• Proceedings of the Korea Information Processing Society Conference
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• 2010.04a
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• pp.672-673
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• 2010

애드 혹 네트워크는 모바일 노드의 이동성에 따라 특정 위치에 노드들이 집중 분포되는 형태를 보임으로써 부하가 집중되는 현상이 발생할 수 있다. 본 논문에서는 집중 분포되는 모바일 노드의 부하에 따라 능동적으로 대처함으로써 손실되는 패킷을 줄이고 종단 간 전송 속도를 향상 시키는 라우팅 알고리즘을 제안한다.

• Journal of the Korea Society of Computer and Information
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• v.7 no.2
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• pp.101-114
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• 2002

The real multimedia application in wide area communication needs the guaranteed performance of communication service. Therefore, the resource is reserved at the moment of traffic burst and the region of connection admission possibility is widened at the basis of maximum cell rate. This of study shows that the end-to-end traffic delay to the traffic of burst state is guaranteed when the total of maximum transmission rate is higher than link speed by using the region of deterministic delay. The network load rate of connection admission can be improved by the inducement of delay bounds consideration each traffic characteristic to guarantee the end-to-end delay of network from single switch. This suggested buffering system using deterministic service do not give any influence to service quality and can guarantee the bounds of end-to-end delay. And it can also reduce the load of network even if the delay is increased according to the burst traffic characteristic. The above suggested system can be applied effectively to the various kinds of general network specification which admit both real time trafnc service and non-real time traffic service.

• Journal of Ocean Engineering and Technology
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• v.31 no.3
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• pp.219-226
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• 2017

In this study, the impact characteristics of subsea pipelines that were installed in various soil types and burial depths were evaluated by a numerical method. An impact scenario replicated a dropped ship anchor that fell vertically and impacted an installed subsea pipeline. In order to calculate the impact force through terminal velocity, FLUENT, a computational fluid dynamic program and MDM (Moving Deforming Mesh) technique were applied. Next, a dynamic finite element program, ANSYS Explicit Dynamics, was used for impact analysis between the anchor and pipeline (or, subsea if they were buried). Three soil types were considered: loose sand, dense sand and soft clay by applying the Mohr-coulomb model to the seabed. The buried depth was assumed to be 0 m, 1 m and 2 m. In conclusion, a subsea pipeline was the most stable when buried in dense sand at a depth of 2 m to prevent impact damage.

• Electronics and Telecommunications Trends
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• v.20 no.6 s.96
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• pp.77-86
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• 2005

인터넷, HDTV, VoD 등 통신 및 방송 수요의 증가에 따라 가입자망까지 광섬유를 포설하는 이른바 FTTH의 구현이 현실화되고 있다. 광가입자망 기술은 전달망과 가입자간을 연결하기 위한 전송(선로종단, 망종단) 장치와 전송매체 등의 설비로 구성되며, 고속 액세스 전송은 일반적으로 가입자에게 수 Mb/s 사용대역을 제공하는 기술을 말하는 것이다. 특히 가입자망에서 수백 Mb/s 이상의 가입자 사용 대역을 제공할 수 있는 것은 광통신 기술만이 가능하다. 세계적으로 광가입자망의 구축은 이미 2002년부터 시작되어 미국의 경우 SBC, Verizon을 중심으로 FTTx 서비스를 시작하여 2005년5월 현재 37개 주의 217곳에서 서비스가 진행중이며 일본의 경우 e-Japan Project로2007년까지 FTTH 천만 가입자를 목표로 2004년 말에 이미 200만 가입자를 돌파하는 등 광가입자망 분야에서는 세계적으로 가장 앞서가고 있는 실정이다. 한국의 경우전세계적으로 초고속 인터넷 보급률 1위로 기존의 VDSL에 의한 초고속 전송망이 이미 미국, 유럽 등의 광가입자망 대역폭과 근접한 속도를 보이고 있어 FTTH 구축은 오히려 늦어지고 있는 실정이다. 그러나 향후 방송/통신 융합 등 급격히 늘어날 대역폭요구를 수용하기 위해서는 광가입자(FTTH) 기술로의 전개가 필수적이고 이를 수용할수 있는 광가입자망 기술에 대해 살펴 본다.

