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Velocity equation for grenades while impacting on dry sand media

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Defence Technology（防务技术） 2024年第5期35卷 168-173页

作者： Martin Macko Xuan son Bui Kongsathit Phanthavong Duc Hung Pham van Gion Do van Minh Do Jiri Skala University of Defence BrnoCzech Republic le Quy Don Technical University Ha NoiViet Nam

This paper deals with the collision of sphere shape grenades with sand *** central issue of the article is the establishing of an empirical velocity equation of the grenade while impacting on sand that is used to solve motion equations of the mechanical mechanism inside the impact grenade *** paper focuses on impact velocities that are lower than 5 m s^(-1).An experiment was conducted to study the velocity of the grenade while impacting on dry sand.A high-speed camera video was used to capture the grenade *** grenade velocity in the impact process was generated from these video *** types of fitting curves are used to regress the velocity equation of the grenade while interacting with the sand media and the best-fitting model is *** result shows the regression curve has a high correlation with the experiment data for grenade velocities below 5 m s^(-1).The received regression equation is useful for analyzing the working ability of the inertial mechanism inside the impact grenade or analyzing and choosing the appropriate parameters of each part in the inertial mechanism to meet the required characteristics of the mechanism.

关键词： Dynamic response Impact velocity Impact grenade Low-velocity impact

Determination of the Pore Water Velocity Using a Salt Tracer Combined with Self-Potential Measurements

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Journal of Geoscience and Environment Protection 2023年第1期11卷 15-27页

作者： Huong Huynh Thi Thu son le van Hieu Tran Trong Hai Lai Viet Quang Nguyen Huu Luan Phan Thi Department of Tracer Techniques Center for Applications of Nuclear Technique in Industry Dalat Vietnam

The tracer technique is recommended as an effective tool in surveying abnormal seepage through lakes and dams. By injecting a tracer into a known upstream location and monitoring the appearance of the tracer in the downstream leak point, it is possible to determine the direction and the average water velocity of the preferential flow through the dam. The detailed result achieved depends on the number of samples and the sampling locations to analyze tracer concentration over time in the field. This study proposes to use noninvasive self-potential measurements to determine the location and time the salt tracer moves through the seepage zone. The connection between the potential signal according to the propagation of the NaCl salt tracer and the water velocity was demonstrated through an experiment on a sandbox model. Experimental results express a good agreement between the time to reach the maximum value of the potential variation and the salt concentration variation with the time that water comes to monitoring locations. The result indicates an ability to determine the pore water velocity of the seepage zone based on the recording of potential signals produced by a salt tracer movement. The salt tracer test using NaCl combined with self-potential measurements was then applied to survey a leaking earth dam in the Dong Nai river basin (Vietnam).

关键词： Earthen Dams Tracer Technique leakage Interstitial Velocity

Exploring the Interplay between Job Stress,Work Performance,and Attitudes toward Professional Psychological Help among Employees

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International Journal of Mental Health Promotion 2024年第7期26卷 531-545页

作者： Cong Minh le son van Huynh Ky Luu Quynh-Nhi Ngoc Ho van Thi le Nguyen Vinh-Long Tran-Chi Center for Mental Health Research and Support University of Social Sciences and HumanitiesVietnam National University Ho Chi Minh CityHo Chi Minh City700000Vietnam Faculty of Psychology Ho Chi Minh City University of EducationHo Chi Minh City700000Vietnam Faculty of Tourism College of BusinessUniversity of Economics Ho Chi Minh CityHo Chi Minh City700000Vietnam Scientific Management Department Dong A UniversityDa Nang500000Vietnam

Objective:This study explores the interplay between job stress,job-related factors,work performance,and attitudes toward seeking professional psychological help among Vietnamese ***:A total of 374 employees in Vietnam were surveyed using random sampling and an online questionnaire from November 07 to November 28,*** data and self-reported from three scales:The New Job Stress Scale(NJSS),Work Performance(WP),and Attitudes Toward Seeking Professional Psychological Help(ATSPPH_SF)were ***:Significant variations were found across several variables,including forms of work,operating hours,education levels,monthly income,numbers of daily working hours,and the presence of a psychological counseling department within the *** analysis has highlighted direct relationships between key latent *** who were more open to seeking professional help tended to report higher levels of job *** negative relationship was found between job stress and attitudes toward seeking professional ***,work effort was positively associated with work *** analyses revealed the influence of co-worker support on role expectation conflict and work effort,role expectation conflict and work-life balance,as well as interactions between role expectation conflict and attitudes needed toward seeking professional *** analyses showed that work effort mediated relationships between openness to seeking professional help,co-worker support,work-life balance,role expectation conflict,and work *** toward seeking professional help also mediated relationships between work-life balance,job stress,and work ***:The study highlights the complex dynamics surrounding job stress,job-related factors,work performance,and attitudes toward seeking professional psychological help among Vietnamese *** highlights the importance of addressing help-seeking barriers,promoting work engagement

