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Publication

A Composite Method for Improving the Pulse Shape Discrimination Efficiency of a Scintillation Detector Using EJ-301 Liquid

( 2021)

Phan Van Chuan

;

Nguyen Xuan Hai

;

Nguyen Ngoc Anh

;

Pham Dinh Khang

;

Nguyen Quang Hung

;

Truong Van Minh

;

Nguyen Duy Ly

This article presents a composite (COM) method to obtain the high-resolution pulse shape discrimination (PSD) for the neutron and gamma-ray pulses generated from scintillation detectors. The method, which is based on a selective combination of the digital charge integration (DCI) with the reference pulse method, aims to reduce the mixed radiation events in the low-energy range. An EJ-301 liquid scintillation detector together with a fast sampling analog-to-digital converter (ADC) is used to measure and digitize the pulses induced from the radioactive decays of 60 Co and 252 Cf, which are then analyzed by our COM method. The proposed method is evaluated using the figure of merit (FoM) and separation quality function F(u), and the results are compared with three known methods, namely the DCI, standard event fit (SEF), and artificial neural network (ANN) methods. We show that the average values of FoM and F(u) obtained within the COM method are about ten times higher than those obtained within the DCI and SEF in the whole energy range from 50 to 1000 keV electron equivalent (keVee). In particular, by using the COM method, the percentage of gamma events being confused as neutrons ranges from 0.32% to 8.80% when the energy is reduced from 400 to 50 keVee. This finding, which is significantly lower than those obtained by using the DCI and SEF, indicates that the proposed COM method should be considered as a leading method for producing a neutron/gamma PSD counter system with high resolution.

Publication

A new flowchart for parameters calculation of Hybrid Active Power Filter with Injection Circuit

( 2021)

Tung Khac Truong

;

Chau Minh Thuyen

;

Seyedali Mirjalili

This paper presents a new flowchart for parameters calculation of Hybrid Active Power Filter with Injection Circuit (IHAPF). The first is the necessity to use the IHAPF model and the parameters of the IHAPF needed to search have been shown. Next, the constraints of the parameters to be searched and the objective function to be reached are given. Since then a flowchart is designed to look for parameters of IHAPF using the Jaya optimization algorithm. The Jaya algorithm has the advantage of simplicity, few parameters, and good performance. Therefore it reduces search time. Compared to the flowchart using the firefly algorithm, particle swarm optimization algorithm, and simulated annealing algorithm, the simulation results performed on an IHAPF 10kV-50Hz model have proven that: the proposed flowchart gives better results in minimizing the compensation errors, minimum phase shift angle between supply current, and source voltage, minimum total harmonic distortion of supply current.

Publication

A note on the smallest semicopula-based universal integral and an application

( 2022)

Tran Nhat Luan

;

Do Huy Hoang

;

Tran Minh Thuyet

;

Huynh Ngoc Phuoc

;

Kieu Huu Dung

In this paper, we study two properties of the seminormed fuzzy integral. By applying these results, we propose alternative proof of the monotone convergence theorems for smallest semicopula-based universal integrals, which are proposed by J. Borzová-Molnárová et al. in 2015.

Publication

A Solar Chimney for Natural Ventilation of A Three – Story Building

( 2021)

Nguyễn Quốc Ý

Energy consumption of buildings can be significantly reduced with appropriate design for natural ventilation, particularly based on solar energy. Solar heat gained on the building envelope can be converted into thermal effects to induce air flow for natural ventilation or cooling of the building interior and the building envelope. For the ventilation application, the solar chimney should provide sufficient air flow rate. In this study, we investigated a solar chimney for ventilation of a three – story building. The chimney was assumed to be integrated into the building envelope and connected to all three stories of the building. To predict the air flow rate induced by the chimney through each story, a computational model was built based on the Computational Fluid Dynamics (CFD) method. By changing the design parameters (locations and dimensions of the air inlets) of the chimney, the ventilation rate through each story was computed. Temperature and velocity distributions in the chimney were also obtained for different design scenarios. From the results, the optimal design of the chimney which can provide nearly equal ventilation rate for all three stories was found. This study can serve as a demonstration for applications of the CFD technique in design of sustainable buildings.

