• 한국초전도ㆍ저온공학회논문지
• /
• 제21권2호
• /
• pp.31-35
• /
• 2019

Andong-dam was built up in 1967 and it is one of the biggest dams in Korea. Previous studies showed that the sediments are highly contaminated with heavy metals such as arsenic, cadmium, and lead. Many research projects are going on to find out the source of the contamination, to evaluate the toxicities to ecosystem, to estimate the volume of sediment to be treated and to find out a good remediation method. Reports show that the sediment is highly contaminated and the main contamination source is supposed to be abandoned mines and a zinc refinery located upper stream of the river. A magnetic separation has been tested as a treatment method for the dredged sediment. Lab scale test showed that the magnetically captured portion is about 10% in weight but the contamination of heavy metal is much higher than the contamination of the passed portion. This indicates that a magnetic separation could be applied for the purpose of reduction of sediment to be treated and for increasing the volume of low toxic sediments which can be dumped as general waste. A magnetic separation using a HGMS has been tested for the sediment with variable magnetic field and the results showed the higher magnetic field increase the captured portion but the concentrating effect of heavy metal was weakened. Further study is needed to establish a useful technology and optimization between decontamination and reduction of sediment volume.

• Structural Engineering and Mechanics
• /
• 제69권2호
• /
• pp.221-230
• /
• 2019

In this paper, shear behavior of non-persistent joint surrounded in concrete and gypsum layers has been investigated using experimental test and numerical simulation. Two types of mixture were prepared for this study. The first type consists of water and gypsum that were mixed with a ratio of water/gypsum of 0.6. The second type of mixture, water, sand and cement were mixed with a ratio of 27%, 33% and 40% by weight. Shear behavior of a non-persistent joint embedded in these specimens is studied. Physical models consisting of two edge concrete layers with dimensions of 160 mm by 130 mm by 60 mm and one internal gypsum layer with the dimension of 16 mm by 13 mm by 6 mm were made. Two horizontal edge joints were embedded in concrete beams and one angled joint was created in gypsum layer. Several analyses with joints with angles of $0^{\circ}$, $30^{\circ}$, and $60^{\circ}$ degree were conducted. The central fault places in 3 different positions. Along the edge joints, 1.5 cm vertically far from the edge joint face and 3 cm vertically far from the edge joint face. All samples were tested in compression using a universal loading machine and the shear load was induced because of the specimen geometry. Concurrent with the experiments, the extended finite element method (XFEM) was employed to analyze the fracture processes occurring in a non-persistent joint embedded in concrete and gypsum layers using Abaqus, a finite element software platform. The failure pattern of non-persistent cracks (faults) was found to be affected mostly by the central crack and its configuration and the shear strength was found to be related to the failure pattern. Comparison between experimental and corresponding numerical results showed a great agreement. XFEM was found as a capable tool for investigating the fracturing mechanism of rock specimens with non-persistent joint.

• 한국정보통신학회논문지
• /
• 제24권8호
• /
• pp.1077-1085
• /
• 2020

부설된 기뢰를 소해하기 위해 기뢰매설 예상구역에 대한 탐색을 수행한다. 이 때 기뢰탐색은 기뢰의 위험성, 아군의 안정성 등을 고려하여 자율무인잠수정을 이용한다. 매설된 기뢰를 식별하기 위한 소나시스템은 측면주사소나, 합성개구소나 등을 탑재한다. 본 논문은 측면주사소나 특성에 따른 기뢰탐색효과도 분석에 대해 기술한다. 각 측면주사소나의 특성을 바탕으로 음향조사역 및 인식확률을 모델링 하였고, AUV의 주행패턴에 따라 분석을 수행하였다. AUV의 주행패턴은 측면주사소나 음영구역의 유무에 따라 3가지 탐색패턴을 정의하였다. 분석결과는 각 탐색패턴 마다 탐지시간, 탐지확률을 도출하고 최종적으로 측면주사소나 음영구역의 유무에 따른 탐색 향상도를 도출하였다.

