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empirical algorithm for Significant Wave Height Retrieval from Wave Mode Data Provided by the Chinese Satellite Gaofen-3

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REMOTE SENSING 2018年第3期10卷 363-363页

作者： Wang, He Wang, Jing Yang, Jingsong Ren, Lin Zhu, Jianhua Yuan, Xinzhe Xie, Chunhua State Ocean Adm Natl Ocean Technol Ctr Tianjin 300112 Peoples R China Zhejiang Ocean Univ Marine Acoust & Remote Sensing Lab Zhoushan 316000 Peoples R China State Ocean Adm Inst Oceanog 2 State Key Lab Satellite Ocean Environm Dynam Hangzhou 310012 Zhejiang Peoples R China State Ocean Adm Natl Satellite Ocean Applicat Serv Beijing 100081 Peoples R China

Gaofen-3 (GF-3), the first Chinese civil C-band synthetic aperture radar (SAR), was successfully launched by the China Academy of Space Technology on 10 August 2016. Among its 12 imaging modes, wave mode is designed to monitor the ocean surface waves over the open ocean. An empirical retrieval algorithm of significant wave height (SWH), termed Quad-Polarized C-bandWAVE algorithm for GF-3 wave mode (QPCWAVE_GF3), is developed for quad-polarized SAR measurements from GF-3 in wave mode. QPCWAVE_GF3 model is built using six SAR image and spectrum related parameters. Based on a total of 2576 WaveWatch III (WW3) and GF-3 wave mode match-ups, 12 empirical coefficients of the model are determined for 6 incidence angle modes. The validation of the QPCWAVE_GF3 model is performed through comparisons against independent WW3 modelling hindcasts, and observations from altimeters and buoys from January to October in 2017. The assessment shows a good agreement with root mean square error from 0.5 m to 0.6 m, and scatter index around 20%. In particular, applications of the QPCWAVE_GF3 model in SWH estimation for two storm cases from GF-3 data in wave mode and Quad-Polarization Strip I mode are presented respectively. Results indicate that the proposed algorithm is suitable for SWH estimation from GF-3 wave mode and is promising for other similar data.

关键词： Satellite Gaofen-3 significant wave height empirical algorithm

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INTELLIGENT HEART RATE MONITORING USING empirical algorithm AND DYNAMIC TIME WRAPPING

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INTERNATIONAL JOURNAL OF INNOVATIVE COMPUTING INFORMATION AND CONTROL 2017年第3期13卷 953-966页

作者： Lee, Shih-Hsiung Yang, Chu-Sing Natl Cheng Kung Univ Dept Elect Engn Inst Comp & Commun Engn 1 Univ Rd Tainan 701 Taiwan

This paper lays emphasis on heartbeat monitoring. The polyvinylidene difluoride (PVDF) material is used as the sensor for signal acquisition. There are two crucial subjects in this paper that shall be solved for heart rate calculation. First, the difference in signal amplitude shall be overcome (each analyte has a different heartbeat amplitude or intensity), so that the algorithm can calculate the heart rate effectively. Secondly, the difference in signal frequency or cycle is overcome (each analyte has a different heart rate or cycle), so that the accuracy of calculated heart rate is increased. Finally, the signal acquisition makes noise, which influences the calculation of heartbeat. The signal shall be preprocessed to remove the noise. Added to this, the sensor is placed in different positions, and the algorithm shall identify the signal as heartbeat signal or other signals, which contributes to calculating the heart rate rapidly. Our algorithm can calculate the heart rate effectively when the sensor is placed in different positions (chest and wrist) and overcome the effect of different signal cycle lengths.

关键词： DTW empirical algorithm Heart rate monitoring PVDF

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Long-term monitoring of total suspended matter concentration in fishponds in the Guangdong-Hong Kong-Macao Greater Bay Area

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ENVIRONMENTAL MONITORING AND ASSESSMENT 2025年第2期197卷 1-24页

作者： Zhou, Tao Yang, Xiankun Cai, Shirong Yang, Qianqian Zhang, Wenxin Li, Zhen Ran, Lishan Guangzhou Univ Sch Geog & Remote Sensing Guangzhou 510006 Peoples R China Guangzhou Univ Rural Nonpoint Source Pollut Comprehens Management Guangzhou 510006 Peoples R China Univ Padua Dept Land Environm Agr & Forestry TESAF Viale Univ 16Agripolis I-35020 Legnaro Italy Univ Hong Kong Dept Geog Pokfulam Rd Hong Kong 999077 Peoples R China

