We investigated the association of time to prostate-specific antigen nadir （TTPN） and logarithm of prostate-specific antigen velocity after progression Log（PSAVAP） in metastatic prostate cancer with prior primary ...We investigated the association of time to prostate-specific antigen nadir （TTPN） and logarithm of prostate-specific antigen velocity after progression Log（PSAVAP） in metastatic prostate cancer with prior primary androgen deprivation therapy （ADT）. All metastatic prostate cancer patients treated with primary ADT from 2000 to 2009 were reviewed. Patients who developed disease progression were included in the subsequent analyses. Patients were categorized into three groups according to their TTPN： TTPN of 〈3 months, 3-17 months, and 〉17 months. We compared the Log（PSAVAP） between the different TTPN groups using Mann-Whitney U-test and Kruskal-Wallis test. Further multiple linear regression analyses on Log（PSAVAP） were performed to adjust for other potential confounding factors. Among 419 patients who were treated with primary ADT, 306 patients developed disease progression with a median follow-up of 28 months, Longer TTPN was associated with lower Log（PSAVAP） （P = 0.008） within all subgroup analyses （TTPN of 〈3 vs 3-17 months, P = 0.020; TTPN of 3-17 vs 〉17 months, P = 0.009; and TTPN of 〈3 vs 〉17 months, P = 0.001）. Upon multiple linear regression analyses, baseline PSA （regression coefficient 0.001, P = 0.045）, PSA nadir （regression coefficient 0.002, P = 0.040）, and TTPN （regression coefficient -0.030, P = 0.001） were the three factors that were significantly associated with Log（PSAVAP）. In conclusion, a longer TTPN was associated with lower Log（PSAVAP） in metastatic prostate cancer patients following primary ADT. TTPN cut-offs at 3 months and 17 months appeared to have prognostic significance in predicting Log（PSAVAP）. TTPN may serve as a good prognostic indicator in deciding the treatment strategy in patients with disease progression.展开更多
Background: Most newly diagnosed prostate cancers in Benin are metastatic diseases and patients are reluctant to undergo orchiectomy. Still, chemical androgen deprivation therapy is not always available and not every ...Background: Most newly diagnosed prostate cancers in Benin are metastatic diseases and patients are reluctant to undergo orchiectomy. Still, chemical androgen deprivation therapy is not always available and not every patient can afford it. Thus, it will be interesting to evaluate the results of that therapy in the country. Objective: To analyze the survival rate and factors influencing it in metastatic prostate cancer patients who underwent triptorelin-based androgen deprivation therapy at the former Military Teaching Hospital of Cotonou from January 1, 2012, to December 31, 2022. Patients and Method: Metastatic prostate cancer patients received intragluteal injections of triptorelin 11.25 mg every 3 months. We retrospectively collected follow-up data from the patients’ medical records. By means of the software StataTM version 15, we performed a descriptive analysis of qualitative data. We used Kaplan-Meir method to estimate the overall survival rate in the whole cohort and in specific subgroups of patients. We compared survival rates by using the log-rank test. Results: 68 metastatic prostate cancer patients aged 47-86 years (mean = 69.9) with initial PSA ranging from 24.25 to 6334 ng/mL (mean = 666.1) started triptorelin-based castration. The tumor grade in 21 (33.3%), 14 (22.2%), 15 (23.8), 8 (12.7%), and 5 (7.9%) patients was respectively ISUP grade groups 5, 4, 3, 2, and 1. 15 (22.1%), 4 (5.9%), 2 (2.9%), 1 (1.5%), 11 (16.2%), and 7 (10.3%) patients respectively had hypertension, diabetes mellitus, peptic ulcer, asthma, unilateral or bilateral hydronephrosis, and paralysis. The mean nadir PSA level was 22.5 ng/mL (range: 0.01-220.25). The mean time to nadir PSA level was 8.9 months (range: 3-57). The overall survival rate was 42.6%. There was no significant survival difference between age groups (p = 0.475), relating to the presence of diabetes or hypertension (p = 0.757) or to the presence of paralysis or hydronephrosis (p = 0.090). The initial PSA level exerted no significant impact on patients’ surviv展开更多
