• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
• /
• pp.1025-1028
• /
• 2009

Earth and rock fill dam is our typical dam because of their inherent flexibility and adaptability to various fundation conditions. In order to secure structural safety, rockfill materials are used angular particles obtained by blasting parent rock or rounded particles collected from river beds. Concrete-faces rockfill dams(CFRD) and Concrete-faces gravelfill dams(CFGD) have become popular in the last 20 years as s result of their good performance and low cost compared with the rockfill dam. These Dams are also constructed by the materials. A key factor in the design of the dams is the deformations induced during construction and upon reservoir filling. These can be predicted using the stress-strain and strength properties can be adequately define. However the stress-strain properties of rockfill are difficult to determine because the properties are affected by such factors as particle grading, size and shape of particles, stress conditions, and particle crushing. In our study, testing of the behavior of the rockfill materials are essential prerequisites to the realistic analysis and design of the CFGD. This paper deals with laboratory testing of particle crushing among the study.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제53권6호
• /
• pp.293-299
• /
• 2004

In this paper, thermal and mechanical properties of electric epoxy with water aging were discussed. We made elastic epoxy specimen adding a ratio of 0〔phr〕20〔phr〕, 35〔phr〕 and 53〔phr〕 with modifier to existing epoxy. We studied mechanical property of elastic resin after absorption in water from 0 to 484 hours. As a result, diffusion factor of elastic epoxy showed 20-21${\times}$10$^{-4}$ $\textrm{mm}^2$/s and general epoxy showed 9.5${\times}$10$^{-4}$ $\textrm{mm}^2$/s. Elastic property increased linearly according to addiction and decreased according to water absorption. Tensile strength was reduced according to addition. It was affected by water absorption of micro-void of elastic epoxy. Hardness inclined to decrease after increasing according to absorbed time. In water-absorption state, it was experimented a change of heat flow by temperature of elastic epoxy and change of thermal expansion coefficient. DSC (Differential Scanning Calorimetry) and TMA (Thermomechanical Analysis) equipments were used to measure Tg. A temperature ringe of DSC was from -0($^{\circ}C$) to 200($^{\circ}C$). One of TMA was from -0($^{\circ}C$) to 350($^{\circ}C$). In addition, we investigated structural analysis of water absorbed specimen using SEM (Scanning Electron Microscope).

• 펄프종이기술
• /
• 제47권4호
• /
• pp.102-108
• /
• 2015

Agricultural cultivation papers treated with water repellent were investigated in order to analyse mechanical properties and durability. The water repellency was optimal when papers are treated with Wb and Sa water repellents. Also, WCPs with 5% water repellent were more effective than those of 3 and 10%. In addition, water repellency of WCPs with Wb and Sa water repellents were kept constant in correlation with aging time. Finally, WCP with Wb water repellent possesses efficiency in terms of mechanical properties and durability.

• 대한기계학회논문집B
• /
• 제28권11호
• /
• pp.1322-1331
• /
• 2004

This paper presents studies on the design of water hydraulic system and components to replace oil with tap-water as the pressure transmission medium in hydraulic systems. In order to improve the performance of water hydraulic system, the thermal and hydraulic properties of tap-water are first investigated. Based on these characteristics, the design parameters, such as the clearances of the moving parts, the cross-sectional area of pipes and relative roughness, are proposed so that the performance of water hydraulic system is the same as that of oil. In addition, the operating ranges, which show the possibility of using water hydraulic system, are examined.

• 한국의류산업학회지
• /
• 제14권4호
• /
• pp.641-647
• /
• 2012

This study investigates the sound properties of fabric frictional sound (SPL, ${\Delta}L$, ${\Delta}f$) according to the film type of PTFE laminated vapor-permeable water-repellent fabrics in order to understand the relationship between SPL and the basic properties of fabrics such as layer, yarn type, and thickness of fiber. This study accesses their mechanical properties and determines how to control them to minimize SPL. Eight PTFE laminated water-repellent fabrics, composed of four different film types (A, B, C, D) and with two different fabrics, were used as test specimens. Frictional sounds generated at 1.21m/s were recorded by using a fabric sound generator and SPLs were analyzed through Fast Fourier Transformation (FFT). The mechanical properties of fabrics were measured by KES-FB. The SPL value was lowest at 74.4dB in film type A and highest as 85.5dB in type D. Based on ANOVA and post-hoc test, specimens were classified into less Loud Group (A, B) and Loud Group (C, D). It was shown that SPL was lower when 2 layer (instead of 3 layer), filament yarn than staple, and thin fiber than thick were used. In Group I, shearing properties (G, 2HG5), geometrical roughness (SMD), compressional properties (LC, RC) and weight (W) showed high correlation with SPL however, elongation (EM) and shear stiffness (G) did with SPL in Group II.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1996년도 가을 학술발표회 논문집
• /
• pp.175-182
• /
• 1996

This paper deals with the properties of water permeability and porosity of cement mortar substrate coated with siliceous slurry coating under the exposure environment. Conditions of exposure enviornment are four kinds of in constant temperature water and humidity box, in indoor and outdoor exposure. Coated mortar substrate was expected continually increase in water and humidity condition, but was not in dry condition. Watertightness effect of siliceous coating was better in the condition of humidity then the dry condition, and the pore volume was decreased in that condition.

