• 대한간호학회지
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• 제6권1호
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• pp.72-79
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• 1976

Contemper nursing literature place much importance on human- centered and individualized care. Nursing research has related stress during hospitalization of adolescent patients to adaptation to a new environment, isolation from friends, limitation due to illness, over protection of parents and communication with member of the medical team. The investigator conducted this study in the hope that an understanding of adolescents responses to hospitalization, their perceptions, the kinds and levels of stress, and the relationships between stressors and individual characteristics would contribute to the improvement of adolescent patient care. The objective of the study was to obtain informations related to the adolescents psychological stress experience during hospitalization, specifically stress from interpersonal relationships and communication, isolation from the family, social or economic problems, illness and from the treatment environment and nursing care. An interview schedule adopted from Holmes and Rahe's Social Readjustment Rating Scale and selected items from Voicer's instrument on stress-producing events was used with 120 adolescent inpatients aged 13 to 18 years three general hospitals in Seoul during Aug. 10, to Sep. 30, 1975. 1. The sample consisted of 66 male and 54 female patients. Sixty-six percent were late adolescents, aged 16 to 18 years: 4% were early adolescents, aged 13 to 15 years. The primary cause for hospitalization was for orthopedic problems (35.8%). More than half of these (54.4%) were due to injury or accident. 2. Stress eclated to illness revealed the highest score (4.97), followed by stress related to treatment environment and nursing care (4.34) , isolation from family and social or economic problems (4.01) and interpersonal relationships and communication (3.96). 3. The perceived indifference of doctors and nurses was a serious cause of stress (mean=4.83). Fellow patients and visitors caused least stress (mean=2.06). 4. Discontinuation of education or unemployment were major stressful events (mean=4.71). Least stressful was isolation from the family (mean=3.47). 5. More than 94% of the respondents expressed fears related to body image (mean=4.97) 6. Within the category of treatment environment and nursing care, items related to restrictions because of treatment, discomfort because of treatment, inadequate explanation from nurses about procedures were rated as severe stress events (mean=4.6). Items related to the ward environment and to having a relative stay with them were seen by the group as less serious events (mean=3.7). 7. Stress related to interpersonal relationships and communication was correlated positively with female patients and those preferring passive activities. (P〈0.05) 8. Stress related to family problems was positively related to female and early adolescent patients (P< 0.05). Stress related to social problems was positively , elated to students and those preferring active pursuits (P< 0.05). 9. There were no correlation between the high stress related to disease and any of the characteristic items. (P> 0.05) 10. Stress related to treatment environment and nursing care was positively related of early adolescent and female and student patients. (P< 0.05) This group of hospitalized adolescents reported high level of stress related to treatment environment and nursing care, due to lack of consideration of normal growth and development and individual characteristics. The findings have important implications for the planning of effective, individualized, comprehensive nursing care of adolescents during hospitalization.

• 한방재활의학과학회지
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• 제20권4호
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• pp.147-157
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• 2010

Objectives : The study is performed to investigate the influence of psychological stress on neck muscles tone and heart rate variability(HRV). Methods : This study was carried out with the data from stress response index score(SRI), surface electromyography(sEMG) and HRV. First subjects were divided into two group according to the SRI points. Subjects in group A had points of SRI in which lower than 30 points. Subjects in group B had points of SRI in which higher than 30 points. Then we investigated how to difference of the index of sEMG and HRV according to each groups. Results : In this study, the muscle contraction of both upper trapezius muscle in stress group were higher than non-stress group significantly. Complexity, root mean square of successive differences of R-R intervals(RMSSD), standard deviation difference between adjacent normal to normal intervals(SDSD), high frequency oscillation power(Ln(HF)), normalized HF(Norm HF) in stress group were lower than non-stress group significantly and normalized LF(Norm LF) was higher. Conclusions : This results show that the stress was associated with neck muscle condition and autonomic nervous system.

