• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.592-596
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• 2001

Near field technology makes it possible to overcome the diffraction limit of laser beam and create the small spot. Because of the small spot size, the pit size and track pitch can be decreased. So the high performance actuator is needed for near field recording system. And the light mass and the small form factor are also important properties of the NFR actuator in order to be used for hand held device. The purpose of this paper is the optimal design of the NFR coarse actuator to maximize actuating force. The structure of NFR coarse actuator is the same as HDD VCM actuator. The permeance method is used for modeling of the coarse actuator. The optimal result and the FEM simulation result are presented.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.251-254
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• 2001

In this paper, we analyzed the properties change of electric wire when the thermal stress was applied to NFR-8 and FR-PVC 600[V] wire. Messurement is made of the attenuation of a light beam by smoke accumulating with in a closed chamber due to nonflaming pyrolytic decomposition and flaming combustion. Results are expressed in terms of specific optical density which is derived from a geometrical factor and the measured optical density a measurement characteristic of the concentration of smoke. Referenced documents were ASTM E662 standard test method for specific Ds genalated by solid materials. The furnace control system shall maintain the required irradiance level under steady-state condition with the chamber door closed of $2.5{\pm}0.04[w/cm^{2}]$ for 20 min. According to the results of the smoke density analysis of NFR-8 and FR-PVC the highest decomposition flaming smoke density range of NFR-8 and FR-PVC were 25.2 to 37.5 and 51.1 respectively. Nonflaming smoke density range of NFR-8 and FR-PVC were 100.4 to 112.2 and 126.5 to 398.8. The amount of carbon monoxide generated was found to be much higher in FR-PVC decomposition than in NFR-8 due to incomplete combustion of FR-PVC which has high content of carbon in compound.

• Transactions of the Society of Information Storage Systems
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• v.1 no.1
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• pp.58-66
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• 2005

Pseudo-Near Field Recording (Pseudo-NFR) system is proposed to prevent contamination and oxidation of media surface occurred in conventional NFR systems. To solve these critical problems of the NFR systems, we investigate the optimal thickness of cover layer for Pseudo NFR. This paper presents the theoretical analysis for cover layer thickness based on the measured length of dust particle and numerical simulation for the temperature distribution using Finite Difference Time Domain (FDTD) method and heat conduction equation. To verify the simulation results, we conduct and compare simulation results in case of far field MO recording and near field MO recording. A measured dust particle length in general environment was mostly less than $20{\mu}m$, and the optimal thickness of cover layer is $30{\mu}m$ in this case. Based on the designed optimal cover layer thickness, temperature distribution is simulated to have $800{\~}850^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.251-254
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• 2001

In this paper, we analysed the properties change of electric wire when the thermal stress was applied to NFR-8 and FR-PVC [600] wire. Measurement is made of the attenuation of a light beam by smoke accumulating with in a closed chamber due to nonflamining pyrolytic decomposition and flaming combustion. Results are expressed in terms of specific optical density which is derived from a geometrical factor and the measured optical density a measurement characteristic of the concentration of smoke. Referenced documents were ASTM E662 standard test method for specific Ds generated by solid materials. The furnace control system shall maintain the required irradiance level under steady-state condition with the chamber door closed of 2.5${\pm}$0.04[w/$\textrm{cm}^2$] for 20 min. According to the results of the smoke density analysis of NFR-8 and FR-PVC the highest decomposition flaming smoke density range of NFR-8 and FR-PVC were 7.2 to 77.5 and 51.1 respectively. Nonflaming smoke density range of NFR-8 and FR-PVC were 100.4 to 112.2 and 126.5 to 398.8. The amount of carbon monoxide generated was found to be much higher in FR-PVC decomposition than in NFR-8 due to incomp1ete combustion of FR-PVC which has high content of carbon in compound.

