• Korean Journal of Optics and Photonics
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• v.12 no.4
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• pp.289-293
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• 2001

A metal capillary splice fiber-optic sensor was fabricated for use as an intensity-based macro-bending sensor. As the radius of curvature due to the macro-bending decreases, the angular misalignment of the fiber ends inside the metal capillary increases, i.e., the coupling efficiency of the fiber splice is reduced. Thus, macro-bending can be detected by the measurement of the reduction of transmitted power. The detectable range of macro-bending. was measured approximately from 20 mm to 85 mm. The center wavelengths of the fiber Bragg gratings are 1543.3 nm and 1549.5 nm, respectively. The maximum bending loss of this sensor was measured about -11.92 dB. Using this metal capillary spliced fiber sensor and fiber Bragg gratings, macro-bending detection has been demonstrated, and it is shown to have potential for multi-point macro-bending sensors. nsors.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.525-530
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• 2007

Although just developed in recent years, curved box girder has widely used in modern highway system due to their load resistance capacity as well as aesthetic considerations. According to recent literature reviews on curved box girder designs, distortional load was not considered as much as it deserves to be. In practice, the effect of distributional force is very small in straight bridge systems but yet unknown how it is in curved bridge systems. For the reason, this paper will show up an extensive parametric study on distortional behavior of curved box girder with trapezoidal section. Based on Dabrowski formulas, using finite element method, various bridges were investigated. In this study, following parameters will be included: span length, curvature radius, section height, section width, and internal section angle (web slope). From the obtained results, some initial geometric parameters are proposed for curved box girder bridges.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.3
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• pp.534-546
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• 1990

In this work, an optimum shape synthesis for rolling contact components was done to minimize contact forces considering dynamic characteristics of the system. Even this method was applied to an OHC type cam follower system, it can be expanded to general rolling contact shape design problems which are strictly forced to follow predetermined motion. First, the follower optimum angular motion was derived to minimize the valve peak acceleration while satisfying all the constraints of valve motion. Then the cam and follower contact shape were synthesized to give the proposed follower motion. Theoretically, two components shape to generate a predetermined motion can not be uniquely determined. So the cam shape was syntehsized with parametric synthesis method to minimize the peak contact force between cam and follower when the follower shape is assumed as a circle or an ellipse.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.2
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• pp.120-124
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• 2016

In this study, we fabricate transparent and bendable a-IGZO (amorphous indium gallium zinc oxide) TFTs (thin-film transistors) with a-IZO (amorphous indium zinc oxide) transparent electrodes on plastic substrates and investigate their electrical characteristics under bending states. Our a-IGZO TFTs show a high transmittance of 82% at a wavelength of 550 nm. And these TFTs have an $I_{on}/I_{off}$ ratio of $1.8{\times}10^8$, a field effect mobility of $15.4cm^2/V{\cdot}s$, and a subthreshold swing of 186 mV/dec. The good electrical characteristics are retained even after bending with a curvature radius of 18 mm corresponding to a strain of 0.5% owing to mechanical durability of the transparent electrodes used in this study.

• Bulletin of the Korean Chemical Society
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• v.33 no.11
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• pp.3805-3809
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• 2012

Results for molecular dynamics simulation method of small liquid drops of argon (N = 1200-14400 molecules) at 94.4 K through a Lennard-Jones intermolecular potential are presented in this paper as a preliminary study of drop systems. We have calculated the density profiles ${\rho}(r)$, and from which the liquid and gas densities ${\rho}_l$ and ${\rho}_g$, the position of the Gibbs' dividing surface $R_o$, the thickness of the interface d, and the radius of equimolar surface $R_e$ can be obtained. Next we have calculated the normal and transverse pressure tensor ${\rho}_N(r)$ and ${\rho}_T(r)$ using Irving-Kirkwood method, and from which the liquid and gas pressures ${\rho}_l$ and ${\rho}_g$, the surface tension ${\gamma}_s$, the surface of tension $R_s$, and Tolman's length ${\delta}$ can be obtained. The variation of these properties with N is applied for the validity of Laplace's equation for the pressure change and Tolman's equation for the effect of curvature on surface tension through two routes, thermodynamic and mechanical.

