Pub Date : 2019-04-13DOI: 10.32508/STDJ.V20IK8.1668
H. Thuan, N. Huấn, Võ Thị Thương, Nguyen T. H. Nhi, Tran Ky Anh, Nguyễn Hữu Lương
The compatibility/incompatibility of crude oils will affect the asphaltene precipitation and finally for sludge deposition if such oils are storaged or blending together. Normally, the refineries process a mixture of several crude oils owing to economic, technical and political aspects. In this study, four crude oils were characterized and investigated in order to determine physical-chemical properties and insolubility number (IN) and blending solubility number (SBN). The result revealed that two pair of crude oils are fully compatible and the remaining are partly compatible. The volume limitation of each crude oil in the mixture is proposed. In addition, the relationship between the compatibility and physico-chemical properties of crude oils is discussed. In fact, the crude oil which possessed high wax content and low resins to asphaltenes ratio possesses low stability. This finding might provide a new and valuable strategy for solving the foulings in crude oil tanks and processing units in refineries.
{"title":"Investigation of crude oils compatibility and relationship with their properties","authors":"H. Thuan, N. Huấn, Võ Thị Thương, Nguyen T. H. Nhi, Tran Ky Anh, Nguyễn Hữu Lương","doi":"10.32508/STDJ.V20IK8.1668","DOIUrl":"https://doi.org/10.32508/STDJ.V20IK8.1668","url":null,"abstract":"The compatibility/incompatibility of crude oils will affect the asphaltene precipitation and finally for sludge deposition if such oils are storaged or blending together. Normally, the refineries process a mixture of several crude oils owing to economic, technical and political aspects. In this study, four crude oils were characterized and investigated in order to determine physical-chemical properties and insolubility number (IN) and blending solubility number (SBN). The result revealed that two pair of crude oils are fully compatible and the remaining are partly compatible. The volume limitation of each crude oil in the mixture is proposed. In addition, the relationship between the compatibility and physico-chemical properties of crude oils is discussed. In fact, the crude oil which possessed high wax content and low resins to asphaltenes ratio possesses low stability. This finding might provide a new and valuable strategy for solving the foulings in crude oil tanks and processing units in refineries. \u0000 ","PeriodicalId":285953,"journal":{"name":"Science and Technology Development Journal","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130321113","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-04-13DOI: 10.32508/STDJ.V20IK8.1664
D. Le, V. N. Dieu, Ngo Quoc Hung
This paper presents an application of improved particle sawrm optimization (IPSO) algorithm for solving the optimal reactive power dispatch (ORPD) problem in power systems and a case study for a practical 110kV power system of Shoutern Vietnam. The IPSO is an improvement of PSO with an integration of pseudo- gradient to enhance the search ability of PSO for application to large-scale systems. The proposed IPSO has been tested on the IEEE 30 bus system and the obtained results have indicated that the proposed method is enffective for the ORPD problem via result comparations with other methods. From the obtained results, the IPSO method has been also implemented to the ORPD problem for the 110 kV Southern Vietnam power system and the the obtained result is verified by the PSS/E program. The obtained results have indicated that the IPSO method is very effective for solving the large-scale practical systems.
