• Geomechanics and Engineering
• /
• 제17권4호
• /
• pp.355-365
• /
• 2019

It is normal to observe the presence of numerous cracks in coal body. And it has significantly effective on the mechanical characteristics and realistic failure models of coal mass. Therefore, this paper is to investigate the influence of crack parameters on coal body by comprehensive using theoretical analysis, laboratory experiments and numerical simulation through prepared briquette specimens. Different from intact coal body possessing single peak in stress-strain curve, other specimens with crack angle can be illustrated to own double peaks. Moreover, the unconfined compressive strength (UCS) of specimens decreases and follow by increasing with the increase of crack angle. It seems to like a parabolic shape with an upward opening. And it can be demonstrated that the minimum UCS is obtained in crack angle $45^{\circ}$. In terms of failure types, it is interesting to note that there is a changing trend from tensile failure to tensile-shear mixing failure with tension dominant follow by shear dominant with the increase of crack angle. However, the changing characteristics of UCS and failure forms can be explained by elastic-plastic and fracture mechanics. Lastly, the results of numerical simulations are good consistent with the experimental results. It provides experimental and theoretical foundations to reveal fracture mechanism of coal body with non-penetrating single crack further.

• 대한토목학회논문집
• /
• 제44권2호
• /
• pp.215-221
• /
• 2024

정부는 신재생에너지 정책을 통해 신재생에너지 시설확대를 독려하고 있다. 그러나 신재생에너지 발전시설 설치로 인해 발생하는 경관훼손, 전자파발생, 부동산 가치하락, 환경오염 등의 사유로 인해 지역주민들의 민원이 발생한다. 이는 발전사업자와 주민들 사이에서 갈등을 만들며, 사업 진행을 어렵게 만든다. 본 연구는 비협조적 게임이론을 적용하여, 주민참여를 통해 발전사업자와 주민들의 갈등을 해결한 신재생에너지 발전 사업 8가지 사례를 분석하고자 한다. 인근 이해당사자인 지역주민들의 투자를 받아, 주민들은 최대 25 %에서 최소 4.1 %의 수익률을 얻었다. 주민들은 발전사업 추진에 동의하고, 발전사업자는 수익의 일부를 주민들과 공유하는 것이 게임이론 분석을 통해 모두에게 우월전략임을 확인했다. 우월 전략이 만나는 지점은 내쉬균형을 형성하며, 동시에 파레토최적점이 되어 발전사업자와 주민 모두에게 이익이 된다는 분석결과를 도출하였다.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2002년도 ICCAS
• /
• pp.33.6-33
• /
• 2002

For RF sensitivity enhancement, the previous assisted GPS acquisition architecture adopts not only the coherent integration technique but also the non-coherent integration technique since the long coherent integration time increases the number of the frequency search cells. But the non-coherent integration technique induces the squaring loss, which is the dominant factor among the acquisition losses of assisted GPS dealing with weak GPS signals. This paper proposes an efficient architecture for weak signal acquisition in assisted GPS. In this paper, it is explained that the proposed architecture reduces the squaring loss using a modified non-coherent integration technique. Furthermore, it is..

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2003년도 춘계학술대회 논문집
• /
• pp.569-572
• /
• 2003

In VLM-ST process, the fine detailed shape processing process is needed due to the use of thick sheets for layers. The developed process perform the fine detailed shape processing in VLM-ST parts using non-contact hot tool. To predict the heat-affected zone and temperature distribution of VLM-ST parts in detailed shaping, the heat flux from the tool to the surface was calculated for the finite element analysis by modeling the tool as a heat source of radiation. The dominant process parameters such as the radiated heat input, the tool speed, and the gap between the tool tip and the foam sheet (tool height) were considered in the analysis. The results showed a good agreement with the experiments.

• Journal of Information Processing Systems
• /
• 제12권3호
• /
• pp.538-547
• /
• 2016

Cloud computing is a new style of computing in which dynamically scalable and reconfigurable resources are provided as a service over the internet. The MapReduce framework is currently the most dominant programming model in cloud computing. It is necessary to protect the integrity of MapReduce data processing services. Malicious workers, who can be divided into collusive workers and non-collusive workers, try to generate bad results in order to attack the cloud computing. So, figuring out how to efficiently detect the malicious workers has been very important, as existing solutions are not effective enough in defeating malicious behavior. In this paper, we propose a security protection framework to detect the malicious workers and ensure computation integrity in the map phase of MapReduce. Our simulation results show that our proposed security protection framework can efficiently detect both collusive and non-collusive workers and guarantee high computation accuracy.

• 한국임상수의학회지
• /
• 제29권1호
• /
• pp.23-26
• /
• 2012

This study was conducted on 85 non-racing pleasure horses raised in Busan race park of Korea Racing Authority to investigate the prevalence of stereotypic behavioral problems in horses. the observation had been continued from March to October of 2010, and the study animals included warm-bloods, Jeju ponies and donkeys. Although there was no temperament problem detected, a wide range of well-known stable vices were observed in 15 horses. The most frequently observed stereotype was cribbing (8.2%), and it was followed by weaving (1.2%), biting (1.2%), eating too fast (1.2%), pawing (1.2%) and scraping the teeth on something (1.2%) with the equal prevalence rate. These behavioral disorders were only detected in warm-bloods, while those were absent in Jeju ponies and donkeys. In addition, primary behavioral disorders were more dominant than mimicking behaviors.

