• 한국농공학회논문집
• /
• 제61권3호
• /
• pp.43-53
• /
• 2019

It is well-known fact that the stone-mastic asphalt (SMA) mixture has shown superior rut resistance, compared with the dense-graded asphalt (DGA) mixture in highway pavements. However, the SMA is measured to be inferior to DGA mixes when tested by well-known high-temperature test methods, such as the wheel tracking (WT), asphalt pavement analyzer, the Marshall Stability and Kim Test. Therefore, this study examined the reasons why it was measured to be inferior, and devised a potential procedure by which the superiority of SMA could be measured at $60^{\circ}C$. The strength against deformation ($S_D$), which was known to show very high correlation with WT results for DGA mixes, was measured by the Kim Test on the specimen confined in the compacted mold. In standard Kim Test, which used the specimen without confinement, the DGA was measured to show higher $S_D$ than the SMA. But by confining specimen, it was found that the $S_D$ of SMA was measured to be higher than that of DGA. Therefore, the confined static test protocol devised in this study was found to be feasible for evaluating rut resistance of SMA mix.

• 헤리티지:역사와 과학
• /
• 제48권3호
• /
• pp.46-59
• /
• 2015

본 연구는 문화재에 적용 가능한 다양한 훈증방법 중에서 에틸렌 옥사이드(Ethylene oxide)를 포함하는 훈증 약제가 문화재 재질에 미치는 영향을 평가하였다. 이를 위해 지류, 섬유, 금속, 안료 등 4종류의 시험편을 제작하고 훈증처리 전 후의 색상, 무게, 표면 변화, 그리고 지류와 섬유 시험편에 대한 적외선 분광분석을 실시하였다. 훈증처리는 약제를 처리하지 않은 무처리군을 대조군으로 하고 에틸렌 옥사이드 + $HFC_{134a}$, 에틸렌 옥사이드 + $CO_2$ 등 2종류의 훈증제 처리군을 실험군으로 하였다. 색차 측정 결과, 소다회를 이용하여 증해한 한지, 은, 면, 견, 모시, 황색 안료 등에서 색상 변화가 확인되었으며 특히, 은 시험편에서 평균 6.0 이상의 높은 색차 변화가 측정되었다. 그러나 은 시험편의 경우 훈증제를 처리하지 않은 무처리 시험편의 색차가 약제를 처리한 것보다 오히려 높게 나타나 훈증제 처리가 시험편의 색상 변화에 결정적인 영향을 미치지 않은 것으로 판단되나 훈증처리 시 주의가 요구된다. 무게 측정에서는 전체적으로 0~2% 정도의 변화가 나타났으며, 금속 시험편의 변화가 가장 적었고 지류 시험편의 변화가 가장 큰 것으로 나타났다. 시험편의 표면을 현미경으로 관찰한 결과, 일부 시험편 표면에서 색상 변화가 관찰되었으며, 은 시험편에서 가장 큰 변화가 확인되었다. 그러나 지류와 섬유 시험편을 대상으로 한 적외선 분광분석 결과에서 성분상 변화는 확인되지 않았다.

• 한국세라믹학회지
• /
• 제32권1호
• /
• pp.113-119
• /
• 1995

The green body was fabricated by a new forming method, pressureless powder packaing forming method, and the characteristics of sintered specimen were investigated. It was found that alumina ceramics prepared by the present method showed porous structure with narrow pore size distribution, and in case of abrasive powder sintered body, compared with dry-pressed specimen, had the nearly same density. Especially, the specimen prepared with spray-dried granules showed the characteristic that granules were not either deformed or fractured during forming and sintering process. Therefore, it was found that this new forming method was effective method in fabrication of porous ceramics on account of easy control of porosity and pore size and its high thermal stability.

• 한국주조공학회지
• /
• 제1권2호
• /
• pp.10-18
• /
• 1981

In this paper tensile strength and fatigue propagation rate were investigated by aging treatment $(T_6)$ and thermomechanical treatment (TMT) of 7075-Al Alloy specimen. The results of teat showed that TMT improved tensile strength and fatigue crack propagation due to bomogenization of microstructure. In TMT, the results of comparison between T-H' AHA and T-AHA and $T-AH{\cdot}{\cdot}{\cdot}$and $T-HA{\cdot}{\cdot}{\cdot}$were showed that T-AHA and $T-AH{\cdot}{\cdot}{\cdot}$treatments, after solution treatment, which are aging treated before rolling have higher tensile strength. Our investigation on high temperature stability at the Specimen for $T_6$, T-AHA, $T-AH{\cdot}{\cdot}{\cdot}$treatments resulted in rapid reduction of tensile strength over $150^{\circ}C$, but the reduction of tensile strength for specimen of TMT was smoothed than $T_6$.

• 한국가구학회지
• /
• 제18권2호
• /
• pp.143-146
• /
• 2007

This study was carried out to assess the dimensional stability of wood material treated by plastic processing for bentwood and compression wood. The evaluation method was different between two wood materials, but the treatments for them were very similar to each other. One of the main methods is heat treatment with sufficient water vapor. In bentwood, the used species were painted maple (Acer mono), bitter wood (Picrasma quassioides) and birch (Betula schmidtii). Steaming was the worst treatment method for dimensional stabilization of bentwood. The best results could be attained with PEG treatment for dimensional stabilization of bentwood. Dimensional stability of bitter wood was found to be conspicuous. However the steaming treatment at lower temperatures, i.e., about $130^{\circ}C$ was not suitable for dimensional stability of bentwood. In compression wood, the used specimen was Italian poplar wood (Populus euramericana). Two heat compressive pressing conditions, an open-press system and an air-tighten closed-press system, were used. The recovery rate was measured after boiling and/or absorbing in water to estimate the dimensional stability of heat compressed wood. The best dimensional stability of compressed wood in the air-tighten closed-press system was found to be better at $200^{\circ}C$ than $180^{\circ}C$. The best compression rate for dimensional stability was 73 percent.

