By means of a logarithm law for the velocity profile, a corrected formula of bed resistance coefficient, which involves many factors such as gradient of still water depth, variation of surface elevation, flow directio...By means of a logarithm law for the velocity profile, a corrected formula of bed resistance coefficient, which involves many factors such as gradient of still water depth, variation of surface elevation, flow direction, and so on, is derived from the 3D governing equations of tidal current by averaging over the whole water depth. Theoretical analysis and application have shown that the 2D plane tidal current numerical model would be more reasonable and could be applied to steep bottom topography when the corrected bed resistance coefficient is used, therefore the results of reproduction simulation and engineering calculation would be more scientific and reasonable.展开更多
This paper presents a further study of the Manning and Darcy-Weisbach resistance coefficients, as they play a significant role in assessing the cross-sectional mean velocity, conveyance capacity and determining the la...This paper presents a further study of the Manning and Darcy-Weisbach resistance coefficients, as they play a significant role in assessing the cross-sectional mean velocity, conveyance capacity and determining the lateral distribution of depth mean velocity and local boundary shear stress in compound channels. The relationships between the local, zonal and overall resistance coefficients, and a wide range of geometries and different roughness between the main channel and the flood plain are established by analyzing a vast amount of experimental data from a British Science and Engineering Research Council Flood Channel Facility （SERC-FCF）. And the experimental results also show that the overall Darcy-Weisbach resistance coefficient for a compound channel is the function of Reynolds number, but the function relationship is different from that for a single channel. By comparing and analyzing the conventional methods with the experimental data to predict composite roughness in compound channels, it is found that these methods are not suitable for compound channels. Moreover, the reason why the conventional methods cannot assess correctly the conveyance capacity of compound channels is also analyzed in this paper.展开更多
In order to improve the shift decision strategy for an off-road vehicle with automated manual transmission（AMT）,the generalized road resistance coefficient is defined based on the longitudinal dynamics analysis.Vehi...In order to improve the shift decision strategy for an off-road vehicle with automated manual transmission（AMT）,the generalized road resistance coefficient is defined based on the longitudinal dynamics analysis.Vehicle mass and generalized road resistance coefficient are estimated using the recursive least square（RLS）method with multiple forgetting factors.The improved shift schedule is designed based on the generalized road resistance coefficient under uphill road condition.The simulation and real vehicle test verify the effectiveness of improved shift strategy and the improvement of vehicle dynamic performance.展开更多
In this paper,a novel parallel mechanism which can be used to evaluate body-to-bogie yawtorque is proposed.It can satisfy experimental testing for rotation resistance coefficient(RRC) with various types of bogies,diff...In this paper,a novel parallel mechanism which can be used to evaluate body-to-bogie yawtorque is proposed.It can satisfy experimental testing for rotation resistance coefficient(RRC) with various types of bogies,different rotational speeds,and different states of air spring.Aiming at the problem that computing speed of Newton iterative method for solving rotational angle is incompetence to meet the real-time requirements,and also that other methods adopting physical device such as laser displacement sensor to solve rotational angle possess larger measurement error,the analytical techniques method used for solving rotational angle is presented.Finally,by using the upper-single-6-DOF motion platform as an authentic urging mean to simulate a real vehicle,the test was carried out under the speeds of 0.2 and 1.0(°)/s,with the air spring at the inflated and deflated states,respectively.The results showthat the RRC of the bogie under various conditions is less than 0.06,which meets the standard requirement EN-14363.It was also found that the speed of vehicles moving along curves and the state of air spring were key factors influencing the RRC.The feasibilities of this model and test method are verified in this study.展开更多
Aquatic vegetation zone is now receiving an increasing attention as an effective way to protect the shorelines and riverbeds. To simulate the flow through the vegetation zone, the vegetation elements are often simplif...Aquatic vegetation zone is now receiving an increasing attention as an effective way to protect the shorelines and riverbeds. To simulate the flow through the vegetation zone, the vegetation elements are often simplified as equidistant rigid cylinders, and in the whole zone, the porous media approach can be applied. In this study, a non-constant inertial resistance coefficient is introduced to model the unevenly distribution of the drag forces on the cylinders, and an improved porous media approach is applied to one circular array of cylinders positioned in a 2-D flume. The calculated velocity profile is consistent with the experimental data.展开更多
