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Forest Change and Its Effect on Biomass in Yok Don National Park in Central Highlands of Vietnam Using Ground Data and Geospatial Techniques

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Advances in Remote Sensing 2015年第2期4卷 108-118页

作者： nguyen Viet luong Ryutaro Tateishi nguyen Thanh Hoan To Trong Tu Space Technology Institute Vietnam Academy of Science and Technology Hanoi Vietnam Center for Environmental Remote Sensing Chiba University Chiba Japan Institute of Geography Vietnam Academy of Science and Technology Hanoi Vietnam

this paper assesses the changes in forest cover in Yok Don National Park of Vietnam between 2004 and 2010, and the implications of such changes on the biomass stocks of this national park. Remote sensing and GIS tools along with the ground truth data collected from the field were employed for classifying the forest types of the study area from SPOT HRV satellite imagery for years 2004 and 2010. The total area considered in this study is 115.5 thousand ha. Five different categories of forests were identified. The results demonstrated that between 2004 and 2010, the Evergreen broad leaved rich quality forest decreased by 11.2 thousand ha (3.5 Mega tons of biomass) and the Dry open dipterocarps medium quality forest decreased by 15.3 thousand ha (2.5 Mega tons of biomass). In that time period, the Evergreen broad leaved medium quality forest increased by 3.2 thousand ha (0.8 Mega tons of biomass), the Evergreen broad leaved poor quality forest increased by 2.5 thousand ha (0.24 Mega tons of biomass), and the Dry open dipterocarps poor quality forest increased by 3.2 thousand ha (0.69 Mega tons of biomass). Total biomass of the study area decreased by 4.3 Mega tons.

关键词： Satellite Data SPOT HRV Land Cover Change Tropical Forest Biomass

Density Functional Study of Electronic Properties of Perovskite Systems La1-xSrxFeO3

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材料科学与工程（中英文B版） 2012年第2期2卷 131-135页

作者： nguyen Duy Huy nguyen Thuy Trang luong Van Viet Faculty of Physics Hanoi University of Science VNU

The electronic properties of perovskite systems La1-xSrxFeO3 (x = 0, 0.67, 0.75, 1) for periodic structures and x = 0.5 for clusters) were investigated basing on density functional theory (DFT) using Dmol3 code. Our results show that LaFeO3 is antiferromagnetic insulator and SrFeO3 expresses itself as conducting material with dominated antiferomagnetic phase. The calculations also confirmed an existence of iron ions with different valences. Especially, for La0.33Sr0.67FeO3 iron ions may have valences ?+5. Investigation on polarization of clustering La0.5Sr0.5FeO3 structure reveals that this system is spontaneously strongly polarized with the polarization vector magnitude ?102 times larger than that of the well-known ferroelectric BaTiO3.

关键词：钙钛矿氧化物密度泛函理论电子性质 SrFeO3 周期性结构 tic相调查结果偏振矢量

A Study on Effects of Blade Pitch on the Hydrodynamic Performances of a Propeller by Using CFD

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Journal of Shipping and Ocean Engineering 2018年第1期8卷 36-42页

作者： nguyen Chi Cong luong Ngoc Loi NGO Van He Vietnam Marine University Haiphong 180000 Vietnam Hanoi University of Science and Technology Hanoi 10000 Vietnam

The main objective of this work is to use the CFD （Computational Fluid Dynamics） technique to study the effects of pitch ratio on the controllable pitch propeller＇s thrust characteristic. The propeller analyzed is at the following design condition： diameter of 3.65 m, speed of 200 rpm, blade number of 4, average pitch of 2.459 m, pitch ratio at 0.7 of 0.6737. The first stage involves the mesh generation and refinement on domain of the designed propeller. The second stage deals with the identification of initial and boundary conditions of the mesh-equipped module. In the final stage, various results are calculated and analyzed for pitch ratio affecting on the propeller＇s thrust characteristic. The achieved results are the basis design and improving efficiency of the controllable pitch propeller.

关键词： Controllable pitch propeller propeller blade pitch ship CFD thrust.

Effects of CuO-CeO<sub>2</sub>Addition on Structure and Catalytic Properties of Three Way Catalysts

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Journal of Materials Science and Chemical Engineering 2017年第12期5卷 28-39页

作者： nguyen The luong nguyen Duy Tien Eiji Yamasue Hideyuki Okumura Keiichi N. Ishihara Department of Internal Combustion Engine School of Transportation Engineering Hanoi University of Science and Technology Hanoi Vietnam Department of Socio-Environmental Energy Science Graduate School of Energy Science Kyoto University Kyoto Japan

