• 한국해양공학회지
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• 제28권2호
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• pp.140-146
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• 2014

This study investigated the engineering characteristics of non-sintering binder-stabilized mixtures consisting of different ratios of a hardening agent(3%, 6%, 9%, 12%) for recycling industrial by-products through several series of laboratory tests. The hardening agents consisted of two kinds of non-sintering binders(NSB-1, NSB-2), which were developed by using inter-chemical reactions among blast furnace slag, phospho-gypsum, and an alkali activator. In addition, ordinary Portland cement(OPC) was used to compare the engineering characteristics of the stabilized mixture. An unconfined compressive test showed that the unconfined compressive strength increased with the curing time and mixing ratio. Experimental test results indicated that the 7-day strength of the NSB-1 mixture was similar to that of the OPC mixture. However, its 28-day strength was higher than that of the OPC mixture. The secant module of elasticity showed a range of $E_{50}=(42-109)q_u$ regardless of the agents. Based on the results of triaxial tests, the cohesion and friction angle increased with the mixing ratio.

• 아동학회지
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• 제36권1호
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• pp.65-83
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• 2015

The purpose of this study was to validate the newly developed K-WPPSI-IV using other current IQ tests in common use in Korea such as the K-ABC and K-CTONI-2. Fifty three 2~7 year olds were tested with both the K-WPPSI-IV and K-ABC in a counterbalanced order. Simultaneous, cognitive, information processing as well as acquisition indices of K-ABC were moderately correlated with the total IQ of K-WPPSI-IV, ranging .44~.58. The results of these tests were comparable with US data: Correlations among WPPSI-IV & DAS-II subscales were .31~.67. The correlations among K-WPPSI-IV & K-CTONI-2 subscales in sixty two children ranged from .43~.49. WMI(Working memory index) as well as PSI(Processing speed index) of K-WPPSI showed low correlations with non-verbal IQ. These results indicated that nonverbal IQ does not test processing speed which in turn is very important in WMI & PSI Indices of K-WPPSI-IV. Further studies are needed to broaden the concurrent validities using K-WISC-IV or K-BSID-2. In addition, predictive as well as discriminate validity studies need to be conducted for better understanding of K-WPPSI-IV.

• 한국지반신소재학회논문집
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• 제8권4호
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• pp.35-40
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• 2009

본 논문에서는 순환골재 다공질 콘크리트말뚝(RAPP : Recycled-Aggregate Porous Concrete Pile)에 의한 압밀촉진효과를 파악하기 위하여 일련의 실내모형실험을 수행하였다. 본 연구에서 얻어진 실험 결과를 동일한 조건에서 수행한 모래다짐말뚝과 쇄석다짐말뚝에 대한 기존의 실험결과(유승경, 2009)와 비교하여 RAPP로 개량된 복합지반의 시간에 따른 침하량의 변화 특성과 압밀시간에 대하여 비교, 분석하였다. 또한 일련의 수치해석을 수행하여 실내모형실험 결과를 평가하였다. 분석 결과로부터 RAPP에 의한 일차압밀과 이차압밀에 대한 침하저감효과가 타 공법에 비해 탁월함을 알 수 있었으며 압밀 종료시간도 상대적으로 빠르게 나타나 RAPP에 의한 압밀촉진효과가 우수함을 입증할 수 있었다.

• 한국지반공학회논문집
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• 제19권1호
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• pp.111-120
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• 2003

본 연구에서는 점성토지반의 침하량 평가에 보다 적합한 새로운 응력경로시험을 소개하였다. 새로운 시험기법에서는 배압평형과정을 채택함으로써 특정 응력경로상의 모든 점에 대응하는 변형특성을 하나의 시험을 통해 파악할 수 있다. 따라서, 제안된 시험기법을 적용하는 경우, 응력경로법의 실용적인 적용을 위해 필요한 지반의 전반적인 변형거동을 몇 개의 시험만으로 예측할 수 있으며 나아가 기존의 시험기법으로는 수행이 불가능했던 이방적 압밀응력 경로에 대한 변형거동의 평가 역시 실험적으로 가능해진다. 이와 함께 본 연구에서는 성형 카올리나이트 시료에 대해 다양한 응력경로시험을 수행하여 제안된 시험기법의 실험적 적용성을 확인하였으며, 그 결과를 활용하여 전반적인 변형거동과 침하량을 평가하는 실제 과정을 제시하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.424-433
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• 2006