{"title":"Application of improved PSO algorithm to optimal reactive power dispatch and implementation to the 110 kV Southern Vietnam power system","authors":"D. Le, V. N. Dieu, Ngo Quoc Hung","doi":"10.32508/STDJ.V20IK8.1664","DOIUrl":"https://doi.org/10.32508/STDJ.V20IK8.1664","url":null,"abstract":"This paper presents an application of improved particle sawrm optimization (IPSO) algorithm for solving the optimal reactive power dispatch (ORPD) problem in power systems and a case study for a practical 110kV power system of Shoutern Vietnam. The IPSO is an improvement of PSO with an integration of pseudo- gradient to enhance the search ability of PSO for application to large-scale systems. The proposed IPSO has been tested on the IEEE 30 bus system and the obtained results have indicated that the proposed method is enffective for the ORPD problem via result comparations with other methods. From the obtained results, the IPSO method has been also implemented to the ORPD problem for the 110 kV Southern Vietnam power system and the the obtained result is verified by the PSS/E program. The obtained results have indicated that the IPSO method is very effective for solving the large-scale practical systems.","PeriodicalId":285953,"journal":{"name":"Science and Technology Development Journal","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114563136","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-04-13DOI: 10.32508/STDJ.V20IK8.1667
P. T. Huyen, Pham Huu Loc
The bacterium Staphylococcus aureus is able to cause many diseases that are risky to human life. At present, the resistance of S. aureus to multiple antibiotics is a very difficult problem for healthcare industry in Vietnam and some other countries in the world. Streptomyces flaveus, an actinomycete isolated previously from the adjacent area of Ho Chi Minh City, is able to produce antibiotics against the methicillin-resistant S. aureus (MRSA). In this paper, we present the results of the investigation on effects of the initial concentrations of different ingredients in the stach – casein medium on fermentation by S. flaveus for production of antibiotics against the MRSA. While increasing the starch concentration, antibiotics produced were increased. Meanwhile, high concentrations of casein inhibited the actinomycete to produce antibiotics. For KNO3 and NaCl, both were neccesary for the antibiotic production. Though the increase in KNO3 concentration did not change the production of antibiotics against MRSA, the increase in NaCl concentration reduced the antibiotic production.
{"title":"Study on effects of the initial concentrations of ingredients in the starch – casein medium on production of antibiotics against the methicillin-resistant Staphylococcus aureus by Streptomyces flaveus","authors":"P. T. Huyen, Pham Huu Loc","doi":"10.32508/STDJ.V20IK8.1667","DOIUrl":"https://doi.org/10.32508/STDJ.V20IK8.1667","url":null,"abstract":"The bacterium Staphylococcus aureus is able to cause many diseases that are risky to human life. At present, the resistance of S. aureus to multiple antibiotics is a very difficult problem for healthcare industry in Vietnam and some other countries in the world. Streptomyces flaveus, an actinomycete isolated previously from the adjacent area of Ho Chi Minh City, is able to produce antibiotics against the methicillin-resistant S. aureus (MRSA). In this paper, we present the results of the investigation on effects of the initial concentrations of different ingredients in the stach – casein medium on fermentation by S. flaveus for production of antibiotics against the MRSA. While increasing the starch concentration, antibiotics produced were increased. Meanwhile, high concentrations of casein inhibited the actinomycete to produce antibiotics. For KNO3 and NaCl, both were neccesary for the antibiotic production. Though the increase in KNO3 concentration did not change the production of antibiotics against MRSA, the increase in NaCl concentration reduced the antibiotic production. \u0000 ","PeriodicalId":285953,"journal":{"name":"Science and Technology Development Journal","volume":"213 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121328260","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Orthotropic composite material is the particular type of anisotropic materials and their products have been extensively used in a wide range of engineering applications. Study on mechanical behaviors of such materials under working conditions is very essential. In this study, an extended meshfree moving Kriging interpolation method (namely as X- MK) is presented for crack analyzing in 2D orthotropic materials models. The Gaussian function is used for constructing the moving Kriging shape functions. Typical advantages of the MK shape function are the high-order continuity and the satisfaction of the Kronecker’s delta property. To calculate the stress intensity factors (SIFs), interaction integral method is used with orthotropic auxiliary fields. Several numerical tests including static SIFs calculating and crack propagation predicting are performed to verify the accuracy of the present approach. The obtained results are compared with available refered results and they have shown a very good performance of the present method.
