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Advances in Chemical Engineering and Science 2022年第1期12卷 40-53页

作者： Sabar Simanungkalit Mingming Zhu gia hung pham Zhezi Zhang Dongke Zhang Centre for Energy (M473) The University of Western Australia Crawley Australia

A series of mesoporous alumina (MA) supported cobalt (Co/MA) catalysts with MA isomorphically substituted by zirconium (Zr) were synthesised and evaluated for their performance in the Fischer-Tropsch synthesis. The Zr/(Zr + Al) atomic ratios varied from 1% - 15%. A zirconium-impregnated Co/MA catalyst prepared by wet impregnation with a Zr/(Zr + Al) atomic ratio of 5% was also evaluated to examine Zr incorporation’s effect method. The catalysts synthesised were characterised using N2 adsorption-desorption, X-ray Powder Diffraction (XRD), Transmission Electron Microscopy (TEM), and X-Ray Photoelectron Spectroscopy (XPS). It was found that Zr4+ ions were incorporated into the framework of MA and kept intact up to a Zr/(Zr + Al) atomic ratio of 5%. The cobalt dispersion and reducibility were improved as the Zr/(Zr + Al) atomic ratio increased to 50%. The performance of these catalysts for Fischer-Tropsch synthesis was evaluated using a fixed bed reactor at temperature and pressure of 493 K and 20 bar, respectively. The feed syngas had an H2/CO ratio of 2, diluted with 10% Ar. For isomorphically Zr-substituted Co/MA, the CO conversion and selectivity of diesel (C10 - C20) increased

关键词： Cobalt Catalyst Fischer-Tropsch Synthesis Isomorphic Substitution Mesoporous Alumina Zirconium

Assessment of soil quality indicators under different agricultural land uses and topographic aspects in Central Vietnam

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International Soil and Water Conservation Research 2018年第4期6卷 280-288页

作者： Tung gia pham hung Trong Nguyen Martin Kappas Cartography GIS and Remote Sensing DepartmentGottingen UniversityGeorge August University of GoettingenGoldschmidstr.537077 GoettingenGermany University of Agriculture and Forestry Hue UniversityVietnam Ministry of Natural Resources and Environment Vietnam

Soil quality assessment is valuable for agricultural production. In this research, 155 soil samples at two soil depths were collected from four land use types in an agricultural area of the A Luoi district in the Central Vietnam. Differences of soil organic carbon, total nitrogen in soil and soil pH under different land use types and topographic aspects were compared. Soil organic carbon contents in arable land and plantation forest are higher than those in natural forest and grassland (p < 0.05). Conversely, the total nitrogen in natural forest was significantly lesser in comparison to other land use types. Meanwhile there were no significant differences of the total nitrogen content (p < 0.05) among arable land, plantation forest, and grassland. The soil of grassland, natural and plantation forests land use types were more significantly acidic than those of the soils of the arable land use type. Soil organic carbon and total nitrogen showed a decreasing trend while soil depth increased in all land use types. The soil pH in plantation forest and arable land use types showed no significant change in relation to soil depth. Significant differences were not found in topographic aspects and soil organic carbon content;however, the different changing trends of soil organic carbon content between land use types and aspects were found. The impact of slope, elevation, farming system or soil texture accounted for the differences in these soil indicators under different land use types in the A Luoi district.

关键词： Central Vietnam Land use type Hilly area Soil quality Topographic aspects

Integrated universal soil loss equation (USLE) and Geographical Information System (GIS) for soil erosion estimation in A Sap basin:Central Vietnam

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International Soil and Water Conservation Research 2018年第2期6卷 99-110页

作者： Tung gia pham Jan Degener Martin Kappas Cartography GIS and Remote Sensing DepartmentGottingen UniversityGermany University of Agriculture and Forestry Hue UniversityVietnam

