• Journal of Korean Tunnelling and Underground Space Association
• /
• v.23 no.3
• /
• pp.183-198
• /
• 2021

The EPB (Earth Pressure Balanced) shield TBM method restrains the ground deformation through continuous excavation and support. Still, the significant surface settlement occurs due to the ground conditions, tunnel dimensions, and construction conditions. Therefore, it is necessary to clarify the settlement behavior with its influence factors and evaluate the possible settlement during construction. In this study, the analytical model of surface settlement based on the influence factors and their mechanisms were proposed. Then, the parametric study for controllable factors during excavation was conducted by numerical method. Through the numerical analysis, the settlement behavior according to the construction conditions was quantitatively derived. Then, the qualitative trend according to the ground conditions was visualized by coupling the numerical results with the analytical model of settlement. Based on the results of this study, it is expected to contribute to the derivation of the settlement prediction algorithm for EPB shield TBM excavation.

• Journal of Korean Society of Steel Construction
• /
• v.19 no.6
• /
• pp.575-585
• /
• 2007

In this study, a new design equation was presented for square CFTs with high-strength concrete subjected to axial compression and bending. In a previous study, a design equation for square CFTs with normal strength concrete was proposed. A parametric study by fiber analysis was performed taking the width-to-thickness ratio (b/t) and the relative concrete strength to the yield strength of the steel tube (fck/Fy) as the main parameters of this study to determine the maximum moment and the axial load at the maximum moment. A new constitutive model for concrete was adopted for fiber analysis in order to take into account the effect of high-strength concrete. The results of the parametric study were embedded into the method which was presented in the previous study to formulate a new design equation that can be easily used for estimating the strength of square CFTs with high-strength concrete.

• Water for future
• /
• v.28 no.3
• /
• pp.159-173
• /
• 1995

This study is to develop the suitable hydrologic models for determination of the size and location of detention storage facilities to restrain stormwater runoff in urban areas. Fictitious areas of two levels are considered to seize the hydrologic response characteristics. A one-square-kilometer area is selected for the catchment level, and a 10-square-kilometer area consisting of 10 catchments is adapted at the watershed level as representative of urban drainage area. In this analysis, different rainfall frequencies, land uses, drainage patterns, basin shapes and detention storage policies are considered. Flow reduction effect of detention storage facilities is deduced from storage ratio and detention basin factor. A substantial saving in detention storage volumes is achieved when the detention storage is planned at the watershed level than the catchment level. For the application of real watersheds, two watersheds in Seoul metropolitan area-Jamshil 2, Seongnae 1-are selected on the basis of hydrologic response characteristics. Through the regression analysis between dimensionless detention storage volume, dimensionless upstream area ratio and reduction rate of storage ratio, the regression equations to determine the size and location of detention storage facilities are presented.

• Journal of the Korean Geotechnical Society
• /
• v.33 no.3
• /
• pp.17-28
• /
• 2017

We performed laboratory spudcan penetration and extraction tests considering various geometries. Jumunjin sand, representative standard sand in South Korea, and kaolinite were used for uniform sand and clay layers, respectively. The measured vertical bearing and pull-out capacities were compared to empirical equations for shallow foundations. The results showed good agreement between measured and calculated bearing capacity from laboratory test and previous study at shallow depths. The effect of spudcan geometry is shown to depend on site condition. The influence of a sharp spigot is not significant in clays. The slope of the spudcan surface is shown to influence the pull-out capacity. The characteristics of spudcan penetration and extraction behavior considering various geometries can be a useful reference for determining spudcan geometries.

• Journal of Korean Society of Steel Construction
• /
• v.27 no.2
• /
• pp.181-193
• /
• 2015

High-frequency staircases are widely used nowadays to meet aesthetics and functionality needed in modern architecture. Unfortunately, no design guide is available in domestic practice to predict response or evaluate the vibration performance of high-frequency staircases. SCI-P354 published by the Steel Construction Institute of UK provides the formula for effective impulsive force. However, this formula was shown to overestimate the response of high-frequency staircases excited by fast ascending and descending over 2.2Hz pace frequency because it was developed based on the walking test in a slow pace frequency. This study proposes a semi-analytical formula to predict the response of stiff staircases based on analytical and experimental studies of response acceleration for various walking frequencies covering 1.4~4.5Hz.