Publication

A Study of Physical Layer Security in SWIPT-Based Decode-and-Forward Relay Networks with Dynamic Power Splitting

( 2021)

Van-Duc Phan

;

Tan N. Nguyen

;

Anh Vu Le

;

Miroslav Voznak

In this paper, we study the physical layer security for simultaneous wireless information and power transfer (SWIPT)-based half-duplex (HD) decode-and-forward relaying system. We consider a system model including one transmitter that tries to transmit information to one receiver under the help of multiple relay users and in the presence of one eavesdropper that attempts to overhear the confidential information. More specifically, to investigate the secrecy performance, we derive closed-form expressions of outage probability (OP) and secrecy outage probability for dynamic power splitting-based relaying (DPSBR) and static power splitting-based relaying (SPSBR) schemes. Moreover, the lower bound of secrecy outage probability is obtained when the source’s transmit power goes to infinity. The Monte Carlo simulations are given to corroborate the correctness of our mathematical analysis. It is observed from simulation results that the proposed DPSBR scheme outperforms the SPSBR-based schemes in terms of OP and SOP under the impact of different parameters on system performance.

Publication

Adaptive Integral Second-Order Sliding Mode Control Design for Load Frequency Control of Large-Scale Power System with Communication Delays

( 2021)

Anh-Tuan Tran

;

Bui Le Ngoc Minh

;

Phong Thanh Tran

;

Van Van Huynh

;

Van-Duc Phan

;

Viet-Thanh Pham

;

Tam Minh Nguyen

;

Rui Wang

Nowadays, the power systems are getting more and more complicated because of the delays introduced by the communication networks. The existence of the delays usually leads to the degradation and/or instability of power system performance. On account of this point, the traditional load frequency control (LFC) approach for power system sketches a destabilizing impact and an unacceptable system performance. Therefore, this paper proposes a new LFC based on adaptive integral second-order sliding mode control (AISOSMC) approach for the large-scale power system with communication delays (LSPSwCD). First, a new linear matrix inequality is derived to ensure the stability of whole power systems using Lyapunov stability theory. Second, an AISOSMC law is designed to ensure the finite time reachability of the system states. To the best of our knowledge, this is the first time the AISOSMC is designed for LFC of the LSPSwCD. In addition, the report of testing results presents that the suggested LFC based on AISOSMC can not only decrease effectively the frequency variation but also make successfully less in mount of power oscillation/fluctuation in tie-line exchange.

Publication

An Assessment for Fatigue Strength of Shaft Parts Manufactured from Two Phase Steel

( 2021)

Tăng Hà Minh Quân

Duplex stainless steel (Duplex) is a new material that has superior properties compared to other stainless steels in terms of avoiding corrosion stress and extremely good yield strength, high flow resistance and cheaper than austenite stainless steel series. However, fatigue strength that always leads to destruction occurs during the working process of axle-shaped machine parts under phase changes. In this paper, the evaluation of fatigue strength of Duplex steel to predict the longevity, maintenance plan for axial-shaped machine parts as well as the advanced mechanical heat treatment mode for Duplex steel are investigated. Samples are made from Duplex SAF 2205 (ISO 1143: 2009) to run fatigue tests by “Staircase” method to determine fatigue strength for Duplex 2205. In addition, this study also provides heat treatment mode for Duplex 2205: heating temperature 950 °C, heat retention time of 15 min and cooling down in the same furnace. The results indicate that supplied-stage Duplex 2205 steel will not be destroyed by fatigue under load under phase changes with 360 MPa stress, which is about 50% higher than AISI 304 (240 MPa) stainless steel. Duplex 2205 steel after heat treatment is enhanced mechanical properties and better durability than Duplex 2205 steel in the supply state.

Publication

An In Depth Analysis of Ocr Errors for Unconstrained Vietnamese Handwriting

( 2020)

Nguyễn Quốc Dũng

OCR post-processing is an essential step to improve the accuracy of OCR-generated texts by detecting and correcting OCR errors. In this paper, the OCR texts are resulted from an OCR engine which is based on the attention-based encoder-decoder model for unconstrained Vietnamese handwriting. We identify various kinds of Vietnamese OCR errors and their possible causes. Detailed statistics of Vietnamese OCR errors are provided and analyzed at both character level and syllable level, using typical OCR error characteristics such as error rate, error mapping/edit, frequency and error length. Furthermore, the statistical analyses are done on training and test sets of a benchmark database to infer whether the test set is the appropriate representative of the training set regarding the OCR error characteristics. We also discuss the choice of designing OCR post-processing approaches at character level or at syllable level relying on provided statistics of studied datasets.

