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Persistence of bounded solutions to degenerate Sobolev-Galpern equations

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Science china mathematics 2010年第11期53卷 2831-2846页

作者： zhu changrong1 & zhang weinian2. 1school of mathematics, chongqing university, chongqing 400044, china 2Yangtze Center of mathematics and Department of mathematics, Sichuan university, Chengdu 610064, china school of mathematics Chongqing University Chongqing China Yangtze Center of mathematics and Department of mathematics Sichuan University Chengdu China

In this paper the persistence of bounded solutions to degenerate evolution equations of Sobolev-Galpern type is discussed. In order to define the evolution operator well, we study the existence and uniqueness of solutions to its linear form. On this basis we discuss exponential dichotomies of the evolution operator and give the Fredholm alternative result for bounded solutions of nonhomogeneous linear degenerate equations. This result enables us to give a condition for the persistence of bounded solutions of a general degenerate nonlinear autonomous equation under a nonautonomous perturbation.

关键词： degenerate evolution equation Sobolev-Galpern type boundedness Fredholm alternative exponential dichotomy

In^(3+)-doped Sr_(2)Fe_(1.5)Mo_(0.5)O_(6−δ)cathode with improved performance for an intermediate-temperature solid oxide fuel cell

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Nano Research 2024年第1期17卷 407-415页

作者： Yumei Ma Lijie zhang Kang zhu Binze zhang Ranran Peng changrong Xia Ling Huang State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources College of ChemistryXinjiang UniversityUrumqi 830046China Department of Materials Science and Engineering University of Science and Technology of ChinaHefei 230026China

Promoting the oxygen reduction reaction(ORR)is critical for commercialization of intermediate-temperature solid oxide fuel cells(IT-SOFCs),where Sr_(2)Fe_(1.5)Mo_(0.5)O_(6)−δ(SFM)is a promising cathode by working as a mixed ionic and electronic *** this work,doping of In^(3+)greatly increases the oxygen vacancy concentration and the content of adsorbed oxygen species in Sr_(2)Fe_(1.5)Mo_(0.5−x)InxO_(6−δ)(SFMInx),and thus effectively promotes the ORR *** a typical example,SFMIn_(0.1)reduces the polarization resistance(R_(p))from 0.089 to 0.046Ω∙cm^(2)at 800°C,which is superior to those doped with other metal *** addition,SFMIn0.1 increases the peak power density from 0.92 to 1.47 W∙cm^(−2)at 800°C with humidified H_(2)as the fuel,indicating that In3+doping at the Mo site can effectively improve the performance of SOFC cathode material.

关键词： solid oxide fuel cell cathode In3+doping oxygen reduction reaction(ORR) Sr_(2)Fe_(1.5)Mo_(0.5)O_(6-δ)

A Distributed Computing Algorithm for Electricity Carbon Emission Flow and Carbon Emission Intensity

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Protection and Control of Modern Power Systems 2024年第2期9卷 138-146页

作者： Xingping Wu Wei Yang Ning zhang Chunlei Zhou Jinwei Song chongqing Kang Big Data Center of china Network Chinese Society of Electrical Engineering State Network Big Data Center Department of Electrical Engineering Tsinghua UniversityBeijingChina 不详 Big Data Center State Grid Corporation of ChinaBeijing 100052China Department of Electrical Engi-neering Tsinghua UniversityBeijingChina

The calculation of the indirect carbon emis-sion is essential for power system policy making,carbon market development,and power grid *** em-bedded carbon emissions of the electricity system are commonly calculated by carbon emission flow ***,the calculation procedure is time-consuming,especially for a country with 500-1000 thousand nodes,making it challenging to obtain nationwide carbon emis-sions intensity ***,the calculation procedure requires to gather all the grid data with high classified levels from different power grid companies,which can prevent data sharing and cooperation among different *** paper proposes a distributed computing algorithm for indirect carbon emission that can reduce the time consumption and provide privacy *** core idea is to utilize the sparsity of the nodes’flow matrix of the nationwide grid to partition the computing procedure into parallel sub-procedures exe-cuted in multiple *** flow and structure data of the regional grid are transformed irreversibly for pri-vacy protection,when transmitted between terminals.A 1-master-and-N-slave layout is adopted to verify the *** algorithm is suitable for large grid compa-nies with headquarter and branches in provinces,such as the State Grid Corporation of china.

