• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.52 no.7
• /
• pp.421-428
• /
• 2003

After the cable is installed, many geometric factors, such as bowing types of the cable and the length difference of the cable between each minor section will cause the impedance unbalance between cables. The impedance unbalance will increase or decrease the sheath circulating currents, which are critical to human safety and sustaining the capabilities of electric power. Accordingly, in this paper, a new method is also proposed to reduce the sheath circulating currents and an reduction equipment according to the theory of the new method is developed. The reduction equipment is tested when the cable is on service. The test results show that it can reduce the sheath circulating currents by up to 97.8［%］. This confirms the validation of the new method and the reduction equipment, and assures the safe operation of the transmission cables. In order to illustrate the safe operation of the cable with new current reduction equipment at transient state due to lightning and single line-to-ground fault, extensive simulations have been made. Then the protection scheme of sheath circulating currents reduction equipment is proposed by adopting the new device of RDP(Reduction Device Protector).

• Proceedings of the Korean Institute of Intelligent Systems Conference
• /
• 2003.09a
• /
• pp.616-619
• /
• 2003

In this paper, we develop an input device equipped with accelerometers and gyroscopes. The installed sensors measure the inertial measurements i.e., accelerations and angular rates produced by the movement of the system when a user is writing on the plane surface or in the three dimensional space. The gyroscope measurement are integrated once to give the attitude of the system and consequently used to remove the gravity included in the acceleration measurements. The compensated accelerations bin doubly integrated to yield the position of the system. Due to the integration processes involved in recovering the users'motions, the accuracy of the position estimation significantly deteriorates with time. Among various error sources of the system incorrect estimation of attitude causes the largest portion of the positioning error since the gravity is not fully cancelled. In order to solve this problem, we propose a Kalman filler-based attitude estimation algorithm which fuses measurement data from accelerometers and gyroscopes by fuzzy logic approach. In addition, the online calibration of the gyroscope biases are performed in parallel with the attitude estimation to give more accurate attitude estimation. The effectiveness and the feasibility of the presented system is demonstrated through computer simulations and actual experiments.

• Architectural research
• /
• v.7 no.2
• /
• pp.47-54
• /
• 2005

A photoelectric dimming control system for a small private office space with a double skin envelope system was analyzed for the purpose of examining optimum control performances under a variety of daylight conditions. Computer simulations were performed for the three different photosensor types positioned at the center of ceiling in the space. They were applied in both a south and north-facing room. Daylight conditions were a fixed horizontal venetian blind on an external envelope and a retractable shading device on an internal envelope under a clear, intermediate and overcast sky at different times of a day and year. Partially-shielded photosensors provided good control performances providing the required electric light output under clear and intermediate sky conditions. Unshielded photosensors failed to provide necessary illuminance levels producing less electric output and fully-shielded photosensors generally provided excessive light output. Reasonable electric lighting energy savings were achieved except under overcast sky conditions where the control system did not contribute to energy savings due to the less daylight through envelopes. The retractable shading device covering 50% of the internal envelope reduced energy savings up to 19.62%, but the workplane illuminance levels were maintained within recommended ranges. The coefficients of determination between workplane illuminance and photosensor illuminance due to daylight ranged from 0.74 to 0.98. Partially-shielded conditions provided best correlations and the north-facing room yielded stronger correlation than the south-facing room.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.5 no.1
• /
• pp.157-165
• /
• 2001

We analyzed the electrical characteristics of platinum silicide schottky junction to develope the voltage swing in Integrated Schottky Logic gates, and simulated the characteristics with the programs in this junctions. Simulation programs for analytic characteristics are the Medichi tool for device structure, Matlab for modeling and SUPREM V for fabrication process. The silicide junctions consist of PtSi and variable silicon substrate concentrations in ISL gates. Input parameters for simulation characteristics were the same conditions as process steps of the device farications process. The analitic electrical characteristics were the turn-on voltage, saturation current, ideality factor in forward bias, and has shown the results of breakdown voltage between actual characteristics and simulation characteristics in reverse bias. As a result, the forward turn-on voltage, reverse breakdown voltage, barrier height were decreased but saturation current and ideality factor were increased by substrates increased concentration variations.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.24 no.2
• /
• pp.14-27
• /
• 2020

Differential scanning calorimetry and numerical analysis were performed to estimate the performance degradation and ignition characteristics of the pyrotechnic device due to aging. The reaction kinetics extracted from the calorimetry are implemented into the numerical simulation of the igniter and the pyrotechnic delay, subjected to natural, thermal, and hygrothermal aging conditions. Also, combustion experiments are conducted to confirm that aging due to moisture is a major cause of performance failure of the pyrotechnic device as shown from the present numerical simulations.

