• Journal of the Korean Geographical Society
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• v.43 no.6
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• pp.808-823
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• 2008

Sediment abrasion in rivers is caused by the interaction between bedrock channel bed and sediment particles transported through the river. Abrasion rate of sediment particles in rivers is controlled by two major factors; Sediment transport conditions including hydraulic conditions form the erosive forces and physical and chemical strengths of the particles form a resistance force against abrasion and other erosional processes. Physical experiments were performed to find the role of each variable on sediment abrasion process. Total 266 sediment particles were used in this experiment. All sediment particles were divided into 11 independent sediment groups with sediment particle size and sediment loads. Each sediment groups were abraded in tumbling mill for up to 8 hours. Changes in weight were recorded by run and total: 2,128 cases of abrasion rate were recoded. Physical strength of rock particles was measured with point load strength index. It is found that sediment abrasion rate has a negative functional relationship point load strength index ($I_{a(50)}$) ($R^2=0.22$). It was suggested that physical strength of sediment particles set the "maximum possible abrasion rate'. As sediment flux increases, abrasion rates of sediment particles with similar point load strength index were changed. It could be concluded that not only physical characteristics of sediment particles, but also sediment transport conditions control sediment abrasion rates.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.50-50
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• 2020

하천, 강어귀 및 해안 지역의 점착성 유사는 흐름 내에 입자의 충돌에 의한 흡탈착으로 인해 다양한 크기의 플록을 형성한다. 이 플록은 오염물과도 군집을 형성하여 하상이 퇴적되는 경우가 많으며 홍수 등과 같은 외부 충격으로 인해 재부 되어 하천 환경 및 생태계에 악영향을 미친다. 군집의 형성은 화학적인 결합과 물리적인 응집으로 분류할 수 있는데, 미세 점착성 유사의 군집형성에 대한 연구는 주로 화학적인 결합에 대한 연구가 활발하다. 반대로 물리적인 결합 혹은 외부 충격에 대한 플록형성 매커니즘에 대한 연구는 미비한 실정이다. 따라서, 본 연구에서는 교반기를 활용한 실험을 통하여 점착성 유사에 대한 물리적인 흡탈착 과정을 분석하였다. 유입된 점착성 유사를 교반기로 외부충격을 주어 흡착과 탈착하는 정도를 탁도와 농도를 통해 정량화하였다. 실험은 원통 수조에서 수행되었으며, 교반기의 RPM을 조절하면서 외부충격의 강도를 조절하였다. 초기 실험을 통해 탁도-농도의 관계를 제시하였고 이를 활용하여 교반강도와 점착성 유사의 농도를 분석하였다. 실험 결과 교반강도가 증가할수록 플록 형성이 활발하게 진행되었으나, 일정 교반강도 이상에서는 다른 흡착 과정을 보였다. 이를 토대로 점착성 유사의 흡탈착의 임계값을 제시하였다. 향후 본 연구결과와 유속 혹은 난류강도 등의 하천특성과 연관성을 분석한다면 하천 내 오염물 관리에 효과적으로 사용될 것으로 기대된다.

• The Journal of Engineering Geology
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• v.34 no.1
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• pp.25-38
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• 2024

Laboratory tests of accelerated artificial weathering compared the effects of seawater and acidified distilled water on rock weathering. The experiments simulated chemical and physical weathering of five different types of volcanic rock by applying 45 freeze-thaw cycles using seawater and acidified distilled water (pH 3), both at 70℃. The physical properties and uniaxial compressive strength (UCS) of the rocks were measured after 15 and 45 cycles of artificial weathering. Most of degradation of physical properties appeared within the first 15 cycles, and acidified distilled water had a greater effect than seawater. Analysis of variance (ANOVA) statistically evaluated the differences in UCS of the different rock types during the tests. The rate of UCS reduction after 45 cycles was similar across the samples, being independent of the rock type and the trend of changes in physical properties. In contrast to the changes in the physical properties, the UCS was more affected by seawater than by acidified distilled water.

• Proceedings of the KSEG Conference
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• 2004.03a
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• pp.17001-17013
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• 2004

암석의 물리적 성질이란 암석이 공학적으로 보편화 된 조건인 상온, 상압 하에서 고유하게 지니고 있는 특성으로 비중, 공극율, 강도 등이 있다. 물리적 성질은 무결암을 대상으로 주로 실험실내에서 정해진 방법에 따라 정량적으로 측정할 수 있으며, 특정 암석에서 측정한 여러 가지 간은 해당 암석의 특성을 고유하게 나타내고 있으므로 이를 암석의 물질 정수라고도 한다. 현재 암석의 물리적 성질을 측정하기 위한 방법으로는 국제암반공학회(ISRM. International Society for Rock Mechanics)가 제안한 방법(Brown, 1901)이 가장 널리 적용되고 있다. (중략)

• Tunnel and Underground Space
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• v.13 no.3
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• pp.215-224
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• 2003

Weathering in nature was simulated by freeze-thaw cyclic test which represents mechanical weathering. Measured physical properties were elastic wave velocities, absorption rate, volume change and weight change. Uniaxial compression tests were also conducted before and after the weathering tests. The change in weight and volume of the specimens were not clearly related to the weathering process, but P, S wave velocities, uniaxial compression strength and Young's modulus were clearly decreased as weathering progresses. Test result can be used for the assessment of long-term stability of rock slopes.

