• Fibers and Polymers
• /
• v.4 no.2
• /
• pp.49-53
• /
• 2003

Polyurethane (PU) layer and copolymer consisted of the different molecular weights (1000 and 2000 g/mol) of poly(propylene glycol) (PPG) were prepared. The damping and mechanical properties of these materials were compared with PU 1000 made by PPG having the molecular weight of 1000 g/mol. The optimum composition of PU2000 used for PU layer and copolymer was diphenylmethane diioscynate (MDI)/propylene glycol (PPG)/butanediol (BD) (1/0.3/0.7) based on the damping and mechanical properties. The damping peak of PU copolymer was higher than those of PU layer and PUI 1000 in low temperature range (-30- $10^{\circ}C$). For application in noise reduction, the transmission loss of the mechanical vibration through solid structure was measured. PU layer and copolymer were used as a damping layer. The transmission loss of PU copolymer was more effective than those of PU layer and PU 1000 in the experimental frequency range.

• Polymer(Korea)
• /
• v.29 no.3
• /
• pp.300-303
• /
• 2005

Polyurethane multi-layer and foam multi-layer were prepared with PU1000 and PU2000 made by poly(propylene glycol) (PPG) having the molecular weight of 1000 and 2000 g/mol, respectively. The damping and transmission loss of these materials were compared with PU1000 used as a reference. The damping peak of polyurethane multi-layer was shifted to the lower temperature compared with PU1000, while the damping peak of polyurethane foam multi-layer was shifted to the higher temperature and broaden. In terms of noise reduction, the transmission loss of polyurethane multi-layer was effective at the specific frequency range such as less than 100 Hz and around 600 Hz compared with PU1000. The transmission loss of polyurethane foam multi-layer was most effective in the whole experimental frequency range.

• Journal of the Korean Chemical Society
• /
• v.43 no.3
• /
• pp.315-320
• /
• 1999

Novel electroluminescent materials, polymer material, PU-BCN and low molar mass material, D-BCN with the same chromophores were designed and synthesized. A molecular structure of chromophore was composed of bisstyrylbenzene derivative with cyano groups as electron injection and transport and phenylamine groups as hole injection and transport. Device structures with PU-BCN and D-BCN as an emission layer were fa-bricated, which were a single-layer device(SL), Indium-tin oxide(ITO)/emission layer/MgAg, and two kinds of double-layer devices which were composed of ITO/emission layer/oxadiazole derivative/MgAg as a DL-E device and ITO/triphenylamine derivative/emission layer/MgAg as a DL-H device. The two emission materials, PU-BCN and D-BCN with the same emission-chromophore were evaluated as having excellent performance of charge injection and transport and revealed almost the same emission characteristics in high current density. EL emission maximum peaks of two material were detected at about 640 nm wavelength of red emission region.

• Journal of Sensor Science and Technology
• /
• v.8 no.2
• /
• pp.177-183
• /
• 1999

A Polymer material, PU-BCN and a low molar mass material D-BCN with the same chromophore were evaluated by fabricating various electroluminescent(EL) devices. A molecular structure of the chromophore was composed as two cyano groups for electron-injection and transport and two triphenylamine groups for hole-injection and transport. Various kinds of EL devices with two different types of EL materials, PU-BCN and D-BCN were fabricated, which were an Indium-tin oxide(ITO)/PU-BCN or D-BCN/MgAg device as a single-layer device(SL) and an ITO/PU-BCN or D-BCN/oxadiazole ferivative/MgAg as a double-layer device(DL-E) and an ITO/triphenylamine derivative/D-BCN/MgAg as a double-layer device(DL-H) device. Two kinds of materials, PU-BCN and D-BCN showed the same emission characteristics in the high current density and excellent EL characteristics even in the SL devices. Maximum EL peaks revealed red emission of about 640 nm, which were corresponded with the fluorescence peaks of the films of two materials.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.23 no.6
• /
• pp.800-808
• /
• 1999

The demand for PU coated synthetic leather is increasing as a high fashion material. But it has some faults of water vapor permeability surface tacky property and static electricity. Therefore the purpose of this study was the produce of PU coated fabric added collagen with hydrophilic property and soft touch. In the PU coated fabric water vapor permeability water vaper absorption and frictional electronic voltage were investigated surface bending and compression properties were also examined by the use of KES-FB System. The followings were the results of this study. 1. There was no Cr in the collagen so that Cr was not treated in the collagen. 2. The surface and cross sectional layer of PU coated fabric with collagen were highly developed by micro porous structure. 3. The water vapor permeability of PU coated fabric was increased as collagen concentration increased. 4. The water vapor absorption of PU coated fabric was increased as collagen concentration increased. 5. The frictional electronic voltage of PU coated fabric was decreased in accordance with the increase of collagen concentration. Especially it effectively decreased by the use of only 5% collagen concentration. 6,. The bending and compression properties of PU coated fabric were increased in accordance with the increase of collagen concentration so that it became stiff. 7. The Value of MIU, SMD was decreased in accordance with the increase of collagen concentration so that the PU coated fabric became smooth.

