• New & Renewable Energy
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• v.3 no.1 s.9
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• pp.38-45
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• 2007

To characterize thermo-chemical feature of sugar conversion of woody biomass, poplar wood ($Populus\;alba{\times}glandulosa$) powder was treated with supercritical water system. Supercritical water treatment (SCWT) was performed for 60 seconds at different temperatures (subcritical zone 350; supercritical zone $300,\;400,\;425^{\circ}C$) under two pressures $230{\pm}10atm$ as well as $330{\pm}10atm$, respectively, using flow type system. After separation of solid residues from SCWT products, the monomeric sugars in aqueous part converted from poplar wood powder were quantitatively determined by high performance anionic exchange chromatography [HPAEC] equipped with PAD detector and Carbo Pac PA10 column. As the temperature treated increased, the degradation of poplar wood powder was enhanced and ca 83% of woody biomass was dissolved into the water at $425^{\circ}C$. However, the pressure didn't help the degradation of biomass components. At subcritical temperature range, xylose was first formed by degradation of xylan, which is main hemicellulose component in hardwood species, while cellulose degradation started at the transition zone between sub and supercritical conditions and was remarkably accelerated at the supercritical temperature. In the supercritical water system the maximum yield of monomeric sugars amounts to ca. 7.3% based on oven dried wood weight at $425^{\circ}C$.

• Journal of Welding and Joining
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• v.33 no.3
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• pp.19-24
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• 2015

Joint properties of electric control unit (ECU) module using Sn-Cu-(X)Al(Si) lead-free solder alloy were investigated for automotive electronics module. In this study, Sn-0.5Cu-0.01Al(Si) and Sn-0.5Cu-0.03Al(Si) (wt.%) lead-free alloys were fabricated as bar type by doped various weight percentages (0.01 and 0.03 wt.%) of Al(Si) alloy to Sn-0.5Cu. After fabrications of lead-free alloys, the ball-type solder alloys with a diameter of 450 um were made by rolling and punching. The melting temperatures of 0.01Al(Si) and 0.03Al(Si) were 230.2 and $230.8^{\circ}C$, respectively. To evaluation of properties of solder joint, test printed circuit board (PCB) finished with organic solderability perseveration (OSP) on Cu pad. The ball-type solders were attached to test PCB with flux and reflowed for formation of solder joint. The maximum temperature of reflow was $260^{\circ}C$ for 50s above melting temperature. And then, we measured spreadability and shear strength of two Al(Si) solder materials compared to Sn-0.7Cu solder material used in industry. And also, microstructures in solder and intermetallic compounds (IMCs) were observed. Moreover, thickness and grain size of $Cu_6Sn_5$ IMC were measured and then compared with Sn-0.7Cu. With increasing the amounts of Al(Si), the $Cu_6Sn_5$ thickness was decreased. These results show the addition of Al(Si) could suppress IMC growth and improve the reliability of solder joint.

• Tribology and Lubricants
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• v.30 no.1
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• pp.29-35
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• 2014

The temperature-dependent tribological properties of brake discs for a train were examined in this study. The discs were produced using heat-resistant alloy steel, which showed different thermal conductivity after the heat treatments. A commercial brake friction material was used to evaluate the friction effectiveness, and the friction tests were carried out using a 1/5 scale dynamometer under various initial braking temperature conditions. The results showed that the tribological property of the disc was strongly affected by the heat treatment schedule. At low temperatures (below $250^{\circ}C$), the friction coefficient increased as a function of disc temperature, indicating that frictional heat increased the adhesion between the disc and pad. In addition, fade was observed at high temperatures (above $250^{\circ}C$); it was pronounced in the case of the disc with low thermal conductivity. The different fade resistances observed in the discs with different heat treatment schedules appear to be influenced by microstructural changes such as carbide redistribution occurring during the heat treatments, which affected the thermal conductivity.

• Journal of the Korea Convergence Society
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• v.11 no.11
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• pp.233-237
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• 2020

In this study, the thermal analysis on the brake disc of electric kickboard was analyzed. The different heat is transmitted depending on the pad contact surface of brake disc. The trend that the temperature decreases at the part away from the contact surface was almost constant. And model A showed a slightly lower temperature distribution than model B. Model A has a maximum equivalent stress of 7% higher than model B. By being applied with the higher heat transfer above the contact surface, it is thought that model B has a greater strength than model A if the design takes into account the corner of the brake disc. If this study result is utilized to the design of electric kickboard, the design of brake disc with better strength is considered to be established. The durability of brake against the heat can be evaluated by applying this study result to the brake disc of electric kickboard. And it is seen that the result can be the design of brake with strength and the aesthetic convergence.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.4
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• pp.395-403
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• 2012

This is direct bonding many of the metal bumps between FPCB and HPCB substrate. By using an ultrasonic horn mounted on an ultrasonic bonding machine, it is possible to bond gold pads onto the FPCB and HPCB at room temperature without an adhesive like ACA or NCA and high heat and solder. This ultrasonic bonding technology minimizes damage to the material. The process conditions evaluated for obtaining a greater bonding strength than 0.6 kgf, which is commercially required, were 40 kHz of frequency; 0.6MPa of bonding pressure; and 0.5, 1.0, 1.5, and 2.0 s of bonding time. The peel off test was performed for evaluating bonding strength, which was found to be more than 0.80 kgf.

