A 1∶2.5 scale tundish model was set up in laboratory for a six-strand billet continuous casting tundish with different configurations to investigate fluid flow characteristics under different operational conditions b...A 1∶2.5 scale tundish model was set up in laboratory for a six-strand billet continuous casting tundish with different configurations to investigate fluid flow characteristics under different operational conditions by measuring residence time distribution curves.It was found that minimum residence time,maximum concentration time and average residence time of the three strands on the same side of the tundish with the former configuration under normal operation,that is,six strands were open,were small and non-uniform and the tundish had large dead volume fraction.Vortexes easily formed on the liquid surface in the pouring zone of the tundish.The fluid flow characteristics in the tundish with the optimal turbulence inhibitor and baffles were improved and became less non-uniform among the strands.Vortexes were not found on the pouring zone surface in the optimal tundish.For non-normal operation,that is,one strand was close,it was important to choose which strand to be closed for maintaining flow characteristics of the rest two strands.It was found from this investigation that fluid flow characteristics in the optimal configuration tundish with closing strand 2 were better than those with closing strand 3 on the same side.展开更多
Improper flow control devices in a multi-strand tundish can cause some problems, for example, liquid steel cannot reach every nozzle at the same time and the liquid steel in nozzles far away from the entry zone has a ...Improper flow control devices in a multi-strand tundish can cause some problems, for example, liquid steel cannot reach every nozzle at the same time and the liquid steel in nozzles far away from the entry zone has a lower temperature. The water model experiment of a six-strand tundish of Tianjin Iron ＆ Steel Co. Ltd. was performed, a new ＂U＂ type baffle was obtained, and its parameters were defined by perpendicular analysis. The ＂U＂ baffle can not only improve those imperfections, but also prolong the residence time of nonmetallic inclusions, which is good for their flotation and separation.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
Stewart platform(SP) is a promising choice for large component alignment, and interactive force measurements are a novel and significant approach for high-precision assemblies. The designed position and orientation(P&...Stewart platform(SP) is a promising choice for large component alignment, and interactive force measurements are a novel and significant approach for high-precision assemblies. The designed position and orientation(P&O) adjusting platform, based on an SP for force/torquedriven(F/T-driven) alignment, can dynamically measure interactive forces. This paper presents an analytical algorithm of measuring six-dimensional F/T based on the screw theory for accurate determination of external forces during alignment. Dynamic gravity deviations were taken into consideration and a compensation model was developed. The P&O number was optimized as well.Given the specific appearance of repeated six-dimensional F/T measurements, an approximate cone shape was used for spatial precision analysis. The magnitudes and directions of measured F/Ts can be evaluated by a set of standards, in terms of accuracy and repeatability. Experiments were also performed using a known applied load, and the proposed analytical algorithm was able to accurately predict the F/T. A comparison between precision analysis experiments with or without assembly fixtures was performed. Experimental results show that the measurement accuracy varies under different P&O sets and higher loads lead to poorer accuracy of dynamic gravity compensation. In addition, the preferable operation range has been discussed for high-precision assemblies with smaller deviations.展开更多
A six-axis force sensor with parallel 8/4-4 structure is introduced and its measurement principle is analyzed.Based on condition numbers of Jacobian matrix spectral norm of the sensor,the relationship between the forc...A six-axis force sensor with parallel 8/4-4 structure is introduced and its measurement principle is analyzed.Based on condition numbers of Jacobian matrix spectral norm of the sensor,the relationship between the force and moment isotropy and some structural parameters is deduced.Orthogonal test methods are used to determine the degree of primary and secondary factors that have significant effect on sensor characteristics.Furthermore,the relationship between each performance index and the structural parameters of the sensor is analyzed by the method of the atlas,which lays a foundation for structural optimization design of the force sensor.展开更多