关键词： Stress co-worker support work-life balance role expectation conﬂict professional psychological help-seeking

Transient responses of double-curved sandwich two-layer shells resting on Kerr's foundations with laminated three-phase polymer/GNP/fiber surface and auxetic honeycomb core subjected to the blast load

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Defence Technology（防务技术） 2024年第5期35卷 222-247页

作者： Nguyen Thi Hai van Thi Hong Nguyen Researcher&lecturer Faculty of Industrial EducationThe University of Danang-University of Technology and Education48 Cao ThangDanang550000Viet Nam Researcher&lecturer Faculty of Mechanical EngineeringThuyloi University175 Tay SonDong DaHanoi100000Viet Nam

This work uses refined first-order shear theory to analyze the free vibration and transient responses of double-curved sandwich two-layer shells made of auxetic honeycomb core and laminated three-phase polymer/GNP/fiber surface subjected to the blast *** of the two layers that make up the double-curved shell structure is made up of an auxetic honeycomb core and two laminated sheets of three-phase polymer/GNP/*** exterior is supported by a Kerr elastic foundation with three *** key innovation of the proposed theory is that the transverse shear stresses are zero at two free surfaces of each *** contrast to previous first-order shear deformation theories,no shear correction factor is ***'s exact solution was used to treat the double-curved shell problem with a single title boundary,while the finite element technique and an eight-node quadrilateral were used to address the other boundary *** ensure the accuracy of these results,a thorough comparison technique is employed in conjunction with credible *** problem model's edge cases allow for this kind of *** study's findings may be used in the post-construction evaluation of military and civil works structures for their ability to sustain explosive *** addition,this is also an important basis for the calculation and design of shell structures made of smart materials when subjected to shock waves or explosive loads.

关键词： Blast load Two-layer shell Polymer/GNP/Fiber surface Auxetic honeycomb Shear connectors

Peculiar Characteristics of （Vietnamese） Painting Language： Oil Painting and Contributions From Notable Painters Including le van Mien, Thang Tran Phenh and Nam son

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Journal of Literature and Art Studies 2017年第5期7卷 548-554页

作者： Nguyen van Doan (Wentuan Ruan) School of Art Hunan Normal University Hunan China Ho Chi Mirth City University of Fine Arts Ho Chi Mirth City Vietnam

This paper summarizes the painting artistry from three painters： le van Mien, Nam son, and Thang Tran Phenh with the following notable characteristics： realism, impressionism, and contemporary humanism. It is visible from their works that these three artists have managed to define their ways to create arts reflecting the Vietnamese people in the period of transition between 19th and 20th Century Vietnam. Contemporary humanism has always been a great aspiration to any painter in any time period. During the life and work of painters, it is the visible themes of human beings in their work that best reflect how the artists perceive life. While considered to be the pioneering figures in Vietnamese oil painting registry of art, the three painters le van Mien, Nam son, and Thang Tran Phenh all happened to favor the humanism theme in their oil painting works. There were two most commonly accepted explanations for this choice. First of all, most artistic geometry lessons for beginners often choose the human figure to be the starting model for study and creative development. Secondly, during the tram-century period when Eastern and Western cultures collided in Vietnam during the late 19th early 20th Century, humans and most notably the Confucianists were the most vivid storytellers of the day and age.

