• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.4
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• pp.104-111
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• 2008

The objective of this study is to evaluate micro end-milling characteristics and tool wear behavior of AlN-hBN composites. First, AlN based composites with hBN contents in the range of 10 to 20vol% were prepared by hot-pressing. Vickers hardness and flexural strength of the prepared composite specimens were measured and compared according to the vol% of hBN variations. Then, cutting force variations were measured and analyzed using a tool dynamometer during the micro end-milling experiments; and machined surface shapes and roughness were investigated using a 3D non-contact type surface profiler. After micro end-milling, worn tools were investigated using a tool microscope and SEM images. From the experimental results, it can be observed that the cutting forces decreased, and surface qualities were improved with increasing hBN contents. At low content of hBN, tool chipping was observed; and tool wear rate decreased with increasing hBN contents. The results of this study insist that proper machining conditions, including tool wear behavior investigation, should be determined for the micro end-milling of AlN-hBN composites for its further application.

• Design & Manufacturing
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• v.13 no.1
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• pp.5-12
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• 2019

In this paper, we studied the micro tool deflection, micro cutting with low temperature, and deformation of micro ribs caused by cutting forces. First, we performed an integrated machining error compensation method based on captured images of tool deflection shapes in micro cutting process. In micro cutting process, micro tool deflection generates very serious problems in contrast to macro tool deflection. To get the real images of micro tool deflection, it is possible to estimate tool deflection in cutting conditions modeled and to compensate for machining errors using an iterative algorithm correcting tool path. Second, in macro cutting fields, the cryogenic cutting process has been applied to cut the refractory metal but, the serious problem may be generated in micro cutting fields by the cryogenic environment. However, if the proper low temperature is applied to micro cutting area, the cooling effect of cutting heat is expected. Such effect can make the reduction of tool wear and burr formation. For verifying this passibility, the micro cutting experiment at low temperature was performed and SEM images were analyzed. Third, the micro pattern was deformed by the cutting forces and the shape error occurred in the sidewall multi-step cutting process were minimized. As the results, the relationship between the cutting conditions and the deformation of micro-structure during micro cutting process was investigated.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.8
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• pp.720-725
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• 2011

Most ultrasonic vibration cutting tools are operated at the resonance condition of the longitudinal vibration of the structure consisting of booster, horn and bite. In this study, a transverse vibration tool with beam shape is designed to utilize the vibration characteristics of the beam. Design point of the transverse vibration tool is to match the resonance frequency of the bite to the frequency of the signal to excite the piezoelectric element in the booster. The design process to match the natural frequency of the longitudinal vibration mode of the horn and that of the transverse vibration mode of the bite is presented. Dimensions of the horn and bite are searched by trend analysis through which the standard shapes of the horn and bite are determined. After the dimensions of each component of the cutting tool consisting of booster, horn and bite are determined, the assembled structure was experimentally tested to verify that true resonant condition is achieved and proper vibrational displacement are obtained to ensure that enough cutting force is generated.

• Journal of Mechanical Science and Technology
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• v.19 no.7
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• pp.1478-1487
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• 2005

A small mixed-type turbine with a diameter of 19.9 mm has been substituted for a rotational part of pencil-type air tool. Usually, a vane-type rotor is applied to the rotational part of the air tool. However, the vane-type rotor has some problems, such as friction, abrasion, and necessity of accurate assembly etc.,. These problems make the life time of the vane-type air tool short, but air tools operated by mixed-type turbines are free of friction and abrasion because the turbine rotor dose not contact with the casing. Moreover, it is assembled easily because of no axis offset. These characteristics are merits for using air tools, but loss of power is inevitable on a non-contacting type rotor due to flow loss, tip clearance loss, and profile loss etc.,. In this study, four different rotors are tested, and their characteristics are investigated by measuring the specific output power. Additionally, optimum nozzle location against the rotor is studied. Output powers are obtained through measured pressure, temperature, torque, rotational speed, and flow rate. The experimental results obtained with four different rotors show that the rotor blade shape greatly influences to the performance, and the optimum nozzle location exists near the mid span of the rotor.

• Journal of the Korea Computer Graphics Society
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• v.21 no.5
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• pp.1-10
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• 2015

This study proposes a method of developing authoring tool that can easily and intuitively generate diverse digital leaves that compose virtual landscape. The main system of the proposed authoring tool consists of deformation method for the contour of leaf blade based on image warping, procedural modeling of leaf vein and visualization method based on mathematical model that expresses the color and brightness of leaves. First, the proposed authoring tool receives leaf input image and searches for contour information on the leaf blades. It then designs leaf blade deformation method that can generate diverse shapes of leaf blades in an intuitive structure using feature-based image warping. Based on the computed leaf blade contour, the system implements the generalized procedural modeling method suitable for the authoring tool that generates natural vein patterns appropriate for the leaf blade shape. Finally, the system applies visualization function that can express color and brightness of leaves and their changes over time using a mathematical model based on convolution sums of divisor functions. This paper provides texture support function so that the digital leaves that were generated using the proposed authoring tool can be used in a variety of three-dimensional digital contents field.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.125-126
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• 2012

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.643-646
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• 1997

Gear trains are used in many machinery for variable speed ratios. Typical shapes of gear trains are tivo categories : simple gear trains and planetary gear trains. This paper presents the kinematic ctraracteristics for planetary gear trains. The characteristics are the constraints of geometric relationships, number of gears, speed of each gear. and speed ratio of the train. The objective goal of this paper provides the CAI) software, which is the academic tool for understanding the kinematics of the planetary gear trains.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1996.10a
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• pp.91-95
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• 1996

One must observe abrasive grain of grinding wheel and know their behaviors to understand the grinding mechanism. The behaviors of abrasive grain on the wheel surface. such as shapes distributions and changes were studied to make the grinding mechanism clear but the behaviors of abrasive grains on CBN wheel are not known enough. From this paper the working surface of a grinding wheel is observed by photography in which a picture of a wheel surface is taken by the camera through the microscope on the grinding machine and analyzed with the computer.

• MALSORI
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• no.35_36
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• pp.121-129
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• 1998

In this paper, articulatory simulator 'Artsim' is used as a tool for the experiments to examine the articulatory characteristics of 6 different vowels. Each vowels are defined by some articulatory points from their vocal tract area functions and shapes of tongues. Each points are varied systematically to synthesize vowels and the synthesized sound is evaluated by human listners. Finally distributions of each vowels within vowel space is obtained. From the experimental results it is verified that our articulatory simulator can be used effectively to investigate the articulatory characteristics of speech.

• Journal of Astronomy and Space Sciences
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• v.34 no.3
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• pp.225-235
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• 2017

The energy balance in a satellite needs to be designed properly for the satellite to safely operate and carry out successive missions on an orbit. In this study, an analysis program was developed using the MATLAB(R) graphic user interface (GUI) for nanosatellites. This program was used in a simulation to confirm the generated power, consumed power, and battery power in the satellites on the orbit, and its performance was verified with applying different satellite operational modes and units. For data transmission, STK(R)-MATLAB(R) connectivity was used to send the generated power from STK(R) to MATLAB(R) automatically. Moreover, this program is general-purpose; therefore, it can be applied to nanosatellites that have missions or shapes that are different from those of the satellites in this study. This power simulation tool could be used not only to calculate the suitable power budget when developing the power systems, but also to analyze the remaining energy balance in the satellites.