检索结果-南通市图书馆

Heat treatment of novel low-carbon multi-alloyed anti-wear marine steel

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2011年第3期21卷 254-261页

作者： Jing-hua JIANG~(1,2),Qiu-yue WANG~1,Ai-bin MA~(1,2),Jun SHI~1,Liu-yan ZHANG~1, Hui-dong YANG~(2,3),Fu-min LU~2,Qi ZHOU~2 1.National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety, hohai university,nanjing 210098,china 2.College of Mechanics and Materials,hohai university,nanjing 210098,china 3.Department of Mechanical and Aerospace Engineering,North Carolina State university, Raleigh,North Carolina 27695-7919,USA [a] National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety Hohai University Nanjing 210098 China [b] College of Mechanics and Materials Hohai University Nanjing 210098 China [c] Department of Mechanical and Aerospace Engineering North Carolina State University Raleigh North Carolina 27695-7919 USA

A low-carbon anti-wear steel,multi-alloyed with Si-Cr-Mn-Al-Ni-Mo-（Nb,RE）,was designed for vane pumps of ships. The novel cast steel after various heat treatments was characterized by microstructure observations and mechanical properties measurement in order to achieve an optimal process correlated with good abrasive resistance for a long marine *** scanning calorimetry and hardness analyses deduced a complete austenitizing temperature of 1 000℃,based on the alloying element homogenization and defective structure elimination without grain *** optimal austempering process（austenitized at 1 000℃,quick cooled for holding at 350℃for 1.5 h and then air-cooled to room temperature） produced a uniform mixture structure of fine carbide-free aciculate bainites and few lath martensites,resulting in the tensile strength increase of 34%and impact toughness increase of 50%compared with that of the as-cast *** abrasive wheel tests show that the austempered steel has good wear resistance with a mass-loss rate of 170 mg/（km·cm2） under applied load of 70 N in acidic *** new grade steel （containing anti-corrosion elements of Cr and rare earth） can find wide application in marine engineering,with further enhanced comprehensive properties via melting process improvement.

关键词： abrasive resistance carbide-free bainite marine steel mechanical performance heat treatment

NUMERICAL STUDY ON THE PURIFICATION PERFORMANCE OF RIVERBANK

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2007年第5期19卷 643-652页

作者： DAI Yu WANG De-guan College of Environmental Science and Engineering Hohai University Nanjing 210098 China

During the rain time, the runoff infiltrates into the riverbank through the collecting gutter and slope surface. The city runoff is generally polluted by organic, oil, heavy metal particulates, etc. The pollutants moving with the water through the riverbank experience advection, dispersion, diffusion, adsorption, biochemical reaction and plant uptaking processes. In this article, a mathematical model was developed to simulate the performance of pollutant removal of the riverbank. The model took those main mechanisms into account. The modified Richards equation was used in simulating flow field. The mass balance law was employed in deriving the equation for pollutant transport, where the diffusion and dispersion were described with the Fick-type law, the adsorption was macroscopically expressed as form isotherm, and the bio-chemical degradation process was assumed to follow the Monod kinetics. The NH3-N and TP were considered in the present model. The mathematical model was descritized with a finite element numerical model, which was applied to two types of model riverbanks. In the model test, the hydraulic loading was assumed to have the intermittent pattern simulating the storm runoff of certain return period, and the values of the rainfall runoff and concentrations of the NH3-N and TP were taken from the model test. The computed overall removal rates for the NH3-N and TP in 6 cases are in the range of 88%-98%, 87%-97%, respectively. The differences between the computed and tested overall removal rates for the NH3-N and TP are less than 5%. The time-varying oscillation pattern of the concentrations of the NH3-N and TP were rationally simulated, which shows that the model presented in this article can be used to assess the purification performance of the riverbank constructed with sand or soil.

