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A Modified semianalytical algorithm for Remotely Estimating Euphotic Zone Depth in Turbid Inland Waters

IEEE JOURNAL OF SELECTED TOPICS IN APPLIED EARTH OBSERVATIONS AND REMOTE SENSING 2015年第4期8卷 1545-1554页

作者： Yang, Wei Matsushita, Bunkei Yoshimura, Kazuya Chen, Jin Fukushima, Takehiko Beijing Normal Univ State Key Lab Earth Surface Proc & Resource Ecol Beijing 100875 Peoples R China Japan Agcy Marine Earth Sci & Technol Dept Environm Geochem Cycle Res Yokohama Kanagawa 2370001 Japan Univ Tsukuba Grad Sch Life & Environm Sci Tsukuba Ibaraki 3058572 Japan

Euphotic zone depth (Z(eu)), defined as the depth where photosynthetic available radiation (PAR) is 1% of its surface value, is of great importance in studies of water biogeochemical processes. Satellite remote sensing is a powerful technique to obtain Zeu, as it can cover large areas at very frequent intervals. Several remote-sensing algorithms for estimating Zeu have been developed for oceanic water bodies;however, remote estimation of Zeu is still a challenging task for inland waters. In this study, an existing semianalytical algorithm (named as Lee07 in this study) was modified for remotely estimating Zeu in turbid inland waters by replacing the original quasi-analytical algorithm (QAA) by QAA_Turbid, an algorithm specially developed for remotely estimating total absorption and backscattering coefficients in turbid waters. Performance of the modified algorithm was evaluated using in situ radiometric data collected in Japan's Lake Kasumigaura, known to be turbid. Results showed that yielded acceptable estimation accuracy for Zeu (ranging from 1.15 to 2.26 m) with root-mean-square error (RMSE) of 0.12 m, normalized root-mean-square error (NRMS) of 8.01%, and mean normalized bias (MNB) of -1.84%, significantly outperforming the original version as well as three other Zeu retrieval algorithms. These results indicate its great potential for accurately estimating Zeu over widespread turbid inland waters from satellite images.

关键词： Euphotic zone depth inland waters QAA_Turbid remote-sensing reflectance semianalytical algorithm

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Application of a semianalytical algorithm to Remotely Estimate Diffuse Attenuation Coefficient in Turbid Inland Waters

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IEEE GEOSCIENCE AND REMOTE SENSING LETTERS 2014年第6期11卷 1046-1050页

作者： Yang, Wei Matsushita, Bunkei Chen, Jin Yoshimura, Kazuya Fukushima, Takehiko Beijing Normal Univ State Key Lab Earth Surface Proc & Resource Ecol Beijing 100875 Peoples R China Univ Tsukuba Grad Sch Life & Environm Sci Tsukuba Ibaraki 3058572 Japan

Remote estimation of the vertically averaged diffuse attenuation coefficient over a water layer (K) over bar (d)(lambda) is of great importance in understanding and modeling the physical, chemical, and biological processes in water bodies. A semianalytical algorithm was previously proposed to remotely estimate (K) over bar (d)(lambda) based on the retrieval of the total absorption and backscattering coefficients (a and b(b)). The algorithm has been effectively applied to clear and slightly turbid oceanic waters, but its applicability in turbid inland waters is still unknown. In this study, the relationship between a and b(b) on the one hand with (K) over bar (d)(lambda) used in the semianalytical algorithm was first validated by the measured a and b(b). Second, the semianalytical algorithm was combined with the so-called QAA_Turbid (quasi-analytical algorithm for turbid waters) to remotely estimate (K) over bar (d)(lambda) for highly turbid waters. We tested the performance of the combined algorithm at wavelengths of 443, 556, and 669 nm by using a data set collected from a turbid lake in Japan. The validation results demonstrated that it could estimate (K) over bar (d)(lambda) (ranging from 1.94 to 9.47 m(-1)) with root-mean-square error and relative error values of 0.17 and 12.96%, respectively. These results indicate the great potential of the semianalytical algorithm to accurately monitor the spectra of (K) over bar (d)(lambda) for turbid inland waters from satellite observations.

