• Journal of the Korea Institute of Military Science and Technology
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• v.3 no.2
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• pp.101-120
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• 2000

A synthetic aperture radar (SAR) system can provide all-weather, day and night, superior imaging capability, and thus is very useful in surveillance for military applications. In this paper, a X-band spaceborne SAR system design concept is introduced with the key design parameters for mission and system requirements characterized by small satellite system. The SAR imaging mode design procedure is presented, and the standard imaging mode design results are analyzed as an example. In line with the given mission and system requirements, the X-band SAR payload and ground reception/processing subsystems are designed and presented with the key design results. The designed small satellite SAR system shows the wide range of imaging capability, and proves to be an effective surveillance system in light-weight, high-performance and cost-effective points of view.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.7
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• pp.417-423
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• 2004

The headway in Korean national railway normally runs from 6 to 10 minutes. It turns out that the current signal system can not decrease the running headway of the High Speed trains, which are scheduled to set out in April, 2004, between Seoul and Daejeon, since both the existing classical trains and the High Speed ones run on the section. Thus, a new signal system is to be introduced to secure safe and reduced headway. The present paper attempts to analyze the headway between this particular section Seoul-Daejeon of the classical line, where we expect the most severe bottleneck situation to occur. We employed two modes in our analysis : the Ground Signal mode and the On-board Signal mode. which are to be adopted starting from 2006.

• Bulletin of the Korean Chemical Society
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• v.15 no.9
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• pp.762-765
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• 1994

Picosecond time-resolved resonance Raman spectroscopy has been used to study the photochemistry of Cr(CO$)_6$ in cyclohexane following photoexcitation at 266 nm. Photodissociative loss of CO is found to occur within our pulse width of ${\leq}$5 ps by probing the 533 c$m^{-1}$ vibrational mode of ground state Cr(CO$)_6$. The subsequent dynamics after photodissociation are interpreted in terms of solvation, vibrational and electronic relaxations. The vibrational relaxation time of 100 ps and 83 ps are observed by monitoring v=O and v=l of the 381 c$m^{-1}$ transient mode, respectively. No evidence was found for solvation and electronic relaxation occurring on a time scale of ${\leq}$5 ps.

• Bulletin of the Korean Chemical Society
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• v.18 no.10
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• pp.1076-1082
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• 1997

The infrared, Raman, and jet-cooled laser-induced fluorescence excitation spectra of 1,2,3,4-tetrahydronaphthalene have been recorded and analyzed. The observed vibrations have been assigned to understand the conformational behaviors in its electronic ground (S0) and excited (S1) states. Ab initio at the HF/6-31G** level and molecular mechanics (MM3) force field calculations have been carried out to generate the complete normal mode frequencies of the molecule in its S0 state. The vibrational frequencies calculated from the ab initio method show a better agreement with the observed infrared and Raman frequencies than those calculated from the MM3 method. In several cases, the normal mode calculations were very helpful to clarify some ambiguities of previous assignments. In addition, the ring inversion process between two twisted conformers of 1,2,3,4-tetrahydronaphthalene has been reexamined utilizing ab initio calculation. The results show that the ring inversion energy is in the range of 3.7-4.3 kcal/mol which is higher than the previously reported AM1 value of 2.1 kcal/mol.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.1
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• pp.56-61
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• 2019

In this study, a reduction method of leakage current in a three-level photovoltaic power-conditioning system (PCS) is proposed and verified by simulation and experiment. Leakage current generation is analyzed through an equivalent model of the common mode voltage considering a significant parasitic capacitance existing between the photovoltaic array and ground. A leakage current reduction method using pulse-width modulation (PWM) method is also proposed, and a 10-kW three-level photovoltaic PCS simulation and experiment is performed with a $1{\mu}F$ parasitic capacitor based on 100 nF/kW. The proposed method using the PWM method is verified to reduce the leakage current by 73% compared with the conventional PWM method.

• Structural Engineering and Mechanics
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• v.54 no.1
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• pp.169-188
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• 2015

This study presents the effects of the spatial variation of ground motions in a hard rock site on the seismic responses of a base-isolated nuclear power plant (BI-NPP). Three structural models were studied for the BI-NPP supported by different number of lead rubber bearing (LRB) base isolators with different base mat dimensions. The seismic responses of the BI-NPP were analyzed and investigated under the uniform and spatial varying excitation of El Centro ground motion. In addition, the rotational degrees of freedom (DOFs) of the base mat nodes were taken to consider the flexural behavior of the base mat on the seismic responses under both uniform and spatial varying excitation. Finally, the seismic response results for all the analysis cases of the BI-NPP were investigated in terms of the vibration periods and mode shapes, lateral displacements, and base shear forces. The analysis results indicate that: (1) considering the flexural behavior of the base mat has a negligible effect on the lateral displacements of base isolators regardless of the number of the isolators or the type of excitation used; (2) considering the spatial variation of ground motions has a substantial influence on the lateral displacements of base isolators and the NPP stick model; (3) the ground motion spatial variation effect is more prominent on lateral displacements than base shear forces, particularly with increasing numbers of base isolators and neglecting flexural behavior of the base mat.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.9
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• pp.409-415
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• 2014