关键词： Carbon emission flow cooperative computing carbon emission intensity matrix block par-tition power flow tracing parallel computing privacy protection

Effect of surface nanocrystallization on the corrosion behavior of Zircaloy-4

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Science china(Technological Sciences) 2009年第8期52卷 2227-2231页

作者： zhu YuTao1,2 & zhang XiYan1,2,3 1 College of Materials Science and Engineering, chongqing university, chongqing 400045, china 2 National Engineering Research Center for Magnesium Alloys, chongqing university, chongqing 400044, china 3 school of Physical Science and Engineering Technology, Guangxi university, Nanning 530004, china College of Materials Science and Engineering Chongqing University Chongqing China National Engineering Research Center for Magnesium Alloys Chongqing University Chongqing China school of Physical Science and Engineering Technology Guangxi University Nanning China

The contrastive corrosion experiments between surface nanocrystallined Zircaloy-4 and coarse-grained Zircaloy-4 under the condition of 673 K/10.3 MPa in pure water are carried out, and the microstructure of oxide films has been studied. The results indicate that the growth rate of oxide films formed on the nanocrystalline Zircaloy-4 is lower than that of oxide films formed on the coarse-grained Zircaloy-4. Simultaneously, the oxide/metal interface of the former is more regular and glossy than that of the latter. For nanocrystalline Zircaloy-4, the low oxygen diffusion rate through the oxide/metal interface can hinder the reaction of oxygen ion with metal ion. Furthermore, more tetragonal ZrO2 are observed in the oxide films, which can delay the martensite phase transition from tetragonal to monoclinic phase in oxide films.

关键词： nanocrystalline Zircaloy oxide film microstructure

Effect of Pre-treatment on the Bi-2223/Ag Tapes Fabricated with Different Powders

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稀有金属材料与工程 2011年第S3期40卷 325-328页

作者： Li Mingya1, Chen Xingpin2, Ye Chengli1, Yu Liang1, zhu Xu1 1 Northeastern university at Qinhuangdao, Qinhuangdao 066004, china 2 chongqing university, chongqing 400044, china NE Univ Qinhuangdao Dept Mat Sci & Engn Qinhuangdao 066004 Peoples R China chongqing Univ Chongqing 400044 Peoples R China

Samples of Bi-2223/Ag tapes fabricated with powders contained different lead oxide compounds were annealed at a temperature lower than the formation temperature of Bi-2223 phase before traditional heat treatment, which was called pretreatment. In pre-treatment stage, samples were heat treated at 780 ℃ in 8.5% O2, and the dwelling time is different. Experimental results show that pre-treatment had different influence on the formation and size of the Bi-2223 grains for tapes fabricated with powders contained different lead oxide compounds. For tapes contained both Ca2PbO4 and the 3321 phase, the decomposition of the 3321 phase enhanced the growth of Bi-2212 grains during pre-treatment process, which promoted the formation of Bi-2223 phase and enhanced the superconducting properties of Bi-2223/Ag tapes.

关键词： pre-treatment Bi-2223/Ag tapes lead oxide compounds critical current

The integration of methanogenesis with denitrification and anaerobic ammonium oxidation in an expanded granular sludge bed reactor

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Journal of Environmental Sciences 2003年第3期15卷 423-432页

作者： zhang Dai-jun 1,2 (1. Department of Environmental Science, chongqing university, Campus A, chongqing 400044, china 2. Key Laboratory for the Southwest china Resources Exploitation and Environmental Disaster Control Engineering, Ministry of Education, china.) Department of Environmental Science Chongqing University Campus A 重庆 400044

The integration of methanogenesis with denitrification and anaerobic ammonium oxidation(ANAMMOX) was studied in an expanded granular sludge bed(EGSB) reactor in this work. Experimental results from the continuous treatment of wastewater with nitrite and ammonium, which lasted for 107 days, demonstrated that wastewater with high nitrite and ammonium could be anaerobically treated in an expanded granular sludge bed reactor. More than 91% to 97% of COD were removed at up to about 3.9 g COD/(L·d) of COD volumetric loading rate. More than 97% to 100% of nitrite was denitrified at up to about 0.8 g NO -_2-N/(L·d), which is 16 times higher than that in a conventional activated sludge system with nitrification/denitrification(0.05 gN/(L·d)). No dissimilatory reduction of nitrite to ammonium occurred in the process. However, maximum of about 40% ammonium was found to be lost. Batch tests of 15 days with sludge from the reactor showed that 100% of nitrite was denitrified completely, and about 3% of ammonium was removed when only ammonium (34.3 mg/L) and nitrite(34.3 mg/L) were added into the sludge suspension medium. Furthermore, about 15% of ammonium amounts were lost with organic COD addition. It suggested that the methanogenesis in the system could enhance ANAMMOX because of intermediate hydrogen produced during methanogenesis.

