• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.1115-1120
• /
• 2003

The recent tendency in the automobile industries is toward light weighting vehicle body to improve the problems by environmental pollution as well as improving fuel cost. The effective way to reduce the weight of vehicle body seems to be application of new materials for body structure and such trend is remarkable. Among the various materials for vehicle body, stainless steel sheet (for example, 301L and 304L), TRIP steel and cold rolled steel sheets are under the interests. However, in order to guarantee reliability of new material and to establish the long life design criteria of body structure, it is important and require condition to assess spot weldability of them and fatigue strength of spot welded lap joints which were fabricated under optimized spot welding condition. And, recently, a new issue in the design of the spot welded structure is to predict economically fatigue design criterion without additional fatigue tests. In general, for fatigue design of the spot-welded thin sheet structure, additional fatigue tests according to the welding condition, material, joint type, and fatigue loading condition are generally required. This indicates that much cost and time for it should be consumed. Therefore, in this paper, the maximum stresses at nugget edge of spot weld were calculated through nonlinear finite element analysis first. And next, obtained the ${\Delta}P-N_{f}$ relation through the actual fatigue tests on spot welded lap joints of similar and dissimilar high strength steel sheets. And then, the ${\Delta}P-N_{f}$ relation was rearranged in the ${\Delta}{\sigma}-N_{f}$ relation. From this ${\Delta}{\sigma}-N_{f}$ relation, developed the fatigue design technology for spot welded lap joints of them welded using the optimized welding conditions.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2011.05a
• /
• pp.212-216
• /
• 2011

현재 하천 건천화에 따른 수생태계 교란 및 수질악화 등의 근본적인 문제가 발생하고 있으며, 최근 정부의 저탄소 녹색성장기조에 따라 조성되고 있는 신도시, 소규모 및 대규모 택지개발사업의 경우는 환경 친화적인 단지조성 요구에 부응하기 위해 기존 도심하천의 복원 및 인공하천의 녹색성장을 고려한 친환경적 생태하천으로 조성하고자 하는 다양한 노력이 시도되고 있으나 안정적인 생태복원의 수원확보 방안을 마련하지 못해 실제 설계가 반영되지 못하고 있다. 또한, 조성하고자 하는 소하천 혹은 실개울 등의 수질보전 및 생태계 보호 등 하천이 본래의 기능을 유지할 수 있도록 생태하천유량을 확보하는 다양한 기술들이 개발되어 있지만, 공사 유형과 주변 환경에 적합한 생태하천유량 확보 방안을 선정할 수 있는 비구조적 대책마련이 부족한 실정이다. 이러한 실정과 문제점을 고려해 볼 때, 조성하고자 하는 도시 내 자연하천 및 인공하천 조성 등 수변환경을 고려한 단지조성에 맞는 생태하천유량 확보 방안 및 평가에 대한 연구가 단계적으로 이루어져야 할 것이다. 따라서 본 연구에서는 생태하천유량 확보와 하천수질 개선이 필요한 특정 지역 또는 다양한 유형의 공사 지구 내 하천이 정상적인 기능을 수행할 수 있도록 적용 가능한 생태하천유량 확보 방안들과 수리해석 모델인 HEC-RAS(River Analysis System), 생태하천유량 산정 모델인 PHABSIM(Physical HABitat SIMulation)을 연계한 물리서식처 평가 모듈을 개발하고, 이를 기초로 가중치부여매트릭스 평가(국토해양부, 2006) 기법을 적용한 최적의 생태하천유량 확보 방안과 수질개선 방안을 제시해 줄 수 있는 의사결정지원 시스템을 구축 하고자 한다. 본 연구에서 개발된 최적의 생태하천유량 확보 방안 도출을 위한 의사결정지원 시스템의 활용으로 필요유량은 물론, 기준을 만족하는 수질의 확보가 절실히 요구되는 중 소규모 하천에 실질적으로 적정수질의 생태하천유량을 확보함으로서 하천으로서의 역할을 위한 본 기능의 회복과 동시에 소하천, 도심하천 및 인공하천 등 중 소규모 수계의 수문순환을 정상화하여 하천의 지속 가능한 개발과 관리가 효율적으로 이루어지도록 하는데 이용될 수 있을 것으로 예상되어진다.

