• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.181-191
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• 2016

This study examined the effects of exercise intensity and type on insulin resistance, cardiovascular disease risk factors, and exercise time. Obese thirty-two subjects (>body fat 30%) were randomly assigned one of four experimental groups: VO2 max 50% aerobic exercise group (MAE, n=8), VO2 max 80% aerobic exercise group (VAE, n=8), VO2 max 50% + resistance exercise group (MARE, n=8), and VO2 max 80% + resistance exercise group (VARE, n=8). Body fat significantly decreased in all groups and insulin resistance decreased significantly in MARE and VARE (p<.05 & p<.01) after exercise. CRP and IL-6 were slightly reduced after exercise, although these did not reach statistical significance, whereas the IL-6 level of the VAE group decreased significantly (p<.05). TNF-${\alpha}$ significantly decreased in the MAE group (p<.05) but significantly increased in the VARE group after exercise (p<.05). For exercise time, higher intensity exercise groups were significantly less than the lower intensity exercise groups (p<.001). These results suggest that body fat is affected by all kinds of exercise intensity and type while CRP is not. Insulin resistance and TNF-${\alpha}$ were affected by exercise type, whereas IL-6, TNF-${\alpha}$, and exercise time were affected by exercise intensity.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.4
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• pp.53-60
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• 2017

Fly ash(FA) which is a byproduct in the coal combustion in thermal power plant contributes to pore structure densification due to pozzolanic reaction, and this leads to long-term strength development and excellent resistance to chloride penetration. In the work, compressive strength and chloride resistance in OPC(Ordinary Portland Cement) and FA-based concrete are evaluated, and the relationships are investigated considering ages. For the work, 3 different W/B (Water to Binder) ratios of 37%, 42%, and 47% are prepared, and 3 substitution ratio of fly ash(0%, 30%, and 50%) are considered as well. At the age of 28 days and 180 days, test results of compressive strength, diffusion coefficients based on Tang's method, and passed charges referred to ASTM C 1202 and KS F 2711 are obtained. With increasing replacement ratio of FA and decreasing W/B, the resistances to chlorides(diffusion coefficient and passed charge) are improved, and the results at the age of 180 days decrease to only 15% level at the age of 28 days due to pozzolanic reaction in FA 50 mixture, which shows that resistance to chloride is much dependent on age effect than strength development. After 180 days, more clear linear relationships are observed between strength and resistance to chloride.

• Korean Journal of Materials Research
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• v.8 no.1
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• pp.64-70
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• 1998

자동차의 엔진밸브 스프링으로 사용되는 Si-Cr 스프링강의 영구 변형 저항성과 내피로성이 우수한 고강도강을 개발하기 위하여 탄소함량을 증대시키고 Mo, V, W와 같은 합금원소를 기존의 SAE 9254 스프링강에 첨가하여 개발강을 제조했다. SEM및 EDX가 부착된 TEM을 이용하여 미세조직을 관찰했고, 크립시험 및 피로시험기를 이용하여 스프림의 영구 변형 저항성 및 스프링의 내피로성을 조사했다. 실험결과, 개발강은 피로 특성치는 기존강과 동등 수준이면서 인장강도가 기존강의 것보다 10%가 더높은 2100MPa 급의 고강도를 나타내었으며 또한 영구 변형 저항성도 현저하게 개선되었는데 이는 W, Mo의 첨가로 인해 템퍼링시에 세멘타이트의 성장이 억제되어서 세멘타이트의 석출물이 미세하게 되었기 때문이다.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.287-288
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• 2016

기존 자가발전 운동기구의 경우, 가변저항을 사용하여 운동강도를 조절하기 때문에 Generator에서 생성된 에너지가 모두 소모되는 문제점이 있다. 또한 계통연계형 자가발전 운동기구의 경우에는 에너지 회수는 가능하지만 운동 강도 조절이 불가능한 단점이 존재한다. 따라서 본 논문에서는 계통연계를 통해 에너지 회수가 가능하고, 운동 강도 조절이 가능한 자가발전 운동기구용 DC/DC 컨버터를 제안한다. 제안회로는 가변저항을 사용하지 않고 입력임피던스를 통해 운동 강도를 조절하기 때문에 높은 에너지를 생성할 수 있고 계통연계를 통해 에너지 회수도 가능한 장점이 있다. 본 논문에서는 제안된 회로의 이론적 특성을 분석하고 모의실험을 통해 확인하였으며, 계통연계형 자가발전 운동기구에 적용하여 실험을 통해 우수성을 검증하였다.

