• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.3
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• pp.210-217
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• 2023

Various performances of ultra-high performance concrete (UHPC) applied with microplastics and expanded polystyrene (EPS) beads were evaluated. CompressIve and flexural strength, performance after ignition, flow-down in fresh state, and effective bond strength were evaluated. Designed weight of the cement panel with these mixtures was calculated based on the flexural strength. As a result of the experiments, it was confirmed that the EPS could reduce the density of UHPC with largest range. By maximum addition of EPS beeds, the density of UHPC decreased to 1300 kg/m³, and the compressive and flexural strengths for this mixtures were in ranges of 20-30 MPa and 15-20 MPa, respectively. On the other hand, lightest cement panel could be designed with UHPC having a density ranges about 2.0 g/cm³.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.117-124
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• 2002

The lightness of components required in automobile and machinery industry is requiring high strength of components. In particular, manufacturing process and new materials development for solving the fatigue fracture problem attendant upon high strength of suspension of automobile are actively advanced. In this paper, the effect of compressive residual stress of spring steel(JISG SUP-9) by shot-peening on fatigue crack growth characteristics in high temperatures($100^{\circ}C,\;150^{\circ}C,\;180^{\circ}C$) was investigated with considering fracture mechanics. So, we can obtain followings. (1) Compressive residual stress is decreased in high temperature, that is, with increasing temperature. (2) The effect of compressive residual stress on fatigue crack growth behavior in high temperature is increased below ${\Delta}K=17{\sim}19MPa\sqrt{m}$. The fatigue crack growth rate is increased with increasing temperature. The fatigue life is decreased with increasing temperature. (3) The dependence of temperature and compressive residual stress on the parameters C and m in Paris' law formed the formulas such as equations (3),(4),(5),(6),(7),(8),(9),(10). (4) It was investigated by SEM that the constraint of compress residual stress for plastic zone of fatigue crack tip was decreased in high temperature as compared with room temperature.

• Journal of the Korean Society of Safety
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• v.21 no.4 s.76
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• pp.1-6
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• 2006

The lightness of components that was required in automobile and machinery industry requires high strength of components. In particular, manufacturing process and new materials development for solving the fatigue facture problem attendant upon high strength of suspension of automobile are actively advanced. In this paper, the effect of compressive residual stress of spring steel(JISG SUP-9)by shot-peening on fatigue crack growth characteristics in high temperature($100^{\circ}C,\;150^{\circ}C,\;180^{\circ}C$)was investigated with considering fracture mechanics. So, we can obtaint the followings. (1) Compressive residual stress is decreased with increasing the test temperature. (2) The effect of compressive residual stress on fatigue crack growth behavior in high temperature is increased below ${\Delta}K=17{\sim}19MPa{\sqrt{m}}$. (3) It was investigated by SEM that the constraint of compress residual stress for plastic zone of fatigue crack tip was decreased in high temperature as compared with room temperature.

• Journal of Power System Engineering
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• v.5 no.4
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• pp.67-73
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• 2001

Recently the steel parts used at automobiles are required to be used under high stress more than ever before in need of the weight down. To achieve this requirement of a high strength steel, it must be necessary to decrease inclusion content and surface defect as like decarburization, surface roughness etc.. In this study, the surface conditions are measured to know the influence on fatigue properties by two cases of two-stage shot peening iud single-stage shot peening for two kinds of spring steel(SUP7, SAE9254). This study shows the outstanding improvement of fatigue properties at the case of two-stage shot peening in the rotary bending fatigue test and this is assumed to be from decreasing the surface roughness unchanging the surface hardness increasing the compressive residual stress. Results also show fatigue failures originated at inclusion near surface, and this inclusion type is turned out to be a alumina of high hardness.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.338-343
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• 2001

Recently the steel parts used at automobiles are required to be used under high stress more than ever before in need of the weight down. To achieve this requirement of a high strength steel, it must be necessary to decrease inclusion content and surface defect as like decarburization, surface roughness etc., In this study, the surface conditions are measured to know the influence on fatigue properties by two cases of shot peening of two-stage shot peening and single-stage shot peening. And for this study, two kinds of spring steel(SAE 9254, DIN 50CrV4) are made. This study shows the outstanding improvement of fatigue properties at the case of two-stage shot peening in the rotary bending fatigue test and this is assumed to be from (1) on low stress condition, the single stage shot peening is not affected by nonmetallic inclusion under metal. (2) it is possible that the two-stage shot peening increases the fatigue life and the high stress, but, that is affected by nonmetallic inclusion under metal. (3) so far, beeasily 50CrV4 have made high stress. But, results also show fatigue failures originated at inclusion near surface, and this inclusion type is turned out to be a alumina of high hardness.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.1053-1062
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• 1993

