• Elastomers and Composites
• /
• v.58 no.4
• /
• pp.208-215
• /
• 2023

In this study, the properties of polyurethane-polydimethylsiloxane (PU-PDMS) hybrid foams containing different types and contents of physical blowing agents (PBAs) were investigated. Two types of blowing agents, namely physical blowing agents and thermally expandable microspheres (TEM), were applied. The apparent density was measured using precisely cut foam samples, and the pore size was measured using image software. In addition, the microstructure of the foam was confirmed via scanning electron microscopy and transmission electron microscopy. The thermal conductivities related to the microstructures of the different foams were compared. When 0.5 phr of the hydrocarbon-based PBA was added, the apparent density and pore size of the foam were minimal; however, the pore size was larger than that of neat foam. In contrast, the addition of 3 phr of TEM effectively reduced both the apparent density and pore size of the PBAs. The increase in resin viscosity owing to TEM could enhance bubble production stability, leading to the formation of more uniform and smaller pores. These results indicate that TEM is a highly efficient PBA that can be employed to decrease the weight and pore size of PU-PDMS hybrid foams.

• Composites Research
• /
• v.21 no.5
• /
• pp.23-30
• /
• 2008

Stab threats using sharp edged or pointed Instruments could be easily encountered by police officers or soldiers. In this study, the shear thickening fluids (STF) was impregnated into Kevlar fabrics to improve the stab protection and the resistance of STF impregnated Kevlar fabrics was experimentally investigated. The puncture and cut resistance were tested using a drop test machine withspike and knife indenters fabricated based on the National Institute of Justice (NIJ) standard. The STF was filled with spherical $SiO_2$ particles having an average diameter of 100nm, 300nm, and 500nm. The effect of particle size on puncture and cut resistance of STF impregnated Kevlar fabrics was also investigated. The measured impact load histories showed that STF impregnation into fabric leads to withstand higher peak loads than that of neat fabrics under spike test. The test results showed that Kevlar impregnated with STF exhibit remarkable improvements in puncture resistance while it is slightly influential on the cut resistance. Specifically, particle size is the one of the dominant factors controlling fabric resistance to puncture under spike impact test.

• Journal of Animal Science and Technology
• /
• v.48 no.6
• /
• pp.943-948
• /
• 2006

This study carried out to investigate the effect of cutting stimulation on time of cutting, yield and length of antler in Sika deer. There was no significance between surgical stimulation and length of antler, but length was the longest in one side cutting group and the shortest in both side cutting group. Development of point was increased as the number of wounds in the second year (P<0.05). Time of casting was 2 weeks earlier in one side cutting group (P<0.05) than in both sides cutting group. Yields of velvet antler were 148±23g when pedicle was not cut, and 126±61g, 179±63g, 170g, and 48±25g when pedicle was cut by 0.3cm, 0.4cm, 0.5cm and 0.6cm thickness, respectively. In case of 0.6cm, yield was significantly smaller than others (P<0.05). The most desirable thickness of pedicle cut was 0.4～0.5mm. Yield of antler was increased as the size of wound in the first year, and 588, 790 and 657g in control, one-cut and both-cut, respectively. Yields of antler in one-cut is significantly high (P<0.05).

• Korean Journal of Agricultural Science
• /
• v.33 no.2
• /
• pp.115-121
• /
• 2006

This study carried out to investigate the effect of cutting stimulation on time of cutting, yield and length of antler in Sika deer. There was no significance between surgical stimulation and length of antler, but length was the longest in one side cutting group and the shortest in both side cutting group. Development of point was increased as the number of wounds in the second year (P<0.05). Time of casting was 2 weeks earlier in one side cutting group (P<0.05) than in both sides cutting group. Yields of antler were $148{\pm}23g$ when pedicle was not cut, and $126{\pm}61g$, $179{\pm}63g$, 170g, and $48{\pm}25g$ when pedicle was cut by 0.3cm, 0.4cm, 0.5cm and 0.6cm, respectively. The most desirable thickness of pedicle cut was 0.4-0.5mm. Yield of antler was increased as the size of wound in the first year, and 588, 790 and 657g in control, one-cut and both-cut, respectively. Yields of antler in one-cut is significantly high (P<0.05).

