• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2007.04a
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• pp.167-170
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• 2007

동일한 집단에 속하는 개체를 다른 집단에 속하는 개체로부터 구별할 수 있는 염기의 특징을 해당 집단의 시그너쳐라고 한다. 학습 데이터는 두 집단에 속하는 염기서열들이고, 염기서열에 대한 시그너쳐는 개체를 다른 집단과 구별할 수 있는 위치의 염기들로 구성된 서열이다. 제안한 방법에서는 각 집단에 대해서 위치별로 염기의 발생빈도를 계산하고, 가장 발생빈도가 높은 염기를 결정한 다음, 다른 집단의 대응 위치에서 해당 염기의 빈도를 계산하여, 빈도차이가 지정한 분류임계값 이상이면, 해당 위치의 염기를 시그너쳐를 구성하는 특징으로 간주한다. 시그너쳐를 대한 임의의 염기서열에 대한 부합정도는 시그너쳐에 속하는 염기의 학습집단에서의 상대빈도값을 가중치로 하여 계산한다. 임의의 염기서열이 특정 집단에 속하는지 판단하기 위해서는 해당 집단의 시그너쳐에 대한 부합정도를 계산하게 되는데, 부합정도가 얼마이상이 되어야 해당 집단에 속하는 것으로 간주할지 기준이 되는 임계값을 엄밀도 임계값이라고 한다. 엄밀도 임계값은 학습 데이터 집합에 대해서 주어진 시그너쳐에 대한 엄밀도 임계값이 민감도와 특이도를 최대로 하는 것을 선택한다. 제안한 방법을 구현한 바이오인포매틱스 도구를 개발하여, 한국형 HIV-1 바이러스 시그너쳐 추출에 적용하여 분류특성이 우수한 시그너쳐를 추출할 수 있음을 확인하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.64-70
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• 2018

Rollover is a major concern for vehicles with a higher center of gravity and for improving driving performance. This study investigates a tilting system to prevent rollover, which was successfully implemented for high-speed trains. It may be useful to apply the concept of the tilting system to a large truck such as a trailer. Even a small adjustment in the tilting angle can improve the driving stability during a steep turn. The equation of motion was derived from a dynamic model of the trailer with the tilting system. The balance of the centrifugal force and normal force determines the rollover critical speed for a given radius of the turn and load. To obtain a more conservative criterion, the rollover critical state was defined as the instant when any side wheel loses contact with the road. To actuate the tilting system, the optimal tilting angle must be calculated from the steering angle and the vehicle speed. Using a simplified model of a large truck, the effects of the tilting angle and load on the rollover critical speed were investigated.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.55.2-55.2
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• 2010

기존의 thermal spray coating은 분사시 가스와 입자가 높은 열을 동반하여 상대적으로 차가운 기판과의 충돌되는 과정에서 기판과 입자 사이에 열응력이 발생하게 되고, 이것은 코팅 특성을 저하시킨다. 또한 고온의 가연성 가스등의 사용으로 작업 시 안전문제 등의 단점이 있었다. 이러한 단점을 보완하기 위하여 분사 시 운동에너지를 주로 이용하는 cold spray coating 공정이 개발되었다. 이 공정은 코팅 입자를 임계속도 이상으로 가속시켜 입자와 기판이 충돌시 소성 변형을 통해 적층되는 코팅기술이다. Cold spray coating공정은 상온 코팅이 가능하기 때문에 주입입자의 물성이 비교적 그대로 유지되고, 고온의 열로 인한 기판의 변질을 막을 수 있다. Cold Spray coating에서 주로 원형 노즐을 사용하나 본 연구에서는 분사 효율 향상을 위한 광폭노즐을 사용하여 코팅 시간 단축을 기대하고 있다. 임계속도 이상의 입자 확보를 위하여 노즐의 expansion ratio와 노즐 shape의 변화를 주어 그에 따른 노즐내의 유동장을 수치해석을 통해 계산하였다. 분사되는 출구면과 기판 사이의 입자 속도 분포를 해석하였고, 이를 통해 임계속도 이상의 속도를 갖는 유효 입자들의 분포 및 유효 분사 면적을 예측하였다. 또한, 기존의 원형 노즐과 광폭 노즐과의 유동장 비교 및 각 노즐 분사면을 분석하여 cold spray coating공정에서의 효율적인 노즐 형상을 디자인하였다.