This paper studies the field applicability of the Special Chemical grouting Method(SCM) in reinforcing and reducing permeability of the back of an existing continuous wall. SCM uses double rod which imposes intermediate pressure$(981\sim9,810kPa)$ to disturb, cut, discharge, and mix the ground. It is observed that a bulb is formed by using cement paste and environmentally friendly injection materials with minimal alkali leaching. Uniaxial compression tests, test for chemical properties and fish poison test are performed. Test results indicate that the method results in higher durability, less leaching through use of the environmentally friendly injection material, and faster mobilization of the strength. In addition, field tests confirm the formation of the bulb and the seepage cutoff wall.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.974-981
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• 2005

Because general laboratory tests for sand compaction pile method including unit-cell test device have fixed outside diameter, as area replacement ratio increase, diameter of sand pile increase. These condition can bring about overestimation of stiffness of composite ground. In addition, existing large soil box which consist of bellows type loading plate can occur serious mistake in checking the amount of drained water because there are additional drainage along the inside wall in device. Overcoming these shortcoming, this paper developed modified large scale soil box consist of piston type load plate. In this study, using this device, series of modified large scale soil box tests were performed, and investigated the settlement and stress transportation characteristics with area replacement ratio in sand compaction pile method.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.261-273
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• 2004

이 연구에서는 경제적이고 실용적인 지반의 동적물성치 계측 기술 개발을 위해 인홀시험법을 연구하였다. 이번 연구에서는 개발한 인홀 장비는 NX 크기의 검측공에서 사용할 수 있고 맨손으로 다룰 수 있을 정도로 작고 가볍다. 그리고 기존의 인홀 장비를 보다 편리하게 개량하였다. 또한, 인홀 시험에 있어서 최적의 댑퍼를 개발하였다. 이 장비는 여러 현장에서 크로스홀 시험과 인홀 시험을 통해 성능을 검증하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.407-414
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• 2004

Interfacial properties between rock mass and shotcrete play a significant role in the transmission of loads from the ground to shotcrete. These properties have a major effect on the behaviours of rock mass and shotcrete. They, however, have merely been assumed in most of numerical analyses, and little care has been taken in identifying them. This paper aimed to identify interfacial properties including cohesion, tension, friction angle, shear stiffness, and normal stiffness, through direct shear tests as well as interface normal compression tests for shotcrete/rock cores obtained from a tunnel sidewall. Mechanical properties such as compression strength and elastic modulus were also measured to compare them with the time-dependent variation of interfacial properties. Based on experiments, interfacial properties between rock and shotcrete showed a significant time-dependent variation similar to those of its mechanical properties. In addition, the time-dependent behaviours of interfacial properties can be well regressed through exponential and logarithmic functions of time.

• 한국과학교육학회지
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• 제19권2호
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• pp.266-274
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• 1999

본 연구에서는 협동적인 CAI와 개별적인 CAI가 중학생들의 과학 개념, 학업 성취도, 수업 환경에 대한 인식, 그리고 학습동기에 미치는 효과를 조사하였다. 중학교 3개 학급을 대상으로 분자 운동 단원에 대해 5차시 동안 협동적 CAI, 개별적 CAI, 전통적 수업을 실시하였다. 분석 결과 개념, 수업 환경에 대한 인식, 학습동기 검사에서 협동학습 집단의 평균이 전통적 수업 집단에 비해 유의미하게 높았으며, 개념의 파지 검사에서 협동학습 집단의 개념 이해도가 더 높게 나타났다. 또한, 개념의 파지 및 학습동기 검사에서 수업 처치와 사전 성취 수준 사이의 상호작용 효과가 있었다. 이에 대한 교육학적 함의를 논의하였다.

• 대한기계학회논문집A
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• 제24권11호
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• pp.2845-2852
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• 2000

When welding a car frame with one spot welding there are same limitations because many parts of it cannot be simplified by one spot welding alone. It is presented two spot welding model for the description of the spot welding which is usually used in a car frame structure. This study primarily covers fatigue behavior taking spot welded SPCC(Steel plate carbon C) with different ungget intervals as a tension shear specimen. It was prepared that intervals between two nuggets are varied as 9mm, 14mm, and 20mm respectively. The tensile tests and fatigue tests were executed to know the mechanical properties under static and fatigue load condition. In addition, the relationship between fatigue life and nugget intervals was illustrated by finite element method.