• 한국지반환경공학회 논문집
• /
• 제12권2호
• /
• pp.15-22
• /
• 2011

본 연구에서는 폐광산의 산성광산배수(Acid Mine Drainage, AMD)의 발생을 억제하기 위해 산성광산배수의 주원인인 황철석 표면을 천연광물 및 시멘트를 사용하여 화학적으로 코팅하여 산성광산배수의 문제를 해결하고자 한다. 표면 코팅에 필요한 철이온의 생성을 위해 먼저 산화제 $H_2O_2$, NaClO 를 이용하여 표준황철석, 영동탄광, 신림광산 시료의 표면을 산화시켰다. 그리고 천연광물(인회석(Apatite), 석회석(Limestone), 망간광(Mangnite), 돌로마이트(Dolomite), 벤토나이트(Bentonite), 시멘트(Cement))를 이용하여 발생된 철이온과 천연광물의 이온을 결합시켜 표면 코팅을 진행하였다. 그 결과 시멘트와 시료의 양을 1:1로 이용하고 4일 이상 진행하였을 때 위의 실험조건에서 가장 효과적으로 황철석의 표면을 코팅하여 ${SO_4}^{2-}$의 발생이 억제되었다.

• 동남아시아연구
• /
• 제23권3호
• /
• pp.93-134
• /
• 2013

This paper examines the formation and evolution of Chinese society in Penang over 155 years. Since it was ruled by the British in 1786, many immigrants gathered in Penang. Among them, much of the population was Chinese. It could be offered to clarify the historical process of the development of Chinese society in Penang by paying attention to the three items - opium, tin, and rubber. All the conflict and friction over these products were main causes of prosperity and decay for the Chinese society in Penang. In the early 19th century, the Chinese colossus could get their capital accumulation by taking advantage of 'opium farm'. They amassed their fortune through development of tin mines newly discovered in Perak during the late 19th century. It was the age of Chinese Colossuses deeply connected with Chinese secret societies. After the rubber plantations were developed by the Western capital in the early 20th century, the age of Chinese Colossuses was gradually fallen down. From this point of view one can be provided a new perspective on the history of Penang and the Chinese society of its own. The three scopes for history enable us to make a new interpretation about the issue of stratification within Chinese society in Penang. Especially this research focused on the economic characteristics of Chinese secret societies as 'social capital', and on the identity conflicts between traditional Strait Chinese(peranakan) elite and emerging sinkeh Chinese merchants. The identity problem between 'Laokeh' and 'Sinkeh' in the early 20th century was intentionally exaggerated by modern researchers. Their conflicts seems to be caused by different economic interests rather than identity. We need to consider again the rise and fall of Chinese society in Penang with flexible thinking.

• Journal of Ecology and Environment
• /
• 제45권1호
• /
• pp.1-9
• /
• 2021

Background: Abandoned coal piles after the closure of mines have a potential negative influence on the environment, such as soil acidification and heavy metal contamination. Therefore, revegetation by efficient species is required. For this, we wanted to identify the role of Silene acaulis in the succession of coal piles as a pioneer and a nurse plant. S. acaulis is a well-studied cushion plant living in the Arctic and alpine environments in the northern hemisphere. It has a highly compact cushion-like form and hosts more plant species under its canopy by ameliorating stressful microhabitats. In this research, we surveyed vegetation cover on open plots and co-occurring species within S. acaulis cushions in coal piles with different slope aspects and a control site where no coal was found. The plant cover and the similarity of communities among sites were compared. Also, the interaction effects of S. acaulis were assessed by rarefaction curves. Results: S. acaulis was a dominant species with the highest cover (6.7%) on the coal piles and occurred with other well-known pioneer species. Plant communities on the coal piles were significantly different from the control site. We found that the pioneer species S. acaulis showed facilitation, neutral, and competition effect in the north-east facing slope, the south-east facing slope, and the flat ground, respectively. This result was consistent with the stress gradient hypothesis because the facilitation only occurred on the north-east facing slope, which was the most stressed condition, although all the interactions observed were not statistically significant. Conclusions: S. acaulis was a dominant pioneer plant in the succession of coal piles. The interaction effect of S. acaulis on other species depended on the slope and its direction on the coal piles. Overall, it plays an important role in the succession of coal piles in the High Arctic, Svalbard.

