• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2002.05a
• /
• pp.97-102
• /
• 2002

The ability to pass between bars is one of the most important performance of self-compacting concrete or high-flowability concrete since it determines the final filling capacity which influences the strength and durability of hardened concrete in structure. Therefore it has been evaluated by many researchers using different kinds of testing apparatuses. The assessments of passing ability, however, differ largely according to the style, the dimension and the criteria in apparatuses, and the value obtained from one apparatus cannot be converted those of the others. There needs a rheological approach to the better understanding of the passing behavior of fresh concrete between reinforcing bars, where the flow velocity of concrete becomes slow and the blockade sometimes occurs due to the interference between aggregates and reinforcing bars. Experimental works were conducted to clarity the effects of the clearance between reinforcing bars, the volume of aggregate and the rheological properties of matrix on the behavior from the rheological point view and showed the rational mix proportioning of concrete.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.46 no.7
• /
• pp.55-67
• /
• 2004

In this paper, the flowability, strengths, impact resistance and sulfuric acid resistance of steel fiber reinforced high performance concrete (SFHPC) for the steel fiber content and fly ash and blast furnace slag as admixtures were presented. For evaluating flowability particularly, tests of slump flow, box-type passing ability and L-type filling ability were performed. The slump flow of SFHPC was some decreased with increase of the steel fiber content. At the box-type passing ability, the difference of box height of SFHPC is greatly increased with increasing the fiber content. The L-type filling ability of SFHPC was not excellent above $0.75\% of the steel fiber content. Also, the compressive strength of SFHPC was decreased with increase of the steel fiber content, but the flexural strength of SFHPC was much higher than that of the concrete without the steel fiber. At the impact resistance, drop number of SFHPC for reaching final fracture was increased with increase of the fiber content. Also, the drop number for reaching initial fracture of lmm was increased with increase of the fiber content. At the sulfuric acid resistance, 4-week weight change of SFHPC with the steel fiber was almost similarity that of HPC without the steel fiber and was in the range of 73.6 to 81.5.

• Journal of Information Technology Services
• /
• v.11 no.4
• /
• pp.1-23
• /
• 2012

The growing interest in smartphones has increased the number of studies conducted on technology acceptance and user satisfaction. It is now over two years since the launching of smartphones, but there are not many researches on the usage behavior of today's smartphone users. Smart devices have evolved from smartphone to smart pad and smart TV, but there are still not many studies on variables such as knowledge about the parent product and the ability to use it. With this, I decided to study how the motivation and the ability of using smartphones affected the smartphone user's intention to use smartpads. This study presents the usage behavior of smartphone users and proves that the ability to use a parent product (smartphone) affects the user's intention to use an extension product (smartpad). The research results showed that the smartphone usage ability affected both variety of use and rate of use. The convenience and passing time factors affected variety of use; and the social interaction, entertainment and passing time factors affected rate of use. As for the intention to use smartpads, the smartphone usage ability and variety of use positively affected the smartphone user's intention to use smartpads. This study showed that the more the user used a smartphone to pass time and for convenience, the more effectively the user could use various functions. It proves that the variety of use of smartphone is highly related to the acceptance of smartpads. This study also proves that usage ability is an important factor in using innovative products, such as smart devices.

• Advances in concrete construction
• /
• v.15 no.2
• /
• pp.85-96
• /
• 2023

The characteristics of self-compacting concrete (SCC) made with fly ash and reinforced with polyester fibers were investigated in this research. Polyester fibers of 12 mm long and 15 micrometer diameters were utilized in M40 grade SCC mixtures at five different volume fractions 0.025%, 0.05%, 0.075%, 0.1%, 0.3% as a fiber reinforcement. To understand the influence of polyester fibers on passing ability, flowability, segregate resistance the J ring, L box, V funnel, slump flow and U box tests were performed. Polyester fibers have a direct influence, with a maximum of 0.075% polyester fibers producing excellent characteristics. ANN models were constructed using the testing data as inputs to anticipate the fresh and hardened characteristics as targeted outputs. The research revealed that R² values ranging from 0.900 to 0.997 appears to be a good correlation. The performance of ANN models and regression models for predicting the new characteristics of SCC is also evaluated.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.45 no.7
• /
• pp.27-37
• /
• 2003

This study was performed to examine the flowing ability and filling ability of polypropylene fiber reinforced high performance concrete. The slump flow was decreased with increasing the polypropylene fiber content, rapidly. At the box-type filling ability, the difference of box height was increased with increasing the fiber content and the box-type passing ability was closed in fiber content 1 %. The final flowing distance of L-type was decreased with increasing the fiber content. Also, it was decreased above 0.75% of polypropylene fiber content, rapidly. The filling ability of L-type was badly showed above polypropylene fiber content 0.75%. Also, the compressive strength was decreased with increasing the fiber content, but the flexural strength was shown higher than that of the concrete without fiber. At the impact resistance, drop numbers for reaching in final fracture were increased with increasing the fiber content. Also, the drop numbers for reaching initial fracture of 1mm were increased with increasing the fiber content. At the acid resistance, the percent of original mass was decreased with increasing the fiber content.

