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Damage behavior of tungsten fiber-reinforced copper matrix composite after high-speed impact

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Rare Metals 2014年第3期33卷 330-336页

作者： Zhe wu Chun-Mei Yang Qian-Jun Liu Yan Ma College of Mechanical and Electrical Engineering Northeast Forestry University

Wf/Cu82Al10Fe4Ni4composite was fabricated by means of infiltration casting. By the microstructure observation of the composite with the aid of scanning electron microscopy（SEM） and transmission electron microscopy（TEM）, it can be found that there are（Fe, Ni）,AlFe, Al3 Ni, and Cu3 Al precipitated phases existing in the matrix alloy. By two-stage light gas gun, Wf/Cu82Al10-Fe4Ni4composite hypervelocity projectile into concrete target test with the speed of 2.2 kmás-1is finished. By microstructure observation, it can be found that the failure mode of Wf/Cu82Al10Fe4Ni4composite projectile during penetration is the rapid peeling of tungsten fibers from the projectile, which makes the projectile display good selfsharpening property. Meanwhile, it can be found that microstructure morphology change of Wf/Cu82Al10Fe4Ni4composite occurs after hypervelocity impact. The density of dislocations around the large-dimensional（Fe, Ni）,AlFe, Al3 Ni, and Cu3 Al precipitated phases in the matrix alloy rises sharply. At the same time, there are largedimensional deformed twins existing in local regions and stacking faults existing inside the twins.

关键词： Composites Microstructure Damagebehavior High-speed impact

云贵高原典型区域气象灾害时空演变特征及影响因素分析

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时空信息学报 2024年第1期31卷 118-128页

作者：向曦张素金赵婧彭艳秋雷蔼玲朱思瑾吴慧霞赵飞云南省气象服务中心昆明650100 云南大学地球科学学院昆明650500 大理白族自治州气象局大理671000 云南大学国际河流与生态安全研究院昆明650500

目前气象灾害研究主要以时空分布规律和典型气象灾害风险评估为主,在对气象灾害进行系统的时空演变及影响因素研究方面还相对薄弱。为了揭示云贵高原典型气象灾害时空演变特征及影响因素,本研究基于大理州1984~2021年的历史气象灾害灾... 详细信息

目前气象灾害研究主要以时空分布规律和典型气象灾害风险评估为主,在对气象灾害进行系统的时空演变及影响因素研究方面还相对薄弱。为了揭示云贵高原典型气象灾害时空演变特征及影响因素,本研究基于大理州1984~2021年的历史气象灾害灾情统计数据,利用Arc GIS的标准差椭圆法、新兴时空热点分析和地理探测器,分析了大理州气象灾害时空演变特征及影响因素。结果表明:(1)时间上,大理州气象灾害集中发生在5~9月,历史气象灾害时间在年际变化上可分为三个阶段;(2)空间上,气象灾害发生密度较高的县(市)主要分布在大理市和鹤庆县;(3)时空变化上,5~7月气象灾害中心集中分布在大理市,移动方向为先北再西南后向北移动,鹤庆县出现新增热点;(4)地理探测器结果显示,24 h累计降水量、坡度和河网密度是引起暴雨洪涝灾害的主要原因。研究成果有助于认识大理州气象灾害的时空演变趋势和主要影响因素,从而为气象灾害防治工作提供技术支撑与理论指导。

关键词：云贵高原大理州气象灾害时空演变影响因素

Study on Edge Extraction Methods for Image-based Icing On-line Monitoring on Overhead Transmission Lines

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高电压技术 2008年第12期34卷 2687-2693页

作者： WANG Xiao-peng HU Jian-lin wu Bin DU Lin SUN Cai-xin State Key Laboratory of Power Transmission Equipment & System Security and New Technology Chongqing University Chongqing 400044 China Chongqing Electric Power Co. Chongqing 400014 China

A new method of measuring the icing thickness of transmission lines on-line is proposed in this *** this method,the pictures of transmission lines which are photoed by the camera on the iron tower are processed immediately to extract the edges of the transmission line conductor and transmission line *** icing thickness can be gained by comparing the edges of the iced transmission line and the uniced *** icing image edge extraction methods are described in detail,that is,a method based on the combination of the wavelet transform and the floating threshold method and a method based on the combination of the optimal threshold method and the mathematical morphology *** icing images from the artificial climatic chamber and transmission lines are used to test the methods *** results show that the method based on the wavelet transform and the floating threshold method does well in the extraction of relatively smooth edges,such as glaze icing on conductor and icing on the insulator;meanwhile,the method based on the optimal threshold method and the mathematical morphology transform does well in the edge extraction of icing on the conductor,especially the opaque rime icing on the conductor with complicated edges.

