With the development of Global Navigation Satellite Systems(GNSS),geodetic GNSS receivers have been utilized to monitor sea levels using GNSS-Interferometry Reflectometry(GNSS-IR)technology.The multi-mode,multi-freque...With the development of Global Navigation Satellite Systems(GNSS),geodetic GNSS receivers have been utilized to monitor sea levels using GNSS-Interferometry Reflectometry(GNSS-IR)technology.The multi-mode,multi-frequency signals of GPS,GLONASS,Galileo,and Beidou can be used for GNSS-IR sea level retrieval,but combining these retrievals remains problematic.To address this issue,a GNSS-IR sea level retrieval combination system has been developed,which begins by analyzing error sources in GNSS-IR sea level retrieval and establishing and solving the GNSS-IR retrieval equation.This paper focuses on two key points:time window selection and equation stability.The stability of the retrieval combination equations is determined by the condition number of the coefficient matrix within the time window.The impact of ill-conditioned coefficient matrices on the retrieval results is demonstrated using an extreme case of SNR data with only ascending or descending trajectories.After determining the time window and removing ill-conditioned equations,the multi-mode,multi-frequency GNSS-IR retrieval is performed.Results from three International GNSS Service(IGS)stations show that the combination method produces high-precision,high-resolution,and high-reliability sea level retrieval combination sequences.展开更多
For a multi-frequency non-reciprocal optical device,we first realize multi-frequency optical non-reciprocal transmission using a non-Hermitian multi-mode resonator array.Practically,multi-frequency operation can add c...For a multi-frequency non-reciprocal optical device,we first realize multi-frequency optical non-reciprocal transmission using a non-Hermitian multi-mode resonator array.Practically,multi-frequency operation can add channels to the non-reciprocal optical device and the non-reciprocity can route optical signals and prevent the reverse flow of noise.Using the Scully–Lamb model and gain saturation effect,we accomplish dual-frequency non-reciprocal transmission by introducing nonlinearity into a linear array of four-mode resonators.The accomplishment is directly demonstrated by the non-reciprocal transmission phenomena present in the non-divergent peaks.For example,a directional cyclic amplifier is constructed with non-reciprocal units.Regarding potential applications,non-reciprocal optical systems can be employed in dual-frequency control,parallel information processing,photonic integrated circuits,optical devices and so on.展开更多
【目的】随着智慧城市建设中信息技术的深度应用,GNSS轨迹数据呈爆炸式增长,但其轨迹生成过程易受信号干扰与传感器故障影响而产生噪声。本文旨在设计新型噪声识别与修复算法,以提升原始GNSS轨迹数据的处理精度与质量。【方法】针对轨...【目的】随着智慧城市建设中信息技术的深度应用,GNSS轨迹数据呈爆炸式增长,但其轨迹生成过程易受信号干扰与传感器故障影响而产生噪声。本文旨在设计新型噪声识别与修复算法,以提升原始GNSS轨迹数据的处理精度与质量。【方法】针对轨迹噪声识别问题,本文提出基于密度矩阵的自适应DBSCAN算法,其具有超参数无关特性,可敏感捕获低幅值噪声点,同时避免连续转向点的误判。针对噪声修复问题,提出基于轨迹分段的函数构造式修复算法:首先采用道格拉斯-普克(Douglas-Peucker,DP)算法压缩轨迹数据实现分段;其次定位含噪声轨迹段,基于段内有效点构造拟合函数;最终依据相邻点时空属性修复噪声数据。相较于主流插值算法(如拉格朗日、牛顿、埃尔米特、线性、三次样条及最近邻插值),本方法通过规避全局特征依赖,显著保留了噪声点蕴含的局部信息特征。【结果】基于长春市1500名志愿者2024年8月19日—9月1日的原始GNSS轨迹数据,设计2组对比实验。第1组将新型识别算法与原始DBSCAN及其主流衍生算法(KANN-DBSCAN、BDT-ADBSCAN)进行对比。实验表明:新算法在轮廓系数(SC)、Calinski-Harabasz指数(CHI)、Da‐vies-Bouldin指数(DBI)3项指标均取得最优值,优化幅度分别为40.17%~381.80%、20.03%~235.18%、23.42%~79.53%。第2组实验对比新型修复算法与6类经典插值方法(拉格朗日、牛顿、埃尔米特、线性、三次样条、最近邻),结果显示:新算法在轨迹相似性度量指标(Dynamic Time Warping,DTW)上全面优于对比方法,整体优化幅度达43.18%~80.43%。【结论】本文提出的噪声识别与修复算法显著提升了原始GNSS轨迹的质量精度,可高效支撑大规模轨迹数据预处理任务,为时空轨迹挖掘研究提供高质量数据基础。展开更多
现有GNSS水汽层析研究主要聚焦于如何提升卫星观测数据利用率,但在卫星信号数据优选方面研究较少,导致穿过同一组网格集的层析观测方程线性近似且方程系数矩阵列向量元素多数为零,水汽层析模型病态严重。针对该现状,本文提出一种GNSS卫...现有GNSS水汽层析研究主要聚焦于如何提升卫星观测数据利用率,但在卫星信号数据优选方面研究较少,导致穿过同一组网格集的层析观测方程线性近似且方程系数矩阵列向量元素多数为零,水汽层析模型病态严重。针对该现状,本文提出一种GNSS卫星信号自适应优选的水汽层析方法,解决层析模型设计矩阵零元素较多和层析模型病态的难题。该方法基于网格覆盖率最大原则确定层析区域水平网格划分,并发展联合卫星高度角与方位角阈值的卫星信号自适应优选方法,克服水汽层析模型观测方程线性近似的难题。本文选取香港地区2013年5月2日—2013年5月7日共6 d 12个GNSS测站及1个无线电探空站数据为例进行试验。与现有方法相比,本文方法能在降低卫星信号利用率的同时保证网格覆盖率,克服相似卫星信号造成层析模型设计矩阵病态的现状。以无线电探空数据为真值,发现本文方法反演水汽密度廓线的平均RMS、MAE和Bias分别为1.03、0.80和0.13 g/m^(3),优于传统方法的1.25、0.97和0.10 g/m^(3),其RMS改善率为20.78%;此外,本文方法在模型解算效率方面也优于传统方法,其模型计算效率平均提升9.51%。展开更多
