• Coupled systems mechanics
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• 제11권6호
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• pp.485-504
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• 2022

This paper presents nonlinear oscillations of a carbon nanotube reinforced composite beam subjected to lateral harmonic load with damping effect based on the modified couple stress theory. As reinforcing phase, three different types of single walled carbon nanotubes distribution are considered through the thickness in polymeric matrix. The non-linear strain-displacement relationship is considered in the von Kármán nonlinearity. The governing nonlinear dynamic equation is derived with using of Hamilton's principle.The Galerkin's decomposition technique is utilized to discretize the governing nonlinear partial differential equation to nonlinear ordinary differential equation and then is solved by using of multiple time scale method. The frequency response equation and the forced vibration response of the system are obtained. Effects of patterns of reinforcement, volume fraction, excitation force and the length scale parameter on the nonlinear responses of the carbon nanotube reinforced composite beam are investigated.

• 여성건강간호학회지
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• 제24권1호
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• pp.33-48
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• 2018

Purpose: The purpose of this study was to develop a scale to evaluate parenting stress of international marriage immigrant women from Vietnam and the Philippines. Methods: The concept of parenting stress of international marriage immigrant women was analysed with a hybrid model. Data were collected from 273 international marriage immigrant women from Vietnam and the Philippines who were raising their children aged 1 to 6 years. These collected data were subjected to exploratory factor analysis, multitrait/multi-item matrix assessment, Pearson correlation coefficient analysis, and Cronbach's alpha internal consistency measurement. Results: The final instrument consisted of 28 items. The following six factors were extracted by exploratory factor analysis: 'insufficiency of parenting support system', 'role burden of mothers', 'maladjustment of children', 'confusion of parenting methods due to cultural differences', 'unskilled Korean communication', and 'ordinary difficulties'. Construct validity (factor analysis, convergent validity, and discriminant validity) and criterion-related validity were confirmed. Cronbach's ${\alpha}$ value of total items was .92(95% CI .91-.94). Cronbach's ${\alpha}$ of values for these factors ranged from .76 to .85. Conclusion: The parenting stress scale for international marriage immigrant women is a valid and reliable tool.

• 한국전산구조공학회논문집
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• 제19권4호
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• pp.429-440
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• 2006

이 연구의 목적은 두 가지로 대별할 수 있다. 첫째는, 베리오그램 모델링에 기초를 둔 정규크리깅 보간법의 p-적응적 유한요소법으로의 적용성이다. 둘째는, 수정된 초수렴 팻취복구 기법을 사용한 사후오차평가기와 연계된 계층적 p-체눈 세분화의 적응적 유한요소 과정을 제시하는 것이다. 가중치를 부여한 보간기법중의 하나인 정규크리깅 방법은 가우스 적분점에서의 응력데이타로 부터 소위 준정해를 얻는데 적용된다. 가중치를 동일하게 가정하는 종래의 보간기법과는 달리 실험적 및 이론적 베리오그램을 작성한 후 보간을 위한 가중치를 결정하게 된다. 한편, 적응적 p-체눈 세분화는 해석영역의 각 체눈에서 p-차수를 만족할만한 정확도를 얻을 수 있도록 프로그램내에서 자동으로 사후오차평가를 통해 불균등 또는 선택적으로 증가시킨다. 수정된 초수렴 팻취복구기법을 검증하기 위해 극한치를 사용한 새로운 오차평가기가 제안된다. 제안된 알고리즘의 정당성은 선형탄성파괴역학의 대표적 문제들인 중앙균열판, 일변균열 및 양변균열 해석을 통해 테스트되었다.

