• 한국지반공학회논문집
• /
• 제30권8호
• /
• pp.5-11
• /
• 2014

본 연구의 목적은 신뢰성해석을 통해 교량의 하부구조인 교대에 대해 주요설계변수와 신뢰성계수의 관계를 정립하여 하중저항계수설계를 위한 신뢰성해석방법을 개발하는 것이다. 하중조건으로는 사하중, 연직토압 및 수평토압, 상재하중, 그리고 통행차량에 의한 활하중을 고려하였다. 고려한 하중에 대해 지반의 허용지지력, 전도, 활동 등을 반영하는 한계상태함수를 정의하여 신뢰성 해석을 몬테-카를로 시뮬레이션을 이용하여 수행하였다. 신뢰성 해석 결과 신뢰성지수에 가장 큰 영향을 미치는 인자는 내부마찰각이었으며 민감도해석 결과 신뢰성 지수는 저항계수와 수평토압의 변화에 따라 민감하게 변화하는 것을 알 수 있었다.

• 대한수의학회지
• /
• 제46권3호
• /
• pp.249-254
• /
• 2006

To determine the effects of exposure to formalin on the secondary stress indices, changes in haematology and blood chemistry were monitored in healthy crucian carps (Carassius auratus). Fishes were separately exposed in a concentration range of 125 to 500 ppm formalin for 60 min. After exposure, red blood cell (RBC) count and packed cell volume (PCV) were elevated in the 500 ppm formalin exposed group. However, mean corpuscular volume (MCV) and mean corpuscular haemoglobin (MCH) were decreased significantly in the 500 ppm formalin exposed group. Total protein, albumin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatinine, total bilirubin, inorganic phosphorus (IP) and magnesium were significantly increased at a concentration of 500 ppm. Alkaline phosphatase (ALP) and glucose were increased at a concentration of 500 ppm, but this was not significant. Lactate dehydrogenase (LDH) and calcium were significantly decreased at concentrations of 250 and 500 ppm. AST, ALT, glucose and magnesium were significantly increased in the 250 ppm formalin exposed group. These results suggests that formalin exposure might cause some damage in the liver and kidney of crucian carp.

• 전기학회논문지
• /
• 제58권5호
• /
• pp.1050-1056
• /
• 2009

Heart Rate Variability(HRV) is a parameter that represents monitoring variability of time intervals between R-peak in electrocardiography. HRV serves to various applications, such as indices of autonomic functions, prediction of cardiac sudden death, assessment of stress and emotional, etc. However, as measuring R-peak in ECG needs at least 3-electrodes, and it is inconvenient for end users. In this paper, we suggested the modified laplacian electrodes for measuring HRV at one-point, which are producted by MEMS fabrication and have the two circular electrodes on the pad. For optimal position and direction, we performed an experiment that compared with pearson correlation coefficient and the amplitude of signals, between standard lead II and proposed electrodes. We analyzed the HRV parameters, such as standard deviation of the NN interval(SDNN), high frequency(HF), low frequency(LF), LF/HF ratio. The result showed that the average correlation coefficient and amplitude are 0.967 and 0.685 mVpp at the position 2. The coeffiecient correlation between the standard HRV and proposed electrode-HRV is 0.999

• 동서간호학연구지
• /
• 제24권2호
• /
• pp.171-181
• /
• 2018

Purpose: The study aimed to validate a structural model of self-concept among children and adolescents from multicultural families. Methods: Data were collected from 325 mothers of multicultural families and their 417 children. Confirmatory factor analysis, path analysis and multiple mediation analysis with a phantom variable approach were used to assess construct validity and relations between model variables. Results: Goodness of fit indices of the modified theoretical model, the standardized ${\chi}^2$ (2.75), RMR (.02), RMSEA (.07), NFI (.90), TLI (.92), CFI (.94), GFI (.89), and AGFI (.87), met criteria. Social support and mental health problem had significant direct effects on self-concept, whereas residential environment and school adjustment had significant indirect effects, accounting in combination for 53% of the variance in self-concept. Conclusion: Based on the results, mental health problem mediated the relationships of self-concept and parenting stress.

