• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.1
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• pp.31-37
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• 2010

Based on the analyses of satellite range measurement, the optimal operation for satellite range measurement of KOMPSAT II, which operates in the low-earth orbit, was proposed in this paper. The orbital motion of the satellite was analyzed in viewpoints of radial velocity, acceleration and speed of acceleration. Correspondingly the effects for satellite ranging signal due to satellite motion were analyzed in viewpoints of doppler phenomena, which are doppler frequency, doppler rate and speed of doppler rate. The accuracy and ambiguity probability of the satellite range measurement were quantitatively analyzed under various circumstances. The optimal operation parameters for satellite range measurement were also analyzed based on the analyzed results. The analyzed results in this paper can be utilized in design of small-sized ground station for satellite range measurement.

• Investigative Magnetic Resonance Imaging
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• v.10 no.1
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• pp.26-31
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• 2006

Purpose : To evaluate the effect of global scaling analysis on brain activation for sensory and motor functional MR imaging study. Materials and methods : Four normal subjects without abnormal neurological history were included. Arm extension-flexion movement was used for motor function and 1KHz pure tone stimulation was used for auditory function. Functional magnetic resonance imaging was performed at 3T MRI (GE, Milwaukee, USA) using BOLD-EPI technique and SPM2 was employed for data analysis. On data analysis, the brain activation images were obtained with and without global scaling by fixing other parameters such as motion correction and realignment. Results : The difference in brain activation between no scaling and global scaling was not large in case of right upper extremity movement (p<0.000001). For auditory test, brain activation with global scaling showed larger activation than that of without global scaling (p<0.05). Conclusion : A caution must be taken into account when analyzing functional imaging data with global scaling especially for functional study of small local BOLD signal change.

• Smart Structures and Systems
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• v.20 no.2
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• pp.163-173
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• 2017

Structural health monitoring (SHM) of civil infrastructure using fiber Bragg grating sensor networks (FBGSNs) has received significant public attention in recent years. However, there is currently little research on the health-monitoring technology of high-piled wharfs in coastal ports using the fiber Bragg grating (FBG) sensor technique. The benefits of FBG sensors are their small size, light weight, lack of conductivity, resistance corrosion, multiplexing ability and immunity to electromagnetic interference. Based on the properties of high-piled wharfs in coastal ports and servicing seawater environment and the benefits of FBG sensors, the SHM system for a high-piled wharf in the Tianjin Port of China is devised and deployed partly using the FBG sensor technique. In addition, the health-monitoring parameters are proposed. The system can monitor the structural mechanical properties and durability, which provides a state-of-the-art mean to monitor the health conditions of the wharf and display the monitored data with the BIM technique. In total, 289 FBG stain sensors, 87 FBG temperature sensors, 20 FBG obliquity sensors, 16 FBG pressure sensors, 8 FBG acceleration sensors and 4 anode ladders are installed in the components of the back platform and front platform. After the installation of some components in the wharf construction site, the good signal that each sensor measures demonstrates the suitability of the sensor setup methods, and it is proper for the full-scale, continuous, autonomous SHM deployment for the high-piled wharf in the costal port. The South 27# Wharf SHM system constitutes the largest deployment of FBG sensors for wharf structures in costal ports to date. This deployment demonstrates the strong potential of FBGSNs to monitor the health of large-scale coastal wharf structures. This study can provide a reference to the long-term health-monitoring system deployment for high-piled wharf structures in coastal ports.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.7
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• pp.3370-3392
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• 2017

Next Generation Beyond 4G/5G systems will rely on the deployment of small cells over conventional macrocells for achieving high spectral efficiency and improved coverage performance, especially for indoor and hotspot environments. In such heterogeneous networks, the expected performance gains can only be derived with the use of efficient interference coordination schemes, such as Fractional Frequency Reuse (FFR), which is very attractive for its simplicity and effectiveness. In this work, femtocells are deployed according to a spatial Poisson Point Process (PPP) over hexagonally shaped, 6-sector macro base stations (MeNBs) in an uncoordinated manner, operating in hybrid mode. A newly introduced intermediary region prevents cross-tier, cross-boundary interference and improves user equipment (UE) performance at the boundary of cell center and cell edge. With tools of stochastic geometry, an analytical framework for the signal-to-interference-plus-noise-ratio (SINR) distribution is developed to evaluate the performance of all UEs in different spatial locations, with consideration to both co-tier and cross-tier interference. Using the SINR distribution framework, average network throughput per tier is derived together with a newly proposed harmonic mean, which ensures fairness in resource allocation amongst all UEs. Finally, the FFR network parameters are optimized for maximizing average network throughput, and the harmonic mean using a fair resource assignment constraint. Numerical results verify the proposed analytical framework, and provide insights into design trade-offs between maximizing throughput and user fairness by appropriately adjusting the spatial partitioning thresholds, the spectrum allocation factor, and the femtocell density.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.2
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• pp.45-53
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• 2002

This paper presents an algorithm for the appropriate parameter selection of a power system stabilizer and power converters in two-area power systems with a series HVDC links. The method for PSS is one of the classical techniques by allocating properly poly-zero positions to fit as closely as desired the ideal phase lead and by changing the gain to produce a necessary damping torque. Proper parameter of power converters are obtained in order to have sufficient speed and stability margin to cope with changing reference values and disturbances based on the Root-locus technique. The small signal and transient stability studies using the PSS and power converters parameters obtained from these methods show that a natural oscillation frequency of the study case system is adequately damped. The simulation used in the paper was performed by the Power System Toolbox software program based on MATLAB.

