• Korean Journal of Environment and Ecology
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• v.21 no.3
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• pp.290-298
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• 2007

The results of this research on the diversity, zonation of vegetation and micro-topography by TWINSPAN classification and DECORANA ordination, executed with Sinduri coastal dunes of Korea, are as follows: The vegetation and micro-topography of coastal dunes formed a noticeably clear zonation structure. The beach in the direction of the coastline saw a lot of appearance of Salsola komarovi and the primary dune was dominated by Elymus mollis. Imperata cylindrica var. koenigii and Carex pumila formed a colony at flat area of the sand hills and Calamagrostis epigeios was widely distributed at the wet slack. The secondary dune was dominated mostly by Ischaemum anthephoroides and Imperata cylindrica var. koenigii, and it showed an aspect of the distribution of Vitex rotundifolia and Rosa rugosa. while the hinterland hillside in the direction of inland was dominated by Robinia pseudo-acacia and Pinus thunbergii. However, Carex kobomugi, known as the pioneer species of the coastline-bound areas at the coastal dune, dominantly occupied the secondary dune of the rear side and continentally-inclined Miscanthus sinensi and Oenothera biennis of naturalized plant were irregularly spread over the whole of the coastal dune, so the stabilization of micro-topography seemed to be uncertain. Particularly, Miscanthus sinensis was predicted to be changed into dominant species of the primary dune, and secondary dune and slack having a commonly high species gathering inclination with the more progress of stabilization of the coastal dune. The expansion of sand hill wetlands and roads located between the primary dune and secondary dune was judged to have an effect on the zonation structure of plant distribution.

• The Journal of Advanced Prosthodontics
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• v.1 no.2
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• pp.75-84
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• 2009

STATEMENT OF PROBLEM. A number of studies about the nano-treated surfaces of implants have been conducting along with micro-treated surfaces of implants. PURPOSE. The purpose of this study was to get information for the clinical use of nano-treated surfaces compared with micro-treated surfaces by measuring removal torque and analyzing histological characteristics after the placement of various surface-treated implants on femurs of dogs. MATERIAL AND METHODS. Machined surface implants were used as a control group. 4 nano-treated surface implants and 3 micro-treated surface implants [resorbable blast media surface (RBM), sandblast and acid-etched surface (SAE), anodized RBM surface] were used as experimental groups. Removal torque values of implants were measured respectively and the histological analyses were conducted on both 4weeks and 8weeks after implant surgery. The surfaces of removed implants after measuring removal torque values were observed by scanning electron microscopy (SEM) at 8 weeks. RESULTS. 1. Removal torque values of the nano-treated groups were lower than those of micro-treated groups. 2. Removal torque values were similar in the anodized RBM surface groups. 3. On the histological views, there was much of bone formation at 8 weeks, but there was no difference between 4 and 8 weeks, and between the types of implant surfaces as well. CONCLUSION. it is suggested that implant topography is more effective in removal torque test than surface chemistry. To get better clinical result, further studies should be fulfilled on the combined effect of surface topography and chemistry for the implant surface treatments.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.4
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• pp.369-374
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• 2009

In micro/nano-scale contacts in MEMS and NEMS, capillary and van der Waals forces generated around contacting micro-asperities significantly influence the performance of concerning device as they are closely related to adhesion and stiction of interacting surfaces. In this regard, it is of prime importance to accurately estimate the magnitude of surface forces so that an optimal solution for reducing friction and adhesion of micro/nano-surfaces may be obtained We introduced an effective method to calculate these surface forces based on topography information obtained from an atomic force microscope. This method was used to calculate surface forces generated in the contact interface formed between diamond-like carbon coating and $Si_3N_4$ ball. This method is shown to effectively demonstrate the influence of capillary force in the contact area, especially in humid atmosphere.

• Korean Journal of Optics and Photonics
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• v.18 no.5
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• pp.303-308
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• 2007

We report here on the application of a digital holographic microscope as a metrology tool for the inspection and the micro-topography reconstruction of different micro-structures of phase shift photo-mask (PSM). The lithography by phase shift photo-mask uses the interference and the pattern of the PSM is not imaged by general optical microscope. The technique allows us to obtain digitally a high-fidelity surface topography description of the phase shift photo-mask with only one hologram image acquisition, allowing us to have relatively simple and compact set-ups able to give quantitative information of PSM.

• Tribology and Lubricants
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• v.24 no.6
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• pp.320-325
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• 2008

The recent industrial application requires technical methods to get the cutting fluid droplet surfaces in particular from the viewpoint of topography and micro texture. To characterize the surface topography of droplet, the combination of the confocal laser scanning microscope (CLSM) and wavelet filtering is well suited for obtaining the droplet geometry encountered in tribological research. This technique indicates a better agreement in obtaining an appropriate droplet surface obtained by the CLSM over a detail range of surface accuracy (resolution: $2{\mu}m$). And the results allow an excellent accuracy in a measurement of a droplet surface. The combination of extended focal depth measurement configured and multi-scale wavelet filtering has proven that it can construct a droplet surface in a successive and accurate way. A multi-scale approach of wavelet filtering was developed based on the decomposition and reconstruction of droplet surface by 2D wavelet transform using db9 (a mother wavelet of daubechies). Also this technique can be extended to characterize the quantification of droplet properties and other field in a wide range of scales. Finally this method is verified to be a better droplet surface modeling in a micro scale arising in a mist machining.