Publication

Aspidistra sonlaensis (Asparagaceae, Nolinoideae), a new species from northern Vietnam

( 2021)

NGOC BON TRINH

;

VAN THE PHAM

;

THANH SON NGUYEN

;

THI THANH HA DO

;

KHANG SINH NGUYEN

;

LE TUAN ANH

;

MAXIM S. NURALIEV

;

NIKOLAY A. VISLOBOKOV

A new species of Aspidistra, A. sonlaensis, is described and illustrated from Son La Province in northern Vietnam. The new species is morphologically close to A. micrantha, but differs in number of perigone lobes, anther position and pistil shape. The new species is accessed as Data Deficient (DD) according to the IUCN categories and criteria.

Publication

AUGMENTATION OF SOLAR WATER DISTILLER PERFORMANCE WITH PV/T

( 2020)

Nguyen Viet Linh Le

;

Tri Hieu Le

;

Thi Minh Hao Dong

;

Van Vang Le

;

Dinh Tung

Recently, due to global warming and urbanization, there are many major cities that may face the challenge of day zero next decades. Obviously, water is an indispensable component for maintaining life on the earth. Although portable water is required of the hour, the quantity of available freshwater is impacted significantly by sea-level rise and pollution from industrialization. As a consequence of the global water crisis, different methods for clean water production from brackish water have been studied and developed in practice, however, the solar distillation of water is the most economical and desirable approach due to this method utilize solar energy that is the environmentally friendly and economical resource. Over the last 15 years, the impressive price drop of the photovoltaic solar collector (PV/T) makes them popular and easy to access. As a result, the employment of PV/T in solar stills is emerging as a potential device for water distillation. Therefore, in this paper, an active solar distiller combined with a photovoltaic panel has been reviewed for improvement of the distillate yield and effectiveness of solar photovoltaic. This review work presents a variety of studies on various types of solar still (for example conventional solar still (CSS), double slope solar still (DSSS), stepped solar distiller, and cascade solar still) couples with different solar water collectors (such as flat plate collector (FPC) and evacuated tubes collector (ETC)) and solar photovoltaic modules. It is obtained that the hybrid PV/T active solar still improves the distillate yield, energy efficiency, and exergy efficiency as compared to passive mode. The cooling method enhances the performance of the photovoltaic solar collector as well as the productivity of solar still. Moreover, the environmental economic estimation reveals that the solar still coupled with the PV/T mitigated considerably the amount of CO2. It can be stated that it is suitable to commercialize the hybrid PV/T active solar still for supplying not only electricity but drinking water also. Finally, this review paper also suggests the scope for the research in the future.

Publication

Automatic fuzzy genetic algorithm in clustering for images based on the extracted intervals

( 2020)

Dinh Phamtoan

;

Tai Vovan

This research proposes the method to extract the characteristics of images to become the intervals. These intervals are used to build the automatic fuzzy genetic algorithm for images (AFGI). In the proposed model, the overlap measure is the criterion to evaluate the closeness of intervals, and the new Davies and Bouldin index is the objective function. The AFGI can determine the proper number of clusters, the images in each cluster, and the probability to belong to clusters of images at the same time. The experiments with different types of images illustrate the steps of AFGI, and show its significant benefit in comparing to other algorithms.

Publication

Calculation of stability constants of new metal-thiosemicarbazone complexes based on the QSPR modeling using MLR and ANN methods

( 2021)

Quang Nguyen Minh

;

An Tran Nguyen Minh

;

Tat Pham Van

;

Thuy Bui Thi Phuong

;

Duoc Nguyen Thanh

In this study, the stability constants (log 11) of twenty-eight new complexes between several ion metals and thiosemicarbazone ligands were predicted on the basis of the quantitative structure property relationship (QSPR) modeling. The stability constants were calculated from the results of the QSPR models. The QSPR models were built by using the multivariate least regression (QSPRMLR) and artificial neural network (QSPRANN). The molecular descriptors, physicochemical and quantum descriptors of complexes were generated from molecular geometric structure and semi-empirical quantum calculation PM7 and PM7/sparkle. The best linear model QSPRMLR involves five descriptors, namely Total energy, xch6, xp10, SdsN, and Maxneg. The quality of the QSPRMLR model was validated by the statistical values that were R2 train = 0.860, Q2 LOO = 0.799, SE = 1.242, Fstat = 54.14 and PRESS = 97.46. The neural network model QSPRANN with architecture I(5)-HL(9)-O(1) was presented with the statistical values: R2 train = 0.8322, Q2 CV = 0.9935 and Q2 test = 0.9105. Also, the QSPR models were evaluated externally and achieved good performance results with those from the experimental literature. In addition, the results from the QSPR models could be used to predict the stability constants of other new metal-thiosemicarbazones.

