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Spatio-Temporal Analysis of Drought in the North-Eastern Coastal Region of Vietnam Using the Standardized Precipitation Index (SPI)

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Atmospheric and Climate Sciences 2023年第2期13卷 175-200页

作者： nguyen Van tuan nguyen Van Hieu nguyen khac Bang Pham Hoang Hai nguyen Khanh Van Le Vinh Ha Tran Thi Hoa Lê Trọng Hiếu Institute of Water Resources Planning Hanoi Vietnam Institute of Environment and Public Health Vietnam Union of Science and Technology Associations Hanoi Vietnam Thai Binh University Thai Binh Vietnam Faculty of Electronics and Telecommunications Electric Power University Hanoi Vietnam

Spatio-temporal analysis of drought provides valuable information for drought management and damage mitigation. In this study, the Standardized Precipitation Index at the time scale of 6 months (SPI-6) is selected to reflect drought conditions in the North-Eastern coastal region of Vietnam. The drought events and their characteristics from 1981 to 2019 are detected at 9 meteorological stations and 10 Chirps rainfall stations. The spatio-temporal variation of drought in the study region is analyzed on the basis of the number, duration, severity, intensity, and peak of the detected drought events at the 19 stations. The results show that from 1981 to 2019 the drought events mainly occurred with 1-season duration and moderate intensity and peak. The number, duration, severity, and peak of the drought events were the greatest in the period 2001-2010 and were the smallest in the period 2011-2019. Among the 19 stations, the drought duration tends to decrease at 11 stations, increase at 7 stations, and has a slight variant at 1 station;the drought severity tends to decrease at 14 stations, increase at 4 stations, and has not a significant trend at 1 station;the drought intensity tends to decrease at 17 stations, increase at 1 station, and has a slight variant at 1 station;and the drought peak tends to decrease at 18 stations and increase at 1 station.

关键词： Spatio-Temporal Analysis of Drought Standardized Precipitation Index (SPI) Drought Characteristics

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Artificial neural network approach for multiphase segmentation of battery electrode nano-CT images

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npj Computational Materials 2022年第1期8卷 255-265页

作者： Zeliang Su Etienne Decencière tuan-Tu nguyen Kaoutar El-Amiry Vincent De Andrade Alejandro A.Franco Arnaud Demortière Laboratoire de Réactivitéet Chimie des Solides(LRCS) CNRS UMR 7314Universitéde Picardie Jules VerneHub de l’EnergieRue Baudelocque80039Amiens CedexFrance Réseau sur le Stockage Electrochimique de l’Energie(RS2E) CNRS FR 3459Hub de l’EnergieRue Baudelocque80039Amiens CedexFrance MINES ParisTech–PSL Research University CMMCenter for Mathematical Morphology35 rue Saint HonoréFontainebleauFrance Renault Technocentre 78084GuyancourtFrance Advanced Photon Source Argonne National LaboratoryLemontUSA Institut Universitaire de France 101 Boulevard Saint Michel75005ParisFrance ALISTORE-European Research Institute CNRS FR 3104Hub de l’EnergieRue Baudelocque80039Amiens CedexFrance

The segmentation of tomographic images of the battery electrode is a crucial processing step,which will have an additional impact on the results of material characterization and electrochemical ***,manually labeling X-ray CT images(XCT)is time-consuming,and these XCT images are generally difficult to segment with histographical *** propose a deep learning approach with an asymmetrical depth encode-decoder convolutional neural network(CNN)for real-world battery material *** network achieves high accuracy while requiring small amounts of labeled data and predicts a volume of billions voxel within few *** applying supervised machine learning for segmenting real-world data,the ground truth is often *** results of segmentation are usually qualitatively justified by visual *** try to unravel this fuzzy definition of segmentation quality by identifying the uncertainty due to the human bias diluted in the training *** CNN trainings using synthetic data show quantitative impact of such uncertainty on the determination of material’s ***-XCT datasets of various battery materials have been successfully segmented by training this neural network from *** will also show that applying the transfer learning,which consists of reusing a well-trained network,can improve the accuracy of a similar dataset.