Excessive total suspended matter (TSM) concentrations can exert a considerable impact on the growth of aquatic organisms in fishponds, representing a significant risk to aquaculture health. This study revised existing unified models using empirical data to develop an optimized TSM retrieval model tailored for the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) (R2 = 0.69, RMSE = 7.78 mg/L, and MAPE = 0.23). Employing top-of-atmosphere (TOA) reflectance data from Landsat satellites, accessed via Google Earth Engine (GEE), the refined model facilitated the generation of TSM datasets for fishponds across the GBA from 1986 to 2019. Over these 34 years, there was a marked decline in TSM levels in fishponds, with an approximate 50% reduction in annual average TSM. This decline was particularly notable in the northern, western, and eastern GBA regions, leading to a spatial distribution characterized by higher TSM concentrations in the central and southern regions and lower concentrations in the peripheral regions. Seasonally, TSM levels in GBA fishponds are significantly higher during spring and summer compared to autumn and winter. Regarding natural factors, wind speed shows a significant positive correlation with long-term TSM fluctuations in these environments (p < 0.01). Stocking density, regulated artificially, emerges as a pivotal factor affecting TSM fluctuations. Specifically, TSM concentrations are elevated during periods of high stocking density in the rapid growth phase, and decrease during the mature and harvesting phases when stocking densities are reduced. Furthermore, fishponds situated in impervious areas exhibit significantly higher TSM concentrations compared to those in cropland or forested areas. The economic costs associated with aquaculture drive variations in stocking densities across different land uses within the GBA, contributing to the observed spatial variations in TSM levels. Given the status of the GBA as one of China's most advanced aquacult

关键词： Total suspended matter Fishponds Guangdong-Hong Kong-Macao Greater Bay Area Google Earth Engine empirical algorithm

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Assessment of empirical algorithms for bathymetry extraction using Sentinel-2 data

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INTERNATIONAL JOURNAL OF REMOTE SENSING 2019年第8期40卷 2855-2879页

作者： Casal, Gema Monteys, Xavier Hedley, John Harris, Paul Cahalane, Conor McCarthy, Tim Maynooth Univ Natl Ctr Geocomputat Maynooth Kildare Ireland Geol Survey Ireland Dublin Ireland Numer Opt Ltd Tiverton Devon England Rothamsted Res Sustainable Soil & Grassland Syst Harpenden Devon England Dublin Inst Technol Sch Surveying & Construct Management Dublin Ireland

Bathymetry estimated from optical satellite imagery has been increasingly implemented as an alternative to traditional bathymetric survey techniques. The availability of new sensors such as Sentinel-2 with improved spatial and temporal resolution, in comparison with previous optical sensors, offers innovative capabilities for bathymetry derivation. This study presents an assessment of the fit between satellite data and the underlying models in the most widely used empirical algorithms: the linear band model and the log-transformed band ratio model using Sentinel-2A data. Both models were tested in two study areas of the Irish coast with different morphological and environmental conditions. Results showed that the linear band model fitted better than the log-transformed band ratio model providing coefficient of determination values, R-2, between 0.83 and 0.88 (0 m-10 m) for the five images considered in the study. The closest fit was found in the depth range 2 m-6 m. Atmospheric correction, bottom type influence, and water column conditions proved to be key factors in the bathymetric derivation using these satellite datasets.

关键词： Bathymetry empirical algorithm atmospheric correction coastal applications

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Multiple Images Improve Lake CDOM Estimation: Building Better Landsat 8 empirical algorithms across Southern Canada

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REMOTE SENSING 2021年第18期13卷 3615-3615页

作者： Koll-Egyed, Talia Cardille, Jeffrey A. Deutsch, Eliza McGill Univ Dept Nat Resource Sci Macdonald Stewart Bldg Montreal PQ H9X 3V9 Canada McGill Univ Dept Nat Resources Sci Macdonald Stewart Bldg Montreal PQ H9X 3V9 Canada McGill Univ Bieler Sch Environm Macdonald Stewart Bldg Montreal PQ H9X 3V9 Canada Univ Toronto Dept Ecol & Evolutionary Biol 25 Willcocks St Toronto ON M5S 3B2 Canada

Coloured dissolved organic matter (CDOM) is an important water property for lake management. Remote sensing using empirical algorithms has been used to estimate CDOM, with previous studies relying on coordinated field campaigns that coincided with satellite overpass. However, this requirement reduces the maximum possible sample size for model calibration. New satellites and advances in cloud computing platforms offer opportunities to revisit assumptions about methods used for empirical algorithm calibration. Here, we explore the opportunities and limits of using median values of Landsat 8 satellite images across southern Canada to estimate CDOM. We compare models created using an expansive view of satellite image availability with those emphasizing a tight timing between the date of field sampling and the date of satellite overpass. Models trained on median band values from across multiple summer seasons performed better (adjusted R-2 = 0.70, N = 233) than models for which imagery was constrained to a 30-day time window (adjusted R-2 = 0.45). Model fit improved rapidly when incorporating more images, producing a model at a national scale that performed comparably to others found in more limited spatial extents. This research indicated that dense satellite imagery holds new promise for understanding relationships between in situ CDOM and satellite reflectance data across large areas.

