• Tunnel and Underground Space
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• v.25 no.4
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• pp.373-382
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• 2015

This study presents a method to calculate carbon dioxide emissions of diesel vehicles operated in an underground mine using Geographic Information Systems (GIS). An underground limestone mine in Korea was selected as the study area. A GIS database was constructed to represent the haulage roads as a 3D vector network. The speed of dump trucks at each haulage road was investigated to determine the carbon dioxide emission factor. The amount of carbon dioxide emissions related to the truck's haulage work could be calculated by considering the carbon dioxide emission factor at each haulage road and the haulage distance determined by GIS-based optimal route analysis. Because diesel vehicles are widely utilized in the mining industry, the method proposed in this study can be used and further improved to calculate the amount of carbon dioxide emissions in mining sites.

• Tunnel and Underground Space
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• v.26 no.4
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• pp.253-265
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• 2016

In this study, travel time data collection of mine equipments was conducted in an underground mine using a reverse Radio Frequency IDentification (RFID) system. In the reverse RFID system, RFID readers and antennas are mounted on mine equipments, and RFID tags are attached to the underground mine gallery. Indoor experiments were performed to analyze how RFID reader transmission power levels affect tag readable area and tag recognition rates. The results showed that travel time measurement become precise when the reader transmission power was reduced, however tag recognition rates were reduced. The field experiments indicated that setting the reader transmission power to 28 dBm maintained the tag recognition rate while minimizing the tracking location error. In addition, the results revealed that the reverse RFID system can be used successfully in an underground mine to collect the travel time data of haulage trucks.

• Tunnel and Underground Space
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• v.18 no.1
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• pp.1-9
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• 2008

Acoustic emission (AE) and Microseimsic (MS) activities are law-energy seismic events associated with a sudden inelastic deformation such as the sudden movement of existing fractures, the generation of new fractures or the propagation of fractures. These events rapidly increase before major failure and happen within a given rock volume and radiate detectable seismic waves. The main difference between AE and MS signals is that the seismic motion frequencies of AE signals are higher than those of MS signals. As the failure of geotechnical structures usually happens as a high velocity and small displacement, it is nat easy ta determine the precursor and initiation stress level of failure in displacement detection method. To overcame this problem, AE/MS techniques far detection of structure failure and damage have recently adapt in civil engineering. This study deal with the basic theory of AE/MS and state of arts in monitoring technique using AE/MS.

• Tunnel and Underground Space
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• v.26 no.5
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• pp.409-417
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• 2016

The shale gas is emerging as one of the oil and gas resources which can replace the traditional oil and gas resources. As the shale layer where the shale gas is deposited has low permeability, the hydrofracturing method is required to improve the productivity. This study is designed to conduct the laboratory hydrofracturing test on the samples which are modeled after the drilling hole having the general drilling hole and spiral groove. And compare the initial fracturing pressure and fluid contact between them in order to the result of the hydrofracturing depending on the shape of the drilling hole. In addition, the results were compared with the numerical modeling values from 3DEC and they were also compared with the data from the advance researches. It was found from the study that rather than the contact area of the high pressures water, the force concentration depending on the form of guide hole was more effective in the hydrofracturing.

• Tunnel and Underground Space
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• v.26 no.5
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• pp.339-347
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• 2016

The world's first underground repository for low- and intermediate- level radioactive waste (SFR1) has been in operation since 1988. SFR1 can accommodate $1,000m^3$ of radioactive waste per year with 4 chambers and 1 silo with a total capacity of $63,000m^3$ of radioactive waste. With extended operation time of 10 of the 12 nuclear power reactors and dismantling of the other 2 nuclear reactors, more nuclear waste need to be disposed in the future. Therefore, Swedish Nuclear Fuel and Waste Management Company (SKB) submitted a license application for a repository extension (SFR3) that consists of 6 additional rock chambers with a capacity of $108,000m^3$ of radioactive waste and for accommodating 9 boiling water reactor tanks. In this study, plans for the extension SFR3 are presented with the geological, geomechanical and hydrogeological issues to be considered.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1527-1539
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• 2015

In this paper the hardware implementation of the direct torque control based on the fuzzy logic technique of induction motor on the Field-Programmable Gate Array (FPGA) is presented. Due to its complexity, the fuzzy logic technique implemented on a digital system like the DSP (Digital Signal Processor) and microcontroller is characterized by a calculating delay. This delay is due to the processing speed which depends on the system complexity. The limitation of these solutions is inevitable. To solve this problem, an alternative digital solution is used, based on the FPGA, which is characterized by a fast processing speed, to take the advantage of the performances of the fuzzy logic technique in spite of its complex computation. The Conventional Direct Torque Control (CDTC) of the induction machine faces problems, like the high stator flux, electromagnetic torque ripples, and stator current distortions. To overcome the CDTC problems many methods are used such as the space vector modulation which is sensitive to the parameters variations of the machine, the increase in the switches inverter number which increases the cost of the inverter, and the artificial intelligence. In this paper an intelligent technique based on the fuzzy logic is used because it is allows controlling the systems without knowing the mathematical model. Also, we use a new method based on the Xilinx system generator for the hardware implementation of Direct Torque Fuzzy Control (DTFC) on the FPGA. The simulation results of the DTFC are compared to those of the CDTC. The comparison results illustrate the reduction in the torque and stator flux ripples of the DTFC and show the Xilinx Virtex V FPGA performances in terms of execution time.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.829-831
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• 2009