{"title":"Extended meshless moving Kriging method for crack propagation analyzing in orthotropic media","authors":"Nguyen Thanh Nha, Nguyen Ngoc Minh, Bui Quoc Tinh, Truong Tich Thien","doi":"10.32508/STDJ.V20IK8.1666","DOIUrl":"https://doi.org/10.32508/STDJ.V20IK8.1666","url":null,"abstract":"Orthotropic composite material is the particular type of anisotropic materials and their products have been extensively used in a wide range of engineering applications. Study on mechanical behaviors of such materials under working conditions is very essential. In this study, an extended meshfree moving Kriging interpolation method (namely as X- MK) is presented for crack analyzing in 2D orthotropic materials models. The Gaussian function is used for constructing the moving Kriging shape functions. Typical advantages of the MK shape function are the high-order continuity and the satisfaction of the Kronecker’s delta property. To calculate the stress intensity factors (SIFs), interaction integral method is used with orthotropic auxiliary fields. Several numerical tests including static SIFs calculating and crack propagation predicting are performed to verify the accuracy of the present approach. The obtained results are compared with available refered results and they have shown a very good performance of the present method.","PeriodicalId":285953,"journal":{"name":"Science and Technology Development Journal","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121873388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-04-10DOI: 10.32508/STDJ.V22I1.1216
C. Nguyen, X. Tran, K. Nguyen, H. Tran, Tan Thanh Mai
To date, most of the oil and gas production in Cuu Long Basin (CLB) is contributed from structural traps, making them more and more depleted after years of exploitation. Exploration activities in CLB, therefore, are shifting towards other traps, including stratigraphic and/or combination ones. The results of exploration and appraisal activities in recent years have increasingly discovered more hydrocarbons in the Oligocene section; some of them were discovered in combination/ stratigraphic traps. Many studies on Oligocene targets in Southeast CLB have been carried out but only a few mention nonstructural traps. This leads to uncertainty about the forming mechanisms and distribution, as well as unevaluated hydrocarbon potential of these traps. An integrated approach- utilizing methods of seismic sequence stratigraphy, seismic attribute interpretation, and petrophysical/ petrographical analysis- was applied in this research to identify the forming mechanisms of Oligocene combination/ stratigraphic traps in southeast area of CLB and to evaluate their reservoir quality. The research results show that the key forming factor for stratigraphic traps of sand body is lithology change and the one for pinch-out stratigraphic traps is tapering off of sand layers landward or toward the horsts. The reservoir quality of these traps ranges from moderate to good. By integratedly applying the methods, the forming mechanisms and reservoir quality of Oligocene stratigraphic traps could be delineated. In order to optimize the next-stage exploration strategy in CLB, detailed studies on petroleum system, especially top and bottom seals, and the hydrocarbon potential of these stratigraphic traps, need to be carried out.
{"title":"The forming mechanisms of Oligocene combination/stratigraphic traps and their reservoir quality in southeast Cuu Long Basin offshore of Vietnam","authors":"C. Nguyen, X. Tran, K. Nguyen, H. Tran, Tan Thanh Mai","doi":"10.32508/STDJ.V22I1.1216","DOIUrl":"https://doi.org/10.32508/STDJ.V22I1.1216","url":null,"abstract":"To date, most of the oil and gas production in Cuu Long Basin (CLB) is contributed from structural traps, making them more and more depleted after years of exploitation. Exploration activities in CLB, therefore, are shifting towards other traps, including stratigraphic and/or combination ones. The results of exploration and appraisal activities in recent years have increasingly discovered more hydrocarbons in the Oligocene section; some of them were discovered in combination/ stratigraphic traps. Many studies on Oligocene targets in Southeast CLB have been carried out but only a few mention nonstructural traps. This leads to uncertainty about the forming mechanisms and distribution, as well as unevaluated hydrocarbon potential of these traps. An integrated approach- utilizing methods of seismic sequence stratigraphy, seismic attribute interpretation, and petrophysical/ petrographical analysis- was applied in this research to identify the forming mechanisms of Oligocene combination/ stratigraphic traps in southeast area of CLB and to evaluate their reservoir quality. The research results show that the key forming factor for stratigraphic traps of sand body is lithology change and the one for pinch-out stratigraphic traps is tapering off of sand layers landward or toward the horsts. The reservoir quality of these traps ranges from moderate to good. By integratedly applying the methods, the forming mechanisms and reservoir quality of Oligocene stratigraphic traps could be delineated. In order to optimize the next-stage exploration strategy in CLB, detailed studies on petroleum system, especially top and bottom seals, and the hydrocarbon potential of these stratigraphic traps, need to be carried out. \u0000 ","PeriodicalId":285953,"journal":{"name":"Science and Technology Development Journal","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124744336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-04-02DOI: 10.32508/STDJ.V22I1.1053
T. Hung
The chi-square distribution with degrees of freedom has an important role in probability, statistics and various applied fields as a special probability distribution. This paper concerns the relations between geometric random sums and chi-square type distributions whose degrees of freedom are geometric random variables. Some characterizations of chi-square type random variables with geometric degrees of freedom are calculated. Moreover, several weak limit theorems for the sequences of chi-square type random variables with geometric random degrees of freedom are established via asymptotic behaviors of normalized geometric random sums.
