An optimization of polarimetric contrast enhancement method is proposed to detect ships with lowship-to-clutter power ratio.The received power is calculated with Kennaugh matrix and an iterative algo-rithm is adopted ...An optimization of polarimetric contrast enhancement method is proposed to detect ships with lowship-to-clutter power ratio.The received power is calculated with Kennaugh matrix and an iterative algo-rithm is adopted to get the optimal polarimetric states.The optimization method depresses the power of o-cean clutter and increases the power of ship signal.With the double effects,the contrast of ship to oceanis dramatically increased.Thus small ship or weak signals of low ship-to-ocean power ratio can easily bedetected.Ship signals can be distinguished from speckle noise using the different variation trend after op-timization,and thus the threshold problem can be avoided.Moreover,the analyses of different ship'sKennaugh matrices give two implications.One is that the results are affected little by choosing differentKennaugh matrices of ships with strong intensity from Synthetic Aperture Radar(SAR)images.The otheris that ship's Kennaugh matrix chosen from real SAR images is more favorable than that of ideal scatter-ing.Finally,the optimization results are confirmed by polarimetric scattering angle and co-polarizationphase difference.展开更多
Algal blooms caused by Prorocentrum donghaiense occurred frequently in the East China Sea （ECS） during spring in recent years. In this study, a coupled biophysical model was used to hindcast a massive P. donghaiense...Algal blooms caused by Prorocentrum donghaiense occurred frequently in the East China Sea （ECS） during spring in recent years. In this study, a coupled biophysical model was used to hindcast a massive P. donghaiense bloom that occurred in 2005 and to determine the factors influencing bloom initiation and development. The model comprised the Regional Ocean Modeling System tailored for the ECS that utilized a multi-nested configuration and a population dynamics model for 19. donghaiense. Comparisons between simulations and observations revealed that the biological model is capable of reproducing the characteristics of 19. donghaiense growth under different irradiances and phosphorus limitation scenarios. The variation of intracellular phosphorus and the effects of 19. donghaiense on ambient nutrients conditions were also reproduced. The biophysical model hindcasted the hydrodynamics and spatiotemporal distributions of the P. donghaiense bloom reasonably well. Bloom development was consistent with observations reported in earlier studies. The results demonstrate the capability of the model in capturing subsurface incubation during bloom initiation. Then model＇s hindcast solutions were further used to diagnose the factors controlling the vertical distribution. Phosphate appeared to be one of the factors controlling the subsurface incubation, whereas surface wind fields played an important role in determining P. donghaiense distribution. The results highlight the importance of nutrient-limitation as a mechanism in the formation of P. donghaiense subsurface layers and the dispersing of P. donghaiense blooms. This coupled biophysical model should be improved and used to investigate 19. donghaiense blooms occurring in different scenarios.展开更多
In the East China Sea(ECS), the succession of causative species responsible for blooms is a recurrent phenomenon during the spring, which changes from diatoms to dinoflagellates. Observations from space and in situ cr...In the East China Sea(ECS), the succession of causative species responsible for blooms is a recurrent phenomenon during the spring, which changes from diatoms to dinoflagellates. Observations from space and in situ cruises captured this pattern of succession during spring of 2005. In this study, we coupled two biological models, which were developed previously for Skeletonema costatum and Prorocentrum donghaiense,into a circulation model tailored for the ECS. The coupled biophysical model was used to hindcast the blooms and to test the hypothesis proposed in earlier studies that phosphate(PO4 3–) is the first-order decider of the succession. The coupled model successfully reproduced the hydrodynamics(as described in a companion paper by Sun et al.(1), the spatiotemporal distribution of the chlorophyll a(Chl a) concentration, and the species succession reasonably well. By analyzing the effects of different factors on the surface Chl a distribution, we confirmed that the offshore boundaries of the blooms were confined by PO4 3–. In addition, we suggest that surface wind fields may modulate the horizontal distribution of blooms. Thus, during the dispersal of blooms, surface winds coupled with PO4 3– may control the succession of blooms in the ECS. The proposed coupled model provides a benchmark to facilitate future improvements by including more size classes for organisms, multiple nutrient schemes, and additional processes.展开更多
