• Journal of the Korean Institute of Intelligent Systems
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• v.25 no.1
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• pp.91-96
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• 2015

In this study, we introduce robust face recognition system with illumination variation realized with the aid of CT preprocessing method. As preprocessing algorithm, Census Transform(CT) algorithm is used to extract locally facial features under unilluminated condition. The dimension reduction of the preprocessed data is carried out by using $(2D)^2$PCA which is the extended type of PCA. Feature data extracted through dimension algorithm is used as the inputs of proposed radial basis function neural networks. The hidden layer of the radial basis function neural networks(RBFNN) is built up by fuzzy c-means(FCM) clustering algorithm and the connection weights of the networks are described as the coefficients of linear polynomial function. The essential design parameters (including the number of inputs and fuzzification coefficient) of the proposed networks are optimized by means of artificial bee colony(ABC) algorithm. This study is experimented with both Yale Face database B and CMU PIE database to evaluate the performance of the proposed system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.2 s.105
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• pp.101-109
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• 2006

A broadband, DC to 40 GHz 5-bit MMIC digital attenuator has been developed. The ultra broadband attenuator has been achieved by adding transmission lines in the conventional Switched-T attenuator and optimizing the transmission line parameters. Momentum simulation was performed in design for accurate performance prediction at high frequencies and Monte Carlo analysis was applied to verify the performance stability against the MMIC process variation. The attenuator has been fabricated with $0.15\;{\mu}m$ GaAs pHEMT process. This attenuator has 1 dB resolution and 23 dB dynamic ranges. High attenuation accuracy has been achieved over all attenuation ranges and 40 GHz bandwidth with the reference state insertion loss of less than 6 dB at 20 GHz. The input and output return losses of the attenuator are better than 14 dB over all attenuation states and frequencies. The measured IIP3 of the attenuator is 33 dBm.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.2048-2061
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• 1991

As compared with other cutting types, the ball end milling process causes a complexity in cutting system and a falling-off of machinability. In order to increase the productivity and efficiency in th NC machining of sculptured surfaces, this study carried out the qualitative linearized evaluation about the ball end milling system and applied their practical expressions to the technological processor at the cutter path planning stage. The evaluated expressions were proved to be adequate for practical use from an accuracy point of view and the estimation models were applied to sculptured surface machining processes for finding variable machining conditions. Consequently, it was recognized that variable machining conditions bring about the dispersion of force system and the reduction of machining time by more than 50%.

• The Journal of the Acoustical Society of Korea
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• v.21 no.1
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• pp.47-55
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• 2002

This paper proposes a new improved lumped element equivalent circuit analysis method to analyze withdrawal weighted SAW resonators of irregular electrode configurations, which enables to calculate the frequency response of withdrawal weighted SAW resonators. This method has led to the derivation of Smith equivalent circuit's y-parameters for a single ground electrode and formulated the resonator's admittance by calculating the total current into an IDT assembly. To illustrate the effectiveness of the technique, this method was applied to the design of a simple ladder filter and the change of the filter performance was investigated in relation to the weighting of the series and parallel resonators, respectively. The results shows that the withdrawal weighted resonator ladder filters provide better performance in their bandwidth and transition characteristics than normal ones. This new equivalent circuit analysis method can also serve as a better tool to design and analyze general SAW resonator filters.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.9
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• pp.841-848
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• 2016

In this paper, a microstrip-fed dual-band monopole antenna with DGS(: Defected Ground System) for WLAN(: Wireless Local Area Networks) applications was designed, fabricated and measured. The proposed antenna is based on a microstrip-fed structure, and composed of two strip lines and DGS structure and then designed in order to get dual band characteristics. We used the simulator, Ansoft's High Frequency Structure Simulator(: HFSS) and carried out simulation about parameters W2, L10, W3, and DGS to get the optimized parameters. The proposed antenna is made of $21.0{\times}36.0{\times}1.6mm3$ and is fabricated on the permittivity 4.4 FR-4 substrate. The experiment results are shown that the proposed antenna obtained the -10 dB impedance bandwidth 700 MHz(2.10~2.80 GHz) and 1,780 MHz(5.02~6.80 GHz) covering the WLAN bands. Also, the measured gain and radiation patterns characteristics of the proposed antenna are presented at required dual-band(2.4GHz band/5.0GHz band), respectively.

