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Search Results: 1 - 10 of 7139 matches for " Nguyen Tien Lam "
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Prediction of shrinkage cracking age of concrete with and without expansive additive
Dung Tien Nguyen,Raktipong Sahamitmongkol,Lam Nguyen Trong,Sontaya Tongaroonsri
Songklanakarin Journal of Science and Technology , 2010,
Abstract: The aim of this research is to propose a model for predicting cracking age of concrete due to restrained shrinkage. Thisstudy focuses on analyzing shrinkage and expansion mechanisms in the expansive concrete to formulate a model that can beemployed to predict whether shrinkage cracking occurs or not. In case of conventional (non-expansive) concrete, this modelcan be applied by neglecting the early expansion due to expansive additive. Parameters considered in this model are restrainedexpansion, free shrinkage, cracking strain that can be experimentally measured by experiment and tensile creep which isderived by back calculation. The model was verified by test results of expansive concrete mixtures as well as normal concretemixtures both with and without fly ash.
Fitting a Probability Distribution to Extreme Precipitation for a Limited Mountain Area in Vietnam  [PDF]
Nguyen Tien Thanh
Journal of Geoscience and Environment Protection (GEP) , 2017, DOI: 10.4236/gep.2017.55007
Abstract: In this paper, an analysis of adapted 20 extreme precipitation indices is calculated for a limited mountain area in southern Vietnam. The daily precipitation data from four stations in the period of more than 30 years are selected. The statistical characteristics of maximum, minimum, mean, standard deviation, skewness, and kurtoris for each index are also analysed. A variety of distributions such as Normal, Lognormal, Beta, Gamma, Exponential, Loglogistic, and Johnson is used to find the best fit probability distribution for this area on the basic of the highest score. The scores are estimated based on the ranking of statistical goodness of fit test. The goodness of fit tests is the Anderson-Darling and Shapiro-Wilks tests. The best fit distribution for each index of extreme precipitation at each station is found out. Results revealed that the Johnson distribution is the best fit distribution to the data of very heavy precipitation days greater than 50 mm. Over a limited mountain area, it is difficult to fit a probability distribution to the precipitation fraction due to extremely wet days, number of extremely wet days, and number of extremely wet days when precipitation greater than 99 percentage. The lognormal, Johnson, and Loglogistic distribution are the best choices to fit most of the extreme precipitation indices over this area.
WHO Antiretroviral Therapy Guidelines 2010 and Impact of Tenofovir on Chronic Kidney Disease in Vietnamese HIV-Infected Patients
Daisuke Mizushima, Junko Tanuma, Fumihide Kanaya, Takeshi Nishijima, Hiroyuki Gatanaga, Nguyen Tien Lam, Nguyen Thi Hoai Dung, Nguyen Van Kinh, Yoshimi Kikuchi, Shinichi Oka
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0079885
Abstract: Objective The 2010 WHO antiretroviral therapy (ART) guidelines have resulted in increased tenofovir use. Little is known about tenofovir-induced chronic kidney disease (CKD) in HIV-infected Vietnamese with mean body weight of 55 kg. We evaluated the prevalence and risk factors of CKD in this country. Design Cross-sectional study was performed. Methods Clinical data on HIV-infected Vietnamese cohort were collected twice a year. To evaluate the prevalence of CKD, serum creatinine was measured in 771 patients in October 2011 and April 2012. CKD was defined as creatinine clearance less than 60 ml/min at both time points. Multivariate logistic regression was used to determine the factors associated with CKD Results Tenofovir use increased in Vietnam from 11.9% in April 2011 to 40.3% in April 2012. CKD was diagnosed in 7.3%, of which 7% was considered moderate and 0.3% was severe. Multivariate analysis of October-2011 data identified age per year-increase (OR: 1.229, 95%CI, 1.170-1.291), body weight per 1 kg-decrement (1.286, 1.193-1.386), and tenofovir use (2.715, 1.028-7.168) as risk factors for CKD. Conclusions Older age, low body weight and tenofovir use were independent risk factors for CKD in Vietnam. Further longitudinal study is required to evaluate the impact of TDF on renal function in Vietnam and other countries with small-body weight patients.
