• Journal of Advanced Marine Engineering and Technology
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• v.35 no.6
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• pp.786-795
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• 2011

This paper described the characteristic of vibration in wind turbine system including gearbox housing, gear drive, blade, generator. Especially, in planetary gear set, planet gears are supported by flexible pin. So, in planet gear, to consider not only torsional movement but also lateral movement. And include housing movement, because wind turbine system is supported by mount. To find out the characteristic of vibration, take the excitation source and study campbell diagram in operating range. Results of campbell diagram, resonances are occurred at 81.2HZ, 104.7Hz by 2nd tooth passing frequency. And resonance are also occurred at 264.5HZ, 377Hz, 424.6Hz by 3th tooth passing frequency. From the result, take vibration reduced measures.

• Journal of Advanced Navigation Technology
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• v.24 no.5
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• pp.444-449
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• 2020

I proposed small ambulatory robot actuators using piezoelectric benders. In order to make the motion of the biomimetic robot legs similar to the movements of the cockroaches or similar insects, two pairs of legs in the diagonal direction in the four leg structures are required to make the same movement. And elliptical displacement is realized by taking into account horizontal and vertical displacement of multimode oscillations and driving them by electrical signals with differences step by step, for example of 90° the T-shaped robot actuator showed wide range of speed (From 2 mm/sec. up to 266 mm/sec.) and ability of transportation (up to 10 g with 50 mm/s). Locomotive performance of the robot was competitive to the preceding robots, and moreover, the modular type actuators of a segmented myriapods robot could be added and removed for different tasks or performances.

• Journal of the Korea Convergence Society
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• v.9 no.5
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• pp.145-150
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• 2018

In the machine tool spindle, various tasks ranging from roughing to finishing must be possible, and the functions of constant speed movement or rotation positioning must be performed. Therefore, there are many variables to be considered in the spindle design. The Swiss Turn Type spindle automatic lathe is a good machine tool for working pins with thinner shafts than a fixed automatic lathe. The Swiss Turn Type spindle is mainly used for precision machining of small products, so the machining precision should be high. The maximum outer diameter limit shall be Ø32 and the inner diameter limit shall be Ø6. In this study, the static and dynamic characteristics of the SCM440 material used in the spindle type automatic lathe were analyzed by applying it to the Swiss turn type spindle automatic lathe. Numerical analysis was used to obtain optimal design technique with high speed and high accuracy considering the factors affecting the static and dynamic characteristics of the spindle.

• Journal of the Korean Institute of Gas
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• v.20 no.2
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• pp.10-15
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• 2016

This paper is to analyze and study the failure examples of refrigerant gas in automotive air conditioner. The first example, the air conditioner compressor continually operated that the refrigerant was leaked in air conditioner system. By lubrication shortage, the piston was partially sticked on cylinder of air conditioner compressor inner part. This was caused the phenomenon of engine operation trouble by load increasing with engine rpm variation during engine running. The second example, it sought the fact that the air conditioner refrigerant gas was leaked from air conditioner compressor to condenser high pressure pipe toward rear air conditioner checking with the lines of air conditioner. The third example, the refrigerant gas of air conditioner found that was leaked imperceptible from condenser inner by crack that was generated on the fins of air conditioner condenser. Therefore, the air conditioner system that maintain the air conditioner by decreasing the in-car temperature must meticulously manage to not leak the air conditioner refrigerant gas.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.2
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• pp.129-138
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• 2012

In this study, three types of large scale multi-tasking machine tools together with core technologies involved have been developed and introduced; a multi-tasking machine tool for large scale marine engine crankshafts, a multi-tasking vertical lathe for windmill parts, and a large scale 5-axis machine tool of gantry type. Several special purpose devices has been necessarily developed for the purpose of handling and machining big and heavy workpieces accurately, such as PTD (Pin Turning Device) with revolving ring spindle for machining eccentric crankshaft pins, hydrostatic rotary table and steady rest for supporting and resting heavy workpieces, and 2-axis automatic swiveling head for high-quality free surface machining. Core technologies have been also developed and adopted on their detail design stage; 1) structural design optimization with FEM structural analysis, 2) theoretical hydrostatic analysis for the PTD and rotary table bearings, 3) box-in-box type cross-rail and octagonal ram design to secure machine rigidity and accuracy, 4) constant spindle rpm control against gravitational torque due to unbalanced workpiece.

