• Journal of the Korean Society of Radiology
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• v.16 no.3
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• pp.217-223
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• 2022

In this study, images taken using a grid and images taken using Air Gap Technique were evaluated in X-ray chest radiography. Subjective Evaluation The ROC (Receiver Operating Characteristic) evaluation was evaluated by 5 radiologists who had worked for more than 10 years in the radiology department of a university hospital. Objective evaluation SNR (Signal to noise ratio) was evaluated. As a result of the analysis, the Cronbach Alpha value was 0.714, which was significantly higher. In the Air Gap Technique, the distance between the phantom and the subject was set at 20 cm, and the image was taken with a tube voltage of 100 kVp, a tube current and a recording time of 8 mAs. In the ROC (Receiver Operating Characteristic) evaluation, the highest score was obtained with 18 score and an objective evaluation SNR (signal to noise ratio) of 6,149 scored. Also, in the imaging method using a grid, when the distance between the phantom and the constant receptor is 15 cm apart, and the tube voltage is 110 kVp, the tube current and the recording time are taken at 8 mAs, the ROC evaluation score is 19 and the objective evaluation SNR (Signal to noise ratio) is the highest with 6.622 scored. Therefore, if the Air Gap Technique imaging method is used, which overcomes the shortcomings such as delay in reading, increase in patient's exposure dose, and shortening of mechanical lifespan, as well as re-radiography due to the cut-off phenomenon of the grid that appears using the grid, the It is thought that it will be very helpful for chest imaging, including the case of using a portable X-ray imaging device.

• Applied Biological Chemistry
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• v.39 no.4
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• pp.260-264
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• 1996

Process of particle bombardment for efficient transformation of Cymbidium virescence rhizome microcross sections was investigated using Biolistic particle delivery system with pBI121 harboring the ${\beta}-glucuronidase$(GUS) and the neomycin phosphotransferaseII(nptII). The best result was obtained from the combination of $1.11{\;}{\mu}m$ tungsten particles coated with pBl121, $77.33kg/cm^2$ helium pressure, 6.35 mm gap distance, and 7.0 cm target distance. Transient expression of the reporter gene, GUS, bombarded into the rhizome microsections was observed by the histochemical assay. The marker gene, nptII, delivered by bombarding the tungsten particles coated with the plasmid DNA was identified in the transformed rhizome by polymerase chain reaction.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.5
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• pp.491-498
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• 2007

Flame characteristics of a methane-air premixed flame stabilized in a heat-regenerative small combustor were investigated experimentally. A small combustor having two counter-current shallow channels and a combustion space at one side was developed. In which the channel-gap was less the ordinary quenching distance of a stoichiometric methane-air premixed flame. Two design parameters of channel gap and thickness of the middle wall, which is located between two channels for unburned and burned gases, were varied. Flame stabilization conditions and characteristic flame behaviors were experimentally examined. Conclusively, Blowout conditions were governed mostly by the scale of the combustion space, and flashback conditions into the channel are dominated by the channel gap. Surface temperatures of the combustor were between 100 to 500$^{\circ}C$. Additionally, two distinctive flame stabilization modes of radiation and well-stirred?reaction were observed and their applicability was discussed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.2
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• pp.261-267
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• 2008

One of the most important issues in fence-type PDP is low luminance and luminous efficiency. To improve luminance and luminous efficiency, new sustain electrode structure which contains long discharge gap is necessary. However, it causes rise of firing voltage. In this paper, a new fence electrode structure is proposed in order to solve these problems. To drop the firing voltage, tow hump shaped electrodes is added on the main discharge electrode, and distance between two humps is controlled. The experimental results show that the test panel with the narrow horizontal gap(40um) between two humps shows low firing voltage by 17V compared with 80um gap in spit of similar luminance and luminous efficiency.