Surface Water and Ocean Topography(SWOT)is a next-generation radar altimeter that offers high resolution,wide swath,imaging capabilities.It has provided free public data worldwide since December 2023.This paper aims t...Surface Water and Ocean Topography(SWOT)is a next-generation radar altimeter that offers high resolution,wide swath,imaging capabilities.It has provided free public data worldwide since December 2023.This paper aims to preliminarily analyze the detection capabilities of the Ka-band radar interferometer(KaRIn)and Nadir altimeter(NALT),which are carried out by SWOT for internal solitary waves(ISWs),and to gather other remote sensing images to validate SWOT observations.KaRIn effectively detects ISW surface features and generates surface height variation maps reflecting the modulations induced by ISWs.However,its swath width does not completely cover the entire wave packet,and the resolution of L2/L3 level products(about 2 km)cannot be used to identify ISWs with smaller wavelengths.Additionally,significant wave height(SWH)images exhibit blocky structures that are not suitable for ISW studies;sea surface height anomaly(SSHA)images display systematic leftright banding.We optimize this imbalance using detrending methods;however,more precise treatment should commence with L1-level data.Quantitative analysis based on L3-level SSHA data indicates that the average SSHA variation induced by ISWs ranges from 10 cm to 20 cm.NALTs disturbed by ISWs record unusually elevated SWH and SSHA values,rendering the data unsuitable for analysis and necessitating targeted corrections in future retracking algorithms.For the normalized radar cross section,Ku-band and four-parameter maximum likelihood estimation retracking demonstrated greater sensitivity to minor changes in the sea surface,making them more suitable for ISW detection.In conclusion,SWOT demonstrates outstanding capabilities in ISW detection,significantly advancing research on the modulation of the sea surface by ISWs and remote sensing imaging mechanisms.展开更多
Docetaxel-based chemotherapy remains the first-line treatment for patients with metastatic castration-resistant prostate cancer （mCRPC） in China; however, the prognostic factors associated with effects in these pati...Docetaxel-based chemotherapy remains the first-line treatment for patients with metastatic castration-resistant prostate cancer （mCRPC） in China; however, the prognostic factors associated with effects in these patients are still controversial. In this study, we retrospectively reviewed the data from 71 eligible Chinese patients who received docetaxel chemotherapy from 2009 to 2016 in our hospital and experienced a reduction of prostate-specific antigen （PSA） level 〉50% during the treatment and investigated the potential role of time to nadir （TTN） of PSA. TTN was defined as the time from start of chemotherapy to the nadir of PSA level during the treatment. Multivariable Cox regression models and Kaplan-Meier analysis were used to predict overall survival （OS）. In these patients, the median of TTN was 17 weeks. Patients with TTN ≥17 weeks had a longer response time to chemotherapy compared to TTN 〈17 weeks （42.83 vs 21.50 weeks, P 〈 0.001）. The time to PSA progression in patients with TTN ：〉17 weeks was 11.44 weeks compared to 5.63 weeks when TTN was 〈17 weeks. We found several factors to be associated with OS, including TTN （hazard ratio [HR]. 3.937, 95% confidence interval [CI]： 1.502-10.309, P = 0.005）, PSA level at the diagnosis of cancer （HR： 4,337, 95% CI： 1.616-11.645, P= 0.004）, duration of initial androgen deprivation therapy （HR： 2.982, 95% CI： 1.104-8.045, P= 0.031）, neutrophil-to-lymphocyte ratio （HR： 3.963, 95% CI： 1.380-11.384, P = 0.011）, and total PSA response （Class 1 [〈0 response] compared to Class 2 [0-50% response], HR： 3.978, 95% CI： 1.278-12.387, P = 0.017）. In conclusion, TTN of PSA remains an important prognostic marker in predicting therapeutic outcome in Chinese population who receive chemotherapy for mCRPC and have 〉50% PSA remission.展开更多
