• Journal of Digital Contents Society
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• 제8권2호
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• pp.165-171
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• 2007

The penetration of malicious code and the function of security blocking are performed on the same course of traffic pathway. The security domain is the concept to distinguish the domain from the group handling with the traffic on the structure of network which is performed with the function of penetration and security. The security domain could be different from the criterion of its realm and function, which requires the development and the application of security mechanism for every domain. For the establishment of security domain it is needed to show what criterion of net work should be set up. This study is to research the criterion for topology factor, security domain. structure map selection, and blocking location and disinfection net. It is shown to increase the effective rate blocking the virus with the proposed method in this paper rather than the traditional network architecture. The purpose of this paper is to suggest the necessity of development of security mechanism and the distinguished blocking function according to the level of security domain.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• 제19권4호
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• pp.418-426
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• 2008

In this paper, investigations on the impedance characteristics of a DGS(Defected Ground Structure) slot in the groud plane of microstripline are presented in spectral domain and applied to the characteristic improvement of stepped impedance microstrip low pass filter(LPF). In this method, expressions for the impedance of a DGS slot are derived from self-reaction of the angular spectrum of plane waves and the discontinuity in the modal voltage. The numerical results are compared with those of the rigorous full-wave method and are shown to produce reasonably accurate data. And the stepped impedance microstrip low pass filter is designed and fabricated with the uniform and nonuniform DGS slots for improving the frequency responses. The experiments show that the proposed filter with slots in the ground plane has a wider stopband and sharper cutoff response.

• Journal of Korea Multimedia Society
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• 제17권2호
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• pp.208-217
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• 2014

This paper propose an adaptive control of symmetry contribution based generalized symmetry transform. which can be controlled symmetry contribution according to the intensity orientation of two pixels. In the proposed method, we define the C-D(convergent and divergent)plane which represents convergence and divergence region of gradient pairs. and used the gaussian phase wight function, with respect to the distance from the gradient pair to an extreme point, in calculating the symmetry contribution. The proposed method can be detect the object more efficiently by adaptive controlling the cut-off frequency of the gaussian phase wight function. To evaluate a performance of the proposed method, we compare the proposed method and conventional GST method in various images including IR image. we prove that the proposed method have better performance in object detection.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제17권3호
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• pp.698-704
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• 2013

The image process for image enhancement applies differently the same algorithm for each application. So, the optimized value for each application is required. In this paper, the X-ray medical image using a high-pass filter was improved edges. The result image was improved edge and the contrast of flat area using a constant multiplier and offset. Therefore, the high-frequency emphasis filter optimized for medical image is required. These optimized values are the gaussian high-pass filter, the distance of cutoff frequency=0.05 and offset=0.5. From the result of optimaized simulation, The proposed method has enhanced contrast and edge of the image in the contrast of existing mothods.

• Proceedings of the Korea Information Processing Society Conference
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• 한국정보처리학회 2002년도 춘계학술발표논문집 (하)
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• pp.971-974
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• 2002

일반적으로 악의적인 사용자는 시스템에 공격을 가해 관리자 권한을 취득한 후 그 시스템에 쉽게 침입하기 위해 백도어를 설치해 놓는다. 이전의 백도어는 대부분 사용자 영역에서 수행중인 응용 프로그램의 형태로 설치가 되었다. 그러나 최근에는 로더블 모듈과 같은 운영체제의 확장 방법을 이용하여 커널 영역에서 수행되는 백도어가 나타나게 되었다. 이러한 커널 백도어를 구현하는 방식은 크게 시스템 콜 테이블을 수정하는 방법과 시스템 콜 처리 루틴을 수정하는 방법의 두 가지로 나눌 수 있다. 본 논문에서는 기존에 구현된 커널 백도어의 특성 분석을 하였으며, 이를 기반으로 커널 백도어를 효율적으로 차단 및 탐지할 수 있는 방안을 제안하고 있다. 본 논문에서 언급하는 방안은 커널 메모리 영역에 대한 분석을 통하여 백도어가 시스템 콜 테이블을 수정하거나 시스템 콜 처리 루틴을 변경할 수 없도록 하는 보호 메커니즘을 적용하고 있다. 이를 통하여 커널 내부로 적재되어 백도어를 생성하는 악의적인 모듈의 가능성을 원천적으로 방지할 수 있다.

