• 대한수학회논문집
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• 제17권2호
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• pp.349-361
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• 2002

The ill-posed elliptic wave propagation problems can be transformed into well-posed initial value problems of the reflection and transmission operators characterizing the material structure of the given model by the combination of wave field splitting and invariant imbedding methods. In general, the derived scattering operator equations are of first-order in range, nonlinear, nonlocal, and stiff and oscillatory with a subtle fixed and movable singularity structure. The phase space and path integral analysis reveals that construction and reconstruction algorithms depend crucially on a detailed symbol analysis of the scattering operators. Some information about the singularity structure of the scattering operator symbols is presented and analyzed in the transversely homogeneous limit.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1996년도 춘계학술대회
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• pp.27-30
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• 1996

PR interval variability has been proposed as a noninvasive tool for in-vestigating the autonomic nervous system as welt as heart rate variability. The goal of this paper is to determine whether PR interval variability is generated from deterministic nonlinear dynamics. The data used in this study is a 24-hour bolter ECGs of 20 healthy adults. We developed an automatic PR interval measurement algorithm, and tested it using MIT ECG Databases. The general discriminants of nonlinear dynamics, such as, correlation dimension and phase space reconstruction are used. Surrogate data is generated from simpler linear models to have similar statistical characteristics with the original data. Nonlinear discriminants are applied to both data, and compared for any significant results. It was concluded that PR interval variability shows non-linear characteristics.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1996년도 추계학술대회
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• pp.258-262
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• 1996

The physiological systems have nonlinear complex phenomena. Expecially, the flow of capillary blood vessel has a nonlinear dynamic system. Thus, this study analyzes nonlinear characteristics of the flow of capillary blood vessel in physiological systems using chaotic tools(phase space reconstruction, correlation dimension, largest lyapunov exponent). Experimental data have been acquired from examining 10 rabbits. The results of chaotic analysis showed a decreasing largest lyapunov exponent and correlation dimension according to increasement glocose index. And we also know the chaotic behavior.

• Steel and Composite Structures
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• 제36권5호
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• pp.521-531
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• 2020

The behavior variation of concrete dam is investigated, based on a new method for analyzing the data model of concrete dam in service process for the limitation of wavelet transform for solving concrete dam service process model. The study takes into account the time and position of behavior change during the process of concrete dam service. There is no dependence on the effect quantity for overcoming the shortcomings of the traditional identification method. The panel data model is firstly proposed for analyzing the behavior change of composite concrete dam. The change-point theory is used to identify whether the behavior of concrete dams changes during service. The phase space reconstruction technique is used to reconstruct the phase plane of the trend effect component. The time dimension method is used to solve the construction of multi-transformation model of composite panel data. An existing 76.3-m-high dam is used to investigate some key issues on the behavior change. Emphasis is placed on conversion time and location for three time periods consistent with the practical analysis report for evaluating the validity of the analysis method of the behavior variation of concrete dams presented in this paper.

• Investigative Magnetic Resonance Imaging
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• 제5권1호
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• pp.57-65
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• 2001

목적 : 초고속 Echo Planar Imaging (EPI) 의 데이터 측정시간을 반으로 단축시킨 half courier EPI와 임상에서 널리 사용하는 $T_2$ 강조 영상을 결합한 $T_2$-weighted half courier EPI(T2HEPl) 영상기법을 제안하였다. 제안한 방법으로 강한 $T_2$ 대조도를 갖는 $128{\times}128$의 고해상도 EPI 영상을 single scan으로 얻고자 한다. 대상 및 방법 : 초고속 EPI 기법의 데이터 측정시간을 줄이기 위하여 k-space의 절반만을 측정하고, 나머지 절반은 conjugate symmetry 성질을 이용하여 재구성한다. 따라서 64개의 에코로 $128{\times}128$의 고해상도 single shot 영상을 얻을 수 있다. 또한 k-space 데이터의 순서를 시간 축에서 조절하여 강한 $T_2$ 대조도를 갖는 영상을 얻을 수 있다 Eddy current의 영향으로 phase encoding 방향으로 잔류 경사자계가 있을 경우 측정된 데이터들은 k-space에서 이동이 되며 , 이것은 재구성 영상에 심각한 문제점을 초래하게 된다. 본 논문에서는 pre-scan에서 얻은 기준 데이터와 dc에 해당하는 에코간의 상관도를 측정하여 이동을 추정하며, 초기의 phase encoding gradient의 크기를 조정하여 이러한 이동을 제거한다. 결과 : 제안한 $T_2$-weighted half courier EPI 영상기법을 1.0 Tesla 전신 MRI 시스템에 적용하였다. 실험 조건은 single shot으로 TR은 무한대이고, TE는 72ms와 96ms로 설정하였다. 제안한 영상기법을 이용하여 single scan으로 강한 $T_2$ 대조도를 갖는 128x128의 고해상도 EPI 영상을 얻을 수 있었다. 결론 : 제안한 Half Fourier기법을 이용하여 기존의 $64{\times}64$ 영상보다 해상도를 높인 $128{\times}128$ EPI영상을 single scan으로 얻을수 있었으며, 에코의 적절한 배치를 통해 임상에서 널리 사용되는 $T_2$ 대조도를 얻을 수 있었다. 제안한 방법은 특별한 하드웨어의 추가 없이, 펄스 시퀀스와 tuning 및 재구성 알고리즘 등의 소프트웨어적인 방법만으로 구현이 가능하여 많은 임상 응용이 기대된다.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.429-431
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• 2002