关键词： neural network battery

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Antibiotic usage in surgical sperm retrievals among IVF centers

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Asian Journal of Andrology 2022年第6期24卷 633-638页

作者： Le Dang Khoa Ngo Dinh Trieu Vy nguyen Minh Tai Loc Le Duc Thang Dang tuan Anh nguyen Phuc Hieu Giang Huynh Nhu nguyen Dinh Tao Le Hoang David J Handelsman IVFTA Tam Anh General HospitalHo Chi Minh 700000Vietnam IVFTA Tam Anh General HospitalHa Noi 100000Vietnam IVF Center 16A Ha Dong HospitalHa Noi 100000Vietnam ANZAC Research Institute University of Sydney and Concord Repatriation General HospitalHospital RoadConcordNSW 2139Australia

Surgical sperm retrieval(SSR)is currently one of the most common procedures in in vitro fertilization(IVF).However,a gap between the guidelines and routine clinical practice regarding antibiotic use in sSR,which might lead to antibiotic resistance,is a challenging problem worldwide.A cross-sectional survey was conducted from May 1,2021,to July 15,2021,to investigate antibiotic usage by medical professionals when performing SSR in IVF centers in *** confidential questionnaire comprised 12 items,including characteristics of the study population,awareness of antimicrobial resistance,attitude toward prescribing antibiotics,and current practice of prescribing antibiotics when performing *** were completed by 30 of 45 registered IVF centers(66.7%).Among 67 physicians working at those centers,the age and work-experience years(mean±standard deviation[s.d.])were 38.6±6.6 years and 11.2±7.0 years,*** 60%of them held a degree in Obstetrics and Gynecology,and over four-fifths were *** respondents"often/very often/always"raised awareness of antimicrobial resistance to their patients(83.3%),but only half of them"often/occasionally"prescribed antibiotics to patients with SSR in cases where the prescription would be *** one-tenth of respondents followed the recommendation from the American Urological Association using"prophylaxis only"for SSR *** more invasive SSR,physicians tended to prescribe more complicated and sometimes inappropriate *** conclusion,antibiotic usage in SSR was not always appropriate among IVF *** studies may define specific recommendations for regimens,intervention strategies,and programs to promote appropriate antibiotic use for SSR patients among IVF specialists.

关键词： antibiotic usage in vitro fertilization prophylaxis surgical sperm retrieval treatment

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Forecasting the Convergence State of per Capital Income in Vietnam

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American Journal of Operations Research 2013年第6期3卷 487-496页

作者： nguyen khac Minh Pham Van Khanh Military Technical Academy Hanoi Vietnam National Economics University Hanoi Vietnam

Convergence problem of an economic variable represents an underlying forecast of neoclassical economic growth model. This paper aims to analyze the convergence of provincial per capita GDP stability in Vietnam over the period of 1991-2007. This can be done by two approaches including bias data-based regression method for testing convergence and Markov chain model for describing features of long-term tendency of per capita income in Vietnam growth in provinces. The regression method results in the signs of convergence. To apply Markov process, we divide total pattern into 5 per capita income classes. Result estimated from the Markov chain model shows the poor convergence.

关键词： Convergence Regression Method Markov Proces

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Gravitationally lensed extended sources: the case of QSO RXJ0911

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Research in Astronomy and Astrophysics 2013年第7期13卷 803-814页

作者： Do Thi Hoai Pham Tuyet Nhung Pham tuan Anh Frederic Boone Pierre Darriulat Pham Ngoc Diep Pham Ngoc Dong nguyen Van Hiep nguyen Thi Thao VATLY INST179Hoang Quoc VietCau GiayHanoiVietnam IRAP 14avenue Edouard BelinF31400 ToulouseFrance

