• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.105-108
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• 1996

The positive active material for polymer film battery was prepared by using Polyphenylenediamine(PPD) synthesized in our lab. and 2.5-dimercapto-1, 3, 4-thiadiazole(DMcT) in various mixture ratio. The transference measurement of surface morphology and thermal stability of prepared composite film was carried out by using SEM and TGA, respectively. Electrocyhemical property and electrical conductivity of composite film were also measured by using cyclic voltammetry and four-probe method in dry box, respectively. The thermal stability of prepared composite film is more than 20$0^{\circ}C$. The electrical conductivity of composite film increased and showed the highest value(about 3 S/cm)when doped at 0.4% LiClO$_4$solution. And we could confirm that DMcT effect on reactiviation of PPD through cyclic voltammogram.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.11
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• pp.1019-1022
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• 2003

We studied the nematic liquid crystal (NLC) aligning capabilities using the new alignment material of a-C:H thin film as working gas at 30W rf bias condition. A high pretilt angle of about 5$^{\circ}$ by ion beam(IB) exposure on the a-C:H thin film surface was measured. A good LC alignment by the IB alignment method on the a-C:H thin film surface was observed at annealing temperature of 250$^{\circ}C$, and the alignment defect of the NLC was observed above annealing temperature of 300$^{\circ}C$. Consequently, the high LC pretilt angle and the good thermal stability of LC alignment by the IB alignment method on the a-C:H thin film surface as working gas at 30W rf bias condition can be achieved.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.301-304
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• 2001

Hot-compression tests were carried out to investigate the hot workability of Ti64 and Ti6246 alloys at different temperatures and strain rates. Processing maps were developed on the basis of the dynamic material model unifying the relationship among constitutive behavior, hot workability and microstructure development. Stable regions, defined on the basis of four stability criteria 0${\delta}log(m)/\frac{\bot}{\varepsilon})<0$, s<1 and ${\delta}log(s)/\frac{\bot}{\varepsilon})<0$, were found to be associated with dynamic recovery and recrystallization.

• Journal of Power System Engineering
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• v.14 no.6
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• pp.47-53
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• 2010

A stabilizer link connects the stabilizer bar to the lower arm of the suspension. When a vehicle is turning, lateral forces from the tire are transmitted through the stabilizer link into the stabilizer bar. The stabilizer bar will twist, thus adding rigidity to the vehicle body. In this study, the stabilizer link body was manufactured by using composite material with POM-GF25%. Therefore, the strength evaluation of stability link body with composite material carried out from tensile, wear and fatigue test. The tensile strength between the stability link body with composite material and the rod with knurling was the largest of four types of rod. In Analyzing materials property using optical sensing technique of stabilizer link for automobile parts, its has been identified the safety.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.153-159
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• 1999

A material handling crane is composed of many complex structural components which require sufficient strength, stiffness and stability throughout its service life and need to be light in weight, and satisfy the required functions under the entire range of operating conditions. In this study, the analysis system for material handling cranes is presented. This program integrate various structural analyses modules with the GU(Graphic User Interface) concept. Utilizing basic variables as input data, the analysis system performs quasi-static, eigenvalue, buckling, fatigue and stability analysis. Using this program, the designer can generate optimal design data for the cranes without my actual measurements. This system will also be extended to other mechanical structures with kinematic motion like crane.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.502-505
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• 2003

We synthesized high thermal photoalignment material with hydroxyl aromatic polyimide, and studied the liquid crystal (LC) aligning capabilities on the photopolymer layers. Also, electro-optical (EO) performances for the twisted-nematic (TN)-liquid crystal display (LCD) photoaligned with linearly polarized UV exposure were investigated. A good LC alignment with UV exposure on the photopolymer surface can be obtained. However, the low pretilt angles were obtained below $1^{\circ}$. The Voltage-transmittance (V-T) curve without backflow bounce in the photoaligned TN cell with UV exposure was observed. The response time of photoaligned TN cell was measured about 24 ms.

