• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.2120-2125
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• 2015

In this paper, a rectangular waveguide probe with a ridge-loaded straight slot (RLSS) is presented for a near-field scanning microwave microscope (NSMM). The RLSS is located laterally at the end wall of the cavity and is loaded on double ridges in a narrow straight slot to improve the spatial resolution compared with a straight slot. The probe consists of a rectangular cavity with an RLSS and a feed section of a WR-90 rectangular waveguide. When the proposed NSMM is located at distance of 0.1mm in front of a substrate without patches or strips, the simulated full width at half maximum (FWHM) of the probe improve by approximately 31.5 % compared with that of a straight slot without ridges. One dimensional scanning of the E-plane on a sample under test was conducted, and the reflection coefficient of the near-field scanning probe is presented.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.303-306
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• 2011

An experimental study has been conducted to investigate the effects of an ultrasonic standing-wave field to the behavior of methane/air premixed flame. Visualization technique utilizing the schlieren method was employed for the observation of premixed flame behavior. The shape of flame front and local flame velocity were measured according to the variation of reactants pressure and chamber opening/closing condition. The flame front was distorted and severely deformed to a lotus-type flame by the interaction of ultrasonic standing-wave and the reflection wave coming from an end wall of reactor.

• Journal of Advanced Navigation Technology
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• v.5 no.2
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• pp.158-164
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• 2001

We presented a channel model for the inter vehicle radio link including the reflection from the road surface, side road vehicle and concrete wall. Then we theoretically derived the path loss and delay profile characteristics using the Ray tracing method efficiently analyzing millimeter wave or optic wave. Finally, we shown the improvement of propagation characteristics by diversity techniques, BCH coding and convolution coding techniques. At the result, MRC diversity techniques and BCH coding can't obtained PER = $10^{-6}$ which is considered to be data service criterion. But, we knew that Packet Error Rate Characteristic can obtained PER = $10^{-6}$, which is considered to be data service criterion, when convolution coding scheme are adopted in Rician fading.

• Nuclear Engineering and Technology
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• v.41 no.8
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• pp.1045-1052
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• 2009

A calculation model is developed to predict the transient free surface flow on the containment floor following a loss-of-coolant accident (LOCA) of pressurized water reactors (PWR) for the use of debris transport evaluation. The model solves the two-dimensional Shallow Water Equation (SWE) using a finite volume method (FVM) with unstructured triangular meshes. The numerical scheme is based on a fully explicit predictor-corrector method to achieve a fast-running capability and numerical accuracy. The Harten-Lax-van Leer (HLL) scheme is used to reserve a shock-capturing capability in determining the convective flux term at the cell interface where the dry-to-wet changing proceeds. An experiment simulating a sudden break of a water reservoir with L-shape open channel is calculated for validation of the present model. It is shown that the present model agrees well with the experiment data, thus it can be justified for the free surface flow with accuracy. From the calculation of flow field over the simplified containment floor of APR1400, the important phenomena of free surface flow including propagations and interactions of waves generated by local water level distribution and reflection with a solid wall are found and the transient flow rates entering the Holdup Volume Tank (HVT) are obtained within a practical computational resource.

• Korean Journal of Materials Research
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• v.12 no.2
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• pp.160-165
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• 2002

High-frequency dielectric and microwave absorbing properties have been investigated in ferroelectric materials (BaTiO$_3$(BT), (1-x)Pb$Mg_{\frac{1}{3}}Nb_{\frac{2}{3}}$)O$_3$-xPbTiO$_3$(PMN-PT), (1-x)Pb$Mg_{\frac{1}{3}}Nb_{\frac{2}{3}}$O$_3$-xPb(Zn_{\frac{1}{3}}Nb_{\frac{2}{3}}$)O$_3$(PMN-PZN) for the aim of thin microwave absorbers in the frequency range of mobile telecommunication. The specimenns are prepared by conventional ceramic processing and complex permittivity has been measured by transmission/reflection method. The ferroelectric materials show high dielectric constant and dielectric loss in the microwave range and their domiant loss mechanism is considered to be domain wall relaxation. The microwave absorbance of BT 0.9PMN-0.1PT, and 0.8PMN-0.2PZN specimen (determined at 2) are found to be 99.5% (at a thickness of 4.5 mm), 50% (2.5 mm), and 30% (2.5 mm), respectively. It is suggested that PMN-PT or PMN-PZN ferroelectrics are good candidate materials for the spacer of λ/4 absorber. The use of ferroelectric materials is effective in reducing the thickness of absorber with their advantage of high dielectric constant.