• Steel and Composite Structures
• /
• 제41권6호
• /
• pp.787-803
• /
• 2021

The size-dependent nonlinear thermomechanical vibration analysis of pre- and post-buckled tapered two-directional functionally graded (2D-FG) microbeams is presented in this study. In the context of the modified couple stress theory, the formulations are derived based on the parabolic shear deformation beam theory and von Karman nonlinear strains. Different thermomechanical material properties are assumed to be temperature-dependent and smoothly vary in both length and thickness directions using the power law and the physical neutral axis concept is employed. The nonlinear governing equations are derived using the Hamilton principle and the resulting variable coefficient equations of motion are solved using the differential quadrature method (DQM) and iterative Newton's method for clamped-clamped and simply supported boundary conditions. Comparison studies are presented to validate the derived model and solution procedure. The impacts of induced thermal moments, temperature power index, two gradient indices, nonuniform cross-section, and microstructure length scale parameter on the frequency-temperature configurations are explored for both clamped and simply supported microbeams.

• Nuclear Engineering and Technology
• /
• 제55권6호
• /
• pp.2053-2068
• /
• 2023

Following a loss of coolant accident (LOCA), prestressing concrete containment vessels (PCCVs) may experience high thermal load as well as internal pressure. The high temperature stress would increase the risk of premature damage to the containment, which reduces the safety margin during the increasing internal pressure. However, current investigations cannot clearly address the issues of thermal-pressure coupling effect on damage propagation and thus safety of the containment. Thus, this paper offers three simple and powerful damage parameters to differentiate the severity of damage of the containment. Moreover, despite of the temperature action severely threatening the pressure performance of the containment, the research regarding the improvement of the resistant performance of the containment is quite scarce. Therefore, in this paper, a comprehensive comparison of damage propagation and mechanism between conventional and fiber-reinforced concrete (FRC) containments is performed. The effects of fiber characteristics parameters on damage propagation of structures following the LOCA are also specifically revealed. It is found that the proposed damage indices can properly indicate state of damage in the containment body and the addition of fiber can be used to obviously mitigate the damage propagation in PCCV considering the thermal-pressure coupling.

• 한국환경과학회지
• /
• 제32권10호
• /
• pp.713-722
• /
• 2023

This study was conducted to examine the effects of care farming activities on the brain waves of adults with developmental disabilities from September 2022 to December 2022, with a total of 16 sessions held once a week. For 28 adults with developmental disabilities, 15 participants in the care farm program and 13 participants who did not participate were used as the control group. Before and after the care farming activities, participants' self-esteem, happiness levels, and brain function indices were measured through surveys and electroencephalography (EEG). Consequently, the self-esteem of the participants in the experimental group significantly increased after the activity, and as for the brain function index, the left brain activity index related to stress, attention, brain function, and emotional state increased compared to the control group in the experimental group of adults with developmental disabilities, especially intellectual disabilities. Notably, the effect of care farming activities was greater for women than for men with intellectual disabilities. Therefore, considering the differential effects of care farming activities based on the type of developmental disability and sex, it is deemed advantageous to primarily apply these activities to women with intellectual disabilities in order to maximize the healing effect of care farming.

• Steel and Composite Structures
• /
• 제49권2호
• /
• pp.231-244
• /
• 2023

Many of the recent investigations in the field of geotechnical engineering focused on the bearing capacity theories of multilayered soil. A number of factors affect the bearing capacity of the soil, such as soil properties, applied overburden stress, soil layer thickness beneath the footing, and type of design analysis. An extensive number of finite element model (FEM) simulation was performed on a prototype slope with various abovementioned terms. Furthermore, several non-linear artificial intelligence (AI) models are developed, and the best possible neural network system is presented. The data set is from 3443 measured full-scale finite element modeling (FEM) results of a circular shallow footing analysis placed on layered cohesionless soil. The result is used for both training (75% selected randomly) and testing (25% selected randomly) the models. The results from the predicted models are evaluated and compared using different statistical indices (R² and RMSE) and the most accurate model BBO (R²=0.9481, RMSE=4.71878 for training and R²=0.94355, RMSE=5.1338 for testing) and TLBO (R²=0.948, RMSE=4.70822 for training and R²=0.94341, RMSE=5.13991 for testing) are presented as a simple, applicable formula.

