• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권3호
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• pp.1330-1347
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• 2018

Mobile Ad hoc Network (MANET) is a collection of nodes or communication devices that wish to communicate without any fixed infrastructure and predetermined organization of available links. The effort has been made by proposing a scheme to overcome the critical security issue in MANET. The insufficiency of security considerations in the design of Ad hoc On-Demand Distance Vector protocol makes it vulnerable to the threats of collaborative black hole attacks, where hacker nodes attack the data packets and drop them instead of forwarding. To secure mobile ad hoc networks from collaborative black hole attacks, we implement our scheme and considered sensor's energy as a key feature with a better packet delivery ratio, less delay time and high throughput. The proposed scheme has offered an improved solution to diminish collaborative black hole attacks with high performance and benchmark results as compared to the existing schemes EDRIAODV and DRIAODV respectively. This paper has shown that throughput and packet delivery ratio increase while the end to end delay decreases as compared to existing schemes. It also reduces the overall energy consumption and network traffic by maintaining accuracy and high detection rate which is more safe and reliable for future work.

• 제어로봇시스템학회논문지
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• 제17권6호
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• pp.579-586
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• 2011

It is very critical for image processing of IIR (Imaging Infrared) seekers to achieve improved guidance performance for missile systems to determine appropriate thresholds in various environments. In this paper, we propose automatic threshold determination methods for proper thresholds to extract definite target signals in an EOCM (Electro-Optical Countermeasures) environment with low SNR (Signal-to-Noise Ratios). In particular, thresholds are found to be too low to extract target signals if one uses the Otsu method so that we suggest a Shifted Otsu method to solve this problem. Also we improve extracting target signal by changing Shifted Otsu thresholds according to the TBR (Target to Background Ratio). The suggested method is tested for real IIR images and the results are compared with the Otsu method. The HPDAF (Highest Probabilistic Data Association Filter) which selects the target originated measurements by taking into account of both signal intensity and statistical distance information is applied in this study.

• 대한임베디드공학회논문지
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• 제10권2호
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• pp.91-99
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• 2015

The electric power consumed by the embedded devices has become a critical issue because the reduction of power consumption is an important factor to prolong the battery-operated devices' lifetime. Many researches and techniques to reduce the power consumption have been proposed and developed but any power method cannot guarantee optimal power consumption of an embedded device - it would be faced with numerous situation - in all ways. Specifically, power researches for embedded devices deployed in the industry field have hardly been done. In this paper, low power service is proposed to minimize power reduction with the several usage status of embedded devices in the industry field. The usage status is basically classified according to the distance between the device and the user which is obtained by the ultrasonic and PIR sensor. The performance evaluation shows that the proposed scheme can reduce the power consumption by up to 45.3% compared to the device with no power reduction scheme. It also shows that the power consumption of the proposed scheme is 5.2% ~ 16.8% lower than that of the timeout scheme.

• 한국안전학회지
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• 제31권6호
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• pp.6-11
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• 2016

CFRP composite laminates are widely used as structural materials for airplanes, automobile and aerospace vehicles because of their high strength and stiffness. This study aims to examine an effect of curvature on the penetration fracture characteristic of an orthotropic composite laminated shell. For the purpose, we manufactured orthotropic CFRP shell specimen with different curvatures, and conducted a penetration test using an air-gun. Those specimens were prepared to varied curvature radius(${\infty}$, 200mm, 150mm and 100mm)and were stacked to $[O^{\circ}{_3}/90^{\circ}{_3}]_s$. When the specimen is subjected to transverse impact by a steel sphere(${\Phi}10$), the velocity of steel sphere was measured both before and after impact by determining the time for it to pass two ball-screen sensors located a known distance apart. As the curvature increases, the absorption energy and the critical penetration energy increased linearly because the resistance to the bending moment. Patterns of cracks caused by the penetration of CFRP laminated shells included fiber breakage, lamina fracture, matrix crack interlaminar crack and intralaminar crack.

• 한국항행학회논문지
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• 제13권6호
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• pp.907-915
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• 2009

새로운 서비스의 출현 및 스펙트럼 부족으로 인하여 기존 무선통신 서비스와의 주파수 공유가 매우 중요하다. 향후 IMT 서비스에 할당된 후보대역 중 C 대역(3400-4200MHz)은 기존에 FSS 서비스에서 활발히 이용되고 있어 유해한 간섭이 예상된다. 본 논문에서는 향후 IMT 서비스와 기존 FSS 서비스간의 주파수 공유를 평가하기 위해, 서비스 지역에 따른 클러터 손실 및FSS 지구국 앙각 등 시스템간 간섭영향의 주요 요인을 고려하여, I/N=-10dB 간섭보호 기준치를 이용한 최소 이격거리를 분석한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.501-506
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• 2001

