity of 40.5μmolCOgcat^(-1).s^(-1)at 300℃and high stability of about 120 *** on comprehensive studies of electronic structure,pyrolysis strategy has significant effect on enhancing metal-support interaction and then stabilizing interfacial Cu^(+)species under reaction *** Cu^(+)species and generated oxygen vacancies over Cu/CeO_(2)-MOF catalyst played a key role in CO molecule activation and H2O molecule dissociation,*** collaborated closely and then promoted WGSR catalytic performance in comparison with traditio nal supported *** study shall offer a robust approach to harvest highly dispersed catalysts with finely-tuned metal-support interactions for stabilizing the most interfacial active metal species in diverse heterogeneous catalytic reactions.

关键词： Cu-based catalyst MOF derivative Water-gas shift reaction Metal-support interaction

Critical couplings in topological-insulator waveguide-resonator systems observed in elastic waves

在线全文

学校读者我要写书评

暂无评论

National Science Review 2021年第2期8卷 83-94页

作者： Si-Yuan Yu cheng He xiao-chen sun Hong-Fei Wang Ji-Qian Wang Zi-Dong Zhang Bi-Ye Xie Yuan Tian Ming-Hui Lu Yan-Feng chen National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering Nanjing University Collaborative Innovation Center of Advanced Microstructures Nanjing University Jiangsu Key Laboratory of Artificial Functional Materials Nanjing University

Waveguides and resonators are core components in the large-scale integration of electronics, photonics and phononics, both in existing and future scenarios. In certain situations, there is critical coupling of the two components; i.e. no energy passes through the waveguide after the incoming wave couples into the resonator. The transmission spectral characteristics resulting from this phenomenon are highly advantageous for signal filtering, switching, multiplexing and sensing. In the present study, adopting an elastic-wave platform, we introduce topological insulator(TI), a remarkable achievement in condensed matter physics over the past decade, into a classical waveguide-ring-resonator configuration. Along with basic similarities with classical systems, a TI system has important differences and advantages, mostly owing to the spin-momentum locked transmission states at the TI boundaries. As an example, a two-port TI waveguide resonator can fundamentally eliminate upstream reflections while completely retaining useful transmission spectral characteristics, and maximize the energy in the resonator, with possible applications being novel signal processing, gyro/sensing, lasering, energy harvesting and intense wave–matter interactions, using phonons, photons or even electrons. The present work further enhances confidence in using topological protection for practical device performance and functionalities, especially considering the crucial advantage of introducing(pseudo)spins to existing conventional configurations. More in-depth research on advancing phononics/photonics, especially on-chip, is foreseen.

关键词： topological insulators phononic crystals ring resonators waveguide-resonator systems critical couplings

Spindle and Chromosome Analysis of Non-Fertilized Oocytes from Conventional in vitro Fertilization for Non-Male Factor Infertiliy: Significance of Rescue ICSI?

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Reproduction and Contraception 2011年第1期22卷 1-10页

作者： xiao-lin LONG, Han-yan LIU Xin-jie chen xiao-fang sun Center for Reproductive Medicine Research Institute of Gynecology and Obstetrics of Guangzhou Third Affiliated Hospital of Guangzhou Medical University Guangzhou 510150 China

Objective To determine whether rescue intracytoplasmic sperm injection （ICSI） is associated with improved outcomes for non-male factor infertility. Methods The changes of micro-structure, including meiotic spindle and chromosome distribution, sperm penetration, as well as oocyte activation were compared in IVF （in vitro fertilization）fertilization failure （1VF FF） patients, ICSI patients with non-fertilized oocytes （ICSI NF） and oocytes in vitro maturation （IVM）. Results A total of 164 unfertilized oocytes （93 oocytes in IVF and 71 oocytes in ICSI） and 56 IVM oocytes were available for this study. The abnormality of spindle and chromosomes was significantly higher in IVF FF group than that in ICSI NF group or IVM group （abnormal spindle rates were 80.6%, 64.8% and 57.1%, respectively; abnormal chromosome rates were 91.4%, 80.3% and 75.0%, respectively）. No sperm penetration after IVF and sperm expulsion after ICSI were 78.5% and 40.8%, respectively. Activation failure occurred in 16.1% of the IVF FF cases and 49.3% of ICSI NF oocytes. Conclusion Rescue ICSI of fertilization-failed oocytes fails to lead outcome improvement due to the internal defects of oocytes.

关键词： IVF failure ICSI rescue ICSI spindle chromosome outcome

Various topological phases and their abnormal effects of topological acoustic metamaterials

在线全文

学校读者我要写书评

暂无评论

Interdisciplinary Materials 2023年第2期2卷 179-230页

作者： Yan-Feng chen Ze-Guo chen Hao Ge cheng He Xin Li Ming-Hui Lu xiao-chen sun Si-Yuan Yu Xiujuan Zhang National Laboratory of Solid-State Microstructures&Department of Materials Science and Engineering Nanjing UniversityNanjingChina Collaborative Innovation Center of Advanced Microstructures Nanjing UniversityNanjingChina Jiangsu Key Laboratory of Artificial Functional Materials Nanjing UniversityNanjingChina School of Materials Science and Intelligent Engineering Nanjing UniversitySuzhouChina School of Mechanical Engineering Nanjing University of Science and TechnologyNanjingChina

The last 20 years have witnessed growing impacts of the topological concept on the branches of physics,including materials,electronics,photonics,and *** describes objects with some global invariant property under continuous deformation,which in mathematics could date back to the 17th century and mature in the 20th *** physics,it successfully underpinned the physics of the Quantum Hall effect in *** date,topology has been extensively applied to describe topological phases in acoustic *** artificial structures,acoustic metamaterials could be well theoretically analyzed,on-demand designed,and easily fabricated by modern techniques,such as three-dimensional *** new theoretical topological models were first discovered in acoustic metamaterials analogous to electronic counterparts,associated with novel effects for acoustics closer to *** this review,we focused on the concept of topology and its realization in airborne acoustic crystals,solid elastic phononic crystals,and surface acoustic wave *** also introduced emerging concepts of non-Hermitian,higher-order,and Floquet topological insulators in *** has been shown that the topology theory has such a powerful generality that among the disciplines from electron to photon and phonon,from electronic to photonics and acoustics,from acoustic topological theory to acoustic devices,could interact and be analogous to fertilize fantastic new ideas and prototype devices,which might find applications in acoustic engineering and noisevibration control engineering in the near future.

关键词： acoustic materials robust propagation topological acoustic metamaterials topological phases