• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.3
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• pp.189-196
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• 2018

Propeller performance measurement system for high altitude UAV was designed and applied to the wind tunnel test for 2 propeller models with a diameter around 1 m. Mechanical power of the propeller was directly measured by using the torque sensor installed on the rotating axis. The thrust of whole operation body including the propeller was measured by thrust road cell. The guide rail system was suggested to reduce the weight influence of operation body on the thrust road cell. The influence of each measured variables on the aerodynamic coefficients was studied with the repeatability and uncertainty analysis. This analysis result shows that the accuracies of the road cell and the wind velocity were major factors for the thrust coefficient. Propeller performance with typical RPM was measured with various wind speeds and the test results was summarized by performance coefficients for 5 different RPM.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.381-384
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• 2011

Wave drag reduction due to the repetitive laser induced energy deposition over a flat-nosed cylinder is experimentally conducted in this study. Irradiated laser pulses are focused by a convex lens installed in side of the in-draft wind tunnel of Mach 1.94. The maximum frequency of the energy deposition is limited up to 80. Time-averaged drag force is measured using a low friction piston which was backed by a load cell in a cavity as a controlled pressure. Stagnation pressure history, which is measured at the nose of the model, is synchronized with corresponding sequential schlieren images. With cylinder model, amount of drag reduction is linearly increased with input laser power. The power gain only depends upon the pulse energy. A drag reduction about 21% which corresponds to power gain of energy deposition of approximately 10 was obtained.

• The Journal of the Convergence on Culture Technology
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• v.9 no.4
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• pp.393-399
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• 2023

Upper limb amputees wear an upper limb prosthesis for both aesthetic purposes and functional necessity, and in particular, in the case of amputee with both hands, it is essential to wear a myoelectric prosthetic hand capable of gripping action. The prosthetic hand operated by the EMG signal of the remaining muscles is a public insurance benefit item of the Industrial Accident Compensation Insurance, and test method standards are needed to be developed for the safety of the user and the effectiveness of the product performance. In this study, we developed systems for measuring the gripping force of myoelectric hand prosthesis by a load cell and for durability test of the prosthesis over repeated use with a proximity sensor, and propose a test method standard. Since the international test method standard has not yet been established, it is expected that Korea will be able to play a leading role in this standardization field in the future.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.1A
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• pp.1-10
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• 2012

Along with the development of coasts, islands and mountains, the demand of long-span bridges increases which, in turn, brings forth the construction of cable-supported bridges like suspension and cable-stayed bridges. There are various types of statically indeterminate structures widely applied that supported the main girder with stay cables, main cables, hanger cables with aesthetic structural appearance. As to the cable-supported bridges, the health monitoring of a bridge can be identified by measuring tension force on cable repeatedly. The tension force on cable is measured either by direct measurement of stress of cable using load cell or hydraulic jack, or by vibration method estimating tension force using cable shape and measured dynamic characteristics. In this study, a method to estimate dynamic characteristics of hanger cables by using a digital image processing is suggested. Digital images are acquired by a portable digital camcorder, which is the sensor to remotely measure dynamic responses considering convenient and economical aspects for use. A digital image correlation(DIC) technique is applied for digital image processing, and an image transform function(ITF) to correct the geometric distortion induced from the deformed images is used to estimate subpixel. And, the correction of motion of vision-based measurement system using a fixed object in an image without installing additional sensor can be enhanced the resolution of dynamic responses and modal frequencies of hanger cables.

• Journal of Bio-Environment Control
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• v.18 no.3
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• pp.238-243
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• 2009

To investigate the characteristics of moisture content (MC), moisture distribution and starting point of drainage in a rockwool slab culture, time domain reflectometry (TDR) sensors were used in a drip irrigation system. MC values ($0{\sim}100%$) measured by TDR sensors in a slab were compared to those by loadcells. Seventy two seedlings of paprika (Capsicum annuum L.) were cultured for $5{\sim}6$ months in a green-house and the starting point of irrigation was determined by the average value of three TDR sensors which were inserted diagonally across the slabs under the plants. MCs as a standard for starting point of irrigation by TDR were determined with 40%, 50%, and 60%. Distribution of MCs in a slab measured with five TDR sensors equally spaced from two irrigation points were not much different when the MC in the slab increased from zero to saturation point. The saturated MCs in the slab were presented at $58{\sim}65%$ and the drain was started when the MC became around $50{\sim}55%$. At the saturated MC in the slab, TDR sensors presented 100% but the values from the loadcell showed 90% at the same time. However, measurement errors between two methods for MC remarkably decreased with a decrease in the MC in a slab. Especially when the MC was maintaining below 60%, the errors between TDR and loadcell methods for measuring MC in the rock-wool slab were less than 5%. There were no significant differences in number of fruits and fresh and dry weights of fruits when they were cultured under the different MC conditions with three irrigation regimes (40%, 50%, and 60%). These results indicated that the MC control by TDR sensors in a rock-wool based paprika culture can be suggested as a method to determine the starting point of irrigation for a soilless culture system.