Research progresses on Cherenkov and transit-time high-power microwave(HPM)sources in National University of Defense Technology(NUDT)of China are presented.The research issues are focused on the following aspects.The ...Research progresses on Cherenkov and transit-time high-power microwave(HPM)sources in National University of Defense Technology(NUDT)of China are presented.The research issues are focused on the following aspects.The pulse-shortening phenomenon in O-type Cerenkov HPM devices is suppressed.The compact coaxial relativistic backward-wave oscillators(RBWOs)at low bands are developed.The power efficiency in M-Type HPM tubes without guiding magnetic field increased.The power capacities and power efficiencies in the triaxial klystron amplifier(TKA)and relativistic transit-time oscillator(TTO)at higher frequencies increased.In experiments,some exciting results were obtained.The X-band source generated 2 GW microwave power with a pulse duration of 110 ns in 30 Hz repetition mode.Both L-and P-band compact RBWOs generated over 2 GW microwave power with a power efficiency of over 30%.There is approximately a 75% decline of the volume compared with that of conventional RBWO under the same power capacity conditions.A 1.755 GHz MILO produced 3.1 GW microwave power with power efficiency of 10.4%.A 9.37 GHz TKA produced the 240 MW microwave power with the gain of 34 dB.A 14.3 GHz TTO produced 1 GW microwave power with power efficiency of 20%.展开更多
In order to reduce the external magnetic field and improve the conversion efficiency of high-power microwave generation devices with low external magnetic field,a novel diode with an embedded soft magnetic and shieldi...In order to reduce the external magnetic field and improve the conversion efficiency of high-power microwave generation devices with low external magnetic field,a novel diode with an embedded soft magnetic and shielding structure is proposed.The soft magnetic material is designed to enhance the local magnetic field in the diode region.Moreover,the diode applies a shielding structure which can reduce the radial electric field.From simulation research,it is found that the emission and transmission quality of the electron beam with low magnetic field is greatly improved when loading this diode.Through simulation research,it is verified that the diode can increase the conversion efficiency of the transit-time oscillator(TTO)from 30%to 36.7%.In our experimental study,under the conditions of a diode voltage of 540 kV and a current of 10.5 kA,the output microwave power is 1.51 GW when loading the novel diode and the microwave frequency is 4.27 GHz when an external guiding magnetic field of 0.3 T is applied.The corresponding conversion efficiency is improved from 20.0%to 26.6%,which is 6.6%higher than that of a device loaded with a conventional diode.Our experiments have verified that this novel diode can effectively improve the conversion efficiency of high-power microwave sources operating with low magnetic field,and contribute to the miniaturization and compactness of high-power microwave devices.展开更多
According to the transit-time difference measurement method,we proposed a design scheme of ultrasonic heat meter based on TDC-GP21.The measurement unit TDC-GP21 mainly completes transit-time measurement and inlet,outl...According to the transit-time difference measurement method,we proposed a design scheme of ultrasonic heat meter based on TDC-GP21.The measurement unit TDC-GP21 mainly completes transit-time measurement and inlet,outlet temperature measurement functions.Control unit and data processing unit based on MSP430F4152 of TI corporation complete functions including peripherals control,data analysis,temperature compensation algorithm,flow pattern compensation algorithm and low power consumption control.The design meets the Town Construction Professional Standard CJ 128-2007,and furthermore,some performances can be improved.展开更多
Transit-time flow technology is considered as a quality of care in bypass surgery especially in off pump revascularization. Transit time flow measurement is a real time, direct, easy and handy tool for assessment qual...Transit-time flow technology is considered as a quality of care in bypass surgery especially in off pump revascularization. Transit time flow measurement is a real time, direct, easy and handy tool for assessment quality of anastomosis and graft blood flow.展开更多
The C-band three-cavity transit-time effect oscillator (3C TTTO) is a novel high power microwave device based on the transit-time effect of the three-cavity (3C) resonator. The operational principle of this device is ...The C-band three-cavity transit-time effect oscillator (3C TTTO) is a novel high power microwave device based on the transit-time effect of the three-cavity (3C) resonator. The operational principle of this device is briefly expounded in this paper, and the theoretical and experimental researches on the radial insulation diode, the 3C resonator, the double-gap output cavity and the circular waveguide bevel cut radiation antenna are presented in detail. By using the analytic method, the eigen modes and their field distributions of the 3C resonator are developed, and some basic laws of the transit-time effect are obtained in non-π mode field of the 3C resonator. At last, the experimental results are given. This device generated RF peak power in excess of 400MW with 15ns FWHM, and its beam-wave power conversion efficiency is about 17%.展开更多
以大理岩为研究对象,从其典型力学——特性脆-延转化特性入手,利用三维快速拉格朗日连续体分析(fast Lagrangian analysis of continua in 3 dimensions,FLAC3D)研究了试样在不同围压三轴试验条件下的全应力-应变曲线,分析了峰值强度、...以大理岩为研究对象,从其典型力学——特性脆-延转化特性入手,利用三维快速拉格朗日连续体分析(fast Lagrangian analysis of continua in 3 dimensions,FLAC3D)研究了试样在不同围压三轴试验条件下的全应力-应变曲线,分析了峰值强度、残余强度及峰后特性,验证了Hoek-Brown强度准则可较为准确地描述大理岩的脆-延转化特性,并对岩石发生破裂扩展的成因及力学机理进行了分析。利用应力腐蚀(stress corrosion,SC)本构模型,分析了某抽水蓄能电站岔洞围岩在历时10 a前后的最大主应力、位移及塑性区分布,并采用塑性区分布等效表征破裂扩展区域,以此验证了时间效应对岩石强度及破裂扩展的影响。针对岩体强度的时效性变化与破裂扩展的时效特征,相关研究成果对于认识地下工程结构的稳定性、指导制定合理的支护措施均具有重要的理论意义和工程价值。展开更多
基金supported by the National Natural Science Funds Fund of China under Grant No.11505288Provincial Natural Science Foundation of Hunanscientific effort project of NUDT.
