• 대한기계학회논문집
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• 제15권6호
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• pp.1908-1918
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• 1991

본 연구에서는 피로 잔류강도저하(fatigue residual strength degradation) 개념을 이용하여 복합재료의 잔류강도와 피로수명을 예측하고 실험을 통하여 비교 평 가하였으며, 설계시 고려되어야 할 인자를 파악하여 파손방지를 위한 유한 수명설계 및 손상허용설계의 기본자료를 집적함으로서 새로운 소재인 탄소섬유 강화 복합재료의 신뢰성 향상을 위한 개발과 고강도 경량화를 위한 이용설계에 활용할 수 있도록 하는 데 그 목적이 있다.

• 한국도로학회논문집
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• 제14권5호
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• pp.75-83
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• 2012

PURPOSES: Suggestion of asphalt binder constitutive model based on time-temperature superposition principle and overstress concept in order to describe behavior of asphalt binders. METHODS: A series of temperature sweep tests and multiple stress creep and recovery(MSCR) tests are performed to verify the applicability of time-temperature superposition principle(t-Ts) and to develop viscoelastoplastic constitutive equation based on overstress concept. For the tests, temperature sweep tests at various high temperature and various frequency and MSCR test at $58^{\circ}C$, $64^{\circ}C$ $70^{\circ}C$, $76^{\circ}C$, and $82^{\circ}C$ are performed. From the temperature sweep tests, dynamic shear modulus mastercurve and time-temperature shift function are built and the shift function and MSCR at $58^{\circ}C$ are utilized to determine model coefficients of VBO model. RESULTS: It is observed that the time-temperature shift function built at low strain level of 0.1% is applicable not only to 1.0% strain level temperature sweep test but also maximum 500,00% strain level of MSCR test. As well, the modified VBO model shows perfect prediction on MSCR measured strain at the other temperatures. CONCLUSIONS: The Time-temperature superposition principle stands hold from very low strain level to very high strain level and that the modified VBO model can be applicable for various range of strain and temperature region to predict elastic, viscoelastic, and viscoplastic strain of asphalt binders.

• 터널과지하공간
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• 제17권2호
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• pp.119-127
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• 2007

임계면법을 적용하여 횡등방성 암석의 강도이방성을 해석하는 방법을 제안하였다. 암석의 파괴는 Hoek-Brown 파괴기준을 따르는 것으로 가정하였다. Hoek-Brown의 경험적 파괴기준식에 대응되는 Mohr 포착선식을 이용하고 강도상수인 m과 s를 방향에 따른 스칼라 함수로 정의하여 이방성 파괴함수를 구성하였다. 이방성 파괴함수를 최대고 하는 임계면의 방향을 찾기 위하여 직접 최적화기법의 하나인 공액구배법을 적용하였다. 횡등방성 안석에 대한 기존 이방성 강도모델이 대부분 삼축압축실험과 동일한 응력조건에서만 적용할 수 있는데 반하여 이 연구에서 제안된 방법은 일반적인 3차원 응력조건에도 쉽게 적용할 수 있다는 장점을 가지고 있다. 삼축압축실험의 모사를 통하여 얻어진 삼축압축강도와 파괴면의 경사에 분석을 통하여 제안된 방법의 적합성을 검토하였다.

• Tuberculosis and Respiratory Diseases
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• 제85권2호
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• pp.137-146
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• 2022

Background: Farinelli breathing (FB) exercise is a typical breathing exercise used by singers. This study aimed to compare effects of FB exercise and diaphragmatic breathing (DB) exercise on respiratory function and symptoms in patients with chronic obstructive pulmonary disease (COPD). Methods: Sixteen patients aged 51-80 years with mild or moderate COPD were recruited for this study. They were divided into two groups: DB group (n=8) and FB group (n=8). Both groups received complete breathing exercise training five times per week for 8 weeks. Their respiratory functions, COPD symptoms, cytokine levels, and oxidative stress variables were analyzed during pre- and post-tests. Dependent variables were compared between pre- and post-tests using paired t-tests. An independent t-test was used to compare variables between the groups. Differences were considered significant at p<0.05. Results: The maximal expiratory pressure (MEP), maximum oxygen consumption (VO₂max), and COPD Assessment Test (CAT) scores changed significantly in the DB group after the 8-week intervention compared to those at pre-test, whereas force vital capacity, forced expiratory volume in the first second, maximum voluntary ventilation, maximal inspiratory pressure (MIP), MEP, VO₂max, CAT score, tumor necrosis factor-α, and malondialdehyde level changed significantly in the FB group at post-test compared to those at pre-test. Moreover, both MIP and MEP in the FB group were significantly higher than those in the DB group. Conclusion: FB exercise improved respiratory functions and COPD symptoms of patients with COPD. It might be an alternative breathing exercise in pulmonary rehabilitation programs for patients with COPD.