{"title":"On chi-square type distributions with geometric degrees of freedom in relation to geometric sums","authors":"T. Hung","doi":"10.32508/STDJ.V22I1.1053","DOIUrl":"https://doi.org/10.32508/STDJ.V22I1.1053","url":null,"abstract":"The chi-square distribution with degrees of freedom has an important role in probability, statistics and various applied fields as a special probability distribution. This paper concerns the relations between geometric random sums and chi-square type distributions whose degrees of freedom are geometric random variables. Some characterizations of chi-square type random variables with geometric degrees of freedom are calculated. Moreover, several weak limit theorems for the sequences of chi-square type random variables with geometric random degrees of freedom are established via asymptotic behaviors of normalized geometric random sums.","PeriodicalId":285953,"journal":{"name":"Science and Technology Development Journal","volume":"81 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130224355","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Thanh Dinh Duc, A. Nguyen, T. Nguyen, Hang Thi La, P. Le
Introduction: LiFePO4/C composites were synthesized via physical mixing assisted solvothermal process. Different kinds of carbon materials were investigated including 0D (carbon Ketjen black), 1D (carbon nanotubes) and 2D (graphene) materials. X-rays diffraction patterns of carbon coated LiFePO4 synthesized by solvothermal was indexed to pure crystalline phase without the emergence of second phase. LiFePO4 platelets and rods were in range size of 80-200 nm and dispersed well in carbon matrix. The lithium ion diffusion kinetics was evaluated through the calculated diffusion coefficients to explore the impact of carbon mixing. Methods: In this work, we studied the structure, morphologies and the lithium ion diffusion kinetic of LiFePO4/C composites for Li-ion batteries. Different characterization methods were used including powder X-rays (for crystalline structure); Transmission Electron Microscopy (for particle and morphologies observation) and Cyclic voltammetry (for electrochemical kinetic study). Results: The study indicated LiFePO4/C composites were successfully obtained by mixing process and the electrochemical performance throughout the calculated diffusion coefficient was significantly improved by adding the carbon types. Conclusion: The excellent ion diffusion was obtained for composites LiFePO4/Ketjen black (KB) and LiFePO4/CNT compared to LiFePO4/Graphene. KB could be a potential candidate for large-scale production due to low-cost, stable and high electrochemical performance.
介绍:采用物理混合辅助溶剂热法合成LiFePO4/C复合材料。研究了不同种类的碳材料，包括0D(碳Ketjen黑)，1D(碳纳米管)和2D(石墨烯)材料。溶剂热法合成的碳包覆LiFePO4的x射线衍射图显示为纯晶相，未出现第二相。片状和棒状LiFePO4粒径在80 ~ 200 nm之间，在碳基体中分散良好。通过计算的扩散系数评价锂离子的扩散动力学，探讨碳混合的影响。方法:研究了锂离子电池用LiFePO4/C复合材料的结构、形貌和锂离子扩散动力学。使用了不同的表征方法，包括粉末x射线(用于晶体结构);透射电镜(用于颗粒和形态观察)和循环伏安法(用于电化学动力学研究)。结果:LiFePO4/C复合材料通过混合工艺制备成功，在计算的扩散系数范围内，添加碳的种类显著提高了LiFePO4/C复合材料的电化学性能。结论:与LiFePO4/石墨烯相比，LiFePO4/Ketjen black (KB)和LiFePO4/CNT复合材料具有优异的离子扩散性能。KB具有低成本、稳定、电化学性能高等优点，具有大规模生产的潜力。
{"title":"The impact of carbon additives on lithium ion diffusion kinetic of LiFePO4/C composites","authors":"Thanh Dinh Duc, A. Nguyen, T. Nguyen, Hang Thi La, P. Le","doi":"10.32508/STDJ.V22I1.462","DOIUrl":"https://doi.org/10.32508/STDJ.V22I1.462","url":null,"abstract":"Introduction: LiFePO4/C composites were synthesized via physical mixing assisted solvothermal process. Different kinds of carbon materials were investigated including 0D (carbon Ketjen black), 1D (carbon nanotubes) and 2D (graphene) materials. X-rays diffraction patterns of carbon coated LiFePO4 synthesized by solvothermal was indexed to pure crystalline phase without the emergence of second phase. LiFePO4 platelets and rods were in range size of 80-200 nm and dispersed well in carbon matrix. The lithium ion diffusion kinetics was evaluated through the calculated diffusion coefficients to explore the impact of carbon mixing. \u0000Methods: In this work, we studied the structure, morphologies and the lithium ion diffusion kinetic of LiFePO4/C composites for Li-ion batteries. Different characterization methods were used including powder X-rays (for crystalline structure); Transmission Electron Microscopy (for particle and morphologies