检索结果-南通市图书馆

Comparative Studies on Mass Spectrometric Fragmentation of Linear Chiral Secondary Alcohols (R)-1-(4-Alkylphenyl) and (R)-1-(4-Alkoxyphenyl/Alkylthiophenyl) Alcohols

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2006年第3期22卷 347-350页

作者： ZHANG Qi-han su Xian-bin XU jia-xi Key Laboratory of Bioorganic Chemistry and Molecular Engineering College of Chemistry and Molecular Engineering Peking University Beijing 100871 P.R. China

Mass spectrometric behaviour of （R） -1- （ 4-alkylphenyl ） alcohols, 1- （4-alkoxylphenyl） alcohols, and 1- （4-alkylthiophenyl） alcohols were studied with the aid of mass-analyzed ion kinetic energy spectrometry under electron impact ionization. All the title compounds show a tendency to eliminate a water molecule to form alkene ions and undergo an a-cleavago to produce protonated aldehyde ions by the loss of alkyl radicals. Except these two common fragment ions, they also show some different fragmentations due to with or without oxy/thioether-linkage.

关键词： 1-(4-Alkylphenyl) alcohol 1-(4-Alkoxylphenyl) alcohol 1-(4-Alkylthiophenyl) alcohol Electron impact ionization Fragmentation mechanism Mass spectrometry

Molecular identification, expression and function analysis of peroxidasin in Chilo suppressalis

在线全文

学校读者我要写书评

暂无评论

Insect Science 2020年第6期27卷 1173-1185页

作者： Chun-Ping Ma zi-Mu Guo Feng-Li Zhang jian-Ya su Key Laboratory of Integrated Management of Crop Diseases and Pests(Ministry of Education) College of Plant ProtectionNanjing Agricultural UniversityNanjingChina

Peroxidasin plays a unique role in the formation and stability of extracellular matrix(ECM)in the animal kingdom;however,it was only characterized in Diptera,not in other insect *** this study peroxidasin(CsPxc/)was first identified and characterized from Chilo suppressalis,a lepidopteran *** complementary DNA with a 4080 bp open reading frame encodes a peptide of 1359 amino acids;the derived amino acid sequence of CsPxd harbors the typical structural characteristics of peroxidasin family in heme-peroxidase superfamily,including the signal peptide at N-terminal,leucine-rich repeat domain,Ig-loop motifs and peroxidase domain,signifying the extracellular location of protein and the involvement in ECM *** expression reveals CsPxd protein displays peroxidase activity on H2O2,justifying the membership of *** analysis shows the monophyletic evolution pattern of peroxidasin in insect phyle,and moreover only one peroxidasin is present in each species of insects,suggesting its evolutionary conservation on *** messenger RNA is mainly expressed in egg and the final instar larvae *** of peroxidasin double-stranded RNA into the final instar larvae impacts the cuticle sclerotization during the metamorphosis from larvae to pupa,and eventually lead to lethality of larvae and *** results suggest the presence of collagen crosslink in chorion and cuticle of insects,and indicate peroxidasin plays a role in the development of chorion and cuticle;furthermore peroxidasin might be the one of potential target genes for pest control using RNA interference.

关键词： Chilo suppressalis cuticle sclerotization peroxidase peroxidasin RNA interference

Hierarchical Dragonfly Wing： Microstructure-Biomechanical Behavior Relations

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Bionic Engineering 2012年第2期9卷 185-191页

作者： Yinglong Chen Xishu Wang Huaihui Ren Hang Yin su jia Department of Engineering Mechanics AML School of Aerospace Tsinghua University Beijing 100084 P. R. China Beijing Aeronautical Engineering Technology Center Beijing 100076 P. R. China

The dragonfly wing, which consists of veins and membrane, is of biological hierarchical material. We observed the cross-sections of longitudinal veins and membrane using Environmental Scanning Electron Microscopy （ESEM）. Based on the experiments and previous studies, we described the longitudinal vein and the membrane in terms of two hierarchical levels of organization of composite materials at the micro- and nano-scales. The longitudinal vein of dragonfly wing has a complex sandwich structure with two chitinous shells and a protein layer, and it is considered as the first hierarchical level of the vein. Moreover, the chitinous shells are concentric multilayered structures. Clusters of nano-fibrils grow along the circumferential orientation embedded into the protein layer. It is considered as the second level of the hierarchy. Similarly, the upper and lower epidermises of membrane constitute the first hierarchical level of organization in micro scale. Similar to the vein shell, the membrane epidermises were found to be a paralleled multilayered structure, defined as the second hierarchical level of the membrane. Combining with the mechanical behavior analysis of the dragonfly wing, we concluded that the growth orientation of the hierarchical structure of the longitudinal vein and membrane is relevant to its biomechanical behavior.