After a brief reminder of the mechanism of gravitational lensing of ex- tended sources, the particular case of the host galaxy of QSO RXJ0911, a high red-shift （z - 2.8） quadruply imaged quasar, is explored. The non linearity of the problem, together with the proximity of the source to a cusp of the lens inner caustic, has impor-tant consequences on the dependence of the image appearance on the size and shape of the source. Their expected main features and their interpretation in terms of source extension and shape are investigated in a spirit of simplicity and in preparation for the analysis of high sensitivity and spatial resolution images that will soon be within reach with the completion of the Atacama Large Millimeter/submillimeter Array （ALMA）. In particular, the information on source size carded by relative image brightness is dis-cussed. Extension of the results to other types of quadruply imaged quasars is briefly considered.

关键词： gravitational lensing - galaxies: high-redshift

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A Chance–Constrained Data Envelopment Analysis Approach to Problem Provincial Productivity Growth in Vietnamese Agriculture from 1995 to 2007

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Open Journal of Statistics 2011年第3期1卷 217-235页

作者： nguyen khac Minh Pham Van Khanh 不详

This study employs a chance-constrained data envelopment analysis (CDEA) approach with two models (model A and model B) to decompose provincial productivity growth in Vietnamese agriculture from 1995 to 2007 into technological progress and efficiency change. The differences between the chance - constrained programming model A and model B are assumptions imposed on the covariance matrix. The decomposition allows us to identify the contributions of technical change and the improvement in technical efficiency to productivity growth in Vietnamese production. Sixty-one provinces in Vietnam are classified into Mekong - technology and other -technology categories. We conduct a Mann-Whitney test to verify whether the two samples, the Mekong technology province sample and the other technology sample, are drawn from the same productivity change populations. The result of the Mann-Whitney test indicates that the differences between the Mekong technology category and the other technology category from two models are more significant. Two important questions are whether some provinces in the samples could maintain their relative efficiency rank positions in comparison with the others over the study period and how to further examine the agreements between the two models. The Kruskal - Wallis test statistic shows that technical efficiency from both models for some provinces are higher than those of them in the study period. The Malmquist results show that production frontier has contracted by around 1.3 percent and 0.31 percent from chance-constrained model A and model B, respectively, a year on average over the sample period. To examine the agreements or disagreements in the total factor productivity indexes we compute the correlation between Malmquist indexes, which is positive and not very high. Thus there is a little discrepancy between the two Malmquist indexes, estimated from the chance - constrained models A and B.

关键词： Total Factor Productivity Technical Efficiency Change Technological Progress Chance-Constrained Programming

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Impacts of Exchange Rate Volatility and FDI on Technical Efficiency—A Case Study of Vietnamese Agricultural Sector

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American Journal of Operations Research 2015年第4期5卷 317-325页

作者： nguyen khac Minh Pham Van Khanh nguyen Viet Hung Economics and Management Faculty Thang Long University Hanoi Vietnam Institute of Economics and Corporate Group Hanoi Vietnam Faculty of Economics National Economics University Hanoi Vietnam

The objective of this research is to examine impacts of exchange rate volatility and FDI on efficiency of the Vietnamese agricultural sector at the provincial level for the period 1998-2011. Due to the characteristic of high uncertainty in agricultural production, the chance-constrained programming model would be used to estimate efficiency of the agricultural production sector. In order to study impacts of exchange rate volatility and FDI, we employ the two-stage model. In the first stage, we use the chance-constrained programming model to measure technical efficiency and ARIMA model to quantify exchange rate volatility. In the second stage, we use the fixed effect model to evaluate impacts of exchange rate volatility and FDI on efficiency of agricultural production in poor and rich provinces. The estimated results show that fluctuation in exchange rate volatility would reduce efficiency in agricultural production but FDI has an insignificant impact on the efficient production in Vietnam agricultural sector.

