• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.6
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• pp.1238-1245
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• 1988

Friction and wear characteristics of short fiber reinforced and particulate filled composites were investigated experimentally. Two kinds of fiber composites, chopped graphite fiber reinforced PAI(polyamide-imide) and glass fiber reinforced PAI, and a particulate composite, TiO$_{2}$ powder filled PAI, were selected for the friction and wear test since these are important engineering materials based on a new high temperature engineering plastic. All the specimens were cut into proper size for cylinder-on-plate type wear test. Frictional forces were measured by employing a load transducer and wear rates were calculated by measuring weight loss during wear test. The experimental results are reported in this paper and carefully discussed to explain the friction and wear behavior qualitatively. The frictional behavior is interpreted by considering four basic friction components which are believed to the genesis of friction and the wear behavior is explained by applying delamination theory of wear.

• Tunnel and Underground Space
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• v.31 no.6
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• pp.469-479
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• 2021

As a material for preventing spalling of concrete, the effectiveness of PP fiber has already been confirmed. However, it is necessary to consider the maximum temperature that occurs during a fire, and to solve the mixing problem and the strength reduction problem that occur depending on the mixing amount. In this study, the fire resistance performance of tunnel segment linings according to the PP fiber content and air volume under the RABT fire scenario was investigated. As a result, no spalling or cross-sectional loss occurred in all test specimens, and when the PP fiber content was small, the maximum temperature was relatively high and the maximum temperature arrival time was also fast. On the other hand, no trend was found for the maximum temperature and arrival time according to the difference in air volume. In the internal temperature distribution results for the PP fiber mixing amount of 0.75, 1.0, 1.5, and 2.0 kg/m³, the results of 0.75 and 1.0 kg/m³ showed similar temperature distribution, and the results of 1.5 and 2.0 kg/m³ were similar. It was confirmed that the internal temperature distribution tends to decrease at the same depth when the amount of PP fiber mixed is large, and it was confirmed that a remarkable difference occurred from the results of 1.0 kg/m³ and 1.5 kg/m³ of PP fiber mixed amounts.

• Journal of the Korea Institute of Building Construction
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• v.12 no.4
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• pp.442-450
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• 2012

In this study, fire resistance and residual strength were examined after the addition of PF fiber and bonding fireproofing gypsum board to a high strength concrete-model column of 50 MPa grade. At the beginning of the experiment, all the properties of base concrete appeared to satisfy the target range. In terms of the internal temperature record, a trend of slightly high temperature was shown when the fireproofing gypsum board was not bonding, and when the fireproofing gypsum board was bonding, as PF content increased gradually, the temperature was gradually lowered. In terms of the relationship, as time elapsed a low temperature was shown when fiber was mixed, and when the board was bonding, the trend of lower temperature could be confirmed. Meanwhile, in terms of spalling property, a severe explosive fracture was generated at PF 0%, and falling off was prevented as the fiber content was increased; however, discoloration and a multitude of cracks were discovered, and when the board was bonding, the trend in which the exterior became satisfactory when the content was increased emerged. In terms of the residual compressive strength, measuring of strength could not be performed at PF 0% without bonding of board, and the strength was increased as the fiber content was increased; however, there was a decrease in strength of about 30 ~ 40%, and in the case of PF 0% with the bonding of board, the strength could be measured; however, about an 80% decrease in strength was shown, and only about a 10 ~ 20% decline in strength was displayed, as the range of decrease was reduced as the fiber content was increased. Considering all of these factors, it was determined that a more efficient enhancement of fire resistance was obtained when two methods are applied in combination rather than when the PF fiber content and bonding of fireproofing gypsum board are utilized individually.

• Journal of the Korean Geotechnical Society
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• v.33 no.12
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• pp.141-150
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• 2017

Geosynthetics are generally utilized to restrain the leakage of leachate and other contaminants during the construction of offshore waste landfill. Therefore, geosynthetic-soil interface is formed inevitably. In this study, 2 dimensional numerical analysis is performed to assess the dynamic behaviour of the offshore waste landfill including geosynthetic-soil interface. Offshore waste landfill can be divided into rubble mound revetment and retaining wall types and analyzed on each type. Effective stress analysis is conducted to consider the variation of pore water pressure and axial force and shear displacement of the interface are compared based on the characteristics of seismic frequency. Consequently, retaining wall type demonstrates more stable behavior against liquefaction potential and favorable forces and shear displacement.

