• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.10
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• pp.979-986
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• 2013

In this paper, a TVS diode which is commonly used as a ESD protector in wireless communication devices could cause antenna wireless sensitivity to decrease has been analyzed. When a smartphone doesn't have enough space to place many components, there would be its speaker near antenna area. In order to protect ESD coming through the speaker there also could be a TVS within antenna GND area. Digital audio signal which was sent to speaker and CDMA RF communication signal coupled from antenna was mixed by TVS. And this leakage current running through TVS resulted in decrease of antenna wireless sensitivity. The results of various experiments can be explained using circuit simulation. Following works will give us some insights that can reduce unwanted summation of digital and RF signal due to nonlinearity of ESD protectors.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.39 no.2
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• pp.118-123
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• 2002

A torque transmission system, which is composed of serveral gears and couplings, is flexible. Therefore, the torsion vibration occurs when the motor speed abruptly changes. Consequently, for accuracy characteristic response of motor, we must suppressed vibration. Therefore, vibration suppression is very important motor control. In order to suppress the vibration, various control method have been proposed. Specially, one method of vibration suppression is used disturbance observer and filter. The disturbance observer is used to suppress the vibration in this method. By feedback of the estimated torsion torque, the vibration can be suppressed. The coefficient diagram method is used to design the filter and proportional controller. But using coefficient diagram method, not adapted controller parameter in disturbance. In order to solve this problem. we used fuzzy controller for auto tuning controller parameter $K_P$. We proved of this approach is confirmed by simulation. 

• Journal of the Korea Computer Graphics Society
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• v.23 no.1
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• pp.9-16
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• 2017

Simulating the clumping and stiffness of wet hair or fur is a challenging problem. The dynamics of wet hair or fur is characterized by the clumping and stiffness at the tip, which is easily seen in running animals or headbanging scenes. Existing methods address these phenomenon within pre-set scenarios. But there is no consensus on the method of depicting the details of wet hair. Hence, the present paper proposes a new method of modeling the clumping and stiffness of wet hair or fur. Previous studies focused on modeling the absorption of water into hair or fur, whereas this paper highlights a realistic simulation of wet hair. Unlike dry hair strands, wet hair strands adjacent to one another are subjected to the clumping force and gather together, while at the same time becoming stiff as the saturation of water increases. The proposed method builds on the surface tension model based on SPH (smoothed particle hydrodynamics) to simulate the clumping force and to adjust the hair elasticity by giving stiffness constraints. The present method enables a realistic simulation of wet hair by maintaining the clumping force of the wet hair even in dynamic motions, and by simulating the stiffness of hair in line with water saturation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.1
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• pp.28-35
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• 2010

In this paper, we designed and fabricated a ultra-wideband(UWB) bandpass filter with a good performance of a stopband, and a notched band in passband. The transformed equivalent circuit of the highpass filter was realized by distributed element. A wide-passband with 3-dB fractional bandwidth of more than 100 % was achieved by using optimum response of the HPF. For improving lower and upper stopband characteristic, a cross coupling between feed lines was employed, which was analyzed by desegmentation technique. In order to reject interference of Wireless LAN and Hyper LAN(5.15~5.825 GHz), the narrow notched(rejection) band was realized by a spurline. The fabricated BPF indicated the passband from 3.1 to 10.55 GHz and the flat group delay of less than 0.94 ns over the entire passband except the rejection band. The filter shown sharp attenuation both inside and outside the band and notched band from 5.2 to 6.12 GHz.

• Journal of the Korea Computer Graphics Society
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• v.20 no.4
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• pp.9-16
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• 2014

This paper proposes a novel method that couples fluid and deformation/fracture. Our method considers two interaction types: fluid-object interaction and fluid-fluid interaction. In fluid-fluid interaction, we simulate water and smoke separately and blend their velocities in the intersecting region depend on their densities. Our method separates projection process into two steps for each of water and smoke. This reduces the number of grid cells required for projection in order to optimize the number of iterations for convergence and improve stability of the simulation. In water projection step, smoke region regarded as the cells with Dirichlet boundary condition. The smoke projection step solves water region with Neumann boundary condition. To take care of fluid-object interaction, we make use of the fluid pressure to update velocities of the each of the mass points so that the object can deform or fracture. Although our method doesn't provide physically accurate results, the various examples show that our method generate appealing visuals with good performance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.5
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• pp.1035-1041
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• 2017

