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Search Results: 1 - 10 of 12765 matches for " Nguyen Huy Dan "
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Thermal Behavior and Magnetic Properties of Nd-Fe-B Based Exchange Spring Nanocomposites Nd4-xTbxFe83.5Co5Cu0.5Nb1B6 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1) Melt-Spun Ribbons  [PDF]
Palash Chandra Karmaker, Mohammad Obaidur Rahman, Nguyen Huy Dan, Samia Islam Liba, Per Nordblad, Dilip Kumar Saha, Sheikh Manjura Hoque
Advances in Materials Physics and Chemistry (AMPC) , 2017, DOI: 10.4236/ampc.2017.76018
Abstract: Co-rich Nd-Fe-B nanocomposite ribbons with Tb substituted have been fabricated by single roller melt spinning technique of Nd4-xTbxFe83.5Co5Cu0.5Nb1B6 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1) alloys in an argon (Ar) atmosphere at a circumferential speed of 40 m/s. According to the differential scanning calorimeter (DSC) traces the nanocomposite samples have been annealed at different temperatures like 675°C, 687°C, 700°C, 712°C and 725°C for 10 min. Crystallization behavior was studied by X-ray diffraction in which it was found that the XRD patterns are characterized by broad diffused pattern which demonstrate the amorphous state of materials. The ribbon samples were also characterized by vibration sample magnetometer (VSM) and Mössbauer spectroscopy at as-cast and annealed condition. Co-rich and Tb substitution has significantly enhanced the value of coercivity (Hc) and maximum energy product (BH)max. Highest value of Hc and (BH)max has been obtained as 2.36 kOe and 6.11 MGOe for the sample annealed at 700°C for 10 min with higher concentration of Tb. The M-H hysteresis loops show extremely soft natures which do not possess any area. We have found reduced remanent ratio (Mr/Ms) up to 0.49 at optimal annealing temperature 700°C. However, with the annealing of the samples in the above mentioned temperature, evolution of large coercivity was observed due to the formation of exchange couple hard and soft nanocrystal composites. We have investigated the variation of Curie temperature (Tc) with annealing temperature of the melt spun ribbon samples. Mossbauer spectroscopy was carried out to study the hyperfine parameters such as hyperfine field, hyperfine field distribution for full width half maximum (FWHM) and isomer shift of Fe species of these two phases.
Outcome of Cataract Surgery in Patients Treated for Retinopathy of Prematurity  [PDF]
Huy Nguyen, Kimberly G. Yen
Open Journal of Ophthalmology (OJOph) , 2017, DOI: 10.4236/ojoph.2017.74038
Background/Aims: Pediatric patients with treated retinopathy of prematurity (ROP) may develop visually significant cataracts. We report the outcome of cataract surgery in patients who had ROP treatment. Method: Retrospective chart review of 19 eyes from 16 patients who had ROP treatment and subsequent cataract surgery between August, 2002 and March, 2015. Results: Eighteen of 19 eyes received laser treatment for ROP; 1 eye received intravitreal bevacizumab. 5 eyes received lens-sparing pars plana vitrectomy (LSPPV) in addition to laser. Average follow up was 10.1 ± 5.5 years. Average visual acuity improved from 20/324 prior to and 20/110 after cataract surgery (p = 0.06). 13/19 (68%) of the eyes received laser only and developed cataracts an average of 6.2 ± 5.6 years after laser treatment. 5/19 (26%) eyes developed cataracts an average of 6.4 ± 4.2 years after LSPPV and laser. In one eye, a cataract developed after a bevacizumab injection 2.9 years after the injection. Visual axis opacification (VAO) developed in 2/5 (40%) eyes after Ce/PCIOL/PPC-Antvx, 8/10 eyes (80%) after CE/IOL, and in 0/4 eyes after CE/PPC-AntVx. Ocular comorbidities included strabismus, nystagmus, amblyopia, optic atrophy, corneal band keratopathy, and phthisis bulbi. Conclusion: Cataract surgery in patients who have a history of ROP can be complicated by anatomical changes from prematurity and prior vitreoretinal surgeries. Vision improvement is limited by other ocular comorbidities.
Modeling and Adaptive Self-Tuning MVC Control of PAM Manipulator Using Online Observer Optimized with Modified Genetic Algorithm  [PDF]
Ho Pham Huy Anh, Nguyen Thanh Nam
Engineering (ENG) , 2011, DOI: 10.4236/eng.2011.32016
Abstract: In this paper, the application of modified genetic algorithms (MGA) in the optimization of the ARX Model-based observer of the Pneumatic Artificial Muscle (PAM) manipulator is investigated. The new MGA algorithm is proposed from the genetic algorithm with important additional strategies, and consequently yields a faster convergence and a more accurate search. Firstly, MGA-based identification method is used to identify the parameters of the nonlinear PAM manipulator described by an ARX model in the presence of white noise and this result will be validated by MGA and compared with the simple genetic algorithm (GA) and LMS (Least mean-squares) method. Secondly, the intrinsic features of the hysteresis as well as other nonlinear disturbances existing intuitively in the PAM system are estimated online by a Modified Recursive Least Square (MRLS) method in identification experiment. Finally, a highly efficient self-tuning control algorithm Minimum Variance Control (MVC) is taken for tracking the joint angle position trajectory of this PAM manipulator. Experiment results are included to demonstrate the excellent performance of the MGA algorithm in the NARX model-based MVC control system of the PAM system. These results can be applied to model, identify and control other highly nonlinear systems as well.
