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        검색결과 19

        6.
        2018.05 구독 인증기관·개인회원 무료
        Subsurface cavities in the asphalt pavement which can cause road depression and cave-in accidents influence on the safety of pedestrians and vehicle drivers in the urban area. The existence of subsurface cavity can increase the tensile strain at the bottom of asphalt layer which is an indicator of fatigue cracking potential, and leads to the weakening of the pavement structural capacity. In this study, the finite element (FE) analysis was conducted to examine the relationship between the critical pavement responses and influencing factors, such as cavity depth and size, asphalt layer thickness, and asphalt concrete modulus. The surface deflections and tensile strains calculated from the ABAQUS FE program were compared to those from ILLIPAVE. It is found from this comparison that there are a good relationship between two analysis results. A three dimensional finite element model which is essential to simulate the hexahedral cavity were used to generate the synthetic database of critical pavement responses. To validate the developed model, the deflection data obtained from field Falling Weight Deflectometer (FWD) testing in four different locations were compared to FE deflections. It is found that the center deflections obtained from the FWD testing and FE analysis are similar to each other with an error values of 2.7, 4.4, 5.5, and 11.9 % respectively. The FE model developed in this study seems to be acceptable in simulating actual field cavity condition. On the basis of the data in the database, various analyses were conducted to estimate the effect of influencing factors on the critical pavement responses. It was found that the tensile strain at the bottom of asphalt layer is affected by all the factors but the most affected by the cavity depth and asphalt concrete modulus. Further studies are recommended to properly account for the effect of cavity’s geometry to pavement response.
        7.
        2018.05 구독 인증기관·개인회원 무료
        Pavement performance usually depends on the pavement’s material property, traffic and environmental conditions. Current pavement design programs such as the Mechanistic Empirical Pavement Design Guide use these factors in assessing the pavement life and performance in terms of different distresses like rutting and fatigue cracking. Theoretically, the cracking and rutting behaviour of pavements are based on accumulated strains experienced by the pavement which is brought by the weight and loading speed of vehicles. A steady state loading device was used in the field to evaluate pavement deflection’s behaviour in varying loading frequencies. It was observed that the pavement deflection increases as the loading frequency also increases until it approaches a certain frequency wherein the deflection decreases thereafter. In this study, a three-dimensional finite element pavement model was established using ABAQUS wherein the effect of the vehicle’s loading frequencies was analysed. The calculated static deflection and stress from the finite element (FE) model were found to have good correlation with the KENPAVE measured deflection and stress. The deflections of different pavement conditions were further studied and analysed by generating several pavement geometries and strength from the FE model using a frequency sweep response analysis. It was found that the geometric condition and the current modulus of the pavement can amplify the pavement deflection by a factor, β, depending on the loading frequency. The peak deflection was found to be occurring when the loading frequency approaches one of the pavement’s natural frequencies. Based on the finding from this study, the natural frequency is an important factor to be considered in designing pavements. Further study is recommended to understand more on how to minimize the effect of natural frequency to pavement life.
        8.
        2018.05 구독 인증기관·개인회원 무료
        In this study, several approaches in evaluating moisture sensitivity of asphalt mixtures were investigated and compared. To evaluate the moisture damage resistance, twenty types of asphalt mixtures with and without anti stripping additives were tested in the laboratory. Uniaxial compressive strength (UCS) and indirect tensile (IDT) testing were performed to determine the Tensile Strength Ratio (TSR) and Cohesion Strength Ratio (CSR). Stone Mastic Asphalt (SMA) mixtures were found to provide good moisture damage resistance compared to other mixtures. It also does not require anti stripping additives to improve its moisture resistance. Moreover, the correlation coefficient between the TSR test and CSR tests is 0.99 with an average error of 1.5%, which indicates that the TSR test following AASHTO T-283 is still the most reasonable criteria in evaluating the moisture damage of AC mixtures. Marshall Stability Ratio (MSR) and Marshall Stability to Flow Ratio (MSFR) were conducted and were compared to TSR test results. It was found that MSFR value may be used to evaluate the moisture damage resistance of AC mixtures instead of TSR test. Finally, Dynamic Immersion (DI) test was performed to evaluate moisture resistance for loose asphalt mixtures. The DI results showed good correlation also when evaluating moisture resistance compared to TSR. When using DI testing in evaluating moisture resistance, it is recommended to test after 48 hours since it showed higher correlation with the TSR values. Further study is recommended to improve current testing evaluating moisture susceptibility of asphalt mixtures to properly associate it with TSR values.
