The estimation of the quality factor Q plays a fundamental role in enhancing seismic resolution via absorption compensation in the near-surface layer.We present a new geometry that can be used to acquire field data by...The estimation of the quality factor Q plays a fundamental role in enhancing seismic resolution via absorption compensation in the near-surface layer.We present a new geometry that can be used to acquire field data by combining surface and cross-hole surveys to decrease the effect of geophone coupling on Q estimation.In this study,we drilled number of receiver holes around the source hole,each hole has different depth and each geophone is placed geophones into the bottom of each receiver hole to avoid the effect of geophone coupling with the borehole wall on Q estimation in conventional cross-hole seismic surveys.We also propose a novel tomographic inversion of the Q factor without the effect of the source signature,and examine its stability and reliability using synthetic data.We estimate the Q factors of the near-surface layer in two different frequency bands using field data acquired in the Dagang Oilfield.The results show that seismic absorption in the nearsurface layer is much greater than that in the subsurface strata.Thus,it is of critical practical importance to enhance the seismic solution by compensating for near-surface absorption.In addition,we derive different Q factors from two frequency bands,which can be treated,to some extent,as evidence of a frequency-dependent Q.展开更多
We design and construct a resonant photodetector(RPD)with a Q factor of 320.83 at the resonant frequency of38.5 MHz on the basis of a theoretical analysis.Compared with the existing RPD under the same conditions,the s...We design and construct a resonant photodetector(RPD)with a Q factor of 320.83 at the resonant frequency of38.5 MHz on the basis of a theoretical analysis.Compared with the existing RPD under the same conditions,the signalto-noise-ratio of the error signal is increased by 15 dB and the minimum operation power is reduced from-55 dBm to-70 dBm.By comparing the standard deviations of the stability curves,we confirm that the RPD has a dramatic improvement on ultralow power extraction.In virtue of the RPD,we have completed the demonstration of channel multiplexing quantum communication.展开更多
Thin-film lithium niobate has attracted great interest in high-speed communication due to its unique piezoelectric and nonlinear properties.However,its high photorefraction and slow electro-optic response relaxation i...Thin-film lithium niobate has attracted great interest in high-speed communication due to its unique piezoelectric and nonlinear properties.However,its high photorefraction and slow electro-optic response relaxation introduce the possibility of transmission bit errors.Recently,lithium tantalate,another piezoelectric and nonlinear material,has emerged as a promising candidate for active photonic integrated devices because of its weaker photorefraction,faster electro-optic response relaxation,higher optical damage threshold,wider transparency window,and lower birefringence compared with lithium niobate.Here,we developed an ultralow-loss lithium tantalate integrated photonic platform,including waveguides,grating couplers,and microring cavities.The measured highest optical Q factor of the microring cavities is beyond 10^(7),corresponding to the lowest waveguide propagation loss of~1.88 dB∕m.The photorefractive effect in such lithium tantalate microring cavities was experimentally demonstrated to be 500 times weaker than that in lithium niobate microcavities.This work lays the foundation for a lithium tantalate integrated platform for achieving a series of on-chip optically functional devices,such as periodically poled waveguides,acousto-optic modulators,and electro-optic modulators.展开更多
