• 한국자원식물학회지
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• 제17권3호
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• pp.257-264
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• 2004

Selection of stress-tolerant ginseng lines in fields is very difficult because it is almost impossible to control properly the environmental conditions of soil. On the contrary, it can be studied with ease to search for stress-tolerant ginseng lines through in vitro culture because of easy manipulation of stress conditions. This study was conducted for the selection of ginseng pure lines tolerant to salt stress. Murashige ＆amp; Skoog(MS) media with 2.5 folds of KNO$_3$, NH$_4$NO$_3$, MgSO$_4$.7$H_2O$, KH$_2$PO$_4$, and CaC1$_2$.2$H_2O$ was established for the selection of ginseng pure lines tolerant to salt stress in vitro. Among 88 ginseng pure lines bred by Korea Ginseng and Tobacco Research Institute, Punggi Hwangsuk, 78093, 82886, 78135, 86024 and KG104 lines was tolerant to salt stress. For the stable production of quality Korean ginseng, genetic tolerance to salt stress is one of important factors since relatively high salt concentrations in the ginseng nursery soil environment of Korea. Ginseng inbred pure lines were tested for their tolerance to salt stress through in vitro culture technique.

• Smart Structures and Systems
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• 제26권3호
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• pp.331-343
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• 2020

In this paper, based on the CPT, motion equations for a sandwich plate containing a core and two integrated face-sheets have derived. The structure rests on the Visco-Pasternak foundation, which includes normal and shear modules. The piezo-magnetic core is made of CoFe₂O₄ and also is subjected to 3D magnetic potential. Two face sheets at top and bottom of the core are under electrical fields. Also, in order to obtain more accuracy, the effect of flexoelectricity has took into account at face sheets' relations in this work. Flexoelectricity is a property of all insulators whereby they polarize when subject to an inhomogeneous deformation. This property plays a crucial role in small-scale rather than macro scale. Employing CPT, Hamilton's principle, flexoelectricity considerations, the governing equations are derived and then solved analytically. By present work a detailed numerical study is obtained based on Piezoelectricity, Flexoelectricity and modified couple stress theories to indicate the significant effect of length scale parameter, shear correction factor, aspect and thickness ratios and boundary conditions on natural frequency of sandwich plates. Also, the figures show that there is an excellent agreement between present study and previous researches. These finding can be used for automotive industries, aircrafts, marine vessels and building industries.

• 식품보건융합연구
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• 제7권5호
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• pp.19-31
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• 2021

The purpose of this study is to examine whether there is a mediating effect of hopelessness the relationship between perceived stress and suicidal ideation in college students. For this study, a survey was conducted on perceived stress, suicidal ideation, and mental health, self-esteem, problem drinking, and stress among 103 college studentsin Gyeonggi do. The results of this study are as follows. It was found that COVID-19 correlated with perceived stress, hopelessness, and suicidal ideation of college students. The hopelessness completely mediated between perceived stress and suicidal thoughts of college students, which is consistent with previous studies. This study is meaningful in that it confirmed relationship between the perceived stress, hopelessness, and suicidal ideations in college students due to COVID-19, reflecting the new situation of the times. Coronavirus will worsen people's mental health disorders and cause new stress-related disorders. Therefore, mental health researchers, clinicians, and people working in trauma-related fields should find ways to reduce the incidence of coronavirus-related trauma stress and prevent its effects. It is necessary to expand the psychological vaccine program to improve the resilience of the public. Since there are individual differences in resilience, it is necessary to strengthen the psychological vaccine program for each subject considering resilience.

• Steel and Composite Structures
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• 제50권2호
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• pp.237-247
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• 2024

Research on interfacial crack formation in orthotropic bi-materials has experienced a notable increase in recent years, driven by growing concerns about structural integrity and reliability. The existence of a crack at the interface of bi-materials has a substantial impact on mechanical strength and can ultimately lead to fracture. The primary objective of this article is to introduce a comprehensive analytical model and establish stress relationships for investigating interfacial crack between two non-identical orthotropic materials with desired crack-fiber angles. In this paper, we present the application of the Interfacial Maximum Tangential Stress (IMTS) criterion, in combination with the Reinforcement Isotropic Solid (RIS) model, to investigate the behavior of interfacial cracks in orthotropic bi-materials under mixed-mode I/II loading conditions. We analytically characterize the stress state at the interfacial crack tip using both Stress Intensity Factors (SIFs) and the T-stress term. Orthotropic materials, due to their anisotropic nature, can exhibit complex crack tip stress fields, making it challenging to predict crack initiation behavior. The secondary objective of this study is to employ the IMTS criterion to predict the crack initiation angle and explore the notable impact of the T-stress term on fracture behavior. Furthermore, we validate the effectiveness of our approach in evaluating Fracture Limit Curves (FLCs) for interfacial cracks in orthotropic bi-materials by comparing our FLCs with relevant experimental data from existing literature.

