• Journal of the Korea Concrete Institute
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• v.29 no.4
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• pp.389-397
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• 2017

Friedel's salt is an important product of chemical adsorption between cement hydrate and chloride ions because it contains chlorine in its structure. When cement reacts with water in the presence of chloride ions, the $C_3A$ phase, and $C_4AF$ phase react with chloride to produce Friedel's salt. If chloride ions penetrate into concrete from external environments, many calcium aluminate hydrates, including AFm, can bind chloride ions. It is very important, therefore, to investigate the chloride binding isotherm of $C_3A$ phase, $C_4AF$ phase, and AFm phase to gain a better understanding of chloride binding in cementitious materials. Meanwhile, the adsorption isotherm can provide us with the fundamental information for the understanding of adsorption process. The experimental results of the isotherm can supply not only the quantitative knowledge of the cement-Friedel's salt system, but also the mechanism of adsorption and the properties of their interactions. The purpose of this study is to explore the time dependant behaviors of chloride ions adsorption with $C_3A$, $C_4AF$ and AFm phases. The chloride adsorption isotherm was depicted with Langmuir isotherm and the adsorption capacity was low in terms of the stoichiometric point of view. However, the chloride adsorption of AFm phase was depicted with Freundlich isotherm and the value was very low. Since the amount of the adsorption was governed by temperature, the affecting parameters of isotherm were expressed as a function of temperature.

• Journal of the Korea Institute of Building Construction
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• v.16 no.3
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• pp.237-245
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• 2016

Structural performance and durability of ultra high performance concrete could demonstrate optimal performance when unity was kept. Accordingly, it is necessary to involve the characteristics and quantitative surface treatment at the same time in order to retain oneness of Ultra-High-Performance Concrete(UHPC) according to construction joint occurrence. Therefore, this study derives a reasonable surface treatment method in a material's point of view through the shear adhesion performance evaluation according to the construction joints surface processing method as a part for securing the adhesion performance of the construction joints when casting UHPC. 180 MPa of required average strength was used for mix of UHPC and surface treatment method was set to totally 7 level that MN, GR-10-0, GR-20-0, GR-30-0, SH-30-5, SH-30-10. After the specimen were manufactured to a size of $150{\times}150{\times}150mm$, Direct shear test was performed to evaluate the shear adhesion strength. As a result, it was confirmed that the adhesion performance was improved when executing a surface treatment for the construction joint interface and standard of failure mode of specimen was over Type C. Also, It was considered that interface of cross section and depth of concavo-convex should be concerned.

• Journal of Broadcast Engineering
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• v.22 no.6
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• pp.713-723
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• 2017

Since the panoramic image can overcome the limitation of the viewing angle of the camera and have a wide field of view, it has been studied effectively in the fields of computer vision and stereo camera. In order to generate a panoramic image, stitching images taken by a plurality of general cameras instead of using a wide-angle camera, which is distorted, is widely used because it can reduce image distortion. The image stitching technique creates descriptors of feature points extracted from multiple images, compares the similarities of feature points, and links them together into one image. Each feature point has several hundreds of dimensions of information, and data processing time increases as more images are stitched. In particular, when a panorama is generated on the basis of an image photographed by a plurality of unspecified cameras with respect to an object, the extraction processing time of the overlapping feature points for similar images becomes longer. In this paper, we propose a preprocessing process to efficiently process stitching based on an image obtained from a number of unspecified cameras for one object or environment. In this way, the data processing time can be reduced by pre-grouping images based on camera sensor information and reducing the number of images to be stitched at one time. Later, stitching is done hierarchically to create one large panorama. Through the grouping preprocessing proposed in this paper, we confirmed that the stitching time for a large number of images is greatly reduced by experimental results.

• Journal of The Korean Association of Information Education
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• v.6 no.3
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• pp.328-337
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• 2002

Looking at multimedia education contents from a design point of view, the instructor's design model may differ from the child's understanding model due to gap of the instructor's and child's knowledge. This fact implies it impacts the effectiveness of the education contents. The learning efficiency of Korean typography in WBI for children depends on the font-family, line space, font-size, the age of user, the output device such as the monitor, and other various factors. In this paper, we measured and analyzed on readability of Korean typography in WBI for children by reading speed method. The results of experiments show that readability depends on the font-family of typography, age(grade), and sex of children. In detail, "Goolymche" has the shortest time to be read, and girl and the highest grade students of elementary school have shorter time than boy and the lower grade students. Moreover, we consider the elegance of typography in WBI for holding children's interests because they prefer "Yopseoche". We provide some CSSs in WBI for children based on the experimental results, to used in school fields.

• Korean Journal of Food Science and Technology
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• v.6 no.3
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• pp.138-146
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• 1974

The present study was undertaken to investigate the nutritive value of various defatted oil-seed flours in the diet by studying the effect of alternative diets on growing rats, to attention growth, food intake, weight of organs and the levels of total cholesterol, phospholipid and triglyceride in serum and liver tissue. Sixty male Albino rats (Splague Dowley) weighing 47-55 g were divided into five experimental groups and one control group of ten each, and were fed for 24 weeks with the respective diets. Each of five different diets was supplemented with defatted flours as dietary protein sources. Four of other diets were composed of 7.5 sesame seed, rapeseed, sunflower seed and cottonseed flour respectively, with the same amount of defatted soybean flour, while the fifth diet tested was prepared with 15% soybean flour. The results of this study were as follows. 1) It was noteworthy that the five defatted oilseed flour diets demonstrated much improvement of nutritive value. Sesame seed flour and sunflower seed flour, especially appeared to be worthwhile as human foods. 2) From the results of biochemical tests of the serum and liver lipid content of Albino rats, after feeding with the respective diets, it can be concluded that, from a nutritional point of view, the toxic effects of oilseed flours like rapeseed and cottonseed flour, which contain toxic substances, are reduced when they are mixed with soybean flour.