Near-nadir observations by the Multispectral Instrument (MSI) onboard the Sentinel-2 and the Operational Land Imager (OLI) onboard Landsat 8 were collected during two Simultaneous Nadir Overpasses (SNO). Multispectral...Near-nadir observations by the Multispectral Instrument (MSI) onboard the Sentinel-2 and the Operational Land Imager (OLI) onboard Landsat 8 were collected during two Simultaneous Nadir Overpasses (SNO). Multispectral images with 10, 20, and 30 m resolution from a spatially uniform area in the Saharan desert were acquired for direct comparison of MSI and OLI Top- Of-Atmosphere (TOA) reflectances. This paper presents an initial radiometric cross-calibration of the 8 corresponding spectral bands of the Sentinel-2 MSI and Landsat 8 OLI sensors. With the well-calibrated Landsat 8 OLI as a reference, the comparison indicates that 6 MSI bands are consistent with OLI within 3% in terms of spectral band adjustment factors Bi . The Near-Infra-Red (NIR) and cirrus bands are exceptions. They yield radiometric differences on the order of 8% and 15% respectively. Cross-calibration results show that the radiometric difference of the 7 corresponding bands are consistent to OLI within 1% or better, except on cirrus band. A pixel-by-pixel match between the MSI and OLI observations for different land covers showed that. This initial study suggests that the red-edge band B8A of MSI can be used to replace the NIR band B08 when conducting vegetation monitoring.展开更多
Satellite altimetry has been widely used in measuring ocean topography from space. The conventional altimeter system is the nadir radar altimeter system which has the limitations of one-dimensional measurement and is ...Satellite altimetry has been widely used in measuring ocean topography from space. The conventional altimeter system is the nadir radar altimeter system which has the limitations of one-dimensional measurement and is unable to get both high temporal and spatial resolution. The InSAR altimetry system using InSAR altimeter instead of nadir radar altimeter is an improvement which can get both high cross-track and along-track resolution and wide swath. However, the conventional SAR interferometry only can achieve meter level height accuracy. This paper focuses on a method of radar echo-tracking for InSAR altimeter system in order to correct the slant range measurements and finally to improve the height measurement accuracy to several centimeters＇ level. Radar slant range （from observed pixels to radar antenna） estimation error affects the height measurement accuracy badly, nevertheless not considered in the conventional SAR interferometry. The proposed method is ameliorated based on the traditional echo-model used in nadir radar altimeter system, focusing on the echo signals from observed pixels with different incident angles. Simulations of sea surface height measurements are performed in the last part of this paper, and the conclusions are drawn that, with corrected slant range, the accuracy of InSAR altimetry can be much better than the conventional SAR interferometry.展开更多
The baseline roll and length errors for wide-swath altimeters are major error sources in sea surface measurements that exhibit strong spatial characteristics in the cross-track direction.These errors can be identified...The baseline roll and length errors for wide-swath altimeters are major error sources in sea surface measurements that exhibit strong spatial characteristics in the cross-track direction.These errors can be identified and estimated in accordance with height differences at crossover points generated with nadir altimeters after excluding the interference from other error sources.Most of the wide-swath altimeter baseline estimation methods considered only the roll error in previous studies.A numerical simulation was conducted in