• Journal of ILASS-Korea
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• v.18 no.1
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• pp.35-43
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• 2013

The empirical correlations for the prediction of breakup length of liquid jet in uniform cross flow are reviewed and classified in this study. The breakup length of liquid jets in cross flow was normally discussed in terms of the distances from the nozzle exit to the column breakup location in the x and y directions, called as column fracture distance and column fracture height, respectively. The empirical correlations for the prediction of column fracture distance can be classified as constant form, momentum flux ratio form, Weber number form and other parameter form, respectively. In addition, the empirical correlations for the prediction of column fracture height can be grouped as momentum flux ratio form, Weber number form and other parameter form, respectively. It can be summarized that the breakup length of liquid jet in a cross flow is a basically function of the liquid to air momentum flux ratio. However, Weber number, liquid-to-air viscosity ratio and density ratio, Reynolds number or Ohnesorge number were incorporated in the empirical correlations depending on the investigators. It is clear that there exist the remarkable discrepancies of predicted values by the existing correlations even though many correlations have the same functional form. The possible reasons for discrepancies can be summarized as the different experimental conditions including jet operating condition and nozzle geometry, measurement and image processing techniques introduced in the experiment, difficulties in defining the breakup location etc. The evaluation of the existing empirical correlations for the prediction of breakup length of liquid jet in a uniform cross flow is required.

• Journal of Korean Association for Spatial Structures
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• v.21 no.3
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• pp.9-14
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• 2021

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.12
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• pp.1282-1287
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• 2001

This study presents the numerical analysis of natural convection of a micro- environments with air permeability in the clothing air-layer. As a numerical model the clothing air layer of shoulder and arm were adopted. Finite volume method for two-dimensional laminar flow was used for the analysis of flow and thermal characteristics of velocity, temperature and concentration in the air layer between body and clothing. As temperature boundary conditions, a body skin has a high temperature with $34^{\circ}C$ and the environmental temperatures are 5, 15 and $25^{\circ}C$ for various permeability coefficients. The distributions of concentration, temperature and velocity are shown that two large cells form at horizontal and vertical air layer, respectively. As the temperature difference between body skin and environment decreases, the heat transfer is decreased rapidly.

• Journal of the Korea Safety Management & Science
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• v.12 no.1
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• pp.105-111
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• 2010

The air logistics process is complex and need many informations because various agencies participate in the logistics service and there are many stakeholders in air logistics. But it is hard to improve the infra of facilities because of an enormous expense, so it needs to simplify air logistics process for growing air freight. When documents are sent, it needs to change the form of documents in spite of same document due to different form by agencies. Also documents are changed even though different documents have same informations. Consequently, errors are increased because the names of the same data are different from each other and stakeholders reproduce the documents. In order to mitigate these problems, we selected documents and analyzed data of documents for the interface optimization in general air logistics process. Next, we unified the names of data and defined contents of data. Also we set the type of the defined data on DB type, and gave the code to the defined data. It made easy to exchange informations among the stakeholders to match documents corresponding with the defined data.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.5
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• pp.5-10
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• 2003

• Journal of the Chungcheong Mathematical Society
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• v.21 no.4
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• pp.573-583
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• 2008

In this paper, we introduce the techniques of estimating the probability of failure in reliability analysis. The basic idea of each technique is explained and drawbacks of these techniques are examined.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2002.05a
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• pp.21-26
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• 2002

This paper is intended to verify the efficiency of anti-freeze agent and insulating form by analyzing the temperature history and the property of strength-increase about the concrete that is placed in the insulating form and normal form, using new type anti-freeze agent in batcher plant According to the results about the temperature history, while the lowest temperature shows 3$^{\circ}C$ in case of normal concrete + euroform, 4$^{\circ}C$ in case of normal concrete + insulating form, it shows 6$^{\circ}C$ in anti-freeze agent + the insulating form, so the effect is most favorable. The compressive strength with mixing anti-freeze agent or not, shows high in order of standard curing, structure-managing and open air-placed specimen and the concrete mixing anti-freeze agent shows the highest compressive strength-increase.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.29 no.1
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• pp.74-81
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• 2021

UAM(Urban Air Mobility) systems have evolved in the form of helicopters in the 1960~1970s, tiltrotors in the 1980s, small aircraft transportation systems in the 2000s, and electric-powered Vertical Take-Off and Landing (eVTOL) in the 2010s; accordingly, the early heliport has evolved to its current form of a Vertiport. Vertical Takeoff and Landing Sites, Vertiports, are important factors for the successful introduction of UAM, along with the resolution of air traffic control (ATC), air security, and noise problems. However, there are no domestic or international installation standards and guidelines yet. Therefore, in this study, installation standards were prepared by referring to domestic and international case studies, ICAO standards, and MIT research papers. The study proposes to establish standards for Final Approach and Takeoff Area (FATO) as 1.5D, 1D for Touchdown and Lift-Off Area (TLOF), and 1.5D for Safety Area (SA). It also proposes to add "UAM Vertiport Installation Standards" to the 「Act on the Promotion and Foundation of Drone Utilization, Drone Act」.

• Journal of Environmental Health Sciences
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• v.2 no.1
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• pp.25-28
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• 1975

The main purpose of the aeration units in activated sludge process is to enable micro-organisms to metabolize the constituents of the waste effectively by supplying sufficient oxygen for their respiration. Normally, aeration is achieved by bringing the mixture of waste and sludge into intimate contact with air. The main type of aeration unit is diffused air unit in which air is injected into the liquid in the form of bubbles. The object of these laboratory studies is to compare the performance of three laboratory scale aeration systems at various depths of submergence, aerating water with and without the addition of a surface active agent.

• The Journal of the Acoustical Society of Korea
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• v.3 no.1
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• pp.9-15
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• 1984

Thermoacoustic oscillation induced by a heater in a tube with air current is studied theoretically. Linearized perturbation equations are derived in dimensionless form under the assumption that the system is one dimensional. The equation to predict the acoustic power generation from a heating surface is derived and calculated by solving differential equations numerically. The effect of the mean velocity of the air current is illustrated. The energy conversion mechanism is shown by pressure-volume diagram like a heat engine.