• 한국진공학회지
• /
• 제8권2호
• /
• pp.136-140
• /
• 1999

The stability and response time of $WO_3$ thin films for EC device are critical problems being solved. Those are affected by the species of electrolyte, preparation conditions and fabricating methods of specimen. In this paper, we compared the stabilities of three kinds of tungsten oxide film in electrolyte. Each of three films was prepared by different manufacturing conditions, that is, one is a thermal oxidation film of tungsten metal deposited on pure glass substrate, another is a $WO_3$ film made on ITO glass directly, the other is a thermally oxidized film on tungsten plate. It was observed that thermally oxidized $WO_3$ films has a remarkable stability (the lifetime was above $10^6$ cycle). From these results, we found that the stability was closely related to the stoichiometric bonding between tungsten and oxygen atoms in addition to crystallinity and density of film.

• 한국세라믹학회지
• /
• 제34권7호
• /
• pp.781-789
• /
• 1997

Pressure sintered SiC specimens were joined using MgO-Al2O3-SiO2 (MAS) glass which has a thermal expansion coefficient similar to that of SiC. MAS melt showed excellent behavior of wetting on the SiC substrate over 148$0^{\circ}C$, and the wettability was much influenced by the joining atmosphere. The joining was conducted at 150$0^{\circ}C$ for 30 min in Ar atmosphere. The flexural strength of the joined specimen shows 342~380 MPa up to 80$0^{\circ}C$, which is almost the same as that of as-recieved SiC specimen. However, the flexural strength of the joined specimen decreased to about 80 MPa at 90$0^{\circ}C$ due to softening of the glass melt. The analyses od XRD and WDS show that the reaction between the SiC specimen and the MAS melt produces the oxycarbide glass, which had a high strength and a good stability at high temperatures.

• 한국안전학회지
• /
• 제37권5호
• /
• pp.7-13
• /
• 2022

Digital image correlation (DIC) is a method used to measure the displacement and strain of structures. It involves transforming and analyzing images before and after deformation using correlation coefficients from irregular light and shade on the surface of structures. In the present study, a microspeckle pattern was applied to the surface of a specimen to identify initial cracking. The test specimen constituted CFRP composites laminated on a curved Al liner The specimen was manufactured by stacking 100 ply of CFRP prepregs in the 0° and 90° directions in a three-point bending test. The equivalent strain was evaluated through DIC analysis after monitoring deformation using a CCD camera. Fracture shape was observed using a microscope. The equivalent strain contour distribution was checked until the maximum load fracture occurred at the center of the test specimen. Variations in the strain indicated the initial occurrence and progression of microcracks. These results can be used to improve the accuracy of detecting micro crack initiation and to achieve structural stability.

• 대한족부족관절학회지
• /
• 제7권2호
• /
• pp.151-156
• /
• 2003

Purpose: Proximal crescentic metatarsal osteotomy(PMO) is one of the most common procedures for correcting moderate to severe degree hallux valgus deformity. Although screw fixation is used for osteotomy site stability, loss of reduction can occur. The purpose of this study is to compare the sagittal plane stability of the conventional crescentic PMO fixed with a single screw with that of the crescentic PMO fixed with 1 screw and 2 supplemental K -wires. Material and Methods: Ten matched pairs of cadaveric foot specimens were used for the proximal crescentic metatarsal osteotomy. For one foot specimen of each pair, crescentic osteotomy was fixed with 4mm long threaded cannulated screw, while the matched pair was prepared by adding two axial 1.6mm K-wires to the conventionally fixed 4mm screw. The extensometer was used to measure the osteotomy gap as the metatarsal head was loaded continuously until failure using a servohydraulic MTS Mini Bionix test frame. The strength of fixation was normalized with the bone mineral density (BMD) of the paired specimen $(N{\times}cm^{2}/gm)$, Result: The average strength of the crescentic PMO with axial K-wire fixation ($458.8cm^{2}/gm$, S.D. 434.3) was significantly higher than the standard crescentic PMO ($367.5cm^{2}/gm$, S.D. 397,9) (p=0.05). Conclusion: Supplemental fixation with two axial K-wires can be added to the crescentic PMO to enhance the initial fixation stability to prevent the loss of reduction or dorsal malunion.

• 한국해양공학회지
• /
• 제13권4호통권35호
• /
• pp.28-36
• /
• 1999

Wet underwater arc welding process is investigated by using experimentally developed flux coated underwater arc welding electrode and SS400 steel plate of 12mm thickness as base metal. Three kinds of different flux covered wet arc welding electrode of 4mm diameter(BK-01, BK-02, BK-03) are individually developed, and one of the improved underwater welding electrode (BK-03) may be put to practical use for underwater wet arc welding process. The results obtained from this experimental study are as follows : 1. Arc stability of developed underwater wet welding electrode is better than that of the domestic covered arc welding electrode. 2. Workability of welding electrode, remove ability of slag and bead appearances using improved underwater wet welding electrode are remarkably better than that of others. 3. Heat affected zone of test specimen welded in the underwater gets to become a lot smaller than that of test specimen welded in the air, and the maximum hardness of heat affect zone of developed underwater wet welding electrode is lower to that of domestic arc welding electrode.