• Transactions of Materials Processing
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• v.24 no.4
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• pp.227-233
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• 2015

In this paper, the effect of flow stress, friction, temperature, and velocity on finite element predictions of metal flow lines after cylindrical upsetting is presented. An actual three-stage hot forging process involving an upsetting step is utilized and experimental metal flow lines are measured to study the effect of the various process variables. It was found that temperature and velocity for reasonable values of friction have little influence on metal flow lines especially those located deep within the cylinder but that flow stress has a direct influence on the flow lines. It was shown that a pure power law material model cannot reflect the real flow stress of hot material because it underestimates the flow stress especially around the dead-metal zone for the upsetting of a cylindrical specimen. It is thus recommended that a proper lower limit of flow stress be assumed to alleviate this issue.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.12
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• pp.128-141
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• 1998

We propose the robust nonlinear controller design methodology for the multivariable system which has hard nonlinearities (Coulomb friction, dead-zone, etc) and the structured real parameter uncertainty. The hard nonlinearity can be linearized by the RIDF technique and structured real parameter uncertainty can be modelled as the sense of Peterson-Hollot's quadratic Lyapunov bound. For this system, we apply the robust QLQG/H$_{\infty}$ control and then can obtain four Riccati equations. Because of the system's nonlinearity, however, one Riccati equation contains the nonlinear correction term that is very difficult to solve numerically, In order to treat this problem, using some transformations to Riccati equations, the nonlinear correction term can be eliminated. Then, only two Riccati equations need to design a controller. Finally, the robust nonlinear controller is synthesized via IRIDF techniques. To test this proposed control method, we consider the direct-drive robot manipulator system that has Coulomb frictions and varying inertia.

• Journal of Biosystems Engineering
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• v.35 no.3
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• pp.189-196
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• 2010

This study was conducted to develop an non-contact ultrasonic transducer for measurement of fruit firmness. The center frequency of non-contact ultrasonic transducer was 500 kHz. As an active element of non-contact ultrasonic transducer, the 1-3 piezoelectric composite material was selected. That material has high piezoelectric properties such as electro-mechanical coupling factor, $k_t$ and piezoelectric voltage constant, $d_{33}$ and also that material has low acoustical impedance which enables to matching the acoustical impedances between piezoelectric material and air. As a front matching material between 1-3 piezoelectric composite material and air, various kinds of paper with different thickness were tested. To control the dead-zone of the fabricated non-contact ultrasonic transducer, the backing material composed of epoxy resin and tungsten powder were made and evaluated. The fabricated non-contact ultrasonic transducer for fruit showed that the cneter frequency, bandwidth and beamwidth were approximately 480 kHz, 30 % and 12 mm, respectively. It was concluded that non-contact measurement of apple firmness would be possible by using the fabricated non-contact ultrasonic transducer.

• Proceedings of the Safety Management and Science Conference
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• 2005.11a
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• pp.93-100
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• 2005

Small & medium sized company is the most efficient way of management to prevent my accident in the area of industry. Employees are more than 30 to less than 50 persons and which is liable for securing a safety manager on site, is gradually seen on the surface. Even a small company is nothing less than a dead zone from a safety since it's free from his obligation of employing a safety manager. Let us now think about the effective measures against a industrial accident by collecting, reviewing a variety of preventive measures, which is being carried out for preventing an industrial accident happening in a small company, and comparing, analyzing the effect according to the respective measures. Through this research, it's expected to contribute to both the development of small & medium sized company and our national economy with the improvement of a company's competitiveness and the accumulation a technical background by way of prevention from occurring industrial accident in a small & medium sized company, in accordance with an friendly environment of work room to protect the employee from leaving his job.

• Journal of Advanced Navigation Technology
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• v.15 no.5
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• pp.906-912
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• 2011

In this paper, we structured the intelligent cluster surveillance network which can be managed scattered-the emergency light without communication line. Will not be interfered in location of emergency light and not to be will be able to establish the system. And the surveillance network there is by a destroyer and the communication relay system is born breakdown but the dead zone without condition of emergency light implemented the emergency light management system where the monitoring and management are possible. And we implemented the emergency light surveillance equipment and the emergency light monitoring system. Some experiments were conducted to verify so as to proposed system, and the system processes such as the surveillance network, the status information measurement and initialization were well performed.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.76
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• pp.1-20
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• 2017

