• Analytical Science and Technology
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• v.13 no.2
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• pp.222-228
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• 2000

A detector for monitoring carbon monoxide (CO) in ambient air by nondispersive infrared (NDIR) spectroscopy has been developed and investigated its sensitivity and stability. The essential parts of the absorption cell are three spherical concave mirrors so as to improve the sensitivity by increasing the light path length in the cell. The radius and center of curvature of mirrors and position in the cell was calculated by computer simulation in order that the light path length may be 16m into the 50cm cell. The number of traversals and optical path properties were confirmed by laser beam alignment in transparent absorption cell. The photoconductive type lead selenide (PbSe) was used as CO sensing material, which was cooled to increase the responsibility by thermoelectric cooling method. The detection limit and span drift of the developed CO detector was 0.24ppm and 0.03ppm(v/v) respectively.

• Explosives and Blasting
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• v.31 no.1
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• pp.41-48
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• 2013

Progressive collapse is generally defined as a local failure of structural members occurring due to abnormal load which results in the partial collapse or total collapse of a structure. Unlike progressive collapse, explosive demolition is a method of inducing the total collapse of structure by removing all or portion of structural members. In explosive demolition the partial collapse of the structural members can be controlled at appropriate time intervals by blasting, to induce the progressive collapse of the structure and control the collapse behavior. In this study, a nonlinear dynamic analysis was carried out in order to apply the progressive collapse process to explosive demolition design of the RC structure. The occurrence of progressive collapse of analytical models was examined according to the number of floors, the removed column height and span length. For models that resisted progressive collapse, progressive collapse resisting capacity was evaluated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.311-318
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• 2010

In this study, the conventional plane tip, double squealer tip, and various groove tip blades were tested in a linear cascade in order to measure the effect of the tip shapes on tip surface heat transfer coefficient distributions. Detailed heat transfer coefficient distributions were measured using a hue-detection based transient liquid crystals technique. Two tip gap clearances of 1.5% and 2.3% of blade span were investigated and the Reynolds number based on cascade exit velocity and chord length was $2.48{\times}10^5$. Results showed that the overall heat transfer coefficients on the tip surface with various grooved tips were lower than those with plane tip blade. The overall heat transfer coefficient on grooved along suction side tip was lower than that on the squealer tip.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.6
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• pp.467-474
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• 2012

UAVs for reconnaissance and intelligence operations require long endurance capability, which demands high efficiency of the propulsion system. The distributed propulsion system(DPS) generates the thrust by replacing a large propulsion system with a number of small propulsion systems. A DPS distributed along the wing span can produce gains in propulsion efficiency by reducing ejection velocity. Also, the ingestion of boundary layers through the distributed DPS inlet and ejecting flow from the outlet can improve the lift to drag ratio of the vehicle. This study investigates the effects of locations and size of the inlet and outlet of the DPS on the blended-wing-body design based on Eppler 337 airfoil, with a CFD tool. The fans in the DPS are modeled as actuator disks for computational efficiency. The best location and aspect ratio of the inlet and outlet are found from lift-to-drag ratio and pitching moment considerations.

• Journal of Aerospace System Engineering
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• v.11 no.4
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• pp.36-43
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• 2017

Blade design optimization of QTP-UAV prop-rotor was conducted using ModelCenter(R). Performance efficiency of the blade in hover and forward flight were adopted as the multi-objective function. Required power and pitch link force applied to constraint in each flight mode and limited lower than the value of the baseline blade. Design variables of root chord length of the blade, taper ratio, twist slope, twist angle at 0.5R of the blade, anhedral angle, parabolic coefficient of a tip shape and location of airfoil were used to generate the blade planform. CAMRAD-II, the comprehensive analysis program of rotorcraft, was used for performance analysis of prop-rotor blade in design process. Performance of the optimized blade improved 1.6% of figure of merit in hover and 13.6% of propulsive efficiency in forward flight. Pitch link force also reduced approximately 30% less than that of the baseline blade.

• Journal of agriculture & life science
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• v.50 no.1
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• pp.273-281
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• 2016

In this study, after carrying out a bending test that targeted the frames of plastic film greenhouse, the load-displacement relationship was analyzed to be used as basic data to develop greenhouse construction and maintenance guidelines. As a result, regardless of the shapes of the specimen, the yield and the maximum load increased as the size of the specimen increased. The displacement also showed the same pattern. A steel pipe showed lower yield and maximum load than a square pipe, and the displacement was large. In the steel pipe case, the displacement under the yield and maximum load was in the range of approximately 1.42-4.20mm and 5.80-24.13mm, respectively. In the square pipe case, the displacement under the yield and maximum load was in the range of approximately 1.62-3.00mm and 3.13-8.01mm, respectively. Further, a large difference was observed between the result of this test and the values calculated by a conventionally provided standard. In particular, not much difference was found from the result of this test in the case of a purlin member from the values provided by previous researches. However, a large difference was observed in the column or main rafter members. Furthermore, when a wide-span and venlo type, which is a glasshouse, was used as a target(h/100 and h/80), the displacement under the yield and maximum load was approximately 28.0mm and 35.0mm, respectively, which showed a large difference compared with the Netherlands standard(14.0mm) of a glasshouse. Further, in the main rafter case, a large difference was observed in the displacement limit according to the width(i.e., span) of the greenhouse where members are used. Therefore, because the displacement limit can vary depending on various factors such as type, form, and size of a greenhouse, we determined that studies or tests that consider these factors should be carried out to reflect them in the construction and maintenance of greenhouses.