• 대한기계학회논문집A
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• 제24권2호
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• pp.472-480
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• 2000

A macroscopic yield criterion for porous solids with pressure-sensitive matrices modeled by Coulomb's yield criterion was obtained by generalizing Gurson's yield criterion with consideration of the hydrostatic yield stresses for a spherical thick-walled shell and by fitting the finite element results of a voided cube. The macroscopic yield criterion is valid for negative mean normal stresses as well as for positive mean normal stresses. From the yield criterion, a plastic potential function for the porous solids was derived either for plastic normality flow or for plastic non-normality flow of pressure- sensitive matrices. In addition, the elastic relation, an evolution equation of the plastic flow stress of the matrices and an evolution equation of the void volume fraction were presented to complete a set of constitutive relations. The set of constitutive relations was implemented into a finite element code ABAQUS to analyze the material behavior of rubber-toughened epoxies. The cavitation and the deformation behavior were analyzed around a crack tip under three-point bending and around notch tips under four-point bending. In the numerical analyses, the cavitation of rubber particles was considered via a stress-controlled nucleation model. The numerical results indicate that a reasonable cavitation zone can be obtained with void nucleation controlled by the macroscopic mean normal stress, and a plastic zone is smaller around a notch tip under compression than under tension. These numerical results agree well with corresponding experimental results on the cavitation and plastic zones.

• 품질경영학회지
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• 제23권1호
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• pp.15-28
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• 1995

We consider a step-stress life testing which is devised for a two-component parallel system with considerably long life time. To describe such a system, we use an exponential distribution as the survival function. The lift distribution is assumed between the log mean life time and the stress with the cumulative exposure model. The criterion for optimality is to minimize the sum of the variances of the maximum likelihood estimators of the mean life times of each part under the normal stress.

• Archives of Plastic Surgery
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• 제49권1호
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• pp.115-120
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• 2022

Background In addition to vascular endothelial cells, vascular smooth muscle cells (VSMCs) are subject to continuous shear stress because of blood circulation. The angiogenic properties of VSMCs in extracranial arteriovenous malformations (AVMs) may exceed those of normal blood vessels if the body responds more sensitively to mechanical stimuli. This study was performed to investigate the hypothesis that rapid angiogenesis may be achieved by mechanical shear stress. Methods VSMCs were obtained from six patients who had AVMs and six normal controls. The target genes were set to angiopoietin-2 (AGP2), aquaporin-1 (AQP1), and transforming growth factor-beta receptor 1 (TGFBR1). Reverse-transcriptase polymerase chain reaction (RT-PCR) and real-time PCR were implemented to identify the expression levels for target genes. Immunofluorescence was also conducted. Results Under the shear stress condition, mean relative quantity values of AGP2, AQP1, and TGFBR1 in AVM tissues were 1.927±0.528, 1.291±0.031, and 2.284±1.461 when compared with neutral conditions. The expression levels of all three genes in AVMs were higher than those in normal tissue except for AQP1 under shear stress conditions. Immunofluorescence also revealed increased staining of shear stress-induced genes in the normal tissue and in AVM tissue. Conclusions Shear stress made the VSMCs of AVMs more sensitive. Although the pathogenesis of AVMs remains unclear, our study showed that biomechanical stimulation imposed by shear stress may aggravate angiogenesis in AVMs.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.220-225
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• 2004

The mesh-insensitive structural stress procedure by Dong is modified to apply to the welded joints with local thickness variation and inignorable shear/normal stresses along local discontinuity surface. In order to make use of the structural stress based K solution for fatigue correlation of welded joints, a proper crack growth model needs to be developed. There exist some significant discrepancies in inferring the slope or crack growth exponent in the conventional Paris law regime. Two-stage crack growth model was not considered since its applications are focused upon the fatigue behavior in welded joints in which the load ratio effects are considered negligible. In this paper, a two-stage crack growth law considering high mean loading is proposed and proven to be effective in unifying the so-called anomalous short crack growth data.

