• Wind and Structures
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• v.15 no.6
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• pp.509-529
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• 2012

Traditionally, a quasi steady response concerning the aerodynamic force and moment coefficients acting on a flat plate while 'flying' through the air has been assumed. Such an assumption has enabled the flight paths of windborne debris to be predicted and an indication of its potential damage to be inferred. In order to investigate this assumption in detail, a series of physical and numerical simulations relating to flat plates subject to autorotation has been undertaken. The physical experiments have been carried out using a novel pressure acquisition technique which provides a description of the pressure distribution on a square plate which was allowed to auto-rotate at different speeds by modifying the velocity of the incoming flow. The current work has for the first time, enabled characteristic pressure signals on the surface of an auto-rotating flat plate to be attributed to vortex shedding.

• Wind and Structures
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• v.13 no.2
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• pp.169-189
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• 2010

This paper describes the use of coupled Computational Fluid Dynamics (CFD) and Rigid Body Dynamics (RBD) in modelling the aerodynamic behaviour of wind-borne plate type objects. Unsteady 2D and 3D Reynolds Averaged Navier-Stokes (RANS) CFD models are used to simulate the unsteady and non-uniform flow field surrounding static, forced rotating, auto-rotating and free-flying plates. The auto-rotation phenomenon itself is strongly influenced by vortex shedding, and the realisable k-epsilon turbulence modelling approach is used, with a second order implicit time advancement scheme and equal or higher order advection schemes for the flow variables. Sequentially coupling the CFD code with a RBD solver allows a more detailed modelling of the Fluid-Structure Interaction (FSI) behaviour of the plate and how this influences plate motion. The results are compared against wind tunnel experiments on auto-rotating plates and an existing 3D analytical model.

• Wind and Structures
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• v.35 no.2
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• pp.109-120
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• 2022

The force coefficients of rotating plates in the acceleration stage will vary with rotation rate from 0 to stable rotation rate w₀, which are important for quasi-steady theory of plate-like windborne debris to simulate the trajectory. In this paper, a wind tunnel experiment is carried out to study the effects of geometry and the Reynolds number on the variations of mean force coefficients of rotating plates. The rotational lift coefficients are sensitive to both geometry effect and Reynolds number effect, while the rotational drag and moment coefficients are only sensitive to geometry effect. In addition, new empirical formulas for the rotational lift coefficient and moment coefficients are proposed. Its accuracy is verified by comparing the predicted results with existing test data. Based on the experimental data of rotating plates, a new rotational force model for quasi-steady theory, which can be applied to a wider scope, is proposed to calculate the trajectory of plate-like windborne debris. The results show that the new model provides a better match with the tested trajectories than previous quasi-steady theories.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.11
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• pp.978-983
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• 2015

A study on the speed limit and sizing of auxiliary fixed-wing of compound gyroplane was performed. The performance of the plane that uses the same rotor system and power of BO-105 helicopter was compared with that of BO-105 helicopter. The wing area which is used to compensate in lift, was calculated considering the aerodynamic characteristics and lift sharing ratio of the rotor. Achievable flight speeds were observed for two types of fuselage; BO-105 and streamlined bodies. The study showed that the autorotating rotor can share 1/2 of lift at high speed and the parasite power of compound gyroplane having streamlined body and small wing can be minimized, accordingly it can fly faster than helicopter with airspeed more than twice.

• Science of Emotion and Sensibility
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• v.18 no.1
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• pp.27-38
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• 2015

Vestibulo-ocular reflex (VOR) is a compensatory response of the extraocular muscles generated by vestibular signals to stabilize images on the retina during head/body movements. It has been reported that mismatches between retinal and vestibular information, which cause motion sickness or cybersickness, modify VOR. To investigate the characteristic changes of VOR in subjects experiencing cybersickness, we developed a low-cost, multi-purpose VOR measurement system using LabVIEW and Arduino. To test the applicability of the system, we performed two experiments. In Experiment 1, horizontal and vertical VORs of four participants were measured using a vestibular autorotation task. In Experiment 2, eight participants were exposed to a virtual navigation to measure changes of VORs as an index of cybersickness. We observed significantly greater head rotations and eye movements while the participants were exposed to the virtual navigation than to a static image. The results suggest that the present system can help understand the psychophysiological mechanisms of cybersickness symptoms.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.13 no.1
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• pp.44-52
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• 1991

Internal measurement technique has been commonly and classically used to guide down-fractured maxilla by Le Fort I osteotomy into its new position during intraoperative procedure for correlating preoperative model works with surgery. However, It has been challenged now by several authors due to some problems as its inaccuracy in three-dimensional changes at surgery, difficulty to measure during surgery and impossibility of rechecking at the end of surgery etc. The purpose of this study was to evaluate the accuracy of maxillary movement by external measuring technique and to determine its accuracy between the prediction tracing and a new maxillary position. The results indicate that the external measuring technique was predictable in the vertical, horizontal and transverse change of the maxilla as its prediction, however, it has a tendency to shift the maxilla more anterior and inferior in overall direction than prediction. Post-operative canting difference were mimic, however Ehange of the maxillary dental midline was large and had a right-shifting tendency.1 The precise methods to keep maxillary dental midline as same as prediction and the avoidance of uneven force applied to the mandible for autorotation should be necessary during surgery in use of external measurement technique.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.8
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• pp.573-581
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• 2022

This paper deals with the development of CanSat system, which ejects two maple seed-type autorotating science payloads and collects weather information. The CanSat consists of two autorotating science payloads and a container. The container is equipped with devices for launching science payloads and communication with the ground station, and launches science payloads one by one at different designated altitudes. The science payload consists of a space for loading and a large wing, and rotates to generate lift for slowing down the fall speed. Specifically, after being ejected, it descends at a speed of 20 m/s or less, measures the rotation rate, atmospheric pressure, and temperature, and transmits the measured value to the container at a rate of once per second. The communication system is a master-slave structure, and the science payload transmits all data to the master container, which aggregates both the received data and its own data, and transmits it to the ground station. All telemetry can be checked in real time using the ground station software developed in-house. A simulation was performed in the simulation environment, and the performance of the CanSat system that satisfies the mission requirements was confirmed.