• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.31 no.1 s.49
• /
• pp.85-89
• /
• 2005

An aim of this study is to study the correlation between rheological properties and sedimentation of capsules in aqueous polymer solution with low viscosity. Rheological properties of aqueous polymer solutions were controlled by carbomer (C), acylate/C10-30 alkyl acylate crosspolymer (AC), and ammonium acryloyldimethyltaurate/VP copolymer (AV). Small amount of polymer C solution had the highest viscosity and yield stress of polymer AV solution was higher than that of polymer C solution in the same viscosity when the concentration of polymer AV exceeded $0.35 wt\%$. Each aqueous polymer solution was tested and the results showed that as viscosity and yield stress increased, the sedimentation ratio of capsules decreased. The viscoelasticity data also showed the same tendency in a shear stress range of 0.1 to 2.0 Pa. These results demonstrated that the rheological properties of polymer solutions had a strong correlation with the sedimentation of capsules. When polymer I and AV were used, there was a synergistic effect and the correlation between rheological properties and sedimentation of capsules was very complicated. It was assumed that the characteristics of polymer structure and interaction between polymers caused this phenomena.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.5
• /
• pp.20-26
• /
• 2019

Where hydraulic structures are to be installed over the entire width of a river or stream, usually a bed protection structure is to be installed. However, a local scour occurs in which the river bed downstream of the river protection system is eroded due to the influence of the upstream flow characteristics. This local scour is dominant in the flow and turbulence characteristics at the boundary of the flow direction and in the material of the bed materials, and may gradually become dangerous over time. Therefore, in this study, we compared the turbulence patterns in the local scour hole at the downstream of the river bed protection with the results of the analysis of the mobile bed experiment, and compared with the application of OpenFoam, a three dimensional numerical analysis model. The distribution of depth-averaged relative turbulence intensities along the flow direction was analyzed. In addition to this result, the stabilization of scour hole was compared with the bed shear stress and Shields parameter, and the results were compared by changing the initial turbulent flow conditions. From the results, it was confirmed that the maximum depth of generation of the three-stage was dominantly developed by the magnitude of depth-averaged relative turbulence intensity rather than the mean flow velocity. This result also suggests that design, construction or gate control are needed to control the depth-averaged relative turbulence intensities in order to reduce or prevent the local scour faults that may occur in the downstream part of the bed protection.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.33 no.6
• /
• pp.419-426
• /
• 2020

The structural design of the steel eccentrically braced frame (EBF) was developed and analyzed in this study through multiobjective optimization (MOO). For the optimal design, NSGA-II which is one of the genetic algorithms was utilized. The amount of structure and interfloor displacement were selected as the objective functions of the MOO. The constraints include strength ratio and rotation angle of the link, which are required by structural standards and have forms of the penalty function such that the values of the objective functions increase drastically when a condition is violated. The regulations in the code provision for the EBF system are based on the concept of capacity design, that is, only the link members are allowed to yield, whereas the remaining members are intended to withstand the member forces within their elastic ranges. However, although the pareto front obtained from MOO satisfies the regulations in the code provision, the actual nonlinear behavior shows that the plastic deformation is concentrated in the link member of a certain story, resulting in the formation of a soft story, which violates the capacity design concept in the design code. To address this problem, another constraint based on the Eurocode was added to ensure that the maximum values of the shear overstrength factors of all links did not exceed 1.25 times the minimum values. When this constraint was added, it was observed that the resulting pareto front complied with both the design regulations and capacity design concept. Ratios of the link length to beam span ranged from 10% to 14%, which was within the category of shear links. The overall design is dominated by the constraint on the link's overstrength factor ratio. Design characteristics required by the design code, such as interstory drift and member strength ratios, were conservatively compared to the allowable values.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.26 no.2
• /
• pp.43-50
• /
• 2022

Even though the structural safety is confirmed in the design stage, the structural safety is not guaranteed in the construction stage because the structural system is not completed. In addition, since the construction period is shorter than the period of use of the building after completion, it is excessive to apply the same seismic load to the construction stage as in the design stage. ASCE 37-14 presents the concept of seismic load reduction factor during construction, but does not provide a clear application method. Therefore, in this study, the seismic load reduced according to the return period was applied to the example model of a residential middle-rise RC building. The construction stage of the example model was divided into five-story units, and seismic load with the change of the return period was applied to the construction stage models to analyze the change of seismic load during construction and to check the sectional performances of structural members. By comparing the design strength ratio of the shear wall at the design stage and the construction stage, the range of seismic load magnitudes that can assure the safety during construction of a residential middle-rise RC building was analyzed in terms of the return period.