this study using nadir altimeters to estimate the roll and length errors simultaneously to provide a selectable scheme for baseline error estimation and correction for future wide-swath altimeters.Results based on the parameters of the surface water and ocean topography mission and Sentinel-3A show that the correlation coefficient of the roll error between the estimated and simulated values is 0.89,while the correlation coefficient of the length error is 0.85.The sea surface height root mean square error(RMSE)can be reduced from 12.18 cm to 6.45 cm based on the two estimated results.The estimation effect can be increased by using multiple nadir altimeters to form an observation constellation.The numerical simulation of the five nadir altimeter constellation shows that the correlation coefficients of the roll and length errors would increase to 0.97,which reduces the sea surface height RMSE to 2.88 cm.In addition,the stability of this method is indicated in simulation experiments,which introduce different degrees of sea state errors.展开更多
Background:Various prediction tools have been developed to predict biochemical recurrence(BCR)after radical prostatectomy(RP);however,few of the previous prediction tools used serum prostate-specific antigen(PSA)nadir...Background:Various prediction tools have been developed to predict biochemical recurrence(BCR)after radical prostatectomy(RP);however,few of the previous prediction tools used serum prostate-specific antigen(PSA)nadir after RP and maximum tumor diameter(MTD)at the same time.In this study,a nomogram incorporating MTD and PSA nadir was developed to predict BCR-free survival(BCRFS).Methods:A total of 337 patients who underwent RP between January 2010 and March 2017 were retrospectively enrolled in this study.The maximum diameter of the index lesion was measured on magnetic resonance imaging(MRI).Cox regression analysis was performed to evaluate independent predictors of BCR.A nomogram was subsequently developed for the prediction of BCRFS at 3 and 5 years after RP.Time-dependent receiver operating characteristic(ROC)curve and decision curve analyses were performed to identify the advantage of the new nomogram in comparison with the cancer of the prostate risk assessment post-surgical(CAPRA-S)score.Results:A novel nomogram was developed to predict BCR by including PSA nadir,MTD,Gleason score,surgical margin(SM),and seminal vesicle invasion(SVI),considering these variables were significantly associated with BCR in both univariate and multivariate analyses(P<0.05).In addition,a basic model including Gleason score,SM,and SVI was developed and used as a control to assess the incremental predictive power of the new model.The concordance index of our model was slightly higher than CAPRA-S model(0.76 vs.0.70,P=0.02)and it was significantly higher than that of the basic model(0.76 vs.0.66,P=0.001).Time-dependent ROC curve and decision curve analyses also demonstrated the advantages of the new nomogram.Conclusions:PSA nadir after RP and MTD based on MRI before surgery are independent predictors of BCR.By incorporating PSA nadir and MTD into the conventional predictive model,our newly developed nomogram significantly improved the accuracy in predicting BCRFS after RP.展开更多
电网受扰后频率最低点预测对新型电力系统的频率安全评估非常重要,而目前已有频率动态分析模型较难快速、准确、灵活地预测电网受扰后频率最低点,其中同步发电机调速系统的低阶通用建模以及新能源接入的影响建模是主要挑战。首先提出了...电网受扰后频率最低点预测对新型电力系统的频率安全评估非常重要,而目前已有频率动态分析模型较难快速、准确、灵活地预测电网受扰后频率最低点,其中同步发电机调速系统的低阶通用建模以及新能源接入的影响建模是主要挑战。首先提出了充分考虑频率响应特性的发电机调速系统低阶通用模型,结合新能源场站的通用频率响应模型,建立了新能源接入电网的通用平均系统频率(generic average system frequency,G-ASF)模型,在保证准确度的同时有效降低了模型阶数。然后,基于G-ASF模型直接预测电网在给定功率损失下的频率最低点。最后,在IEEE 3机9节点系统以及含新能源的IEEE 10机39节点系统中进行了仿真,结果表明提出的模型和方法在不同扰动或不同系统结构下均能准确预测频率最低点,且能够用于快速计算频率安全约束下的新能源渗透率极限值,验证了模型的准确性和通用性。展开更多
针对含大规模风电的电力系统在大停电后负荷恢复阶段的频率安全问题,考虑风电机组的虚拟惯量和一次调频响应过程,基于系统等值摇摆方程构建含风电电力系统动态频率响应模型,推导出初始频率变化率(rate of change of frequency,RoCoF)和...针对含大规模风电的电力系统在大停电后负荷恢复阶段的频率安全问题,考虑风电机组的虚拟惯量和一次调频响应过程,基于系统等值摇摆方程构建含风电电力系统动态频率响应模型,推导出初始频率变化率(rate of change of frequency,RoCoF)和最低点频率的解析表达式,并将其作为系统动态频率安全约束;在此基础上,以恢复负荷量最大和恢复时间最短为目标,提出考虑动态频率安全约束的系统多时段恢复优化调度模型,并给出非线性约束的线性化方法,以提高恢复决策的效率;以改进的IEEE-39节点系统进行算例验证,结果表明所提模型能够给出保证频率动态安全的风电、负荷的有序接入及常规机组出力方案,且恢复速度快。展开更多