High resistance thin film chip resistors(0603 type) were studied,and the specifications are as follows:1 k? with tolerance about ±0.1% after laser trimming and temperature coefficient of resistance(TCR) less than...High resistance thin film chip resistors(0603 type) were studied,and the specifications are as follows:1 k? with tolerance about ±0.1% after laser trimming and temperature coefficient of resistance(TCR) less than ±15×10-6/℃.Cr-Si-Ta-Al films were prepared with Ar flow rate and sputtering power fixed at 20 standard-state cubic centimeter per minute(sccm) and 100 W,respectively.The experiment shows that the electrical properties of Cr-SiTa-Al deposition films can meet the specification requirements of 0603 ty...展开更多
As a metal alloy,NiCr films have a relatively high resistivity and low temperature coefficient of resistance (TCR) and are widely used in electronic components and sensors.However,the resistivity of pure NiCr is insuf...As a metal alloy,NiCr films have a relatively high resistivity and low temperature coefficient of resistance (TCR) and are widely used in electronic components and sensors.However,the resistivity of pure NiCr is insufficient for high-resistance and highly stable film resistors.In this study,a quaternary NiCrAlSi target (47:33:10:10,wt.%) was successfully used to prepare resistor films with resistivities ranging from 1000 to 10 000μΩcm and TCR within±100 ppm/K.An oxygen flow was introduced during the sputtering process.The films exhibit hightemperature stability at 450℃.The films were analyzed using Auger electron spectroscopy,x-ray diffraction,time-of-flight secondary-ion mass spectrometry,and x-ray photoelectron spectroscopy.The results show that the difference in the oxide proportion of the films caused the differences in resistivity.The near-zero TCR values were considered to be due to the competition between silicon and other metals.This study provides new insights into the electrical properties of NiCr-based films containing Si,which will drive the manufacturing of resistors with high resistivity and zero TCR.展开更多
We demonstrate the first successful attempt to partially substitute Cu into the Mn_(3)AgN-antiperovskite system to form Mn_(3)Ag_((1-x))Cu_((x))N thin films with an ultra-low temperature coefficient of resistance(TCR)...We demonstrate the first successful attempt to partially substitute Cu into the Mn_(3)AgN-antiperovskite system to form Mn_(3)Ag_((1-x))Cu_((x))N thin films with an ultra-low temperature coefficient of resistance(TCR)for fabrication of ultra-precise passive components.Films were grown by reactive magnetron sputtering on alumina and glass substrates and were found to be amorphous in nature with highly negative TCR of-233 to-351 ppm/℃in their as-grown state.Increasing Cu alloying from x=0 to 1,resulted in increased sheet resistance,a negative shift of TCR and a change of grain morphology from spherical to elongated.Post-deposition heat treatment at 300-375℃,resulted in a positive shift of TCR and an ultra-low TCR of-4.66 ppm/℃for films with x=0.6.The heat treatment induces grain growth,surface roughness and the formation of a manganese oxide upper surface layer up until temperatures of 350℃,after which surface oxidation begins to dominate.The growth rate of the surface layer is controlled by the Cu concentration and heat treatment temperature,which both play a central role in the development of these novel ultralow TCR Mn_(3)Ag_((1-x))Cu_((x))N thin film structures.展开更多
According to the load-structure method, the wall rock with lining can bear the load caused by the surrounding rock, and the rock resistant coefficient (RRC) is a key parameter for evaluating the capacity of this wall ...According to the load-structure method, the wall rock with lining can bear the load caused by the surrounding rock, and the rock resistant coefficient (RRC) is a key parameter for evaluating the capacity of this wall rock. Based on the Mohr-Coulomb yield criterion, this paper develops a formula for calculating the RRC, which has been applied to the real engi-neering project, such as Xiamen Xiang’an East Passage Underwater Tunnel Project. The fact shows that this formula is helpful for designers to determine the RRC value.展开更多
Titanium aluminum nitride （TiAlN） film, as a possible substitute for the conventional tantalum nitride （TAN） or tantalum-aluminum （TaAl） heater resistor in inkjet printheads, was deposited on a Si（100） substra...Titanium aluminum nitride （TiAlN） film, as a possible substitute for the conventional tantalum nitride （TAN） or tantalum-aluminum （TaAl） heater resistor in inkjet printheads, was deposited on a Si（100） substrate at 400 ℃ by radio frequency （RF） magnetron co-sputtering using titanium nitride （TIN） and aluminum nitride （AlN） as ceramic targets. The temperature coefficient of resistivity （TCR） and oxidation resistance, which are the most important properties of a heat resistor, were studied depending on the plasma power density applied during sputtering. With the increasing plasma power density, the crystallinity, grain size and surface roughness of the applied film increased, resulting in less grain boundaries with large grains. The Ti, Al and N binding energies obtained from X-ray photoelectron spectroscopy analysis disclosed the nitrogen deficit in the TiAlN stoichiometry that makes the films more electrically resistive. The highest oxidation resistance and the lowest TCR of-765.43×10^-6 K-l were obtained by applying the highest plasma power density.展开更多