• Journal of Korean Society of Forest Science
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• v.101 no.3
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• pp.538-545
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• 2012

This study addressed soil disturbances following harvesting as well as soil physical and hydrological properties within three first-order headwater catchments characterized by ephemeral-intermittent streams. Four treatments representing a range of potential Best Management Practices(BMPs) for ephemeral-intermittent streams were used; BMP1, BMP2, clearcut and reference. This study includes 1 year of pre- and post-harvest observations. Results showed that post-harvest disturbances were closely related with harvesting intensity and generally tended to reflect changes in soil physical and hydrological properties following harvest with the except of bulk density and porosity. Forest clearcutting decreased macroporosity and saturated hydraulic conductivity, and increased soil resistence as a result of severe soil disturbances thereby increasing soil erosion. These impacts were reduced by implementing two BMP treatments during harvesting activities. The finding support the use of either BMP treatments for ephemeral-intermittent streams, however, the additional measure of leaving logging debris in BMP2 did not cover enough soil surface to reduce erosion.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.313-316
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• 2008

As high rise buildings with 100 or more stories are being constructed, it is inevitable to use high performance materials including high performance concrete. What is most important in high performance concrete is extremely high strength in order to reduce the section of members in high rise buildings. During the last several years, there have been active researches on Ultra high strength concrete. While these researches have been mostly focused on strength development, however, other accompanying physical properties have not been studied sufficiently. Thus, the present study purposed to obtain and analyze data on the physical mechanical properties of Ultra high strength concrete through experiments and to use the results as basic information on required performance of concrete used in high rise buildings.

• 전기의세계
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• v.45 no.8
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• pp.4-10
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• 1996

사람은 누구나 쾌적하고 안전하고 좋은 환경에서 살며 일하기를 바란다. 또한 그런 환경을 만들고자 꾸준히 노력하고 있다. 좋은 환경이란 사람이 건강하고 행복하게 살 수 있는 환경이라고 할 수 있다. 여기서 필자는 물리적 환경과 그에 관련된 인체의 변화, 사람들의 인식, 물리적 환경을 개선하려는 인간의 노력에 대해 간략하게 설명하고자 한다.

• KSBB Journal
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• v.11 no.6
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• pp.718-725
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• 1996

Old newsprint was deinked with endoglucanase, exoglucanase and their various compositions from Trichoderma viride. The yield decreased with an increase in enzyme concentration. Especially, it was the lowest in the treatment of endo-exo mixture(1:1). It may be regarded as a synergistic actions of the cellulase components. The brightness was the highest in pulp deinked with endo-exo mixture(1:1). Maximum brightness was observed when 0.5mg/mL of the endo-exo mixture was used. The physical strength increased with increasing concentration in exoglucanase. But, it decrease with increasing concentration in endoglucanse and endo-exo mixture(1:1). Also, we investigated the yield, brightness and physical strength of endoglucanase in combination with exoclucanase(12:1, 8:1, 4:l, 1:1, 1:4, 1:8, 1:12). Maximal deinking conditions, obtained at a specific optimal ratio of endoglucanase to exoglucanse are as follow ; 12:1 for yield, 12:1 for brightness, 4:1 for tensile strength, 12:1 for bursting strength, and 8:1 for tearing strength. These results indicated that the deinking depended largely upon the action of endoglucanase. Exoglucanase was occupying more than 60% of the total crude cellulase contents. Therefore, the most effective deinking must repress the action of exoglucanase.

• The Journal of Natural Sciences
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• v.10 no.1
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• pp.81-91
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• 1998

Studied on the changes of physical properties according to frequency of washing of sample such as cotton, ramie, wool, cotton knit, T/C. The results are as follows :1. The tensile strength in cotton, wool, and T/C was not changed by 5 times washing but in cotten knit was increased because hang-down phenomenon. 2.The crease resistance of cellulose fiber was decreased by repeated washing. In the case of wool, That was decreased considerably because of decreasing of elasticity and increasing of density caused by shrinking after washing. 3.The abrasion strength of wool was increased with increase in frequency of washing because of thickness caused by shrinking. 4.By repeated washing, the pills was generated in all of the samples and quantity of pills was increased with increase in frequency of washing, the pills was generated in all of the samples and quantity of pills was increased with increased in frequency of washing. Specially, in the case of cotton knit and wool, the pilling was remarkable. 5.The physical properties of dry cleaned wool was superior than that of wet cleaned wool.