• 대한기계학회논문집
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• 제12권4호
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• pp.790-805
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• 1988

본 연구에서는 유리섬유 강화 에폭시 복합재료의 파괴 강도와 피로 수명을 정 규분포, 로그 정규 분포와 2모수 및 3모수 Weibull 분포 함수의 기대값으로 살펴 보았 다. 2연속 응력 피로 실험 [작은 응력에서 큰 응력으로의 실험(low-high test), 큰 응력에서 작은 응력으로의 실험(high-low test)]의 결과도 분포 함수들을 사용하여 분 석하였다. 비통계학적 누적 손상 법칙들(non-statistical cumulative damage rules) 을 2연속 응력 피로 수명 분산 예측에 이용하기 위해서 동등 순위 가정(equal rank assumption)을 확장하여 수정하였다. 수정한 누적 손상 모형은 Miner의 법칙, Brou- tman과 Sahu의 손상모형 및 Hashin과 Rotem의 모형 등이다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.475-480
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• 1997

It is common to assum identical allowable safety factors in static strength, defined by mean stress and in fatigue, defined by stress amplitude. Under the load with asymmetrical cycles the safety factor is not the same. In this paper, with the consideration of unequal allowable safety factors a general method for estimating fatigue reliability of a machine element under a combined state of stress is derived based on the theory proposed by Prof. Kececioglu and normal distribution. The calculation of fatigue reliability for limited life is discussed with example.

• 대한인간공학회지
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• 제28권4호
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• pp.91-99
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• 2009

A visual stress may provoke migraine, cephalalgia, intervene a long term reading and learning capability and reduce the productivity of a laborer who uses computer for a good while. In this study, a web based screening tool for visual stress was developed, it applied to 72 visually normal young persons in parallel with traditional questionnaire about symptoms of visual stress. To estimate visual stress, It is proposed to measure difference of visual search time of Han Gul characters as targets between visual stressful pattern and non-visual stressful pattern as global background of characters. As a result of test, 5 subjects were screened whose mean visual search time in the stressful pattern with 6 CPD spatial frequency increase significantly more than in none stressful pattern(t-test, one-tailed, p=$1.0407\times10^{-11}$). 2 of them were diagnosed as mild visual stress syndrome in the clinic. None had visual distortion and 50% of subjects had visual discomfort in results of the questionnaire. Correlation between visual search time increase rate and normalized number of visual discomfort may be slight(C. coefficient=0.1355). This study may contribute as a basic research for screening person with migraine, visual reading disabilities and VDT syndrome. It is required to apply the test to visual reading disabilities, migraine with visual distortion and/or visual discomfort as well as normal person for higher reliability of the screening tool.

• 대한통합의학회지
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• 제6권3호
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• pp.11-16
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• 2018

Purpose: Stress tends to cause sympathetic hyperactivity and increase blood cortisol levels. The vagus nerve is a parasympathetic nerve that is involved in relaxing the body. The purpose of this study was to investigate the effects of electrical stimulation of the vagus nerve on stress hormone (cortisol) levels and heart rate variability (HRV) in humans. Methods: A total of 10 healthy subjects participated in the pilot experiment. All subjects underwent electrical vagus nerve stimulation for 20 minutes in the cymba conchae of the left ear. An electro cardiogram meter was used to measure HRV. Blood samples were collected and analyzed for cortisol levels. The standard deviation of all normal N-N intervals (SDNN), root mean square of successive differences (RMSSD), low frequency, high frequency, and cortisol levels were compared in pre and post mean values after the intervention. Data were analyzed using the Wilcoxon's signed-rank test. Results: Coritsol levels were observed to decrease after vagus nerve electrical stimulation. The mean SDNN and RMSSD values were increased after the intervention, but not significantly. Conclusion: Vagus nerve electrical stimulation has been shown to increase the ability of the parasympathetic nerve to adapt to upward regulation and stress. Vagus nerve electrical stimulation could thus be an effective treatment for modern social psychological stress control.