The effect of loading speed on soil failure was studied by using a high speed triaxial compression test. Tests were conducted at 0.35-6.2m/s loading speed to compress soil specimens of sandy loam at different moisture contents. The axial stress at fracture increased with increase in loading speed up to certain critical speeds, however they decreased as the speed up to certain critical speeds, however they decreased as the speed increased further. Experiments were also conducted in the field of sandy loam soil with the vibrating tillage tool. Tests were done at 0.33-0.85m/s tractor speed oscillating frequency 13.7hz and oscillating amplitude 59mm. The maximum oscillating velocity of tillage tool was 2.5m/s. It was observed that for the oscillating operation, initially draft slightly increased with increase in forward speed and then it decreased .For the non-oscillating operation, draft increased continuously with increase in forward speed. Approach of studying soil failure in the laboratory test can be related to the field experiments.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.69-74
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• 2003

This study evaluated durability through measurement of substituted test piece's pH degree and experiments of neutralization. Comparing and evaluating cared test piece's pH degrees which we got before the neutralization and after the neutralization. After evaluating neutralization depth through neutralization, evaluating neutralization properties by Fly Ash replacement ratio. pH degree was decreased by cement replacement ratio of Fly Ash. And in the case of substitution of the same amount of Fly Ash, fine aggregate replacement ratio was increased. When the test piece, which had been cared in high temperature, was promoted to neutralization, Among the test piece which was replaced with Fly Ash 40%, the test piece which has high rate of fine aggregate proved opposition of neutralization Through the test, Ⅰ summarized that the test piece cared in high temperature was mostly effected by compress strength, the test piece cared in low temperature was mostly effected by pH degree.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.149-152
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• 2005

To make artificial light-weight aggregate with EAF-dust and estimate ability to apply to concrete, characteristics of the aggregate were considered in density, weight of unit volume, fineness modulus and so on. And then it was executed to experiments of the concrete mixed with the light-weight aggregate. As it was results that artificial light-weight aggregate with EAF-dust was heavier and more watertight than with only clay, concrete weight of unit volume was heavier than with expended clay aggregate. But it was regarded that concrete with EAF-dust artificial aggregate was able to field application as light-weight concrete because concrete of the weight of unit volume was lighter and compress strength and workability were similar to normal concrete.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.483-490
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• 2005

At present around 50 companies have their own crushing plants, which manufacture rock into crushed sand, over around 350 different quarry throughout the nation. However, in most plants the stone dust sludge is left as it is in their plants so that they have difficulty to utilize. Furthermore, environmental pollution may be even caused due to dust generated when it is dried. Recycling is starting capturing the attention of the people working over the quarry due to the reasons described above. This research has studied in the quarters the usability as landfill liner of the stone dust sludge, which is industrial waste. We investigated what technological properties it would have after mixing the stone dust sludge with SM(sandy soil) first and then with blast furnace slag or reject ash, which is waste, and cement as the stabilizer. As the result of three tests; compacting test, strength test, and permeability test; to satisfy the regulatory guideline of the government that is the compress strength over 5 $kgf/cm^2$, the flexibility over 1 $kgf/cm^2$, and the permeability under $1.0{\times}10^{-7}cm/sec$ From this research, we could confirm that stone dust sludge would be used as waste landfill liner if it were mixed with other waste by the proper mixing ratio.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.6
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• pp.1327-1332
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• 2011

In the mobile meteorological information services, an existing sensor system should be expanded to serve precise information. This is because of large cost problem to add the existing sensors. This thesis proposes a system architecture to construct scalable mobile meteorological information services and suggests mobile phone, sensor network, and public traffic vehicle as expended sensors. The proposed scalable sensors are compared each other and analysed the results to evaluated their strength and weakness. In this system, based on the characteristics of the sense data collected at server, a data processing methods are proposed to support efficient query processing. The proposing data processing methods have several benefits. They compress some data volume sensed by various sources on some area at some time to a logical unit. Still it could preserve same services quality.