• Journal of the Korean Society for Precision Engineering
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• v.25 no.7
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• pp.72-78
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• 2008

The line-of-sight(LOS) stabilization system is a precision electro-mechanical gimbals assembly for suppressing vibration due to its environment and tracking the target in a desired direction. This paper describes the design of gimbals system to reject the disturbance and to improve stabilization. The controller consists of a DSP with transducer and actuator interfaces. Unknown parameters of the gimbals are estimated by the signal compression method. The cross-correlation coefficient between the impulse response from the assumed model and the one from model of the gimbals is used to obtain the better estimation. The quasi-impulse response through linear element included in the gimbals could be obtained by the signal compression method. The unknown parameter of the linear element could be estimated as comparing the bode plots for impulse response from gimbals with them from model's response.

• ETRI Journal
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• v.23 no.3
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• pp.121-128
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• 2001

In this paper, the theoretical as well as experimental results of BER characteristics of three different modulation schemes, ASK, FSK and BPSK, in a multi-path Rician channel are addressed. These BER characteristics are analyzed as a function of $E_b/N_o$ and the power ratio of the line of sight (LOS) component to the Rayleigh scattered component. The theoretical as well as computer simulation results shows the ASK is the most suitable modulation scheme for the dedicated short range communication (DSRC) in terms of implemental cost and system complexity. The decision feedback equalizer is proved to be very effective in canceling the multi-path interference in the DSRC channel environment. The simulation result of the equalized ASK, reveals the performance enhancement achievable with decision feedback (DFE) equalizer for the first generation DSRC system. The multi-ray DSRC channel model is also provided to predict the received carrier power and fluctuation, which are quite dependent on the surroundings of a cell.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.5
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• pp.320-326
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• 2000

The canned motor of 3-phase induction is used for main coolant pump(MCP). The type of motor is canned-motor that stator and rotor are welded by sealed can. So, cooling water flows in the air gap of the canned motor as an independent cycling cooling system from the air gap to yoke of the motor to prevent high temperature of stator can and to lubricate bearing. Heat exchange is occurred between cooling water in the air gap and cooling water from the exterior pump to prevent rising of temperature in the motor. I has to analyze the characteristics of can exactly because the loss and the heat in the can are very important to design MCP. Therefore, thermal analysis is studied considering the effect of eddy-current los induced in the can.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.233-236
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• 2008

There are several kinds of service standards for 3G($3^{rd}$-Generation) wireless communication as WCDMA, CDMA2000 and WiBro(Wireless Broadband Internet). Especially WiBro Wave2 system is a marked currnt issue. In this paper, we describe on the cell plan tool to desgin WiBro Wave2 network. For this, we treat from basic theory to practical substance to produce new(or modified) path loss prediction model for 2.3GHz. And we explain the method how to implement new technology MIMO(Multiple Input Multiple Output) deployed in Wave2 system. Also we emphasize on the importance of LOS(Line Of Sight) analysis in WiBro network design.

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.3
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• pp.387-394
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• 2016

This paper proposes a new disturbance observer(DOB). The purpose of the DOB is to realize the plant performing like a model in the presence of disturbances which come from external environment and inherent nonlinearities and uncertainties in the plant. It is shown that the proposed DOB compensates those disturbances, nonlinearities and uncertainties, effectively. And it is theoretically proved that the proposed DOB can be guaranteed its stability for the stable plant. Its availability is shown by applying the DOB to the stabilization platform for EOTS(Electro Optical Tracking System).

• Journal of Advanced Navigation Technology
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• v.5 no.1
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• pp.62-73
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• 2001

In this paper, performance of DSRC systems is analyzed with considering the real roads and height of vehicles. The channels are modeled as 2-Ray and 4-Ray with a direct wave and reflected waves by a road and buildings in a physical layer because DSRC keeps LOS propagation characteristics, and the pass loss for each model is calculated respectively. Rician factor is obtained through the calculated path loss on two models for DSRC, and the performance of the systems is analyzed in AWGN and Rician fading channels, Impulsive noise and Rician fading channels respectively. As a result, in Rician fading channels with impulsive noise(A=0.2, ${\Gamma}^{\prime}=0.22$), BER is below $10^{-6}$ when the distance is farther than 80[m] and 40[m] in 2-Ray model and 4-Ray model respectively. For performance improvement, BCH coding scheme and MRC diversity scheme are adopted.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.1
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• pp.129-133
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• 2016

This paper insists that the accessibility and transfer facility has also to be included in railway investment because railway mode can not be, what is called, a door to door service. At present those facility are not included in the railway investment with them in negligence. Since those facility is not treated with railway system there is no room to get a budget from the central government. This paper suggests that all the measurements have to be implemented, based on the LOS (Level of Service) of accessibility and transfer at railway stations. The LOS has to be as low as reasonably practical (ALARP) which can be derived from the consensus between government and citizens. Also, a couple of procurement methods are suggested for accessibility and transfer facility separately. Finally, improvement of regulations are also suggested.

