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Nguyen Ngoc Vinh,Younghan Kim 한국통신학회 2013 한국통신학회 학술대회논문집 Vol.2013 No.6

A Numerical Calculation of the Nuclear Spin-Parity and Magnetic Moment Based on the Single-Particle Shell Model

Nguyen Ngoc Duy,Latsamy Xayavong,Nguyen Kim Uyen,Vinh Nguyen Thanh Pham,Tran Viet Nhan Hao 한국물리학회 2019 새물리 Vol.69 No.10

Nuclear physics is an obligatory subject for the general physics program of undergraduates in most of the natural science universities worldwide. In nuclear physics, the shell model is one of the most important models, and is well used to determine the spin-parity and the magnetic moment of a nucleus. Over ten years of teaching general physics, we have realize that most undergraduate students find calculating these parameters by using this shell model to be difficult due to the classification of the subshells and the intrinsic spin of nucleons. With the hope to help these students, in the present study, we introduce a graphical-user-interface (GUI) program to execute our selfdeveloped Shell Model Calculator (SMC) code written in the Visual Basic 6.0 (VB6) programming language. Our SMC validation results for the quantum quantities in a series of nuclei Z = 1 - 20 were compared with experimental data and found to be in good agreement. In general, we successfully developed an SMC program that can be used for teaching, learning, and researching nuclear physics in universities.

Strain rate-dependent behaviors of mechanical properties of structural steel investigated using indentation and finite element analysis

Nguyen, Ngoc-Vinh,Pham, Thai-Hoan,Kim, Seung-Eock Elsevier 2019 Mechanics of materials Vol.137 No.-

<P><B>Abstract</B></P> <P>In this study, a series of experiments, which consist of constant strain rate indentation, and optical microscope examination, and finite element analysis were performed to investigate the strain rate-dependent behaviors of the mechanical properties of SS400 structural steel. The microstructures of SS400 steel was characterized using optical microscope examination. The influences of strain rate indentation on the characteristics of the loading/unloading curves were presented and the results showed a higher applied load, a higher loading curvature, and a higher loading work for a higher strain rate level. The strain rate-dependent behaviors of indentation hardness (<I>H</I>), yield strength (<I>σ<SUB>y</SUB> </I>), and work hardening (<I>n</I>) were investigated. When the strain rate level increased, both <I>H</I> and <I>σ<SUB>y</SUB> </I> strongly increased, while work hardening showed an almost linear increase. The strain rate-dependent behaviors of material properties were validated through the experimental and the numerical verifications. The strain rate sensitivity (SRS) value of 0.056 ± 0.02 was reported for SS400 steel and was highly consistent with the general trend reported for several types of structural steel in the literature.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The pile-up phenomena occurred at all strain rate indentation levels, while the pop-in events can be observed to be more pronounced at low strain rate. </LI> <LI> The results showed higher applied load, higher loading curvature, higher total work, and higher contact stiffness for higher strain rate condition. </LI> <LI> The strain rate sensitivity of 0.056 ± 0.03 was well reported for SS400 steel. </LI> <LI> As the strain rate increased, indentation hardness yield stress strongly increased, while work hardening showed an almost linear increase. </LI> <LI> The strain rate-dependent behaviors of both yield stress and work hardening were validated through the experimental and numerical verifications. </LI> </UL> </P>

Re-examination of Energy-Loss Straggling Calculations of Alpha Particles at 5.486 MeV

Nguyen Ngoc Duy,Nguyen Kim Uyen,Vinh N. T. Pham 한국물리학회 2020 New Physics: Sae Mulli Vol.70 No.2

We report on an evaluation of energy-loss straggling calculations performed using the LISE++ code and theoretical models. The energy-loss straggling of the alpha particles at 5.486 MeV in Al, Cu, Ag, Tb, Ta, and Au was calculated by using the LISE++ code and the Titeica model. The results of the calculations were compared to the measured data to improve the accuracy of the straggling predictions. The results show that the straggling is increased by the energy loss at a rate of 8.0 keV/%. The uncertainties of the LISE++ and Titeica calculations were reduced to about 15% by adding fitting parameters. We also propose a new semi-empirical formula which well reproduces the measured data with an uncertainty of about 20% for 5.486-MeV alpha particles in the materials used in the research.