The numerous factors influencing the air-sea carbon dioxide（CO_2） transfer velocity have been discussed for many years, yet the contributions of various factors have undergone little quantitative estimation. To bett...The numerous factors influencing the air-sea carbon dioxide（CO_2） transfer velocity have been discussed for many years, yet the contributions of various factors have undergone little quantitative estimation. To better understand the mechanism of air-sea transfer, the effects of different factors are discussed on the air-sea transfer velocity and the various parametric models describing the phenomenon are classified and compared.Then, based on GAS EX-98 and ASGAMAGE data, wind models are evaluated and the effects of some factors are discussed quantitatively, including bubbles, waves, wind and so on by considering their interaction through a piecewise average approach. It is found that the air-sea CO_2 transfer velocity is not only the function of the wind speed, but is also affected by bubbles, wave parameters and other factors. Stepwise and linear regressions are used. When considering the wind speed, bubbles mediated and the significant wave height, the root mean square error is reduced from 34.53 cm/h to 16.96 cm/h. Discussing the various factors quantitatively can be useful in future assessments of a large spatial scale and long-term air-sea CO_2 flux and global change.展开更多
海冰密集度数据是开展全球海洋监测和应对气候变化研究的重要数据源,为了研制出分辨率更高,误差更小的北极海冰密集度融合资料,本文使用了多源海冰密集度资料,以OSTIA(Operational Sea Surface Temperature and Ice Analysis)数据集为...海冰密集度数据是开展全球海洋监测和应对气候变化研究的重要数据源,为了研制出分辨率更高,误差更小的北极海冰密集度融合资料,本文使用了多源海冰密集度资料,以OSTIA(Operational Sea Surface Temperature and Ice Analysis)数据集为融合背景场,采用以下方案开展融合研究。首先,对现有5种海冰资料进行质量控制;其次,以OSI SAF(Ocean and Sea Ice Satellite Application Facility)资料为基准,采用概率密度匹配法订正各资料的系统误差;然后,利用小波分解将各资料分解为低频信息和高频信息,对低频信息和高频信息分别计算融合权重和卡尔曼滤波处理;最后,利用小波重构将各资料进行融合,生成0.05°分辨率的北极逐日海冰密集度融合资料。通过对比国际上广泛认可的OISST(Optimum Interpolation Sea Surface Temperature)、OSTIA海冰密集度资料,验证结果显示:融合资料与OISST、OSTIA海冰密集度资料在北极的空间分布上高度一致,相关系数均超过0.967。相对于前人的研究,本融合资料与OISST的偏差由–1.170%减少到–0.108%,与OSTIA的偏差由0.276%减少到–0.156%;与OISST和OSTIA的均方根误差分别由9.835%减少为8.010%以及由7.427%减少为5.140%。本融合资料的偏差以及均方根误差都得到了显著的提升,具有较高的质量。展开更多
电化学阻抗谱(electrochemical impedance spectroscopy,EIS)蕴含丰富的电池健康状态(state of health,SOH)信息,但不同频率的电化学阻抗数据间并不相互独立,直接利用全频段EIS数据构建SOH估计模型,往往存在精度低、计算复杂度高等问题...电化学阻抗谱(electrochemical impedance spectroscopy,EIS)蕴含丰富的电池健康状态(state of health,SOH)信息,但不同频率的电化学阻抗数据间并不相互独立,直接利用全频段EIS数据构建SOH估计模型,往往存在精度低、计算复杂度高等问题。鉴于此,本文提出了一种基于特征选择和高斯过程回归的SOH估计方法,可通过序贯前向搜索策略,结合交叉验证均方根误差指标,逐步搜索阻抗特征子集。基于此,采用基于水平图的多目标可视化决策方法,以均衡模型复杂度与精度为目标,综合考虑特征个数与交叉验证均方根误差,实施阻抗特征子集优选。所提方法已成功地应用于公开发表数据集。相比全频段EIS建模方法,本文作者所提方法可显著提升SOH估计精度,大幅降低EIS测试时间,为电化学阻抗技术应用于SOH在线估计提供理论和技术支撑。展开更多
基金the High Technology Research and Development Programme of China(No.2002AA633120)Sharing and Opening Projects of ENVISAT ASAR Data
文摘An optimization of polarimetric contrast enhancement method is proposed to detect ships with lowship-to-clutter power ratio.The received power is calculated with Kennaugh matrix and an iterative algo-rithm is adopted to get the optimal polarimetric states.The optimization method depresses the power of o-cean clutter and increases the power of ship signal.With the double effects,the contrast of ship to oceanis dramatically increased.Thus small ship or weak signals of low ship-to-ocean power ratio can easily bedetected.Ship signals can be distinguished from speckle noise using the different variation trend after op-timization,and thus the threshold problem can be avoided.Moreover,the analyses of different ship'sKennaugh matrices give two implications.One is that the results are affected little by choosing differentKennaugh matrices of ships with strong intensity from Synthetic Aperture Radar(SAR)images.The otheris that ship's Kennaugh matrix chosen from real SAR images is more favorable than that of ideal scatter-ing.Finally,the optimization results are confirmed by polarimetric scattering angle and co-polarizationphase difference.
