• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.492-498
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• 2000

As the disk rotation speed increases in information storage devices, aerodynamically excited disk vibration is induced by airflow around the disk. This paper investigates theoretical and experimental studies on the disk flutter instability in CD-ROM drives. The effect of airflow on the disk vibration is modeled as the distributed damping and lift forces. By analyzing the eigenvalue problem of the aero-elastic coupling model, we introduces a novel technique to predict the flutter speed by comparing experimental natural frequencies with analytical ones of a disk rotating in vacuum. The new method predicts that the vibration mode with two nodal diameters in a CD disk experiences the first flutter instability at 12,000 rpm.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.260-264
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• 2003

In this paper, a $\lambda/4$ hairpin resonator is proposed to reduce the size of planar resonators for a LTCC MLC bandpass filter. The $\lambda/4$ hairpin resonator operates as stepped impedance resonator (SIR) without changing the width of the planar resonator. It is composed of two sections those are parallel coupled line and transmission line. The characteristic impedance of two sections is different each other. The design formulas of the bandpass filter using the coupling element at the arbitrary position are derived from even and odd-mode analysis. The formulas can take account of the arbitrary coupling of lumped ana/or distributed resonators. The advantage of this filter is its abilities to change freely the coupling structure between two resonators. Experimental bandpass filters for 2.4GHz Band are implemented and their performances are shown.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.7
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• pp.97-104
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• 1997

Using the ray optics technique, we derive the analytic expressions of TE mode coupling coefficient for five-layer distributed feedback (DFB) structure devices. We compare the coupling coefficient calculated by the ray optics technique with those calulated by the extended additional layer method (EALM) which may be a most accurate method of calculating the coupling coefficient. The difference between the results of the ray optics technique and those of the EALM is small for most cases of grating depth and forms being practically made. In the case of rectangular gratings, the difference increases as the duty cycle of graing deviates from 0.5. In the case of the trapezoidal grating, the difference increases as the ratio of the top to the period of grating deviates from 0.5 and as the length of the top becomes longer than that of the base. The difference of theree-layer DFB structures is smaller than that of five-layer DFB structures.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1337-1338
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• 2015

In this paper, a new control technique using WIPDC(Weighted Integral Parallel Distributed Compensation) and ISMC(Integral Sliding Mode Control) is proposed for high performance and robust trajectory tracking control of a wheeled mobile robot. The WIPDC reduces the steady-state error by adding a weighted integral controller to the PDC. So, the trajectory tracking control using the WIPDC can obtain more accurate control performance than the PDC. And the ISMC based control input gives the mobile robot to preserve the system dynamics controlled by the WIPDC control input in spite of external disturbances. Therefore, the proposed control method shows a robust and precise trajectory tracking performance.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.563-564
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• 2015

Recently, distributed generation using renewable energy resources have increased due to the limitation of conventional energy. To utilize these energy source effectively, a method of applying the energy storage system(ESS) in distribution system has been considered. In this paper, we simulated the one line-to-ground fault in power system with ESS. Based on these simulations, we analyzed the effect on Over Current Relay(OCR) operation. As a result, ESS operation modes result fault current fluctuation. Thus, OCR need to reset the pick up current. This paper analyze effect of ESS in distribution system according to OCR setting by using ElectroMagnetic Transient Program(EMTP).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.9
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• pp.1641-1647
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• 1994

This paper describes an optimal communication protocol for high-speed networks. This scheme can support multimedia services and provide fast data transmission using the distributed gueue scheme and the dynamic bandwidth allocation architecture, based on ATM(Asynchronous Transfer Mode). Performance analyses and simulation results are presented to illustrate the effectiveness of the proposed scheme in a variety of communication environments.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.11
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• pp.4331-4346
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• 2015

The femtocell network, which is designed for low power transmission and consists of consumer installed small base stations, coexists with macrocells to exploit spatial reuse gain. For its realization, cross-tier interference mitigation is an important issue. To solve this problem, we propose a joint access and power control scheme that requires limited information exchange between the femto and macro networks. Our objective is to maximize the network throughput while satisfying each user's quality of service (QoS) requirement. To accomplish this, we first introduce two distributed interference detection schemes, i.e., the femto base station and macro user equipment based schemes. Then, the proposed scheme dynamically adjusts the transmission power and makes a decision on the access mode of each femto base station. Through extensive simulations, we show that the proposed scheme outperforms earlier works in terms of the throughput and outage probability.

• Journal of Sensor Science and Technology
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• v.27 no.1
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• pp.25-30
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• 2018

Closed-form analytical expressions and 3-dimensional normalized charts for the homogeneous sensing and surface sensing structures are derived to provide the conditions for the maximum sensitivity of integrated-optic biosensors based on evanescent-wave and stepindex planar optical waveguides. The analysis is made for transverse electric (TE) polarization mode, in both cases where the measurand is homogeneously distributed in the cover (namely, homogeneous sensing), and where it is an ultrathin film on the waveguide-cover interface (namely, surface sensing).

• Structural Engineering and Mechanics
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• v.3 no.5
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• pp.497-509
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• 1995

Effectiveness of multiple tuned mass dampers (MTMD) in suppressing the dynamic response of base excited structure for first mode vibration is investigated. The effectiveness of the MTMD is expressed by the ratio of the root mean square (RMS) displacement of the structure with MTMD to corresponding displacement without MTMD. The frequency content of base excitation is modelled as a broad-band stationary random process. The MTMD's with uniformly distributed natural frequencies are considered for this purpose. A parametric study is conducted to investigate the fundamental characteristics of the MTMD's and the effect of important parameters on the effectiveness of the MTMD's. The parameters include: the fundamental characteristics of the MTMD system such as damping, mass ratio, total number of MTMD, tuning frequency ratio, frequency spacing of the dampers and frequency content of the base excitation. It has been shown that MTMD can be more effective and more robust than a single TMD with equal mass and damping ratio.

• Journal of the Korea Society of Computer and Information
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• v.5 no.2
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• pp.98-104
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• 2000

One of the main features of ABR service is the employment of a rate-based flow control mechanism, and congestion control plays an important role in the effective and stable operation of ATM networks Feedback from the network switches to the end system gives users the information necessary to adjust transmission rates appropriately according to the current networks load. Congestion controls by feedback mechanism are classified as EFCI and ER mode. We analyze the performance of EFCI and ER and propose a new ABR traffic control strategy by integrating EFCI and ER modes to improve the traditional traffic control. Through the distributed simulation. the performance improved by the proposed control strategy is analyzed.