The noble metals (Pt, Pd, Rh) supported on Cu-Ce mixed oxides with γ-Al2O3 washcoat/FeCrAl substrate were investigated as catalytic performance of Three Way Catalysts (TWC) under simulated automotive exhaust feed gas. The structural, morphological features and catalytic activity were observed by X-ray diffractometry (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS) and GC-TCD (Varian CP-4900). The catalytic performance of noble metals (Pt, Rh, Pd) supported on Cu-Ce mixed oxides with γ-Al2O3 washcoat/FeCrAl substrate was be compared with noble metals (Pt, Rh, Pd) supported on Ce-Zr mixed oxides with γ-Al2O3 washcoat/FeCrAl substrate and only γ-Al2O3 washcoat/FeCrAl substrate at various stoichiometric ratio of oxygen. The results showed that the addition of Cu-Ce mixed oxides improved CO oxidation reaction at lower temperature during stable lambda of 1, the highest CO conversion of 99% is observed for the noble metals (Pt, Pd, Rh) support on Cu-Ce with γ-Al2O3 washcoat/FeCrAl substrate. The results also showed that, the addition of Cu-Ce mixed oxides promoted released oxygen, thus it improved strongly CO and C3H8 conversion at lean oxygen stoichiometric operation.

关键词： Three-Way Catalysts (TWCs) Noble Metals γ-Al2O3 Washcoat CuO-CeO2 CeO2-ZrO2

Hydrodeoxygenation of Bio-Oil on Bimetallic Catalysts: From Model Compound to Real Feed

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Journal of Sustainable Bioenergy Systems 2015年第4期5卷 151-160页

作者： Thuan Minh Huynh Udo Armbruster luong Huu nguyen Duc Anh nguyen Andreas Martin Leibniz Institute for Catalysis at University of Rostock Rostock Germany Vietnam Petroleum Institute Hanoi Vietnam

Two series of bimetallic Ni-Co catalysts and corresponding monometallic catalysts with ca. 20 wt% metal loading were evaluated in hydrodeoxygenation (HDO) of phenol as a model compound for bio-oil. The bimetallic catalysts outperformed the corresponding monometallic catalyst in terms of conversion and cyclohexane selectivity. this could be attributed to the formation of Ni-Co alloy, which caused a decrease in metal particle size and stabilized Ni active sites in the near surface region. The balanced combination of formed Ni-Co alloy with acidity from supports allowed performing all individual steps in the reaction network toward desired products at high rate. Consequently, the two best-performing catalysts were tested in HDO of wood based bio-oil, showing that the bimetallic catalyst 10Ni10Co/HZSM-5 was more effective than 20Ni/HZSM-5 in terms of degree of deoxygenation and upgraded bio-oil yield. These findings might open an opportunity for development of a novel cheap but effective catalyst for a key step in the process chain from biomass to renewable liquid fuels.

关键词： Bimetallic Catalysts Hydrodeoxygenation Phenol Bio-Oil Ni-Co Alloy

Spectral Features for the Detection of Land Cover Changes

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Journal of Geoscience and Environment Protection 2019年第5期7卷 81-93页

作者： Ram C. Sharma Hoan Thanh nguyen Saeid Gharechelou Xiulian Bai luong Viet nguyen Ryutaro Tateishi Department of Informatics Tokyo University of Information Sciences Chiba Japan Institute of Geography Vietnam Academy of Science and Technology Hanoi Vietnam Graduate University of Science and Technology Vietnam Academy of Science and Technology Hanoi Vietnam Faculty of Civil Engineering Shahrood University of Technology Shahrood Iran College of Resource and Environmental Economics Inner Mongolia University of Finance and Economics Hohhot China Space Technology Institute Vietnam Academy of Science and Technology Hanoi Vietnam Center for Environmental Remote Sensing Chiba University Chiba Japan

Derivation of more sensitive spectral features from the satellite data is immensely important for better retrieving land cover information and change monitoring, such as changes in snow covered area, forests, and barren lands as some examples from local to the global scale. The major objectives of this paper are to present the potential of water-resistant snow index (WSI) for the detection of snow cover changes in the Himalayas, extant two composite images, biophysical image composite (BIC) and forest cover composite (FCC) for the detection of changes in barren lands and forested areas respectively, and two newly designed composite images, water cover composite (WCC) and urban cover composite (UCC) for the detection of changes in water and urban areas respectively. this research implemented the image compositing technique for the detection and visualization of land cover changes (water, forest, barren, and urban) with respect to local administrative areas where a significant land cover change occurred from 2001 to 2016. A case study was also conducted in the Himalayan region to identify snow cover changes from 2001 to 2015 using the WSI. Analysis of the annual variation of the snow cover in the Himalayas indicated a decreasing trend of the snow cover. Consequently, the downstream areas are more likely to suffer from snow related hazards such as glacial outbursts, avalanches, landslides and floods. The changes in snow cover in the Himalayas may bring significant hydrophysical and livelihood changes in the downstream area including the Mekong Delta. Therefore, the countries sharing the Himalayan region should focus on adapting the severe impacts of snow cover changes. The image compositing approach presented in the research demonstrated promising performance for the detection and visualization of other land cover changes as well.