关键词： dragonfly wing longitudinal vein membrane hierarchical structure biomechanical behavior

ANALYSIS OF OVERFLOW CRITICAL VALUE FOR TiAl BASED ALLOY MELT DURING PROCESS OF CENTRIFUGAL CASTING

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

中国有色金属学会会刊：英文版 1999年第2期9卷 3-8页

作者： Guo, Jingjie Sheng, Wenbin su, Yanqing Ding, Hongsheng jia, Jun Harbin Inst of Technology Harbin China

１ＩＮＴＲＯＤＵＣＴＩＯＮＴｉＡｌｂａｓｅｄａｌｏｙｓｈａｖｅａｔｒａｃｔｅｄａｇｒｅａｔｄｅａｌｏｆａｔｅｎｔｉｏｎｂｅｃａｕｓｅｏｆｔｈｅｉｒｐｏｔｅｎｔｉａｌｙａｔｒａｃｔｉｖｅｐｒｏｐｅｒｔｉｅｓｆｏｒｈｉｇ... 详细信息

１ＩＮＴＲＯＤＵＣＴＩＯＮＴｉＡｌｂａｓｅｄａｌｏｙｓｈａｖｅａｔｒａｃｔｅｄａｇｒｅａｔｄｅａｌｏｆａｔｅｎｔｉｏｎｂｅｃａｕｓｅｏｆｔｈｅｉｒｐｏｔｅｎｔｉａｌｙａｔｒａｃｔｉｖｅｐｒｏｐｅｒｔｉｅｓｆｏｒｈｉｇｈｔｅｍｐｅｒａｔｕｒｅｓｔｒｕ...

关键词： angular velocityTiAl base alloypressure distributioncentrifugal casting

Paleogene integrative stratigraphy,biotas,and paleogeographical evolution of the Qinghai-Tibetan Plateau and its surrounding areas

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2024年第4期67卷 1290-1325页

作者： jia LIU Ai SONG Lin DING Tao su Zhekun ZHOU CAS Key Laboratory of Tropical Forest Ecology Xishuangbanna Tropical Botanical GardenChinese Academy of SciencesMengla 666303China State Key Laboratory of Palaeobiology and Stratigraphy Nanjing Institute of Geology and PalaeontologyChinese Academy of SciencesNanjing 210008China Institute of Paleontology Yunnan UniversityKunming 650500China State Key Laboratory of Tibetan Plateau Earth System Environment and Resources(TPESER)Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China

The Paleogene is a crucial period when terrestrial and marine ecosystems recovered from major disruptions and gradually approached their modern *** the Qinghai-Tibetan Plateau and its surrounding regions,the Paleogene also represents a significant phase of tectonic evolution in the Qinghai-Tibetan Plateau-Himalaya orogeny,reorganization of Asian climates,and evolution of *** to limitations in research conditions and understanding,there are still many controversies regarding stratigraphic divisions in the Qinghai-Tibetan Plateau and its surrounding *** recent years,extensive studies on sedimentary petrology,magnetostratigraphy,and isotope dating have been conducted in the *** fossils have been discovered and reported,contributing to a more systematic understanding of *** studies have laid a solid foundation for the comprehensive investigation of the stratigraphy,biotas and paleogeographic evolution of the Qinghai-Tibetan Plateau and its surrounding regions during the *** this paper,we integrate recent research on fossils,isotopic dating,magnetostratigraphy,and geochemistry to refine the stratigraphic divisions and correlation framework of different tectonic units in the region,building upon previous *** the Second Tibetan Plateau Scientific Expedition and Research,the knowledge of Paleogene floras has gradually *** paper discusses the biostratigraphic significance of extinct and newly appeared taxa based on the latest dating results of these plant *** new understanding of fossil species such as the“Eucalyptus”and Arecaceae establishes connections between the Paleogene flora of the Qinghai-Tibetan region and the biotas of Gondwana,specifically Oceania and South *** evolutionary history of key taxa near the Yarlung Zangbo suture zone indicates that the collision between the Indian and Eurasian plates occurred approximately 65-54 *** reconstructions,based o

关键词： Qinghai-Tibetan Plateau Fossils Biostratigraphy Paleoenvironment Paleogeography Paleogene

Adaptive estimation and nonlinear variable gain compensation of the contouring error for precise parametric curve following

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2017年第10期60卷 1494-1504页

作者： jia ZhenYuan SONG DeNing MA jianWei ZHAO XiaoXuan su WeiWei Key Laboratory for Precision and Non-traditional Machining Technology of the Ministry of Education School of Mechanical Engineering Dalian University of Technology Dalian 116024 China

