• Journal of the Korean GEO-environmental Society
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• v.17 no.7
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• pp.5-13
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• 2016

This research is focused on the seepage behavior of embankment which had the weak zone with big permeability. The distributed TDR (Time Domain Reflectometer) and point sensors such as settlement gauge, pore water pressuremeter, vertical total stressmeter, and FDR (Frequency Domain Reflectometer) sensor were used to measure the seepage characteristics and embankment behavior. Also, the measured data were compared to the data of 2-D and 3-D numerical analysis. The dimension of model embankment was 7 m length, 5 m width and 1.5 m height, which is composed of fine-grained sands and the water level of embankment was 1.3 m height. The seepage behavior of measuring and numerical analysis were very similar, it means that the proper sensing system can monitor the real-time safety of embankment. The result by 2-D and 3-D numerical analysis showed similar saturation processing, however in case of weak zone, the phreatic lines of 2-D showed faster movement than that of 3-D analysis, and finally they converged.

• Journal of Korea Water Resources Association
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• v.40 no.2 s.175
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• pp.183-190
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• 2007

Soil layer in vegetation filter strip is one of the very important factor for reduction of non-point pollutants by physical, chemical and biological reactions of it through infiltration process. This study was carried out to prepare more effective vegetation filter strip through modification of soil layer for river water quality improvement. Therefore, the main aims of this study are to compare and evaluate normal (straighten type) and modified (step type) vegetation filter strip, which make artificially change the soil layer to improve infiltration ability, through bench scale experiments. In the results of this study, vegetation filter strip of step type is much more highly reduction effectiveness of pollutants in surface flow compared with normal vegetation filter strip. In case of below effluent, however, it appeared that the vegetation filter strip modified soil layer showed lower reduction effectiveness of pollutants than the general vegetation filter strip. This result was judged because effluent through the vegetation filter strip of step type passed bigger size of aggregate or sand than the vegetation filter strip of straighten type. If we compare it as a definition of pollutant load to estimate total amount of reduced pollutants by vegetation filter strip, reduced pollutants load by step type showed higher than those by straighten type because below effluent amount relied on total effluent amount was higher at step type (4%) than at straighten type (2%). In conclusion, the vegetation filter strip of step type to improve infiltration effect is much more reduction effectiveness of pollutants than vegetation filter strip of straighten type.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.5
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• pp.499-507
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• 2004

We have studied tile detection techniques, which can determine the location and the weight of an intruder into infrastructure, by using fiber-optic ROTDR (Rayleigh optical time domain reflectometry) sensor and fiber-optic BOTDA (Brillouin Optical time domain analysis) sensor, which can use an optical fiber longer than that of ROTDR sensor Fiber-optic sensing plates of ROTDR sensor, which arc buried in sand, were prepared to respond the intruder effects. The signal of ROTDR was analyzed to confirm the detection performance. The constructed ROTDR could be used up to 10km at the pulse width of 30ns. The location error was less than 2 m and the weight could be detected as 4 grades, such as 20kgf, 40kgf, 60kgf and 80kgf. Also, fiber optic BOTDA sensor was developed to be able to detect intrusion effect through an optical fiber of tells of kilometers longer than ROTDR sensor. fiber-optic BOTDA sensor was constructed with 1 laser diode and 2 electro-optic modulators. The intrusion detection experiment was peformed by the strain inducing set-up installed on an optical table to simulate all intrusion effect. In the result of this experiment, the intrusion effort was well detected as the distance resolution of 3m through the fiber length of about 4.81km during 1.5 seconds.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.2
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• pp.94-101
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• 2016

