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실리카퓸을 혼합한 시멘트 콘크리트의 역학적 특성 및 내구성
이승태,이승헌,Lee, Seung-Tae,Lee, Seung-Heun 한국세라믹학회 2010 한국세라믹학회지 Vol.47 No.5
This paper presents the results of experimental work on both mechanical properties and durability of concrete or mortar incorporating silica fume. The aim of this study was to investigate the effect of replacement of silica fume on the performance of hardened concrete or mortar. The replacement levels of silica fume that replaced cement in this work were 0%, 5%, 10% and 15%, respectively. The results of this study indicate that both mechanical properties and durability of concrete are greatly dependent on the replacement levels of silica fume. As the replacement level of silica fume increased, the mechanical properties including compressive and flexural strengths, and static modulus of elasticity were proportionally enhanced. Furthermore, it was found that silica fume had some beneficial effects on the resistances to both chloride ions penetration and sodium sulfate attack. However, it exhibited poor resistances to both freezing-thawing action and magnesium sulfate attack.
가압벨트 착용이 탄성밴드를 이용한 PNF 스프린터 패턴 훈련 시 뇌졸중 환자의 다리 근력 및 보행에 미치는 영향
이승태,배세현,김경윤,Lee, Seung-tae,Bae, Sea-hyun,Kim, Kyung-yoon 대한정형도수물리치료학회 2021 대한정형도수물리치료학회지 Vol.27 No.1
Background: This study was conducted to investigate the effects of pressure belt during proprioceptive neuromuscular facilitation sprinter pattern training using a Thera-band on leg muscle strength and gait in stroke patients with stroke. Methods: Nine patients with stroke underwent training five times a week for four weeks, and changes in the muscle strength and walking ability of the paralyzed leg before and after training were measured. Muscle strength was measured using a Digital muscle tester, and walking ability was measured using a G-WAKER and the timed up and go (TUG) test. Results: Results showed that the quadriceps, hamstring, tibialis anterior, gastrocnemius, cadence, stride length, and stance phase significantly increased (p<.05). The swing phase, gait cycle duration, and TUG test results significantly decreased (p<.05). Conclusion: This study demonstrated that a pressure belt is a very useful tool for improving muscle strength and walking ability in patients with stroke.
콘크리트의 강도 및 내구성에 대한 고로슬래그미분말 분말도의 영향
이승태,Lee, Seung Tae 대한토목학회 2014 대한토목학회논문집 Vol.34 No.4
본 연구는 콘크리트의 강도특성 및 내구성에 대한 고로슬래그미분말 분말도의 영향을 평가하기 위하여 수행되었다. 본 실험에 사용된 고로슬래그미분말의 분말도는 3종류(4,450, 6,000 및 $8,000cm^2/g$)를 선정하였으며, 보통포틀랜드시멘트에 대하여 50%를 대체하여 공시체를 제조하였다. 강도실험 결과에 따르면, 분말도가 $8,000cm^2/g$인 고로슬래그미분말을 사용한 콘크리트의 압축 및 쪼갬인장강도는 초기재령에서는 보통 포틀랜드시멘트 콘크리트에 비하여 다소 작았으나, 장기재령에서는 잠재수경성의 촉진으로 인하여 강도가 우수하게 나타났다. 내구성 분석결과에 의하면, 고분말도(6,000 및 $8,000cm^2/g$) 고로슬래그미분말 사용 콘크리트의 동결융해 저항성이 다소 작게 나타난 반면, 염소이온 침투저항성은 분말도 크기에 관계없이 고로슬래그미분말 적용 콘크리트가 우수하게 관찰되었다. 한편, 고로슬래그미분말을 사용한 모르타르의 황산염침식 저항성은 침식환경에 지배적인 영향을 받는 것으로 조사되었다. This paper presents the results of experimental work on both strength characteristics and durability of concrete or mortar having 50% ground granulate blastfurnace slag(GBS) with different fineness levels (4,450, 6,000 and $8,000cm^2/g$). Compressive and split tensile strength test results indicated that the concrete with a higher fineness level of GBS exhibited a better strength development due to the acceleration of latent hydraulic property at the later curing stage compared with ordinary portland cement concrete. Meanwhile, it was found that a higher fineness level of GBS showed some negative effects on the resistance against freezing-thawing action. However, incorporation of GBS to concrete, irrespective of fineness levels, significantly enhanced the chloride ions penetration resistance. The resistance against sulfate attack of mortar with GBS was greatly dependent on the attacking sources from sulfate environments.
노출조건에 따른 시멘트 모르타르의 황산염침식 저항성 평가
이승태(Lee, Seung Tae) 대한토목학회 2012 대한토목학회논문집 A Vol.32 No.6A
본 연구는 보통 및 혼합시멘트계 모르타르의 황산염침식 저항성에 대한 노출조건의 영향을 평가하기 위하여 수행되었다. 모르타르를 제조한 후, 3종류 노출조건, 즉 1) 연속 완전침지, 2) 연속 반침지 및 3) 건습반복 조건에서 모르타르의 팽창, 강도, 밀도 등 역학적 성능변화를 52싸이클까지 주기적으로 관찰하였다. 실험결과에 따르면, 연속 반침지(Exposure B) 조건에 노출된 OPC 모르타르가 황산염침식에 의한 다량의 균열이 발생하므로써, 연속 완전침지 조건 및 건습반복 조건에 노출된 모르타르에 비하여 성능저하가 상대적으로 크게 나타났다. 그러나, 고로슬래그미분말 및 실리카퓸을 사용한 혼합시멘트계 모르타르는 낮은 투수성 및 조직구조의 밀실화효과에 의하여 노출조건에 관계없이 우수한 황산염침식 저항성을 보였다. 따라서, 콘크리트 구조물이 황산염침식 환경에 노출될 경우, 노출조건에 대한 고려가 반드시 이루어져야 할 것으로 판단된다. In order to evaluate the effects of exposure conditions on the resistance to sulfate attack of normal and blended cement mortars, several mechanical characteristics of the mortars such as expansion, strength and bulk density were regularly monitored for 52 cycles under sodium sulfate attack. The mortar specimens were exposed to 3 different types of exposure conditions; Ⅰ) continuous full immersion(Exposure A), continuous half-immersion(Exposure B) and cyclic wetting-drying(Exposure C). Experimental results indicated that the maximum deterioration was noted in OPC mortar specimens subjected to Exposure B, showing the wide cracks in the portions where attacking solution is adjacent to air. Additionally, the beneficial effect of ground granulated blast-furnace slag and silica fume was clearly observed showing a superior resistance against sodium sulfate attack, because of its lower permeability and densified structure. Thus, it is suggested that when concrete made with normal cement is exposed to sulfate environment, proper considerations on the exposure conditions should be taken.
엔진 실린더 행정 검출 및 정밀한 CVVT 동작을 위한 캠축 위치 센서 제어 로직 개발
이승태(Lee, Seung Tae),김다숙(Kim Da Sook),권우영(Kwon, Woo Young) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
The enhancement of the Camshaft position senor(CMPS) sensing characteristics is important in terms of the durability and reliability of vehicles. Recently, because of cost reduction demands for vehicle, Camshaft processing defects induced Run-out and magnetization has occurred frequently. Therfore Camshaft position sensor attached on the engine has to be needed the effort to improve sensitivity and also important to solve problems about Cylinder stroke detection defects caused by missing signal. This paper presents the development of the sensing algorithm to reduce the CVVT and Cylinder stroke detection defects.