Nathaniel Hawthorne not only strongly condemns the belief that men are more evil than good, but also conveys the inclination towards good through the Scarlet Letter. The characters like Hester Prynne, Dimmesdale, ...Nathaniel Hawthorne not only strongly condemns the belief that men are more evil than good, but also conveys the inclination towards good through the Scarlet Letter. The characters like Hester Prynne, Dimmesdale, Chillingworth and even the community are the specific examples. Despite the fact that good and evil coexist in human nature, human beings are liable to be strongly affected and controlled by the striving towards good.展开更多
Rock bolts are widely used in rock engineering projects to improve the shear capacity of the jointed rock mass.The bolt inclination angle with respect to the shear plane has a remarkable influence on the bolting perfo...Rock bolts are widely used in rock engineering projects to improve the shear capacity of the jointed rock mass.The bolt inclination angle with respect to the shear plane has a remarkable influence on the bolting performance.In this study,a new artificial molding method based on 3D scanning and printing technology was first proposed to prepare bolted joints with an inclined bolt.Then,the effects of the bolt inclination angle and boundary conditions on the shear behavior and failure characteristic of bolted joints were addressed by conducting direct shear tests under both CNL and CNS conditions.Results indicated that rock bolt could significantly improve the shear behavior of rock joints,especially in the post-yield deformation region.With the increase of bolt inclination angle,both the maximum shear stress and the maximum friction coefficient increased first and then decreased,while the maximum normal displacement decreased monotonously.Compared with CNL conditions,the maximum shear stress was larger,whereas the maximum normal displacement and friction coefficient were smaller under the CNS conditions.Furthermore,more asperity damage was observed under the CNS conditions due to the increased normal stress on the shear plane.展开更多
External return mechanism is a mechanical structure applied to axial piston pumps.To study its lubrication characteristics,the Reynolds equation applied to an external return spherical hinge pair was deduced based on ...External return mechanism is a mechanical structure applied to axial piston pumps.To study its lubrication characteristics,the Reynolds equation applied to an external return spherical hinge pair was deduced based on the vector equation of relative-motion velocity of the external return spherical hinge pair under the influence of external swash plate inclination and offset distance.The results show that the total friction,axial leakage flow,and maximum value of the maximum oil-film pressure increase with increasing pump-shaft speed and decrease with increasing offset distance in one working cycle when the external-swash-plate inclination is constant.However,the varying offset distance has little effect on the axial leakage flow.The maximum value of the maximum oil-film pressure decreases with increasing external-swash-plate inclination and the total leakage flow increases with increasing external-swash-plate inclination in one working cycle when the offset distance is constant.It can be seen that the abovementioned parameters are important factors that affect the lubrication characteristics of external return spherical hinge pairs.Therefore,the complex effects of different coupling parameters should be comprehensively considered in the design of the external return mechanism.展开更多
In this research,one hundred and ten samples（ten sampling localities）were drilled by a portable petrol-driven drill in the Tongtianhe area along the highway where developes Yaxicuo Group,Oligocene. Complete demagnet...In this research,one hundred and ten samples（ten sampling localities）were drilled by a portable petrol-driven drill in the Tongtianhe area along the highway where developes Yaxicuo Group,Oligocene. Complete demagnetization were finished in University of California,Santa Cruz（UCSC）.These remanence data were collected:Dg=334.2,Ig=52.3,α<sub>95</sub>=7.1,k=7.3（before structural correction）;Ds=27.2, Is=66.6,α<sub>95</sub>=7.3,k=7.0（after structural correction）.展开更多
Because of actual requirement,shield machine always excavates with an inclined angle in longitudinal direction.Since many previous studies mainly focus on the face stability of the horizontal shield tunnel,the effects...Because of actual requirement,shield machine always excavates with an inclined angle in longitudinal direction.Since many previous studies mainly focus on the face stability of the horizontal shield tunnel,the effects of tensile strength cut-off and pore water pressure on the face stability of the longitudinally inclined shield tunnel are not well investigated.A failure mechanism of a longitudinally inclined shield tunnel face is constructed based on the spatial discretization technique and the tensile strength cut-off criterion is introduced to modify the constructed failure mechanism.The pore water pressure is introduced as an external force into the equation of virtual work and the objective function of the chamber pressure of the shield machine is obtained.Moreover,the critical chamber pressure of the longitudinally inclined shield tunnel is computed by optimal calculation.Parametric analysis indicates that both tensile strength cut-off and pore water pressure have a significant impact on the chamber pressure and the range of the collapse block.Finally,the theoretical results are compared with the numerical results calculated by FLAC3D software which proves that the proposed approach is effective.展开更多
A stability analysis approach of tunnel face considering a longitudinally inclined tunnel angle and anisotropic purely cohesive soils based on a continuous velocity field (CVF) is investigated in this study. Based on ...A stability analysis approach of tunnel face considering a longitudinally inclined tunnel angle and anisotropic purely cohesive soils based on a continuous velocity field (CVF) is investigated in this study. Based on the kinematic approach of limit analysis and the discretization technique, an improved three-dimensional CVF model for longitudinally inclined tunnels driven by pressurized shields is proposed. With the proposed model, the critical support pressure acted on tunnel face is determined by the work-balance equation. A serial of finite element numerical models are conducted to validate the proposed model. Finally, the effects of tunnel inclination angles, several dimensionless parameters as well as soil anisotropy on the critical support pressure are investigated. The numerical results show that the effects of the soil anisotropy and the tunnel inclination angle on tunnel faces should be considered in the actual design of tunneling engineering.展开更多