• Steel and Composite Structures
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• v.33 no.1
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• pp.133-142
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• 2019

In the present study, microstructure-dependent static stability analysis of inhomogeneous tapered micro-columns is performed. It is considered that the micro column is made of functionally graded materials and has a variable cross-section. The material and geometrical properties of micro column vary continuously throughout the axial direction. Euler-Bernoulli beam and modified couple stress theories are used to model the nonhomogeneous micro column with variable cross section. Rayleigh-Ritz solution method is implemented to obtain the critical buckling loads for various parameters. A detailed parametric study is performed to examine the influences of taper ratio, material gradation, length scale parameter, and boundary conditions. The validity of the present results is demonstrated by comparing them with some related results available in the literature. It can be emphasized that the size-dependency on the critical buckling loads is more prominent for bigger length scale parameter-to-thickness ratio and changes in the material gradation and taper ratio affect significantly the values of critical buckling loads.

• Korean Journal of Materials Research
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• v.31 no.8
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• pp.427-432
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• 2021

This study uses silicone monomer, DMA, crosslinking agent EGDMA, and initiator AIBN as a basic combination to prepare hydrogel lenses using fluorine-based perfluoro polyether and iron oxide and zinc oxide nanoparticles as additives. After manufacturing the lens using iron oxide nanoparticles and zinc oxide nanoparticles, the optical, physical properties, and polymerization stability are evaluated to investigate the possibility of application as a functional hydrogel lens material. As a result of this experiment, it is found that the addition of the wetting material containing fluorine changes the surface energy of the produced hydrogel lens, thereby improving the wettability. Also, the addition of iron oxide and zinc oxide nanoparticles satisfies the basic hydrogel ophthalmic lens properties and slightly increases the UV blocking performance; it also increases the tensile strength by improving the durability of the hydrogel lens. The polymerization stability of the nanoparticles evaluated through the eluate test is found to be excellent. Therefore, it is judged that these materials can be used in various conditions as high functional hydrogel lens material.

• Journal of the Korean Applied Science and Technology
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• v.23 no.2
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• pp.147-152
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• 2006

The accidents occurred by unstable material which is easily exploded or burnt up were caused by heat and collision under the condition of relatively low temperature without oxygen, have been reported frequently. However, the amount of the unstable material is getting higher by development of fine ceramic research area even though its dangerous characteristic is disregarded. This research studied a heat stability and measured boiling point of various carpet material. Carpet has been used in home as well as general indoor usage. Now a day, carpet material which is hardly burnt has been on commercial, but its detailed unstable conditions is not mentioned. This research reports the measurement of the initial temperature of generation heat and heat-radiation change on differential scanning calorimeter (DSC). The DSC data of nylon bulked continuous filament (N-BCF) yam 100%, nylon (NY), poly propylene (PP), and a new material named polytrimethylene terephthalate (PTT) are studied and researched about the effect of them using TGA, furnace, and direct-burning experiment.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.5
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• pp.421-424
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• 2007

Thermal behavior of $Li_{1-x}CoO_2$ has been investigated employing DSC (Differential Scanning calorimetry) and TGA (Thermogravimetry Analyzer), and the crystal parameters were calculated from XRD (X-ray diffraction).for the commercial rectangular pouch cell(1000 mAh).The cathode materials coated over aluminium foil current collector is made up of a blend consisting of active material $LiCoO_2$(size $20\;{\mu}m$, 94 wt%), conducting material super p black (SPB, 3 wt%) and binder polyvinylidene fluoride (PVDF, 3 wt%). The anode is a mix consisting of carbon (92 wt%) and PVDF(8 wt%) coated over copper foil. The cells for the experiments were first preconditioned by cycling three times and stabilized at OCV=3.0, 3.5, 4.2, 4.35 and 4.5 V. The stabilized cathode material was used for thermal and crystal parameter investigations.