• The Journal of Engineering Geology
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• v.16 no.3 s.49
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• pp.293-300
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• 2006

The groundwater movement in the west costal landfill area was analyzed by measuring N value by Standard Penetration Test, coefficient of permeability by falling head method, linear structure analysis by Digital Elevation Method, groundwater flow direction and rate by flowmeter logging due to tidal variation in the each borehole. The coefficients of permeability of the weathered zone and of the marine deposit showed similar values although some values of weathered zone show smaller values than those of the marine deposit. The major groundwater flow and rate in the marine deposit observed as east-west direction due to tidal variation, but on the other hand it was observed as N45E in weathered zone which is the major direction of the linear structures in the area. 2 hours delayed changes of the groundwater flow direction was observed during the 24 hours observation, and it seems to be a travel time of the tidal wave which cause the continuous change of the hydaulic gradient of the groundwater.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.16 no.2
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• pp.225-233
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• 1998

It is necessary to check the water quality of the lake on a continuous basis to determine the appearance of water pollution; however, it not only takes much time and expenses but it is considerably difficult to investigate the wide range of the area. If we use the remote sensing technique through the use of satellites, the status of water quality can be checked covering many wide areas simultaneously; and because the same area can be measured on a periodic basis, it is extremely effective in investigating the water quality. Furthermore, as some of the Landsat sensors carry characteristics which sense objects according to wave length, the distribution of water quality can be checked relatively accurately within a short period of time, while its image can be displayed in color. Hence, this research has attempted to extract water quality elements, such as transparency, water depth, and surface water temperature by utilizing the satellite data, and has prepared the water quality distribution image map of the Lake Hwajinpo by presenting the related empirical formula of the water quality elements. If the water quality distribution image map is prepared after extracting the water quality elements from the DN of the Landsat TM image and then carrying out TIN analysis through the use of GIS, relatively more accurate pattern can be learned covering a wide rage of area than the pattern presented based on the value obtained from actual observation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.6
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• pp.555-563
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• 2015

This paper presents signal processing algorithms of a frequency-modulated continuous-wave(FMCW) radar altimeter and provides a practical assessment technique. The radar altimeter is initially operated in search mode, when the radar altimeter detects a valid altitude, search mode is switched to track mode and a altitude being tracked is displayed. The sweep bandwidth in each mode is a function of altitude to narrow the beat frequency bandwidth. In addition, transmit power and receiver gain in each mode are controlled to compensate for the dynamic range of wide altitude range. To assess more realistic operation, the radar altimeter was tested using the crane setup. The crane test demonstrated that signal processing algorithms described in this paper resulted in a reduced measurement error rate.

• Korean Journal of Optics and Photonics
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• v.10 no.2
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• pp.162-168
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• 1999

A new design of four-pass dye laser amplifier affording a narrow-bandwidth pulsed output is demonstrated to suppress the amplified spontaneous emission(ASE) carried by the amplifier output and reduce the possibility of parasitic oscillation in the amplifier. By the direct pulsed amplification of a cw 100 mW dye laser under a Q-switched doubled Nd:YAG laser pumping with energy of 5.6 mJ/pulse, high-peak-power pulsed output with 1.5-mJ energy in 130-MHz bandwidth is obtained corresponding to a power gain greater than $2{\times}10^6$ and an energy efficiency of 27%. The ASE ratio in the four-pass amplifier output is dramatically reduced by using a diffraction grating in the amplifier. Compared with the results obtained from the normal operation of the amplifier with no frequency-selective device, the ASE ratio is reduced by a factor in excess of 10 to remain under 1.5% of the amplifier output whereas the total output energy is slightly increased by ~4%.

