BACKGROUND Management of non-neurogenic,non-obstructive dysuria represents one of the most challenging dilemmas in urological practice.The main clinical symptom is the increase in residual urine.Voiding dysfunction is...BACKGROUND Management of non-neurogenic,non-obstructive dysuria represents one of the most challenging dilemmas in urological practice.The main clinical symptom is the increase in residual urine.Voiding dysfunction is the main cause of dysuria or urinary retention,mainly due to the decrease in bladder contraction(the decrease in contraction amplitude or duration)or the increase in outflow tract resistance.Sacral neuromodulation(SNM)has been used for>10 years to treat many kinds of lower urinary tract dysfunction.It has become increasingly popular in China in recent years.Consequently,studies focusing on nonneurogenic,non-obstructive dysuria patients treated by SNM are highly desirable.AIM To assess the outcome of two-stage SNM in non-neurogenic,non-obstructive dysuria.METHODS Clinical data of 54 patients(26 men,28 women)with non-neurogenic,nonobstructive dysuria treated by SNM from January 2012 to December 2016 in ten medical centers in China were retrospectively analyzed.All patients received two or more conservative treatments.The voiding diary,urgency score,and quality of life score before operation,after implantation of tined lead in stage I(test period),and during short-term follow-up(latest follow-up)after implantation of the implanted pulse generator in stage II were compared to observe symptom improvements.RESULTS Among the 54 study patients,eight refused to implant an implanted pulse generator because of the unsatisfactory effect,and 46 chose to embed the implanted pulse generator at the end of stage I.The conversion rate of stage I to stage II was 85.2%.The average follow-up time was 18.6 mo.There were significant differences between baseline(before stage I)and the test period(after stage I)in residual urine,voiding frequency,average voiding amount,maximum voiding amount,nocturia,urgency score,and quality of life score.The residual urine and urgency score between the test period and the latest follow-up time(after stage II)were also significantly different.No significant differences were observed for other parameters.No wound infection,electrode breakage,or other irreversible adverse events occurred.CONCLUSION SNM is effective for patients with non-neurogenic,non-obstructive dysuria showing a poor response to traditional treatment.The duration of continuous stimulation may be positively correlated with the improvement of residual urine.展开更多
For qualifying the anti-shock performance of shipboard equipments and simulating actual underwater explosion environments, a novel dual-wave shock test machine is proposed to increase testing capability of shock test ...For qualifying the anti-shock performance of shipboard equipments and simulating actual underwater explosion environments, a novel dual-wave shock test machine is proposed to increase testing capability of shock test machines as well as to meet certain shock testing specification. The machine can generate a double-pulse acceleration shock for test articles according to specification defined in BV043/85. On the basis of the impact theory, a nonlinear dynamic model of the hydraulically-actuated test machine is established with thorough analysis on its mechanism which involves conversion of gas potential energy and dissipation of kinetic energy. Simulation results have demonstrated that the machine can produce a double-pulse acceleration shock in the time domain or a desired shock response spectrum in the frequency domain, which sets a theoretical base for the construction of the proposed machine.展开更多
A novel efficient circuit for Ultra-WideBand(UWB) balanced sub-nanosecond monocycle pulse generation is presented.The pulse generator employs wideband bipolar transistor,step recovery diodes,Schottky diodes,and simple...A novel efficient circuit for Ultra-WideBand(UWB) balanced sub-nanosecond monocycle pulse generation is presented.The pulse generator employs wideband bipolar transistor,step recovery diodes,Schottky diodes,and simple charging and discharging circuitry.Simple transient analysis and design of the circuit are presented along with their operating principle.The pulse generator produces truly balanced monocycle pulse with 500 ps pulse-width and 800 mV peak voltage.The generated monocycle pulse also has very symmetrical positive and negative portions and low ringing level.The presented pulse generator can be used as both a transmitter feeding UWB balanced antennas without broadband baluns and a balanced switching pulse generator that used in UWB receiver.展开更多
A hybrid control strategy has been designed and developed for the electro-hydraulic posi-tion servo control system with generalized Pulse code modulation (GPCM), which is suitable for the area where the work conditi...A hybrid control strategy has been designed and developed for the electro-hydraulic posi-tion servo control system with generalized Pulse code modulation (GPCM), which is suitable for the area where the work condition is poor and a large flow rate is required. It is difficult to control the GPCM system because the system is discrete. With consideration of the stability and speediness of the GPCM position servo control system, a control strategy is developed through the theoretical and ex-perimental analyses. The control strategy integrates the merits of Bang-Bang control, PID control and fuzzy control. With this hybrid control strategy, the electro hydraulic control system has good per-formances, and the servo control is carried out with GPCM through on-off valves.展开更多
