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Measurement of boiling heat transfer coefficient in liquid nitrogen bath by inverse heat conduction method

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第5期10卷 691-696页

作者： Tao JIN Jian-ping HONG Hao ZHENG Ke TANG Zhi-hua gan Institute of Refrigeration and Cryogenics Zhejiang University Hangzhou 310027 China

Inverse heat conduction method (IHCM) is one of the most effective approaches to obtaining the boiling heat transfer coefficient from measured results. This paper focuses on its application in cryogenic boiling heat transfer. Experiments were conducted on the heat transfer of a stainless steel block in a liquid nitrogen bath, with the assumption of a 1D conduction condition to realize fast acquisition of the temperature of the test points inside the block. With the inverse-heat conduction theory and the explicit finite difference model, a solving program was developed to calculate the heat flux and the boiling heat transfer coefficient of a stainless steel block in liquid nitrogen bath based on the temperature acquisition data. Considering the oscillating data and some unsmooth transition points in the inverse-heat-conduction calculation result of the heat-transfer coefficient, a two-step data-fitting procedure was proposed to obtain the expression for the boiling heat transfer coefficients. The coefficient was then verified for accuracy by a comparison between the simulation results using this expression and the verifying experimental results of a stainless steel block. The maximum error with a revised segment fitting is around 6%, which verifies the feasibility of using IHCM to measure the boiling heat transfer coefficient in liquid nitrogen bath.

关键词： Inverse heat conduction method (IHCM) Liquid nitrogen bath Boiling heat transfer coefficient

Biodegradable Microspheres with Poly(N-isopropylacrylamide) Enriched Surface: Thermo-responsibility, Biodegradation and Drug Release

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Chinese Journal of Polymer Science 2015年第11期33卷 1598-1605页

作者： Yin Yuan 孙培健 Xu-dong Shi Zhi-hua gan 王佛松 CAS Key Laboratory of Engineering Plastics Institute of Chemistry Chinese Academy of Sciences the Key Laboratory of Tobacco Chemistry Zhengzhou Tobacco Research Institute China National Tobacco Corporation State Key Laboratory of Organic-inorganic Composites Beijing Laboratory of Biomedical MaterialsCollege of Life Sciences and Technology

Microspheres with thermo-responsible surface were fabricated by PCL-b-PEO-b-PNIPAM triblock copolymers. Thermo-responsible morphological changes of PCL-b-PEO-b-PNIPAM microspheres immersed in aqueous solution at temperatures above the LCST（e.g. 37 ℃） were observed from porous surface structure to compact surface layer. Enzymatic degradation and in vitro drug release results showed that the thermo-responsible surface layer greatly influenced the degradation of microspheres as well as the drug release behavior from microspheres. With the copolymerization of PNIPAM block into PCL-b-PEO copolymers, the drug release could be well regulated by changing temperatures and microspheres composition, which revealed the great potentials of microspheres with thermo-responsible surface for controlled drug release.

关键词： Microspheres Poly(N-isopropylacrylamide) Thermo-sensitive Biodegradation

Effect of molecular weight on reaction-induced phase separation of epoxy resin modified with fluorocarbon chain terminated polyetherimide

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Science China Chemistry 2005年第6期48卷 560-566页

作者： gan Wenjun LI hua HU Zhiqiang LI Liang LI Shanjun Key Laboratory of Molecular Engineering of Polymer Ministry of Education Department of Macromolecular ScienceFudan UniversityShanghai 200433China

A series of fluorocarbon chain terminated polyetherimide is added to epoxy resin,and the effect of molecular weight on the process of phase separation is studied by time-resolved light scattering(TRLS),differential scanning calorimeter(DSC),scanning microscopy(SEM).The results indicate that the phase separation rate decreases due to the preventing effect in-duced by low surface energy of fluorocarbon chain terminated *** addition,evolu-tion time of morphology is shortened and the domain size decreases with the introduction of fluorocarbon chain terminated ***,when the molecular weight of fluorocarbon chain terminated polyetherimide increases,the morphology can change from dis-persed phase to co-continuous ***,changing the molecular weight of fluorocarbon chain terminated polyetherimide can control the morphology of the epoxy/polyetherimide blend,which is of great significance in many industries.

关键词： fluorocarbon chain terminated polyetherimide epoxy molecular weight reaction-induced phase separa-tion time-resolved light scattering.