• Korean Business Review
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• v.11
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• pp.365-384
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• 1998

Under the rapid change of the world shipping industry, the liner shipping company in Korea should initiate the adaptation power, counterplot for survival, and continuous development. The world shipping industry is in the middle of the wave for the liberalization and openness of it. According to this change in world shipping industry, it is the fact that government policy for shipping industry should start turning its direction from the protectionism to the liberalism. Under this kinds of situations, this study firstly treated the liner shipping company and its governmental policy of Korea and Japan. Based on those studies, analysis of the liner shipping company operation and management reality was executed. Through the execution of studies, the problems which should be solved for development occurred. Furthermore, this thesis takes two way of researches of literature and actual proof for reinforcement plan of international competitiveness. This standard time period of study is set in 1993 except the irregular liner shipping company.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.5
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• pp.567-577
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• 1998

When continuous and discontinuous microstrip is analyzed with FDTD(Finite Difference Time Domain) method, we used Berenger's 3D-PML as absorbing boundary condition, and IST(Inner Source Technique) was used for source excitation instead of front excitation that is existing method. In the case using IST, we have observed that analyzed characteristic is not affected by the reduced computational domain of the side and top face in which evanescent field and radiation field is exist. Also, if we control the position of the inner source, we could effectively reject the influence of the reflective wave by mean of imperfective boundary condition. In this paper, by using IST, we have calculated dispersive characteristic and characteristic impedance of the microstrip. And we have calculated magnitude and phase of the scattering coefficient, and obtained equivalent circuit of the open microstrip end.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.11
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• pp.1297-1306
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• 2012

This work presents a 77 GHz radar transmitter for the automotive radar system. An integrated 13 GHz frequency synthesizer fabricated using 130 nm RF CMOS process drives a commercial W-band compound semiconductor monolithic multifunction amplifier(MPA), which includes a frequency multiplier by six to generate 77 GHz transmitting signal. The 13 GHz frequency synthesizer includes a high efficiency injection buffer of 4 dBm output power to drive the MPA. The output power of 77 GHz radar transmitter is higher than 13.99 dBm and the magnitude of the reference spur relative to the carrier is -36.45 dBc. The phase noise is -81 dBc/Hz at 1 MHz offset frequency from the carrier.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.11
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• pp.1019-1022
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• 2016

In this paper, a 2~16 GHz GaN wideband power amplifier MMIC s designed and fabricated using the nonuniform power amplifier design technique that utilizes drain shunt capacitors to simultaneously provide each transistor with the optimum load impedance and phase balance between input and output transmission lines. The power amplifier MMIC chip that is fabricated using the $0.25{\mu}m$ GaN HEMT foundry process of Win Semiconductors occupies an area of $3.9mm{\times}3.1mm$ and shows a linear gain of larger than 12 dB and an input return loss of greater than 10 dB. Under a continuous-wave mode, it has a saturated output power of 36.2~38.5 dBm and a power-added efficiency of about 8~16 % in 2 to 16 GHz.

• Journal of IKEEE
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• v.24 no.1
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• pp.339-346
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• 2020

In this paper, we propose an angle estimator that is designed to be applied to Bluetooth low-power application technology based on multiple signal classification (MUSIC) algorithm, and present the result of implementation in FPGA. The MUSIC algorithm is designed for H/W high-speed design because it requires a lot of calculations due to high accuracy, and the snapshot variable is designed to cope with various resolution requirements of indoor systems. As a result of the implementation with Xilinx zynq-7000, it was confirmed that 9,081 LUTs were implemented, and it was designed to operate at =the operating frequency of 100MHz.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.6
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• pp.798-802
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• 2013

In a conventional DC power supply used for CO2 laser, the circuit elements such as a rectifier bridge, a current-limiting resistor, a high voltage switch, energy storage capacitors ans a high-voltage isolation transformer using high turn ratio are necessary. Consequently, those supplies are expensive and require a large space. Thus, laser resonator and power supply should be optimally designed. In this paper, we propose a new power supply using high frequency resonance phenomena for CW(Continuous wave) CO2 laser (maximum output of 23W with discharge length of 450mm). It consists of a transformer including leakage inductance, magnetizing inductance and half-bridge converter, a three-stage Cockcroft-Walton and PFC(Power factor correction) circuit. The output ripple voltage can be controlled the minimum of 0.24% under the high frequency switching of 231kHz. Furthermore, the output efficiency was improved to 16.4% and the laser output stability of about 5.6% was obtained in this laser system.