Phase-sensitive optical time domain reflectometry(Ф-OTDR)is an effective way to detect vibrations and acoustic waves with high sensitivity,by interrogating coherent Rayleigh backscattering light in sensing fiber.In p...Phase-sensitive optical time domain reflectometry(Ф-OTDR)is an effective way to detect vibrations and acoustic waves with high sensitivity,by interrogating coherent Rayleigh backscattering light in sensing fiber.In particular,fiber-optic distributed acoustic sensing(DAS)based on theФ-OTDR with phase demodulation has been extensively studied and widely used in intrusion detection,borehole seismic acquisition,structure health monitoring,etc.,in recent years,with superior advantages such as long sensing range,fast response speed,wide sensing bandwidth,low operation cost and long service lifetime.Significant advances in research and development(R&D)ofФ-OTDR have been made since 2014.In this review,we present a historical review ofФ-OTDR and then summarize the recent progress ofФ-OTDR in the Fiber Optics Research Center(FORC)at University of Electronic Science and Technology of China(UESTC),which is the first group to carry out R&D ofФ-OTDR and invent ultra-sensitive DAS(uDAS)seismometer in China which is elected as one of the ten most significant technology advances of PetroChina in 2019.It can be seen that theФ-OTDR/DAS technology is currently under its rapid development stage and would reach its climax in the next 5 years.展开更多
Objective:To evaluate the anatomical characteristics and patterns of neurovascular compression in patients suffering trigeminal neuralgia,using 3D high-resolution magnetic resonance imaging methods and fusion technolo...Objective:To evaluate the anatomical characteristics and patterns of neurovascular compression in patients suffering trigeminal neuralgia,using 3D high-resolution magnetic resonance imaging methods and fusion technologies.Methods:The analysis of the anatomy of the facial nerve,brain stem and the vascular structures related to this nerve was made in 100 consecutive patients for TN.3D high resolution MRI studies(3D SPGR,T1 enhanced 3D MP-RAGE and T2/T1 3D FIESTA) simultaneous visualization were used to assessed using the software 3D DOCTOR. Results:In 93 patients(93%),there were one or several locals of neurovascular compression (NVC).The superior cerebellar artery was involved in 71 cases(76%),the other vessels including the antero-inferior cerebellar artery,the basilar artery,the vertebral artery,and some venous structures.The mean distance between NVC and nerve origin site in the brainstem was(3.76±2.90) mm).In 39 patients(42%),the vascular compression was located proximally and in 42(45%) the compression was located distally.Nerve dislocation or distortion by the vessel was observed in 30 cases(32%).Conclusions:This 3D high resolution MRI and image fusion technology could be useful for diagnostic and therapeutic decisions in TN.展开更多
In this paper, the effect of phase-shifting between pumping lightand input signal light in a optical Phase-Sensitive Amplifier(PSA)ondispersion compensation for optical fiber communication systems usingPSA as In-line ...In this paper, the effect of phase-shifting between pumping lightand input signal light in a optical Phase-Sensitive Amplifier(PSA)ondispersion compensation for optical fiber communication systems usingPSA as In-line amplifiers is theoretically analyzed by computersimulation. From ur simulation we've got the result that Theeye-pattern degradation of the high-speed signal increase rapidlywith the accretion of fiber dispersion and also Increase with theincreasing of phase shift. But if the phase shift is controlled in acertain range, it won't affect the System performance. Otherwise, thesystem performance will be seriously degraded. At all events, theshifting Range of PSA's phase, which shifts at both sides of zero,will be half of that which shifts at only one side.展开更多
