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        검색결과 274

        62.
        2018.05 구독 인증기관·개인회원 무료
        Recently, there is an increasing the pavement distresses such as rutting with an increase in heavy vehicles on the road in Mongolia. Rutting is the longitudinal depression in the wheel path in asphalt pavements and it causes a hydroplaning and severe safety concern for users. This study aims to develop paving material that can prevent rutting on the road pavement by improving the durability of the asphalt mixture in Mongolia. Therefore, this study was carried out using the technique of reinforcing the material by adding fibers to conventional asphalt mixture. Fibers have been used to reinforce various materials for many decades in various parts of the world. It is generally understood that asphalt is strong in compression and weak in tension. Adding fibers with high tensile strength can help increase the strength of a mixture[1]. A mixture of glass fibers was used in this study to evaluate the performance characteristics. In coordination with the City of Ulaanbaatar, The test section selected in this study was Peace Avenue in Ulaanbaatar. The test section was a bus lane with severe rutting by heavy vehicles. The designated road test section performed cutting and overlay using five asphalt mixtures: Glass Fiber-reinforced Asphalt, Hot Mix Asphalt(10mm, 19mm), Polymer Modify Asphalt(2 types). The performance survey was conducted after the summer. As a result, No noticeable cracks were observed in glass-reinforced mixture section and the rut-depth of the glass-reinforced mixture is lower than other mixtures[2].
        63.
        2018.05 구독 인증기관·개인회원 무료
        Recently, Cambodia has been investing a lot of money in the construction and maintenance of roads, which are social infrastructures. However, damage to the existing pavement is accelerating due to the old age of the road pavement, poor drainage facilities and increase in heavy traffic. To solve this problem, a fundamental solution such as a high-performance asphalt mixture is required to extend the life of road pavement. In this study, a high performance glass fiber reinforced asphalt mixture developed in Korea was applied to Cambodia. Prior to field application, Marshall stability tests were performed on glass fiber reinforced asphalt mixtures, SBS modified asphalt mixtures and asphalt mixtures commonly used in Cambodia. The Marshall stability test showed that the glass fiber reinforced asphalt mixture and the SBS modified asphalt mixture had the same strength (about 1.3 times higher strength than the usual asphalt mixture). In addition, the test construction was carried out on the National Highway 2 of Cambodia for the evaluation of the performance of the three mixtures. In the future, the long-term performance evaluation of each mixture will be conducted through follow-up survey of the test construction area.
        64.
        2018.05 구독 인증기관·개인회원 무료
        Roller Compacted Concrete Pavement (RCCP) is placed by roller compaction of a mixture of less cement and unit water content and more aggregates and provides excellent early strength development with the help of interlocking of aggregates and hydration. The unit cement content of RCC pavements accounts for 85% of conventional pavements, with low drying shrinkage. As low drying shrinkage leads to smaller crack widths than ordinary concrete, RCC pavements can help elevate reflecting crack resistance if applied to a base layer of a composite pavement system. In a composite pavement with an asphalt surface laid over a concrete base, pavement temperature change is important in predicting pavement performance. As movement of the lower concrete layer is determined by temperature depending on pavement depth, temperature data of the pavement structure serves as an important parameter to prevent and control reflecting crack. Among the causes of reflecting crack, horizontal behavior of the lower concrete layer and curling-caused vertical behavior of joints/cracks are considered closely related to temperature change characteristics of the lower concrete course (Baek, 2010). Previous studies at home and abroad about reflecting crack have focused on pavement behavior depending on daily and yearly in-service temperature changes of a composite pavement (Manuel, 2005). Until now, however, studies have not been conducted on initial temperature characteristics of concrete in composite pavements where asphalt surface is placed over an RCC base. Annual temperature changes of in-service concrete pavements go up to 60 ℃, and those of asphalt overlays become around the twice at 110 ℃. This study evaluated initial crack behavior of composite pavement by investigating pavement temperature by depth of an RCC base and analyzing joint movement depending on change to temperatures of continuously jointed pavements. Findings from the study suggest that in composite pavements and asphalt overlays, time of laying asphalt has an important impact on crack behavior and reflecting crack.
