• Korean Journal of Optics and Photonics
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• v.11 no.2
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• pp.102-107
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• 2000

We propose a new scheme for generating a pedestal-free, femtosecond soliton pulse train by utilizing quasI-adiabatic high order soliton pulse evolution in dispersion decreasing fiber in conjunction with the intermediate pedestal suppression stage. Compression factor over 280 was achieved from lOGHz sinusoidal input, to 176 is soliton pulse train. train.

• Journal of Ocean Engineering and Technology
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• v.2 no.1
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• pp.90-94
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• 1988

본 논문은 반 잠수식 시추선과 선박과의 충돌해석에의 정적 압축법의 응용에 대해 다루었다. 선박이 시추선의 취약 부재에 충돌하는 경우를 가정하였으며 이 취약한 부재의 충돌에너지 흡수능력을 상세 해석 없이 추출하는 방법으로, 관련된 구조물 전체 강성 매트릭스를 부재의 양단에 정적 압축을 시켜 양단 유연도를 추출한 뒤 이 유연도를 양단에 가진 원통형 부재를 해석함으로써 외력-변형 관계를 얻을수 있었다. 충돌에너지 양은 외력-변형 선도를 적분함으로써 얻을 수 있다. 새로운 방법에 의한 결과를 3차원 수치해석 방법과 강체 프라스틱 방법에 의해서 얻어진 결과와 상호 비교하였으며, 이 새로운 방법이 해양구조물 충돌해석이 매우 효과적으로 응용될 수 있음을 알게 되었다.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.4
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• pp.588-592
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• 2012

This study concentrates the effect of hybridisation on the collapse mode and energy absorption for composite cylinders. The static collapse behavior of laminated(Al/CFRP/GFRP) circular-cylindrical composite shell under quasi-static axial compressive load has been investigated experimentally. Eight different hybrids of laminated(Al/CFRP/GFRP) circular-cylindrical composite shell were fabricated by autoclave. Eight types of composites were tested, namely, Al/carbon fiber/epoxy, Al/glass fiber/epoxy, Al/carbon-carbon-glass/epoxy, Al/carbon-glass-carbon/epoxy, Al/carbon-glass-glass/epoxy, Al/glass-glass-carbon/epoxy, Al/glass-carbon-glass/epoxy and Al/glass-carbon-carbon/epoxy. Collpase modes were highly dominated by the effect of hybridisation. The results also showed that the hybrid member with material sequence of Al-glass-carbon-carbon/epoxy exhibited good energy absorption capability.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.1
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• pp.77-86
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• 1992

This paper discusses the thermodynamic study on the suction cooling-steam injected gas turbine cycle. The aim of this study is to improve the thermal efficiency and the specific output by steam injection produced by the waste heat from the waste heat recovery boiler and by cooling compressor inlet air by an ammonia absorption-type suction cooling system. The operating region of this newly devised cycle depends upon the pinch point limit and the outlet temperature of refrigerator. The higher steam injection ratio and the lower the evaporating temperature of refrigerant allow the higher thermal efficiency and the specific output. The optimum pressure ratios and the steam injection ratios for the maximum thermal efficiency and the specific output can be found. It is evident that this cycle considered as one of the most effective methods which can obtain the higher thermal efficiency and the specific output comparing with the conventional simple cycle and steam injected gas turbine cycle.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1997.10a
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• pp.129-134
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• 1997

현재 외부 가압 공기베어링이 사용되어지는 분야는 PCB 기판, 엔진의 연료분사노즐 등의 고속가공용 스핀들, 전자 기기, 광학 기기 등에 사용되는 초정밀 부품가공용 스핀들, 정밀 측정 기기, 의료 기기, 저온 팽창기등 상대운동을 하는 많은 분야에서 이용되고 있으며, 이들 분야의 고속화 및 고정밀화 추세에 따라 고속에서의 안정성과 높은 운전정밀도가 보장된 외부 가압 공기 베어링이 요구되고 있다. 정밀 스핀들 시스템에 공기베어링이 사용되는 이유는 윤활제인 공기의 압축성에 기인된 평균화효과로 인하여 어느 정도 형상오차가 존재하더라도 축의 회전 시 떨림 진폭이 흡수되어 높은 운전정밀도를 유지하며 운전이 가능하기 때문이다. 그러나, 공기의 압축성에 의한 평균화효과로 어느 정도의 떨림 진폭은 흡수되나 형상오차에 의한 떨림 진폭은 작은 크기라도 여전히 남아있게 된다. 따라서, 초정밀 가공 기기나 정밀 측정 기기 등 높은 운전정밀도가 요구되는 곳에 공기베어링이 사용될 경우에 있어서 형상오차는 운전정밀도에 영향을 미치는 중요한 인자가 된다. 본 연구에서는 각각 두 개의 오비 가압 공기 저널 및 스러스트 베어링으로 구성된 스핀들 시스템에 대한 축과 베어링의 직각도 오차가 운전정밀도에 미치는 영향에 대해 해석하고 결과를 고찰하여 스핀들 시스템에 있어서 형상 공차에 대한 기초 설계자료를 제시하고자 한다.