• Composites Research
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• v.20 no.2
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• pp.1-9
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• 2007

To evaluate and investigate the aging characteristics and the structural service lifetime of the CFV(carbon fiber pressure vessel), natural aging tests were carried out using the CFVs, which had been placed and aged at outdoor and indoor laboratories for 10 and 15 years, respectively. To obtain the probabilistic characteristics of ageing characteristics in aged CFVs, inner pressure loading test was conducted with ring specimens taken from aged CFVs. And, to observe the interface morphology of aged CFVs, the micro-photographs were taken by SEM microscope and the fractured interfaces between the carbon fiber and the matrix resin were scrutinized. Based on the Weibull parameters of the tensile failure strain of aged CFVs, the degradation of the 10 and the 15 year aged CFV occur by 19% and 23%, respectively, and the effect of the placement, whether being placed inside the laboratory or not, is not so significant. However, the outer layer protection, such as painting, is found very advantageous to prevent CFV from aging.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.296-300
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• 2007

우리나라에 내리는 대부분의 강수량은 6월${\sim}$8월의 장마기간 혹은 태풍의 영향으로 인해 발생한다. 특히 국지적으로 발생하는 집중호우로 인해 많은 인명, 재산 피해 등이 발생한다. 우리나라에서 집중호우로 인한 피해는 거의 매년 발생하고 있으며, 집중호우의 발생 지역은 특정 지역에 국한되어 있지 않다. 따라서 집중호우 발생으로 인한 피해 방지를 위해 사전에 충분한 준비를 해야 한다. 2006년 7월 8일부터 10일까지 3일 동안 진주지역 306.5mm, 합천지역 259.5mm, 산청지역 366.0mm의 집중호우가 발생하였으며, 이 기간 동안 이들 지역 외에도 전국적으로 태풍 에위니아(EWINIAR)의 영향으로 많은 호우가 발생하였다. 본 연구에서는 2006년 7월 진주지역 집중호우 특성 연구를 위해 진주지역 시강우 자료를 이용하여 자료를 분석하였다. 시강우 자료를 이용하여 진주지역 재현기간별 확률강우량을 산정하였고 2006년 7월 8일부터 10일까지의 강우분포형태를 설계강우분포형과 비교하였다. 또한 2006년 7월 발생했던 진주지역 집중호우의 무차원 누가곡선을 작성하여 분석을 실시하였다. 분석 결과 일최대 강우량의 경우 그 크기가 50년 혹은 80년 이내였으며, 강우분포형의 경우 하천정비기본계획의 경우 Mononobe 중앙집중형이였지만, 지난 호우의 경우 후방위의 강우가 연속적으로 발생한 형태였다. 또한 대부분의 강우가 6시간 이내에 내려 첨두홍수 발생에 많은 영향을 미쳤을 것으로 판단된다. 앞으로 이상기후와 같은 자연 현상에 대비하기 위해서는 단시간 호우에 대한 정확한 분석과 강우분포에 대한 연구가 더욱 필요할 것으로 생각된다.적자색의 미려한 결정이 석출되므로 이 결정을 여과하여 ethanol로 세척하고 진공 desiccator중에서 건조시켰다. 수득량 1.2~1.3g.)와의 조환가는 11.9565의 상인연소현상을 보였다. 삭과색(Y) 경색(R) 유전자간에는 어느것이나 연소현상이 보이지 않았다. 4. 단일반응성의 변이는 연소적이며 우성은 거의 인정되지 않았고 인자간의 상호작용도 인정되지 않았으며 상가적 유전을 보였다. 광의와 협의의 유전력은 각각 89.50%로서 실용적으로 대단히 높은 것으로 생각되었으며 단일반응성에 관여하는 유전자수는 2대의 인자로 추정하였고 다시 양친의 유전자형을 aabb AABB라고 측정하여 각인자의 작용가는 11.136일로 산출되었고 분해법에 의한 유전분석결과 유전자형의 관찰빈도분포와 이론빈도분포는 서로 잘 적합되었다. 단일반응성에 있어서 유전력이 대단히 높았으므로 비교적 초기세대에서 본 형질의 선발이 가능할 것 같았다. 5. 단일반응성과 엽형 및 엽병색 유전자와의 사이에 $F_2$, $BC_1$ 및 $BC_2$에서 각각 유의적인 상관관계를 볼 수 있었으므로 이들 형질간에 연소가 있는 것으로 인정되었다. 더욱 엽형과 엽병색과의 연소가 있는 것으로 인정되는 이상단일반응성 유전자와의 사이에 연소군이 인정된다. 6. 섬유중 유전자와 엽병색 및 엽형유전자와의 사이에 $F_2$$BC_1$ 및 $BC_2$에서 각각 유의적 상관관계를 볼 수 있었으므로 이를 형질간에 연소가 있는 것으로 인정되었다. 더욱 엽형과 엽병색과의 연소가 있는 것으로 인정되는 이상 섬유중 유전