The reliability of post grouting pile axial resistance was studied by proposing a design method for its probabilistic limit state,which is represented by the partial coefficients of load,end,and side resistance.The hy...The reliability of post grouting pile axial resistance was studied by proposing a design method for its probabilistic limit state,which is represented by the partial coefficients of load,end,and side resistance.The hyperbolic,modified hyperbolic,and polynomial models were employed to predict the ultimate bearing capacity of test piles that were not loaded to damage in field tests.The results were used for the calculation and calibration of the reliability index.The reliability of the probabilistic limit state design method was verified by an engineering case.The results show that the prediction results obtained from the modified hyperbolic model are closest to those obtained through the static load test.The proposed corresponding values of total,side,and end resistance partial coefficients are 1.84,1.66,and 2.73 when the dead and live load partial coefficients are taken as 1.1 and 1.4,respectively.Meanwhile,the corresponding partial coefficients of total,side,and end resistance are 1.70,1.56,and 2.34 when the dead and live load partial coefficients are taken as 1.2 and 1.4,respectively.展开更多
The Ti（C,N）precipitation and texture evolution in ultra-low carbon Ti-bearing enamel steel were studied to discover their correlation.Two different cooling paths of simulative coiling were adopted to gain different ...The Ti（C,N）precipitation and texture evolution in ultra-low carbon Ti-bearing enamel steel were studied to discover their correlation.Two different cooling paths of simulative coiling were adopted to gain different morphologies of Ti（C,N）precipitate in hot strips.It is found that the Ti（C,N）precipitate in hot strip using Path 2（put into asbestos box and air cooled）are finer and much more in quantity than that in hot strip using Path 1（held at 730℃ for 30min and furnace cooled）.The morphology of Ti（C,N）precipitate in hot strip has great effect on recrystallization texture in the subsequent cold-rolled annealed sheet.γ-fiber texture of strong recrystallization is gained in coldrolled and annealed sheet came from Path 1.On the contrary,in the one came from Path 2,theγ-fiber texture is weak.This may be due to the pinning force of numerous fine Ti（C,N）precipitate which retard the growth of preferential nucleated{111}orientated grains.Annealed steel sheets in the test came from both paths have excellent fishscale resistance.展开更多
The change of the temperature coefficient of resistivity (a) with the particle size, dp, and the grain size, dc, in the nanostructured Ag bulk samples was investigated. dp and dc were controlled by heating the nano-Ag...The change of the temperature coefficient of resistivity (a) with the particle size, dp, and the grain size, dc, in the nanostructured Ag bulk samples was investigated. dp and dc were controlled by heating the nano-Ag powders over the temperature range from 393 to 453 K. The electrical resistance measurements of the nanostructured Ag bulk samples obtained by compacting the Ag powders after heat treatments showed a change in the sign of a with dP and dc. When dp and dc are smaller or equal to 18 and 11 nm below room temperature or 20 and 12 nm above room temperature, respectively, the sign of the temperature coefficient of resistivity changes from positive to negative. The negative a arises mainly from the high resistivity induced by the particle interfaces with very lowly ordered or even disordered structure, a large volume fraction of interfaces and impurities existing in the interfaces, and the quantum size effect appearing in the nano-Ag grains.展开更多
During the design of pipeline,the determination of local resistant coefficient is often come arcoss.The sudden enlargement local resistant coefficient ξ 1=1-A 1A 2 2 is determined through theory.In the paper,the ...During the design of pipeline,the determination of local resistant coefficient is often come arcoss.The sudden enlargement local resistant coefficient ξ 1=1-A 1A 2 2 is determined through theory.In the paper,the sudden enlargement local resistant coefficient under the conditions of three kinds of A 1A 2 was studied in experiment.In the end ,the result shows that ξ 1 is related not only to two flow cross sections,but also to the velocity.Through experimental research,the relationship between ξ 1,A 1A 2 and V 1 was determined.In a word,the hydraulic calculation of pipeline can be done by taking correspondent ξ 1 ,according to the design velocity V 1 and A 1A 2.展开更多