• Journal of Biosystems Engineering
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• v.29 no.4
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• pp.347-356
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• 2004

치아인회석, 키토산, 시아노아크릴레이트 등의 생분해성 생체재료를 이용해 새로운 생체흡수성 골시멘트를 개발하고자 하였다. 이들 골시멘트들에 대해서 중합온도, 응고시간 등의 조작특성과 압축강도, 전단강도 등의 물성을 분석하였다. 특히, 치아인회석과 키토산의 미립가루와 부틸 시아노아크릴레이트의 강력접착제를 이용한 시멘트(B)에 대해서는 직접 접촉방법과 XTT 방법을 통해 세포독성을 분석하였고, 또한 쥐를 이용한 동물실험에서 시멘트(B)의 처리그룹에 따라 생체적합성을 분석하였다. 시아노아크릴레이트를 이용한 골시멘트의 최대중합온도는 약 33$^{\circ}C$, 조작(응고)시간은 3-6분, 압축강도는 약 15-25㎫, 전단강도는 약 0.4-l.7 ㎫를 나타내었다. 첨가제로 사용된 Lipiodol은 골시멘트의 주사성과 강력접착제의 초기 중합지연도를 높였고, 특히 송진가루는 시아노아크릴레이트의 초기중합을 지연시켰다. 시아노아크릴레이트를 이용한 시멘트(B)의 세포독성을 분석한 결과, 대부분의 처리 그룹에서 낮게 나타났고, 특히 키토산과 치아인회석을 사용한 경우 각각 세포 독성이 더 낮게 나타났다. 그리고 골시멘트(B)의 동물 생체적합성 실험의 방사선상 및 조직학적 분석에서도 뼈 형성 및 결합이 우수하게 나타났다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.2
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• pp.50-59
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• 2020

Superabsorbent Polymer (SAP) expands inside concrete by absorbing water and contracts as it discharges water. Through this process, concrete can achieve the internal curing effect, but the space occupied by the expanded SAP remains as a void. In this study, the effects of SAP internal curing and voids were evaluated by evaluating the fundamental properties and chloride penetration resistance of SAP mixed concrete. Also, to evaluate the internal curing effect by SAP, the tests were carried out under water and sealed curing conditions, respectively. From the result, the compressive strength of water curing did not differ significantly according to the mixing ratio of SAP. In the case of sealed curing, however, the compressive strength tended to increase as the mixing ratio of SAP increased. The internal curing effect of sealed curing was considered to have influenced the increase in compressive strength. In the case of the chloride diffusion coefficient, the diffusion coefficient tended to decrease as the mixing ratio of SAP increased. In particular, as the sealed curing is applied, the chloride penetration resistance is further improved due to internal curing effect. If the curing conditions are different, it is considered inappropriate to estimate the chloride penetration resistance by the surface electrical resistivity.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.54-62
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• 2019

In this paper, a stress-strain model for high-strength confined concrete is proposed using compressive fracture energy. In the compression test performed by author in Reference [6], an acrylic bar with strain gauges was embedded in the center of the specimen to measure the local strain distribution. It was found from the test that the local strain measurement by this acrylic rod is very effective. The local fracture zone length was defined based on the local strain distribution measured by the acrylic rod. Specifically, it was defined as the length where the local strain increases more than twice of the strain corresponding to maximum stress. In addition, the stress-strain relationship of confined concrete with compressive fracture energy is proposed on the assumption that the amount of energy absorbed by the compressive members subjected to the given lateral confining pressure is constant regardless of the aspect ratio and size. The proposed model predicts even results from other researchers accurately.

• Journal of the Korea Institute of Building Construction
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• v.11 no.4
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• pp.371-378
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• 2011

Concrete is affected by various deterioration factors, such as $CO_2$ and chloride ions from the sea, which cause carbonation and salt attack on concrete. These deterioration phenomena cause steel corrosion in RC structures. Although a great deal of research has been carried out in this area thus far, it is difficult to know the point at which corrosion will occur to a reinforced bar. As the diffusion of deterioration factors depends on the water content in concrete, it is imperative to assess the condition of absorbed water content. A mass measuring method was applied to calculate the absorbed water diffusion coefficient, as well as non-linear finite element method(FEM) analysis. As a result, it was found that W/C and unit water content in concrete mixture affect the diffusion coefficient decision.

• Polymer(Korea)
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• v.34 no.5
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• pp.434-441
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• 2010

Sodium polyacrylate (PAANa) was synthesized by inverse emulsion polymerization method to absorb excess water in concrete. Liquid paraffin was used as a continuous phase. Acrylic acid (AA) was neutralized by aqueous sodium hydroxide solution (8 M). Different amount of N,N'-methylene bisacrylamide (MBA) was used as a crosslinking agent to change crosslinking density of the synthesized PAANa. The size distribution of synthesized particles was measured by particle size analyzer. Swelling ratio of crosslinked PAANa was evaluated from the equation in D. I. water, cement aqueous solution, and $Ca(OH)_2$ aqueous solution. The FTIR spectroscopy was used to characterize $Ca^{2+}$ ion interaction with PAANa. Incorporation of 1.0 wt% PAANa into cement increased compressive and flexural strength approximately 30% and 10%, respectively, compared with those of ordinary portland cement.