• Journal of the Korea Concrete Institute
• /
• v.25 no.6
• /
• pp.657-665
• /
• 2013

The purpose of this study is the basic research of self-compacting concrete using Alkali-Activated Slag (AAS) binder in order to emphasize the durability of structures and facilitate casting the fresh concrete in field. The AAS binder emitted low carbon dioxide ($CO_2$) is eco friendly material of new concept because AAS products not only emit little $CO_2$ during production but also reuse the industrial by-products such as ground granulated blast-furnace slag (GGBS) of the steel mill. Until now, almost of domestic and foreign research are using Ordinary Portland Cement (OPC) for self-compacting concrete, and also, nonexistent research about AAS. The self-compacting concrete must get the performance of flowability, segregation resistance, filling and passing ability. Nine concrete mixes were prepared with the main parameter of unit amount of binder (400, 500, 600 $kg/m^3$) and 3 types of water-binder (W/B) ratio. The results of test were that fresh concretes were satisfied with flowability, segregation resistance, and filling ability of JSCE. But the passing ability was not meet the criteria of EFNARC because of higher viscosity of AAS paste than OPC. This high viscosity of AAS paste enables the manufacturing of self compacting concrete, segregation of which does not occur without the using of viscosity agent. It is necessary that the development of high fluidity AAS binders of higher strength and the study of better passing ability of AAS concrete mixes in order to use self compacting AAS concrete in field.

• Korean Journal of Human Ecology
• /
• v.17 no.1
• /
• pp.35-43
• /
• 2008

The purpose of this study is to develop evaluation tools for young children's mathematical ability based on the content standards of NCTM and to verify the suitability of the tools. The tools consist of 5 sub-tests with 90 items, including number and operation, algebra, geometry, measurement, data analysis and probability. The tool analysis was examined with 300 three-to five-years-old children and 31 math education professionals. The results of this research are as follows : First, in order of age the passing rate increased. The gap between high and low score group reveals a statistically meaningful difference. Second, the internal consistency reliability coefficient, Cronbach ${\alpha}$, is .96. Test-retest reliability is around .90. The concurrent validity correlation between this tools and Choi Hye-Jin's test(2003) is .85. The analysis of the content validity was proved appropriately by math education professionals.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.461-464
• /
• 2008

This study is compactability and Passing ability to get to know the flowing characteristic of high flowing self-compacting concrete with mixing steel fiber of various size and diameter. After flowing test, size and diameter are getting longer, flowing performance is getting lower. It meets the standard of combined high flowing self-compacting concrete of JSCE 2 grade and passing performance from ASTM C 1621. Through this study, it can be possible to be applied in site of HSCC with mixing steel fiber.

• Computers and Concrete
• /
• v.18 no.2
• /
• pp.201-214
• /
• 2016

In this paper, a multilaminate based model have been developed and presented to predict the strain hardening behavior of rock. In this multilaminate model, the stress-strain behavior of a material is obtained by integrating the mechanical response of an infinite number of predefined oriented planes passing through a material point. Essential features such as the variable deformations hypothesis and multilaminate model are discussed. The methodology to be discussed here is modeling of strains on the 13 laminates passing through a point in each loading step. Upon the presented methodology, more attention has been given to hardening in non-linear behaviour of rock in going from the peak to residual strengths. The predictions of the derived stress-strain model are compared to experimental results for marble, sandstone and dense Cambria sand. The comparisons demonstrate the ability of this model to reproduce accurately the mechanical behavior of rocks.

• Journal of the Korean School Mathematics Society
• /
• v.4 no.2
• /
• pp.1-9
• /
• 2001

Since the computer is becoming more and more indispensible tool in every fields of the modern society, it is needed and desirable to utilize the computer as a basic tool from the very early stage of the education process. Recently Maple is gaining its popularity as a comprehensive mathematical software with its power of symbolic calculations and graphics as well as its great numerical computational ability. We demonstrate the suitability of this software as a tool for the mathematical education and presents several examples of the applications of Maple. For the middle and the high school mathematics courses, we give the application examples for the quadratic functions and their graphs, statistics, the three dimensional shapes, algebraic problems. Through the examples, we confirm that mathematical education can be much more effective and simple by using Maple. If we establish computer-assisted mathematical classes, we can draw more attention and excitement from the attendants than traditional classes and eventually improve more rapidly their problem-solving ability On the other hand, the excess of the computer-aided education give to obstacle of psychological, not to be passing over the fact.