文摘We investigated the association of time to prostate-specific antigen nadir （TTPN） and logarithm of prostate-specific antigen velocity after progression Log（PSAVAP） in metastatic prostate cancer with prior primary androgen deprivation therapy （ADT）. All metastatic prostate cancer patients treated with primary ADT from 2000 to 2009 were reviewed. Patients who developed disease progression were included in the subsequent analyses. Patients were categorized into three groups according to their TTPN： TTPN of 〈3 months, 3-17 months, and 〉17 months. We compared the Log（PSAVAP） between the different TTPN groups using Mann-Whitney U-test and Kruskal-Wallis test. Further multiple linear regression analyses on Log（PSAVAP） were performed to adjust for other potential confounding factors. Among 419 patients who were treated with primary ADT, 306 patients developed disease progression with a median follow-up of 28 months, Longer TTPN was associated with lower Log（PSAVAP） （P = 0.008） within all subgroup analyses （TTPN of 〈3 vs 3-17 months, P = 0.020; TTPN of 3-17 vs 〉17 months, P = 0.009; and TTPN of 〈3 vs 〉17 months, P = 0.001）. Upon multiple linear regression analyses, baseline PSA （regression coefficient 0.001, P = 0.045）, PSA nadir （regression coefficient 0.002, P = 0.040）, and TTPN （regression coefficient -0.030, P = 0.001） were the three factors that were significantly associated with Log（PSAVAP）. In conclusion, a longer TTPN was associated with lower Log（PSAVAP） in metastatic prostate cancer patients following primary ADT. TTPN cut-offs at 3 months and 17 months appeared to have prognostic significance in predicting Log（PSAVAP）. TTPN may serve as a good prognostic indicator in deciding the treatment strategy in patients with disease progression.
文摘Background: Most newly diagnosed prostate cancers in Benin are metastatic diseases and patients are reluctant to undergo orchiectomy. Still, chemical androgen deprivation therapy is not always available and not every patient can afford it. Thus, it will be interesting to evaluate the results of that therapy in the country. Objective: To analyze the survival rate and factors influencing it in metastatic prostate cancer patients who underwent triptorelin-based androgen deprivation therapy at the former Military Teaching Hospital of Cotonou from January 1, 2012, to December 31, 2022. Patients and Method: Metastatic prostate cancer patients received intragluteal injections of triptorelin 11.25 mg every 3 months. We retrospectively collected follow-up data from the patients’ medical records. By means of the software StataTM version 15, we performed a descriptive analysis of qualitative data. We used Kaplan-Meir method to estimate the overall survival rate in the whole cohort and in specific subgroups of patients. We compared survival rates by using the log-rank test. Results: 68 metastatic prostate cancer patients aged 47-86 years (mean = 69.9) with initial PSA ranging from 24.25 to 6334 ng/mL (mean = 666.1) started triptorelin-based castration. The tumor grade in 21 (33.3%), 14 (22.2%), 15 (23.8), 8 (12.7%), and 5 (7.9%) patients was respectively ISUP grade groups 5, 4, 3, 2, and 1. 15 (22.1%), 4 (5.9%), 2 (2.9%), 1 (1.5%), 11 (16.2%), and 7 (10.3%) patients respectively had hypertension, diabetes mellitus, peptic ulcer, asthma, unilateral or bilateral hydronephrosis, and paralysis. The mean nadir PSA level was 22.5 ng/mL (range: 0.01-220.25). The mean time to nadir PSA level was 8.9 months (range: 3-57). The overall survival rate was 42.6%. There was no significant survival difference between age groups (p = 0.475), relating to the presence of diabetes or hypertension (p = 0.757) or to the presence of paralysis or hydronephrosis (p = 0.090). The initial PSA level exerted no significant impact on patients’ surviv
基金The National Natural Science Foundation of China under contract Nos U2006207 and 42006164.