The coefficient of strain resistance for metals,solid solutions and ordering alloys in annealing state decreases,while K increases in cold working state.The value K of pure metals and solid solutions invaraibly decrea...The coefficient of strain resistance for metals,solid solutions and ordering alloys in annealing state decreases,while K increases in cold working state.The value K of pure metals and solid solutions invaraibly decreases with temperature increass.The main factors influencing the coefHcient of strain resistance are crystal defect,dispersion and degree of atomic arrangement.展开更多
Y^3＋-doped （Bi 1/2 Na 1/2） TiO 3-CaTiO 3-BaTiO 3 （BNCBT） positive temperature coefficient of resistivity （PTCR） ceramics sintered in air atmosphere were investigated in this study. （Bi 1/2 Na 1/2） TiO 3 （BNT...Y^3＋-doped （Bi 1/2 Na 1/2） TiO 3-CaTiO 3-BaTiO 3 （BNCBT） positive temperature coefficient of resistivity （PTCR） ceramics sintered in air atmosphere were investigated in this study. （Bi 1/2 Na 1/2） TiO 3 （BNT） component can remarkably increase the onset temperature T c of PTCR ceramics with the expense of the resistivity R 25 increase. CaTiO 3 （9–27 mol%） component can decrease the resistivity, and adjust the effects of BNT phase on the T c point. For the sample containing 3 mol% CaTiO 3 , T c raises from 122 ℃ to 153 ℃ when only 0.6 mol% BNT added, while for the ones with higher CaTiO 3 content （9–27 mol%）, T c is only increased by a rate of 8–9℃/1.0 mol% BNT. The effects of BNT and CaTiO 3 components on R25/Rmin （negative temperature coefficient effect） are also discussed.展开更多
In this article,computational fluid dynamics(CFD)are used to explore the dynamics of water transport inside the pitted thickening of a plant xylem vessel.A pitted thickening model combined with the Bernoulli equation ...In this article,computational fluid dynamics(CFD)are used to explore the dynamics of water transport inside the pitted thickening of a plant xylem vessel.A pitted thickening model combined with the Bernoulli equation is used to analyze the influence of various factors(namely,the inner diameter,thickening width,thickening height,thickening spacing,number of laps and adjacent pit axial rotation).The pressure drop and the flow resistance coefficient are the variable parameters for our analysis.The results show that these two parameters are proportional to the thickening height and thickening width,and inversely proportional to the inner diameter,thickening spacing and number of laps.Three different wall thickening structures of the vessel are compared and the pitted thickening vessel is shown to provide the largest structural flow resistance,the annular thickening vessel has the second largest resistance and the helical thickening vessel corresponds to the smallest resistance of the three structures.展开更多
In this paper, a numerical study of flow in the turbulence boundary layer with adverse and pressure gradients （APGs） is conducted by using Reynolds-averaged Navier-Stokes （RANS） equations. This research chooses si...In this paper, a numerical study of flow in the turbulence boundary layer with adverse and pressure gradients （APGs） is conducted by using Reynolds-averaged Navier-Stokes （RANS） equations. This research chooses six typical turbulence models, which are critical to the computing precision, and to evaluating the issue of APGs. Local frictional resistance coefficient is compared between numerical and experimental results. The same comparisons of dimensionless averaged velocity profiles are also performed. It is found that results generated by Wilcox （2006） k-co are most close to the experimental data. Meanwhile, turbulent quantities such as turbulent kinetic energy and Reynolds-stress are also studied.展开更多
Water permeability is an important property of nonwoven geotextiles used in drainage field, and usually it is obtained by testing individual layer or multi-layered nonwoven geotextiles. However, the permeability coeff...Water permeability is an important property of nonwoven geotextiles used in drainage field, and usually it is obtained by testing individual layer or multi-layered nonwoven geotextiles. However, the permeability coefficient tested by using different layers would be different for the same nonwoven geotextile. In this paper, the relation between them is studied based on Darcy's law. The study shows that vertical permeability coefficients are theoretically invariable no matter how many layers are tested; but experimental results show that vertical permeability coefficients decrease with the increase of nonwoven geotextile layers number.展开更多
