• Journal of the Korea Concrete Institute
• /
• v.25 no.4
• /
• pp.371-379
• /
• 2013

This paper investigates the cracking and tension-stiffening behavior of 100 MPa shrinkage-compensated strain-hardening cement composite (SHCC) and conventional concrete tie elements in monotonic and cyclic tension. Strain and surface crack formation of tension ties were monitored with two strain displacement transducers and a photo microscope with a lens of magnification 50 times. Three different cement composites such as conventional concrete, shrinkage-compensated SHCC, and normal SHCC were used in the tie specimens to investigate the influence of the cement composite type on the tension stiffening and cracking behavior. Test results indicated that initial shrinkage of the ultra high-strength cement composites is greatly reduced as the 10% replacement of cement by the shrinkage-compensating admixture based on calcium sulfo-aluminate (CSA). The test results on the SHCC tension ties showed that the first cracking load decreases proportionally to the initial shrinkage strain. Reinforced ultra high-strength SHCC ties with the initial shrinkage compensation exhibited improved tension stiffening and smaller crack spacings, i.e. the reduction in crack width. Cyclic loading did not have a significant effect on tension stiffening and cracking behavior of tension ties with normal concrete and SHCC materials.

• Journal of the Korea Concrete Institute
• /
• v.19 no.2
• /
• pp.233-239
• /
• 2007

The main objective of this study was to evaluate the effect of recycled PET fiber made from waste PET bottle on the control of plastic shrinkage cracking of cement based composites. PET is blown as a plastic material and used in a variety products such as a beverage bottle. However, waste PET bottles are thrown after the usage, raising huge problems in terms of the environment. Thus, the research on the method to recycle the PET bottles indicates important aspects in environment and economy. The method to recycle waste PET bottles as a reinforcing fiber for cement based composites is one of effective methods in terms of the recycle of waste PET bottles. In this research, the effect of recycled PET fiber geometry and length on the control of plastic shrinkage was examined through thin slab tests. A test program was carried out to understand the influence of fiber geometry, length and fiber volume fraction. Three type of recycled PET fibers including straight, twist crimped and embossed type. Three volume fraction and two fiber length were investigated for each of the three fiber geometry. Test results indicated that recycled PET fibers are effective in controlling plastic shrinkage cracking in cement based composites. In respect to effect of length of fiber, longer fiber was observed to have efficient cracking controlling with low volume fraction in same fiber geometry while shorter fiber controled plastic shrinkage cracking efficiently as addition rate increase. Also, embossed type fibers were more effective in controlling plastic shrinkage cracking than other geometry fiber at low volume fraction. But, for high volume fraction, straight type fibers were most effective in plastic shrinkage cracking controlling in cement based composites.

• The Korean Journal of Rheology
• /
• v.8 no.3_4
• /
• pp.207-214
• /
• 1996

사출성형은 많은 장점과 유용성에도 불구하고 싱크마크나 휨과 같은 변형문제를 피 하기 어렵다. 이것은 성형품의 부위별 온도분포 및 냉각속도 차이에 의한 잔류응력에 기인 하는 것으로 구조가 복잡하거나 크기가 쿤 경우에 더욱 더 문제가 되기 쉽다. 이와 같은 문 제를 해결하기 위하여 성형품의 내부에 기포를 형성시켜 수지의 수축분을 기포의 성장으로 보상하여 주는 가스사출성형이 개발되어 많이 활용되고 있는 실정이다. 한편 일반 가스성형 과 달리 수지를 완전히 채운후 저압의 공기를 이용하여 기포를 발생시켜 수지의 체적수축분 을 보상해주는 PFP성형기술은 가스사출의 나점인 공기의 유동조절문제를 해결하고 비용이 저렴한 등의 잇점을 가지고 있다. 이 과정은 가스성형공정의 2차 침투과정과 매우 유사하나 아직까지 이에대한 이해나 연구는 매우 부족한 실정이다 본 연구는 기포의 성장이 수지의 체적수축에 의한 것이라는 가정에 근거하여 기포성장길이에 관한 모델링을 수행한 것이다. 실험결과와의 비교를 통하여 기본 가정에 대한 타당성을 검증하고 여러 인자들의 영향을 살 펴보았다. 본 연구는 PFP성형공정에 대한 이해를 증진시켜 금형설계 및 성형조건 설정에 대한 가이드라인을 제시하며 아울러 PFP공정에 대한 보다 체계적인 이해 및 일반가스성형 의 2차 침투과정 등의 관련 현상에 대한 이해 및 연구에 도움이 될것으로 기대된다.

• International Area Studies Review
• /
• v.15 no.3
• /
• pp.55-76
• /
• 2011

In this paper, we estimate a model that incorporates key features of business cycles, co-movement among economic variables and switching between regimes of expansion and recession, to aggregate quarterly data for the NAFTA region. Two common factors reflecting the permanent and transitory components of the business cycle in the region, along with the turning points from one regime to the other, were extracted from the data by using the Kalman filter and maximum likelihood estimation approach of Kim (1994). Estimation results confirm that a typical aspect of business cycles are also observed (i.e., recessions are steeper and shorter than recoveries) in the region, and that both co-movement and that regime switching are found to be important features of the business cycle. The two common factors produce sensible representations of the trend and cycle, and the estimated turning points are in line with independently determined chronologies. It also turns out that the degree of synchronization between the NAFTA region and Korea, has significantly increased since the entry into force of the NAFTA.

• Journal of IKEEE
• /
• v.23 no.2
• /
• pp.681-686
• /
• 2019

This paper proposes a CMOS temperature sensor using inverter delay chains of the same size based on the pulse shrinking method. A temperature-pulse converter (TPC) uses two different temperature delay lines with inverter chains to generate a pulse in proportion to temperature, and a time-digital converter (TDC) shrinks the pulse using inverter chains of the same size to convert pulse width into a digital value to be insensitive to process changes. The chip was implemented with a $0.49{\mu}m{\times}0.23{\mu}m$ area using a $0.35{\mu}m$ CMOS process with a supply voltage of 3.3V. The measurement results show a resolution of $0.24^{\circ}C/bit$ for 9-bit data for a temperature sensor range of $0^{\circ}C$ to $100^{\circ}C$.

• 대한핵의학회:학술대회논문집
• /
• 2004.11a
• /
• pp.389.2-389.2
• /
• 2004

• 대한핵의학회:학술대회논문집
• /
• 1992.06a
• /
• pp.194.2-195
• /
• 1992

• The Science & Technology
• /
• v.16 no.10 s.173
• /
• pp.8-18
• /
• 1983

- 기업기술 지원센터 발족(기계연에, 5백개 기술집약기업 중점육성) - 재일 한국과기협 결성키로(모국 과학기술 발전에 동참기대) - '83학술회의 추계워크숍 개최 - 대상에 PVC수축필름 제조방법('83발명전, 우수상은 식기자동 세척기)

• Proceedings of the KSMRM Conference
• /
• 2006.11a
• /
• pp.55-55
• /
• 2006

• 대한핵의학회:학술대회논문집
• /
• 1987.05a
• /
• pp.121.2-121.2
• /
• 1987