• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.8
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• pp.1241-1246
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• 2013

Currently, The general transportation system arranges the armature on the full length of transportation lines. However, when this method is applied to the long distance transportation system, it causes an increase of material cost and manufacturing time. Thus, in order to resolve this problem, discontinuous arrangement method of the armature has been proposed. However, in the method of using stationary discontinuous armatures, mover can stop in the freewheeling section which is non-installations section when disturbance is generated and the mover can not be moved because armature control is impossible. Thus, the distance determination of armature is very important. Also, when the armature is arranged discontinuously the edge always exists due to the structure. Due to this edge, the cogging force is greatly generated during the entry and ejection of the mover to the armature. This cogging force causes thrust force ripple generating noise, vibration and decline of performance, it must be reduced. Therefore, in this paper, we examined the end edge cogging force generated by the stationary discontinuous armatures through 2-D numerical analysis using finite element method (FEM) and we figured out distance of armature for end edge cogging force minimization.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.7
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• pp.37-42
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• 2004

In order to monitor the impact locations in smart structures, multipoint ultrasonic sensors are to be employed. In this study, a multiplexing demodulator with wide dynamic range was proposed to detect the impact locations using FBG sensors, and a stabilization controlling system was also developed for the maintenance of maximum sensitivity of sensors. Two FBG sensors were attached on the bottom side of the aluminum beam specimen and low velocity impact tests were performed to detect the one-dimensional impact locations. As a result, multiplexed in-line FBG sensors could detect the moment of impact precisely, and found the impact locations with the average location error below 0.58mm.

• Journal of Navigation and Port Research
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• v.31 no.10
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• pp.845-852
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• 2007

An OWC-type Wave Energy Conversion passes through 3 steps energy conversion process. This paper deal with the impulse turbine with staggered blade to improved performance by numerical analysis using commercial CFD code, FLUENT Maximum value of axial airflow velocity during exhalation is higher than that during inhalation This paper deal with special-type of Impulse Turbine so-called "Staggered Blade" for more efficiency to making air flow direct to on pressure side. Also, this paper has proposed special-type turbine with self-pitched blade more efficient.

• Journal of Aerospace System Engineering
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• v.14 no.3
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• pp.69-77
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• 2020

Airframe structure development of the 35 kg class 'Disaster and Public Safety Multicopter' UAV is described in this paper. To reduce the airframe weight, T-700 grade CFRP composite material was used, and the fuselage was designed with the semi-monocoque structure and plate installed with the control and communication devices designed in a sandwich structure. The specimen tests for the laminated plate and pipe were conducted to verify the strength and stiffness of the designed parts. The stacking sequence of composite materials was determined by the static strength and vibration analysis, and landing gear strut was designed by the nonlinear analysis with decent speed and ground clearance requirements. The static strength test was performed to evaluate the structural integrity and to verify the landing gear behavior.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.4
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• pp.129-134
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• 2021

A power tool is a tool used to manufacture and process various structures using a motor that is a power source. Using a motor that uses electricity as a power source, a reduction device, power transmission and conversion device functions are built-in to make the tool rotate, reciprocate, and vibrate. It is a work tool designed to assist the user's movement skills. In the case of Korea, the power tool industry has a short history and is lagging behind advanced countries such as Germany, the United States, and Japan in terms of technology level, market share, and recognition. In addition, electric drivers used in Korea are foreign products from the US and European countries, and the domestic market also prefers 100% foreign companies, and multinational companies are investing a lot in the domestic market. Therefore, technological development must follow in order to develop domestic technology and secure a consistently high market share. The purpose of this thesis is to design a motor driver with high output performance of motor performance, miniaturization, and high speed in accordance with the basic performance requirements of power tools, and finally research developments that can be applied to industrial and medical applications.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.2
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• pp.142-149
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• 2004

PMLSM(Permanent Magnet linear Synchronous Motor) has widely applied to industrial automations, machine tools and semiconductor equipments due to the merit on the reduction of noise, vibration and the superior dynamic characteristics in comparison to the conventional method, which uses mechanical transfer equipments. Especially, in the case of applying to Z-axis operation structure, control system needs the method of an initial angle setting and the improvement of up/down operation characteristics. This paper proposes an initial angle setting algorithm and a variable gain schedule using real speed and moving direction to improve up/down operation characteristics. The effectiveness of proposed algorithms Is demonstrated by comparing to a conventional gain system via 4-point absolute positions profile with each velocity, acceleration and deceleration.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.3
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• pp.48-54
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• 2015

In this study, we propose an innovative lateral force distribution building system between tall buildings by utilizing the difference of moment of inertia, resulting the reduction of lateral displacement and the lateral forces in terms of an alternative for the dense human and increased cost of lands in highly integrated city area. A successive collapse prevention means by providing additional bearing plate between connections is proposed. In addition to that, a more economical vibration reduction is expected due to the suggested tuned mass damper on the surface of spacial structure. In the considered verification examples, reduced drifts at the top location of the building systems are validated against static wind pressure loads and static earthquake loads. The suggested hybrid building system will improve the safety and reliability of the new or existing building system in terms of more than 30% reduced drift and vibration through the development of convergence of tall buildings and spatial structures.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.523-526
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• 2010

In this study, we demonstrated a development of a non-releasing bolt which is fastened with a target by expanding a certain area of a bolt body. Being released a bolt causes many problems in a field where bolts are used. In order to figure out the problems, currently, many types of a non-releasing bolt have been developed and have been using. Unfortunately, however, they do not perfectly function not to be released. Therefore, the structures builded with bolts have many problems caused by external stress such as vibration and shock, and thus the bolts have to be regularly tightened for maintenance. With the important factors of internal geometry, the amount of explosive, and the firing pin, we developed a technology which could control the expansion degree of a certain area on a bolt body. Based on the results, it was founded that the performance of non-releasing was linearly proportional to the degree of body expansion.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.2
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• pp.120-126
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• 2019

Recently, there is an increasing need for highly precise processing with the rapid development of precision machinery, electrical and electronics, and semiconductor industries. Cutting machine control relies on the operator's sense and experience in tradition, but it has been greatly enhanced by the adoption of CNC(Computerized Numeric Controller). In addition, cutting dynamics technology has been paid attention to reflect the operating state of machine in real time. This paper presents a method to detect and stabilize tool vibration by attaching an acoustic sensor to a CNC machine. The sensed acoustic data is synchronized with the tool position and the abnormal vibration frequency is separated from the collected acoustic frequency, then analyzed to detect the tool vibration. Also the reliability the tool vibration detection and stabilization is improved by applying the cutting dynamic method. The proposed method is analyzed and evaluated in terms of the surface roughness.

• Journal of KIISE:Software and Applications
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• v.34 no.10
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• pp.900-909
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• 2007

This paper describes an experiment on the evaluation of human sensibility by monitoring responses to changes In the frequency and amplitude of a tactile display system. Preliminary tasks were performed to obtain effective adjectives concerning texture perception. The number of collected adjectives was originally 33. This number of adjectives was reduced to 14 by a suitability survey that asked whether an adjective is suitable for expressing a texture feeling. Finally after performing a semantic similarity evaluation, the number of adjectives was further reduced to ten and these ten were used in the main experiment. In the main experiment, selected sandpaper types and 15 selected combinations of frequencies and amplitudes of a tactile display were utilized to quantitatively evaluate the ten adjectives using a bipolar seven-point scale. The data show that a relationship exists between the independent variables(frequency, amplitude, and grit site) and the dependent variable(perceived texture). That is, the change of frequency and amplitude is directly related to perceived roughness or essential elements of human tactile sensitivity found in the preliminary experiment.