• 한국치위생학회지
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• 제16권3호
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• pp.435-446
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• 2016

Objectives: The purpose of the this study is to investigate parenting stress of married dental hygienists having preschool and school aged children. Methods: A self-reported questionnaire was completed by 242 married dental hygienists from September to December, 2015 via e-mail and ordinary mail. The questionnaire consisted of demographics, job-related characteristics, family life satisfaction, and parenting stress. The data were analyzed using Stata 13.0 program. Results: As for job-related characteristics, 36.6% of the subjects answered 'not possible' in work hour flexibility. The reasons why family-work balance is difficult were 'parenting and education(58.7%)' and 'burden of family-work balance(32.4%)'. Family life satisfaction was 3.03, and parenting stress was 2.41. Parenting stress gets higher if their children are younger, monthly income is lower, and mother/father's age are lower. And parenting stress becomes higher if their career as dental hygienists is less, they are contract worker, and frequency to change jobs is higher. Concerning the reason why work-family balance is difficult, parenting stress is found to be high when they choose 'parenting and education', 'burdens of work-family balance', and 'relationship in workplace'. Family life satisfaction reduced parenting stress. According to the results of multiple linear regression analysis, frequency to change job influences parenting stress. Conclusions: Parenting stress increases turnover and career interruption of married dental hygienists. It is hard to improve work environment without policy support. It will be necessary to establish policy for employed mothers and create a work atmosphere where the policy can be utilized without difficulty.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2002년도 학술.기술논문발표회
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• pp.29-36
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• 2002

High fluid concrete unlike OPC concrete is made with various material, and the phase of fresh concrete is considerably different. In order to understand fluidity phase and mix properties of high fluid concrete, concrete is required to access as suspension structure which consists of aggregate and paste. The focus of this paper is to analyze the test results and quantify the effect of mix proportions of molar and fineness modulus of ,and on the properties of fresh mortar. The effect of water-binder ratio, sand-binder ration, content; of ggbs (by mass of total cementitious materials), and various contents of water reducing agent on the yield stress and plastic viscosity of the mix is studied. Based on the experimental results, the following conclusion; can be drawn: (1) The mixing time needed (or high fluid mortar was approximately two times more than that of ordinary portland mortar. (2) The fluidity phase of mortar could be explained by yield stress of mix and the fluidity of mortar. (3) As the content of ggbs increased, yield stress of mortar was decreased and plastic viscosity of it was increased. (4) For the high fluid mortar, it was appeared that sand-binder ratio should be below 1.5.

• 비파괴검사학회지
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• 제29권3호
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• pp.214-218
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• 2009

The occlusal force of the tooth leads to loss of tooth tissue owing to attrition and abrasion, and may cause abfraction and pathological change of the dentin. Thus, we developed finite element models, examined them by applying ordinary occlusal force, and analyzed the stress distribution. Specimens used were mandibular first premolars from 15 Korean males and 13 females and were made into finite element models from medical images that were obtained using a Micro-CT. We have found that the irregular feature of the tooth is not only useful to masticating and pronouncing as well known, but it is also suitable for protecting inner tissue by dispersing stress and delivering proper pressure to periodontal tissue to continue a physiological action. Also, image analysis could let us know the factor that is the cause of a disorder due to stress concentration in the cervical line. These results are expected to support the field of dental treatment planning, operating procedure and clinical trial, and the advance of technical expertise to develop implants and dentures.

• Journal of Mechanical Science and Technology
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• 제20권11호
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• pp.1920-1933
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• 2006

Piezoelectric materials produce an electric field by deformation, and deform when subjected to an electric field. The coupling nature of piezoelectric materials has acquired wide applications in electric-mechanical and electric devices, including electric-mechanical actuators, sensors and structures. In this paper, a hollow sphere composed of a radially polarized spherically anisotropic piezoelectric material, e.g., PZT_5 or (Pb) (CoW) $TiO_3$ under internal or external uniform pressure and a constant potential difference between its inner and outer surfaces or combination of these loadings has been studied. Electrodes attached to the inner and outer surfaces of the sphere induce the potential difference. The governing equilibrium equations in radially polarized form are shown to reduce to a coupled system of second-order ordinary differential equations for the radial displacement and electric potential field. These differential equations are solved analytically for seven different sets of boundary conditions. The stress and the electric potential distributions in the sphere are discussed in detail for two piezoceramics, namely PZT _5 and (Pb) (CoW) $TiO_3$. It is shown that the hoop stresses in hollow sphere composed of these materials can be made virtually uniform across the thickness of the sphere by applying an appropriate set of boundary conditions.