Assessment of Microalbuminuria for Early Diagnosis and Risk Prediction in Dengue Infections
Nguyen Thi Hanh Tien, Phung Khanh Lam, Huynh Thi Le Duyen, Tran Van Ngoc, Phan Thi Thanh Ha, Nguyen Tan Thanh Kieu, Cameron Simmons, Marcel Wolbers, Bridget Wills
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0054538
Abstract: Background Dengue is the most important arboviral infection of humans. Following an initial febrile period, a small proportion of infected patients develop a vasculopathy, with children at particular risk for severe vascular leakage and shock. Differentiation between dengue and other common childhood illnesses is difficult during the early febrile phase, and risk prediction for development of shock is poor. The presence of microalbuminuria is recognized as a useful early predictor for subsequent complications in a number of other disorders with vascular involvement. Significant proteinuria occurs in association with dengue shock syndrome and it is possible that early-phase microalbuminuria may be helpful both for diagnosis of dengue and for identification of patients likely to develop severe disease. Methodology/Principal Findings We measured formal urine albumin to creatinine ratios (UACRs) in daily samples obtained from a large cohort of children with suspected dengue recruited at two outpatient clinics in Ho Chi Minh City, Vietnam. Although UACRs were increased in the 465 confirmed dengue patients, with a significant time trend showing peak values around the critical period for dengue-associated plasma leakage, urine albumin excretion was also increased in the comparison group of 391 patients with other febrile illnesses (OFI). The dengue patients generally had higher UACRs than the OFI patients, but microalbuminuria, using the conventional cutoff of 30 mg albumin/g creatinine discriminated poorly between the two diagnostic groups in the early febrile phase. Secondly UACRs did not prove useful in predicting either development of warning signs for severe dengue or need for hospitalization. Conclusion/Significance Low-level albuminuria is common, even in relatively mild dengue infections, but is also present in many OFIs. Simple point-of-care UACR tests are unlikely to be useful for early diagnosis or risk prediction in dengue endemic areas.
Geographic Object-Based Image Analysis of Changes in Land Cover in the Coastal Zones of the Red River Delta (Vietnam)  [PDF]
Simona Niculescu, Chi Nguyen Lam
Journal of Environmental Protection (JEP) , 2019, DOI: 10.4236/jep.2019.103024
Abstract: The majority of the population and economic activity of the northern half of Vietnam is clustered in the Red River Delta and about half of the country’s rice production takes place here. There are significant problems associated with its geographical position and the intensive exploitation of resources by an overabundant population (population density of 962 inhabitants/km2). Some thirty years after the economic liberalization and the opening of the country to international markets, agricultural land use patterns in the Red River Delta, particularly in the coastal area, have undergone many changes. Remote sensing is a particularly powerful tool in processing and providing spatial information for monitoring land use changes. The main methodological objective is to find a solution to process the many heterogeneous coastal land use parameters, so as to describe it in all its complexity, specifically by making use of the latest European satellite data (Sentinel-2). This complexity is due to local variations in ecological conditions, but also to anthropogenic factors that directly and indirectly influence land use dynamics. The methodological objective was to develop a new Geographic Object-based Image Analysis (GEOBIA) approach for mapping coastal areas using Sentinel-2 data and Landsat 8. By developing a new segmentation, accuracy measure, in this study was determined that segmentation accuracies decrease with increasing segmentation scales and that the negative impact of under-segmentation errors significantly increases at a large scale. An Estimation of Scale Parameter (ESP) tool was then used to determine the optimal segmentation parameter values. A popular machine learning algorithms (Random Forests-RFs) is used. For all classifications algorithm, an increase in overall accuracy was observed with the full synergistic combination of available data sets.
