• Journal of IKEEE
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• v.15 no.1
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• pp.1-9
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• 2011

Cable leakage criterion of technical regulations on CATV transmission system was reinforced considering interference against CDMA mobile communication system in 2007. The criterion is $3{\mu}V$/m(at 10m) over 824~849MHz. But generally it is difficult for us to decide if a given CATV transmission facilities conform to it or not through simple measurement methods. In this paper, the problems on measuring cable leakage is identified theoretically and the measuring model with spectrum analyzer, LNA, and antenna is proposed to settle the problems. Also, the model is proved to be useful by practically measuring outdoors and analysing the results and the process to decide to fit to the criterion or not is established.

• Steel and Composite Structures
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• v.27 no.1
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• pp.109-122
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• 2018

In This work an analysis of the propagation of waves of functionally graduated plates is presented by using a high order hyperbolic (HSDT) shear deformation theory. This theory has only four variables, which is less than the theory of first order shear deformation (FSDT). Therefore, a shear correction coefficient is not required. Unlike other conventional shear deformation theories, the present work includes a new field of displacement which introduces indeterminate integral variables. The properties of materials are supposed classified in the direction of the thickness according to two simple distributions of a power law in terms of volume fractions of constituents. The governing equations of the wave propagation in the functionally graded plate are derived by employing the Hamilton's principle. The analytical dispersion relation of the functionally graded plate is obtained by solving an eigenvalue problem. The convergence and the validation of the proposed theoretical numerical model are performed to demonstrate the efficacy of the model.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.14-14
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• 2009

High frequency electromagnetic(EM) waves are increasingly being applied in industries because of saturationat lower frequency bands as a result of huge demand. However, electromagneticinterference (EMI) has become a serious problem, and as a result, highfrequency EM absorbers are now being extensively studied. Also, recentdevelopments in absorber technology have focused on producing absorbers thatare thin, flexible, and strong. Hence, one-dimension ferrous nano-materials area potential research field, because of their interesting electronic andmagnetic properties. Commercially, EM wave absorbing products are made ofcomposites, which blend the insulating polymer with magnetic fillers. Inparticular, the shape of the magnetic fillers, such flaky, acicular, or fibrousmagnetic metal particles, rather than spherical, is essential for synthesizingthin and lightweight EM wave absorbers with higher permeability. High aspectratio materials exhibit a higher permeability value and therefore betterabsorption of the EM wave, because of electromagnetic anisotropy. Nanowires areusually fabricated by drawing, template synthesis, phase separation, selfassembly, and electrospinning with a thermal treatment and reduction process.Producing nanowires by the electrospinning method involves a conventionalsol-gel process that is simple, unique, and cost-effective. In thispresentation, Magnetic nanowire and dielectric materials coated magneticnanowire with a high aspect ratio were successfully synthesized by theelectrospinning process with heat treatment and reduction. In addition toestimating the EM wave absorption ability of the synthesized magnetic anddielectric materials coated magnetic nanowire with a network analyzer, weinvestigated the possibility of using these nanowires as high-frequency EM waveabsorbers. Furthermore, a wide variety of topics will be discussed such as thetransparent conducting nanowire and semiconducting nanowire/tube with theelectrospinning process.

• Journal of computational fluids engineering
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• v.4 no.1
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• pp.19-26
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• 1999

This paper describes a numerical method for predicting the incompressible unsteady laminar three-dimensional flows with free-surface. The Navier-Stokes equations governing the flows have been discretized by means of finite-difference approximations, and the resulting equations have been solved via the SIMPLE-C algorithm. The free-surface is defined by the motion of a set of marker particles and the interface behaviour was investigated by means of a "Lagrangian" technique. Using the GALA concept of Spalding, the conventional mass continuity equation is modified to form a volumetric or bulk-continuity equation. The use of this bulk-continuity relation allows the hydrodynamic variables to be computed over the entire flow domain including both liquid and gas regions. Thus, the free-surface boundary conditions are imposed implicitly and the problem formulation is greatly simplified. The numerical procedure is validated by comparing the predicted results of a periodic standing waves problems with analytic solutions. The results show that this numerical method produces accurate and physically realistic predictions of three-dimensional free-surface flows.