• Geomechanics and Engineering
• /
• 재33권6호
• /
• pp.625-633
• /
• 2023

The volume changes associated with moisture or suction variation in expansive soils are of geotechnical and geoenvironmental design concern. These changes can impact the performance of infrastructure projects and lightweight structures. Assessment of unsaturated function for these materials leads to better interpretation and understanding, as well as providing accurate and economic design. In this study, expansive soils from different regions of Saudi Arabia were studied for their basic properties including gradation, plasticity and shrinkage, swelling, and consolidation characteristics. The unsaturated soil functions of saturated water content, air-entry values, and residual states were determined by conducting the tests for the entire soil water characteristic curves (SWCC) using different techniques. An attempt has been made to provide a prediction model for unsaturated properties based on the basic properties of these soils. Once the profile of SWCC has been predicted the time and cost for many tests can be saved. These predictions can be utilized in practice for the application of unsaturated soil mechanics on geotechnical and geoenvironmental projects.

• 한국농공학회논문집
• /
• 제62권5호
• /
• pp.15-26
• /
• 2020

There are fifteen non-point pollution management areas in Korea and three of them (Doam lake, Daegi district and Golji-cheon) are located in the upstream of the Namhan river watershed. Many efforts to reduce non-point sources (NPS) pollution have been conducted, however, water quality pollution in the watershed is still serious. To solve these problems, it is a priority to grasp water quality using statistical techniques. In this study, a trend analysis was conducted to evaluate the effect of NPS management in the watershed. The long-term trends from 1996 to 2018 of water quality properties were analyzed using data collected from the water environment information system. Seventeen monitoring stations were selected along the main stream in Namhan river basin. Monthly water quality properties (BOD, COD, TN, TP, TN/TP ratio, Conductivity, SS and Chlorophyll-a) were collected and analyzed by Mann-Kendall test and LOWESS. The results showed that the Conductivity tended to increase in all regions and was the highest level in Jijangcheon. Organic pollution such as BOD and COD tended to increase in the Jungseon area. SS did not show a large tendency, but it showed high concentration in the Doam watershed. In all regions, 40% of water quality properties showed a tendency to 'UP', 15% of water quality properties tended to 'DOWN', and 46% indicated no tendency. In order to determine the cause of this, additional research and measures for improvement are necessary. This study will be used for the establishment of water quality policy in the future.

• 콘크리트학회논문집
• /
• 제12권3호
• /
• pp.39-46
• /
• 2000

This study is to investigate the watertightness properties of waterproofing admixture mixed redispersible polymer and siliceous powder. Series I deals with change in micro-structure of mortar by waterproofing admixture according to the water/cement ratios of 0.5, 0.6, 0.7 and 0.8 Crystal growth in micro-structure was observed through SEM to estimate on the watertightness effect of it. SeriesII deals with watertightness properties of waterproofing admixture on water permeability coefficient, crack restoration capacity and carbonation depth. SeriesII deals with watertightness properties of waterproofing admixture on water permeability coefficient, crack restoration capacity and carbonation depth. The result of this study can be summarized as follows. 1) Fluidity of mortar and concrete was increased by adding waterproofing admixture. 2) From observation through SEM. Crystals grew larger and denser in micro-structure as fiberic crystalization. 3) Waterproofing admixture is good watertightness properties in a level of high water/cement ratios and long limit of time. 4) Crack restoration capacity was appeared and durability was progressed by waterproofing admixture.

• 한국해양공학회지
• /
• 제12권3호통권29호
• /
• pp.31-41
• /
• 1998

Single fiber fragmentation technique was used to evaluate the change of interfacial properties by degradation of fiber tensile strength in the fiber reinforced composites. The influences of fiber tensile strength on the interfacial properties have been evaluated by the fragmentation specimens(weak fiber samples) of glass fiber/epoxy resin that was made using the pre-degraded glass fiber in distilled water at $80^{circ}C$ for specified periods. The effects of the immersion time on the interfacial properties in the distilled water at $80^{circ}C$ also have been evaluated by the fragmentation specimens(original fiber samples) of glass fiber/epoxy resin that was made using the received glass fiber. As the result, the tensile strength of glass fiber was decreased with the increasing of the treatment time in the distilled water at $80^{circ}C$ and the interfacial shear strength was independent of the change of the glass fiber strength in the single fiber fragmentation test. But in the durability test using the single fiber fragmentation specimen, interfacial shear strength decreased with the increasing of the immersion time in distilled water ar $80^{circ}C$. And it turned out that the evaluating of interfacial shear strength using original fiber tensile strength was valuable in the durability test for the water environment by the single fiber fragmentation technique.