A specially designed fluid damper used as negative shock pulse generator in the shock resistance test system to dissipate the shock input energy in transient time duration is presented. The theoretical modeling based ...A specially designed fluid damper used as negative shock pulse generator in the shock resistance test system to dissipate the shock input energy in transient time duration is presented. The theoretical modeling based on the three-dimensional equation of heat transfer through a fluid element is created to predict the viscous heating in the fluid damper under shock conditions. A comprehensive experimental program that investigates the problem of viscous heating in the fluid damper under different shock conditions is conducted on the shock test machine to validate the analytical expression. Temperature histories for the fluid within the damper at two locations, the annular-oriflce and the-end-of stroke of the damper, are recorded. The experimental results show that the theoretical model can offer a very dependable prediction for the temperature histories in the damper for increasing input velocity. The theoretical model and experimental data both clearly indicate that the viscous heating in the damper is directly related to the maximum shock velocity input and the pressure between the two sides of the piston head.展开更多
We report on controllable pulse shaping in a Yb-doped stretched-pulse fiber laser followed by a high-power chirped pulse amplifier. We demonstrate that the pulses after an extra-cavity grating pair change their intens...We report on controllable pulse shaping in a Yb-doped stretched-pulse fiber laser followed by a high-power chirped pulse amplifier. We demonstrate that the pulses after an extra-cavity grating pair change their intensity profile from Lorentz to Gaussian and then to sech2 shapes by adjusting the intra-cavity polarization through a quarter-wave plate inside the fiber laser cavity. The laser pulses with different pulse shapes exhibit pulse-to-pulse amplitude fluctuation of -- 1.02%, while the sech2-shaped pulse train is provided with a more stable free-running repetition rate as a result of the stronger self-phase modulation in the fiber laser cavity than Lorentz- and Gaussian-shaped pulse trains.展开更多
A sub-nanosecond pulse discharge tube is a gas discharge tube which can generate a rapid high-voltage pulse of kilo-volts in amplitude and sub-nanoseconds in width. In this paper, the sub-nanosecond pulse discharge tu...A sub-nanosecond pulse discharge tube is a gas discharge tube which can generate a rapid high-voltage pulse of kilo-volts in amplitude and sub-nanoseconds in width. In this paper, the sub-nanosecond pulse discharge tube and its working principles are described. Because of the phenomenon that the deformation process of the mercury film on the electrode surface lags behind the charging process, the mercury film deformation process affects the dynamic breakdown voltage of the tube directly. The deformation of the mercury film is observed microscopically, and the dynamic breakdown voltage of the tube is messured using an oscillograph. The results show that all the parameters in the charging process, such as charging resistance, charging capacitance and DC power supply, affect the dynamic breakdown voltage of the tube. Based on these studies, the output pulse amplitude can be controlled continuously and individually by adjusting the power supply voltage. When the DC power supply is adjusted from 7 kV to 10 kV, the dynamic breakdown voltage ranges from 6.5 kV to 10 kV. According to our research, a kind of sub-nanosecond pulse generator is made, with a pulse width ranging from 0.5 ns to 2.5 ns, a rise time from 0.32 ns to 0.58 ns, and a pulse amplitude that is adjustable from 1.5 kV to 5 kV.展开更多
A new rectangular pulse trigger generator has been developed which can generate two 10 kV pulses with a risetime less than 1 ns, a jitter of 0.2 ns and a width of about 10 ns and 40 ns, respectively. This generator us...A new rectangular pulse trigger generator has been developed which can generate two 10 kV pulses with a risetime less than 1 ns, a jitter of 0.2 ns and a width of about 10 ns and 40 ns, respectively. This generator uses two polymer-foil switches and 25 ohm Blumlein transmission lines composed of two-parallel standard coaxial cables discharging into two 50 ohm output cables. The pulse width and the delay between two pulses can be adjusted by changing the length of the cables.展开更多
A gas-liquid coupling excitation mode is proposed and the gas-liquid excitation experimental system is developed. Air from pulse generator is mixed with liquid,through which the generated cavitation bubbles can strip ...A gas-liquid coupling excitation mode is proposed and the gas-liquid excitation experimental system is developed. Air from pulse generator is mixed with liquid,through which the generated cavitation bubbles can strip contaminants adhered to the pipe inner wall rapidly. The kinematics equation of the bubble inside the hydraulic oil is established and the numerical simulations are carried out. The influential factors such as gas pressure, excitation frequency,initial bubble radius and fluid viscosity are analyzed.The results show that the cavitation will evolve from steady state to transient state with the increasing gas pressure and initial bubble radius. The pulse generator frequency has a slightly effect on the growth of the bubble radius,and the breakup time of the bubble is shortened with the rising frequency. Similarly, the increasing viscosity of liquid has minimal impact on cavitation effect,which can weaken the growth and the collapse of the bubble. Moreover,the temperature inside the cavitation bubble is investigated,indicating that the instantaneous temperature inside the bubble increases with the rising gas pressure. Once the gas pressure is raised to a certain value greater than the fluid static pressure, the instantaneous temperature inside the bubble will rise sharply. So, it can be concluded that the gas-liquid coupling excitation-induced cavitation process is controllable, and some theoretical basis of the new excitation mode is presented,which is expected to be applied in the online cleaning of the complex hydraulic system.展开更多