Effects of performing an R-factor analysis of observed variables based on population models comprising R- and Q-factors were investigated. Although R-factor analysis of data based on a population model comprising R- a...Effects of performing an R-factor analysis of observed variables based on population models comprising R- and Q-factors were investigated. Although R-factor analysis of data based on a population model comprising R- and Q-factors is possible, this may lead to model error. Accordingly, loading estimates resulting from R-factor analysis of sample data drawn from a population based on a combination of R- and Q-factors will be biased. It was shown in a simulation study that a large amount of Q-factor variance induces an increase in the variation of R-factor loading estimates beyond the chance level. Tests of the multivariate kurtosis of observed variables are proposed as an indicator of possible Q-factor variance in observed variables as a prerequisite for R-factor analysis.展开更多
We design a channel-drop filter(CDF)with a linear gradient microcavity in a two-dimensional(2D)photonic crystal(PC).The model of three-port CDF with reflector is used to achieve high quality factor(Q-factor)and 100%ch...We design a channel-drop filter(CDF)with a linear gradient microcavity in a two-dimensional(2D)photonic crystal(PC).The model of three-port CDF with reflector is used to achieve high quality factor(Q-factor)and 100%channel-drop efficiency.The research indicates that adjusting the distance between reference plane and reflector can simultaneously influence the Q-factor due to coupling to a bus waveguide and the phase retardation occurring in the round trip between a microcavity and a reflector.The calculation results of 2D finite-difference time-domain(FDTD)method show that the designed filter can achieve the drop efficiency of 96.7%and ultra-high Q-factor with an ultra-small modal volume.展开更多
Low quality(Q) factor is often the limiting factor for high performance carbon nanotube(CNT) resonators. The most commonly used approach to enhance the Q factor of CNTs is to reduce/eliminate the intrinsic defects.Her...Low quality(Q) factor is often the limiting factor for high performance carbon nanotube(CNT) resonators. The most commonly used approach to enhance the Q factor of CNTs is to reduce/eliminate the intrinsic defects.Herein, we show surprisingly that hole defects of suitable size and position are able to enhance the Q factor of CNT, which strongly contradicts to the common notion that the presence of defects promote intrinsic dissipation via defects dissipation. By analyzing the strain distribution, we find that such abnormal enhancement in Q factor of defected CNT originates from a coupling competition mechanism between the atomic mismatch around defected atoms and the thermoelastic damping. Although the presence of holes will introduce an additional defect dissipation source, suitable holes are capable of reducing the energy dissipation arisen from the thermoelastic damping, through changing the spatial strain field of defected CNT. This coupling competition mechanism provides a new route for designing high performance CNT resonators via defects engineering.展开更多
The quality factor Q, which reflects the energy attenuation of seismic waves in subsurface media, is a diagnostic tool for hydrocarbon detection and reservoir characterization. In this paper, we propose a new Q extrac...The quality factor Q, which reflects the energy attenuation of seismic waves in subsurface media, is a diagnostic tool for hydrocarbon detection and reservoir characterization. In this paper, we propose a new Q extraction method based on the energy ratio before and after the wavelet attenuation, named the energy-ratio method（ERM）. The proposed method uses multipoint signal data in the time domain to estimate the wavelet energy without invoking the source wavelet spectrum, which is necessary in conventional Q extraction methods, and is applicable to any source wavelet spectrum; however, it requires high-precision seismic data. Forward zero-offset VSP modeling suggests that the ERM can be used for reliable Q inversion after nonintrinsic attenuation（geometric dispersion, refl ection, and transmission loss） compensation. The application to real zero-offset VSP data shows that the Q values extracted by the ERM and spectral ratio methods are identical, which proves the reliability of the new method.展开更多