For laser assisted machining,shape of preheating laser heat source is changed irregularly because of complexity of material shape.So,the preheating temperature should be controlled by adjusting the feed rate or the la...For laser assisted machining,shape of preheating laser heat source is changed irregularly because of complexity of material shape.So,the preheating temperature should be controlled by adjusting the feed rate or the laser power.Thermal analyses of the laser assisted machining process for inclination planes were performed.By analyzing the obtained temperature profile,a proper feed rate control method was proposed according to the inclination angles.In addition,the temperature distribution of the cross section after feed rate control was predicted.The correlation equation between inclination angles and adjusted proper feed rate was proposed.The results of this analysis can be used to predict the preheating effect on workpiece and can be applied as a preheating temperature control method in laser assisted machining processes.展开更多
Current distribution in a drained aluminum reduction cell is critical due to its influence on the current efficiency, electrolysis stability, anodes and cathodes integrity. A finite element model was developed to simu...Current distribution in a drained aluminum reduction cell is critical due to its influence on the current efficiency, electrolysis stability, anodes and cathodes integrity. A finite element model was developed to simulate the electric field in a 75 kA drained aluminum reduction cell. The current distribution and influences of the cathode inclination angle and anode-cathode distance (ACD) were studied. The results show that relatively large horizontal current density appears in the aluminum film, and the maximum value reaches 600 kA/m2. As the cathode inclination angle increases from 2° to 15°, the maximum current density of the metal pad increases by 15%, while the maximum current density of the aluminum-wettable coating layer decreases by 27%. The influence of the ACD on the current distribution is not obvious.展开更多
Flame is prone to lose its stability in micro-combustors due to the large amount of heat loss from the external walls. On the other hand, heat recirculation through the upstream combustor walls can enhance flame stabi...Flame is prone to lose its stability in micro-combustors due to the large amount of heat loss from the external walls. On the other hand, heat recirculation through the upstream combustor walls can enhance flame stability. These two aspects depend on the structural heat transfer, which is associated with the thickness and thermal conductivity of the combustor walls. In the present study, the effects of wall thickness and material on flame stability were numerically investigated by selecting two thicknesses (δ=0.2 and 0.4 mm) and two materials (quartz and SiC). The results show that when δ=0.2 mm, flame inclination occurs at a certain inlet velocity in both combustors, but it happens later in SiC combustor. For δ=0.4 mm, flame inclination still occurs in quartz combustor from a larger inlet velocity compared to the case of δ=0.2 mm. However, flame inclination in SiC combustor with δ=0.4 mm does not happen and it has a much larger blowout limit. Analysis reveals that a thicker wall can enhance heat recirculation and reduce heat loss simultaneously. Moreover, SiC combustor has larger heat recirculation ratio and smaller heat loss ratio. In summary, the micro-combustor with thicker and more conductive walls can harvest large flame stability limit.展开更多
In the manufacturing process, we often encounter so me location machining of space arbitrary straight lines and planes that are not on ly unparalleled but also not vertical with the machine tool spindle or the cutti n...In the manufacturing process, we often encounter so me location machining of space arbitrary straight lines and planes that are not on ly unparalleled but also not vertical with the machine tool spindle or the cutti ng tool. In the past, we can do the location machining through the methods of dr awing line and making level in the ordinary machine tool. In the numerical contr ol machining of the CNC machine tool and manufacturing center, however, the spac e location and angle of the arbitrary straight lines and planes must be precisel y calculated in advance. So that precisely locating can be guaranteed in machini ng. Therefore, how to work out the space location angle of the arbitrary straigh t lines and planes to be machined both conveniently and precisely, turns out to be the must-be-solved chief problem in the numerical control machining. In thi s paper, through the deeply research of this problem, a new kind of calculating formula that calculates and defines the space location angle of the arbitrary st raight lines and planes by using the methods of analytic calculating. The formul a has been applied in the practical manufacturing calculation. It is proved that the new space angle calculating methods of arbitrary straight lines and planes is convenient in calculating and precise in locating. And it provides us a n ew, brief and precise calculating method in the numerical control machining of t he numerical control machine tool and manufacturing center.展开更多
英语中有不少包含two和second的习惯用语。本文在参考多部词典及有关资料的基础上,对此作一归纳。1.put two and two together根据事实推理,综合起来判断。例如:He is inclined to put two and two togetherand make five.他爱捕风捉影...英语中有不少包含two和second的习惯用语。本文在参考多部词典及有关资料的基础上,对此作一归纳。1.put two and two together根据事实推理,综合起来判断。例如:He is inclined to put two and two togetherand make five.他爱捕风捉影,听风就是雨。展开更多
