• Proceedings of the Korea Inteligent Information System Society Conference
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• 2005.11a
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• pp.197-204
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• 2005

In this paper, we propose a method to an obstacle avoidance of chaotic robots that have unstable limit cycles in a chaos trajectory surface in the ubiquitous environment. We assume all obstacles in the chaos trajectory surface have a Van der Pol equation with an unstable limit cycle. We also show computer simulation results of Chua's equation, Lorenz equation, Hamilton and Hyper-chaos equation trajectories with one or more Van der Pol as an obstacles. We proposed and verified the results of the method to make the embedding chaotic mobile robot to avoid with the chaotic trajectory in any plane.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.265-269
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• 2006

본 논문에서는 간헐성 카오스를 이용한 장해물 회피 문제를 다루었다. 본 본문은 Chua's 방정식을 이용한 카오스 회로를 이동 로봇에 내장하여 카오스 이동 로봇을 구성하고 이 카오스 이동 로봇이 어느 임의 평면을 카오스 궤적을 가지고 주행하다가 고정 장애물, 또는 은닉 이동 장애물을 만나면 이를 회피하는 알고리즘을 제시하였다. 간헐성 카오스 로봇의 장애물 회피의 경우 고정 장애 and, 이동 장애물, 장애물 위험에 따른 로봇의 접근 등에서 잘 회피됨을 확인하였으며 만족할 만한 결과를 얻었다.

• Proceedings of the Korean Society of Potoscience Conference
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• 2005.06a
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• pp.91-91
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• 2005

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2006.11a
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• pp.113-116
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• 2006

본 본문은 Arnold 방정식, Chua's 방정식과 같은 여러 종류의 카오스 회로를 이동 로봇에 내장하여 카오스 이동 로봇을 구성하고 이 카오스 이동 로봇이 어느 임의 평면을 카오스 궤적을 가지고 탐색하다가 목표물을 만나면 목표물을 집중 탐색하는 방법을 제시하고 그 결과를 검증 하였다. 목표물 탐색을 위해서 BVP 모델을 이용하여 목표물로 가정하여 카오스 제적을 가지고 집중적으로 탐색하도록 하는 알고리즘을 개발하고 그 결과를 검증하였으며 이에 대한 타당성을 확인하였다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2006.11a
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• pp.119-122
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• 2006

본 본문은 Arnold 방정식, Chua's 방정식 같은 여러 종류의 카오스 회로를 이동 로봇에 내장하여 카오스 이동 로봇을 구성하고 이 카오스 이동 로봇이 어느 임의 평면을 카오스 궤적을 가지고 탐색하다가 장애물을 만나거나 근접하게 되면 장애물을 회피하는 방법을 제시하고 그 결과를 검증하였다. 장애물 회피를 위해서 장애물을 고정 장애물과 BVP 모델을 이용한 은닉 장애물로 장애물을 가정하여 카오스 제적을 가지고 회피하도록 하는 알고리즘을 개발하고 그 결과를 검증하였으며 이에 대한 타당성을 확인하였다.

• ETRI Journal
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• v.41 no.2
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• pp.224-234
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• 2019

This paper proposes a new spectrum forecasting (SF) model to estimate the spectrum demands for future mobile broadband (MBB) services. The model requires five main input metrics, that is, the current available spectrum, site number growth, mobile data traffic growth, average network utilization, and spectrum efficiency growth. Using the proposed SF model, the future MBB spectrum demand for Malaysia in 2020 is forecasted based on the input market data of four major mobile telecommunication operators represented by A-D, which account for approximately 95% of the local mobile market share. Statistical data to generate the five input metrics were obtained from prominent agencies, such as the Malaysian Communications and Multimedia Commission, OpenSignal, Analysys Mason, GSMA, and Huawei. Our forecasting results indicate that by 2020, Malaysia would require approximately 307 MHz of additional spectrum to fulfill the enormous increase in mobile broadband data demands.

