• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.5
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• pp.215-221
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• 2014

In this paper, the improved power durability test system and method for an reliability analysis of SAW device is proposed and the failure mechanism through failure analysis is analyzed. As a result of the failure analysis using microscope, SEM and EDX, the failure mechanism of the SAW device is electromigration due to joule heating under high current density and high temperature condition. The electromigration makes voids and hillocks in the IDT electrode and the voids and hillocks can lead to short circuit and open circuit faults, respectively, increasing the insertion loss of an SAW filter. The accelerated life testing of the SAW filter for 450MHz CDMA application using the proposed power durability test system and method is carried out. $B_{10}$ lifetime of the SAW filter using Eyring model and Weibull distribution is estimated as about 98,500 hours.

• Journal of the Korean Electrochemical Society
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• v.6 no.1
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• pp.48-52
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• 2003

A mathematical dynamic model of fuel cell was formulated in order to design the control system which will meet the control object. The control objective is set to regulate the airflow in the load change by utilization of airflow and the pressure difference between anode and cathode is maintained below a limit range. Simulation result of 10kW polymer electrolyte membrane fuel cell (PEMFC) clearly demonstrates that response time need to be less. than 1 seconds for the control requirements. Besides, pressure difference was allowed in pressure range less than 0.01 atm.

• Applied Chemistry for Engineering
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• v.9 no.4
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• pp.475-480
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• 1998

A study on the electrochemical reduction of uranium (VI) to uranium (IV) was carried out in the mixed phases of an organic phase with uranium (VI) and aqueous phase of nitric acid by use of a highly packed glassy carbon (GC) fiber column electrode system, and a model for in-situ electrolytic stripping of uranium (VI) was suggested. The electrochemical reduction of uranium (VI) occurred faster in organic phase than in aqueous phase of the mixed phases. The uranium stripping yield increased and then became constant with the increase of organic flow rate of the electrolytic system due to the increase of diffusion resistance of uranium ions in the organic phase into the aqueous phase. Aqueous flow rate, on the other hand, didn't affect the total uranium (VI) reduction current in the system. The system combined with electrochemical reduction was confirmed to be much more effective than the simple system without it in stripping uranium.

• Journal of Digital Contents Society
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• v.7 no.1
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• pp.47-52
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• 2006

This paper proposes an algorithm for human sensibility evaluation using 4-channel EEG signals of the prefrontal and the parietal lobes. The algorithm uses an artificial neural network and the multiple templates. The linear prediction coefficients are used as the feature parameters of human sensibility. Comfortableness and temperature/humidity are evaluated. Many conventional researches have emphasized that a wave of left prefrontal lobe is activated in case of positive sensibility and that of right prefrontal lobe is activated in case of negative sensibility. So the power ratio of n wave is obtained from for computation and the results are compared. The results of the comfortableness evaluation for temperature and humidity showed that the outputs of the proposed algorithm coincided with corresponding sensibilities depending on the task of the temperature and the humidity. The conventional method using a wave is hardly related with comfortableness. And it is also observed that the uncomfortable state due to the high temperature and humidity can be easily changed to the comfortable state by small drop of the temperature and the humidity.

• Korean Journal of Materials Research
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• v.11 no.3
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• pp.207-214
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• 2001

Silica glass is a core material for optical fiber in optical telecommunications, but its centrosymmetry eliminates the second order nonlinearity. But it is experimentally well known that the space charge polarization induces the Second Harmonic Generation (SHG) when a strong DC voltage is applied to silica glass for a long period of time with metal blocking electrodes. In this report, the results of a theoretical calculation of the nonlinear optical property caused by the space charge polarization, and a model of a numerical analysis to predict the small chance in nonlinear optical property as functions of time and space are provided. Assuming that amorphous silica is a solid state electrolyte and sodium ion is the only mobile charge carrier, 'Finite Difference Method' was employed for modeling of numerical analysis. The distributions of the concentration of sodium ion and electric field as functions of a normalized length of the specimen and a normalized applied voltage were simulated.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.1
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• pp.18-26
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• 2001