We demonstrated a novel method to measure the unloaded quality factor(Q factor) of high-Q resonant cavities. This method was used to obtain data with low errors and calculate the unloaded Q factor. This procedure was ...We demonstrated a novel method to measure the unloaded quality factor(Q factor) of high-Q resonant cavities. This method was used to obtain data with low errors and calculate the unloaded Q factor. This procedure was more reliable than traditional methods. The data required for the method were near the resonant frequency,not at the half-power points of the reflection coefficient curve or Smith chart. We applied the new method to measure a resonant cavity with an unloaded Q factor of^100,000, obtaining good agreement between the measured and theoretical results.展开更多
为进一步提高有载分接开关(on-load tap changer,OLTC)机械状态监测的准确性,文中基于优化品质因数可调小波变换(tunable quality wavelet transform,TQWT)对OLTC切换过程中的振动信号进行了分析。即使用人工鱼群算法(artificial fish s...为进一步提高有载分接开关(on-load tap changer,OLTC)机械状态监测的准确性,文中基于优化品质因数可调小波变换(tunable quality wavelet transform,TQWT)对OLTC切换过程中的振动信号进行了分析。即使用人工鱼群算法(artificial fish swarm algorithm,AFSA)基于分解余量与整体正交系数研究了TQWT的优化分解方法,计算得到了OLTC振动信号的多个子序列,构建了基于优化孪生支持向量机(twin support vector machine,TWSVM)的OLTC机械故障诊断模型。对某CM型OLTC正常与典型机械故障下振动信号的分析结果表明,所提优化TQWT分解方法有效提高了OLTC振动信号分解结果的准确性。相对于其他诊断模型,所构建AFSA-TWSVM的OLTC机械故障诊断模型分类效果好且收敛速度更快。展开更多
为提升时间序列的聚类精度,提出一种融合优化可调Q因子小波变换的改进密度峰值聚类(improved density peaks clustering based on optimal tunable Q-factor wavelet transform,OTQWT-IDPC)算法,该算法利用可调Q因子小波变换的能量优化...为提升时间序列的聚类精度,提出一种融合优化可调Q因子小波变换的改进密度峰值聚类(improved density peaks clustering based on optimal tunable Q-factor wavelet transform,OTQWT-IDPC)算法,该算法利用可调Q因子小波变换的能量优化选择策略及改进粒子群优化算法确定的最佳Q因子分解时序信号,通过最优特征子带的能量、均值、标准差和模糊熵构建特征子空间,并采用主成分分析降低特征维度,以减少特征冗余。同时,考虑到距离较远而周围密集程度较大的K近邻样本对局部密度的贡献率,引入权重系数及K近邻重新定义DPC的局部密度,并利用共享最近邻描述样本间的相似性。在BONN癫痫脑电信号和CWRU滚动轴承数据集上进行对比实验,结果表明,该算法的聚类精度分别为95%、94%,且Jacarrd、FMI和F_(1)值指标均优于其他对比算法,证明了OTQWT-IDPC算法的有效性。展开更多
All-optical regenerators can be used to suppress amplified spontaneous emission(ASE) noise introduced by cascaded erbium doped fiber amplifiers(EDFAs) in optical fiber communication systems and lead to the improvement...All-optical regenerators can be used to suppress amplified spontaneous emission(ASE) noise introduced by cascaded erbium doped fiber amplifiers(EDFAs) in optical fiber communication systems and lead to the improvement of optical receiver sensitivity. By introducing the Q-factor transfer function(QTF), we evaluate the Q-factor performance of degenerate four-wave mixing(DFWM) regenerators with clock pump and reveal the differences between the optimal input powers determined from the static and dynamic power tranfer function(PTF) and the QTF curves. Our simulation shows that the clock-pump regnerator is capable of improving the Q-facor and receiver sensitivity for 40 Gbit/s ASE-degraded return-to-zero on-off keying(RZ-OOK) signal by 2.58 dB and 4.2 d B, respectively.展开更多
The attenuation factor or quality factor(Q-factor or Q) has been used to measure the energy attenuation of seismic waves propagating in underground media. Many methods are used to estimate the Q-factor. We propose a m...The attenuation factor or quality factor(Q-factor or Q) has been used to measure the energy attenuation of seismic waves propagating in underground media. Many methods are used to estimate the Q-factor. We propose a method to calculate the Q-factor based on the prestack Q-factor inversion and the generalized S-transform. The proposed method specifies a standard primary wavelet and calculates the cumulative Q-factors; then, it finds the interlaminar Q-factors using the relation between Q and offset(QVO) and the Dix formula. The proposed method is alternative to methods that calculate interlaminar Q-factors after horizon picking. Because the frequency spectrum of each horizon can be extracted continuously on a 2D time–frequency spectrum, the method is called the continuous spectral ratio slope(CSRS) method. Compared with the other Q-inversion methods, the method offers nearly effortless computations and stability, and has mathematical and physical significance. We use numerical modeling to verify the feasibility of the method and apply it to real data from an oilfield in Ahdeb, Iraq. The results suggest that the resolution and spatial stability of the Q-profile are optimal and contain abundant interlaminar information that is extremely helpful in making lithology and fluid predictions.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.41174117 and 41474109)the National Key Basic Research Development Program of China(Grant No.2013CB228606)