关键词： le van Mien Nam son Thang Tran Phenh oil painting

First Records of Megophrys daweimontis Rao and Yang, 1997 and Amolops vitreus(Bain, Stuart and Orlov, 2006)(Anura: Megophryidae, Ranidae) from Vietnam

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Asian Herpetological Research 2015年第1期6卷 66-72页

作者： Dzung Trung le Anh van PHAM son Hung Lan NGUYEN Thomas ZIEGleR Truong Quang NGUYEN Faculty of Biology Hanoi National University of Education Faculty of Biology and Chemistry Tay Bac University AG Zoologischer Garten Kln Institute of Ecology and Biological Resources Vietnam Academy of Science and Technology

Two amphibian species,Megophrys daweimontisandAmolops vitreus,are recorded for the ifrst time from Vietnam, on the basis of a new amphibian collection from Dien Bien and son La provinces. In addition, acoustic analysis ofA. vitreus is also provided based on the advertisement calls recorded in Muong Nhe Nature Reserve of Dien Bien Province, Vietnam.

关键词： Amolops vitreus Megophrys daweimontis new records advertisement call Dien Bien Province son La Province

Velocity equation for grenades while impacting on dry sand media

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Optimization of machine learning models for predicting the compressive strength of fiber-reinforced self-compacting concrete

Defence technology 2024年第5期 168页

作者： Martin Macko Xuan son Bui Kongsathit Phanthavong Duc Hung Pham van Gion Do van Minh Do Jiri Skala

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结构与土木工程前沿:英文版 2023年第2期17卷 284-305页

作者： Hai-van Thi MAI May Huu NGUYEN son Hoang TRINH Hai-Bang LY Civil Engineering Department University of Transport TechnologyHanoi 100000Vietnam Civil and Environmental Engineering Program Graduate School of Advanced Science and EngineeringHiroshima UniversityHiroshima 739-8527Japan

Fiber-reinforced self-compacting concrete(FRSCC)is a typical construction material,and its compressive strength(CS)is a critical mechanical property that must be adequately *** the machine learning(ML)approach to estimating the CS of FRSCC,the current research gaps include the limitations of samples in databases,the applicability constraints of models owing to limited mixture components,and the possibility of applying recently proposed *** study developed different ML models for predicting the CS of FRSCC to address these *** neural network,random forest,and categorical gradient boosting(CatBoost)models were optimized to derive the best predictive model with the aid of a 10-fold cross-validation technique.A database of 381 samples was created,representing the most significant FRSCC dataset compared with previous studies,and it was used for model *** findings indicated that CatBoost outperformed the other two models with excellent predictive abilities(root mean square error of 2.639 MPa,mean absolute error of 1.669 MPa,and coefficient of determination of 0.986 for the test dataset).Finally,a sensitivity analysis using a partial dependence plot was conducted to obtain a thorough understanding of the effect of each input variable on the predicted CS of *** results showed that the cement content,testing age,and superplasticizer content are the most critical factors affecting the CS.

关键词： compressive strength self-compacting concrete artificial neural network decision tree CatBoost

Engineering a light–matter strong coupling regime in perovskite-based plasmonic metasurface: quasi-bound state in the continuum and exceptional points

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Photonics Research 2020年第12期8卷 I0005-I0014页

作者： leRAN LU QUYNH le-van LYDIE FERRIER EMMANUEL DROUARD CHRISTIAN SEASSAL HAI son NGUYEN Universitéde Lyon Institut des Nanotechnologies de LyonINL/CNRSEcole Centrale de Lyon36 avenue Guy de Collongue69130 EcullyFrance College of Engineering and Computer Science VinUniversityHanoi 14000Vietnam Universitéde Lyon Institut des Nanotechnologies de LyonINL/CNRSINSA-Lyon7 avenue Jean Capelle69621 VilleurbanneFrance Institut Universitaire de France(IUF) ParisFrance

We present theoretically the formation of exciton–photon polaritons and exciton-surface plasmon polaritons in a perovskite-based subwavelength lattice on the metallic *** is shown that the later polaritons will be achieved as the perovskite layer is ultra-thin(le the co-existence of both polaritons will dominate,as the thickness of the perovskite metasurface approaches *** the two cases,the lower polaritonic branches consist of dark and bright modes corresponding to infinite and finite radiative quality factors,*** salient property in this work is that it allows one to obtain exceptional points(EPs)in momentum space with a four-fold enhancement of local density of states through engineering the perovskite *** findings show that the perovskite metasurface is an attractive and rich platform to make polaritonic devices,even with the presence of a lossy metallic layer.

关键词： surface. perovskite exceptional