• Journal of the Korean Institute of Landscape Architecture
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• v.29 no.4
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• pp.24-33
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• 2001

The purpose of this paper is to examine the differences of user´s satisfaction of development elements of natural recreation forest(NFR) developed by public and private bodies in order to answer the research question: What is the differences of user´s satisfaction of development elements of NFR\ulcorner After reviewing the literature, mechanism of outdoor recreation, and development elements in NRF, we constructed the conceptual framework and have formulated the hypothesis of this research. We had obtained data through a questionnaire, which surveyed 584 visitors at 10 of the 72 natural recreation forests in Korea in 1999. We have analyzed the data using he descriptive statistical method, the mean difference test, and logistic regression method. We have found that 1) all the development elements have turned out to be significantly different from the mean difference test, 2) the two elements of atmosphere and activity have turned out to be statistically significant in determining the difference of NFR developed by public and private body in logistic regression analysis while user´s satisfaction in recreational resources, facilities and service make no differences between public and private NRF, 3) the higher the degree of user´s satisfaction in atmosphere and activity at NFR, the more the NFR developed by private body, and 4) their relative contribution of atmosphere and activities on whether the NFR is developed by public or private body have been turned out to have 0.258 and 0.242 respectively, which have a similar importance. The research results suggest that a guideline for the creation of marketable NFR by public and private developer, and development of use-programs and recreational atmosphere be recommended in the planning and development process of NRF. The approach and anlaysis method adopted by this research is highly useful for an evaluation of NRF developed by the tow bodies and development of devices for increasing user´s satisfaction and marketing positioning of NRF by the tow developers. It is recommended that more empirical study on individual development elements affecting user´s satisfaction be performed in the future.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.718-721
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• 2001

For higher recording density in optical data storage, near field optics is being actively researched as one of the promising alternatives. But the tight assembling tolerance in NFR is one of big barriers to overcome for the realization of it. In this paper, the tolerances in assembling optic components of NFR system are analyzed. Some of key tolerances can be loosened by the optimization of objective lens design. But one of them become too tight by the optimization and should be controlled by other means. One of possible methods to control the tolerance is discussed.

• Transactions of the Society of Information Storage Systems
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• v.3 no.1
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• pp.17-22
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• 2007

[ $TiO_2$ ] nanoparticles are added into UV curable resin to increase the refractive index of the cover-layer which is laminated on the media for cover-layer incident NFR. High refractive index is required for the cover-layer operating for the solid immersion lens optics with high effective numerical aperture. The eyepattern could be achieved from the cover-layer coated 20 GB ROM disc in which the refractive index of the cover-layer was 1.75, but the gap servo was unstable due to the rough surface of the cover-layer. Even though the light loss due to the nanoparticles is not serious, the rough microstructure is developed by adding the nanoparticles in the organic binder material. To achieve smooth surface for the stable gap servo, some special techniques should be added, for example the solubility of the nanoparticles should be enhanced by the optimization of the surface of the nanoparticles.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.1165-1169
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• 2003

This paper presents an approach to optimally design the air-bearing surface (ABS) of the optical flying head for near-field recording technology (NFR). NFR is an optical recording technology using very small beam spot size by overcoming the limit of beam diffraction. One of the most Important problems in NFR is a head disk interface (HDI) issue over the recording band during the operation. A multi-criteria optimization problem is formulated to enhance the flying performances over the entire recording band during the steady state. The optimal solution of the slider, whose target flying height is 50 nm, is automatically obtained. The flying height during the steady state operation becomes closer to the target values than those fur the initial one. The pitch and roll angles are also kept within suitable ranges over the recording band. Especially, all of the air-bearing stiffness are drastically increased by the optimized geometry of the air bearing surface.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.1146-1151
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• 2003

So far the study of near-field optical recording(NFR) suspensions has not been investigated sufficiently. In this study the optimization of a NFR suspension is performed using finite element method. NFR suspensions are required to have low compliance modes to allow the slider to comply with the rotating disk, and high tracking stiffness modes to maximize the servo bandwidth of the tracking controller First of all, a basic integrated type suspension model is obtained using topology optimization And the parametric study on the sensitivities of the compliance modes and tracking stiffness modes is performed. Finally, a model satisfying static characteristics is elected and shape optimization is performed to improve dynamic characteristics.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.586-591
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• 2001

Dynamic analysis using impulse responses is formulated to estimate effect of slider rail shape on dynamic responses. Impulse responses are obtained on numerical nonlinear model including rigid motion of slider and fluid motion of air bearing under the slider. Dynamic characteristics of slider motion are evaluated by utilizing the decay ratio of impulse responses and modal frequencies from frequency response functions. The dynamic characteristics of the developed NFR(Near Field Recording) slider are checked by comparing those of HDD sider(Nutcracker). Also, sensitivities of slider position conditions and rotation speed on the dynamic characteristics are investigated. The researches show that the utilized method is a good indicator of designing the better slider.