• 한국경영과학회지
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• 제35권2호
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• pp.71-88
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• 2010

A density-based outlier detection such as an LOF (Local Outlier Factor) tries to find an outlying observation by using density of its surrounding space. In spite of several advantages of a density-based outlier detection method, the computational complexity of outlier detection has been one of major barriers in its application. In this paper, we present an LOF algorithm that can reduce computation time of a density based outlier detection algorithm. A kd-tree indexing and approximated k-nearest neighbor search algorithm (ANN) are adopted in the proposed method. A set of experiments was conducted to examine performance of the proposed algorithm. The results show that the proposed method can effectively detect local outliers in reduced computation time.

• 대한기계학회논문집A
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• 제25권7호
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• pp.1155-1162
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• 2001

Sihs minimum strain energy density criterion(SED) often used in the mixed mode problem has the ambiguity of the choice of minimum values. In this paper, as the method to solve the problem of SED, maximum minimum strain energy density criterion is proposed that the crack propagates in the direction of having the maximum among the minimum values of modified strain energy density factor(MS), i.e., sign($\sigma$(sub)$\theta$).Smin.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권4호
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• pp.226-232
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• 2000

In magnetic systems, distribution of electromagnetic force density causes mechanical deformation, which results in noise and vibration. In this paper, Korteweg-Helmholtzs energy method and equivalent magnetic charge method are employed for comparison of their resulting distributions of force density. The force density from the Korteweg-Helmholtzs method is expresses with two Maxwell stresses on the inside and the outside fo magnetic material respectively. The other is calculated using the magnetic Coulombs law. In the numerical model of an electromagnet, their numerical results are compared. The distributions by the two methods are almost the same. And their total forces are also shown to be the same to the one calculated from the conventional Maxwell stress tensor. But the magnetic charge method is easier and more efficient in numerical calculation.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권9호
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• pp.468-474
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• 2003

This paper describes the development of an open frame type high power density switching converter. It is based on the active clamp forward converter with synchronous rectifier, and packaged by using the open frame and multi-layer printed circuit board (PCB) technology to achieve the higher power density. Furthermore, the windings of transformer and inductor are also realized by multi-layer PCB so that it also contributes to achieve higher power density. Through the experiment on the prototype converter of 50[W], it is confirmed that power density of 50[W/i$n_3$] and maximum efficiency of over 91[%] are obtained.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권12호
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• pp.4492-4507
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• 2021

In camera sensor networks (CSNs), in order to better identify the point, full-view problem requires capture any facing direction of target (point or intruder), and its coverage prediction and sensor density issues are more complicated. At present, a lot of research supposes that a large number of homogeneous camera sensors are randomly distributed in a bounded square monitoring region to obtain full-view rate which is close to 1. In this paper, we deduce the sensor density prediction model in heterogeneous deployed CSNs with arbitrary full-view rate. Aiming to reduce the influence of boundary effect, we introduce the concepts of expanded monitoring region and maximum detection area. Besides, in order to verify the performance of the proposed sensor density model, we carried out different scenarios in simulation experiments to verify the theoretical results. The simulation results indicate that the proposed model can effectively predict the sensor density with arbitrary full-view rate.

• 한국정보통신학회논문지
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• 제18권8호
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• pp.1981-1986
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• 2014

본 논문에서 다루는 문제는 채널의 위쪽 행에 위치한 P가지 색을 가지는 점들을 아래쪽 행의 점들에 밀도가 최소가 되도록 연결하는 채널 라우팅 문제이다. 위쪽 행에 위치한 점들이 동일한 색을 가지거나 단지 2가지 색을 가지는 경우는 [1, 2]에서 다루어졌다. 본 논문에서는 P가지 색을 가지는 경우로 일반화한다. 우선 임의의 값 d가 주어질 때, d이하의 밀도를 가지는 할당이 존재하는지 결정하는 문제를 O(p(n+m)log(n+m))시간에 풀 수 있음을 보인다. 이를 이용해서 최소 밀도 값의 할당을 찾는 문제를 해결할 수 있음을 보인다.

• 한국컴퓨터정보학회논문지
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• 제20권12호
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• pp.15-20
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• 2015

In this paper, we propose a modified fuzzy clustering algorithm which can overcome the center deviation due to the Euclidean distance commonly used in fuzzy clustering. Among fuzzy clustering methods, Fuzzy C-Means (FCM) is the most well-known clustering algorithm and has been widely applied to various problems successfully. In FCM, however, cluster centers tend leaning to high density clusters because the Euclidean distance measure forces high density cluster to make more contribution to clustering result. Proposed is an enhanced algorithm which modifies the objective function of FCM by adding a center-scattering term to make centers not to be close due to the cluster density. The proposed method converges more to real centers with small number of iterations compared to FCM. All the strengths can be verified with experimental results.

• 한국세라믹학회지
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• 제43권12호
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• pp.859-864
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• 2006

For the pressure compaction process of the ceramic powder, the green density is very different with both the ceramic body shape and the processing conditions. The density difference cause non-uniform shrinkages and deformations, and make cracks in the sintered ceramics. In this paper, Material properties of the alumina powder mixed with binder and the friction coefficient between the powder and the tool set were determined through the simple compaction experiments: Also the powder flow characteristics were simulated and the green density was analyzed during the powder compaction process with Finite Element Method (FEM). The results show that the density distributions of the green body were improved at the optimized processing condition and both the possibility of the farming crack generation and rho deformation of the sintered Alumina body were reduced.

• Communications for Statistical Applications and Methods
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• 제23권1호
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• pp.71-83
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• 2016

In this paper we discuss a deconvolution density estimator obtained using the support vector machines (SVM) and Tikhonov's regularization method solving ill-posed problems in reproducing kernel Hilbert space (RKHS). A remarkable property of SVM is that the SVM leads to sparse solutions, but the support vector deconvolution density estimator does not preserve sparsity as well as we expected. Thus, in section 3, we propose another support vector deconvolution estimator (method II) which leads to a very sparse solution. The performance of the deconvolution density estimators based on the support vector method is compared with the classical kernel deconvolution density estimator for important cases of Gaussian and Laplacian measurement error by means of a simulation study. In the case of Gaussian error, the proposed support vector deconvolution estimator shows the same performance as the classical kernel deconvolution density estimator.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권3호
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• pp.258-261
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• 2005

The Preisach model needs a distribution function or Everett function to simulate the hysteresis phenomena. To obtain these functions, many experimental data obtained from the first order transition curves are usually required. In this paper, a simple procedure to determine the Preisach density function using the Gaussian distribution function and genetic algorithm is proposed. The Preisach density function for the interaction field axis is known to have Gaussian distribution. To determine the density and distribution, genetic algorithm is adopted to decide the Gaussian parameters. With this method, just basic data like the initial magnetization curve or saturation curves are enough to get the agreeable density function. The results are compared with experimental data and we got good agreements comparing the simulation results with the experiment ones.