关键词： satellite remote sensing Landsat 8 OLI coloured dissolved organic matter Canadian lakes NSERC Canadian Lake Pulse Network empirical algorithm

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Landsat 8 Lake Water Clarity empirical algorithms: Large-Scale Calibration and Validation Using Government and Citizen Science Data from across Canada

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REMOTE SENSING 2021年第7期13卷 1257-1257页

作者： Deutsch, Eliza S. Cardille, Jeffrey A. Koll-Egyed, Talia Fortin, Marie-Josee Univ Toronto Dept Ecol & Evolutionary Biol 25 Willcocks St Toronto ON M5S 3B2 Canada McGill Univ Dept Nat Resources Sci Macdonald Stewart Bldg Montreal PQ H9X 3V9 Canada McGill Univ Bieler Sch Environm Macdonald Stewart Bldg Montreal PQ H9X 3V9 Canada

Water clarity has been extensively assessed in Landsat-based remote sensing studies of inland waters, regularly relying on locally calibrated empirical algorithms, and close temporal matching between field data and satellite overpass. As more satellite data and faster data processing systems become readily accessible, new opportunities are emerging to revisit traditional assumptions concerning empirical calibration methodologies. Using Landsat 8 images with large water clarity datasets from southern Canada, we assess: (1) whether clear regional differences in water clarity algorithm coefficients exist and (2) whether model fit can be improved by expanding temporal matching windows. We found that a single global algorithm effectively represents the empirical relationship between in situ Secchi disk depth (SDD) and the Landsat 8 Blue/Red band ratio across diverse lake types in Canada. We also found that the model fit improved significantly when applying a median filter on data from ever-wider time windows between the date of in situ SDD sample and the date of satellite overpass. The median filter effectively removed the outliers that were likely caused by atmospheric artifacts in the available imagery. Our findings open new discussions on the ability of large datasets and temporal averaging methods to better elucidate the true relationships between in situ water clarity and satellite reflectance data.

关键词： Landsat 8 OLI Secchi disk depth water clarity Canadian lakes empirical algorithm

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Adaptation of empirical Methods to Predict the LogD of Triazine Macrocycles

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ACS MEDICINAL CHEMISTRY LETTERS 2023年第10期14卷 1378-1382页

作者： Patterson-Gardner, Casey J. Pavelich, Gretchen M. Cannon, April T. Menke, Alexander J. Simanek, Eric E. Texas Christian Univ Dept Chem & Biochem Ft Worth TX 76129 USA

Octanol/water partition coefficients guide drug design, but algorithms do not always accurately predict these values. For cationic triazine macrocycles that adopt a conserved folded shape in solution, common algorithms fall short. Here, the logD values for 12 macrocycles differing in amino acid choice were predicted and then measured experimentally. On average, AlogP, XlogP, and ChemAxon predictions deviate by 0.9, 2.8, and 3.9 log units, with XlogP overestimating lipophilicity and AlogP and ChemAxon underestimating lipophilicity. Importantly, however, a linear relationship (R (2) > 0.98) exists between the values predicted by AlogP and the experimentally determined logD values, thus enabling more accurate predictions.

关键词： empirical algorithm AlogP logP Triazine Macrocycle Hydrazone Dynamiccovalent chemistry

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Seasonal Variation of Colored Dissolved Organic Matter in Barataria Bay, Louisiana, Using Combined Landsat and Field Data

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REMOTE SENSING 2015年第9期7卷 12478-12502页

作者： Joshi, Ishan D'Sa, Eurico J. Louisiana State Univ Dept Oceanog & Coastal Sci Baton Rouge LA 70803 USA