基金The National Natural Science Foundation of China(NSFC)under contract Nos 41276186,41506015 and 41606038the NSFC-Shandong Joint Fund for Marine Science Research Centers under contract No.U1606405the Postdoctoral Innovation Foundation of Shandong Province under contract No.201502031
文摘Algal blooms caused by Prorocentrum donghaiense occurred frequently in the East China Sea （ECS） during spring in recent years. In this study, a coupled biophysical model was used to hindcast a massive P. donghaiense bloom that occurred in 2005 and to determine the factors influencing bloom initiation and development. The model comprised the Regional Ocean Modeling System tailored for the ECS that utilized a multi-nested configuration and a population dynamics model for 19. donghaiense. Comparisons between simulations and observations revealed that the biological model is capable of reproducing the characteristics of 19. donghaiense growth under different irradiances and phosphorus limitation scenarios. The variation of intracellular phosphorus and the effects of 19. donghaiense on ambient nutrients conditions were also reproduced. The biophysical model hindcasted the hydrodynamics and spatiotemporal distributions of the P. donghaiense bloom reasonably well. Bloom development was consistent with observations reported in earlier studies. The results demonstrate the capability of the model in capturing subsurface incubation during bloom initiation. Then model＇s hindcast solutions were further used to diagnose the factors controlling the vertical distribution. Phosphate appeared to be one of the factors controlling the subsurface incubation, whereas surface wind fields played an important role in determining P. donghaiense distribution. The results highlight the importance of nutrient-limitation as a mechanism in the formation of P. donghaiense subsurface layers and the dispersing of P. donghaiense blooms. This coupled biophysical model should be improved and used to investigate 19. donghaiense blooms occurring in different scenarios.
基金The National Natural Science Foundation of China under contract Nos 41276186,41506015 and 41606038the NSFC-Shandong Joint Fund for Marine Science Research Centers under contract No.U1406404the Postdoctoral Innovation Foundation of Shandong Province under contract No.201502031
文摘In the East China Sea(ECS), the succession of causative species responsible for blooms is a recurrent phenomenon during the spring, which changes from diatoms to dinoflagellates. Observations from space and in situ cruises captured this pattern of succession during spring of 2005. In this study, we coupled two biological models, which were developed previously for Skeletonema costatum and Prorocentrum donghaiense,into a circulation model tailored for the ECS. The coupled biophysical model was used to hindcast the blooms and to test the hypothesis proposed in earlier studies that phosphate(PO4 3–) is the first-order decider of the succession. The coupled model successfully reproduced the hydrodynamics(as described in a companion paper by Sun et al.(1), the spatiotemporal distribution of the chlorophyll a(Chl a) concentration, and the species succession reasonably well. By analyzing the effects of different factors on the surface Chl a distribution, we confirmed that the offshore boundaries of the blooms were confined by PO4 3–. In addition, we suggest that surface wind fields may modulate the horizontal distribution of blooms. Thus, during the dispersal of blooms, surface winds coupled with PO4 3– may control the succession of blooms in the ECS. The proposed coupled model provides a benchmark to facilitate future improvements by including more size classes for organisms, multiple nutrient schemes, and additional processes.
基金The Shanghai Sailing Program of Science and Technology Commission of Shanghai Municipality of China under contract No.14YF1410300the Special Fund for Basic Scientific Research Business of Central Public Research Institutes of 2015 of China under contract No.JG1503+3 种基金the Postdoctoral Research Projects in Zhejiang Province of China under contract No.BSH1502044the Shanghai Young University Teachers Training Support Plan of Shanghai Municipal Education Commission of China under contract Nos A1-2035-15-0021-11and ZZegd14015the 2014 Research Projects of Shanghai Second Polytechnic University of China under contract No.A01GY14GX33the Project Funded by the Local College Capacity Building Program of Science and Technology Commission of Shanghai Municipality of China under contract No.13230502000
文摘The numerous factors influencing the air-sea carbon dioxide（CO_2） transfer velocity have been discussed for many years, yet the contributions of various factors have undergone little quantitative estimation. To better understand the mechanism of air-sea transfer, the effects of different factors are discussed on the air-sea transfer velocity and the various parametric models describing the phenomenon are classified and compared.Then, based on GAS EX-98 and ASGAMAGE data, wind models are evaluated and the effects of some factors are discussed quantitatively, including bubbles, waves, wind and so on by considering their interaction through a piecewise average approach. It is found that the air-sea CO_2 transfer velocity is not only the function of the wind speed, but is also affected by bubbles, wave parameters and other factors. Stepwise and linear regressions are used. When considering the wind speed, bubbles mediated and the significant wave height, the root mean square error is reduced from 34.53 cm/h to 16.96 cm/h. Discussing the various factors quantitatively can be useful in future assessments of a large spatial scale and long-term air-sea CO_2 flux and global change.
文摘电化学阻抗谱(electrochemical impedance spectroscopy,EIS)蕴含丰富的电池健康状态(state of health,SOH)信息,但不同频率的电化学阻抗数据间并不相互独立,直接利用全频段EIS数据构建SOH估计模型,往往存在精度低、计算复杂度高等问题。鉴于此,本文提出了一种基于特征选择和高斯过程回归的SOH估计方法,可通过序贯前向搜索策略,结合交叉验证均方根误差指标,逐步搜索阻抗特征子集。基于此,采用基于水平图的多目标可视化决策方法,以均衡模型复杂度与精度为目标,综合考虑特征个数与交叉验证均方根误差,实施阻抗特征子集优选。所提方法已成功地应用于公开发表数据集。相比全频段EIS建模方法,本文作者所提方法可显著提升SOH估计精度,大幅降低EIS测试时间,为电化学阻抗技术应用于SOH在线估计提供理论和技术支撑。