• The Journal of the Acoustical Society of Korea
• /
• 제22권4E호
• /
• pp.161-166
• /
• 2003

We present an adaptive wavelet packet based speech enhancement method with robust voice activity detection (VAD) in non-stationary noise environment. The proposed method can be divided into two main procedures. The first procedure is a VAD with adaptive wavelet packet transform. And the other is a speech enhancement procedure based on the proposed VAD method. The proposed VAD method shows remarkable performance even in low SNRs and non-stationary noise environment. And subjective evaluation shows that the performance of the proposed speech enhancement method with wavelet bases is better than that with Fourier basis.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2008년도 추계학술대회B
• /
• pp.2524-2529
• /
• 2008

The thermal system like a combustion chamber is believed to experience a significant instability problem with vibration in case that the thermal energy or the acoustic energy are transformed into a different form through a relevant path. This study deals with a numerically- predicted, Thermoacoustic instability in a Rijke tube by using a non-linear model for a heat source. The heating part where the energy transformation occurs actively is modeled after simulating two-dimensional cylinder case with constant surface temperature, and a nonlinear model that accounts for the transfer function of magnitude- and phase-characteristics is properly implemented so as to be dependent on the pulsation strength in the tube. The heat source model is observed to result in equivalent Thermoacoustic instabilities in the Rijke tube except low flow-rate cases in which the natural convection is dominant.

• Animal Systematics, Evolution and Diversity
• /
• 제19권1호
• /
• pp.11-17
• /
• 2003

1997-1999년에 걸쳐 충청남도 서산 간척 수답에서 발생하는 깔따구를 채집하여 25종의 깔따구를 동정하였다. 그 중 1신종 Tanytarsus seosanensis (서산장부깔따구, 신칭)과 국내 1미기록종 Chironomus javanus (자바깔따구, 신칭)을 확인하였기에 형태적 특징을 그림과 함께 기술하였다.

• 지질공학
• /
• 제14권1호
• /
• pp.1-20
• /
• 2004

본 연구는 2000년 시드니올림픽사이트의 해안가를 따라 인위적인 매립으로 인한 지하수 내 수리화학적인 특징을 규명하는데 그 목적이 있다. 올림픽게임지역을 3개의 지역, 즉 간척지역(reclaimed area, 과거에는 강구하였으나 폐기물로 매립되어 있으며 현재는 조수간만 보다 높은 지역), 매립지역(landfill area, 해수면 위에 폐기물을 매립한 지역), 그리고 자연 상태지역(non-infilled area, 폐기물의 매립이 전혀 없었던 지역))으로 나누어 조사하였다. 또한 시추공 심도별로 심부시추공, 천부시추공 및 스텐드파이프로 구분하여 상대적인 농도들의 거동을 상오 비교하였다. 그 결과 간척지역 내 지하수는 Na, K 그리고 Mg 이온이 지배적이지만 매립지역은 Na 그리고 K가 지배적인 이온이다. 또한 간척지역 및 자연 상태지역의 지하수는 Mg 및 Ca 농축이 특징이지만, 매립지역은 K 및 $NO_3$의 농축이 특징이다. 그러나 시추공심도 별로 살펴보면 심부시추공 지하수는 Na와 Mg가 지배적이지만 천부시추공 및 스텐드파이프 지하수는 Na와 K가 지배적인 원소로 나타났다. 간척지역, 매립지역 그리고 자연 상태지역 지하수 내 전기전도도와 중금속 농도와는 명확한 상관관계를 보여 주지 않는다. 간척지역 및 자연 상태지역과 비교 시 매립지역 지하수의 Fe 및 Mn의 농도는 pH가 감소함에 따라 현저히 증가하는 양상을 보여준다. 심부시추공과 천부시추공 지하수 내 평균 전기전도도 값은 스텐드파이프보다 높지만 스텐드파이프 지하수 내 전기전도도 값의 최대 및 최소 값은 현저한 차이를 보이는데 이는 국부적인 공동의 영향으로 사료된다. 심부시추공, 천부시추공, 그리고 스텐드파이프 지하수 내 pH 대비 중금속(Cu, Pb, Zn, Cr) 농도사이의 상관관계는 없었지만 이들 지하수 내 Fe와 Mn은 pH가 감소하면 농도가 증가하는 양상을 보여준다. 지하수 내 농축된 중금속 농도는 매립된 폐기물의 성상과 밀접한 관계를 보이며 해안가를 따라 매립되어 있는 지역의 토양 내 중금속의 용출은 주변 환경에 대한 잠재적인 환경위험을 결정 시 중요한 역할을 한다.