The existing research of the flow behavior in emitter micro-channels mainly focuses on the single-phase flow behavior.And the recent micro-particle image velocimetry（PIV） experimental research on the flow characteri...The existing research of the flow behavior in emitter micro-channels mainly focuses on the single-phase flow behavior.And the recent micro-particle image velocimetry（PIV） experimental research on the flow characteristics in various micro-channels mainly focuses on the single-phase fluid flow.However,using an original-size emitter prototype to perform the experiments on the two-phase flow characteristics of the labyrinth channels is seldom reported.In this paper,the practical flow of water,mixed with sand escaped from filtering,in the labyrinth channel,is investigated.And some research work on the clogging mechanism of the labyrinth channel＇s structure is conducted.Computational fluid dynamics（CFD） analysis has been performed on liquid-solid two-phase flow in labyrinth-channel emitters.Based on flow visualization technology-micro-PIV,the flow in labyrinth channel has been photographed and recorded.The path line graph and velocity vector graph are obtained through the post-treatment of experimental results.The graphs agree well with CFD analysis results,so CFD analysis can be used in optimal design of labyrinth-channel emitters.And the optimized anti-clogging structures of the rectangular channel and zigzag channel have been designed here.The CFD numerical simulation and the micro-PIV experiments analysis on labyrinth-channel emitter,make the ＂black box＂ of the flow behavior in the emitter channel broken.Furthermore,the proposed research promotes an advanced method to evaluate the emitter＇s performance and can be used to conducting the optimal design of the labyrinth-channel emitters.展开更多
In this article, the UDF technology in Fluent software is used to simulate three-dimensional flow fields and to obtain various flow parameters. The standard k -ε model and the RNG k -ε model are both used to calcula...In this article, the UDF technology in Fluent software is used to simulate three-dimensional flow fields and to obtain various flow parameters. The standard k -ε model and the RNG k -ε model are both used to calculate the inner flow field of the basal meter, and a comparison of the calculated results between two models shows that RNG k - ε model is more effective for calculations of the inner flow of rotary wing mechanism. The influence of tip clearance on the characteristics of the basal meter is studied. The influence of the bottom ribs on the heat meter is evaluated by the numerical simulation method. This article also simulates the flow of disturbance located at the inlet of the basal meter, and shows that a swirl located at the front of the basal meter can affect the stability of the heat meter.展开更多
A higher quality of service （QoS） is provided for ad hoc networks through a multi-channel and slotted random multi-access （MSRM） protocol with two-dimensional probability. For this protocol, the system time is slo...A higher quality of service （QoS） is provided for ad hoc networks through a multi-channel and slotted random multi-access （MSRM） protocol with two-dimensional probability. For this protocol, the system time is slotted into a time slot with high channel utilization realized by the choice of two parameters p1 and p2, and the channel load equilibrium. The protocol analyzes the throughput of the MSRM protocol for a load equilibrium state and the throughput based on priority. Simulations agree with the theoretical analysis. The simulations also show that the slotted-time system is better than the continuous-time system.展开更多
Rock is generally complex and heterogeneous,therefore the heterogeneity effects of effective stress and temperature on permeability should be taken into account.In this study,two-part Hooke’s model（TPHM） is introdu...Rock is generally complex and heterogeneous,therefore the heterogeneity effects of effective stress and temperature on permeability should be taken into account.In this study,two-part Hooke’s model（TPHM） is introduced to understand the influences of effective stress and temperature on permeability of soft and hard parts（two parts） of rock based on coupling thermo-hydro-mechanical tests.Under a fixed temperature level（25 ℃.35 ℃.50 ℃.65 ℃.80 ℃.90 ℃ and 95 ℃）.the tests were carried out in a conventional triaxial system whereas the confining pressure was remained at 50 MPa.and the pore pressure was increased to the specified levels step by step.i.e.8 MPa,18 MPa.28 MPa.38 MPa.41 MPa,44 MPa.46 MPa and 48 MPa.The temperature-dependent relationships for two parts permeabilities are proposed on the basis of the initial test results.We point out that temperature of 65 ℃-90 ℃ is the threshold for the development of CO2-plume geothermal（CPC） reservoir sandstone cracking under low effective stress（2-9 MPa） based on the relationship between temperature and soft part permeability.Furthermore,we discuss the effect of temperature on the two parts in the rock.The results indicate that as the temperature increases from 25 ℃ to 65 ℃.the flow channel in the hard part has a stronger response to temperature than that in the soft part at a fixed effective stress level,which is opposite to the situation of effective stress.Considering that natural rock is generally heterogeneous with non-uniform pore structure,we suggest a physical interpretation of the phenomenon that before the thermal cracking threshold the two parts have different responses to temperature.展开更多