Under submerged conditions, compared with traditional self-excited oscillating pulsed waterjets(SOPWs), annular fluid-enhanced self-excited oscillating pulsed waterjets(AFESOPWs) exhibit a higher surge pressure throug...Under submerged conditions, compared with traditional self-excited oscillating pulsed waterjets(SOPWs), annular fluid-enhanced self-excited oscillating pulsed waterjets(AFESOPWs) exhibit a higher surge pressure through self-priming. However, their pressure frequency and cavitation characteristics remain unclear, resulting in an inability to fully utilize resonance and cavitation erosion to break coal and rock. In this study, high-frequency pressure testing, high-speed photography, and large eddy simulation(LES) are used to investigate the distribution of the pressure frequency band, evolution law of the cavitation cloud, and its regulation mechanism of a continuous waterjet, SOPW, and AFESOPW. The results indicated that the excitation of the plunger pump, shearing layer vortex, and bubble collapse corresponded to the three high-amplitude frequency bands of the waterjet pressure. AFESOPWs have an additional self-priming frequency that can produce a larger amplitude under a synergistic effect with the second high-amplitude frequency band. A better cavitation effect was produced after self-priming the annulus fluid, and the shedding frequency of the cavitation clouds of the three types of waterjets was linearly related to the cavitation number. The peak pressure of the waterjet and cavitation erosion effect can be improved by modulating the waterjet pressure oscillation frequency and cavitation shedding frequency.展开更多
基金National Natural Science Foundation of China(No.42004018)。
文摘With the development of Global Navigation Satellite Systems(GNSS),geodetic GNSS receivers have been utilized to monitor sea levels using GNSS-Interferometry Reflectometry(GNSS-IR)technology.The multi-mode,multi-frequency signals of GPS,GLONASS,Galileo,and Beidou can be used for GNSS-IR sea level retrieval,but combining these retrievals remains problematic.To address this issue,a GNSS-IR sea level retrieval combination system has been developed,which begins by analyzing error sources in GNSS-IR sea level retrieval and establishing and solving the GNSS-IR retrieval equation.This paper focuses on two key points:time window selection and equation stability.The stability of the retrieval combination equations is determined by the condition number of the coefficient matrix within the time window.The impact of ill-conditioned coefficient matrices on the retrieval results is demonstrated using an extreme case of SNR data with only ascending or descending trajectories.After determining the time window and removing ill-conditioned equations,the multi-mode,multi-frequency GNSS-IR retrieval is performed.Results from three International GNSS Service(IGS)stations show that the combination method produces high-precision,high-resolution,and high-reliability sea level retrieval combination sequences.
基金supported by the National Nature Science Foundation of China(Grant Nos.12475019 and 12073056)the Major National Science and Technology Project of China(Grant No.BX2024B054)+1 种基金National Lab of Solid State Microstructure of Nanjing University(Grant Nos.M35040,M35053,and M37014)the Natural Science Foundation of Shandong Province(Grant No.ZR2024MA038)。
文摘For a multi-frequency non-reciprocal optical device,we first realize multi-frequency optical non-reciprocal transmission using a non-Hermitian multi-mode resonator array.Practically,multi-frequency operation can add channels to the non-reciprocal optical device and the non-reciprocity can route optical signals and prevent the reverse flow of noise.Using the Scully–Lamb model and gain saturation effect,we accomplish dual-frequency non-reciprocal transmission by introducing nonlinearity into a linear array of four-mode resonators.The accomplishment is directly demonstrated by the non-reciprocal transmission phenomena present in the non-divergent peaks.For example,a directional cyclic amplifier is constructed with non-reciprocal units.Regarding potential applications,non-reciprocal optical systems can be employed in dual-frequency control,parallel information processing,photonic integrated circuits,optical devices and so on.
