• Korean Chemical Engineering Research
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• v.48 no.5
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• pp.615-620
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• 2010

In this study, five series of novel polyurethanes was synthesized by the polyaddition reaction of diisocyanates such as 2,6-tolylene diisocyanate(2,6-TDI), 2,5-tolylene diisocyanate(2,5-TDI), 2,4-tolylene diisocyanate(2,4-TDI), and 1,4-phenylene diisocyanate(1,4-PDI), hexamethylene diisocyanate(HDI) with 4,4'-Bis(3-hydroxypropoxy)biphenyl (BP3), 4,4'-bis(3-hydroxypropoxy)biphenyl exhibited a smectic type mesophase. Monotropic mesophase was found for all synthesized liquid crystalline polyurethanes except HDI/BP3. In contrast, 1,4-PDI/BP3 without a methyl substituent in the phenylene unit exhibited no explicit mesomorphic behavior, which was confirmed by DSC and polarizing microscopy experiments. Structures of the compound were identified by FT-IR and $^1H$-NMR spectroscopies. Their phase transition temperatures and thermal stability were also investigated by differential scanning calorimetry(DSC), polarized optical microscopy(POM) and x-ray diffraction analysis.

• Korean Journal of Optics and Photonics
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• v.8 no.4
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• pp.340-344
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• 1997

We proposed and demonstrated a tunable wavelength optical add/drop multiplexer(OADM) employing piezoactuated fiber grating pairs and polarization beam splitters. We used piezostack act as a fiber stretcher, using the fact that the resonant wavelength of the grating can be controlled by the axial strain along the fiber grating. The polarization controlled configuration showed high stability because the reflected signals from the two identical gratings are dropped or added not by interference but by polarizations of the beams. We could add and drop not noly 1549.3nm signal channel(original gratings), but also 1550.1nm(tuned gratings) with PZT actuators and in both cases, we found that the rejection of adjacent channels was more than -26dB, and signal leakage at the gratings was less than -34dB.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.1
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• pp.15-22
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• 2007

A hybrid experimental-numerical method is presented for determining the stresses around a circular hole in a finite-width, tensile loaded plate. Measured fringe orders along straight lines provided the input information on the external boundary of the hybrid element. In order to see the effects of varying stress field, different numbers of terms in a power-series representation of the complex type conformal mapping stress function were tested. For qualitative comparison, actual isochromatic fringes were compared with reconstructed theoretical fringes using stress-optic law. For quantitative comparison, relative errors and standard deviations with respective to relative errors were analyzed for all measured points by changing the number of terms of stress function. The hybrid results are highly comparable with those predicted by FEA. The results show that this approach is effective and promising because isochromatic data along the straight lines in photoelasticity can be conveniently measured by use of phase shifting photoelasticity.

• Journal of Sensor Science and Technology
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• v.9 no.1
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• pp.15-21
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• 2000

Optical fiber temperature sensor, using resonance wavelength shifting of single mode fiber-to-planar waveguide coupler by heat, was fabricated. Thermo-optic polymers, have large change of refractive index due to heat, were used for planar waveguide. The device fabrication procedure including fiber polishing steps was illustrated and the device structure with independent polarization was demonstrated experimentally. The resonance wavelength difference of fabricated device was less than 2nm. The resonance wavelength shifting owing to temperature variation, from room temperature($24^{\circ}C$) to $90^{\circ}C$, was showed $-0.54nm/^{\circ}C$, $-3nm/^{\circ}C$.

• Korean Journal of Optics and Photonics
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• v.13 no.6
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• pp.506-509
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• 2002

An optical system for a stereoscopic video recorder is designed with the field of view 42$^{\circ}$ and effective diameter 22 mm. We can use it by attaching it to the front lens of any video camera or camcorder to record a stereoscopic scene. This system is a double Kepler type afocal system to make the image erect and a bi-ocular type to record and display the stereoscopic scene. The optical tube length is folded with several flat mirrors and a beam splitter to be compact. This optical system is composed of 4 groups of lenses and each group serves as a relay lens for minimizing the vignetting effect. Whole field stereoscopic scenes may be captured by perpendicularly polarized alternated recording with a chopper and two perpendicular polarizers, without any loss of light energy. The displayed images may be seen stereoscopically with polarized spectacles and are kinetic because of an afterimage effect.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.8
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• pp.1776-1782
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• 2010