• Structural Engineering and Mechanics
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• v.17 no.5
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• pp.611-626
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• 2004

On the basis of a structural analysis of radial gate (i.e. Tainter gate), the current paper focuses on weight minimization according to the location of the arms on a radial gate. In spite of its economical significance, there are hardly any previous studies on the optimum design of radial gate. Accordingly, the present study identifies the optimum position of the support point for a radial gate that guarantees the minimum weight satisfying the strength constraint conditions. This study also identifies the optimum position for 2 or 3 radial arms with a convex cylindrical skin plate relative to a given radius of the skin plate curvature, pivot point, water depth, ice pressure, etc. These optimum designs are then compared with previously constructed radial gates. Local genetic and hybrid-type genetic algorithms are used as the optimum tools to reduce the computing time and enhance the accuracy. The results indicate that the weights of the optimized radial gates are appreciably lower than those of previously constructed gates.

• International Journal of Air-Conditioning and Refrigeration
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• v.12 no.2
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• pp.79-86
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• 2004

An analytical and experimental study has been conducted to determine the optimal charging mass of working fluid for the maximum heat transport capacity of heat pipe with axially grooved wick. When the heat pipe is operated in a steady state, the liquid-vapor meniscus recession of working fluid to the bottom of groove is occurred in the evaporator region. In this work, the optimal charging mass of working fluid was obtained by considering the meniscus recession from the axial variation of capillary pressure, the radius of curvature and wetting angle of meniscus of liquid-vapor interface. Experimental results were also obtained by varying the charging mass of working fluid within a heat pipe, and presented for the trend of maximum heat transport capacity corresponding to the operating temperature and the elevation of heat pipe. Finally, the analytical results of the optimal charging mass of working fluid were compared with those from the experiment, both of which were in good agreement with each other.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.9
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• pp.669-678
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• 2007

In this study, the ventilation characteristics is investigated numerically of the longitudinal ventilation method in the curved long road tunnel. Numerical work has been conducted for the jet fan location by utilizing the commercial finite-volume code, FLUENT. Configuration of the tunnel is three-lane, 1600 m long, $120m^2$ in area, 3000 m curvature radius. The velocity profile, distribution of mono-dioxide carbon and flow rate of air are examined in the tunnel. Through the analysis, it is found that the difference of ventilation flow rate Is a little by the jet fan location, but tunnel outlet setup (CASEIII) of jet fans is the most efficient concerned with CO concentration.

• Journal of Korea Water Resources Association
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• v.39 no.12 s.173
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• pp.1023-1030
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• 2006

The characteristics of the longitudinal velocity in a $180^{\circ}$ constant-radius, recirculating laboratory channel were investigated. Three-dimensional velocity fields were measured using a side-looking ADV. The shortcomings of existing equations for longitudinal velocity are discussed. An eddy viscosity model is adopted in the downstream momentum equation. A mathematical equation was developed to describe the vertical distribution of longitudinal velocity. The comparisons of the longitudinal velocity show generally good agreement. It is found that the curvature change in the curved channel affects the vertical location of maximum velocity and the vertical profile of longitudinal velocity.

• KIEAE Journal
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• v.5 no.3
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• pp.3-9
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• 2005

Venetian blinds are used with windows to improve the uniformity ratio of illuminance and interior daylighting distribution under direct sunlit conditions. The main objective of Venetian blinds shading system is to obstruct direct sunlight and at the same time allow daylight to penetrate into the room. Venetian blinds would have greater effect on the interior daylighting condition under clear sky which has both skylight and sunlight than overcast sky which has only skylight. However, due to the lack of data, design and evaluation tools, it is difficult for architects to choose or install venetian blinds during the building design stages. The purpose of this study was to develop an analysis method for shading and daylighting effects of Venetian blinds using the RADIANCE program. The major variables related to the venetian blinds included blinds's slat angle and the ratio of slat width to window height, the radius slat of curvature and the building azimuth. In this study, a series of parametric physical mock-up model measurements and genblinds command in the RADIANCE simulations. The results of this study will provide building designers with the design data at early design stages.