• Journal of Forest and Environmental Science
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• v.13 no.1
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• pp.114-133
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• 1997

Perforation plate was observed in 78 species(45 genera, 25 families) of Korean native hardwoods using SEM and it was divided into three types, i.e., simple, scalariform and multiple perforation plates, Based on occurance of these types, the species examined were classfied into the following six groups : (1) 60species(35 genera, 21 families) having exclusively simple perforation, (2) 5 species(2 genera, 1 families) having exclusively scalariform perforation plates, (3) 4 species(4 genera, 3 families) having simple and scalariform perforation plates, (4) 2 species(2 genera, 1 families) having simple and multiple perforation plates, (5) 5 species(3 genera, 3 families) having scalariform and multiple perforation plates and (6) 2 species(2 genera, 2 families) having simple, scalariform and multiple perforation plates. Mismatching perforation plates were found in two species of Betulaceae, Alnus hirsuta var. sibirica and Alnus hirsuta and peculiar substructure between the bars of the scalariform perforation plate was observed in Betulaceae, Betula davurica and Cercidiphyllaceae, Cerdiphyllum japonicum and the vestured perforation plate was found in Quercus aliena.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.3 no.2
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• pp.56-62
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• 1989

자연채광에 관한 에너지 해석을 하기 위해서는 주광조도를 예측하여야 하며, 주광조도를 예측하기 위해서는 천공상태를 추정할 수 있어야만 한다. 즉, 천공상태의 최저상태나 최소설계기준을 추정할 수 있어야만 자연채광에 의한 에너지 절약을 해석할 수가 있다. 천공상태를 추정하는데에는 CIE에서 개발한 정적 천공모델이 많이 이용되어 왔다. 그러나 천공은 정적광원이 아니라 시간에 따라 동적으로 변하고 있음으로 자연채광설계에서 에너지의 영향을 평가하기 위해서는 보다 융통성이 있는 천공모델이 요구된다. 따라서 이 논문은 그동안 동적천공을 나타낼 수 있도록 개발된 비표준천공의 추정방법, 동적 천공상태의 추정방법, 주광조도와 천공휘도의 추정방법, 주광의 유용성 평가방법 등을 비교분석함으로써, 앞으로 우리나라 기후상태에 적합한 자연채광용 천공모델을 개발하는데 기초자료화하였다.

• Tunnel and Underground Space
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• v.18 no.6
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• pp.480-490
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• 2008

The drilling monitoring is a technique to assess rock mass properties by analyzing the mechanical quantities measured by drilling process. Since drilling survey can be conducted on real-time-basis for excavating blast holes or rockbolt holes, it may enables fast and quantitative prediction and evaluation of rock mass. Though a number of studies have been conducted on the drilling data, the selection of drilling parameters and numerical quantification of mechanical quantities or rock mass have not been well established yet. In this study, drilling tests were conducted with homogeneous rock specimen to identify drilling parameters and the relation of the drilling data. As a result, it is verified that above all drilling parameters, the percussion was the most important factor on the excavatability of hydraulic drilling.

• Journal of the Korean GEO-environmental Society
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• v.17 no.9
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• pp.13-20
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• 2016

This study carried out field measurements of rock drilling where two PRD (Percussion Rotary Drilling) methods, T-4 drilling method and dual drilling method, were considered and the study examined the characteristics of vibration level, noise level, drilling speed, and drillig verticality of the two method. The results of field measurements were compared and analyzed in details to provide the drilling information so that the problems due to rock drilling is minimized and the drilling efficiency is improved in the future. The limited measurements in the field indicated that the dual drilling method showed lower vibration and noise levels and better drilling speed and verticality.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2010.04a
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• pp.16-20
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• 2010

본 연구는 지하 냉동 창고 화재발생시 천공이 화재진압의 방법으로써 화재성상에 미치는 영향 등 천공의 효과를 검증하고 화재진압 기술에 대한 기초연구로서 천공의 위치, 천공 개방 시간, 천공 개방에 따른 근접 건축물로의 화재 전파양상을 FDS를 통하여 시뮬레이션 하여 분석하였다. 천공의 개방은 내부 화재의 요인을 빨리 소모시켜 온도 및 발열량을 빠르게 낮춘다. 이와 같이 천공의 유무에 따라 화재에 양상이 바뀌기 때문에 화재 진행 사항 및 화재 장소 가연물에 형태 등 각 화재 형태에 따라 적절한 천공의 위치 및 개방시간등이 마련되어야 할 것이다.

