• 한국도로학회논문집
• /
• 제15권1호
• /
• pp.1-9
• /
• 2013

PURPOSES: The purpose of this study is to evaluate physical properties, durability, fatigue resistance, and long-term performance of poly-urethane concrete (PU) which can be possible application of thin layer on long-span orthotropic steel bridge and to check structural stability of bridge structure. METHODS : Various tests of physical properties, such as flexural strength, tensile strength, bond strength and coefficient of thermal expansion tests were conducted for physical property evaluation using two types of poly urethane concrete which have different curing time. Freezing and thawing test, accelerated weathering test and chloride ion penetration test were performed to evaluate the effect of exposed to marine environment. Beam fatigue test and small scale accelerated pavement test were performed to assess the resistance of PU against fatigue damage and long-term performance. Structural analysis were conducted to figure out structural stability of bridge structure and thin bridge deck pavement system. RESULTS: The property tests results showed that similar results were observed overall however the flexural strength of PUa was higher than those of PUb. It was also found that PU materials showed durability at marine environment. Beam fatigue test results showed that the resistances of the PUa against fatigue damage were two times higher than those of the PUb. It was found form small scale accelerated pavement test to evaluate long-term performance that there is no distress observed after 800,000 load applications. Structural analysis to figure out structural stability of bridge structure and thin bridge deck pavement system indicated that bridge structures were needed to increase thickness of steel deck plate or to improve longitudinal rib shape. CONCLUSIONS: It has been known that the use of PU can be positively considered to thin layer on long-span orthotropic steel bridge in terms of properties considered marine environment, resistance of fatigue damage and long-term performance.

• Earthquakes and Structures
• /
• 제10권4호
• /
• pp.939-963
• /
• 2016

According to the new directives about the rational and efficient use of energy, thermal bridges in buildings have to be avoided, and the thermal insulation (TI) layer should run without interruptions all around the building - even under its foundations. The paper deals with the seismic response of multi-storeyed reinforced concrete (RC) frame building structures founded on an extruded polystyrene (XPS) layer placed beneath the foundation slab. The purpose of the paper is to elucidate the problem of buildings founded on a TI layer from the seismic resistance point of view, to assess the seismic behaviour of such buildings, and to search for the critical parameters which can affect the structural and XPS layer response. Nonlinear dynamic and static analyses were performed, and the seismic response of fixed-base (FB) and thermally insulated (TI) variants of nonlinear RC building models were compared. Soil-structure interaction was also taken into account for different types of soil. The results showed that the use of a TI layer beneath the foundation slab of a superstructure generally induces a higher peak response compared to that of a corresponding system without TI beneath the foundation slab. In the case of stiff structures located on firm soil, amplification of the response might be substantial and could result in exceedance of the superstructure's moment-rotation plastic hinge capacities or allowable lateral roof and interstorey drift displacements. In the case of heavier, slenderer, and higher buildings subjected to stronger seismic excitations, the overall response is governed by the rocking mode of oscillation, and as a consequence the compressive strength of the XPS could be insufficient. On the other hand, in the case of low-rise and light-weight buildings, the friction capacity between the layers of the applied TI foundation set might be exceeded so that sliding could occur.

• 생태와환경
• /
• 제34권1호통권93호
• /
• pp.9-19
• /
• 2001

본 연구는 1993년 4월부터 1994년 11월까지 대청호 17개 조사지점에서 수온 성충 및 수체 혼합 현상을 평가하였다. 조사기간 동안 하절기 장마 강도의 차이는 뚜렷한 수리 수문학적 연 변화를 가져왔다. 1993년 하절기에 이론적 평균 수체류 시간은 27일로서, 1994년 하절기 (125일)에 비해 3개월 이상 짧았다. 1993년에 수온 성층화와 수층혼합 정도를 조절하는 중요한 물리적 요인은 밀도가 높은 중층수 유입현상(Interflow　current)에 의한 것으로 평가되었다. 1993년 하절기동안 상류 유입수는 호수 중류역 (댐으로 부터 27km 부근)에서 수직 하강되어 10${\sim}$20 m 수층을 통과함으로써 표충수인 호수물과는 혼합되지않는 현상을 보였다. 중층수 유입은 수온 성층화 현상의 약화, 하류역의 중층－심층에서 평균 $4＾{\circ}C$ 이상의 온도상승 효과 및 13 m 이상의 수층혼합을 가져왔다. 전자와　비교해볼 때, 1994년 하절기 중층수 유입현상은 관측되지 않았으며, 호수전체에 강한 성층이 형성되고 있음을 보였다. 1993년 온도 저항력 (Thermal resistance)은 $4.0\;{\time}\;10^5\;erg$로서, 1994년의 값($8.2\;{\time}\;10^5\;erg$)에 비해 절반 수준을 보임으로서, 수체의 물리적 불안정 상태를 시사하였다. 본 호수는 연중 겨울에 1회 수층혼합을 보이는 Warm monomixis 특성을 보였으나, 두해 사이의 수충혼합 시기는 차이를 보였다. 1993년 수층혼합은 1994년에 비해 약 1개월 일찍 일어났다. 하절기 동안 심충 수온 변화(Y)는 댐으로부터의 방류량(X)에 의해 98%까지 설명되었다($Y=4.35-0.06X+0.10X^2$, f<0.0001), 총체적으로 본 수체에서 수온 안정성, 수층혼합 시기 및 수 체류시간은 1차적으로 하절기 몬순 강도에 의해 조절되는 것으로 사료된다.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1997년도 추계학술대회 논문집
• /
• pp.969-972
• /
• 1997