In this paper, the feasibility study of chemical flooding is carried out for ultra-high porosity and high permeability heavy oil field with permeability higher than 10 μm<sup>2</sup> and porosity greater ...In this paper, the feasibility study of chemical flooding is carried out for ultra-high porosity and high permeability heavy oil field with permeability higher than 10 μm<sup>2</sup> and porosity greater than 35%. The viscosity-concentration relationship of four kinds of oil flooding systems such as hydrolyzed polyacrylamide, structural polymer A, structural polymer B and gel was studied. The results showed that the viscosity of ordinary polymer and structural polymer B was lower compared with other two types of oil displacement agents, and the viscosity of structural polymer A was higher. The higher the concentration, the higher the viscosity retention rate. The gel system has the highest viscosity and best anti-shear ability. The resistance coefficient and residual resistance coefficient of structural polymer A and gel system were further studied. The results show that permeability, velocity and polymer concentration all affect the resistance coefficient and residual resistance coefficient. From the point of view of resistance establishment ability, it is considered that structural polymer A is not suitable for permeability formation above 10 μm<sup>2</sup>. Gel system has stronger ability to establish resistance coefficient than structural polymer A flooding system, and it is more feasible for formation system with permeability above 10 μm<sup>2</sup>.展开更多
基金National Natural Science Foundation of China(Grant No.49971064)
文摘By means of a logarithm law for the velocity profile, a corrected formula of bed resistance coefficient, which involves many factors such as gradient of still water depth, variation of surface elevation, flow direction, and so on, is derived from the 3D governing equations of tidal current by averaging over the whole water depth. Theoretical analysis and application have shown that the 2D plane tidal current numerical model would be more reasonable and could be applied to steep bottom topography when the corrected bed resistance coefficient is used, therefore the results of reproduction simulation and engineering calculation would be more scientific and reasonable.
基金The project supported by the National Natural Science Foundation of China(50279024)the National Key Basic Research and Development Program of China(973 Program)(2003CB415202)the Specialized Research Fund for the Doctoral Program of Higher Education(2
文摘This paper presents a further study of the Manning and Darcy-Weisbach resistance coefficients, as they play a significant role in assessing the cross-sectional mean velocity, conveyance capacity and determining the lateral distribution of depth mean velocity and local boundary shear stress in compound channels. The relationships between the local, zonal and overall resistance coefficients, and a wide range of geometries and different roughness between the main channel and the flood plain are established by analyzing a vast amount of experimental data from a British Science and Engineering Research Council Flood Channel Facility （SERC-FCF）. And the experimental results also show that the overall Darcy-Weisbach resistance coefficient for a compound channel is the function of Reynolds number, but the function relationship is different from that for a single channel. By comparing and analyzing the conventional methods with the experimental data to predict composite roughness in compound channels, it is found that these methods are not suitable for compound channels. Moreover, the reason why the conventional methods cannot assess correctly the conveyance capacity of compound channels is also analyzed in this paper.
基金Supported by the National High Technology Engineering Program(303002011421)
文摘In order to improve the shift decision strategy for an off-road vehicle with automated manual transmission（AMT）,the generalized road resistance coefficient is defined based on the longitudinal dynamics analysis.Vehicle mass and generalized road resistance coefficient are estimated using the recursive least square（RLS）method with multiple forgetting factors.The improved shift schedule is designed based on the generalized road resistance coefficient under uphill road condition.The simulation and real vehicle test verify the effectiveness of improved shift strategy and the improvement of vehicle dynamic performance.
基金National Natural Science Foundation of China(No.51575232)Jilin University Youth Science and Technology Innovation Fund,China(No.450060507032)
文摘In this paper,a novel parallel mechanism which can be used to evaluate body-to-bogie yawtorque is proposed.It can satisfy experimental testing for rotation resistance coefficient(RRC) with various types of bogies,different rotational speeds,and different states of air spring.Aiming at the problem that computing speed of Newton iterative method for solving rotational angle is incompetence to meet the real-time requirements,and also that other methods adopting physical device such as laser displacement sensor to solve rotational angle possess larger measurement error,the analytical techniques method used for solving rotational angle is presented.Finally,by using the upper-single-6-DOF motion platform as an authentic urging mean to simulate a real vehicle,the test was carried out under the speeds of 0.2 and 1.0(°)/s,with the air spring at the inflated and deflated states,respectively.The results showthat the RRC of the bogie under various conditions is less than 0.06,which meets the standard requirement EN-14363.It was also found that the speed of vehicles moving along curves and the state of air spring were key factors influencing the RRC.The feasibilities of this model and test method are verified in this study.