Combining Methods of Lyapunov for Exponential Stability of Linear Dynamic Systems on Time Scales  [PDF]
Nguyen Ngoc Huy, Dang Dinh Chau
Applied Mathematics (AM) , 2014, DOI: 10.4236/am.2014.521323
Abstract: Consider the linear dynamic equation on time scales\"\" (1) where\"\" ,\"\" ,\"\" is a rd-continuous function, T is a time scales. In this paper, we shall investigate some results for the exponential stability of the dynamic Equation (1) by combinating the first approximate method and the second method of Lyapunov.
The Role of Museums in the Preservation of Living Heritage: Experiences of the Vietnam Museum of Ethnology
Nguyen Van Huy
International Journal of Intangible Heritage , 2006,
Abstract: The author stresses the high respect that the Vietnam Museum of Ethnology (VME) has for cultural diversity, as seen in its approaches to the following three areas: people, space, and time. The VME has given priority first and foremost to the representation of everyday life – problems, stories, and concerns of peoples and of ethnic communities. The Museum’s role as a research and educational institution, as well as a body that appreciates and supports the intangible value of crafts are shown in two research case studies: learning to make pottery in the classroom for children, and giving voices to craft artisans in a photovoice project. The author also addresses current challenges of the VME, especially as it expands its research and display policies to include the cultures and daily life of ethnic peoples in other Southeast Asian Countries.
Binary Independent Component Analysis with OR Mixtures
Huy Nguyen,Rong Zheng
Mathematics , 2010, DOI: 10.1109/TSP.2011.2144975
Abstract: Independent component analysis (ICA) is a computational method for separating a multivariate signal into subcomponents assuming the mutual statistical independence of the non-Gaussian source signals. The classical Independent Components Analysis (ICA) framework usually assumes linear combinations of independent sources over the field of realvalued numbers R. In this paper, we investigate binary ICA for OR mixtures (bICA), which can find applications in many domains including medical diagnosis, multi-cluster assignment, Internet tomography and network resource management. We prove that bICA is uniquely identifiable under the disjunctive generation model, and propose a deterministic iterative algorithm to determine the distribution of the latent random variables and the mixing matrix. The inverse problem concerning inferring the values of latent variables are also considered along with noisy measurements. We conduct an extensive simulation study to verify the effectiveness of the propose algorithm and present examples of real-world applications where bICA can be applied.
Sharp Strichartz estimates for water waves systems
Quang-Huy Nguyen
Mathematics , 2015,
Abstract: Water waves are well-known to be dispersive at the linearization level. Considering the fully nonlinear systems, we prove for reasonably smooth solutions the optimal Strichartz estimates for pure gravity waves and the semi-classical Strichartz estimates for gravity-capillary waves; for both 2D and 3D waves. Here, by optimal we mean the gains of regularity (over the Sobolev embedding from Sobolev spaces to H\"older spaces) obtained for the linearized systems. Our proofs combine the paradifferential reductions of Alazard-Burq-Zuily \cite{ABZ1, ABZ3} with a dispersive estimate using a localized wave package type parametrix of Koch-Tataru \cite{KT}.
Global Conformal Invariants of Submanifolds
Andrea Mondino,Huy The Nguyen
Mathematics , 2015,
Abstract: The goal of the present paper is to investigate the algebraic structure of global conformal invariants of submanifolds. These are defined to be conformally invariant integrals of geometric scalars of the tangent and normal bundle. A famous example of a global conformal invariant is the Willmore energy of a surface. In codimension one we classify such invariants, showing that under a structural hypothesis the integrand can only consist of an intrinsic scalar conformal invariant, an extrinsic scalar conformal invariant and the Chern-Gauss-Bonnet integrand. In particular, for codimension one surfaces, we show that the Willmore energy is the unique global conformal invariant, up to the addition of a topological term (the Gauss curvature, giving the Euler Characteristic by the Gauss Bonnet Theorem). A similar statement holds also for codimension two surfaces, once taking into account an additional topological term given by the Chern-Gauss-Bonnet integrand of the normal bundle. We also discuss existence and properties of natural higher dimensional generalizations of the Willmore energy.
A Gap Theorem for Willmore Tori and an application to the Willmore Flow
Andrea Mondino,Huy The Nguyen
Mathematics , 2013, DOI: 10.1016/j.na.2014.02.015
Abstract: In 1965 Willmore conjectured that the integral of the square of the mean curvature of a torus immersed in $R^3$ is at least $2\pi^2$ and attains this minimal value if and only if the torus is a M\"obius transform of the Clifford torus. This was recently proved by Marques and Neves. In this paper, we show for tori there is a gap to the next critical point of the Willmore energy and we discuss an application to the Willmore flow. We also prove an energy gap from the Clifford torus to surfaces of higher genus.
Pseudo-local property of gravity water waves system
Quang-Huy Nguyen
Mathematics , 2015,
Abstract: By proving a weighted contraction estimate for the flow of gravity water waves, we show that this nonlocal system is in fact pseudo-local in the following sense: locally in time, the dynamic far away from a given bounded region has a small effect on that region (again, in a sense that we will make precise in the article). Our estimate on the flow also implies a new spatial decay property of the waves.
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