This paper presents an investigation into the durability alkali-activated materials(AAM) mortar and paste samples manufactured using fly-ash(FA) and ground granulated blast furnace slag(GGBFS) exposed to a sulfate environment with different GGBFS replace ratios(0, 30, 50 and 100%), sodium silicate modules($Ms[SiO_2/Na_2O]$ 1.0, 1.5 and 2.0) and initial curing temperatures($23^{\circ}C$ and $70^{\circ}C$). The tests involved immersions for a period of 6 months into 10% solutions of sodium sulfate and magnesium sulfate. The evolution of compressive strength, weight, length expansion and microstructural observation such as x-ray diffraction were studied. As a results, as higher GGBFS replace ratio or Ms shown higher compressive strengths on 28 days. In case of immersed in 10% sodium sulfate solution, the samples shows increase in long-term strength. However, for samples immersed in magnesium sulfate solutions, the general observation was that the compressive strength decreased after immersion. The most drastic reduction of compressive strength and expansion of weight and length occurred when GGBFS or Ms ratios were higher. Also, the XRD analysis of samples immersed in magnesium sulfate indicated that expansion of AAM caused by gypsum($CaSO_4{\cdot}2H_2O$); the gypsum increased up to 6 months continuously.

• Journal of Sensor Science and Technology
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• v.10 no.3
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• pp.163-172
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• 2001

Fiber optic BOTDA (Brillouin Optical Time Domain Analysis) sensor was developed to be able to detect intrusion effect through several ten kilometer optical fiber. Fiber optic BOTDA sensor was constructed with 1 laser diode and 2 electro-optic modulators. The intrusion detection experiment was peformed by the strain inducing set-up installed on an optical table to simulating an intrusion effect. In the result of this experiment, the intrusion effect was well detected as the distance resolution of 3 m through the fiber length of about 4.81 km during 1.5 seconds.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.229-238
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• 2006

암반터널굴착을 위한 발파시 이로 인한 암반의 최종 손상영역을 예측하는 것은 터널의 안전성을 위해 매우 중요하다. 그러나 복잡한 발파거동은 손상영역을 적절히 예측하는데 상당한 어려움이 있다. 이러한 어려움을 효과적으로 해결하기 위해 발파하중을 응력파와 가스압으로 분리한 많은 연구가 진행되었다. 응력파는 발파공 주위에 분쇄한(crushing annulus)과 파쇄균열대(fracture zone)를 형성시키며, 상당시간 지속되는 준정적인 가스는 파쇄균열대의 닫힌 균열내부에 침투하여 균열을 다시 진행시키는 역할을 하게 된다. 즉, 가스압은 최종적으로 암반에 손상을 가하는데 기여를 한다. 따라서 본 논문은 이러한 가스압에 의해 생성되는 균열의 최종 진행 길이를 예측함으로써 발파로 인한 최종 손상영역을 간단하게 예측할 수 있는 방법을 제시하고자 한다. 이를 위해 무한 탄성평면에서 발파공 주위에 대칭으로 형성되는 균열을 모델로 사용하였다. 이 모델에서 균열이 진행할 수 있는 조건과 가스의 질량이 일정하다는 두가지 조건을 사용하였다. 그 결과 응력집중계수는 균열이 진행할수록 감소하여 최종균열의 길이를 예측할 수 있었고, 그와 동시에 발파공에 작용하는 압력도 감소하는 것을 확인할 수 있었다.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1532-1533
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• 2007

Hollow형 미세바늘 어레이는 주사기와 패치의 장점을 결합하여 여러 종류의 약물을 통증 없이, 전달할 수 있게 한다. 본 논문에서는 건식 식각 방법과 습식 식각 방법을 이용하여 hollow형 실리콘 미세바늘 어레이를 제작하는 제작 공정과 그 결과를 제시하였다. 미세바늘 어레이의 형태는 실리콘 웨이퍼의 앞면에서 세 번의 식각 공정을 이용해 제작되었는데, 첫 번째 건식 식각 공정으로 피부에의 침투를 원활히 하기 위해 바늘 끝을 형성하고, 두 번째 건식 식각 공정으로 바늘의 길이를 조절하며, 마지막 HNA solution을 이용한 습식 식각 공정으로 바늘을 더 가늘게 만들면서 끝을 더 날카롭게 식각한다. 바늘을 통해 약물전달이 가능하도록 웨이퍼의 뒷면으로부터 건식 식각 공정을 이용해 약물 주입통로를 형성하였다. 제작된 Hollow형 실리콘 미세바늘 어레이는 $170\;{\mu}m$의 너비와 $230\;{\mu}m$의 길이, 직경 $40\;{\mu}m$의 약물 주입통로를 가지고 있으며, $1\;cm^2$의 시편 위에 $1000\;{\mu}m$의 피치로 $9{\times}9$ 개의 바늘을 형성하였다.

