This work aims to establish a suitable numerical simulation model for hybrid laser-electric arc heat source welding of dissimilar Mg alloys between AZ31 and AZ80. Based on the energy conservation law and Fourier’s la...This work aims to establish a suitable numerical simulation model for hybrid laser-electric arc heat source welding of dissimilar Mg alloys between AZ31 and AZ80. Based on the energy conservation law and Fourier’s law of heat conduction, the differential equations of the three-dimensional temperature field for nonlinear transient heat conduction are built. According to the analysis of nonlinear transient heat transfer, the equations representing initial conditions and boundary conditions are obtained. The “double ellipsoidal heat source + 3D Gaussian heat source”combination was chosen to construct the laser-electric arc hybrid heat source. The weld bead morphologies and the distribution of temperature, stress, displacement and plastic strains are numerically simulated. The actual welding experiments were performed by a hybrid laser-electric arc welding machine. The interaction mechanism between laser and electric arc in the hybrid welding of Mg alloys is discussed in detail. The hybrid heat source can promote the absorption of laser energy and electric arc in the molten pool, resulting in more uniform energy distribution in the molten pool and the corresponding improvement of welding parameters. This work can provide theoretical guidance and data supports for the optimization of the hybrid laser-electric arc welding processes for Mg alloys.展开更多
Based on the simulated aerospace thermal cycling tests,the effect of thermal cycle on the void damage evolution mechanism of LF6 aluminum alloy welded joint was investigated.The results show that micro-voids form arou...Based on the simulated aerospace thermal cycling tests,the effect of thermal cycle on the void damage evolution mechanism of LF6 aluminum alloy welded joint was investigated.The results show that micro-voids form around the second phase particles under the thermal cycling tests.The thermal stress coupled with external stress leads to dislocations pile-up around the particles,and when the dislocation density reaches a certain degree,the stress concentration will exceed the bonding strength at the interface between particles and matrix,resulting in the formation of micro-cracks.The numerical simulation is successfully implemented with the finite element to describe the void damage evolution of the welded joint under thermal cycling conditions.展开更多
We theoretically investigate a device consisting of two quantum dots （QDs） side-coupled to a quantum wire which has many physical ingredients of an artificial heavy fermion system. An extra parameter, the distance L...We theoretically investigate a device consisting of two quantum dots （QDs） side-coupled to a quantum wire which has many physical ingredients of an artificial heavy fermion system. An extra parameter, the distance L between the two QDs, is introduced and it plays an important role on the competition of the Kondo temperature and magnetic coupling. Three different phases are found： antiferromagnetic phase, Kondo phase with spin S = 1/2, and Kondo phase with S = 1, depending on the distance L, the magnetic properties are qualitatively different for different phases： conductance tends to the unitary value 2e2 /h; for the S ： the distance. coupling, and the Kondo temperature. Quantum transport for the S = 1 Kondo and the antiferromagnetic phases, the 1/2 Kondo phase the conductance is strongly dependent onthe distance.展开更多
This paper proposes a joint network-channel codingbased on turbo codes for user cooperation. The scenario under consideration is one in which two ＂partners＂--UE1 and UE2---cooperate in transmitting information to th...This paper proposes a joint network-channel codingbased on turbo codes for user cooperation. The scenario under consideration is one in which two ＂partners＂--UE1 and UE2---cooperate in transmitting information to the base station （BS）. Each partner transmits both locally generated information and the relayed information that originated at the other partner. The local information and relayed information are jointly network-channel coded to form a superimposed codeword, and the adjacent codewords transmitted in turn by the two partners are tightly correlative like a chain. It is shown via simulation that the proposed scheme achieves full diversity gain compared with the other user cooperation schemes, including those based on coded cooperation and distributed space-time coded cooperation.展开更多
