检索结果-南通市图书馆

Metal Dusting-Mechanisms and Preventions

在线全文

学校读者我要写书评

暂无评论

中国腐蚀与防护学报 2009年第4期29卷 262-276页

作者： j. Q. zhang D. j. YOUNG School of Materials Science and Engineering University of New South Wales Sydney NSW 2052 Australia

Metal dusting attacks iron,low and high alloy steels and nickel-or cobalt-base alloys by disintegrating bulk metals and alloys into metal particles in a coke *** occurs in strongly carburising gas atmospheres(carbon activity a_C>1) at elevated temperatures(400℃～1000℃).This phenomenon has been studied for decades,but the detailed mechanism is still not well *** methods of protection against metal dusting are either directed to the process conditions-temperature and gas composition-or to the development of a dense adherent oxide layer on the surface of the alloy by selective ***,metal dusting still occurs by carbon dissolving in the base metal via defects in the oxide *** research work at UNSW is aimed at determining the detailed mechanism of metal dusting of both ferritic and austenitic alloys,in particular the microprocesses of graphite deposition,nanoparticle formation and underlying metal *** work was carried out using surface observation,crosssection analysis by focused ion beam and electron microscopic examination of coke deposits at different stages of the *** was found that surface orientation affected carbon deposition and metal dusting at the initial stage of the *** dusting occurred only when graphite grew into the metal interior where the volume expansion is responsible for metal disintegration and *** was also found that the metal dusting process could be significantly changed by alterations in alloy *** was found to affect the iron dusting process by destabilising Fe_3C but increasing the rate of carbon deposition and dusting,which questions the role of cementite in ferritic alloy *** adding copper to iron did not change the carburisation kinetics,cementite formation and coke morphology,copper alloying reduced nickel and nickel-base alloy dusting rates *** of these fundamental results to the dusting behaviour of engineering al

关键词：金属腐蚀氧化防护机械装置

Simulating canopy stomatal conductance of winter wheat and its distribution using remote sensing information

在线全文

学校读者我要写书评

暂无评论

j.urnal of Environmental Sciences 2001年第4期13卷 439-443页

作者： zhang, j.-h. Fu, C.-b. Kanzawa, H. START Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China

The canopy stomatal movement, a plant physiological process, generally occurs within leaves but its influence on exchange of CO2, water vapor, and sensible heat fluxes between atmosphere and terrestrial ecosystem. Many studies have documented that the interaction between leaf photosynthesis and canopy stomatal conductance is obvious. Thus, information on stomatal conductance is valuable in climate and ecosystem models. In current study, a newly developed model was adopted to calculate canopy stomatal conductance of winter wheat in Huang-Huai-Hai (H-H-H) Plain of China (31.5 - 42.7°N, 110.0 - 123.0°E). The remote sensing information from NOAA-AVHRR and meteorological observed data were used to estimate regional scale stomatal conductance distribution. Canopy stomatal conductance distribution pattern of winter wheat on March 18, 1997 was also presented. The developed canopy stomatal conductance model might be used to estimate canopy stomatal conductance in land surface schemes and seems can be acted as a boundary condition in regional climatic model runs.

关键词： Carbon dioxide Data reduction Ecosystems Heat flux Meteorology Photosynthesis Physiology Plants (botany) Remote sensing Vapors

Deformation behaviors of Cu bicrystals with an inclined twin boundary at multiple scales

在线全文

学校读者我要写书评

暂无评论

j.urnal of Materials Science & Technology 2017年第7期33卷 698-702页

作者： L.L.Li Z.j.zhang P.zhang j.Tan j.B.Yang Z.F.zhang Shenyaag National Laboratory for Materials Science lastitute of Metal Research Chinese Academy of Sciences Shenyaag 110016 China

Cu bicrystals of different sizes with a sole twin boundary（TB） inclined at 45？with respect to the loading direction were deformed under unidirectional and cyclic loading, respectively. It is found that the slip bands（SBs） parallel to the TB can be activated near the TB at all scales without obeying the Schmid＇s *** is concerned with the local stress enhancement in the macroscale while it is more closely related to the scarce dislocation sources in the microscale. Moreover, a wedge-shaped zone formed near the TB in the microscale ascribed to the limited specimen size.