Publication

Classifying maturity of cherry tomatoes using Deep Transfer Learning techniques

( 2021)

Danh Phuoc Huynh

;

My Van Vo

;

Nghin Van Dang

;

Tri Quoc Truong

This research studies a method to classify the tomatoes’ maturity by using deep transfer learning techniques. We carry out sorting systems adopting three pre-trained convolutional neural networks of VGG16, VGG19, and ResNet101. The experimental results show that the VGG19 model obtains a high precision on both the train set and the test set

Publication

Crashworthiness analysis and optimization of standard and windowed multi-cell hexagonal tubes

( 2021)

T. N. Tran

;

Ahmad Baroutaji

;

Quirino Estrada

;

Arun Arjunan

;

HuuSon Le

;

N. P. Thien

Recently, multi-cell structures have received increased attention for crashworthiness applications due to their superior energy absorption capability. However, such structures were featured with high peak collapsing force (PCL) forming a serious safety concern, and this limited their application for vehicle structures. Accordingly, this paper proposes windowed shaped cuttings as a mechanism to reduce the high PCL of the multi-cell hexagonal tubes and systemically investigates the axial crushing of different windowed multi-cell tubes and also seeks for their optimal crashworthiness design. Three different multi-cell configurations were constructed using wall-to-wall (WTW) and corner-to-corner (CTC) connection webs. Validated finite element models were generated using explicit finite element code, LS-DYNA, and were used to run crush simulations on the studied structures. The crashworthiness responses of the multi-cell standard tubes (STs), i.e., without windows, and multi-cell windowed tubes (WTs) were determined and compared. The WTWconnection type was found to be more effective for STs and less favorable for WTs. Design of experiments (DoE), response surface methodology (RSM), and multiple objective particle swarm optimization (MOPSO) tools were employed to find the optimal designs of the different STs and WTs. Furthermore, parametric analysis was conducted to uncover the effects of key geometrical parameters on the main crashworthiness responses of all studied structures. The windowed cuttings were found to be able to slightly reduce the PCL of the multi-cell tubes, but this reduction was associated with a major negative implication on their energy absorption capability. This work provides useful insights on designing effective multi-cell structures suitable for vehicle crashworthiness applications.

Publication

Decoration of silver nanoparticles on nitrogen-doped nanoporous carbon derived from zeolitic imidazole framework-8 (ZIF-8) via in situ auto-reduction

( 2021)

Vediyappan Veeramani

;

Nguyen Van Chi

;

Yi-Lin Yang

;

Nguyen Thi Hong Huong

;

Thuan Van Tran

;

Tansir Ahamad

;

Saad M. Alshehri

;

Kevin C.-W. Wu

We discovered an in situ auto-reduction method to embed silver nanoparticles onto a nanoporous carbon (NC) derived from the zeolitic imidazole framework-8 (ZIF-8), without any requirement of the reducing agents. The detailed analysis demonstrated the formation of Ag NPs by the replacement of the metallic Zn residue in the NC with Ag ions. The synthesized Ag@NC exhibited a superior catalytic activity toward the reduction reaction of 4-nitrophenol into 4-aminophenol.

Publication

Density estimation of a mixture distribution with unknown point-mass and normal error

( 2021)

Dang Duc Trong

;

Nguyen Hoang Thanh

;

Nguyen Dang Minh

;

Nguyen Nhu Lan

We consider the model Y = X + ξ where Y is observable, ξ is a noise random variable with density fξ , X has an unknown mixed density such that P(X = Xc ) = 1 − p, P(X = a) = p with Xc being continuous and p ∈ (0, 1), a ∈ R. Typically, in the last decade, the model has been widely considered in a number of papers for the case of fully known quantities a, fξ . In this paper, we relax the assumptions and consider the parametric error ξ ∼ σN(0, 1) with an unknown σ > 0. From i.i.d. copies Y1, . . . , Ym of Y we will estimate (σ, p, a, fXc ) where fXc is the density of Xc . We also find the lower bound of convergence rate and verify the minimax property of established estimators.

