• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.3
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• pp.26-31
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• 2005

An efficient estimation of the aerodynamic characteristics for missile configurations is essential in the preliminary stage of a missile design. In this study, a Missile DATCOM family code based on the semi-empirical method was utilized for this purpose. In order to check the accuracy and reliability of the code several test cases have been considered: subsonic flow with high angles of attack and supersonic flow with moderate angles of attack. It turned out that the code in general provides prediction in qualitative agreement with the experimental data and results by other works. Finally, the code was applied to a more complicated missile configuration with canard and freely spinning tail fin.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.3
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• pp.220-228
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• 2008

In this study the aerodynamic characteristics of a canard-controlled missile with freely spinning tailfins were investigated by using a semi-empirical method and a CFD code. The mean aerodynamic coefficients for the rolling and roll damping moments were first calculated and then used to predict the roll-rate of freely spinning tailfins. The calculation of roll-rate in the CFD code was carried out by combining a Chimera overset grid system and 6-DOF analysis module. The predicted roll-rate was in good agreement with the experimental data for the roll and yaw canard control inputs. It was also shown that the results are in good agreement with the prediction by a CFD code. This indicates that the semi-empirical method can be used to predict the roll-rate of a canard-controlled missile with freely spinning tailfins.

• Journal of IKEEE
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• v.15 no.2
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• pp.171-178
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• 2011

In this paper, a novel pulse repetition interval (PRI) jittering coder based on quasi-random M-sequence codes is proposed for improvement of counter-countermeasure capability in a radar. Each of the proposed jittered 256 PRI codes has a unique code chip combination with 256 code chips, such that any set of three consequent code chips (4 pulses) from any code appears only once among the entire code chip sequences of the codes. This indicates that only 4 of received pulses are enough to determine uniquely the exact timing position of the incoming pulse train (or code chip sequence) required for counter-countermeasure, as well as the identity of the transmitted code. To prove the proposed idea experimentally, the jittered PRI coder is implemented and demonstrated.

• Journal of Intelligence and Information Systems
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• v.13 no.4
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• pp.35-44
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• 2007

This paper proposes a new method of weighted template matching for machine-printed numeral recognition. The proposed weighted template matching, which emphasizes the feature of a pattern using adaptive Hamming distance on local feature areas, improves the recognition rate while template matching processes an input image as one global feature. Template matching is vulnerable to random noises that generate ragged outlines of a pattern when it is binarized. This paper offers a method of chain code trimming in order to remove ragged outlines. The method corrects specific chain codes within the chain codes of the inner and the outer contour of a pattern. The experiment compares confusion matrices of both the template matching and the proposed weighted template matching with chain code trimming. The result shows that the proposed method improves fairly the recognition rate of the machine-printed numerals.

• The KIPS Transactions:PartC
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• v.11C no.7 s.96
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• pp.959-970
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• 2004

It has become more difficult to correspond an cyber attack quickly as patterns of attack become various and complex. However, current so curity mechanisms just have passive defense functionalities. In this paper, we propose new network suity architecture to respond various cyber attacks rapidly and to chase and isolate the attackers through cooperation between security zones. The proposed architecture makes it possible to deal effectively with cyber attacks such as IP spoofing or DDoS(Distributed Denial of Service), by using active packet technology including a mobile code on active network. Also, it is designed to have more active correspondent than that of existing mechanisms. We im-plemented these mechanisms in Linux routers and experimented on a testbed to verify realization possibility of attacker response framework using mobile code. The experimentation results are analyzed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.6A
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• pp.885-892
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• 2000

A multi-used detector(MUD) using a radial basis function(RBF) network is proposed in a multicarrier-code division multiple access (MC-CDMA) system. In the proposed scheme, a RBF network is connected to the frequency domain in order to effectively utilize the frequency diversity. Simulations have been performed over the frequency selective and multipath fading channel. From these simulations, the proposed receiver is verified to be used for making the performance improvement in combating near-far effects and increasing the number of active users. The system capacity is increaed about 1.8 times at a BER of $10^{-3}$ under a single cell when the proposed scheme is compared with MUD using a parallel interference canceller(PIC).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.8A
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• pp.918-927
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• 2004