基金Project supported by the Special Fund of Marine-Fishery Science-Technology Extension in Guangdong Province(Grant No.A201401B08)
文摘Aquatic vegetation zone is now receiving an increasing attention as an effective way to protect the shorelines and riverbeds. To simulate the flow through the vegetation zone, the vegetation elements are often simplified as equidistant rigid cylinders, and in the whole zone, the porous media approach can be applied. In this study, a non-constant inertial resistance coefficient is introduced to model the unevenly distribution of the drag forces on the cylinders, and an improved porous media approach is applied to one circular array of cylinders positioned in a 2-D flume. The calculated velocity profile is consistent with the experimental data.
基金Supported by Science and Technology Committee of Tianjin (No.06YFGPGX08400)Ministry of Science and Technology of China (No.2009GJF20022)Innovation Fund of Tianjin University
文摘High resistance thin film chip resistors(0603 type) were studied,and the specifications are as follows:1 k? with tolerance about ±0.1% after laser trimming and temperature coefficient of resistance(TCR) less than ±15×10-6/℃.Cr-Si-Ta-Al films were prepared with Ar flow rate and sputtering power fixed at 20 standard-state cubic centimeter per minute(sccm) and 100 W,respectively.The experiment shows that the electrical properties of Cr-SiTa-Al deposition films can meet the specification requirements of 0603 ty...
基金support from the Innovation Foundation of the Shanghai Institute of Technical Physics,Chinese Academy of Sciences。
文摘As a metal alloy,NiCr films have a relatively high resistivity and low temperature coefficient of resistance (TCR) and are widely used in electronic components and sensors.However,the resistivity of pure NiCr is insufficient for high-resistance and highly stable film resistors.In this study,a quaternary NiCrAlSi target (47:33:10:10,wt.%) was successfully used to prepare resistor films with resistivities ranging from 1000 to 10 000μΩcm and TCR within±100 ppm/K.An oxygen flow was introduced during the sputtering process.The films exhibit hightemperature stability at 450℃.The films were analyzed using Auger electron spectroscopy,x-ray diffraction,time-of-flight secondary-ion mass spectrometry,and x-ray photoelectron spectroscopy.The results show that the difference in the oxide proportion of the films caused the differences in resistivity.The near-zero TCR values were considered to be due to the competition between silicon and other metals.This study provides new insights into the electrical properties of NiCr-based films containing Si,which will drive the manufacturing of resistors with high resistivity and zero TCR.
文摘We demonstrate the first successful attempt to partially substitute Cu into the Mn_(3)AgN-antiperovskite system to form Mn_(3)Ag_((1-x))Cu_((x))N thin films with an ultra-low temperature coefficient of resistance(TCR)for fabrication of ultra-precise passive components.Films were grown by reactive magnetron sputtering on alumina and glass substrates and were found to be amorphous in nature with highly negative TCR of-233 to-351 ppm/℃in their as-grown state.Increasing Cu alloying from x=0 to 1,resulted in increased sheet resistance,a negative shift of TCR and a change of grain morphology from spherical to elongated.Post-deposition heat treatment at 300-375℃,resulted in a positive shift of TCR and an ultra-low TCR of-4.66 ppm/℃for films with x=0.6.The heat treatment induces grain growth,surface roughness and the formation of a manganese oxide upper surface layer up until temperatures of 350℃,after which surface oxidation begins to dominate.The growth rate of the surface layer is controlled by the Cu concentration and heat treatment temperature,which both play a central role in the development of these novel ultralow TCR Mn_(3)Ag_((1-x))Cu_((x))N thin film structures.
文摘According to the load-structure method, the wall rock with lining can bear the load caused by the surrounding rock, and the rock resistant coefficient (RRC) is a key parameter for evaluating the capacity of this wall rock. Based on the Mohr-Coulomb yield criterion, this paper develops a formula for calculating the RRC, which has been applied to the real engi-neering project, such as Xiamen Xiang’an East Passage Underwater Tunnel Project. The fact shows that this formula is helpful for designers to determine the RRC value.
基金Project (M-2009-01-0029) supported by Fundamental R&D Program for Core Technology of Materials, Korea
文摘Titanium aluminum nitride （TiAlN） film, as a possible substitute for the conventional tantalum nitride （TAN） or tantalum-aluminum （TaAl） heater resistor in inkjet printheads, was deposited on a Si（100） substrate at 400 ℃ by radio frequency （RF） magnetron co-sputtering using titanium nitride （TIN） and aluminum nitride （AlN） as ceramic targets. The temperature coefficient of resistivity （TCR） and oxidation resistance, which are the most important properties of a heat resistor, were studied depending on the plasma power density applied during sputtering. With the increasing plasma power density, the crystallinity, grain size and surface roughness of the applied film increased, resulting in less grain boundaries with large grains. The Ti, Al and N binding energies obtained from X-ray photoelectron spectroscopy analysis disclosed the nitrogen deficit in the TiAlN stoichiometry that makes the films more electrically resistive. The highest oxidation resistance and the lowest TCR of-765.43×10^-6 K-l were obtained by applying the highest plasma power density.