关键词： Bicrystal Micropillar Twin boundary Schmid factors Size effect

Polar Coronal Holes During Solar Cycles 22 and 23

在线全文

学校读者我要写书评

暂无评论

Chinese j.urnal of Astronomy and Astrophysics 2005年第5期5卷 531-538页

作者： j.n zhang j. Woch S. Solanki National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 Max-Planck-Institut fiir Sonnensystemforschung Katlenburg-Lindau D-37191 Germany

Data from the Solar Wind Ion Composition Spectrometer （SWICS） on Ulysses and synoptic maps from Kitt Peak are used to analyze the polar coronal holes of solar activity cycles 22 and 23 （from 1990 to end of 2003）. In the beginning of the declining phase of solar cycles 22 and 23, the north polar coronal holes （PCHs） appear about one year earlier than the ones in the south polar region. The solar wind velocity and the solar wind ionic charge composition exhibit a characteristic dependence on the solar wind source position within a PCH. From the center toward the boundary of a young PCH, the solar wind velocity decreases, coinciding with a shift of the ionic charge composition toward higher charge states. However, for an old PCH, the ionic charge composition does not show any obvious change, although the latitude evolution of the velocity is similar to that of a young PCH.

关键词： Sun: coronal - Sun: particle emission - Sun: solar wind

INVESTIGATION ON THE FORMATION MECHANISM OF TITANIUM CARBIDE PREPARED BY IN SITU REACTION IN MOLTEN ALUMINUM

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 1997年第6期10卷 485-488页

作者： Yang, B. Wang, Y.Q zhang, j. Zhou, B.L. Inst of Metal Research Chinese Acad of Sciences Shenyang China

A novel technique in which TiC particulate are prepared by an in situ reaction in molten aluminum was introduced for producing TiC/Al composite. In order to reveal the characteristics of the technique, the formation mechanism of TiC particulate prepared by this method was studied. Both theoretical and experimental results show that the TiC particulate is formed by a diffusion mechanism when the molar fraction of aluminum in the preforms is higher than 20.02%. On the contrary, the TiC particulate is formed by a solution-precipitation mechanism when the fraction of aluminum in the preforms is lower than 20.02%.

关键词： Aluminum metallurgy In situ processing Metallic matrix composites Titanium carbide

GAS-SOLIDS FLOW BEHAVIOR WITH A GAS VELOCITY CLOSE TO ZERO

在线全文

学校读者我要写书评

暂无评论

China Particuology 2006年第3期4卷 167-177页

作者： H. zhang j.-X. Zhu Department of Chemical Engineering University of Western Ontario London Ontario Canada N6A 5B9 Canada

In a 9.3 m high and 0.10 m i.d. gas-solids downflow fluidized bed （downer）, the radial and axial distributions of the local solids holdups and particle velocities along the downer column were measured with the superficial gas velocity set to zero. A unique gas-solids flow structure was found in the downer system with zero gas velocity, which is completely different from that under conditions with higher gas velocities, in terms of its radial and axial flow structures as well as its micro flow structure. The gas-solids flow pattern under zero gas velocity conditions, together with that under low gas velocity conditions, can be considered as a special regime which differs from that under higher gas velocity conditions. According to the hydrodynamic properties of the two regimes, they can be named the ＂dense annulus＂ regime for the flow pattern under zero or low gas velocity conditions and the ＂dense core＂ regime for that under higher gas velocity conditions.

关键词： downer reactor gas-solids cocurrent downflow fluidized bed hydrodynamics flow development particle velocity solids holdup solids flux flow regime

The conduction mechanism of stress induced leakage current through ultra-thin gate oxide under constant voltage stresses

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

Chinese Physics B 2005年第9期14卷 1886-1891页

作者：王彦刚许铭真谭长华 zhang j. F 段小蓉 Institute of Microelectronics Peking University Beijing 100871 China School of Engineering Liverpool John Moores University UK

The conduction mechanism of stress induced leakage current （SILC） through 2nm gate oxide is studied over a gate voltage range between 1.7V and stress voltage under constant voltage stress （CVS）. The simulation results show that the SILC is formed by trap-assisted tunnelling （TAT） process which is dominated by oxide traps induced by high field stresses. Their energy levels obtained by this work are approximately 1.9eV from the oxide conduction band, and the traps are believed to be the oxygen-related donor-like defects induced by high field stresses. The dependence of the trap density on stress time and oxide electric field is also investigated.

