• International Journal of Fuzzy Logic and Intelligent Systems
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• 제1권1호
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• pp.44-49
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• 2001

For minimum phase systems, the conventional fuzzy logic controllers (FLCs) use the error and the change-of-error as fuzzy input variables. Then the control rule table is a skew symmetric type, that is, it has UNLP (Upper Negative and Lower Positive) or UPLN property. This property allowed to design a single-input FLC (SFLC) that has many advantages. But its control parameters are not automatically adjusted to the situation of the controlled plant. That is, the adaptability is still deficient. We here design a single-input direct adaptive FLC (SDAFLC). In the AFLC, some parameters of the membership functions characterizing the linguistic terms of the fuzzy rules are adjusted by an adaptive law. The SDAFLC is designed by a stable error dynamics. We prove that its closed-loop system is globally stable in the sense that all signals involved are bounded and its tracking error converges to zero asymptotically. We perform computer simulations using a nonlinear plant and compare the control performance between the SFLC and the SDAFLC.

• The Transactions of the Korean Institute of Electrical Engineers C
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• 제48권6호
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• pp.462-468
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• 1999

Room temperature vulcanizing (RTV) silicone rubber has been widely used to coat porcelain insulators to render water repellency to prevent formation of water film on the surface and thus to suppress the leakage current and consequently flashover. However, the electrical property and the hydrophobicity of RTV silicone rubber coating under outdoor condition may be influenced by many environmental factors. In this studyvarious treatments, such as salt-fog, salt water immerging and UV irradiation were applied to the samples to investigate the change of the electrical property and hydrophobicity. As a result the leakage current increased and contact angle decreased asthe degradation time is longer. But the degraded RTV silicone rubber has recovered its hydrophobicity during the drying time in ambient condition because LMW(Low Molecular Weight) silicone fluid diffused from the bulk to the surface.

• Proceedings of the IEEK Conference
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.341-342
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• 2008

A conductivity of soot at microwave frequency is presented using a novel technique for complex permittivity of materials. The method overcomes limitations of conventional methods which are cavity perturbation and transmission/reflection method. Resonant frequencies and Q factors are measured and simulated for the cylindrical cavity, and they are compared to each other. Similar material property of both real material and simulation material produce similar values of resonant frequency and Q factor. The complex permittivity of material can be determined by simulating the cavity to change material property until the simulation results are nearly the same as the measurement results. Cylindrical cavity has been realized for measurement at 880 MHz, and conductivity of soot is measured. A sample was made by depositing the soot on the glass. The proposed method shows that the conductivity of soot is 11 S/m.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1324-1327
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• 2003

The compressed fracture of spine caused by osteoporosis is one of the most frequent diseases in bone fracture. Recently the vertebroplasty has drawn much attention as a medical treatment for the compressed fracture of spine, which strengthens the vertebral body and corrects deformity, and relieves pain in patients by injecting bone cement. The finite element analysis is used to investigate the vertebroplasty quantitatively. Previous works with finite element analysis have drawbacks in their simplified models geometry of vertebral body and with material properties of bone. In this paper the exact geometry of vertebral body has been constructed from medical image data and the biomechanical property changes of vertebral body in vertebroplasty have been investigate by using three dimensional finite element analysis.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제15권4호
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• pp.274-286
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• 2003

Numerical simulations are performed to investigate the turbulent convective heat transfer of the supercritical carbon dioxide flows in vertical and horizontal square ducts. The gas cooling process at the supercritical state experiences a sudden change in thermodynamic and transport properties. This results in the extraordinary variations of the heat transfer coefficients in the supercritical state, which are much different from those of single or two phase flows. Algebraic second moment closure which can include the effects of large thermophysical property variations of carbon dioxide and of buoyancy is employed to model the Reynolds stresses and turbulent heat fluxes in the governing equations. The previous correlations for the turbulent heat transfer coefficient for the supercritical carbon dioxide flows couldn't reflect the buoyancy effect. The present results are used to establish a new heat transfer coefficient correlation including the effects of large thermophysical property variation and buoyancy on in-duct cooling process of supercritical carbon dioxide.