The bridge piles located in high-steep slopes not only endure the loads from superstructure, but also the residual sliding force as well as the resistance from the slope. By introducing the Winkler foundation theory, ...The bridge piles located in high-steep slopes not only endure the loads from superstructure, but also the residual sliding force as well as the resistance from the slope. By introducing the Winkler foundation theory, the mechanical model of piles-soils-slopes system was established, and the equilibrium differential equations of pile were derived. Moreover, an analytic solution for identifying the model parameters was provided by means of power series method. A project with field measurement was compared with the proposed method. It is indicated that the lateral loads have great influences on the pile, the steep slope effect is indispensable, and reasonable diameter of the pile could enhance the bending ability. The internal force and displacements of pile are largely based upon the horizontal loads applied on pile, especially in upper part.展开更多
The main objective of this work is to investigate analytically the steady nanofluid flow and heat transfer characteristics between nonparallel plane walls. Using appropriate transformations for the velocity and temper...The main objective of this work is to investigate analytically the steady nanofluid flow and heat transfer characteristics between nonparallel plane walls. Using appropriate transformations for the velocity and temperature, the basic nonlinear partial differential equations are reduced to the ordinary differential equations. Then, these equations have been solved analytically and numerically for some values of the governing parameters, Reynolds number, Re, channel half angle, α, Prandtl number, Pr, and Eckert number, Ec, using Adomian decomposition method and the Runge-Kutta method with mathematic package. Analytical and numerical results are searched for the skin friction coefficient, Nusselt number and the velocity and temperature profiles. It is found on one hand that the Nusselt number increases as Eckert number or channel half-angle increases, but it decreases as Reynolds number increases. On the other hand, it is also found that the presence of Cu nanoparticles in a water base fluid enhances heat transfer between nonparallel plane walls and in consequence the Nusselt number increases with the increase of nanoparticles volume fraction. Finally, an excellent agreement between analytical results and those obtained by numerical Runge-Kutta method is highly noticed.展开更多
Based on the functional theory, catastrophe theory, simultaneity principle and the idea of strength reduction method （SRM）, the bearing capacity functional anti SRM of pile group foundation were established, and the...Based on the functional theory, catastrophe theory, simultaneity principle and the idea of strength reduction method （SRM）, the bearing capacity functional anti SRM of pile group foundation were established, and the criteria of ultimate load and the concept of safety storage coefficient （Css） were advanced. The inclined ultimate loads by the static loading test, load increment method （LIM） and SRM are compared. Theoretically, the ultimate load of piles does not change with the loading levels when it is calculated by SRM. When the one strength reduction parameter is applied in the calculation boundary, there are calculating errors because the bearing capacity action of soils happened in the finite zone. The inclined 10adings are 108, 132 and 144 kN, and SSC are 1.07, 0.94 and 0.79, respectively, so the calculation values of ultimate loads are about 115.56, 124.08 and 113.76 kN, respectively. The error between calculations and observation values is less than 6%. But .the error between calculations of LIM and observations is 20%. Because of the effect of inclined loading, the push-rotation phenomenon of screw pile group appears. Under this testing, the ultimate bearing capacity of piles is mostly determined by the horizontal ultimate bearing capacity, and the effect of the vertical component of inclined load should also be considered.展开更多
In this work,the reflux classifier with closely spaced inclined channels is used as the pre-concentration facility to improve the separation efficiency before the shaking table separation.Three operating parameters of...In this work,the reflux classifier with closely spaced inclined channels is used as the pre-concentration facility to improve the separation efficiency before the shaking table separation.Three operating parameters of reflux classifier(RC)to pre-concentrate fine(0.023−0.15 mm)tailings of antimony oxide were optimized by response surface methodology(RSM)using a three-level Box-Behnken design(BBD).The parameters studied for the optimization were feeding speed,underflow,and ascending water speed.Second-order response functions were produced for the Sb grade and recovery rate of the concentrate.Taking advantage of the quadratic programming,when the factors of feeding,underflow and ascending water are respectively 225,30 and 133 cm^3/min,a better result can be achieved for the concentrate grade of 2.31% and recovery rate of 83.17%.At the same time,70.48% of the tailings with the grade of 0.20% were discarded out of the feeding.The results indicated that the reflux classifier has a good performance in dealing with fine tailings of antimony oxide.Moreover,second-order polynomial equations,ANOVA,and three-dimensional surface plots were developed to evaluate the effects of each parameter on Sb grade and recovery rate of the concentrate.展开更多
The intention of this investigation is to study the effects of heat transfer and inclined magnetic field on the peristaltic flow of Williamson fluid in an asymmetric channel through porous medium. The governing two-di...The intention of this investigation is to study the effects of heat transfer and inclined magnetic field on the peristaltic flow of Williamson fluid in an asymmetric channel through porous medium. The governing two-dimensional equations are simplified under the assumption of long wavelength approximation. The simplified equations are solved for the stream function, temperature, and axial pressure gradient by using a regular perturbation method. The expression for pressure rise is computed numerically. The profiles of velocity, pressure gradient, temperature, heat transfer coefficient and stream function are sketched and interpreted for various embedded parameters and also the behavior of stream function for various wave forms is discussed through graphs. It is observed that the peristaltic velocity increases from porous medium to non-porous medium, the magnetic effects have increasing effect on the temperature, and the size of the trapped bolus decreases with the increasing of magnetic effects while the trend is reversed with the increasing of Darcy number. Moreover, limiting solutions of our problem are in close agreement with the corresponding results of the Newtonian fluid model.展开更多
