Erbium-Doped Silicon-Rich Oxide Waveguides Fabricated by Using an Electro-Chemical Method

Pham Van Hoi,Bui Huy,Tran Thi Cham,Ha Xuan Vinh,Do Khanh Van 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.3

In this article, we describe and electro-chemical method for fabricating erbium-doped silicon-rich oxide (SRO) waveguides. The porosity, the Er-ion concentration and the refractive index can be controlled by varying the current density (continuous or pulsed currents) during the production process. The refractive index difference between the core and the cladding layers and the profile of the SRO waveguides were tested by using an m-line spectrometer and Field-emission scanning electron microscope (FE-SEM). The photo-luminescent (PL) emission of Er-ions at 1550 nm in the SRO waveguides could be obtained even when the excitation wavelength was away from the resonance absorption band of the Er-ions. This result revealed that Er-ions are possibly excited from the ground state 4I15/2 to the first excited state 4I13/2 by energy transfer from excited Si nanocrystallites. The Er-doped SRO waveguides can be applied to optoelectronic devices compatible with Si-based integrated circuit technology.

Nano-porous Silicon Microcavity Sensors for Determination of Organic Fuel Mixtures

Van Hoi Pham,Huy Bui,Le Ha Hoang,Thuy Van Nguyen,The Anh Nguyen,Thanh Son Pham,Quang Minh Ngo 한국광학회 2013 Current Optics and Photonics Vol.17 No.5

We present the preparation and characteristics of liquid-phase sensors based on nano-porous silicon multilayer structures for determination of organic content in gasoline. The principle of the sensor is a determination of the cavity-resonant wavelength shift caused by refractive index change of the nano-porous silicon multilayer cavity due to the interaction with liquids. We use the transfer matrix method (TMM)for the design and prediction of characteristics of microcavity sensors based on nano-porous silicon multilayer structures. The preparation process of the nano-porous silicon microcavity is based on electrochemical etching of single-crystal silicon substrates, which can exactly control the porosity and thickness of the porous silicon layers. The basic characteristics of sensors obtained by experimental measurements of the different liquids with known refractive indices are in good agreement with simulation calculations. The reversibility of liquid-phase sensors is confirmed by fast complete evaporation of organic solvents using a low vacuum pump. The nano-porous silicon microcavity sensors can be used to determine different kinds of organic fuel mixtures such as bio-fuel (E5), A92 added ethanol and methanol of different concentrations up to 15%.

A Vapor Sensor Based on a Porous Silicon Microcavity for the Determination of Solvent Solutions

Huy Bui,Thuy Van Nguyen,The Anh Nguyen,Thanh Binh Pham,Quoc Trung Dang,Thuy Chi Do,Quang Minh Ngo,Roberto Coisson,Van Hoi Pham 한국광학회 2014 Current Optics and Photonics Vol.18 No.4

A porous silicon microcavity (PSMC) sensor has been made for vapors of solvent solutions, and a method has been developed in order to obtain simultaneous determination of two volatile substances with different concentrations. In our work, the temperature of the solution and the velocity of the air stream flowing through the solution have been used to control the response of the sensor for ethanol and acetone solutions. We study the dependence of the cavity-resonant wavelength shift on solvent concentration, velocity of the airflow and solution temperature. The wavelength shift depends linearly on concentration and increases with solution temperature and velocity of the airflow. The dependence of the wavelength shift on the solution temperature in the measurement contains properties of the temperature dependence of the solvent vapor pressure, which characterizes each solvent. As a result, the dependence of the wavelength shift on the solution temperature discriminates between solutions of ethanol and acetone with different concentrations. This suggests a possibility for the simultaneous determination of the volatile substances and their concentrations.

Front-view Car Detection and Counting with Occlusion in Dense Traffic Flow

Van Huy Pham,이병룡 제어·로봇·시스템학회 2015 International Journal of Control, Automation, and Vol.13 No.5

In dense traffic flow, car occlusion is usually one of the great challenges of vehicle detection and tracking in traffic monitoring systems. Current methods of car hypothesis such as symmetry or shadow based method work only with non-occluded cars. In this paper, we proposed an approach to car detection and counting using a new method of car hypothesis based on car windshield appearance which is the most feasible cue to hypothesize cars in occlusion situations. In hypothesis stage, Hough transformation is used to detect trapezoid-like regions where a car’s windshield could be located, and then candidate car regions are estimated by the windshield region and its size. In verification stage, HOG descriptor and a well-collected dataset are used to train a linear SVM classifier for detecting cars at a high accuracy rate. Then, a tracking process based on Kalman filter is used to track the movement of detected cars in consecutive frames of traffic videos, followed by rule-based reasoning for counting decision. Experimental results on real traffic videos showed that the system is able to detect, track and count multiple cars including occlusion in dense traffic flow in real-time.

