Lee D.Y.,Daelim University College |
Lee K.-H.,Daelim University College |
Kim B.-Y.,Incheon National University |
Cho N.-I.,Sun Moon University
Journal of Sol-Gel Science and Technology | Year: 2010
Silver (Ag) nanoparticles were prepared in PAN nanofibrous film by a sol-gel derived electrospinning and subsequent chemical reduction for 30 min in hydrazine hydroxide (N2H5OH) aqueous solution. Antimicrobial properties of the AgNO3/PAN precursor solution against gram positive Staphylococcus aureus ATCC 6538 and gram negative Escherichia coli ATCC 25922 were investigated. The formation of clear zone suggested that the PAN solution containing Ag+ ions were effective on the inhibition of bacterial growth. The Ag/PAN nanocomposite film, characterized by XRD, TEM and UV absorption spectrophotometer, revealed that highly crystallized cubic Ag particles with diameters of less than 5.8 nm were dispersed homogeneously in PAN nanofibers. © 2010 Springer Science+Business Media, LLC.
Moon J.-H.,Daelim University College |
Pahk H.J.,Seoul National University |
Lee B.-G.,Daelim University College
International Journal of Advanced Manufacturing Technology | Year: 2011
We developed a novel piezoelectrically actuated 6 degree-of-freedom (DOF) stage for micropositioning. To achieve a parallel mechanism with high stiffness, compact size, and low parasitic motion for 6-DOF positioning, an orthogonal actuator configuration is proposed and actuation units are carefully designed. For the purpose of suppressing parasitic motion in the overall stage, the ratios of the lateral stiffness to actuating directional stiffness of the actuation units are minimized under the condition that the stress at any point in the stage does not exceed the allowable strength. Flexure hinges and lever linkages are effectively applied to the horizontal and vertical actuation units. A physics-based model of the stage is developed to ensure low system order and high reliability. The model parameters are estimated by experiment and finite element analysis. Open-loop tests including sinusoidal and step responses verify low parasitic motion and reliability of the model. Closed-loop step responses with a model-based controller validate the high micropositioning performance of the stage. © 2010 Springer-Verlag London Limited.
Kim H.S.,Kyonggi University |
Cho Y.M.,Seoul National University |
Moon J.H.,Daelim University College
Smart Materials and Structures | Year: 2010
In this paper, we present an active vibration control system which is constructed based on a novel three-degrees-of-freedom(DOF) precision micro-stage. Unlike the traditional tripod systems, the proposed micro-stage is established to guarantee the compactness (60mm(h) × 160mm(d)) and the simplicity of its structure as well as the appropriate vertical/horizontal stiffness and the repeatability, which are essential in achieving the accuracy of sub-micrometers. First, combined with a finite element method(FEM), a physical model for the proposed micro-stage is constructed and its physical parameters, such as stiffness and damping coefficients, are estimated to predict the experimental results with high fidelity. In order to overcome the dynamic variations naturally stemming from the payload as well as the parameter uncertainties, a robust control system is then proposed to efficiently mitigate the vibration with a scale of sub-micrometers. Compared to the conventional control strategy, the proposed robust control scheme successfully establishes the active vibration control system and its performance is examined and validated through extensive experiments. © 2010 IOP Publishing Ltd.
Kim H.,Daelim University College |
Lee H.-M.,Kyonggi University
Proceedings of 6th European Conference on Antennas and Propagation, EuCAP 2012 | Year: 2012
An integration of a wireless power transfer system is presented to obtain both high power transfer efficiency and a compact wireless power transfer structure. To have all these characteristics, transmitter and receiver parts suggested in previous researches are all integrated to new resonant coils fabricated on Teflon substrates. To verify this characteristic, an equivalent circuit model is presented. Using this basic theory, the optimized performance through EM simulations is predicted, and the proposed wireless power transfer is realized with a practical load. © 2012 IEEE.
Byeon H.,Daelim University College |
Byeon H.,Ajou University |
Lee Y.,Ajou University
Laryngoscope | Year: 2013
Objectives/Hypothesis: This study's objectives were to assess the prevalence rate of laryngeal pathologies in the Korean elderly, and to examine the association of smoking and alcohol consumption with laryngeal diseases. Study Design: Cross-sectional study. Methods: Data were from the 2008 Korea National Health and Nutritional Examination Survey. Subjects were 663 elderly persons (261 men and 402 women) between the ages of 65 and 84 years who completed the laryngoscopic examination. Weighted prevalence of laryngeal pathologies was compared by demographic characteristics, smoking, alcohol drinking, body mass index, and self-reported voice problems. Multiple logistic regression analyses were conducted to examine the independent as well as combined influence of smoking and alcohol consumption on laryngeal lesions. Results: The prevalence of laryngeal pathologies in the Korean elderly between the ages of 65 and 84 years was 8.1%. The prevalence of laryngeal lesions increased with age and was higher among men, middle school and high school graduates, manual workers, current smokers, current alcohol drinkers, and those with self-reported voice problems. Adjusting for covariates, current smokers, compared with nonsmokers, were more likely to have laryngeal pathologies (odds ratio [OR], 2.18; 95% confidence interval [CI], 1.01-4.67). Current alcohol drinking was not independently associated with laryngeal diseases. Concurrent smoking and alcohol drinking, however, were associated with a significantly higher risk of laryngeal pathologies (OR, 3.29; 95% CI, 1.22-8.88). Conclusions: Smoking and alcohol consumption may increase the risk of laryngeal diseases in later life. Copyright © 2012 The American Laryngological, Rhinological, and Otological Society, Inc.
