• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.2
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• pp.83-96
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• 2011

Currently, the commonly used tunneling method in Korea is NATM (New Austrian Tunneling Method). This method uses the rock bolt, shotcrete, and supporting system to maintain the strength of original soil and ensures the stability of tunnel by stabilizing the soil using the original strength of the soil in maximum after the excavation. In past years, wire-mesh reinforced shotcrete was common ones but currently steel-fiber reinforced shotcrete is being widely used for the tunnel construction site in Korea to save construction time with the advanced construction technology. The results further indicate that needs for the establishment of not only the specifications for shotcrete but the strengthening methods for the under reinforced shotcrete sections. Therefore, this study deals with the development of a new steel-fiber to ensure the stability of tunnels that are under reinforced with steel-fibers and to overcome the shortcomings of conventional method.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.5
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• pp.105-113
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• 2009

In this paper, a vehicle antenna for AM, FM, TDMB, GPS systems was designed and implemented. AM antenna loaded into small space of shark shape was designed by ferrite turn style antenna. For the FM and TDMB antenna, folded monopole antenna which helical is folded was applied. GPS antenna for achieving characteristics both bandwidth and gain improvement was designed microstrip patch that has air substrate and fractal structure. Receiving signal strengths by the measurement were presented for the AM, FM and TDMB antenna. AM signal strength was -65.7dBm, this strength is almost as same conventional pole antenna as -63.4dBm. It can be replaced conventional pole or glass antenna by the studied antenna. Signal strengths for FM and TDMB were -55.66 and -43.50dBm at center frequency, they are 5~10dB higher than conventional antenna. Measurements of bandwidth and gain for the GPS antenna showed 135 MHz under VSWR 2 : 1 and 4.31dBi, gains over GPS band were 3~5dB higher than ceramic patch antenna.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.04a
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• pp.10-10
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• 1998

본 연구에서는 제트 추진 기관의 터빈 익렬에서의 유동과 대기 중에 부유되어 있는 입자 또는 연소 생성물들이 제트엔진 내부로 유입될 경우 이에 따른 압축기 및 터빈 날개의 마모 및 충돌 부위를 예측하기 위하여 수치해석을 수행하였다. 일반적으로 각종 항공기의 추진 기관용 가스 터빈 엔진은 대기중에 부유되어 있는 각종 입자들의 영향을 받게 된다. 특히, 확산 지역을 통과하는 항공기나 먼지 입자 부유물이 많은 공업지대 또는 사막지역을 비행하는 항공기의 경우는 모래 알갱이, 먼지 및 연소 입자의 직접적인 영향을 받아 각 요소들에 심각한 부식 및 마모가 발생됨으로써 성능 저하 및 냉각 통로의 막힘, 압축기와 터빈 날개의 손상 등이 예측되어진다. 특히 항공기용 추진 기관은 엔진 입구에 유입 공기를 정화하기 위한 여과장치의 설치가 불가능하며, 자동차용 가스터빈 엔진의 경우는 여과 장치를 부착하여도 미세한 입자들이 여과 장치에 여과되지 않고 엔진 내부로 침투하게 되므로 치명적인 손상이 예상된다. 이러한 손상들은 초기에는 미세하게 발생하지만, 손상 정도가 점점 누적됨에 따라서 항공기의 안전 운전에 심각한 위험 요소로서 작용할 수 있으며, 경제적으로도 기관의 유지 보수비용의 증가를 가져올 수 있다. 따라서 압축기에 화산재 또는 대기중에 부유되어 있는 금속 입자나 먼지입자 등이 유입되었을 경우, 압축기 날개의 손상 부위와 정도를 예측하는 것이 필요하다. 따라서 본 연구에서는 Lagangian방법을 적용하여 압축기 날개위의 부유 입자 충돌 부위를 예측하고, 설계 시 이를 보완할 수 있는 기준을 제시하였다. 아울러 설계 입구각과 크게 벗어난 유동의 유입시에 발생되는 박리 현상과 이에 따른 입자의 유동 및 날개의 입자 접착 부위를 예측하였다. 본 연구에서는 여러 크기의 입자(다양한 Stokes 수)들을 주어진 속도에서 유선을 따라 압축기 입구에서 압축기 유로로 여러 위치에서 부유 시켜서 그 입자들의 궤적 및 충돌, 점착 위지를 고찰하고, 정량적인 충돌량을 해석하기 위하여 입자 충돌 계수를 정의하여 압축기 날개 표면의 충돌특성을 알아보았다. 이러한 예측을 통하여 압축기 날개 표면의 충돌 부위를 예측하고, 날개의 표면을 코팅하는 등 보호 개선책을 제시할 수 있고, 연소의 반응물 입자가 터빈 날개에 충돌하여 발생되는 날개 표면의 파손, 냉각 홀의 막임, 연소 입자의 점착 부위 등을 예측하여 보완책을 준비할 수 있도록 하였다.

• Geophysics and Geophysical Exploration
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• v.5 no.4
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• pp.291-298
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• 2002

We have developed a two-dimensional (2-D) magnetotelluric (MT) inversion algorithm, which can include topographic effects in inversion. We use the finite element method (FEM) to incorporate topography into forward calculation. Topography is implemented simply by moving nodes of rectangular elements in z-direction according to the elevation of air-earth interface. In the inversion process, we adopt a spatially variable Lagrangian multiplier algorithm in the smoothness-constrained least-squares inversion. The inversion algorithm developed in this study reconstructs subsurface resistivity structure quite well when topography variation exists. Also, it turns out to be effective in both resolution and stability from a model study and field data application.