This paper presents a study of the relationship between the magnetic properties and microstructure of nanocomposite Ni/MnO, Ni/CoO, Co/MnO, Co/CoO. The objective is to understand how the coupling interface FM/AFM （fe...This paper presents a study of the relationship between the magnetic properties and microstructure of nanocomposite Ni/MnO, Ni/CoO, Co/MnO, Co/CoO. The objective is to understand how the coupling interface FM/AFM （ferromagnetic/anti-ferromagnetic） manifests itself in magnetic response of these materials to an applied field. Sample preparation was performed using mechanochemical synthesis by means of a ball mill planetary type high power at normal atmosphere. The characterization was done by XRD （X-ray diffraction）, SEM （scanning electron microscopy） and VSM （vibrating sample magnetometry）. Analyzing the XRD peaks of the samples studied, there was a decrease in the average particle diameter with increasing milling time, which is important in the magnetic interactions of the atoms of the surface. In addition, the diffraction pattern showed formation of new phases by oxidation interfering with the magnetic measurements. Analyses by SEM show chipboard multiform nano- and micrometer-sized grains on the surface of the clusters being responsible for the interaction. The magnetic measurements show a strong coupling between the phases present in nanocomposites showing once again that the MS （mechanosynthesis） is a powerful technique for this kind of purpose. The effect of the decrease in crystallite size leads to large variations of magnetic properties of the material which have been specifically observed changes in HC （coercive field） in the RM （remanent magnetization） and SM （saturation magnetization）. The decrease in crystallite size in the course of grinding intensifies the effects that depend on the surface-to-volume ratio of the material. M vs. T measures were taken for different values of applied field and found a jump in the moment of the sample near the N6el temperature of the antiferromagnetic.展开更多
This paper presents the results of the search of biologically active uranium compounds such as amino acids. We first received and examined X-ray and IR （infrared radiation） spectroscopy of uranium complexes with α-...This paper presents the results of the search of biologically active uranium compounds such as amino acids. We first received and examined X-ray and IR （infrared radiation） spectroscopy of uranium complexes with α- and β-amino acids in aqueous and organic solution. We proposed a method for direct synthesis of complex organic compounds of uranium chloride UO2Cl2 with α- andβ-amino acids for the synthesis of drugs for the treatment of cancer.展开更多
当我与Edward L. Tatum由于我们的“……基因靠调节化学事件而起作用的发现”并与Joshua Lederberg由于他的“……关于细菌遗传物质构成的发现,”一起分享诺贝尔奖金崇高荣誉的机会,我简要描述一下,由Tatum和我于1940年开始研究链孢霉...当我与Edward L. Tatum由于我们的“……基因靠调节化学事件而起作用的发现”并与Joshua Lederberg由于他的“……关于细菌遗传物质构成的发现,”一起分享诺贝尔奖金崇高荣誉的机会,我简要描述一下,由Tatum和我于1940年开始研究链孢霉的背景,看来是合适的。我将留给我的共同获奖者去仔细叙述,在链孢霉中我们初次成功之后的发展情况,及其对细菌遗传学兴起的关系。细菌遗传学的兴起,主要是由于继接合作用和转导作用之后,遗传重组的研究。展开更多
Objective: To evaluate the efficacy of Cotrel-Dubeusset （CD） instrumentation combined with translaminar facet joint screw （TLS） in the treatment of thoracolumbar fracture.Methods: A total of six L2-L4 spines were ...Objective: To evaluate the efficacy of Cotrel-Dubeusset （CD） instrumentation combined with translaminar facet joint screw （TLS） in the treatment of thoracolumbar fracture.Methods: A total of six L2-L4 spines were used to establish unstable fracture model with three-dimensional range of motion （ROM） of the spines measured. Fixation with CD and fixation with CD combined with translaminar facet joint screw were achieved to compare their stability. Thirty cases of thoracolumbar fracture, in whom the anterior edge of vertebral body was compressed to 59% and the posterior edge compressed to 88%, were treated by pedicle screw fixation combined with TLS. Among them, 19 received posterolateral or anterior-posterior bone graftingResults: There was significant difference in ROM between the two techniques except that in extension. In Group CD+TLS, ROM was （5.38）% lower, lateral bending （4.91）% lower and axial rotation （11.85）% lower than those in Group CD respectively. In the clinical group, the average anterior edge restored to 97% and posterior edge to 98%. The duration of follow-up was 5-24 months （mean, 10 months）. The rate of correction loss on the anterior edge was （4.5）%. Among the 19 cases of bone grafting, all of them achieved bony fusion （mean fusion time, （4.3） month） with a correction loss rate of （3.4）%.Conclusions: In the treatment of thoracolumbar fracture, pedicle screw fixation combined with TLS can strengthen the stability of pedicle screws, especially anti-rotation stability and enhance fusion rate and reduce correction loss.展开更多
