• The Journal of the Korea Contents Association
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• v.1 no.1
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• pp.74-82
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• 2001

Visual cryptography made it possible to decrypt the Information encrypted by thresholding scheme not with digital system but with human vision system. This method, however, has some limit in it because of the rack of resolution in both the spatial and amplitude domain. Optical visual cryptography, which used laser system instead of human eyesight, was proposed by conjunction of the optical theory with the cryptography. However, it also had some difficulties because it did not overcome the existing problem of visual cryptography completely. The problem occurred in the process of transferring data processing system from visual to optics. Therefore, it is appropriate to approach these problems in terms of optics. In this paper, we analysis, in the aspect of frequency, the security characteristics and the noise level occurred in the process of optical visual encryption.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.6
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• pp.187-193
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• 2013

In multi-agent systems, How to coordinate the behaviors of the agents through learning is a very important problem. The most important problems in the multi-agent system are to accomplish a goal through the efficient coordination of several agents and to prevent collision with other agents. In this paper, we propose a novel approach by using hybrid learning strategy. It is used hybrid learning strategy to control the multi-agent system efficiently by using the spatial relationship among the agents. Through experiments, we can see approximate faster the goal then other strategies and avoids collision among the agents.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2010.06a
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• pp.175-179
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• 2010

This study was to evaluate of installation location and management problem for a closed circuit television according to the present situation and installation environment when the CCTV doesn't take a location, surrounding environment, mechanical function in the campus. This methodology used network analysis, mechanical characterization and Streetlight illuminance. As a result, we confirmed in Kyung-Buk National University that was problem of unrelated location of walk pattern in students, a short of illuminance location, only 25 CCTV can be used to crime prevention of student in the night but, the other one is need to some improvement under 44 CCTV.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.633-638
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• 2009

This paper presents an optimal design of a magnetorheological(MR) fan clutch based on finite element analysis and also presents torque control of engine cooling fan using a sliding mode control. The MR fan clutch is constrained in a specific volume and the optimization problem identifies the geometric dimension of the fan clutch that minimizes an objective function. The objective function for the optimization problem is determined based on the solution of the magnetic circuit of the initially designed clutch. Under consideration of spatial limitation, design parameters are optimally determined using finite element analysis. After describing the configuration of the MR fan clutch, the viscous torque and controllable torque are obtained on the basis of the Bingham model of MR fluid. Then, a sliding mode controller is designed to control the torque of the fan clutch according to engine room temperature and control performance is evaluated through computer simulation.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.4
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• pp.31-36
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• 2012

In this paper, we proposed spectrum sensing using cooperative relay to solve problem of sensing performance degradation due to CPE (Customer-Premises equipments) which causes low SNR (signal-to-noise ratio) problem. In cooperative communication system, AF (amplify-and-forward) and DF (decoded-and-forward) is widely used for relay mechanism. Also, it is expected that cooperative relay scheme guarantees the high sensing performance by its diversity gain. Based on these backgrounds, in this paper, we apply to cooperative relay scheme to the CR (Cognitive Radio) system, and simulation results show comparison of the sensing performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.7
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• pp.3112-3127
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• 2018

Since time series clustering is performed without prior information, it is used for exploratory data analysis. In particular, clusters of time series with similar shapes can be used in various fields, such as business, medicine, finance, and communications. However, existing time series clustering algorithms have a problem in that time series with different shapes are included in the clusters. The reason for such a problem is that the existing algorithms do not consider the limitations on the size of the generated clusters, and use a dimension reduction method in which the information loss is large. In this paper, we propose a method to alleviate the disadvantages of existing methods and to find a better quality of cluster containing similarly shaped time series. In the data preprocessing step, we normalize the time series using z-transformation. Then, we use piecewise aggregate approximation (PAA) to reduce the dimension of the time series. In the clustering step, we use density-based spatial clustering of applications with noise (DBSCAN) to create a precluster. We then use a modified K-means algorithm to refine the preclusters containing differently shaped time series into subclusters containing only similarly shaped time series. In our experiments, our method showed better results than the existing method.

