The modelling of one kind of nonlinear parabolic distributed parameter control system with moving boundary, which had extensive applications was presented, Two methods were used to investigate the basic characteristic...The modelling of one kind of nonlinear parabolic distributed parameter control system with moving boundary, which had extensive applications was presented, Two methods were used to investigate the basic characteristics of the system: I) transforming the system it? the variable domain into that in the fixed domain; 2) transforming the distributed parameter system into the lumped parameter system. It is found that there are two critical values for the control variable : the larger one determines whether or not the boundary would move, while the smaller one determines whether or not the boundary, would atop automatically. For one-dimensional system of planar, cylindrical and spherical cases the definite solution problem can be expressed as a unified form. By means of the computer simulation the open-loop control system and close-cycle feedback control system have been investigated. Numerical results agree well with theoretical results. The computer simulation shows that the system is well posed, stable, measurable and controllable.展开更多
A type of mesh called a body-fi tted Cartesian mesh,very different from the traditional structured body-fi tted mesh,is established.At f irst,the right parallelepiped mesh is generated,then,a feature analysis is done ...A type of mesh called a body-fi tted Cartesian mesh,very different from the traditional structured body-fi tted mesh,is established.At f irst,the right parallelepiped mesh is generated,then,a feature analysis is done on the cross sections.These cross sections are the intersections of the casting shape with the right parallelepiped grids(under the Cartesian coordinate system).On the basis of the feature analysis,two sorts of body-f itted boundary grids,shape-keeping grids and shape-distortion grids,are def ined.Shape-distortion grids can be removed or weaken by increasing the number of grids or moving the coordinates of the mesh generation region,so actually the body-fitted Cartesian mesh generation is to get shape-keeping grids.A shape-keeping grid mainly consists of two sorts of surfaces(I type face and II type face),and each of them is joined by two types of points(I type point and II type point).If only these two types of points were given,the shape-keeping mesh would be constructed.In this paper,the cases of the above two boundary grids being generated were discussed.An algorithm was put forward to get the shape-keeping grids.Several body-fi tted Cartesian meshes generated on castings show the validity of the algorithm.The mesh generation examples show that the body-fi tted Cartesian mesh is more excellent than the right parallelepiped mesh in aspects of decreasing grids number and being closer to the shape of the casting solid.展开更多
The bubble radius at the early stage of discharge in water is investigated using high-speed photography. Some simulation results on the bubble radius are presented, which are in agreement with the experimental results...The bubble radius at the early stage of discharge in water is investigated using high-speed photography. Some simulation results on the bubble radius are presented, which are in agreement with the experimental results, with a maximum difference of about 10%. The reasons why the peak pressure of the first shock wave is only related to the energy released in the bubble during the first half period are addressed. The energy released in the bubble after the first half period increases the bubble pulsation period, but it produces no more than 10% under the peak pressure of the second shock wave.展开更多
The study of damage in rotating machineries is of fundamental interest in the fields of machine and structure design. A rotating system, supported by bearings and under some dynamic conditions, can generate a variety ...The study of damage in rotating machineries is of fundamental interest in the fields of machine and structure design. A rotating system, supported by bearings and under some dynamic conditions, can generate a variety of problems that are encountered in many different types of rotating machines. One of these problems is the unbalance due to non-homogeneous mass distribution along the shaft. One of the techniques which are widespread today is the identification of parameters and excitation forces that may well followed by monitoring the evolution and change of possible variations of these parameters. Although several methods for the identification of unbalance excitation force are available in the literature, none of them can be considered unrestricted to be applied for all rotating systems. In this study, two methodologies to identify unknown excitations, such as unbalance, have been proposed. This project refers to the analysis of unbalanced forces from displacement parameters and speed by using methods of identification by Fourier series and Legendre polynomials together with the finite element method, state observers in reasons of the problem of absence of signs of rotational displacement, bandpass filter were used to noise suppression of the data collected from the experimental part, Quasi-Newton method to minimize a function in which the bearing stiffness and its damping are unknowns, and also the experimental verification of the methodology, using for this system owned by a rotary mechanical vibrations of the Department of Mechanical Engineering of Faculty of Engineering, campus of llha Solteira.展开更多
Due to rejecting order in a single supply chain for lack of adequate capacity, a multi-chain system is introduced to avoid this potential operational risk. Based on four categories of order： direct order, reserve ord...Due to rejecting order in a single supply chain for lack of adequate capacity, a multi-chain system is introduced to avoid this potential operational risk. Based on four categories of order： direct order, reserve order, chain-to-chain order and rejected order, the framework of order selection in multi-chain system（MCS） is presented, and the model of order selection and planning under chain-to-chain collaboration is formulated. Then, the Lagrange algorithm is used to solve this problem through Lagrange relaxation and decomposition. Finally, numerical study show that opportunity cost of rejecting reserve order and production cost of chain-to-chain order have significant impacts on order selection, and there exists a critical threshold value of the combination of two factors. Through the combination, the multi-chain system can obtain the optimal status, meanwhile manager can utilize this to realize different strategies in MCS.展开更多
