• 소음진동
• /
• 제9권5호
• /
• pp.1005-1011
• /
• 1999

Generation of hole-tones and the instability of circular impinging jets are investigated based on the frequency characteristics and the radiated sound field. The experiment is carried out with varying hole sizes, jet speeds and impinging distances. It is found that hole-tones occur by both the low-speed laminar jet and the high-speed turbulent jet, but not by the transient jet, while plate-tones without holes are produced only in the high-speed turbulent impinging jet. When the diameter ratio of the hole to the nozzle is nearly one, hole-tones occur most easily. At low speed, it is found that hole-tones are due to the symmetrical unstable jet and the impinging distance decreases with jet speed. And the Strouhal number and the sound pressure level increase with jet speed. At high speed, hole-tones show the same characteristics as plate-tones. It is found that the ratio of the convection speed varies with the Strouhal number and the jet speed.

• 대한교통학회지
• /
• 제12권2호
• /
• pp.47-63
• /
• 1994

The purposes of this study are to identify Traffic Flow characteristics and to develop approach delay model of unsignalized intersection based on the travel speed in the conflicting area. The results of this study are as following ; 1. The cumulative frequency distributions of Left-turning speed show a few differences among approaches and they are distributed to lower range of speeds. On the other hand, those of through speed show obvious differences among bounds. The similar results also show in the analysis of Percentile speed. 2. The effectiveness of conflicting movements to travel speed in the conflicting area are analyzed using regression analysis. Left-turning speed model shows that Left-and Right-Conflicting speed. Through-speed model is also developed, when approaching through volume is less than 420vph. 3. Since the lost time due to the acceleration stop, and decelerlation is occured in the conflicting area, approach delay model is delivered using the travel speed models under the condition of small queuing delay.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2009년도 춘계학술대회 논문집
• /
• pp.1249-1253
• /
• 2009

Enhancements of transport capacity in Gyeongbu line are continuous with the operating cost reduction and Korean economic development. Besides, requirements of a people about speed-up and customer service after the opening of high-speed railway(KTX) are being increased nowadays. Therefore, development and effort for speed increase of high-speed railway(KTX) have to be encouraged and supported by the government. In this study, market and technology trends for speed increase of high-speed train in Korea and abroad were investigated. As a result, we suggested to improve the railway infra for speed increase of high-speed train in Gyeongbu line.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2008년도 춘계학술대회 논문집
• /
• pp.862-867
• /
• 2008

High-speed railway is important transportation in the world because it is very comfortable, environmental benefits, energy savings, etc. The increase of demand for high-speed railway influence to develop of new hish-speed trains. Many countries introduced new high-speed train in the market. It meets to the market's needs. They adopt new technology and systems like that active suspension, synchronous permanent magnetic motor, distributed drive system, aero acoustics, etc. In Korea, the project for R&D of new high-speed train is launched last year. We need analysis of technical trend of new high-speed trains in the world. This paper presents a overview of technical trend of new high speed trains and what is key issues in development of high-speed train. It is very useful to develop a next generation high-speed train in Korea.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
• /
• pp.26-29
• /
• 2004

In order to speed up basic concept is to enhance high speed, curve limit speed, cross limit speed, acceleration/deceleration speed. It is important to optimal interface fundamental technology of vehicle, rail, electrical power, and signal system. Tilting train has advantage minimizing investment cost of infra railway system for increasing train limit speed in curve. the developed tilting train should be operated to commercial service speed 180Km/h of 200Km/h at KNR upgrade railroad. This paper proposed the basic model of system engineering for developing of tilting EMU (maximum operation speed : 180km/h) with speed-up of conventional railway system.

• 반도체디스플레이기술학회지
• /
• 제13권4호
• /
• pp.71-76
• /
• 2014

This paper presents the implementation for the BLDC motor speed control system using VHDL and FPGA. The BLDC motor is widely used in automation for its good robustness and easy controllability. In order to control the speed of the BLDC motor, the PI controller used for static RPM output of the BLDC motor to variations in load. In addition, by using the DA converter, we were able to monitor the BLDC motor reference speed and the current speed through real time. The motor speed command and the parameters of the PI speed controller were modified easily by the FPGA and the AD converter. Finally, in order to show the feasibility of the control algorithm the speed control characteristics of the motor was monitored using an oscilloscope and the DA converter. Further, the speed control system was designed in this paper has shown the applicability of the drive system of the factory automation.