Bae S.,Daelim University College |
Kim M.,Soongsil University |
Bae M.,Soongsil University
International Conference on ICT Convergence | Year: 2013
In speech or audio processing, coding may be define as a digital representation of signal that provides efficient storage, transmission, recovery, and perceptually faithful reconstruction of the original signal. In the coding methods, the waveform coding method can maintain the high quality and intelligibility, but the major drawback of this method is large amount of data required. Therefore, we proposed a waveform coding method using the non-uniform sampling and variables low pass filter of speech or audio signals. Simulation results show that this algorithm is robust in noisy environments. © 2013 IEEE.
Park J.I.L.,Daelim University College |
Park H.S.,Daelim University College
Communications in Computer and Information Science | Year: 2011
In this paper, we studied VOR receiver system designed for digital communication system. A VOR provides the user with a bearing to the station. Digital hardware was used to determine the phase relationship between the two 30Hz signal. The design in this paper acquires the phase of the 30Hz variable and reference signals from the composite audio output of a VOR receiver using DSP and FPGA methods implemented in software. VOR signal generator using a frequency 108MHz, -70dBm to receive input power to the system, the developed system was verified by operation. © 2011 Springer-Verlag.
Kwon S.,Daelim University College
Information Sciences | Year: 2014
This paper proposes an identity-based (ID-based) signature (IBS) scheme which is strongly unforgeable in the standard model whose security is reduced to the hardness of the computational Diffie-Hellman (CDH) problem in bilinear groups. Currently, the ID-based encryption scheme (IBE) due to Waters is known to be the most practically efficient IBE whose security is guaranteed in the standard model depending on the decisional bilinear Diffie-Hellman (BDH) assumption. While as a solution for an ID-based signature of a total ID-based public key cryptosystem cooperating with Waters IBE, we share Waters's construction and system parameters to keep a key pair corresponding to each identity unchanged, our IBS needs only one group element for signing of messages and two elements for its randomness as supplementary parameters plus the original system parameters. Accordingly, thanks to requiring about half the system parameters against previous ID-based signatures proved secure without using random oracles under the standard complexity assumptions like CDH or BDH, our IBS is the more suitable for storage and communication requirements. In particular, this covers a stronger security property called strong unforgeability in the standard model in itself without applying any transformation technique. © 2013 Elsevier Inc. All rights reserved.
Lee H.-Y.,Daelim University College
Transactions of the Korean Institute of Electrical Engineers | Year: 2014
In this paper, a high gain waveguide array antenna combining horn antenna on slot radiator was designed. And the fabricated antenna showed enough gain, improved efficiency and broadband characteristics for receiving satellite signals, compare to conventional microstrip antenna which has dielectric loss and radiation loss on transmission line. For easy fabrication, the waveguide structure was composed by 3-stages of radiator, signal coupler and transmission line. By experiment, the array waveguide antenna of 4 by 16 showed 28.3[dBi] gain and 2:1 of VSWR. And by combining horn antenna structure, the gain was increased 1[dB], The received signal from Koreasat 6 by measurement showed 16[dBc] of C/N on BS(Broadcasting Satellite)-band and 14[dBc] of C/N on CS(Communication Satellite)-band.
Moon J.-H.,Daelim University College |
Lee B.-G.,Daelim University College
Mechanism and Machine Theory | Year: 2010
This paper aims at accurate modeling and sensitivity analysis for a pneumatic vibration isolation system (PVIS) as a foundation for practical design. Even though the PVIS is widely used for its effective performance in vibration isolation, its design has depended largely on trial-and-error methods. In previous studies, nonlinear characteristics of the diaphragm and the air flow restrictor, which significantly affect the performance of a PVIS, have been investigated. However, several hurdles, such as the absence of a mathematical model for the diaphragm, still remain with regard to the model-based prediction of performance. Therefore, a fractional derivative model for the diaphragm and a quadratic damping model for the air flow restrictor are newly developed based on the careful examination of previous studies. Then, sensitivities of vibration isolation performance indices with regard to major design variables are analyzed and new approximation formulas are created based on the dynamic characteristics of the PVIS. Our models with a transmissibility-computing algorithm are verified by comparison with experimental data. The sensitivity analyses and approximation formulas are expected to be useful for practical PVIS design owing to their simplicity and accuracy. © 2010 Elsevier Ltd.