• Korean Journal of Soil Science and Fertilizer
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• v.29 no.4
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• pp.336-341
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• 1996

This study was conducted to investigate the effects of compost application on the soil loss and physico-chemical properties at the slope land from 1990 to 1991. Lysimeters with 15% slope. 5m slope length. 2m width and 1.2m depth were constructed in 1984 and filled with sandy loam, loam, clay loam. and clay soils. Treatments were bare soil, compost(1.5ton/10a) and non-compost with soybean-barley cropping system from 1984. Losses of soil were increased with the order of sandy loam, clay, loam and clay loam. Run-off was increased with the order of sandy loam, loam, clay loam and clay, but leachate was decreased with the same order. Compost treatments decreased 33.6-44.6% of soil loss and 17.0-24.0% of run-off but increased 17.1-33.7.% of leachate as compared with the non-compost treatments. The amount of soil loss was positively correlated with the amount of run-off by Y = 12.125+0.063X (r=$0.970^{**}$)and negatively correlated with the leachate by Y=43.425-0.096X(r=$-0.917^{**}$). The application of compost increased soil pH, OM, CEC and extractable cations. Application of compost decreased bulk density but increased porosity, water stable aggregate and available water. These results provide that the compost application plays an important role in conserving soil and water, and improving soil physico-chemical properties.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.4
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• pp.10-17
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• 2000

This work presents an investigation of aerodynamic characteristics of fuel spray injected from a high pressure hollow cone swirl injector into a constant volume chamber. Laser tomography visualization was used to interrogate the fuel and air mixing characteristics and the effect of chamber pressure and temperature increase was analyzed, Preliminary results on spray development showed that mixing effect tends to increase with the increase of injection pressure and chamber gas pressure yielding a decrease of spray penetration and an attenuation of well-defined vortex structure. Topological analysis of the spray structure has been performed to initiate the understanding of mixing and vaporization process. For the present experimental conditions fuel injection pressure and chamber gas pressure appear as the dominant factors which govern the transient mixing characteristics. Moreover spray atmixation characteristics are improved by increasing chamber gas temperature.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1318-1322
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• 2006

보는 낙차공과 함께 하천에서 자주 시공되는 하천 구조물로 매년 태풍이나 홍수로 큰 피해를 나타내는 대표적인 시설물 중 하나이다. 구미의 경우에는 보 하류부에 정수지(stilling basin)등을 설치하여 에너지를 적절히 소산시켜 하류로 흘려보내는 공법을 사용하고 있으나 우리나라와 기후조건이 유사한 일본에서는 보하류부에 물받이 및 하상보호공을 설치하는 방법으로 보 설계를 하고 있어 하상보호공에 대한 설계개념에 차이가 있다. 현재 국내의 보 설계는 Bligh공식에 따라 물받이 및 하상보호공을 결정하였으나 지반의 침투영향을 고려하여 도출된 공식이므로 수리적 특성를 고려하지 못하는 한계성을 가지고 있다. 따라서 보에서 수리특성을 고려한 물받이 및 하상보호공 설계를 위한 수리실험을 통해 설계지침을 보완할 필요가 있다. 본 연구에서는 수리조건에 따른 하상보호공 길이를 제안하는데 목적이 있으며 이를 위해 난류유속강도를 주요영향 요소로 선정하여 도수 및 도수 후 구간에 대해 난류강도 변화를 분석하였다.