Ultrasonic machining technology has been developed over recent years for he manufacture of cost-effective and quality-assured precision parts for several industrial application such as optics, semiconductors, aerospace, and automobile application. The past decade has seen a tremendous in the use of ceramic in structural application. The excellent thermal, chemical and wear resistance of these material can be realized because of recent improvement in the overall strength and uniformity of advanced ceramics. Ultrasonic machining, in which abrasive particles in slurry with water are presented to the work surface in the presence of an ultrasonic-vibrating tool, is process which should be of considerable interest, as its potential is not limited by he electrical or chemical characteristics of the work material, making it suitable for application to ceramics. In order to improve the currently used ultrasonic machining using ultrasonic energy, technical accumulation is needed steadily through development of exciting device of ultrasonic machine composed of piezoelectric vibrator and horn. This paper intends to further the understanding of the basic mechanism of ultrasonic machining for brittle material and ultrasonic machining of ceramics based in the fracture-mechanic concept has been analyzed.

• Journal of Welding and Joining
• /
• 제18권5호
• /
• pp.98-104
• /
• 2000

Aluminum alloys are being employed in automobile parts as strive to reduce overall vehicle weight to meet demands for improved fuel economy and reduction in vehicle emissions. Al-based composites reinforced with ceramic ($Al_2O_3,\;SiC,\;TiC\;and\;B_4C$) applications in a variety of components in automotive engines, such as liners, where the tribological properties of the material are important. In this study, Al-base composites reinforced with TiC particle powders has been developed for producing plasma spray coatings. The composite plasma spray powders were prepared Al-13Si-3Mg(wt%) alloy with TiC(40, 60 and 80wt%) particles ($0.2~5{\mu}textrm{m}$) by drum type ball milling. The composite powders ($36~76{\mu}textrm{m}$) were sprayed with plasma torch. Plasma sprayed coatings were heat-treated at $500^{\circ}C$ for 3 hours. The wear resistances of the plasma sprayed coatings were found to decrease with increasing TiC content and improved with heat treatment. AlSiMg-40% TiC heat-treated coatings were showed the best wear resistance in this study.

• 조명전기설비학회논문지
• /
• 제27권9호
• /
• pp.1-5
• /
• 2013

We developed high-efficient 6W-LED package with simple structure by applying Heat Slug and silicone-reflector. LED package was manufactured in $8.5{\times}8.5mm$ sized multi-chip structure having thickness of $500{\mu}m$ achieved by bonding silicon-reflector with prepreg on top of the plate after implementing the reflector placed on copper substrate Half Etching by thickness of $200{\mu}m$. The luminous flux, luminous efficacy, correlated color temperature, color rendering index and thermal resistance of developed LED was evaluated, and it verified the application of products by applying it to 120W-LED road luminaires through simulation. The luminous efficacy of LED package reached over 130lm/W, and it is possible to be manufactured into 120W-LED road luminaires using 18 packages. In addition, the simulation results showed average of horizontal illuminance and overall illuminance uniformity that is suitable for three-lane road.

• Journal of Microbiology and Biotechnology
• /
• 제31권5호
• /
• pp.676-685
• /
• 2021

RNA-binding proteins are involved in RNA metabolism and posttranscriptional regulation of various fundamental biological processes. The PUF family of RNA-binding proteins is highly conserved in eukaryotes, and its members regulate gene expression, mitochondrial biogenesis, and RNA processing. However, their biological functions in Aspergillus species remain mostly unknown in filamentous fungi. Here we have characterized the puf genes in the model organism Aspergillus nidulans. We generated deletion mutant strains for the five putative puf genes present in the A. nidulans genome and investigated their developmental phenotypes. Deletion of pufA or pufE affected fungal growth and asexual development. pufA mutants exhibited decreased production of asexual spores and reduced mRNA expression of genes regulating asexual development. The pufE deletion reduced colony growth, increased formation of asexual spores, and delayed production of sexual fruiting bodies. In addition, the absence of pufE reduced both sterigmatocystin production and the mRNA levels of genes in the sterigmatocystin cluster. Finally, pufE deletion mutants showed reduced trehalose production and lower resistance to thermal stress. Overall, these results demonstrate that PufA and PufE play roles in the development and sterigmatocystin metabolism in A. nidulans.