        9.
        2017.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        PURPOSES:The objective of this study is to evaluate the performance of asphalt mixtures containing inorganic additive and a high content of reclaimed asphalt pavement (RAP).METHODS:The laboratory tests verified the superior laboratory performance of inorganic additive compared to cement, in cold recycled asphalt mixtures. To investigate the moisture susceptibility of the specimens, tensile strength ratio (TSR) tests were performed. In addition, dynamic modulus test was conducted to evaluate the performance of cold recycled asphalt mixture.RESULTS:It was determined that NaOH solution mixed with Na2SiO3 in the ratio 75:10 provides optimum performance. Compared to Type B and C counterparts, Type A mixtures consisting of an inorganic additive performed better in the Indirect tensile strength test, tensile strength ratio test, and dynamic modulus test.CONCLUSIONS:The use of inorganic additive enhances the indirect strength and dynamic modulus performance of the asphalt mixture. However, additional experiments are to be conducted to improve the reliability of the result with respect to the effect of inorganic additive.
        4,000원
        10.
        2017.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        PURPOSES:The objective of this study is to evaluate the effect of anti-stripping on asphalt mixtures constituting anti-stripping agents.METHODS:Based on the literature review, asphalt mixture added with anti-stripping agents was prepared, and these asphalt mixtures were evaluated for anti-stripping properties for each anti-stripping agent through various lab tests, namely, tensile strength ratio (TSR), dynamic immersion test, uniaxial compression test, and indirect tensile strength test (IDT). The liquid anti-stripping agents used in the lab test were premixed with each asphalt binder (PG 64-22, PG 76-22) before being mixed with the aggregate.RESULTS:The result of the TSR test revealed that the effect of anti-stripping was highest when hydrated lime and liquid anti-stripping agent W were added. The correlation coefficient R2 between the TSR result and cohesion ratio is 0.99, which indicates that the sensitivity of the TSR to moisture damage is reliable from the mechanical point of view. The covering ratio of the asphalt binder to the liquid anti-stripping agent W was determined to be higher than that to the other liquid anti-stripping agents.CONCLUSIONS:It is considered that the improved moisture resistance of asphalt mixture as a result of the use of anti-stripping agents can reduce the incidence of various pavement damages such as portholes caused by stripping, and the performance life of the asphalt road pavement can be prolonged.
        4,000원
        11.
        2013.06 구독 인증기관 무료, 개인회원 유료
        The cultivation methods of Acanthopanax in Korea need to be optimized. Hence, this study investigated the effect of different fertilizer ratios and planting dates on the growth and acanthoside D content of two (2) Acanthopanax species. The current recommended fertilizer rate of 10.5-8.5-8.5 kg/ha- (N-P2O5-K2O, respectively) produced the best plant growth of Acanthopanax. For the first year, the acanthoside D content resulting from the 2P (2x phosphate) rate was higher than that from the other fertilizer ratios, yet there were no significant differences resulting from the various treatments for either Acanthopanax divaricatus or Acanthopanax koreanum. Similarly, for the second year, there were no significant differences in the acanthoside D content resulting from the various fertilizer ratios, although for both species the acanthoside D content resulting from the 2P rate was slightly higher than that from the other treatments. Therefore, the results indicated that doubling the amount of phosphate increased the acanthoside D content. Plus, the optimum planting date with respect to growth and productivity for Acanthopanax divaricatus was identified as April 15. The cultivation methods of Acanthopanax in Korea need to be optimized. Hence, this study investigated the effect of different fertilizer ratios and planting dates on the growth and acanthoside D content of two (2) Acanthopanax species. The current recommended fertilizer rate of 10.5-8.5-8.5 kg/ha- (N-P2O5-K2O, respectively) produced the best plant growth