The surface carbonitriding of cast iron is investigated in an aqueous solution of acetamide and glycerin. Microstructure, chemical and phase composition and corrosion performance of the carbonitriding layers are inves...The surface carbonitriding of cast iron is investigated in an aqueous solution of acetamide and glycerin. Microstructure, chemical and phase composition and corrosion performance of the carbonitriding layers are investigated by scanning electron microscopy, energy dispersive spectroscopy and x-ray diffraction, as well as potentiodynamic polarization testing. X-ray diffraction results show that the carbonitriding coatings are composed of martensite, anstenite(γ-Fe), Fe2C, Fe3C, Fe5 C2, FeN and ε-Fe2-3N. After the plasma electrolytic carbonitriding treatment the corrosion resistance of cast iron is clearly improved compared to the substrate, and the coatings produced at 350 V for 30s give the best corrosion resistance.展开更多
The plasma electrolytic carbonitriding(PEC/N)process is applied to cast iron using an aqueous solution of acetamide and glycerin as the electrolyte.Mechanical properties of the carbonitriding layers on cast iron are i...The plasma electrolytic carbonitriding(PEC/N)process is applied to cast iron using an aqueous solution of acetamide and glycerin as the electrolyte.Mechanical properties of the carbonitriding layers on cast iron are investigated.After the PEC/N treatment,the microhardness and wear resistance of cast iron are improved significantly compared to the untreated substrate.When the substrate is processed at 350V for 60 s,the coating presents the highest microhardness and it is about 554.14HK0.02,and the coating with the highest hardness has the best wear resistance.展开更多
Ceramic coatings are synthesized on AZ31 magnesium alloy in alkaline silicate solution by the method of plasma electrolytic oxidation. The effect of two different duty cycles (10% and 50%) on the structure and corro...Ceramic coatings are synthesized on AZ31 magnesium alloy in alkaline silicate solution by the method of plasma electrolytic oxidation. The effect of two different duty cycles (10% and 50%) on the structure and corrosive properties of the coatings is investigated. It is found that the coatings are mainly composed of MgO, Mg2SiO4 and MgF2 through XRD analysis. SEM images indicate that coatings formed at 50% duty cycle have a relatively coarse surface with larger pore size and fewer pores, and have a slower growth rate than those formed at 10% duty cycle with the same treatment time. However, the results of potentiodynamic polarization tests demonstrate that coatings formed at 50% duty cycle exhibit better corrosion resistance as a result of more compact microstructure.展开更多
A new process and technology of rapid prototyping for a μ-micro motor is presented as a nontraditional machining and an advanced manufacturing technology (AMT) to be realized by using masks, including the operation p...A new process and technology of rapid prototyping for a μ-micro motor is presented as a nontraditional machining and an advanced manufacturing technology (AMT) to be realized by using masks, including the operation principle of the motor, structure design, technique, driven circuit, and quality examination with Raman spectrum. The μ-micro motor is fabricated by the micro electro-mechanical systems (MEMS) process, the structure design must be considered to fabricate or assembly the parts during machining the motor in the meantime. The research proved that integration of IC (integrated circuit) process and MEMS using masks is effective in obtaining the rapid prototyping manufacturing of the μ-micro motor. With the mature technique to fabricate the motor, there are advantages to produce the motor in short time and with lower cost than before. The motor is a common power source of micro machines in military and civilian applications, for example, applied to micro robot, micro bio medicine, and micro machine. The size of the motor is 190 μm in maximum diameter by 125 μm in height that is bulk machined in array with the number of hundreds of micro motors on a substrate.展开更多
We study the Andreev reflection(AR)at the interface of the topological insulator with hexagonal warping and superconductor junction.Due to the hexagonal warping effect,the double ARs are found in a certain range of th...We study the Andreev reflection(AR)at the interface of the topological insulator with hexagonal warping and superconductor junction.Due to the hexagonal warping effect,the double ARs are found in a certain range of the incident angle,where for one incident electron beam,two beams of holes are reflected back.Interestingly,both the beams of holes are reflected as retro-AR on the same side of the normal line of the interface but with different reflection angles,different from the previously reported double AR with one retro-AR and one specular-AR.The double reflections owing to the warping effect show the optics-like property of the Dirac fermion and can stimulate the double reflections of light in anisotropic crystals.In addition,we find that the double ARs are dependent on the hexagonal warping parameter nonmonotonically,and in an intermediate strength the double AR phenomenon is prominent,providing a possibility to explore the warping parameter of topological insulators.展开更多