• Journal of the Korean Society of Clothing and Textiles
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• v.20 no.2
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• pp.350-361
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• 1996

The objectives of this study mere 1) to investigate whether the different nonwoven fabric types influenced on the objective and subjective wear performances of the experimental pesticide protective pants, 2) to detect whether the different finishes treated to the nonwoven fabrics influenced on the objective and subjective wear performances of the experimental pants, and 3) to detect the relationships between objective wear performances and subjective wear sensation. Three types of nonwoven fabrics (T (Tyvek$\textregistered$), 5 (Sontara$\textregistered$) and K (Kimlon$\textregistered$)) were used as test specimens. By pad-dry.cure method, each of the specimen was treated with fluorocarbon compound for water-oil repellent finish (Tw, Sw, Kw). And each of specimen was treated with organic silicon quarternary ammonium salts and then treated with fluorocabon compound for dual functional finish (76, 50, Kd). Using the three water-oil repellent finished fabrics and the three dual functional finished fabrics, six experimental protective pants (Cl (Tw), C2 (Sw), C3 (Kw), C4 (76), C5 (56), C6 (Kd)) were made according to the same pattern suggested by the Rual Guidance Office. The wear trials of experimental pesticide protective pants were performed in a conditioned vinyl plastic hothouse ($30\pm1^{\circ}C$, $70\pm5%$R.H., 0.25m/sec air velocity). The measurements of skin temperature, microclimate temperature and humidity on the subjects were obtained by the themohygromenter. The subjective wear sensations were measured using previously developed thermal, humidity and overall comfort scales. The results obtained from this study were as follows: 1) There were siginificant differences among nonwoven fabric types on the objective and subjective wear performances, therefore, the skin temperature, microclimate temperature and humidity of subjects who wore the experimental pants made with Sontara were siginificantly lower than those who wore the others. And, the experimental pants made with Sontara were assessed as more comfortable than the others in terms of the subjective thermal, humidity and overall wear sensations. 2) There were no significant differences between two finish types on the objective and subjective wear Performances. 3) The microclimate humidity on the thigh was highly correlated with the overall subjective comfort sensations and the next highly correlated one was the mean skin temperature. That is, the higher the microclimate humidity and the mean skin temperature, the higher the overall subjective comfort sensation ratings which mean the overall subjective sensation was very uncomfortable.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.241-248
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• 1999

The existing bridge with deck joint has many problems during construction and maintenance. To overcome these difficulties, an integral bridge, which is defined as the practice of constructing bridges without deck joints, is proposed in this study. A test bridge with 3 spans of PC beam was selected to verify the function of the bridge and is under construction. Characteristics of integral bridge are followings: $\circled1$ Flexible H-piles under the abutment are installed to accommodate thermal movements of the superstructures of bridge. $\circled2$ PC beam of the superstructure and the abutment are integrated. $\circled3$ The existing approach and relief slabs are applied to minimize the stress transfer occurred from the bridge deck to the pavement. $\circled4$ A cyclic control joint is installed between approach and relief slabs to absorb the thermal movement. $\circled5$ It is used a dual direction bearing which is cheaper than single direction bearing and has a good workability as well. It is also installed a shear block on the top of pier coping to protect the lateral movement caused by temperature change and earthquake.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2001.11a
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• pp.75-87
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• 2001

Three different kinds of substrate used in this study : bare Cu substrate, Ni-P/Cu substrate with a Ni-P layer thickness of $5\mu\textrm{m},$ and Au/Ni-P/Cu substrate with the Ni-P and Au layers of $0.15\mu\textrm{m}$ and $5\mu\textrm{m}$ thickness respectively. The wettability of various Sn-base solders was affected by the substrate metal finish used, i.e., nickel, gold and copper. On the Au/Ni-F/Cu substrate, Sn-base solders wet better than any of the other substrate metal finishes tested. The interfacial reaction between various substrate and Sn-base solder was investigated at $70^{\circ}C,$ $100^{\circ}C,$ $120^{\circ}C,$ $150^{\circ}C,$ $170^{\circ}C$ and $200^{\circ}C$ for reaction times ranging from 0 day to 60 day. Intermetallic phases was formed along a Sn-base solder/ various substrate interface during solid-state aging. The apparent activation energy for growth of Sn-Ag/Cu, Sn-Ag-Bi/Cu, and Sn-Bi/Cu couples were 65.4, 88.6, and 127.9 Kj/mol, respectively. After isothermal aging, the fracture surface shoved various characteristics depending on aging temperature and time, and the types of BGA pad.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.5
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• pp.218-223
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• 2001

The chemical-mechanical polishing process was carried out for 2"-dia. sapphire wafer grown by horizontalBridgman method on the urethane lapping pad with the silica sol. The polished wafer shows the full-width at halfmaximum of 200~400 arcsec in double-crystal X-ray diffraction, indicating that the slicing, grinding and lapping processes before the polishing process affected the crystalline structural property of the wafer surface by the mechanical residual stress. For the inclusion of surface treatments after chemical-mechanical polishing such as the thermal annealing at the temperature of $1,200^{\circ}C$for 4 hrs. and chemical etching, the crystalline quality was sigdicantly enhanced with the reduced full-width at half maximum up to 8.3 arcsec.arcsec.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.1
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• pp.25-31
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• 2003

Airborne contaminant particles are intruded into optical disk drives(ODD) due to the flow caused by disk rotation and can be adhered to lens or disk surfaces, which causes decrease of laser power and increase of read/write errors. Such a phenomenon can be more serious as the space between the disk and the lens is reduced fur high-density storage devices. The purpose of this paper is to understand design parameters to reduce the particle intrusion into an ODD. Suggestions are made to prevent the particle intrusion that can decrease the stability of an ODD and also prevent the potential heat build-up problem. The sealing effect of drive and the forced injection of clean air (using HEPA filter) into the drive minimizes intrusion of the outside air and dusts in an ODD remarkably. Moreover it is proved by experiments that the installation of a heatproof pad to isolate heat generation part (PCB) from information read/write sections and the forced injection of dust-free air reduce the gas temperature inside the drive as well as the amount of particles intruded.