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%.

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.

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.

A Novel Bandwidth Estimation Method Based on MACD for DASH

( Van-huy Vu ),( Ibrahim Mashal ),( Tein-yaw Chung ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.3

Nowadays, Dynamic Adaptive Streaming over HTTP (DASH) has become very popular in streaming multimedia contents. In DASH, a client estimates current network bandwidth and then determines an appropriate video quality with bitrate matching the estimated bandwidth. Thus, estimating accurately the available bandwidth is a significant premise in the quality of video streaming, especially when network traffic fluctuates substantially. To cope with this challenge, researchers have presented various filters to estimate network bandwidth adap-tively. However, experiment results show that current schemes either adapt slowly to net-work changes or adapt fast but are very sensitive to delay jitter and produce sharply changed estimation. This paper presents a novel bandwidth estimation scheme based on Moving Av-erage Convergence Divergence (MACD). We applied an MACD indicator and its two thresholds to classifying network states into stable state and agile state, based on the network state different filters are applied to estimate network bandwidth. In the paper, we studied the performance of various MACD indicators and the threshold values on bandwidth estimation. Then we used a DASH proxy-based environment to compare the performance of the present-ed scheme with current well-known schemes. The simulation results illustrate that the MACD-based bandwidth estimation scheme performs superior to existing schemes both in the speed of adaptively to network changes and in stability in bandwidth estimation.

Study Design for the 2016 Baseline Survey of a Health System Strengthening Project in Quoc Oai District, Hanoi, Vietnam

Van Minh Hoang,오주환,Bao Ngoc Nguyen,Le Minh Dat,이종구,Thi Giang Huong Tran,Van Huy Nguyen,이승표,방경숙,조영태,김선영,이화영,Quang Cuong Le,Narshil Choi,Thai Son Dinh,Ngoc Hoat Luu 대한의학회 2019 Journal of Korean medical science Vol.34 No.5

Background: In order to provide essential scientific evidence on the population's health status and social health determinants as well as the current capacity of the health care system in Vietnam to health policy makers and managers, Vietnam Ministry of Health, Hanoi University of Public Health, Hanoi Medical University, and Ho Chi Minh University of Medicine and Pharmacy collaborated with Seoul National University (Korea) and conducted a health system survey in the Quoc Oai district (of Hanoi capital) that represented northern rural Vietnam. Methods: The study design was a cross-sectional study. The survey covered different topics (more than 200 questions) and was administered in three separate questionnaires: 1) Basic information of all household members; 2) Household characteristics; and 3) Individual characteristics. Socio-demographic characteristics among the households and individuals were collected from 2,400 households sampled by multi-stage cluster sampling method: more than 200 questions. Results: The household size of Quoc Oai was larger than the national average and there was no significant difference in gender composition. In addition, the proportions of pre-elderly, age 55–64, and elderly group (65 years old and over) were higher than the national population statistics. In this context, demographic transition has begun in Quoc Oai. Conclusion: This study design description provides the basic information about a baseline survey of a future prospective cohort (as a part of a collaborative project on strengthening the health system in Vietnam) to the prospective data user of this survey.

Genetic diversity of spotted scat (Scatophagus argus) in Vietnam based on COI genes

Huy Van Nguyen,Minh Tu Nguyen,Nghia Duc Vo,Nguyen Thi Thao Phan,Quang Tan Hoang 한국수산과학회 2022 Fisheries and Aquatic Sciences Vol.25 No.12

A spotted scat, Scatophagus argus, has a high nutritional value and is among Asia’s most widely consumed fish species. Thua Thien Hue’s consumption market considers this species to be of high economic value and requires protection and conservation of the population. However, the studies on the identification and genetic diversity of S. argus distributed in Vietnam are still lacking. Therefore, mitochondrial cytochrome c oxidase subunit I (COI) gene was utilized to distinguish different populations and investigate the genetic diversity of two populations of S. argus from Tam Giang lagoon, Thua Thien Hue province (n = 31) and Ca Mau province (n = 14). The sequencing results indicated 13 distinct haplotypes among 45 sequences. Five single nucleotide polymorphisms were observed to distinguish Hue spotted scat population. The S. argus population in Ca Mau province was higher haplotype diversity (Hd) and nucleotide diversity (π) than those of Thua Thien Hue province, which demonstrates that there are minor differences between haplotypes. There were genetic distances ranging from 0%–4% within the populations and 6.67% between the two populations. In addition to the sequencing, the comparison of morphology, biology, culture, and the growth rate was sufficient to distinguish the spotted scat S. argus in Thua Thien Hue from Ca Mau.