• Journal of Satellite, Information and Communications
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• v.8 no.3
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• pp.41-46
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• 2013

In this paper, we present the compatibility study results including the frequency sharing criteria between new allocation to maritime mobile satellite service and Earth exploration satellite service in the 7/8 GHz. The transmitting Earths station of MMSS in the 8025 - 8400 MHz band would make harmful interference to the receiving Earth station of EESS operating in the same frequency band. In order to ensure the compatibility with EESS, the separation distance is provided as a frequency sharing criteria. The republic of Korea has a plan to launch the geostationary satellite around 2017 and EESS Earth station will be operated in 8025 - 8400 MHz band. Therefore, we calculate the interference levels and separation distance using the system parameters of two Earth station systems. As results of the study, the separation distances for LOS path and Non-LOS path due to the geographical characteristics are shown around 471 km and 200 km, respectively.

• Journal of The Korean Astronomical Society
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• v.38 no.4
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• pp.437-443
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• 2005

The Solar Radio Burst Locator (SRBL) is a spectrometer that can observe solar microwave bursts over a wide band (0.1-18 GHz) as well as detect the burst locations without interferometry or mechanical scanning. Its prototype has been operated at Owens Valley Radio Observatory (OVRO) since 1998. In this study, we have evaluated the capability of the SRBL system in flux and radio burst location measurements. For this, we consider 130 microwave bursts from 2000 to 2002. The SRBL radio fluxes of 53 events were compared with the fluxes from USAF/RSTN and the burst locations of 25 events were compared with the optical flare locations. From this study, we found: (1) there is a relatively good correlation (r = 0.9) between SRBL flux and RSTN flux; (2) the mean location error is about 8.4 arcmin and the location error (4.7 arcmin) of single source events is much smaller than that (14.9 arcmin) of multiple source events; (3) the minimum location error usually occurred just after the starting time of burst, mostly within 10 seconds; (4) there is a possible anti-correlation (r = -0.4) between the pointing error of SRBL antenna and the location error. The anti-correlation becomes more evident (r=-0.9) for 6 strong single source events associated with X-class flares. Our results show that the flux measurement of SRBL is consistent with that of RSTN, and the mean location error of SRBL is estimated to be about 5 arcmin for single source events.

• International Journal of Highway Engineering
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• v.14 no.6
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• pp.131-138
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• 2012

PURPOSES : Two-lane highways have one lane in each direction, and lane changing and passing maneuvers take place in the opposing lane depending on the availability of passing sight distance. 2001 Korea Highway Capacity Manual (KHCM) is classified into two classes of two-lane highways (Type I, II), and average travel speed and time-delayed rate are used as measures of effectiveness (MOEs). However, since existing two-lane highways have both uninterrupted and interrupted traffic flow-system elements, a variety of free-flow speeds exhibits in two-lane highways. In addition, it is necessary to check if the linear-relationship between volumes and time-delayed rate is appropriate. Then, this study is to reestablish the relationship between average travel speed, time-delayed rate, and flow. METHODS : TWOPAS model was selected to conduct this study, and the free-flow speeds of passenger cars and the percentage of following vehicles observed in two-lane highways were applied to the model as the input. The revised relationships were developed from the computer simulation. RESULTS : In the revised average travel speed vs. flow relationship, the free-flow speed of 90km/h and 70km/h were added. It shows that the relationship between time delayed-rate and flow appeared to be appropriate with the log-function form and that there was no difference in time-delayed rate between the free flow speeds. In addition to revise the relationships, the speed prediction model and the time-delayed rate prediction model were also developed. CONCLUSIONS : The revised relationships between average travel speed, time-delayed rate, and flow would be useful in estimating the Level of Service(LOS) of a two-lane highway.