• The KSFM Journal of Fluid Machinery
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• v.16 no.5
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• pp.24-28
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• 2013

Visualization of internal flow of a regenerative blower has been made by injecting a tracer directly into the flow. For the convenience of visualization, working fluid has been replaced by water and marbling color oil has been used as a tracer. Oil droplet has been injected near the inlet of the blower and the streak has been recorded using a high speed camera with the illumination of high power light sources. At first, droplets have irregular motion in the near inlet area and enter into a groove of the impeller. Then the droplets circulate inside the groove while translated by the rotational motion of the impeller. When the droplets get out of the impeller groove, their speed is lower than that of impeller. And the droplets repeatedly enter into the groove and circulate inside the grooves. Then the droplets either flow to the outlet or reenter into the inlet area through stripper. Through this experimental study, internally circulating motion of the flow inside a regenerative blower has been characterized.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.37.1-37.1
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• 2013

We present our study of analyzing the photometric properties of the globular cluster (GC) system which resides in the extended halo of the central bright Coma cluster galaxy NGC 4874. The core of the Coma cluster of galaxies (Abell 1656) was observed with both the HST Advanced Camera for Surveys (ACS) in the F475W (g475) and F814W (I814) and Wide Field Camera 3 IR Channel (WFC3/IR) in the F160W (H160) filters. The data analysis procedure and GC candidate selection criteria are briefly described. We investigate the interesting "tilt" features in color-magnitude diagrams for this GC system and their link to the nonlinear color-metallicity relation for GCs. The NGC 4874's GC system exhibits a bimodal distribution in the optical g475-I814 color and much more than half the GCs fall in the red side at g475-I814 ~ 1.1. This bimodality is weakened in the optical-IR I814-H160 color; the quantitative analysis on the features of both color distributions using the Gaussian Mixture Modeling code proves the bimodalities are different. Both colors, thus, cannot linearly reflect the bimodality of an underlying metallicity, supporting the suggestion that observed bimodalities in extragalactic GC colors are the metallicity-to-color projection effect.

• Journal of Chest Surgery
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• v.25 no.4
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• pp.347-355
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• 1992

The precise mechanism of the Excitation-Contraction Coupling is still uncertain. But the concept that Ca2+ induced Ca2+ release [CICR] from the Ryanodine receptor in the sarcoplasmic reticulum [foot structure] may play a major role in E-C coupling has been widely accepted since 1970`s. It is believed that increased cytosolic Ca2+ followed by CICR is main contributor for E-C coupling of striated muscle. Resulting phenomena of ischemic /post-reperfusion myocyte is increased cytosolic Ca2+, even to the absence of Ca2+ in reperfusate. So intracellular inhibitor to CICR might prevent the ischemic and reperfusion damage of myocardial cells. The relatively purified foot protein, especially heavy sarcoplasmic reticulum rich, of the skeletal muscle was incorporated into the black lipid bilayer [Phosphatidyl ethanolamine: Phosphatidyl serine=l: 1]. Under the steady state of membrane potential [+20 mV], ionic current through Ryanodine receptor was measured with Cs+ as charge carrier. In the cis chamber [Cytoplasmic side], Mg2+ strongly inhibited CICR of Ryanodine receptor[Kd=6.2 nM]. In conclusion, naturally existing intracellular free Mg2+ can inhibit CICR from intracellular Ca2+ reservior [heavy SR]. So post-ischemic or post-reperfusing myocardium could be preserved using additional free Mg2+ in cardioplegic solution or reperfusate, otherwise the optimal concentration is undetermined.

• KIPS Transactions on Computer and Communication Systems
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• v.2 no.9
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• pp.393-398
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• 2013

This paper introduces a new collision attack on first-order masked AES. This attack is a known plaintext attack, while the existing collision attacks are a chosen plaintext attack. In addition, our method is more efficient than the second-order power analysis and requires about 1/27.5 power measurements by comparison with the last collision attack. Some experiment results of this paper support this fact. In this paper, we also introduce a simple countermeasure, which can protect against our attack.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2000.04a
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• pp.342-351
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• 2000