文摘The estimation of the quality factor Q plays a fundamental role in enhancing seismic resolution via absorption compensation in the near-surface layer.We present a new geometry that can be used to acquire field data by combining surface and cross-hole surveys to decrease the effect of geophone coupling on Q estimation.In this study,we drilled number of receiver holes around the source hole,each hole has different depth and each geophone is placed geophones into the bottom of each receiver hole to avoid the effect of geophone coupling with the borehole wall on Q estimation in conventional cross-hole seismic surveys.We also propose a novel tomographic inversion of the Q factor without the effect of the source signature,and examine its stability and reliability using synthetic data.We estimate the Q factors of the near-surface layer in two different frequency bands using field data acquired in the Dagang Oilfield.The results show that seismic absorption in the nearsurface layer is much greater than that in the subsurface strata.Thus,it is of critical practical importance to enhance the seismic solution by compensating for near-surface absorption.In addition,we derive different Q factors from two frequency bands,which can be treated,to some extent,as evidence of a frequency-dependent Q.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62027821,11654002,11874250,and 11804207)the National Key R&D Program of China(Grant No.2016YFA0301401)+3 种基金the Key R&D Program of Shanxi,China(Grant No.201903D111001)the Program for Sanjin Scholar of Shanxi Provincethe Program for Outstanding Innovative Teams of Higher Learning Institutions of Shanxi,Chinathe Fund for Shanxi“1331 Project”Key Subjects Construction,China。
文摘We design and construct a resonant photodetector(RPD)with a Q factor of 320.83 at the resonant frequency of38.5 MHz on the basis of a theoretical analysis.Compared with the existing RPD under the same conditions,the signalto-noise-ratio of the error signal is increased by 15 dB and the minimum operation power is reduced from-55 dBm to-70 dBm.By comparing the standard deviations of the stability curves,we confirm that the RPD has a dramatic improvement on ultralow power extraction.In virtue of the RPD,we have completed the demonstration of channel multiplexing quantum communication.
基金Research Grants Council of Hong Kong(C4050-21E,RFS2324-4S03,14203623)The Chinese University of Hong Kong(Group Research Scheme)。
文摘Thin-film lithium niobate has attracted great interest in high-speed communication due to its unique piezoelectric and nonlinear properties.However,its high photorefraction and slow electro-optic response relaxation introduce the possibility of transmission bit errors.Recently,lithium tantalate,another piezoelectric and nonlinear material,has emerged as a promising candidate for active photonic integrated devices because of its weaker photorefraction,faster electro-optic response relaxation,higher optical damage threshold,wider transparency window,and lower birefringence compared with lithium niobate.Here,we developed an ultralow-loss lithium tantalate integrated photonic platform,including waveguides,grating couplers,and microring cavities.The measured highest optical Q factor of the microring cavities is beyond 10^(7),corresponding to the lowest waveguide propagation loss of~1.88 dB∕m.The photorefractive effect in such lithium tantalate microring cavities was experimentally demonstrated to be 500 times weaker than that in lithium niobate microcavities.This work lays the foundation for a lithium tantalate integrated platform for achieving a series of on-chip optically functional devices,such as periodically poled waveguides,acousto-optic modulators,and electro-optic modulators.