A design of broadband dual-polarized antenna with low cross polarization and high isolation was presented. The antenna is composed of a cross dipole, a folded ground, two feeding networks, and a reflector. The impedan...A design of broadband dual-polarized antenna with low cross polarization and high isolation was presented. The antenna is composed of a cross dipole, a folded ground, two feeding networks, and a reflector. The impedance bandwidth was enhanced by utilizing the mutual coupling between the two dipoles. A kind of meandering folded Marchand balun was skillfully integrated on the support column of the antenna to excite the dipole differentially, which can deliver both balanced (within 0.5 dB) power splitting and consistent (±5°) phase shifting from 1.71 GHz to 2.17 GHz. The standing wave ratios (SWRs) of each port are less than 1.5. By using this feeding network, the antenna has good performance in isolation (〉 45 dB) and cross polarization (〉 30 dB) over the entire operating frequency band. Moreover, the gain (-8.6 dB) of the proposed antenna is stable with frequency and the antenna structure is very firm due to the support column. The proposed antenna can be easily formed an array for digital cellular system (DCS), personal communications service (PCS) and 3rd generation (3G) applications.展开更多
This paper considers a discrete-time Geo/G/1 queue under the Min(N,D)-policy in which the idle server resumes its service if either N customers accumulate in the system or the total backlog of the service times of the...This paper considers a discrete-time Geo/G/1 queue under the Min(N,D)-policy in which the idle server resumes its service if either N customers accumulate in the system or the total backlog of the service times of the waiting customers exceeds D,whichever occurs first(Min(N,D)-policy).By using renewal process theory and total probability decomposition technique,the authors study the transient and equilibrium properties of the queue length from the beginning of the arbitrary initial state,and obtain both the recursive expression of the z-transformation of the transient queue length distribution and the recursive formula for calculating the steady state queue length at arbitrary time epoch n^+.Meanwhile,the authors obtain the explicit expressions of the additional queue length distribution.Furthermore,the important relations between the steady state queue length distributions at different time epochs n^-,n and n^+ are also reported.Finally,the authors give numerical examples to illustrate the effect of system parameters on the steady state queue length distribution,and also show from numerical results that the expressions of the steady state queue length distribution is important in the system capacity design.展开更多
Owing to their high performance and earth abundance,copper sulfides(Cu_(2-x)S)have attracted wide attention as a promising medium-temperature thermoelectric material.Nanostructure and grain-boundary engineering are ex...Owing to their high performance and earth abundance,copper sulfides(Cu_(2-x)S)have attracted wide attention as a promising medium-temperature thermoelectric material.Nanostructure and grain-boundary engineering are explored to tune the electrical transport and phonon scattering of Cu_(2-x)S based on the liquid-like copper ion.Here multiscale architecture-engineered Cu_(2-x)S are fabricated by a room-temperature wet chemical synthesis combining mechanical mixing and spark plasma sintering.The observed electrical conductivity in the multiscale architecture-engineered Cu_(2-x)S is four times as much as that of the Cu_(2-x)S sample at 800 K,which is attributed to the potential energy filtering effect at the new grain boundaries.Moreover,the multiscale architecture in the sintered Cu_(2-x)S increases phonon scattering and results in a reduced lattice thermal conductivity of 0.2 W·m^(-1)·K^(-1) and figure of merit(zT)of 1.0 at 800 K.Such a zT value is one of the record values in copper sulfide produced by chemical synthesis.These results suggest that the introduction of nanostructure and formation of new interface are effective strategies for the enhancement of thermoelectric material properties.展开更多
The principle of optical eigenfunction is used in the analysis of speckle reduction in laser projection display.When the moving diffiuser is used in the speckle reduction approach,the speckle contrast is decided by bo...The principle of optical eigenfunction is used in the analysis of speckle reduction in laser projection display.When the moving diffiuser is used in the speckle reduction approach,the speckle contrast is decided by both the degree of freedom (DOF) of the projector and the area of resolving cell of the eyes on the screen.It can gain high DOF of the projector by increasing the space-bandwidth product,i.e.,adopting a projection lens with a high numerical aperture or a large viewing field.The best scheme is equalizing the DOF of the scattering wave from a moving diffiuser to that of the projection lens.The experimental results are in accordance with the conclusion drawn by optical eigenfunction.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 10675165, and the Project of International Cooperation and Exchanges NSFC-KOSEF (No 10811140326).
