• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.1
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• pp.108-118
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• 2017

In this paper, the path tracking controller for a surface vessel based on the sliding mode control (SMC) with the switching law is proposed. In order to have no restriction on movement and improved tracking performance, the proposed control system is developed as follows: First, the kinematic and dynamic models in Cartesian coordinates are considered to solve the singularity problem at the origin. Second, the new multiple sliding surfaces are designed with the SMC and approach angle concept to solve the under-actuated property. Third, the switching control system is designed to improve tracking performance. To prove the stability of the proposed switching system under the arbitrary switching, the Lyapunov stability analysis method with the common Lyapunov function is used. Finally, the computer simulations are performed to demonstrate the performance, effectiveness and stability of the proposed tracking controller of a surface vessel.

• Journal of the Semiconductor & Display Technology
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• v.14 no.1
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• pp.19-25
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• 2015

Strengthened glass is widely used in the display industry for the smart phone and the tablet PC's, the market of which shows steady growth. The strengthened glass is prone to the fracture due to the machined surface defects such as crack and notch. The surface defects are caused mostly by the vibrations of the laser cutter. In this study, the vibrations of the laser cutter were investigated through the frequency response experiment and the computer simulation. The main reasons of the structural vibrations were analyzed, and further the design alterations were deduced and applied to the machine to check the effects of those alterations and to eventually improve the structural stability. The result shows that simple design modifications without major structural change can substantially suppress the vibrations, and improve the quality of the machined surface.

• Korean Journal of Materials Research
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• v.18 no.5
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• pp.277-282
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• 2008

The effects of the field emission property in relation to the surface morphology and adhesion force were investigated. The single-wall-nanotube-based cathode was obtained by use of an in-situ arc discharge synthesis method, a screen-printing method and a spray method. The morphologies of the formed emitter layers were very different. The emission stability and uniformity were dramatically improved by employing an in-situ arc discharge synthesis method. In this study, it was confirmed that the current stability and uniformity of the field emission of the cathode depend on the surface morphology and adhesion force of the emitters. The current stability of the field emission device was also studied through an electrical aging process by varying the current and electric field.

• Journal of Magnetics
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• v.17 no.3
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• pp.185-189
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• 2012

The coercivity of near single domain size $Nd_2Fe_{14}B$-type particles prepared by ball milling of HDDR-treated $Nd_{12.5}Fe_{80.6}B_{6.4}Ga_{0.3}Nb_{0.2}$ alloy was investigated. The feasibility of a surface nitrogenation for improving the coercivity stability of the fine $Nd_2Fe_{14}B$-type particles was also studied. The near single domain size $Nd_2Fe_{14}B$-type particles had a high coercivity of over 9 kOe. However, the coercivity radically deteriorated as the temperature increased in air (< 2 kOe at $200^{\circ}C$). This coercivity reduction was attributed to the soft magnetic phases, ${\alpha}$-Fe and $Fe_3B$, which formed on the surface of the fine particle due to oxidation. Surface nitrogenation of the fine particles significantly improved the stability of their coercivity. The improvement in coercivity stability was attributed to the formation of a thin nitrogenated layer on the surface of the fine $Nd_2Fe_{14}B$-type particles, which enhanced the anisotropy field and gave improved resistance to oxidation (dissociation).

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.1
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• pp.131-143
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• 2007

Statement of the problem: In case of poor bone quality or immediately loaded implant, various strategies have been developed focusing on the surface of materials to improve direct implant fixation to the bone. The microscopic properties of implant surfaces play a major role in the osseous healing of dental implant. Purpose of study: This study was undertaken to evaluate bone response of ion beam-assisted deposition(IBAD) of hydroxyapatite(HA) on the anodized surface of subperiosteal titanium implants. Material and methods: Two half doughnut shape subperiosteal titanium implants were made. The control group was treated with Anodized surface treatment and the test group was treated with IBAD of HA on control surface. Then two implants inserted together into the subperiosteum of the skull of 30 rats and histological response around implant was observed under LM(light microscope) and TEM(transmission electron microscope) on 4th, 6th and 8th week. Results: Many subperiosteal implants were fixed with fibrous connective tissue not with bony tissue because of weak primary stability. The control group observed poor bone response and there was no significant change at any observation time. However the test group showed advanced bone formation and showed direct bone to implant contact under LM on 8th week. The test group observed much rER in the cell of osteoblast but the control group showed little rER under TEM. Conclusions: The test group showed better bone formation than the control group at the condition of weak primary stability. With these results IBAD surface treatment method on Anodized surface, may be good effect at the condition of weak primary stability.