The creep crack growth properties in 3.5NiCrMoV steel were investigated at $550^{\circ}C$ by using CT specimen under constant $C_t$ condition that was held during crack growth of 1mm distance. $C_t$ lely on load line displacement rate and $C^*$ usually increase with crack length though load is reduced in order to maintain constant $C_t$ value as crack growth. Fully coalesced area(FCA) ahead of crack tip tend to increase as $C_t$ increase to the critical value, and after that value FCA decrease. For the tertiary creep stage of crack growth test, the most of displacement is due to the steady state creep, except only small part due to the primary creep and other effects. Therefore, tests were mainly interrupted in the tertiary stage to obtain high value of $C_t$. At constant load and $C_t$ region, crack growth slope was 0.900 and 0.844 each, on the other hand $C^*$ slope was 0.480.

• 한국BIM학회 논문집
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• 제7권4호
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• pp.31-38
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• 2017

Big Cyprus watershed, which is located in the Southwestern Florida and covers Everglades National Park that has high proportions of endangered species' habitats, plays an important role for the entire Florida ecosystem. Due to the rapid urbanization and high population growth, however, the watershed has been continuously polluted and the current regional watershed plan is not created to accommodate the speed of growth. The purpose of this study is to suggest proper protection policies and strategies for the Big Cyprus watershed by employing the Inverse Distance Weighted interpolation tool in Geographic Information System. The findings show that conservation priorities should be given in the North and South portion of the watershed area, which are proven to be the most important aisle for the habitats in the Big Cyprus. The study concludes with policy suggestions that local environmental planners should concentrate for adopting their new watershed plan in the near future.

• 한국산학기술학회논문지
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• 제13권1호
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• pp.364-369
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• 2012

유비쿼터스 컴퓨팅 시대로 진입하면서 사물의 위치 정보가 더욱 중요시 되고 있다. 대표적인 실내 위치 인식 시스템인 크리켓은 노드 간의 거리를 인식하기 위해서 RF 신호와 초음파 신호를 주기적으로 전송한다. 하지만 배치되어 있는 센서 노드 수가 증가할수록 신호간의 간섭 및 충돌 횟수가 증가하여 위치 인식 시스템의 정확도를 떨어뜨린다. 본 논문에서는 초음파 위치인식 시스템을 구성하기 위해, 무선 센서 네트워크 표준인 IEEE 802.15.4 MAC 프로토콜을 사용하였다. 신호간의 간섭과 충돌 횟수를 감소시키기 위해, 노드 번호와 이동통신에서 사용하는 주파수 재사용 방식을 변형하여 오차율을 감소시키는 알고리즘을 제안하였다. 성능평가 결과 제안한 알고리즘이 기존의 크리켓시스템보다 수율과 에너지 효율 면에서 더 좋은 성능을 보였다.

• 한국산학기술학회논문지
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• 제13권1호
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• pp.33-38
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• 2012

본 연구에서는 나선형 형태의 와이어를 자동차 무선통신(5.925GHz)용 차량 커넥터에 적용 가능성을 제안하였다. 이 나선형 와이어 형태의 커넥터 설계는 나선형 평균 반경, 나선형 피치, 나선형 와이어 자체의 반경, 나선형와이에서 접지 부분까지의 거리를 중요 설계인자로 판단하여 실시하였다. 이 같은 설계 해석 및 결과는 자동차 통신용 커넥터 설계를 위한 가장 적합한 나선형 와이어 치수 결정에 사용될 수 있을 것이다. 나선형 와이어가 삽입된 최적화된 자동차 WAVE용 커넥터는 삽입손실이 5.925GHz 대역에서 -0.76dB 이내로 발생되었다. 이 삽입손실 결과는 기존의 일반 커넥터에 비하여 21% 성능이 향상된 것이다. 따라서, 본 커넥터 해석결과는 자동차 통신을 위한 고주파대역의 최적 커넥터 설계에 유용하게 사용할 수 있을 것이다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권4호
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• pp.253-260
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• 1999

In this paper, the impedance characteristic of wire-plate pulsed plasma reactor was investigated by experiment. The experiment have carried out under the several conditions of voltage, wire length and wire-plate distance. The impedance of reactor wad decreased with increasing voltage and wire length. The nature of discharge in reactor was changed from streamer corona to spark with increasing incident energy, from which we understood the critical energy density between the two discharges. Fromthis experiment, we proposed the method for the impedance matching between pulse generator and pulsed plasma reactor. Additionally, we succeeded in the analysis ofstray inductance of 0.5MW reactor using EMTP (ElectroMagnetic Transients Program). This means that EMTP is also useful for the analysis of inevitable stray inductance of forthcoming a large scale reactor.