• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.3
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• pp.296-302
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• 2013

The binary offset carrier (BOC) modulation has attracted much attention as a new physical layer implementation for satellite communication and global navigation satellite systems. In this paper, we propose a new correlation function for sine-phased BOC signals. Specifically, we separate a sub-carrier pulse into several rectangular pulses, and then, generate a number of partial correlation functions. Finally we combine the partial correlation functions to yield an unambiguous correlation function with no side-peak. From numerical results, it is demonstrated that the proposed correlation function provides a significant tracking performance improvement over the conventional correlation functions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.9C
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• pp.581-588
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• 2011

In this paper, we propose a novel unambiguous code tracking scheme for cosine phased binary offset carrier (BOC) signals. We first obtain the sub-correlation functions composing the BOC autocorrelation function, and then, re-combine the sub-correlation functions generating a correlation function with no side-peak. Finally, by using the correlation function with no side-peak in the delay lock loop, the proposed scheme performs unambiguous signal tracking. Numerical results demonstrate that the proposed scheme provides a performance improvement over the conventional unambiguous scheme in terms of the tracking error standard deviation (TESD).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.7
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• pp.1453-1463
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• 2004

The conventional image segmentation method using level set has been disadvantage since level set function in the gradient-based model evolves depending on the local profile of the edge. In this paper, a new model is introduced by hybridizing level set formulation and complementary smooth function in order to smooth the driving force. We consider an alternative way of getting the complementary function(CF) which is much easier to simulate and makes sense for most cases having no triple junctions. The rule of thumb is that CF must be computed such that the difference between their average and the original CF function should be able to introduce a reliable driving force for the evolution of the level set function. This proposed hybrid method tries to minimize drawbacks the conventional level set method.

• Investigative Magnetic Resonance Imaging
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• v.15 no.1
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• pp.57-66
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• 2011

Purpose : A new inhomogeneity correction method based on two-point Dixon sequence is proposed to obtain water and fat images at 0.35T, low field magnetic resonance imaging (MRI) system. Materials and Methods : Joint phase-magnitude density function (JPMF) is obtained from the in-phase and out-of-phase images by the two-point Dixon method. The range of the water signal is adjusted from the JPMF, and 3D inhomogeneity map is obtained from the phase of corresponding water volume. The 3D inhomogeneity map is used to correct the inhomogeneity field iteratively. Results : The proposed water-fat imaging method was successfully applied to various organs. The proposed 3D inhomogeneity correction algorithm provides good performances in overall multi-slice images. Conclusion : The proposed water-fat separation method using JPMF is robust to field inhomogeneity. Three dimensional inhomogeneity map and the iterative inhomogeneity correction algorithm improve water and fat imaging substantially.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.1
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• pp.83-91
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• 2004

Nonlinear system responses of an impact system under randomly perturbed harmonic excitations are predicted in the probability domain by adopting the semi-analytical procedure previously developed. The semi-analytical procedure is obtained by solving the Fokker-Planck equation corresponding to the stochastic differential equation of the given impact system by utilizing the path-integral solution. The evolutionary joint probability density functions are generated by using the method, and the characteristics of nonlinear dynamic response behaviors of the system are examined. Noise effects on the responses are also examined. It Is found that the semi-analytical method can provides the accurate information of the responses via the joint probability functions for the impact system. It is found that the noises weaken and eventually terminate the chaos in the responses, but it is also found that the chaotic signatures reside in the presence of the external noise with relatively high intensity. The joint probability density function shows that the ensemble of the system responses are weakly stationary.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.10 no.4
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• pp.165-173
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• 1998

Analytical solutions to predict the movement rate of submerged mound are derived using the convection coefficient and the joint distribution function of wave heights and periods. Assuming that the sediment is moved onshore due to the velocity asymmetry of Stokes' second order nonlinear wave theory, the micro-scale bedload transport equation is applied to the sediment conservation. The nonlinear convection-diffusion equation can then be obtained which governs the migration of submerged mound. The movement rate decreases exponentially with increasing the water depth, but the movement rate tends to increase as the spectral width parameter, $ u$ increases. In comparison of the analytical solution with the measured data, it is found that the analytical solution overestimates the movement rate. However, the agreement between the analytical solution and the measured data is encouraging since this over-estimation may be due to the inaccuracy of input data and the limitation of sediment transport model. In particular, the movement rates with respect to the water depth predicted by the analytical solution are in very good agreement with the estimated result using the discritization technique with the hindcast wave data.