• 화약ㆍ발파
• /
• 제40권1호
• /
• pp.29-38
• /
• 2022

최근 전자뇌관은 다양한 건설현장과 석산에서 폭넓게 사용되고 있다. 보안물건이 근접한 지역을 비롯하여 발파작업에 의한 파쇄도 개선과 2차 소할 비용 절감을 통한 작업효율성을 극대화하거나 공사기간을 단축시켜 비용을 절감하기 위해 전자뇌관을 이용하는 경우가 점차 늘어나고 있는 추세이다. 본 사례는 도심지에서 시공 중인 수도권 광역급행철도 A노선 민간투자사업 건설공사 00공구 현장에서 전자뇌관을 적용한 사례이다. 당 현장은 설계에 비전기뇌관을 이용하여 시공하도록 되어 있었으나, 발파작업을 진행하던 중 인근에 위치한 보안물건에 대한 피해와 민원을 최소화하면서 안전하고 빠른 굴착작업을 위해 전자뇌관을 이용한 발파공법을 검토하였다. 전자뇌관을 적용하여 발파소음과 진동에 대한 환경규제기준을 충족시켰으며 인근의 보안물건에 대한 손상을 방지할 수 있었다.

• 한국군사과학기술학회지
• /
• 제25권3호
• /
• pp.231-238
• /
• 2022

Mine detection has been mainly studied with images of the forward-looking sonar. Forward-looking sonar assumes the propagation path of the sound wave as a straight path, creating the surrounding images. This might lead to errors in the detection by ignoring the refraction of the sound wave. In this study, we propose a mine localization method that can robustly identify the location of mines in an underwater environment by considering the refraction of sound waves. We propose a method of estimating the elevation angle of arrival of the target echo signal in a single receiver, and estimate the mine location by applying the estimated elevation angle of arrival to ray tracing. As a result of simulation, the method proposed in this paper was more effective in estimating the mine localization than the existing method that assumed the propagation path as a straight line.

• 터널과지하공간
• /
• 제31권6호
• /
• pp.460-468
• /
• 2021

TBM은 원형의 커터헤드를 회전하여 전단면으로 터널을 굴착하는 장비로 빠른 굴진속도와 안전한 시공이 장점이다. 건설현장에서 터널 굴착에 주로 사용되는 TBM은 정보통신기술의 적용이 용이한 장비로서 현재 무인화 및 자동화에 관련한 연구가 활발히 진행 중이다. 본 연구에서는 국외에서의 광물 및 에너지 자원 개발을 위한 TBM의 적용 사례를 살펴보고, 광물 및 에너지 자원 개발과 토목 건설현장에서 TBM 적용에 대한 차이를 살펴보았다. 그리고, TBM 선정 시에 기술적으로 고려해야 하는 지질조건, 심도, 현장 접근, 발진, 선형과 경사, TBM 크기 등을 알아보았다. 마지막으로 광산에서 TBM 적용 시의 장점과 단점 및 성공적인 광산 적용을 위하여 TBM이 기술적으로 갖추어야 하는 사항을 정리하였다.

• 터널과지하공간
• /
• 제32권2호
• /
• pp.93-106
• /
• 2022

본 연구에서는 광산 현장에서 트럭 운전자들이 스마트 기기를 이용해 원석 생산 데이터를 기록하고, 이를 이용해 PC 환경에서 작업일지(운행일지)를 작성할 수 있는 애플리케이션을 개발하였다. 이를 위해 국내에서 가행 중인 4곳의 광산을 연구지역으로 선정한 다음 현장에서 사용하고 있는 작업일지를 확보하였다. 광산별로 작업일지에 포함되는 정보 요소를 분석하였다. 광산별로 작업일지 작성을 위해 기록하는 정보와 양식이 서로 다르므로, 원석 생산 데이터 기록과 작업일지 작성을 위한 애플리케이션은 연구지역 맞춤형으로 4종을 개발하였다. 블루투스 비콘의 신호를 수신하는 방법과 사용자가 직접 애플리케이션을 조작하는 방법으로 원석 생산 데이터를 기록할 수 있다. 기록된 데이터 파일은 클라우드 서버에 업로드되고, 업로드된 파일은 PC 환경에서 작업일지 작성 애플리케이션에 의해 현장에서 사용하는 형태의 작업일지로 변환할 수 있다.