• Tribology and Lubricants
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• v.20 no.5
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• pp.237-244
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• 2004

Micro/nano tribological characteristics of PTFE coating films were experimentally studied. PTFE (polytetrafluoroethylene) modified polyethylene and low molecular weight PTFE were used as a coating materials. These films were deposited on Si-wafer (100) by IBAD (ion beam assisted deposition) method. The Ar ion beam sputtering was performed to change the surface topography of films using a hollow cathode ion gun under different Ar ion dose conditions in a vacuum chamber. Micro/nano tribological characteristics, water wetting angles and roughness were measured with a micro tribotester, SPM (scanning probe microscope), contact anglemeter and profilometer, respectively. The durability of the films were measured with macro tribotester. Results showed that the PTFE coating surfaces were converted to hydrophobic. The water contact angle of coated surfaces and surface roughness increased with the coating thickness. Adhesion and friction in micro and nano scale were governed by magnitude of normal load in soft material such as PTFE films. As the increase of sputtering time on low molecular weight PTFE films, the surface roughness was increased and nano adhesion and friction were decreased. The nano tribological characteristics of surfaces are mainly improved by chemical modification such as PTFE coating and given a synergy effect by the physical modification such as topographic modification.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.10
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• pp.109-116
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• 2007

Focused ion beams are a potential tool for micro/nano structure fabrication while several problems still have to be overcome. Redeposition of sputtered atoms limits the accurate fabrication of micro/nano structures. The challenge lies in accurately controlling the focused ion beam to fabricate various arbitrary curved shapes. In this paper a basic approach for the focused ion beam induced direct fabricate of fundamental features is presented. This approach is based on the topography simulation which naturally considers the redeposition of sputtered atoms and sputtered yield changes. Fundamental features such as trapezoidal, circular and triangular were fabricated with this approach using single or multiple pass box milling. The beam diameter(FWHM) and maximum current density are 68 nm and $0.8 A/cm^2$, respectively. The experimental investigations show that the fabricated shape is well suited for the pre-designed fundamental features. The characteristics of ion beam induced direct fabrication and shape formation will be discussed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.4
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• pp.929-940
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• 1995

The fatigue strength and fracture topography in the friction welded interface of high speed steel (HSS-Co) to SM55C carbon steel have been investigated through the fatigue test, SEM fractograph and EDS (energy dispersive spectrometer) analysis. Three kinds of specimens used in this research are the friction welded joints, HSS-Co and SM55C carbon steel with circumferential notch, saw notch and smooth, respectively. The notch sensitivity factor, .eta. of the friction welded joints is lower than that of the base materials, and that represents a superiority of the joint performance of FRW. Fracture topography of the FRW specimens with a notch showed a cleavage or brittle appearance, while that of the FRW smooth specimen appeared to be ductile. Furthermore, although fatigue crack likely initiated near the weld interface of the FRW smooth specimen, crack propagation continued into the HAZ of SM55C steel. Finally, fatigue fractures of the base materials were associated primarily with the inclusions located at the outer periphery of the specimen.

• Journal of Environmental Science International
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• v.26 no.10
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• pp.1111-1124
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• 2017

This study aimed to understand the distribution of vegetation in the eastern and western sides of the Baekdudaegan (ridge) dividing the Odaesan National Park, as influenced by its topography and climate. The actual vegetation, topography and climate for each side were used in the overlay analysis. The results of the analysis of actual vegetation showed a high distribution rate of Quercus mongolica forest on both the eastern and western sides. On the eastern side, the distribution rate of Pinus densiflora forest and P. densiflora-Q. variabilis forest was high, while the western side had a high distribution rate of deciduous broad-leaved tree forest and Abies hollophylla forest. A clear trend was identified for vegetation distribution with respect to elevation but not with respect to slope or aspect. The results of micro-landform analysis showed that the P. densiflora forests in the ridge and slope and the deciduous broad-leaved tree forest in the valley were respectively distributed with a high ratio. In terms of climate, the eastern side revealed an oceanic climate, with a relatively high average annual temperature, while the western side was characterized by relatively high average annual humidity and average annual precipitation. The distribution rate of P. densiflora forest was found to be high on the eastern side of the mountain range.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.235-236
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• 2002

Tribological phenomena such as wear or transfer are influenced by various factors and have complicated behavior. Therefore, it is difficult to predict the behavior of the gribological phenomena because of their complexity. But, those tribological phenomena can be considered simply as to transfer micro material particles from the sliding interface. Then, we proposed the numerical simulation method for tribological phenomena such as wear of transfer using stochastic process models. This numerical simulation shows the change of the 3-D surface topography. In this numerical simulation, initial 3-D surface toughness data are generated by the method of non-causal 2-D AR (autoregressive) model. Processes of wear and transfer for some generated initial 3-D surface data are simulated. Simulation results show successfully the change of the 3-D surface topography.