• 지역사회간호학회지
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• 제24권1호
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• pp.87-98
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• 2013

Purpose: This study was conducted for the purpose of a structural model analysis of family health of women who came to Korea for being married to Korean men. Methods: The data were collected from 260 immigrant women at multicultural centers located in C and B cities from May 10th to 30th, 2012. The variance analysis on the samples was conducted by using the maximum likelihood minimization function with AMOS 7.0. The fitness was evaluated by means of the SRMR, RMSEA, CFI, and TLI with a 90% confidence interval. Results: First, immigrant women's self-esteem and acculturative stress were found to have significant direct effects on their family health. Second, their self-esteem and acculturative stress have direct effects on their marital adjustment. Third, their marital adjustment was found to have significant direct effects on their family health. Forth, immigrant women's Korean language ability was found not to have significant direct effects on their marital adjustment and family health. Conclusion: In order to enhance the family health of immigrant women, it is necessary to develop and apply nursing programs in consideration of immigrant women's self-esteem, marital adjustment and acculturative stress.

• 구강회복응용과학지
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• 제18권4호
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• pp.251-276
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• 2002

The purpose of this study was to compare and analyze the stress distribution and displacement of the fully bone anchored bridge and implant-supported overdenture in edentulous mandible on certain conditions such as number of implants, different design of superstructure. Three dimensional analysis was used and nine kinds of models designed for this study. FEM models were created using commercial software[$Rhinoceros^{(R)}$ (Ver. 1.0 Robert McNeel & Associates, USA)], and analyze using commercial software [Cosmos/$Works^{TM}$(Ver. 4.0 Structural Research & Analysis Corp., US A)]. A vertical load and $45^{\circ}$ oblique load of 17kgf were applied at the left 1st. molar. The results were as follows : (1) In the group of OVD, the displacement was reduced as increasing the number of fixture under vertical loading but there was no specific difference in Von Mises stress. Under oblique loading, the displacement was same at the vertical loading but Von Mises stress was reduced in order of OVD-3, OVD-4, OVD-2. But, bending moment reduced according to increasing the number of fixture. (2) In the group of FBAB, under vertical and oblique loading, the magnitude of Von Mises stress and displacement reduced according to increasing the number of fixtures. FBAB-4 and FBAB-5 showed similar score and distribution, but FBAB-6 showed lower value relatively. (3) In cantilever design, the maximum displacement reduced under vertical loading but increased under oblique loading. However, von mises stresses on fixtures increased under vertical and oblique loading. (4) In comparing OVD-group with FBAB-group, FBAB showed low magnitude of displacement in respect of oblique loading. However OVD-group was more stable in respect of stress distribution.

• 대한치과보철학회지
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• 제44권2호
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• pp.197-206
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• 2006

Statement of problem: One of common problems associated with single teeth dental implant prosthetic is the loosening of screws that retain the implants. Purpose: The maintenance of screw joint stability is considered a function of the preload achieved in the screw when the suggested initial tightening torque is applied. The purpose of this study was to investigate acquired preload after initial clamping torque for estimating screw joint stability. Material and methods: A comparative study on the effect of initial clamping of two types of implant systems with different connections was conducted Three dimensional non-linear finite element analysis is adopted to compare the characteristics of screw preloads and stress distributions between two different types of implant systems composed with abutment, screw, and fixture under the same loading and boundary conditions. Results: 1. When the initial clamping torque of 32Ncm was applied to the implant systems, all types of implants generated the maximum effective stress at the first helix region of screw. 2. Morse taper connection types of implants generate lower stress distributions compared to those by butt joint connection types or implants due to large contact surface between abutment and fixture. 3. The internal types of implant systems with friction grip type implant systems have higher resistance to screw loosening than that of the external types of implant systems since the internal types of implant systems generated larger preload than that generated by the external types for the same tightening moments.

• 한국안전학회지
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• 제31권3호
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• pp.8-15
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• 2016

The purpose of this study is to design a model with the structural stability so as not to lose the operational function due to structural plastic or fail of a sliding blast door by blast pressure to this aim, a numerical simulation was performed using full-size experiments and M&S (Modeling & Simulation) of the sliding blast door. The sliding blast door ($W3,000{\times}H2,500mm$) under the blast load is in the form of a sliding type 2-way metal grill, which was applied by a design blast pressure (reflected pressure $P_r$) of 17 bar. According to the experimental results of a real sliding blast door under blast load, the blast pressure reached the sliding blast door approximately 4.3 ms after the explosion and lasted about 4.0 ms thereafter. The maximum blast pressure($P_r$) was 347.7 psi (2,397.3 kPa), it is similar to the UFC 3-340-02 of Parameter(91 %). In addition, operation inspection that was conducted for the sliding blast door after real test showed a problem of losing the door opening function, which was because of the fail of the Reversal Bolt that was installed to prevent the shock due to rebound of the blast door from the blast pressure. According to the reproduction of the experiment through M&S by applying the blast pressure measurement value of the full-size experiments, the sliding blast door showed a similar result to the full-size experiment in that the reversal bolt part failed to lose the function. In addition, as the pressure is concentrated on the failed reversal bolt, the Principal Tensile Failure Stress was exceeded in only 1.25 ms after the explosion, and the reversal bolt completely failed after 5.4 ms. Based on the result of the failed reversal bolt through the full-size experiment and M&S, the shape and size of the bolts were changed to re-design the M&S and re-analyze the sliding blast door. According to the M&S re-analysis result when the reversal bolt was designed in a square of 25 mm ($625mm^2$), the maximum pressure that the reversal bolt receives showed 81% of the principal tensile failure stress of the material, in plastic stage before fail.