• Journal of Power Electronics
• /
• 제10권4호
• /
• pp.382-387
• /
• 2010

This paper presents a novel design method for determining the PID gains of a speed controller for a servo system compensating variations in bandwidth at a low speed. The variations in bandwidth of a speed controller are measured at a low speed and the relationship between the bandwidth and the damping ratio are verified by determining the location of the closed loop pole. The proposed algorithm uses the z-transform of a plant and speed controller and applies the time-varying sampling method for determining the PID gains of the speed controller at low speed. The magnitude and the phase condition are considered for finding a suitable control gain. The usefulness and effectiveness of the proposed method is demonstrated through experimental results such as low speed control and robust disturbance responses.

• Wind and Structures
• /
• 제28권6호
• /
• pp.369-380
• /
• 2019

Statistical distributions are very useful in describing wind speed characteristics and in predicting wind power potential of a specified region. Although the Weibull distribution is the most popular one in wind energy literature, it does not seem to be able to perfectly fit all the investigated wind speed data in nature. Thus, many studies are still being conducted to find flexible distribution for modelling wind speed data. In this study, we propose a new Odd-Burr Rayleigh distribution for wind speed characterization. The Odd-Burr Rayleigh distribution with two shape parameters is flexible enough to model different shapes of wind speed data and thus it can be an alternative wind speed distribution for the assessment of wind energy potential. Therefore, suitability of the Odd-Burr Rayleigh distribution is investigated on real wind speed data taken from different regions in the South Africa. Numerical results of the conducted analysis confirm that the new Odd-Burr Rayleigh distribution is suitable for modelling most of the considered real wind speed cases and it also can be used for predicting wind power.

• 대한토목학회논문집
• /
• 제41권1호
• /
• pp.57-64
• /
• 2021

도시부도로에서 변속차로는 도로가 연결되는 지점에 설치되어 상대속도를 낮추도록 함으로써 교통소통을 원활하게 하고 있다. 그러나 도심내 안전 속도 "5030"시행에 따른 제한속도 30 km/h의 경우 기준이 모호하여 변속차로 설치에 대한 지적이 나오고 있다. 본 연구는 변속차로에 대한 이론적 고찰 후 안전속도 "5030" 정책 시행 예정 구간을 중심으로 변속차로 통행패턴을 사례조사를 실시하였다. 현장조사 후 도로조건 및 교통 조건 등에 따라 주도로의 통행 속도별 통행 패턴을 분석한 결과 안전속도 "5030"시행에 따른 변속차로의 실효성을 분석하였다. 본 연구수행을 통해 제시된 속도별 변속차로 설치기준은, 통행속도 30 km/h 구간인 경우는 변속차로를 미설치 하도록 하고, 50 km/h인 경우는 반드시 설치토록 하는 기준을 제시하였다. 향후 도시지역에서 다른 시설의 연결에 대한 공학적 기준을 정립할 때 참고할 수 있을 것으로 판단되며, 변속차로 설치 및 회전반경 확대를 통한 속도별 원활한 교통소통 및 안전성을 확보하고 개인의 사유재산권 행사에 대한 불필요한 제약을 최소화하는데 기여할 수 있을 것으로 기대된다.

• 해양환경안전학회지
• /
• 제28권2호
• /
• pp.254-261
• /
• 2022

모든 선박은 충돌을 피하기 위해 안전속력을 준수하여야 하고, 우리나라 영해 및 내수에서 속력의 제한규칙을 준수하여야 한다. 그리고 선박교통관제사는 선박이 안전속력과 속력의 제한규칙을 준수하도록 적절히 관제하여야 한다. 국제해상충돌예방규칙에서 안전속력은 선박이 명시적으로 몇 노트의 속력으로 항행하여야 하는지 규정하고 있지 않다. 반면에 국내법에서는 교통안전특정해역 등에서 제한속력을 지정하여 이를 준수하도록 하고 있다. 이 속력의 제한규칙은 주로 대지속력을 기준으로 하고 있으나, 대수속력을 기준으로 하는 곳도 있다. 이 논문은 최근 5년간 발생한 해양사고와 제한속력 위반율에 대해 분석하였고, 국제해상충돌예방규칙상 안전속력, 국내외법상 속력의 제한규칙 및 해양안전심판원 재결 중 안전속력을 준수하지 아니한 사례에 대해 살펴보았다. 그 결과, 이 논문에서는 국내법상 속력의 제한규칙이 선박에서 해양사고 예방을 위해 반드시 준수되어야 한다는 것과 선박이 이 규칙을 준수하기 쉽고, 선박교통관제사가 선박을 적절히 관제할 수 있도록 대수속력으로 규정된 속력의 제한규칙을 대지속력으로 개정할 필요가 있다는 것을 제시하였다.