• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.149-152
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• 2008

In structural design provision, maximum punching shear stress of slabs is prescribed as combined stress of direct shear occurred by balanced gravity load and eccentric shear occurred by unbalanced moment. This means that the effect of unbalanced moment is considered to decide the punching shear stress. However, from the resistance capacity standpoint, the effect of unbalanced moment strength is not considered for deciding punching shear strength. For this problem, a model to show unbalanced moment-punching shear interrelation was proposed. In the model, the relation between load effect and resistance capacity in unbalanced moment-punching shear was two-dimensionally expressed. Using the interrelation model, a method how unbalanced moment strength should be considered to decide the punching shear strength was proposed. Additionally, a effective width enlargement factor for deciding the unbalanced moment strength of flat plates with shear reinforcements was proposed. The interrelation model proposed in this paper is very effective for the design because not only punching shear and unbalanced moment strengths but also failure modes of flat plates can be accurately predicted.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.6
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• pp.707-714
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• 2021

An important factor that causes delays at roundabouts is unbalanced traffic conditions. The majority of domestic studies have tendedto focus on the proportion of entering traffic rather than conflicting traffic in order to explain unbalanced traffic conditions. Also, there is scant research on the proper distance between a signalized intersection and a roundabout. In this study, therefore, unbalanced traffic conditions and optimal distance between two intersections were analyzed using SIDRA software based on the Gajwa-ro roundabout in Icheon, where unbalanced traffic conditions occur during afternoon peak hours, and its position is 295 m from a signalized intersection. It was found that a state of unbalanced traffic conditions in the form of conflicting traffic caused delays at Gajwa-ro roundabout, and the queuing length on each approach was removed when there was 850 m of distance between two intersections.

• Information Systems Review
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• v.24 no.4
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• pp.23-40
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• 2022

Although Support Vector Machine(SVM) has been used in various fields such as bankruptcy prediction model, the hyperplane learned by SVM in class imbalance problem can be severely skewed toward minority class and has a negative impact on performance because the area of majority class is expanded while the area of minority class is invaded. This study proposed optimized uneven margin SVM(OPT-UMSVM) combining threshold moving or post scaling method with UMSVM to cope with the limitation of the traditional even margin SVM(EMSVM) in class imbalance problem. OPT-UMSVM readjusted the skewed hyperplane to the majority class and had better generation ability than EMSVM improving the sensitivity of minority class and calculating the optimized performance. To validate OPT-UMSVM, 10-fold cross validations were performed on five sub-datasets with different imbalance ratio values. Empirical results showed two main findings. First, UMSVM had a weak effect on improving the performance of EMSVM in balanced datasets, but it greatly outperformed EMSVM in severely imbalanced datasets. Second, compared to EMSVM and conventional UMSVM, OPT-UMSVM had better performance in both balanced and imbalanced datasets and showed a significant difference performance especially in severely imbalanced datasets.

• Proceedings of the KAIS Fall Conference
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• 2009.12a
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• pp.678-681
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• 2009

사출성형은 열가소성수지의 가공법으로써 정밀도나 고품질의 제품을 효과적으로 생산하는데 널리 이용되며 플라스틱은 현재 광범위하게 사용되고 있는 공업재료 중의 하나이다. 과거에는 플라스틱을 일회용품 및 외장재로 사용하였다. 그러나 산업기술이 발전하며 플라스틱은 금속을 대체 할 수 있는 재료로서 사용할 수 있다는 인식의 변화로 점차 기계요소용 재료로 사용되고 있으며 기계요소용 재료로 사용됨에 따라 플라스틱 제품이 정밀한 부품으로 사용되기 위해서는 금형의 가공뿐만 아니라 사출성형 시 용융수지가 금형의 각 캐비티에 균형적으로 충전되는것이 요구된다. 이러한 요구조건을 만족하기 위해서는 각 캐비티의 가공치수는 매우 높은 정밀도를 유지해야 하며, 각 캐비티에서의 충전과 냉각도 동일한 상태를 유지해야 한다. 충전 불균형은 성형품의 품질에 큰 저해 요인으로서 플라스틱 제품의 치수성, 밀도, 외관품질, 강도 등에 불균일한 결과를 가져오는 요인으로 지적되고 있다. 실제로 충전 불균형은 충전 단계에서 런너 내에서 발생하는 불균일한 전단분포에 기인하여 발생되므로 점도변화에 영향을 주는 수지의 물성, 런너의 배열과 같은 외부 요인과 사출압력, 사출속도, 수지온도, 금형온도와 같은 성형공정 조건에 의한 요인에 의한 충전 불균형의 양상이 달라지게 된다. 본 연구는 다수 캐비티 금형에서 충전 불균형 현상에 대한 원인을 검토하고 실제로 사출성형을 실시하기 전 사출성형해석 소프트웨어를 이용하여 시뮬레이션을 하여 다수 캐비티에 대한 충전 패턴을 미리 예측하여 보았다.