• Journal of the Optical Society of Korea
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• 제20권4호
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• pp.510-514
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• 2016

The conventional liquid crystal displays (LCDs) have been using optically uniaxial liquid crystal (LC) medium and this often causes a significant image change at oblique viewing angles. We simulated the viewing angle properties of the biaxial nematic (N_b) phase of a bent-core liquid crystal (BLC) and compared the results with the vertically aligned (VA)- and the in-plane switching (IPS)-LCDs. The N_b phase of the BLC showed a smaller transmittance at the dark state as well as a greater contrast ratio at wide viewing angle. The viewing angle property of the N_b-mode without any compensation film was slightly superior to the IPS-mode with the compensation films eliminating the decross of the polarizers at oblique viewing angle.

• Textile Coloration and Finishing
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• 제10권2호
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• pp.18-28
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• 1998

in order to overcome disadvantage of the conventional two bath dyeing method of polyester/cotton blends, it had prompted significant effort to the development of the one bath dyeing method which can accomplish sayings in time, energy and water usage. Also, when dyeing polyester/cotton blends by the one bath dyeing method, the high salt concentrations needed for the reactive dye can cause particles of disperse dye, used for the polyester component, to aggregate. A supplementary problem that can occasionally be happened is the change of hue that occurs on dyed polyester in an alkaline dyebath. To improve dyeing property of polyester/cotton blends, cotton component was pretreated with epichlolohydrine-trimethylamine hydrochloride in aqueous solution of sodium hydroxide to produce a cationized cotton that can be dyed under neutral conditions with reactive dye in a non-electrolytic or il little electrolytic dyebath. The one bath dyeing method of polyester/cationized cotton blends with disperse dye/reactive dye mixture resulted in a satisfactory dyeing property and color yield in comparison with ordinary two bath dyeing method.

• Transactions of the Korean Society of Mechanical Engineers B
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• 제20권2호
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• pp.641-648
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• 1996

Thermophoretic particle deposition on a circular cylinder in a uniform laminar air flow was numerically investigated using a control volume method based on the generalized non-orthogonal coordinate system. Variation of air properties due to the change of temperature was taken into account. Effects of variable property on the distribution of heat transfer and deposition rates of particle were discussed. A new correlation of thermophoretic particle deposition on a circular cylinder was proposed in the present study.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.184.1-184.1
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• 2014

Nanostructures on Graphene surface receive highly attraction for many applications ranging from sensing technologies to molecular electronics. Recently J. Jasuja et al. reported the electrical property tailoring and Raman enhancement by the implantation and growth of dendritic gold nanostructures on graphene derivatives [ACSNANO, 3, 2358, 2013] Here, we introduced Si vapor on the graphen to induce the nanostructure. The surface property change of graphene by controlling the amount of Si and the thickness of graphene were investigated using high resolution photoemission spectroscopy (HRPES), and atomic force microscopy (AFM). The Si nanostructures on graphene show the thickness dependency of graphene, and the size of Si nano-structure reached to 7 nm and 15 nm on the mono and the multilayered graphene after $30{\AA}$ Si evaporation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제14권3호
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• pp.234-240
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• 2001

Using RF magnetron sputtering, amorphous carbon(a-C) thin films as electron filed emitter were fabricated. these a-C thin films were deposited on Si(001) substrate at several temperatures. The field electron emission property of these a-C thin films was estimated by a diode technique. As the result, we observed that the field emission properties of the films were changed singnificantly with the substrate temperature and structural features of a-C film. The field emission properties were promoted by higher substrate temperatures. Furthermore N-doped a-C film exhibits more field emission property than that of undoped a-C film. These results are explained as change of surface morphology and structural properties of a-C film.