• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.6
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• pp.39-44
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• 2005

Due to mismatch of thermal expansion coefficients between aluminum sheet and glass/epoxy sheet, thermal residual stresses generally appear in the FML. These stresses will affect the yield and fatigue strength of the FML. The numerically determined residual stresses in the Fiber-Metal-Laminates(FML) have been compared to the residual stresses measured from the curvature and tensile test methods. These two experimental methods have been developed for assessing the influence of residual stress in FML. Post-stretching process has been applied to remove the thermal residual stress and reverse the stress distribution. After post-stretching process, the residual stress has been measured from experiments. The results obtained show that analytical and experimental data are well agreed. The thermal residual stress can be removed by post-stretching process and it will increase the yield strength of FML.

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.6
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• pp.557-569
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• 2011

Steel Fiber Reinforced Concrete (SFRC) is widely used for tunnel structures such as shotcrete and segments. Corrosion of steel fibers and steel reinforcements may affect on the long-term durability of the concrete structures with steel fibers and reinforcement. Therefore, a study on the feasible method to evaluate corrosion possibility and permeability of the concrete structures is required. This experimental study examines the effect of steel fibers and internal reinforcement on the surface resistivity. Steel fiber mix ratio and corrosion of internal reinforcement were considered as variables. In the results, steel fibers significantly reduce the surface resistivity due to those conductive characteristic. In the case of 3% mix ratio, it was difficult to evaluate rate and permeability of corrosion due to the great reduction of resistivity by mixing of steel fibers.

• Bulletin of the Korean Chemical Society
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• v.29 no.4
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• pp.805-810
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• 2008

Using metallic Ti powder as raw materials and 1,2-diaminocyclohexane (DACH) as the trial template, two novel reduced titanophosphate open-structures were hydrothermally isolated by varying the $H_3PO_4/H_2O$ ratio to adjust the pH value. TiPO-1 crystallizes in orthorhombic Pbca space group with cell parameters a = 21.956(3) $\AA$, b = 8.6268(11) $\AA$, c = 7.2883(9) $\AA$, V = 1380.5(3) $\AA^3$, Z = 4. TiPO-2 crystallizes in triclinic space group P$\bar{1}$ with parameters a = 5.1620(10) $\AA$, b = 8.815(2) $\AA$, c = 10.655(3) $\AA$, $\alpha$ = $99.45^{\circ}$, $\beta$ = $102.94^{\circ}$, $\gamma$ = $91.06^{\circ}$, V = 465.34 $\AA^3$. TiPO-1 is constructed by infinite -Ti-O-Ti-O- linkage that is capped by $PO_4$ groups to form a chain structure with protonated DACH molecules occupying the interchain spaces. TiPO-2 represents a rare 3-D reduced titanophosphate with 12-MR channels. The structure of TiPO-2 is a neutral framework with water molecules located in the channels.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.3
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• pp.32-38
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• 2005

FBG sensors have been studied more actively than any other fiber optic sensor because of good multiplexing capabilities among many fiber optic sensors. The demodulation method of FBG sensors is based on the detection of wavelength shift of their sensor peaks and properties such as strain and temperature can be measured by detecting them. However, the signal stability of FBG sensors can be influenced by the strain gradient induced by structural geometry or cracks on the surface when FBG sensors are embedded into or attached on the structure. In this study, the signal characteristics of reflected spectra of FBG sensors under strain gradient were verified and the relations between the grating length of FBG sensors and the amount of strain gradient were investigated. From the experimental results, the recommended working range of FBG sensors under strain gradients was shown quantitatively with respect to grating lengths of them.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.6
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• pp.451-461
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• 2010

Utilization of the fiber reinforced polymer (FRP) material has been enlarged as a substitution material to the general construction materials having certain long-term problems such as corrosion, etc. However, it could be difficult to apply the FRP material, which has a linear shape generally, to an arch-shaped tunnel structure. Therefore, an attempt has been made in this study to develop a device to form a designed cross section of FRP material by pulling out with a curvature. A sample of the circled FRP product was successfully produced and then the sample has been tested to identify its physical characteristics. Then, intensive feasibility studies on the circled FRP panel to be used for a tunnel lining structure have been carried out by numerical analyses. As a result, it appears that the new circled FRP-concrete composite panel has a high capability to be used for a tunnel lining material without any structural problem.

• Electronics and Telecommunications Trends
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• v.33 no.6
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• pp.94-106
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• 2018

A quantum key distribution (QKD) provides in principle an unconditional secure communication unlike the standard public key cryptography depending on the computational complexity. In particular, free-space QKD can give a secure solution even without a fiber-based infrastructure. In this paper, we investigate an overview of recent research trends in the free-space QKD system, including satellite and handheld moving platforms. In addition, we show the key components for a free-space QKD system such as the integrated components, single photon detectors, and quantum random number generator. We discuss the technical challenges and progress toward a future free- space QKD system and components.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.29.4-30
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• 2008

We present elemental abundances of 12 red giants obtained with the BOAO 1.8m telescope and its fiber-fed echelle spectrograph. We perform the abundance analysis using the Kurucz model atmosphere and MOOG. Comparisons of our alpha- and neutron-capture elemental abundances and those in globular clusters and nearby dwarf galaxies will be presented.

• Electrical & Electronic Materials
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• v.11 no.10
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• pp.24-31
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• 1998

Interfacial effect in polymetric composites have been studied extensively. This report deals mainly with the effects of interfacial space charge and interface structure. A model for the dynamic process of interfacial space charge accumulation is proposed. The new model might interpret some interface phenomena which is difficult to be explained in terms of traditional Maxwell-Wagner theory. An interface structure is also presented, by which the importance of surface treatment of glass Fiber for improving the properties of FRP could be well understood.

• Bulletin of the Korean Space Science Society
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• 1992.10a
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• pp.231-238
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• 1992

We have developed a proto-type four-channel photoelectric photometer and control software for the 61-cm reflector of the Sobaeksan Astronomy Observatory. The photometer consists of five main units which has a manipulator, a set of four-opticsassemblies, a light detection units, Pulse counting electronics and a host computer. The software to control the chopper, filter wheel and photon counter has also been developed..

• Korean Institute of Interior Design Journal
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• v.17 no.2
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• pp.91-101
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• 2008

The purpose of this study is to suggest the design guidelines of exhibition space for conservation of collection in a museum. With the purpose of this study, examined the concept and a condition of conservation which is focused on deterioration in a exhibition space, investigated the actual condition of total 42 facilities and analyzed the specific instance which is excellent by factor of environment plan. Hereupon, the results of this study are as follows. First, exhibition space should be equipped with sufficient 'Filtering Space' before the outdoor and located central territory in a museum facility. Second, exhibition space should be partition off an area into the quality of collection, and then controlled by each of them. Third, in consideration of the annual air fluctuation of our country, the database which is adaptable for setting up the standard of temperature and RH must be prepared. Fourth, it is necessary to establish a 'Reference Exhibition Room' which is formed cellular type and a 'Garnering Exhibition Center'. Fifth, for the prevention of deterioration which is generated in exhibition space, the showcase must be high air-tight. Sixth, it is necessary to reduce a inside space of high air-tight showcase. Seventh, art-sorb is suitable for control the organic matter of collection and a except of fiber optics is not suitable for lighting of showcase. Eighth, wall-type showcase should be have air-chamber which is formed like museum storage and run over 8 hours a day.