Metabolic analysis of biological tissues, the interventional radiology in MRT (Magnetic Resonance Treatment) and for clinical diagnoses, representation of 4-Dimensional (4D) structural information (x,y,z,t) of biological tissues is required. This paper discusses image representation techniques for those 4D MR Images. We have proposed an image reconstruction method for ultra-fast 3D MRI. It is based on image interpolation and prediction of un-acquired pictorial data in both of the real and the k-space (the acquisition domain in MRI). A 4D MR image is reconstructed from only two 3D MR images and acquired a few echo signals that are optimized by prediction of the tissue motion. This prediction can be done by the phase of acquired echo signal is proportioned to the tissue motion. On the other hand, reconstructed 4D MR images are represented as a 3D-movie by using computer graphics techniques. Rendered tissue surfaces and/or ROIs are displayed on a CRT monitor. It is represented in an arbitrary plane and/or rendered surface with their motion. As examples of the proposed representation techniques, the finger and the lung motion of healthy volunteers are demonstrated.

• 토지주택연구
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• 제5권3호
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• pp.151-167
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• 2014

Urban space structure in South Korea when through drastic changes ever since public housing policies began their full-fledge implementation. That is, public housing policies represent the main cause for formation of the current urban space structure, as the public houses are constructed in accordance with changes of demographic/social structure, considering changes of housing demand, in urban spaces demanded by the end users. After rapid industrialization and urbanization in the 1960's, each government in different periods have implemented housing supply policies through massive urban developments, to resolve the issue of housing shortage and residential instability. Phase 1 New Towns were developed in the 1980's resulting in suburbanization of the Seoul Area, followed by urban sprawl due to construction of small-size New Towns after deregulation in the 1990's, and construction of Phase 2 New Towns for resolution of housing shortage in the early 2000's and the resulting urban problems. In the mid-2000's, construction of Bogeumjari houses in GB areas led to insufficient housing supply in downtown areas, and the period after 2010 witnessed continuous deterioration of existing urban areas and acceleration of the rental housing crisis caused by rental housing shortage in downtown areas. Moreover, the residentially vulnerable classes consisting of young, 1~2-member households is expanding, with the real estate market in recess. Therefore, the government is trying to achieve urban regeneration through public housing policies so as to resolve the urban space problem and the housing problem at the same time, and the Happiness Housing Project has been implemented as a policy to achieve that goal. The Happiness Housing Project for young, residentially vulnerable classes in downtown areas, is going through diversification aimed at conjunction with urban regeneration projects in downtown areas, as exemplified by conversion of rental houses in residential environment improvement project districts and redevelopment/reconstruction project districts into happiness housing, and supply of happiness housing in conjunction with small reorganization projects for deteriorated residential areas in such areas as those excluded from New Town designation. Continuous supply of Happiness Housing in conjunction with urban regeneration requires mixed-use residential development which includes convenience facilities and public facilities, along with improvement of rental conditions (rental period/rent) and diversification of project methods, considering that the project is implemented in downtown areas.