关键词：输电线路覆冰层边缘提取方法小波转换图像

Variation in carbon,nitrogen and phosphorus partitioning between above-and belowground biomass along a precipitation gradient at Tibetan Plateau

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Journal of Mountain Science 2016年第4期13卷 661-671页

作者： HONG Jiang-tao WANG Xiao-dan wu Jian-bo Institute of Mountain Hazards and Environment Academy of Sciences of SciencesChengdu 610041China University of Chinese Academy of Sciences Beijing 100049China

Precipitation is a potential factor that significantly affects plant nutrient pools by influencing biomass sizes and nutrient concentrations. However, few studies have explicitly dissected carbon(C), nitrogen(N) and phosphorus(P) pools between above- and belowground biomass at the community level along a precipitation gradient. We conducted a transect(approx. 1300 km long) study of Stipa purpurea community in alpine steppe on the Tibet Plateau of China to test the variation of N pool of aboveground biomass/N pool of belowground biomass(AB/bb N) and P pool of aboveground biomass/P pool of belowground biomass(AB/bb P) along a precipitation gradient. The proportion of aboveground biomass decreased significantly from mesic to drier sites. Along the belt transect, the plant N concentration was relatively stable; thus, AB/bb N increased with moisture due to the major influences by above- and belowground biomass allocation. However, P concentration of aboveground biomass decreased significantly with increasing precipitation and AB/bb P did not vary with aridity because of the offset effect of the P concentration and biomass allocation. Precipitation gradients do decouple the N and P pool of a S. purpurea community along a precipitation gradient in alpine steppe. The decreasing of N:P in aboveground biomass in drier regions may indicate much stronger N limitation in more arid area.

关键词：地上生物量地下生物量生物量分配生物量氮磷浓度青藏高原梯度分布降水梯度

Secondary Structural Elements of the HCV X-region Involved in Viral Replication

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Journal of Clinical and Translational Hepatology 2015年第1期3卷 1-8页

作者： Nidhi Gupta Catherine H.wu George Y.wu Department of Medicine Division of Gastroenterology-Hepatology University of Connecticut Health Center Farmington CT USA

Background and Aims:The noncoding regions in the 3'-untranslated region (UTR) of the hepatitis C virus (HCV)genome contain secondary structures that are important for *** aim of this study was to identify detailed conformational elements of the X-region involved in HCV ***:Ribonucleic acid (RNA) structural analogs X94,X12,and X12c were constructed to have identical conformation but 94%,12%,and 0% sequence identity,respectively,to the X region of HCV genotype *** of structural analogs on replication of HCV genotypes 1b and 2a HCV RNA were studied by quantitative reverse transcriptase polymerase chain ***:In replicon bb7 cells,a constitutive replication model,HCV RNA levels decreased to 55%,52%,53%,and 54% after transfection with expression plasmids generating RNA structural analogs 5B-46,X-94,X-12,and X-12c,respectively (p<0.001 for all).In an HCV genotype 2a infection model,RNA analogs 5B-46,X-94,and X-12 in hepatic cells inhibited replication to 11%,9%,and 12%,*** the X-12 analog was only 12% identical to the corresponding sequence of HCV genotype 2a,the sequence per se,or antisense effects were unlikely to be ***:The data suggest that conformation of secondary structures in 3'-UTR of HCV RNA genome is required for HCV *** expression of RNA analogs predicted to have identical stem-loop structures might inhibit HCV infection of hepatocytes in liver and may represent a novel approach to design anti-HCV agents.

关键词： HCV RNA genome HCV X-region Hepatitis C virus Infection Japanese Fulminant Hepatitis Virus RNA secondary structure

Selective propylene epoxidation in liquid phase using highly dispersed Nb catalysts incorporated in mesoporous silicates

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Chinese Journal of Chemical Engineering 2018年第6期26卷 1278-1284页

作者： Wenjuan Yan Yuhui wu Xiang Feng Chaohe Yang Xin Jin Jian Shen State Key Laboratory of Heavy Oil Processing College of Chemical EngineeringChina University of Petroleum Department of Environmental Science and Engineering Xiangtan University

Selective propylene epoxidation to propylene oxide(PO) with hydrogen peroxide(H_2O_2) was carried out in a catalytic semi-batch *** propylene epoxidation activity(44 h^(-1)) was observed over Nb based mesoporous silicate materials Nb-TUD-1 under mild operating *** physical and chemical properties of the Nb based silicates characterized using BET,FTIR,TPD,TEM and UV–Vis revealed that the site isolation and surface acidity are crucial for PO *** synthesis methods were investigated for their effects on PO productivity,PO selectivity and H_2O_2 utilization *** is found that Nb-TUD-1 material synthesized by the sol–gel method is more active and selective than impregnated materials for liquid phase propylene *** characterization confirms that thus synthesized Nb-TUD-1 catalysts have more Lewis acidity and less Bronsted acidity compared to the catalysts by impregnation.