• 기본간호학회지
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• 제26권2호
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• pp.75-85
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• 2019

Purpose: The purpose of this study was to examine effects of music intervention on environmental stress and sleep quality in liver transplant patients who are receiving care in one-person isolation rooms of an ICU. Methods: The study was a quasi-experimental design pre-and-post nonequivalent control group. Participants were 37 patients (18 in the experimental group and 19 in the control group) who, after receiving liver transplant, were hospitalized in one-person isolation rooms of the ICU. The study covered patients admitted between August 2016 and December 2017. Earplugs and sleep shades were provided as ordinary care to both experimental and control groups, and music intervention was provided to the experimental group three times a day for 30 minutes each from the first day of hospitalization. Results: The first hypothesis, "The experimental group who received music intervention will experience a lower environmental stress level than the control group" was supported (Z=-3.212, p<.001). The second hypothesis, "The experimental group who received music intervention will experience a higher sleep quality than the control group" was also supported (t=3.715, p=.001). Conclusion: Findings show that music intervention is an effective nursing intervention to reduce environmental stress and improve sleep quality in liver transplant patients in the ICU.

• 디지털산업정보학회논문지
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• 제13권1호
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• pp.173-183
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• 2017

The purpose of this study is to find out the difference of sense of self-efficacy and stress encountering strategy of university students under the stress situation depending on the smart-phone user group (addiction group, general user group). For this purpose, the study issues are established as follows. First, it has analyzed what is the correlation of smart-phone addiction, sense of self-efficacy, and stress encountering strategy. Second, it has studied if there is any difference of sense of self-efficacy and stress encountering strategy for the smart-phone user group. In order to verify such study issues, For 1,670 university students in the Chungcheong area, smart-phone addiction scale, sense of self-efficacy scale, and stress encountering method scale were administered. Looking into the study result, first, as a result of the relativity analysis, it displayed the correlation of preference of test difficulty, self-control efficacy and important negative from the smart-phone addiction and sense of self-efficacy. In addition, all sub-variables of smart-phone addiction and avoidance orientation from the stress encountering strategy displayed the important positive correlation, and from the smart-phone addiction, the virtual world orientation and pursuit of social-support displayed the important negative correlations, and all sub-variables (interference with ordinary living, virtual world striving direction, withdrawal, resistance) of smart-phone addiction and problem solving-orientation displayed the negative correlation. Second, as a result of verification for the difference of the smart-phone addiction group and general use group following the sense of self-efficacy, the general use group is shown to have higher self-control efficacy sense than the addiction group. And third, as a result of verifying the difference of stress encountering following the smart-phone addiction group and general use group, the addiction group is shown to be lower than the general use group in terms of social support pursuit and problem solution orientation with the avoidance orientation shown to be higher. This type of result is expected to provide the base data when developing the smart-phone addiction preventive education program by finding out in details for the characteristics of smart-phone addiction group for university students.

• Steel and Composite Structures
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• 제17권1호
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• pp.105-121
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• 2014

A fundamental limitation of steel structures is the decrease in their load-bearing capacity at high temperatures in fire situations such that structural members may require some additional treatment for fire resistance. In this regard, this paper evaluates the structural stability of fire-resistant steel, introduced in the late 1999s, through tensile coupon tests and proposes some experimental equations for the yield stress, the elastic modulus, and specific heat. The surface temperature, deflection, and maximum stress of fire-resistant steel H-section columns were calculated using their own mechanical and thermal properties. According to a comparison of mechanical properties between fire-resistant steel and Eurocode 3, the former outperformed the latter, and based on a comparison of structural performance between fire-resistant steel and ordinary structural steel of equivalent mechanical properties at room temperature, the former had greater structural stability than the latter through $900^{\circ}C$.