of Acanthopanax. For the first year, the acanthoside D content resulting from the 2P (2x phosphate) rate was higher than that from the other fertilizer ratios, yet there were no significant differences resulting from the various treatments for either Acanthopanax divaricatus or Acanthopanax koreanum. Similarly, for the second year, there were no significant differences in the acanthoside D content resulting from the various fertilizer ratios, although for both species the acanthoside D content resulting from the 2P rate was slightly higher than that from the other treatments. Therefore, the results indicated that doubling the amount of phosphate increased the acanthoside D content. Plus, the optimum planting date with respect to growth and productivity for Acanthopanax divaricatus was identified as April 15. The cultivation methods of Acanthopanax in Korea need to be optimized. Hence, this study investigated the effect of different fertilizer ratios and planting dates on the growth and acanthoside D content of two (2) Acanthopanax species. The current recommended fertilizer rate of 10.5-8.5-8.5 kg/ha- (N-P2O5-K2O, respectively) produced the best plant growth of Acanthopanax. For the first year, the acanthoside D content resulting from the 2P (2x phosphate) rate was higher than that from the other fertilizer ratios, yet there were no significant differences resulting from the various treatments for either Acanthopanax divaricatus or Acanthopanax koreanum. Similarly, for the second year, there were no significant differences in the acanthoside D content resulting from the various fertilizer ratios, although for both species the acanthoside D content resulting from the 2P rate was slightly higher than that from the other treatments. Therefore, the results indicated that doubling the amount of phosphate increased the acanthoside D content. Plus, the optimum planting date with respect to growth and productivity for Acanthopanax divaricatus was identified as April 15. The cultivation methods of Acanthopanax in Korea need to be optimized. Hence, this study investigated the effect of different fertilizer ratios and planting dates on the growth and acanthoside D content of two (2) Acanthopanax species. The current recommended fertilizer rate of 10.5-8.5-8.5 kg/ha- (N-P2O5-K2O, respectively) produced the best plant growth of Acanthopanax. For the first year, the acanthoside D content resulting from the 2P (2x phosphate) rate was higher than that from the other fertilizer ratios, yet there were no significant differences resulting from the various treatments for either Acanthopanax divaricatus or Acanthopanax koreanum. Similarly, for the second year, there were no significant differences in the acanthoside D content resulting from the various fertilizer ratios, although for both species the acanthoside D content resulting from the 2P rate was slightly higher than that from the other treatments. Therefore, the results indicated that doubling the amount of phosphate increased the acanthoside D content. Plus, the optimum planting date with respect to growth and productivity for Acanthopanax divaricatus was identified as April 15. The cultivation methods of Acanthopanax in Korea need to be optimized. Hence, this study investigated the effect of different fertilizer ratios and planting dates on the growth and acanthoside D content of two (2) Acanthopanax species. The current recommended fertilizer rate of 10.5-8.5-8.5 kg/ha- (N-P2O5-K2O, respectively) produced the best plant growth of Acanthopanax. For the first year, the acanthoside D content resulting from the 2P (2x phosphate) rate was higher than that from the other fertilizer ratios, yet there were no significant differences resulting from the various treatments for either Acanthopanax divaricatus or Acanthopanax koreanum. Similarly, for the second year, there were no significant differences in the acanthoside D content resulting from the various fertilizer ratios, although for both species the acanthoside D content resulting from the 2P rate was slightly higher than that from the other treatments. Therefore, the results indicated that doubling the amount of phosphate increased the acanthoside D content. Plus, the optimum planting date with respect to growth and productivity for Acanthopanax divaricatus was identified as April 15.
        4,000원
        12.