• Coupled systems mechanics
• /
• 제12권5호
• /
• pp.429-444
• /
• 2023

The comprehension and structural modeling of masonry constructions is fundamental to safeguard the integrity of built cultural assets and intervene through adequate actions, especially in earthquake-prone regions. Despite the availability of several modeling strategies and modern computing power, modeling masonry remains a great challenge because of still demanding computational efforts, constraints in performing destructive or semi-destructive in-situ tests, and material uncertainties. This paper investigates the shear behavior of masonry walls by applying a plane-stress FE continuum model with the Modified Masonry-like Material (MMLM). Epistemic uncertainty affecting input parameters of the MMLM is considered in a probabilistic framework. After appointing a suitable probability density function to input quantities according to prior engineering knowledge, uncertainties are propagated to outputs relying on gPCE-based surrogate models to considerably speed up the forward problem-solving. The sensitivity of the response to input parameters is evaluated through the computation of Sobol' indices pointing out the parameters more worthy to be further investigated, when dealing with the seismic assessment of masonry buildings. Finally, masonry mechanical properties are calibrated in a probabilistic setting with the Bayesian approach to the inverse problem based on the available measurements obtained from the experimental load-displacement curves provided by shear compression in-situ tests.

• KSBB Journal
• /
• 제24권2호
• /
• pp.131-139
• /
• 2009

본 연구에서는 일정기간 스트레스를 받을 때 흰목이버섯 추출물 식이가 스트레스로 인한 생체내의 산화적 손상지표 변화를 보아 사람의 나이 20대에 받은 스트레스가 노년기인 60대 이상에 접어들었을 때에 혈청과 간의 대사산물 변화에 있어 식품 재료로써 흰목이버섯 추출물의 장단기적 보호 효과와 식이의 안정성을 살펴보았다. ICR 마우스를 사람의 나이 20대에 해당되는 5개월까지 사육한 후, 8주간의 스트레스를 가하고 사람의 나이 노년기에 해당되는 18개월 될 때까지 사육하여 스트레스로 인한 생체 내의 산화적 손상지표로 혈청과 간의 대사산물의 변화를 조사하였다. 그 결과, 스트레스는 장 단기적으로 모두 혈청의 TG, AST 함량을 증가시키고, HDL-cholesterol 함량을 저하시키는 것에 반해, 여기에 흰목이버섯 추출물의 투여는 스트레스를 받은 쥐에서 혈청 TG, LDL-cholesterol과 AST의 함량을 감소시키고, HDL-cholesterol의 함량을 증가시키는 효과를 보여주었다. 스트레스는 간조직의 TAS 함량, SOD활성 감소와 MDA 함량 증가를 야기시켰으며, 스트레스 시 흰목이버섯 추출물의 투여 쥐는 TAS 함량, SOD활성을 증진시키고, MDA의 함량을 저하시키는데 긍정적 영향을 주었다. 따라서 젊었을 때 한때 받은 스트레스는 노년기의 TG, HDL-cholesterol, LDL-cholesterol, AST, TAS, SOD 그리고 MDA의 수치 모두에 있어서 부정적인 영향을 미치는 것으로 나타났다. 또한, 7개월과 18개월 그룹의 흰목이버섯 추출물 식이군이 대조군에 대해 MDA의 유의적 감소와 AST의 유의적 차이가 없음은 흰목이버섯 추출물이 장단기적으로 독성을 나타내지 않는 안전한 천연제제물로 사용할 수 있으리라 사료된다. 이러한 결과를 통해서 한때 어느 기간 받은 스트레스는 시간이 지난 노년기까지 혈청과 간조직에 부정적 영향을 주므로, 천연제제로써 흰목이버섯 추출물을 식용하면 어느 정도 장단기적 보호 효과를 얻을 수 있을 것으로 보인다. 또한 안전한 식품이므로 흰목이버섯 추출물의 식이는 과도한 스트레스에 노출되어 있는 현대인들을 위해 매우 유용할 것이며 장복하므로 노후 질병의 예방에도 많은 도움이 될 것으로 생각된다.