• Analytical Science and Technology
• /
• v.19 no.1
• /
• pp.18-30
• /
• 2006

This paper describes the cumulative deposition of fallout Pu in soil and lichen at the present time and give the characteristics of fallout Pu deposits in the soil. In the soil of the forest, the accumulated depositions of $^{239,240}Pu$ were estimated to be in the range of 34.0 to $101.2Bq\;m^{-2}$ with an average value of $65.3{\pm}21.6Bq\;m^{-2}$. The average inventory of $^{239,240}Pu$ in the forest was calculated to be two times higher than that in the hill. Also, the deposited activities of $^{239,240}Pu$ in cultivated soil were significantly lower than those in the hill or forest. However, the cumulative depositions of fallout Pu in the volcanic ash soil on Cheju Island were much higher than those in the forest and hill soils. The measured activity concentrations of Pu isotopes in lichens and mosses showed large variations, due to characteristics of species and life span of lichen and moss colonies. From depth profiles, it was found that most of the fallout Pu has been accumulated in upper 10 cm layer of soil. Except for a few cases, the concentrations of $^{239,240}Pu$ in soil tended to decrease exponentially with increasing soil depth. Among parameters affecting the cumulative deposition of fallout Pu, organic substances and rainfall play an important role in the retention and relative mobility of fallout Pu in the soil. However, pH showed a weak correlation with the deposition of fallout Pu in the soil. From sequential leaching experiments, Pu was found to be associated predominantly with the "organic" and "oxy-hydroxy" fractions. Both the activity ratios of $^{238}Pu/^{239,240}Pu$ and $^{241}Pu/^{239,240}Pu$ in soils, lichens and mosses and the atomic ratios of $^{240}Pu/^{239}Pu$ in soils are close to those observed in the cumulative deposit global fallout from nuclear weapon testings. The results obtained from this research make it possible to interpret and predict the behavior of fallout Pu under natural conditions.

• Proceedings of the Korean Institute of Industrial Safety Conference
• /
• 2002.11a
• /
• pp.311-315
• /
• 2002

Polyurethane 발포체는 우수한 단열 및 흡음특성 그리고 반응물질인 polyol과 isocyanate의 성분 및 배합비에 따라 여러가지 제품군으로 특성 설계가 가능하여 LNG 저장탱크, LNG 유조선의 cryogenic insulator, 육상 및 해상용 냉동 및 냉장시설물, 가전제품, 건축단열판넬 등에 널리 사용되고 있다. 그러나 난연성의 결여로 화재 발생시 급격한 연소반응과 유해가스 발생을 동반하여 화재안전 및 건강보건상 중대한 단점을 가지고 있다. 본 연구진은 PU발포체의 물성개선을 통한 난연특성 연구의 일환으로서 montmorillonite, hectorite, vermiculite의 layer silicate를 urethane 원료물질과 혼성발포 공정을 통해 난연복합체를 제조하여 UL94V, LOI, Morphology 등의 시험을 수행하였다.(중략)

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.6 no.9
• /
• pp.2323-2340
• /
• 2012

Recent advances in cognitive radio technology have drawn immense attention to higher layer protocols above medium access control, such as transmission control protocol (TCP). Most proposals to improve the TCP performance in cognitive radio (CR) networks have assumed that either all nodes are in CR networks or the TCP sender side is in CR links. In those proposals, lower layer information such as the CR link status could be easily exploited to adjust the congestion window and improve throughput. In this paper, we consider a TCP network in which the TCP sender is located remotely over the Internet while the TCP receiver is connected by a CR link. This topology is more realistic than the earlier proposals, but the lower layer information cannot be exploited. Under this assumption, we propose an enhanced TCP protocol for CR networks called TCP for cognitive radio (TCP-CR) to improve the existing TCP by (1) detection of primary user (PU) interference by a remote sender without support from lower layers, (2) delayed congestion control (DCC) based on PU detection when the retransmission timeout (RTO) expires, and (3) exploitation of two separate scales of the congestion window adapted for PU activity. Performance evaluation demonstrated that the proposed TCP-CR achieves up to 255% improvement of the end-to-end throughput. Furthermore, we verified that the proposed TCP does not deteriorate the fairness of existing TCP flows and does not cause congestions.

• International Journal of Highway Engineering
• /
• v.15 no.1
• /
• 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.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.16 no.5
• /
• pp.55-62
• /
• 2007

With the developments in knitting, manufacturing, and polymers, coated gloves have been evolved in a way to maximize occupational safety and functionality. In this paper, we have considered the PU-coating process for the glove knitted by Dyneema to reduce the occurrence of the defects due to air bubble. This paper classifies the types of defect due to air bubble and traces their forming mechanisms. The air between coating layer of glove and mold's surface forms the defects if it is not evacuated fully in the process of submerging into water. The defects can be suppressed or avoided by forming air-evacuating path on the surface of the molds.