• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.06a
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• pp.159-165
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• 2000

In this paper the residual stresses on lubricated sliding surfaces were measured during break-in procedure and up to scuffing by the X-ray diffraction method. The cylinder-on-disk type tribometer was used with the line-contact geometry. Scuffing tests were done using a constant load. In the break-in procedure the loads were increased from very low values in several steps. It was found that the sliding surfaces with break-in represented relatively higher values of residual compressive stresses than those without break-in. The residual stresses below the surfaces showed the small amount of stress increases. The results of scuffing tests with and without break-in showed the same trends as break-in tests did. However, in case of tests with break-in procedure the stresses below the surfaces showed very large increases in the residual compressive stresses. From the tests of break-in and scuffing, it was found that the increases in scuffing lives were related with the increases of residual stresses on the lubricated sliding surfaces with break-in.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.207-208
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• 2002

In the present study, the friction and wear properties of boundary lubricated textured surfaces were investigated. The capability of textured surfaces to feed lubricant into the interface of a sliding contact and to isolate wear partices was studied and related to the properties of the textured surfaces. Well-defined surface textures were produced by lithography and anisotropic etching of silicon wafers. Different widths and distributions of parallel groves were manufactured and subsequently the wafers were PVD coated with thin wear resistant TiN or DLC coatings, retaining the substrate texture. The surfaces were evaluated in reciprocating sliding against a ball bearing steel ball under starved or boundary lubricated conditions.

• Geomechanics and Engineering
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• v.6 no.5
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• pp.469-485
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• 2014

A series of bearing capacity tests was conducted with eccentrically loaded model surface and shallow strip footings resting close to a slope to investigate behavior of such footings (ultimate loads, failure surfaces, load-displacement curves, rotation of footing, etc.). Ultimate loads of footing close to slope decreased with increasing eccentricity for both surface and shallow footings. Failure surfaces were not symmetrical, primary failure surfaces occurred on the eccentricity side (the slope side) and secondary failure surfaces occurred on the other side. Lengths of failure surfaces decreased with increasing eccentricity. Footings always rotated towards eccentricity side a few degrees. For eccentrically loaded footing, decrease in ultimate load with increasing eccentricity is roughly in agreement with Customary Analysis.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.11
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• pp.1067-1073
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• 2011

In this paper, the methodology of a CA (Control Allocation) based FTNCS (Fault-Tolerant Networked Control System) is proposed. Control allocation is a control surface management technique by redistributing the redundant control surfaces in overactuated systems. In modern high performance aircrafts, they adopt many redundant control surfaces to provide high performance and to satisfy various tactical requirements. Moreover, redundant control surfaces provide an opportunity to compensate performance degradation due to failures in more than one actuator by re-allocating redundant control surfaces. Simulation results with an F-18 HARV demonstrate that the proposed CA based FTNCS can achieve a fast and accurate tracking performance even in the presence of actuator faults.

• Honam Mathematical Journal
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• v.38 no.3
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• pp.593-611
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• 2016

This paper is concerned with the classifications of quadric surfaces of first and second kinds in Euclidean 3-space satisfying the Jacobi condition with respect to their curvatures, the Gaussian curvature K, the mean curvature H, second mean curvature $H_{II}$ and second Gaussian curvature $K_{II}$. Also, we study the zero and non-zero constant curvatures of these surfaces. Furthermore, we investigated the (A, B)-Weingarten, (A, B)-linear Weingarten as well as some special ($C^2$, K) and $(C^2,\;K{\sqrt{K}})$-nonlinear Weingarten quadric surfaces in $E^3$, where $A{\neq}B$, A, $B{\in}{K,H,H_{II},K_{II}}$ and $C{\in}{H,H_{II},K_{II}}$. Finally, some important new lemmas are presented.