The interferometric fiber optic gyroscopes (FOGs) are well known as sensors of rotation, which are based on Sagnac effect, and have been under development for a number of years to meet a wide range of performance requirements. This paper describes the development of open-loop FOG and digital signal processing techniques implemented on FPGA. Our primary goal was to obtain intermediate accuracy (pointing grade) with a good bias stability (0.22deg) and scale factor stability, extremely low angle random walk (0.07deg) and significant cost savings by using a single mode fiber. A secondary goal is to design all digital FOG signal processing algorithms with which the SNR at the digital demodulator output is enhanced substantially due to processing gain. The Cascaded integrator bomb(CIC) type of decimation filter only requires adders and shift registers, low cost processors which has low computing power still can used in this all digital FOG processor.

• Journal of the Korean Vacuum Society
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• v.9 no.3
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• pp.254-257
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• 2000

We report spectroscopic ellipsometric (SE) measurements on $Cd_{1-x}Mg_x/Te$ (0$\leq$x$\leq$0.43) films grown on GaAs substrate. When compared with previous bulk data, at first, current spectrum shows clear interference oscillations below $E_0$ band gap energy, which means the transparent characteristic of direct transition material below $E_0$ edge. It proves that the film samples used for this work have the most interrupted surface of high quality reported so far by SE. Secondly the best resolution of $E_2$-peak is observed, so we can report clear splitting of E$_2$and $E_0'$ band gap energies. We also performed the multilayer calculation necessary to remove this interference oscillations to observe $E_0'$ band gap energy of $Cd_{1-x}Mg_x/Te$ (x=0.23) film.

• Applied Chemistry for Engineering
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• v.23 no.6
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• pp.577-582
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• 2012

In this work, vibrational circular dichroism (VCD) technique was applied for the determination of %EE of chiral compounds. It may provide an easy way to determine the %EE with a proper accuracy within 2% error ranges as well as the absolute configuration of enantiomers. We demonstrated herein a flow cell VCD (FT-VCD) technique for time-dependent %EE measurements. The simultaneous monitoring of the mole fraction and %EE for two chiral species (epichlorohydrin and glycidol mixture) in the mixture was shown to be successful without any further separation steps. Thus, we demonstrate that FT-VCD is an appropriate analytical tool to monitor the kinetics of reactions involving chiral molecules. FT-VCD also provides a convenient nondestructive approach for the time dependent determination of the optical purity of individual components in a reaction mixture containing chiral molecules.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.2
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• pp.189-196
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• 2001

Photoelasticity is one of the most widely used methods for whole field stress analysis. In photoelasticity, the difference and the directions of the principal stresses we given isochromatic and isoclinic fringe patterns. Conventionally, principal stress directions are measured manually by relating the polarizer and analyzer of a plane polariscope at the same time. This is known to be the Tardy compensation method. This measurement can be very tedious and time consuming in whole field analysis. It is not possible to separate isoclincs from photoelastic fringes by conventional photoelastic technique. In this study, photoelastic theory is represented by Jones matrices and 4-steps and 8-steps phase shifting methods are described A feasibility study using computer simulation is done to separate isoclincs and isochomatics from photoelastic fringes of a circular disk under diametrical compression. Fringe patterns of the disk are generated using stress optic law. The magnitudes of isoclincs and isochromatics obtained from 8-step phase shifting method are compared with those of theories. From computer simulation, it is verified to separate isoclincs and isochomatics from photoelastic fringes.

• The Korean Journal of Quaternary Research
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• v.23 no.2
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• pp.13-33
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• 2009

Mineralogical analysis with petrographic microscope and XRD was carried out to verify manufacturing technique of the tiles(9 samples) and kiln wall materials(5 samples) from the Anchang-ri history site in Wonju county. One of the results we found is such that during the tile manufacturing process fine tile fragments or wall materials might be added instead of chamottes to maintain tile pattern. Abandoned tiles or wall materials were recycled repeatedly, which may be supported by the recycled chamottes that made from iron-rich fine aggregates or disposed kiln wall materials in many samples analyzed. The tiles and wall materials are divided into 3 types, including low temperature type (below $800^{\circ}C$), intermediate temperature type ($800-930^{\circ}C$) and high temperature type ($930-1470^{\circ}C$) as a function of firing temperature which deduced by mineral assemblages identified under petrographic microscope and by XRD composition. Both Kiln A8 of Choseon Dynasty and wall material AW5 were burned at the highest temperature among the all analyzed samples.