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.7 s.178
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• pp.1810-1816
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• 2000

A hybrid composite APAL(Aramid Patched Aluminum alloy) , consisting of Al 2024-T3 aluminum alloy plate sandwiched between two aramid/epoxy laminates, was developed. The characteristics of tensile s trength were investigated and statistical properties of tensile strength were studied in terms of Weibull distribution probability with number of AFRP laminates. The tensile strength of APAL was inproportional to number of AFRP laminates and followed the two-parametic Weibull distribution.

• Korean Journal of Materials Research
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• v.8 no.2
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• pp.120-125
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• 1998

CO$_{2}$gas중에서 산화된 활성탄소섬유를 77K에서 질소흡착에 의해 흡착등온곡선을 구하였다. 미세공부피와 외부표면적은 t-법으로 구하였으며, 평균기공크기와 기공분포는 Dubinin-Astakhov법으로 구하여 기공발당과정을 고찰하였다. 산화반응 초기(약 40% burn-off까지)에 섬유내부에 발달하는 미세공은 burn-off가 40%를 넘으면 서서히 큰 미세공으로 성장하며, burn-off가 약 60%이상되면 미세기공은 확대 또는 합체되어 점차 중기공으로 성장하는 것으로 관찰되었다. 또한 고온산화반응으로 발달한 기공은 저온에서 생성된 기공보다 크다.

• Journal of the Korean Society of Food Science and Nutrition
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• v.26 no.4
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• pp.639-646
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• 1997

The contents of free sugars, organic acids, amino acids, total carotenoids and pectin of pumpkin were analysed. Weight percentage of flesh was 84% of total weight. Rind and funicular attachment of seed were 10% and 3.5%, respectively. Major free sugars in pumpkin were fructose, glucose, sucrose. In flesh, fructose and glucose were the major free sugars, corresponding to 87% of total free sugars . Total sugar content in the flesh was three times higher than that in the funicular attachment of seed. Contents and composition of free amino acids were quite different according to the different parts of pumpkin. Non-volatile organic acids in pumpkin was malic, succinic and fumaric acid. The major acid in the flesh and funicular attachment of seed was malic acid and the contents in these parts were 85.2mg% and 226.5mg%, corresponding to 63% and 70% of the total organic acids, respectively. Eigh-tyseven percent of total carotenoids in the pumpkin was in the funicular attachment of seed, amounting 65.3mg%. However flesh and rind contained 6.6mg% and 3.3mg%, respectively. Water soluble pectin consisted 58% of the total soluble pectin in different parts of pumpkin, and soluble Pectin content was higher in funicular attachment of seed than in flesh. The major neutral sugars of the pectin in flesh and funicular attachment of seed were galactose and glucose consisting 45% and 36.5% of total neutral sugars.

• Journal of the Korea Concrete Institute
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• v.17 no.6 s.90
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• pp.911-922
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• 2005

A theoretical study was performed to investigate the behavioral chracteristics and shear strength of fiber reinforced concrete slender beams. In the fiber reinforced concrete beam, the shear force applied to a cross section of the beam was resisted by both compressive zone and tensile zone. The shear capacity of the compressive zone was defined addressing the interaction with the normal stresses developed by the flexural moment in the cross section. The shear capacity of the tensile zone was defined addressing the post-cracking tensile strength of fiber reinforced concrete. Since the magnitude and distribution of the normal stresses vary according to the flexural deformation of the beam, the shear capacity of the beam was defined as a function of the flexural deformation of the beam. The shear strength of the beam and the location of the critical section were determined at the intersection between the shear capacity and shear demand curves. The proposed method was developed as a unified shear design method which is applicable to conventional reinforced concrete as well as fiber reinforced concrete.