• 드라이브 ㆍ 컨트롤
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• 제21권1호
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• pp.22-30
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• 2024

Gearboxes designed for reciprocating motion operating mechanisms operate under conditions where both the load and speed undergo continuous variations. When conducting durability tests on gearboxes designed for such applications, operating the target gearbox under conditions similar to the intended usage is essential. The gearbox must be operated for the required number of cycles to validate its durability under conditions mirroring its intended usage. This study devised an accelerated test method for gearboxes, which reduces operating angles and operational strokes. The reliability of the accelerated test was verified by comparing the stresses imposed on the gears under general and acceleration conditions through multi-body dynamic simulations. The results confirmed that the maximum contact stress levels under normal and accelerated conditions were within a 0.1% error range, indicating a minimal difference in the gear damage rates. However, a difference in the maximum contact stress results between the normal and accelerated conditions was observed when inertial forces acted on the output shaft due to the operational acceleration of the gearbox. Therefore, when conducting this acceleration test, caution should be exercised to ensure that the operational load on the gearbox, which affects inertia, does not significantly deviate from the conditions observed under normal operating conditions.

• Child Health Nursing Research
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• 제23권2호
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• pp.249-257
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• 2017

Purpose: The aim of this study was to assess the body weight perception of adolescents and to investigate the difference between mental health and weight control behavior according to body weight perception. Methods: Study data on 12-18 years old adolescents with normal BMI was obtained from the 6th Korea National Health and Nutrition Examination Survey (2013-2015). Rao-Scott Chi-square test and ANOVA were used for the analysis. Results: The percentage of adolescents with a misperception of body weight was 43.3%, and their subjective health status (p=.013), stress perception (p=.001), and depression (p=.001) were worse than for adolescents who had the correct perception of their body weight. The percentage of adolescents who were trying to lose weight while perceiving their body weight as normal was 36.9%. Body weight control behavior had significant differences according to dietary intake (frequency of eating dinner (p=.015)), energy intake (p=.004), and carbohydrate intake (p<.001), but there was no significant difference according to exercise. Conclusion: Parents, school teachers, and nurses should make efforts to ensure that Korean adolescents perceive their body weight correctly, and prevent unhealthy weight control behaviors.

• 반도체디스플레이기술학회지
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• 제22권2호
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• pp.30-34
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• 2023

Since dishing in the CMP process is a major factor that hinders the uniformity of the semiconductor thin film, many studies have focused this issue to improve the non-uniformity of the film due to dishing. In the metal layer, the dishing mainly occurs in the central part of the metal due to a difference in a selection ratio between the metal and the dielectric, thereby generating a step on the surface of the metal layer. Factors that cause dishing include the shape of the thin film, the chemical reaction of the slurry, thermal deformation, and the rotational speed of the pad and head, and dishing occurs due to complex interactions between them. This study analyzed the stress generated on the metal layer surface in the CMP process using ANSYS software, a commercial structure analysis program. The stress caused by the vertical load applied from the pad was analyzed by changing the area density and line width of the dummy metal. As a result of the analysis, the stress in the active region decreased as the pattern density and line width of the dummy metal increased, and it was verified that it was valid compared with the previous study that studied the dishing according to the dummy pattern density and line width of the metal layer. In conclusion, it was confirmed that there is a relationship between dishing and normal stress.

• 보건의료생명과학 논문지
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• 제9권2호
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• pp.363-372
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• 2021

이 연구에서는 중년기 이후 대사증후군 유병률이 증가하는 중년여성을 대상으로 대사증후군과 스트레스 및 3대 영양소 섭취와의 관계를 파악해보고자 국민건강영양조사 제7기 3차년도(2018년) 자료를 이용하여 분석하였다. 분석결과를 요약하면 다음과 같다. 첫째, 정상군과 대사증후군 중년여성의 탄수화물 섭취는 유의미한 차이를 보였다. 둘째, 스트레스가 있는 중년여성은 탄수화물을 적정기준 이상 과다 섭취할수록 대사증후군 유병확률이 2.419배 증가하는 것으로 나타났다. 셋째, 정상군과 대사증후군 중년여성의 스트레스 유·무에 따른 지방과 단백질의 섭취정도는 중년여성의 대사증후군 유병확률에 유의한 영향을 미치지 않는 것으로 나타났다. 연구 결과, 스트레스가 있는 중년여성의 경우 고탄수화물 섭취가 대사증후군과 유의한 관련이 있는 것이 나타났으므로 이를 감소하고 개선시키기 위한 심리사회적인 중재가 필요하다.

• Geomechanics and Engineering
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• 제7권3호
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• pp.233-246
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• 2014

Estimation of fracture initiation pressure is one of the most difficult technical challenges in hydraulic fracturing treatment of vertical or horizontal oil wells. In this study, the influence of in-situ stresses and pore pressure values on fracture initiation pressure and its profile in vertical and horizontal oil wells in a normal stress regime have been investigated. Cohesive elements with traction-separation law (XFEM-based cohesive law) are used for simulating the fracturing process in a fluid-solid coupling finite element model. The maximum nominal stress criterion is selected for initiation of damage in the cohesive elements. The stress intensity factors are verified for both XFEM-based cohesive law and analytical solution to show the validation of the cohesive law in fracture modeling where the compared results are in a very good agreement with less than 1% error. The results showed that, generally by increasing the difference between the maximum and minimum horizontal stress, the fracture pressure and its profile has been strongly changed in the vertical wells. Also, it's been clearly observed that in a horizontal well drilled in the direction of minimum horizontal stress, the values of fracture pressure have been significantly affected by the difference between overburden pressure and maximum horizontal stress. Additionally, increasing pore pressure from under-pressure regime to over-pressure state has made a considerable fall on fracture pressure in both vertical and horizontal oil wells.