• Journal of Korean Society of Steel Construction
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• v.21 no.2
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• pp.165-173
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• 2009

Hanger cables in suspension bridges are constrained by the horizontal clamp. So, the accuracy of estimated tension of hange cable using existing methods based on the simple mathematical model of singel cable decreases as the length of cable decreases because of the flexural rigidity. Therefore, back analysis and system identification techniques based on the finite element model are proposed recently. In this paper, the applicability of the back analysis and system identification techniques are compared using the hanger cable of Gang-An Bridge. The experimental results show that the back analysis and system identification techniques are more reliable than the existing string theory and linear regression method in the view point of the error of natural frequencies. However, the estimation error of tension can be varied according to the accuracy of finite element model in the model based methods. Especially, the boundary condition is more affective when the length of cable is short, so it is important to identify the boundary condition through experiment if it is possible. The tension estimation method using system identification technique is more attractive because it can easily consider the boundary condition and it is not sensitive to the number of input measured natural frequencies.

• Journal of the Korea Concrete Institute
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• v.18 no.2 s.92
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• pp.283-290
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• 2006

The paper describes m experimental study on the shear strengthening of concrete beams with exposed wire rope. The strengthening method is using the mechanical bolting of wire rope tensioned on the exterior of beam section. There are two shear strengthening types. The first is closed type wrapped beam section with wire rope like as closed stirrup. The second is U type tensioned at the anchor located in the side of beam section. The main parameters of specimens are strengthening spacings of wire rope with 150, 200, and 250mm for the closed and U type respectively. The shear span ratio of specimens applied by 3-point loading is 4. The results showed that the ultimate shear strength and ductility of strengthened beams increased significantly compared with non-strengthened beams. Especially, the strengthening effect of closed type was very preferable to U type. Therefore, the shear strengthening method with wire rope is very reasonable in view of repair and rehabilitation of beams.

• Journal of the Korea Concrete Institute
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• v.13 no.6
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• pp.544-552
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• 2001

Korea is classified into low and moderate seismic zone from the view-point of seismic hazard level. Korean seismic provisions has been developed based on UBC and ATC 3-06. Thus, in calculation of design base shear according to Korean provisions response modification factor (R) is included in the formula of design base shear. The major role of this factor is to reduce the elastic design base shear whereby structures can behave in inelastic range during design level earthquake ground motions(mean return period of 475 yrs.). R factor is assigned according to material and structural systems. In this study, R factor for bearing wall system is considered. Most of the walls of apartment buildings in Korea resist gravity and seismic loads simultaneously so that this wall system can be classified into bearing wall system. Structural details of these walls are different from those used in Japan and U.S.. They are all rectangular in sectional shape rather than barbell in shape, and also have special lateral reinforcement details at the boundaries of a wall. In Korean seismic design provisions(1988), two different values(3.0 and 3.5) of R factor are assigned to the bearing wall systems according to the wall details. However, in updated seismic provisions(2000), only one value is assigned to R factor(3.0) irrespective of wall details. In this study, the design base shear values in Korean seismic design provisions(1988, 2000), ATC 3-06, UBC are compared. Also experimental study was carried out to evaluate the seismic performance of structural walls. For this purpose, five test specimens were made which have special details used in apartment bearing wall systems in Korea. Based on the results of this study, response modification factor for bearing wall system is discussed.

• Journal of Navigation and Port Research
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• v.27 no.5
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• pp.527-537
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• 2003

The characteristics of ship induced waves caused by navigation become widely different from both ship's speed and water depth condition. The ship induced waves specially generated in coastwise routes frequently give rise to call unforeseen danger for swimmers and small boats as well as shoreline erosion or sea wall destruction in coastal zones. The main concern of ship induced wave study until now is either how to reduce ship resistance or how to manoeuvre the ship safely under a constant water depth in the view point of shipbuilding engineers. Moreover, due to the trends for appearance of the high speed ships at the shallow coastal water, we are confronted with the danger of damages from those ship induced waves. Therefore, it is necessary to examine the development of ship induced waves and the influence of their deformation effects according to its propagation ray. In present study, in order to predict the development of the ship induced waves and their propagation under the conditions of complicate and variable shallow water depth with varying ship's speed, we constructed a computer model using Boussinesq equation with a fixed coordinate system and verified the model results by comparison with experimental results. Additionally, the model was applied under the variable water depth based on actual passage and we then confirmed the importance of the variable water depth consideration.

• Journal of the Korea Concrete Institute
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• v.19 no.3
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• pp.283-292
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• 2007

A research projects is currently being conducted to develop a nonlinear finite element analysis methods for predicting the structural behavior of reinforced concrete frame structures, exposed to fire. As part of this, reinforced concrete frames subjected to fire loads were analyzed using the nonlinear finite-element program DIANA. Two numerical steps are incorporated in this program. The first step carries out the nonlinear transient heat flow analysis associated with fire and the second step predicts the structural behavior of reinforced concrete frames subjected to the thermal histories predicted by first step. The complex features of structural behavior in fire conditions, such as thermal expansion, plasticity, cracking or crushing, and material properties changing with temperature are considered. A concrete material model based on nonlinear fracture mechanics to take cracking into account and plasticity models for concrete in compression and reinforcement steel were used. The material and analytical models developed in this paper are verified against the experimental data on simple reinforced concrete beams. The changes in thermal parameters are discussed from the point of view of changes of structure and chemical composition due to the high temperature exposure. Although, this study considers codes standard fire for reinforced concrete frame, any other time-temperature relationship can be easily incorporated.