• International Journal of Highway Engineering
• /
• v.10 no.4
• /
• pp.281-292
• /
• 2008

In Korea-LTPP(Long Tenn Pavement Performance) project, the full depth asphalt pavement test sections are constructed on the national highway to evaluate the structural capacity of asphalt pavement reinforced with glass fiber. Truck loading test and FWD test were performed to measure the structural capacity of test sections. Test results showed that the reinforcement of glass fiber installed at between surface and intermediate asphalt layer decreased the strain at the bottom of surface layer and moved up the stress neutral axis in asphalt layer. As a result, the tensile stress was developed at the bottom of intermediate asphalt layer of reinforced asphalt pavement, while the compressive stress was developed at the bottom of intermediate asphalt layer of unreinforced asphalt pavement. On the other hand, the tensile strain at the bottom of asphalt base layer didn't show a difference between glass fiber reinforced and unreinforced pavements. From the FWD test, it was shown that the surface deflection of asphalt pavement reinforced with glass fiber decreased 24 percents comparing to that of unreinforced asphalt pavement. This shows that the reinforcement with glass fiber appears to improve the rutting resistance of asphalt pavement.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.37 no.5
• /
• pp.775-786
• /
• 2017

Monitoring sediment flux is crucial especially for maintaining river systems to understand morphological behaviors. Recently, hydroacoustic backscatter (or SNR) as a surrogate to empirically estimate suspended sediment concentration has been increasingly highlighted for more efficient acquisition of sediment dataset, which is difficult throughout direct sediment sampling. However, relevant contemporary researches have focused on wide range solution applicable for large natural rivers where H-ADCPs with relatively low acoustic frequency have been widely utilized to seamlessly measure streamflow discharge. In this regard, this study aimed at investigating hydroacoustical characteristics based on a very recently released H-ADCP (SonTek SL-3000) with high acoustic frequency of 3 MHz in order to capitalize its capacity to be applied for suspended sediment monitoring in laboratory conditions. SL-3000 was tested in a laboratory flume to collect SNR in conjunction with LISST-100X for actual sediment concentration and particle distribution in both sand and silt sediment injection in various amount. Conventional algorithms to correct signal attenuations for water and sediment were carefully tested to validate whether they can be applied for SL-3000. As result of analyzing the SNR-SSC correlation trand, through further study in the future, it is confirmed that SSC can be observed indirectly by using the SNR.

• Food Science of Animal Resources
• /
• v.28 no.1
• /
• pp.39-44
• /
• 2008

This study was conducted to evaluate the effects of nutritional levels on the growth and pork quality of Korean native black pigs (54 pigs from 35-75kg). Three nutritional levels (high, medium and low in ME and lysine) were tested. As nutritional levels increased, the average daily gain improved, and the days to market weight were reduced. There were no significant differences in dressing percentage, backfat thickness, loin eye area and % lean among the dietary treatments. However, barrows showed thicker (p<0.05) for backfat than gilt. The analysis of Korean native black pig carcass traits indicated that the fatty acid composition of loin-eye muscle, intra-muscular fat content, sarcomere length, and muscle ratio between red- and white-muscles did not show any statistically significant variation. However, regarding intra-muscular fat, H carcasses (high energy diet) contained higher levels of saturated fatty acids with lower levels of unsaturated fatty acids compared to the carcasses from the other two energy groups (M and L). In addition, the levels of n-3 tended to be lower as the energy/lysine level in the diet increased, while the ratio of n-6/n-3 tended to decrease as the energy/lysine level increased, even though the differences were not statistically significant. Even with no statistically significant differences, it was interesting to observe that the sarcomere length tended to increase as the energy level of the diet increased, and with muscle ratio analysis, the red muscle ratio from the L-group, and the white muscle ratio from the M-group were higher than the other energy groups.

• Journal of the Korean Vacuum Society
• /
• v.16 no.4
• /
• pp.244-249
• /
• 2007

Deadweight piston gauge have been widely used as a fundamental instrument of precise pressure measurement because they are robust, accurate, potable, convenient to use and are able to realize the definition of pressure as farce per unit area. Basically, a deadweight piston gauge consists of a piston mounted vertically in a close-fitting cylinder filled with a gas and weights of known mass values. The pressure to be measured is applied to the base of the piston generating an upward vertical force, and is balanced by the downward gravitational force generated by weights. These instruments can be used to measure pressures above 10 kPa because of tare weights including piston. However, using a variable bell-jar pressure method and a newly developed weight loading device we can extend the application range of deadweight piston gauge to lower pressures. In this paper, we present the practical calibration results for two CDGs(Capacitance diaphragm gauge, MKS) with full-scale ranges of 1.33 kPa and 13.3 kPa, respectively.

• Korean Journal of Materials Research
• /
• v.4 no.3
• /
• pp.287-294
• /
• 1994

PAN-based carbon fiber roving and fabric were heat treated at the temperature of $2170^{\circ}C$. Using non-heat treated and heat treated fabric, greenbodies of CFRP and GFRP were manufactured in the Autoclave. After the analysis of heat treated and non-heat treated carbon fiber roving and two types of greenbodies, the variations of physical and mechanical properties of carbon fibers and greenbodies with heat treatment were studied. Observing the cross-section of carbon fiber with SEM, we knew the diameter of carbon fiber was decreased from 6.8gm to 6.4p1. The results of TGA showed that the oxidation resistence was enhanced after heat treatment. The tensile strength of carbon fiber was decreased from (3.11$\pm 0.32)\times 10^3$ MPa to (1.87$\pm 0.26)\times 10^3$MPa, but tensile modulus was increased from (1.94$\pm 0.06)\times 10^5$ MPa to (2.02$\pm 0.11)\times 10^5$MPa after heat treatment. The interlaminar shear strengths of CFRP and GFRP were 148.8$\pm$1.6Mpa and 82.2$\pm$1.1Mpa, respectively. Torch test showed that CFRP was abraded smoothly but GFRP was delaminated.