The giant magneto-impedance(GMI)effect of amorphous wire was analyzed theoretically.The amorphous wire had strong GMI effect in the stimulation of sharp pulse of 680kHz and18 mV.A pulse generator was designed to pro...The giant magneto-impedance(GMI)effect of amorphous wire was analyzed theoretically.The amorphous wire had strong GMI effect in the stimulation of sharp pulse of 680kHz and18 mV.A pulse generator was designed to provide high frequency pulse to a magnetic impedance(MI)element.The induced voltage on the pickup coil wound on the amorphous wire was sampled and held with a detect circuit using analog switch.A stable magnetic sensor was constructed.A three-dimension micro magnetic field detector was designed with a central controller MSP430F449.High stability and sensitivity were obtained in the MI sensor with the detect circuit.Experiment results showed that the resolution of the detector was 1nT in the full scale of±2 Oe and the detector worked stably from the room temperature to about 80℃.A small ferromagnetic target was detected by the three-dimension detector in laboratory environment without magnetic shielding.The target moving direction was ascertained with the wave shape of axis parallel in that direction.展开更多
We present an efficient and realizable scheme for the generation of an ultrashort single attosecond(as) pulse from H atom with a 800-nm fundamental laser field combined with a terahertz(THz) field. The high-order ...We present an efficient and realizable scheme for the generation of an ultrashort single attosecond(as) pulse from H atom with a 800-nm fundamental laser field combined with a terahertz(THz) field. The high-order harmonic generation(HHG) can be obtained by solving the time-dependent Schr dinger equation accurately and efficiently with time-dependent generalized pseudo-spectral(TDGPS) method. The result shows that the plateau of high-order harmonics is extended and the broadband spectra can be produced by the combined laser pulse, which can be explained by the corresponding ionization probability. The time–frequency analysis and semi-classical three-step model are also presented to further investigate this mechanism. Besides, by the superposition of the harmonics near the cutoff region, an isolated 133-as pulse can be obtained.展开更多
Ultrabroadband systems and ultrafast electronics require the generation,transmission,and processing of high-quality ultrashort pulses rang-ing from nanoseconds(ns)to picoseconds(ps),which include well-established and ...Ultrabroadband systems and ultrafast electronics require the generation,transmission,and processing of high-quality ultrashort pulses rang-ing from nanoseconds(ns)to picoseconds(ps),which include well-established and emerging applications of time-domain reflectometry,arbitrary wave-form generation,sampling oscilloscopes,frequency synthesis,through-wall radar imaging,indoor communication,radar surveillance,and medical radar detection.Impulse radar advancements in industrial,scientific,and medical(ISM)domains are,for example,driven by ns-scale-defined ultrawideband(UWB)technologies.Nevertheless,the generation of ultrashort ps-scale pulses is highly desired to achieve unprecedented performances in all these ap-plications and future systems.However,due to the variety and applicability of different pulse generation and compression techniques,the selection of optimum or appropriate pulse generators and compressors is difficult for practitioners and users.To this end,this article aims to provide a comprehen-sive overview of ultrashort ns and ps pulse generation and compression techniques.The proposed and developed pulse generators available in the litera-ture and on the market,which are characterized by their corresponding pros and cons,are also explored.The theoretical analysis of pulse generation us-ing a nonlinear transmission line(NLTL)presented in the literature is briefly explained as well.Additionally,a holistic overview of these pulse genera-tors from the perspective of applications is given to describe their utilization in practical systems.All of these techniques are well summarized and com-pared in terms of fundamental pulse parameters,and research gaps in specified areas are highlighted.A thorough discussion of previous research work on various topologies and techniques is presented,and potential future directions for technical advancement are examined.展开更多
A novel scheme was proposed to generate a millimeter-wave (MMW) optical pulse by combining pulse repetition rate multiplication (PRRM) technology and temporal Talbot effect (TTE). A cascaded Mach- Zehnder interf...A novel scheme was proposed to generate a millimeter-wave (MMW) optical pulse by combining pulse repetition rate multiplication (PRRM) technology and temporal Talbot effect (TTE). A cascaded Mach- Zehnder interferometer (MZI) lattice was used for PRRM, and a linearly chirped fiber grating (LCFG) was used as TTE. The basic principle was analyzed by using a Gaussian input short pulse and its characteristics were discussed by numerical simulation. It is shown that the proposed scheme is feasible for MMW signal generation and has potential merits for practical application of radio over fiber (ROF) technology.展开更多
A novel approach to generate and distribute ultra-wideband (UWB) pulses in optical domain is investigated. In this proposed scheme, a dual-electrode Mach-Zehnder modulator (DE-MZM) is biased at its quadrature poin...A novel approach to generate and distribute ultra-wideband (UWB) pulses in optical domain is investigated. In this proposed scheme, a dual-electrode Mach-Zehnder modulator (DE-MZM) is biased at its quadrature point so as to realize the linear response. Then the intensity of output optical field can be assumed to the subtraction of two input Gaussian pulses. If the input Gaussian pulses are with the same sharp parameters but different time delays, a quasi-monocycle-waveform UWB signal can be generated. If the input Gaussian pulses are with different amplitudes and full-width at half-maximum (FWHM), a quasi-doublet-waveform UWB signal can be generated. A transmission of the UWB signals through a 25-km single mode fiber is carried out successfully. The results in both temporal and frequency domains are also presented.展开更多