Molecular docking is an important tool in screening large libraries of compounds to determine the interactions between potential drugs and the target proteins. The molec- ular docking problem is how to locate a good c...Molecular docking is an important tool in screening large libraries of compounds to determine the interactions between potential drugs and the target proteins. The molec- ular docking problem is how to locate a good conformation to dock a ligand to the large molecule. It can be formulated as a parameter optimization problem consisting of a scoring function and a global optimization method. Many docking methods have been developed with primarily these two parts varying. In this paper, a variety of particle swarm optimization （PSO） variants were introduced to cooperate with the semiempir- ical free energy force field in AutoDock 4.05. The search ability and the docking accu- racy of these methods were evaluated by multiple redocking experiments. The results demonstrate that PSOs were more suitable than Lamarckian genetic algorithm （LGA）. Among all of the PSO variants, FIPS takes precedence over others. Compared with the four state-of-art docking methods-GOLD, DOCK, FlexX and AutoDock with LGA, AutoDock cooperated with FIPS is more accurate. Thus, FIPS is an efficient PSO vari- ant which has promising prospects that can be expected in the application to virtual screening.展开更多
基金Project(52004154) supported by the National Natural Science Foundation of ChinaProject(ZR2020QE002) supported by the Shandong Provincial Natural Science Foundation,ChinaProject(6142005190208) supported by the National Key Laboratory Foundation of China。
文摘This work aims to establish a suitable numerical simulation model for hybrid laser-electric arc heat source welding of dissimilar Mg alloys between AZ31 and AZ80. Based on the energy conservation law and Fourier’s law of heat conduction, the differential equations of the three-dimensional temperature field for nonlinear transient heat conduction are built. According to the analysis of nonlinear transient heat transfer, the equations representing initial conditions and boundary conditions are obtained. The “double ellipsoidal heat source + 3D Gaussian heat source”combination was chosen to construct the laser-electric arc hybrid heat source. The weld bead morphologies and the distribution of temperature, stress, displacement and plastic strains are numerically simulated. The actual welding experiments were performed by a hybrid laser-electric arc welding machine. The interaction mechanism between laser and electric arc in the hybrid welding of Mg alloys is discussed in detail. The hybrid heat source can promote the absorption of laser energy and electric arc in the molten pool, resulting in more uniform energy distribution in the molten pool and the corresponding improvement of welding parameters. This work can provide theoretical guidance and data supports for the optimization of the hybrid laser-electric arc welding processes for Mg alloys.
基金Project(90205035) supported by the National Natural Science Foundation of China
文摘Based on the simulated aerospace thermal cycling tests,the effect of thermal cycle on the void damage evolution mechanism of LF6 aluminum alloy welded joint was investigated.The results show that micro-voids form around the second phase particles under the thermal cycling tests.The thermal stress coupled with external stress leads to dislocations pile-up around the particles,and when the dislocation density reaches a certain degree,the stress concentration will exceed the bonding strength at the interface between particles and matrix,resulting in the formation of micro-cracks.The numerical simulation is successfully implemented with the finite element to describe the void damage evolution of the welded joint under thermal cycling conditions.
基金supported by National Science Foundation of China under Grant Nos.10974236 and 11074174
文摘We theoretically investigate a device consisting of two quantum dots （QDs） side-coupled to a quantum wire which has many physical ingredients of an artificial heavy fermion system. An extra parameter, the distance L between the two QDs, is introduced and it plays an important role on the competition of the Kondo temperature and magnetic coupling. Three different phases are found： antiferromagnetic phase, Kondo phase with spin S = 1/2, and Kondo phase with S = 1, depending on the distance L, the magnetic properties are qualitatively different for different phases： conductance tends to the unitary value 2e2 /h; for the S ： the distance. coupling, and the Kondo temperature. Quantum transport for the S = 1 Kondo and the antiferromagnetic phases, the 1/2 Kondo phase the conductance is strongly dependent onthe distance.
文摘This paper proposes a joint network-channel codingbased on turbo codes for user cooperation. The scenario under consideration is one in which two ＂partners＂--UE1 and UE2---cooperate in transmitting information to the base station （BS）. Each partner transmits both locally generated information and the relayed information that originated at the other partner. The local information and relayed information are jointly network-channel coded to form a superimposed codeword, and the adjacent codewords transmitted in turn by the two partners are tightly correlative like a chain. It is shown via simulation that the proposed scheme achieves full diversity gain compared with the other user cooperation schemes, including those based on coded cooperation and distributed space-time coded cooperation.