• Advances in nano research
• /
• 제15권3호
• /
• pp.253-261
• /
• 2023

This study investigates the application of nano-composite materials in physical education, specifically focusing on improving the performance of sports hall flooring. The research centers on carbon nanotube reinforced polyvinyl chloride (PVC) composites, which offer enhanced mechanical properties and durability. The incorporation of carbon nanotubes as reinforcements in the PVC matrix provides notable benefits, including increased strength, improved thermal stability, electrical conductivity, and resistance to fatigue. The key parameters examined in this study are the weight percentage of carbon nanotubes and the temperature during the fabrication process. Through careful analysis, it is found that higher weight percentages of carbon nanotubes contribute to a more uniform dispersion within the PVC matrix, resulting in improved mechanical properties. Additionally, higher fabrication temperatures aid in repairing macroscopic defects, leading to enhanced overall performance. The findings of this study indicate that the utilization of carbon nanotube reinforced PVC composites can significantly enhance the strength and durability of sports hall flooring. By employing these advanced materials, the safety and suitability of physical education environments can be greatly improved. Furthermore, the insights gained from this research can contribute to the optimization of composite material design and fabrication techniques, not only in the field of physical education but also in various industries where composite materials find applications.

• Advances in nano research
• /
• 제4권1호
• /
• pp.15-29
• /
• 2016

A low cost environmentally benign surface coating binder is highly desirable in the field of material science. In this report, castor oil based hyperbranched polyester/bitumen modified fly ash nanocomposites were fabricated to achieve the desired performance. The hyperbranched polyester resin was synthesized by a three-step one pot condensation reaction using monoglyceride of castor oil based carboxyl terminated pre-polymer and 2,2-bis (hydroxymethyl) propionic acid. Also, the bulk fly ash of paper industry waste was converted to hydrophilic nano fly ash by ultrasonication followed by transforming it to an organonano fly ash by the modification with bitumen. The synthesized polyester resin and its nanocomposites were characterized by different analytical and spectroscopic tools. The nanocomposite obtained in presence of 20 wt% styrene (with respect to polyester) was found to be more homogeneous and stable compared to nanocomposite without styrene. The performance in terms of tensile strength, impact resistance, scratch hardness, chemical resistance and thermal stability was found to be improved significantly after formation of nanocomposite compared to the pristine system after curing with bisphenol-A based epoxy and poly(amido amine). The overall results of transmission electron microscopic (TEM) analysis and performance showed good exfoliation of the nano fly ash in the polyester matrix. Thus the studied nanocomposites would open up a new avenue on development of low cost high performing surface coating materials.

• Journal of the Optical Society of Korea
• /
• 제20권6호
• /
• pp.807-812
• /
• 2016

Transparent film heaters (TFHs) based on Joule heating are currently an active research area. However, TFHs based on an indium tin oxide (ITO) monolayer have a number of problems. For example, heating is concentrated in only part of the device. Also, heating efficiency is low because it has high sheet resistance ($R_s$). To address these problems, this study introduced hybrid layers of ITO/Ag/ITO deposited by magnetron sputtering, and the electrical, optical, and thermal properties were estimated for various thicknesses of the metal interlayer. The $R_s$ of ITO(40)/Ag/ITO(40 nm) hybrid TFHs were 5.33, 3.29 and $2.15{\Omega}/{\Box}$ for Ag thicknesses of 10, 15, and 20 nm, respectively, while the $R_s$ of an ITO monolayer (95 nm) was $59.58{\Omega}/{\Box}$. The maximum temperatures of these hybrid TFHs were 92, 131, and $145^{\circ}C$, respectively, under a voltage of 3 V. And that of the ITO monolayer was only $32^{\circ}C$. For the same total thickness of 95 nm, the heat generation rate (HGR) of the hybrid produced a temperature approximately $100^{\circ}C$ higher than the ITO monolayer. It was confirmed that the film with the lowest $R_s$ of the samples had the highest HGR for the same applied voltage. Overall, hybrid layers of ITO/Ag/ITO showed excellent performance for HGR, uniformity of heat distribution, and thermal response time.