To guide the illuminating design to improve the on-state performances of gallium arsenide(GaAs)photoconductive semiconductor switch(PCSS),the effect of spot size on the operation mode of GaAsPCSS based on a semi-insul...To guide the illuminating design to improve the on-state performances of gallium arsenide(GaAs)photoconductive semiconductor switch(PCSS),the effect of spot size on the operation mode of GaAsPCSS based on a semi-insulating wafer with a thickness of 1 mm,triggered by a 1064-nm extrinsic laser beam with the rectangular spot,has been investigated experimentally.It is found that the variation of the spot size in length and width can act on the different parts of the output waveform integrating the characteristics of the linear and nonlinear modes,and then significantly boosts the PCSS toward different operation modes.On this basis,a two-channel model containing the active and passive parts is introduced to interpret the relevant influencing mechanisms.Results indicate that the increased spot length can peak the amplitude of static domains in the active part to enhance the development of the nonlinear switching,while the extended spot width can change the distribution of photogenerated carriers on both parts to facilitate the linear switching and weaken the nonlinear switching,which have been proved by comparing the domain evolutions under different spot sizes.展开更多
Synthesis of ultra-wideband （UWB） linear frequency modulation radar signals is a very important technology for microwave imaging, target identification and detection of low radar-cross-section （RCS） targets. A new...Synthesis of ultra-wideband （UWB） linear frequency modulation radar signals is a very important technology for microwave imaging, target identification and detection of low radar-cross-section （RCS） targets. A new method of UWB radar signals generation with two-channel signal generator is presented. The realization structure is given; the principle and errors of signal synthesis are analyzed. At the same time, an automatic .adjustment measure of signal phase is proposed because of phase discontinuity of waveform in this method. The simulation experiment and analysis results indicate that radar signals with large instantaneous bandwidth can be generated by means of this method on the condition that the high-speed digital devices are limited.展开更多
Overcoming the sub-5 nm gate length limit and decreasing the power dissipation are two main objects in the electronics research field. Besides advanced engineering techniques, considering new material systems may be h...Overcoming the sub-5 nm gate length limit and decreasing the power dissipation are two main objects in the electronics research field. Besides advanced engineering techniques, considering new material systems may be helpful. Here, we demonstrate two-dimensional(2D) subthermionic field-effect transistors(FETs) with sub-5 nm gate lengths based on ferroelectric(FE) van der Waals heterostructures(vdWHs).The FE vd WHs are composed of graphene, MoS2, and CuInP2S6 acting as 2D contacts, channels, and ferroelectric dielectric layers, respectively. We first show that the as-fabricated long-channel device exhibits nearly hysteresis-free subthermionic switching over three orders of magnitude of drain current at room temperature. Further, we fabricate short-channel subthermionic FETs using metallic carbon nanotubes as effective gate terminals. A typical device shows subthermionic switching over five-to-six orders of magnitude of drain current with a minimum subthreshold swing of 6.1 mV/dec at room temperature. Our results indicate that 2D materials system is promising for advanced highly-integrated energy-efficient electronic devices.展开更多
Photodetectors based on two-dimensional(2D)semiconductors have attracted many research interests owing to their excellent optoelectronic characteristics and application potential for highly integrated applications.How...Photodetectors based on two-dimensional(2D)semiconductors have attracted many research interests owing to their excellent optoelectronic characteristics and application potential for highly integrated applications.However,the unique morphology of 2D materials also restricts the further improvement of the device performance,as the carrier transport is very susceptible to intrinsic and extrinsic environment of the materials.Here,we report the highest responsivity(172 A/W)achieved so far for a PbI_(2)-based photodetector at room temperature,which is an order of magnitude higher than previously reported.Thermal scanning probe lithography(t-SPL)was used to pattern electrodes to realize the ultrashort channel(~60 nm)in the devices.The shortening of the channel length greatly reduces the probability of the photo-generated carriers being scattered during the transport process,which increases the photocurrent density and thus the responsivity.Our work shows that the combination of emerging processing technologies and 2D materials is an effective route to shrink device size and improve device performance.展开更多