This paper describes a three-dimensional structured light scanning system to generate a virtual model of a dental arch, from the patient＇s mouth, and the scheme ofa 2 ＋ 1 DOF （degree of freedom） parallel/serial Ro...This paper describes a three-dimensional structured light scanning system to generate a virtual model of a dental arch, from the patient＇s mouth, and the scheme ofa 2 ＋ 1 DOF （degree of freedom） parallel/serial Robot for implant positioning, both positioned on a platform held in a fixed position with respect to the patient＇s head. Presently, dental prosthesization requires quite a long time to be completed. This process, in fact, involves the detection of the shape of the dental arch, its plaster model generation, scanning of it, prosthesis preparation and its implant. The procedur＇e is even longer when use of dental implants is required, while early loading of the implants is considered a positive solution. Current research effort is focused on the development of devices for the direct intra-oral determination of the shape of dental prostheses and inserts. These devices, however, are able to detect limited portions of the dental arch, since they must be hand-held by the doctor without external supports, and this may produce relatively large errors due to the sum of relatively small ones. Furthermore, to place an implant correctly, the doctor can use a new system to guide the implant position, but this requires sending the information in Sweden to obtain a special mask in return.展开更多
Implantable deep brain stimulation(DBS)systems are utilized for clinical treatment of diseases such as Parkinson's disease and chronic pain.However,long-term efficacy of DBS is limited,and chronic neuroplastic cha...Implantable deep brain stimulation(DBS)systems are utilized for clinical treatment of diseases such as Parkinson's disease and chronic pain.However,long-term efficacy of DBS is limited,and chronic neuroplastic changes and associated therapeutic mechanisms are not well understood.Fundamental and mechanistic investigation,typically accomplished in small animal models,is difficult because of the need for chronic stimulators that currently require either frequent handling of test subjects to charge battery-powered systems or specialized setups to manage tethers that restrict experimental paradigms and compromise insight.To overcome these challenges,we demonstrate a fully implantable,wireless,battery-free platform that allows for chronic DBS in rodents with the capability to control stimulation parameters digitally in real time.The devices are able to provide stimulation over a wide range of frequencies with biphasic pulses and constant voltage control via low-impedance,surface-engineered platinum electrodes.The devices utilize off-the-shelf components and feature the ability to customize electrodes to enable broad utility and rapid dissemination.Efficacy of the system is demonstrated with a readout of stimulation-evoked neural activity in vivo and chronic stimulation of the medial forebrain bundle in freely moving rats to evoke characteristic head motion for over 36 days.展开更多
文摘The modelling of one kind of nonlinear parabolic distributed parameter control system with moving boundary, which had extensive applications was presented, Two methods were used to investigate the basic characteristics of the system: I) transforming the system it? the variable domain into that in the fixed domain; 2) transforming the distributed parameter system into the lumped parameter system. It is found that there are two critical values for the control variable : the larger one determines whether or not the boundary would move, while the smaller one determines whether or not the boundary, would atop automatically. For one-dimensional system of planar, cylindrical and spherical cases the definite solution problem can be expressed as a unified form. By means of the computer simulation the open-loop control system and close-cycle feedback control system have been investigated. Numerical results agree well with theoretical results. The computer simulation shows that the system is well posed, stable, measurable and controllable.
基金financially supported by the fund of the State Key Laboratory of Solidif ication Processing in NWPU(No:SKLSP201006)the fund of the National Basic Research Program of China(No:2011CB610402)
文摘A type of mesh called a body-fi tted Cartesian mesh,very different from the traditional structured body-fi tted mesh,is established.At f irst,the right parallelepiped mesh is generated,then,a feature analysis is done on the cross sections.These cross sections are the intersections of the casting shape with the right parallelepiped grids(under the Cartesian coordinate system).On the basis of the feature analysis,two sorts of body-f itted boundary grids,shape-keeping grids and shape-distortion grids,are def ined.Shape-distortion grids can be removed or weaken by increasing the number of grids or moving the coordinates of the mesh generation region,so actually the body-fitted Cartesian mesh generation is to get shape-keeping grids.A shape-keeping grid mainly consists of two sorts of surfaces(I type face and II type face),and each of them is joined by two types of points(I type point and II type point).If only these two types of points were given,the shape-keeping mesh would be constructed.In this paper,the cases of the above two boundary grids being generated were discussed.An algorithm was put forward to get the shape-keeping grids.Several body-fi tted Cartesian meshes generated on castings show the validity of the algorithm.The mesh generation examples show that the body-fi tted Cartesian mesh is more excellent than the right parallelepiped mesh in aspects of decreasing grids number and being closer to the shape of the casting solid.
文摘The bubble radius at the early stage of discharge in water is investigated using high-speed photography. Some simulation results on the bubble radius are presented, which are in agreement with the experimental results, with a maximum difference of about 10%. The reasons why the peak pressure of the first shock wave is only related to the energy released in the bubble during the first half period are addressed. The energy released in the bubble after the first half period increases the bubble pulsation period, but it produces no more than 10% under the peak pressure of the second shock wave.