• Steel and Composite Structures
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• 제19권3호
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• pp.569-583
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• 2015

Recent years, explosive welding structures have been widely used in many engineering fields. The bonding state detection of explosive welding structures is significant to prevent unscheduled failures and even catastrophic accidents. However, this task still faces challenges due to the complexity of the bonding interface. In this paper, a new method called dual-tree complex wavelet transform based permutation entropy (DTCWT-PE) is proposed to detect bonding state of such structures. Benefiting from the complex analytical wavelet function, the dual-tree complex wavelet transform (DTCWT) has better shift invariance and reduced spectral aliasing compared with the traditional wavelet transform. All those characters are good for characterizing the vibration response signals. Furthermore, as a statistical measure, permutation entropy (PE) quantifies the complexity of non-stationary signals through phase space reconstruction, and thus it can be used as a viable tool to detect the change of bonding state. In order to more accurate identification and detection of bonding state, PE values derived from DTCWT coefficients are proposed to extract the state information from the vibration response signal of explosive welding structure, and then the extracted PE values serve as input vectors of support vector machine (SVM) to identify the bonding state of the structure. The experiments on bonding state detection of explosive welding pipes are presented to illustrate the feasibility and effectiveness of the proposed method.

• 한국농촌건축학회논문집
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• 제25권4호
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• pp.25-35
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• 2023

According to this study, it is estimated that the ILDU historic house was constructed around the late Goryeo period, approximately in the year 1360, and the founder moved to Hamyang no earlier than 1350. The main house, the inner store-house, the inner gatehouse, and the ancestral shrine, which are situated on elevated ground, were initially constructed around 1360, and substantial expansions and renovations occurred around 1620. The shrine was relocated and reconstructed in its present location and form around 1843. Subsequent to that period, it underwent various architectural changes, including repairs and reconstructions. The sub-main house was originally constructed around 1620 and underwent a reconstruction in 1843. The main storehouse was built in 1930. Also, the man's part of house, located on lower ground, was erected in 1843, while the other sub-main house seems to constructed around 1860. The auxiliary buildings, the main gatehouse and the outer storehouse, were initially constructed around 1360. It is estimated that they were similarly relocated and reconstructed in their current form, along with the construction of the man's part of house in 1843. It has undergone a four-stage transformation process, influenced by various internal and external factors, including the local indigenization of the ILDU families of the same clan, as well as the popularization of Confucian ideology. These four stages include its formative period, growth phase, developmental stage, and maturity. It actively incorporated the contemporary factors of change into its residential architecture. This continuous adaptation is evident in its the space and floor plan, ultimately leading to its present-day architectural legacy.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제21권3호
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• pp.257-265
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• 1999

골재생유도술에 의한 골재생과정의 생물학적 현상을 보다 구체적으로 이해하고자, 백서의 대퇴골에 인위적인 골결손부를 형성하고 비흡수성 차폐막을 설치한 다음 골재생유도 과정에서의 미세혈관의 구축 양상을 통상적인 광학 현미경적 소견 및 미세혈관주형 표본 관찰법을 중심으로 관찰한바 다음과 같은 결과를 얻었다. 광학 현미경적 소견의 초기 즉 술후 1주 및 2주 소견상 차폐막에 의해 피개된 실험부에서 보다 정연한 골성회복이 이루어졌으며, 이는 차폐막으로 인한 혈관망 형성의 양상에 의해 영향을 받는 것으로 나타났다. 즉, 차폐막에 의한 연조직 침입이 차단됨으로 인해 인접 골조직으로부터 수평적으로 들어온 혈관에 의해 규칙적인 혈관 분포를 나타내나, 대조군의 경우 연조직에서 유입된 혈관망에 의해 불규칙한 혈관망을 나타내었다. 시간이 경과되면서 재생된 결손부의 골은 재구성되면서 대조군과 실험군 사이에 골성회복의 양상은 유사하였으나, 인접 실험군의 골조직으로부터 유입된 혈관에 의해 형성된 규칙적인 혈관망이 연조직으로부터 침입한 혈관에 의해 그 규칙적인 배열이 흐트러진 대조군에 비하여 골성회복의 속도가 빨라진다는 사실을 확인하였다. 이상의 결과는 차폐막에 의한 골재생 유도과정에서 혈관의 유래와 혈관망의 정렬상태가 골성회복의 속도와 밀접한 관련이 있음을 보여주는 것이다.