Algan/gan MISHEMTs with Sodium-Beta-Alumina as the Gate Dielectrics

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Chinese Physics Letters 2013年第2期30卷 169-173页

作者： tian Ben-Lang CHEN Chao ZHANG Ji-hua ZHANG Wan-Li LIU Xing-Zhao The State Key Laboratory of Electronic Thin Films and Integrated Devices University of Electron Science and Technology of ChinaChengdu 610054

Algan/gan metal-insulator-semiconductor high-electron-mobility transistors(MISHEMTs)with sodium beta-alumina(SBA)thin films as the gate dielectrics are ***/gan metal-semiconductor high-electron-mobility transistors(MESHEMTs)and MISHEMTs with Al_(2)O_(3) thin-film gate dielectrics are also fabricated for comparative *** MISHEMTs with SBA gate dielectrics show nearly four orders of magnitude lower gate leakage current and an approximately 60%increase in maximum transconductance,indicating that SBA can serve as an effective dielectric for Algan/gan ***,SBA gate dielectrics result in threshold voltage modulation of Algan/gan *** with those of Algan/gan MESHEMTs,the threshold voltages of Algan/gan MISHEMTs with Al_(2)O_(3) gate dielectrics shift negatively from-5.5 V to-7.5 *** contrast with the normally used gate dielectrics,the threshold voltages of MISHEMTs with SBA gate dielectrics shift positively from-5.5 V to-3.5 *** on an x-ray photoelectron spectrum study and energy band spectrum calculation,the primary mechanism of the threshold voltage modulation is attributed to the decrease in the surface valence-band maximum and the increase in the barrier height by SBA gate dielectrics.

关键词： Algan/gan MISHEMT HEMTs

A new species of the genus Amolops(Anura:Ranidae)from Yunnan,China

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Zoological Research 2020年第2期41卷 188-193页

作者： Yu-Lu gan Guo-hua Yu Zheng-Jun Wu Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection(Guangxi Normal University) Ministry of EducationGuilinGuangxi 541004China Guangxi Key Laboratory of Rare and Endangered Animal Ecology College of Life ScienceGuangxi Normal UniversityGuilinGuangxi 541004China

DEAR EDITOR,A new species of the genus Amolops,Amolops tuanjieensis ***.,is described from Yunnan,*** new species can be distinguished by the following characters:dorsolateral folds present;dorsal and ventral surfaces smooth;top of head and dorsum brown-red with irregular gray and dark spots;flank green;side of head black,from tip of snout,diffusing posteriorly to axilla,continuing as black streak below edge of dorsolateral fold;SVL 39.5-40.4 mm in males,56.8-60.7 mm in females;tympanum distinct;supratympanic fold indistinct;vomerine teeth in two oblique rows between choanae,closer to each other than choanae;vocal sacs present;nuptial pads present;outer metatarsal tubercle absent,supernumerary tubercles absent;all fingertips expanded into discs;limbs dorsally brown with dark brown bars and irregular dark brown blotches.

关键词： black closer brown

An in-depth mechanistic insight into the redox reaction and degradation of aqueous Zn-MnO_(2) batteries

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Chinese Chemical Letters 2023年第4期34卷 531-536页

作者： Zongyuan You Wei hua Na Li huanyan Liu Jian-gan Wang State Key Laboratory of Solidication Processing Center for Nano Energy MaterialsSchool of Materials Science and EngineeringNorthwestern Polytechnical UniversityShaanxi Joint Lab of Graphene(NPU)Xi’an 710072China

Rechargeable aqueous Zn/MnO_(2)batteries raise massive research activities in recent years. However, both the working principle and the degradation mechanism of this battery chemistry are still under debate. Herein, we provide an in-depth electrochemical and structural investigation on this controversial issue based on α-MnO_(2)crystalline nanowires. Mechanistic analysis substantiates a two-electron reaction pathway of Mn2+/Mn4+redox couple from part of MnO_(2)accompanying with a reversible precipitation/dissolution of flaky zinc sulfate hydroxide(ZSH) during the discharge/charge processes. The formation of the ZSH layer is double-edged, which passivates the deep dissolution of MnO_(2)upon discharging,but promotes the electrochemical deposition kinetics of active MnO_(2)upon charging. The cell degradation originates primarily from the corrosion failure of metallic zinc anode and the accumulation of irreversible ZnMn2O_(4)phases on the cathode. The addition of MnSO_(4)to the electrolyte could afford supplementary capacity contribution via electro-oxidation of Mn2+. However, a high MnSO_(4)concentration will expedite the cell failure by corroding the metallic zinc anodes. The present study will shed a fundamental insight on developing new strategies toward practically viable Zn/MnO_(2)batteries.