关键词： stress induced leakage current oxygen-related donor-like defects trap-assisted tunnelling ultra-thin gate oxide

DEFORMATION OF THE EASTERN HIMALAYAN SYNTAXIS: EVIDENCES FROM STRUCTURES AND KINEMATICS OF ITS WESTERN BOUNDARY

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

地学前缘 2000年第S1期7卷 18-20页

作者： zhang j.,Zhong D.,Ding L.,j. j.,He S(Institute of Geology and Geophysics, Chinese Academy of Sciences, Beij.ng 100029,China)

The western boundary of the Eastern Himalayan Syntaxis (EHS) is a deformation belt up to 30km wide (Fig.1). Trending ca. N35°E, it separates the Gangdise magmatic belt in the west from the gneiss of EHS in the east. Its rock association, mica\|schist, quartzite, marble, and amphibolite, can be traced to the south to Gangdise belt and they were probably metamorphosed from the sediments along Yarlung Zangbo. This belt consists of several intensive deformation zones, the largest one of which is along the belt’s western margin from Dongj.g to Mainling and we called this ca. 10km wide shear zone as the Dongj.g\|Mainling shear zone (DMSZ).DMSZ experienced earlier ductile shear and later ductile\|brittle normal faulting. The earlier deformation produced mylonitic rocks. Their foliation trends N30°～40°E and dips northwest with the angle ranging from 55°to 80°, steepening northeastward. The penetrative kinematic lineation in the rocks has a varying attitude along the trend of DMSZ. It dips southwest with an angle of ca.35° in the southwest near Mainling, whereas dips northeast in the northeast. Moreover, the northeast dipping lineation steepens northeastwards, e.g., its angle ranges form 30° to 45° in the segment from Serkyim La to Dongj.g but becomes 60～70° in the northeast most in another zone near Parlung. Kinematic indicators show that the motion of DMSZ had a left\|lateral slipping component, but the vertical motion components were different in the southwest from the northeast. From Serkyim La to the northeast, DMSZ had a kinematics of NW plate (Gangdise belt) thrusting over the SE plate (EHS) and its thrusting component increased toward northeast. However, the DMSZ has a vertical motion with the SE plate (EHS) as the uplifting plate.

关键词： Eastern Himalayan Syntaxis indentation uplift

Bacillus Licheniformis Dhs-40, a Flocculating Active Strain and Its Flocculating Activity

在线全文

学校读者我要写书评

暂无评论

j.urnal of Environmental Science and Engineering 2010年第5期4卷 53-59页

作者： Y.S. zhang j. Wang j.A. Hao X.Z. zhang Y. Cheng The Institute of Seawater Desalination and Multipurpose Utilization SOA Tianjin 300192 China

Microbial flocculants have become a hot spot in recent years. A bacterial strain with high flocculating activity was isolated from seawater samples. The strain was defined as Bacillus licheniformis dhs-40 by 16S rDNA identification and Biolog test. Ultrasonication test confirmed the flocculating activity of the strain was both in fermentation supernatant and cell. According to flocculating activity curve, the ideal fermentation time for collecting flocculating active substances was two days. The flocculating activity of the strain was sensitive to pH. The strain could only preserve flocculating activity while pH varied from 7 to 11. However, it could preserve flocculating activity while temperature varied from -20℃to 100 ℃ Saccharide, protein, lipid, nucleic acids qualitative test and RNase, Proteinase K treatment confirmed the flocculating active substances were proteins. Their flocculating activities were insensitive to Proteinase K.

关键词： Flocculating activity bacteria isolation and identification active substances.