• 한국건설관리학회논문집
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• 제9권5호
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• pp.186-193
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• 2008

흙막이를 지지하는 버팀대를 가설재가 아닌 주(主)구조체로 이용하는 SPS(Strut as a Permanent System) 공법이 개발되어 최근 국내 공사현장에서 활발하게 활용되고 있다. 이 공법은 건축공사 현장에서 원가절감, 공기단축, 구조적 안정성 향상, 건설환경 개선 등 다양한 이점을 주는 반면 지하층고의 증가와 철골부위 내화피복을 추가로 수행하여야 하는 문제점이 있다. 지하층고의 증가는 흙막이 깊이 및 지하 최저부위 굴착량 증가의 문제점을 유발하고, 내화피복 공사는 공사환경을 열악하게 함은 물론 공사비 증대의 요인이 된다. 따라서 본 연구는 SPS 공법의 문제점을 개선한 모듈화된 철골철근 복합 구조시스템(modularized hybrid structure system)을 제안하는 것을 목적으로 한다. 제안된 공법은 구성원리와 함께 실험을 통하여 구조적 성능을 검증되고 다양한 공사조건을 만족시키는 시공성능이 분석된다.

• 지구물리와물리탐사
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• 제7권1호
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• pp.80-87
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• 2004

During excavation work for the construction of a highway bridge in a limestone area in Korea, several cavities were found, and construction work was stopped temporarily. Cavities under the bridge piers might seriously threaten the safety of the planned bridge, because they could lead to excessive subsidence and differential settlement of the pier foundations. In order to establish a method for reinforcement of the pier foundations, borehole radar reflection and tomography surveys were carried out, to locate cavities under the planned pier locations and to determine their sizes where they exist. Since travel time data from the crosshole radar survey showed anisotropy, we applied an anisotropic tomography inversion algorithm assuming heterogeneous elliptic anisotropy, in order to reconstruct three kinds of tomograms: tomograms of maximum and minimum velocities, and of the direction of the symmetry axis. The distribution of maximum velocity matched core logging results better than that of the minimum velocity. The degree of anisotropy, defined by the normalized difference between maximum and minimum velocities, was helpful in deciding whether an anomalous zone in a tomogram was a cavity or not. By careful examination of borehole radar reflection and tomography images, the spatial distributions of cavities were delineated, and most of them were interpreted as being filled with clay and/or water. All the interpretation results implied that two faults imaged clearly by a DC resistivity survey were among the most important factors controlling the groundwater movement in the survey area, and therefore were closely related to the development of cavities. The method of reinforcement of the pier foundations was based on the interpretation results, and the results were confirmed when construction work was resumed.

• 한국토양비료학회지
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• 제49권3호
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• pp.235-241
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• 2016

The soil does not only serve as a medium for plant growth but also for engineering construction purposes. It is very weak in tension, very strong in compression and fails only by shearing. The behaviour of the soil under any form of loading and the interactions of the earth materials during and after any engineering construction work has a major influence on the success, economy and the safety of the work. Soils and their management have therefore become a broad social concern. A limitless variety of soil materials are encountered in both agronomy and engineering problems, varying from hard, dense, large pieces of rock through gravel, sand, silt and clay to organic deposits of soft compressible peat. All these materials may occur over a range of physical properties, such as water contents, texture, bulk density and strength of soils. Therefore, to deal properly with soils and soil materials in any case requires knowledge and understanding of these physical properties. The desired value of bulk density varies with the degree of stability required in construction. Bulk density is also used as an indicator of problems of root penetration,soil aeration and also water infiltration. This property is also used in foundation engineering problems. While not conforming to standard test procedures, this work attempts to add to the basic information on such important soil parameters as water content, bulk density.