• Journal of Auto-vehicle Safety Association
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• v.7 no.1
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• pp.7-12
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• 2015

NCAP(New Car Assessment Program) makes vehicle manufacturer improve safety performance through free competition and customers guarantee vehicle selection by providing information of vehicle safety. That's why it is important not only to meet the regulation, but also to cope with NCAP. EuroNCAP(European New Car Assessment Program) side tests have conducted by using Progressive MDB and Euro SID II in order to reproduce crash test between two vehicles over 10 years. However various researches report that Progressive MDB and Euro SID II do not reflect evolving vehicle design, impact performance and biofidelity of human. Therefore EuroNCAP has the plan to conduct AE-MDB side crash test using WorldSID which is more evolved from 2015 by replacing Progressive MDB and EuroSID II. Automobile manufacturers need to develop safety performance for new test closely. This paper is to find test set-up parameters which affect into dummy injury instead of restraint system and to research on its tendency. It is processed with mini and small car to know influence as changing vehicle size and also analyzed by DFSS(Design for six sigma) which is one of optimization tools. DFSS is vaildated by simulating CAE with L18 orthogonal array of 6 control factors adjustable as EuroNCAP requirement.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.2
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• pp.165-170
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• 2016

Nano-scale power splitter based on curved plasmonic waveguides are designed by utilizing the multimode interference (MMI) coupler. To analyze easily the adaptive properties of plasmonic curverd multimode interference coupler(PC-MMIC), the curved form transforms equivalently into a planar form by using conformal transformation method. Also, effective dielectric method and longitudinal modal transmission-line theory are used for simulating the light propagation and optimizing the structural parameters at 3-D guiding geometry. The designed $2{\times}2$ PC-MMIC does not work well for quasi-TM mode case due to the bending structure, and it does not exist 3dB coupling property, in which the power splitting ratio is 50%:50%, for quasi-TE mode case. Further, the coupling efficiency is better when the signal is incident at channel with large curvature radius than small curvature radius.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.12
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• pp.51-59
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• 1993

A 4${\times}10^{19}cm^{3}$ carbon-doped base AlGaAs/GaAs HBY was grown using carbontetracholoride(CCl$_4$) by atmospheric pressure MOCVD. Abruptness of emitter-base junction was characterized by SIMS(secondary ion mass spectorscopy) and the doping concentration of base layer was confirmed by DXRD(double crystal X-ray diffractometry). Mesa-type HBTs were fabricated using wet etching and lift-off technique. The base sheet resistance of R$_{sheet}$=550${\Omega}$/square was measured using TLM(transmission line model) method. The fabricated transistor achieved a collector-base junction breakdown voltage of BV$_{CBO}$=25V and a critical collector current density of J$_{O}$=40kA/cm$^2$ at V$_{CE}$=2V. The 50$\times$100$\mu$$^2$ emitter transistor showed a common emitter DC current gain of h$_{FE}$=30 at a collector current density of JS1CT=5kA/cm$^2$ and a base current ideality factor of ηS1EBT=1.4. The high frequency characterization of 5$\times$50$\mu$m$^2$ emitter transistor was carried out by on-wafer S-parameter measurement at 0.1~18.1GHz. Current gain cutoff frequency of f$_{T}$=27GHz and maximum oscillation frequency of f$_{max}$=16GHz were obtained from the measured Sparameter and device parameters of small-signal lumped-element equivalent network were extracted using Libra software. The fabricated HBT was proved to be useful to high speed and power spplications.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.12
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• pp.2615-2621
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• 2010

The multi-band six-port phase correlator using metamaterial was designed and fabricated in this paper. The lumped metamaterial structure that can process the dual-band receiving signal was analyzed. Based on the analyzed results, the small-sized metamatrial six-port phase correlator for multi-band direct conversion method was proposed and fabricated. Also, the resistive power divider and $90^{\circ}$ hybrid coupler that comprises the six-port phase correlator were implemented based on the scattering parameters of metamatrial six-port phase correlator. The measured results of the proposed six-port phase correlator show the good agreement with simulation results. The performance of the six-port phase correlator shows the reflection loss below -20 dB in the dual-band. Also, the proposed six-port phase correlator got a good transmission characteristic within 1 dB gain difference and ${\pm}4.1^{\circ}$ phase imbalance, respectively.

• Journal of IKEEE
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• v.17 no.1
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• pp.77-82
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• 2013

In this paper, dc-dc buck converter controled by the peak current-mode pulse-width-modulation (PWM) presented. Based on the small-signal model, we propose the novel methods of the power stage and the systematic stability designs. To improve the reliability and performance, over-temperature and over-current protection circuits have been designed in the dc-dc converter systems. To prevent electrostatic An electrostatic discharge (ESD) protection circuit is proposed. The proposed dc-dc converter circuit exhibits low triggering voltage by using the gate-substrate biasing techniques. Throughout the circuit simulation, it confirms that the proposed ESD protection circuit has lower triggering voltage(4.1V) than that of conventional ggNMOS (8.2V). The circuit simulation is performed by Mathlab and HSPICE programs utilizing the 0.35um BCD (Bipolar-CMOS-DMOS) process parameters.