In this paper, the resonant characteristics and modes of the film bulk acoustic wave resonator (FBAR) used in 1~2 GHz frequency region are analyzed by it's input impedance which was calculated by three dimensional finite element method formulated as eigenvalue problem using electro-mechanical wave equation and boundary condition. It was extracted that the resonant and the spurious characteristics considering the effects of electrode area and shape variation and unsymmetry of upper and lower electrode. Those effects couldn't be analyzed by on dimensional analysis, e.g. Mason equivalent model. The simulation result was confirmed by comparing with the simulation data from Mason model analysis and the measured data of the ZnO FBAR fabricated using micro-machining technique. Also, through the simulation of the area variations of FBAR, it was obtained that the optimum ratio of length and thickness is 20:1 and the minimum ratio is 5:1 to operate thickness vibration mode.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.981-984
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• 2005

This study is to realize its threshold voltage shift after programming operation in charge trap type SONOS memory by simulation. SONOS devices are charge trap type nonvolatile memory devices in which charge storage takes place in traps in the nitride-blocking oxide interface and the nitride layer. For simulation of their threshold voltage as a function of the memory states, traps in the nitride layer have to be defined. However, trap models in the nitride layer are not developed in commercial simulator. So, we propose a new method that can simulate their threshold voltage shift by an amount of charges induced to the electrodes as a function of a programming voltages and times as define two electrodes in the tunnel oxide-nitride interface and the nitride-blocking oxide interface of SONOS structures.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.4
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• pp.468-480
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• 1993

In this paper, at first, the characteristics of double mode SAW (DMS) resonator are analysed by applying the wave guide model and coupled mode theory to 1-port resonator. The DMS resonators (2-pole), which are arranged in a close, parallel configuration of two identical 1-port resonators on a single plate, and 4-pole DMS filters are designed and fabricated at the center frequency of 150.15 MHz with 3-dB bandwidth of 80 KHz. The empirical design characteristics are obtained from the comparison of experimental and theoretical values resulted from several fabrications, and the narrow bandpass filters are implemented on the basis of the above empirical results, which can be used to mobile communication systems. A ST-cut quartz substrate is selected for the stable temperature-frequence characteristics, and high resolution photolithography is applied to the fabrication of filter to get the fine electrode patterns.

• Geophysics and Geophysical Exploration
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• v.7 no.3
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• pp.197-206
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• 2004

Because the minute displacement of ground accompanied by excessive pumping of groundwater at specified site is mainly generated from ill-balancing of water budget within groundwater basin, It is necessary to monitor the variation of micro-subsidence for a long time at representative points. We made up the conceptual model using two-dimensional electrical resistivity survey and three-dimensional soil profile consisted of loam and sand. In verifying the reliability of this conceptual model using numerical modeling for ground settlement and groundwater flowing, two-dimensional electrical resistivity survey with short distance of electrode following soil sampling with hand auger would be useful for interpreting hydrogeological structure related to the minute displacement of ground consisted of loam and sand.

• Journal of Biomedical Engineering Research
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• v.20 no.3
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• pp.315-321
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• 1999

The purpose of this study is to develop a mathematical model for system identification in order to predIct muscle force based on eledromyographic signal. Therefore, a finding of the relalionship between characteristics of electromyographic signal and the corre spondng muscle force should be necessiiry through dynamic, joint model. To develop the dynamic joint model, the upper limb mcludmg the wrist and elbow joint has been considered. The kinematic and dynamic data, such as joint angular displacement, velocity, deceleration along with the moment of inertla, required to establish the dynamic model has been obtained by electrical flexible goniometer which has two degree-of-frcedoms. ln this model, muscle force can be predicted only electromyographs through the relationship between the integrated lorce and the mtegrated electromyographic signal over the duration of muscle contraclion in this study.