• The KSFM Journal of Fluid Machinery
• /
• v.13 no.5
• /
• pp.43-53
• /
• 2010

This study investigates a design optimization of a rotating two-pass rectangular cooling channel with staggered arrays of pin-fins. The radial basis neural network method is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis of fluid flow and heat transfer with shear stress transport turbulent model. The ratio of the diameter to height of the pin-fins and the ratio of the streamwise spacing between the pin-fins to height of the pin-fin are selected as design variables. The optimization problem has been defined as a minimization of the objective function, which is defined as a linear combination of heat transfer related term and friction loss related term with a weighting factor. Results are presented for streamlines, velocity vector fields, and contours of Nusselt numbers, friction coefficients, and turbulent kinetic energy. These results show how fluid flow in a two-pass square cooling channel evolves a converted secondary flows due to Coriolis force, staggered arrays of pin-fins, and a $180^{\circ}$ turn region. These results describe how the fluid flow affects surface heat transfer. The Coriolis force induces heat transfer discrepancy between leading and trailing surfaces, having higher Nusselt number on the leading surface in the second pass while having lower Nusselt number on the trailing surface. Dean vortices generated in $180^{\circ}$ turn region augment heat transfer in the turning region and in the upstream region of the second pass. As the result of optimization, in comparison with the reference geometry, thermal performance of the optimum geometry shows the improvement by 30.5%. Through the optimization, the diameter of pin-fin increased by 14.9% and the streamwise distance between pin-fins increased by 32.1%. And, the value of objective function decreased by 18.1%.

• The Korean Journal of Applied Statistics
• /
• v.16 no.2
• /
• pp.247-259
• /
• 2003

In Korea, quota sampling is mainly adopted in telephone surveys, instead of random sampling which requires call-back procedure and random selection of respondent within households. The contact mode based on the se $x^{*}$age quotas is economically more advantageous and less time-consuming. However, it lacks theoretical ground for valid statistical inference, so that it is hardly accepted in academic circles despite of widely spread practice. Subsequently, survey theoreticians argued that random sampling-based telephone surveys should be tried. In response, Research & Research (R&R), a private research company in Seoul, executed atelephone survey by random sampling mode for the prediction of 2002 Ulsan City Mayor Election. The aim of this case study is to find out various effects of the call-back rule with random selection of respondents by statistically re-analyzing R&R’s Ulsan Survey Data.s by statistically re-analyzing R&R’s Ulsan Survey Data.

• The Korean Journal of Applied Statistics
• /
• v.26 no.3
• /
• pp.375-387
• /
• 2013

Unit non-response of surveys reduces the efficiency of the estimates and also causes non-response bias especially when there is large difference between respondents and non-respondents. Non-response weighting adjustments have usually been used to compensate for non-response. It is not easy to examine the non-response bias as well as to obtain information on the non-respondents in sample surveys. A household panel survey, called The Survey of Household Finances, was conducted in both 2010 and 2011. In this paper, we assume that non-response households in Wave 2 have strong non-response (non-cooperative) tendency. We classify those households into non-response households in Wave 1. Under this assumption, the characteristics of non-response households, the non-response bias and the effect of non-response adjustments are investigated.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.33 no.1
• /
• pp.20-25
• /
• 2005

The thickness, loading, and broadband noise generated from the trailing edge of the UH-1H main rotor are numerically compared each other. The Kocureck and Tangler's prescribed wake model is adopted to represent the wake geometry during the hovering motion. Three tip Mach numbers of $M_{T}$ = 0.2, 0.4, and 0.8, are selected to analyze the effects of different tip Mach numbers. At $M_{T}$ = 0.8, in considering the A-weighting and audible frequency band, the random noise is smaller than the tonal noises such as the thickness and the loading noise which have the low frequency characteristics. Especially most of the random noise frequency spread on the ultrasound region. On the other hand, below $M_{T}$ = 0.4, the band of random noise moves to the audible frequency region, and the random noise becomes larger than the tonal noise. It turns out that the random noise analysis of the rotor should be necessary at low speed operating condition.