Background The automatic, threshold tracking, pacing algorithm developed by St.Jude Medical, verifies ventricular capture beat by beat by recognizing the evoked response following each pacemaker stimulus. This functio...Background The automatic, threshold tracking, pacing algorithm developed by St.Jude Medical, verifies ventricular capture beat by beat by recognizing the evoked response following each pacemaker stimulus. This function was assumed to be not only energy saving but safe. This study estimated the extension in longevity obtained by AutoCapture (AC) compared with pacemakers programmed to manually optimized, nominal output. Methods Thirty-four patients who received the St. Jude Affinity series pacemaker were included in the study. The following measurements were taken: stimulation and sensing threshold, impedance of leads, evoked response and polarization signals by 3501 programmer during followup, battery current and battery impedance under different conditions. For longevity comparison, ventricular output was programmed under three different conditions: (1) AC on; (2) AC off with nominal output, and (3) AC off with pacing output set at twice the pacing threshold with a minimum of 2.0 V. Patients were divided into two groups: chronic threshold is higher or lower than 1 V. The efficacy of AC was evaluated. Results Current drain in the AC on group, AC off with optimized programming or nominal output was (14.33±2.84) mA, (16.74±2.75) mA and (18.4±2.44) mA, respectively (AC on or AC off with optimized programming vs. nominal output, P〈0.01). Estimated longevity was significantly extended by AC on when compared with nominal setting [(103±27) months, (80±24) months, P〈0.01). Furthermore, compared with the optimized programming, AC extends the longevity when the pacing threshold is higher than 1 V. Conclusion AC could significantly prolong pacemaker longevity; especially in the patient with high pacing threshold.展开更多
A scheme of multi-wavelength pulse generator using optical frequency comb and arrayed waveguide grating (AWG) is proposed and experimentally demonstrated. A flattop optical frequency comb is shaped into multiple nar...A scheme of multi-wavelength pulse generator using optical frequency comb and arrayed waveguide grating (AWG) is proposed and experimentally demonstrated. A flattop optical frequency comb is shaped into multiple narrowband Gaussian spectra by using an AWG which contains a number of Gaussian channels, and then multi-wavelength optical pulses are achieved. In the experiment, six wavelength pulses with full width at half-maximum (FWHM) of 14.6 ps at I0 GHz are obtained, and two wavelength-interleaved pulse trains at 20 GHz and four wavelength-interleaved multi-wavelength optical pulses. This scheme has and time-interval can be readily controlled. pulse trains at 40 GHz are demonstrated by using the flexibility because the pulse width, the repetition rate,展开更多
This paper presents a transmitter IC with BPSK modulation for an ultra-wide band system.It is based on up-conversion with a high linearity passive mixer.Unlike the traditional BPSK modulation scheme,the local oscillat...This paper presents a transmitter IC with BPSK modulation for an ultra-wide band system.It is based on up-conversion with a high linearity passive mixer.Unlike the traditional BPSK modulation scheme,the local oscillator (LO) is modulated by the baseband data instead of the pulse.The chip is designed and fabricated by standard 0.18μm CMOS technology.The transmitter achieves a high data rate up to 400 Mbps.The amplitude of the pulse can be adjusted by the amplitude of the LO and the bias current of the driver amplifier.The maximum peak-to-peak amplitude of the pulse is 600 mV.It consumes only 20.3 mA current with a supply voltage of 1.8 V when transmitting a pulse at the maximum data rate.The energy efficiency is 91.4 pJ/pulse.The die area is 1.4×1.4 mm^2.展开更多
An actively mode-locked laser with tunable repetition rate is proposed and experimentally demonstrated based on a programmable electrical pattern generator. By changing the repetition rate of the electrical patterns a...An actively mode-locked laser with tunable repetition rate is proposed and experimentally demonstrated based on a programmable electrical pattern generator. By changing the repetition rate of the electrical patterns applied on the in-cavity modulator, the repetition rate of the output optical pulse sequences changes accordingly while the pulse width of the optical pulse train remains almost constant. In other words, the output ultra-short pulse train has a tunable duty cycle. In a proof-of-principle experiment, optical pulses with repetition rates of 10, 5, 2.5 and 1.25 GHz are obtained by adjusting the electrical pattern applied on the in-cavity modulator while their pulse widths remain almost unchanged.展开更多
The efficient generation of a 1.17-mJ laser pulse with 360 ps duration using an ytterbium (Yb)-doped fiber amplifier chain seeded by a homemade mode-locked fiber laser is demonstrated experimentally. A specially des...The efficient generation of a 1.17-mJ laser pulse with 360 ps duration using an ytterbium (Yb)-doped fiber amplifier chain seeded by a homemade mode-locked fiber laser is demonstrated experimentally. A specially designed figure-of-eight fiber laser acts as the seed source of a chirped-pulse amplification (CPA) system and generates mode-locked pulses with hundreds of picosecond widths. Two kinds of large-mode-area (LMA) double-clad Yb-doped fibers are employed to construct the pre-amplifier and main amplifier. All of the adopted instruments help avoid severe nonlinearity in fibers to raise sub-nanosecond pulse energy with acceptable signal-to-noise ratio (SNR). The output spectrum of this fiber-based CPA system shows that amplified spontaneous emission (ASE) is suppressed to better than 30 dB, and the onset of stimulated Raman scattering is excluded.展开更多
An 8×10 Gb/s optical time-division-multiplexing (OTDM) system was demonstrated with an electroab-sorption modulator (EAM) based short pulse generator followed by a two-stage nonlinear compression scheme which gen...An 8×10 Gb/s optical time-division-multiplexing (OTDM) system was demonstrated with an electroab-sorption modulator (EAM) based short pulse generator followed by a two-stage nonlinear compression scheme which generated stable 10-GHz, 2-ps full-width at half-maximum (FWHM) pulse train, an optoelectronic oscillator (OEO) that extracted 10-GHz clock with a timing jitter of 300 fs from 80-Gb/s OTDM signal and a self cascaded EAM which produced a switching window of about 10 ps. A back-to-back error free demultiplexing experiment with a power penalty of 3.25 dB was carried out to verify the system performance.展开更多
基金Supported by National Key Research and Development Program of China,No.2018YFC2002202.