• Smart Structures and Systems
• /
• v.14 no.4
• /
• pp.659-678
• /
• 2014

The study is aimed at investigating the feasibility of a high TRL solution for a wing flap segment characterized by morphable camber airfoil and properly tailored to be implemented on a real-scale regional transportation aircraft. On the base of specific aerodynamic requirements in terms of target airfoil shapes and related external loads, the structural layout of the device was preliminarily defined. Advanced FE analyses were then carried out in order to properly size the load-carrying structure and the embedded actuation system. A full scale limited span prototype was finally manufactured and tested to: ${\bullet}$ demonstrate the morphing capability of the conceived structural layout; ${\bullet}$ demonstrate the capability of the morphing structure to withstand static loads representative of the limit aerodynamic pressures expected in service; ${\bullet}$ characterize the dynamic behavior of the morphing structure through the identification of the most significant normal modes. Obtained results showed high correlation levels with respect to numerical expectations thus proving the compliance of the device with the design requirements as well as the goodness of modeling approaches implemented during the design phase.

• Architectural research
• /
• v.14 no.3
• /
• pp.99-108
• /
• 2012

An innovative multi-story Semi-Active Tuned Mass Damper (SATMD) building system is proposed to control seismic response of existing structures. The application of adding new stories as large tuned mass and semi-active (SA) resettable actuators as central features of the control scheme is derived. For the effective control of the structures, the optimal tuning parameters are considered for the large mass ratio, for which a previously proposed equation is used and the practical optimal stiffness is allocated to the actuator stiffness and rubber bearing stiffness. A two-degree-of freedom (2-DOF) model is adopted to verify the principal efficiency of the suggested structural control concept. The simulations for this study utilizes the three ground motions, from SAC project, having probability of exceedance of 50% in 50 years, 10% in 50 years, and 2% in 50 years for the Los Angeles region. 12-story moment resisting frames, which are modified as '12+2' and '12+4' story structures, are investigated to assess the viability and effectiveness of the system that aims to reduce the response of the buildings to earthquakes. The control ability of the SATMD scheme is compared to that of an uncontrolled and an ideal Passive Tuned Mass Damper (PTMD) building system. From the performance results of suggested '12+2' and '12+4' story retrofitting case studies, SATMD systems shows significant promise for application of structural control where extra stories might be added.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.11 no.6
• /
• pp.31-39
• /
• 2011

For rapid formed the ad hoc wireless backbone network in disaster scene, It is necessary for real-time deployment scheme of wireless ad hoc relay devices by first responders without pre-planning. However, in order to realize this scheme, redundant deployment should be minimized, as well as optimal location of relay devices should be selected to expand communication coverage. Therefore, in this paper, we propose a new deployment scheme of relay devices to optimize communication coverage and then through simulations showed that improved performance of algorithm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.04b
• /
• pp.37-38
• /
• 2009

SiC power device possesses attractive features, such as high breakdown voltage, high-speed switching capability, and high temperature operation. In general, device design has a significant effect on the switching characteristics. It is known that in SiC power MOSFET, the JFET region width is one of the most important parameters. In this paper, we demonstrated that the switching performance of DMOSFET is dependent on the with width of the JFET region by using 2-D Mixed-mode simulations. The 4H-SiC DMOSFETs with a JFET region designed to block 800 V were optimized for minimum loss by adjusting the parameters of the n JFET region, CSL, and n-drift layer. It has been found that the JFET region reduces specific on-resistance and therefore the switching characteristics depend on the JFET region.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07a
• /
• pp.392-395
• /
• 2003

For the first time, the new dual trench gate Emitter Switched Thyristor is proposed for eliminating snap-back effect which leads to a lot of serious problems of device applications. Also, the parasitic thyristor that is inherent in the conventional EST is completely eliminated in the proposed EST structure, allowing higher maximum controllable current densities for ESTs. Moreover, the new dual trench gate allows homogenous current distribution throughout device and preserves the unique feature of the gate controlled current saturation of the thyristor current. The conventional EST exhibits snap-back with the anode voltage and current density 2.73V and $354/{\S}^2$, respectively. But the proposed EST exhibits snap-back with the anode voltage and current density 0.93V and $58A/{\S}^2$, respectively. Saturation current density of the proposed EST at anode voltage 6.11V is $3797A/{\S}^2$. The characteristics of 700V forward blocking of the proposed EST obtained from two dimensional numerical simulations (MEDICI) is described and compared with that of the conventional EST.