• Journal of the Korean Society for Railway
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• v.11 no.1
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• pp.7-12
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• 2008

An experimental study has been conducted to investigate the effect of tunnel slope on critical velocity by using the model funnel of the 1/20 reduced-scale applying the Floods scaling law. the square liquid pool burners were used for methanol, acetone and n-heptane fires. tunnel. Tunnel slopes varied as five different degrees $0^{\circ}$, $2^{\circ}$, $4^{\circ}$, $6^{\circ}$ and $8^{\circ}$. The mass loss rate and the temperatures are measured by a load celt and K-type thermocouples for tunnel slope. Present study results in bigger the critical velocity than the research of Atikinson and Wu using the propane burner. Therefore, when estimating the critical velocity in slope tunnel, the variations of the heat release rate is an important factor. The reason is the ventilation velocity directly affects variation of heat release rate when slope tunnel fire occurred.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.49 no.3
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• pp.98-105
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• 2012

This paper describes a new method for a speech playback speed control with high quality. The proposed method provides an adaptive threshold filtering solution for detecting active regions of a speech signal that are followed by playback speed. For a given playback speed, threshold value is adaptively determined with the statistics(:mean and standard deviation) of each frame in speech, and is used to select only active blocks within the current frame. To minimize quality degradation(i.e., pitch degradation) caused due to high-speed playback, the threshold filtering priorly eliminates relatively low-activity blocks including voice and unvoice. Simulation results show that the proposed scheme provides a playback speed control solution with higher quality than SOLA(Synchonized OverLap Add) method using the pitch extraction of speech.

• Tunnel and Underground Space
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• v.29 no.2
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• pp.124-134
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• 2019

Subcritical crack growth in rock material can occur under monotonic and cyclic loading. Subcritical crack growth plays an important role in evaluating the long-term stability of structures in rocks. This paper presents the results of studies conducted to determine subcritical crack growth parameters under monotonic and cyclic loading in rock-like material. The constant stress rate method was employed for monotonic loading. The subcritical crack growth parameter of n under cyclic loading was determined by the relation between the rate of crack growth per cycle and stress intensity factor range. The specimens contained pre-existing flaws with 45 and 60 degrees of inclination angle and flaws spacing and continuity were varied to arrange crack growth in shear or tensile manner. The results show that the parameter of n is almost constant regardless of the applied load conditions such as monotonic and cyclic or shear and tension.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10b
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• pp.401-403
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• 1999

본 논문에서 우리는 제약이 없는 배경화면에서 얼굴의 움직임을 이용한 응시점 추적을 위해 얼굴의 특징점(눈, 코, 그리고 입)들을 찾고 head orientation을 구하는 효？거이고 빠른 방법을 제안한다. 얼굴을 찾는 방법이 많이 연구 되어 오고 있으나 많은 부분이 효과적이지 못하거나 제한적인 사항을 필요로 한다. 본 논문에서 제안한 방법은 이진화된 이미지에 기초하고 완전 그래프 매칭을 이용한 유사성을 구하는 방법이다. 즉, 임의의 임계치 값에 의해 이진화된 이미지를 레이블링 한 후 각 쌍의 블록에 대한 유사성을 구한다. 이때 두 눈과 가장 유사성을 갖는 두 블록을 눈으로 선택한다. 눈을 찾은 후 입과 코를 찾아간다. 360$\times$240 이미지의 평균 처리 속도는 0.2초 이내이고 다음 탐색영역을 예상하여 탐색 영역을 줄일 경우 평균 처리속도는 0.15초 이내였다. 그리고 본 논문에서는 얼굴의 움직임을 구하기 위해 각 특징점들이 이루는 각을 기준으로 한 템플릿 매칭을 이용했다. 실험은 다양한 조명환경과 여러 사용자를 대상으로 이루어졌고 속도와 정확성면에서 좋은 결과를 보였다. 도한, 명안정보만을 사용하므로 흑백가메라에서도 사용가능하여 경제적 효과도 기대할 수 있다.

