• Journal of Positioning, Navigation, and Timing
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• 제7권1호
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• pp.25-35
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• 2018

This paper describes the measurement of pulse positioning (input time) to calculate a time of arrival (TOA) that takes from transmitting a signal from the target of multilateration (MLAT) system to receiving the signal at the receiver. In this regard, this paper analyzes performances of simple threshold method and level adjust system (LAS) method, which is one of the adaptive threshold detector (ATD) methods, among many methods to calculate pulse positioning of signal received at the receiver. To this end, Cramer-rao lower bound (CRLB) with regard to pulse positioning, which was measured when signals transmitted from a transponder mounted at the target were received at the receiver, was induced and then deviation sizes with regard to pulse positioning, which was measured with simple threshold and LAS methods through MATLAB simulations, were compared. Next, problems occurring according to a difference in amplitude of signals inputted to each receiver are described when pulse positioning is measured at multiple receivers located at a different distance from the target as is the case in the MLAT system. Furthermore, LAS method to resolve the problems is explained. Lastly, this study analyzes whether a pulse positioning error occurring due to the signal noise satisfies the requirement (6 nsec. or lower) recommended for the MLAT system when using these two methods.

• 한국소음진동공학회논문집
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• 제14권11호
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• pp.1123-1128
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• 2004

An experimental study on firing noise of K2 rifle was performed. Firing noises of K2 rifle were measured at close distance to rifle. Firing noise of K2 rifle which made in Korea, has not measured before. The measurement of firing noise at close distance is not simple, because the amplitude of firing noise is much bigger than the measuring limit of ordinary sound level meter even though it uses a signal attenuator. The measurement of firing noise at close distance is necessary for noise source positioning and for obtaining the sound power of K2 rifle. By this experimental study, the firing noise levels of K2 rifle at different positions are obtained and these data can be used to Predict the sound pressure level at any distance from muzzle of the rifle. Also these data can be used to calculate the threshold shift of gunner's ear.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2019년도 춘계학술대회
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• pp.344-346
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• 2019

본 논문에서는 Ultra-Wideband(UWB) 시스템에서 합성곱 신경망을 이용한 거리 추정 기법을 제안한다. 합성곱 신경망을 이용한 딥러닝 모델을 학습하는데 사용하는 학습 데이터는 MATLAB 프로그램을 통해 생성하였으며, IEEE 802.15.4a 표준을 활용한다. 기존 거리 추정에 사용하는 문턱값 기반의 거리추정 기법과 성능 비교를 통해 제안하는 거리 추정 기법의 성능을 검증한다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1995년도 추계학술대회 논문집
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• pp.67-70
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• 1995

Amorpous As$\sub$10/Ge$\sub$15/Te$\sub$75/ device shows the memory switching characterisite under d.c. bias. In bulk material, a-As$\sub$10/Ge/sub15/Te$\sub$75/s switching voltage range is above 100 volts. Our purposes in this gaudy are decreasing a switching threshold voltage, finding the properties of d.c., a.c. conduction, and the characterisitics of switching threshold voltage fur a-As$\sub$10/Ge$\sub$15/Te$\sub$75/. As the results, the d.c.and a.c. conductivities increase with temperature. From the data of conductivity, various electrical and physical properties are obtained experimentally. The switching threshold voltages decrease with increasing annealing temperature and time, but increase with increasing film thickness and distance of electrode for d.c. bias.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
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• pp.219-222
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• 2004

The effects of short fiber and particle hybrid reinforcement on fatigue crack propagation behaviors in aluminum matrix composites have been investigated. Single and hybrid reinforced 6061 aluminum containing same 20 $Al_2O_3\;volume\%$ with four different constituent ratios of short fibers and particles were prepared by squeeze casting method and tested to check the near-threshold and stable crack growth behavior. The fatigue threshold of the composites increased with portion of particle contents and showed the improved crack resistance especially in low stress intensity range. Addition of particle instead of short fiber also increased fracture toughness due to increase of inter-reinforcement distance. These increase in both fatigue threshold and fracture toughness eventually affected the fatigue crack growth behavior such that the crack growth curve shift low to high stress intensity factor value. Overall experimental results were shown that particle reinforcement was enhanced the fatigue crack resistance over the whole stress intensity factor range.

