• Earthquakes and Structures
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• 제12권4호
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• pp.389-395
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• 2017

In this paper a simple approach is presented for spectral matching of ground motions utilizing the wavelet transform and a recently developed metaheuristic optimization technique. For this purpose, wavelet transform is used to decompose the original ground motions to several levels, where each level covers a special range of frequency, and then each level is multiplied by a variable. Subsequently, the vibrating particles system (VPS) algorithm is employed to calculate the variables such that the error between the response and target spectra is minimized. The application of the proposed method is illustrated through modifying 12 sets of ground motions. The results achieved by this method demonstrate its capability in solving the problem. The outcomes of the VPS algorithm are compared to those of the standard colliding bodies optimization (CBO) to illustrate the importance of the enhancement of the algorithm.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권1호
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• pp.123-145
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• 2017

Due to the increasing demand for spectrum resources, cognitive radio networks and dynamic spectrum access draw a lot of research into efficiently utilizing limited spectrum resources. To set up cluster-based CR ad-hoc common channels, conventional methods require a relatively long time to successfully exchange the initialization messages. In this paper, we propose a fast and reliable common channel initialization protocol for CR ad-hoc networks. In the proposed method, the cluster head sequentially broadcasts a system activation signal through its available channels with a predetermined correlation pattern. To detect the cluster head's broadcasting channels and to join the cluster, each member node implements fast Fourier transform (FFT) and computes autocorrelation of an FFT bin sequence for each available channel of the member node. This is compared to the predetermined reference pattern. The join request and channel decision procedures are also presented in this paper. In a simulation study, the performance of the proposed method is evaluated.

• Nuclear Engineering and Technology
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• 제49권4호
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• pp.825-837
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• 2017

Due to the severe impacts of recent earthquakes, the use of seismic isolation is paramount for the safety of nuclear structures. The diversity observed in seismic events demands ongoing research to analyze the devastating attributes involved, and hence to enhance the sustainability of base-isolated nuclear power plants. This study reports the seismic performance of a seismically-isolated nuclear reactor containment building (NRCB) under strong short-period ground motions (SPGMs) and long-period ground motions (LPGMs). The United States Nuclear Regulatory Commission-based design response spectrum for the seismic design of nuclear power plants is stipulated as the reference spectrum for ground motion selection. Within the period range(s) of interest, the spectral matching of selected records with the target spectrum is ensured using the spectral-compatibility approach. NRC-compliant SPGMs and LPGMs from the mega-thrust Tohoku earthquake are used to obtain the structural response of the base-isolated NRCB. To account for the lack of earthquakes in low-to-moderate seismicity zones and the gap in the artificial synthesis of long-period records, wavelet-decomposition based autoregressive moving average modeling for artificial generation of real ground motions is performed. Based on analysis results from real and simulated SPGMs versus LPGMs, the performance of NRCBs is discussed with suggestions for future research and seismic provisions.

• 한국음향학회지
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• 제3권1호
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• pp.25-35
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• 1984

This paper analysis the Dynamic Time Warping algorithms for time normalization of speech pattern and discusses the Dynamic Programming algorithm for spoken Korean isolated digits recognition. In the DP matching, feature vectors of the reference and test pattern are consisted of first three formant frequencies extracted by power spectrum density estimation algorithm of the ARMA model. The major differences in the various DTW algorithms include the global path constrains, the local continuity constraints on the path, and the distance weighting/normalization used to give the overall minimum distance. The performance criterias to evaluate these DP algorithms are memory requirement, speed of implementation, and recognition accuracy.

• 조명전기설비학회논문지
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• 제13권1호
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• pp.9-14
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• 1999

삼파장 형광등의 제작에서 문제가 되는 것은 원하는 목표 색을 맞추기 위하여 혼합하는 세 가지 형광물질의 혼합비율이다. 한 형광체의 광 스펙트럼이 약간 변형되거나, 공정변수에 의하여 변경되거나, Ar과 Kr 같은 불활성가스의 스펙트럼이 혼재하거나 또는 재래 할로인산칼슘이 공존할 경우 원하는 정확한 색을 찾기가 매우 힘들어지게 된다. 이 연구에서는 원하는 목표 색을 빠르게 찾는 방법을 연구하였다. 세 개의 각각의 단일색의 형광등과 3색을 서로 다른 비율로 혼합한 형광등을 만들고 각각의 스펙트럼을 측정한 후 이로부터 알곤과 수은의 스펙트럼을 빼서 변형 색 좌표를 얻었다. 이 변형 색 좌표로부터 적생에 대한 청색과 녹색의 광속비를 그의 무게 비에 대하여 도시하여 무게 대 광속비의 관계를 구하였다. 이 관계식을 이용하여 생산라인에서 삼파장 형광체의 단일 도포 및 할로인산칼슘을 1차로 도포하는 2중 도포를 실시하여 목표색을 조합해본 결과 만족할만한 결과를 얻었다.

• Wind and Structures
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• 제36권2호
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• pp.121-131
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• 2023

Aiming at the problem that fatigue characteristics of metal roof rely on local physical tests and lacks the cyclic load sequence matching with regional climate, this paper proposed a method of constructing the fatigue load spectrum based on integration of wind load model, measured data of long-span metal roof and climate statistical data. According to the turbulence characteristics of wind, the wind load model is established from the aspects of turbulence intensity, power spectral density and wind pressure coefficient. Considering the influence of roof configuration on wind pressure distribution, the parameters are modified through fusing the measured data with least squares method to approximate the actual wind pressure load of the roof system. Furthermore, with regards to the wind climate characteristics of building location, Weibull model is adopted to analyze the regional meteorological data to obtain the probability density distribution of wind velocity used for calculating wind load, so as to establish the cyclic wind load sequence with the attributes of regional climate and building configuration. Finally, taking a workshop's metal roof as an example, the wind load spectrum is constructed according to this method, and the fatigue simulation and residual life prediction are implemented based on the experimental data. The forecasting result is lightly higher than the design standards, consistent with general principles of its conservative safety design scale, which shows that the presented method is validated for the fatigue characteristics study and health assessment of metal roof.

