• Fire Science and Engineering
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• v.25 no.6
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• pp.83-88
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• 2011

This study presented the structure and characteristics of vinyl cords used for wiring electric equipment and appliances and analyzed the photographs of damaged flat-type vinyl cords (VFF, $1.25mm^2$) and the metallic cross-sectional structure of melted conductors. Normal VFFs were made by twisting several strands together and the surface of the conductor was red brown. In addition, from the analysis of the metallic structure of the conductor, it was found that its grains had been elongated. The surface of a VFF damaged by normal flame showed no sheen with carbonized insulation material fused on the conductor surface. In addition, from the analysis of the cross-sectional structure of the melted area, it was found that voids of a certain shape were formed on it but that the cord's own elongation structure could not be checked. The cross-sectional analysis of the melted conductor damaged by the external flame applied to a VFF to which electric current was being applied showed no elongation structure for each cord, and revealed that irregular voids and a columnar structure had grown. The surface of the VFF damaged by overcurrent was uniformly carbonized and the cross-sectional structure analysis of the melted conductor revealed that the dendritic structure had grown. The analysis of the characteristics of the VFF melted by short-circuit showed that even though some part of the surface was contaminated, it showed little sheen and that the area rebounded by melting was round in shape. In addition, the cross-sectional structure analysis using a metallurgical microscope showed the boundary surface and columnar structure and revealed an amorphous structure like normal copper at areas other than the melted conductor.

• The Transactions of the Korea Information Processing Society
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• v.5 no.10
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• pp.2725-2736
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• 1998

In this paper. we present a new pitch determination method for speech analysis. namely VFF(Variable Forgetting Factor) based. by using the WRLS-VFF-VT(Weighted Recursive Least Square-Variable Forgetting Factor-Variable Threshold) algorithm. A proposed method uses VFF to identify the glottal closure points which correspond to the instants of the main excitation pulses for voiced speech. The modified EGG

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.179-182
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• 2001

본 논문에서는 기존의 VFF PASTd 알고리듬의 개선안을 제시하였다. 이 알고리듬은 각 부공간마다 가변망각인자를 각각 사용하던 기존 방법과는 달리 최종 잔류 오차를 이용하여 하나의 망각인자를 계산하고 이것을 이용함으로써 계산량을 줄임과 동시에 망각인자를 보다 정확히 구할 수 있다. 여기서는 주파수 추정 문제에 대한 모의 실험을 통해 제안된 알고리듬이 우수함을 입증하였다.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.1
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• pp.58-63
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• 1999

In this paper, We present a direction indicator algorithm for a mobile robot which uses VFF and neural networks. The structure of this neural network navigation system is composed of sensor system, backpropagation learning controllers for adjusting weight and the motion control system for real-time execution. The experimental results show that the direction indicator system operates properlv and strongly at any circumstance

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.218-218
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• 2004

• The Journal of the Acoustical Society of Korea
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• v.19 no.2E
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• pp.8-13
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• 2000

In this paper, we present an adaptive formant tracking algorithm for speech using closed phase WRLS-VFF-VT method. The pitch synchronous closed phase methods is known to give more accurate estimates of the vocal tract parameters than the pitch asynchronous method. However the use of a pitch-synchronous closed phase analysis method has been limited due to difficulties associated with the task of accurately isolating the closed phase region in successive periods of speech. Therefore we have implemented the pitch synchronous closed phase WRLS-VFF-VT algorithm for speech analysis, especially for formant tracking. The proposed algorithm with the variable threshold(VT) can provide a superior performance in the boundary of phone and voiced/unvoiced sound. The proposed method is experimentally compared with the other method such as two channel CPC method by using synthetic waveform and real speech data. From the experimental results, we found that the block data processing techniques, such as the two-channel CPC, gave reasonable estimates of the formant/antiformant. However, the data windows used by these methods included the effects of the periodic excitation pulses, which affected the accuracy of the estimated formants. On the other hand the proposed WRLS-VFF-VT method, which eliminated the influence of the pulse excitation by using an input estimation as part of the algorithm, gave very accurate formant/bandwidth estimates and good spectral matching.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.355-358
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• 2000

기존의 Rayleigh fading 환경에서 칼만 필터를 사용한 다중 사용자 검출에서는 비동기적으로 들어온 다른 사용자 신호의 상태가 바뀜에 따라서 수렴하던 신호에 영향을 미친다. 이러한 특성은 결국 전체 시스템에 영향을 미쳐서 검출 성능을 떨어뜨린다. 본 논문에서는 에러가 발생하였을 때의 경우를 고려하기 위해 VFF(Variable forgetting factor)를 도입하였고 이를 이용해 추정된 신호의 가중 합을 기반으로 시스템을 구성한 결과 성능이 향상되었음을 보이고자 한다.

• The Journal of the Acoustical Society of Korea
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• v.22 no.1E
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• pp.19-25
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• 2003

Ryu et al. recently proposed a multiple target angle-tracking algorithm without a data association problem. This algorithm, however, shows the degraded performance on evasive maneuvering targets, because the estimated signal subspace is d,:graded in the algorithm. In this Paper, we proposed a new algorithm, in which VFF-PASTd (Variable Forgetting Factor PASTd) algorithm is applied to Ryu's algorithm to effectively handle the evasive target tracking with better time-varying signal subspace.

• Congress of the korean instutite of fire investigation
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• 2010.12a
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• pp.80-90
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• 2010

대부분의 전기화재는 전기제품의 전원코드나 확장형 콘센트 등 저압 배선에서 주로 발생한다. 최초발화에 기인한 단락흔(1차 단락흔)의 외형적 판단기준을 제시하고자 발화원인이 규명된 전기화재의 감정사례로부터 비닐평형코드에 형성된 단락흔의 형태학적 비교분석결과 단락흔 자체 형태만으로 1차단락으로 판정하기는 용이하지 않지만 1차 단락흔은 2차 단락흔과 달리 용융방울이 미세하게 형성되고, 흑색으로 착색되는 경향이 있으며, 특히 절연피복의 손상을 줄 수 있는 선행된 원인이 있는 곳에서 만 특징을 나타내는 것을 알 수 있었다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.4
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• pp.759-764
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• 2011

This paper deals with the method of using the amended virtual force field technique to avoidance the front environment(wall, obstacles etc.) in navigating by using the environmental informations recognized by a ultrasonic-ring and pan/tilt CCD camera equipped on a mobile robot. we will give an explanation for the robot system architecture designed and implemented in this study and a short review of existing techniques, since there exist several recent thorough books and review paper on this paper. It is proposed the rusult from the experimental run based on a virtual force field(VFF) method to support the validity of the aforementioned architecture of mobile service robot for local navigation and obstacle avoidance for autonomous mobile robots. We will conclude by discussing some possible future extensions of the project. The results show that the proposed algorithm is apt to identify obstacles in an indoor environments to guide the robot to the goal location safely.