The fluid flow characteristics of the single bunch inclined jet impingement were investigated with different jet flow velocities,nozzle diameters,jet angles and jet-to-target distances for ultra-fast cooling technolog...The fluid flow characteristics of the single bunch inclined jet impingement were investigated with different jet flow velocities,nozzle diameters,jet angles and jet-to-target distances for ultra-fast cooling technology.The results show that the peak pressure varying significantly from nearly 0.5 to above 13.4 kPa locates at the stagnation point with different jet diameters,and the radius of impact pressure affected zone is small promoted from 46 to 81 mm in transverse direction,and 50 to 91 mm in longitude direction when the jet flow velocity changes from 5 to 20 m/s.However,the fluid flow velocity is relatively smaller near the stagnation point,and increases gradually along the radius outwards,then declines.There is an obvious anisotropic characteristic that the flow velocity component along the jet direction is about twice of the contrary one where the jet anlge is 60°,jet diameter is 5 mm,jet length is 8 mm and jet height is 50 mm.展开更多
This investigation numerically examined the combined impacts of different turbulator shapes,Al_(2)O_(3)/water nanofluid,and inclined magnetic field on the thermal behavior of micro-scale inclined forward-facing step(M...This investigation numerically examined the combined impacts of different turbulator shapes,Al_(2)O_(3)/water nanofluid,and inclined magnetic field on the thermal behavior of micro-scale inclined forward-facing step(MSIFFS).The length and height for all turbulators were considered 0.0979 and 0.5 mm,respectively,and the Reynolds number varied from 5000 to 10000.In order to compare the skin friction coefficient(SFC) and the heat transfer rate(HTR)simultaneously,the thermal performance factor parameter(TPF) was selected.The results show that all considered cases equipped with turbulators were thermodynamically more advantageous over the simple MSIFFS.Besides,using Al_(2)O_(3)/water nanofluid with different nanoparticles volume fractions(NVF) in the presence of inclined magnetic field(IMF)increased HTR.With an increment of NVF from 1% to 4% and magnetic field density(MFD) from 0.002 to 0.008 T,HTR and subsequently TPF improved.The best result was observed for MSIFFS equipped with a trapezoidal-shaped turbulator with 4% Al_(2)O_(3) in the presence of IMF(B=0.008 T).The TPF increased with the augmentation of Re,and the maximum value of it was 5.2366 for MSIFFS equipped with a trapezoidal-shaped turbulator with 4% Al_(2)O_(3),B=0.008 T,and Re=10000.展开更多
The couple effect of soil displacement and axial load on the single inclined pile in cases of surcharge load and uniform soil movement is discussed in detail with the methods of full-scale field tests and finite eleme...The couple effect of soil displacement and axial load on the single inclined pile in cases of surcharge load and uniform soil movement is discussed in detail with the methods of full-scale field tests and finite element method. Parametric analyses including the degree of inclination and the distance between soil and pile are carried out herein. When the displacement of soil on the left side and right side of a pile is identical, deformation of a vertical pile and an inclined pile is highly close in both cases of surcharge load and uniform soil movement. When the couple effect of soil displacement and axial load occurs, settlement of an inclined pile is greater than that of a vertical pile under the same axial load, and bearing capacity of an inclined pile is smaller than that of a vertical pile. This is quite different from the case when the inclined pile is not affected by soil displacement. For inclined piles, P-Δ effect of axial load would lead to a large increase in bending moment, however, for the vertical pile, P-Δ effect of axial load can be neglected. Although the direction of inclination of piles is reverse, deformation of piles caused by uniform soil movement is totally the same. For the inclined piles discussed herein, bending moment(-8 m to-17 m under the ground) relies heavily on uniform soil movement and does not change during the process of applying axial load. When the thickness of soil is less than the pile length, the greater the thickness of soil, the larger the bending moment at lower part of the inclined pile. When the thickness of soil is larger than the pile length, bending moment at lower part of the inclined pile is zero.展开更多
Time domain dynamic analysis of inclined dam-reservoir-foundation interaction was conducted using finite difference method （FDM）. The Timoshenko beam theory and the Euler-Bemoulli beam theory were implemented to dra...Time domain dynamic analysis of inclined dam-reservoir-foundation interaction was conducted using finite difference method （FDM）. The Timoshenko beam theory and the Euler-Bemoulli beam theory were implemented to draw out governing equation of beam. The interactions between the dam and the soil were modeled by using a translational spring and a rotational spring. A Sommerfeld＇s radiation condition at the infinity boundary of the fluid domain was adopted. The effects of the reservoir bottom absorption and surface waves on the dam-reservoir-foundation interaction due to the earthquake were studied. To avoid the instability of solution, a semi-implicit scheme was used for the discretization of the governing equation of dam and an explicit scheme was used for the discretization of the governing equation of fluid. The results show that as the slope of upstream dam increases, the hydrodynamic pressure on the dam is reduced. Moreover, when the Timoshenko beam theory is used, the system response increases.展开更多
文摘Nathaniel Hawthorne not only strongly condemns the belief that men are more evil than good, but also conveys the inclination towards good through the Scarlet Letter. The characters like Hester Prynne, Dimmesdale, Chillingworth and even the community are the specific examples. Despite the fact that good and evil coexist in human nature, human beings are liable to be strongly affected and controlled by the striving towards good.