• Journal of the Korean Society of Food Science and Nutrition
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• v.37 no.11
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• pp.1465-1471
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• 2008

This study was carried out to make water-soluble tocopherol emulsion which can be applicable directly in water. The molecular weight of tocopherol was 340 to 360 and tocopherol emulsion model was decided as O/O/W/W type. In correlation between stability of emulsion and surface tension, the stability in surface tension of emulsion was from 40 to 46 dyne/cm. In the case of lower than 40 dyne/cm of surface tension, the stability of the emulsion was lower. Lipophilic surfactants, especially for a polyglycerine polyricinoleate in 20%, 30% and 40% tocopherol emulsion, was the most effective in emulsion stability. A higher stability of the emulsion among hydrophilic surfactants in the tocopherol emulsion was obtained in the following order; polyglycerine monostearate> polyglycerine monooleate> polyoxyethylene (20) sorbitan monooleate$\geq$ polyoxyethylene (20) sorbitan monolaurate.

• Journal of the Korean Society of Food Science and Nutrition
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• v.22 no.6
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• pp.743-752
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• 1993

To elucidate the effects of natural gums, i.e. carrageenan, locust bean gum and xanthan gum and synthetic gums, i.e. carboxymethyl cellulose(CMC) and methyl cellulose(MC) on the foaming properties of sodium caseinate, surface tension, absolute viscosity, turbidity, foaming ability, foam stability, and heat stability of the foams of the caseinate solutions with added gums were examined. The surface tension of sodium caseinate solution(5%) adding to gums at pH 4.0 and 5.0 were higher than those at pH 7.0 and 8.0. The viscosities of the solutions adding to gums(0.1, 0.2, 0.3 and 0.5%) ap pH 4.0, 5.0, 7.0 and 8.0 were 2.4~170.0, 2.5~190.0, 5.3~180.0 and 6.3~99.0 cps, respectively. Especially xanthan gums predominantly increased the viscosity. Turbidities were 97.3~98.2 at pH 4.0 and 5.0 and 93.0~95.8 at pH 7.0 and 8.0. Foaming abilities of the solution adding to xanthan gum, carrageenan and locust bean gum were increased, while those of CMC and MC were decreased. Additions of xantham gum, CMC and MC increased the foam stability, especially xanthan gum did predominantly. Xanthan gum, MC and locust bean gum were more effective than CMC and carrageenan for heat stability. For improving the foaming properties of sodium caseinate xanthan gum were best of five kinds of gums. Surface tensions and turbidities of the solution were related to foaming ability, and the viscosities were related to foam stability and heat stability.

• Journal of the Korean GEO-environmental Society
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• v.22 no.7
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• pp.5-12
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• 2021

The reliable seismic stability evaluation of the natural slopes and geotechnical structures has become a critical factor of the design. Pseudo-static or permanent displacement methods are typically employed to evaluate the seismic slope performance. In both methods, the effect of input ground motion on the sliding surface is ignored, and failure surface from the limit equilibrium method is used. For the assessment of the seismic sensitivity of failure surface, two-dimensional non-linear finite element analyses are performed. The performance of the finite element model was validated against centrifuge measurements. A parametric study with a range of input ground motion was performed, and numerical results were used to assess the influence of ground motion characteristics on the sliding surface. Based on the results, it is demonstrated that the characteristics of input ground motion have a significant influence on the location of the seismically induce failure surface. In addition to dynamic analysis, pseudo-static analyses were performed to evaluate the discrepancy. It is observed that sliding surfaces developed from pseudo-static and dynamic analyses are different. The location of the failure surface change with the amplitude and T_m of motion. Therefore, it is recommended to determine failure surfaces from dynamic analysis

• Proceedings of the Korean Geotechical Society Conference
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• 1991.10a
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• pp.62-74
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• 1991

The stability of the Carsington dam at Derbyshire in middle Eng1and is analysed using the Kinematical Element Method (Program LSDKSLOP). The thin yellow clay layer and the pore pressure at the failure surface, which goes through the core and boot, are considered. The influence of the pre-existing shears of the yellow clay on the stability of the Carsington dam is studied. Comparisons with the calculated and the observed failure surface are presented.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.164-164
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• 2014

Characteristics of electrolyte are those; electrical stability, ion conductivity, viscosity, high temperature work, cell application. Theoretically, GBL has high oxidation voltage. Also, boiling point of GBL is $206^{\circ}C$ and flash point is over $280^{\circ}C$.