• Korean Journal of Food Science and Technology
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• v.21 no.5
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• pp.655-661
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• 1989

Optimal drying conditions consisting of air temperature and relative humidity were searched by the simulation-optimization technique for minimizing quality changes in red pepper drying. Optimized drying conditions were analysed in the viewpoint of quality change kinetics and effects of control variables on the state variables. Optimal drying conditions were nearly same in both cases for carotenoid maximization and browning minimization. In two staged optimized drying, relative humidity took a lower search limit of about 10%, and air temperature in the first stage was near the lower limit of $50^{\circ}C$ and in second stage increased to a higher temperature varying with total drying time and stage changing time. Response surface analysis of time invariable drying confirmed the location of the optimal point lying on the vertex of lower limit humidity and a lowest drying temperature which ensures to attain target moisture of 0.2g water/g dry solid. Two stage drying can attain the higher objective function of quality by 3-5% than time invariable drying for shorter total drying times.

• Journal of the Korea Institute of Building Construction
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• v.17 no.1
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• pp.15-21
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• 2017

WHO reported that millions of people die every year because of diseases induced from environmental pollution. In 2012, approximately 7 million people were killed due to air pollution. Major cause of such pollution includes toxin, chemical waste, radiation and air pollution. Therefore, the significance and interest to indoor air quality has been continuously increased. Especially, the interest in radon, the ARC group 1 carcinogen, is rapidly increasing, and banning the use of construction materials that release radon, repairing aged buildings, and developing ventilators. To reduce the level of radon gas was inflowed to indoors and outdoors, this study is to research and develop a radon gas absorption board using absorbents. The absorbents utilized to absorb the radon gas were porous diatomite, natural zeolite, 4A zeolite and 13X zeolite and employed bentonite and illite, montmorillonites with the property of exchanging anions. As the main binder, magnesium oxide was used, with a content of 25% magnesium chloride.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.961-966
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• 2007

Recently the regulation related the environment is getting more and more strengthened. Needs for sustainable building is growing more and more interested in construction industry. However, most of the research has been conducted is focused on material production or maintaining phases. There are not enough research especially in construction phase. And it still exists a lot of environmental barrier factor which could not be easily quantified in construction fields. It makes problems that contractors make an effort only an adequate regulation and they does not take an interest in reducing efforts of environmental pollution. This research defines factor categories which have to be mainly managed and provides the integrated construction management method for sustainable building to reduce environmental pollution through analysis of environmental barrier factor in each work package and effective adjustment of construction plan.

• Journal of the Korean GEO-environmental Society
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• v.9 no.2
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• pp.47-59
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• 2008

Application of mechanically stabilized earth wall (MSEW) abutment has been rapidly increasing in United States of America, Pennsylvania since 2002. MSEW is effective for reducing construction cost and period compared to general concrete reinforced wall. In the paper, theoretical background and conventional criterion of MSEW abutment that is widely used abroad are analyzed. Based on the results, application of suitable MSEW abutment to domestic bridge type is examined. For the application of MSEW abutment in Korea, load interacting with upper shoe in domestic bridge types and structural analyses of beam seat and pile are investigated. As a result, all applications are possible except for PSC BOX Bridge that has heavy self-weight of girder. Through two and three dimensional numerical analyses, horizontal behaviour mechanisms between pile and MSEW were analyzed and field tests are also carried out for seven piles behind earth walls. From results of field tests, it is confirmed that an angle of internal friction of backfill material needs to be greater than 34 degree to use H-Pile as foundation of MSEW.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.4
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• pp.445-451
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• 2019

In this study, we evaluated the durability of concrete produced with recycled polymer that could replace synthetic polymer, which is the main raw material of bridge deck concrete pavement. As a result of the slump and air content test, the requirements of the Korea Highway Corporation Standard were satisfied with all mixing conditions. The slump was lowered when incorporating the recycled bio-polymer, compared to other mix proportions concrete. In contrast, the compressive strength was increased by 6.3~24.4% when the recycled bio-polymer was mixed, compared to the concrete produced with synthetic polymer. It should be noted that the compressive strength was lowered when synthetic polymer was added to concrete mixture. Durability test results showed the best durability when incorporating synthetic polymer. The durability of concrete also increased as the amount of recycled bio-polymer increased, however, the impact was slightly smaller than that of synthetic polymer.

• Smart Media Journal
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• v.8 no.4
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• pp.38-45
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• 2019

When there is a spray flow such as from a pesticide nozzle, winds affect the droplet flow of a rotary-wing drone accompanied by a strong wake, with a severe oscillation. Especially, during forwarding flights or when winds come from the side, compare to a simple hovering flight as the droplet is in the effect of aerodynamic drag force, the effect of spraying region becomes even larger. For this reason, the spraying of pesticides using drones may cause a greater risk of scattering or a difference in droplet dispersion between locations, resulting in a decrease in efficiency. Therefore, through proper numerical modeling and its applied simulation, an indication tool is required applicable for the various flight and atmospheric conditions. In this research, we completed both experiment and numerical analysis for the strong downwash from the rotor and flight velocity of the drone by comparing the probability density function of droplet distribution to build a spraying system that can improve the efficiency when spraying droplets in the pesticide spray drone.