• Journal of Korean Neurosurgical Society
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• 제47권5호
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• pp.345-351
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• 2010

Objective : In this study, the Mindfulness Based Stress Reduction (MBSR) program was applied to patients presenting with depression and anxiety after surgery from spontaneous subarachnoid hemorrhage (SAH) and the effects were assessed. Methods : The subjects were patients admitted for cerebral aneurysm rupture and treated by means of surgery from March to December, 2007. More than 6 months had passed after surgery, without any special lesions showing up on computed tomography (CT), and the Glasgow outcome scale (GOS) was 5 points. Among patients with anxiety and depression symptoms, 11 patients completed the program. The MBSR program was conducted once a week, 2.5 hours each, for 8 weeks. The evaluation criteria were : 1) the Beck Depression Inventory (BDI): it measures the type and level of depression, 2) the State-Trait Anxiety Inventory : the anxiety state of normal adults without mental disorder, and 3) Heart Rate Variability (HRV) : the influence of the autonomous nervous system on the sinoarterial node varies continuously in response to the change of the internal/external environment. Results : The BDI value was decreased from 18.5 ${\pm}$ 10.9 to 9.5 ${\pm}$ 7.1 (p = 0.013) : it was statistically significant, and the depression level of patients was lowered. The state anxiety was decreased from 51.3 ${\pm}$ 13.9 to 42.3 ${\pm}$ 15.2; the trait anxiety was reduced from 50.9 ${\pm}$ 12.3 to 41.3 ${\pm}$ 12.8, and a borderline significant difference was shown (p = 0.091, p = 0.056). In other words, after the treatment, although it was not statistically significant, a decreased tendency in anxiety was shown. In the HRV measurement, standard deviation normal to normal (SDNN), square root of the square root of the mean sum of squared differences between adjacent normal to normal intervals (RMSSD), and total power (TP) showed significant increase, Physical Stress Index (PSI) showed a significant reduction, and thus an improvement in the homeostatic control mechanism of the autonomic nervous system was ween. Conclusion : The MBSR program was applied to the patients showing anxiety and depression reaction after SAH treatment, and a reduction in depression symptoms and physiological reactions were observed. The application of the MBSR program may be considered as a new tool in improving the quality of life for patients after surgery.

• 한국공작기계학회논문집
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• 제10권6호
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• pp.95-101
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• 2001

This work is concerned with construction of the intelligence stress predictor far compression strength evaluation using neural network-ultrasonic waves. The contact pressure in jointed plates was measured by using ultrasonic technique. Neural network is used to evaluate and predict contact pressure from the results of the calibration curves. The organized neural system was leaned with the accuracy of 99%, as a result of learning the ultrasonic echo ratio to the contact pressure measurement between SM45C and STS410 materials. And it could be evaluated and predicted with the accuracy of 90% in the evaluation of ultrasonic echo ratio difference in the same surface roughness and contact pressure, and 85% in the prediction of virtual ultrasonic echo ratio. Thus the proposed stress predictor is very useful for the evaluation and prediction of the contact pressure between SM45C and STS410 materials.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.191-192
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• 2006

The deformation under radial pressure of rectangular dies for metal powder compaction has been investigated by FEM. The explored variables have been: aspect ratio of die profile, ratio between diagonal of the profile and die height, insert and ring thickness, radius at die corners, interference, different insert materials, i. e. conventional HSS, HSS from powders, cemented carbide (10% Co). The analyses have ascertained the unwanted appearance of tensile normal stress on brittle materials, also "at rest", and even some dramatic changes of stress patterns as the die height increases with respect to the rectangular profile dimensions. Different materials behave differently, mainly due to difference of thermal expansion coefficients. Profile changes occur when the dies are heated up to the temperature required for warm compaction. The deformation patterns depend on compaction temperature and thermal expansion coefficients.

• Nuclear Engineering and Technology
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• 제49권5호
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• pp.1031-1043
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• 2017

A structural model for stress distributions of coated Zircaloy subjected to realistic incore pressure difference, thermal expansion, irradiation-induced axial growth, and creep has been developed in this study. In normal operation, the structural integrity of coating layers is anticipated to be significantly challenged with increasing burnup. Strain mismatch between the zircaloy and the coated layer, due to their different irradiation-induced axial growth, and creep deformation are found to be the most dominant causes of stress. This study suggests that the compatibility of the high temperature irradiation-induced strains (axial growth and creep) between zircaloy and the coating layer and the capability to undergo plastic strain should be taken as key metrics, along with the traditional focus on chemical protectiveness.

• Steel and Composite Structures
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• 제18권6호
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• pp.1465-1478
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• 2015

The effect of cutting off fibers on transient load in a polymeric matrix composite lamina was studied in this paper. The behavior of fibers was considered to be linear elastic and the matrix behavior was considered to be linear viscoelastic. To model the viscoelastic behavior of matrix, a three parameter solid model was employed. To conduct this research, finite difference method was used. The governing equations were obtained using Shear-lag theory and were solved using boundary and initial conditions before and after the development of break. Using finite difference method, the governing integro-differential equations were developed and normal stress in the fibers is obtained. Particular attention is paid the dynamic overshoot resulting when the fibers are suddenly broken. Results show that considering viscoelastic properties of matrix causes a decrease in dynamic load concentration factor and an increase in static load concentration factor. Also with increases the number of broken fibers, trend of increasing load concentration factor decreases gradually. Furthermore, the overshoot of load in fibers adjacent to the break in a polymeric matrix with high transient time is lower than a matrix with lower transient time, but the load concentration factor in the matrix with high transient time is lower.