• 대한수학교육학회지:수학교육학연구
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• 제9권1호
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• pp.279-294
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• 1999

The level-based task learning had an effect on enhancing the math achievement of enrichment and ordinary classes. Besides, the analysis of mathematical attitude change showed that the level-based task learning took effect in the experimental class in every domain, including self-confidence, flexibility, will power, reaction and value, while it made little difference to the comparative class. The findings were as follows in detail. 1. The Outcome of the Achievement Test 1) The Enrichment Class In the first two tests, there were little differences in the enrichment class, But the disparity between the experimental and comparative classes became larger as this study advanced with 4.3 for the third test, 6.4 for the fourth and 6.1 for the fifth. 2) The Ordinary Class In the first to fifth achievement tests, the ordinary class made less difference than the enrichment class did. But there appeared some effect as this study progressed, since the mean grade disparity between the experimental and comparative classes was 2.1 for the first test, 3.5 for the second, 3.9 for the third, 4.4 for the fourth and 6.3 for the fifth. 3) The Supplementary Class The supplementary class showed no big difference in the first two tests. But, like the ordinary class, there was some effect with the lapse of the third 2.9 for the test, 3.2 for the fourth and 4.1 for the fifth. 2. The Change of Mathematical Attitude 1) The Experimental Class The task learning by level had a great deal of effect on the experimental class, as the pre-and post-comparative analyses showed that this class's grades were 5.1 for self-confidence, 10.8 for flexibility, 11.3 for will power, 9.7 for curiosity, 10.9 for reaction and 2.8 for value. 2) The Comparative Class The relative comparison between the comparative class and experimental class revealed that there was a hole effect on the comparative class. 3. The Outcome of Questionnaire Survey 1) They showed a positive reaction, as 40.1% of them answered the level-based task loaming served to raise their achievement, and 48.0% told so-so, and 11.9% replied they weren't helped by it. 2) The results after the experiment were;37.8% of the students say they under- stood practically everything while 12.6% of them say they under stood almost half. 3) The will to learn after the experiment shows dramatic changes between the two classes, The students in the enrichment class showed better will to learn than the students in the ordinary and supplementary classes did.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권1호
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• pp.224-241
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• 2015

Multiview plus depth (MVD) videos are widely used in free-viewpoint TV systems. The best-known technique to determine depth information is based on stereo vision. In this paper, we propose a novel local stereo matching algorithm which is radiometric invariant. The key idea is to use a combined matching cost of intensity and gradient based similarity measure. In addition, we realize an adaptive cost aggregation scheme by constructing an adaptive support window for each pixel, which can solve the boundary and low texture problems. In the disparity refinement process, we propose a four-step post-processing technique to handle outliers and occlusions. Moreover, we conduct stereo reconstruction tests to verify the performance of the algorithm more intuitively. Experimental results show that the proposed method is effective and robust against local radiometric distortion. It has an average error of 5.93% on the Middlebury benchmark and is compatible to the state-of-art local methods.

• Geomechanics and Engineering
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• 제17권1호
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• pp.57-67
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• 2019

Water-induced strength reduction is one of the most critical causes for rock deformation and failure. Understanding the effects of water on the strength, toughness and deformability of rocks are of a great importance in rock fracture mechanics and design of structures in rock. However, only a few studies have been conducted to understand the effects of water on fracture properties such as fracture toughness, crack propagation velocity, consumed energy, and microstructural damage. Thus, in this study, we focused on the understanding of how microscale damages induced by water saturation affect mesoscale mechanical and fracture properties compared with oven dried specimens along three notch orientations-divider, arrester, and short transverse. The mechanical properties of calcite-cemented sandstone were examined using standard uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS) tests. In addition, fracture properties such as fracture toughness, consumed energy and crack propagation velocity were examined with cracked chevron notched Brazilian disk (CCNBD) tests. Digital Image Correlation (DIC), a non-contact optical measurement technique, was used for both strain and crack propagation velocity measurements along the bedding plane orientations. Finally, environmental scanning electron microscope (ESEM) was employed to investigate the microstructural damages produced in calcite-cemented sandstone specimens before and after CCNBD tests. As results, both mechanical and fracture properties reduced significantly when specimens were saturated. The effects of water on fracture properties (fracture toughness and consumed energy) were predominant in divider specimens when compared with arrester and short transverse specimens. Whereas crack propagation velocity was faster in short transverse and slower in arrester, and intermediate in divider specimens. Based on ESEM data, water in the calcite-cemented sandstone induced microstructural damages (microcracks and voids) and increased the strength disparity between cement/matrix and rock forming mineral grains, which in turn reduced the crack propagation resistance of the rock, leading to lower both consumed energy and fracture toughness ($K_{IC}$).

• 한국지반공학회논문집
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• 제40권2호
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• pp.19-28
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• 2024

본 연구에서는 유동성 채움재의 장기 압축강도 저하를 확인하고, 그 원인을 규명하고자 유동성 채움재와 물의 배합 비율 1:1 적용하여 시료를 제작하였으며, 재령 7일, 28일 기준 일축압축강도 시험을 수행하였다. 일축압축시험 결과 재령 28일 기준 압축강도는 7일 대비 2.85배 감소하였다. 또한, 똑같은 배합 조건에서 팽창제를 첨가하였을 경우 압축강도가 대폭 감소하였다. 현장에서 배합된 유동성 채움재를 재령 7일, 28일 기준으로 점하중강도 시험을 수행하였으며, 똑같은 배합 조건 및 재령 일 기준으로 일축압축강도와의 차이가 재령 7일 기준 29.27~58.76배, 재령 28일 기준 48.19~95.13배로 나타났다. 본 연구결과가 선행연구 결과와 다소 차이를 나타내고 있음에 대한 이유는 시험방법 및 시료 제작 과정에서의 정밀도 차이에 의한 것임으로 유동성 채움재 평가를 위하여 명확한 시험방법에 대한 규제가 필요하다.