Landscapes and Ecosystems of Tropical Limestone: Case Study of the Cat Ba Islands, Vietnam

Van, Quan Nguyen,Duc, Thanh Tran,Van, Huy Dinh The Ecological Society of Korea 2010 Journal of Ecology and Environment Vol.33 No.1

The Cat Ba Islands in Hai Phong City, northern Vietnam, consist of a large limestone island with a maximum height of 322 m above sea level and 366 small limestone islets with a total area of about $180\;km^2$. The islands are relicts of karst limestone mountains that became submerged during the Holocene transgression 7000 - 8000 year ago. The combination of the longtime karst process and recent marine processes in the monsoonal tropical zone has created a very diversity landscape on the Cat Ba Islands that can be divided into 3 habitat types with 16 forms. The first habitat type is the karst mountains and hills, including karst mountains and hills, karst valleys and dolines, karst lakes, karst caves, and old marine terraces. The second habitat type is the limestone island coast, including beaches, mangrove marshes, tidal flats, rocky coasts, marine notch caves, marine karst lakes, and bights. The third habitat type is karst plains submerged by the sea, including karst cones (fengcong) and towers (fengling), bedrock exposed on the seabed, sandy mud seabed, and submerged channels. Like the landscape, the biodiversity is also high in ecosystems composed of scrub cover - bare hills, rainy tropical forests, paddy fields and gardens, swamps, caves, beaches, mangrove forests, tidal flats, rocky coasts, marine krast lakes, coral reefs, hard bottoms, seagrass beds and soft bottoms. The ecosystems on the Cat Ba Islands that support very high species biodiversity include tropical evergreen rainforests, soft bottoms; coral reefs, mangrove forests, and marine karst lakes. A total of 2,380 species have been recorded in the Cat Ba Islands, included 741 species of terrestrial plants; 282 species of terrestrial animals; 30 species of mangrove plants; 287 species of phytoplankton; 79 species of seaweed; 79 species of zooplankton; 196 species of marine fishes; 154 species of corals; and 538 species of zoobenthos. Many of these species are listed in the Red Book of Vietnam as endangered species, included the white-headed or Cat Ba langur (Trachypithecus poliocephalus), a famous endemic species. Human activities have resulted in significantly changes to the landscape end ecosytems of the Cat Ba islands; however, many natural aspects of the islandsd have been preserved. For this reason, the Cat Ba Islands were recognized as a Biological Reserved Area by UNESCO in 2004.

Healthcare Workers’ Knowledge and Attitudes Regarding the World Health Organization’s “My 5 Moments for Hand Hygiene”: Evidence From a Vietnamese Central General Hospital

Huy Van Nguyen,Hieu Trung Tran,Long Quynh Khuong,Thanh Van Nguyen,Na Thi Nhi Ho,An Thi Minh Dao,Minh Van Hoang 대한예방의학회 2020 예방의학회지 Vol.53 No.4

Objectives: Although the World Health Organization (WHO) initiative “My 5 Moments for Hand Hygiene” has been lauded as effective in preventing hospital-associated infections, little is known about healthcare workers (HCWs)’ hand hygiene behavior. In this study, we sought to assess knowledge and attitudes towards the concepts in this initiative, as well as associated factors, among Vietnamese HCWs at a general hospital. Methods: A structured questionnaire was administered to HCWs at a central Vietnamese general hospital in 2015. Multiple logistic regression analysis was used to identify factors associated with HCWs’ knowledge and attitudes towards hand hygiene. Results: Of 120 respondents, 65.8% and 67.5% demonstrated appropriate knowledge and a positive attitude, respectively, regarding all 5 hand hygiene moments. Logistic regression indicated better knowledge of hand hygiene in workers who were over 30 years old, who were direct HCWs (rather than managers), who had frequent access to clinical information, and who received their clinical information from training. Those who worked in infectious and tropical disease wards, who had frequent access to clinical information, and who received information from training were more likely to have a positive attitude towards hand hygiene than their counterparts. Conclusions: Although many Vietnamese HCWs displayed moderate knowledge and positive attitudes towards the WHO hand hygiene guidelines, a key gap remained. Regular education and training programs are needed to increase knowledge and to improve attitudes and practices towards hand hygiene. Furthermor

Automatic Machine Fault Detection based on Vibration Signal

Van Bui,Van Hoa Nguyen,Huy Nguyen,Yeong Min Jang 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.2

Machine maintenance is important in the smart factory, which requires lots of attention to improve both accuracy and general performance. Nowadays, predictive maintenance and automatic fault detection are improving due to the application of IoT networks and real-time analysis in the factory environment. One of the main signals that can be used for predictive maintenance is the machine vibration signal, which can be collected, analyzed with high accuracy and efficiency, make fault detection easy to implement. In our study, we use the Spectra Quest’s Gearbox Prognostics Simulator data as the input data for the classification system. The AI algorithms are Artificial Neural Network, Linear Regression, and Support Vector Machine. The highest accuracy reached is 100%.

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.