• 대한원격탐사학회지
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• 제25권6호
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• pp.547-557
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• 2009

LIDAR (LIght Detection And Ranging) is an active remote sensing technology which provides 3D coordinates of the Earth's surface by performing range measurements from the sensor. Early small footprint LIDAR systems recorded multiple discrete returns from the back-scattered energy. Recent advances in LIDAR hardware now make it possible to record full digital waveforms of the returned energy. LIDAR waveform decomposition involves separating the return waveform into a mixture of components which are then used to characterize the original data. The most common statistical mixture model used for this process is the Gaussian mixture. Waveform decomposition plays an important role in LIDAR waveform processing, since the resulting components are expected to represent reflection surfaces within waveform footprints. Hence the decomposition results ultimately affect the interpretation of LIDAR waveform data. Computational requirements in the waveform decomposition process result from two factors; (1) estimation of the number of components in a mixture and the resulting parameter estimates, which are inter-related and cannot be solved separately, and (2) parameter optimization does not have a closed form solution, and thus needs to be solved iteratively. The current state-of-the-art airborne LIDAR system acquires more than 50,000 waveforms per second, so decomposing the enormous number of waveforms is challenging using traditional single processor architecture. To tackle this issue, four parallel LIDAR waveform decomposition algorithms with different work load balancing schemes - (1) no weighting, (2) a decomposition results-based linear weighting, (3) a decomposition results-based squared weighting, and (4) a decomposition time-based linear weighting - were developed and tested with varying number of processors (8-256). The results were compared in terms of efficiency. Overall, the decomposition time-based linear weighting work load balancing approach yielded the best performance among four approaches.

• 한국건설관리학회논문집
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• 제8권5호
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• pp.142-151
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• 2007

해상에서 이루어지는 암굴착 공사는 평균해수면 이하를 기준으로 수중으로 설계가 되어 있다고 하더라도, 조석간만의 차가 심한 서해와 남해의 경우에는 조석의 주기에 따라 해수면 위로 작업면이 노출되는 동안 육상작업이 가능해진다. 이를 활용할 경우 수중 작업 시 작업자의 위험성 증대, 작업효율의 저하 및 공사비 증대에 관한 수중공사의 단점을 보완할 수 있는 하나의 대안이 될 수 있다. 그러나 작업해야할 암굴착면의 높이와 조석에 따라 변화하는 수면의 높이에 따라 작업면의 노출시간, 즉 작업가능시간이 변화하게 되며 이에 따라 공사비의 변화도 발생하게 된다. 따라서 본 연구에서는 해상 암굴착 공사를 수행할 때 수중 작업과 비교하여 조석간만의 차를 이용한 공사의 경제성을 분석하고, 작업가능시간을 산정하여 작업시간별 경제성을 분석할 수 있는 방법을 제시함으로써, 조석간만의 차를 이용한 해상 암굴착 공사방식의 적용가능성을 모색해 보고자한다.

• 대한원격탐사학회지
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• 제37권3호
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• pp.543-557
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• 2021

에어로솔은 입자의 크기와 조성 및 관측센서에 따라 상이한 분광특성을 보이기 때문에, 다양한 센서의 에어로솔 산출물에 대한 비교분석이 반드시 필요하다. 그러나, 우리나라에서 다종위성의 공식적인 AOD (Aerosol Optical Depth) 산출물을 대상으로 수년간의 자료를 수집하여 정확도 비교평가를 수행한 사례는 아직 보고된 바가 없다. 이에, 본 연구에서는 2015년 1월부터 2019년 12월까지 MODIS (Moderate Resolution Imaging Spectroradiometer), VIIRS (Visible Infrared Imaging Radiometer Suite), Himawari-8, Sentinel-3 AOD 산출물과 AERONET (Aerosol Robotic Network) 지상 태양광도계 자료의 비교분석을 통하여 위성 AOD의 성능을 평가하고, 계절적 및 지리적 차이에 따른 정확도 특성을 분석하였다. 오랜 기간 축적되어온 산출 기술에 MAIAC (Multiangle Implementation of Atmospheric Correction) 알고리듬을 추가하여 최적화된 MODIS 산출물이 가장 높은 정확도를 나타냈고(CC=0.836), VIIRS와 Himawari-8이 그보다 약간 낮은 정도의 성능을 보였으며, Sentinel-3는 비교적 최근에 발사되어 알고리듬 최적화가 아직 덜 이루어진 관계로 정확도가 낮게 나타났다. MODIS, VIIRS, Himawari-8 AOD 산출물은 계절에 따라, 그리고 도시/비도시에 따라 별다른 정확도 차이를 보이지는 않았지만, 일부 해안지역에서는 혼합화소 문제로 인하여 약간 정확도가 떨어지는 경우도 존재했다. AOD는 위성영상 대기보정의 핵심 인자이기 때문에, 본 연구의 AOD 비교평가는 향후 국토위성, 농림위성 등의 대기보정 연구에도 중요한 참고자료가 될 것으로 사료된다.

