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Nguyen Huu Khanh Nhan,Tran Hoang Quang Minh,Nguyen Doan Quoc Anh 보안공학연구지원센터 2016 International Journal of Database Theory and Appli Vol.9 No.4
In this paper, a novel solution and application of the red Y2O3:Eu3+ dopant phosphor for enhancing color rendering index to more 86 for multi-chip white LED lamps (MCW-LEDs), which have correlated color temperature (CCT) of 7700 K, 6600 K, 5600 K, are presented. Then the effect of the concentration of Y2O3:Eu3+ phosphor on the color rendering index (CRI) is simulated, analyzed and demonstrated. After that the lumen output of MCW-LEDs depended on concentration Y2O3:Eu3+ phosphor is discovered. The lumen output has a decrease tendency at large weight range due to the enhancement extinction coefficient, according to Mie-scattering theory. Simulation results provided important conclusions for selecting and developing the phosphor materials in MCW-LEDs manufacturing.
Nhan, Nguyen Huu,Loc, Nguyen Hoang The Korean Society of Plant Biotechnology 2018 식물생명공학회지 Vol.45 No.4
In this study, the effect of elicitors such as yeast extract (YE), methyl jasmonate (MeJA) and salicylic acid (SA) on the accumulation of eurycomanone in Eurycoma longifolia cell cultures were investigated. Suspension cells of E. longifolia was cultured in Murashige and Skoog (MS) medium supplemented with 30 g/L sucrose, 1.25 mg/L naphthaleneacetic acid (NAA) and 1 mg/L kinetin at a shaking speed of 120 rpm. Elicitors were added in the culture at different concentrations and times to stimulate eurycomanone accumulation in the Eurycoma longifolia cells. Eurycomanone content was determined by HPLC with a C18 column, flow rate of 0.8 mL/min, run time of 17.5 min, and a detector wavelength of 254 nm. The stationary phase was silica gel and the mobile phase was acetonitrile: $H_2O$. Non-elicited cells were used as the control. The study showed the effect of different elicitor concentrations, YE at 200 mg/L, MeJA at $20{\mu}M$ and SA at $20{\mu}M$ stimulated high production of eurycomanone. In which, treatment of $20{\mu}M$ MeJA after 4 days of culture resulted in the highest accumulation of this compound (17.36 mg/g dry weight), approximately 10-fold higher than that of untreated cells (1.70 mg/g dry weight).
Nguyen Huu Khanh Nhan,Tran Hoang Quang Minh,Tan N. Nguyen,Miroslav Voznak 한국광학회 2017 Current Optics and Photonics Vol.1 No.6
Due to optimal advances such as chromatic performance, durability, low power consumption, highefficiency, long-lifetime, and excellent environmental friendliness, white LEDs (WLEDs) are widely usedin vehicle front lighting, backlighting, decorative lighting, street lighting, and even general lighting. In thispaper, the remote packaging WLEDs (RP-WLEDs) with bi-layer red-emitting Sr2Si5N8: Eu2+ and yellowemittingYAG:Ce phosphor was proposed and investigated. The simulation results based on the MATLABsoftware and the commercial software Light Tools indicated that the color rendering index (CRI) of bi-layerphosphor RP-WLEDs had a significant increase. The CRI had a considerable increase from 72 to 94. Inconclusion, the results showed that bi-layer red-emitting Sr2Si5N8:Eu2+ and yellow-emitting YAG:Cephosphor could be a prospective approach for manufacturing RP-WLEDs with enhanced optical properties.
A DSVM Method for Matrix Converters to Suppress Common-mode Voltage With Reduced Switching Losses
Huu-Nhan Nguyen,Hong-Hee Lee Institute of Electrical and Electronics Engineers 2016 IEEE transactions on power electronics Vol. No.
<P>This paper proposes a direct space-vector modulation (DSVM) method that can reduce the common-mode voltage (CMV) as well as the switching losses for matrix converters in a high voltage transfer ratio. Even though the previous DSVM improvements can reduce the CMV peak value to 42%, compared to the conventional DSVM method, they incur high switching losses. The DSVM method proposed in this paper provides the same CMV peak value as previous methods with lower switching losses. The switching losses are theoretically analyzed through the accumulated switched voltage in a switching period and compared to those of previous methods. Simulation and experimental results are given to verify the input/output waveforms, CMV reduction, and lower switching losses of the proposed DSVM method.</P>
A Modulation Scheme for Matrix Converters With Perfect Zero Common-Mode Voltage
Huu-Nhan Nguyen,Hong-Hee Lee Institute of Electrical and Electronics Engineers 2016 IEEE transactions on power electronics Vol. No.