基金The National Natural Science Foundation of China(No.51878160,52008100,52078128).
文摘The reliability of post grouting pile axial resistance was studied by proposing a design method for its probabilistic limit state,which is represented by the partial coefficients of load,end,and side resistance.The hyperbolic,modified hyperbolic,and polynomial models were employed to predict the ultimate bearing capacity of test piles that were not loaded to damage in field tests.The results were used for the calculation and calibration of the reliability index.The reliability of the probabilistic limit state design method was verified by an engineering case.The results show that the prediction results obtained from the modified hyperbolic model are closest to those obtained through the static load test.The proposed corresponding values of total,side,and end resistance partial coefficients are 1.84,1.66,and 2.73 when the dead and live load partial coefficients are taken as 1.1 and 1.4,respectively.Meanwhile,the corresponding partial coefficients of total,side,and end resistance are 1.70,1.56,and 2.34 when the dead and live load partial coefficients are taken as 1.2 and 1.4,respectively.
基金Sponsored by National Natural Science Foundation of China(50527402)National Basic Research Program(973Program)of China(2011CB606306-2)
文摘The Ti（C,N）precipitation and texture evolution in ultra-low carbon Ti-bearing enamel steel were studied to discover their correlation.Two different cooling paths of simulative coiling were adopted to gain different morphologies of Ti（C,N）precipitate in hot strips.It is found that the Ti（C,N）precipitate in hot strip using Path 2（put into asbestos box and air cooled）are finer and much more in quantity than that in hot strip using Path 1（held at 730℃ for 30min and furnace cooled）.The morphology of Ti（C,N）precipitate in hot strip has great effect on recrystallization texture in the subsequent cold-rolled annealed sheet.γ-fiber texture of strong recrystallization is gained in coldrolled and annealed sheet came from Path 1.On the contrary,in the one came from Path 2,theγ-fiber texture is weak.This may be due to the pinning force of numerous fine Ti（C,N）precipitate which retard the growth of preferential nucleated{111}orientated grains.Annealed steel sheets in the test came from both paths have excellent fishscale resistance.
基金the National Natural Science FOundation of China under grant! No.19974041the National Major Fundamental ResearCh Program-Nal
文摘The change of the temperature coefficient of resistivity (a) with the particle size, dp, and the grain size, dc, in the nanostructured Ag bulk samples was investigated. dp and dc were controlled by heating the nano-Ag powders over the temperature range from 393 to 453 K. The electrical resistance measurements of the nanostructured Ag bulk samples obtained by compacting the Ag powders after heat treatments showed a change in the sign of a with dP and dc. When dp and dc are smaller or equal to 18 and 11 nm below room temperature or 20 and 12 nm above room temperature, respectively, the sign of the temperature coefficient of resistivity changes from positive to negative. The negative a arises mainly from the high resistivity induced by the particle interfaces with very lowly ordered or even disordered structure, a large volume fraction of interfaces and impurities existing in the interfaces, and the quantum size effect appearing in the nano-Ag grains.
文摘During the design of pipeline,the determination of local resistant coefficient is often come arcoss.The sudden enlargement local resistant coefficient ξ 1=1-A 1A 2 2 is determined through theory.In the paper,the sudden enlargement local resistant coefficient under the conditions of three kinds of A 1A 2 was studied in experiment.In the end ,the result shows that ξ 1 is related not only to two flow cross sections,but also to the velocity.Through experimental research,the relationship between ξ 1,A 1A 2 and V 1 was determined.In a word,the hydraulic calculation of pipeline can be done by taking correspondent ξ 1 ,according to the design velocity V 1 and A 1A 2.
文摘The coefficient of strain resistance for metals,solid solutions and ordering alloys in annealing state decreases,while K increases in cold working state.The value K of pure metals and solid solutions invaraibly decreases with temperature increass.The main factors influencing the coefHcient of strain resistance are crystal defect,dispersion and degree of atomic arrangement.