        2012.09 구독 인증기관 무료, 개인회원 유료
        본 연구는 미세유체시스템 내부에 효소가 고정된 PEG 하이드로젤 마이크로 어레이를 이용한 알코올 감지 바이오센서 제작에 대한 방법을 소개한다. 모델 알코올인 에탄올은 알코올 옥시다아제(Alcoholoxidase,AOX)를 포함한 PEG 하이드로젤 마이크로 어레이에 의해 광학적으로 분석되며, 다중의 미세채널구조를 이용하여 동시에 여러 농도의 알코올을 측정할 수 있다. 에탄올과 알코올 옥시다아제와의 효소촉매작용을 통해 H2O2이 생성되며 이는 페록시다아제 (Peroxidase,POD)와 반응하여 무색의 Amplex Red reagent를 붉은 형광을 띄는 resorufin으로 바꿔준다. 결과적으로 형광측정을 통해 에탄올의 농도를 확인할 수 있다. 에탄올의 농도가 높을수록 H2O2의 생성이 많아지고 resorufin의 형광강도가 강해지는 메카니즘을 통해 손쉽게 측정이 가능하다. 여섯줄의 미세유체채널을 포함하는 미세유체시스템 내부에 각각 에탄올에 반응하는 알코올 옥시다아제가 고정된 PEG 하이드로젤 마이크로 어레이를 제조하고 체내의 에탄올 농도인 1.0∼10mM을 반응시켜 형광변화를 통한 동시 측정이 가능한 바이오센서를 제작하였다.
        4,000원
        13.
        2010.10 구독 인증기관·개인회원 무료
        Insects or insect remains found in beer are one of major issues in consumer claim. Accurate estimation of inflow time isa critical factor for the settlement of such claims related with beer-contaminating insects but no reliable methods have been developed. In an attempt to establish a molecular marker-based diagnostic method, the degradation rates of 18S rRNA genes in the insectssoaked in 500 ml beer were investigated by quantitative real-time PCR (qPCR) over one month period at room temperature. Among the six insect species tested, the house fly (Musca domestica) and honey bee (Apis mellifera) revealed high correlations (r2=0.974-0.990) between the degradation of 18S rRNA gene and inflow time. In these insects, statistically significant distinction was possible between the samples stored in beer less than 14 days and more than 14 days. Other insects, including the fruit fly, common house mosquito, German cockroach and Indian meal moth, displayed poor correlations, which appeared attributed to the inefficient genomic DNA extraction likely due to small sample size or disintegration of body parts during storage in beer. With proper improvement in DNA extraction, this 18S rRNA-based diagnostic method would be applicable for estimating the inflow time of beer-contaminating insects.
        16.
        1988.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        제 2 계 2 차모벤 프 밴언 점자합 포불체 근 사법의 역파정의 연산을 구하여 신뢰성설계에 적 용할 수 있 도 록 하였으며 , 파괴 점을 二,'-하기 위한 신뢰성조낀 1선의 연산과정 을 수정하여 한계상태함수가 비선형인 경우 에도 문- 제마다 식 을 새로 수립하는 번 거로웅을 피하도록 하였다. SOSM j RC 조합방법을 이용하면 견 파적인 파괴확률은 목표파괴확률 에 부합하며 넓은 범위의 하중비 에 대해 시 의 일정 한 부분안 전 계수릎 얻 올 수 있다.
        4,000원
        17.
        2013.12 서비스 종료(열람 제한)
        Neutropenic enterocolitis (NE), the most serious gastrointestinal complication, has been reported as a clinical syndrome that occurs in the setting of disease- or chemotherapy-induced neutropenia. Complications of NE include bowel necrosis with perforation, fistula, stenosis, massive bleeding, abscess formation, and pneumatosis intestinalis (PI). Most physicians recommend initial conservative management with bowel rest, intravenous fluids, total parenteral nutrition, broad-spectrum antibiotics, and normalization of neutrophil counts. Surgical intervention is recommended in the event of obstruction, perforation, persistent gastrointestinal bleeding despite correction of thrombocytopenia and coagulopathy, or clinical deterioration. We experienced a patient whose abdominal computed tomography scan showed pneumoretroperitoneum, intramural gas in the colon, and inferior vena caval gas. Her condition improved after treatment with granulocyte colony-stimulating factor and broad-spectrum antibiotics. We report on this case along with a review of the literature.