• Journal of Internet Computing and Services
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• v.14 no.6
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• pp.1-8
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• 2013

Data mining techniques are used to find important and meaningful information from huge databases, and pattern mining is one of the significant data mining techniques. Pattern mining is a method of discovering useful patterns from the huge databases. Frequent pattern mining which is one of the pattern mining extracts patterns having higher frequencies than a minimum support threshold from databases, and the patterns are called frequent patterns. Traditional frequent pattern mining is based on a single minimum support threshold for the whole database to perform mining frequent patterns. This single support model implicitly supposes that all of the items in the database have the same nature. In real world applications, however, each item in databases can have relative characteristics, and thus an appropriate pattern mining technique which reflects the characteristics is required. In the framework of frequent pattern mining, where the natures of items are not considered, it needs to set the single minimum support threshold to a too low value for mining patterns containing rare items. It leads to too many patterns including meaningless items though. In contrast, we cannot mine any pattern if a too high threshold is used. This dilemma is called the rare item problem. To solve this problem, the initial researches proposed approximate approaches which split data into several groups according to item frequencies or group related rare items. However, these methods cannot find all of the frequent patterns including rare frequent patterns due to being based on approximate techniques. Hence, pattern mining model with multiple minimum supports is proposed in order to solve the rare item problem. In the model, each item has a corresponding minimum support threshold, called MIS (Minimum Item Support), and it is calculated based on item frequencies in databases. The multiple minimum supports model finds all of the rare frequent patterns without generating meaningless patterns and losing significant patterns by applying the MIS. Meanwhile, candidate patterns are extracted during a process of mining frequent patterns, and the only single minimum support is compared with frequencies of the candidate patterns in the single minimum support model. Therefore, the characteristics of items consist of the candidate patterns are not reflected. In addition, the rare item problem occurs in the model. In order to address this issue in the multiple minimum supports model, the minimum MIS value among all of the values of items in a candidate pattern is used as a minimum support threshold with respect to the candidate pattern for considering its characteristics. For efficiently mining frequent patterns including rare frequent patterns by adopting the above concept, tree based algorithms of the multiple minimum supports model sort items in a tree according to MIS descending order in contrast to those of the single minimum support model, where the items are ordered in frequency descending order. In this paper, we study the characteristics of the frequent pattern mining based on multiple minimum supports and conduct performance evaluation with a general frequent pattern mining algorithm in terms of runtime, memory usage, and scalability. Experimental results show that the multiple minimum supports based algorithm outperforms the single minimum support based one and demands more memory usage for MIS information. Moreover, the compared algorithms have a good scalability in the results.

• Nuclear Engineering and Technology
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• v.23 no.3
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• pp.306-315
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• 1991

This paper considered the out-of-plane motion of the piping system conveying fluid through the elbow connecting two straight pipes. The extended Hamilton's principle is used to derive equations of motion. It is found that dynamic instability does not exist for the clamped-clamped, clamped-pinned and pinned-pinned boundary conditions. The frequency equations for each boundary conditions are solved numerically to find the natural frequencies. The effects of fluid velocity and Coriolis force on the natural frequencies of piping system are investigated. It is shown that buckling-type instability may occur at certain critical velocities and fluid pressures. Equivalent critical velocity, which is defined as a function of flow velocity and fluid pressure, are calculated for various boundary conditions.

• Journal of the Korean Society for Marine Environment & Energy
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• v.6 no.4
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• pp.52-66
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• 2003

Generally we have difficulty in removing oil using mechanical devices because recovery rate and recovery efficiency decrease remarkably when operating in thin oil films or in oils of very high viscosity In the Present study a series of experiments were carried out to study the effect of operating conditions on the rate of recovery for the spilled oil using a drum type skimmer. For each set of experiments depth of immersion, oil film thickness and the circumferential speeds were varied systematically to find the effects on the recovery rate. The results shows that recovery rate is dependent on the contact angle for the depth of immersion and the highest rate of oil recovery shows in the case of a contact angle of 45°(h/d=0.15). For the removal of spilled oil the optimal circumferential speed can be found as the critical value to reach the saturated recovery rate for a given oil film thickness and depth of immersion. Even in thin oil thickness we have enough recovery rate and recovery efficiency within critical circumferential speed this way.