文摘This paper presents a study of the relationship between the magnetic properties and microstructure of nanocomposite Ni/MnO, Ni/CoO, Co/MnO, Co/CoO. The objective is to understand how the coupling interface FM/AFM （ferromagnetic/anti-ferromagnetic） manifests itself in magnetic response of these materials to an applied field. Sample preparation was performed using mechanochemical synthesis by means of a ball mill planetary type high power at normal atmosphere. The characterization was done by XRD （X-ray diffraction）, SEM （scanning electron microscopy） and VSM （vibrating sample magnetometry）. Analyzing the XRD peaks of the samples studied, there was a decrease in the average particle diameter with increasing milling time, which is important in the magnetic interactions of the atoms of the surface. In addition, the diffraction pattern showed formation of new phases by oxidation interfering with the magnetic measurements. Analyses by SEM show chipboard multiform nano- and micrometer-sized grains on the surface of the clusters being responsible for the interaction. The magnetic measurements show a strong coupling between the phases present in nanocomposites showing once again that the MS （mechanosynthesis） is a powerful technique for this kind of purpose. The effect of the decrease in crystallite size leads to large variations of magnetic properties of the material which have been specifically observed changes in HC （coercive field） in the RM （remanent magnetization） and SM （saturation magnetization）. The decrease in crystallite size in the course of grinding intensifies the effects that depend on the surface-to-volume ratio of the material. M vs. T measures were taken for different values of applied field and found a jump in the moment of the sample near the N6el temperature of the antiferromagnetic.
文摘This paper presents the results of the search of biologically active uranium compounds such as amino acids. We first received and examined X-ray and IR （infrared radiation） spectroscopy of uranium complexes with α- and β-amino acids in aqueous and organic solution. We proposed a method for direct synthesis of complex organic compounds of uranium chloride UO2Cl2 with α- andβ-amino acids for the synthesis of drugs for the treatment of cancer.
文摘当我与Edward L. Tatum由于我们的“……基因靠调节化学事件而起作用的发现”并与Joshua Lederberg由于他的“……关于细菌遗传物质构成的发现,”一起分享诺贝尔奖金崇高荣誉的机会,我简要描述一下,由Tatum和我于1940年开始研究链孢霉的背景,看来是合适的。我将留给我的共同获奖者去仔细叙述,在链孢霉中我们初次成功之后的发展情况,及其对细菌遗传学兴起的关系。细菌遗传学的兴起,主要是由于继接合作用和转导作用之后,遗传重组的研究。
文摘Objective: To evaluate the efficacy of Cotrel-Dubeusset （CD） instrumentation combined with translaminar facet joint screw （TLS） in the treatment of thoracolumbar fracture.Methods: A total of six L2-L4 spines were used to establish unstable fracture model with three-dimensional range of motion （ROM） of the spines measured. Fixation with CD and fixation with CD combined with translaminar facet joint screw were achieved to compare their stability. Thirty cases of thoracolumbar fracture, in whom the anterior edge of vertebral body was compressed to 59% and the posterior edge compressed to 88%, were treated by pedicle screw fixation combined with TLS. Among them, 19 received posterolateral or anterior-posterior bone graftingResults: There was significant difference in ROM between the two techniques except that in extension. In Group CD+TLS, ROM was （5.38）% lower, lateral bending （4.91）% lower and axial rotation （11.85）% lower than those in Group CD respectively. In the clinical group, the average anterior edge restored to 97% and posterior edge to 98%. The duration of follow-up was 5-24 months （mean, 10 months）. The rate of correction loss on the anterior edge was （4.5）%. Among the 19 cases of bone grafting, all of them achieved bony fusion （mean fusion time, （4.3） month） with a correction loss rate of （3.4）%.Conclusions: In the treatment of thoracolumbar fracture, pedicle screw fixation combined with TLS can strengthen the stability of pedicle screws, especially anti-rotation stability and enhance fusion rate and reduce correction loss.
基金This work was under Grand by the Natural Science Foundation of China （No. 60803074）, and the Fundamental Research Funds for the Central Universi- ties （No. DUT10JR06）.
文摘Molecular docking is an important tool in screening large libraries of compounds to determine the interactions between potential drugs and the target proteins. The molec- ular docking problem is how to locate a good conformation to dock a ligand to the large molecule. It can be formulated as a parameter optimization problem consisting of a scoring function and a global optimization method. Many docking methods have been developed with primarily these two parts varying. In this paper, a variety of particle swarm optimization （PSO） variants were introduced to cooperate with the semiempir- ical free energy force field in AutoDock 4.05. The search ability and the docking accu- racy of these methods were evaluated by multiple redocking experiments. The results demonstrate that PSOs were more suitable than Lamarckian genetic algorithm （LGA）. Among all of the PSO variants, FIPS takes precedence over others. Compared with the four state-of-art docking methods-GOLD, DOCK, FlexX and AutoDock with LGA, AutoDock cooperated with FIPS is more accurate. Thus, FIPS is an efficient PSO vari- ant which has promising prospects that can be expected in the application to virtual screening.