Central Vietnam is very susceptible to soil erosion due to its complicated terrain and heavy rainfall. The objective of this study was to quantify soil erosion in the A Sap river basin, A Luoi district, Thua Thien Hue Province, Vietnam, using the Universal Soil Loss Equation (USLE) and Geographical Informa-tion System (GIS). The results showed that 34% of land area lost accumulated to 10 t ha-1 year-1 while 47% of the total area lost less than 1 t ha-1 year-1. Natural forest land lost the most with an average of about 19 t ha-1 year-1, followed by plantation forest with approximately 7 t ha-1 year-1 and other agricultural lands at 3.70 and 1.45 t ha-1 year-1 for yearly crops and paddy rice, respectively. Soil erosion was most sensitive to the topographic factor (LS), followed by the practice support factor (P), soil erodibility factor (K), cropping management (C), and the rainfall erosivity factor (R). Implications are that changes to the cultivated calendar and implementing intercropping are effective ways to prevent soil erosion in cultivated lands. Furthermore, introducing broad leaves trees for mountainous areas in A Sap basin was the most effective practice in reducing soil erosion. The study also pointed out that the combination of available data sources used with the USLE and GIS technology is a viable option to cal-culate soil erosion in Central Vietnam, which would allow targeted attention toward a solution is to reduce future soil erosion.

关键词： Central Vietnam GIS Soil erosion USLE

Drought and conflicts at the local level: Establishing a water sharing mechanism for the summer-autumn rice production in Central Vietnam

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International Soil and Water Conservation Research 2019年第4期7卷 362-375页

作者： Chuong Van Huynh Catharien Terwisscha van Scheltinga Ty Huu pham Non Quoc Duong Phuong Thi Tran Linh Hoang Khanh Nguyen Tung gia pham Ngoc Bich Nguyen Jos Timmerman Hue University Viet Nam Climate Change and Adaptive Land and Water Management Group Wageningen Environmental ResearchNetherlands University of Agriculture and Forestry Hue UniversityViet Nam

In recent years,water for agricultural production gradually became a significant challenge in the context of climate change in *** solutions are required,which consider the use of resources for both human needs and ecology,and that account for the equitable distribution and the livelihood of the farmers now and in the *** particular,the farmers in the province of Quang Nam faring water shortage in the cultivation of paddy in the summer-autumn *** arise regarding the sharing of the water between the farmers,the drinking water company and the hydropower *** the context of climate change,the water shortage is expected to increase in the *** article presents the results of participatory action research (PAR) approach to develop a local level mechanism for water sharing,in which stakeholders actively *** sharing mechanism was developed,envisioning a sustainable solution for inclusive water *** mechanism was successfully implemented in two cases,one at commune level (Tho stream) and one at the district level (Mo stream).The participatory approach proved to be successful in setting up a broadly acceptable mechanism that will need to be further incorporated in the institutional set-up.

关键词： Adaptation Agriculture Climate change Governance Rice production Water sharing

Distribution of the Sample Correlation Matrix and Applications

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Open Journal of Statistics 2014年第5期4卷 330-344页

作者： Thu pham-gia Vartan Choulakian Department of Mathematics and Statistics Université de Moncton Moncton Canada

For the case where the multivariate normal population does not have null correlations, we give the exact expression of the distribution of the sample matrix of correlations R, with the sample variances acting as parameters. Also, the distribution of its determinant is established in terms of Meijer G-functions in the null-correlation case. Several numerical examples are given, and applications to the concept of system de- pendence in Reliability Theory are presented.

关键词： Correlation Normal Determinant Meijer G-Function No-Correlation Dependence Component Formatting Style Styling Insert

A Practical Specialization of MDA/MBSE Approach to Develop AUV Controllers

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Journal of Marine Science and Application 2021年第1期20卷 102-116页

作者： Ngo Van Hien pham gia Diem Department of Ship Engineering and Fluid Mechanics School of Transportation EngineeringHanoi University of Science and TechnologyHanoi 10000Vietnam

The model-driven architecture(MDA)/model-based systems engineering(MBSE)approach,in combination with the real-time Unified Modeling Language(UML)/Systems Modeling Language(SysML),unscented Kalman filter(UKF)algorithm,and hybrid automata,are specialized to conveniently analyze,design,and implement controllers of autonomous underwater vehicles(AUVs).The dynamics and control structure of AUVs are adapted and integrated with the specialized features of the MDA/MBSE approach as *** computation-independent model is defined by the specification of a use case model together with the UKF algorithm and hybrid automata and is used in intensive requirement *** platform-independent model(PIM)is then built by specializing the real-time UML/SysML’s features,such as the main control capsules and their dynamic evolutions,which reflect the structures and behaviors of *** detailed PIM is subsequently converted into the platform-specific model by using open-source platforms to quickly implement and deploy AUV *** study ends with a trial trip and deployment results for a planar trajectory-tracking controller of a miniature AUV with a torpedo shape.