Methodology to extract constitutive equation at a strain rate level from indentation curves

Nguyen, Ngoc-Vinh,Kim, Jung J.,Kim, Seung-Eock Elsevier 2019 International journal of mechanical sciences Vol.152 No.-

<P><B> <B>Abstra</B>ct</B></P> <P>In this study, a methodology to determine constitutive equation at a strain rate level from indentation curves was proposed. The constitutive equation for structural steel consists of elastic modulus (<I>E</I>), yield strength (σ<SUB> <I>y</I> </SUB>), work hardening (<I>n</I>), and a plastic property (α) that represents the plastic plateau stage of structural steel. Four dimensionless equations that show the basic relationship between constitutive parameters, strain rate, and the characteristics of the loading-unloading curve were established. A finite element model to simulate the indentation process was developed for the necessity of constructing four accurate dimensionless equations in the forms of third order polynomial equations. The proposed methodology was then used to determine constitutive equations at a strain rate level from indentation curves for SS400 and SM490 structural steel. The resultant constitutive equations were validated through loading tensile tests for SS400 and SM490 structural steel. Moreover, the proposed methodology was used to determine the strain rate sensitivity of SM490 steel via nanoindentation experiments.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A method to extract a constitutive equation from indentation curves was proposed. </LI> <LI> Six dimensionless equations were constructed by performing the dimensional analysis. </LI> <LI> FE models were developed for the necessity of constructing dimensionless equations. </LI> <LI> The new method was used to estimate constitutive equations of SS400 and SM490 steel. </LI> <LI> The resultant constitutive equations were validated through experimental verification. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Strain rate sensitivity behavior of a structural steel during low-cycle fatigue investigated using indentation

Nguyen, Ngoc-Vinh,Pham, Thai-Hoan,Kim, Seung-Eock Elsevier 2019 Materials science & engineering. properties, micro Vol.744 No.-

<P><B>Abstract</B></P> <P>In this study, a series of experiments consisting of low-cycle fatigue, constant loading rate indentation, creep indentation experiments, optical microscopy examination, and transmission electron microscopy were performed to investigate the strain rate sensitivity behavior of SS400 structural steel under cyclic loading conditions. 400 indentations were conducted in the displacement control mode at different strain rate indentations varied from 0.02 s<SUP>−1</SUP> to 0.2 s<SUP>−1</SUP> and the effects of strain rate indentation on mechanical properties were investigated on four fatigue failure specimens. An analytical method was used to estimate mechanical properties of the structural steel from the loading/unloading curves. The results indicated that the yield strength and the strain hardening exponent strongly depended on both the strain rate indentation and the strain amplitude. Yield strength and strain hardening exponent tended to increase when the strain amplitude increased. The strain rate sensitivity (SRS) was also determined from the yield strength and the creep indentation data, and the dependency of the strain rate sensitivity on the strain amplitude level was examined. The results showed that the strain rate sensitivity exhibited decrease almost linearly when the strain amplitude increased from 0.4% to 1.0%. The results of the present study were used to assess and understand the strain rate sensitivity behavior of SS400 structural steel during low-cycle fatigue.</P>

Key Determinants of Repurchase Intention toward Organic Cosmetics

Phuong Ngoc Duy NGUYEN,Vinh Tan NGUYEN,Nguyen Ngoc Thao VO 한국유통과학회 2019 The Journal of Asian Finance, Economics and Busine Vol.6 No.3

This paper aims to discover factors and their influences degree to repurchase organic cosmetic in Vietnam. In addition, this research also discloses the main segments that have high demand re-buying intention based on demographic groups of gender, age, income, educational level, job, type of products, and place of production. Twenty-eight scale was designed based on previous studies and adjusted to match the 5-point Likert scale to conduct measurement. By using survey method to test hypotheses and set up conceptual models to collect 295 Vietnamese consumers who have experience in consuming organic cosmetic by explain the results through Smart PLS software. The findings show that there is positive attitude of customers to the intention of acquiring organic cosmetics, green perceived and customer satisfaction. In addition, customer satisfaction, knowledge of products, safety values, and environmental protection consciousness also play important roles to form a positive attitude of customers for products. Moreover, the consciousness of green living of consumers accounts for a high proportion in creating customer satisfaction for organic products. The results show useful information for current premises to determine the factors that influence the decision to repurchase organic cosmetic product, that provide business strategies.

