• Current Optics and Photonics
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• v.5 no.4
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• pp.375-383
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• 2021

We present a simulation method to design antireflection coating (ARCs) for fiber-coupled superconducting nanowire single-photon detectors. Using a finite-element method, the absorptance of the nanowire is calculated for a defined unit-cell structure consisting of a fiber, ARC layer, nanowire absorber, distributed Bragg reflector (DBR) mirror, and air gap. We develop a method to evaluate the uncertainty in absorptance due to the uncontrollable parameter of air-gap distance. The validity of the simulation method is tested by comparison to an experimental realization for a case of single-layer ARC, which results in good agreement. We show finally a double-layer ARC design optimized for a system detection efficiency of higher than 95%, with a reduced uncertainty due to the air-gap distance.

• Radiation Oncology Journal
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• v.7 no.1
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• pp.113-121
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• 1989

The inclusion of air filled cavities in treatment fields creates a potential dosimetric problem due to the rebuildup phenomenon near the air-tissue interface using a simulated phantom, such as air gap, air cylinder, and air cavity, the amount of rebuldup along the various field sizes and air cavity dimensions was measured. The results are as follows. 1. As the field size becomes larger in comparison with the cavity size, or as the cavity size gets bigger when the field size is equal to the cavity size, rebuildup decreases. 2. When the distance between the phantom surface and the air cavity is less than 1.5cm, there is prominent rebuildup. And when the distance is more than 1.5cm, rebuildup is relatively constant, 3. The change according to the depth of the cavity is affected by the field size and the cavity size, rebuildup usually increases when the depth of the cavity increases. 4. It is suggested that tissue equivalent material should be applied on the skin to make tissue thickness over the air cavity more than 1.5cm and that the field size should include the air cavity with at least 1cm margin.

• PNF and Movement
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• v.13 no.1
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• pp.47-53
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• 2015

Purpose: This study examined the effects of space fabric type air insole pressure differences on young adults' dynamic balance ability. Method: The subjects of this study were 17 young female adults without musculoskeletal system disease. Balance ability was measured by dividing the subjects into three groups: an experimental group which did not wear an air insole (insole-off group), an experimental group which wore an air insole to which air pressure of $0.55kg/cm^2$ was applied (insole-0.55 group), and an experimental group which wore an air insole to which air pressure of $0.75kg/cm^2$ was applied (insole-0.75 group). For dynamic balance, the subjects stood on a balance pad, and perimeter length and medium speed were measured three times. The averaged values were recorded and statistically processed. Result: There were significant differences in average speed, and the insole-0.75 group's average speed decreased compared to the insole-off group and the insole-0.55 group. Although the total movement distance did not statistically differ, the insole-75 group's movement distance decreased compared to the insole-off group and the insole-0.55 group. Conclusion: Application of a space fabric type air insole, in particular insole-0.75, was helpful in improving balance ability. This is considered to occur because the space fabric structure was conducive to decreasing sway and producing balance.

• Korean Journal of Applied Biomechanics
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• v.16 no.1
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• pp.139-149
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• 2006

This study is to analyze the kinematic variables of inward $1{\frac{1}{2}}$ somersault in platform diver. For the manner, 3 people form the national diving team in the year 2000were chosen as the subjects and two S-VHS video cameras set in 60frames/sec were used for recording their motions. Coordinated raw positions data through digitizing are smoothing by butter-worth's low-pass filterin method at a cut off frequency 6.0Hz. and the direct linear transformation(DLT) method was employed to obtain 3-D position coordinates. The conclusions were as follows. However, horizontal distance which is the change of the COG, form the point of the jump to the point of Event 3 where the player is out of the board range completely, Subject B showed 105.1cm and 71.1cm of the vertical distance which are shorter horizontal distance and higher vertical distance, thus, took a great advantage of the position to prepare for the entry. Therefore, if a player takes higher position by speeding up the vertical velocity at the moment of the jumping off the board, and stays in the air longer, the player can have more time to show his skill. Because of the use of the characteristics of the inward somersault, keeping the safe distance form the board is important but in order to higher the completeness, it is ideal to keep the horizontal distance little over 100cm. Also, the angles of shoulder and elbow from Event 1 to 4, depending on swing of the arms, motions in the air, getting ready for the entry, showed some difference individual by individual, according to the velocity of the thigh and shank showed much difference while getting ready and take-off, and it's because of the individual's different bending and straightening for horizontal and vertical distance.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.6
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• pp.855-860
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• 1999

An experimental study of jet impingement on the surface with linear temperature gradient is conducted with the presentation of the turbulent characteristics and the heat transfer rates measured when this jet impinges normally to a flat plate. The jet Reynolds number ranges from 30,000 to 90,000, the temperature gradient of the plate is 2~$4.2^{\circ}C$/cm and the dimensionless nozzle to plate distance(H/D) is from 6 to 10. The results show that the peak of heat transfer rate occurs at the stagnation point, and the heat transfer rate decreases as the radial distance from the stagnation point increases. A remarkable feature of the heat transfer rate is the existence of the second peak. This is due to the turbulent development of the wall jet. Maximum heat transfer rate occurs when the axial distance from the nozzle to nozzle diameter(H/D) is 8. The heat transfer rate can be correlated as a power function of Prandtl number, Reynolds number and the dimensionless nozzle to plate distance(H/D). It has been found that the heat transfer rate increases with increasing turbulent intensity.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.2
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• pp.213-221
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• 2009