• Bulletin of the Korean Chemical Society
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• v.33 no.9
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• pp.2855-2860
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• 2012

The coating N-acetyl cysteine (NAC) on gold surfaces may be used to design the distribution of either gold particle adsorbed to the $ZrO_2$ surface or vice versa by adjusting the electrostatic interactions. In this study, it was performed to find out electrostatic properties of the NAC-coated-gold surface and the $ZrO_2$ surface. The surface forces between the surfaces were measured as a function of the salt concentration and pH value using the AFM. By applying the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory to the surface forces, the surface potential and charge density of the surfaces were quantitatively acquired for each salt concentration and each pH value. The dependence of the potential and charge density on the concentration was explained with the law of mass action, and the pH dependence was with the ionizable groups on the surface.

• Journal of the Korean Mathematical Society
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• v.54 no.3
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• pp.999-1013
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• 2017

In the present study we consider the generalized rotational surfaces in Euclidean spaces. Firstly, we consider generalized tractrices in Euclidean (n + 1)-space $\mathbb{E}^{n+1}$. Further, we introduce some kind of generalized rotational surfaces in Euclidean spaces $\mathbb{E}^3$ and $\mathbb{E}^4$, respectively. We have also obtained some basic properties of generalized rotational surfaces in $\mathbb{E}^4$ and some results of their curvatures. Finally, we give some examples of generalized Beltrami surfaces in $\mathbb{E}^3$ and $\mathbb{E}^4$, respectively.

• Bulletin of the Korean Chemical Society
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• v.30 no.9
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• pp.2071-2076
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• 2009

The single-walled carbon nanotubes (SWCNTs) produced by chemical vapor deposition (CVD) were directly fluorinated with fluorine ($F_2$) gas in a temperature range 20 ~ 400 ${^{\circ}C}$. The surface properties and morphology of the SWCNTs were investigated in terms of fluorination temperature. As a result, Raman spectra showed a pair of bands at 1340 and 1590 $cm^{-1}$ peculiar to disordered $sp^2$-carbons. These results indicated that C-F bonds were formed on the rear surfaces of the nanotubes by fluorination, while the external surfaces as well as the layers between the internal and external surfaces retained their $sp^2$-hybridization. XPS analysis exhibited that fluorine atoms were bonded to carbon atoms on internal surfaces (rear surfaces) of the nanotubes and the amount of fluorine attached on the nanotubes was increased with increasing the fluorination temperature. Consequently, the direct fluorination of carbon nanotubes led to functionalization and modification of pristine nanotubes with respect to surface and morphological properties.

• Restorative Dentistry and Endodontics
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• v.16 no.2
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• pp.197-212
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• 1991

The purpose of this study was to roughness on the polished surface of visible light composite resins and was to observe the polished surfaces under Scanning Electrom Microscope(ISI DS 130 AKASHI Co. JAPAN). The surface roughness tester(Surfcom 700A Seimtsu profilometer Tokyo, Japan) was used to measure roughness of polished surfaces. In this study, 5 brands of visible of composite resins were examined, Pyrofile light bond Anterior Lite fil anterior Photo clearfil anterior & posterior Palfique light Anterior and posterior Silux Anterior. White point, Silicure point, Super snap Sof-Lex medium disk as cutting instrument, and celluloid matrix were used. The results obtained were as follows. 1. The Celluloid matrix produced the smoothest surfaces. 2. The surfaces made by Soflex medium disk was smoother than the surfaces made by any other polishing instruments. 3. The values of surface roughness made by White point, Silicon point and Super snap were similer. 4. Palfique light (AP) visible light composite resin showed the smoothest surface after polishing with Silicone point, Super snap disk and Soflex mediuem disk in all tested materials.

• Bulletin of the Korean Mathematical Society
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• v.52 no.2
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• pp.377-394
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• 2015

In this paper, we generalize some results about Bertrand curves and Razzaboni surfaces in Euclidean 3-space to the case that the ambient space is Minkowski 3-space. Our discussion is divided into three different cases, i.e., the parent Bertrand curve being timelike, spacelike with timelike principal normal, and spacelike with spacelike principal normal. For each case, first we show that Razzaboni surfaces and their mates are related by a reciprocal transformation; then we give B$\ddot{a}$cklund transformations for Bertrand curves and for Razzaboni surfaces; finally we prove that the reciprocal and B$\ddot{a}$cklund transformations on Razzaboni surfaces commute.