文摘The surface carbonitriding of cast iron is investigated in an aqueous solution of acetamide and glycerin. Microstructure, chemical and phase composition and corrosion performance of the carbonitriding layers are investigated by scanning electron microscopy, energy dispersive spectroscopy and x-ray diffraction, as well as potentiodynamic polarization testing. X-ray diffraction results show that the carbonitriding coatings are composed of martensite, anstenite(γ-Fe), Fe2C, Fe3C, Fe5 C2, FeN and ε-Fe2-3N. After the plasma electrolytic carbonitriding treatment the corrosion resistance of cast iron is clearly improved compared to the substrate, and the coatings produced at 350 V for 30s give the best corrosion resistance.
基金by the National Natural Science Foundation of China under Grant Nos 10735090 and 11005151(Young Scientists Fund).
文摘The plasma electrolytic carbonitriding(PEC/N)process is applied to cast iron using an aqueous solution of acetamide and glycerin as the electrolyte.Mechanical properties of the carbonitriding layers on cast iron are investigated.After the PEC/N treatment,the microhardness and wear resistance of cast iron are improved significantly compared to the untreated substrate.When the substrate is processed at 350V for 60 s,the coating presents the highest microhardness and it is about 554.14HK0.02,and the coating with the highest hardness has the best wear resistance.
基金Supported by the National Natural Science Foundation of China under Grant No 10675165, and the Joint Project of NSFC- KOSEF under Grant No 10811140326.
文摘Ceramic coatings are synthesized on AZ31 magnesium alloy in alkaline silicate solution by the method of plasma electrolytic oxidation. The effect of two different duty cycles (10% and 50%) on the structure and corrosive properties of the coatings is investigated. It is found that the coatings are mainly composed of MgO, Mg2SiO4 and MgF2 through XRD analysis. SEM images indicate that coatings formed at 50% duty cycle have a relatively coarse surface with larger pore size and fewer pores, and have a slower growth rate than those formed at 10% duty cycle with the same treatment time. However, the results of potentiodynamic polarization tests demonstrate that coatings formed at 50% duty cycle exhibit better corrosion resistance as a result of more compact microstructure.
基金Supported by Foundation of Department of Mechanical and Electrical Engineering of Xiamen University (No. Y03001)
文摘A new process and technology of rapid prototyping for a μ-micro motor is presented as a nontraditional machining and an advanced manufacturing technology (AMT) to be realized by using masks, including the operation principle of the motor, structure design, technique, driven circuit, and quality examination with Raman spectrum. The μ-micro motor is fabricated by the micro electro-mechanical systems (MEMS) process, the structure design must be considered to fabricate or assembly the parts during machining the motor in the meantime. The research proved that integration of IC (integrated circuit) process and MEMS using masks is effective in obtaining the rapid prototyping manufacturing of the μ-micro motor. With the mature technique to fabricate the motor, there are advantages to produce the motor in short time and with lower cost than before. The motor is a common power source of micro machines in military and civilian applications, for example, applied to micro robot, micro bio medicine, and micro machine. The size of the motor is 190 μm in maximum diameter by 125 μm in height that is bulk machined in array with the number of hundreds of micro motors on a substrate.
基金was supported by GDUPS(2017)the National Natural Science Foundation of China(Grant Nos.11874016,11474106,and 11904107)the Key Program for Guangdong NSF of China(Grant No.2017B030311003).
文摘We study the Andreev reflection(AR)at the interface of the topological insulator with hexagonal warping and superconductor junction.Due to the hexagonal warping effect,the double ARs are found in a certain range of the incident angle,where for one incident electron beam,two beams of holes are reflected back.Interestingly,both the beams of holes are reflected as retro-AR on the same side of the normal line of the interface but with different reflection angles,different from the previously reported double AR with one retro-AR and one specular-AR.The double reflections owing to the warping effect show the optics-like property of the Dirac fermion and can stimulate the double reflections of light in anisotropic crystals.In addition,we find that the double ARs are dependent on the hexagonal warping parameter nonmonotonically,and in an intermediate strength the double AR phenomenon is prominent,providing a possibility to explore the warping parameter of topological insulators.