Evaluation of Pt-based alloy/graphene nanohybrid electrocatalysts for triiodide reduction in photovoltaics

Dao, Van-Duong,Larina, Liudmila L.,Tran, Quoc Chinh,Bui, Van-Tien,Nguyen, Van-Toan,Pham, Thanh-Dong,Mohamed, Ibrahim M.A.,Barakat, Nasser A.M.,Huy, Bui The,Choi, Ho-Suk Elsevier 2017 Carbon Vol.116 No.-

<P>This work focuses on systematic studies of dissolution engineering for Pt0.9M0.1/graphene(M = Au, Co, Cu, Fe, Mo, Ni, Pd, Ru, and Sn) counter electrodes (CEs). The developed nanohybrid materials exhibit higher catalytic activity and electrical conductivity compared with those of Pt/graphene CEs. The results also indicate the improved stability of the developed CEs in iodide electrolyte. Furthermore, the trend in the variation of the reactivity of the PtM alloys agrees well with the concept of density functional theory (one-electron description). An enhancement in the catalytic activity of the developed nanohybrids results from the electronic effect that originates from an upward shift of the platinum d-band to the Fermi energy level upon alloying. Thus, the Pt(0.9)M(0.1)graphene nanohybrids are cost-effective alternative CE materials to the expensive Pt. The obtained results provide a foundation for enhancing the catalytic activities of CEs for dye-sensitized solar cells (DSCs). The implementation of the Pt0.9M0.1/graphene nanohybrids offers significant potential for increasing the efficiency of DSCs. (C) 2017 Elsevier Ltd. All rights reserved.</P>

Online Actor-critic Reinforcement Learning Control for Uncertain Surface Vessel Systems with External Disturbances

Van Tu Vu,Quang Huy Tran,Thanh Loc Pham,Phuong Nam Dao 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.3

This article addresses a trajectory tracking control approach for an uncertain surface vessel using the new cascade structure of adaptive reinforcement learning (ARL) algorithm and kinematic controller, feed-forward term. Since a surface vessel is decoupled by kinematic sub-system and dynamic sub-system, the cascade control system is an ideal method for obtaining the tracking problem. In the proposed control structure, the dynamic control loop is designed to be the optimized method of the corresponding dynamic sub-system and the kinematic control loop is implemented by a nonlinear controller combining with feed-forward term. The online actor-critic architecture is considered in ARL algorithm to overcome the challenge of solving the Hamilton-Jacobi-Bellman (HJB) equation. Additionally, the proposed controller is able to handle the difficulty of the non-autonomous optimal control problem by designing the ARL technique for the corresponding system with a small number of state variables. Based on theoretical analysis, the ARL based control design has been made to guarantee the uniformly ultimately bounded (UUB) stability of the closed system. Finally, the simulation results are illustrated to verify the effectiveness of the proposed control scheme.

Effect of adding non-ferromagnetic nanoparticles to grain boundary on coercivity of sintered Nd-Fe-B magnet

Pham Thi Thanh,Nguyen Van Duong,Nguyen Hai Yen,Nguyen Huy Ngoc,Nguyen Mau Lam,Kieu Xuan Hau,유성조,Nguyen Huy Dan 한국물리학회 2018 Current Applied Physics Vol.18 No.3

In this work, we investigated the influence of additional compounds of Nd-Cu-Al, Dy-Nb-Al, Dy-Zr-Al and Nb-Cu-Al on coercivity of sintered Nd-Fe-B magnets. The additional nanoparticles with size in the range of 40e80 nmwas mixed with the micrometer Nd-Fe-B powder before sintering process. The results show that the coercivity of the sintered Nd-Fe-B magnets can be improved by introducing additional nanoparticles to their grain boundaries. The improvement of the coercivity of the magnets is clearly dependent on composition and fraction of the additional compounds. While the Dy-Nb-Al, Dy-Zr-Al and Nb-Cu-Al compounds degrade the coercivity of the sintered Nd-Fe-B magnets, the Nd-Cu-Al nanoparticles considerably improve this quantity. The coercivity the sintered Nd16.5Fe77B6.5 magnets has been enhanced about 40% by adding 3 wt% of the Dy-free compound of Nd40Cu30Al30.

