• Journal of the Korea Institute of Building Construction
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• v.4 no.1
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• pp.133-140
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• 2004

This study is intended to investigate the properties of bleeding reduction of concrete using AE water reducing agent for the type of bleeding reduction with the replacement admixture. According to the results, when the adding ratio of AE water reducing agent for the type of bleeding reduction increases, a range of normal fluidity and aimed air content are satisfied, setting time is faster than that of normal AE water reducing agent. And bleeding amount decreases, bleeding speed is highest between 60 and 90 min, and sinking depth increases drastically in 50 min. When AE oater reducing agent for the type of bleeding reduction is added, compressive strength shows a slight variation by air content, but there is not a large influence by addition of AE water reducing agent for the type of bleeding reduction. Synthetically, it proves that AE water reducing agent for the type of bleeding reduction satisfies aimed air content in the range of normal slump and can reduce only bleeding without quality variation of compressive strength.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2019.11a
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• pp.141-143
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• 2019

Vessel Traffic Service (VTS) increases the efficiency of maritime traffic in terms of reducing marine accidents and the efficient use of port facilities. This means that ports and waterways have their own capacities and can be safely adapted to their capacity through proper traffic management of the VTS. Proper traffic management can reduce the number of vessels and unnecessary waiting in ports, which can lead to economic benefits of ups and port terminals. On the other hand, Korean ports and waterways have restrictions on the maximum speed for safety, but there is no restriction on the minimum speed. However, ships that operate at low speeds in ports and waterways may be able to occupy long periods of operational routes, which may impede efficient port operation. Therefore, the purpose of this study is to propose the minimum speed of ship for efficient port and waterway use. To this end, we reviewed the current laws and systems and proposed the appropriate minimum speed in the waterway using the theory of queue.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.3
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• pp.32-38
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• 2004

Recently, the system of high speed milling(HSM) is widely used for reducing the operation time and maximizing efficiency of work. The most research of high speed milling system is still leaves much to be desired. Specially the research of mass pocket high speed processing with high precision is the first and probably the last. So this paper showed mass pocket processing of high precision with a duralumin and then confirmed a cause of inferior goods through the CAD/CAM pattern simulation and experimentation. And this paper showed high speed processing system reduce the rate of inferior from this optimal pattern.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.171-175
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• 1998

This paper proposes a speed sensorless vector control of induction motor using a minimum-order EKF(extended kalman filter). Minimum-order EKF has the advantage of reducing the computational estimation cost because the stator current is not estimated. EKF does not deteriorate the performance of the overall speed control system, even though the measurements are relatively noisy. The estimated rotor speed is used for vector control and overall speed control. Computer simulations of the speed sensorless vector control are carried out to test the usefulness of the minimum-order EKF algorithm.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.340-343
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• 2002

Electromagnetic(EM) radiation problems and their possible solutions are addressed in this paper for the split power plane of high-speed digital systems. Stitching and decoupling capacitors are proved to be very effective fur reducing signal noise, ground bounce as well as electromagnetic radiation from the split power plane. Simulations based on 3D-Finite Difference Time Domain (FDTD) method are utilized for the analysis of practical high frequency multi-layered PC main board

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.708-713
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• 2013

본 연구의 목적은 400km/h 급 고속철도 소음저감용 방음벽 상단장치를 개발하기 위함이다. 이를 위해 우선 현장에서의 소음측정을 통한 400km/h 급 고속철도(HEMU) 및 300km/h 급 KTX의 주파수특성을 분석하였다. 그리고, 해석적 기법(BEM) 및 시작품 제작을 통한 실내실험을 수행하여 3dB(A) 이상의 소음을 저감시킬 수 있는 상단장치를 설계하였다. 마지막으로, 상단장치 시작품을 제작하여 옥외시험실에서의 성능시험을 수행하였으며, 고속철도의 주파수특성을 반영한 상단장치 설치 전후의 감음량을 평가하였다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.4 no.1 s.6
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• pp.97-106
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• 2005

Since traffic engineering in 1950's, 'speed control technology' has experienced tremendous growth and developed constantly. However, speeding remains a major safety concern on many roadways. Many crashes is believed to be the result of driving too fast. Recently the speed reduction device, the speed monitoring display with ITS technologies have developed and introduced in many countries including our nation, Korea. Therefore This paper describes an evaluation of the use of a speed monitoring display, speed limit sign, and school zone sign. Two conditions were evaluated; without installation of Speed Monitoring Display, in Operation of Speed Monitoring Display.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1081-1099
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• 2010

The TVM 430 system manufactured by Ansaldo STS in France is currently used in ground signalling system for Kyungbu HSR. It transmits the speed information to the on-board signalling system in the form of continuous signal via the track, and the rolling stock in Kyungbu HSR runs with 300km/h max. operating speed by using the corresponding information. Looking from the recent international trends in HSR, reducing the travelling time and increasing of the line capacity is promoting via the improvement of train speed. In case of TGV Est, they are realizing the normal operation with 320km/h max. operating speed by using TVM SEI signalling system, which is similar to TVM 430. Furthermore, in case Honam HSL, which is under construction, is looking over faster speed than the limited one of Kyungbu HSR(i.e. over 300km/h). In this paper, it is assumed that the existing TVM 430 ground signalling system is used and train speed is improved, therefore the number of block section to be increased depending on the increase of train speed and the standard speed to be used in this case is drawn via the simulation of the train model and described the method accordingly.

• The KSFM Journal of Fluid Machinery
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• v.9 no.1 s.34
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• pp.40-46
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• 2006

Efficiency of a centrifugal pump is known to drop rapidly with a decrease of specific speed $n_s$. However, below $n_s=60\;[min^{-1},\;m^3/min,\;m]$, the pump characteristics are not yet clear. Therefore, present study is aimed to investigate the influence of large change of specific speed on the performance of a very low specific speed centrifugal pump. Moreover, influence of impeller configuration on the performance of very low specific speed pump is investigated. The results show that very low specific speed can be accomplished by reducing volute throat sectional area using circular spacer. Influence of the spacer's location and configuration in the discharge passage on the pump performance is very small. Best efficiency of very low specific speed centrifugal pump decreases proportionally to the specific speed but the best efficiency decreases on a large scale in the range of $n_s<40$. Influence of impeller configuration on the pump performance and radial thrust of centrifugal pump are considerably small in the range of extremely low specific speed $(n_s=25)$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.2
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• pp.237-244
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• 2014

In this paper, we presented a study on the design of permanent magnet rotor for exterior rotor type brushless direct current(BLDC) motor. To reduce the cogging torque and torque ripple, the specific shape and magnetization pattern of permanent magnets in BLDC motors are suggested. Firstly, four permanent magnet models with different shapes and magnetization arrays are presented. The results from the finite element method(FEM), the most effective model for reducing cogging torque and torque ripple was presented. In addition, to confirm the steady state performance, the torque-speed characteristic analysis has been performed with variable speed and load. Finally, the best permanent magnet model for reducing cogging torque and torque ripple with appropriate torque-speed performance was selected through the comparison according to the device volume.