文摘Surface Water and Ocean Topography(SWOT)is a next-generation radar altimeter that offers high resolution,wide swath,imaging capabilities.It has provided free public data worldwide since December 2023.This paper aims to preliminarily analyze the detection capabilities of the Ka-band radar interferometer(KaRIn)and Nadir altimeter(NALT),which are carried out by SWOT for internal solitary waves(ISWs),and to gather other remote sensing images to validate SWOT observations.KaRIn effectively detects ISW surface features and generates surface height variation maps reflecting the modulations induced by ISWs.However,its swath width does not completely cover the entire wave packet,and the resolution of L2/L3 level products(about 2 km)cannot be used to identify ISWs with smaller wavelengths.Additionally,significant wave height(SWH)images exhibit blocky structures that are not suitable for ISW studies;sea surface height anomaly(SSHA)images display systematic leftright banding.We optimize this imbalance using detrending methods;however,more precise treatment should commence with L1-level data.Quantitative analysis based on L3-level SSHA data indicates that the average SSHA variation induced by ISWs ranges from 10 cm to 20 cm.NALTs disturbed by ISWs record unusually elevated SWH and SSHA values,rendering the data unsuitable for analysis and necessitating targeted corrections in future retracking algorithms.For the normalized radar cross section,Ku-band and four-parameter maximum likelihood estimation retracking demonstrated greater sensitivity to minor changes in the sea surface,making them more suitable for ISW detection.In conclusion,SWOT demonstrates outstanding capabilities in ISW detection,significantly advancing research on the modulation of the sea surface by ISWs and remote sensing imaging mechanisms.
基金This study was partially supported by the National Natural Science Foundation of China （NSFC 81202014 to KJW, NSFC 81130041 to DLH） and the Fundamental Research Funds for the Central Universities （to KIW）.
文摘Docetaxel-based chemotherapy remains the first-line treatment for patients with metastatic castration-resistant prostate cancer （mCRPC） in China; however, the prognostic factors associated with effects in these patients are still controversial. In this study, we retrospectively reviewed the data from 71 eligible Chinese patients who received docetaxel chemotherapy from 2009 to 2016 in our hospital and experienced a reduction of prostate-specific antigen （PSA） level 〉50% during the treatment and investigated the potential role of time to nadir （TTN） of PSA. TTN was defined as the time from start of chemotherapy to the nadir of PSA level during the treatment. Multivariable Cox regression models and Kaplan-Meier analysis were used to predict overall survival （OS）. In these patients, the median of TTN was 17 weeks. Patients with TTN ≥17 weeks had a longer response time to chemotherapy compared to TTN 〈17 weeks （42.83 vs 21.50 weeks, P 〈 0.001）. The time to PSA progression in patients with TTN ：〉17 weeks was 11.44 weeks compared to 5.63 weeks when TTN was 〈17 weeks. We found several factors to be associated with OS, including TTN （hazard ratio [HR]. 3.937, 95% confidence interval [CI]： 1.502-10.309, P = 0.005）, PSA level at the diagnosis of cancer （HR： 4,337, 95% CI： 1.616-11.645, P= 0.004）, duration of initial androgen deprivation therapy （HR： 2.982, 95% CI： 1.104-8.045, P= 0.031）, neutrophil-to-lymphocyte ratio （HR： 3.963, 95% CI： 1.380-11.384, P = 0.011）, and total PSA response （Class 1 [〈0 response] compared to Class 2 [0-50% response], HR： 3.978, 95% CI： 1.278-12.387, P = 0.017）. In conclusion, TTN of PSA remains an important prognostic marker in predicting therapeutic outcome in Chinese population who receive chemotherapy for mCRPC and have 〉50% PSA remission.
