• 대한토목학회논문집
• /
• 제28권3A호
• /
• pp.305-313
• /
• 2008

본 연구에서는 교량의 노면조도 및 교량과 차량 사이의 상호작용을 고려한 수치해석방법을 사용하여 구한 도로교의 동적하중허용계수(DLA)를 LRFD 형식으로 신뢰도이론의 2차 모멘트법을 적용하여 보정하였다. 대상교량은 건설교통부에서 제정한 "도로교 상부구조 표준도"에 수록되어 있는 단순 PSC빔교와 단순 강판형교, 그리고 LRFD로 설계된 개구제형 단면을 갖는 강박스형교를 사용하고, "보통의 도로"에 대하여 생성시킨 10개의 노면조도를 사용하였다. 차량은 5축 트랙터-트레일러인 표준트럭(DB-24)을 3차원 차량모델로 모델링하고, 교량은 주형을 보요소로, 콘크리트 바닥판은 쉘요소로 이상화시켰으며 주형과 콘크리트 바닥판 사이는 Rigid Link를 사용하여 3차원으로 모델링하였다. 3가지 형식에 대한 10개의 교량에 각각 10개의 노면조도를 사용하여 해석적 방법으로 구한 100개의 해석결과와 OHBDC에서 사용한 보정 식을 사용하여 PSC빔교, 강판형교, 강박스형교 및 전체 대상교량에 대한 LRFD 형식의 DLA를 통계적으로 추정하였다.

• 대한토목학회논문집
• /
• 제31권4D호
• /
• pp.511-518
• /
• 2011

축중계를 통한 화물차량의 축하중 자료는 도로의 설계, 유지관리, 시설물 보호 등의 위해서 필수적인 자료이다. 이와 같은 용도로 고속축중계의 자료는 도로계획, 연구자, 공무들은 고속축중계 자료를 활용한다. 또한 최근에는 중차량에 대한 단속에도 고속축중계의 자료를 활용하고 있다. 따라서 본 연구에서는 일반국도에서 수집된 고속축중계 자료를 활용하여 축하중을 추정하는 모형을 개발하였다. 추정된 축하중 추정 모형은 기존의 평균값을 이용한 방법과의 비교를 통하여 개발된 모형에 대한 비교 평가하였다. 축중량 추정에 있어 기존의 평균값을 적용하는 것보다 회귀모형을 적용하는 것이 모든 차종에 걸쳐서 작은 오차를 보이는 것으로 분석되었다. 향후 이러한 모형은 현장에서 운영되는 고속축중계의 결측자료 보정, 재보정 여부에 대한 평가 등의 목적으로 활용될 수 있을 것이다.

• 한국환경성돌연변이발암원학회지
• /
• 제21권2호
• /
• pp.122-127
• /
• 2001

4-tert-octylphenol (OP) is a surfactant additive widely used in the manufacture of a variety of detergents and plastic products. Also, OP is known to have estrogenic activity by interacting with development and functions of endocrine system. This study was carried out to obtain toxicokinetic parameters of OP in male Sprague-Dawley rats. Male rats were administered OP, by either single oral (gavage) applications of 50, 100 or 200 mg/kg body weight. or a single intravenous injections of 1, 5 or 10 mg/kg body weight. Blood samples taken at several time intervals after administration were obtained from the femoral artery. Analysis of blood samples for OP was performed by gas chromatography mass spectrometry (GC/MS). The detection limit of OP was 1.9 ng/$m\ell$ at SIM (selected ion monitoring) mode of GC/MS. Calibration curve for analysis of the concentrations of OP in plasma was (OP/butylphenol peak area ratio) = 0.0294 $\times$ (plasma cone.) + 0.028 ($r^2$= 0.9991). The OP plasma concentration was 3921 ng/$m\ell$ immediately after single intravenous application, decreased rapidly within 45 min, and was detectable at low concentration up to 6 hr after application. When administered orally in rats (50, 100 and 200 mg/kg), OP was detected in the blood early after gavage administration, indicating the rapid initial uptake from gastrointestinal tract, with Tmax obtained from 0.67~0.83 hr. Using the AUC (area under the curve) of plasma concentration vs. time, low oral bioavailabilities of 1.2, 5.0 and 5.3% were calculated for the 50, 100 and 200 mg/kg groups, respectively.

