• Journal of Mechanical Science and Technology
• /
• 제20권4호
• /
• pp.494-504
• /
• 2006

This research proposes a reliability-based topology optimization (RBTO) using the finite element method. RBTO is a topology optimization based on probabilistic (or reliability) constraints. Young's modulus, thickness, and loading are considered as the uncertain variables and RBTO is applied to static and eigenvalue problems. The RBTO problems are formulated and a sensitivity analysis is performed. In order to compute probability constraints, two methods-RIA and PMA-are used. Several examples show the effectiveness of the proposed method by comparing the classical safety factor method.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2017년도 춘계 학술논문 발표대회
• /
• pp.214-215
• /
• 2017

Extreme loads such as impact and explosion have higher strain rate than static loading condition. Therefore, it is necessary to evaluate mechanical properties at high strain rate in order to apply fiber reinforced cement composites to ensure safety performance against impact and explosion. In this study, the compressive properties of fiber reinforced cement composites by strain rate were evaluated.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2009년도 춘계 학술발표회
• /
• pp.512-517
• /
• 2009

Resistance factors for static bearing capacity of driven steel pipe piles were calibrated in the framework of reliability theory. A comprehensive foundation design case study on an actual bridge was performed using resistance factors developed in this study. Comparing with Allowable Stress Design (ASD), LRFD design method provides quantitative evaluation of safety level of designed foundation and exhibits considerable potential economy in design.

• Journal of Magnetics
• /
• 제19권2호
• /
• pp.174-180
• /
• 2014

In this paper, a new and simple method is proposed to quickly estimate the induced electric field in the human child exposed to a 100 kHz-10 MHz magnetic field, for the sake of electromagnetic field (EMF) safety assessment. The quasi-static finite-difference time-domain (FDTD) method is used to calculate the induced electric fields in high resolution 3D human child models with various body size parameters, in order to derive the correction factor for the estimation equation. The calculations are repeated for various frequencies and incident angles of the magnetic field. Based on these calculation results, a new and simple estimation equation for the 99th percentile value of the body electric field is derived that depends on the body size parameters, and the incident magnetic field. The estimation errors were equal to or less than 5.1%, for all cases considered.

• 대한전기학회논문지
• /
• 제38권9호
• /
• pp.733-739
• /
• 1989

유한요소법과 반복법을 적용하여 Grad-Shafranov식을 풀어 축대칭 토로이달 플라즈마의 고정경계 MHD평형을 해석하였다. 토로이달 전류항은 플라즈마 압력과 토로이달 자장함수로 표현하였고 해의 타당성 검증을 위하여 수치해석 결과를 해석적 평형과 비교하였다. 서울대의 SUNT-79장치에 적용하여 압력과 자장함수 변화에 따른 자기면 형상과 전류분포를 고찰하였고 안전인자와 ${\beta}$값도 함께 산출하였다.

• 한국기계기술학회지
• /
• 제13권1호
• /
• pp.95-103
• /
• 2011

Robots in various types carry and assemble parts through repeatedly and accurately moving to stored locations by combining linear motions. And, linear systems are used in orthogonal axes of robots and driven via ball screws, such as 2-axis cartesian coordinate robot in this paper. This paper presents the effect of the linear motion guide that is used in $2^{nd}$ axis in 2-axis cartesian coordinate robot. Some simulation results show that the linear motion guide influence greatly in robot performance such as the nominal life of linear guide. When use LM guide that have capacity near in $2^{nd}$ axis, this paper show that the nominal life on LM block of $1^{st}$ axis increases 37.4% and that the specification of $2^{nd}$ axis LM guide influences greatly the nominal life of $1^{st}$ axis LM block.

• 한국정보처리학회:학술대회논문집
• /
• 한국정보처리학회 2008년도 추계학술발표대회
• /
• pp.734-736
• /
• 2008

차량의 정보를 실시간으로 수집할 수 있는 텔레매틱스 기술의 발전과 함께, 운전자의 주행정보를 실시간으로 분석함으로써, 운전자의 주행에 대한 안전지수를 산출하는 방법과 그에 따라서 고려되어야 할 요소에 대하여 논의하고자 한다. 본 논문에서는 안전지수 산출을 위해, 관련요소를 Static Information, Dynamic Information, Duration Information, Human Factor로 세분화 하고 각각의 요인에 대한 수집 방법 및 특성을 소개한다.