文摘BACKGROUND Management of non-neurogenic,non-obstructive dysuria represents one of the most challenging dilemmas in urological practice.The main clinical symptom is the increase in residual urine.Voiding dysfunction is the main cause of dysuria or urinary retention,mainly due to the decrease in bladder contraction(the decrease in contraction amplitude or duration)or the increase in outflow tract resistance.Sacral neuromodulation(SNM)has been used for>10 years to treat many kinds of lower urinary tract dysfunction.It has become increasingly popular in China in recent years.Consequently,studies focusing on nonneurogenic,non-obstructive dysuria patients treated by SNM are highly desirable.AIM To assess the outcome of two-stage SNM in non-neurogenic,non-obstructive dysuria.METHODS Clinical data of 54 patients(26 men,28 women)with non-neurogenic,nonobstructive dysuria treated by SNM from January 2012 to December 2016 in ten medical centers in China were retrospectively analyzed.All patients received two or more conservative treatments.The voiding diary,urgency score,and quality of life score before operation,after implantation of tined lead in stage I(test period),and during short-term follow-up(latest follow-up)after implantation of the implanted pulse generator in stage II were compared to observe symptom improvements.RESULTS Among the 54 study patients,eight refused to implant an implanted pulse generator because of the unsatisfactory effect,and 46 chose to embed the implanted pulse generator at the end of stage I.The conversion rate of stage I to stage II was 85.2%.The average follow-up time was 18.6 mo.There were significant differences between baseline(before stage I)and the test period(after stage I)in residual urine,voiding frequency,average voiding amount,maximum voiding amount,nocturia,urgency score,and quality of life score.The residual urine and urgency score between the test period and the latest follow-up time(after stage II)were also significantly different.No significant differences were observed for other parameters.No wound infection,electrode breakage,or other irreversible adverse events occurred.CONCLUSION SNM is effective for patients with non-neurogenic,non-obstructive dysuria showing a poor response to traditional treatment.The duration of continuous stimulation may be positively correlated with the improvement of residual urine.
基金supported by China Naval Armament Department (No. 05131/1046).
文摘For qualifying the anti-shock performance of shipboard equipments and simulating actual underwater explosion environments, a novel dual-wave shock test machine is proposed to increase testing capability of shock test machines as well as to meet certain shock testing specification. The machine can generate a double-pulse acceleration shock for test articles according to specification defined in BV043/85. On the basis of the impact theory, a nonlinear dynamic model of the hydraulically-actuated test machine is established with thorough analysis on its mechanism which involves conversion of gas potential energy and dissipation of kinetic energy. Simulation results have demonstrated that the machine can produce a double-pulse acceleration shock in the time domain or a desired shock response spectrum in the frequency domain, which sets a theoretical base for the construction of the proposed machine.
文摘A novel efficient circuit for Ultra-WideBand(UWB) balanced sub-nanosecond monocycle pulse generation is presented.The pulse generator employs wideband bipolar transistor,step recovery diodes,Schottky diodes,and simple charging and discharging circuitry.Simple transient analysis and design of the circuit are presented along with their operating principle.The pulse generator produces truly balanced monocycle pulse with 500 ps pulse-width and 800 mV peak voltage.The generated monocycle pulse also has very symmetrical positive and negative portions and low ringing level.The presented pulse generator can be used as both a transmitter feeding UWB balanced antennas without broadband baluns and a balanced switching pulse generator that used in UWB receiver.
文摘A hybrid control strategy has been designed and developed for the electro-hydraulic posi-tion servo control system with generalized Pulse code modulation (GPCM), which is suitable for the area where the work condition is poor and a large flow rate is required. It is difficult to control the GPCM system because the system is discrete. With consideration of the stability and speediness of the GPCM position servo control system, a control strategy is developed through the theoretical and ex-perimental analyses. The control strategy integrates the merits of Bang-Bang control, PID control and fuzzy control. With this hybrid control strategy, the electro hydraulic control system has good per-formances, and the servo control is carried out with GPCM through on-off valves.