• 대한안전경영과학회지
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• 제18권1호
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• pp.89-97
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• 2016

This current research investigated whether job stress mediates the relationship between physical environment and safety behavior of members in organization. Furthermore, we hypothesized that safety climate functions as moderator between physical environment-job stress link. In order to examine the hypotheses, 870 employees in various fields of companies were sampled. Using structural equation modeling(SEM), we conducted moderated mediation model analysis which cab elaborately test the significance of our hypotheses. The results showed that job stress mediated the link between physical environment and safety behavior of members. Moreover, the relationship between physical environment and job stress was moderated by safety climate. The implications and limitations of our study and suggestions for future research were discussed.

• Structural Engineering and Mechanics
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• 제33권5호
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• pp.573-588
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• 2009

In this paper a four-node hybrid stress element is proposed for analysing arbitrarily shaped plates on a two parameter elastic foundation. The element is developed by combining a hybrid plate stress element and a soil element. The formulation is based on Hellinger-Reissner variational principle in which both inter element compatible boundary displacement and equilibrated stress fields for the plate as well as the foundation are chosen separately. This formulation also allows a low order polynomial interpolation functions. Numerical examples are presented to show that the validity and efficiency of the present element for the plate analysis resting on an elastic foundation. In these examples the effect of soil depth, interaction between closed plates on soil parameters, comparison with Winkler hypothesis is investigated.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.286-291
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• 2001

Applications of bonded dissimilar materials such as IC package, ceramic/metal and resin/metal bonded joints, are very increasing in various industry fields. It is very important to analyze the thermal stress and stress singularity at interface edges in bonded joints of dissimilar materials. In orer to understand the package crack emanating from the edge of Die pad and Resin, fracture mechanics of bonded dissimilar materials and material properties are obtained. In this paper, the thermal stress and its singularity index for the IC package were analyzed using 2-dimensional elastic boundary element method. Crack propagation angle and path by thermal stress were numerically simulated with boundary element method.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.111-116
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• 2000

A semi-infinite interfacial crack propagated with constant velocity in two bonded anisotropic strip under out-of-plane clamped displacements is analyzed. The asymptotic stress and displacement fields near the crack tip are obtained, where the results get more general expressions applicable not only to isotropic/orthotropic materials but also to the extent of the anisotropic material having one plane of elastic symmetry for the interfacial crack. The dynamic stress intensity factor is obtained as a closed form, which is decreased as the velocity of crack propagation increases. The critical velocity where the stress intensity factor comes to zero is obtained, which agrees with the lower value between the critical values of parallel crack merged in the material 1 and 2 adjacent to the interface. The dynamic energy release rate is also obtained as a form related to the stress intensity factor.

• 아동학회지
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• 제27권1호
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• pp.17-30
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• 2006

The goal of this research was to clarify how a child's maladjustment affects the teacher-child relationship and leads to teaching stress. Subjects were 178 teacher-child pairs in kindergartens or day care centers. The child was 3 to 5-years-old and perceived by its teacher as having maladjusted behavior. Teachers responded to the Index of Teaching Stress(Greene, Abidin, & Kmetz, 1997) and the Student-Teacher Relationships Scale(Pianta 1991). The maladjusted behaviors observed by teachers were correlated with each other. ADHD was the biggest problem perceived by teachers. Most fields of maladjusted children's behaviors caused stress to teachers except those of intellectual deficit and academic Problems. Frustration peaked during the teaching process. More severely maladjusted behaviors resulted in greater conflict in teacher-child relationships.

• 한국분말재료학회지
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• 제27권4호
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• pp.318-324
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• 2020

In the present work, an explicit finite element analysis technique is introduced to analyze the thermal stress fields present in the additive manufacturing process. To this purpose, a finite element matrix formulation is derived from the equations of motion and continuity. The developed code, NET3D, is then applied to various sample problems including thermal stress development. The application of heat to an inclusion from an external source establishes an initial temperature from which heat flows to the surrounding body in the sample problems. The development of thermal stress due to the mismatch between the thermal strains is analyzed. As mass scaling can be used to shorten the computation time of explicit analysis, a mass scaling of 108 is employed here, which yields almost identical results to the quasi-static results.