文摘Effects of performing an R-factor analysis of observed variables based on population models comprising R- and Q-factors were investigated. Although R-factor analysis of data based on a population model comprising R- and Q-factors is possible, this may lead to model error. Accordingly, loading estimates resulting from R-factor analysis of sample data drawn from a population based on a combination of R- and Q-factors will be biased. It was shown in a simulation study that a large amount of Q-factor variance induces an increase in the variation of R-factor loading estimates beyond the chance level. Tests of the multivariate kurtosis of observed variables are proposed as an indicator of possible Q-factor variance in observed variables as a prerequisite for R-factor analysis.
基金supported by the Natural Science Foundation of the Higher Education Institutions of Guangxi Province in China(No.201202ZD010)
文摘We design a channel-drop filter(CDF)with a linear gradient microcavity in a two-dimensional(2D)photonic crystal(PC).The model of three-port CDF with reflector is used to achieve high quality factor(Q-factor)and 100%channel-drop efficiency.The research indicates that adjusting the distance between reference plane and reflector can simultaneously influence the Q-factor due to coupling to a bus waveguide and the phase retardation occurring in the round trip between a microcavity and a reflector.The calculation results of 2D finite-difference time-domain(FDTD)method show that the designed filter can achieve the drop efficiency of 96.7%and ultra-high Q-factor with an ultra-small modal volume.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51605172 and 51775201)the Natural Science Foundation of Hubei Province (Grant No. 2016CFB191)+1 种基金the Fundamental Research Funds for the Central Universities (Grant No. 2015MS014)the Hong Kong Scholars Program (No. XJ2020043)。
文摘Low quality(Q) factor is often the limiting factor for high performance carbon nanotube(CNT) resonators. The most commonly used approach to enhance the Q factor of CNTs is to reduce/eliminate the intrinsic defects.Herein, we show surprisingly that hole defects of suitable size and position are able to enhance the Q factor of CNT, which strongly contradicts to the common notion that the presence of defects promote intrinsic dissipation via defects dissipation. By analyzing the strain distribution, we find that such abnormal enhancement in Q factor of defected CNT originates from a coupling competition mechanism between the atomic mismatch around defected atoms and the thermoelastic damping. Although the presence of holes will introduce an additional defect dissipation source, suitable holes are capable of reducing the energy dissipation arisen from the thermoelastic damping, through changing the spatial strain field of defected CNT. This coupling competition mechanism provides a new route for designing high performance CNT resonators via defects engineering.
基金supported by the Major Project of the Ministry of Science and Technology of China(No.2011ZX05024-001-01)National Nature Science Foundation of China(No.41140033)
文摘The quality factor Q, which reflects the energy attenuation of seismic waves in subsurface media, is a diagnostic tool for hydrocarbon detection and reservoir characterization. In this paper, we propose a new Q extraction method based on the energy ratio before and after the wavelet attenuation, named the energy-ratio method（ERM）. The proposed method uses multipoint signal data in the time domain to estimate the wavelet energy without invoking the source wavelet spectrum, which is necessary in conventional Q extraction methods, and is applicable to any source wavelet spectrum; however, it requires high-precision seismic data. Forward zero-offset VSP modeling suggests that the ERM can be used for reliable Q inversion after nonintrinsic attenuation（geometric dispersion, refl ection, and transmission loss） compensation. The application to real zero-offset VSP data shows that the Q values extracted by the ERM and spectral ratio methods are identical, which proves the reliability of the new method.
基金supported by the National Key Research and Development Program of China(No.2016YFA0401902)
文摘We demonstrated a novel method to measure the unloaded quality factor(Q factor) of high-Q resonant cavities. This method was used to obtain data with low errors and calculate the unloaded Q factor. This procedure was more reliable than traditional methods. The data required for the method were near the resonant frequency,not at the half-power points of the reflection coefficient curve or Smith chart. We applied the new method to measure a resonant cavity with an unloaded Q factor of^100,000, obtaining good agreement between the measured and theoretical results.