基金Chinese Navy Warship Research Center(No.05131-1046)
文摘A specially designed fluid damper used as negative shock pulse generator in the shock resistance test system to dissipate the shock input energy in transient time duration is presented. The theoretical modeling based on the three-dimensional equation of heat transfer through a fluid element is created to predict the viscous heating in the fluid damper under shock conditions. A comprehensive experimental program that investigates the problem of viscous heating in the fluid damper under different shock conditions is conducted on the shock test machine to validate the analytical expression. Temperature histories for the fluid within the damper at two locations, the annular-oriflce and the-end-of stroke of the damper, are recorded. The experimental results show that the theoretical model can offer a very dependable prediction for the temperature histories in the damper for increasing input velocity. The theoretical model and experimental data both clearly indicate that the viscous heating in the damper is directly related to the maximum shock velocity input and the pressure between the two sides of the piston head.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11274115 and 10990101)the National Key Project for Basic Research of China(Grant No.2011CB808105)+2 种基金the National Key Scientific Instrument Project,China(Grant No.2012YQ150092)the Natural Science Foundation of Shanghai,China(Grant No.11ZR1410900)the Innovation Program of Shanghai Municipal Education Commission,China(Grant No.2014Z10269011)
文摘We report on controllable pulse shaping in a Yb-doped stretched-pulse fiber laser followed by a high-power chirped pulse amplifier. We demonstrate that the pulses after an extra-cavity grating pair change their intensity profile from Lorentz to Gaussian and then to sech2 shapes by adjusting the intra-cavity polarization through a quarter-wave plate inside the fiber laser cavity. The laser pulses with different pulse shapes exhibit pulse-to-pulse amplitude fluctuation of -- 1.02%, while the sech2-shaped pulse train is provided with a more stable free-running repetition rate as a result of the stronger self-phase modulation in the fiber laser cavity than Lorentz- and Gaussian-shaped pulse trains.
基金supported by the National Key Laboratory Foundation of China (No.9140C530103110C5301)
文摘A sub-nanosecond pulse discharge tube is a gas discharge tube which can generate a rapid high-voltage pulse of kilo-volts in amplitude and sub-nanoseconds in width. In this paper, the sub-nanosecond pulse discharge tube and its working principles are described. Because of the phenomenon that the deformation process of the mercury film on the electrode surface lags behind the charging process, the mercury film deformation process affects the dynamic breakdown voltage of the tube directly. The deformation of the mercury film is observed microscopically, and the dynamic breakdown voltage of the tube is messured using an oscillograph. The results show that all the parameters in the charging process, such as charging resistance, charging capacitance and DC power supply, affect the dynamic breakdown voltage of the tube. Based on these studies, the output pulse amplitude can be controlled continuously and individually by adjusting the power supply voltage. When the DC power supply is adjusted from 7 kV to 10 kV, the dynamic breakdown voltage ranges from 6.5 kV to 10 kV. According to our research, a kind of sub-nanosecond pulse generator is made, with a pulse width ranging from 0.5 ns to 2.5 ns, a rise time from 0.32 ns to 0.58 ns, and a pulse amplitude that is adjustable from 1.5 kV to 5 kV.
基金supported by National 863-803 Project of China (No.2002AA833050)
文摘A new rectangular pulse trigger generator has been developed which can generate two 10 kV pulses with a risetime less than 1 ns, a jitter of 0.2 ns and a width of about 10 ns and 40 ns, respectively. This generator uses two polymer-foil switches and 25 ohm Blumlein transmission lines composed of two-parallel standard coaxial cables discharging into two 50 ohm output cables. The pulse width and the delay between two pulses can be adjusted by changing the length of the cables.
基金National Natural Science Foundation of China(No.U1404513)
文摘A gas-liquid coupling excitation mode is proposed and the gas-liquid excitation experimental system is developed. Air from pulse generator is mixed with liquid,through which the generated cavitation bubbles can strip contaminants adhered to the pipe inner wall rapidly. The kinematics equation of the bubble inside the hydraulic oil is established and the numerical simulations are carried out. The influential factors such as gas pressure, excitation frequency,initial bubble radius and fluid viscosity are analyzed.The results show that the cavitation will evolve from steady state to transient state with the increasing gas pressure and initial bubble radius. The pulse generator frequency has a slightly effect on the growth of the bubble radius,and the breakup time of the bubble is shortened with the rising frequency. Similarly, the increasing viscosity of liquid has minimal impact on cavitation effect,which can weaken the growth and the collapse of the bubble. Moreover,the temperature inside the cavitation bubble is investigated,indicating that the instantaneous temperature inside the bubble increases with the rising gas pressure. Once the gas pressure is raised to a certain value greater than the fluid static pressure, the instantaneous temperature inside the bubble will rise sharply. So, it can be concluded that the gas-liquid coupling excitation-induced cavitation process is controllable, and some theoretical basis of the new excitation mode is presented,which is expected to be applied in the online cleaning of the complex hydraulic system.