The industrial technology (including trade secrets), which is commonly understood as systematic and applied technical knowledge, can be transferred to third parties by contracting for the transfer of technology or by granting of a licence. The activity of industrial espionage, due to the gradual increase of the economic interests of intellectual property, is displaying intensively in order to gain advanced technology information. With our outstanding high technology, but compared to the level of the advanced countries, the technical protection systems, the legal protection measures and the systematic management thereof may still be insufficient. Our industrial technology outflow abroad, due to the vulnerability to the security control system in our country, has been increasing since the 2000. Computer software and SNS, such as smart devices, appear as a rapid change in the technical information environment. In order to minimize the dead zone of a new industrial security, the country's organic activity is being conducted. In 2006, Industrial Technology Outflow Prevention and Protection Law was enacted, which emphasized the responsibilities of the country. In this paper for the economic entity's efforts to prevent technology leakage oversea, I have looked to how the industrial technology can be protected in terms of national security and economic benefits of our enterprises. To solve the above-mentioned problems hereof, Korean government should willingly establish a reliable legal system for supporting to enterprise's operations, and Korean companies should autonomously introduce a synthetic technology protection system and incorporate the confidentiality clauses in an international transfer of technology agreement with third parties.

• Journal of The Korea Institute of Healthcare Architecture
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• v.20 no.3
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• pp.7-15
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• 2014

Purpose: This study is to propose direction for healing environment design in hospital architecture considering the characteristics of elderly patients. The primary goal of a public hospital is providing cheap health care and quality service chance to the underprivileged and elderly in the dead zone. Compared to the rapid increase of the aged population and chronic diseases, Ministry of Health & Welfare is currently planning model of health promotion hospital in development plans of local based public hospital. Due to the increased elderly medical expenses, elderly patients' high utilization is considered. Methods: The literature on the design factors of healing environments were investigated. based on this, analyzed drawings of surveyed hospitals ward in architectural characteristics and observe and evaluate directly healing environment design through field surveys. Results: The design of hospital environment affects patient's therapeutic effect. There is no any official formula for hospital design but environment that architect create could be a big part of the healing process. To increase the quality of the environment, apply the characteristic factors and harmonize well as a human-centered healing environment. Implications: Healing environment design for the elderly is first necessary condition due to high proportion of elderly patients.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.3
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• pp.183-190
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• 2016

In this study, we conduct linear and nonlinear modeling of the DC motor driving system of a wheeled mobile robot, which is a nonlinear system involving dead zone, friction, and saturation. The DC motor driving system consists of a DC motor, a wheel, and gears. A linear DC motor driving system is modeled using a steady-state response and parameter measurements. A nonlinear DC motor driving model is identified with the use of the Hammerstein-Wiener method. By using these models, PID controllers for the DC motor system are then established. Each PID controller is applied as a low-level controller in order to achieve posture stabilization control for the real mobile robot. We also compare the performance of the proposed PID controllers in posture stabilization experiments by using several different final robot postures.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.4
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• pp.465-472
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• 2008

An automotive windshield wiper system is modeled mainly for vibration analysis purpose. The model is composed of solid links, ideal joints, imperfect joints to simulate unavoidable manufacturing defects and bushings having stiffness, contact between a wiper blade and a wind screen glass, friction, a spring and an actuator. Main stream of wiper dynamics analysis has been obtaining a closed form of system of equations using Newton's or Lagrange's formula and doing a numerical simulation study to understand and predict the behavior of it. However, the modeling process is complex since a wiper system is of multibody and a contact problem occurs. When imperfection, such as dead zone of a joint and stiffness of a rubber bushing, should be included, the added complexity makes the modeling difficult. Since the imperfection is understood as main cause of problematic vibration, the dynamics model of a wiper system aiming vibration analysis should include such unavoidable manufacturing defects in the model. An open form of dynamic model of a automotive windshield wiper system with imperfect joints using a commercial software is obtained and a simulation analyssis is conducted for vibration reduction study.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.7
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• pp.127-133
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• 2009

We present a $3-{\underline{P}}RS$ compliant parallel manipulator actuated by PZTs. The motion ranges are $400-{\mu}m$ translation to the z-direction and 5.7-mrad rotation about any axis on the x-y plane. A mechanical amplifier whose advantage is approximately 5.5 is designed and integrated with flexure revolute and spherical joints in a monolithic way. We evaluated the performance of the system: kinematic and dynamic characteristics. In kinematic point of view, the flexures play the roles of conventional mechanism but any nonlinearity such as dead-zone and backlash, which make it possible to achieve the steady-state resolution less than $0.1{\mu}m$. The system shows resonance near 86 Hz with high magnitude and, therefore, poor transient response. But the settling is faster when the flexures are strained higher.