• Journal of the Korea Society of Computer and Information
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• 제13권5호
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• pp.179-186
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• 2008

In proportion as the growth of the wireless sensor network applications, we need for more accuracy wireless channel information. In the case of indoor or outdoor wireless sensor networks, multipath propagation causes severe problems in terms of fading. Therefore, a path-loss model for multipath environment is required to optimize communication systems. This paper deals with log-normal path loss modeling of the indoor 2.4 GHz channel. We measured variation of the received signal strength between the sender and receiver of which separation was increased from 1 to 30m. The path-loss exponent and the standard deviation of wireless channel were determined by fitting of the measured data. By using the PRR(Packet Reception Rate) of this model. Wireless sensor channel is defined CR(Connect Region), DR(Disconnected Region). In order to verify the characteristics of wireless channel, we performed simulations and experiments. We demonstrated that connection ranges are 24m in indoor, and 14m in outdoor.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제20권3호
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• pp.455-464
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• 2019

The sensorless control based on the flux linkage of PM synchronous motors has excellent position estimation characteristics at low speeds. However, a limitation arises because the integrator of flux estimator is saturated by the DC offset generated during the analog to digital conversion(ADC) process of the measured current. In order to overcome this limitation, HPF with a low cutoff frequency is used. However, the estimation performance is deteriorated (Ed- the verb deteriorate already includes the meaning of 'problem') at high speed due to the low cutoff frequency, and increasing the cutoff frequency of the HPF induces further problems of phase leading and initial starting failure at low speeds. In this paper, the cutoff frequency of HPF was synchronized to the operation frequency of the motor: at low speeds the cutoff frequency was set to low in order to reduce the phase leading of the estimated flux, and at high speeds it was set to high to raise the DC offset removal performance. As a result, the operating range was increased by 200%. Furthermore, a phase compensation algorithm is proposed to reduce the phase leading of the HPF to less than 1.5 degrees over the full operating range. The proposed sensorless control algorithm was verified by experiment with a PM synchronous motor for a washing machine.

• Journal of the Society of Cosmetic Scientists of Korea
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• 제44권2호
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• pp.183-189
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• 2018

Blue light is the highest energy wavelengths in the visible light region and induces skin aging and active oxygen. Studies on harmful mechanism of skin are under way. Research on blue light blocking materials in cosmetics and formulation studies are in the early stage, and the test methods related to blue light blocking measurement are not established. The blue light blocking efficacy was established by referring to the test method of the sunscreen in vitro test(COLIPA guideline, ISO 24443, FDA Final Rule on Sunscreen Testing and Labeling). The blue light blocking effect was evaluated for 17 kinds out of 27 kinds of sunscreen raw materials suggested in KFDA guideline. The Effect was 14.97% for zinc oxide and 16.32% for bishexyloxyphenol methoxyphenyl triazine, 35.47% for methylene bis-benzotriazolyltetramethylbutylphenol, and 65.96% for titanium dioxide. In addition, the effect of micro-titanium dioxide was twice as high as that of the nano-titanium dioxide. The results suggested that the light blocking effect test method can be used to search for blue light blocking materials and study cosmetic formulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제24권10B호
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• pp.1885-1894
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• 1999

The higher mode cutoff frequencies in Crawford TEM cells computed by the Galerkin method(GM) describe in this paper. The authors also report the half mode boundaries to solve not only the cut-off frequencies of symmetric TEM cells and those of asymmetric TEM cells. It is shown that the measured resonant frequencies of the present symmetric TEM cells and a designed asymmetric TEM cell are agreed with the calculated results.

• The Transactions of the Korean Institute of Power Electronics
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• 제2권3호
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• pp.1-10
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• 1997

3-레벨 ZVS PWM DC/DC 컨버터는 풀브리지 ZVS PWM DC/DC 컨버터와 같은 동작 특성을 가지면서 입력전압의 반을 스위칭 소자의 차단전압으로 갖기 때문에 높은 입력을 갖는 DC-DC 변환시스템에 적합한 구조라 할 것이다. 그러나 부유 인덕턴스의 영향으로 인한 내외측 소자간의 차단전압 불균형의 문제와 경부하에서 영전압 스위칭 동작을 하지 못하므로 부하범위가 작다는 문제점을 가지고 있다. 이와 같은 문제점들은 시스템의 신뢰도를 낮추며, 경부하로 갈수록 효율을 떨어뜨리게 된다. 철도 차량과 같은 고압, 대용량의 시스템에서 이러한 문제들은 더욱 두드러 진다. 본 논문에서는 내외측 소자간의 차단전압 불균형의 문제를 없애며, 무부하에서 전부하까지 모든 부하 영역에서 영전압 스위칭 동작을 할 수 있는 새로운 3-레벨 ZVS PWM DC/DC 컨버터를 제시한다. 제안한 회로의 동작 특성과 타당성을 시뮬레이션 및 실험 결과를 통하여 입증한다.