An aircraft collision accident is a disaster that causes great losses of inventories and lives. Though a collision avoidance warning function is provided automatically to pilots in the aircrafts by the enhancement of the aircraft capability, achieving fast decision-making to escape a collision situation is a complex and dangerous work for pilots. If an in-flight collision situation is controlled by the air traffic control system which monitors all airplanes in the air, it would be more efficient to prevent in-flight collisions because it can handle the emergency before the pilot's action. In this paper, we develop the collision avoidance warning function in the air traffic control system. Specifically, we design and implement the five stages of the collision avoidance function, and propose a visualization method which could effectively provide the operators with the trajectories and altitudes of the aircrafts in a collision situation. By developing an in-flight collision warning function in the air traffic control system that visualizes flight patterns through the state transition data of in-flight aircrafts on the flight path lines, it can effectively prevent in-flight collisions with traffic alerts. The developed function allows operators to effectively select and control the aircraft in a collision situation by providing the operators with the expected collision time, the relative distance, and the relative altitude while assessing the level of alert, and visualizing the alert information which includes the Attention-Warning-Alert phase via embodying the TCAS standard. With the developed function the air traffic control system could sense an in-flight collision situation before the pilot's decision-making moment.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.34 no.3
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• pp.231-242
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• 2016

As of late, air quality information has been actively gathered and investigated in order to find possible environmental risk factors that may affect the onset of cardiovascular disease. Nevertheless, existing studies are limited in the detailed analysis because they take advantage of the air quality information of the macro statistics divided into administrative districts. This paper proposes the construction of distance-based air quality dataset using a domestic hospital’s geographical location information as a reliable data gathering step for a more detailed analysis of environmental risk factors. For the construction of the dataset, air quality information was obtained by utilizing the geographical location of a hospital—in which a patient with cardiovascular disease had been admitted—and then matching the hospital with a meteorological and air pollution station in its vicinity. An air quality acquisition system based on GMap.net was devised for the purpose of data gathering and visualization. The reliability of the experiment was confirmed by evaluating the matching rate and error of air quality values between the acquired dataset with existing area-based air quality datasets from matched distances. Therefore, this dataset, which considers geographical information, can be utilized in multidisciplinary research for the discovery of environmental risk factors that can affect not only cardiovascular diseases but also potentially other epidemic diseases.

• Journal of Environmental Science International
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• v.22 no.9
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• pp.1187-1197
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• 2013

The result of a small electrostatic precipitator which is in order to decrease indoor air pollution for optimal efficiency was shown as follows. Although the closer distance between the discharge electrode and dust collecting electrode shows the better throughput efficiency by forming strong electrostatic Field, it does not have profound impact in case of optimal dust collecting area. G.P(gas passage) which is the distance from dust collecting electrode to dust collecting electrode is a crucial factor to decide dust collecting efficiency. The narrower distance of G.P shows the better throughput efficiency whereas it decreases when the distance is too narrow since sparks ensue by increasing the capacity of electrostatic charging system 5 mm regards as optimal efficiency in this experiment. Although the higher voltage shows the higher dust collecting efficiency overall, the experiment was not able to keep performing since the sparks which decrease dust collecting efficiency ensue over 40 kV. The efficient and safe voltage state is considered 3.6 kV in this experiment. The most crucial factor for dust collecting efficiency of an electrostatic precipitator which is in order to decrease indoor air pollution is applied voltage. In addition, optimal raw gas flow rate(2.4 m/sec) is more important factor than the excessive increase of dust collecting area.

• Journal of Environmental Science International
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• v.19 no.6
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• pp.671-680
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• 2010

The present study evaluated residential exposure to atmospheric formaldehyde and acetaldehyde according to distance from the a dyeing industry complex (DIC). This purpose was achieved by measuring concurrently the outdoor air concentrations in residences near the DIC and a certain distance away, plus the outdoor air concentrations at two industrial areas within the DIC boundary. Formaldehyde concentrations (median values of 24.3 and $22.5{mu}g/m^3$ in IS1 and IS2, respectively) were higher than acetaldehyde concentrations (median values of 7.4 and $7.3{mu}g/m^3$ in IS1 and IS2, respectively) at both sites. However, there was no significant difference in the industrial outdoor air concentrations of both formaldehyde and acetaldehyde between the two sites. In addition, the median formaldehyde concentration from the residential site near the DIC (RS1) was about 1.5 times higher than that from the residential site far away from the DIC(RS2), and the median acetaldehyde concentration from RS1 was about 1.3 times higher than that from RS2. It is noteworthy that the mean or median risk as well as these maximum risks are well above the USEPA's permissible risk level of $10^{-6}$ from environmental exposure. This suggests that appropriate management for formaldehyde and acetaldehyde is necessary in order to decrease risk of the residents of study areas, regardless of the distance from the DIC.

• Explosives and Blasting
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• v.37 no.3
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• pp.1-12
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• 2019

The analysis methods of blast analysis models are classified into direct analysis and indirect analysis, and the latter is divided into semi-empirical and numerical analysis methods. In order to evaluate the applicability of the ELS blast analysis program, which is a program for analyzing the semi-empirical models, this study selected a simplified analytical model and examined the blast load characteristics of free-air burst explosion and surface burst explosion by using AT-Blast, RC-Blast, and Kinney and Graham's empirical equations, which are the semi-empirical analysis programs. As a result of analyzing the explosion pressure for the scaled distance and the incidence angle for the simplified analytical model, an appropriate analysis can be performed when the range of the scaled distance in the free-air burst explosion analysis was 0.3~0.461 and when the range of the scaled distance in the surface burst explosion analysis was 0.378~0.581. In terms of the incidence angle, the results analyzed within $45^{\circ}$ were considered to be appropriate.