• Journal of KIISE:Information Networking
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• v.35 no.4
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• pp.301-310
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• 2008

In the existing literature, the handover process reveals numerous problems manifested by high movement detection latency. FMIPv6 can reduce packet loss using a tunnel-based handover mechanism. However, this mechanism may cause performance degradation due to the out-of-sequence packets. Recently. Proxy Mobile IPv6 is proposed for network-based mobility management to reduce overhead in mobile node. PMIPv6 can decrease handover latency which related overhead in MN by using network agent. In this paper, we proposed optimized fast handover scheme called Fast Proxy Mobile IPv6 (EF-PMIPv6). The proposed EF-PMIPv6 can support fast handover using fast IAPP and ND schemes. Further, a mathematical analysis is provided to show the benefits of our scheme. In the analysis, various parameters are used to compare our scheme with the current procedures, while our approach focuses on the reduction of handover latency.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.25 no.4
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• pp.817-827
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• 2015

In this modern society, people are having a close relationship with smartphone. This makes easier for hackers to gain the user's information by installing the malware in the user's smartphone without the user's authority. This kind of action are threats to the user's privacy. The malware characteristics are different to the general applications. It requires the user's authority. In this paper, we proposed a new classification method of user requirements method by each application using the Principle Component Analysis(PCA) and Probabilistic K-Nearest Neighbor(PKNN) methods. The combination of those method outputs the improved result to classify between malware and general applications. By using the K-fold Cross Validation, the measurement precision of PKNN is improved compare to the previous K-Nearest Neighbor(KNN). The classification which difficult to solve by KNN also can be solve by PKNN with optimizing the discovering the parameter k and ${\beta}$. Also the sample that has being use in this experiment is based on the Contagio.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.1
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• pp.8-14
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• 2016

In this paper, a compact CPW-fed antenna for 5 GHz (5.15-5.35 GHz, 5.725-5.825 GHz) band WLAN applications is presented. The designed antenna's shape is step structure. The antenna is fabricated and measured into FR-4 substrate of dielectric comstant 4.2 and thickness 1.0 mm with optimized parameters obtained by simulation. We confirm that it is operated as antenna for WLAN applications by obtaining the measured return loss level of < -10 dB in 5.133-5.982 GHz. The dimensions of the antenna ($20.0{\times}16.0{\times}1.0mm^3$) shows an compactness of about 67.17% with respect to a conventional folded slot antenna.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.12
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• pp.2933-2942
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• 2015

This paper proposes a new method which traces significant element of 2-dimensional natural images and encrypts them by using Fresnelet transform (FRNLT). After analyzing property of the subbands obtained by the FRNLT, we estimated the information for ciphering 2D images. Considering FRNLT levels, energy of subbands, and visual effect, we estimated the optimized point for encryption. By selecting various levels and encrypting region, we can encrypt 2D image with various robustness. Encryption effectiveness was showed by analyzing numerical result, executing time for encryption, area of encrypted region, and visual observation. Therefore encryption for various application can be applied by using the suggested parameters without additional analysis. Identifying the experimental result, in the case of $L_{TH}=4$ and $L_{TH}=4$, an image was not recognized through encrypting only 0.42% among the entire data.

• KIPS Transactions on Software and Data Engineering
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• v.2 no.11
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• pp.801-808
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• 2013

In the virtual space with the interactive 3D contents, the degree of mental satisfaction is determined by how fully it reflect the real world. There are a few factors for getting the high completeness of virtual space. The first is the modeling technique with high-polygons and high-resolution textures which can heighten an visual effect. The second is the functionality. It is about how realistic represents dynamic actions between the virtual space and the user or the system. Although the studies on the techniques for animating and controlling the virtual characters have been continued, there are problems such that the long production time, the high cost, and the animation without expected behaviors. This paper suggest a method of behavior control of animation by designing the optimized skeleton which produces the movement of character and applying the procedural technique using physical law and mathematical analysis. The proposed method is free from the constraint on one-to-one correspondence rules, and reduce the production time by controlling the simple parameters, and to increase the degree of visual satisfaction.