关键词：硅酸盐材料催化剂丙烯 Nb 氢过氧化物液体合并化学性质

Antibacterial Activity of Polymeric Quaternary Ammonium Compounds Tuned by Incorporating Hydrophilic co-Monomer

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Chemical Research in Chinese Universities 2015年第1期31卷 160-166页

作者： ZUO Huajiang WEN Wanhua wu Dingcai FU Ruowen TANG Chunyi PCFM Laboratory School of Chemistry and Chemical Engineering Sun Yat-sen University Guangzhou 510275 P R. China College of Biological and Chemical Engineering Guangxi University of Science and Technology Liuzhou 545006 P. R. China

Copolymers of quaternary ammonium monomer（QAM） and hydrophilic co-monomer were successfully synthesized by free radical polymerization. It was discovered that the hydrophilic co-monomers with poor antibac- terial activity significantly enhanced the activity of QAM substituted with a long alkyl chain[i.e., N,N-dimethyl-N-dodecyl methacrylate ammonium bromide（DMAEMA-DB）]. When a suitable molar ratio of DMAEMA-DB to co-monomer was selected, the activity of the copolymers was up to 123 times that of the homopolymer of DMAEMA-DB against S. aureus, and 282 times that of it against E. colt. But unlike DMAEMA-DB, the co-monomers might weaken the activity of QAM substituted with a short alkyl chain[i.e., N,N-dimethyl-N-butyl methacrylate ammonium bromide（DMAEMA-bb）]. Moreover, it was found that copolymers of DMAEMA-DB were much more biocidal than those of DMAEMA-bb. Therefore, it could be speculated that the long alkyl chain plays an important role in the antibacterial activity, and that the hydrophilie co-monomers are beneficial to polymeric guaternary ammonium compounds（PQACs） to exert the positive effect of the long alkyl chain to the greatest degree.

关键词： Polymeric quaternary ammonium compound Antibacterial mechanism Copolymerization Hydrophobic/hydrophilic balance

Modulation response performances of a Fabry-Perot semiconductor laser subjected to light injection from another Fabry-Perot semiconductor laser

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Chinese Science Bulletin 2009年第20期54卷 3643-3648页

作者： XIA GuangQiong wu ZhengMao YANG Qi LIN XiaoDong School of Physics Southwest University Chongqing 400715 China State Key Laboratory of Millimeter Waves Southeast University Nanjing 210096 China

The modulation response characteristics of a Fabry-Perot semiconductor laser(slave FP-LD) subjected to light injection from another Fabry-Perot semiconductor laser(master FP-LD) have been investigated *** results show that the modulation response performances of the slave FP-LD depend on the light injection strength,the central mode frequency detuning Δf and the mode spacing difference Δλ between the slave FP-LD and the master *** the increase of the light injection strength from the master FP-LD,the 3 dB modulation bandwidth of the slave FP-LD will be enhanced;however,if the injection strength is increased to certain degree,the front side of the relaxation oscillation peak will be reduced to below 3 dB,which results in the rapid decrease of the 3 dB modulation *** the increase of Δf,for a relatively small injection strength level,the 3 dB modulation bandwidth will behave a monotonous enlargement until the slave FP-LD operates in a period-one state(P1).For a relatively strong optical injection level,the slave FP-LD has a broad injection-locked frequency detuning *** the injection-locked area,with the increase of frequency detuning Δf,the 3dB modulation bandwidth increases at first and then decreases after experiencing a maximum *** given light injection strength and frequency detuning,the 3 dB modulation bandwidth of the slave FP-LD has two maximums and behaves a symmetrical distribution with the change of Δλ.By choosing reasonable parameters,the 3 dB modulation bandwidth can be significantly *** the parameter values selected in this paper,the 3 dB modulation bandwidth can increase 5.5 times compared with the case of free running.

关键词：半导体激光器注射曝光表演调制

Molecular Evidences for the Biosynthesis of Pederin by Endosymbiont

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Agricultural Sciences in China 2009年第11期8卷 1339-1350页

作者： LIU Zhi-ping wu Xuan WANG Jin-jun HUANG Fang Key Laboratory of Entomology and Pest Control Engineering College of Plant Protection Southwest University Chongqing 400716 P.R.China Chongqing Animal Disease Control Center Chongqing 401147 P.R.China College of Medicine Shanxi Datong University Datong 037008 P.R.China

Pederin belongs to a group of antitumor compounds found in terrestrial beetles and marine sponges. It is apparently used by some members of the rove beetle Paederus as a chemical defense against predators. A recent cluster analysis of the putative pederin biosynthesis gene （ped） strongly suggests that pederin is produced by bacterial symbionts. This paper reviewed the criteria for proving symbiontic origin of bioactive metabolite, indirect and molecular evidences for pederin bacterial origin, as well as three sets ofped clusters and putative biosynthesis process of pederin.

关键词： pederin PKS/NRPS endosymbiont