• Wind and Structures
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• v.37 no.4
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• pp.315-329
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• 2023

We investigated the wind characteristics in the near-surface layer during the landfall of Typhoon Mujigae (2015) based on observations from wind towers in the coastal areas of Guandong province. Typhoon Mujigae made landfall in this region from 01:00 UTC to 10:00 UTC on October 4, 2015. In the region influenced by the eyewall of the tropical cyclone, the horizontal wind speed was characterized by a double peak, the wind direction changed by >180°, the vertical wind speed increased by three to four times, and the angle of attack increased significantly to a maximum of 7°, exceeding the recommended values in current design criteria. The vertical wind profile may not conform to a power law distribution in the near-surface layer in the region impacted by the eyewall and spiral rainband. The gust factors were relatively dispersed when the horizontal wind speed was small and tended to a smaller value and became more stable with an increase in the horizontal wind speed. The variation in the gust factors was the combined result of the height, wind direction, and circulation systems of the tropical cyclone. The turbulence intensity and the downwind turbulence energy spectrum both increased notably in the eyewall and spiral rainband and no longer satisfied the assumption of isotropy in the inertial subrange and the -5/3 law. This result was more significant in the eyewall area than in the spiral rainband. These results provide a reference for forecasting tropical cyclones, wind-resistant design, and hazard prevention in coastal areas of China to reduce the damage caused by high winds induced by tropical cyclones.

• KIPS Transactions on Software and Data Engineering
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• v.8 no.12
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• pp.491-498
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• 2019

Digital twin is a technology that virtualizes physical objects of the real world on a computer. It is used by collecting sensor data through IoT, and using the collected data to connect physical objects and virtual objects in both directions. It has an advantage of minimizing risk by tuning an operation of virtual model through simulation and responding to varying environment by exploiting experiments in advance. Recently, artificial intelligence and machine learning technologies have been attracting attention, so that tendency to virtualize a behavior of physical objects, observe virtual models, and apply various scenarios is increasing. In particular, recognition of each robot's motion is needed to build digital twin for co-robot which is a heart of industry 4.0 factory automation. Compared with modeling based research for recognizing motion of co-robot, there are few attempts to predict motion based on sensor data. Therefore, in this paper, an experimental environment for collecting current and inertia data in co-robot to detect the motion of the robot is built, and a motion prediction model based on the collected sensor data is proposed. The proposed method classifies the co-robot's motion commands into 9 types based on joint position and uses current and inertial sensor values to predict them by accumulated learning. The data used for accumulating learning is the sensor values that are collected when the co-robot operates with margin in input parameters of the motion commands. Through this, the model is constructed to predict not only the nine movements along the same path but also the movements along the similar path. As a result of learning using SVM, the accuracy, precision, and recall factors of the model were evaluated as 97% on average.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.4
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• pp.227-234
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• 2009

Using a finite volume ocean circulation model based on an unstructured grid (FVCOM), we studied the structure of a fresh water bulge that influences on the Region Of Freshwater Influence. Fresh water discharged a river forms a coastal boundary current to the righthand side and a cyclonically circulation freshwater bulge that grows with time. In the middle of the bulge, vertical motions bring fresh water to the bottom. When tidal motions are included, the bulge disappears while the boundary currents becomes wider. Through a simple comparison of areas occupied low salinity water we quantified vertical and horizontal mixing due to the tide and showed that the tidal motion enhances the vertical mixing. During the first few tidal cycles right after the onset of the river discharge, due to tidal excursion the horizontal mixing becomes stronger. The vertical mixing by the tide mixes the fresh water After a certain time the water around the river mouth is well mixed and the horizontal excursion of the fresh water near the river mouth does not have much effect on the horizontal mixing. When there is no tidal motion horizontal mixing is mainly by the inertial instability at the surface and the horizontal mixing becomes stronger over time.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.983-989
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• 2013

The current research reviewed the design conditions that would maximize the efficiency of the hybrid collector that combines in one unit "cyclone-inertial impaction-bag filter". The computational analysis for the shape of cyclone entry predicts that a design that installs the guide vane at the entry of the tangential type cyclone brings a high-rpm and powerful vortex, very effective in promoting the deflection of coarse particles from the streamline at the cyclone. As the lower part of the cyclone is venturi-shaped, however, a strong flow downward of 4 to 5 m/sec persists through the lower part of the hopper, revealing the likely reentrainment of collected dust. And the removal of the venturi at the lower part of the cyclone would solve the problem of the reentrainment of collected dust. The acceleration of the flow velocity through the adjustment of the gap of the collision baffle would increase the effect of collision, but as the interference with the dust separation is expected, the original design should be kept for the baffle.

• Current Research on Agriculture and Life Sciences
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• v.31 no.2
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• pp.131-138
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• 2013

The precision aerial application of small farms, such as paddy, upland and orchard fields using agricultural unmanned helicopters became a new paradigm. The objective of this study was to evaluate the performance of a GPS module and algorithm, controlling drift of agricultural helicopter by the crosswind and maintaining the position for emergency landing. Purpose of the drift control, of which an algorithm works while hovering is related with the emergency sequence that coping with abnormal conditions of rotorcraft system. However, the inertial attitude control cannot detect a drifting motion of fuselage moving at the constant velocity, thus the crosswind takes the helicopter away from the landing position. Performance of the drift control module, based on the GPS that a hovering position did not deviate within 5m in diameter, were tested and evaluated. Initially, the reaction against a disturbing gust wind was sensitive, soon the helicopter maintained its locking position and azimuth within 5m in diameter. It was, however, difficult for the helicopter to recognize the swaying and nodding, the some deviation was expected due to the discrepancy characteristics of the GPS signal. The performance of the drift control proved the effectiveness of the module to maintain the position against an unintended drift during the emergency landing or hovering.