The paper is concerned about the discovery of new physics of the old oriental philosophy of the yin-Yang '||'&'||' five elements. the physical properties of Five Elements are defined, similarly as in thermodynamics, as five different characteristic state in a cyclic system of nature or a human body. Wood is defined as "warm and soft", Fire as "hot and dispersive", Earth as "agglomerating and sticky", Metal as "tensile and crystallizing", and Water as "cool and slippery" state, respectively. Based on the physics of Five Elements and Qi channel theory, five different constitution classification s are made according to the shape of human face, such as long, inverse triangle, circle, square, and triangle geometry, respectively.Since the constitution implies the relative size or strength of 5 major organs, this theory can be applies successfully to the prediction of the susceptibility to specific diseases as well as the analyses of personal character such as emotion and sensibility. The specific character is analyzed with four different aspects; that is, the first and second are caused by the positive and negative side of the strongest organ, the third character by determined the weakest organ, and finally the fourth by the abnormal psychology due to serious illness.bnormal psychology due to serious illness.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.4
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• pp.67-72
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• 2004

A regenerative cooling system has been designed through empirical 1-D analysis for a liquid rocket engine of 30-ton-level thrust. The hot-gas-side wall temperature from 1-D analysis shows 100K difference compared to 3D CFD analysis. Two variations of design with same cooling performance are suggested for different maximum channel widths i.e., 4mm and 2mm. The coolant pressure drop of the latter design is higher by 20%. The maximum liner temperature is about 700K when TBC and the thermal resistance of carbon deposit are considered. So film cooling is recommended to increase the cooling capacity as the present cooling capacity is insufficient

• Fisheries and Aquatic Sciences
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• v.14 no.1
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• pp.62-69
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• 2011

The effects of actively stimulating devices (ASD) on juvenile flatfish escape were studied to increase escape rates from the cod end by encouraging fish to approach the net wall. Two kinds of ASD were designed: a fluttering net panel, i.e., a free-end flag-like net panel, and a double conical rope array. Escape responses of juvenile bastard halibut were observed in a circulating water channel using two model cod ends, one made with diamond-shaped 43-mm-mesh-size polyethylene (PE) as a high-contrast cod end and the other with polyamid (PA) mono-ply as a low-contrast cod end. Retention rate was significantly lower with the double conical rope-array ASD in the PE cod end than with conventional PE cod ends only or the fluttering net-panel ASD inside the PE cod end. Mean retention rate with the low-contrast PA cod end was also significantly lower than that with the high-contrast PE conventional cod end. Therefore, active fluttering devices using a double conical rope array together with less visible low-contrast netting in the cod end could help to reduce the bycatch of juvenile flatfish by weakening their optomotor response and actively driving fish to the side net panel.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.213-219
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• 2005

Small liquid rocket engine (SLRE) with calorimeter were developed and tested to evaluate cooling characteristics in the liquid rocket engine. Therefore, cooling performance analysis was performed to predict the heat transfer coefficient on gas side wall in 10 calorimeter channel. A heat transfer empirical formula was determined by results of firing test and computational simulation.

• Wind and Structures
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• v.11 no.5
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• pp.345-359
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• 2008

An experimental investigation of the flow over the rectangular body located in close proximity to a ground board was reported using the particle image velocimetry (PIV) technique. The present experiments were conducted in a closed-loop open surface water channel with the Reynolds number, $Re_H=1.2{\times}10^4$ based on the model height. In addition to the PIV measurements, flow visualization studies were also carried out. The PIV technique provided instantaneous and time-averaged velocity vectors map, vorticity contours, streamline topology and turbulent quantities at various locations in the near wake. In the vertical symmetry plane, the upperbody flow is separated from the sharp top leading edge of the model and formed a large reverse flow region on the upper surface of the model. The flow structure downstream of the model has asymmetric double vortices. In the horizontal symmetry plane, identical separated flow regions occur on both vertical side walls and a pair of primary recirculatory bubbles dominates the wake region.

• The Journal of the Acoustical Society of Korea
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• v.23 no.2
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• pp.134-145
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• 2004

The study aims to develop the underwater wireless telephone system. The system is designed based on the underwater acoustic communication channel parameters such as ambient noise, multipath effect and diver breathing noise. The system adopts SSB modem and its carrier frequency is about 33 kHz in which ambient noise level is low and therefore a high S/N ratio is easily obtained. The source level of the transmitter is designed as 131 dB re 1μPa. Its intelligibility index of sentence shows as 80% or mure in the range of less than 300m in the sea trial.