• 대한기계학회논문집B
• /
• 제27권6호
• /
• pp.714-725
• /
• 2003

The theory of the current-type electromagnetic flowmeter for a high temporal resolution was developed for two-phase flow measurements. To predict the output of the current-type flowmeter, the three-dimensional virtual potential distribution C and the newly introduced flow pattern coefficient f were derived and computed. The output of flowmeter depends on the liquid conductivity (sensitive to temperature) and flow configurations of the two-phase flow with the sinusoidal excitation over 100 Hz. The flow pattern coefficient was specially devised to separate the dependency on the flow configuration of the two-phase flow from that on the liquid conductivity which can be expressed with the calibration of single-phase flow. Using the finite difference method, the three-dimensional virtual potential distributions were computed for the electrode of finite size. By taking derivative of the virtual potential, the weight functions were evaluated and compared with existing analytic series solution for the point-electrode. There was a reasonable correspondence between the present and existing results. In addition, the flow pattern coefficients were evaluated for annular flows with various film thicknesses, and compared with the experimental results by the impedance spectroscopy. The numerical results agreed well with the experimental data.

• Computers and Concrete
• /
• 제25권5호
• /
• pp.383-400
• /
• 2020

Due to higher stiffness to weight, higher corrosion resistance, higher strength to weight ratios and good durability, concrete composite structures provide many advantages as compared with conventional materials. Thus, they have wide applications in the field of concrete construction. This research focuses on the structural behavior of steel-tube CFRP confined concrete (STCCC) columns under axial concentric loading. A nonlinear finite element analysis (NLFEA) model of STCCC columns was simulated using ABAQUS which was then, calibrated for different material and geometric models of concrete, steel tube and CFRP material using the experimental results from the literature. The comparative study of the NLFEA predictions and the experimental results indicated that the proposed constitutive NLFEA model can accurately predict the structural performance of STCCC columns. After the calibration of NLFEA model, an extensive parametric study was performed to examine the effects of different critical parameters of composite columns such as; (i) unconfined concrete strength, (ii) number of CFRP layers, (iii) thickness of steel tube and (iv) concrete core diameter, on the axial load capacity. Furthermore, a large database of axial strength of 700 confined concrete compression members was developed from the previous researches to give an analytical model that predicts the ultimate axial strength of composite columns accurately. The comparison of the predictions of the proposed analytical model was done with the predictions of 216 NLFEA models from the parametric study. A close agreement was represented by the predictions of the proposed constitutive NLFEA model and the analytical model.

• 재활복지공학회논문지
• /
• 제8권3호
• /
• pp.187-196
• /
• 2014

본 논문은 경사로에 위치하는 Mobile Walker의 안전성 확보를 위한 직진성 향상알고리즘을 제안한다. Mobile Walker는 경사면주행 시 로봇의 무게와 경사도에 의한 외력으로 인해 경로 이탈을 하게 된다. 이를 보정하기 위해 본 논문에서는 노면의 기울기에 따른 외력을 추정하고, 이를 모터출력에 가감하는 제어기를 사용하였다. 또한 사용자가 입력하는 목표 회전각속도와 로봇의 회전각속도와의 비교를 통해 각 구동축에 가중치를 인가하는 알고리즘을 사용하였다. 제안한 보정 제어기를 적용한 결과, 경사면 이동 시 이탈거리는 무보정 실험의 경우 발산하지만 경사로 보정 알고리즘을 적용하였을 경우에는 이탈거리가 최대 10cm 이내로 안정적인 주행을 하는 것을 확인할 수 있었으며, 이탈거리 변화율 또한 1m 이후 안정화되어 더 이상의 변화가 발생하지 않는 것을 확인할 수 있었다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 춘계학술대회
• /
• pp.1951-1956
• /
• 2004