Contour following is one of the most important issues faced by many computer-numerical-control(CNC) machine tools to achieve high machining precision. This paper presents a new real-time error compensation method aiming at reducing the contouring error caused by facts such as servo lag and dynamics mismatch in parametric curved contour-following tasks. Due to the lack of high-precision contouring-error estimation method for free-form parametric curved toolpath, the error can hardly be compensated effectively. Therefore, an adaptive accurate contouring-error estimation algorithm is proposed first, where a tangential-error backstepping method based on Taylor's expansion is developed to rapidly find the closest point on the parametric curve to the actual motion position. On this foundation, the contouring error is compensated using a proposed nonlinear variable-gain compensation method, where the compensation gain is obtained according to not only the contouring-error magnitude but also its direction variation. The stability of the system after compensation is analyzed afterwards according to the Jury stability *** design of the compensator in accordance with the presented contouring-error compensation method as well as the stability analyzation result, the balance between the response speed and the contour control stability can be effectively made. Experimental tests demonstrate the feasibility of the presented methods in both contouring-error estimation and contour-accuracy *** of this research are significant for enhancing the contour-following performance of the CNC machine tools.

关键词： contouring error contour control adaptive error estimation variable gain compensation free-form parametric curves

Investigation on the performance of a helico-axial multiphase pump under slug flow

在线全文

学校读者我要写书评

暂无评论

Petroleum Science 2022年第4期19卷 1812-1824页

作者： jia-Xiang Zhang Jin-Ya Zhang Ye Zhou zi-Yi-Yi Cheng Guang-Da Cao College of Mechanical and Transportation Engineering China University of PetroleumBejing102249China Beijing Key Laboratory of Process Fluid Filtration and Separation China University of PetroleumBejing102249China China Institute of Water Resources and Hydropower Research Beijing100044China

The helico-axial multiphase pump is often used for gas-liquid mixture transportation in offshore oilfields,and slug flow is the main reason for the unstable operation of the *** for slug flow condition,a self-designed three-stage multiphase pump is set to the object to perform unsteady simulations and fluid-structure interaction calculations,and the inlet gas void fraction(IGVF)is set from 20%to 80%.The results show that affected by the flow from the slug,the gas-liquid two-phase flow pattern in the multiphase pump changes sharply,resulting in severe fluctuations in the differential pressure,spindle torque and deformation of the multiphase *** gas-phase enters the first-impeller along the suction blade surface when affected by Taylor bubbles,while the second and third-stage impellers gas-phases are in the form of small air masses flow into the impeller along the pressure blade *** deformation trend of impeller torque,differential pressure and the main pump spindle is similar to that of trigonometric function,while the fluctuation of torque is more intense,and the shape variable of spindle increases with the inflow of liquid plug,and the maximum deformation amount increases by10.9%at high GVF relative to IGVF.

关键词： Multiphase pump Slug flow Gas void fraction(GVF) Hydraulic performance Fluid-structure interaction

Properties of a Bound Polaron under a Perpendicular Magnetic Field

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2007年第5X期48卷 930-934页

作者： LIU jia XIAO Jing-Lin HUO Shu-Fen CHEN zi-Yui Department of Physics Beijing University of Aeronautics and Astronautics Beijing 100083 China College of Physics and Electromechanics Inner Mongolia University for Nationalities Tongliao 028043 China

We investigate the influence of a perpendicular magnetic field on a bound polaron near the interface of a polar-polar semiconductor with Rashba effect. The external magnetic field strongly changes the ground state binding energy of the polaron and the Rashba spin-orbit （SO） interaction originating from the inversion asymmetry in the heterostructure splits the ground state binding energy of the bound polaron. In this paper, we have shown how the ground state binding energy will be with the change of the external magnetic field, the location of a single impurity, the wave vector of the electron and the electron areal density, taking into account the SO coupling. Due to the presence of the phonons, whose energy gives negative contribution to the polaron＇s, the spin-splitting states of the bound polaron are more stable, and we find that in the condition of week magnetic field, the Zeeaman effect can be neglected.

关键词： asymmetric heterostructures spintronics Rashba spin-orbit interaction

Attack Vulnerability of Network with Duplication-Divergence Mechanism

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2007年第4X期48卷 754-758页

作者： WANG Li YAN jia-Ren LIU zi-Ran ZHANG jian-Guo Department of Physics Hunan Normal University Changsha 410081 China

We study the attack vulnerability of network with duplication-divergence mechanism. Numerical results have shown that the duplication-divergence network with larger retention probability a is more robust against target attack relatively. Furthermore, duplication-divergence network is broken down more quickly than its counterpart BA network under target attack. such result is consistent with the fact of WWW and Internet networks under target attack. So duplication-divergence model is a more realistic one for us to investigate the characteristics of the world wide web in future. We also observe that the exponent γ of degree distribution and average degree are important parameters of networks, reflecting the performance of networks under target attack. Our results are helpful to the research on the security of network.

关键词： complex network systems attack vulnerability statistical dynamics