关键词： Diffuse attenuation coefficient estimation inland waters remote sensing semianalytical algorithm

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Research on eddy current losses algorithm in solid rotor of high speed squirrel cage induction motor

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IET ELECTRIC POWER APPLICATIONS 2020年第6期14卷 1023-1029页

作者： Chou, Weixiang Liang, Yanping Gao, Lianlian Wang, Dongmei Harbin Univ Sci & Technol Coll Elect & Elect Engn Harbin Peoples R China

Aiming at the shortcomings of the analytical algorithm and numerical algorithm for calculating the eddy current losses in the solid rotor of high speed squirrel cage induction motor, this study proposes a semi-analytical algorithm. Based on the magnetic field of the rotor surface and Maxwell's equations, the analytical formula of this algorithm is derived. According to the law of energy conservation, the losses in rotor and rotor bars are calculated, respectively, so that the eddy current losses in the solid rotor are calculated indirectly. Taking a high speed squirrel cage induction motor as an example, the eddy current losses in the solid rotor are calculated by the semi-analytical method. The calculation result is verified by the two-dimensional transient finite-element method, and the calculation result meets the basic requirements of engineering practice.

关键词： rotors squirrel cage motors finite element analysis eddy current losses energy conservation magnetic fields Maxwell equations eddy current losses algorithm solid rotor analytical algorithm numerical algorithm semianalytical algorithm rotor surface rotor bars semianalytical method high speed squirrel cage induction motor magnetic field Maxwell equations energy conservation two-dimensional transient finite-element method

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Mathematical simulation of ultrashort light pulse propagation in a highly scattering medium

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Mathematical Models and Computer Simulations 2010年第1期2卷 22-32页

作者： Kuznetsov, V.S. Nikolaeva, O.V. Bass, L.P. Bykov, A.V. Priezzhev, A.V. Scientific Center Research “Kurchatov Institute ” Moscow Russian Federation Keldysh Institute of Applied Mathematics Russian Academy of Sciences Keldysh Russian Federation Moscow State University Moscow Russian Federation University of Oulu Oulu Finland

The problem of probing a nonhomogeneous medium imitating the biological tissue by an ultrashort light pulse is investigated. The pulse propagation in the medium is described by a transient transport equation. A grid algorithm for its solution based on the analytical presentation of the density of the unscattered photon flux is presented as well as a semianalytical algorithm for computing the density of the flux of singly scattered photons. Methodological calculations carried out by the grid method and by the alternative Monte Carlo method are given. © 2010, Pleiades Publishing, Ltd.

关键词： nonhomogeneous medium biological tissue semianalytical algorithm mathematical simulation photon flux Monte Carlo technique Pulse propagation ultrashort light pulse TISSUES (BIOLOGY)

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Construction of a High Spatiotemporal Resolution Dataset of Satellite-Derived pCO2 and Air-Sea CO2 Flux in the South China Sea (2003-2019)

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IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 2023年 61卷 1页

作者： Song, Zigeng Yu, Shujie Bai, Yan Guo, Xianghui He, Xianqiang Zhai, Weidong Dai, Minhan Minist Nat Resources Inst Oceanog 2 State Key Lab Satellite Ocean Environm Dynam Hangzhou 310012 Peoples R China Zhejiang Univ Ocean Coll Zhoushan 316021 Peoples R China Xiamen Univ Coll Ocean & Earth Sci State Key Lab Marine Environm Sci Xiamen 361102 Peoples R China Southern Marine Sci & Engn Guangdong Lab Zhuhai Zhuhai 519080 Peoples R China

The South China Sea (SCS) is one of the largest marginal seas in the world. It includes a river-dominated, highly productive ocean margin on the northern shelf and an oligotrophic ocean-dominated basin along with other subregions with various features. It was a challenge to estimate the air-sea CO2 flux in this area. We developed a retrieval algorithm for sea surface partial pressure of CO2 (pCO(2)) by a combination of our previously established mechanistic semianalytical method (MeSAA) and machine learning (ML) method, named MeSAA-ML-SCS, built upon a large dataset of sea surface pCO(2) collected from in situ measurements during 44 cruises /legs to the SCS in the last two decades. We set several semianalytical parameters, including pCO(2_therm) represented the combined effect of thermodynamics and the atmospheric CO2 forcing on seawater pCO(2);upwelling index (UISST) and mixing layer depth (MLD) to characterize the mixing processes;and chlorophyll-a concentration (Chl-a) with remote sensing reflectance at 443 and 555 nm [Rrs(443) and Rrs(555)], which were proxies of biological effects and other characteristics for distinguishing shelf, basin, and subregions. We set the difference between seawater pCO(2) and atmospheric pCO(2)(Delta pCO(2)(Sea-Air)) as the output, and the seawater pCO(2) was finally obtained by summing atmospheric pCO(2) and Delta pCO(2)(Sea-Air). We compared several ML models, and the XGBoost model was confirmed as the best. Independent cruisebased datasets that are not involved in the model training were used to validate the satellite products, with low root-mean-square error (RMSE = 11.69 mu atm) and mean absolute percentage deviation (APD = 1.59%). The increasing trend of time-series satellite-derived pCO(2) (2.44 +/- 0.24 mu atm/year) was validated by the in situ data at the Southeastern Asia Time-series Study (SEATS) station, showing good consistency. Results indicate that

