• 전자공학회논문지
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• 제52권12호
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• pp.109-117
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• 2015

본 논문에서는 DSP(Digital Signal Processor)를 이용하여 LED(Light Emitting Diode)에 전류 또는 전압을 공급하고, 이에 따라 나타나는 전압 또는 전류 특성을 분석하는 시스템에서, 전원 공급 또는 측정하는 회로의 비선형 오차 및 임의로 발생하는 오차를 감소시키는 방법을 제안하였다. 임의 오차를 줄이기 위해서는 재귀 평균 방법을 이용하였으며, 비선형 오차를 줄이기 위해서는 보정과정에서 획득한 데이터들을 2차 다항 회귀분석 방법을 이용하여 보정계수를 구하였으며, 이를 이용하여 LED를 생산 시 측정하는 항목인 역방향전류(IR), 역방향 전압(VR), 순방향전압(VF1, VF2, VF3)에 적용하여 오차를 교정하였다. 실험 결과에서는 오차율이 0.017 ~ 0.043 %로 관찰되었다.

• 한국전자파학회논문지
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• 제26권11호
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• pp.1027-1030
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• 2015

항공 SAR(Synthetic Aperture Radar)에서는 일반적으로 바람과 같은 외부 영향에 의해 발생한 요동으로 인해 해상도가 저하될 뿐만 아니라, 사이드로브가 증가하게 되어 영상 화질이 저하되므로 본 논문에서는 사이드로브를 감소시키기 위한 기법을 제시한다. 이를 위해 비행경로를 분할한 다음, 분할된 경로에서 획득된 각각의 데이터에 대해 스퀸트 각도를 추정하여 임무영역을 계산한다. 또한, 재설정된 임무영역 중심에 대하여 1차 요동보상을 수행한 후, 생성된 SAR 영상에서 사이드로브 영향이 두드러지는 영역을 추출한 다음에, 사이드로브 감소 필터를 반복적으로 적용한 후 전체 영상에 대해 확장하여 영상 화질을 향상시키는 방법을 제시한다.

• 항공우주기술
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• 제6권2호
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• pp.21-28
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• 2007

본 논문의 목표는 고장허용제어시스템에 대한 기반 연구로서 무인비행기 안전성 향상을 위하여 조종면 작동불능과 같은 고장에 대해 검출 방법을 제시하는 것이다. 조종면 고장검출을 위한 실시간 시스템식별 알고리듬은 퓨리에 변환기법을 사용하였으며 프로그램 성능 및 검증을 위해 HILS 시험과 비행시험을 수행하였다. 엘리베이터 조종면 고장은 피칭모멘트에 대한 조종면 효과를 나타내는 조종미계수를 실시간 추정하여 정상상태의 값과 비교함으로써 검출된다. 비행시험 결과를 통해 고장상태의 조종미계수 값은 정상상태의 값보다 작다는 것을 확인하였다.

• Journal of Mechanical Science and Technology
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• 제19권spc1호
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• pp.388-394
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• 2005

Recently, the authors have developed a method for real-time dynamics of multibody systems, which combines a semi-recursive formulation to derive the equations of motion in dependent relative coordinates, along with an augmented Lagrangian technique to impose the loop closure conditions. The following numerical integration procedures, which can be grouped into the so-called structural integrators, were tested : trapezoidal rule, Newmark dissipative schemes, HHT rule, and the Generalized-${\alpha}$ family. It was shown that, for large multi body systems, Newmark dissipative was the best election since, provided that the adequate parameters were chosen, excellent behavior was achieved in terms of efficiency and robustness with acceptable levels of accuracy. In the present paper, the performance of the described method in combination with another group of integrators, the Implicit Runge-Kutta family (IRK), is analyzed. The purpose is to clarify which kind of IRK algorithms can be more suitable for real-time applications, and to see whether they can be competitive with the already tested structural family of integrators. The final objective of the work is to provide some practical criteria for those interested in achieving real-time performance for large and complex multibody systems.

• 한국멀티미디어학회논문지
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• 제20권2호
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• pp.244-253
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• 2017

Reversible DNA watermarking is capable of continuous DNA storage and forgery prevention, and has the advantage of being able to analyze biological mutation processes by external watermarking by iterative process of concealment and restoration. In this paper, we propose a reversible DNA watermarking method based on histogram multiple shifting of noncoding DNA sequence that can prevent false start codon, maintain original sequence length, maintain high watermark capacity without biologic mutation. The proposed method transforms the non-coding region DNA sequence to the n-th code coefficients and embeds the multiple bits of the n-th code coefficients by the non-recursive histogram multiple shifting method. The multi-bit embedding process prevents the false start codon generation through comparison search between adjacent concealed nucleotide sequences. From the experimental results, it was confirmed that the proposed method has higher watermark capacity of 0.004-0.382 bpn than the conventional method and has higher watermark capacity than the additional data. Also, it was confirmed that false start codon was not generated unlike the conventional method.

