With the development of activated sludge model, the simulation software for the design and operation of wastewater treatment plant （WWTP） was produced and has been widely used. The dynamic change of the quality and ...With the development of activated sludge model, the simulation software for the design and operation of wastewater treatment plant （WWTP） was produced and has been widely used. The dynamic change of the quality and flow of influent are major factors causing the unstable operation of wastewater treatment process. As a basic model, ASMI model was used for the simulation of activated sludge process, and double exponential model was selected for the simulation of secondary sedimentation tank. The influences of influent change to the aeration tank and secondary sedimentation tank were investigated, and the relationship among influent change, the quality of effluent and the level of sludge blanket in secondary sedimentation tank was established. On the basis of the simulation results, the operation of the WWTP could be adjusted under the dynamic change of the influent. Furthermore, the controlling strategy combined the feed-forward on the influent flow and the feedback on the level of sludge blanket in the secondary sedimentation tank was studied.展开更多
The accuracy of an articulated torque analysis influences the comprehensive performances of heavy-duty multi-legged robots. Currently, the extremal estimation method and some complex methods are employed to calculate ...The accuracy of an articulated torque analysis influences the comprehensive performances of heavy-duty multi-legged robots. Currently, the extremal estimation method and some complex methods are employed to calculate the articulated torques, which results in a large safety margin or a large number of calculations. To quickly obtain accurate articulated torques, an analysis method for the articulated torque is presented for an electrically driven heavy-duty six-legged robot. First, the rearmost leg that experiences the maximum normal contact force is confirmed when the robot transits a slope. Based on the ant-type and crab-type tripod gaits, the formulas of classical mechanics and MATLAB software are employed to theoretically analyze the relevant static torques of the joints. With the changes in the joint angles for the abductor joint, hip joint, and knee joint, variable tendency charts and extreme curves are obtained for the static articulated torques. Meanwhile, the maximum static articulated torques and the corresponding poses of the robot are also obtained. According to the poses of the robot under the maximum static articulated torques, ADAMS software is used to carry out a static simulation analysis. Based on the relevant simulation curves of the articulated torques, the maximum static articulated torques are acquired. A comparative analysis of the maximum static articulated torques shows that the theoretical calculation values are higher than the static simulation values, and the maximum error value is approximately 10%. The proposed method lays a foundation for quickly determining accurate articulated torques to develop heavy-duty six-legged robots.展开更多
A generalized steady-state model is being developed for an internal heat integrated distillation column (IHIDiC). A procedure incorporating the Newton-Raphson method is devised for solving the model equations. Separat...A generalized steady-state model is being developed for an internal heat integrated distillation column (IHIDiC). A procedure incorporating the Newton-Raphson method is devised for solving the model equations. Separation of an ethanol-water binary mixture is simulated and analyzed with the model. Two pinch points are found within the process, making the separation extremely difficult and expensive. Two sharp fronts in the temperature and the composition profiles are being observed. With the introduction of heat integration, satisfactory separation may be obtained in a limited number of stages with lower reflux ratios. Increasing the pressure difference between the rectifying and the stripping sections, however, would bring about a reduced relative volatility between the two components involved, creating adverse separation performances. It is obvious that optimization of the IHIDiC is of prime importance.展开更多
Stress concentration and large displacements are usual problems in the components of the structure of agricultural machinery such harvesters coffee, and that finite element method (FEM) can be a tool to minimize its e...Stress concentration and large displacements are usual problems in the components of the structure of agricultural machinery such harvesters coffee, and that finite element method (FEM) can be a tool to minimize its effects. The goal of this paper is to get results of stresses and displacements of a coffee harvester structure by using FEM for static simulation. The main parts of the coffee harvester analyzed were: engine frame, body right and left sides, front and rear end, main beam, coffee reservoir, wheels and fuel tank. Two different design concepts of a coffee harvester machine were analyzed (structure with rear wheels aligned and misaligned) and the results were compared. It was observed that the model with rear wheels misaligned showed maximum displacement lower than the model with rear wheels aligned. Although higher stress was found in the rear wheels misaligned, it was observed that average stresses for the misaligned wheels design were lower in most structural components analyzed. Based on FEM results, the coffee harvester machine with misaligned rear wheels was built and subjected to operational tests without showing any structural failure.展开更多