• The Journal of Korean Medicine
• /
• v.18 no.1
• /
• pp.456-469
• /
• 1997

The cerebral infarction arised from occulsion of cerebral artery has a high mortality rate and fatal sequelae. Sohabhyangwon(蘇合香元) is generally regarded to have a effect of walking up the patient from unconsiousness and promoting the flow of Qj(氣) by warming channel. METHOD The purpose of this study is to find out the effections of Sohabhyangwon(蘇合香元) on regional cerebral blood flow and relative cerebral infarction area in the experimentally induced infartion in rats In this experiment, 12 Spraque-Dawley rats weighting 280-350g were used. Cerebral ischemia induced by intraluminal suture technique of Kozumi's and Zea-Longer's method. $Co_{2},\;O_2$, pH, arterial blood pressure in rats were checked by Blood Gas Analyzer every 30 minutes for 2 hours. And regional cerebral blood flow were checking by hydrogen clearance technique, cerebral infarcted area was megsured by Image Analysis System. RESULTS 1. During the experiment, $CO_{2},\;O_2$, pH, arterial blood pressure in rats had no change in both sample group and control group. 2. Cortical cerebral blood flow decreased at same rate in both sample group and control group after inducing cerebral infarction. 3. On comparison of relative cerebral infarcted area, Sohabhyangwon(蘇合香元) perfused group showed a significant decrease. CONCLUSION According to the result above, Sohabhyangwon has a protection effect on cranial nerve and-has no effect on cerebral blood flow.

• Korean Journal of Construction Engineering and Management
• /
• v.16 no.2
• /
• pp.86-96
• /
• 2015

Real estate market has rapidly grown by active use of project financing in the early 2000s. However, many projects have been in trouble due to global economic recession after that period. It is mainly because those projects were pushed forward a business without comprehensive business feasibility analysis. This paper investigated current evaluation system for real estate development projects and then introduced new evaluation system including evaluation factor and criteria for real estate development projects to prevent implementation of the project without business value and to be able to evaluate potential projects in objective manner. This new evaluation system for real estate development projects can be applied to any type of real estate development projects by modifying evaluation items and weighting factor in accordance with the type and characteristics of project. Through the new evaluation system, the evaluation process for real estate development projects will be able to be standardized, be consistent, and the results of evaluation can be accumulated in consistent way.

• YAKHAK HOEJI
• /
• v.60 no.3
• /
• pp.112-117
• /
• 2016

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the determination of caffeine in forensic aqueous sample. The centrifuged sample ($100{\mu}l$) was diluted 50-fold with distilled water. The diluted sample ($400{\mu}l$) was then diluted further with $200{\mu}l$ of 0.1% formic acid solution and $400{\mu}l$ of acetonitrile containing 500 ng of caffeine-(3-methyl-$^{13}C_3$) prior to LC-MS/MS analysis. The mobile phase was composed of 0.1% formic acid in distilled water (A) and acetonitrile (B). Chromatographic separation was performed by using a Zorbax SB-C18 ($100mm{\times}2.1mm$ i.d., $3.5{\mu}m$) column and caffeine was eluted within 1.1 min. Linear least-squares regression with a 1/x weighting factor was used to generate a calibration curve with the coefficients of determination ($r^2=0.9983$). The lower limit of quantification was $25ng/ml$ for the analyte. The process efficiency was 98.6~100.1%. Intra- and inter-day precisions were not more than 2.1% and 1.7%, while intra- and inter-day accuracies were ranged from -6.8 to 4.5%, respectively. The suitability of the method was examined by analyzing unknown forensic aqueous samples.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.30 no.5
• /
• pp.445-452
• /
• 2017

The wing leading edge skin in this research is an essential structural factor for improving wings' aeromechanical functions, protecting the interior elements of the wings from external damage including birds, and navigating planes safely. The study compared and reviewed models manufactured for optimal light-weight wings of composite UAVs. It compared and investigated displacement forms of torsion loads through finite element analysis using MSC. Patran/Nastran. By confirming the improvement of light-weighting performance according to lamination type, thickness change and shape through torsion strength tests of each model, the research suggested the optimal light-weight wing leading edge skin for small composite UAVs.