An Autler-Townes（AT） spectroscopy based on phase conjugate six-wave mixing（SWM） is proposed to detect AT doublet of high-lying state in a Doppler-broadened cascade four-level system.It is found that the SWM spectr...An Autler-Townes（AT） spectroscopy based on phase conjugate six-wave mixing（SWM） is proposed to detect AT doublet of high-lying state in a Doppler-broadened cascade four-level system.It is found that the SWM spectrum is dependent strongly on the ratios between the magnitudes of the wave vectors.We discuss how the Doppler broadening affects the SWM spectrum from a time-domain viewpoint and find that,due the atomic motion,the atomic polarizations acquire different phases for atoms with different velocities as time evolves.The Doppler free SWM spectrum can be obtained only when the atomic polarization can be rephasing again at certain time after the interactions of all the incident fields.展开更多
By using six-qubit decoherence-free （DF） states as quantum carriers and decoy states, a robust quantum secure direct communication and authentication （QSDCA） protocol against decoherence noise is proposed. Four si...By using six-qubit decoherence-free （DF） states as quantum carriers and decoy states, a robust quantum secure direct communication and authentication （QSDCA） protocol against decoherence noise is proposed. Four six-qubit DF states are used in the process of secret transmission, however only the ｜0＇〉 state is prepared. The other three six-qubit DF states can be obtained by permuting the outputs of the setup for ｜0＇〉. By using the ｜0＇〉 state as the decoy state, the detection rate and the qubit error rate reach 81.3%, and they will not change with the noise level. The stability and security are much higher than those of the ping-pong protocol both in an ideal scenario and a decoherence noise scenario. Even if the eavesdropper measures several qubits, exploiting the coherent relationship between these qubits, she can gain one bit of secret information with probability 0.042.展开更多
The electrically driven six-legged robot with high carrying capacity is an indispensable equipment for planetary exploration, but it hinders its practicability because of its low efficiency of carrying energy. Meanwhi...The electrically driven six-legged robot with high carrying capacity is an indispensable equipment for planetary exploration, but it hinders its practicability because of its low efficiency of carrying energy. Meanwhile, its load capacity also affects its application range. To reduce the power consumption, increase the load to mass ratio, and improve the stability of robot, the relationship between the walking modes and the forces of feet under the tripod gait are researched for an electrically driven heavy-duty six-legged robot. Based on the configuration characteristics of electrically driven heavy-duty six-legged, the typical walking modes of robot are analyzed. The mathematical models of the normal forces of feet are respectively established under the tripod gait of typical walking modes. According to the MATLAB software, the variable tendency charts are respectively gained for the normal forces of feet. The walking experiments under the typical tripod gaits are implemented for the prototype of electrically driven heavy-duty six-legged robot. The variable tendencies of maximum normal forces of feet are acquired. The comparison results show that the theoretical and experimental data are in the same trend. The walking modes which are most available to realize the average force of distribution of each foot are confirmed. The proposed method of analyzing the relationship between the walking modes and the forces of feet can quickly determine the optimal walking mode and gait parameters under the average distribution of foot force, which is propitious to develop the excellent heavy-duty multi-legged robots with the lower power consumption, larger load to mass ratio, and higher stability.展开更多
The method to predict roll deformation precisely and efficiently is vital for the strip shape control of a six-high rolling mill. Traditional calculation methods of roll deformation, such as the finite element method ...The method to predict roll deformation precisely and efficiently is vital for the strip shape control of a six-high rolling mill. Traditional calculation methods of roll deformation, such as the finite element method and the influence function method, have been widely used due to their accuracies. However, the required calculation time is too long to be applied to the realtime control. Therefore, a rapid calculation method for predicting roll deformation of a six-high rolling mill was proposed, which employed the finite difference method to calculate the roll deflection and used a polynomial to describe the nonlinear relationship between roll flattening and roll contact pressure. Furthermore, a new correction strategy was proposed in the iteration, where the roll center flattening and the roll flattening deviation were put forward and corrected simultaneously in the iteration process according to the static equilibrium of roll. Finally, by the comparison with traditional methods, the proposed method was proved to be more efficient and it was suitable for the online calculation of the strip shape control.展开更多