Activating non-basal<c+a>slip is a key method to improve room temperature ductility and formability of Mg alloys.However,the detailed criterion for activation of the<c+a>slip in multicomponent Mg alloys,wh...Activating non-basal<c+a>slip is a key method to improve room temperature ductility and formability of Mg alloys.However,the detailed criterion for activation of the<c+a>slip in multicomponent Mg alloys,which can be utilized in commercial Mg alloys,requires further understanding.The present authors investigated the mechanism and criterion using a molecular statics simulation on dislocation behaviors in multicomponent Mg alloys.We found that if multicomponent Mg alloys have an equivalent dislocation binding intensity to associated binary Mg alloys that are optimized to minimize the critical resolved shear stress anisotropy and thus activate the<c+a>slip,then the critical resolved shear stress anisotropy between slip systems of the multicomponent Mg alloys can also be minimized,resulting in activation of the<c+a>slip.The activation is maximized in multicomponent Mg alloys when alloying a large amount of weak dislocation binding elements.It was confirmed through experiments that the multicomponent Mg alloys satisfying the above criterion show higher room-temperature tensile elongation and formability than other alloys.展开更多
In this paper,a semi-analytical method was proposed to evaluate the acoustic nonlinearity parameter for single crystals of Cu,Ag and Au.The acoustic nonlinearity parameter can be derived analytically by general expres...In this paper,a semi-analytical method was proposed to evaluate the acoustic nonlinearity parameter for single crystals of Cu,Ag and Au.The acoustic nonlinearity parameter can be derived analytically by general expressions in terms of the interatomic potentials with the distances between each pair of atoms in these transition metals.To evaluate the acoustic nonlinearity parameter,one needs to conduct one step molecular static simulation and obtain the equilibrium positions of all the atoms.Further,based on this method,numerical experiments with molecular dynamic code LAMMPS were given to compute the acoustic nonlinearity parameter of Cu,Ag and Au.To illustrate the validity of these expressions,comparison was made between calculation results and data in the literature.Reasonable agreement is observed.Because of the analytical nature of this method,it provides a fundamental understanding of the nonlinear elastic behavior of these transition metals.展开更多
Twin formation energy is an intrinsic quantity for bulk crystals.At the nanoscale,the twin formation energy of covalent SiC nanowires goes up with decreasing dimension.In contrast,this article reports that the twin fo...Twin formation energy is an intrinsic quantity for bulk crystals.At the nanoscale,the twin formation energy of covalent SiC nanowires goes up with decreasing dimension.In contrast,this article reports that the twin formation energy of metallic nanowires goes down with decreasing dimension.This result is based on classical molecular statics simulations of four representative metals.Cu and Al represent face-centered cubic(FCC)metals of low and high twin formation energies.Ta represents a body-centered cubic(BCC)metal,and Mg represents a hexagonal close-packed(HCP)metal.For all the four metals,the dependence of twin formation energy on size correlates with lower twin formation energy near surfaces,according to atomic-level analysis.Based on this atomic-level insight,the authors propose a core–shell model that reveals the twin formation energy as inversely proportional to the diameter of nanowires.This dependence is in agreement with the results of molecular statics simulations.展开更多
文摘With the development of activated sludge model, the simulation software for the design and operation of wastewater treatment plant （WWTP） was produced and has been widely used. The dynamic change of the quality and flow of influent are major factors causing the unstable operation of wastewater treatment process. As a basic model, ASMI model was used for the simulation of activated sludge process, and double exponential model was selected for the simulation of secondary sedimentation tank. The influences of influent change to the aeration tank and secondary sedimentation tank were investigated, and the relationship among influent change, the quality of effluent and the level of sludge blanket in secondary sedimentation tank was established. On the basis of the simulation results, the operation of the WWTP could be adjusted under the dynamic change of the influent. Furthermore, the controlling strategy combined the feed-forward on the influent flow and the feedback on the level of sludge blanket in the secondary sedimentation tank was studied.
基金supported by National Basic Research Program of China(973 Program, Grant No. 2013CB035502)International Science and Technology Cooperation Project with Russia (Grant No. 2010DFR70270)+2 种基金National Natural Science Foundation of China (Grant No. 51275106)"111" Project (Grant No. B07018)Key Laboratory Opening Funding of Aerospace Mechanism and Control, China (Grant No. HIT. KLOF.2010057)
文摘The accuracy of an articulated torque analysis influences the comprehensive performances of heavy-duty multi-legged robots. Currently, the extremal estimation method and some complex methods are employed to calculate the articulated torques, which results in a large safety margin or a large number of calculations. To quickly obtain accurate articulated torques, an analysis method for the articulated torque is presented for an electrically driven heavy-duty six-legged robot. First, the rearmost leg that experiences the maximum normal contact force is confirmed when the robot transits a slope. Based on the ant-type and crab-type tripod gaits, the formulas of classical mechanics and MATLAB software are employed to theoretically analyze the relevant static torques of the joints. With the changes in the joint angles for the abductor joint, hip joint, and knee joint, variable tendency charts and extreme curves are obtained for the static articulated torques. Meanwhile, the maximum static articulated torques and the corresponding poses of the robot are also obtained. According to the poses of the robot under the maximum static articulated torques, ADAMS software is used to carry out a static simulation analysis. Based on the relevant simulation curves of the articulated torques, the maximum static articulated torques are acquired. A comparative analysis of the maximum static articulated torques shows that the theoretical calculation values are higher than the static simulation values, and the maximum error value is approximately 10%. The proposed method lays a foundation for quickly determining accurate articulated torques to develop heavy-duty six-legged robots.