In magnetic resonance-based wireless power transfer (WPT) systems, frequency splitting phenomenon, in which power transfer efficiency (PTE) decreases seriously as resonators are close to each other, is the problem that we should address for reliable power transfer in short distance. In this paper, we present WPT systems using an equivalent circuit model and analyze PTE and marginal coupling coefficient ($k_{split}$) where the frequency splitting occurs. In addition, we perform circuit-level simulations using Advanced Design System, and show that the achievable PTE is different for the structures of resonators when k>$k_{split}$. We confirm that higher PTE can be ensured as k increases in the case of identical resonators, while PTE is degraded as k increases in the case of non-identical resonators. Therefore, in short distance, in which k>$k_{split}$, it is more efficient for achieving reliable PTE to use identical resonators rather than non-identical resonators.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.506-510
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• 2004

A torque transmission system composed of several gears and couplings is flexible. In order to get an exact response of motor, the torsional vibration due to an unexpected change of motor speed must be suppressed. Therefore, it is very important that motor control suppress vibration. Various methods to control it including dual inertia system are proposed. Specially, the method of vibration suppression is that vibration can be suppressed to fee㏈ack the estimated torsion torque via the disturbance observer filter being of normal filter. The suitable Proportional controller and coefficient parameter can be designed using CDM and the torsional vibration also be suppressed, but it has a low degree of adaptability to disturbance. The PID controller can be designed easily, but makes the excessive overshoot and oscillation for system response in the early period. To resolve these problems, simple and practical PID controller with two degree of freedom is proposed recently that it ran improve performance of obeying the reference unconcerned in any disturbance by changing the proportional gain by two degree of freedom parameter. But it has also the defect that parameter a must be changed to obtain the ideal Proportional parameter. On this paper, we design the controller which automatically adjusts parameter u using fuzzy Algorithm to overcome such defects. Also, we compare the proposed method with established one and evaluate them to confirm performance of the designed controller.

• Journal of IKEEE
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• v.28 no.3
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• pp.329-336
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• 2024

Organic light emitting diode(OLED) is distributed in layers with different refractive index, which leads to total internal reflection and low light extraction efficiency. As a result, light extraction technologies have been investigated that include structures such as MLA. However, technologies such as MLA are using petroleum-based polymers, which cause environmental problems during disposal. Therefore, this study investigates the use of eco-friendly polymers hydroxyethyl cellulose(HEC) and tannic acid(TA) to produce external light extraction films. HEC is biodegradable and has high transparency, making it suitable for eco-friend external light extraction films. The TA used as an additive is a polyphenolic molecule, which is expected to form strong hydrogen bonds with HEC. In addition, TA can protect OLED from damage by UV light through its phenolic groups. HECTA MLA films were produced by dissolving HEC and TA in water without using additional solvents and then imprinting them on MLA mould. When the HECTA MLA film was attached to the outside of the OLED and analysed, it showed a high Haze of more than 80%, and the external quantum efficiency and current efficiency of the OLED were improved by 38% and 39%, respectively, compared to the reference.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.1
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• pp.63-72
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• 2020

As the design complexity and performances are increased in satellite electronic board, noise related problems are also increased. To minimize the noise issues, various design improvements are performed by power integrity and signal integrity analysis in this research. Static power and dynamic power design are reviewed and improved by DC IR drop and power impedance analysis. Signal integrity design is reviewed and improved by time domain signal wave analysis and PCB(Printed Circuit Board) design modifications. And also power planes resonance modes are checked and mitigation measures are verified by simulation. Finally, it is checked that radiated noise is reduced after design improvements by EMC(Electro Magnetic Compatibility) RE(Radiated Emission) measurement results.

• Korean journal of communication and information
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• v.74
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• pp.177-196
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• 2015

This paper aims to plan a new research program on the parallel relationship between Korean press and political power, by providing concepts on the mode of existence of professional journalists in Korea. In the midst of the economic crisis of Korean journalism, relative deteriorisation in the political democracy and the liberty of press, and changes in news ecosystem due to the revolution of digital news, the status of professional journalists is at stake. In these circumstances, this paper argues that many existing researches on journalistic professionalism need to be reconstructed in the perspective of professional project. It enables, first of all, an evaluation on actual issues of professional journalists from the actor perspective, i.e. economic interests, social closure, regulative bargain with the authority. Secondly, concerning decoupling phenomenon of journalism and democracy which became salient in the contemporary society, this study raises a necessity to create new logical relations around concepts of journalist professionalism. And we will find, in this situation, a beginning of new evaluation on the mode of existence of professional journalists, that has been possibly developped within the old, assymetric relationship between State-press. And finally, this study proposes to consider a category of professional journalists as a vehicle that helps to conceptualize the old, parallel relationship between Korean press and political power.