关键词： Zinc-ion battery MnO_(2)cathode Working mechanism Degradation mechanism Zinc anode

Scheme for the excitation of thorium-229 nuclei based on electronic bridge excitation

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Nuclear Science and Techniques 2023年第2期34卷 88-97页

作者： Lin Li Zi Li Chen Wang Wen‑Ting gan Xia hua Xin Tong State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan 430071China University of Chinese Academy of Sciences Beijing 100049China Wuhan Institute of Quantum Technology Wuhan 430206China

Thorium-229 possesses the lowest first nuclear excited state,with an energy of approximately 8 *** extremely narrow linewidth of the first nuclear excited state,with an uncertainty of 53 THz,prevents direct laser excitation and realization of the nuclear *** present a proposal using the Coulomb crystal of a linear chain formed by229Th^(3+)ions,where the nuclei of229Th3+ions in the ion trap are excited by the electronic bridge(EB)*** 7 P1∕2state of the thorium-229 nuclear ground state is chosen for EB *** the two-level optical Bloch equation under experimental conditions,we calculate that 2 out of 36 prepared thorium ions in the Coulomb crystal can be excited to the first nuclear excited state,and it takes approximately 2 h to scan over an uncertainty of 0.22 *** advantage of the transition enhancement of EB and the long stability of the Coulomb crystal,the energy uncertainty of the first excited state can be limited to the order of 1 GHz.

关键词： Coulomb crystal Thorium-229 Electronic bridge transition Isomeric state

CNN-LSTM based incremental attention mechanism enabled phase-space reconstruction for chaotic time series prediction

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Journal of Electronic Science and Technology 2024年第2期22卷 77-90页

作者： Xiao-Qian Lu Jun tian Qiang Liao Zheng-Wu Xu Lu gan Bidding and Purchasing Center University of Electronic Science and Technology of ChinaChengdu611731China Yibin Research Institute University of Electronic Science and Technology of ChinaYibin644000China School of Information and Communication Engineering University of Electronic Science and Technology of ChinaChengdu611731China

To improve the prediction accuracy of chaotic time series and reconstruct a more reasonable phase space structure of the prediction network,we propose a convolutional neural network-long short-term memory(CNN-LSTM)prediction model based on the incremental attention ***,a traversal search is conducted through the traversal layer for finite parameters in the phase ***,an incremental attention layer is utilized for parameter judgment based on the dimension weight criteria(DWC).The phase space parameters that best meet DWC are selected and fed into the input ***,the constructed CNN-LSTM network extracts spatio-temporal features and provides the final prediction *** model is verified using Logistic,Lorenz,and sunspot chaotic time series,and the performance is compared from the two dimensions of prediction accuracy and network phase space ***,the CNN-LSTM network based on incremental attention is compared with long short-term memory(LSTM),convolutional neural network(CNN),recurrent neural network(RNN),and support vector regression(SVR)for prediction *** experiment results indicate that the proposed composite network model possesses enhanced capability in extracting temporal features and achieves higher prediction ***,the algorithm to estimate the phase space parameter is compared with the traditional CAO,false nearest neighbor,and C-C,three typical methods for determining the chaotic phase space *** experiments reveal that the phase space parameter estimation algorithm based on the incremental attention mechanism is superior in prediction accuracy compared with the traditional phase space reconstruction method in five networks,including CNN-LSTM,LSTM,CNN,RNN,and SVR.

关键词： Chaotic time series Incremental attention mechanism Phase-space reconstruction

Stress corrosion behavior of 2195-T8 Al-Li alloy with an artificial pit exposed to a 30vol%HNO3 solution

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Chinese Journal of Aeronautics 2023年第2期36卷 304-315页

作者： Dejun LIU gan tian Zhengwei YANG Guofeng JIN Wei ZHANG Yin WANG huali WEI School of Missile Engineering Rocket Force University of EngineeringXi'an 710038China Xi'an Institute of Aerospace Composites Xi'an 710025China

This paper experimentally studied the stress corrosion behavior of 2195-T8 Al-Li alloys with prefabricated pits in 30vol%*** microstructure was observed and determined by the scanning electron microscopy and the transmission electron *** typical corrosion features,i.e.,regular or irregular corrosion pits and sub/intergranular corrosion,were investigated,and the role of stress were *** statistical results of the number and area of corrosion pits in various sizes were studied using an improved image processing *** results demonstrate that stress affects the intergranular corrosion or sub-intergranular corrosion of the alloy most,and promotes them to evolve into cracks under stress *** also plays a role in accelerating corrosion severity of certain corrosion *** number of corrosion pits with an area of 0–50μm~2 can be seen as an index to reflect the degree of ***,a corrosion phenomenon,i.e.,the pit bottom in the site with the maximum stress locally suffering from no severe corrosion,was observed and discussed.

关键词： Al-Li alloy Artificial pit Corrosion features Image processing Stress corrosion