文摘为进一步提高有载分接开关(on-load tap changer,OLTC)机械状态监测的准确性,文中基于优化品质因数可调小波变换(tunable quality wavelet transform,TQWT)对OLTC切换过程中的振动信号进行了分析。即使用人工鱼群算法(artificial fish swarm algorithm,AFSA)基于分解余量与整体正交系数研究了TQWT的优化分解方法,计算得到了OLTC振动信号的多个子序列,构建了基于优化孪生支持向量机(twin support vector machine,TWSVM)的OLTC机械故障诊断模型。对某CM型OLTC正常与典型机械故障下振动信号的分析结果表明,所提优化TQWT分解方法有效提高了OLTC振动信号分解结果的准确性。相对于其他诊断模型,所构建AFSA-TWSVM的OLTC机械故障诊断模型分类效果好且收敛速度更快。
文摘为提升时间序列的聚类精度,提出一种融合优化可调Q因子小波变换的改进密度峰值聚类(improved density peaks clustering based on optimal tunable Q-factor wavelet transform,OTQWT-IDPC)算法,该算法利用可调Q因子小波变换的能量优化选择策略及改进粒子群优化算法确定的最佳Q因子分解时序信号,通过最优特征子带的能量、均值、标准差和模糊熵构建特征子空间,并采用主成分分析降低特征维度,以减少特征冗余。同时,考虑到距离较远而周围密集程度较大的K近邻样本对局部密度的贡献率,引入权重系数及K近邻重新定义DPC的局部密度,并利用共享最近邻描述样本间的相似性。在BONN癫痫脑电信号和CWRU滚动轴承数据集上进行对比实验,结果表明,该算法的聚类精度分别为95%、94%,且Jacarrd、FMI和F_(1)值指标均优于其他对比算法,证明了OTQWT-IDPC算法的有效性。
基金supported by the National Natural Science Foundation of China(No.61671108)the Fundamental Research Funds for the Central Universities(No.ZYGX2014J005)the Program for Changjiang Scholars and Innovative Research Team in University
文摘All-optical regenerators can be used to suppress amplified spontaneous emission(ASE) noise introduced by cascaded erbium doped fiber amplifiers(EDFAs) in optical fiber communication systems and lead to the improvement of optical receiver sensitivity. By introducing the Q-factor transfer function(QTF), we evaluate the Q-factor performance of degenerate four-wave mixing(DFWM) regenerators with clock pump and reveal the differences between the optimal input powers determined from the static and dynamic power tranfer function(PTF) and the QTF curves. Our simulation shows that the clock-pump regnerator is capable of improving the Q-facor and receiver sensitivity for 40 Gbit/s ASE-degraded return-to-zero on-off keying(RZ-OOK) signal by 2.58 dB and 4.2 d B, respectively.
基金supported by The National Key Research and Development Program Plane(No.2017YFC0601505)National Natural Science Foundation(No.41672325)Science&Technology Department of Sichuan Province Technology Project(No.2017GZ0393)
文摘The attenuation factor or quality factor(Q-factor or Q) has been used to measure the energy attenuation of seismic waves propagating in underground media. Many methods are used to estimate the Q-factor. We propose a method to calculate the Q-factor based on the prestack Q-factor inversion and the generalized S-transform. The proposed method specifies a standard primary wavelet and calculates the cumulative Q-factors; then, it finds the interlaminar Q-factors using the relation between Q and offset(QVO) and the Dix formula. The proposed method is alternative to methods that calculate interlaminar Q-factors after horizon picking. Because the frequency spectrum of each horizon can be extracted continuously on a 2D time–frequency spectrum, the method is called the continuous spectral ratio slope(CSRS) method. Compared with the other Q-inversion methods, the method offers nearly effortless computations and stability, and has mathematical and physical significance. We use numerical modeling to verify the feasibility of the method and apply it to real data from an oilfield in Ahdeb, Iraq. The results suggest that the resolution and spatial stability of the Q-profile are optimal and contain abundant interlaminar information that is extremely helpful in making lithology and fluid predictions.