文摘The study of damage in rotating machineries is of fundamental interest in the fields of machine and structure design. A rotating system, supported by bearings and under some dynamic conditions, can generate a variety of problems that are encountered in many different types of rotating machines. One of these problems is the unbalance due to non-homogeneous mass distribution along the shaft. One of the techniques which are widespread today is the identification of parameters and excitation forces that may well followed by monitoring the evolution and change of possible variations of these parameters. Although several methods for the identification of unbalance excitation force are available in the literature, none of them can be considered unrestricted to be applied for all rotating systems. In this study, two methodologies to identify unknown excitations, such as unbalance, have been proposed. This project refers to the analysis of unbalanced forces from displacement parameters and speed by using methods of identification by Fourier series and Legendre polynomials together with the finite element method, state observers in reasons of the problem of absence of signs of rotational displacement, bandpass filter were used to noise suppression of the data collected from the experimental part, Quasi-Newton method to minimize a function in which the bearing stiffness and its damping are unknowns, and also the experimental verification of the methodology, using for this system owned by a rotary mechanical vibrations of the Department of Mechanical Engineering of Faculty of Engineering, campus of llha Solteira.
基金Supported by the National Natural Science Foundation of China(71472143,71171152)the Ministry of Education of China Program(15YJA630035)
文摘Due to rejecting order in a single supply chain for lack of adequate capacity, a multi-chain system is introduced to avoid this potential operational risk. Based on four categories of order： direct order, reserve order, chain-to-chain order and rejected order, the framework of order selection in multi-chain system（MCS） is presented, and the model of order selection and planning under chain-to-chain collaboration is formulated. Then, the Lagrange algorithm is used to solve this problem through Lagrange relaxation and decomposition. Finally, numerical study show that opportunity cost of rejecting reserve order and production cost of chain-to-chain order have significant impacts on order selection, and there exists a critical threshold value of the combination of two factors. Through the combination, the multi-chain system can obtain the optimal status, meanwhile manager can utilize this to realize different strategies in MCS.
文摘This paper describes a three-dimensional structured light scanning system to generate a virtual model of a dental arch, from the patient＇s mouth, and the scheme ofa 2 ＋ 1 DOF （degree of freedom） parallel/serial Robot for implant positioning, both positioned on a platform held in a fixed position with respect to the patient＇s head. Presently, dental prosthesization requires quite a long time to be completed. This process, in fact, involves the detection of the shape of the dental arch, its plaster model generation, scanning of it, prosthesis preparation and its implant. The procedur＇e is even longer when use of dental implants is required, while early loading of the implants is considered a positive solution. Current research effort is focused on the development of devices for the direct intra-oral determination of the shape of dental prostheses and inserts. These devices, however, are able to detect limited portions of the dental arch, since they must be hand-held by the doctor without external supports, and this may produce relatively large errors due to the sum of relatively small ones. Furthermore, to place an implant correctly, the doctor can use a new system to guide the implant position, but this requires sending the information in Sweden to obtain a special mask in return.
基金support from the National Institute of Biomedical Imaging and Bioengineering of the National Institutes of Health T32EB000809(A.B.)the ARCS Foundation(A.B.).The University of Arizona Department of Biomedical Engineering startup funds(P.G.)and Core Facilities Pilot Program(CA-CFPP NANO-3310342)(P.G.).5.M.W.acknowledges the support by the MSIT(Ministry of Science and IC〇,Korea,under the ICT Creative Consilience program(IITP-2020-0-01821)+2 种基金by Nano Material Technology Development Program(2020M3H4A1A03084600)through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT of KoreaThe Eunice Kennedy Shriver National Institute of Child Health&Human Development(K12HD073945,F.V.).University of Pennsylvania Department of Neurosurgery startup funds(A.G.R.).
文摘Implantable deep brain stimulation(DBS)systems are utilized for clinical treatment of diseases such as Parkinson's disease and chronic pain.However,long-term efficacy of DBS is limited,and chronic neuroplastic changes and associated therapeutic mechanisms are not well understood.Fundamental and mechanistic investigation,typically accomplished in small animal models,is difficult because of the need for chronic stimulators that currently require either frequent handling of test subjects to charge battery-powered systems or specialized setups to manage tethers that restrict experimental paradigms and compromise insight.To overcome these challenges,we demonstrate a fully implantable,wireless,battery-free platform that allows for chronic DBS in rodents with the capability to control stimulation parameters digitally in real time.The devices are able to provide stimulation over a wide range of frequencies with biphasic pulses and constant voltage control via low-impedance,surface-engineered platinum electrodes.The devices utilize off-the-shelf components and feature the ability to customize electrodes to enable broad utility and rapid dissemination.Efficacy of the system is demonstrated with a readout of stimulation-evoked neural activity in vivo and chronic stimulation of the medial forebrain bundle in freely moving rats to evoke characteristic head motion for over 36 days.