• Journal of the Korean Society of Food Culture
• /
• v.4 no.2
• /
• pp.167-172
• /
• 1989

Kimchi during fermentation with different periods of storage at room temperature were evaluated for the textural properties, titratable acidity, pH value and thickness of leaves in salting, during fermentation. Thickness of internal leaves in Korean cabbage were decreased of 50% for external leaves. but less decreased on the thickness of leaves in salting. Cutting force of leaves were increased with salting and during kimchi fermentation before 7 days. Stress (force vs area) in kimchi and Korean cabbage was same result of cutting force. Equation of pH change was y=-0.23x+6.13 (r=-0.97). Titratable acidity equation was y=0.09x-0.01(r=0.96). A desirable pH value and titratable acidity were 4.2 and 0.63% in kimchi fermentation.

• Journal of the Society of Disaster Information
• /
• v.11 no.1
• /
• pp.135-147
• /
• 2015

Recent underground common utility tunnels are underground facilities for jointly accommodating more than 2 kinds of air-conditioning and heating facilities, vacuum dust collector, information processing cables as well as electricity, telecommunications, waterworks, city gas, sewerage system required when citizens live their daily lives and facilities responsible for the central function of the country but it is difficult to cope with fire accidents quickly and hard to enter into common utility tunnels to extinguish a fire due to toxic gases and smoke generated when various cables are burnt. Thus, in the event of a fire, not only the nerve center of the country is paralyzed such as significant property damage and loss of communication etc. but citizen inconveniences are caused. Therefore, noticing that most fires break out by a short circuit due to electrical works and degradation contact due to combustible cables as the main causes of fires in domestic and foreign common utility tunnels fire cases that have occurred so far, the purpose of this paper is to scientifically analyze the behavior of a fire by producing the model of actual common utility tunnels and reproducing the fire. A fire experiment was conducted in a state that line type fixed temperature detector, fire door, connection deluge set and ventilation equipment are installed in underground common utility tunnels and transmission power distribution cables are coated with fire proof paints in a certain section and heating pipes are fire proof covered. As a result, in the case of Type II, the maximum temperature was measured as $932^{\circ}C$ and line type fixed temperature detector displayed the fire location exactly in the receiver at a constant temperature. And transmission power distribution cables painted with fire proof paints in a certain section, the case of Type III, were found not to be fire resistant and fire proof covered heating pipes to be fire resistant for about 30 minutes. Also, fire simulation was carried out by entering fire load during a real fire test and as a result, the maximum temperature is $943^{\circ}C$, almost identical with $932^{\circ}C$ during a real fire test. Therefore, it is considered that fire behaviour can be predicted by conducting fire simulation only with common utility tunnels fire load and result values of heat release rate, height of the smoke layer, concentration of O2, CO, CO2 etc. obtained by simulation are determined to be applied as the values during a real fire experiment. In the future, it is expected that more reliable information on domestic underground common utility tunnels fire accidents can be provided and it will contribute to construction and maintenance repair effectively and systematically by analyzing and accumulating experimental data on domestic underground common utility tunnels fire accidents built in this study and fire cases continuously every year and complementing laws and regulations and administration manuals etc.