A closed-form solution can be obtained for kinematic analysis of spatial mechanisms by using analytical method.However,extra solutions would occur when solving the constraint equations of mechanism kinematics unless t...A closed-form solution can be obtained for kinematic analysis of spatial mechanisms by using analytical method.However,extra solutions would occur when solving the constraint equations of mechanism kinematics unless the constraint equations are established with a proper method and the solving approach is appropriate.In order to obtain a kinematic solution of the spherical Stephenson-III six-bar mechanism,spherical analytical theory is employed to construct the constraint equations.Firstly,the mechanism is divided into a four-bar loop and a two-bar unit.On the basis of the decomposition,vectors of the mechanism nodes are derived according to spherical analytical theory and the principle of coordinate transformation.Secondly,the structural constraint equations are constructed by applying cosine formula of spherical triangles to the top platform of the mechanism.Thirdly,the constraint equations are solved by using Bezout’ s elimination method for forward analysis and Sylvester’ s resultant elimination method for inverse kinematics respectively.By the aid of computer symbolic systems,Mathematica and Maple,symbolic closed-form solution of forward and inverse displacement analysis of spherical Stephenson-III six-bar mechanism are obtained.Finally,numerical examples of forward and inverse analysis are presented to illustrate the proposed approach.The results indicate that the constraint equations established with the proposed method are much simpler than those reported by previous literature,and can be readily eliminated and solved.展开更多
We studied the local structure and properties of six-fold coordinated silicon(Si[6]) in BaOSiO2-P2O5 glasses. Nuclear magnetic resonance(NMR) and Raman spectroscopy revealed the existence of sixfold coordinated silico...We studied the local structure and properties of six-fold coordinated silicon(Si[6]) in BaOSiO2-P2O5 glasses. Nuclear magnetic resonance(NMR) and Raman spectroscopy revealed the existence of sixfold coordinated silicon species and network former units(NFUs) in the BaO-SiO2-P2O5 glasses. The glass transition temperature(Tg), which was measured by differential scanning calorimetry, increased rapidly along with the increase of SiO2 from 0 to 10 mol%, then declined and finally increased again, which showed a "Z" trend along with the increase of SiO2 while the density of the glasses showed the opposite trend. When the addition of SiO2 is 16 mol%, Tg decreased to an extremely low value(807.9 K). Besides, the Vickers indentation hardness(Hv) had been significantly enhanced from 4.66 to 6.63 GPa by adding 16 mol% SiO2. Furthermore, the liquid fragility index(m) of the glasses declined slowly firstly and then increased rapidly when the amount of SiO2 is greater than 13 mol%.展开更多
Being as unique nonlinear components of block ciphers,substitution boxes（S-boxes） directly affect the security of the cryptographic systems.It is important and difficult to design cryptographically strong S-boxes th...Being as unique nonlinear components of block ciphers,substitution boxes（S-boxes） directly affect the security of the cryptographic systems.It is important and difficult to design cryptographically strong S-boxes that simultaneously meet with multiple cryptographic criteria such as bijection,non-linearity,strict avalanche criterion（SAC）,bits independence criterion（BIC）,differential probability（DP） and linear probability（LP）.To deal with this problem,a chaotic S-box based on the artificial bee colony algorithm（CSABC） is designed.It uses the S-boxes generated by the six-dimensional compound hyperchaotic map as the initial individuals and employs ABC to improve their performance.In addition,it considers the nonlinearity and differential uniformity as the fitness functions.A series of experiments have been conducted to compare multiple cryptographic criteria of this algorithm with other algorithms.Simulation results show that the new algorithm has cryptographically strong S-box while meeting multiple cryptographic criteria.展开更多
We show the enhancement and suppression of a six-wave mixing （SWM） signal in the electromagnetically induced transparency in a five-level SSRb atomic system. The results show the Autler-Townes splitting and the enha...We show the enhancement and suppression of a six-wave mixing （SWM） signal in the electromagnetically induced transparency in a five-level SSRb atomic system. The results show the Autler-Townes splitting and the enhancement or suppression of SWM, which are caused respectively by a self-dressing effect and by an external dressing effect in the presence of mutual dressing between two SWM signals. In addition, we observe the polarization dependence of the enhancement and suppression of the SWM signals.展开更多
Aimed at high content of valuable metals, complicated composition, difficult to separation of precious metals six component alloy wastes, the present paper proposed a new technology of high efficient separation and pu...Aimed at high content of valuable metals, complicated composition, difficult to separation of precious metals six component alloy wastes, the present paper proposed a new technology of high efficient separation and purification. Using fragmentation technology realizes fast dissolution of palladium, silver, copper and zinc in the wastes, and high efficient and complete separation of them from gold and platinum; using evaporation thermal decomposition technology of mixed solution produced by nitric acid dissolving palladium, silver, copper and zinc, complete and high efficient separation of silver from palladium was realized; by control of solution acidity, using hydrazine reduction method, high efficient and complete separation of gold from platinum was realized. Using this new technology, the recovery rates of palladium and silver are above 99%, and gold and platinum above 98%, the grade of pure metals are above 99.95%.展开更多