文摘Near-nadir observations by the Multispectral Instrument (MSI) onboard the Sentinel-2 and the Operational Land Imager (OLI) onboard Landsat 8 were collected during two Simultaneous Nadir Overpasses (SNO). Multispectral images with 10, 20, and 30 m resolution from a spatially uniform area in the Saharan desert were acquired for direct comparison of MSI and OLI Top- Of-Atmosphere (TOA) reflectances. This paper presents an initial radiometric cross-calibration of the 8 corresponding spectral bands of the Sentinel-2 MSI and Landsat 8 OLI sensors. With the well-calibrated Landsat 8 OLI as a reference, the comparison indicates that 6 MSI bands are consistent with OLI within 3% in terms of spectral band adjustment factors Bi . The Near-Infra-Red (NIR) and cirrus bands are exceptions. They yield radiometric differences on the order of 8% and 15% respectively. Cross-calibration results show that the radiometric difference of the 7 corresponding bands are consistent to OLI within 1% or better, except on cirrus band. A pixel-by-pixel match between the MSI and OLI observations for different land covers showed that. This initial study suggests that the red-edge band B8A of MSI can be used to replace the NIR band B08 when conducting vegetation monitoring.
基金funded by the National Nature Science Foundations of China(41404019,41674026)the open fund of Key Laboratory of Space Utilization,Chinese Academy of Sciences(CSUWX-A-KJ-2016-044)
文摘Satellite altimetry has been widely used in measuring ocean topography from space. The conventional altimeter system is the nadir radar altimeter system which has the limitations of one-dimensional measurement and is unable to get both high temporal and spatial resolution. The InSAR altimetry system using InSAR altimeter instead of nadir radar altimeter is an improvement which can get both high cross-track and along-track resolution and wide swath. However, the conventional SAR interferometry only can achieve meter level height accuracy. This paper focuses on a method of radar echo-tracking for InSAR altimeter system in order to correct the slant range measurements and finally to improve the height measurement accuracy to several centimeters＇ level. Radar slant range （from observed pixels to radar antenna） estimation error affects the height measurement accuracy badly, nevertheless not considered in the conventional SAR interferometry. The proposed method is ameliorated based on the traditional echo-model used in nadir radar altimeter system, focusing on the echo signals from observed pixels with different incident angles. Simulations of sea surface height measurements are performed in the last part of this paper, and the conclusions are drawn that, with corrected slant range, the accuracy of InSAR altimetry can be much better than the conventional SAR interferometry.
基金the Shandong Provincial Natural Science Foundation(No.ZR2020MD097)the National Key Research and Development Program of China(No.2016YFC1401004)the National Natural Science Foundation of China(No.62031005)。
文摘The baseline roll and length errors for wide-swath altimeters are major error sources in sea surface measurements that exhibit strong spatial characteristics in the cross-track direction.These errors can be identified and estimated in accordance with height differences at crossover points generated with nadir altimeters after excluding the interference from other error sources.Most of the wide-swath altimeter baseline estimation methods considered only the roll error in previous studies.A numerical simulation was conducted in this study using nadir altimeters to estimate the roll and length errors simultaneously to provide a selectable scheme for baseline error estimation and correction for future wide-swath altimeters.Results based on the parameters of the surface water and ocean topography mission and Sentinel-3A show that the correlation coefficient of the roll error between the estimated and simulated values is 0.89,while the correlation coefficient of the length error is 0.85.The sea surface height root mean square error(RMSE)can be reduced from 12.18 cm to 6.45 cm based on the two estimated results.The estimation effect can be increased by using multiple nadir altimeters to form an observation constellation.The numerical simulation of the five nadir altimeter constellation shows that the correlation coefficients of the roll and length errors would increase to 0.97,which reduces the sea surface height RMSE to 2.88 cm.In addition,the stability of this method is indicated in simulation experiments,which introduce different degrees of sea state errors.
