• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.71-77
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• 2000

An axisymmetric supersonic jet is simulated at a Mach number of 1.5 and a Reynolds number of $10^5$ to identify the mechanism of sound radiation from the jet. The present simulation is performed based on the high-order accuracy and high-resolution ENO(Essentially Non-Oscillatory) schemes to capture the time-dependent flow structure representing the sound source. In this simulation, optimum expansion jet is selected as a target, where the pressure at nozzle exit is equal to that of the ambient pressure, to see pure shear layer growth without effect of change in jet cross section due to expansion or shock wave generated at nozzle exit. Shock waves are generated near vortex rings, and discernible pressure waves called Mach wave are radiated in the downstream direction with an angle from the jet axis, which is characteristic of high speed jet noise. Furthermore, vortex roll-up phenomena are observed through the visualization of vorticity contours.

• Structural Engineering and Mechanics
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• v.76 no.1
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• pp.17-26
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• 2020

The objective of this paper is to study the deformation in transversely isotropic thermoelastic solid using new modified couple stress theory subjected to ramp-type thermal source and without energy dissipation. This theory contains three material length scale parameters which can determine the size effects. The couple stress constitutive relationships are introduced for transversely isotropic thermoelastic solid, in which the curvature (rotation gradient) tensor is asymmetric and the couple stress moment tensor is symmetric. Laplace and Fourier transform technique is applied to obtain the solutions of the governing equations. The displacement components, stress components, temperature change and couple stress are obtained in the transformed domain. A numerical inversion technique has been used to obtain the solutions in the physical domain. The effects of length scale parameters are depicted graphically on the resulted quantities. Numerical results show that the proposed model can capture the scale effects of microstructures.

• Journal of applied mathematics & informatics
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• v.29 no.3_4
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• pp.813-829
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• 2011

In this article, we present a numerical scheme for solving singularly perturbed (i.e. highest -order derivative term multiplied by small parameter) Burgers-Huxley equation with appropriate initial and boundary conditions. Most of the traditional methods fail to capture the effect of layer behavior when small parameter tends to zero. The presence of perturbation parameter and nonlinearity in the problem leads to severe difficulties in the solution approximation. To overcome such difficulties the present numerical scheme is constructed. In construction of the numerical scheme, the first step is the dicretization of the time variable using forward difference formula with constant step length. Then, the resulting non linear singularly perturbed semidiscrete problem is linearized using quasi-linearization process. Finally, differential quadrature method is used for space discretization. The error estimate and convergence of the numerical scheme is discussed. A set of numerical experiment is carried out in support of the developed scheme.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.6
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• pp.833-842
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• 2002

Computer security is considered important due to the side effect generated from the expansion of computer network and rapid increase of use of computers. A attack of intruders using a vulnerability of operating system, protocol and application programs. And so, The attack methods is to be high technology and professional. Thus It must be necessity that we necessary a solution to structure, management for framework of information technology. This paper develope intrusion detecting system for separating intruders form critical system and design IDS model and implementation of it.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.113.1-113.1
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• 2014

Surface-enhanced Raman scattering (SERS) has long been projected as a powerful analytical technique for chemical and biological sensing applications. Pairing with portable Raman spectrometers makes the technique extremely appealing as real-time sensors for field application. However, the lack of reliable, uniform, low cost and ease-of-use SERS enhancement structures has prevented the wide adoption of this technique for general applications. We have discovered a novel hybrid structure based on the high-density and uniform arrays of gold nanofingers over a large surface area for SERS applications. The nanofingers are flexible and their tips can be brought together to trap molecules to mimic the biological system. We report here a rapid, simple, low-cost, and sensitive method of detecting trace level of food contaminants by using nanofinger chips based on portable SERS technique. We also present here the characterization of surface reaction of target molecules with our gold nanofinger substrates and the effect of nanofinger closing towards SERS performance. This new type of nano-structures can potentially revolutionize the medical and biologic research by providing a novel way to capture, localize, manipulate, and interrogate biological molecules with unprecedented capabilities.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2A
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• pp.187-194
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• 2004

We propose priority-based reservation code multiple access (P-RCMA) which can enhance voice traffic quality of the previous RCMA. The proposed protocol maintains two power levels and consider traffic characteristics in contending shared available codes to transmit packets. P-RCMA gives priority to the voice request packets rather than data packets by capture effect at the receiver part of base station. We show numerical results from EPA (equilibrium point analysis) analysis and simulation study in terms of voice packet dropping probability and average data packet transmission delay.