关键词： methanogenesis denitrification ANAMMOX EGSB reactor

Stress distribution rule of roadway affected by overhead mining in gently inclined coal seams group

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中国有色金属学会会刊：英文版 2011年第S3期21卷 529-535页

作者： KANG Qin-rong1, 2, TANG Jian-xin1, 2, HU Hai1, 2, zhang Wei-zhong1, 3 1. College of Resource and Environmental Sciences, chongqing university, chongqing 400030, china 2. State Key Laboratory of Coal Mine Disaster Dynamics and Control, chongqing university, chongqing 400030, china 3. school of Safety Science and Administration, Zhongnan university of Economics and Law, Wuhan 430074, china College of Resource and Environmental Sciences Chongqing University Chongqing 400030 China State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing University Chongqing 400030 China school of Safety Science and Administration Zhongnan University of Economics and Law Wuhan 430074 China

In light of the severe deformation and destruction of the district raise tunnel in the mining area at the northern part of the Lubanshan colliery, by the theoretic analysis and numerical simulation, both the mining stress distribution in seams group and the deformation and destruction mechanism of floor district raise were investigated. The results show that, at the maximum vertical distance of 40 m, the abutment stress has an influence on the recovery of 2# and 3# coal seam and 8# coal seam at distance of 30 m. As a result, the recovery of 8# is rather than those of 2# or 3# coal seam, which contributes to the deformation and destruction of the district raise surrounding rock. The major factors affecting the abutment stress include the mining depth, mining height, residual gob space, adjacent working faces and short spacing coal seam recovery.

关键词： coal seams group stress distribution district raise surrounding rock deformation and destruction abutment stress

Thermal-stress Simulation of Direct-chill Casting of AZ31 Magnesium Alloy Billets

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Journal of Wuhan university of Technology(Materials Science) 2009年第3期24卷 376-382页

作者：胡红军 College of Materials Science and Engineering Chongqing University National Engineering Research Center for Magnesium Alloys Chongqing University College of Material Science and Engineering Chongqing University of Technology

Two-dimensional （2D） transient coupled finite element model was developed to compute the temperature and stress field in cast billets, so as to predict the defects of the I-type billets made from AZ31 magnesium alloy and find the causes and solutions for surface cracks and shrinkages during direct-chill （DC） casting process. Method of equivalent specific heat was used in the heat conduction equation. The boundary and initial conditions used for primary and secondary cooling were elucidated on the basis of the heat transfer during the solidification of the billet. The temperature and the thermal-stress fields were simulated with the thermal-structural coupled module of ANSYS software. The influences of casting parameters on the distributions of temperature and stress were studied, which helped optimize the parameters （at pouring temperature of 680 ℃, casting speed of 2 min/s, heat-transfer coefficient of the second cooling equals to 5 000 W/m^2.℃^-1）. The simulation results of thermal stress and strain fields reveal the formation mechanism of some casting defects, which is favourable for optimizing the casting parameters and obtain high quality billets. Some measures of controlling processes were taken to prevent the defects for direct-chill casting billets.

关键词： magnesium alloy direct-chill casting temperature and stress fields numerical simulation solidification model

Effects of scandium addition on microstructure and mechanical properties of ZK60 alloy

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Progress in Natural Science:Materials International 2011年第1期21卷 59-65页

作者： Fu-sheng PAN~(1,2),Ting-ting LIU~(1,2),Xi-yan zhang~(1,2),Ai-tao TANG~(1,2),Wei-qing WANG~(1,2) 1.National Engineering Research Center for Magnesium Alloys,chongqing university,chongqing 400045,china 2.College of Materials Science and Engineering,chongqing university,chongqing 400045,china National Engineering Research Center for Magnesium Alloys Chongqing University Chongqing 400045 China College of Materials Science and Engineering Chongqing University Chongqing 400045 China

The effects of Sc addition on the microstructure and mechanical properties of the ZK60 wrought magnesium alloy were investigated by using optical microscope,scanning electron microscopy,X-ray diffraction and tensile *** experimental results show that a minor Sc addition to ZK60 alloy has an obvious effect on the refinement of the microstructure of the ZK60 alloy. During hot extrusion,incomplete dynamic recrystallization occurs in all the alloys,and the recrystallized grains become much finer with increasing Sc *** tensile strengths of ZK60 evidently increase with the addition of Sc,but the elongations decrease. The ZK60 alloy with 0.6%(mass fraction) Sc addition is found to have the tensile strength of about 350 MPa and the yield strength of about 280 *** T6 heat treatment,the tensile strength of the alloy containing 0.6%Sc remains almost ***, the yield strength of the alloy increases up to 352 MPa,and the ratio of the tensile strength to the yield strength is close to 1.

关键词： wrought magnesium alloy scandium microstructure mechanical properties