        65.
        2018.05 구독 인증기관·개인회원 무료
        Roller Compacted Concrete Pavement (RCCP) is a pavement placed and compacted using an asphalt paver and a compaction roller by applying a small amount of concrete mixture and shows excellent structural performance as a result of hydration reaction of cement and interlocking of aggregates by roller compaction. It also provides economic advantages over conventional concrete pavements by reducing unit cement content and construction period, simplifying construction process, and decreasing traffic closure time (Wayne, 2006). However, given that it tends to show lower IRI levels than common concrete pavements since its low unit water content and binder weight ratios make uniform quality control difficult and roller compaction after paving makes the surface irregular and rough, with rough profile at the bottom of the pavement being reflected on the surface, RCCP is used mainly in port and industrial roads for low speed (60km/h or less) traffic (Dale Harringtion, 2010; Gregory, 2009). In order to apply RCCP to high-speed roadways, diamond grinding (DG) or asphalt overlay that is highly effective in improving roughness is needed (Fares Abdo, 2014; Gregory, 2009). Applying DG over RCCP leads to excellent skid resistance and noise reduction effects as a great percentage of aggregates makes the pavement surface rough, enhancing durability of concrete and the life of DG functionality. In addition, RCCP can be used as a high performance base layer of composite pavements, as it can reduce reflecting cracking at joints and cracked sections thanks to early strength development and low drying shrinkage of concrete. In this study, we assessed longitudinal roughness improvement effects by roughness-affecting factor by applying DG methods and asphalt overlays to three RCCP sites with a variety of sub-structural conditions and analyzed the effects on roughness of existing RCC pavements depending on surfacing method (DG, APOverlay).
        66.
        2018.05 구독 인증기관·개인회원 무료
        The Semi-Rigid Pavement (SRP) mixture is composed of Gap Graded Asphalt (GGA) mixture (air void = 20~28%) and cement paste. By inserting cement paste into voids in GGA mixture, SRP can provide not only flexibility but also rigidity characteristics on pavement performance. SRP can mitigate pavement surface temperature increase during summer session, provide better smoothness and mitigate rutting distress due to heavy weight vehicles, successfully. In Japan, SRP is widely applied in cross section area, heavy vehicle parking lot and highway ticketing booth in highway network system. In South Korea, SRP was introduced and applied since 2005. However, still more researches and studies are needed to understand material characteristics and improve performance of SRP. Moreover, the current SRP system in South Korea merely follows and adapts the aggregate gradation information from Japan which needs to be amended and customized into original material (i.e. aggregate, binder and cement) situation of South Korea. In this paper, SRP system based on Stone Mastic Asphalt (SMA) mixture design originated from Korea Expressway Corporation (KEC) and enhanced cement paste with addition of fly-ash and slags was developed. In addition, an optimized proportion between asphalt mixture air voids and cement paste amount with consideration of economic benefit was introduced. Based on field evaluation process it can be said that the newly developed SRP system can successfully adapted not only in static site on highway: parking lots or ticketing booth, but also in dynamic site on highway: driving and wheel path.
        67.