We present a theoretical scheme for broadband multi-channel quantum noise suppression and phase-sensitive modulation of continuous variables in a coupled resonant system with quantum entanglement properties.The effect...We present a theoretical scheme for broadband multi-channel quantum noise suppression and phase-sensitive modulation of continuous variables in a coupled resonant system with quantum entanglement properties.The effects of different coupling strengths,pumping power in suppressing quantum noise and controlling the width of quantum interference channels are analyzed carefully.Furthermore,quantum noise suppression at quadrature amplitude is obtained with phase-sensitive modulation.It shows that the entanglement strength of the output field and the quantum noise suppression effect can be enhanced significantly by a strong pumping filed due to interaction of pumping light with the nonlinear crystal.The full width at half maxima(FWHM)of the noise curve at the resonant peak(△=0 MHz)is broadened up to 2.17 times compared to the single cavity.In the strong coupling resonant system,the FWHM at △=0 MHz(△=±3.1 MHz)is also broadened up to 1.27(3.53)times compared to the weak coupling resonant system case.The multi-channel quantum interference creates an electromagnetically induced transparent-like line shape,which can be used to improve the transmission efficiency and stability of wave packets in quantum information processing and quantum memory.展开更多
The phase-sensitive time-domain reflectometer [φ-OTDR] has been popularly used for events detection over a long period of time.In this study,the events classification methods based on convolutional neural networks [C...The phase-sensitive time-domain reflectometer [φ-OTDR] has been popularly used for events detection over a long period of time.In this study,the events classification methods based on convolutional neural networks [CNNs] with different features,i.e.,the temporal-spatial features and time-frequency features,are compared and analyzed comprehensively inφ-OTDR.The developed CNNs aim at distinguishing three typical events:wind blowing,knocking,and background noise.The classification accuracy based on temporal-spatial images is higher than that based on time-frequency images[99.49% versus 98.23%).The work here sets a meaningful reference for feature extraction and application in the pattern recognition of φ-OTDR.展开更多
Robust and fast fat suppression is a challenge in balanced steady-state free precession （SSFP） magnetic resonance imaging. Although single-acquisition phase-sensitive SSFP can provide fat-suppressed images in short ...Robust and fast fat suppression is a challenge in balanced steady-state free precession （SSFP） magnetic resonance imaging. Although single-acquisition phase-sensitive SSFP can provide fat-suppressed images in short scan time, phase errors, especially spatially-dependent phase shift, caused by a variety of factors may result in misplacement of fat and water voxels. In this paper, a novel phase correction algorithm was used to calibrate those phase errors during image reconstruction. This algorithm corrects phase by region growing, employing both the magnitude and the phase information of image pixels. Phantom and in vivo imagings were performed to validate the technique. As a result, excellent fat-suppressed images were acquired by using single-acquisition phase-sensitive SSFP with phase correction.展开更多
针对模拟电路磁通门温度特性差,数字电路磁通门占用接口多且反应慢的难题,提出了一种基于异或运算相敏整流电路的数字式闭环磁通门传感器。该异或运算电路是将高速AD采样得到的二次谐波信号与参考方波信号进行异或逻辑运算后经高速DA完...针对模拟电路磁通门温度特性差,数字电路磁通门占用接口多且反应慢的难题,提出了一种基于异或运算相敏整流电路的数字式闭环磁通门传感器。该异或运算电路是将高速AD采样得到的二次谐波信号与参考方波信号进行异或逻辑运算后经高速DA完成了数字相敏整流功能。采用基于异或运算相敏整流电路的磁通门系统既改善了温度特性,同时也节约了数字接口,减少了数字处理器的运算负担。通过实验测试,结果显示:系统测量范围为±62 900 n T,线性度为2.8×10-4,分辨力约为2 n T,磁通门反馈回路的-3 d B带宽约为240 Hz。展开更多
Objective:Late gadolinium enhancement(LGE) patterns of cardiovascular magnetic resonance (CMR) relying on PSIR(phase-sensitive inversion recovery sequence) techniques had been used to determine the characteristics of ...Objective:Late gadolinium enhancement(LGE) patterns of cardiovascular magnetic resonance (CMR) relying on PSIR(phase-sensitive inversion recovery sequence) techniques had been used to determine the characteristics of LGE in apical hypertrophic cardiomyopathy(ApHCM). Methods:Forty patients pure ApHCM[age,(60.2±10.4) years,31 men]were enrolled.LGE images were acquired using PSIR,and analyzed using a 17-segment model.Summing the LGE areas in all short axis slices yielded the total volume of late enhancement,which was subsequently presented as a proportion of total LV myocardium(%LGE).Results:Mean maximal apical wall thickness was(17.9±2.3) mm,and mean left ventricular(LV) ejection fraction was(67.7±8.0)%.LGE