폐기물, 석탄 등 다양한 시료의 가스화 반응을 통해서 발생되는 합성가스는 CO, $H_2$, $CO_2$가 주성분으로 가스엔진, 가스터빈 등의 연료로 사용하여 발전하거나 합성반응을 통해 다양한 화학원료로의 전환이 가능하다. 또한 폐기물, 석탄 등의 다양한 원료의 가스화 반응에 의해 발생한 합성가스로부터 F-T(Fischer-Tropsch) 합성을 통한 인조합성석유, Non F-T 합성을 통한 메탄올, DME(Dimethyl Ether) 등을 제조할 수 있으며, 메탄화 반응을 통해 대체천연가스(SNG, Substitute Natural Gas)로 제조하여 활용하는 방안도 가능하다. 또한 현재 상업용 규모의 수소 제조 방법 중에서 가장 경제적인 방법으로 천연가스를 개질하여 CO, $H_2$가 주성분인 합성가스를 만든 다음 수성가스 전환, PSA(Pressure Swing Adsorption)통해 $CO_2$와 $H_2$를 분리하여 생산하고 있으나, 천연가스 가격의 상승 및 다양한 시료로부터 향후 경제성 확보가 가능한 수소 제조 방법에 대한 연구가 진행되고 있으며, 석탄 가스화 및 폐기물 가스화를 통해 얻어진 합성가스로부터의 수소 제조 공정이 개발 및 상업화 추진되고 있다. 본 연구에서는 폐기물 가스화를 통해 발생한 합성가스에 대하여 수성가스 전환 반응을 통한 수소 생산 특성 및 수성가스 전환 반응의 공간속도 변화 및 스팀주입량 변화에 따른 반응 특성을 고찰하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.53-56
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• 2007

미량의 Ru을 증진제로 첨가하여 니켈 촉매의 반응 활성을 증진시킴으로써, 저온 환원성과 장시간 반응에 대한 안정성을 확보하고자 하였다. Ni의 담지량은 12 wt%로 고정하였으며 이에 Ru을 각각 0.1, 0.3, 0.5 wt%로 변화시켜 2차 담지하였다. 메탄의 수증기/이산화탄소 복합 개질 반응에 있어 니켈 촉매에 Ru을 2차 담지 한 촉매는 800 $^{\circ}C$, GHSV(gas hourly space velocity) 265,000 $h^{-1}$ 하에서 100 %에 가까운 $CH_{4}$ 전환율을 보였으며, GHSV 1,060,000 $h^{-1}$ 일 때에도 10시간 동안 90 %의 $CH_{4}$ 전환율을 기록하였다. 또한 이 중 0.3 wt%의 Ru를 담지한 경우가 1,060,000 $h^{-1}$의 조건하에서도 95 %이상으로 가장 높은 $CH_{4}$ 전환율로 유지되었다. $H_{2}-TPR$ 분석 결과, Ni(12)/$MgAl_{2}O_{4}$ 와 비교해 볼 때 Ru(0.5)/Ni(12)/$MgAl_{2}O_{4}$와 Ru(0.3)/Ni(12)/$MgAl_{2}O_{4}$ 촉매의 경우 150 $^{\circ}C$에서 저온 환원이 가능한 $RuO_{2}$의 존재를 확인할 수 있었다.

• School Mathematics
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• v.15 no.4
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• pp.743-758
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• 2013

This paper analyses the examples of polygons taken in the 1st grade middle school mathematics textbooks. We analysed generic examples, non-examples and counter-examples represented in these textbooks. And also we classified and analysed with examples of the concept and the application of a procedure. We analysed the differences of methods among these textbooks representing the same concepts or procedures. The findings from the analysis showed that these textbooks mostly make use of generic examples. The examples of concept and procedure vary depending upon the textbooks. Also, many textbooks haven't properly represented various positions and figures of polygons. Textbooks need to represent various and appropriate examples in order to expand the example space of the students.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.7
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• pp.501-510
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• 2011

In this study, water pollution sources of 14 major tributaries of Han river and characteristics of water quality for each target streams were evaluated based on water quality data in 2007.1-2009.12 (14 data sets) using a statistical package, SPSS-17.0. Cluster analysis over time and space for each stream resulted in 4 groups for the spatial variations in which type and density of pollution sources in the basins showed the greatest impact on grouping. Moreover, cluster analysis for the time variation in which rainfall, temperature and eutrophication were shown to contribute to the clustering, produced 2 groups, from summer to fall (July-Oct.) and from winter to early summer (Nov.-June). Four factors were found as responsible for the data structure explaining 71-90% of the total variance of the data set depending on the streams and they were organic matter, nutrients, bacterial contamination. Factor analysis showed main factors (water pollutants) changed according to the season with different pattern for each stream. This study demonstrated that water quality of each stream could produce useful outcomes when factor and pollution source of basin were evaluated together.