• Elastomers and Composites
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• v.34 no.3
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• pp.247-252
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• 1999

Rubber related geosynthetics(GS) as reinforcement and water barrier materials were manufactured by thermal bonding method and examined the their performance for applications to civil and environmental engineering fields. The spunbonded polyester nonwoven, fiber glass mat and fabric type geogrid of a high tenacity polyester filament were used as matrix and polyester film, elastomeric bitumen with SBS polymer and asphalt were used as reinforcements to manufacture the rubber related geosynthetics. A fiber glass mat and geogrid matrix GS showed more excellent mechanical properties and nonwoven and elastomeric bitumen matrix showed the more excellent permittivity. Softening points of rubber and asphalt mixture showed no difference and dimensional stability at high temperature, $120^{\circ}C$, represented no significant shrinkage. Resistance to ultraviolet of rubber related geosynthetics showed no visible alteration.

• Journal of Welding and Joining
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• v.16 no.5
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• pp.56-66
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• 1998

During solidification or welding of alloys, the solute redistribution brings out microsegregation. The microsegregation causes the formation of non-equilibrium second phases, shrinkage and porosity degrading mechanical/chemical properties Therefore, it has been required to predict microsegregation quantitatively. To predict the degree of microsegregation, more exact and appropriate computer simulation technique has been actively used during last two decades. To predict the degree of microsegregation in weld metal, an advanced two dimensional model was suggested. In the new model, both primary and secondary arm regions were defined for the analysis region. The growth in the primary arm regina was assumed to be a planar for effective calculation. Especially, for the growth of a secondary arm, a simple and effective mathematical function was established to show the growing pattern, the solute diffusion in the solid phase was calculated by finite difference method (FDM). The solid-liquid interface movement was considered to be in local equilibrium state. The experiments for welding of 310S stainless steel were carried out in order to examined the reasonability and feasibility of this model. The concentration profiles of the solute predicted by this model were compared with those obtained from experimental works.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.735-738
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• 2003

Downsizing electronics requires precision position control with an accuracy of sub-micron order, which demands development of ultra-fine displacive devices. Piezoelectric transducer is one of devices transferring electric field energy into mechanical energy and being capable for fine displacement control. The transducer has been widely used as fine Position control device Multilayer piezoelectric actuator, one of typical piezo-transducer, is fabricated by stacking alternatively ceramic and electrode layers several hundred times followed by cofiring process. Electrode material should be tolerable in the firing process maintaining at ceramic-sintering temperatures up to $1100{\sim}1300^{\circ}C$. Ag-Pd can be used as stable electrode material in heat treatment above $960^{\circ}C$. Besides, adding small quantity ceramic powder allow the actuator to be fabricated in a good shape by diminishing shrinkage difference between ceramic and electrode layers, resulting in avoidance of crack and delamination at and/or nearby interface between ceramic an electrode layers. This study presents synthesis of nano-oxide-added Ag/Pd powders and its feasibility to candidate material tolerable at high temperature. The powders were formed in a co-precipitation process of Ag and Pd in nano-oxide-dispersed solution where Ag and Pd precursors are melted in $HNO_3$ acid.

• Journal of Korea Foundry Society
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• v.13 no.3
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• pp.268-275
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• 1993

In gravity die casting, die cooling systems are frequently employed with water cooling to remove the heat of the solidifying metal. Thermal modeling is an important technique in mold design for improving the productivity of the process. Computer simulation system which consists of pre-processor, main solidification simulator and post-processor has been developed for three dimensional solidification analysis of cyclic gravity die casting. The pre-processor is used for mesh generation in a PC system. The modified finite difference method is adopted for the main solidification simulation algorithm during all the casting cycles. The post-processor graphically presents the simulation results. Several experiments in automotive cast piston were carried out. The temperature variations in casting and mold with time are measured experimentally, and the results are compared with calculation results. The effects of cycle number on solidification pattern are also studied. Several experimental results for the prediction of shrinkage defects are compared with calculated results.

• Journal of the Korean Society of Clothing and Textiles
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• v.18 no.3
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• pp.287-297
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• 1994

The purpose of this study is to investigate the Improvement of fiber surface, tenacity & elogation, fabric counts, thickness, handle, moisture regain, static voltage, handle, dyeability when polyester fabrics are treated with NaOH solution adding quartemary ammonium salt (Benzyl dimetyl dodecyl ammonium chloride . BDMDAC) The results are as follows. I. In regard to the method of processing VET, when the PET fabrics are alkaline-hydrolyzed adding BDMDAC, the weight loss of PET fabrics increased remarkably to the increse of BDMDAC concentration than when they are treated only in NaOH solution. When PET fabrics are alkaline-hydrolyzed the amount of BDMDAC as the catalyst is proper lg/1 II. The change in physical & chemical properties of alkaline-hydrolyzed PET fabrirs. 1. As the amount of the weight loss on PET fabrics increased, the void space of the PET yale increased but tenacity & elongation and thickness decreased. 2. The fabric counts of PET increased due to shrinkage by alkaline-hydrolydzing. 3. As the amount of of the weight loss on PET fabrics increased. NUMERI, FUKURAMI, increaseed and KOSHI decreased and Total hand value(T.H.V) in all cases increaseed. When the weight Ioss is 30.9% T.H.V. is best. 4. Moisture regain of PET fabrics a little increased by alkaline-hydrolyzing treatment. As the weight loss increased, static voltage is decreased. 5. The last dye absorption is different according to the degree of the Affinity. In regard to the difference of dye color, the dyestuff of low molecular weight dyed for deep color.

