• Proceedings of the IEEK Conference
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• 2004.08c
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• pp.883-884
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• 2004

High-speed IC for time-division multiplexing (TDM) optical transmission systems have been designed and fabricated by using InP heterojunction-bipolar-transistor (HBT) technology. The driver IC was developed for driving external modulators, featuring differential outputs and the operation speed up to 10 Gbps with an output voltage swing of 1.3 Vpp at each output which was the limit of the measurement. Because -3 dB frequency was 20GHz, this circuit will be operated up to 20Gbps. 1.3Vpp differential output was achieved by switching 50 mA into a 50 $\Omega$ load. The power dissipation of the driver IC was 1W using a single supply voltage of -3.5Y. Input md output return loss of the IC were better than 10 dB and 15 dB, respectively, from DC to 20GHz. The chip size of fabricated IC was $1.7{\Box}1.2 mm^{2}$.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.278-281
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• 2008

This study demonstrates the advantages of a shear-free structure designed to modify vertical profiles of wind speed in the atmospheric surface layer. Computational fluid dynamics(CFD) software, FLUENT is used to interpret the velocity field modification around the structure and wind turbine. The shapes of shear-free structure, installed at upstream toward prevailing wind direction, would be fences, buildings and trees, etc. According to the simulation results, it is obvious that wind shear between heights of wind turbine's blades is decreased together with a speed-up advantage. This would lead decrease of periodic wind loading caused by wind shear and power-out increase by flow uniformity and wind speed-up.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.351-354
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• 2005

Research purpose of this project is intending Maintenance Free of freight car and speed up of freight train. At goods transport as heightening traveling by ship speed of freight train shortening raise railway share of physical distribution and stand on tiptoe to Northeast Asia physical distribution main country to contribute expect. This paper is the performance elevation methods of next generation railway freight vehicles.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.203-206
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• 2002

One of the ever-increasing demands on the performances of heterodyne interferometers is to improve the measurement resolution, of which current state-of-the-art reaches the region of sub-nanometers. We propose a new scheme of phase-measuring electronics that reduces the measurement resolution without further increase in clock speed. Our scheme adopts a super-heterodyne technique that lowers the original beat frequency to a level of 1 MHz by mixing it with electrically generated reference signal. The technique enables us to measure the phase of Doppler shift with a resolution of 1.58 nanometer at a sampling rate of 1 MHz. To avoid the undesirable decrease in the maximum measurable speed caused by the lowered beat frequency, a special from of frequency up-down counting technique is combined with the super-heterodyning. This alloys performing required phase unwrapping simply by using programmable digital gates without 2$\pi$ ambiguities up to the maximum velocity of 2.35 m/s.

• Proceedings of the KIEE Conference
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• 2004.10a
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• pp.248-250
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• 2004

Tilting trains are now an established feature of railway operations throughout the world. For intercity traffic, tilt provides operators with increasing speeds, and therefore enhanced competitiveness, on existing routes where insufficient traffic or a lack of funds precludes the construction of a dedicated new high-speed railway. Appling the tilting train, we can expect 30% of speed up on existing lines, but the stability of the electric current would be low because of tilting the train. Also, the spark between the catenary and pantagraph cause environmental problems such as noise, radio wave malfunction. Therefore, the tilting on pantagraph for the power suppling device is very essential for stable electric power supply.

• Proceedings of the KSR Conference
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• 2003.10b
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• pp.297-304
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• 2003

As the high speed rail to be opened at 2004, the. railroad will dominate over the transportation market in the Seoul-Busan corridor compared to road transport. But, it is obvious that the LOS(level of service) of railroad at 2004 will be worse in the areas that are not served KTX. For the speed-up of conventional line, it is a worldwide trend that tilting trains are served on the conventional railway line. That is the reason serving tilting trains is very efficient to use existing facilities and improve cruise time when capacity is available. In this paper, we suggest 10 routes are replaced with present operating trains(saemaeul, mugunghwa) by the tilting train.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.1259-1265
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• 2004

Railway is an important transportation tool for nation's industrial development and public daily life. These days the concern about railway has remarkably been rising due to the April 2004 opening of KTX, Korea High Speed Rail, together with Trans-Continental Railways linking North Korea, China, Russia, through European countries. In the meantime, the issues of train safety and efficiency, arising from the different on-board signaling systems installed on different kinds of trains, have been raised incessantly. In this paper CTCS(Continental Train Control System) is suggested, which can accommodate such various signaling functions as ATP, ATC, ATS, etc. into one single type of on-board signaling system and operate without changing ground signaling systems on the junctions of the Trans-Continental Railways. The development of this CTCS would cause speed-up of exiting lines and possession of railway core solutions for establishing Northeast Asia logistics center bases, which could be an important cornerstone for domestic railway improvements and Korea's role of Northeast Hub.

• Journal of the Korea Society of Computer and Information
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• v.23 no.7
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• pp.57-62
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• 2018

In this paper, we propose an improved algorithm for rendering method to guarantee frame rates based on HMD (Head Mounted Display) motion in an avionics simulator. One of important issues in HMD simulators is to guarantee frame rates despite fast motion of HMD which is more rapid than the aircraft's moving speed to maintain a quality of images. Therefore, we propose an algorithm considering the moving speed of a pilot's head: Improved Speed-Based LOD (Level-Of-Detail) Control (ISBLC). In the proposed algorithm, frame rates are improved by changing dynamic LOD which determines details of objects for rendering images. Throughout the experiments, we show the average frame rates are achieved up to 60 and minimum frame rates are guaranteed up to 40. The proposed algorithms will be used HMD simulation in avionics simulators.

• Proceedings of the IEEK Conference
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• 2003.07b
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• pp.787-790
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• 2003

This paper describes a high speed correlator that can acquire synchronization quickly. The existing addition algorithm is a binary adder tree architecture that will result in extremely slow speed of operation due to many levels of logic required for computation of correlation[2][3]. This paper suggests the new various architectures, which are systolic array architecture, simple pipeline architecture and block systolic array architecture[4][5]. The acquisition performance of the proposed architectures is analyzed and compared with the existing architecture. The comparison results show that the systolic array architecture and the block systolic array architecture reduce the timing delay up to 73% and 31%, respectively. And the results show that the simple pipeline architecture reduces the timing delay up to 53%..

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1277-1282
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• 2003

The purpose of the present paper is to investigate the noise and vibration characteristics of externally pressurized air proceeding bearings with a circular slot restrictor. To do this, the nonlinear transient analysis including rotor imbalance was performed for a rotor-bearing system. The effects of radial clearance and the width of the bearing and mass eccentricity of the rotor on the noise and vibration characteristics of the bearing are also examined. The results show that the noise and vibration of the rotor-bearing system first increase up to critical speed of the system, and then decrease up to instability threshold speed of the system as the rotational speed of the rotor increases, and the noise of the bearing is markedly influenced by the mass eccentricity of the rotor and the radial clearance and the width of the bearing.