关键词： Chance-Constrained Programming DEA Exchange Rate Volatility FDI Technical Efficiency

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Control of Nonlinear Systems with Output Tracking Error Constraints

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Journal of Measurement Science and Instrumentation 2010年第3期1卷 217-223页

作者： khac Duc Do Dang Binh nguyen Anh Duc nguyen School of Mechanical Engineering University of Western Australia WA 6009 Australia Rectoral Office Thainguyen University of Technology Thainguyen Vietnam Department of Electrical Engineering Thainguyen University of Technology Thainguyen Vietnam

A oanstructive method is presented to design controllers that force the output of nonlinear systems in a strict feedback form to track a bounded and sufficient smooth reference trajectory asymptotically. Under suitable condition with the initial output tracking error, the proposed controllers guarantee the output tracking error within a symmtric or an asymmetric pre-specified limit range, and boundedness of all signals of the closed loop system. A transformation is inmxuced to take care of the output tracking error constraint. Smooth and/or p -times differentiable step functions are propsed and incor- porated in the output tracking error transformation to overcome difficulties due to the asynxnetric limit range on the output tracking error. As a result, there are no switchings in the proposed controllers despite of the asymmnetric limit range.

关键词： nonlinear system output constraint backstepping Lyapunov method

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ALMA observations of the circumstellar envelope around EP Aqr

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Research in Astronomy and Astrophysics 2019年第3期19卷 97-110页

作者： Pham Thi Tuyet Nhung Do Thi Hoai Pham tuan-Anh Thibaut Le Bertre Pierre Darriulat Pham Ngoc Diep nguyen Thi Phuong nguyen Thi Thao Jan Martin Winters Department of Astrophysics Vietnam National Space CenterVAST LERMA UMR 8112 CNRS and Observatoire de Paris PSL Research University Graduate University of Science and Technology VAST IRAM 300 rue de la Piscine Domaine Universitaire

Atacama Large Millimetre/sub-millimetre Array(ALMA) observations of CO(1–0) and CO(2–1) emissions from the circumstellar envelope of the asymptotic giant branch(AGB) star EP Aqr have been made with four times better spatial resolution than previously available. They are analysed with emphasis on the de-projection in space of the effective emissivity and flux of matter using as input a prescribed configuration of the velocity field, assumed to be radial. The data are found to display an intrinsic axisymmetry with respect to an axis making a small angle with respect to the line of sight. A broad range of wind configurations, from prolate(bipolar) to oblate(equatorial) has been studied and found to be accompanied by significant equatorial emission. Qualitatively, the effective emissivity is enhanced near the equator to produce the central narrow component observed in the Doppler velocity spectra and its dependence on star latitude generally follows that of the wind velocity with the exception of an omni-present depression near the poles. In particular, large equatorial expansion velocities produce a flared disc or a ring of effective emissivity and mass loss. The effect on the determination of the orientation of the star axis of radial velocity gradients, and possibly competing rotation and expansion in the equatorial disc, is discussed. In general,the flux of matter is found to reach a broad maximum at distances of the order of 500 AU from the *** are given that may be used to favour one wind velocity distribution over another. As a result of the improved quality of the data, a deeper understanding of the constraints imposed on morphology and kinematics has been obtained.

关键词： stars: AGB and post-AGB (stars:) circumstellar matter stars: individual: EP Aqr stars:mass-loss radio lines: stars

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Nonlinear Control of Magnetic Bearings

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Journal of Measurement Science and Instrumentation 2010年第1期1卷 10-16页

作者： khac Duc Do Dang Hoe nguyen Thanh Binh nguyen School of Mechanical Engineering University of Western Australia WA 6009 Australia Vice-Rectoral Office Thainguyen University of Technology Thainguyen Vietnam Dept. of Human Resource University ofThainguyen Thainguyen Vietnam

In this paper, recent results controling nonlinear systems with output tracking error constmints are applied to the design of new tracking controllers for magnetic bearings. The proposed controllers can force the rotor to track a bounded and sufficiently smooth reference trajectory asymptotically and guarantee non-contactedness betweea the rotor and the stator of the magnetic beadngs. Simulation results are included to illustrate the effectiveness of the propsed controllers.

关键词： nonlinear system output constraint bockstepping L yapunov method

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