• Analytical Science and Technology
• /
• v.22 no.1
• /
• pp.51-56
• /
• 2009

The samples from coastal sand dune stratum in Chollipo were dated by Optically Stimulated Luminescence (OSL) with modified Single Aliquots Regeneration (SAR) method. It is possible to choose the OSL signals by thermal treatments such as preheat and cut-heat in SAR procedure. Preheat and cut-heat of $260^{\circ}C$ for 10 sec $-220^{\circ}C$ for 0 sec, and $270^{\circ}C$ for 10 sec $-270^{\circ}C$ for 10 sec were applied for estimation of equivalent dose of the samples. The OSL signals from different thermal treatment were used for OSL dating. Equivalent dose were estimated with 4 fractionated grain distributions with $75{\mu}m$, $150{\mu}m$ and $200{\mu}m$ sieves with above heating treatments. Consequently, the estimated dose were differently valued in sample sizes and applied heating treatments, different stratum ages were calculated. The ages from radiocarbon dating were compared with the OSL ages. The ages varying with grain sizes produce that the site sampled were formed with mixed soil sources.

• Proceedings of the Korean Geotechical Society Conference
• /
• 1999.03a
• /
• pp.47-78
• /
• 1999

About 440,000 $\textrm{km}^2$, about twice the size of the Korean Peninsula is covered by loess deposits in China. Along the middle reaches of the Huanghe River, mainly in Shaanxi and in Gansu province loess plateau covers vast area amounting to 273,000 $\textrm{km}^2$ Chinese studies on loess and loessial slopes are summarized. And some of the U. S. study and others are also presented for comparison.

• Proceedings of the KSR Conference
• /
• 2011.05a
• /
• pp.456-461
• /
• 2011

Recently the design specification has been advanced with preventing earthquake disaster in Korea because of increasing occurrence of large size earthquake. A composite plate with ductile fiber is proposed, which can enhance the performance of built tunnel in both strength and ductility. This study is to focus to verify the effect of strengthening of existing tunnels which is built without earthquake type load scenario, so that it can provide the safety of existing urban subway system against earthquakes.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.10a
• /
• pp.411-414
• /
• 1999

Five reinforced concrete rigid frame and masonry infilled wall and cut off type masonry infilled wall were constructed and tesed during vertical and cycle loads simultaneously. Experimental programs were accomplished to evaluate the structural performance of test spcimens, such as the hysteretic behavior, the maximum horizontal strength, crack propagation, and ductility etc. Test variables are hoop reinforcement ratio and masonry infilled wall with on without. All the specimens were modelling in one-third scale size.

• 전기의세계
• /
• v.30 no.5
• /
• pp.297-305
• /
• 1981

The problem of finding shortest paths between every pair of points in a network is solved employing and optimal network decomposition in which the network is decomposed into a number of subnetworks minimizing the number of cut-set between them while each subnetwork is constrained by a size limit. Shortest path computations are performed on individual subnetworks, and the solutions are recomposed to obtain the solution of the original network. The method when applied to large scale networks significantly reduces core requirement and computation time. This is demonstrated by developing a computer program based on the method and applying it to 30-vertex, 160-vertex, and 273-vertex networks.

• Proceedings of the Korea Air Pollution Research Association Conference
• /
• 2000.04a
• /
• pp.227-228
• /
• 2000

가상 임팩터(virtual impactor)는 가속노즐(acceleration nozzle)아래에 충돌판(impaction plate) 대신 가상의 공간을 가진 수집관(receiving tube)이 설치되어 유선의 방향이 $90^{\circ}$로 바뀔 때, 큰 입자는 유선에서 벗어나 수집노즐에 포집된다(Hounam and Sherwood, 1965). 가상 임팩터에는 관성 임팩터(inertial impactor)와는 다르게, 절단입경(cut-size)보다 큰 입자를 분리할 수 있는 부 유동(minor flow)과 절단입경보다 작은 입자를 분리할 수 있는 주 유동(major flow)으로 나눈다. (중략)