• Journal of Ecology and Environment
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• v.29 no.3
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• pp.185-189
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• 2006

Optimum tapping size and number for sap collection were investigated to minimize damage on tree growth and secure resources for sap by sap collection of Acer mono. The amounts of sap collected by tapping size of 12 mm, 10 mm and 8 mm was 189 L, 140 L and 193 L, respectively. Fusion rates by tapping size were 100% for 8 mm, 89% for 10 mm and 85% for 12 mm, respectively. Amount of sap by size and number of tapping were much at three, two and three tappings to small, middle and large diameter tree in case of 8 mm tapping, and it was large in quantity at two tappings of 12 mm tapping to large diameter tree, respectively. Trees tapped from one to three tappings of 8 mm size for small diameter tree with treatment of DB ointment (mixture of thiophane ointment and 2% bamboo charcoal powder) were completely filled up within 6 months. Diameter growth by number of tapping of 8 mm size was 0.60 mm for one tapping, 1.12 mm for two tappings and 0.47 mm for three tappings to small, middle and large diameter tree, respectively. In case of 12 mm tapping size, diameter growth was fast in the order of large (0.55 mm), middle (0.30 mm) and small (0.23 mm) diameter tree, respectively.

• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.263-272
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• 2003

Various types of geosynthetics have been manufactured and their applications are rapidly extended disregarding unreliable lifetime, chemical and biological persistence and puncture resistance. Puncture resistance of geosynthetics in earth structures and liner systems has been a critical issue to be improved. In this paper, comparative studies were made on a puncture resistance of various geosynthetics that were used to a liner system. Two types of puncture tools and rubles and gravels were used to generate punctures on geosynthetics. From the results it is shown that types of puncture tools affect puncture resistance of materials significantly and puncture forces were irregular depending upon puncture tools and materials.

• Tunnel and Underground Space
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• v.23 no.4
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• pp.271-279
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• 2013

This report introduced the types of drilling equipment and their operation mechanisms. The state of the art technologies of the Top-hammer drill equipment were investigated and the technology level of Korean drill industry was compared to that of the advanced country. Based on the investigation, the necessity of fusion research and development in the Korean drilling technology and industry was discussed, and the future strategy to catch up with the advanced technology was suggested.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.515-519
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• 2002

자동차 및 유체기계의 흡기계나 배기계에 사용되는 소음기의 음향성능은 전달손실로 기계성능은 배압으로 표현된다. 유체가 흐르는 관 사이의 임피던스 부정합을 이용하는 반사형 소음기의 경우, 내부 유로에 천공을 주어 음향감쇠를 시키거나 유동을 안정시키는 경우가 많다. 본 연구에서는 동심관형 공명기의 내부 관에 존재하는 천공의 분포 양상이 소음기의 전달손실과 배압에 미치는 영향을 실험을 통하여 고찰하였다. 내부관의 평균 천공율은 일정하지만 길이 방향을 따라서 천공율이 변하는 다섯가지의 공명기에 대한 실험을 수행하고, 성능에 미치는 영향을 살펴보았다. 전달손실은 천공요소의 임피던스 모델을 고려하여 예측한 결과와 비교하였고, 측정된 배압은 모의 해석 결과와 비교하였다. 분석 결과, 천공율이 점점 작아지는 분포나, 작았다가 커진후 다시 작아지는 형태의 분포를 가질 경우, 배압 측면에서 매우 유리하고, 음향 전달손실도 큰 차이가 없음을 밝혔다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.4
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• pp.561-571
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• 2019

Drilling and charging of the blast holes during NATM tunneling works take more than 30% of construction time among the whole tunneling work process. Prediction of ground condition ahead of tunnel face has been studied by several researchers by correlating percussion pressure and drilling speed during tunneling work with the ground condition and/or RMR values. However, most of the previous researches were conducted in the granite rock condition which is the most representative igneous rock in the Korean peninsula. In this study, drilling speeds in igneous rocks were analyzed and compared with those in sedimentary rocks (most dominantly composed of conglomerates, sandstones, and shales) under the similar RMR ranges; it was identified that the drilling speed is pretty much affected by rock types even in a similar RMR range. Under the similar RMR values, the drilling speed was faster in sedimentary rocks compared with that in igneous rock. Moreover, while the drilling speed was not much affected by change of the RMR values in igneous rocks, it became faster in sedimentary rocks as the RMR values got lower.