基金supported by the National Natural Science Foundation of China (61301032)
文摘A design of broadband dual-polarized antenna with low cross polarization and high isolation was presented. The antenna is composed of a cross dipole, a folded ground, two feeding networks, and a reflector. The impedance bandwidth was enhanced by utilizing the mutual coupling between the two dipoles. A kind of meandering folded Marchand balun was skillfully integrated on the support column of the antenna to excite the dipole differentially, which can deliver both balanced (within 0.5 dB) power splitting and consistent (±5°) phase shifting from 1.71 GHz to 2.17 GHz. The standing wave ratios (SWRs) of each port are less than 1.5. By using this feeding network, the antenna has good performance in isolation (〉 45 dB) and cross polarization (〉 30 dB) over the entire operating frequency band. Moreover, the gain (-8.6 dB) of the proposed antenna is stable with frequency and the antenna structure is very firm due to the support column. The proposed antenna can be easily formed an array for digital cellular system (DCS), personal communications service (PCS) and 3rd generation (3G) applications.
基金supported by the National Natural Science Foundation of China under Grant Nos.71171138,71301111,71571127the Scientific Research Innovation&Application Foundation of Headmaster of Hexi University under Grant Nos.XZ2013-06,XZ2013-09
文摘This paper considers a discrete-time Geo/G/1 queue under the Min(N,D)-policy in which the idle server resumes its service if either N customers accumulate in the system or the total backlog of the service times of the waiting customers exceeds D,whichever occurs first(Min(N,D)-policy).By using renewal process theory and total probability decomposition technique,the authors study the transient and equilibrium properties of the queue length from the beginning of the arbitrary initial state,and obtain both the recursive expression of the z-transformation of the transient queue length distribution and the recursive formula for calculating the steady state queue length at arbitrary time epoch n^+.Meanwhile,the authors obtain the explicit expressions of the additional queue length distribution.Furthermore,the important relations between the steady state queue length distributions at different time epochs n^-,n and n^+ are also reported.Finally,the authors give numerical examples to illustrate the effect of system parameters on the steady state queue length distribution,and also show from numerical results that the expressions of the steady state queue length distribution is important in the system capacity design.
基金financially supported by the National Natural Science Foundation of China(Nos.51702091 and 51702046)the College Outstanding Young Scientific and Technological Innovation Team of Hubei province(No.T201922)+2 种基金the Special Funding of Preventing the Spread of COVID-19,Hubei University of Education(No.20XGZX20)Fok Ying-Tong Education Foundation of China(No.171041)the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning,State Key Laboratory for Modification of Chemical Fibers and Polymer Materials,Donghua University。
文摘Owing to their high performance and earth abundance,copper sulfides(Cu_(2-x)S)have attracted wide attention as a promising medium-temperature thermoelectric material.Nanostructure and grain-boundary engineering are explored to tune the electrical transport and phonon scattering of Cu_(2-x)S based on the liquid-like copper ion.Here multiscale architecture-engineered Cu_(2-x)S are fabricated by a room-temperature wet chemical synthesis combining mechanical mixing and spark plasma sintering.The observed electrical conductivity in the multiscale architecture-engineered Cu_(2-x)S is four times as much as that of the Cu_(2-x)S sample at 800 K,which is attributed to the potential energy filtering effect at the new grain boundaries.Moreover,the multiscale architecture in the sintered Cu_(2-x)S increases phonon scattering and results in a reduced lattice thermal conductivity of 0.2 W·m^(-1)·K^(-1) and figure of merit(zT)of 1.0 at 800 K.Such a zT value is one of the record values in copper sulfide produced by chemical synthesis.These results suggest that the introduction of nanostructure and formation of new interface are effective strategies for the enhancement of thermoelectric material properties.
基金supported by the Region Major Program of Fujian Province Natural Science Foundation of China (No.2009H4003)the Natural Science Foundation of Fujian Province of China (Nos.2009J01277 and 2010J01325)
文摘The principle of optical eigenfunction is used in the analysis of speckle reduction in laser projection display.When the moving diffiuser is used in the speckle reduction approach,the speckle contrast is decided by both the degree of freedom (DOF) of the projector and the area of resolving cell of the eyes on the screen.It can gain high DOF of the projector by increasing the space-bandwidth product,i.e.,adopting a projection lens with a high numerical aperture or a large viewing field.The best scheme is equalizing the DOF of the scattering wave from a moving diffiuser to that of the projection lens.The experimental results are in accordance with the conclusion drawn by optical eigenfunction.