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        검색결과 562

        161.
        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.
        162.
        2018.05 구독 인증기관·개인회원 무료
        Roads in Korea are equipped with PMS (Pavement Management System) computation data that runs on highway, national highway and municipal road. PMS is a program that selects and manages the road pavement optimal maintenance alternative as a indicator of the road pavement structural and functional performance. PMS is a system that has been developed for the primary purpose of maintaining the structural performance of road pavement, and so far does not include any indicators associated with the safety of road users. However, the road cave-in, which have recently become an issue on social networking sites, mass-media, and other issues, should pose systematically because it can make a safety risk to road users, and in particular lead to the structural and functional failure of the PMS program in view of the road pavement. Accordingly, this research has developed a practical use case for developing an integrated road cave-in management program based on the results of various studies on the exploration, analysis, assessment and handling of the existing road cave-in in Korea.
        163.
        2018.05 구독 인증기관·개인회원 무료
        In Sri Lanka, the shoulder in asphalt pavements has been constructed using the materials transported from borrow pit in the iRoad Project due to the low quality of in-situ soils. After excavating 150~200mm thick and 500mm wide shoulder area, the borrow pit materials are placed and compacted according to specifications. The excavated in-situ soils are dumped in designated location. It is estimated that this process of shoulder construction is not economical due to high material transportation cost and can also induce the environmental issues by disposal of in-situ soils. It can also cause distresses such as surface rutting and edge drop-off in soft shoulder section due to bearing capacity failure and off-tracking of vehicle. The heavy rainfall in Sri Lanka can induce severe erosion problem when using the soft shoulder. To improve the strength and durability of pavement shoulders in the iRoad Project, the soil stabilization will be a good alternative to solve the above mentioned problems. The use of in-situ soils with addition of soil stabilizer enables to reduce the construction cost of shoulder section and mitigate the environment issues. The objective of this task is to review the application of soil stabilization method for soft shoulder construction in the iRoad Project. Firstly, the quantitative analysis of soil strength improvement due to soil stabilization was done for soil samples collected from iRoad construction sites. Two types of soils were selected from iRoad Project sites and prepared for soil stabilization testing by the Road Development Authority. Secondly, the appropriate stabilizer was selected at given soil type based on test results. Three different stabilizers, ST-1, ST-2, and ST-3, produced in Korea were used for estimating soil strength improvements. Finally, the optimum stabilizer content was determined for improving shoulder performance. The uniaxial compressive strength (UCS) test was conducted to evaluate the strength of stabilized soil samples in accordance with ASTM D 1633. The use of bottom ash as a stabilizer produced from power plant in Sri Lanka was also reviewed in this task.
        164.
        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.
        165.
        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.
        167.
        2018.04 구독 인증기관·개인회원 무료
        Pine wilt disease (PWD) induced by the pinewood nematode (PWN), Bursaphelenchus xylophilus, is a great threat to pine forests in Europe and East Asia. Identification of interrelation between Monochamus spp., the major vectors of PWD and PWN is the key factor for effective control of PWD because PWN is trasmitted to healthy pine trees only by Monochamus vectors. In this study, direct injection system is designed to apply PWN artificially to M. alternatus just before emergence to adults. After injection of PWN (300~500 nematodes in 10 μl of 1X PBS) using adapted glass pipets, the survival rate of M. alternatus and detection rate of live PWN were 80.0% and 68.8% at 168 h respectively. As a result, we demonstrated the artificial injection methods of nematode to Monochamus vectors for further study of coeffect between vectors and specific stage of PWN including 3rd stage dispersal juvenile.
        168.
        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
        169.
        2017.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The aim of the study was to investigate the effects of incentive spirometry and Ujjayi breathing technique on the pulmonary function of smokers. Subjects were individuals who had a smoking habit of at least a year. Subjects were randomly divided into 3 groups: the incentive spirometry group (n=8), Ujjayi breathing technique (n=9), and a group applying both incentive spirometry as well as Ujjayi breathing technique (n=8). Each intervention was performed twice a day, 5 times a week, for a total of 8 weeks whereupon the change in pulmonary function was evaluated. A spirometer was used to measure FVC, FEV1, and FEV1/FVC. The survey used for this study included the Fagerström Test of Nicotine Dependence (FTND) and the Shortness of Breath Questionnaire (SOBQ). Study results for the comparison within groups showed that in the group that performed both the incentive spirometry and Ujjayi breathing technique, FEV1 improved with statistical significance (p<.05). Furthermore, within this comparison the FEV1/FVC improved with statistical significance. Comparison amongst the groups showed no statistically significant differences in all areas. Following, to effectively increase pulmonary function in young adult smokers, both incentive spirometry and Ujjayi breathing technique should be employed together.