• 한국군사과학기술학회지
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• 제20권3호
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• pp.307-314
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• 2017

Terrain referenced navigation(TRN) system is an attractive method for obtaining position based on terrain measurements and a terrain map. We focus on TRN systems based on the point mass filter(PMF) which is one of the recursive Bayesian method. In this paper, we propose two kinds of performance index for Bayesian filter. The proposed indices are based on entropy and mutual information from information theory. The first index measures roughness of terrain based on entropy of likelihood. The second index named by information gain, which is the mutual information between priori and posteriori distribution, is a quantity of information gained by updating measurement at each step. The proposed two indices are used to determine whether the solution from TRN is adequate for TRN/INS integration or not, and this scheme gives the performance improvement. Simulation result shows that the proposed indices are meaningful and the proposed algorithm performs better than normal TRN algorithm.

• Journal of Advanced Marine Engineering and Technology
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• 제38권5호
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• pp.566-572
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• 2014

Recently, indoor navigation has been applied in large convention centers by using wireless sensor networks (WSNs), which provide not only a user's path to be traveled but also orientation and shopping information to increase user's convenience. This paper presents the localization system for estimating relative coordinates without pre-deployment of the reference node based on ultra wide band (UWB) ranging system, which is relatively suitable for indoor localization compared to other wireless communications, and azimuth sensor. The proposed localization system which consists of an azimuth sensor and a mobile node composed of three nodes estimates relative coordinates of the reference node without applying any recursive and time consumption algorithms. Also, in the process of estimating relative coordinates of the reference node, ranging errors are minimized through the proposed technique and the number of nodes can be reduced. Experimental results show the feasibility and validity of the proposed system.

• 디지털산업정보학회논문지
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• 제6권4호
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• pp.95-105
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• 2010

DNS(Domain Name System) is a huge distributed database that converts host name to IP address. We are expecting the importance of DNS is more increased because many Internet application services appear according to the continuous increase of Internet users and nearly all the Internet application services use DNS. To prevent the interruption of DNS service, DNS server is configured with primary DNS server and a secondary DNS server which takes the place of primary DNS server in case of the service interruption. But this scheme is difficult for providing DNS service constantly in case of DDoS attack, which brings about much network load or network problems in DNS server group. Therefore, This paper proposed the scheme to locally distribute load of DNS server, and the use of address system to group the distributed DNS servers. Also, it proposed the authentication scheme of the correspondent server in case the server is changed in DNS server group having grouping address. In this paper, it is shown that the prosed scheme guarantees the improved service reliability with maintaining the present service performance through the evaluation. Through this, we can expect the high improved DNS service can be provided in the Internet environment in the future.

• Communications for Statistical Applications and Methods
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• 제19권2호
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• pp.293-301
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• 2012

Quantile regression proposed by Koenker and Bassett (1978) is a statistical technique that estimates conditional quantiles. The advantage of using quantile regression is the robustness in response to large outliers compared to ordinary least squares(OLS) regression. A regression tree approach has been applied to OLS problems to fit flexible models. Loh (2002) proposed the GUIDE algorithm that has a negligible selection bias and relatively low computational cost. Quantile regression can be regarded as an analogue of OLS, therefore it can also be applied to GUIDE regression tree method. Chaudhuri and Loh (2002) proposed a nonparametric quantile regression method that blends key features of piecewise polynomial quantile regression and tree-structured regression based on adaptive recursive partitioning. Lee and Lee (2006) investigated wage determinants in the Korean labor market using the Korean Labor and Income Panel Study(KLIPS). Following Lee and Lee, we fit three kinds of quantile regression tree models to KLIPS data with respect to the quantiles, 0.05, 0.2, 0.5, 0.8, and 0.95. Among the three models, multiple linear piecewise quantile regression model forms the shortest tree structure, while the piecewise constant quantile regression model has a deeper tree structure with more terminal nodes in general. Age, gender, marriage status, and education seem to be the determinants of the wage level throughout the quantiles; in addition, education experience appears as the important determinant of the wage level in the highly paid group.

• 한국정보과학회논문지:데이타베이스
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• 제31권2호
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• pp.174-182
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• 2004

정보가 생성되어 소멸되기까지의 과정에서 새로운 정보를 만들어내기 위해서 어떠한 형태로든 서비스되고 있는 정보를 수집하여 이것을 참고하고 인용하여 새로운 정보를 생성하게 된다. 본 논문에서는 인용한 문헌과 인용된 문헌 사이의 관계를 정의하고 관련 정보를 저장하여 서비스에 반영하는 KSCI (Korea Science Citation Index)을 구축하였다. KSCI 시스템은 현재 ISI사에서 서비스하고 있는 SCI(Science Citation Index)가 가지는 문제점인 순환 적인 검색을 해결하기 위하여 패스인코딩(Path Encoding) 색인 기법을 사용하여 본 시스템을 구축함으로서 저장의 측면에서 약 8.98%의 효율과 검색의 측면에서 약 40% 정도의 결과를 얻었다.