关键词： Land Cover Water Cover Composite Urban Cover Composite Snow Cover Composite Biophysical Image Composite Forest Cover Composite Himalayas MODIS Change Detection

Estimation of Tropical Forest Structural Characteristics Using ALOS-2 SAR Data

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Advances in Remote Sensing 2016年第2期5卷 131-144页

作者： luong Viet nguyen Ryutaro Tateishi Hoan Thanh nguyen Ram C. Sharma Tu Trong To Son Mai Le Center for Environmental Remote Sensing Chiba University Chiba Japan Space Technology Institute Vietnam Academy of Science and Technology Hanoi Vietnam Institute of Geography Vietnam Academy of Science and Technology Hanoi Vietnam

The potential of ALOS-2 SAR data for the estimation of tropical forest structural characteristics was assessed in Vietnam by collecting forest inventory data. The effect of polarization and seasonality of the SAR data on the estimation of forest biomass was analyzed. The combination of HH, HV, and HH/HV polarizations using multiple linear regression did not improve the estimation of biomass compared to using the HV channel independently, as the HH and HH/HV variables were not statistically significant. The dry season HV backscattering intensity was highly sensitive to the biomass compared to the rainy season backscattering intensity. The SAR data acquired in the rainy season with humid and wet canopies was not very sensitive to the biomass. The strong dependence of the biomass estimates with the season of SAR data acquisition confirmed that the choice of right season SAR data is very important for improving the satellite based estimates of the biomass. The validation results showed that the dry season HV polarization could explain 54% variation of the biomass.

关键词： Forest Structure Forest Biomass SAR ALOS-2 Backscattering Intensity Sensitivity Analysis

NORMAL FAMILY OF MEROMORPHIC FUNCTIONS SHARING HOLOMORPHIC FUNCTIONS AND THE CONVERSE OF THE BLOCH PRINCIPLE

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Acta Mathematica Scientia 2017年第3期37卷 623-656页

作者： nguyen Van thiN Department of Mathematics Thai Nguyen University of EducationLuong Ngoc Quyen StreetThai Nguyen cityThai NguyenViet Nam

In 1996, C. C. Yang and P. C. Hu [8] showed that： Let f be a transcendental meromorphic function on the complex plane, and a ≠ 0 be a complex number; then assume that n 〉 2, n1,… , nk are nonnegative integers such that n1＋… ＋ nk ≥1; thus fn（f′）n1…（f（k））nk-a has infinitely zeros. The aim of this article is to study the value distribution of differential polynomial, which is an extension of the result of Yang and Hu for small function and all zeros of f having multiplicity at least k ≥2. Namely, we prove that fn（f′）n1…（f（k））nk-a（z） has infinitely zeros, where f is a transcendental meromorphic function on the complex plane whose all zeros have multiplicity at least k≥ 2, and a（z） 0 is a small function of f and n ≥ 2, n1,… ,nk are nonnegative integers satisfying n1＋ …＋ nk ≥1. Using it, we establish some normality criterias for a family of meromorphic functions under a condition where differential polynomials generated by the members of the family share a holomorphic function with zero points. The results of this article are supplement of some problems studied by d. Yunbo and G. Zongsheng [6], and extension of some problems studied X. Wu and Y. Xu [10]. The main result of this article also leads to a counterexample to the converse of Bloeh＇s principle.

关键词： Normal family Nevanlinna theory meromorphic function sharing function differential pOlynomial

Novel Active Contour Model for Image Segmentation Based on Local Fuzzy Gaussian Distribution Fitting

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Journal of Electronic Science and Technology 2012年第2期10卷 113-118页

作者： Quang Tung thieu Marie luong Jean-Marie Rocchisani nguyen Linh-Trung Emmanuel Viennet the L2TI laboratory Université Paris 13 Sorbonne Paris CitéF-93430 Villetaneuse France the Avicenne University Hospital the Faculty of Electronics and Telecommunications University of Engineering and Technology Vietnam National University

A novel active contour model is proposed, which incorporates local information distributions in a fuzzy energy function to effectively deal with the intensity inhomogeneity. Moreover, the proposed model is convex with respect to the variable which is used for extracting the contour. this makes the model independent on the initial condition and suitable for an automatic segmentation. Furthermore, the energy function is minimized in a computationally efficient way by calculating the fuzzy energy alterations directly. Experiments are carried out to prove the performance of the proposed model over some existing methods. The obtained results confirm the efficiency of the method.

关键词： Active contour energy minimization fuzzy energy function local information medical image segmentation.