基金Supported by the National Natural Science Foundation of China(60874100)
文摘The giant magneto-impedance(GMI)effect of amorphous wire was analyzed theoretically.The amorphous wire had strong GMI effect in the stimulation of sharp pulse of 680kHz and18 mV.A pulse generator was designed to provide high frequency pulse to a magnetic impedance(MI)element.The induced voltage on the pickup coil wound on the amorphous wire was sampled and held with a detect circuit using analog switch.A stable magnetic sensor was constructed.A three-dimension micro magnetic field detector was designed with a central controller MSP430F449.High stability and sensitivity were obtained in the MI sensor with the detect circuit.Experiment results showed that the resolution of the detector was 1nT in the full scale of±2 Oe and the detector worked stably from the room temperature to about 80℃.A small ferromagnetic target was detected by the three-dimension detector in laboratory environment without magnetic shielding.The target moving direction was ascertained with the wave shape of axis parallel in that direction.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11174108,11104108,and 11271158)
文摘We present an efficient and realizable scheme for the generation of an ultrashort single attosecond(as) pulse from H atom with a 800-nm fundamental laser field combined with a terahertz(THz) field. The high-order harmonic generation(HHG) can be obtained by solving the time-dependent Schr dinger equation accurately and efficiently with time-dependent generalized pseudo-spectral(TDGPS) method. The result shows that the plateau of high-order harmonics is extended and the broadband spectra can be produced by the combined laser pulse, which can be explained by the corresponding ionization probability. The time–frequency analysis and semi-classical three-step model are also presented to further investigate this mechanism. Besides, by the superposition of the harmonics near the cutoff region, an isolated 133-as pulse can be obtained.
文摘Ultrabroadband systems and ultrafast electronics require the generation,transmission,and processing of high-quality ultrashort pulses rang-ing from nanoseconds(ns)to picoseconds(ps),which include well-established and emerging applications of time-domain reflectometry,arbitrary wave-form generation,sampling oscilloscopes,frequency synthesis,through-wall radar imaging,indoor communication,radar surveillance,and medical radar detection.Impulse radar advancements in industrial,scientific,and medical(ISM)domains are,for example,driven by ns-scale-defined ultrawideband(UWB)technologies.Nevertheless,the generation of ultrashort ps-scale pulses is highly desired to achieve unprecedented performances in all these ap-plications and future systems.However,due to the variety and applicability of different pulse generation and compression techniques,the selection of optimum or appropriate pulse generators and compressors is difficult for practitioners and users.To this end,this article aims to provide a comprehen-sive overview of ultrashort ns and ps pulse generation and compression techniques.The proposed and developed pulse generators available in the litera-ture and on the market,which are characterized by their corresponding pros and cons,are also explored.The theoretical analysis of pulse generation us-ing a nonlinear transmission line(NLTL)presented in the literature is briefly explained as well.Additionally,a holistic overview of these pulse genera-tors from the perspective of applications is given to describe their utilization in practical systems.All of these techniques are well summarized and com-pared in terms of fundamental pulse parameters,and research gaps in specified areas are highlighted.A thorough discussion of previous research work on various topologies and techniques is presented,and potential future directions for technical advancement are examined.
文摘A novel scheme was proposed to generate a millimeter-wave (MMW) optical pulse by combining pulse repetition rate multiplication (PRRM) technology and temporal Talbot effect (TTE). A cascaded Mach- Zehnder interferometer (MZI) lattice was used for PRRM, and a linearly chirped fiber grating (LCFG) was used as TTE. The basic principle was analyzed by using a Gaussian input short pulse and its characteristics were discussed by numerical simulation. It is shown that the proposed scheme is feasible for MMW signal generation and has potential merits for practical application of radio over fiber (ROF) technology.
基金supported by the National Natural Science Foundation of China(No.60771008)the Program for New Century Excellent Talents in University (No.NCET-06-0076)+2 种基金Beijing Natural Science Foundation (No.4082024)the Ph.D.Programs Foundation of Ministry of Education of China(No.200800040002)the Foundation for the Returning Scholars,and Beijing Jiaotong University Foundation(No.2006XM003).
文摘A novel approach to generate and distribute ultra-wideband (UWB) pulses in optical domain is investigated. In this proposed scheme, a dual-electrode Mach-Zehnder modulator (DE-MZM) is biased at its quadrature point so as to realize the linear response. Then the intensity of output optical field can be assumed to the subtraction of two input Gaussian pulses. If the input Gaussian pulses are with the same sharp parameters but different time delays, a quasi-monocycle-waveform UWB signal can be generated. If the input Gaussian pulses are with different amplitudes and full-width at half-maximum (FWHM), a quasi-doublet-waveform UWB signal can be generated. A transmission of the UWB signals through a 25-km single mode fiber is carried out successfully. The results in both temporal and frequency domains are also presented.