关键词： Autonomous underwater vehicles(AUVs) AUV control Model-based mechatronic system design Unscented Kalman filter(UKF) Hybrid automata Real-time UML/SysML MDA/MBSE

Distributions of Ratios: From Random Variables to Random Matrices

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Open Journal of Statistics 2011年第2期1卷 93-104页

作者： Thu pham-gia Noyan Turkkan Dept of Mathematics and Statistics Universite de Moncton Canada

The ratio R of two random quantities is frequently encountered in probability and statistics. But while for unidimensional statistical variables the distribution of R can be computed relatively easily, for symmetric positive definite random matrices, this ratio can take various forms and its distribution, and even its definition, can offer many challenges. However, for the distribution of its determinant, Meijer G-function often provides an effective analytic and computational tool, applicable at any division level, because of its reproductive property.

关键词： Matrix Variate Beta Distribution Generalized-F Distribution Ratios Meijer G-Function Wishart Distribution Ratio

A Study of Factors Affecting the Intention to Use Mobile Payment Services in Vietnam

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Economics World 2016年第6期4卷 249-273页

作者： gia-Shie Liu pham Tan Tai Lunghwa University of Science and Technology Taoyuan City Taiwan

The goal of this paper is to spot out factors affecting the intention to use mobile payment service plan in Vietnam. This study attempts to analyze the impact of various variables extracted from mobility, convenience, compatibility, M-payment knowledge, ease to use, usefulness, risk,, trust, and safe to use on intention to use mobile payment. Quantitative questionnaire is used to measure responses of participants. The statistical analysis method employed in this study is to apply Structural Equation Modeling to test all hypotheses. The results indicate that the strong predictors of the intention to use M-payment are perceived ease of use and perceived usefulness. All respondents show that they do not care about risk when they have intention to use mobile payment services. Convenience of mobility, compatibility, and mobile payment knowledge have impacts on ease to use and usefulness. Among of them, compatibility has the most significant impact o11 ease to use and usefulness in the opinion of those surveyed. Specially, it proved that trust of safe to use has no significant impact on usefulness, but instead has direct impact on intension to use mobile payment services. The outcomes of this research have important connotations for the improvement and development of mobile payment services in Vietnam. Therefore, at the end of this paper, some suggestions based on research results are given for the future development of mobile payment service business in Vietnam.

关键词： convenience of mobility compatibility M-payment knowledge ease to use usefulness trust of safe to use intention to use mobile payment Vietnam

Hypergeometric Functions: From One Scalar Variable to Several Matrix Arguments, in Statistics and Beyond

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Open Journal of Statistics 2016年第5期6卷 951-994页

作者： T. pham-gia Dinh Ngoc Thanh Department of Mathematics and Statistics Université de Moncton Moncton Canada The Applied Multivariate Research Group Université de Moncton Moncton Canada Department of Mathematics and Computer Science University of Science Vietnam National University Ho Chi Minh City Vietnam

Hypergeometric functions have been increasingly present in several disciplines including Statistics, but there is much confusion on their proper uses, as well as on their existence and domain of definition. In this article, we try to clarify several points and give a general overview of the topic, going from the univariate case to the matrix case, in one and then in several arguments. We also survey some results in fields close to Statistics, where hypergeometric functions are actively used, studied and developed.

关键词： Hypergeometric Zonal Polynomial Fractional Calculus Lie Group Cohomology Computation

Inferences on the Difference of Two Proportions: A Bayesian Approach

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Open Journal of Statistics 2017年第1期7卷 1-15页

作者： Thu pham-gia Nguyen Van Thin Phan Phuc Doan Department of Mathematics and Statistics Université de Moncton New Brunswick Canada Faculty of Mathematics and Computer Science Hochiminh University of Science Ho Chi Minh Vietnam

Let π=π1-π2 be the difference of two independent proportions related to two populations. We study the test H0:π≥0 against different alternatives, in the Bayesian context. The various Bayesian approaches use standard beta distributions, and are simple to derive and compute. But the more general test H0:π≥η, with η>0, requires more advanced mathematical tools to carry out the computations. These tools, which include the density of the difference of two general beta variables, are presented in the article, with numerical examples for illustrations to facilitate comprehension of results.

关键词： Proportion Convolution Normal Beta Bayesian Critical Value Appell’s Function