was detected in 130 segments of 30 patients(75.0%),occupying(4.9±5.5)% of LV myocardium.LGE was mainly detected at the junction between left and right ventricles in 12(30%) and at the apex in 28(70%),although LGE-positive areas were widely distributed,and not limited to the apex.Focal LGE at the non-hypertrophic LV segments was found in some ApHCM patients,even without LGE of hypertrophied apical segments.Conclusions:LGE was frequently observed not only in the thickened apex of the heart but also in other LV segments,irrespective of the presence or absence of hypertrophy.The simple presence of LGE on CMR was not representative of adverse prognosis in this population.展开更多
A phase-sensitive optical time domain reflectometer （φ-OTDR） based on a 120°-phase-difference Michelson in- terferometer is proposed. The Michelson interferometer with arm difference of 4m is used to test the ...A phase-sensitive optical time domain reflectometer （φ-OTDR） based on a 120°-phase-difference Michelson in- terferometer is proposed. The Michelson interferometer with arm difference of 4m is used to test the phase difference between the Rayleigh scattering from two sections of the fiber. A new demodulation method called the inverse transmission matrix demodulation scheme is utilized to demodulate the distributed phase from the backward scattering along the long fiber, The experimental results show that the 120°-phase-difference inter- ferometer φ-OTDR can detect the phase along the 3km fiber, and the acoustic signal within the whole human hearing range of 20 Hz-20 kHz is reproduced accurately and quickly.展开更多
Objective:To determine the deference between phase sensitive magnetic resonance(MR) imaging and magnitude reconstruction to detect infracted myocardium.Methods:Twenty patients(16 men;4 women;mean age,56 years),experie...Objective:To determine the deference between phase sensitive magnetic resonance(MR) imaging and magnitude reconstruction to detect infracted myocardium.Methods:Twenty patients(16 men;4 women;mean age,56 years),experienced Q-wave myocardial infarction 2 weeks earlier were examined with a 3.0-T MR system 10 minutes after administration of 0.1 mmol/kg body weight gadobenate dimeglumine.To determine the optimal TI,a TI scout sequence was used.A segmented 2D IR true fast imaging with steady-state precession(trueFISP) sequence that produces both phase-sensitive and magnitude-reconstructed images were used at TI values of 200-600 msec(TI values were varied in 100-msec steps) and at optimal TI(mean value,330 msec).Contrast- noise ratios(CNRs) of normal and infarcted myocardium and the area of infarcted myocardium were determined.Two-tailed unpaired sample Student t test was used to compare CNRs,and area of infarction.Results:MMean CNR phase-sensitive and magnitude-reconstructed images at optimal TI(mean value,330 msec) were 6.2,and 6.1,respectively.For a TI of 200 msec,CNR values were 5.5,and 4.2,respectively;for TI of 600 msec,CNR values were 5.8 and 4.3,respectively.Area of infarcted myocardium was underestimated on magnitude-reconstruction images(P = 0.002-0.03) for short TI values(ie.,200 msec) but not on phase sensitive reconstructed when compared with IR tureFISP images obtained at optimal TI.Conclusions: LPhase-sensitive image reconstruction results in reduced need for precise choice of TI and more consistent image quality.展开更多
We study the colour-locked twin-noisy-field correlation effects in the fifth-order nonlinear susceptibility of ultrafast polarization beats in a cascade four-level system. More importantly, the fifth-order phase-sensi...We study the colour-locked twin-noisy-field correlation effects in the fifth-order nonlinear susceptibility of ultrafast polarization beats in a cascade four-level system. More importantly, the fifth-order phase-sensitive heterodyne detection of ultrafast polarization beats has been exploited. The fifth-order nonlinear optical response can be controlled and modified through the colour-locked correlation of twin noisy fields. Thus, this method with the phase dispersion information is a good way to measure the real and imaginary parts of the fifth-order nonlinear susceptibility.展开更多