关键词： riverbank numerical modelling purification,pollutant experiments

FINE SILT PARTICLE PATHLINE OF DREDGING SEDIMENT IN THE YANGTZE RIVER DEEPWATER NAVIGATION CHANNEL BASED ON EFDC MODEL

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2010年第6期22卷 760-772页

作者： XIE Rui WU De-an YAN Yi-xin ZHOU Hai College of Harbor Coastal and Offshore Engineering Hohai University Nanjing 210098 China Shanghai Institute of Waterways Shanghai 200120 China

Based on the Environmental Fluid Dynamics Code （EFDC）, a three-dimensional baroclinic model for lower reaches of the Yangtze River, Yangtze River Estuary, Hangzhou Bay and the adjacent sea areas was established with the sigma-coordinate in the vertical direction and the orthogonal curvilinear coordinates in the horizontal direction. The fine silt particle tracers were injected during different tides with the calibrated three-dimensional numerical model in the Yangtze River Estuary to simulate the migration tracks of the tracers in the following three days, and thereby study the migration behavior of the fine silt particles of dredged sediment after dumping at different locations in the navigation channel in the Yangtze River Estuary. The study shows that the particle paths of the tracer particles basically migrate to the open sea along the middle axis of river course in the form of reciprocating oscillation, the migration and diffusion directions of tracer particles are basically parallel to the navigation channel in guide levee, similar to long belt distribution, and the tracer particles migrate to the southeast out of the guide levee. The particle which is on the southern and northern sides enter groin and cross the navigation channel in the process of movement, and is easy to deposit in the navigation channel. The migration tracks of the particles released at different layers are basically similar at the same release station, but specifically different, varying at different cross sections. The result can be used for the choice and evaluation of dredging schemes in the Yangtze River Deepwater Navigation Channel.

关键词： deepwater channel EFDC model tracer fine silt particles

EXPERIMENT OF IMPACT OF RIVER HYDRAULIC CHARACTERISTICS ON NUTRIENTS PURIFICATION COEFFICIENT

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2007年第3期19卷 387-393页

作者： WANG Pei-fang WANG Xiao-rong WANG Chao State Key Laboratory of Pollution Control and Resource Reuse School of Environment Nanjing University Nanjing 210093 China State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai University Nanjing 210098 China Key Laboratory of Intergrated Regulation and Resource Development on Shallow Lakes College of Environmental Science and Engineering Hohai University Nanjing 210098 China

Hydraulic characteristics of a river are the key factors for river water quality improvement and river restoration. A simulated river was exploited to study the interactions between water contaminant purification coefficients and the characteristics of the river, such as the cross-section velocity, water depth, Reynolds number, and Froude number. To enhance the purification capacity of the river, detritus with 5 mm to 10 mm in diameter and contact surface area per volume of 87.6 m^2/m^3 were constructed naturally at the bed and along one side of the bank to form half shape of the river cross-section. During the one-month experiment （including 3 periods） from the third of November to the fourth of December, 2005, three categories of hydraulic conditions were investigated. Results show that the purification coefficient （K） of Total Nitrogen （TN） is closely coherent with the hydraulic retention time （T）, river length （L）, Reynolds number （Re） and Froude number （Fr）. The relationship of K and T generally agrees with the power law under the three experimental water hydraulic conditions. Based on these results, the optimal Re and Fr ranges can be obtain to serve as a guideline for ecological re-engineering design to improve river water quality and restore river ecosystem.

关键词： Hydraulic characteristics total nitrogen,purification coefficient interaction simulated river

Improvement of pitting corrosion resistance for Al-Cu alloy in sodium chloride solution through equal-channel angular pressing

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2011年第4期21卷 307-313页

作者： Dan SONG,Ai-bin MA,Jing-hua JIANG,Ping-hua LIN,Liu-yan ZHANG College of Mechanics and Materials,hohai university,nanjing 210098,china College of Mechanics and Materials Hohai University Nanjing 210098 China

Significant corrosion resistance improvement was achieved in solid-solution treated(T4) Al-Cu alloy after severe grain refinement through equal-channel angular *** bulk ultrafine-grained Al-Cu alloy with grain sizes of 200-300 nm has higher pitting potential(elevated by about 34 mV,SCE) and lower corrosion current density(decreased by about 3.88μA/cm~2) in polarization tests than the as-T4 alloy,and increased polarization resistance(increased by about 5.7 kΩ·cm~2) in electrochemical impendence spectrum tests,along with alleviated corrosion damage in immersion *** factors responds to the improved corrosion resistance of the alloy:the first is the refinement of residualθ-phase(Al2Cu) particles leading to the lower micro-galvanic currents and reduced susceptibilities to pitting corrosion,the second is the mass of strain-induced crystalline defects providing more nucleation sites for the formation of more volume fractions of stable oxide film.