基金supported by National Natural Science Foundation of China (Grant Nos. 50675172,50975227)Foundation for the Author of National Excellent Doctoral Dissertation of China (Grant No.FANEDD200740)National Hi-tech Research and Development of China (863 Program,Grant No. 2011AA100507-04)
文摘The existing research of the flow behavior in emitter micro-channels mainly focuses on the single-phase flow behavior.And the recent micro-particle image velocimetry（PIV） experimental research on the flow characteristics in various micro-channels mainly focuses on the single-phase fluid flow.However,using an original-size emitter prototype to perform the experiments on the two-phase flow characteristics of the labyrinth channels is seldom reported.In this paper,the practical flow of water,mixed with sand escaped from filtering,in the labyrinth channel,is investigated.And some research work on the clogging mechanism of the labyrinth channel＇s structure is conducted.Computational fluid dynamics（CFD） analysis has been performed on liquid-solid two-phase flow in labyrinth-channel emitters.Based on flow visualization technology-micro-PIV,the flow in labyrinth channel has been photographed and recorded.The path line graph and velocity vector graph are obtained through the post-treatment of experimental results.The graphs agree well with CFD analysis results,so CFD analysis can be used in optimal design of labyrinth-channel emitters.And the optimized anti-clogging structures of the rectangular channel and zigzag channel have been designed here.The CFD numerical simulation and the micro-PIV experiments analysis on labyrinth-channel emitter,make the ＂black box＂ of the flow behavior in the emitter channel broken.Furthermore,the proposed research promotes an advanced method to evaluate the emitter＇s performance and can be used to conducting the optimal design of the labyrinth-channel emitters.
文摘In this article, the UDF technology in Fluent software is used to simulate three-dimensional flow fields and to obtain various flow parameters. The standard k -ε model and the RNG k -ε model are both used to calculate the inner flow field of the basal meter, and a comparison of the calculated results between two models shows that RNG k - ε model is more effective for calculations of the inner flow of rotary wing mechanism. The influence of tip clearance on the characteristics of the basal meter is studied. The influence of the bottom ribs on the heat meter is evaluated by the numerical simulation method. This article also simulates the flow of disturbance located at the inlet of the basal meter, and shows that a swirl located at the front of the basal meter can affect the stability of the heat meter.
基金Supported by the National Natural Science Foundation of China(Nos. 60362001 and F0424104)the Natural Science Foundationof Yunnan Province (No. 2004F0011R)
文摘A higher quality of service （QoS） is provided for ad hoc networks through a multi-channel and slotted random multi-access （MSRM） protocol with two-dimensional probability. For this protocol, the system time is slotted into a time slot with high channel utilization realized by the choice of two parameters p1 and p2, and the channel load equilibrium. The protocol analyzes the throughput of the MSRM protocol for a load equilibrium state and the throughput based on priority. Simulations agree with the theoretical analysis. The simulations also show that the slotted-time system is better than the continuous-time system.
基金financially supported by the International Science&Technology Cooperation Program of China(Grant No.2012DFA60760)
文摘Rock is generally complex and heterogeneous,therefore the heterogeneity effects of effective stress and temperature on permeability should be taken into account.In this study,two-part Hooke’s model（TPHM） is introduced to understand the influences of effective stress and temperature on permeability of soft and hard parts（two parts） of rock based on coupling thermo-hydro-mechanical tests.Under a fixed temperature level（25 ℃.35 ℃.50 ℃.65 ℃.80 ℃.90 ℃ and 95 ℃）.the tests were carried out in a conventional triaxial system whereas the confining pressure was remained at 50 MPa.and the pore pressure was increased to the specified levels step by step.i.e.8 MPa,18 MPa.28 MPa.38 MPa.41 MPa,44 MPa.46 MPa and 48 MPa.The temperature-dependent relationships for two parts permeabilities are proposed on the basis of the initial test results.We point out that temperature of 65 ℃-90 ℃ is the threshold for the development of CO2-plume geothermal（CPC） reservoir sandstone cracking under low effective stress（2-9 MPa） based on the relationship between temperature and soft part permeability.Furthermore,we discuss the effect of temperature on the two parts in the rock.The results indicate that as the temperature increases from 25 ℃ to 65 ℃.the flow channel in the hard part has a stronger response to temperature than that in the soft part at a fixed effective stress level,which is opposite to the situation of effective stress.Considering that natural rock is generally heterogeneous with non-uniform pore structure,we suggest a physical interpretation of the phenomenon that before the thermal cracking threshold the two parts have different responses to temperature.