        2018.05 구독 인증기관·개인회원 무료
        In Korea, concrete pavements were first applied to highways in 1981 and as a result of continued increase in length over the past years, 2,592 km of concrete pavement network is currently in service, of which 1,399 km(54%) of concrete pavements is 10 years or older, and 233km(9%) is 20 years or older. The length of concrete pavement sections nationwide has been steadily on the rise every year (EXTRI, 2017). Approximately 54% of current concrete pavement highway network will reach the service life limit in 2025 which means around 660 billion won is needed for future pavement repair project (EXTRI, 2017). Given that concrete pavements beyond design life still have a remaining service life, it is economically advantageous to repair them before reconstruction. Asphalt overlays are a major repair method for older concrete pavements. Depending on the concrete pavement condition, thickness and mixture of asphalt overlays are determined. Service life of asphalt overlays varies by the presence, time and size of cracks in existing concrete pavements and reflecting crack at joints. Temperature change of concrete pavement is among the major reaction parameters of reflecting crack. Reflecting crack develops when asphalt bottom-up cracking by longitudinal shrinkage and expansion due to temperature change of the concrete base layer, top-down cracking by temperature difference between top and bottom of concrete, and shear stress by traffic loading are combined (Baek, 2010). Crack and joint behaviors of concrete pavement vary between the base layer and the concrete surface of composite pavement system, and different conductivity by mixture and thickness of asphalt overlay leads to temperature change of concrete base course. This study measured temperatures of each layer of diverse composite pavements in place on site and analyzed differences in temperature change of concrete base layer depending on mixture and thickness of asphalt overlays. Overlay thickness parameters were 5cm and 10cm, two values most widely used, while mixture parameters were SMA and porous asphalt. Based on temperature change of concrete surface, this study also evaluated the difference of temperature change in concrete base layer with an asphalt overlay on top. Findings from this study are expected to be utilized for studies on mechanism and modeling of reflecting crack in old concrete pavements with asphalt overlays.
        68.
        2018.05 구독 인증기관·개인회원 무료
        In case of performing asphalt pavement overlay on existing concrete pavement layer, applying asphalt emulsion tack-coating or spreading prime-coating is considered to improve adhesion between asphalt and concrete layer. After coating work is done a curing process is considered not only for promoting evaporation process in coated (and/or spread) asphalt emulsion, but also for generating a membrane which can act as a bonding agent. Finally, asphalt overlay construction is performed when this curing process is completely done. However, during asphalt overlay construction process remarkable amount of spread tack-coating layer is lost due to asphalt material transfer vehicles (e.g. trucks, approximately 40~50% of total spread tack coating material is lost). In this paper, a new pavement equipment contains simultaneous asphalt emulsion spreading ability and corresponding construction techniques are introduced. Through applying this equipment, non-stop two step sequent working process: spreading asphalt emulsion on to existing concrete pavement layer then paving asphalt material for overlay construction, is available. During pavement working process temperature of asphalt material was kept with ranged between 130ºC and 170ºC. After performing field performance evaluation, it was found that crucial improvement in pavement layer adhesion, crack and rutting resistant ability were observed compared to the conventional paving method.
        69.
        2018.04 구독 인증기관·개인회원 무료
        동남아시아에 발생하던 등검은말벌은 최근 국내 뿐만 아니라 프랑스와 일본, 유럽 전역으로 확산되어 전 세계 양봉 산업에 극심한 피해를 주고 있다. 등검은말벌을 방제하기 위해 다양한 방제 방법들이 연구되고 있으며, 그 중 말벌 유인제에 대해 국제적으로 많은 연구가 진행되어 왔으나 이 역시 지속적인 개발이 필요한 실정이다. 따라서 본 연구에서는 시판 유인제와 최근 (주)다목에코텍에서 새롭게 개발한 신규 개발 유인제에 대한 효능 검정을 수행하였 고 양봉장에 출현하는 국내 발생 말벌속의 발생양상을 조사하였다. 담양 1개소와 곡성 2개소에 기존 유인제과 신규 유인제를 장착한 포획기를 각 3쌍씩 설치하여 2016년 9월부터 11월말까지 주 1~2회 관찰하였다. 그 결과 국내 발생 말벌속 중 등검은말벌(7,787 개체)이 가장 많이 포획되었고, 다음으로 장수말벌, 말벌, 좀말벌, 꼬마장수말벌, 털보말벌 순으로 포획되었다. 두 유인제의 포획력 검정 결과, 신규 개발 유인제가 통계적으로 유의하게(P < 0.01) 등검은말벌 포획력이 높음을 보였다.
        70.
        2018.04 구독 인증기관·개인회원 무료
        Previous phylogenetic results often showed fluctuating positions of Geometroidea in Macroheterocera, particularly from mitochondrial genome (mitogenome)-based analyses. In this study, we sequenced mitogenomes of four geometrid moths to increase taxon diversity for the inference of phylogenetic positions of Geometroidea in Macroheterocera. The general genomic features found in Macroheterocera also were found in the four geometrid moths. Phylogenetic analyses using 71 representative mitogeneome sequences in Macroheterocera yielded the consensus superfamilial relationships (((((Bombycoidea + Lasiocampoidea) + Geometroidea) + Noctuoidea) + Drepanoidea) + Mimallonoidea), confirming the sister relationship of Geometroidea to (Bombycoidea + Lasiocampoidea) in both Bayesian Inference and Maximum-likelihood method.