• Korean Journal of Optics and Photonics
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• v.17 no.4
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• pp.366-370
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• 2006

An optical microphone incorporating a reflective diaphragm and a fiber-optic head was demonstrated. The diaphragm was made of a micromirror membrane which is suspended by a silicon bar connected to a frame, allowing fer a displacement induced by acoustic waves. A compact, simple optical head was implemented by exploiting a single multimode fiber. For the assembled microphone, the static characteristics were investigated to find the operation point defined as the optimum distance between the head and the diaphragm, and a flat frequency response with a variation of $\sim$2dB for the range of up to 2 kHz was accomplished.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.3
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• pp.99-109
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• 2000

Elastic dynamic responses analysis program for ship hulls considering slamming impact loads due to the voyage in large amplitude waves is developed. Ship hull structures are modeled by a thin-walled beam model in order to consider effects of shear deformation. The momentum slamming theory is used to derive nonlinear hydrodynamic forces considering intersection between wave particles and ship section. For the validation of the developed computer program, motions of a V-shaped simple section model and S-175 standard container model are calculated and analyzed. In each numerical example, time histories of relative displacement, velocity and vertical bending moment of a ship section are derived, considering the effect of slamming impacts in various wave conditions.ures near the free surface as well as the wake of the hydrofoil.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.2
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• pp.133-138
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• 2003

In this paper, we analyzed a two-branch polarization diversity at a mobile station in NLOS environment when a base station transmits a circularly polarized wave. In order to calculate the correlation coefficient considering the XPD(cross polarization discrimination) between the received signals for the two diversity branches, a simple theoretical model of circular polarization diversity is adopted. From the analysis results, it can be seen that the XPD of circularly polarized wave is less than vertically polarized wave about 6~7 dB in measurement results. And also, it is clearly seen that the correlation coefficient of circular polarization diversity evaluated by the XPD is less than that of vertical polarization diversity.

• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.118-122
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• 2003

Pulse tube refrigerator, which has no moving parts at its cold section, is attractive fer obtaining higher reliability, simpler construction and lower vibration than Stilting refrigerator or Gifford-McMahon refrigerator. Commonly used means to achieve optimum performance of Stilting type pulse tube refrigerator is an inertance tube. The use of inertance tube is a simple way to generate the phase shift needed to make pulse tube refrigerator operate as efficiently as Stilting refrigerator. In this study, the performance of the inertance pulse tube refrigerator (IPTR) was investigated experimentally. An in-line type IPTR consists of a linear compressor with two reciprocating pistons driven by linear motors, which makes pressure waves, a regenerator a pulse tube with the inertance tube, and a reservoir, The dynamic pressures (the compressor, pulse tube, reservior) and the temperature at the cold heat exchanger are measured to explore the dependence of the inertance tube on the performance of the IPTR. The experimental results show the dependency of cool-down characteristics, no-load temperature and amplitude of the pressures on the length and diameter of the inertance tube.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.3
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• pp.459-464
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• 2013

The purpose of a micro-mixing device is to enhance the mixing by increasing the diffusion effect between different types of flows. There have been many attempts to actively or passively increase mixing. However, those studies were limited to lab-scale experiments because the production of devices requires a series of processes, time, cost, and the mixing quality itself. For this reason, this study attempted to develop a quick and simple process for micro-mixing device fabrication by using conventional machining and bonding processes and applying ultrasonic waves from the outside of the mixing device. The mixing quality was quantified by using the mixing index, and the results showed that the proposed system increases the mixing from ~33% to ~10% with respect to the flow rates.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.1 no.1
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• pp.19-31
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• 2007

RFID tag is detected by an RFID antenna and information is read from the tag detected, by an RFID reader. RFID tag detection by an RFID reader is very important at the deployment stage. Tag detection is influenced by factors such as tag direction on a target object, speed of a conveyer moving the object, and the contents of an object. The water content of the object absorbs radio waves at high frequencies, typically approximately 900 MHz, resulting in unstable tag signal power. Currently, finding the best conditions for factors influencing the tag detection requires very time consuming work at deployment. Thus, a quick and simple RFID tag detection scheme is needed to improve the current time consuming trial-and-error experimental method. This paper proposes a back-propagation learning-based RFID tag detection prediction scheme, which is intelligent and has the advantages of ease of use and time/cost savings. The results of simulation with the proposed scheme demonstrate a high prediction accuracy for tag detection on a water content, which is comparable with the current method in terms of time/cost savings.