• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.3
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• pp.325-331
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• 2010

Three-cup anemometers are popular devices for measuring wind speeds in automated weather stations, environmental monitoring systems, and wind turbines. Cup anemometers usually suffer from lack of long-term stability owing to the wear of the bearing systems that support the rotational parts. The bearing systems are susceptible to external pollutants, vibrations, and gusts. Therefore, these anemometers have to be calibrated regularly to maintain the desired characteristics for measuring wind speed. In the present study, a new in-situ calibration system to help reduce cost and save time by calibrating the cup anemometers at the installation site is proposed. A portable in-situ calibrator was fabricated. After the characteristics of this calibrator were verified, it was used to calibrate cup anemometers. Some of the calibration results were compared with the data obtained by wind tunnel testing.

• Journal of the Korean Society of Marine Environment & Safety
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• v.16 no.1
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• pp.107-113
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• 2010

The criteria of tugboat requirement in domestic trading ports have been determined by the administrator of regional maritime affairs and port office on the basis of the regulations for the tugboat operations and management. But, there is a little confusion that the criteria of tugboat requirement and method for calculation of them are different from port to port and total power calculated on the basis of power per tugboat requirements by the number of tugs is not in accordance with total required power for the use of tug in several ports. The comparison of tugboat requirements among domestic major ports showed that it should be necessary for the criteria to be made in unified form. Because the current criteria are only on the basis q the ordinary condition with wind velocity under 10m/s, the criteria on the condition of the wind velocity over 10m/s are suggested to be necessary for the precautions against a disaster such as unexpected strong winds or typhoon.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2006.06b
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• pp.331-336
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• 2006

The rail clamp is the device to prevent that a crane slips along rails due to the wind blast as well as to locate the crane in the set position for loading and unloading containers. The wedge type rail clamp should be designed to consider the structural instability and the durability because it compresses both rail side with large clamping force by the wedge working as the wind speed increases. In this research, there are two methods which are design of experiment and variation technology in used commercial software and shape optimization was performed. The optimum results obtained by the two methods are compared and examined.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.6
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• pp.465-472
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• 2021

Prior to the actual flight test of the separation-reintegration situation of fixed-wing mother and child UAVs in the air, it is necessary to verify the flight control system of child UAV through simulations. In this paper, we build a simulation environment for the development of a child UAV flight control system in a lab environment based on the wake turbulence of X-Plane. To this end, the aerodynamics analysis of child UAV was performed, and Simulink was used to simulate aircraft, and X-Plane was utilized to implement visualization, wind, gusts, and mother UAV movements. The simulation environment built by performing simulated proximity flights was verified by applying the guidance and control algorithm to the child UAV model within Simulink. Furthermore, the flight results confirm the area in which the child UAV can safely fly from the rear of the mother UAV.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.10
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• pp.1345-1352
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• 2021

Most of weather radar systems are used to monitor the whole weather situation for the very wide and medium-to-long range area. However, as the likelihood of occurrence of the local weather hazards is increased in recent days, it is very important to detect these wether phenomena with a local weather radar. For this purpose, it is necessary to detect the fast varying low altitude weather conditions and the effect of the ground surface clutter is more evident. Therefore, in this paper, the newly suggested method is explained and analyzed for detection of weather hazards such as the gust and wind shear using the fluctuation of wind velocities and the gradient of wind velocities among range cells. It is shown that the suggested method can be used efficiently in the future for faster detection of weather change through the simple algorithm implementation and also the effect of the ground clutter can be minimized in the detection procedure.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.11
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• pp.1492-1499
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• 2020