基金Project supported by the SPAT of Shanghai Committee of Chinese People's Political Consultative Conference and Shanghai Education Development Foundation (Grant No.2008012)
文摘Y^3＋-doped （Bi 1/2 Na 1/2） TiO 3-CaTiO 3-BaTiO 3 （BNCBT） positive temperature coefficient of resistivity （PTCR） ceramics sintered in air atmosphere were investigated in this study. （Bi 1/2 Na 1/2） TiO 3 （BNT） component can remarkably increase the onset temperature T c of PTCR ceramics with the expense of the resistivity R 25 increase. CaTiO 3 （9–27 mol%） component can decrease the resistivity, and adjust the effects of BNT phase on the T c point. For the sample containing 3 mol% CaTiO 3 , T c raises from 122 ℃ to 153 ℃ when only 0.6 mol% BNT added, while for the ones with higher CaTiO 3 content （9–27 mol%）, T c is only increased by a rate of 8–9℃/1.0 mol% BNT. The effects of BNT and CaTiO 3 components on R25/Rmin （negative temperature coefficient effect） are also discussed.
基金supported by the National Natural Science Foundation of China(Grant Nos.51279071,51969009)the Foundation of the Ministry of Education of China for Ph.D candidates in University(Grant No.2013531413002).
文摘In this article,computational fluid dynamics(CFD)are used to explore the dynamics of water transport inside the pitted thickening of a plant xylem vessel.A pitted thickening model combined with the Bernoulli equation is used to analyze the influence of various factors(namely,the inner diameter,thickening width,thickening height,thickening spacing,number of laps and adjacent pit axial rotation).The pressure drop and the flow resistance coefficient are the variable parameters for our analysis.The results show that these two parameters are proportional to the thickening height and thickening width,and inversely proportional to the inner diameter,thickening spacing and number of laps.Three different wall thickening structures of the vessel are compared and the pitted thickening vessel is shown to provide the largest structural flow resistance,the annular thickening vessel has the second largest resistance and the helical thickening vessel corresponds to the smallest resistance of the three structures.
基金Foundation item： Supported by the National Natural Science Foundation of China （Nos.51309040, 51379033, 51209027, 51309025）, Open Research Fund of State Key Laboratory of Ocean Engineering （Shanghai Jiao Tong University） （Grant No.1402）, and Fundamental Research Fund for the Central Universities （DMU3132015089）.
文摘In this paper, a numerical study of flow in the turbulence boundary layer with adverse and pressure gradients （APGs） is conducted by using Reynolds-averaged Navier-Stokes （RANS） equations. This research chooses six typical turbulence models, which are critical to the computing precision, and to evaluating the issue of APGs. Local frictional resistance coefficient is compared between numerical and experimental results. The same comparisons of dimensionless averaged velocity profiles are also performed. It is found that results generated by Wilcox （2006） k-co are most close to the experimental data. Meanwhile, turbulent quantities such as turbulent kinetic energy and Reynolds-stress are also studied.
文摘Water permeability is an important property of nonwoven geotextiles used in drainage field, and usually it is obtained by testing individual layer or multi-layered nonwoven geotextiles. However, the permeability coefficient tested by using different layers would be different for the same nonwoven geotextile. In this paper, the relation between them is studied based on Darcy's law. The study shows that vertical permeability coefficients are theoretically invariable no matter how many layers are tested; but experimental results show that vertical permeability coefficients decrease with the increase of nonwoven geotextile layers number.
文摘In this paper, the feasibility study of chemical flooding is carried out for ultra-high porosity and high permeability heavy oil field with permeability higher than 10 μm<sup>2</sup> and porosity greater than 35%. The viscosity-concentration relationship of four kinds of oil flooding systems such as hydrolyzed polyacrylamide, structural polymer A, structural polymer B and gel was studied. The results showed that the viscosity of ordinary polymer and structural polymer B was lower compared with other two types of oil displacement agents, and the viscosity of structural polymer A was higher. The higher the concentration, the higher the viscosity retention rate. The gel system has the highest viscosity and best anti-shear ability. The resistance coefficient and residual resistance coefficient of structural polymer A and gel system were further studied. The results show that permeability, velocity and polymer concentration all affect the resistance coefficient and residual resistance coefficient. From the point of view of resistance establishment ability, it is considered that structural polymer A is not suitable for permeability formation above 10 μm<sup>2</sup>. Gel system has stronger ability to establish resistance coefficient than structural polymer A flooding system, and it is more feasible for formation system with permeability above 10 μm<sup>2</sup>.