• Journal of Global Scholars of Marketing Science
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• v.4
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• pp.25-51
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• 1999

본 연구의 목적은 우리나라가 경제불황으로 인하여 국내 산업전반에 걸쳐 구조조정을 실시하게 되었음에도 불구하고, 구조조정을 효율적으로 수행하기 위한 구조조정 관리모형이나 구조조정 영향변수 등 선행연구가 전무한 상태였다. 그래서 우리나라 현실에 맞는 구조조정 관리모형을 도출하는데 있다. 이러한 목적올 달성하기 위해 구조조정관련 영향변수와 그리고 이들 변수와 마케팅 성과간의 관계를 검증하고자 한다. 이론적 배경으로는 구조조정 전략 영향변수로 구조조정전 성과, 사전구조조정 경험, 외부압력, 그리고 변화에 대한 저항 정도를 탐색하고, 그리고 구조조정 전략실행강도에 영향을 주는 인적자원의존도, 관리적 강도, 그리고 마케팅 성과에 대해 탐색했다. 실증분석을 통해 얻은 구조조정 관리모형은 인력감소, 사전구조조정 경험, 변화에 대한 저항정도가 구조조정전략 실행강도에 영향을 미치며, 이는 다시 관리적 강도에 영향을 미치는 것으로 나타났다. 그리고 관리적 강도는 마케팅 성과에 영향을 주는 요인으로 발견되었다.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.3
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• pp.261-267
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• 2015

To develop high-strength high-volume ground granulated blast-furnace slag (GGBFS) concrete, this study investigated the characteristics of strength development and durability of concrete with the water-to-binder ratio of 23% and the GGBFS replacement ratio of up to 65%. The results show that the compressive strength of GGBFS blended concrete is lower than that of ordinary Portland cement (OPC) concrete up to 3-day age, but the becomes higher after 7-day age. Together with strength increase, the pore structure becomes tighter, and thus the resistance to chloride ion penetration increases. Therefore, the GGBFS blended concrete has high resistance to freezing and thawing without additional air-entraining, and high resistance to carbonation despite low amount of calcium hydroxide ($Ca(OH)_2$). On the other hand, if silica fume (SF) is blended with GGBFS, the strength becomes lower than that of the concrete blended with GGBFS only, and the resistance to chloride ion penetration deceases. Therefore, it needs further studies on the reaction of SF in high-strength high-volume GGBFS concrete.

• The Journal of Engineering Geology
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• v.12 no.1
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• pp.63-73
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• 2002

To evaluate reinforced region of dike by cement grouting, we investigated both the electrical resistivity and the strength of cement grout having various water-cement ratio with curing time. These investigation results showed that the electric conductivity of grout is much higher than that of water and that the apparent resistivity of grouted region is much lower than that of unoccupied region by grout. It was founded that electrical resistivity survey might be quite effective to detect grout region in dike. As the results of electrical resistivity sounding at three dikes, apparent resistivities after grouting showed several tens to several hundreds of ohm-m which were lower than those of pre-grouting and showed stabilizing trend with curing time. From these results, we could estimate that this behavior of apparent resistivity is due to increasing strength with curing time.

• International Journal of Highway Engineering
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• v.11 no.3
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• pp.51-60
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• 2009

This study investigates the fresh state characteristics, strength, chloride ion penetration resistance and freeze-thaw resistance of the suggested high strength-high durability cement concrete pavement. The required workability and air content could be achieved by using an appropriate admixtures. However its dosage should be carefully determined through field trial batches. Compressive strength increased with the increased cement content and, in particular, high cement volume concrete continuously developed strength up to 90 days. No clear relationship, however, existed between flexural strength and cement content. Chloride penetration resistance seemed as a function of curing age rather than the cement content. Freeze-thaw resistance test was conducted using two different coolants, tap water and 4% NaCl solution. When the tap water was used no severe damage was observed up to 300 cycles regardless the air content. Under 4% NaCl solution, specimens of 326kg/$m^3$ cement content showed severe damage with surface scaling. Based on the experimental investigations herein, it is highly recommended that the cement content be greater than 400kg/$m^3$ for strength-high durability cement concrete pavement structures.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.1
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• pp.182-189
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• 2010

The strengthening performance of FRPs(Fiber Reinforced Polymers) is directly affected by the environmental conditions such as freezing-thawing and moisture because FRPs are usually bonded on the concrete surface. It is, therefore, strongly required to evaluate a durability of bond between FRPs and concrete as well as FRP materials itself. The freezing-thawing resistance of FRPs is evaluated in this study with the variables of freezing-thawing conditions, types of FRP and freezing-thawing cycles. From the test results, it is found that tensile strength and pull-off strength of CFRP are not affected by the freezing-thawing. On the other hands, those of GFRP show a little degradation because of continuous water immersion during thawing process. But, cautions are needed on the bond durability between FRPs and concrete in case of continuous water supplying from adjacent to the concrete.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.3
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• pp.79-87
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• 2011

Concrete incorporating high volume blast-furnace slag placed in cold weather regions might be in danger of initial frost damage because dependently on the mix proportions, the setting and the hardening would be remarkably delayed. Therefore, this study investigated to effect of the degree of frost on the strength development and the resistance to freezing and thawing of the concrete incorporating blast-furnace slag when being subjected to freeze at early age. As the experimental results, the concrete incorporating blast-furnace slag attacked by initial frost damage showed the remarkable reduction of both the compressive strength development and the resistance to freezing and thawing. Especially, the resistance to freezing-thawing of the concrete incorporating high volume blast-furnace slag became much lower than that of the normal concrete.