Coastal bays, such as Barataria Bay, are important transition zones between the terrigenous and marine environments that are also optically complex due to elevated amounts of particulate and dissolved constituents. Monthly field data collected over a period of 15 months in 2010 and 2011 in Barataria Bay were used to develop an empirical band ratio algorithm for the Landsat-5 TM that showed a good correlation with the Colored Dissolved Organic Matter (CDOM) absorption coefficient at 355 nm (a(g)355) (R-2 = 0.74). Landsat-derived CDOM maps generally captured the major details of CDOM distribution and seasonal influences, suggesting the potential use of Landsat imagery to monitor biogeochemistry in coastal water environments. An investigation of the seasonal variation in a(g)355 conducted using Landsat-derived a(g)355 as well as field data suggested the strong influence of seasonality in the different regions of the bay with the marine end members (lower bay) experiencing generally low but highly variable a(g)355 and the freshwater end members (upper bay) experiencing high a(g)355 with low variability. Barataria Bay experienced a significant increase in a(g)355 during the freshwater release at the Davis Pond Freshwater Diversion (DPFD) following the Deep Water Horizon oil spill in 2010 and following the Mississippi River (MR) flood conditions in 2011, resulting in a weak linkage to salinity in comparison to the other seasons. Tree based statistical analysis showed the influence of high river flow conditions, high- and low-pressure systems that appeared to control a(g)355 by 28%, 29% and 43% of the time duration over the study period at the marine end member just outside the bay. An analysis of CDOM variability in 2010 revealed the strong influence of the MR in controlling CDOM abundance in the lower bay during the high flow conditions, while strong winds associated with cold fronts significantly increase CDOM abundance in the upper bay, thus revealing the important rol

关键词： CDOM Barataria Bay Landsat empirical algorithm

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Assessment of satellite-based chlorophyll-a retrieval algorithms for high solar zenith angle conditions

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JOURNAL OF APPLIED REMOTE SENSING 2017年第1期11卷 012004-1-012004-15页

作者： Li, Hao He, Xianqiang Bai, Yan Chen, Xiaoyan Gong, Fang Zhu, Qiankun Hu, Zifeng State Ocean Adm Inst Oceanog 2 State Key Lab Satellite Ocean Environm Dynam Hangzhou 310012 Zhejiang Peoples R China

Numerous empirical algorithms have been operationally used to retrieve global ocean chlorophyll-a (Chla) concentrations from ocean color satellite data, for example, the OC4V4 algorithm for sea-viewing wide field-of-view sensor and the OC3M algorithm for moderateresolution imaging spectroradiometer. However, the algorithms have been established and validated based on in situ data mainly measured under low to moderate solar zenith angle (SZA) (<70 deg). Currently, with the development of geostationary satellite ocean color remote sensing, enabling observations from early morning to late afternoon, it has become necessary to know whether the empirical Chla algorithms can be applied to high SZA. The performances of seven widely used Chla algorithms (i.e., OC2, OC3M, OC3V, OC4V4, Clark, ocean-color index, and Yellow Sea Large Marine Ecosystem Ocean Color Work Group) under high SZAs were evaluated using the global in situ ocean color dataset (NASA bio-optical marine algorithm dataset). The results show that the performances of all seven algorithms decreased significantly under high SZAs compared with those under low to moderate SZAs. For instance, for the OC4V4 algorithm, the relative percent difference (RPD) and root-mean-square error (RMSE) were 13.78% and 1.66 mu g/L for the whole dataset and 3.95% and 1.49 mu g/L for SZAs ranging from 30 deg to 40 deg, respectively. However, RPD and RMSE values increased to 30.45% and 6.10 mu g/L for SZAs larger than 70 deg. Adjusting the coefficients of the algorithms using the in situ dataset with high SZA can only slightly improve the performance. The bidirectional remote sensing reflectance can explain the underestimation of the retrieved Chla under high SZA, and the low sensitivity of the blue-green ratio is responsible for the relatively larger scatter between the retrieved and the in situ Chla under high SZA. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)

关键词： ocean color remote sensing chlorophyll-a concentration empirical algorithm high solar zenith angle

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Protein helical structure determination using CD spectroscopy for solutions with strong background absorbance from 190 to 230 nm

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BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2014年第12期1844卷 2331-2337页

作者： Wei, Yang Thyparambil, Aby A. Latour, Robert A. Clemson Univ Rhodes Engn Res Ctr 501 Dept Bioengn Clemson SC 29634 USA

Conventional empirical methods for the quantification of the helical content of proteins in solution using circular dichroism (CD) primarily rely on spectral data acquired between wavelengths of 190 and 230 nm. The presence of chemical species in a protein solution with strong absorbance within this range can interfere with the ability to use these methods for the determination of the protein's helical structure. The objective of this research was to overcome this problem by developing a method for CD spectral analysis that relies on spectral features above this wavelength range. In this study, we determined that the slopes of CD spectra acquired over the 230 to 240 nm region strongly correlate with the helix contents including alpha-helix and 3(10)-helix of protein as determined using conventional CD algorithms that rely on wavelengths between 190 and 230 nm. This approach (i.e., the 230-240 nm slope method) is proposed as an effective method to determine the helix content within proteins in the presence of additives such as detergents or denaturants with high absorbance of wavelengths up to 230 nm. (C) 2014 Elsevier B.V. All rights reserved.

关键词： Circular dichroism spectroscopy empirical algorithm Protein helical structure Denaturant

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