        4,000원
        170.
        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
        171.
        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
        172.
        2017.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        The electronic and optical characteristics of molybdenum disulphide (MoS2) film significantly vary with its thickness, and thus a rapid and accurate estimation of the number of MoS2 layers is critical in practical applications as well as in basic researches. Various existing methods are currently available for the thickness measurement, but each has drawbacks. Transmission electron microscopy allows actual counting of the MoS2 layers, but is very complicated and requires destructive processing of the sample to the point where it will no longer be useable after characterization. Atomic force microscopy, particularly when operated in the tapping mode, is likewise time-consuming and suffers from certain anomalies caused by an improperly chosen set point, that is, free amplitude in air for the cantilever. Raman spectroscopy is a quick characterization method for identifying one to a few layers, but the laser irradiation causes structural degradation of the MoS2. Optical microscopy works only when MoS2 is on a silicon substrate covered with SiO2 of 100~300 nm thickness. The last two optical methods are commonly limited in resolution to the micrometer range due to the diffraction limits of light. We report here a method of measuring the distribution of the number of MoS2 layers using a low voltage field emission electron microscope with acceleration voltages no greater than 1 kV. We found a linear relationship between the FESEM contrast and the number of MoS2 layers. This method can be used to characterize MoS2 samples at nanometer-level spatial resolution, which is below the limits of other methods.
        4,000원
        175.
        2017.10 구독 인증기관·개인회원 무료
        176.
        2017.10 구독 인증기관·개인회원 무료
        The population of managed honeybees has been dramatically declining the recent past in worldwide. N. ceranae causessignificant detriment to honey production and results in economic losses critically. In our knowledge, Fumagillin is theonly antibiotic approved for control of nosemosis in honeybees. In this study, to select isolate with anti-Nosema activityagainst N. ceranae. Entomopathogenic fungi cultural filtrates were screened using in vitro polar tube germination assay.These fungi cultural filtrates were used to evaluate the safety of honeybees and their inhibition of nosemosis. As a result,P. marquandii 364 and Pochonia sp. 60 showed inhibitory activity on the growth of N. ceranae in honeybees and didnot significantly affect the survival rate of honeybees. These may be employed as antibiotic agents and a good featureto be used in the development of new biocontrol agents of nosemosis.
        177.
        2017.10 구독 인증기관·개인회원 무료
        The baculovirus expression vector system (BEVS) is an effective and widely used system for the production of recombinantproteins in insect cells or larvae. However, the expression efficiency of recombinant proteins using the polyhedrin promotercould not acquire the protein yields observed for native polyhedrin. In this study, we tried to develop hyper expressionvector by the optimal combination of previously reported various enhancer factors. The selected enhancer factors for optimalexpression consists homologous region5 (hr5), VP39 promoter and burst sequences. Seven recombinant viruses were madeto compare EGFP expression level. Each recombinant viruses showed different expression levels respectively, and themost of expression level was observed with higher than those of the previous vectors. This study suggests a new optionfor hyper expression of useful recombinant protein using the BEVS.
        178.
        2017.10 구독 인증기관·개인회원 무료
        The two-spotted spider mite, Tetranychus urticae, and gray mold disease caused by Botrytis cinerea, are importantpest and plant disease. To control these, many people have been relied on chemical methods for a long time. However,their continuous use has resulted in resistance of pest and disease. To surmount or avoid these problems, we evaluatedantifungal activity of the selected fungi with high virulence to mite to explore the potential for the dual control of notonly T. urticae but also B. cinerea. To maximize the use of spores and cultural filtrates, the virulence to mite was evaluatedusing culture products, and effective culture condition was investigated against blastospore production and antifungal activity.Consequently, the 2 fungal isolate selected in this study were confirmed to have diverse potential and would be usedeffectively for dual control agents against the two-spotted spider mite and plant diseases
        179.
        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.
        180.
        2017.10 구독 인증기관·개인회원 무료
        The symptoms of pine wilt disease caused by the pine wood nematode (PWN, Bursaphelenchus xylophilus), whichis recognized as a major forest pest. The PWN is transmitted by Monochamus saltuarius adults to healthy Korean whitepine (Pinus koraiensis). Because flight capacity of vector insects is important to protect pine forests, we tested flightdistance of M. saltuarius adults using flight mills in relation to biological characters (sex, age, and body weight). In addition,flight distance of M. saltuarius adults was compared between mated and unmated beetles to test effect of sexually matureon flight capacity. Although unmated adult beetles were more rapidly die compared with mated adults, total cumulatedflight distance during entire lifespan was differed according to whether mating or not, i.e., unmated adult beetles moretraversed than mated adults. Proportion of intermittent flights in mated females was significantly lower than others.