• 대한간호학회지
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• 제23권3호
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• pp.431-452
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• 1993

This study was done to determine the effect of music therapy on stress and quality of life in patients undergoing hemodialysis. The research design was a nonequivalent control group pre -post test design. The subjects consisted of 21 patients who received hemodialysis in two hospitals located in Kwang Ju. The fourteen receiving treatment in one hospital were assigned to the experimental group and the seven in the other hospital to the control group. Data were gathered from December 14, 1992 to January 16, 1993 through questionnaires and physiological measurement. Data were analyzed by the SAS package using frequency, t-test, paired t-test and Pearson Prod uct - Moment Correlation Coefficient. The results of this study are summarized as follows ; 1. There were no significant differences between the two groups on stress scores and quality of life scores before the treatment. 2. The mean score on the psychological stress scale for the patients undergoing hemodialysis was 2.48 out of a maximum mean score of four, the items with high stress scores were “feeling of weakness and annoyed by everything”, “limitation of food”, “limitation of fluid”, “change in skin color” in that order. The psychological category showed the highest stress score followed by developmental, scoioeconomic and physiological stress categories in that order. 3. In the experimental group, post - test diastolic blood pressure decerased significantly(t=3.24, p=0.0064), but in the control group pre and post - test diastolic blood pressure were not different. 4. There was no difference between the two groups on the pre and post -test psychological stress scores or the depression scores. 5. The mean score of quality of life for patients undergoing hemodialysis was 2.75 out of a maxi-mum mean score of five. The category of ‘emtional state’ showed the highest score followed by ‘self - esteem’, ‘physical state and function’, ‘economic life’, ‘relationship with neighbors’ and ‘family relationship’ categories in that order. There was no significant difference in the pre and post - test quality of life scores between the two groups. 6. Hypothesis 1 that patients undergoing hemodialysis who received music therapy would have less stress than patients undergoing hemodialysis who did not receive music therapy is divided into two sub - hypotheses. 1) The first sub-hypothesis that patients undergoing hemodialysis who received music therapy would have less physiological stress than patients undergoing hemodialysis who did not receive music therapy was partly supported. Among three physiological stress indices (pulse, systolic blood pressure, diastolic blood pressure), only diastolic blood pressure decreased significantly after the treatment in the experimental group. 2) The second sub-hypothesis that patients undergoing hemodialysis who received music therapy would have less psychological stress than patients undergoing hemodialysis who did not receive music therapy was not supported. Psychological stress score and depression score were not significantly different before and after the treatment. 7. Hypothesis 2 that patients undergoing hemodialysis who received music therapy would have a higher quality of life score than patients undergoing. hemodialysis who did not received music therapy was not supported. There were no significant changes in the quality of life scores before and after the treatment.

• 구강회복응용과학지
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• 제18권4호
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• pp.277-288
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• 2002

Seven finite element models were constructed in mandible having single screw-type implant fixture connected to the premolar superstructure, in order to evaluate how the length, diameter and platform shape of a screw-type fixture influence the stress in the supporting tissue around fixtures. Each finite element model was varied in terms of length, diameter, and platform shape of the fixture. In each model, 250N of vertical load was placed on the central pit of an occlusal plane and 250N of oblique load placed on the buccal cusp. The stress distribution in the supporting tissue and the other components was analysed using 2-dimensional finite element analysis and the maximum von Mises stress in each reference area was compared. Under lateral loading, the stress was larger at the abutment/fixture interface, and in the crestal bone, compared to the stress pattern under vertical loading. The amount of stress at the superstructure was similar regardless of the length, diameter and platform shape of a fixture. Around the longer fixture, the stress was decreased at the bone crest and subjacent cancellous bone and increased in the cancellous bone area apical to the fixture. Around the wider fixture, the stress was decreased at the abutment/fixture interface, and the bone crest and increased in the cancellous bone area apical to the fixture. Around the fixture having wider platform, less stress was produced at the abutment/fixture interface and the upper part of the cortical bone, compared to the fixture having standard platform. In conclusion, the stress distribution of the supporting tissue was affected by length, diameter, and platform shape of a fixture, and the fixture which was larger in diameter and length could reduce the stress in the supporting tissues at the bone-fixture interface and bone crest area.