A new hetero-six-nuclear cluster was synthesized and determined by X-ray diffraction technique. The four-carboxylate groups are bound to the Cu(II) atoms to form Cu(OR)4Cu paddle-wheel-type cage between two DMF as the...A new hetero-six-nuclear cluster was synthesized and determined by X-ray diffraction technique. The four-carboxylate groups are bound to the Cu(II) atoms to form Cu(OR)4Cu paddle-wheel-type cage between two DMF as the basis for the cluster. The distance of two copper(II) atoms is 2.642 ?, and they are bridged by the carboxylate groups. A huge system plane was auto-assembled by four host molecules and two Cu (II) ions, which was observed in the crystal structure.展开更多
A six-variable geometrical nonlinear shear deformation laminatedtheory is presented by which normal stress and strain distributioncan be calculated. by considering some affective factors that wereneglected under the f...A six-variable geometrical nonlinear shear deformation laminatedtheory is presented by which normal stress and strain distributioncan be calculated. by considering some affective factors that wereneglected under the finite deformation condition, an improved vonKarman geometrical non- linear deformation-strain relation is usedfor large deformation analysis. After analyzing the bending problemof laminated plates, and comparing it with 3-D elasticity solutionsand J.N.Reddy five-vari- able simple higher-order shear deformationlaminated theory, we can conclude that a satisfactory cal- culationprecision has been achieved, which shows that is especially suitablefor the calculation in the condition of large deformation and thelaminated thick plate analysis.展开更多
Most current biped robots are equipped with two feet arranged in the right and left which inspired by the human body system. Different from the existing configurations, a novel biped robot with inner and outer feet ba...Most current biped robots are equipped with two feet arranged in the right and left which inspired by the human body system. Different from the existing configurations, a novel biped robot with inner and outer feet based on a spatial six-bar 4R2C（R and C denote revolute and cylindric joints, respectively） mechanism is proposed. It can move along a line or a curve by three walking modes that are dwell adjustment mode, limit position adjustment mode and any position adjustment mode. Kinematic, gait planning and stability analyses are performed respectively, and a prototype is developed. Lastly, a potential application is considered and two manipulating modes（sphere and cylinder manipulating modes） are carried out. This interesting mechanism feathering its single dosed-chain structure and unique work performance is expected to motivate the configuration creation of biped robots.展开更多
基金Item Sponsored by National High Technology Research and Development Plan of China(2007AA04Z194)
文摘A 1∶2.5 scale tundish model was set up in laboratory for a six-strand billet continuous casting tundish with different configurations to investigate fluid flow characteristics under different operational conditions by measuring residence time distribution curves.It was found that minimum residence time,maximum concentration time and average residence time of the three strands on the same side of the tundish with the former configuration under normal operation,that is,six strands were open,were small and non-uniform and the tundish had large dead volume fraction.Vortexes easily formed on the liquid surface in the pouring zone of the tundish.The fluid flow characteristics in the tundish with the optimal turbulence inhibitor and baffles were improved and became less non-uniform among the strands.Vortexes were not found on the pouring zone surface in the optimal tundish.For non-normal operation,that is,one strand was close,it was important to choose which strand to be closed for maintaining flow characteristics of the rest two strands.It was found from this investigation that fluid flow characteristics in the optimal configuration tundish with closing strand 2 were better than those with closing strand 3 on the same side.
文摘Improper flow control devices in a multi-strand tundish can cause some problems, for example, liquid steel cannot reach every nozzle at the same time and the liquid steel in nozzles far away from the entry zone has a lower temperature. The water model experiment of a six-strand tundish of Tianjin Iron ＆ Steel Co. Ltd. was performed, a new ＂U＂ type baffle was obtained, and its parameters were defined by perpendicular analysis. The ＂U＂ baffle can not only improve those imperfections, but also prolong the residence time of nonmetallic inclusions, which is good for their flotation and separation.
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.