• Computational Structural Engineering
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• v.9 no.1
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• pp.55-64
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• 1996

Sloshing frequencies of the fluid in rectangular tanks with a bottom-mounted rectangular block are determined by linear water wave theory. Velocity potential is decomposed into those for the wall-induced waves, and the reflected, transmitted, and scattered waves by the block. The reflection and transmission coefficients are determined using the continuity conditions of mass flux and energy flux on the common vertical boundaries of the fluid regions, and the boundary conditions on the both sides of the block. The analysis results indicate that the sloshing frequencies reduce, as the block becomes tall and vade and as the block moves toward the center. The variations of the sloshing frequencies due to the block are found to be more sensitive in broad thanks than is tall tanks.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.9
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• pp.950-954
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• 2003

This paper presents the delivered power and reflection coefficient in metallic shielding enclosure excited by the interior source, which are evaluated with the method of moments, and describes a method for reducing the radiation of electromagnetic fields in the cavity by putting lossy dielectric material in one inside wall. In this paper we introduce carbon polystyrene-foam as lossy dielectric material and observe it's effects of reduction when the thickness and permittivity of lossy dielectric material are changed. The results show that the reduction of the electromagnetic radiation can be achieved by controlling the amount of carbon in lossy dielectric material. The theoretical analysis is verified by the measured delivered power.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.5
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• pp.902-907
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• 2008

Shape of the pulse waveform is affected by the visco-elasticity characteristics of the arterial wall and the reflection waves generated at the bifurcations of arterial branches. This study was designed to improve the accuracy for the extraction of pulse wave features, then proved the superiority of the developed algorithm by clinical evaluation. Upstroke point of the pulse wave was used as an extraction feature since it is minimally affected by the waveform variation. R-peak of the ECG was used as a reference to decide the minimum level, then intersection of the least squares of regression line was used as an upstroke point. Developed algorithm was compared with the existing minimum value detection algorithm and tangent-intersection algorithm using data obtained from 102 subjects. Developed algorithm showed the least standard deviation of $0.29{\sim}0.44\;m/s$ compared with that of the existing algorithms, $0.91{\sim}3.66\;m/s$. Moreover, the rate of standard deviation of more than 1.00m/s for the PWV values reduced with the range of $29.0{\sim}42.4%$, which proved the superiority of the newly developed algorithm.

• Korean Institute of Interior Design Journal
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• v.20 no.5
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• pp.13-22
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• 2011

The purpose of this study is to analyze Alva Aalto's libraries for understanding his efficient induction of natural light. To fulfill this purpose, Alvar Aalto's thought about library and natural light are examined through his working years and building types. The comparison of his libraries on usage of natural light shows different ways of natural light induction based on different locations and programs of libraries. Similarities and differences of Alvar Aalto's library architecture have strong relationship to the usage of natural light in libraries because Alvar Aalto himself regard reading as the core function of library and the efficient use of natural light is the main key of reading. In his natural light planning, regional characteristics including environmental factors and programmatic differences act as a basic standard for natural light plan. Especially, altitude of sun and its path, seasonal features affect the induction way of natural light. While conical skylights used at Viipuri library shows the characteristics of universality in Modernism architecture, later libraries presents not only various kinds of pan-shape plan but different ways of inducing natural light in according to appropriate function. From conical skylight to monitor with curved reflection wall make it possible shed diffused light to reading space and this affects to form Alvar Aalto's organic architecture. As a result, using natural light in Alvar Aalto's library architecture act as the core of forming library concepts and their development.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.6
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• pp.586-595
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• 2007

The analytic solution of wave scattering of monochromatic waves on a pile breakwater by an eigenfunction expansion method is extended to the case of directional irregular waves. The scattering wave spectrum and the force spectrum can be expressed from the reflection coefficient, transmission coefficient and the wave forces obtained from changing frequencies and incident angles in monochromatic waves. By numerical integration of 2-dimensional spectrum which is function of frequencies and incident angles, the representative values for the scattered waves and wave forces are obtained and the dependence of the transmission coefficients and wave forces on the directional distribution function, the principal wave direction, the submergence depth, and porosity is analyzed.