WCDMA system is 3rd generation wireless mobile system specified by 3GPP. In WCDMA downlink, two power control schemes are operated. One is inner loop power control operated in every slot. Another is outer loop power control based on one frame time. Base station (BS) can estimate proper transmission power by these two power control schemes. However, because each MS's transmission power makes a severe effect on BS's performance, BS cannot give excessive transmission power to the specific user. 3GPP defined Power Control Dynamic Range (PCDR) to guarantee proper BS's performance. In this paper, we propose Adaptive PCDR algorithm. By APCDR algorithm, Radio Network Controller (RNC) can estimate each MS's current state using received signal to interference ratio (SIR). APCDR algorithm changes MS's maximum code channel power based on frame. By proposed scheme, each MS can reduce wireless channel effect and endure outages in cell edge. Therefore, each MS can obtain better QoS. Simulation result indicate that APCDR algorithm show more attractive output than fixed PCDR algorithm.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.149.2-149.2
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• 2014

진공용기를 배기하기 시작하면 짧은 시간 동안은 공기의 배기가 주를 이루지만 그 후에는 표면 방출 기체의 배기가 이어지고 표면방출 기체의 대부분은 물이라는 것은 누구나 알고 있는 사실이다. 그러나 배기 계산을 할 때는 막상 물 보다는 공기의 일부로 생각하거나 수분을 다른 기체들과 유사하게 다루는 것에 익숙해져 있다. 이런 계산 결과는 실제 상황을 재현하지 못할 뿐만 아니라 일반적으로 배기능력을 과대평가하게 만들어서 공정 계획대로 진공 시스템을 운전하는 것을 불가능하게 만든다. 물은 일반적인 기체와는 성격이 아주 다르다. 다른 기 체 분자들의 흡착 에너지가 ~0.3 eV이고 기름분자가 ~1 eV 정도인 것에 반해 물은 0.55 eV 내외로 상온에서도 비교적 흡착을 잘하고 또 적당히 방출도 일어나는 특별한 특성 때문에 용기 압력을 지배하면서도 신속한 배기를 방해한다. 만일 이런 물의 흡착률 및 방출률을 제대로 수치화할 수 있다면 배기 계산을 훨씬 현실화할 수 있다. 물의 흡착률은 물분자의 부착계수가 지배하고 방출률은 체류시간에 의해 결정되지만 표면상태에 따라 천차만별이므로 얼마라고 확정하기 어렵다. 우선 이번에는 물의 부착계수 최대값을 0.1 정도로 잡고 흡착량에 따라 직선적으로 줄어드는 것으로 가정하며, 물의 표면 체류시간도 몇 가지 값으로 가정해서 0-D 입자 평형 계산을 수행하여 특정 시스템에서 얻은 실험 결과와 비교하려고 한다. 앞으로 몬테카를로 방법과 연계하여 3차원적 분석을 할 수 있는 코드로 발전시켜 나갈 예정이다.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.3 no.3
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• pp.31-38
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• 2010

It has become more difficult to correspond an cyber attack quickly as patterns of attack become various and complex. However, current security mechanisms just have passive defense functionalities. In this paper, we propose new network security architecture to respond various cyber attacks rapidly and to chase and isolate the attackers through cooperation between security zones. The proposed architecture makes it possible to deal effectively with cyber attacks such as IP spoofing or DDoS(Distributed Denial of Service), by using active packet technology including a mobile code on active network. Also, it is designed to have more active correspondent than that of existing mechanisms. We implemented these mechanisms in Linux routers and experimented on a testbed to verify realization possibility of attacker response framework using mobile code. The experimentation results are analyzed.

• Journal of Internet Computing and Services
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• v.9 no.2
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• pp.69-81
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• 2008

It has become more difficult to correspond a cyber attack quickly as patterns of attack become various and complex. However, current security mechanism just have passive defense functionalities. In this paper, we propose new network security mechanism to respond various cyber attacks rapidly and to chase and isolate the attackers through cooperation between security zones. The proposed mechanism makes it possible to deal effectively with cyber attacks such as IP spoofing, by using active packet technology including a mobile code on active network. Also, it is designed to hove more active correspondent than that of existing mechanisms. We implemented these mechanisms in Linux routers and experimented on a testbed to verify realization possibility of attacker response framework using mobile code. The experimentation results are analyzed.