• Journal of Korea Society of Industrial Information Systems
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• v.5 no.3
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• pp.111-116
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• 2000

There are many recent monitor manufacturing firms not equipped with automatic checking system in their final process. And the check is based on the human perception, so the automatic checking system is needed for the consistency and the accuracy of the checking process to elevate the productivity and the quality. As the performance of computer systems and the vision systems has been increased, the cost for the system is reduced and their applicable algorithms have been developed. In this study we develop monitor checking system which is low-cost, fast, and easy to adopt by the small-scaled manufacturing films. The system is based on the computer vision techniques, and is equipped with the GUI interface and checking functions such as centering, yoke rotation, pincushion, sizing, brightness, and grayscale tracking. Monitor checking system developed in this study can be used in the final checking process thereby we expect the synergy effects both on the efficiency of production and on the reduction of the cost for the facility investments.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.3
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• pp.475-488
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• 2017

Wear prediction of TBM disc cutters is a very important issue for hard rock TBMs as number of cutter head intervention. In this regard, some model such as NTNU, Gehring model, CSM models have been used to predict disc cutter wear and intervention interval. There are some deficiencies in these models. This paper developed a new test method for wear prediction for TBM disc cutter and proposed a new abrasion index. In this regard, different abrasivity indices along with their testing methods are explained. A comparative study is performed to develop the predictability of different cutter life evaluation methods and index. The evaluation of the new methods proposed in this paper shows a very good agreement with the actual cutter life and intervention interval length. The proposed tester and index can be easily used to predict the intervention interval length and cutter wear evaluation in both planning and construction stages of a TBM tunneling project.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.11
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• pp.21-30
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• 1998

In this paper, a digital current control system using a FPGA(Field Programmable Gate Array) was implemented, and the system was applied to an induction motor widely used as an industrial driving machine. The FPGA designed by VHDL(VHSIC Hardware Description Language) consists of a PWM(Pulse Width Modulation) generation block, a PWM protection block, a speed measuring block, a watch dog timer block, an interrupt control block, a decoder logic block, a wait control block and digital input and output blocks respectively. Dedicated clock inputs on the FPGA were used for high-speed execution, and an up-down counter and a latch block were designed in parallel, in order that the triangle wave could be operated at 40 MHz clock. When triangle wave is compared with many registers respectively, gate delay occurs from excessive fan-outs. To reduce the delay, two triangle wave registers were implemented in parallel. Amplitude and frequency of the triangle wave, and dead time of PWM could be changed by software. This FPGA was synthesized by pASIC 2SpDE and Synplify-Lite synthesis tool of Quick Logic company. The final simulation for worst cases was successfully performed under a Verilog HDL simulation environment. And the FPGA programmed for an 84 pin PLCC package was applied to digital current control system for 3-phase induction motor. The digital current control system of the 3 phase induction motor was configured using the DSP(TMS320C31-40 MHz), FPGA, A/D converter and Hall CT etc., and experimental results showed the effectiveness of the digital current control system.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.2
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• pp.261-270
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• 2001

This study was performed to evaluate wear characteristics of light-cured composites when opposed by human enamel. Seven light-cured restorative composites were selected and enamel cusps sectioned from premolars. All samples were stored in distilled water at $37^{\circ}C$ for 10 days. 68.6 N of weight was loaded during the test. The measurements of vertical loss of enamel cusps, weight loss and volume loss of composites, and SEM observations of the polished and abraded surfaces were made after 30,000 cycles. The results obtained were summarized as follows; 1. The highest hardness value of 70.4 was observed in the Spectrum group and the lowest value of 19.8 was observed in the Heliomolar group. Results of Tukey test showed that an overall significant difference was indicated except the Spectrum, Z100 and Clearfil AP-X groups(p<0.05). 2. Enamel showed the good abrasion resistance against the Heliomolar group of microfilled composite and the Palpique Toughwell group containing the submicron hybrid type spherical fillers. 3. The abrasive wear resistance of hybrid composites was improved with the decrease of mean particle size and hybrid of submicron particle fillers. 4. SEM observation of worn surfaces revealed the protrusion, attrition and missing of fillers, cracks developing and delamination in the matrix.