• 한국지반환경공학회 논문집
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• 제12권4호
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• pp.53-63
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• 2011

동적 지진해석 수행 시 적절한 입력지진파를 선정 생성하는 것은 매우 중요하다. 현재 국내에서는 일반적으로 국외에서 계측된 강진 기록이나 인공지진파가 입력지진파로 사용된다. 계측지진기록은 지진파의 고유성질인 시간에 따라서 주파수 특성이 변이하는 비정상(Non-Stationary) 특성을 가지고 있지만 설계 응답스펙트럼과는 일치하지 않으며 주파수영역에서 생성된 인공지진파는 설계 응답스펙트럼과는 일치하지만 정상(Stationary) 특성을 가지고 있는 단점이 있다. 본 연구에서는 계측기록의 Non-stationary 특성을 보존하되 동시에 설계 응답스펙트럼에 상응하는 지진파를 생성하였다. 적용된 기법은 Impulse 함수를 이용하여 시간영역에서 지진기록을 목표 스펙트럼에 상응하도록 보정하는 알고리즘이다. 적용 결과, 시간영역 변화 알고리즘은 성공적으로 계측 지진기록을 설계 응답스펙트럼와 일치하도록 조정할 수 있으며 원 지진기록의 Non-stationary 특성을 보존하는 것으로 나타났다. 나아가 계측 지진기록과 보정된 지진기록을 적용한 비선형 지반응답해석을 수행한 결과, 보정된 지진파를 이용한 결과가 보다 합리적인 것으로 나타났다. 본 연구에서 변환된 지진기록은 기존 기록의 문제점을 보완하는 진보된 입력지진파인 것으로 나타났으며 추후 지진해석 시 이를 준용하는 것이 합리적일 것으로 판단된다.

• 한국분말재료학회지
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• 제25권5호
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• pp.375-378
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• 2018

Conductive and dielectric SiC are fabricated using electroless plating of Ni-Fe films on SiC chopped fibers to obtain lightweight and high-strength microwave absorbers. The electroless plating of Ni-Fe films is achieved using a two-step process of surface sensitizing and metal plating. The complex permeability and permittivity are measured for the composite specimens with the metalized SiC chopped fibers dispersed in a silicone rubber matrix. The original non-coated SiC fibers exhibit considerable dielectric losses. The complex permeability spectrum does not change significantly with the Ni-Fe coating. Moreover, dielectric constant is sensitively increased with Ni-Fe coating, owing to the increase of the space charge polarization. The improvements in absorption capability (lower reflection loss and small matching thickness) are evident with Ni-Fe coating on SiC fibers. For the composite SiC fibers coated with Ni-Fe thin films, a -35 dB reflection loss is predicted at 7.6 GHz with a matching thickness of 4 mm.

• 한국위성정보통신학회논문지
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• 제9권4호
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• pp.69-72
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• 2014

현재 오디오 신호의 가청주파수와 가시광선 스펙트럼의 매칭을 통한 조명 방식은 다양한 분야에서 연구가 진행되고 있으며 관련제품이 상용화 되어 출시 및 판매되고 있다. 하지만 기존 방식들은 단순한 매핑만을 사용함으로써, 감성을 전달하기에 다소 부족한 면이 있다. 따라서 실질적이고 체계적인 감성디자인을 통한 매칭 알고리즘 및 시스템에 대한 요구가 증가되고 있으며, 중요성이 부각되고 있다. 본 논문에서는 디지털 음원 기반의 LED 컬러 제어를 위한 시스템을 구성해 보았다. 해당 시스템 구성을 위해서 알고리즘을 개발하여 디지털 음원 소스를 이용한 LED 컬러 제어 실험을 진행하였으며, 시뮬레이션을 이용한 실제 LED 컬러 제어 시스템을 통해 알고리즘의 유용성을 입증하였다. 본 논문에서 제안하는 디지털 음원 기반의 LED 컬러 제어 시스템은 LED 제어 및 다양한 분야에 응용하여 유용하게 사용될 수 있을 것으로 기대된다.

• Journal of Information Processing Systems
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• 제13권5호
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• pp.1213-1228
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• 2017

The pitch tracking of music has been researched for several decades. Several possible improvements are available for creating a good t-distribution, using the instantaneous robust algorithm for pitch tracking framework to perfectly detect pitch. This article shows how to detect the pitch of music utilizing an improved detection method which applies a statistical method; this approach uses a pitch track, or a sequence of frequency bin numbers. This sequence is used to create an index that offers useful features for comparing similar songs. The pitch frequency spectrum is extracted using a modified instantaneous robust algorithm for pitch tracking (IRAPT) as a base combined with the statistical method. The pitch detection algorithm was implemented, and the percentage of performance matching in Thai classical music was assessed in order to test the accuracy of the algorithm. We used the longest common subsequence to compare the similarities in pitch sequence alignments in the music. The experimental results of this research show that the accuracy of retrieval of Thai classical music using the t-distribution of instantaneous robust algorithm for pitch tracking (t-IRAPT) is 99.01%, and is in the top five ranking, with the shortest query sample being five seconds long.