• The Bulletin of The Korean Astronomical Society
• /
• v.40 no.1
• /
• pp.86.1-86.1
• /
• 2015

고대 천문학의 대표적인 관측기기로 혼의가 있다. 중국도 일찍 혼의가 도입되어 천체 관측에 활용된 것으로 보인다. 중국 고대의 선기옥형이라는 기기가 한(漢) 대에 접어 들어 서양에서 도입된 혼천설의 영향을 받아 혼의로 발전하였다. 초창기 혼의에는 주천도수와 24방위의 눈금을 새겼고, 원주율을 3으로 적용하였다. 한말(漢末)에 혼천설에 따라 혼의 안에 지구를 만들고 혼천의 또는 혼천상이라고 불렀다. 혼천설의 구조를 적용하기 위해 비교적 자세한 원주율의 값이 알려지면서 혼의의 정밀한 눈금을 제작하는 계기를 마련하였다. 더불어 수 개의 환을 혼의에 추가하여 2층 구조의 혼의를 개발하였다. 당(唐) 대에 이르러 육합의, 삼신의, 사유의로 구성된 혼의의 3층 구조가 완성되었다. 송(宋) 대에는 혼의와 혼상에 수격식 자동운행장치를 도입하여 혼천의라고 하고, 이전의 관측용 혼의를 동후의(銅候儀)라고 불렀다. 조선 세종 대에 제작한 혼천의는 송(宋) 대의 자동운행이 결합된 혼의였고, 동후의의 관측기능을 대신하여 간의를 사용하였다. 그 재원은 각각 오징의 "서찬언"과 "원사"에서 빌려왔고, 이를 "제가역상집"에 정리하였다. 혼의의 환에는 한 개의 원주에 주천도수, 12시백각, 24방위 중 한 종류의 눈금을 그렸다. 그러나 간의에서는 한 개의 원주에 두 개의 눈금을 그리는 방법이 시작되었다. 이러한 눈금제작 방식은 조선에서 새롭게 개발된 일성정시의에 적용되었다.

• Proceedings of the KIEE Conference
• /
• 2003.10a
• /
• pp.174-177
• /
• 2003

본 논문에서는 AC PDP의 유지방전구간에서의 인가전압에 따른 방전전류, 공간전압, 벽전하 등의 변화를 새로운 AC PDP를 위한 등가회로모델을 사용하여 효율적이고 간편하게 시뮬레이션 한 결과를 소개한다. 벽전하의 정확한 분석은 안정적이고 효율적인 AC PDP의 구동 방법을 개발하기 위해 계속 연구, 보고 되어 왔지만, 인가되는 전압의 변화에 따른 시간적인 셀 내부의 변화를 빠르고 편리하게 분석하고 이해하는데 효과적인 방법은 제시되지 못하였다. 본 논문에서는 AC PDP의 전극간 물리적인 특성을 고려하여 3개의 직렬 커패시터와 1개의 병렬 커패시터, 2개의 싸이리스터를 사용하여 AC PDP를 위한 등가회로모델을 구성하여 제시하였다. 제안된 등가회로모델은 SPICE와 같은 표준 회로시뮬레이션 툴에 손쉽게 적용가능하며, 이러한 방법으로 분석된 패널내의 전류, 공간전압, 벽전하의 동특성을 소개하였다. 등가회로모델을 이용한 시뮬레이션 결과는 실험을 통한 측정 결과와 비교하여 그 정확성을 검증하였다. 인가전압의 시간적 변화의 따른 유입전류 및 셀 내의 전압 및 전하의 분포를 손쉽고 정확하게 시뮬레이션 할 수 있는 본 AC PDP의 등가회로모델은 AC PDP의 특성을 이해하는 데에 중요한 도구가 될 것이며 효율적인 구동 방식의 개발 및 분석 등에 널리 활용될 수 있을 것이다.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.6 no.1
• /
• pp.34-42
• /
• 2007

Powder blasting technique has been considered one of the most appropriate micro machining methods for hard and brittle materials, since the productivity is high and the heat layers caused by material removal are very thin. Recent development of special purposed parts, such as the parts for semiconductor processing, the parts for LCD, sensors for micro machine fabrication and so on, has been expanded. Thus, it is essential to develop powder blasting technologies for micromachining of hard and brittle materials such as glass, ceramics and so on. In this paper, the characteristics of powder blasted glass surface were tested under various blasting parameters. Finally, we proposed a predictive model for powder blasting process using the neural network and the response surface method. Detail analysis of the simulation results is carried out and the performance of two predictive models is compared.