关键词： Al-Cu alloy equal-channel angular pressing pitting corrosion resistance ultrafine-grained particle

NUMERICAL STUDY OF HYDRODYNAMICS OF MULTIPLE TANDEM JETS IN CROSS FLOW

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2011年第6期23卷 806-813页

作者： XIAO Yang TANG Hong-wu LIANG Dong-fang ZHANG Jiu-ding State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Nanjing 210098 China College of Water Conservancy and Hydropower Engineering Hohai University Nanjing 210098 China Department of Engineering University of Cambridge Cambridge UK

The hydrodynamics of a single jet and four tandem jets in a cross flow are simulated by using the Computational Fluid Dynamics （CFD） software Fluent. The realizable model is used to close the Reynolds-Averaged equations. The flow characteristics of the jets, including the jet trajectory, the velocity field and the turbulent kinetic energy are obtained with various jet-to-cross flow velocity ratios in the range of 2.38-17.88. It is shown that a single jet penetrates slightly deeper than the first jet in a jet group at the same , although the difference decreases with the decrease of . It is also found that the way in which the velo-city decays along the centerline of the jet is similar for both a single jet and the first jet in a group, and the speed of the decay increases with the decrease of . The downstream jets in a group are found to behave differently due to the sheltering effect of the first jet in the group. Compared with the first jet, the downstream jets penetrate deeper into the cross flow, and the velocity decays more slowly. The circulation zone between the two upstream jets in the front is stronger than those formed between the downstream jets. The Turbulent Kinetic Energy （TKE） sees a distinct double-peak across the cross-sections close to each nozzle, with low values in the jet core and high values in the shear layers. The double-peak gradually vanishes, as the shear layers of the jet merge further away from the nozzle, where the TKE assumes peaks at the jet centerline.

关键词： multiple tandem jets jet in cross flow realizable model flow dynamics

Temporal variation of suspended sediment load in the Pearl River due to human activities

在线全文

学校读者我要写书评

暂无评论

International Journal of Sediment Research 2011年第4期26卷 487-497页

作者： Wei ZHANG,Shousheng MU,Yanjing ZHANG,and Kaimin CHEN 1 Assoc.Prof.,State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering,hohai university, nanjing,210098,china, 2,4 Graduate student,College of Harbor,Coastal and Offshore Engineering,hohai university,nanjing,210098, china 3 Prof.,china Institute of Water Resources and Hydropower Research,Beijing,100038,china [a] Assoc. Prof. State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai University Nanjing 210098 China [b] Graduate student College of Harbor Coastal and Offshore Engineering Hohai University Nanjing 210098 China [c] Prof. China Institute of Water Resources and Hydropower Research Beijing 100038 China [d] Graduate student College of Harbor Coastal and Offshore Engineering Hohai University Nanjing 210098 China

Data on sediment flux at three hydrologic stations from the 1950s to 2006 are utilized to study the decadal,annual,and monthly variations in suspended sediment load delivered from the Pearl River to the *** show that variations in sediment flux from three main tributaries,including the West River,the North River and the East River,are spatially *** nearly 90%of the suspended sediment load comes from the West River,its variation has dominated the overall tendency of sediment flux in the entire Pearl *** a significant decreasing trend exists in the annual variation of the total sediment flux,the decadal change can be divided into an increasing phase and a decreasing phase,with the turning point between the two phases in the late *** the 1950s to the 1980s,the average annual river sediment flux increased by 30.43%.However,sediment flux has decreased significantly since the 1990s,with the average sediment flux being 38.60%less in the 2000s than that in the *** current sediment flux is also 52.93%less than its peak in the 1980s. The monthly variation pattern of the suspended sediment load transport to the sea is more interesting. For the West River,all months show a decreasing trend,and for most months the reduction values are ***,for the East River the sediment load shows a decrease trend in the dry season and an increase trend in the wet *** method of regression analysis was used to study the influence of precipitation in the variation on the sediment *** was found that the climate change is not the main driving force behind the variation in suspended sediment *** the 1990s, intensive land use destroyed the vulnerable ecosystem of the upper Pearl River,and speeded up the process of rocky ***,aggravated soil erosion caused an increase in suspended sediment ***,sediment retention within reservoirs had begun to play a dominant role after the massive constru