In a phase-sensitive optical-time domain reflectometry （Ф-OTDR） system, the challenge for dynamic strain measurement lies in large intensity fluctuations from trace to trace. The intensity fluctuation caused by sto...In a phase-sensitive optical-time domain reflectometry （Ф-OTDR） system, the challenge for dynamic strain measurement lies in large intensity fluctuations from trace to trace. The intensity fluctuation caused by stochastic characteristics of Rayleigh backscattering sets detection limit for the minimum strength of vibration measurement and causes the large measurement uncertainty. Thus, a trace-to-trace correlation coefficient is introduced to quantify intensity fluctuation of Ф-OTDR traces and stability of the sensor system theoretically and experimentally. A novel approach of measuring dynamic strain induced by various driving voltages of lead zirconate titanate （PZT） in Ф-OTDR is also demonstrated. Piezoelectric vibration signals are evaluated through analyzing peak values of fast Fourier transform spectra at the fundamental frequency and high-order harmonics based on Bessel functions. High trace-to-trace correlation coefficients varying from 0.824 to 0.967 among 100 measurements are obtained in experimental results, showing the good stability of our sensor system, as well as small uncertainty of measured peak values.展开更多
A novel alkaloid compound with efficacious antihypertension activity was synthesized from one of heptatrienyl derivatives which was obtainod from curcumol by GUO Yong-tian et al. The structural determination of crysta...A novel alkaloid compound with efficacious antihypertension activity was synthesized from one of heptatrienyl derivatives which was obtainod from curcumol by GUO Yong-tian et al. The structural determination of crystalline intermediate is very important for the structural elucidation of final reductive product and for designing and synthesizing展开更多
In this paper,a novel birefringence measurement method through the Rayleigh backscattered lightwave within single-mode fiber is proposed,using a single chirped-pulse with arbitrary state of polarization.Numerical anal...In this paper,a novel birefringence measurement method through the Rayleigh backscattered lightwave within single-mode fiber is proposed,using a single chirped-pulse with arbitrary state of polarization.Numerical analysis is carried out in detail,then pulse-compression phase-sensitive optical time domain reflectometry(PC-O-OTDR)with polarization-diverse coherent detection is employed to verify this method.A 2 km spun single-mode fiber is tested with 8.6cm spatial resolution,and the average birefringence of the fiber under test is measured as 0.234rad/m,which is consistent with previous literatures about single-mode fiber.Moreover,the relationship between the measured birefringence and the spatial resolution is also studied for the first time,and the results show that spatial resolution is crucial for fiber birefringence measurement.展开更多
基金The authors would like to thank all of the members in the FORC at UESTC for their hard work and important contributions to this workThis work was funded by the Natural Science Foundation of China(Grant Nos.41527805 and 61635005)the 111 Poject(Grant No.B14039).
文摘Phase-sensitive optical time domain reflectometry(Ф-OTDR)is an effective way to detect vibrations and acoustic waves with high sensitivity,by interrogating coherent Rayleigh backscattering light in sensing fiber.In particular,fiber-optic distributed acoustic sensing(DAS)based on theФ-OTDR with phase demodulation has been extensively studied and widely used in intrusion detection,borehole seismic acquisition,structure health monitoring,etc.,in recent years,with superior advantages such as long sensing range,fast response speed,wide sensing bandwidth,low operation cost and long service lifetime.Significant advances in research and development(R&D)ofФ-OTDR have been made since 2014.In this review,we present a historical review ofФ-OTDR and then summarize the recent progress ofФ-OTDR in the Fiber Optics Research Center(FORC)at University of Electronic Science and Technology of China(UESTC),which is the first group to carry out R&D ofФ-OTDR and invent ultra-sensitive DAS(uDAS)seismometer in China which is elected as one of the ten most significant technology advances of PetroChina in 2019.It can be seen that theФ-OTDR/DAS technology is currently under its rapid development stage and would reach its climax in the next 5 years.