Publication

Design of small scale, axial flux, permanent magnet wind generator in Vietnam

( 2021)

Le Hung Tien

This paper presents the design of light weight, small scale, disk type, axial flux, permanent magnet (AFPM) generator for wind applications. This article also shows the partial works done under state projects in renewable energy in Vietnam to find out the most suitable, reliable, self – made wind generator types for rural and remote areas. The collaboration project of Hochiminh City University (HCMUT) – Hanoi University of Science and Technology (HUST) – Berlin University of Technology (TU Berlin) resulted in some small scale, axial flux, slow speed, permanent magnet (PM) generators which best suited for Vietnam countryside areas. The researches in rare earth PM from HUST, the electrical machine design knowhow of TU Berlin and the renewable energy research experiences of HCMUT, especially in slow speed wind turbines have shown many promising applications. The small scale, permanent magnet wind generator for remote and rural areas as a cheap source of power supply is necessary in Vietnam. Though there are many large wind farms built in many provinces recently but the needs for telecommunication, family lighting in the heights, mountain, unreachable electric grid communes are still necessary. Further research should be done to match the generator for hydro power stations, diesel coupled internal combustion engine. These prospects are very promising

Publication

Design of the double pass solar collector for drying

( 2021)

Duy Tue Nguyen

;

Tri Nhut Do

Solar energy is the free and nearly endless source which can be applied in various fields. Viet Nam locates near the equation and has enormous solar radiation, so this is the good chance for us to harness it. Moreover, Viet Nam is also the agricultural country with the large number of export product. With the large advantage in having enormous solar radiation, we can save up the large amount of energy for drying and other applications. In this paper, the 2 double pass solar collectors which have fins and without fins for drying were designed and simulated by CFD Ansys in some different conditions. The result displays that with the same size, the outlet temperature of the solar collectors with fins is 2 times higher than the without fins one. This temperature can reach 94.6oC with solar radiation 1026.32W/m2, mass flow rate 0.12kg/s and can reach 68.63oC with the same radiation and mass flow rate 0.18kg/s, so it is eligible for agricultural drying

Publication

Development of quantitative ion physic chemistry properties-activity relationship (QIPAR) and docking simulation for sars-covid-2 protein

( 2021)

Tat Pham Van

;

Quang Nguyen Minh

;

Thuy Bui Thi Phuong

;

Hoa Tran Thai

;

Duoc Nguyen Thanh

Currently, many drugs are being studied and potentially used in the treatment of SARS-CoV-2. Compounds studied are mostly organic substances. This work investigates the ability to inhibit SARS-CoV-2 of various 20 metal ions based on their ability to inhibit several biological systems; the physicochemical properties of metal ions were calculated by quantum chemistry DFT (B3LYP/ LanL2DZ) were used to develop the QIPAR hybrid models. Hybrid models QIPARGA-MLR (k = 4) and QIPARGA-ANN with architecture I(4)-HL(9)-O(1) were developed to predict the biological activity of metal ions. Metal ions were also investigated for their inhibitory potential for the protein SARS-CoV-2 (PDB6LU7) by docking simulation techniques. We predicted the binding sites of metal ions to the active sites of the SARS-CoV-2 protein (PDB6LU7). These studies are consistent with their activities against different biological systems. This research will also contribute to the development of metal oxide nanomaterials.

Publication

Effective reduction of nitrophenols and colorimetric detection of Pb(ii) ions by Siraitia grosvenorii fruit extract capped gold nanoparticles

( 2021)

Van Thuan Le

;

Truong Giang Duong

;

Van Tan Le

;

Thanh Long Phan

;

Thi Lan Huong Nguyen

;

Tan Phat Chau

;

Van-Dat Doan

This study presents a simple and green approach for the synthesis of Siraitia grosvenorii fruit extract capped gold nanoparticles (SG-AuNPs). The SG-AuNPs samples prepared under the optimized conditions were characterized by various techniques (UV-Vis, XRD, FTIR, HR-TEM, EDX, DLS). The biosynthesized nanoparticles were then studied for the reduction of 2-nitrophenol (2-NP) and 3-nitrophenols (3-NP) and for colorimetric detection of Pb2+ ions. The characterization results revealed that the crystals of SGAuNPs were spherical with an average size of 7.5 nm. The FTIR and DLS analyses proved the presence of the biomolecule layer around AuNPs, which played an important role in stabilizing the nanoparticles. The SG-AuNPs showed excellent catalytic activity in the reduction of 3-NP and 2-NP, achieving complete conversion within 14 min. The catalytic process was endothermic and followed pseudo-first-order kinetics. The activation energy was determined to be 10.64 and 26.53 kJ mol 1 for 2-NP and 3-NP, respectively. SG-AuNPs maintained high catalytic performance after five recycles. The fabricated material was also found to be highly sensitive and selective to Pb2+ ions with the detection limit of 0.018 mM in a linear range of 0–1000 mM. The practicality of the material was validated through the analyses of Pb2+ in mimic pond water samples. The developed nanoparticles could find tremendous applications in environmental monitoring.

Journal Articles - Engineering Technology - 2021

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