• The Journal of Korean Physical Therapy
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• v.32 no.4
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• pp.193-197
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• 2020

Purpose: The purpose of this study was to investigate the immediate effects of calf muscle Kinesio taping on ankle joint reposition sense (JRS) and force sense (FS) in healthy elderly. Methods: Thirteen healthy elderly subjects were participated in this study. The error of ankle JRS and FS was evaluated by 3D motion capture device and digital dynamometer depending on three different taping conditions (Kinesio taping, sham taping, and no taping) respectively. All of subjects were asked to perform a proprioceptive task of ankle JRS and FS. One-way repeated ANOVA test was used to compare the error of JRS and FS depending on three different taping conditions. Results: With Kinesio taping over calf muscle, ankle joint reposition sense error and force sense error significantly decreased, if compared with a sham taping or no taping condition. Conclusion: To apply Kinesio taping over calf muscle could enhance ankle proprioceptive sense in the elderly people.

• Asian Journal of Innovation and Policy
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• v.2 no.2
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• pp.212-239
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• 2013

This paper clarifies the change in international technology standardization as a change in innovation. The change comes to be shown in how to take the consensus standard. The tendency to standardize the systematized concept is a rather arduous and complex endeavor. This paper focuses on Mitsubishi Electric Corporation as such a case. The results interpreted from the approach of closed innovation, open innovation, and social innovation. The following findings are clarified by. 1) The consensus standardization is open innovation in which the enterprise creates value. 2) When the value creation is large, the possibility of the maximization of such value capture that achieves the earnings acquisition can be improved. 3. The innovation of the consensus standardization is reciprocal for the stakeholder. The possibility for open and social innovation to supplement the success in innovation mutual and to achieve an effect is suggested.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.2
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• pp.201-210
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• 1999

Cyclones have been extensively used in the industry for removing fine particles from the gaseous streams, based on simplicity in design and construction in association with low cost and flexibility to operate in extreme and harsh environments. However, industrial cyclones are typically not very efficient for particles smaller than 10μm. In this work, in order to improve the separation efficiency of reverse flow cyclones, a simple device named Post Cyclone(Poc) in installed on the top of an existing cyclone. Thereby the residual swirl present at the outlet (vortex finder) of a conventional cyclone has been used to capture the escaped dust from the cyclone in the PoC. The performance of PoC was closely evaluated by changing configuration of the PoC and operation condition. In addition, the dust behaviour in th PoC was investigated based on the hypothesis of residual vortex.

• Structural Engineering and Mechanics
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• v.59 no.3
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• pp.475-502
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• 2016

Nanobeams are widely used as a structural element for nanodevices and nanomachines. The development of nano-sized machines depends on proper understanding of mechanical behavior of these nano-sized beam elements. Small length scales such as lattice spacing between atoms, surface properties, grain size etc. are need to be considered when applying any classical continuum model. In this study, Eringen's nonlocal elasticity theory is incorporated into classical beam model considering the effects of axial extension and the shear deformation to capture unique static behavior of the nanobeams under continuum mechanics theory. The governing differential equations are obtained for curved beams and solved exactly by using the initial value method. Circular uniform beam with concentrated loads are considered. The displacements, slopes and the stress resultants are obtained analytically. A detailed parametric study is conducted to examine the effect of the nonlocal parameter, mechanical loadings, opening angle, boundary conditions, and slenderness ratio on the static behavior of the nanobeam.