• Explosives and Blasting
• /
• v.38 no.1
• /
• pp.30-37
• /
• 2020

In this study the split ring (SR) test was investigated for its applicability to the measurement of the tensile strength of rock specimen of NX size. The concept of the SR test is the same as the half ring (HR) test (Choi et al., 2019) except that the expected fracture plane is perpendicular to the loading direction. Because of this perpendicularity, however, it was believed that the SR test could be more accurate than the HR test. Like the HR specimen, the SR specimen is a curved prismatic bar with a uniform section. Appealing to a basic bending theory in strength of materials, the tensile strength for the special bar can be calculated analytically. Numerical simulations using LS-DYNA revealed, as expected, that the strength errors were 1% and 5% for the tensional and compressional SR tests, respectively, which were much lower than that (12%) of the HR test. To identify the performance of the two SR tests, laboratory experiments were conducted. The HR and Brazilian tests were also performed for comparison. The experiments showed that the ratios of the tensional and compressional SR to Brazilian strengths were 1.2~1.4 and 1.1~1.2, respectively, which are too small compared to empirical values in ordinary bend tests. Consequently, it is concluded that the SR test is not appropriate for use in tensile strength test of rock specimen of NX size. But the ratio of the HR to Brazilian strengths was within 1.7~2.0 for both the previous and present studies, showing a good consistency in their test results.

• Applied Microscopy
• /
• v.32 no.3
• /
• pp.285-290
• /
• 2002

The therapeutic effect of safflower seed powder on experimental osteoporosis in the rat induced by ovariectomy was evaluated. Thirty Sprague-Dawley rats were ovariectomized at the age of 12 weeks. Seven weeks postovariectomy, rats were divided into two groups: control and safflower seed powder treated group. Five animals from each group were sacrificed at the following time points: 1, 3, and 5 weeks. Scanning electron microscopic observation and morphometric analysis of the tibiae epiphysis showed that the administration of safflower seed powder significantly prevented reduction of cortical bone width and bone volume compared with the control group. In conclusion, safflower seed powder contains something that prevent bone loss due to estrogen deficiency, and was effective in preventing the osteoporotic decrease of bone mass.

• Applied Chemistry for Engineering
• /
• v.17 no.5
• /
• pp.471-475
• /
• 2006

$VO_x$ thin films with the thickness of 450 nm were prepared on a $Pt/Ti/SiO_{2}/Si$ substrate at room temperature by a reactive radio frequency (rf) magnetron sputtering method. The deposition rates of $VO_x$ thin films were investigated as a function of $O_{2}$ concentration and rf power. As the $O_{2}$ concentration in a $O_{2}/Ar$ mixture increased, the deposition rate decreased. However, the deposition rate increased with increasing rf power. The deposited $VO_x$ thin films were annealed at $450^{\circ}C$ for 2, 4, and 6 h in $O_{2}$ and $N_{2}$ ambient. After annealing, the phase changes of $VO_x$ thin films were investigated using X-ray diffraction analysis. The plane and cross-sectional views of $VO_x$ thin films before and after annealing were observed by field emission scanning electron microscopy. The metal-insulator transition (MIT) properties of $VO_x$ thin films were measured using current-voltage measurement. The excellent MIT properties were observed in $VO_x$ thin films annealed in $O_{2}$ ambient.

• Applied Chemistry for Engineering
• /
• v.17 no.1
• /
• pp.28-32
• /
• 2006

This study investigated the variation of flow rates in microchannels that consisted of polydimethyl siloxane (PDMS) and glass using various external voltages. Three different microchannel widths and two different depths. PDMS and negative photoresist (SU-8) were used to make the microchannels by the soft lithographic method. For each depth of microchannel ($50{\mu}m$ and $100{\mu}m$), three different widths ($100{\mu}m$, $200{\mu}m$ and $300{\mu}m$) were made. In each case, several different external voltages were applied (0.3 kV, 0.35 kV, 0.4 kV and 0.45 kV) to examine the flow rates. Our results indicated that flow rate increased with an increase of the external voltage at the same microchannel width. This was because the electrical field was increased as the external voltage increased. For the same external voltage, the flow rate increased as the microchannel's width increased. These results showed that the resistance in the microchannel decreased as the microchannel's width increased. Also, to investigate the effect of microchannel's depth and width, the cross-sectional area of the microchannel was increased to the double in area. As a result, the effect of the microchannel's depth was higher at a low external voltage, and the effect of the microchannel's width was higher at a high external voltage.

• Food Science of Animal Resources
• /
• v.26 no.2
• /
• pp.212-217
• /
• 2006

Effects of feeding high quality roughage (timothy hay) in growing period on growth performance and carcass characteristics during 24 month (5 month from 28 month to) in twenty of Hanwoo steers were investigated. The hanwoo steers were randomly allotted to 2 treatments (10 heads/treatment) ; rice straw group (control) and timothy hay group (treatment). The final body weights of rice straw group and timothy hay group on 28 month were 667.70 kg and 681.75kg, respectively. The daily gain of total period was slightly higher in timothy hay group (0.83kg ) than in rice straw group (0.81 kg). The daily roughage intake in the growing period was tended to be higher in timothy hay group (4.27kg ) than rice straw group (3.80 kg). The carcass grades (yield grade and quality grade) and Longissimus dorsi area were significantly higher in timothy hay group ($85.62 cm^2$, 2.02 and 2.20 point) than in rice straw group ($81.29 cm^2$, 2.00 and 1.60 point respectively) (p<0.05), and were affected by the feeding with high quality roughage in the growing period.