基金co-supported by the National Defense Basic Scientific Research (No. A2120132007)the Fund of National Engineering and Research Center for Commercial Aircraft Manufacturing (No. SAMC14-JS-15-055)
文摘Stewart platform(SP) is a promising choice for large component alignment, and interactive force measurements are a novel and significant approach for high-precision assemblies. The designed position and orientation(P&O) adjusting platform, based on an SP for force/torquedriven(F/T-driven) alignment, can dynamically measure interactive forces. This paper presents an analytical algorithm of measuring six-dimensional F/T based on the screw theory for accurate determination of external forces during alignment. Dynamic gravity deviations were taken into consideration and a compensation model was developed. The P&O number was optimized as well.Given the specific appearance of repeated six-dimensional F/T measurements, an approximate cone shape was used for spatial precision analysis. The magnitudes and directions of measured F/Ts can be evaluated by a set of standards, in terms of accuracy and repeatability. Experiments were also performed using a known applied load, and the proposed analytical algorithm was able to accurately predict the F/T. A comparison between precision analysis experiments with or without assembly fixtures was performed. Experimental results show that the measurement accuracy varies under different P&O sets and higher loads lead to poorer accuracy of dynamic gravity compensation. In addition, the preferable operation range has been discussed for high-precision assemblies with smaller deviations.
基金supported by the Open Foundation of Graduate Innovation Base(Laboratory)of Nanjing University of Aeronautics and Astronautics (No.kfjj20170512)the National Natural Science Foundation of China(No. 51175263)
文摘A six-axis force sensor with parallel 8/4-4 structure is introduced and its measurement principle is analyzed.Based on condition numbers of Jacobian matrix spectral norm of the sensor,the relationship between the force and moment isotropy and some structural parameters is deduced.Orthogonal test methods are used to determine the degree of primary and secondary factors that have significant effect on sensor characteristics.Furthermore,the relationship between each performance index and the structural parameters of the sensor is analyzed by the method of the atlas,which lays a foundation for structural optimization design of the force sensor.
基金Project supported by the National Basic Research Program of China(Grant No.2013CB922002)the National Natural Science Foundation of China(Grant Nos.11274376 and 61308011)the National High Technology Research and Development Program of China(Grant No.2011AA120102)
文摘An Autler-Townes（AT） spectroscopy based on phase conjugate six-wave mixing（SWM） is proposed to detect AT doublet of high-lying state in a Doppler-broadened cascade four-level system.It is found that the SWM spectrum is dependent strongly on the ratios between the magnitudes of the wave vectors.We discuss how the Doppler broadening affects the SWM spectrum from a time-domain viewpoint and find that,due the atomic motion,the atomic polarizations acquire different phases for atoms with different velocities as time evolves.The Doppler free SWM spectrum can be obtained only when the atomic polarization can be rephasing again at certain time after the interactions of all the incident fields.
基金supported by the National Natural Science Foundation of China(Grant No.61402058)the Science and Technology Support Project of Sichuan Province of China(Grant No.2013GZX0137)+1 种基金the Fund for Young Persons Project of Sichuan Province of China(Grant No.12ZB017)the Foundation of Cyberspace Security Key Laboratory of Sichuan Higher Education Institutions,China(Grant No.szjj2014-074)
文摘By using six-qubit decoherence-free （DF） states as quantum carriers and decoy states, a robust quantum secure direct communication and authentication （QSDCA） protocol against decoherence noise is proposed. Four six-qubit DF states are used in the process of secret transmission, however only the ｜0＇〉 state is prepared. The other three six-qubit DF states can be obtained by permuting the outputs of the setup for ｜0＇〉. By using the ｜0＇〉 state as the decoy state, the detection rate and the qubit error rate reach 81.3%, and they will not change with the noise level. The stability and security are much higher than those of the ping-pong protocol both in an ideal scenario and a decoherence noise scenario. Even if the eavesdropper measures several qubits, exploiting the coherent relationship between these qubits, she can gain one bit of secret information with probability 0.042.