CD19(+) B Cells Confer Protection against Experimental Cerebral Malaria in Semi-Immune Rodent Model
Lam Quoc Bao, Nguyen Tien Huy, Mihoko Kikuchi, Tetsuo Yanagi, Masachika Senba, Mohammed Nasir Shuaibu, Kiri Honma, Katsuyuki Yui, Kenji Hirayama
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0064836
Abstract: In African endemic area, adults are less vulnerable to cerebral malaria than children probably because of acquired partial immunity or semi-immune status. Here, we developed an experimental cerebral malaria (ECM) model for semi-immune mice. C57BL/6 (B6) mice underwent one, two and three cycles of infection and radical treatment (1-cure, 2-cure and 3-cure, respectively) before being finally challenged with 104 Plasmodium berghei ANKA without treatment. Our results showed that 100% of na?ve (0-cure), 67% of 1-cure, 37% of 2-cure and none of 3-cure mice succumbed to ECM within 10 days post challenge infection. In the protected 3-cure mice, significantly higher levels of plasma IL-10 and lower levels of IFN-γ than the others on day 7 post challenge infection were observed. Major increased lymphocyte subset of IL-10 positive cells in 3-cure mice was CD5(?)CD19(+) B cells. Passive transfer of splenic CD19(+) cells from 3-cure mice protected na?ve mice from ECM. Additionally, aged 3-cure mice were also protected from ECM 12 and 20 months after the last challenge infection. In conclusion, mice became completely resistant to ECM after three exposures to malaria. CD19(+) B cells are determinants in protective mechanism of semi-immune mice against ECM possibly via modulatory IL-10 for pathogenic IFN-γ production.
Managing Software Architectural Evolution at Multiple Levels of Abstraction
Tien N. Nguyen
Journal of Software , 2008, DOI: 10.4304/jsw.3.3.60-70
Abstract: Software development is a dynamic process where engineers constantly modify and refine systems. As a consequence, system architecture evolves over time. Software architectural evolution has been managed at different abstraction levels: the meta level, the architectural level, the application level, and the implementation level. However, management supports for architectural evolution are limited to evolution mechanisms in architectural description languages such as subtyping, inheritance, interface, and genericity. This paper presents a model-oriented version and configuration control approach to managing the evolution of architectural entities and relationships among them in configurations at different levels of abstraction. This paper also illustrates our approach in building an architectural configuration management system, MolhadoArch, that is capable of managing configurations and versions of software architecture across multiple levels of abstraction in a uniform and tightly connected manner. In MolhadoArch, consistent configurations are maintained not only among source code but also with the high-level software architecture. MolhadoArch supports the management of both planned and unplanned evolution of software architecture. We have conducted an experimental study to show that MolhadoArch can handle large and real-world systems. By evaluation, we learned that the benefits outweigh the extra space needed to represent architectural entities.
The one-loop QED in Noncommutative space
Nguyen Tien Binh
Physics , 2003,
Abstract: Returning to the old problems in ordinary QED, by an appropriate extension of the dimensional regularization method in noncommutative space we try to provide a quite coherent look into NCQED.The renormalisation of theories, the $\beta$ function,the vacuum polarisation of photon, the general structure of vertex fermion-photon, the anomalous magnetic moment (AMM) of fermions and the validity of Ward identity at the one-loop level are reinvestigated.
Convergence versus integrability in Poincare-Dulac normal form
Nguyen Tien Zung
Physics , 2001,
Abstract: We show that, to find a Poincare-Dulac normalization for a vector field is the same as to find and linearize a torus action which preserves the vector field. Using this toric characterization and other geometrical arguments, we prove that any local analytic vector field which is integrable in the non-Hamiltonian sense admits a local convergent Poincare-Dulac normalization. These results generalize the main results of our previous paper from the Hamiltonian case to the non-Hamiltonian case. Similar results are presented for the case of isochore vector fields.
Symplectic topology of integrable Hamiltonian systems, I: Arnold-Liouville with singularities
Nguyen Tien Zung
Physics , 2001,
Abstract: The classical Arnold-Liouville theorem describes the geometry of an integrable Hamiltonian system near a regular level set of the moment map. Our results describe it near a nondegenerate singular level set: a tubular neighborhood of a connected singular nondegenerate level set, after a normal finite covering, admits a non-complete system of action-angle functions (the number of action functions is equal to the rank of the moment map), and it can be decomposed topologically, together with the associated singular Lagrangian foliation, to a direct product of simplest (codimension 1 and codimension 2) singularities. These results are essential for the global topological study of integrable Hamiltonian systems.
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