Effect of adding non-ferromagnetic nanoparticles to grain boundary on coercivity of sintered Nd-Fe-B magnet

Thanh, Pham Thi,Van Duong, Nguyen,Yen, Nguyen Hai,Ngoc, Nguyen Huy,Lam, Nguyen Mau,Hau, Kieu Xuan,Yu, Seong Cho,Dan, Nguyen Huy ELSEVIER 2018 CURRENT APPLIED PHYSICS Vol.18 No.3

<P>In this work, we investigated the influence of additional compounds of Nd-Cu-Al, Dy-Nb-Al, Dy-Zr-Al and Nb-Cu-Al on coercivity of sintered Nd-Fe-B magnets. The additional nanoparticles with size in the range of 40-80 nm was mixed with the micrometer Nd-Fe-B powder before sintering process. The results show that the coercivity of the sintered Nd-Fe-B magnets can be improved by introducing additional nanoparticles to their grain boundaries. The improvement of the coercivity of the magnets is clearly dependent on composition and fraction of the additional compounds. While the Dy-Nb-Al, Dy-Zr-Al and Nb-Cu-Al compounds degrade the coercivity of the sintered Nd-Fe-B magnets, the Nd-Cu-Al nanoparticles considerably improve this quantity. The coercivity the sintered Nd16.5Fe77B6.5 magnets has been enhanced about 40% by adding 3 wt% of the Dy-free compound of Nd40Cu30Al30. (C) 2017 Elsevier B.V. All rights reserved.</P>

Well path design by integrating the analysis of wireline logs and the interpretation of seismic data for a fractured basement reservoir in Cuu Long Basin, Viet Nam

Nguyen, Van Trieu,Hwang, Seho,Jang, Seonghyung,Hoang, Ngoc Dong,Pham, Huy Giao Elsevier 2018 Marine and petroleum geology Vol.93 No.-

<P><B>Abstract</B></P> <P>Cuu Long Basin, which is located in southeast offshore Viet Nam, has a number of well fractured granitic basement reservoirs. Though dozens of wells have been drilled in the pre-Tertiary basement, the actual number of wells in which hydrocarbons were discovered is approximately 30% of the total. Therefore, understanding fracture characteristics in the fractured basement is very important and plays a critical role in designing the well path. This study proposes a method to optimize well path design in the fractured granitoid basement rock. Available information, including basin tectonic evolution, basin geological characteristics, seismic interpretation, and wireline logs, especially image and sonic logs, are analyzed in order to understand the fracture characteristics and the distribution of fractures in the study area, which is referred to as Thuy Trieu Do (TTD) structure. There are two key factors related to the flow in basement of TTD structure, namely are solution-enhanced fractures and faults interpreted from seismic images. Solution-enhanced fractures from images are considered to be open fractures that contribute to flow. Within the TTD basement, the solution-enhanced fractures trend in the east-west and sub east-west directions. Faults interpreted from seismic images are complex with different fault directions, having been active in several tectonic phases. They are evaluated and classified, then the faults those are NE-SW 60–70°, E-W, and sub E-W 80–280° have potential in creation fault-related fractures of solution-enhanced fracture type. Fractures are mostly distributed in fracture zones along the fault zone. By displaying faults and fractures together both along the well path and on rose diagrams, combined with production logs analysis, it appears that surrounding faults have increased fracture density and the presence of solution-enhanced fractures in every flow zone. The above relationships were taken in analyses for the next well design in the TTD structure. In this study, for optimal well path design in the fractured basement reservoir, a systematic procedure of interpretation of various geophysical data in Cuu Long Basin has been proposed, and this approach is expected to be applicable to other fractured reservoirs in Viet Nam.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Permeable fractures in granitoid basement are mostly distributed in fracture zones along faults. </LI> <LI> Solution-enhanced fractures are considered to be the main fracture for drainage. </LI> <LI> The proposed drilling well path should cut through faults and solution-enhanced fractures. </LI> </UL> </P>

Comparative proteomic analysis of Celastrus hindsii Benth. phenotypes reveals an intraspecific variation

Nguyen, Van Huy,Pham, Thanh Loan,Ha, Thi Tam Tien,Hoang, Thi Le Thu The Korean Society of Plant Biotechnology 2020 JOURNAL OF PLANT BIOTECHNOLOGY Vol.47 No.4

In Vietnam, Celastrus hindsii Benth, a medicinal plant rich in secondary metabolites, has been used to alleviate distress caused by ulcers, tumors, and inflammation for generations. The occurrence of two phenotypes, Broad Leaf (BL) and Narrow Leaf (NL), has raised questions about the selection of appropriate varieties for conservation and crop improvement to enhance medicinal properties. This study examined molecular differences in C. hindsii by comparing protein profiles between the NL and BL types using 2D-PAGE and MS. Peptide sequences and proteins were identified by matching MS data against the MSPnr100 databases and verified using the MultiIdent tool on ExPASy and the Blast2GO software. Our results revealed notable variations in protein abundance between the NL and BL proteomes. Selected proteins were confidently identified from 12 protein spots, thereby highlighting the molecular variation between NL and BL proteomes. Upregulated proteins in BL were found to be associated with flavonoid and amino acid biosynthesis as well as nuclease metabolism, which probably attributed to the intraspecific variations. Several bioactive proteins identified in this study can have applications in cancer therapeutics. Therefore, the BL phenotype characterized by healthier external morphological features has higher levels of bioactive compounds and could be better suited for medicinal use.