• Journal of the Korean Society of Safety
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• v.26 no.1
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• pp.58-64
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• 2011

This study evaluated the effects of the handle width(shoulder width, 1.25${\times}$shoulder width, 1.5${\times}$shoulder width), height(3 levels : knee, medium, knuckle) and horizontal angle($0^{\circ}$, $10^{\circ}$) on the pushing, lifting, and twisting strengths which were required for carrying single or two wheel barrows. Twelve healthy college students(male) participated in the experiment. In each experimental condition($3{\times}3{\times}2$=18), the subjects exerted three forces(pushing, lifting, and twisting clockwise). The experimental conditions and three forces were tested in random order, and a minimum 2 minutes of rest was provided between exertions. Results showed that the mean and maximum pushing forces showed greater values when the horizontal angle was $0^{\circ}$ than $10^{\circ}$(p=0.016). However, the three independent variables had no statistically significant effects on the lifting forces(p>0.1). The mean and maximum twisting forces increased as the handle width became larger(p<0.05). Also, there was a marginal effect of the horizontal angle(p=0.065) on the twisting force. From the results of this study, the horizontal angle of $0^{\circ}$ and the wider handle width were suggested for the design of single-wheel barrows.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.379-384
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• 2006

Since the monolithic ceramic substrate was introduced for automotive catalytic converters, the durability of the substrate has been a continuing requirement to reduce the emission gas of vehicle. The substrate can occupy a volume as small as 82 $cm^3$ and as large as 8200 $cm^3$ to provide the required substrate for catalytic activity. The long-term durability varies with the size of the substrate from manufacture's point of view. Therefore This study presents that the response surface model using central composite design can explain size effect on the modulus of rupture in a cordierite ceramic monolithic substrate.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.10
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• pp.2473-2481
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• 2014

The majority of next generation information systems will be working on portable mobile devices such as smartphones. REST Open API web services have quickly become popular among mobile application development. The use of REST web services are not only growing in popularity but totally changing the way of mobile applications development. This is because REST web services could be used in application development as a form of building blocks, which is completely independent, compatible, to any platforms. With this strength, REST web services encourage third party application to build add-on functionality. This research proposes the use of REST web service to replace the use of socket APIs into major internet communication APIs. To this end, this paper also provide performance evaluation of the REST web services compared to the conventional socket APIs, focusing on scalability by analytical and experimental evaluations. Finally, we summarize the possibility whether REST Open API web services have enough performance as future major internet communication primitive APIs.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.1
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• pp.247-256
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• 2013

This dissertation is based on the evaluation of service by the home help service users and suggested managing strategy through analyzing importance and performance. The subject is a person receiving the service from the three home long term institutions in S city, Gangwon province, and SPSS 12.0 is used to analyze data to conduct analysis of basic statistic, confidence level, and factors. The result came out that home help service's importance showed 4.55 out of 5, performance 4.26 out of 5. The most improvement needed factor was 'providing quick service' and 'offer service at ease'. Also it seemed that the four categories in tangibles and four categories in reliability and assurance, one category in responsiveness and empathy needs to be improved. The three in reliability and assurance and five properties in responsiveness and empathy need to remain its strength. In conclusion, in order to better the home help service first the progress result in focus improvement area needs to be achieved.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.3
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• pp.1481-1488
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• 2013

The purpose of this experimental research is to suggest a base data to utilize the fine sand of Nakdong-River actively as an alternative aggregate for concrete. For this purpose, after the typical fine sand samples were collected at the mid stream and down stream of main stream of Nakdong-River, the physical properties of them and the mix characteristics of concrete using those were estimated. As a result, it was observed from the test result that mix characteristics between concrete using fine sand and concrete using well-graded reference sand made little differences since unit water content and unit cement content of concrete using fine sand increased only a little than those of concrete using reference sand for specified compressive strength.

• Transactions on Electrical and Electronic Materials
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• v.18 no.4
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• pp.207-210
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• 2017

The suspension arrangement of insulators provides flexibility and assists in power transmission in transmission lines. The performance of the insulator string is strongly influenced by the environmental conditions to which it is exposed, its shape and the inherent material properties of suspension-type insulators. The suspension-type insulators are mostly made from glass, porcelain and ceramic material due to their high resistivity. Irregularity in charge distribution throughout the porcelain insulator may lead to accelerated aging and electrical breakdown. A very high and steep lightning impulse voltage may also cause breakdown of suspension-type insulators. We investigated various material characteristics such as alumina addition, surface morphology, x-ray diffraction pattern and relative density of suspension porcelain insulators manufactured in 1989 (36,000 lbs.), 1995 (36,000 lbs.) and 2001 (36,000 lbs.) by the KRI Company for use in 154 kV high power transmission lines. We compared the material characteristics of these porcelain insulators with that of the top-of-the-line porcelain insulators (36,000 lbs.) manufactured by the NGK Company in 2000. These suspension-type porcelain insulators were exposed to arc and flashover tests to examine their electrical and mechanical strength. It was noted that alumina addition (17 wt.%) for K-2001 was one of the major contributors to the enhancement of the performance of the porcelain insulators and to their ability to withstand very high current generation during the arc test. The porcelain insulators manufactured during 2001 also showed the highest relative density of 95.8% as compared to the other insulators manufactured in 1989 and 1995 respectively 94.2% and 91.5%. We also discuss reports of various failure modes of suspension-type porcelain insulators.