基金supported by Haikou Key Science and Technology Project (2012-075)Haikou Science Technology Information Bureau(2009-049-1)Science Foundation of Haikou Health Bureau(2010-SWY-13-058)
文摘Objective:To evaluate the anatomical characteristics and patterns of neurovascular compression in patients suffering trigeminal neuralgia,using 3D high-resolution magnetic resonance imaging methods and fusion technologies.Methods:The analysis of the anatomy of the facial nerve,brain stem and the vascular structures related to this nerve was made in 100 consecutive patients for TN.3D high resolution MRI studies(3D SPGR,T1 enhanced 3D MP-RAGE and T2/T1 3D FIESTA) simultaneous visualization were used to assessed using the software 3D DOCTOR. Results:In 93 patients(93%),there were one or several locals of neurovascular compression (NVC).The superior cerebellar artery was involved in 71 cases(76%),the other vessels including the antero-inferior cerebellar artery,the basilar artery,the vertebral artery,and some venous structures.The mean distance between NVC and nerve origin site in the brainstem was(3.76±2.90) mm).In 39 patients(42%),the vascular compression was located proximally and in 42(45%) the compression was located distally.Nerve dislocation or distortion by the vessel was observed in 30 cases(32%).Conclusions:This 3D high resolution MRI and image fusion technology could be useful for diagnostic and therapeutic decisions in TN.
文摘In this paper, the effect of phase-shifting between pumping lightand input signal light in a optical Phase-Sensitive Amplifier(PSA)ondispersion compensation for optical fiber communication systems usingPSA as In-line amplifiers is theoretically analyzed by computersimulation. From ur simulation we've got the result that Theeye-pattern degradation of the high-speed signal increase rapidlywith the accretion of fiber dispersion and also Increase with theincreasing of phase shift. But if the phase shift is controlled in acertain range, it won't affect the System performance. Otherwise, thesystem performance will be seriously degraded. At all events, theshifting Range of PSA's phase, which shifts at both sides of zero,will be half of that which shifts at only one side.
基金Project supported by National Natural Science Foundation of China(Grant Nos.11704053 and 52175531)the Science and Technology Research Program of Chongqing Municipal Education Commission(Grant No.KJQN201800629)。
文摘We present a theoretical scheme for broadband multi-channel quantum noise suppression and phase-sensitive modulation of continuous variables in a coupled resonant system with quantum entanglement properties.The effects of different coupling strengths,pumping power in suppressing quantum noise and controlling the width of quantum interference channels are analyzed carefully.Furthermore,quantum noise suppression at quadrature amplitude is obtained with phase-sensitive modulation.It shows that the entanglement strength of the output field and the quantum noise suppression effect can be enhanced significantly by a strong pumping filed due to interaction of pumping light with the nonlinear crystal.The full width at half maxima(FWHM)of the noise curve at the resonant peak(△=0 MHz)is broadened up to 2.17 times compared to the single cavity.In the strong coupling resonant system,the FWHM at △=0 MHz(△=±3.1 MHz)is also broadened up to 1.27(3.53)times compared to the weak coupling resonant system case.The multi-channel quantum interference creates an electromagnetically induced transparent-like line shape,which can be used to improve the transmission efficiency and stability of wave packets in quantum information processing and quantum memory.
基金supported by the Fundamental Research Funds for the Central Universities(No.FRF-TP-20-067A1Z)。
文摘The phase-sensitive time-domain reflectometer [φ-OTDR] has been popularly used for events detection over a long period of time.In this study,the events classification methods based on convolutional neural networks [CNNs] with different features,i.e.,the temporal-spatial features and time-frequency features,are compared and analyzed comprehensively inφ-OTDR.The developed CNNs aim at distinguishing three typical events:wind blowing,knocking,and background noise.The classification accuracy based on temporal-spatial images is higher than that based on time-frequency images[99.49% versus 98.23%).The work here sets a meaningful reference for feature extraction and application in the pattern recognition of φ-OTDR.
基金Project partially supported by the National Natural Science Foundation of China (Grant Nos 10527003 and 60672104)the State Key Development Program for Basic Research of China (Grant No 2006CB705700-05)+1 种基金Joint Research Foundation of Beijing Education Committee (Grant No SYS100010401)Beijing Natural Science Foundation (Grant No 3073019)
文摘Robust and fast fat suppression is a challenge in balanced steady-state free precession （SSFP） magnetic resonance imaging. Although single-acquisition phase-sensitive SSFP can provide fat-suppressed images in short scan time, phase errors, especially spatially-dependent phase shift, caused by a variety of factors may result in misplacement of fat and water voxels. In this paper, a novel phase correction algorithm was used to calibrate those phase errors during image reconstruction. This algorithm corrects phase by region growing, employing both the magnitude and the phase information of image pixels. Phantom and in vivo imagings were performed to validate the technique. As a result, excellent fat-suppressed images were acquired by using single-acquisition phase-sensitive SSFP with phase correction.