A weather radar system generally shows the weather phenomena related with rainfall and wind velocity. These systems are usually very helpful to monitor the relatively high altitude weather situation for the wide and long range area. However, since the weather hazards due to the strong hail and heavy rainfall occurring locally are observed frequently in recent days, it is important to detect these wether phenomena. For this purpose, it is necessary to detect the fast varying low altitude weather conditions. In this environment, the effect of surface clutter is more evident and the antenna dwell time is much shorter. Therefore, the conventional Doppler spectrum estimation method may cause serious problems. In this paper, the AR(autoregressive) Doppler spectrum estimation methods were applied to solve these problems and the results were analyzed. Applied methods show that improved Doppler spectra can be obtained comparing with the conventional FFT(Fast Fourier Transform) method.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.3
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• pp.173-180
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• 2022

The operation and transportation environment for an unmanned aerial vehicle will be completely different from those for the conventional air and ground transportation. The requirement for a traffic management system for its safe operation has been emerging. Accordingly, investigation is being conducted to analyze the danger that unmanned aerial vehicle may encounter during the flight and to provide the countermeasure by the simulation. When the drones operate in an urban environment, they may be affected by the wind around the building. Thus it is essential to predict the influence of the gust and analyze the resulting risk. In this paper, a method for evaluating the safety for a flight mission under the gust is suggested. By using the precise 6-degree-of-freedom flight simulation that is capable of simulating the gust condition, possible deviation from the pre-planned flight path in terms of the attitude orientation will be predicted. A method of quantifying the probability of the flight mission failure will also be presented.

• New & Renewable Energy
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• v.17 no.4
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• pp.1-8
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• 2021

To determine the wind turbine class in the offshore of the Korean Peninsula, the reference wind speed for a 50-y return period at the hub height of a wind turbine was estimated using the reanalysis data sets. The most recent reanalysis data, ERA5, showed the highest correlation coefficient (R) of 0.82 with the wind speed measured by the Southwest offshore meteorological tower. However, most of the reanaysis data sets except CFSR underestimated the annual maximum wind speed. The gust factor of converting the 1 h-average into the 10 min-average wind speed was 1.03, which is the same as the WMO reference, using several meteorological towers and lidar measurements. Because the period, frequency, and path of typhoons invading the Korean Peninsula has been changing owing to the climate effect, significant differences occurred in the estimation of the extreme wind speed. Depending on the past data period and length, the extreme wind speed differed by more than 30% and the extreme wind speed decreased as the data period became longer. Finally, a reference wind speed map around the Korean Peninsula was drawn using the data of the last 10 years at the general hub-height of 100 m above the sea level.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.8
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• pp.1180-1187
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• 2022

As the likelihood of occurrence of the localized microbursts or severe flooding is increased due to the unusual weather changes, it is the very urgent problem to detect these weather hazards with a local weather radar. For a local weather radar of this purpose, it is essential to detect the low altitude and the fast varying weather conditions. Therefore, the very fast update of the weather information and the efficient clutter removal is very important. To achieve this goal, the appropriate method should be applied which does not need the mechanical elevation scanning and has the capability of the efficient clutter removal. Therefore, in this paper, the usefulness of the implementation of elevational filter banks with the spatial FFT algorithm was analyzed and investigated using a simple array antenna. It is shown that the suggested method can be used for both the minimization of the ground clutter and the fast update of weather information.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.7
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• pp.1342-1354
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• 2016

As Internet, and hardware technology are in rapid process, using rate and penetration rate of Internet of Things are increasing. Internet of Things is the physical objects with network which embedded with electronics, software, sensors, and network. Smart Home-kit to operate refrigerators, washing machines, light bulbs, and such internet of things by a smartphone has been realized. However, it is difficult to use a good quality of software based on IoT. It is because that the study related to quality evaluation of software based on IoT is deficient compared with increase amount of IoT devices. Software based on IoT includes mobility, transportability, real time accessibility and hardware characteristics. Therefore, it is necessary to have differentiated quality standards and quality model. Software quality evaluation model for IoT is proposed to satisfy these needs. Evaluation model is mapped by characteristics of IoT software based on ISO/IEC 25000's quality characteristics. Scenario based studies were applied to quality model for verification.