• 한국태양에너지학회 논문집
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• 제26권2호
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• pp.19-25
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• 2006

Methane hydrate, non-polluting new energy resource, satisfies requirement and considered as a precious resource that can prevent the global warming. Fortunately, there are abundant resources of methane hydrate distribute in the earth widely. Therefore, developing the techniques that can utilize these gases effectively is highly desired. The work in this paper here is to develop a skill which can transport and store methane hydrate. As a first step, the equilibrium experiment was carried out by increasing temperatures in the cell at fixed pressures. The influence of gas consumption rates under variable degree of subcooling, stirring and water injection has been investigated formation to clarify kinetic characteristics of the hydrate. The results of present investigation showed that the enhancements of the hydrate formation in terms of the gas/water ratio are closely related to operational pressure, temperature, degrees of subcooling, and water injection.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1994년도 가을 학술발표회 논문집
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• pp.139-148
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• 1994

Rapid industrialization and urbanization caused by the high economic growth of the country requires optimization of land usage as well as the expansion of underground space. Therefore the construction of large and deep basements is inevitable in built up areas where the braced excavation for earth retaining structures may create many problems such as settlement and damages of nearby buildings and underground utilities. In this work, some of major influential factors concerning the stability of braced excavation are investigated and the results are compared with the field observation results. The ground water table, applied strut forces, horezontal wall displacement, infilling materials in the rock joints were found to be the most critical factors influencing the stability of braced walls constructed in the layered ground. Magnituide and type of the wall deformation was closely related to the pattern of the surface settlement. The stability of braced walls are described in terms of strut forces.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.305.2-305.2
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• 2016

Tin monosulfide (SnS) is one promising candidate absorber material which replace the current technology based on cadmium telluride (CdTe) and copper indium gallium sulfide selenide (CIGS) for its suitable optical band gap, high absorption coefficient, earth-abundant, non-toxic and cost-effective. During past years work, thin film solar cells based on SnS films had been improved to 4.36% certified efficiency. In this study, Tin monosul fide was obtained by atomic layer deposition (ALD) using the reaction of Tetrakis (dimethylamino) tin (TDMASn, [(CH3)2N]4Sn) and hydrogen sulfide (H2S) at low temperatures (100 to 200 oC). The direct optical band gap and strong optical absorption of SnS films were observed throughout the Ultraviolet visible spectroscopy (UV VIS), and the properties of SnS films were analyzed by sanning Electron Microscope (SEM) and X-Ray Diffraction (XRD).

• 세라미스트
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• 제10권3호
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• pp.75-85
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• 2007

Over the past few years, due to the great development of optical communications, an increasing R&D activity has been focused on the design and manufacture of the integrated optic amplifiers, with particular reference to their application in wavelength-division-multiplexing (WDM) systems. In this technological context, rare-earth-doped oxide glasses, which had been widely used for solid state lasers, gained much attention as highly performing materials in the third telecom window, around 1.5 micron. The aim of the present paper is to provide a brief overview of the progress made, with particular reference to the authors' work in this area, and to shortly discuss its perspectives.