• Journal of the Korean association of regional geographers
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• v.12 no.5
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• pp.557-570
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• 2006

This study attempts to analyze the spatial disparity between supply and the demand of volunteering activities in Daegu, South Korea. The spatial disparity of volunteering activities has been strongly influenced by the residental disparity in terms of socio-economic level. The ratio of volunteers is mostly determined by income and education level that strongly impact the spatial distribution of residential area. The regional difference of ratio of volunteers is greater among Gu districts than in Dong level. The recipients for the volunteering activities have been likely to reside in a particular area within a Gu district; so, regional difference of the recipients was severe in dong level rather than Gu level. It is strongly recommended to exchange volunteers among regions to reduce the spatial disparity between the volunteers and the recipients.

• The Journal of the Korea Contents Association
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• v.9 no.7
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• pp.141-148
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• 2009

Recently there have been many research efforts focused on imbalanced data classification problems, since they are pervasive but hard to be solved. Approaches to the imbalanced data problems can be categorized into data level approach using re-sampling, algorithmic level one using cost functions, and ensembles of basic classifiers for performance improvement. As an algorithmic level approach, this paper proposes to use multilayer perceptrons with higher-order error functions. The error functions intensify the training of minority class patterns and weaken the training of majority class patterns. Mammography and thyroid data-sets are used to verify the superiority of the proposed method over the other methods such as mean-squared error, two-phase, and threshold moving methods.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.11a
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• pp.133-136
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• 2011

본 논문에서는 SURF 알고리즘을 이용한 직교식 스테레오 카메라 영상의 칼라 불균형 보정 방법 제안한다. 제안 방법에서는 SURF 알고리즘을 이용하여 스테레오 좌, 우 영상의 대응점을 찾은 후, 찾은 대응점들의 칼라 보정 벡터를 영상 획득 모델을 기반으로 계산한다. 영상 전체에서 다양한 칼라 대응점 정보를 추출하기 위하여 본 논문에서는 분할영상을 이용하여 칼라 대응점 정보를 추출한다. 추출된 대응점 정보는 초기 칼라 보정 벡터로 변환할 수 있으며 좌, 우 영상의 모든 픽셀에 대하여 색정보가 가장 유사한 대응점의 보정 벡터를 사용하여 칼라 불균형을 보정한다. 초기 보정 벡터를 이용한 칼라 불균형 보정 후 존재하는 노이즈을 제거하기 위하여 유사한 색공간에 위치한 칼라 보정 벡터에 가우시안 필터를 적용한다. 실험 결과로 원본 영상과 보정된 영상의 칼라 히스토그램을 비교하였으며, 분할 영역의 수에 따른 보정 결과도 비교 제시하였다. 실험 결과는 제안한 방법이 직교식 스테레오 카메라 영상에 효과적인 칼라 불균형 보정 방법임을 보여준다.

• Journal of the Korea Society of Computer and Information
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• v.12 no.3
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• pp.51-58
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• 2007

The shared-nothing multiprocessor architecture has advantages in scalability, this architecture has been adopted in many multiprocessor database system. But, if the data are not uniformly distributed across the processors, load will be unbalanced. Therefore, the whole system performance will deteriorate. This is the data skew problem, which usually occurs in processing parallel hash join. Balancing the load before performing join will resolve this problem efficiently and the whole system performance can be improved. In this paper, we will present an algorithm using merit of very large memory to reduce disk access overhead in performing load balancing and to efficiently solve the data skew problem. Also, we will present analytical model of our new algorithm and present the result of some performance study we made comparing our algorithm with the other algorithms in handling data skew.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.209-214
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• 2011

A method to detect rotor mass imbalance, which is one of the typical faults of wind turbine, is presented for effective condition monitoring of wind turbine. Dynamic analysis for a three-bladed horizontal-axis wind turbine was carried out with adding mass to a blade for inflicting the rotor mass imbalance. It has been found that the added mass induce a resulting centrifugal force to nacelle and this leads to a transverse (relative to the rotor axis) oscillation of the nacelle. It has been also found that the amplitude of the oscillation is almost linearly increased as the added mass is increased.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.6
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• pp.1385-1395
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• 2017

This paper aims to develop an IDS (Intrusion Detection System) that takes into account class imbalanced datasets. For this, we first built a set of training data sets from the Kyoto 2006+ dataset in which the amounts of normal data and abnormal (intrusion) data are not balanced. Then, we have run a number of tests to evaluate the effectiveness of machine learning techniques for detecting intrusions. Our evaluation results demonstrated that the Random Forest algorithm achieved the best performances.