关键词： Pearl River Sediment flux Human activities Rocky desertification Dam construction

A STUDY ON NUMERICAL METHOD OF NAVIER-STOKES EQUATION AND NON-LINEAR EVOLUTION OF THE COHERENT STRUCTURES IN A LAMINAR BOUNDARY LAYER

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2006年第3期18卷 372-377页

作者： LU Chang-gen CAO Wei-dong QIAN Jian-hua State KeyLaboratory of Hydrology-Water Resources and Hydraulic Engineering and College of Environmental Science and Engineering Hohai University Nanjing 210098 China College of Environmental Science and Engineering Hohai University Nanjing 210098 China

A new method for direct numerical simulation of incompressible Navier-Stokes equations is studied in the paper. The compact finite difference and the non-linear terms upwind compact finite difference schemes on non-uniform meshes in x and y directions are developed respectively. With the Fourier spectral expansion in the spanwise direction, three-dimensional N-S equation are converted to a system of two-dimensional explicit-implicit The treatment of equations. The third-order mixed scheme is employed the three-dimensional for time integration. non-reflecting outflow boundary conditions is presented, which is important for the numerical simulations of the problem of transition in boundary layers, jets, and mixing layer. The numerical results indicate that high accuracy, stabilization and efficiency are achieved by the proposed numerical method. In addition, a theory model for the coherent structure in a laminar boundary layer is also proposed, based on which the numerical method is implemented to the non-linear evolution of coherent structure. It is found that the numerical results of the distribution of Reynolds stress, the formation of high shear layer, and the event of ejection and sweeping, match well with the observed characteristics of the coherent structures in a turbulence boundary layer.

关键词： non-uniform meshes compact finite differences scheme Fourier spectral expansion coherent structure boundary layer

RECONSTRUCTION OF PRECIPITATION SERIES AND ANALYSIS OF CLIMATE CHANGE OVER PAST 500 YEARS IN NORTHERN china

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2005年第6期17卷 737-745页

作者： RONG Yan-shu TU Qi-pu College of water Resources and Environment Hohai University Nanjing 210098 China Tianjin Institute of Meteorological Science Tianjin 300074 China nanjing university of Information Science and Technology Nanjing 210044 China

It is important and necessary to get a much longer precipitation series in order to research features of drought/flood and climate change. Based on dryness and wetness grades series of 18 stations in Northern china of 533 years from 1470 to 2002, the Moving Cumulative Frequency Method （MCFM） was developed, moving average precipitation series from 1499 to 2002 were reconstructed by testing three kinds of average precipitation, and the features of ell mate change and dry and wet periods were researched by using reconstructed precipitation series in the present paper. The results showed that there were good relationship between the reconstructed precipitation series and the observation precipiration series sincc 1954 and their relative root mean-square error were below 1.89%, that the relation between reconstructed series and the dryness and wetness grades series were nonlinear and this nonlinear relation implied that reconstructed series were reliable and could became foundation data for researching evolution of the drought and flood. Analysis of climate change upon reconstructed precipitation series revealed that although drought intensity of recent dry period from mid- dle 1970s of 20th century until early 21st century was not the strongest in historical climate of Northern china, intensity and duration of wet period was a great deal decreasing and shortening respectively, climate evolve to aridification situa- tion in Northern china.

关键词： reconstruction series dryness and wetness grades series precipitation series climate change Northern china