• Journal of ILASS-Korea
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• v.16 no.2
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• pp.69-75
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• 2011

This article presents computational fluid dynamics (CFD) simulations of sub-micron particle movements and flow characteristics in laboratory-scale electrostatic precipitator (ESP) without corona discharge, and for simulation, it uses the commercial CFD program (CFD-ACE) including electrostatic theory and Lagrangian-based equation for sub-micron particle movement. For validation of CFD results, a simple cylindrical type of ESP is simulated and numerical prediction shows fairly good agreement with the analytical solution. In particular, the present study investigates the effect of particle diameter, inlet flow rate, and applied electric potential on particle collection efficiency and compares the numerical prediction with the experimental data, showing good agreement. It is found that the particle collection efficiency decreases with increasing inlet flow rate because the particle detention time becomes shorter, whereas it decreases with the increase in sub-micron particle diameter and with the decrease of applied electric voltage resulting from smaller terminal electrostatic velocity.

• Journal of Korean Society of Transportation
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• v.20 no.1
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• pp.121-130
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• 2002

Purpose of this paper is proposing technical evaluation method for safety on two-lane rural highways, this method can contribute to an establishment of the safety evaluation criteria and eventually contribute to the highway safety. In this study, accident data and field data(grade, radius, speed factor) are collected and are analyzed. And new technical evaluation method is proposed by problem in review of existent methods and analysis result. Property of new method is verified by comparing with existent one. Following are results of this study. 1) Proposed technical evaluation method is Proposed by using difference of speed variance and difference of acceleration. 2) In range of field survey, proposed method is more proper than existent one by comparing. 3) Headways under 6 second affect speed of next vehicle. 4) A point with the lowest speed in curve is placed about 35m from the beginning point. 5) Correlation of speed variance and severity of highway(EPDO) is statistically significant. For using proposed method, more tests are needed on other locations with various geometries. Moreover, advanced study is needed about classifying and giving the weight of each criterion.

• Journal of KIISE:Information Networking
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• v.28 no.2
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• pp.236-241
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• 2001

A new scheme is proposed to speed up a known bandwidth measuring method which employs potential bandwidth for filtering out noiscs (in cstirna60nl from time compression caused by a packet queueing ahead of two probe packets. Instead of inerementing the potential bandwidth by a fixed amount as in the original method we increase the potential bandwidth exponentially for faster convergence. To retain its filtering capability as well as its agility to adapt to new bottleneck bandwidth, each trial potential bandwidth(PB) is adjusted using MAX and MIN as upper bound and lower bound. An experiment using known bandwidths shows 45~g9% improvement in conVergence time.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.4
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• pp.700-705
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• 2006

The latest system of GIS has been changing from 2 dimension to 3 dimension. According to the rapid growth of the fields linked to 3D GIS, 3D GIS has variously affected the public field, the national defense field. and the industrial field. This study estimated sight distance safety of curve section considering the environmental impact based on 3D GIS. Sight distance is calculated from the relation between road which keeps the three-dimension character and driver gaze, so it needs to consider both plane and vertical for the accurate measuring. This study made analysis of the sight distance through considering the environmental impact with driving simulation of design speed 80km/h and running speed 60-120km/h.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.07a
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• pp.453-455
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• 2020

본 논문은 시각 장애인을 위한 감정 음성 자막 서비스를 생성하는 종단 간(end-to-end) 감정 음성 합성 시스템(emotional text-to-speech synthesis system, TTS)의 음성 합성 속도를 높이면서도 합성음의 음질을 향상시키는 방법을 제안한다. 기존에 사용했던 전역 스타일 토큰(Global Style Token, GST)을 이용한 감정 음성 합성 방법은 다양한 감정을 표현할 수 있는 장점을 갖고 있으나, 합성음을 생성하는데 필요한 시간이 길고 학습할 데이터의 동적 영역을 효과적으로 처리하지 않으면 합성음에 클리핑(clipping) 현상이 발생하는 등 음질이 저하되는 양상을 보였다. 이를 보안하기 위해 본 논문에서는 새로운 데이터 전처리 과정을 도입하였고 기존의 보코더(vocoder)인 웨이브넷(WaveNet)을 웨이브알엔엔(WaveRNN)으로 대체하여 생성 속도와 음질 측면에서 개선됨을 보였다.

• The Journal of the Acoustical Society of Korea
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• v.41 no.2
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• pp.122-129
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• 2022

In this paper, we propose a method to improve the performance of Transformer-based speech recognizers using data augmentation that locally adjusts the frame rate. First, the start time and length of the part to be augmented in the original voice data are randomly selected. Then, the frame rate of the selected part is changed to a new frame rate by using linear interpolation. Experimental results using the Wall Street Journal and LibriSpeech speech databases showed that the convergence time took longer than the baseline, but the recognition accuracy was improved in most cases. In order to further improve the performance, various parameters such as the length and the speed of the selected parts were optimized. The proposed method was shown to achieve relative performance improvement of 11.8 % and 14.9 % compared with the baseline in the Wall Street Journal and LibriSpeech speech databases, respectively.