文摘Background The automatic, threshold tracking, pacing algorithm developed by St.Jude Medical, verifies ventricular capture beat by beat by recognizing the evoked response following each pacemaker stimulus. This function was assumed to be not only energy saving but safe. This study estimated the extension in longevity obtained by AutoCapture (AC) compared with pacemakers programmed to manually optimized, nominal output. Methods Thirty-four patients who received the St. Jude Affinity series pacemaker were included in the study. The following measurements were taken: stimulation and sensing threshold, impedance of leads, evoked response and polarization signals by 3501 programmer during followup, battery current and battery impedance under different conditions. For longevity comparison, ventricular output was programmed under three different conditions: (1) AC on; (2) AC off with nominal output, and (3) AC off with pacing output set at twice the pacing threshold with a minimum of 2.0 V. Patients were divided into two groups: chronic threshold is higher or lower than 1 V. The efficacy of AC was evaluated. Results Current drain in the AC on group, AC off with optimized programming or nominal output was (14.33±2.84) mA, (16.74±2.75) mA and (18.4±2.44) mA, respectively (AC on or AC off with optimized programming vs. nominal output, P〈0.01). Estimated longevity was significantly extended by AC on when compared with nominal setting [(103±27) months, (80±24) months, P〈0.01). Furthermore, compared with the optimized programming, AC extends the longevity when the pacing threshold is higher than 1 V. Conclusion AC could significantly prolong pacemaker longevity; especially in the patient with high pacing threshold.
基金supported by the National Natural Science Foundation of China under Grant Nos. 60977003and 61032005
文摘A scheme of multi-wavelength pulse generator using optical frequency comb and arrayed waveguide grating (AWG) is proposed and experimentally demonstrated. A flattop optical frequency comb is shaped into multiple narrowband Gaussian spectra by using an AWG which contains a number of Gaussian channels, and then multi-wavelength optical pulses are achieved. In the experiment, six wavelength pulses with full width at half-maximum (FWHM) of 14.6 ps at I0 GHz are obtained, and two wavelength-interleaved pulse trains at 20 GHz and four wavelength-interleaved multi-wavelength optical pulses. This scheme has and time-interval can be readily controlled. pulse trains at 40 GHz are demonstrated by using the flexibility because the pulse width, the repetition rate,
基金supported by the National High Technology Research and Development Program of China(No.2007AA01Z2b2)
文摘This paper presents a transmitter IC with BPSK modulation for an ultra-wide band system.It is based on up-conversion with a high linearity passive mixer.Unlike the traditional BPSK modulation scheme,the local oscillator (LO) is modulated by the baseband data instead of the pulse.The chip is designed and fabricated by standard 0.18μm CMOS technology.The transmitter achieves a high data rate up to 400 Mbps.The amplitude of the pulse can be adjusted by the amplitude of the LO and the bias current of the driver amplifier.The maximum peak-to-peak amplitude of the pulse is 600 mV.It consumes only 20.3 mA current with a supply voltage of 1.8 V when transmitting a pulse at the maximum data rate.The energy efficiency is 91.4 pJ/pulse.The die area is 1.4×1.4 mm^2.
基金supported by the National Natural Science Foundation of China (No.60607008)the National "863" Program of China (No.2007AA01Z271)
文摘An actively mode-locked laser with tunable repetition rate is proposed and experimentally demonstrated based on a programmable electrical pattern generator. By changing the repetition rate of the electrical patterns applied on the in-cavity modulator, the repetition rate of the output optical pulse sequences changes accordingly while the pulse width of the optical pulse train remains almost constant. In other words, the output ultra-short pulse train has a tunable duty cycle. In a proof-of-principle experiment, optical pulses with repetition rates of 10, 5, 2.5 and 1.25 GHz are obtained by adjusting the electrical pattern applied on the in-cavity modulator while their pulse widths remain almost unchanged.
基金supported by the National Key Natural Science Foundation of China under Grant No. 60537060
文摘The efficient generation of a 1.17-mJ laser pulse with 360 ps duration using an ytterbium (Yb)-doped fiber amplifier chain seeded by a homemade mode-locked fiber laser is demonstrated experimentally. A specially designed figure-of-eight fiber laser acts as the seed source of a chirped-pulse amplification (CPA) system and generates mode-locked pulses with hundreds of picosecond widths. Two kinds of large-mode-area (LMA) double-clad Yb-doped fibers are employed to construct the pre-amplifier and main amplifier. All of the adopted instruments help avoid severe nonlinearity in fibers to raise sub-nanosecond pulse energy with acceptable signal-to-noise ratio (SNR). The output spectrum of this fiber-based CPA system shows that amplified spontaneous emission (ASE) is suppressed to better than 30 dB, and the onset of stimulated Raman scattering is excluded.
基金This work was supported by the National Natural Science Foundation of China under Grant No. 60444008904010247 and 60177019.
文摘An 8×10 Gb/s optical time-division-multiplexing (OTDM) system was demonstrated with an electroab-sorption modulator (EAM) based short pulse generator followed by a two-stage nonlinear compression scheme which generated stable 10-GHz, 2-ps full-width at half-maximum (FWHM) pulse train, an optoelectronic oscillator (OEO) that extracted 10-GHz clock with a timing jitter of 300 fs from 80-Gb/s OTDM signal and a self cascaded EAM which produced a switching window of about 10 ps. A back-to-back error free demultiplexing experiment with a power penalty of 3.25 dB was carried out to verify the system performance.