• International Journal of Human Ecology
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• v.13 no.2
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• pp.1-13
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• 2012

This study examined the effects of academic self-concept (internal factor) and maternal parenting behaviors (external factor) on academic delay of gratification (ADOG). Additionally, models predicting ADOG were compared between Korean and Malaysian children. The participants of this study were 100 Korean third graders and their mothers, and 100 Malaysian third graders and their mothers. The children completed the modified versions of the Academic Delay of Gratification Scale for Children, and Academic Self-Concept Questionnaire. The mothers completed the Parenting Attitude Test. Pearson's correlation tests, independent t-tests, and multiple regression analyses were conducted to test the research hypotheses. The results showed that Korean children reported higher ADOG and academic self-concept scores than that of Malaysian children. Moreover, academic self-concept was found to have a significant positive effect on ADOG among both Korean and Malaysian children. There was no significant gender difference in ADOG for both Korean and Malaysian children. However, the effects of maternal parenting behaviors on ADOG were only detected among the Malaysian children, particularly on Achievement Press. That is, only for the Malaysian children, maternal pressure about academic achievement was found to have a significant positive effect on ADOG. In conclusion, only academic self-concept was found to be a significant predictor explaining the variance in ADOG among Korean children. On the other hand, academic self-concept and maternal parenting behaviors were shown as significant predictors explaining the variance in ADOG among Malaysian children.

• Journal of Information Processing Systems
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• v.9 no.2
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• pp.271-286
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• 2013

Recently, a pixel-chaotic-shuffling (PCS) method has been proposed by Huang et al. for encrypting color images using multiple chaotic systems like the Henon, the Lorenz, the Chua, and the Rossler systems. All of which have great encryption performance. The authors claimed that their pixel-chaotic-shuffle (PCS) encryption method has high confidential security. However, the security analysis of the PCS method against the chosen-plaintext attack (CPA) and known-plaintext attack (KPA) performed by Solak et al. successfully breaks the PCS encryption scheme without knowing the secret key. In this paper we present an improved shuffling pattern for the plaintext image bits to make the cryptosystem proposed by Huang et al. resistant to chosen-plaintext attack and known-plaintext attack. The modifications in the existing PCS encryption method are proposed to improve its security performance against the potential attacks described above. The Number of Pixel Change Rate (NPCR), Unified Average Changed Intensity (UACI), information entropy, and correlation coefficient analysis are performed to evaluate the statistical performance of the modified PCS method. The simulation analysis reveals that the modified PCS method has better statistical features and is more resistant to attacks than Huang et al.'s PCS method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.7
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• pp.1064-1068
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• 2002

In this paper, we introduce a hyper-chaos synchronization method using State-Controlled Cellular Neural Network(SC-CNN). We make a hyper-chaos circuit using SC-CNN with the n-double scroll. A hyper-chaos circuit is created by applying identical n-double scrolls with weak coupled method, to each cell. Hyper-chaos synchronization was achieved using drive response synchronization between the transmitter and receiver about each state in the SC-CNN. From the result of the recovery signal through the demodulation method in the receiver, We shown that recovery quality of state variable $$\chi$_3$ is superior to that of ${$\chi$_2}, {$\chi$_1}$ in secure communication.

• Journal of Electrical Engineering and Technology
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• v.3 no.3
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• pp.314-319
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• 2008

Power quality simulation plays an important role in many practical cases, for example, when deciding the capacity of the related mitigation devices, assessing the influence of installing a nonlinear load in the distribution part, dissolving the quality issues between utilities and customers, and so on. For these purposes, many dedicated tools have been used in order to assess the level of quality distortions by various kinds of PQ indices. However, there are few modules that can accurately simulate the flicker phenomenon, that is, $P_{st}$ and the nonlinear and chaotic behavior of the electrical arc furnace, which is one of the representative nonlinear loads. This paper deals with the useful and simple modules for the voltage flicker simulation in the distribution and transmission level under the environment of Matlab/Simulink. With these modules, the various conditions of distribution systems and the capacities of arc furnaces with the chaotic characteristic can be easily taken into account.