The transient nature and complex flow geometries of two-phase gas-liquid flows cause fundamental difficulties when measuring flow velocity using an electromagnetic flowmeter. Recently, a current-sensing flowmeter was introduced to obtain measurements with high temporal resolution (Ahn et $al.^{(1)}$). In this study, current-sensing flowmeter theory was applied to measure the fast velocity transients in slug flows. To do this, the velocity fields of axisymmetric gas-liquid slug flow in a vertical pipe were obtained using Volume-of-Fluid (VOF) method and the virtual potential distributions for the electrodes of finite size were also computed using the finite volume method for the simulated slug flow. The output signal prediction for slug flow was carried out from the velocity and virtual potential (or weight function) fields. The flowmeter was numerically calibrated to obtain the cross-sectional liquid mean velocity at an electrode plane from the predicted output signal. Two calibration parameters are required for this procedure: a flow pattern coefficient and a localization parameter. The flow pattern coefficient was defined by the ratio of the liquid resistance between the electrodes for two-phase flow with respect to that for single-phase flow, and the localization parameter was introduced to avoid errors in the flowmeter readings caused by liquid acceleration or deceleration around the electrodes. These parameters were also calculated from the computed velocity and virtual potential fields. The results can be used to obtain the liquid mean velocity from the slug flow signal measured by a current-sensing flowmeter.

• 대한기계학회논문집B
• /
• 제27권10호
• /
• pp.1385-1392
• /
• 2003

An electromagnetic flowmeter(EMF) was developed and its characteristics were compared with a commercial EMF. The developed EMF was designed as the 100 mm nominal diameter. A signal processing circuit was also developed for generating the magnetic field and converting the flow signal to flowrate and flow quantity. In order to obtain a more stable and reliable flow signal, the double magnetizing frequency was adopted for magnetizing the coil of the EMF. For the characterization of the developed EMF, the uncertainty of calibrator was estimated within $\pm$0.5 %. The evaluation procedure of the uncertainty followed the ISO Guide to the Expression of Uncertainty in Measurement. It was found that the flow signals between the electrodes were about $\pm$60-$\pm$300$\mu$V, which were sufficient for the discrimination of flowmeter and the protection of noise. The test results against the calibrator showed the good linearity in the range of 3 ㎥/h and 70 ㎥/h. A commercialized design of the EMF based on the current study will be technically more competitive in domestic and foreign market.

• 대한기계학회논문집A
• /
• 제22권2호
• /
• pp.353-364
• /
• 1998

This paper describes the design processes and evaluation results of a small-sized six-axis force/torque sensor. The new six-axis force/torque sensor including S-type structure has been developed using a parallel plate structure as a basic sensing element. In order tominimize coupling errors, the location of strain gages has been determined based on the finite element analysis and the connections of strain gages have been made such that the bridge circuit with 4 strain gages becomes balanced. Several design modifications result in a similar strain sensitivity for six-axis forces and moments, and the reduced coupling errors of 2.6% FS between each forces and moments. Calibration test results show that the six-axis load cell developed which has light weight of 135g and the maximum capacities of 196 N in forces and 19.6 N.m in moments is estimated to be within 7.1% FS in coupling error.

• 한국농공학회지
• /
• 제33권4호
• /
• pp.84-95
• /
• 1991

The compaction ratio of the field dry density to the maximum dry density is generally adopted as the index of quality control for embankment of earthfill structures such as Earth Dam, Sea Dike, River Bank and Road. In case of coarse materials are included in the earth material, the compaction ratio will be varied in wide range since the dry density is influenced by quantity of coarse material in the soil. The treatment for the coarse material should be controlled carefully in testing. In this study, the compaction characteristics of the soil contained the coarse materials were researched and calibration of the suitability of field quality control methods were carried out. 28 Samples were made of clay(CL) and sandy soil (SM) mixed with gravel whose content were 0, 4, 6, 8, 10, 12, 15, 20, 25, 30, 35, 40, 45, and 60% in Weight. The compaction characteristics depending on the coarse material content were analysed through 4 types of compaction tests which are A-1, B-i, C-i and D-1. The adjusting coefficients for density and moisture content namely a and ${\beta}$ respectively were proposed in order to consider the effects depending on content of the coarse materials. The test methods to control reasonably and promptly the quality of earthfill were proposed after analysing the ranges of possible errors on the relative compaction ratio between laboratory compaction methods and field density testing methods.