        71.
        2018.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Red meats are important animal foods because of their nutritional aspects, but the over-consumption of red meat produces reactive oxygen species (ROS) caused by heme iron and induces colorectal cancer. The effect of orally administered hemin and calcium provided in drinking water for 6 weeks on colon carcinogenesis was observed in male ICR mice. After the mice were acclimated for 1 week, they received three subcutaneous azoxymethane (AOM, 10 mg/kg b.w.) injections weekly and were provided with 2% dextran sodium sulfate (DSS) via drinking water for the next week. The mice were divided into three groups: the control, hemin, and hemin + calcium groups. The orally administered daily dose of hemin was 2 g/kg b.w., and 0.05% calcium was provided daily via drinking water. Colonic mucosa samples were stained with methylene blue, and then, the numbers of aberrant crypt (AC) and aberrant crypt foci (ACF) were counted. Lipid peroxidation in feces was estimated by thiobarbituric acid-reactive substances (TBARS) assay. The total numbers of AC and ACF per colon in the hemin group were significantly higher than those in the control group. Calcium treatment significantly decreased the numbers of ACF and AC in the colon of mice. The TBARS value in the feces of the hemin + calcium group was significantly lower than that in the feces of the hemin group. These results showed that hemin enhances the formation of pre-neoplastic lesions in the colon of mice and that calcium decreases the risk of colon carcinogenesis.
        4,000원
        72.
        2017.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Colorectal cancer (CRC) is the third most prevalent cancer in the world, and heme iron is known to promote the CRC in an animal model. This study was conducted to investigate the effects of ascorbic acid in the presence of hemin on the formation of pre-neoplastic lesions induced by azoxymethane (AOM)/disodium sulfate (DSS) in mice. After acclimation for 1 week, five-week old mice received three s.c. injections (0-2 weeks of the experiment) of AOM [10 mg/kg body weight (BW)] weekly and were treated with 2% DSS in drinking water for the next week to induce aberrant crypt foci (ACF). All animals were fed the AIN-76A purified rodent diet for experimental period of 6 weeks. Experimental groups were then divided into three groups: carboxymethylcellulose (CMC) alone (control), CMC + Hemin, CMC + Hemin + ascorbic acid (AA). The CMC was used as a solvent for hemin. The daily doses were 534 mg/kg BW hemin and 246 mg/kg BW ascorbic acid administered orally. After the colonic mucosa were stained with methylene blue, aberrant crypt foci (ACF), aberrant crypt (AC) and polyps were counted. Lipid peroxidation in liver was evaluated by the thiobarbituric acid-reactive substances (TBARS) assay. The numbers of ACF, AC and large ACF (≥4 AC/ACF) per colon increased in the hemin group compared to the control group, while they decreased significantly in the hemin + ascorbic acid group compared to the control group or hemin group (p<0.01). The number of polyps/colon in the hemin + AA group was significantly decreased compared to the hemin group (p<0.05). In the liver, the TBARS value of the hemin group was significantly higher than that of the control group (p<0.01). Additionally, the TBARS value of the hemin + AA group decreased slightly compared to that of the hemin group. Taken together, these results suggest that hemin can promote colon carcinogenesis in a mouse model and that ascorbic acid has a protective effect against hemin-promoted colon carcinogenesis.
        4,000원
        73.