文摘针对模拟电路磁通门温度特性差,数字电路磁通门占用接口多且反应慢的难题,提出了一种基于异或运算相敏整流电路的数字式闭环磁通门传感器。该异或运算电路是将高速AD采样得到的二次谐波信号与参考方波信号进行异或逻辑运算后经高速DA完成了数字相敏整流功能。采用基于异或运算相敏整流电路的磁通门系统既改善了温度特性,同时也节约了数字接口,减少了数字处理器的运算负担。通过实验测试,结果显示:系统测量范围为±62 900 n T,线性度为2.8×10-4,分辨力约为2 n T,磁通门反馈回路的-3 d B带宽约为240 Hz。
基金Supported by Haikou Key Science and Technology Project (2012-075)Haikou Science and Technology Planning Project(2009-049-1)Science and Technology Fund of Haikou Health Bureau(2010-SWY-13-058)
文摘Objective:Late gadolinium enhancement(LGE) patterns of cardiovascular magnetic resonance (CMR) relying on PSIR(phase-sensitive inversion recovery sequence) techniques had been used to determine the characteristics of LGE in apical hypertrophic cardiomyopathy(ApHCM). Methods:Forty patients pure ApHCM[age,(60.2±10.4) years,31 men]were enrolled.LGE images were acquired using PSIR,and analyzed using a 17-segment model.Summing the LGE areas in all short axis slices yielded the total volume of late enhancement,which was subsequently presented as a proportion of total LV myocardium(%LGE).Results:Mean maximal apical wall thickness was(17.9±2.3) mm,and mean left ventricular(LV) ejection fraction was(67.7±8.0)%.LGE was detected in 130 segments of 30 patients(75.0%),occupying(4.9±5.5)% of LV myocardium.LGE was mainly detected at the junction between left and right ventricles in 12(30%) and at the apex in 28(70%),although LGE-positive areas were widely distributed,and not limited to the apex.Focal LGE at the non-hypertrophic LV segments was found in some ApHCM patients,even without LGE of hypertrophied apical segments.Conclusions:LGE was frequently observed not only in the thickened apex of the heart but also in other LV segments,irrespective of the presence or absence of hypertrophy.The simple presence of LGE on CMR was not representative of adverse prognosis in this population.
基金Supported by the National Natural Science Foundation of China under Grant Nos U0934001 and 11076028the Science and Technology Commission of Shanghai Municipality under Grant Nos 11DZ1140202 and 13XD1425400the Pudong New Area Science and Technology Development Fund of China under Grant No PKJ2012-D04
文摘A phase-sensitive optical time domain reflectometer （φ-OTDR） based on a 120°-phase-difference Michelson in- terferometer is proposed. The Michelson interferometer with arm difference of 4m is used to test the phase difference between the Rayleigh scattering from two sections of the fiber. A new demodulation method called the inverse transmission matrix demodulation scheme is utilized to demodulate the distributed phase from the backward scattering along the long fiber, The experimental results show that the 120°-phase-difference inter- ferometer φ-OTDR can detect the phase along the 3km fiber, and the acoustic signal within the whole human hearing range of 20 Hz-20 kHz is reproduced accurately and quickly.