文摘【目的】随着智慧城市建设中信息技术的深度应用,GNSS轨迹数据呈爆炸式增长,但其轨迹生成过程易受信号干扰与传感器故障影响而产生噪声。本文旨在设计新型噪声识别与修复算法,以提升原始GNSS轨迹数据的处理精度与质量。【方法】针对轨迹噪声识别问题,本文提出基于密度矩阵的自适应DBSCAN算法,其具有超参数无关特性,可敏感捕获低幅值噪声点,同时避免连续转向点的误判。针对噪声修复问题,提出基于轨迹分段的函数构造式修复算法:首先采用道格拉斯-普克(Douglas-Peucker,DP)算法压缩轨迹数据实现分段;其次定位含噪声轨迹段,基于段内有效点构造拟合函数;最终依据相邻点时空属性修复噪声数据。相较于主流插值算法(如拉格朗日、牛顿、埃尔米特、线性、三次样条及最近邻插值),本方法通过规避全局特征依赖,显著保留了噪声点蕴含的局部信息特征。【结果】基于长春市1500名志愿者2024年8月19日—9月1日的原始GNSS轨迹数据,设计2组对比实验。第1组将新型识别算法与原始DBSCAN及其主流衍生算法(KANN-DBSCAN、BDT-ADBSCAN)进行对比。实验表明:新算法在轮廓系数(SC)、Calinski-Harabasz指数(CHI)、Da‐vies-Bouldin指数(DBI)3项指标均取得最优值,优化幅度分别为40.17%~381.80%、20.03%~235.18%、23.42%~79.53%。第2组实验对比新型修复算法与6类经典插值方法(拉格朗日、牛顿、埃尔米特、线性、三次样条、最近邻),结果显示:新算法在轨迹相似性度量指标(Dynamic Time Warping,DTW)上全面优于对比方法,整体优化幅度达43.18%~80.43%。【结论】本文提出的噪声识别与修复算法显著提升了原始GNSS轨迹的质量精度,可高效支撑大规模轨迹数据预处理任务,为时空轨迹挖掘研究提供高质量数据基础。
文摘现有GNSS水汽层析研究主要聚焦于如何提升卫星观测数据利用率,但在卫星信号数据优选方面研究较少,导致穿过同一组网格集的层析观测方程线性近似且方程系数矩阵列向量元素多数为零,水汽层析模型病态严重。针对该现状,本文提出一种GNSS卫星信号自适应优选的水汽层析方法,解决层析模型设计矩阵零元素较多和层析模型病态的难题。该方法基于网格覆盖率最大原则确定层析区域水平网格划分,并发展联合卫星高度角与方位角阈值的卫星信号自适应优选方法,克服水汽层析模型观测方程线性近似的难题。本文选取香港地区2013年5月2日—2013年5月7日共6 d 12个GNSS测站及1个无线电探空站数据为例进行试验。与现有方法相比,本文方法能在降低卫星信号利用率的同时保证网格覆盖率,克服相似卫星信号造成层析模型设计矩阵病态的现状。以无线电探空数据为真值,发现本文方法反演水汽密度廓线的平均RMS、MAE和Bias分别为1.03、0.80和0.13 g/m^(3),优于传统方法的1.25、0.97和0.10 g/m^(3),其RMS改善率为20.78%;此外,本文方法在模型解算效率方面也优于传统方法,其模型计算效率平均提升9.51%。
基金supported by the program for National Natural Science Foundation of China (Nos. 52174173, 52274188, and 52104190)the Joint Funds of the National Natural Science Foundation of China (No. U24A2091)+1 种基金The Natural Science Foundation of Henan Polytechnic University (No. B2021-2)Double FirstClass Initiative of Safety and Energy Engineering (Henan Polytechnic University) (Nos. AQ20240703 and AQ20230304)。
文摘Under submerged conditions, compared with traditional self-excited oscillating pulsed waterjets(SOPWs), annular fluid-enhanced self-excited oscillating pulsed waterjets(AFESOPWs) exhibit a higher surge pressure through self-priming. However, their pressure frequency and cavitation characteristics remain unclear, resulting in an inability to fully utilize resonance and cavitation erosion to break coal and rock. In this study, high-frequency pressure testing, high-speed photography, and large eddy simulation(LES) are used to investigate the distribution of the pressure frequency band, evolution law of the cavitation cloud, and its regulation mechanism of a continuous waterjet, SOPW, and AFESOPW. The results indicated that the excitation of the plunger pump, shearing layer vortex, and bubble collapse corresponded to the three high-amplitude frequency bands of the waterjet pressure. AFESOPWs have an additional self-priming frequency that can produce a larger amplitude under a synergistic effect with the second high-amplitude frequency band. A better cavitation effect was produced after self-priming the annulus fluid, and the shedding frequency of the cavitation clouds of the three types of waterjets was linearly related to the cavitation number. The peak pressure of the waterjet and cavitation erosion effect can be improved by modulating the waterjet pressure oscillation frequency and cavitation shedding frequency.