Ground-source heat pump (GSHP) systems have become an efficient alternative to conventional cooling and heating methods due to their higher energy efficiency. These systems use the ground as a heat source and the heat sink for cooling mode operation. The purpose of this simulation study is to evaluate the performance of a hypothetical GSHP system in an office building and to assess the energy saving effect against the existing HVAC systems (boiler and turbo chiller). We collected monthly energy consumption data from an actual office building ($32,488m^2$) in Seoul, and created a model to calculate the hourly building loads with EnergyPlus. In addition, we used GLD (Ground Loop Design) V8.0, a GSHP system design and simulation software tool, to evaluate hourly and monthly performance of the GSHP system. The energy consumption for the GSHP system based on the hourly simulation results were estimated to be 582.6 MWh/year for cooling and 593.2 MWh/year for heating, while those for the existing HVAC systems were found to be 674.5 MWh/year and 2,496.4 MWh/year, respectively. The seasonal performance factor (SPF) of the GSHP system was also calculated to be in the range of 3.37~4.28.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.5
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• pp.648-658
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• 1998

In this paper, the effect of the gap in the ground plane on the electromagnetic interference (EMI) is analyzed quantitatively. Because of a lot of advantages compared to other numerical techniques, the FDTD (finite difference time domain) is applied to the EMI effect modeling. The analyzed model is the simplified PCB (printed circuit board) which has a microstrip and ground plane. The inductance induced by the gap is modeled and calculated by gridding the whole PCB based on the FDTD algorithm. When external cables are attached to the PCB, the common-mode current is induced along the attached cable and the resulting electric field strength is calculated and presented along with the FCC and CISPR EMI limits. The results show that the radiated field strength highly depends on the size of the ground plane gap. The numerical simulation results can be used as a reference in the practical PCB design with the ground plane gap.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.165-170
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• 2006

In the Civil Aviation field, the international trend (through ICAO, EUROCONTROL) is to adopt one positioning system that allows to follow more flight phases. This will allow to release themselves by ground installations and optimize the traffic flows following the aRea Navigation (RNAV) concept. In order to realize this goal the European Scientific Community are focusing on Augmentation Systems based on Satellite infrastructure (SBAS - Satellite Based Augmentation System) and on Ground based ones (GBAS - Ground Based Augmentation System). The goal of this work is to present some results on SBAS and GBAS performances. Regarding SBAS, the Department of Applied Sciences of Parthenope University, after the acquisition of a Novatel OEM4 SBAS receiver has created a monitoring station that reflect as much as possible a standardized measure environment for EGNOS Data Collection Network (EDCN), established by Eurocontrol. The Department of Applied Science has decided to carry out a own monitoring survey to verify the performance of EGNOS that can be achieved in South Europe region, a zone not very covered by official (EDCN) monitoring network. Regarding GBAS, we started from a data set of measurements carried out at the GBAS of Milan-Linate airport where we work on a ground installation (GMS - Ground Monitoring Station) that supervises the GBAS signal and that represent, for our purposes, the Aircraft subsystem. So the set of data collected is to be considered in RTK mode and after the measures session we processed them with the software PEGASUS v 4.11. Both experiences give us the possibility to evaluate the GNSS1 performance that can be achieved.

• Journal of Navigation and Port Research
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• v.45 no.1
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• pp.26-32
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• 2021

In ocean field, the spread of the Fourth Industrial Revolution based on information and communication technology requires high precision and stable PNT&D (Position, Navigation, Timing and Data). As the IMO (International Maritime Organization) and IALA (The International Association of Marine Aids to Navigation and Lighthouse Authorities) are requiring backup systems due to mitigate vulnerabilities and the increase of dependency on GNSS (Global Navigation Satellite System), Korea is conducting a research & development of R-Mode. An DGPS (Differentiate Global Positioning System) reference station that uses MF, an existing maritime infrastructure, and AIS (Automatic Identification System) base stations that use 34 integrity station and VHF will be utilized in this study to avoid redundant investment. Because there are radio shadow areas that display low signal levels in the west sea, the establishment of new R-Mode reference and integrity station will be intended to resolve problems regrading the radio shadow area. Because the frequency has a characteristic in that radio wave transmits well along the ground (water surface) in low frequency band, simulation and measurement were conducted therefore this paper to propose candidate sites for R-Mode reference and integrity station resulted through p wave's propagation characteristics analysis. Using this paper, R-Mode reference and integrity station can be established at appropriate locations to resolve radio shadow areas in other regions.