• Proceedings of the Korean Statistical Society Conference
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• 2002.11a
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• pp.163-168
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• 2002

전형적인 시공간모형은 시공간 변이도(semivariogram) 또는 공분산 함수(covariance function)를 필요로 한다. 본 논문에서는 계산하기 어렵고 현실적이지 못한 결합 공분산함수를 통한 고전적 모형 대신, 일련의 독립적인 조건분포를 이용하는 보다 현실적인 베이지안 계층모형을 이용한다. 미국 전 지역에 산재해 있는 138개 기온 관측소로부터 얻어진 61년(1920-1980) 동안의 연기온편차 자료에 시공간 베이지안 계층모형을 적용하고 순수시계열모형에서의 적합값과 제안된 모형의 적합값을 비교분석한다.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2793-2795
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• 2005

고장검출식별시스템의 성능을 좌우하는 가장 중요한 요소는 잔차발생알고리즘이다. 잔차발생기구는 측정된 입출력변수 정보에 근거하여 설계되며 고장의 검출 및 식별이 가능하도록 감결합(decoupling) 특성을 가져야 한다. 본 논문에서는 전달함수 접근 방법 중 최근 제안된 최소차 다항식 기저(minimal polynomial basis)를 이용한 잔차발생기구 설계기법을 소개하고, 이를 VTOL의 센서 및 구동장치고장 검출에 적용하여 그 성능을 검토하였다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2004.04a
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• pp.519-522
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• 2004

본 논문에서는 외향 기반 접근법을 기반으로 한 로봇의 위치 추정 알고리즘을 제안한다. 로봇이 작업을 수행할 공간에서 강한 상관관계를 갖는 영상들을 취득하여 eigenspace로 투영 시킴으로써 주성분의 추출을 수행한다. 이 추출된 주성분은 신경 회로망을 이용해 eigenspace에서의 연속 외향 함수(continuous appearance function)로 나타낼 수 있다. 로봇의 위치 추정을 위해 새로운 영상이 주어지면 이것을 eigenspace로 투영 시킨 후 연속 외향 함수를 통해 로봇의 현재 위치를 추정한다. 최종적으로는, 영상안의 데이터에 칼만 필터를 적용함으로써 로봇의 정확한 위치와 영상으로 획득된 정보 사이의 오차를 이용하여 보다 정확한 이동 로봇의 위치를 추정하는 알고리즘을 제안한다.

• Proceedings of the IEEK Conference
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• 2003.07e
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• pp.1715-1718
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• 2003

본 논문에서 우리는 정규화 된 혼합 노름(norm)을 이용한 다중 채널 영상 복원 알고리즘을 제안한다. 채널 내부와 채널 사이의 결정론적 정보를 이용하는 다중채널 복원 문제를 고려한다. 각 채널에서, LMS(Least Mean Square), LMF(Least Mean Fourth), 평탄 함수가 결합된 함수가 제안되었다. LMS와 LMF 사이의 적절한 분배를 제어하는 혼합 노를 매개변수와 해의 평탄 정도를 정의하는 정규화 매개 변수를 소개하며, 두 매개 변수는 각 채널의 잡음 특성에 따라 매번 반복적으로 갱신된다. 제안된 알고리즘은 각 채널의 잡음분포에 대한 지식이 필요하지 앉고 앞에서 언급된 매개 변수는 부분적으로 복원된 영상에 기반을 두고 조절하게 된다.