• Journal of the Korea Institute of Building Construction
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• v.11 no.5
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• pp.419-425
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• 2011

Topping concrete that is not reinforced with rebar to prevent poor tensile performance is vulnerable to cracking. In this study, jute, which is known to be an excellent natural fiber material for strengthening concrete performance, was compared with other cellulose fibers in terms of its capacity to reduce the cracking of concrete. As a result, it was found that compared with concrete using other fibers, concrete using jute fiber showed more than a 50 % reduction of plastic shrinkage crack resistance with the contents of 0.9 kg/$m^3$ and 1.2 kg/$m^3$ for. For impact strength tests, the final destruction of WF and PULP fibers took up to 5 times the number of falls, while jute has 10-18 circuitry, showing excellent ductility properties.

• Tunnel and Underground Space
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• v.30 no.1
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• pp.87-97
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• 2020

Fracture toughness of rock is a constant that can indicate the initiation and propagation of cracks due to blasting, excavation, etc. Scaled model tests have been applied to the behavior of tunnels and the stability of limestone mines. Through the scaled model, damaged zone evaluation due to blasting is also carried out, and the scale factor is not applied to the failure-related factors. In this study, DCT (diametral compression test) and finite element method ATENA2D numerical analysis results were compared to determine whether the scale factor could be applied to the fracture toughness of rock. The theoretical values of the scale factor applied to the fracture toughness of the rock and the DCT test results and the numerical results are 0.21~0.46, 0.40, and 0.99MPa ${\sqrt{m}}$ respectively, so these three values should be considered when determining scale factor. It is necessary to derive a suitable scale factor in consideration of the length, time, and mass to which the scale factor is applied, as well as the values of the scale factor of major design factors such as uniaxial compressive strength and density.

• International Journal of Highway Engineering
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• v.18 no.1
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• pp.57-62
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• 2016

PURPOSES : Reflection cracking has been one of the major causes of distress when asphalt pavement is laid on top of concrete pavement. This study evaluated the reflection cracking resistance of asphalt mixtures reinforced with asphalt embedded glass fiber and carbon fiber using a Texas Transportation Institute (TTI) overlay tester. METHODS : Different asphalt mixtures such as polymer-modified mastic asphalt (PSMA) and a dense graded asphalt mixture were reinforced with asphalt-embedded carbon fiber and glass fiber. For comparison purposes, two PSMA asphalt mixtures and one dense graded asphalt mixture were evaluated without fiber reinforcement. Two different overlay test modes, the repeated overlay test (R-OT) and monotonic overlay test (M-OT), were used to evaluate the reflection cracking resistance of asphalt mixtures at $0^{\circ}C$. In the R-OT test, the number of repeated load when the specimen failed was obtained. In the M-OT test, the tensile strength at the peak load and tensile strain were obtained. RESULTS : As expected, the fiber-reinforced asphalt mixture showed a higher reflection cracking resistance than the conventional nonreinforced asphalt mixtures based on the R-OT test and M-OT test. The dense graded asphalt mixture showed the least reflection cracking resistance and less resistance than the PSMA. CONCLUSIONS : The TTI overlay tester could be used to differentiate the reflection cracking resistance values of asphalt mixtures. Based on the R-OT and M-OT results, the carbon-fiber-reinforced asphalt mixture showed the highest reflection cracking resistance among the nonreinforced asphalt mixtures and glass-fiber-reinforced asphalt mixture.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.46 no.5
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• pp.79-87
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• 2014

The enrichment with nutrients in rivers and lakes becomes serious problems in Korea. As the environmental friendly solution, the phytoremediation are getting more attention and the water hyacinth could be a strong candidate plant for this. Water hyacinth is a free floating freshwater plant proven to be a effective plant used for a purification of a polluted lakes, sewage wastewater, and livestock wastewater. The biggest obstacles for application of water hyacinth in Korea could be the disposal of the water hyacinth before winter, because there is no feasible use for the water hyacinth until now. In this study, the characteristics of water hyacinth were deeply investigated for providing background data to develop appropriate application of the water hyacinth. The water hyacinth was fractioned three parts, leaf, air blader, root of which morphological properties were evaluated with microscope and field emission scanning electron microscope (FE-SEM). The water contents of each parts of the water hyacinth were 87% for leaf, 96.5% for air bladder, 94.6% for root. The chemical compositions of each parts were also measured and showed around 29% of hot water extract in leaf and air bladder, 42% holocellulose for leaf, 47% holocellulose for air bladder. The application of water hyacinth biomass without root parts to papermaking provided bulkier structure, but the tensile strength was decreased.