• 중소기업융합학회논문지
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• 제6권4호
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• pp.71-77
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• 2016

본 논문에서는 기존의 BIC(Bayesian Information Criterion) 기반 화자변화의 성능 향상을 위하여 GMM-UBM(Gaussian Mixture Model-Universal Background Model) 기반 KL(Kullback Leibler) 거리를 활용한 화자변화 검증을 제안하였다. 정보량의 차이에 민감한 기존의 BIC 기반 화자변화검출 알고리즘을 상대적으로 정보량 차이에 견인한 KL 거리 알고리즘으로 검증하였고, 정보량의 비대칭을 보상하기 위해서 GMM-UBM을 활용하였다. 기존의 BIC 기반 화자변화 검출은 1단계로 비유사도 d가 양수인 구간의 국소 최댓값인 지점을 화자변화 후보지점으로 검출하였고, 2단계로 검출된 화자변화 후보지점 중 ${\Delta}BIC$가 양수인 지점을 화자변화지점으로 결정하였다. 본 논문에서는 BIC 기반 화자변화 검출에 의해 결정된 화자변화지점에 대하여 GMM-UBM 기반 KL 거리 D가 문턱치(threshold)보다 높은 지점을 최종 화자변화 지점으로 검증하였다. 실험결과, MDR(Missed Detection Rate)이 0인 조건에서 문턱치 0.028일 때 FAR(False Alarm Rate) 60.4%로 성능이 향상되었다.

• 동력기계공학회지
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• 제19권2호
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• pp.33-39
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• 2015

In conducting indoor positioning by code division multiple access using spread spectrum ultrasonic waves, it is required to detect signals under the influence of near-far problem occurred by difference on signal power, caused by distance between transmitter and receiver. For discussing robustness to the problem, we verified measuring accuracy on distance from an experiment on a real space with a hardware device where our proposed method is mounted. The proposed method performs automatic signal detection by setting threshold level dynamically. As an experimental result, measurable distance were improved by the proposed method, and measurement errors were up to 50mm in distances from 1000mm to 6000mm; therefore, enough accuracy to realize self-localization or navigation for autonomous mobile robot or human was obtained.

• 한국군사과학기술학회지
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• 제14권6호
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• pp.1073-1080
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• 2011

In this study, a target detection algorithm was proposed for using hyperspectral imagery. The proposed algorithm is designed to have minimal processing time, low false alarm rate, and flexible threshold selection. The target detection procedure can be divided into two steps. Initially, candidates of target pixel are extracted using matching ratio of spectral pattern that can be calculated by spectral derivation. Secondly, spectral distance is computed only for those candidates using Euclidean distance. The proposed two-step method showed lower false alarm rate than the Euclidean distance detector applied over the whole image. It also showed much lower processing time as compared to the Mahalanobis distance detector.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제27권2호
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• pp.146-159
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• 2023

This paper proposes a hybrid algorithm combining K-means clustering and watershed algorithms for flower segmentation and counting. We use the K-means clustering algorithm to obtain the main colors in a complex background according to the cluster centers and then take a color space transformation to extract pixel values for the hue, saturation, and value of flower color. Next, we apply the threshold segmentation technique to segment flowers precisely and obtain the binary image of flowers. Based on this, we take the Euclidean distance transformation to obtain the distance map and apply it to find the local maxima of the connected components. Afterward, the proposed algorithm adaptively determines a minimum distance between each peak and apply it to label connected components using the watershed segmentation with eight-connectivity. On a dataset of 30 images, the test results reveal that the proposed method is more efficient and precise for the counting of overlapped flowers ignoring the degree of overlap, number of overlap, and relatively irregular shape.

• 대한산업공학회지
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• 제34권2호
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• pp.151-159
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• 2008

An efficient location registration scheme is essential to accommodate continuously increasing mobile subscribers and to offer a variety of multimedia services with good quality. In this study, we consider a distance-based registration scheme where the number of location areas varies on the basis of cell-by-cell, not of ring-by-ring, to analyze the optimal size of the location area. Using our proposed cell-by-cell distance-based registration scheme with random walk mobility model, we analyze a variety of circumstances to obtain the optimal number of cells for location area that minimizes total signaling traffic on radio channels. From our analysis results, we show that the optimal number of cells for location area is between 4 and 6 in most cases, and our cell-by-cell distance-based location registration scheme has less signaling traffic than optimal ring-by-ring distance-based location registration scheme where optimal distance threshold is 2 (thus the optimal number of cells for location area is 7).