基金Supported by National Natural Science Foundation of China(Grant Nos.51505335,51275106)National Basic Research Program of China(973Program,Grant No.2013CB035502)
文摘The electrically driven six-legged robot with high carrying capacity is an indispensable equipment for planetary exploration, but it hinders its practicability because of its low efficiency of carrying energy. Meanwhile, its load capacity also affects its application range. To reduce the power consumption, increase the load to mass ratio, and improve the stability of robot, the relationship between the walking modes and the forces of feet under the tripod gait are researched for an electrically driven heavy-duty six-legged robot. Based on the configuration characteristics of electrically driven heavy-duty six-legged, the typical walking modes of robot are analyzed. The mathematical models of the normal forces of feet are respectively established under the tripod gait of typical walking modes. According to the MATLAB software, the variable tendency charts are respectively gained for the normal forces of feet. The walking experiments under the typical tripod gaits are implemented for the prototype of electrically driven heavy-duty six-legged robot. The variable tendencies of maximum normal forces of feet are acquired. The comparison results show that the theoretical and experimental data are in the same trend. The walking modes which are most available to realize the average force of distribution of each foot are confirmed. The proposed method of analyzing the relationship between the walking modes and the forces of feet can quickly determine the optimal walking mode and gait parameters under the average distribution of foot force, which is propitious to develop the excellent heavy-duty multi-legged robots with the lower power consumption, larger load to mass ratio, and higher stability.
基金This work was financially supported by the National Natural Science Foundation of China （51674028）, and Fundamental Research Funds for the Central Universities （FRF-IC- 16-001）.
文摘The method to predict roll deformation precisely and efficiently is vital for the strip shape control of a six-high rolling mill. Traditional calculation methods of roll deformation, such as the finite element method and the influence function method, have been widely used due to their accuracies. However, the required calculation time is too long to be applied to the realtime control. Therefore, a rapid calculation method for predicting roll deformation of a six-high rolling mill was proposed, which employed the finite difference method to calculate the roll deflection and used a polynomial to describe the nonlinear relationship between roll flattening and roll contact pressure. Furthermore, a new correction strategy was proposed in the iteration, where the roll center flattening and the roll flattening deviation were put forward and corrected simultaneously in the iteration process according to the static equilibrium of roll. Finally, by the comparison with traditional methods, the proposed method was proved to be more efficient and it was suitable for the online calculation of the strip shape control.
基金supported by National Natural Science Foundation of China(Grant No.50975186)
文摘A closed-form solution can be obtained for kinematic analysis of spatial mechanisms by using analytical method.However,extra solutions would occur when solving the constraint equations of mechanism kinematics unless the constraint equations are established with a proper method and the solving approach is appropriate.In order to obtain a kinematic solution of the spherical Stephenson-III six-bar mechanism,spherical analytical theory is employed to construct the constraint equations.Firstly,the mechanism is divided into a four-bar loop and a two-bar unit.On the basis of the decomposition,vectors of the mechanism nodes are derived according to spherical analytical theory and the principle of coordinate transformation.Secondly,the structural constraint equations are constructed by applying cosine formula of spherical triangles to the top platform of the mechanism.Thirdly,the constraint equations are solved by using Bezout’ s elimination method for forward analysis and Sylvester’ s resultant elimination method for inverse kinematics respectively.By the aid of computer symbolic systems,Mathematica and Maple,symbolic closed-form solution of forward and inverse displacement analysis of spherical Stephenson-III six-bar mechanism are obtained.Finally,numerical examples of forward and inverse analysis are presented to illustrate the proposed approach.The results indicate that the constraint equations established with the proposed method are much simpler than those reported by previous literature,and can be readily eliminated and solved.
基金Funded by National Natural Science Foundation of China(Nos.51772223,51372180)
文摘We studied the local structure and properties of six-fold coordinated silicon(Si[6]) in BaOSiO2-P2O5 glasses. Nuclear magnetic resonance(NMR) and Raman spectroscopy revealed the existence of sixfold coordinated silicon species and network former units(NFUs) in the BaO-SiO2-P2O5 glasses. The glass transition temperature(Tg), which was measured by differential scanning calorimetry, increased rapidly along with the increase of SiO2 from 0 to 10 mol%, then declined and finally increased again, which showed a "Z" trend along with the increase of SiO2 while the density of the glasses showed the opposite trend. When the addition of SiO2 is 16 mol%, Tg decreased to an extremely low value(807.9 K). Besides, the Vickers indentation hardness(Hv) had been significantly enhanced from 4.66 to 6.63 GPa by adding 16 mol% SiO2. Furthermore, the liquid fragility index(m) of the glasses declined slowly firstly and then increased rapidly when the amount of SiO2 is greater than 13 mol%.
