• Journal of Astronomy and Space Sciences
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• v.29 no.2
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• pp.221-232
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• 2012

We analyzed the manufacturing procedure, specifications, repair history, and details of celestial movements of the water-hammering type $Honsang$ (celestial globe). Results from our study on the remaining $Honsangs$ in China and Japan and on the reconstruction models in Korea were applied to our conceptual design of the water-hammering type $Honsang$. A $Honui$ (armillary sphere) and $Honsang$ using the water-hammering method were manufactured in $Joseon$ in 1435 (the 17th year of King $Sejong$). $Jang$ $Yeong-Sil$ developed the $Honsang$ system based on the water-operation method of $Shui$ $y{\ddot{u}}n$ $i$ $hsiang$ $t'ai$ in China. Water-operation means driving water wheels using a water flow. The most important factor in this type of operation is the precision of the water clock and the control of the water wheel movement. The water-hammering type $Honsang$ in $Joseon$ probably adopted the $Cheonhyeong$ (天衡; oriental escapement device) system of $Shui$ $y{\ddot{u}}n$ $i$ $hsiang$ $t'ai$ in China and the overflow mechanism of $Jagyeongnu$ (striking clepsydra) in $Joseon$, etc. In addition to the $Cheonryun$ system, more gear instruments were needed to stage the rotation of the $Honsang$ globe and the sun's movement. In this study, the water-hammering mechanism is analyzed in the structure of a water clock, a water wheel, the $Cheonhyeong$ system, and the $Giryun$ system, as an organically working operation mechanism. We expect that this study will serve as an essential basis for studies on $Heumgyeonggaknu$, the water-operating astronomical clock, and other astronomical clocks in the middle and latter parts of the $Joseon$ dynasty.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.12C
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• pp.174-180
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• 2001

The technology to efficiently manage computer communication network is in need as the computer communication network becomes more complicated and users want services more diversified. This has brought industries, research institutes and standadization organizations to consider an effective network management protocol. CMIP and the SNMP have considerable differences in structure and capacity Therefore, it is essential to have enables differences between network management protocol to gear for the two communication management system which is the most widely used and will be continuously used. In this thesis we suggest an interworking function Integrated Network Management for the Design of Proxy. According to the suggest algorithm, by using scoping, it stores the management information, so that it may pass the related information at the inner cash efficiently. Therefore, we can not only reduce some unnecessary management operation considerably but also bring some efficiency of saving the total management system response time.

• Design & Manufacturing
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• v.11 no.2
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• pp.29-36
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• 2017

In this study, the non-contact type bicycle generator system considering the recharge is developed to use the eco-friendly energy source when the bicycle is operating. The following three main factors are considered in this study. One of factors is that the intensity of the rotating magnet is in the range of 2,700~4,300 [Gause]. The next factor is that the separation distance of rotating magnet and bicycle rim is in the range of 1.5-3.0 mm. The last factor is that the pedaling speed is in the range of 55 RPM [Wheel speed 5.6Km]~150 RPM [Wheel speed 15.25Km] consirering with the 5 staged gear transmission. The obtained results are as followed. (1) The generator output voltage gradually increases from 3V to 10V with the pedaling speed increases, at the separation distance is less than 2.5 mm and the operating voltage of the LED lamp is generated at a pedaling speed of 60 RPM or more. (2) The output current of the generator increases from 20mA to 40mA with the pedaling speed increases, at a separation distance is less than 2.0 mm and the operating current of the LED lamp is generated at a pedaling speed of 60 RPM or more. (3) When the separation distance was 3.0 mm, the output voltage and current are significantly lower than those of the bicycle LED lamp is generated. (4) The charging time is expected to be 12.24 ~ 17.65 hours when the magnitude of the magnet is 3,400[Gauss] at a pedaling speed of 55 RPM or more. (5) As a result of this study, it is thought that the non-contact type bicycle generator system considering the recharge can replace the conventional friction power generation system.

• Journal of Broadcast Engineering
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• v.27 no.6
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• pp.885-896
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• 2022

Motor failure in manufacturing plays an important role in future A/S and reliability. Motor failure is detected by measuring sound, current, and vibration. For the data used in this paper, the sound of the car's side mirror motor gear box was used. Motor sound consists of three classes. Sound data is input to the network model through a conversion process through MelSpectrogram. In this paper, various methods were applied, such as data augmentation to improve the performance of classifying fault motors and various methods according to class imbalance were applied resampling, reweighting adjustment, change of loss function and representation learning and classification into two stages. In addition, the curriculum learning method and self-space learning method were compared through a total of five network models such as Bidirectional LSTM Attention, Convolutional Recurrent Neural Network, Multi-Head Attention, Bidirectional Temporal Convolution Network, and Convolution Neural Network, and the optimal configuration was found for motor sound classification.

