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On the Multiplicity and the Cohen-Macaulayness of Fiber Cones of Graded Modules

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Algebra Colloquium 2021年第1期28卷 13-32页

作者： nguyen Tien manh Department of Mathematics Hung Vuong University Nguyen Tat Thanh StreetViet Tri CityPhu ThoVietnam

Let(A,m)be a Noetherian local ring with maximal ideal m,I an ideal of A,J an m-primary ideal of A,N a finitely generated A-module,S=■n≥0 Sn a finitely generated standard graded algebra over A and M=■n≥0 Mn a finitely generated graded *** characterize the multiplicity and the Cohen-Macaulayness of the fiber cone F(M)=■n≥0 Mn/JM_(n).As an application,we obtain some results on the multiplicity and the Cohen--Macaulayness of the fiber cone■n≥0 I^(n)N/JI^(n)N.

关键词： (FC)-sequence filter-regular sequence multiplicity Cohen-Macaulay fiber cone

Discrete-time sliding mode control with power rate exponential reaching law of a pneumatic artificial muscle system

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Control Theory and Technology 2022年第4期20卷 514-524页

作者： Quy-Thinh Dao Trung-Kien Le Tri van-Anh nguyen manh-Linh nguyen School of Electrical and Electronic Engineering Hanoi University of Science and TechnologyDai Co VietHanoi 11615Vietnam

This paper develops a discrete-time sliding mode controller with a power rate exponential reaching law approach to enhance the performance of a pneumatic artificial muscle system in both reaching time and chattering *** proposed method dynamically adapts to the variation of the switching function,which is based on an exponential term and a power rate term of the sliding ***,the controlled system can achieve high tracking performance while still obtain chattering-free ***,the effectiveness of the proposed method is validated through multiple experimental tests,focused on a dual pneumatic artificial muscle ***,experimental results show the effectiveness of the proposed approach in this paper.

关键词： Pneumatic artificial muscle Discrete-time sliding mode control Exponential reaching law Chattering

DENSITY ESTIMATES FOR SOLUTIONS OF STOCHASTIC FUNCTIONAL DIFFERENTIAL EQUATIONS

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Acta Mathematica Scientia 2019年第4期39卷 955-970页

作者： nguyen Tien DUNG Ta Cong SON Tran manh CUONG nguyen van TAN Trinh Nhu QUYNH Department of Mathematics FPT University Hoa Lac High Tech Park Hanoi Vietnam Department of Mathematics VNU Hanoi University of Science 334 Nguyen Trai Thanh Xuan Hanoi Vietnam Department of Foundation Academy of Cryptography Techniques Hl Chien Thang Thanh Tri Hanoi Vietnam Military Information Technology Institute 17 Hoang Sam Cau Giay Hanoi Vietnam

In this article, we investigate the density of the solution to a class of stochastic functional differential equations by means of Malliavin calculus. Our aim is to provide upper and lower Gaussian estimates for the d... 详细信息

关键词： Stochastic functional differential equations density estimates Malliavin calculus

A study on flow fields and performance of water wheel turbine using experimental and numerical analyses

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Science China(Technological Sciences) 2018年第3期61卷 464-474页

作者： nguyen manh Hung JEONG Haechang YANG Changjo Graduate School Division of Marine Engineering Mokpo National Maritime University Department of Marine Engineering Mokpo National Maritime University

In this paper, an analysis of the performance and flow fields of water wheel turbines for tidal energy extraction is carried out using experimental and numerical methods. The purpose of this work is to develop a water turbine suitable for sites, where fast and shallow surface flows are available, such as rivers or tidal currents. For both methods, the water wheel turbine is tested over a range of tip speed ratios with a differing number of rotor blades, ranging between three and twelve. The results indicate that the numerical simulation shows agreement with the experiment in most cases. Also, the water wheel turbine operates effectively at a range of small tip-speed ratios, where the highest turbine efficiency is produced. Under the same working conditions, the turbines using between six and nine blades generate a greater efficiency and cause lesser reverse flows than others when submerged in water. In contrast, the 3-bladed turbine is the least efficient design as it produces the lowest amount of energy and causes intense vibrations and noises. These noises are a result of a collision between the incoming flow of the channel and the wheel blades during the experimentation, especially at high load conditions. By adding more blades, the torque generated is improved considerably; however, the upstream and downstream depths of the turbine, in this case, are also elevated ***, in the inlet region, the 3-bladed and 6-bladed turbines have a smaller shock loss and a lower resistance to the main flow from the inlet than the others. Meanwhile, it is found that the flow in the outlet region on the turbines with between nine and twelve blades is in the opposite direction to the wheel's rotation, significantly obstructing the main flow from the inlet.