基金Project(U1865203)supported by the Key Projects of the Yalong River Joint Fund of the National Natural Science Foundation of ChinaProject(51279201)supported by the National Natural Science Foundation of ChinaProjects(2019YFC0605103,2019YFC0605100)supported by the National Key R&D Program of China。
文摘Rock bolts are widely used in rock engineering projects to improve the shear capacity of the jointed rock mass.The bolt inclination angle with respect to the shear plane has a remarkable influence on the bolting performance.In this study,a new artificial molding method based on 3D scanning and printing technology was first proposed to prepare bolted joints with an inclined bolt.Then,the effects of the bolt inclination angle and boundary conditions on the shear behavior and failure characteristic of bolted joints were addressed by conducting direct shear tests under both CNL and CNS conditions.Results indicated that rock bolt could significantly improve the shear behavior of rock joints,especially in the post-yield deformation region.With the increase of bolt inclination angle,both the maximum shear stress and the maximum friction coefficient increased first and then decreased,while the maximum normal displacement decreased monotonously.Compared with CNL conditions,the maximum shear stress was larger,whereas the maximum normal displacement and friction coefficient were smaller under the CNS conditions.Furthermore,more asperity damage was observed under the CNS conditions due to the increased normal stress on the shear plane.
基金Project(GXXT-2019-048)supported by the University Synergy Innovation Program of Anhui Province,ChinaProject(51575002)supported by the National Natural Science Foundation of ChinaProject(gxbj ZD11)supported by the Top-Notch Talent Program of University(Profession)in Anhui Province,China。
文摘External return mechanism is a mechanical structure applied to axial piston pumps.To study its lubrication characteristics,the Reynolds equation applied to an external return spherical hinge pair was deduced based on the vector equation of relative-motion velocity of the external return spherical hinge pair under the influence of external swash plate inclination and offset distance.The results show that the total friction,axial leakage flow,and maximum value of the maximum oil-film pressure increase with increasing pump-shaft speed and decrease with increasing offset distance in one working cycle when the external-swash-plate inclination is constant.However,the varying offset distance has little effect on the axial leakage flow.The maximum value of the maximum oil-film pressure decreases with increasing external-swash-plate inclination and the total leakage flow increases with increasing external-swash-plate inclination in one working cycle when the offset distance is constant.It can be seen that the abovementioned parameters are important factors that affect the lubrication characteristics of external return spherical hinge pairs.Therefore,the complex effects of different coupling parameters should be comprehensively considered in the design of the external return mechanism.
文摘In this research,one hundred and ten samples（ten sampling localities）were drilled by a portable petrol-driven drill in the Tongtianhe area along the highway where developes Yaxicuo Group,Oligocene. Complete demagnetization were finished in University of California,Santa Cruz（UCSC）.These remanence data were collected:Dg=334.2,Ig=52.3,α<sub>95</sub>=7.1,k=7.3（before structural correction）;Ds=27.2, Is=66.6,α<sub>95</sub>=7.3,k=7.0（after structural correction）.
基金Projects(52278395,52208409) supported by the National Natural Science Foundation of ChinaProject(2022JJ40531) supported by the Natural Science Foundation of Hunan Province,China。
文摘Because of actual requirement,shield machine always excavates with an inclined angle in longitudinal direction.Since many previous studies mainly focus on the face stability of the horizontal shield tunnel,the effects of tensile strength cut-off and pore water pressure on the face stability of the longitudinally inclined shield tunnel are not well investigated.A failure mechanism of a longitudinally inclined shield tunnel face is constructed based on the spatial discretization technique and the tensile strength cut-off criterion is introduced to modify the constructed failure mechanism.The pore water pressure is introduced as an external force into the equation of virtual work and the objective function of the chamber pressure of the shield machine is obtained.Moreover,the critical chamber pressure of the longitudinally inclined shield tunnel is computed by optimal calculation.Parametric analysis indicates that both tensile strength cut-off and pore water pressure have a significant impact on the chamber pressure and the range of the collapse block.Finally,the theoretical results are compared with the numerical results calculated by FLAC3D software which proves that the proposed approach is effective.