        2017.12 KCI 등재후보 구독 인증기관 무료, 개인회원 유료
        Excessive iron can promote the production of free radicals, thereby leading to harmful effects on cancer and aging. Ascorbic acid is not only an antioxidant but also a co-factor of iron absorption. The effect of iron-overload with ascorbic acid on experimental colon carcinogenesis was investigated in male ICR mice. Animals were treated weekly with azoxymethane (AOM, 10 mg/kg b.w.) at 0, 1, and 2 week and then drunk 2% dextran sodium sulfate (DSS)-containing water for the next 1 week. There were four experimental groups: carboxymethylcellulose (CMC) alone (control), CMC + ascorbic acid (AA), CMC + Fe, CMC + Fe + AA. The animals fed on AIN-76A purified rodent diet for six weeks. AA or Fe2O3 at the dose of 450 mg/kg b.w. were daily and orally treated for 6 weeks. The colonic mucosa was stained with methylene blue and then aberrant crypt foci (ACF) and polyps were counted. Thiobarbituric acid-reactive substances (TBARS) in serum and liver were determined. Iron concentration in liver was measured by inductively coupled plasma spectrophotometer. Fe-overload with AA strongly increased liver iron contents compared to control or Fe group (p<0.05). There were no significant differences in the number of ACF or polyps among all groups, although ironoverloaded groups had slightly higher numbers compared with the control or AA group. TBARS values in the liver were increased in the iron-overloaded groups compared to control and AA only group (p<0.05), but serum TBARS values were not changed. These results indicate that the excessive iron treatment did not affect the experimental colon carcinogenesis regardless of presence of AA in mice.
        4,000원
        78.
        2017.10 구독 인증기관·개인회원 무료
        It is necessary to understand of temporal and spatial dynamics by establishing a periodical monitoring system for theproper management in small brown planthopper (SBPH). A dataset is including the number of SBPHs by location, collectionmethod [aerial collection net (AeCN) or light trap (LT)] and period (May~Aug.) for five years (2011~2015), and missingvalues were imputed using multiple imputation methods. Of the 15,848 individuals collected, approximately 47% and 52.9%were collected using the AeCN and LT methods, respectively. A high incidence of migratory SBPHs was observed duringJulian days 144-166 using the AeCN method. Generally, the migratory SBPHs from China composed 39.4% of the totalpopulations of SBPHs. These results would provide valuable information to predict the incidence period of migratory SBPHsand establish a proactive management system against SBPH.
        79.
        2017.10 구독 인증기관·개인회원 무료
        Walnuts are economically important for forestry workers in recent, but there are few available data for insect pestsin walnut orchards. In 2017, walnut fruits and leaves were damaged by Conogethes punctiferalis and Acrocercops transecta,respectively. In late summer, damage rates by C. punctiferalis in Buyeo, Gimcheon, and Hwaseong were 22.1%, 20.5%,and 11.7%, respectively. According to A. transecta, damage rates in seedlings (58.5% in average) were higher than inolder trees (11.2% in average) irrespective of study locations.
        80.
        2017.10 구독 인증기관·개인회원 무료
        This study is investigated the growth characteristics(number of available stipe, pileus diameter, pileus thickness, stipe length, stipe thickness, object weight, comparison yield ability of 1 cycle) and storage characteristics of ‘Sanjo 701’ (S7) cultivars according to relative humidity. The S7 growth characteristics were investigated by quantifying the growth and the characteristics according to the relative humidity, The storage stability was investigated every 5 days and freshness was measured by ‘Minamide Method’. S7 pileus diameter is The higher the relative humidity was confirmed becomes larger and the more increased relative humidity also increase the comparison yield ability of 1 cycle. However, pileus diameter or stipe length This could not see the big difference in the three treatment groups, the plieus thickness was no significant difference in the treatment of 80% and 95%. The fresh weight of S7 decreased significantly at 80% and 95% relative humidity after 10 days of storage, but decreased continuity in 65% humiditiry. The elongation percentage of S7 pileus was observe in 95% relative humidity, values of L, a and b (SCI), showed the highest L value in 65% and the a value in 95%. b values were similar in 65%, 80% and 95% treatments. On the ‘Minamide Method’ measure freshness was changed from the 10th day of storage at relative humidity of 95%, but humidity of 65% and 80% treatments, it changed after 15 days of storage. In this study growth characteristics and yield were increased at higher relative humidity, but storage stability was decreased. Therefore, it is deemed necessary to change the relative humidity to produce high quality mushrooms.
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