• KIEAE Journal
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• v.16 no.5
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• pp.5-11
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• 2016

Purpose: Residents in deteriorated residential areas of Seoul have suffered from parking shortage problem. Since it is almost impossible to supply new parking, it is critical to find a way to efficiently utilize existing parking spaces. This study proposes utilizing unused parking spaces in apartment complexes so that residents in multi-unit or multi-family houses can share those parking spaces. Method: Spatial scope of this research is limited to multiplex-clustered neighborhood and apartment complex in Seoul. To identify the nature of parking problem, we reviewed current parking situations in residential areas and policies from the Seoul Metropolitan Government. To understand the amount of parking spaces required to solve parking shortages in multiplex-clustered neighborhoods, this study analyzed car ownership per household and available parking spaces in old residential areas. Then we were able to apprehend the amount of parking spaces that could be used for residents in aged multiplex-clustered areas. Result: Our analysis shows a great potential to utilize surplus parking spaces from apartment complexes for solving parking problems in multiplex-clustered neighborhoods.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.9
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• pp.3751-3770
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• 2015

Many sorts of image processing software facilitate image editing and also generate a great number of doctored images. Forensic technology emerges to detect the unintentional or malicious image operations. Most of forensic methods focus on the detection of single operations. However, a series of operations may be used to sequentially manipulate an image, which makes the operation detection problem complex. Forensic investigators always want to know as much exhaustive information about a suspicious image's entire processing history as possible. The detection of the operation chain, consisting of a series of operations, is a significant and challenging problem in the research field of forensics. In this paper, based on the histogram distribution uniformity of a manipulated image, we propose an operation chain detection scheme to identify histogram equalization (HE) followed by the dither-like operation (DLO). Two histogram features and a local spatial feature are utilized to further determine which DLO may have been applied. Both theoretical analysis and experimental results verify the effectiveness of our proposed scheme for both global and local scenarios.

• ETRI Journal
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• v.37 no.3
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• pp.606-616
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• 2015

In this paper, we propose a novel method for road recognition using 3D point clouds based on a Markov random field (MRF) framework in unstructured and complex road environments. The proposed method is focused on finding a solution for an analysis of traversable regions in challenging environments without considering an assumption that has been applied in many past studies; that is, that the surface of a road is ideally flat. The main contributions of this research are as follows: (a) guidelines for the best selection of the gradient value, the average height, the normal vectors, and the intensity value and (b) how to mathematically transform a road recognition problem into a classification problem that is based on MRF modeling in spatial and visual contexts. In our experiments, we used numerous scans acquired by an HDL-64E sensor mounted on an experimental vehicle. The results show that the proposed method is more robust and reliable than a conventional approach based on a quantity evaluation with ground truth data for a variety of challenging environments.

• Structural Engineering and Mechanics
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• v.44 no.4
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• pp.521-538
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• 2012

In this study, the transverse vibrations of an axially moving flexible beams resting on multiple supports are investigated. The time-dependent velocity is assumed to vary harmonically about a constant mean velocity. Simple-simple, fixed-fixed, simple-simple-simple and fixed-simple-fixed boundary conditions are considered. The equation of motion becomes independent from geometry and material properties and boundary conditions, since equation is expressed in terms of dimensionless quantities. Then the equation is obtained by assuming small flexural rigidity. For this case, the fourth order spatial derivative multiplies a small parameter; the mathematical model converts to a boundary layer type of problem. Perturbation techniques (The Method of Multiple Scales and The Method of Matched Asymptotic Expansions) are applied to the equation of motion to obtain approximate analytical solutions. Outer expansion solution is obtained by using MMS (The Method of Multiple Scales) and it is observed that this solution does not satisfy the boundary conditions for moment and incline. In order to eliminate this problem, inner solutions are obtained by employing a second expansion near the both ends of the flexible beam. Then the outer and the inner expansion solutions are combined to obtain composite solution which approximately satisfying all the boundary conditions. Effects of axial speed and flexural rigidity on first and second natural frequency of system are investigated. And obtained results are compared with older studies.