关键词： water wheel tidal energy tip speed ratio the number of blades

Performance Comparison of Chemically Modified Sugarcane Bagasse for Removing Cd(II) in Water Environment

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Journal of Renewable Materials 2019年第5期7卷 415-428页

作者： manh Khai nguyen Minh Trang Hoang Thi Thuy Pham Bart van der Bruggen Falculty of Environmental Science VNU University of Science334 Nguyen TraiHanoiVietnam Laboratory for Process Engineering for Sustainable Systems Department of Chemical EngineeringKU LeuvenBelgiumCelestijnenlaan 200F3001 LeuvenBelgium

This paper evaluates the adsorption capacity of chemically sugarcane bagasses with sodium hydroxide(SHS),citric acid(CAS),tartaric acid(TAS)and unmodified sugarcane bagasse(SB)for cadmium adsorption in water *** results prove adsorption capacity for Cd(II)increases after chemical modification and the adsorption fits perfectly with the Langmuir *** had the highest maximum adsorption capacity of 45.45 mg/g followed by TAS with 38.46 mg/g and SHS with 29.41 at optimum pH 5.0 and 120 minutes equilibrium time while 1 g SB removed 18.8 mg Cd(II)in the same *** kinetics study of the process followed a pseudo-secondorder rate expression,that indicated a strong interaction between the biosorbents and *** sugarcane bagasse and modified sugarcane bagasse were characterized by scanning electron microscopy(SEM)and Fourier transform infrared spectroscopy(FTIR)*** chemical modification was confirmed by the presence of carboxyl and esters groups created at 1,738 *** estimation of acid groups in modified materials shows the enhancement of this group after *** the other hand,desorption studies showed the high leaching of cadmium ion from the biosorbent leading to the efficient reutilization of materials.

关键词： Cadmium chemical modification citric acid sugarcane bagasse

Structural and luminescent properties of (Eu,Tb) PO_4·H_2O nanorods/nanowires prepared by microwave technique

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Journal of Rare Earths 2011年第12期29卷 1170-1173页

作者： nguyen Thanh Huong nguyen Duc van Dinh manh Tien Do Khanh Tung nguyen Thanh Binh Tran Kim Anh Le Quoc Minh Institute of Materials Science Vietnam Academy of Science and Technology University of Engineering and Technology National University HanoiVietnam

Nanowires/nanorods of europium/terbium orthophosphate monohydrate with Eu^3＋ concentration of 6, 11, and 20 at.% were prepared by microwave synthesis method. The effects of Eu^3＋ doping concentration on structure, morphology and optical properties of nanomaterials were also investigated. The results showed that, for all studied Eu^3＋ doping concentrations, a single-crystalline phase of rhabdophane-type （Eu,Tb）PO4·H2O nanowires/nanorods was obtained by using microwave heating of an aqueous solution of terbium（Ⅲ） nitrate, europium（Ⅲ） nitrate and NH4H2PO4 with pH=2. The length and width of these nanowires/nanorods ranged from 150 to 300 nm and from 10 to 50 nm, respectively. The evidence of energy transfer from Tb^3＋ to Eu^3＋ due to the energy overlap between the donor Tb^3＋ and the acceptor Eu^3＋was observed obviously via a significant enhancement in the luminescent intensity of Eu^3＋. Keywords：

关键词： microwave technique nanowires/nanorods energy transfer fluorescence spectroscopy rare earths

Hybrid model to optimize object-based land cover classification by meta-heuristic algorithm:an example for supporting urban management in Ha Noi,Viet Nam

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International Journal of Digital Earth 2019年第10期12卷 1118-1132页

作者： Quang-Thanh Bui manh Pham van nguyen Thi Thuy Hang Quoc-Huy nguyen nguyen Xuan Linh Pham Minh Hai Tran Anh Tuan Pham van Cu Center for Applied Research in Remote sensing and GIS(CARGIS) VNU University of ScienceHa NoiViet Nam VNU University of Science Ha NoiViet Nam Vietnam Institute of Geodesy and Cartography Ha NoiViet Nam Ministry of Education and Training Ha NoiViet Nam