基金Project(2017YFB1201204)supported by the National Key Research and Development Program of China
文摘A stability analysis approach of tunnel face considering a longitudinally inclined tunnel angle and anisotropic purely cohesive soils based on a continuous velocity field (CVF) is investigated in this study. Based on the kinematic approach of limit analysis and the discretization technique, an improved three-dimensional CVF model for longitudinally inclined tunnels driven by pressurized shields is proposed. With the proposed model, the critical support pressure acted on tunnel face is determined by the work-balance equation. A serial of finite element numerical models are conducted to validate the proposed model. Finally, the effects of tunnel inclination angles, several dimensionless parameters as well as soil anisotropy on the critical support pressure are investigated. The numerical results show that the effects of the soil anisotropy and the tunnel inclination angle on tunnel faces should be considered in the actual design of tunneling engineering.
基金Project(2011-0017407)supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MEST)
文摘For laser assisted machining,shape of preheating laser heat source is changed irregularly because of complexity of material shape.So,the preheating temperature should be controlled by adjusting the feed rate or the laser power.Thermal analyses of the laser assisted machining process for inclination planes were performed.By analyzing the obtained temperature profile,a proper feed rate control method was proposed according to the inclination angles.In addition,the temperature distribution of the cross section after feed rate control was predicted.The correlation equation between inclination angles and adjusted proper feed rate was proposed.The results of this analysis can be used to predict the preheating effect on workpiece and can be applied as a preheating temperature control method in laser assisted machining processes.
基金Project(2005CB623703) supported by the National Basic Research Program of China
文摘Current distribution in a drained aluminum reduction cell is critical due to its influence on the current efficiency, electrolysis stability, anodes and cathodes integrity. A finite element model was developed to simulate the electric field in a 75 kA drained aluminum reduction cell. The current distribution and influences of the cathode inclination angle and anode-cathode distance (ACD) were studied. The results show that relatively large horizontal current density appears in the aluminum film, and the maximum value reaches 600 kA/m2. As the cathode inclination angle increases from 2° to 15°, the maximum current density of the metal pad increases by 15%, while the maximum current density of the aluminum-wettable coating layer decreases by 27%. The influence of the ACD on the current distribution is not obvious.
基金Project(51576084) supported by the National Natural Science Foundation of China
文摘Flame is prone to lose its stability in micro-combustors due to the large amount of heat loss from the external walls. On the other hand, heat recirculation through the upstream combustor walls can enhance flame stability. These two aspects depend on the structural heat transfer, which is associated with the thickness and thermal conductivity of the combustor walls. In the present study, the effects of wall thickness and material on flame stability were numerically investigated by selecting two thicknesses (δ=0.2 and 0.4 mm) and two materials (quartz and SiC). The results show that when δ=0.2 mm, flame inclination occurs at a certain inlet velocity in both combustors, but it happens later in SiC combustor. For δ=0.4 mm, flame inclination still occurs in quartz combustor from a larger inlet velocity compared to the case of δ=0.2 mm. However, flame inclination in SiC combustor with δ=0.4 mm does not happen and it has a much larger blowout limit. Analysis reveals that a thicker wall can enhance heat recirculation and reduce heat loss simultaneously. Moreover, SiC combustor has larger heat recirculation ratio and smaller heat loss ratio. In summary, the micro-combustor with thicker and more conductive walls can harvest large flame stability limit.
文摘In the manufacturing process, we often encounter so me location machining of space arbitrary straight lines and planes that are not on ly unparalleled but also not vertical with the machine tool spindle or the cutti ng tool. In the past, we can do the location machining through the methods of dr awing line and making level in the ordinary machine tool. In the numerical contr ol machining of the CNC machine tool and manufacturing center, however, the spac e location and angle of the arbitrary straight lines and planes must be precisel y calculated in advance. So that precisely locating can be guaranteed in machini ng. Therefore, how to work out the space location angle of the arbitrary straigh t lines and planes to be machined both conveniently and precisely, turns out to be the must-be-solved chief problem in the numerical control machining. In thi s paper, through the deeply research of this problem, a new kind of calculating formula that calculates and defines the space location angle of the arbitrary st raight lines and planes by using the methods of analytic calculating. The formul a has been applied in the practical manufacturing calculation. It is proved that the new space angle calculating methods of arbitrary straight lines and planes is convenient in calculating and precise in locating. And it provides us a n ew, brief and precise calculating method in the numerical control machining of t he numerical control machine tool and manufacturing center.