observation) and Cyclic voltammetry (for electrochemical kinetic study). \u0000Results: The study indicated LiFePO4/C composites were successfully obtained by mixing process and the electrochemical performance throughout the calculated diffusion coefficient was significantly improved by adding the carbon types. \u0000Conclusion: The excellent ion diffusion was obtained for composites LiFePO4/Ketjen black (KB) and LiFePO4/CNT compared to LiFePO4/Graphene. KB could be a potential candidate for large-scale production due to low-cost, stable and high electrochemical performance. \u0000 ","PeriodicalId":285953,"journal":{"name":"Science and Technology Development Journal","volume":"139 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115191650","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-03-31DOI: 10.32508/STDJ.V22I1.1219
D. Nguyen, L. Do, Huynh Thi Ngoc Tuyet, M. Ho, Hai D. T. Nguyen, J. Mortier, P. K. Nguyen
Introduction: Dendriscosticta is a new genus belong the Sticta wrightii group of the family Lobariaceae. This genus of foliose lichen is widely distributed in tropical regions worldwide. The lichen Dendriscosticta platyphylloides is very abundant in Bidoup forest, Lam Dong province, Vietnam. Methods: The structure of these compounds was elucidated through the interpretation of their 1D and 2D-NMR and HR-MS data. The cytotoxic activities of these compounds against liver hepatocellular carcinoma (HepG2), human lung cancer (NCI-H460), human epithelial carcinoma (HeLa) and human breast cancer (MCF-7) cell lines was performed at the concentration of 100 mg/mL using the sulforhodamine B (SRB) assay. Results: In this paper, we reported the isolation of six known compounds, including (1) 15a-acetoxyhopan-22-ol (2) hopane-15a,22-diol, (3) zeorin, (4) cerevisterol, (5) salvigenin, and (6) 5-hydroxy-3',4',7-trimethoxyflavone. Conclusion: This is the first time that these compounds are isolated from Dendriscosticta genus. These compounds showed no cytotoxic activity against four cell lines.
{"title":"Chemical constituents of the lichen Dendriscosticta platyphylloides, Lobariaceae","authors":"D. Nguyen, L. Do, Huynh Thi Ngoc Tuyet, M. Ho, Hai D. T. Nguyen, J. Mortier, P. K. Nguyen","doi":"10.32508/STDJ.V22I1.1219","DOIUrl":"https://doi.org/10.32508/STDJ.V22I1.1219","url":null,"abstract":"Introduction: Dendriscosticta is a new genus belong the Sticta wrightii group of the family Lobariaceae. This genus of foliose lichen is widely distributed in tropical regions worldwide. The lichen Dendriscosticta platyphylloides is very abundant in Bidoup forest, Lam Dong province, Vietnam. \u0000Methods: The structure of these compounds was elucidated through the interpretation of their 1D and 2D-NMR and HR-MS data. The cytotoxic activities of these compounds against liver hepatocellular carcinoma (HepG2), human lung cancer (NCI-H460), human epithelial carcinoma (HeLa) and human breast cancer (MCF-7) cell lines was performed at the concentration of 100 mg/mL using the sulforhodamine B (SRB) assay. \u0000Results: In this paper, we reported the isolation of six known compounds, including (1) 15a-acetoxyhopan-22-ol (2) hopane-15a,22-diol, (3) zeorin, (4) cerevisterol, (5) salvigenin, and (6) 5-hydroxy-3',4',7-trimethoxyflavone. \u0000Conclusion: This is the first time that these compounds are isolated from Dendriscosticta genus. These compounds showed no cytotoxic activity against four cell lines. \u0000 ","PeriodicalId":285953,"journal":{"name":"Science and Technology Development Journal","volume":"73 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125852364","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-03-29DOI: 10.32508/STDJ.V22I1.1222
Nguyen Minh Dien, D. D. Trong
The aim of this paper is of studying the stability of solution of a backward problem of a timefractional diffusion equation with perturbed order. We investigate the well-posedness of the backward problem with perturbed order for t>0. The results on the unique existence and continuity with respect to the fractional order, the source term as well as the final value of the solution are given. At t=0 the backward problem is ill-posed and we introduce a truncated method to regularize the backward problem with respect to inexact fractional order. Some error estimates are provided in Holder type.