• Journal of the Korean Society of Clothing and Textiles
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• v.40 no.2
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• pp.305-314
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• 2016

This paper investigated the applicable possibility of PTT and wool staple fibers to the air vortex system as high quality yarns for a high emotional and comfort garment. It was found that the tactile hand of vortex yarn knitted fabrics was harsher than ring and compact yarns knitted fabrics. It was observed that formability and sewability of air vortex yarn knitted fabrics seemed worse than ring and compact yarns due to low tensile and compressional resilience and high bending and shear hysteresis of air vortex yarn knitted fabrics. It revealed that wicking and drying rates of air vortex yarn knitted fabric were better than ring and compact yarns; in addition, the heat keepability of vortex yarn knitted fabric was higher than ring and compact yarns due to low thermal conductivity and max heat flow rate ($Q_{max}$). Any difference of thermal shrinkage between air vortex and ring yarn knitted fabrics was not shown, but pilling characteristic of air vortex yarn knitted fabric was superior. However, it was shown that wicking, drying, thermal property and pilling characteristics of air vortex yarn knitted fabric were superior due to air vortex yarn structure with parallel fibers in the core part and periodical and fasciated twists in the sheath part of the yarns.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.11a
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• pp.113-117
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• 2003

In this study is investigated the various properties of concrete with the kinds of stabilizing agent of recycling water and solid content in order to suggest a practical use of recycling water. According to the results, fluidity and air content varies slightly with the kinds of stabilizing agent and solid content, but does not make a big difference. Setting time does not differ remarkably from plain concrete at 20℃, but is shortened with an increase of solid content. Bleeding is reduced more largely in the case of S than in the case of R, and is not influenced by solid content. Compressive strength is equal or decreases in comparison with plain concrete at solid content of I and 50%, and shows the highest value at solid content of 3%. Length change by drying shrinkage is larger than plain concrete at solid content of 5%, and decreases at solid content of I and 3%. Therefore, it proves that the influence of the kinds of stabilizing agent is minute, and solid content is most effective at 3%.

• Journal of Biosystems Engineering
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• v.32 no.1 s.120
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• pp.6-12
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• 2007

This study was conducted to investigate the drying characteristics of oak mushroom using stationary far-infrared dryer. Drying characteristics was measured at drying air velocity 0.4 to 0.6 m/s and drying temperature 50, 60, and 70$^{\circ}C$, respectively. With high temperature of far-infrared heater and fast air velocity, the far-infrared drying rate of double air flow system was better than conventional heated-air drying as much as 39%. The value of color difference (E) of oak mushroom before and after drying was 8.95 by using heated air drying and was in the range of 3.76$\sim$6.98 by the far-infrared drying. The shrinkage rate of oak mushroom after heated air drying was higher than that of air velocity, 0.6 m/s of far-infrared drying conditions, and was lower than that of air velocity, 0.4 m/s of far-infrared drying conditions. The content of free amino acid was higher in far-infrared drying than heated air drying.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.113-117
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• 2003

In this study is investigated the various properties of concrete with the kinds of stabilizing agent of recycling water and solid content in order to suggest a practical use of recycling water According to the results. fluidity and air content varies slightly with the kinds of stabilizing agent and solid content, but does not make a big difference. Setting time does not differ remarkably from plain concrete at 2$0^{\circ}C$, but is shortened with an increase of solid content. Bleeding is reduced more largely in the case of S than in the case of R, and is not influenced by solid content. Compressive strength is equal or decreases in comparison with plain concrete at solid content of 1 and 5%, and shows the highest value at solid content of 3%. Length change by drying shrinkage is larger than plain concrete at solid content of 5%, and decreases at solid content of 1 and 3%. Therefore, it proves that the influence of the kinds of stabilizing agent is minute, and solid content is most effective at 3%.

• Korean Journal of Materials Research
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• v.17 no.9
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• pp.489-492
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• 2007

Temperature and injection current dependence of elctroluminescence(EL) spectral intensity of the $In_{0.27}Ga_{0.73}N/GaN$ multi-quantum-well(MQW) have been studied over a wide temperature and as a function of injection current level. EL peaks also show significant broadening into higher photon energy region with the increase of injection current. This is explained by the band-filling effect. When temperature is slightly increased to 300 from 15 K, the EL emission peak showed red-blue-red shift. It can be explained by the carrier localization by potential fluctuation of multiple quantum well and band-gap shrinkage as temperature increase. It is found that a temperature-dependent variation pattern of the EL efficiency under very low and high injection currents show a drastic difference. This unique EL efficiency variation pattern with temperature and current is explained field effects due to the driving forward bias in presence of internal(piezo and spontaneous polarization) fields.