文摘A generalized steady-state model is being developed for an internal heat integrated distillation column (IHIDiC). A procedure incorporating the Newton-Raphson method is devised for solving the model equations. Separation of an ethanol-water binary mixture is simulated and analyzed with the model. Two pinch points are found within the process, making the separation extremely difficult and expensive. Two sharp fronts in the temperature and the composition profiles are being observed. With the introduction of heat integration, satisfactory separation may be obtained in a limited number of stages with lower reflux ratios. Increasing the pressure difference between the rectifying and the stripping sections, however, would bring about a reduced relative volatility between the two components involved, creating adverse separation performances. It is obvious that optimization of the IHIDiC is of prime importance.
文摘Stress concentration and large displacements are usual problems in the components of the structure of agricultural machinery such harvesters coffee, and that finite element method (FEM) can be a tool to minimize its effects. The goal of this paper is to get results of stresses and displacements of a coffee harvester structure by using FEM for static simulation. The main parts of the coffee harvester analyzed were: engine frame, body right and left sides, front and rear end, main beam, coffee reservoir, wheels and fuel tank. Two different design concepts of a coffee harvester machine were analyzed (structure with rear wheels aligned and misaligned) and the results were compared. It was observed that the model with rear wheels misaligned showed maximum displacement lower than the model with rear wheels aligned. Although higher stress was found in the rear wheels misaligned, it was observed that average stresses for the misaligned wheels design were lower in most structural components analyzed. Based on FEM results, the coffee harvester machine with misaligned rear wheels was built and subjected to operational tests without showing any structural failure.
基金the Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science&ICT(2016R1A2B4006680).
文摘Activating non-basal<c+a>slip is a key method to improve room temperature ductility and formability of Mg alloys.However,the detailed criterion for activation of the<c+a>slip in multicomponent Mg alloys,which can be utilized in commercial Mg alloys,requires further understanding.The present authors investigated the mechanism and criterion using a molecular statics simulation on dislocation behaviors in multicomponent Mg alloys.We found that if multicomponent Mg alloys have an equivalent dislocation binding intensity to associated binary Mg alloys that are optimized to minimize the critical resolved shear stress anisotropy and thus activate the<c+a>slip,then the critical resolved shear stress anisotropy between slip systems of the multicomponent Mg alloys can also be minimized,resulting in activation of the<c+a>slip.The activation is maximized in multicomponent Mg alloys when alloying a large amount of weak dislocation binding elements.It was confirmed through experiments that the multicomponent Mg alloys satisfying the above criterion show higher room-temperature tensile elongation and formability than other alloys.
基金financially supported by the National Sci-Tech Support Plan(No.2015BAF06B01)。
文摘In this paper,a semi-analytical method was proposed to evaluate the acoustic nonlinearity parameter for single crystals of Cu,Ag and Au.The acoustic nonlinearity parameter can be derived analytically by general expressions in terms of the interatomic potentials with the distances between each pair of atoms in these transition metals.To evaluate the acoustic nonlinearity parameter,one needs to conduct one step molecular static simulation and obtain the equilibrium positions of all the atoms.Further,based on this method,numerical experiments with molecular dynamic code LAMMPS were given to compute the acoustic nonlinearity parameter of Cu,Ag and Au.To illustrate the validity of these expressions,comparison was made between calculation results and data in the literature.Reasonable agreement is observed.Because of the analytical nature of this method,it provides a fundamental understanding of the nonlinear elastic behavior of these transition metals.
基金The authors acknowledge the financial support of Defense Threat Reduction Agency(HDTRA1-09-1-0027)H.H.also acknowledges the financial support of National Science Foundation(DMR0906349 and CMMI-0856426).
文摘Twin formation energy is an intrinsic quantity for bulk crystals.At the nanoscale,the twin formation energy of covalent SiC nanowires goes up with decreasing dimension.In contrast,this article reports that the twin formation energy of metallic nanowires goes down with decreasing dimension.This result is based on classical molecular statics simulations of four representative metals.Cu and Al represent face-centered cubic(FCC)metals of low and high twin formation energies.Ta represents a body-centered cubic(BCC)metal,and Mg represents a hexagonal close-packed(HCP)metal.For all the four metals,the dependence of twin formation energy on size correlates with lower twin formation energy near surfaces,according to atomic-level analysis.Based on this atomic-level insight,the authors propose a core–shell model that reveals the twin formation energy as inversely proportional to the diameter of nanowires.This dependence is in agreement with the results of molecular statics simulations.