• JSTS:Journal of Semiconductor Technology and Science
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• v.7 no.3
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• pp.177-182
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• 2007

This paper presents the see-saw type RF MEMS switch based on a single crystalline silicon structure with narrow gap vertical comb. Low actuation voltage and high isolation are key features to be solved in electrostatic RF MEMS switch design. Since these parameters in conventional parallel plate RF MEMS switch designs are in trade-off relationship, both requirements cannot be met simultaneously. In the vertical comb design, however, the actuation voltage is independent of the vertical separation distance between the contact electrodes. Therefore, the large separation gap between contact electrodes is implemented to achieve high isolation. We have designed and fabricated RF MEMS switch which has 46dB isolation at 5GHz, 0.9dB insertion loss at 5GHz and 40V actuation voltage.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.5
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• pp.79-84
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• 2011

In this study, breakdown characteristics of a vertical sphere-plane air gap in the presence of combustion flame were examined under the application of a.c. and d.c. high-voltages in order to investigate the effect of flame on the dielectric strength of air. Propane gas is used as the fuel of the flame, and the temperature distribution of air around the flame is measured. The polarity effects for the d.c. voltages and breakdown voltages of air when applied both of a.c. and d.c. voltages were examined in the case of the variation of the gap length and the horizontal distance between the flame and the high-voltage sphere electrode. The influence of relative air density, electrification and shape changes of the flame as factors that affect the breakdown voltages were discussed.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.1
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• pp.100-108
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• 2006

Time-resolved current and voltage measurements for an inductive automotive spark system were made. Also presented are measurements of the total energy delivered to the spark gap. The measurements were made in air for a range of pressures from 1-18atm, at ambient temperatures. The measured voltage and current characteristics were found to be a function of many ignition parameters; some of these include: spark gap distance, internal resistance of the spark plug and high tension wire, and pressure. The voltages presented were measured either at the top of the spark plug or at the spark gap. The measurements were made at different time resolutions to more accurately resolve the voltage and current behavior throughout the discharge process. This was necessary because the breakdown event occurs on a time scale much shorter than the arc and glow phases. The breakdown, are, and glow voltages were found to be functions of spark plug resistance, gas density, and spark plug gap as expected from the literature. Spark duration was found to decrease as either pressure or gap was increased. The transition from the arc to glow phase is usually distinguished by a sudden rise in the voltage across the gap. At pressures above about 7atm this transition was not observed suggesting that a glow phase was not present. Energy delivered to the gap increased with increasing pressure. The effective resistance of the spark gap during discharge was about twice as large for the glow phase as the arc phase.

• Structural Engineering and Mechanics
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• v.67 no.5
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• pp.427-437
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• 2018

Structural pounding is commonly observed phenomenon during major ground motion, which can cause both structural and architectural damages. To reduce the amount of damage from pounding, the best and effective way is to increase the separation distance. Generally, existing design procedures for determining the separation distance between adjacent buildings subjected to structural pounding are based on approximations of the buildings' peak relative displacement. These procedures are based on unknown safety levels. The aim of this research is to estimate probabilistic separation distance between adjacent structures by considering the variability in the system and uncertainties in the earthquakes characteristics through comprehensive numerical simulations. A large number of models were generated using a robust Monte-Carlo simulation. In total, 6.54 million time-history analyses were performed over the adopted models using an ensemble of 25 ground motions as seismic input within OpenSees software. The results show that a gap size of 50%, 70% and 100% of the considered design code for the structural periods in the range of 0.1-0.5 s, leads to have the probability of pounding about 41.5%, 18% and 5.8%, respectively. Finally, based on the results, two equations are developed for probabilistic determination of needed structural separation distance.

• Journal of Creative Information Culture
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• v.7 no.3
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• pp.167-176
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• 2021

In this paper, from the pervious studies investigating the current status of distance learning due to COVID-19, the needs of teachers for effective distance learning were analyzed. As a result, it was found that support related to distance learning contents was necessary. Specifically, it is necessary to establish a platform specialized for content production for distance learning, expand teacher training related to content production and operation, and improve the copyright system related to content production. In addition, since distance classes differ from those of back-to-school classes in system and characteristics, it is necessary to supplement the institutional aspects for distance classes. It is judged that it is necessary to support the evaluation method suitable for distance learning, the authority to operate the curriculum, and the learning management system. In addition, it was analyzed that it is necessary to expand the infrastructure for distance learning, and a structure and platform for self-directed improvement programs and self-directed distance learning are needed to prevent the learning gap problem from repeating due to distance learning.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1061-1062
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• 2013