• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.289-292
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• 2005

Two planar inverted-F antenna (PIFA) arrays are proposed as an alternative model to generate input and radiation characteristics of two orthogonal oriented circular loops, which has polarization diversity, but inherent mechanical instability of two orthogonal loops, in particular, in installation and operation conditions. Two $1\times2$ PIFA sub-arrays are orthogonally placed on a ground plane and two different feeding networks are applied to control horizontal and vertical radiation current flows for each sub-array, respectively. Equivalence of scattering parameters and radiation patterns between two antennas are validated by the available commercial simulator.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.2
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• pp.107-116
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• 2003

This paper presents a systematic design methodology for fault tolerant controller against a fault in actuators and sensors of linear stochastic systems with uncertainties. The scheme is based on fault detection and diagnosis(isolation and estimation) using a bank of robust two-stage Kalman filters, and accommodation of the actuator fault by eigenstructure assignment and immediate compensation of the sensor's faulty measurement. In order to clarify the fault feature in test statistics of residual, noise reduction method is given by multi-scale discrete wavelet transform. The effectiveness of our approach Is shown via simulations for a VTOL(vertical take-off and landing) aircraft subjected to parameter variations, external disturbances, process and sensor noises.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.12
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• pp.977-982
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• 2000

Conventional transistors which have vertical structure show increased parasitic capacitance characteristics in accordance with the increase of non-active base area and collector area. These consequently have disadvantage for high speed switching performance. In this paper, a lateral structure transistor which has minimized parasitic capacitance by using SDB(Silicon Direct Bonding) wafer and oxide sidewall isolation utilizing silicon trench technology is presented. Its structural characteristics are designed by ATHENA(SUPREM4), the process simulator from SILVACO International, and its performance is proven by ATLAS, the device simulator from SILVACO International. The performance of the proposed lateral structure transistor is certified through the V$\_$CE/-I$\_$C/ characteristics curve, h$\_$FE/-I$\_$C/ characteristics, and GP-plot. Cutoff Frequency is 13.7㎓.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.6
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• pp.124-130
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• 1989

For the higher density DRAM'S, innovations in fabrication process and circuit design which have led to dramatic density improvement are discussed from the desinger's perspective. A new dynamic RAM cell called Trench Epitaxial Transistor Cell(TETC) using trench technics and SEG have been developed for use in future megabit DRAMS. Storge electrode with $n^+$-polysilicon and $n^+$-source electrode are self-contacted in TETC. With keeping the storage capacitance large enough to prevent soft errors, the cell size reduced to 30% compare with existing BSE cell by utilizing the vertical capacitor made along the isolation region.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.09a
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• pp.415-422
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• 2001

In this paper, the experimental study was carried out in order to compare the mechanical characteristics of multi-layer elastomeric isolation hearings where the reinforceing elements steel plates case and fiber-reinforcement case. Fiber-reinforced isolater which has the same dimension as the steel reinforced isolator had shown better efficiency in effective damping than NRB. The compression test has shown the corresponding results with the theoretical vertical stiffness in the case of flexible reinforcement. The fiber-reinforced isolator will be significantly lighter and could lead to a much less labor intensive manufacturing process.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.949-954
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• 2000

In terms of vibration damage and the serviceability for occupants in buildings, the purpose of vibration study lies in the reduction of vibration damage. However, only when vibration level of buildings is available, measures of vibration control and base isolation can be taken. The purpose of this paper is to provide a fundamental analysis method to estimate structural vibration. After analysing by using two methods, infinite model, combination method, a comparison between analysed results and the results of previous studies was performed to prove the validity of the prediction on the vibration of building structure. Thus, if the material property of soil and quantity of load sources are known before construction being started, the vibration level could be predicted by using these methods.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.04a
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• pp.115-122
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• 1998

Earthquake damage civil engineering structures every year in the world and bridges are no exception. Bridge structures have proven to be vulnerable to earthquake, sustaining damage to substructure and foundation and being totally destroys as superstructures collapse from their supporting elements. The poor seismic performance of bridge structures is surprising in view of the substantial advance made in design and construction for vertical load. Recently, bridge spans have been pushed further than before, alignment has become increasingly complex and aesthetic requirement have been become more demanding. To reduce the seismic force and to improve the safety of the advanced bridges, the bridge bearings which are the substructures and foundations and their connections to the superstructure become more important and critical elements. Therefore, the functions about seismic devices to be using as bridge bearing are discussed.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.10a
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• pp.136-143
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• 1998

Elastomeric bearing is used as one of the most useful way for isolation structures, because the horizontal stiffness is much lower than the vertical stiffness. The quality of Elastomeric bearing depends on the vulcanization procedure to manufacture, which produces the elasticity of the rubber from the compound of rubber and sulphur. The durability of Elastomeric bearing is affected by the deterioration due to ozone and ultra-violet attack. but the durability during the design life of bridges can be assured by the sufficient size of the bearing in spite of the deterioration in surface. In the design criteria of Elastomeric bearing, the stability of the bearings is evaluated by shear strain due to compression, lateral displacement, and rotation. The question how soft rubber can sustain heavy structure is now able to be solved by Ultimate capacity test of Laminated elastomeric Bearings, which results 1,200kg/$\textrm{cm}^2$ of the max. compressive stress and this shows what a sufficient safety factor Elastomeric bearing has!

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.4
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• pp.476-484
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• 2010

Precise positioning stages are often employed for precise machinery. For the purpose of vibration isolation, these precise positioning stages are mounted on a heavy base structure which is supported by compliant springs. Then the base structure is subjected to residual vibration due to the reactive force and vertical moving load induced by the stage motion. This paper investigates the vibration behavior of a positioning stage base and the associated vibration suppression technique. A dynamic model is developed to investigate the base vibration due to the reactive force and moving load effects by the moving stage. An input shaping technique is also developed to suppress the residual vibrations in base structures. Simulations and experiments show that the developed dynamic model adequately represents the base vibration and that the proposed input shaping technique effectively removes the residual vibrations from the positioning stage base.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.109-112
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• 2006

In this study, an approach that installs seismic isolation bearings was proposed for the seismic retrofit of the existing bridges. The method that replaces all existing bearings with seismic isolators was proposed already. However, in this study, we recommend to utilize the existing bearings for the benefit of safety and cost. According to our proposal, the seismic isolators do not support vertical loads but they just function as the period shifter and the horizontal damper. To verify this approach experimentally, the real scale bearings and isolators for the real highway bridges were designed and fabricated. And the responses of this isolated bridges to the assumed earthquakes were determined by the pseudo dynamic test scheme. The test results were also compared to the responses computed by the well known structural analysis software to check the reliability of the test. From the test results, we found that the retrofitted bridges using the proposed method showed stable performances under earthquakes.