• 대한인간공학회지
• /
• 제26권2호
• /
• pp.45-59
• /
• 2007

The operating tasks of overhead crane have caused undue stress to the operators from physical, mental, and environmental workload. Existing workload assessment models for musculoskeletal disorders such as OWAS, RULA, and QEC have limited applicability to the crane operating tasks because they focus mainly on physical factors and do not consider the relative importance of each factor. The present study was to develop a workload assessment model customized to overhead crane operation, following a systematic process: (1) analyzing task characteristics, (2) selecting workload factors, (3) developing assessment methods, (4) establishing action levels, and (5) computerizing the assessment model. Based on literature review, worksite survey, and focus group interview, 4 physical factors (awkward posture, static posture, repetitive motion, and excessive force), 6 mental factors (visual demand, auditory demand, task complexity and difficulty, time urgency, work schedule related stress, and safety related stress), and 4 environmental factors (noise, vibration, dust, and temperature) were selected and their rating scales and relative weights were determined. Then, based on the workload assessment results of 8 overhead cranes operated at different workplaces, the action levels of each factor category were established. Finally, the crane operation assessment model was computerized for effective analysis and report preparation. The present approach is applicable to develop a customized workload assessment model for an operating task under consideration.

• 산업기술연구
• /
• 제25권B호
• /
• pp.55-62
• /
• 2005

This paper is the results of experimental and numerical works on analyzing the geotechnical engineering behavior and characteristics of excavated clay slope formed by the method of excavated replacement which is one of treatments in soft soil ground. For the centrifuge model tests, models of excavated clay slope were prepared by remolding the marine clayey soil sampled from the field. Tests were performed with changing the slope to investigate the behavior of them. On the other hand, numerical analyses were carried out to analyze the change of safety factor against instability of slope with time. Changes of pore water pressure, shear strength and displacement were also investigated. As results of centrifuge model tests with slopes of 1:1.5 and 1:3 using the confining body of simulating the effect of excavation, for the case of 1:1.5, slope failure occurred right after remove the confining body whereas relatively small displacements within the range of 3.2mm, implying to maintain the stability of slope, were observed for the case of 1:3 slope. From the results of numerical analyses using the software of PLAXIS to investigate the stability of slope after excavation, the minimum safety factor against slope failure was 1.28 for the case of 1:3 slope. The further researches in the future are required with considerations of build up of static pore water pressures during acceleration of centrifuge, depth of excavation influencing the behavior of the slope and permeability of the slope since excavation of the slope was not simulated well resulted from the limitations of apparatus at the stage of excavation during the centrifuge tests.

• 한국식품위생안전성학회지
• /
• 제14권2호
• /
• pp.146-152
• /
• 1999

The present study was performed to investigate the bioconcentration of BPMC, chlorothalonil, dichlorvos and methidathion. The BCFs(bioconcentration factors) and depuration rate constants for four pesticides in zebrafish(brachydanio rerio) were measured under semi-static conditions(OECD guideline 305-B) in a concentration of one-hundredth of the 96 hours LC50 of each pesticide at the equilibrium condition. The results obtained are summarized as follows : The BCFs of BPMC, chlorothalonil, dichlorvos and methidathion were 1.44$\pm$0.09, 2.223$\pm$0.063, 0.81$\pm$0.08 and 5.53$\pm$0.13, respectively. Depuration rate constants of BPMC, chlorothalonil, dichlorvos and methidathion were 0.028, 0.015, 0.220 and 0.152, respectively. The concentrations of BPMC, dichlorovs and methidathion in zebrafish reached an equilibrium in 3 days, and the equilibrium of chlorothalonil was reached after 14 days. Depuration rate of dichlorvos was the fastest followed by methidathion, BPMC and chlorothalonil. The lower BCF of BPMC was due to its relatively high KOW, slow KDEP, and low SW and VP, compared to chlorothalonil and methidathion. The BCF of chlorothalonil was much lower than that excepted on the basis of high KOW, slow KDEP, SW and VP. The reason is that the experimental concentration for chlorothalonil is 1/100~1/1000 lower than that of BPMC, dichlorvos and methidathion. The BCF of dichlorvos was lower than that of other pesticides due to its very rapid KDEP, very high VP and SW, and very low KOW. The BCF of methidathion was higher than that of other pesticides due to its very low VP and SW. Therefore, these data suggest that physicochemical properties of pesticides may be important in the bioconcentration.