• Tribology and Lubricants
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• v.40 no.1
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• pp.8-16
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• 2024

This study conducts numerical modeling and eigen-analysis of a rod-fastened rotor, which is mainly used in aircraft gas turbine engines in which multiple disks are in contact through curvic coupling. Nayak's theory is adopted to calculate surface parameters measured from the tooth profile of the curvic coupling gear. Surface parameters are important design parameters for predicting the stiffness between contact surfaces. Based on the calculated surface parameters, elastoplastic contact analysis is performed according to the interference between two surfaces based on the Greenwood-Williamson model. The equivalent bending stiffness is predicted based on the shape and elastoplastic contact stiffness of the curvic coupling. An equation of motion of the rod-fastened rotor, including the bending stiffness of the curvic coupling, is developed. Methods for applying the bending stiffness of a curvic coupling to the equation of motion and for modeling the equation of motion of a rotor that includes both inner and outer rotors are introduced. Rotordynamic analysis is performed through one-dimensional finite element analysis, and each element is modeled based on Timoshenko beam theory. Changes in bending stiffness and the resultant critical speed change in accordance with the rod fastening force are predicted, and the corresponding mode shapes are analyzed.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.9 no.3
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• pp.257-265
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• 2016

In this study, an optimal design for motor-driven track type traveling system applied into high clearance working machineries in orchard is proposed. Tractive performance and hill climbing ability were predicted and evaluated for the optimal motor traveling system by taking into account of soil characteristics in orchard utilizing the high clearance working machineries. Design criteria for tractive performance were based on the traction force calculated from tractive effort subtracted by motion resistance, while hill climbing ability had its design criteria that fulfill the climbing 20% slope ground at a speed of 3km/h. Based on the evaluation results of traction and climbing ability, two DC48V, 4500rpm, 1.6kW AC motors were independently applied to both left and right side of orbits; each motor is designed to transmit power on driving sprocket of track type traveling system via 50:1 reduction gear ratio. The motor-driven track type traveling system developed in the study found to have 396 kgf of tractive force, which is 12.5% higher than climbing resistance at orchard soil having 20% slope ground (352 kgf), demonstrating sufficient tractive performance and hill climbing ability.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.9
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• pp.667-674
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• 2014

A ship's propulsion shafting system is subjected to varying magnitudes of intermittent loadings that pose great risks such as failure. Consequently, the dynamic characteristic of a propulsion shafting system must be designed to withstand the resonance that occurs during operation. This resonance results from hydrodynamic interaction between the propeller and fluid. For ice-class vessels, this interaction takes place between the propeller and ice. Producing load- and resonance-induced stresses, the propeller-ice interaction is the primary source of excitation, making it a major focus in the design requirements of propulsion shafting systems. This paper examines the transient torsional vibration response of the propulsion shafting system of an ice-class research vessel. The propulsion train is composed of an electric motor, flexible coupling, spherical gears, and a propeller configuration. In this paper, the theoretical analysis of transient torsional vibration and propeller-ice interaction loading is first discussed, followed by an explanation of the actual transient torsional vibration measurements. Measurement data for the analysis were compared with an applied estimation factor for the propulsion shafting design torque limit, and they were evaluated using an existing international standard. Addressing the transient torsional vibration of a propulsion shafting system with an electric motor, this paper also illustrates the influence of flexible coupling stiffness design on resulting resonance. Lastly, the paper concludes with a proposal to further study the existence of negative torque on a gear train and its overall effect on propulsion shafting systems.

• Journal of the Korean Solar Energy Society
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• v.30 no.3
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• pp.98-107
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• 2010

This paper introduces step by step procedures for the design, fabrication and operation of a solar tracking system. The system presented in this study consists of motion controllers, motor drives, step-motors, feedback devices and other accessories to support its functional stability. CdS sensors are used to constantly generate feedback signals to the controller, which assures a high-precision solar tracking even under adverse conditions. It enables instant correction if the system goes off track by strong winds causing gear backlash. A parabolic dish concentrator is mounted on the tracking system whose diameter was 30cm. The solar position data, in terms of azimuth and elevation, sunrise and sunset times were compared with those of the Astronomical Applications Department of the U.S. Naval Observatory. The results presented here clearly demonstrate the high-accuracy of the present system in solar tracking, which are applicable to many existing solar systems.

• Journal of Applied Reliability
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• v.14 no.4
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• pp.213-219
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• 2014

Wind turbine, which is attracting part of the renewable energy and is researching continuously, is going to be large size for high efficiency. There is a yaw system rotating the nacelle, weighted about 600 tons, to be perpendicular with the wind direction blowing in the large wind turbine. The wind turbine is focusing on the reliability improvement because working environment effect is bigger than any other points and specially, the reliability improvement of the yaw drive is required by the customer because it is the key component of the wind turbine. Because of this, the establishment of criteria for yaw drive is required because yaw drive system is the part of the wind turbine closely related with ensuring the reliability. So, this study did the failure analysis of the yaw drive system, which is consisted with 10 sets of yaw drives through researching and analyzing the site conditions. Also this study designed the life test method based on the failure analysis and working condition of the yaw drive. To design the accelerated life test of the yaw drive, this study reviewed the torque, lubrication condition, and frequency of use and etc. Finally, this selected the torque as the acceleration factor which is affected mainly to the system and also, the test equipment was developed based on the requirement of the life and performance test.

• Aerospace Engineering and Technology
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• v.9 no.2
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• pp.22-30
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• 2010

KARI had integrated and tested GEO satellite in cooperation with Astrium Inc., France. In the middle of integration and test, It was necessary to check GEO satellite SA(solar array) status and require electrical interface verification with bus. SA of GEO satellite have different mechanical characteristics in comparison with those of LEO satellite which was tested in KARI. LEO SA has been deployed by simple mechanical hinge system but GEO SA has been done by more complicated method. so in this paper, we designed the test configuration and analyzed the test result of solar array electrical integration of GEO satellite.