基金supported by Haikou Key Science and Technology Project (2012-075)Haikou Science and Technology Planning Project(2009-049-1)Science and Technology Fund of Haikou Health Bureau(2010-SWY-13-058)
文摘Objective:To determine the deference between phase sensitive magnetic resonance(MR) imaging and magnitude reconstruction to detect infracted myocardium.Methods:Twenty patients(16 men;4 women;mean age,56 years),experienced Q-wave myocardial infarction 2 weeks earlier were examined with a 3.0-T MR system 10 minutes after administration of 0.1 mmol/kg body weight gadobenate dimeglumine.To determine the optimal TI,a TI scout sequence was used.A segmented 2D IR true fast imaging with steady-state precession(trueFISP) sequence that produces both phase-sensitive and magnitude-reconstructed images were used at TI values of 200-600 msec(TI values were varied in 100-msec steps) and at optimal TI(mean value,330 msec).Contrast- noise ratios(CNRs) of normal and infarcted myocardium and the area of infarcted myocardium were determined.Two-tailed unpaired sample Student t test was used to compare CNRs,and area of infarction.Results:MMean CNR phase-sensitive and magnitude-reconstructed images at optimal TI(mean value,330 msec) were 6.2,and 6.1,respectively.For a TI of 200 msec,CNR values were 5.5,and 4.2,respectively;for TI of 600 msec,CNR values were 5.8 and 4.3,respectively.Area of infarcted myocardium was underestimated on magnitude-reconstruction images(P = 0.002-0.03) for short TI values(ie.,200 msec) but not on phase sensitive reconstructed when compared with IR tureFISP images obtained at optimal TI.Conclusions: LPhase-sensitive image reconstruction results in reduced need for precise choice of TI and more consistent image quality.
基金Project supported by the National Natural Science Foundation of China(Grant Nos60308002and60678005)the Foundation for the Author of National Excellent Doctoral Dissertation of China(Grant No200339)+2 种基金the Foundation for Key Program of Ministry of Education,China(Grant No105156)the Fok Ying-Tong Education Foundation for Young Teachers in the Higher Education Institutions of China(Grant No101061)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No20050698017)
文摘We study the colour-locked twin-noisy-field correlation effects in the fifth-order nonlinear susceptibility of ultrafast polarization beats in a cascade four-level system. More importantly, the fifth-order phase-sensitive heterodyne detection of ultrafast polarization beats has been exploited. The fifth-order nonlinear optical response can be controlled and modified through the colour-locked correlation of twin noisy fields. Thus, this method with the phase dispersion information is a good way to measure the real and imaginary parts of the fifth-order nonlinear susceptibility.
文摘In a phase-sensitive optical-time domain reflectometry （Ф-OTDR） system, the challenge for dynamic strain measurement lies in large intensity fluctuations from trace to trace. The intensity fluctuation caused by stochastic characteristics of Rayleigh backscattering sets detection limit for the minimum strength of vibration measurement and causes the large measurement uncertainty. Thus, a trace-to-trace correlation coefficient is introduced to quantify intensity fluctuation of Ф-OTDR traces and stability of the sensor system theoretically and experimentally. A novel approach of measuring dynamic strain induced by various driving voltages of lead zirconate titanate （PZT） in Ф-OTDR is also demonstrated. Piezoelectric vibration signals are evaluated through analyzing peak values of fast Fourier transform spectra at the fundamental frequency and high-order harmonics based on Bessel functions. High trace-to-trace correlation coefficients varying from 0.824 to 0.967 among 100 measurements are obtained in experimental results, showing the good stability of our sensor system, as well as small uncertainty of measured peak values.
文摘A novel alkaloid compound with efficacious antihypertension activity was synthesized from one of heptatrienyl derivatives which was obtainod from curcumol by GUO Yong-tian et al. The structural determination of crystalline intermediate is very important for the structural elucidation of final reductive product and for designing and synthesizing
文摘In this paper,a novel birefringence measurement method through the Rayleigh backscattered lightwave within single-mode fiber is proposed,using a single chirped-pulse with arbitrary state of polarization.Numerical analysis is carried out in detail,then pulse-compression phase-sensitive optical time domain reflectometry(PC-O-OTDR)with polarization-diverse coherent detection is employed to verify this method.A 2 km spun single-mode fiber is tested with 8.6cm spatial resolution,and the average birefringence of the fiber under test is measured as 0.234rad/m,which is consistent with previous literatures about single-mode fiber.Moreover,the relationship between the measured birefringence and the spatial resolution is also studied for the first time,and the results show that spatial resolution is crucial for fiber birefringence measurement.