{"title":"Stability of solution of a backward problem of a time-fractional diffusion equation with perturbed order","authors":"Nguyen Minh Dien, D. D. Trong","doi":"10.32508/STDJ.V22I1.1222","DOIUrl":"https://doi.org/10.32508/STDJ.V22I1.1222","url":null,"abstract":"The aim of this paper is of studying the stability of solution of a backward problem of a timefractional diffusion equation with perturbed order. We investigate the well-posedness of the backward problem with perturbed order for t>0. The results on the unique existence and continuity with respect to the fractional order, the source term as well as the final value of the solution are given. At t=0 the backward problem is ill-posed and we introduce a truncated method to regularize the backward problem with respect to inexact fractional order. Some error estimates are provided in Holder type. \u0000 ","PeriodicalId":285953,"journal":{"name":"Science and Technology Development Journal","volume":"83 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114604283","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-03-29DOI: 10.32508/STDJ.V22I1.1049
T. Hung, P. Kien
The geometric sums have been arisen from the necessity to resolve practical problems in ruin prob- ability, risk processes, queueing theory and reliability models, etc. Up to the present, the results related to geometric sums like asymptotic distributions and rates of convergence have been investigated by many mathematicians. However, in a lot of various situations, the results concerned domains of geometric attraction are still limitative. The main purpose of this article is to introduce concepts on the domain of geometric attraction of standard Laplace distribution. Using method of characteristic functions, the necessary and sufficient conditions for a probability distribution belongs to the domain of geometric attraction of standard Laplace distribution are shown. In special case, obtained result is a weak limit theorem for geometric sums of independent and identically distributed random variables which has been well-known as the second central limit theorem. Furthermore, based on the obtained results of this paper, the analogous results for the domains of geometric attraction of exponential distribution and Linnik distribution can be established. More generally, we may extend results to the domain of geometric attraction of geometrically strictly stable distributions.
{"title":"The necessary and sufficient conditions for a probability distribution belongs to the domain of geometric attraction of standard Laplace distribution","authors":"T. Hung, P. Kien","doi":"10.32508/STDJ.V22I1.1049","DOIUrl":"https://doi.org/10.32508/STDJ.V22I1.1049","url":null,"abstract":"The geometric sums have been arisen from the necessity to resolve practical problems in ruin prob- ability, risk processes, queueing theory and reliability models, etc. Up to the present, the results related to geometric sums like asymptotic distributions and rates of convergence have been investigated by many mathematicians. However, in a lot of various situations, the results concerned domains of geometric attraction are still limitative. The main purpose of this article is to introduce concepts on the domain of geometric attraction of standard Laplace distribution. Using method of characteristic functions, the necessary and sufficient conditions for a probability distribution belongs to the domain of geometric attraction of standard Laplace distribution are shown. In special case, obtained result is a weak limit theorem for geometric sums of independent and identically distributed random variables which has been well-known as the second central limit theorem. Furthermore, based on the obtained results of this paper, the analogous results for the domains of geometric attraction of exponential distribution and Linnik distribution can be established. More generally, we may extend results to the domain of geometric attraction of geometrically strictly stable distributions. \u0000 \u0000 \u0000 ","PeriodicalId":285953,"journal":{"name":"Science and Technology Development Journal","volume":"101 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127164897","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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