• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.141-144
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• 2003

This paper proposes an analytical model of off-line feed rate scheduling to obtain an optimum feed rate for high speed machining. Off-line feed rate scheduling is presented as an advanced technology to regulate cutting forces through change of feed per tooth, which directly affects variation of uncut chip thickness. In this paper, the feed rate scheduling model was developed using a mechanistic cutting force model using cutting-condition-independent coefficients. First, it was verified that cutting force coefficients are not changed with respect to cutting speed. Thus, the feed rate scheduling model using the cutting-condition-independent coefficients can be applied to set the proper feed rates for high speed machining as well as normal machining. Experimental results show that the developed fred rate scheduling model makes it possible to maintain the cutting force at a desired level during high speed machining.

• Applied Microscopy
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• v.51
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• pp.7.1-7.9
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• 2021

Neuromorphic systems require integrated structures with high-density memory and selector devices to avoid interference and recognition errors between neighboring memory cells. To improve the performance of a selector device, it is important to understand the characteristics of the switching process. As changes by switching cycle occur at local nanoscale areas, a high-resolution analysis method is needed to investigate this phenomenon. Atomic force microscopy (AFM) is used to analyze the local changes because it offers nanoscale detection with high-resolution capabilities. This review introduces various types of AFM such as conductive AFM (C-AFM), electrostatic force microscopy (EFM), and Kelvin probe force microscopy (KPFM) to study switching behaviors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.349-350
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• 2009

Superconducting magnetic bearing and rotating system were developed by utilizing the high magnetization YBaCuO superconductor. The pellets prepared by quasi-melt process had a high magnetic levitation force and a high magnetic attractive force. The shaft also could be moves its position and orientation of the rotating axis freely. Is is essential to enhance the materials properties and to improve the system design for the application of the system to industrial purpose.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.447-454
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• 1998

The main object of the study is that axial force-moment relationships for high strength concrete structures using reliability theory(Linear statstical method, Monte Carlo Simulation) including probability conception. And mean stress factors and centroid factors proposed to high strength concrete structures using reliability theory(Linear statstical method, Monte Carlo Simulation). Finally, The established experimental data for axial force-moment relationships are compared to the analytical data(data for Linear statstical method and Monte Carlo Simulation) for axial force-moment relationships in this analytical method.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.500-506
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• 1997

The main object of the study is that axial force-moment relationships for high strength concrete structures using reliability theory probability conception. And mean stress factors and centroid factors proposed to high strength concrete structures using reliability theory. Finally, the established experimental data for axial force-moment relationships are compared to the analytical data for the axial force-moment relationships in this analytical method.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.123-128
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• 1998

This paper describes the evaluation of a force-reflecting interface with ultrasonic motors(USMs). The force-reflecting interface allows a human to feel object within virtual environment. To effectively display the mechanical impedance of the human hand we need a haptic device with specific characteristics, such as low inertia, almost zero friction and very high stiffness. USMs have attracted considerable attention as the actuator satisfied these conditions. USMs combine features such as high driving torque at low rotational speed, high holding torque and fast response therefore we studied two degree of freedom force-reflecting haptic system.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.5 s.170
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• pp.167-174
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• 2005

High-speed machining is one of the most effective technologies to improve productivity Because of the high speed and high feed rate, high-speed machining can give great advantages for the machining of dies and molds. This paper describes on the analysis and evaluation of cutting force in high-speed machining. Cutter rotation directions, slope directions, spindle revolution and depth of cut are control factors for cutting force. The effect of the control factors on cutting force is investigated for the high speed machining of STD11.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.12 s.177
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• pp.51-60
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• 2005

This paper describes a robust control scheme for high-speed and long stroke scanning motion of high precision linear motor system consisting of linear motor, air bearing guide and position measurement system using heterodyne interferometer. Nowadays, semiconductor process and inspection of wafer or LCD need high speed and long travel length for their high throughput and extremely small velocity fluctuations or tracking errors. In order to satisfy these conditions, linear motor system are widely used because they have large thrust force and do not need motion conversion mechanisms such as ball screw, rack & pinion or capstan with which the system are burdened. However linear motors have a problem called force ripple. Force ripple deteriorates the tracking performances and makes periodic position errors. So, force ripple must be compensated. To maximize the tracking performance of linear motor system, we propose the control scheme which is composed of a robust control method, Time Delay Controller (TDC) and a feedforward control method, Zero Phase Error Tracking Control (ZPETC) for accurate tracking a given trajectory and an adaptive force ripple compensation (AFC) algorithm fur estimating and compensating force ripple. The adaptive ripple compensation is continuously refined on the basis of tracking error. Computer simulation results based on modeled parameters verify the effectiveness of the proposed control scheme for high-speed, long stroke and high precision scanning motion and show that the proposed control scheme can achieve a sup error tracking performance in comparison to conventional TDC control.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.1
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• pp.9-14
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• 2013

In recent years, high hardness steel is used for most of the material in many areas including aircraft, nuclear power, space exploration and automotive parts. Low CBN tools are widely used in industrial field which can effectively process high hardness steel of HRC 45 or harder. The results of this study demonstrated, when high hardness steel, SCM440 is turned with Low CBN tools coated with TiN and TiAlN coatings respectively, that both the thrust force and cutting force tends to increase with more increase in cutting force than thrust force, as the feed rate increases at constant cutting speed. In addition, the size of the cutting force and thrust force does not change with the increased cutting speed at the same feed rate, but the tool life is reduced if the cutting speed is increased to shorten the machining time. Therefore, it is recommended to limit the cutting speed at 250 m/min maximum or less. Furthermore, comparing the cutting force of the three tools at the same cutting condition, Tin coating tool showed the smallest cutting force and Low CBN was the next, and the TiAlN coating tools showed the largest cutting force.

• The korean journal of orthodontics
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• v.20 no.2
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• pp.409-417
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• 1990

Tooth movement would be impeded by frictional force arised between archwire and tube, bracket or elastics in the fixed orthodontic appliances, which could be changed variably by such several factors as the contact area, normal (perpendicular) force and the condition of contact surface. There were many literatures about frictional force in the orthodontic region, but different results were obtained from little controlled research so that was very difficult in clinical application. Therefore we have reviewed comprehensively previous literatures about frictional force and thus several results were obtained as follows: 1. For use species of the orthodontic wire, frictional force was influenced mainly by surface roughness of wire in the absence of binding, while that was influenced mainly by normal force in high binding angulation. 2. For the cross-section and diameter of the wire, the contact area influenced mainly on frictional force in the absence of binding, while wire stiffness influenced mainly on frictional force in high binding angulation. 3. The greater the bracket width, the greater frictional force, and frictional force of the plastic bracket was larger than that of the metal bracket. 4. For ligation type, frictional force of the stainless steel ligation was larger than that of the elastic ligation, and frictional force was directly proportional to ligation force. 5. Variable frictional force were occured from the saliva combined with such another factors as normal force and mode of surface oxide et al.