基金supported by grants from the Beijing Natural Science Foundation(No.Z200027)National Natural Science Foundation of China(No.61871004)+2 种基金National Key R&D Program of China(No.2018 YFC0115900)Innovation&Transfer Fund of Peking University Third Hospital(No.BYSYZHKC2020111)Peking University Medicine Fund of Fostering Young Scholars’Scientific&Technological Innovation(No.BMU2020PYB002)。
文摘Background:Various prediction tools have been developed to predict biochemical recurrence(BCR)after radical prostatectomy(RP);however,few of the previous prediction tools used serum prostate-specific antigen(PSA)nadir after RP and maximum tumor diameter(MTD)at the same time.In this study,a nomogram incorporating MTD and PSA nadir was developed to predict BCR-free survival(BCRFS).Methods:A total of 337 patients who underwent RP between January 2010 and March 2017 were retrospectively enrolled in this study.The maximum diameter of the index lesion was measured on magnetic resonance imaging(MRI).Cox regression analysis was performed to evaluate independent predictors of BCR.A nomogram was subsequently developed for the prediction of BCRFS at 3 and 5 years after RP.Time-dependent receiver operating characteristic(ROC)curve and decision curve analyses were performed to identify the advantage of the new nomogram in comparison with the cancer of the prostate risk assessment post-surgical(CAPRA-S)score.Results:A novel nomogram was developed to predict BCR by including PSA nadir,MTD,Gleason score,surgical margin(SM),and seminal vesicle invasion(SVI),considering these variables were significantly associated with BCR in both univariate and multivariate analyses(P<0.05).In addition,a basic model including Gleason score,SM,and SVI was developed and used as a control to assess the incremental predictive power of the new model.The concordance index of our model was slightly higher than CAPRA-S model(0.76 vs.0.70,P=0.02)and it was significantly higher than that of the basic model(0.76 vs.0.66,P=0.001).Time-dependent ROC curve and decision curve analyses also demonstrated the advantages of the new nomogram.Conclusions:PSA nadir after RP and MTD based on MRI before surgery are independent predictors of BCR.By incorporating PSA nadir and MTD into the conventional predictive model,our newly developed nomogram significantly improved the accuracy in predicting BCRFS after RP.
文摘电网受扰后频率最低点预测对新型电力系统的频率安全评估非常重要,而目前已有频率动态分析模型较难快速、准确、灵活地预测电网受扰后频率最低点,其中同步发电机调速系统的低阶通用建模以及新能源接入的影响建模是主要挑战。首先提出了充分考虑频率响应特性的发电机调速系统低阶通用模型,结合新能源场站的通用频率响应模型,建立了新能源接入电网的通用平均系统频率(generic average system frequency,G-ASF)模型,在保证准确度的同时有效降低了模型阶数。然后,基于G-ASF模型直接预测电网在给定功率损失下的频率最低点。最后,在IEEE 3机9节点系统以及含新能源的IEEE 10机39节点系统中进行了仿真,结果表明提出的模型和方法在不同扰动或不同系统结构下均能准确预测频率最低点,且能够用于快速计算频率安全约束下的新能源渗透率极限值,验证了模型的准确性和通用性。
文摘针对含大规模风电的电力系统在大停电后负荷恢复阶段的频率安全问题,考虑风电机组的虚拟惯量和一次调频响应过程,基于系统等值摇摆方程构建含风电电力系统动态频率响应模型,推导出初始频率变化率(rate of change of frequency,RoCoF)和最低点频率的解析表达式,并将其作为系统动态频率安全约束;在此基础上,以恢复负荷量最大和恢复时间最短为目标,提出考虑动态频率安全约束的系统多时段恢复优化调度模型,并给出非线性约束的线性化方法,以提高恢复决策的效率;以改进的IEEE-39节点系统进行算例验证,结果表明所提模型能够给出保证频率动态安全的风电、负荷的有序接入及常规机组出力方案,且恢复速度快。