An Approximation of the Synthesis Cross Section for the Unknown 126th Element via 58Ni + 251Cf and 64Zn + 248Cm Combinations

Duy Nguyen Ngoc,Ho Phuong-Thao,Pham Vinh N. T.,Hoan Nguyen Thi Thu 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.1

In this paper, we estimate the production cross section of the unknown super-heavy nuclei 309, 312126 via 58Ni + 251Cf and 64Zn + 248Cm combinations by using approximation methods. For each reaction, the competition between compound nucleus (CN) formation and quasi-fission process is also analyzed. We found that the synthesis cross section for the 309126 isotope is about 3 fb, which is about 5 orders of magnitude higher than that for the 312126 nucleus. The results also suggest that a valley exists around the isotope with A = 313 in the production yields for the 126th element. Moreover, the synthesis of the 310-317126 isotopes is still a challenge for experimental techniques due to the small cross sections, which are less than 1 fb.

Prediction of the Spin-Parities and the Magnetic Moments for the Ground States of Proton-rich Nuclei with Z = 21–30

Ly Nguyen Duy,Xayavong Latsamy,Uyen Nguyen Kim,Pham Vinh N. T.,Hao T. V. Nhan,Duy Nguyen Ngoc 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.11

The present paper reports on the spin-parities and the magnetic moments for the ground states of 44 proton-rich isotopes with Z = 21-30 and A = 36-57, which are important for studies of either reaction rates in X-ray bursts or nuclear structure. These nuclear properties were calculated based on the single-particle shell model. The spins of the concerned nuclei were compared to available experimental data adopted from the NuDat database to evaluate the variations in the astrophysical rates of the rp-process reactions. We found discrepancies, due to the deformed nuclear structure, between the present results and those reported in the NuDat database. The spin uncertainties result in large variations, 13% - 200%, in the astrophysical rates of the rp-process reactions. In particular, the spin uncertainties of the 44V and the 46-49Mn isotopes significantly affect the astrophysical rates of the reverse reactions of the proton captures 43Ti(p,γ)44V$(p,γ)45Cr, 45Cr(p,γ)46Mn(p,γ)47Fe, 47Mn(p,γ)48Fe, 47Cr(p,γ)48Mn(p,γ)49Fe, and 48Cr(p,γ)49Mn(p,γ)50Fe. Moreover, the magnetic moments of most of the isotopes were predicted for the first time. The results show that the magnetic moments are in the order of μp(1f7/2) > μp(2p3/2) > μn(1d3/2)> μn(1f7/2) for the nuclei having an unpaired nucleon in the proton/neutron shells. The present study suggests that reliable calculations and/or measurements for the properties of proton-rich nuclei are highly demanded.

ROBUST TRAFFIC LIGHT DETECTION AND CLASSIFICATION UNDER DAY AND NIGHT CONDITIONS

Phuc Manh Nguyen,Vu Cong Nguyen,Son Ngoc Nguyen,Linh My Thi Dang,Ha Xuan Nguyen,Vinh Dinh Nguyen 제어로봇시스템학회 2020 제어로봇시스템학회 국제학술대회 논문집 Vol.2020 No.10

Recently, traffic light detection and classification systems have been studied and developed to build an autonomous car by many research institutes, universities, and companies. However, the results of existing traffic light detection systems are still not stable under day and night conditions. It is difficult to detect the location of traffic light due to their small size. Moreover, traffic lights’ shapes are also similar to advertisement lights in a city road. Therefore, this paper proposed a new approach to improve the performance of existing traffic light detection systems by using the benefits of hand-crafted features and deep learning techniques. Experimental results show that the proposed system obtained the detection rate of 80% under night conditions, while the color-based density method only got the detection rate of 50.43% under night conditions.