基金supported by the National Natural Science Foundation of China(6060309260975042)
文摘Being as unique nonlinear components of block ciphers,substitution boxes（S-boxes） directly affect the security of the cryptographic systems.It is important and difficult to design cryptographically strong S-boxes that simultaneously meet with multiple cryptographic criteria such as bijection,non-linearity,strict avalanche criterion（SAC）,bits independence criterion（BIC）,differential probability（DP） and linear probability（LP）.To deal with this problem,a chaotic S-box based on the artificial bee colony algorithm（CSABC） is designed.It uses the S-boxes generated by the six-dimensional compound hyperchaotic map as the initial individuals and employs ABC to improve their performance.In addition,it considers the nonlinearity and differential uniformity as the fitness functions.A series of experiments have been conducted to compare multiple cryptographic criteria of this algorithm with other algorithms.Simulation results show that the new algorithm has cryptographically strong S-box while meeting multiple cryptographic criteria.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.10974151,61078002,and 61078020)the Program for New Century Excellent Talents in University of Ministry of Education of China (Grant No.08-0431)the Cross-Disciplinary Project of Xi'an Jiaotong University,China (Grant Nos.2009xjtujc08,XJJ20100100,and XJJ20100151)
文摘We show the enhancement and suppression of a six-wave mixing （SWM） signal in the electromagnetically induced transparency in a five-level SSRb atomic system. The results show the Autler-Townes splitting and the enhancement or suppression of SWM, which are caused respectively by a self-dressing effect and by an external dressing effect in the presence of mutual dressing between two SWM signals. In addition, we observe the polarization dependence of the enhancement and suppression of the SWM signals.
文摘Aimed at high content of valuable metals, complicated composition, difficult to separation of precious metals six component alloy wastes, the present paper proposed a new technology of high efficient separation and purification. Using fragmentation technology realizes fast dissolution of palladium, silver, copper and zinc in the wastes, and high efficient and complete separation of them from gold and platinum; using evaporation thermal decomposition technology of mixed solution produced by nitric acid dissolving palladium, silver, copper and zinc, complete and high efficient separation of silver from palladium was realized; by control of solution acidity, using hydrazine reduction method, high efficient and complete separation of gold from platinum was realized. Using this new technology, the recovery rates of palladium and silver are above 99%, and gold and platinum above 98%, the grade of pure metals are above 99.95%.
基金We are grateful to the National Natural Science Foundation of China(project 20072034)the Natural Science Foundation of Henan province and the Foundation for Young Teacher in Zhenzhou University for the financial support.
文摘A new hetero-six-nuclear cluster was synthesized and determined by X-ray diffraction technique. The four-carboxylate groups are bound to the Cu(II) atoms to form Cu(OR)4Cu paddle-wheel-type cage between two DMF as the basis for the cluster. The distance of two copper(II) atoms is 2.642 ?, and they are bridged by the carboxylate groups. A huge system plane was auto-assembled by four host molecules and two Cu (II) ions, which was observed in the crystal structure.
文摘A six-variable geometrical nonlinear shear deformation laminatedtheory is presented by which normal stress and strain distributioncan be calculated. by considering some affective factors that wereneglected under the finite deformation condition, an improved vonKarman geometrical non- linear deformation-strain relation is usedfor large deformation analysis. After analyzing the bending problemof laminated plates, and comparing it with 3-D elasticity solutionsand J.N.Reddy five-vari- able simple higher-order shear deformationlaminated theory, we can conclude that a satisfactory cal- culationprecision has been achieved, which shows that is especially suitablefor the calculation in the condition of large deformation and thelaminated thick plate analysis.
基金Supported by National Natural Science Foundation of China(Grant Nos.51175030,51505022)Foundation of Talents of Beijing Jiaotong University,China(Grant No.2015RC047)+1 种基金China Postdoctoral Science Foundation(Grant No.2013M531168)the Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.20130009110030)
文摘Most current biped robots are equipped with two feet arranged in the right and left which inspired by the human body system. Different from the existing configurations, a novel biped robot with inner and outer feet based on a spatial six-bar 4R2C（R and C denote revolute and cylindric joints, respectively） mechanism is proposed. It can move along a line or a curve by three walking modes that are dwell adjustment mode, limit position adjustment mode and any position adjustment mode. Kinematic, gait planning and stability analyses are performed respectively, and a prototype is developed. Lastly, a potential application is considered and two manipulating modes（sphere and cylinder manipulating modes） are carried out. This interesting mechanism feathering its single dosed-chain structure and unique work performance is expected to motivate the configuration creation of biped robots.