文摘英语中有不少包含two和second的习惯用语。本文在参考多部词典及有关资料的基础上,对此作一归纳。1.put two and two together根据事实推理,综合起来判断。例如:He is inclined to put two and two togetherand make five.他爱捕风捉影,听风就是雨。
基金Project(51408066)supported by the National Natural Science Foundation of China
文摘The bridge piles located in high-steep slopes not only endure the loads from superstructure, but also the residual sliding force as well as the resistance from the slope. By introducing the Winkler foundation theory, the mechanical model of piles-soils-slopes system was established, and the equilibrium differential equations of pile were derived. Moreover, an analytic solution for identifying the model parameters was provided by means of power series method. A project with field measurement was compared with the proposed method. It is indicated that the lateral loads have great influences on the pile, the steep slope effect is indispensable, and reasonable diameter of the pile could enhance the bending ability. The internal force and displacements of pile are largely based upon the horizontal loads applied on pile, especially in upper part.
文摘The main objective of this work is to investigate analytically the steady nanofluid flow and heat transfer characteristics between nonparallel plane walls. Using appropriate transformations for the velocity and temperature, the basic nonlinear partial differential equations are reduced to the ordinary differential equations. Then, these equations have been solved analytically and numerically for some values of the governing parameters, Reynolds number, Re, channel half angle, α, Prandtl number, Pr, and Eckert number, Ec, using Adomian decomposition method and the Runge-Kutta method with mathematic package. Analytical and numerical results are searched for the skin friction coefficient, Nusselt number and the velocity and temperature profiles. It is found on one hand that the Nusselt number increases as Eckert number or channel half-angle increases, but it decreases as Reynolds number increases. On the other hand, it is also found that the presence of Cu nanoparticles in a water base fluid enhances heat transfer between nonparallel plane walls and in consequence the Nusselt number increases with the increase of nanoparticles volume fraction. Finally, an excellent agreement between analytical results and those obtained by numerical Runge-Kutta method is highly noticed.
基金Project(51178457) supported by the National Natural Science Foundation of ChinaProject(cstc2012jjys0001) supported by the Natural Science Foundation of Chongqing,ChinaProject(L2011231) supported by the Liaoning Education Department,China
文摘Based on the functional theory, catastrophe theory, simultaneity principle and the idea of strength reduction method （SRM）, the bearing capacity functional anti SRM of pile group foundation were established, and the criteria of ultimate load and the concept of safety storage coefficient （Css） were advanced. The inclined ultimate loads by the static loading test, load increment method （LIM） and SRM are compared. Theoretically, the ultimate load of piles does not change with the loading levels when it is calculated by SRM. When the one strength reduction parameter is applied in the calculation boundary, there are calculating errors because the bearing capacity action of soils happened in the finite zone. The inclined 10adings are 108, 132 and 144 kN, and SSC are 1.07, 0.94 and 0.79, respectively, so the calculation values of ultimate loads are about 115.56, 124.08 and 113.76 kN, respectively. The error between calculations and observation values is less than 6%. But .the error between calculations of LIM and observations is 20%. Because of the effect of inclined loading, the push-rotation phenomenon of screw pile group appears. Under this testing, the ultimate bearing capacity of piles is mostly determined by the horizontal ultimate bearing capacity, and the effect of the vertical component of inclined load should also be considered.
基金Project(2015SK20792)supported by Key Province Key Technology Research and Development Program of the Ministry of Science and Technology of Hunan,ChinaProjects(2019zzts703,2020zzts740,2020zzts202)supported by the Fundamental Research Funds for the Central Universities of ChinaProject(2020P4FZG03A)supported by State Key Laboratory of Vanadium and Titanium Resources Comprehensive Utilization,China。
文摘In this work,the reflux classifier with closely spaced inclined channels is used as the pre-concentration facility to improve the separation efficiency before the shaking table separation.Three operating parameters of reflux classifier(RC)to pre-concentrate fine(0.023−0.15 mm)tailings of antimony oxide were optimized by response surface methodology(RSM)using a three-level Box-Behnken design(BBD).The parameters studied for the optimization were feeding speed,underflow,and ascending water speed.Second-order response functions were produced for the Sb grade and recovery rate of the concentrate.Taking advantage of the quadratic programming,when the factors of feeding,underflow and ascending water are respectively 225,30 and 133 cm^3/min,a better result can be achieved for the concentrate grade of 2.31% and recovery rate of 83.17%.At the same time,70.48% of the tailings with the grade of 0.20% were discarded out of the feeding.The results indicated that the reflux classifier has a good performance in dealing with fine tailings of antimony oxide.Moreover,second-order polynomial equations,ANOVA,and three-dimensional surface plots were developed to evaluate the effects of each parameter on Sb grade and recovery rate of the concentrate.