This study proposed a novel object-based hybrid classification model named GMNN that combines Grasshopper Optimization Algorithm(GOA)and the multiple-class Neural network(MNN)for urban pattern detection in Hanoi,*** bands of SPOT 7 image and derivable NDVI,NDWI were used to generate image segments with associated attributes by PCI Geomatics *** segments were classified into four urban surface types(namely water,impervious surface,vegetation and bare soil)by the proposed ***,three training and validation datasets of different sizes were used to verify the robustness of this *** all tests,the overall accuracies of the classification were approximately 87%,and the Area under Receiver Operating Characteristic curves for each land cover type was ***,the performance of this model was examined by comparing several statistical indicators with common benchmark *** results showed that GMNN out-performed established methods in all comparable *** results suggested that our hybrid model was successfully deployed in the study area and could be used as an alternative classification method for urban land cover *** a broader sense,classification methods will be enriched with the active and fast-growing contribution of metaheuristic algorithms.

关键词： Urban remote sensing object-based classification neural network grasshopper optimization algorithm

Effect of heating time on structural,morphology,optical,and photocatalytic properties of g-C3N4 nanosheets

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Chinese Physics B 2020年第5期29卷 504-508页

作者： nguyen manh Hung Le Thi Mai Oanh Lam Thi Hang Pham Do Chung Pham Thi Duyen Dao Viet Thang nguyen van Minh Center for Nano Science and Technology Hanoi National University of Education136 Xuan Thuy RoadCau Giay DistrictHanoi100000Vietnam Department of Physics Hanoi National University of Education136 Xuan Thuy RoadCau Giay DistrictHanoi100000Vietnam Faculty of Basic Sciences Hanoi University of Natural Resources and Environment41A Phu Dien RoadNorth Tu LiemHanoi100000Vietnam Hanoi University of Mining and Geology Duc Thang wardNorth Tu Liem DistrictHanoi100000Vietnam Military science Academy 322 Le Trong Tan streetDinh CongHoang MaiHanoi100000Vietnam

Effect of heating time on the structural,morphology,optical,and photocatalytic properties of graphitic carbon nitride(g-C3N4)nanosheets prepared at 550℃in Ar atmosphere is *** investigations are carried out by using x-ray diffraction(XRD),scanning electron microscopy(SEM),Fourier-transform infrared spectroscopy(FTIR),UV-vis absorption,and photoluminescence(PL).At a heating temperature of 550℃,g-C3N4 nanocrystals are formed after 0.5 h and become more orderly as the heating time *** surface area of the g-C3N4 nanosheets significantly increases as the preparation time *** g-C3N4 prepared in 2.5 h shows the highest photocatalytic performance,decomposing completely 10 ppm RhB solution under xenon lamp irradiation for 2.0 h.

关键词： nanosheets photocatalytic heating time Ar atmosphere

Combining Entropy Optimization and Sobel Operator for Medical Image Fusion

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Computer Systems Science & Engineering 2023年第1期44卷 535-544页

作者： nguyen Tu Trung Tran Thi Ngan Tran manh Tuan To Huu nguyen Faculty of Computer Science and Engineering Thuyloi University175 Tay SonDong DaHanoi010000Vietnam University of Information and Communication Technology Thai Nguyen UniversityThai Nguyen240000Vietnam

Fusing medical images is a topic of interest in processing medical *** is achieved to through fusing information from multimodality images for the purpose of increasing the clinical diagnosis *** fusion aims to improve the image quality and preserve the specific *** methods of medical image fusion generally use knowledge in many differentfields such as clinical medicine,computer vision,digital imaging,machine learning,pattern recognition to fuse different medical *** are two main approaches in fusing image,including spatial domain approach and transform domain *** paper proposes a new algorithm to fusion multimodal *** algorithm is based on Entropy optimization and the Sobel *** transform is used to split the input images into components over the low and high frequency ***,two fusion rules are used for obtaining the fusing *** rule,based on the Sobel operator,is used for high frequency *** second rule,based on Entropy optimization by using Particle Swarm Optimization(PSO)algorithm,is used for low frequency *** algorithm is implemented on the images related to central nervous system *** experimental results of the paper show that the proposed algorithm is better than some recent methods in term of brightness level,the contrast,the entropy,the gradient and visual informationfidelity for fusion(VIFF),Feature Mutual Information(FMI)indices.

关键词： Medical image fusion wavelet entropy optimization PSO Sobel operator