文摘Research progresses on Cherenkov and transit-time high-power microwave(HPM)sources in National University of Defense Technology(NUDT)of China are presented.The research issues are focused on the following aspects.The pulse-shortening phenomenon in O-type Cerenkov HPM devices is suppressed.The compact coaxial relativistic backward-wave oscillators(RBWOs)at low bands are developed.The power efficiency in M-Type HPM tubes without guiding magnetic field increased.The power capacities and power efficiencies in the triaxial klystron amplifier(TKA)and relativistic transit-time oscillator(TTO)at higher frequencies increased.In experiments,some exciting results were obtained.The X-band source generated 2 GW microwave power with a pulse duration of 110 ns in 30 Hz repetition mode.Both L-and P-band compact RBWOs generated over 2 GW microwave power with a power efficiency of over 30%.There is approximately a 75% decline of the volume compared with that of conventional RBWO under the same power capacity conditions.A 1.755 GHz MILO produced 3.1 GW microwave power with power efficiency of 10.4%.A 9.37 GHz TKA produced the 240 MW microwave power with the gain of 34 dB.A 14.3 GHz TTO produced 1 GW microwave power with power efficiency of 20%.
基金Project supported by the National Natural Science Foundation of China (Grant No. 61701516)
文摘In order to reduce the external magnetic field and improve the conversion efficiency of high-power microwave generation devices with low external magnetic field,a novel diode with an embedded soft magnetic and shielding structure is proposed.The soft magnetic material is designed to enhance the local magnetic field in the diode region.Moreover,the diode applies a shielding structure which can reduce the radial electric field.From simulation research,it is found that the emission and transmission quality of the electron beam with low magnetic field is greatly improved when loading this diode.Through simulation research,it is verified that the diode can increase the conversion efficiency of the transit-time oscillator(TTO)from 30%to 36.7%.In our experimental study,under the conditions of a diode voltage of 540 kV and a current of 10.5 kA,the output microwave power is 1.51 GW when loading the novel diode and the microwave frequency is 4.27 GHz when an external guiding magnetic field of 0.3 T is applied.The corresponding conversion efficiency is improved from 20.0%to 26.6%,which is 6.6%higher than that of a device loaded with a conventional diode.Our experiments have verified that this novel diode can effectively improve the conversion efficiency of high-power microwave sources operating with low magnetic field,and contribute to the miniaturization and compactness of high-power microwave devices.
基金National Natural Science Foundation of China(No.61071087)Natural Science Foundation of Shandong Province(No.ZR2011FM018)
文摘According to the transit-time difference measurement method,we proposed a design scheme of ultrasonic heat meter based on TDC-GP21.The measurement unit TDC-GP21 mainly completes transit-time measurement and inlet,outlet temperature measurement functions.Control unit and data processing unit based on MSP430F4152 of TI corporation complete functions including peripherals control,data analysis,temperature compensation algorithm,flow pattern compensation algorithm and low power consumption control.The design meets the Town Construction Professional Standard CJ 128-2007,and furthermore,some performances can be improved.
文摘Transit-time flow technology is considered as a quality of care in bypass surgery especially in off pump revascularization. Transit time flow measurement is a real time, direct, easy and handy tool for assessment quality of anastomosis and graft blood flow.
文摘The C-band three-cavity transit-time effect oscillator (3C TTTO) is a novel high power microwave device based on the transit-time effect of the three-cavity (3C) resonator. The operational principle of this device is briefly expounded in this paper, and the theoretical and experimental researches on the radial insulation diode, the 3C resonator, the double-gap output cavity and the circular waveguide bevel cut radiation antenna are presented in detail. By using the analytic method, the eigen modes and their field distributions of the 3C resonator are developed, and some basic laws of the transit-time effect are obtained in non-π mode field of the 3C resonator. At last, the experimental results are given. This device generated RF peak power in excess of 400MW with 15ns FWHM, and its beam-wave power conversion efficiency is about 17%.
文摘以大理岩为研究对象,从其典型力学——特性脆-延转化特性入手,利用三维快速拉格朗日连续体分析(fast Lagrangian analysis of continua in 3 dimensions,FLAC3D)研究了试样在不同围压三轴试验条件下的全应力-应变曲线,分析了峰值强度、残余强度及峰后特性,验证了Hoek-Brown强度准则可较为准确地描述大理岩的脆-延转化特性,并对岩石发生破裂扩展的成因及力学机理进行了分析。利用应力腐蚀(stress corrosion,SC)本构模型,分析了某抽水蓄能电站岔洞围岩在历时10 a前后的最大主应力、位移及塑性区分布,并采用塑性区分布等效表征破裂扩展区域,以此验证了时间效应对岩石强度及破裂扩展的影响。针对岩体强度的时效性变化与破裂扩展的时效特征,相关研究成果对于认识地下工程结构的稳定性、指导制定合理的支护措施均具有重要的理论意义和工程价值。