文摘The intention of this investigation is to study the effects of heat transfer and inclined magnetic field on the peristaltic flow of Williamson fluid in an asymmetric channel through porous medium. The governing two-dimensional equations are simplified under the assumption of long wavelength approximation. The simplified equations are solved for the stream function, temperature, and axial pressure gradient by using a regular perturbation method. The expression for pressure rise is computed numerically. The profiles of velocity, pressure gradient, temperature, heat transfer coefficient and stream function are sketched and interpreted for various embedded parameters and also the behavior of stream function for various wave forms is discussed through graphs. It is observed that the peristaltic velocity increases from porous medium to non-porous medium, the magnetic effects have increasing effect on the temperature, and the size of the trapped bolus decreases with the increasing of magnetic effects while the trend is reversed with the increasing of Darcy number. Moreover, limiting solutions of our problem are in close agreement with the corresponding results of the Newtonian fluid model.
基金Project(2010CB630800)supported by the National Basic Research Program of ChinaProject(N100307003)supported by the Fundamental Research Funds for the Central Universities,China
文摘The fluid flow characteristics of the single bunch inclined jet impingement were investigated with different jet flow velocities,nozzle diameters,jet angles and jet-to-target distances for ultra-fast cooling technology.The results show that the peak pressure varying significantly from nearly 0.5 to above 13.4 kPa locates at the stagnation point with different jet diameters,and the radius of impact pressure affected zone is small promoted from 46 to 81 mm in transverse direction,and 50 to 91 mm in longitude direction when the jet flow velocity changes from 5 to 20 m/s.However,the fluid flow velocity is relatively smaller near the stagnation point,and increases gradually along the radius outwards,then declines.There is an obvious anisotropic characteristic that the flow velocity component along the jet direction is about twice of the contrary one where the jet anlge is 60°,jet diameter is 5 mm,jet length is 8 mm and jet height is 50 mm.
文摘This investigation numerically examined the combined impacts of different turbulator shapes,Al_(2)O_(3)/water nanofluid,and inclined magnetic field on the thermal behavior of micro-scale inclined forward-facing step(MSIFFS).The length and height for all turbulators were considered 0.0979 and 0.5 mm,respectively,and the Reynolds number varied from 5000 to 10000.In order to compare the skin friction coefficient(SFC) and the heat transfer rate(HTR)simultaneously,the thermal performance factor parameter(TPF) was selected.The results show that all considered cases equipped with turbulators were thermodynamically more advantageous over the simple MSIFFS.Besides,using Al_(2)O_(3)/water nanofluid with different nanoparticles volume fractions(NVF) in the presence of inclined magnetic field(IMF)increased HTR.With an increment of NVF from 1% to 4% and magnetic field density(MFD) from 0.002 to 0.008 T,HTR and subsequently TPF improved.The best result was observed for MSIFFS equipped with a trapezoidal-shaped turbulator with 4% Al_(2)O_(3) in the presence of IMF(B=0.008 T).The TPF increased with the augmentation of Re,and the maximum value of it was 5.2366 for MSIFFS equipped with a trapezoidal-shaped turbulator with 4% Al_(2)O_(3),B=0.008 T,and Re=10000.
基金Project(51208071)supported by the National Natural Science Foundation of ChinaProject(2010CB732106)supported by the National Basic Research Program of China
文摘The couple effect of soil displacement and axial load on the single inclined pile in cases of surcharge load and uniform soil movement is discussed in detail with the methods of full-scale field tests and finite element method. Parametric analyses including the degree of inclination and the distance between soil and pile are carried out herein. When the displacement of soil on the left side and right side of a pile is identical, deformation of a vertical pile and an inclined pile is highly close in both cases of surcharge load and uniform soil movement. When the couple effect of soil displacement and axial load occurs, settlement of an inclined pile is greater than that of a vertical pile under the same axial load, and bearing capacity of an inclined pile is smaller than that of a vertical pile. This is quite different from the case when the inclined pile is not affected by soil displacement. For inclined piles, P-Δ effect of axial load would lead to a large increase in bending moment, however, for the vertical pile, P-Δ effect of axial load can be neglected. Although the direction of inclination of piles is reverse, deformation of piles caused by uniform soil movement is totally the same. For the inclined piles discussed herein, bending moment(-8 m to-17 m under the ground) relies heavily on uniform soil movement and does not change during the process of applying axial load. When the thickness of soil is less than the pile length, the greater the thickness of soil, the larger the bending moment at lower part of the inclined pile. When the thickness of soil is larger than the pile length, bending moment at lower part of the inclined pile is zero.
文摘Time domain dynamic analysis of inclined dam-reservoir-foundation interaction was conducted using finite difference method （FDM）. The Timoshenko beam theory and the Euler-Bemoulli beam theory were implemented to draw out governing equation of beam. The interactions between the dam and the soil were modeled by using a translational spring and a rotational spring. A Sommerfeld＇s radiation condition at the infinity boundary of the fluid domain was adopted. The effects of the reservoir bottom absorption and surface waves on the dam-reservoir-foundation interaction due to the earthquake were studied. To avoid the instability of solution, a semi-implicit scheme was used for the discretization of the governing equation of dam and an explicit scheme was used for the discretization of the governing equation of fluid. The results show that as the slope of upstream dam increases, the hydrodynamic pressure on the dam is reduced. Moreover, when the Timoshenko beam theory is used, the system response increases.