<P>This paper presents a novel space vector modulation (SVM) method combined with a modified four-step commutation to achieve a perfect zero common-mode voltage (CMV) for matrix converters (MCs). The new SVM method was developed by using only rotating input voltage vectors, which results in the CMV for MCs being zero. However, it causes some noise in practical applications that drive MCs with traditional four-step commutation. In order to solve this noise problem, amodified four-step commutation is also proposed to perfectly eliminate the CMV for MCs without any noise. In the modified four-step commutation, a delay time is designed to deal with misjudgment of input voltages. The proposed SVM method and four-step commutation are easily implemented via software and achieve good performance in input/output current waveforms. Prototype experiments were carried out to evaluate the performance of the proposed method.</P>
Mental Health Among Healthcare Workers During the COVID-19 Pandemic in Vietnam
Nhan Phuc Thanh Nguyen,Ha Phan Ai Nguyen,Cao Khoa Dang,Minh Tri Phan,Huynh Ho Ngoc Quynh,Van Tuan Le,Chinh Van Dang,Tinh Huu Ho,Van Trong Phan,Van Trong Phan,Thang Phan,Dang Thi Anh Thu 대한예방의학회 2024 예방의학회지 Vol.57 No.1
Objectives: The objective of this study was to characterize mental health issues among Vietnamese healthcare workers (HCWs) and to identify related factors.Methods: A cross-sectional study was conducted with 990 HCWs in 2021. Their mental health status was measured using the Depression, Anxiety, and Stress Scale.Results: In total, 49.9%, 52.3%, and 29.8% of respondents were found to have depression, anxiety, and stress, respectively. The multivariable linear regression model revealed that factors associated with increased anxiety scores included depression scores (β, 0.45; 95% confidence interval [CI], 0.39 to 0.51) and stress scores (β, 0.46; 95% CI, 0.41 to 0.52). Factors associated with increased depression scores included being frontline HCWs (β, 0.57; 95% CI, 0.10 to 1.10), stress scores (β, 0.50; 95% CI, 0.45 to 0.56), and anxiety scores (β, 0.41; 95% CI, 0.36 to 0.47), while working experience was associated with reduced depression scores (β, -0.08; 95% CI, -0.16 to -0.01). Factors associated with increased stress scores included working experience (β, 0.08; 95% CI, 0.00 to 0.16), personal protective equipment interference with daily activities (β, 0.55; 95% CI, 0.07 to 1.00), depression scores (β, 0.54; 95% CI, 0.48 to 0.59), and anxiety scores (β, 0.45; 95% CI, 0.39 to 0.50), while age was associated with reduced stress scores (β, -0.12; 95% CI, -0.20 to -0.05).Conclusions: Specific interventions are necessary to enhance and promote the mental health of HCWs so they can successfully cope with the circumstances of the pandemic.
Nguyen Huu Nhan,Truong Thi Nhan,Le Thi Phuong Ngoc,Nguyen Thanh Long 경남대학교 수학교육과 2021 Nonlinear Functional Analysis and Applications Vol.26 No.1
In this paper, we investigate an initial boundary value problem for a nonlinear pseudoparabolic equation. At first, by applying the Faedo-Galerkin, we prove local existence and uniqueness results. Next, by constructing Lyapunov functional, we establish a sufficient condition to obtain the global existence and exponential decay of weak solutions.
A Simple SVM Technique to Eliminate Common-mode Voltage for Matrix Converters
Huu-Nhan Nguyen,Tuyen D. Nguyen,Thanh-Luan Nguyen,Hong-Hee Lee 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
In a matrix-converter (MC) system, commonmode voltage (CMV) causes damage to the motor bearings and other equipment. When the MC is controlled by means of space vector modulation (SVM), zero-CMV can be achieved by using only rotating-vector states to drive the MC. However, as the computation becomes quite complicated, it is not easy to apply the rotating-vector states in practice. This paper presents a simple SVM technique using rotating-vector states to eliminate the CMV for MCs. Based on the conventional SVM method, the proposed SVM technique achieves the zero CMV for MCs within a few simple steps by considering the relationship between active-vector and rotating-vector states. The performance and effectiveness of the proposed technique are verified by simulation results.
A New Dimeric Lignan from the Stems of Willughbeia edulis
Nguyen, Hai Xuan,Do, Truong Nhat Van,Le, Tho Huu,Dang, Phu Hoang,Nguyen, Mai Thanh Thi,Nguyen, Nhan Trung The Korean Society of Pharmacognosy 2022 Natural Product Sciences Vol.28 No.2
As part of our continued study on the chemical constituents of Willughbeia edulis stems, a new dimeric lignan named edulignan (1) was isolated from its EtOAc-soluble extract. Based on NMR spectroscopic interpretation, the planar structure of 1 has been suggested to have two 2-substituted 4-chromanone subunits with different stereochemical configurations. In addition, the MS/MS analysis of the products obtained by acid-catalyzed hydrolysis of 1 was supportive of its structure. Unfornatually, the new compound 1 did not show 𝛼-glucosidase inhibitory activity with an IC<sub>50</sub> value > 250 𝜇M.
Effects of Hyper-parameters and Dataset on CNN Training
Huu Nhan Nguyen,Chanho Lee 한국전기전자학회 2018 전기전자학회논문지 Vol.22 No.1
The purpose of training a convolutional neural network (CNN) is to obtain weight factors that give high classification accuracies. The initial values of hyper-parameters affect the training results, and it is important to train a CNN with a suitable hyper-parameter set of a learning rate, a batch size, the initialization of weight factors, and an optimizer. We investigate the effects of a single hyper-parameter while others are fixed in order to obtain a hyper-parameter set that gives higher classification accuracies and requires shorter training time using a proposed VGG-like CNN for training since the VGG is widely used. The CNN is trained for four datasets of CIFAR10, CIFAR100, GTSRB and DSDL-DB. The effects of the normalization and the data transformation for datasets are also investigated, and a training scheme using merged datasets is proposed.