关键词： Air-sea CO2 flux machine learning (ML) satellite retrieval seawater p CO2 semianalytical algorithm South China Sea (SCS)

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The QAA-RGB: A universal three-band absorption and backscattering retrieval algorithm for high resolution satellite sensors. Development and implementation in ACOLITE

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REMOTE SENSING OF ENVIRONMENT 2021年 265卷 112667-112667页

作者： Pitarch, Jaime Vanhellemont, Quinten CNR Ist Sci Marine ISMAR Via Fosso Cavaliere 100 I-00133 Rome Italy Royal Belgian Inst Nat Sci Operat Directorate Nat Environm Vautierstr 29 B-1000 Brussels Belgium

We present the "QAA-RGB", a semianalytical algorithm that retrieves total absorption, particle backscattering, as well as the diffuse attenuation coefficient and the Secchi disk depth, from eighteen metre and decametre satellite sensors, including present and heritage Landsat's data, Sentinel 2 at 10 m and an array of commercial satellites such as PlanetScope, Pleiades and Worldview. The QAA-RGB is a minimal version of the Quasi-Analytical algorithm (QAA), and therefore keeps its robustness and general validity across different water types. It ingests remote-sensing reflectance at only three bands, centred on red, green and blue wavelengths. Retrievals of non-water absorption at 555 nm (a(nw)(555)) are satisfactory, with a standard deviation of sigma similar to 50% up to a(nw)(555) < 2 m(-1), based on in situ datasets. Careful calibration results in unbiased retrievals across all sensors. Validation to independent in situ data is also provided. The QAA-RGB has been implemented in the ACOLITE generic processor, and is openly accessible to the community. Consistency of near-coincident observations from different satellite sensors is demonstrated.

关键词： semianalytical algorithm Coastal Inland Optical Landsat Sentinel PACE Absorption Backscattering Diffuse attenuation Secchi

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Diffuse attenuation coefficient of downwelling irradiance: An evaluation of remote sensing methods

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JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 2005年第C2期110卷 1-9页

作者： Lee, ZP Darecki, M Carder, KL Davis, CO Stramski, D Rhea, WJ USN Res Lab Stennis Space Ctr MS 39529 USA Polish Acad Sci Inst Oceanol Sopot Poland Univ S Florida Coll Marine Sci St Petersburg FL 33701 USA USN Res Lab Washington DC 20375 USA Univ Calif San Diego Scripps Inst Oceanog Marine Phys Lab La Jolla CA 92093 USA

The propagation of downwelling irradiance at wavelength l from surface to a depth (z) in the ocean is governed by the diffuse attenuation coefficient, up down arrow(K) over bar (d)(lambda). There are two standard methods for the derivation of ($) over bar (d)( lambda) in remote sensing, which both are based on empirical relationships involving the blue-to-green ratio of ocean color. Recently, a semianalytical method to derive beta(K) over bar (d)( lambda) from reflectance has also been developed. In this study, using (K) over bar (d)(490) and (K) over bar (d)( 443) as examples, we compare the (K) over bar (d)(lambda) values derived from the three methods using data collected in three different regions that cover oceanic and coastal waters, with (K) over bar (d)(490) ranging from similar to0.04 to 4.0 m(-1). The derived values are compared with the data calculated from in situ measurements of the vertical profiles of downwelling irradiance. The comparisons show that the two standard methods produced satisfactory estimates of (K) over bar (d)(lambda) in oceanic waters where attenuation is relatively low but resulted in significant errors in coastal waters. The newly developed semianalytical method appears to have no such limitation as it performed well for both oceanic and coastal waters. For all data in this study the average of absolute percentage difference between the in situ measured and the semianalytically derived (K) over bar (d) is similar to 14% for lambda = 490 nm and similar to 11% for lambda = 443 nm.

关键词： diffuse attenuation coefficient remote sensing empirical algorithm semianalytical algorithm

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