基金supported in part by the Huxiang Youth Talent Support Program(No.2020RC3030)in part by the Foundation of State Key Laboratory of Pulsed Power Laser Technology(Nos.SKL2021ZR02 and SKL2021KF05)。
文摘To guide the illuminating design to improve the on-state performances of gallium arsenide(GaAs)photoconductive semiconductor switch(PCSS),the effect of spot size on the operation mode of GaAsPCSS based on a semi-insulating wafer with a thickness of 1 mm,triggered by a 1064-nm extrinsic laser beam with the rectangular spot,has been investigated experimentally.It is found that the variation of the spot size in length and width can act on the different parts of the output waveform integrating the characteristics of the linear and nonlinear modes,and then significantly boosts the PCSS toward different operation modes.On this basis,a two-channel model containing the active and passive parts is introduced to interpret the relevant influencing mechanisms.Results indicate that the increased spot length can peak the amplitude of static domains in the active part to enhance the development of the nonlinear switching,while the extended spot width can change the distribution of photogenerated carriers on both parts to facilitate the linear switching and weaken the nonlinear switching,which have been proved by comparing the domain evolutions under different spot sizes.
文摘Synthesis of ultra-wideband （UWB） linear frequency modulation radar signals is a very important technology for microwave imaging, target identification and detection of low radar-cross-section （RCS） targets. A new method of UWB radar signals generation with two-channel signal generator is presented. The realization structure is given; the principle and errors of signal synthesis are analyzed. At the same time, an automatic .adjustment measure of signal phase is proposed because of phase discontinuity of waveform in this method. The simulation experiment and analysis results indicate that radar signals with large instantaneous bandwidth can be generated by means of this method on the condition that the high-speed digital devices are limited.
基金This work was supported by National Key R&D Program of China(2018YFA0703700 and 2016YFA0200700)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB30000000)+2 种基金the National Natural Science Foundation of China(61625401,61851403,11674072,91964203,and 61804146)CAS Key Laboratory of Nanosystem and Hierarchical FabricationThe authors also gratefully acknowledge the support of Youth Innovation Promotion Association CAS.
文摘Overcoming the sub-5 nm gate length limit and decreasing the power dissipation are two main objects in the electronics research field. Besides advanced engineering techniques, considering new material systems may be helpful. Here, we demonstrate two-dimensional(2D) subthermionic field-effect transistors(FETs) with sub-5 nm gate lengths based on ferroelectric(FE) van der Waals heterostructures(vdWHs).The FE vd WHs are composed of graphene, MoS2, and CuInP2S6 acting as 2D contacts, channels, and ferroelectric dielectric layers, respectively. We first show that the as-fabricated long-channel device exhibits nearly hysteresis-free subthermionic switching over three orders of magnitude of drain current at room temperature. Further, we fabricate short-channel subthermionic FETs using metallic carbon nanotubes as effective gate terminals. A typical device shows subthermionic switching over five-to-six orders of magnitude of drain current with a minimum subthreshold swing of 6.1 mV/dec at room temperature. Our results indicate that 2D materials system is promising for advanced highly-integrated energy-efficient electronic devices.
基金supported by the National Key R&D Program of China (Grant Nos.2020YFA0308900 and 2022YFB3602801)the National Natural Science Foundation References of China (Grant No.92064010).
文摘Photodetectors based on two-dimensional(2D)semiconductors have attracted many research interests owing to their excellent optoelectronic characteristics and application potential for highly integrated applications.However,the unique morphology of 2D materials also restricts the further improvement of the device performance,as the carrier transport is very susceptible to intrinsic and extrinsic environment of the materials.Here,we report the highest responsivity(172 A/W)achieved so far for a PbI_(2)-based photodetector at room temperature,which is an order of magnitude higher than previously reported.Thermal scanning probe lithography(t-SPL)was used to pattern electrodes to realize the ultrashort channel(~60 nm)in the devices.The shortening of the channel length greatly reduces the probability of the photo-generated carriers being scattered during the transport process,which increases the photocurrent density and thus the responsivity.Our work shows that the combination of emerging processing technologies and 2D materials is an effective route to shrink device size and improve device performance.