• Korean Journal of Soil Science and Fertilizer
• /
• v.37 no.5
• /
• pp.304-314
• /
• 2004

The objective of this study was to investigate the effect of organic materials (compost, straw, green manure, pig manure, seed production oil cake, and industrial by products including municipal sewage sludge, industrial sewage sludge, leather processing sludge, and alcohol fermentation processing sludge) on physical properties of soils in seven paddy and four upland fields with differential soil textures, sandy loam, loam, or clay loam, etc. The investigated physical parameters were bulk density (BD), air permeability (AP), macroporosity, hardness, shear resistance, frictional resistance, water stability aggregate (WSA), and Middleton's dispersion ratio. Except for coarse sandy loam field with weak structure, a decrease in BD and shear resistance, and an increase in macroporosity and AP in plots with applying organic materials compared to plots without applying organic materials appeared. In upland fields, the positive effect of organic materials on WSA, BD, and air permeability was higher than in paddy fields. The combined plot of NPK and compost had lower BD, hardness, and shear resistance, and higher macroporosity and WSA than plot with compost. Green manure had higher positive effect on physical properties of soils compared to other organic materials and the extent of positive effect had no significant correlation with soil organic matter content. Of industrial byproducts applied in coarse sandy loam soil under upland condition, municipal sewage sludge and pig manure compost had higher effect on increase of WSA than leather processing sludge and alcohol fermentation processing sludge. Unlike WSA, there were no significant differences between industrial byproduct types in other physical properties. in silty clay loam soil under the upland condition, straw had more positive effect on soil physical parameters than hairy vetch and pig manure. Therefore, different organic materials had differently active effect on physical parameters depending on types of soil and land use. Especially, it could be thought that well-decomposed organic materials have the advantage of an increase in organic matter content, while coarse organic materials of an increase in WSA.

• Journal of the Korean Wood Science and Technology
• /
• v.39 no.4
• /
• pp.318-325
• /
• 2011

Pitch pine (Pinus rigida Miller) retaining walls using Steel bar, of which the constructability and strength performance are good at the construction site, were manufactured and their strength properties were evaluated. The wooden retaining wall using Steel bar was piled into four stories stretcher and three stories header, which is 770 mm high, 2,890 mm length and 782 mm width. Retaining wall was made by inserting stretchers into Steel bar after making 18 mm diameter of holes at top and bottom stretcher, and then stacking other stretchers and headers which have a slit of 66 mm depth and 18 mm width. The strength properties of retaining walls were investigated by horizontal loading test, and the deformation of structure by image processing (AlCON 3D OPA-PRO system). Joint (Type-A) made with a single long stretcher and two headers, and joint (Type-B) made with two short stretchers connected with half lap joint and two headers were in the retaining wall using Steel bar. The compressive shear strength of joint was tested. Three replicates were used in each test. In horizontal loading test the strength was 1.6 times stronger in wooden retaining wall using Steel bar than in wooden retaining wall using square timber. The timber and joints were not fractured in the test. When testing compressive shear strength, the maximum load of type-A and Type-B was 130.13 kN and 130.6 kN, respectively. Constructability and strength were better in the wooden retaining wall using Steel bar than in wooden retaining wall using square timber.

• Journal of the Korean Wood Science and Technology
• /
• v.40 no.3
• /
• pp.164-176
• /
• 2012

In the present study, rapeseed flour (RSF), which is a by-product from the production of edible oil and biodiesel extracted from rapeseed, was used to develop alternative adhesives for the production of plywood panels. To examine the effects of the enzyme on the adhesive properties and formaldehyde emission of the RSF-based adhesive resins, three enzymes, such as cellulase (CEL), pectinase (PEC) and protease (ALC), were used either separately or together. As a crosslinking agent, PF prepolymers, which were prepared with 1.5, 1.8 and 2.1 mole formaldehyde and 1 mol phenol (1.8-, 2.1- and 2.4-PF), were added into the RSF hydrolyzates. The adhesive resins formulated with CEL- or CEL-PEC-RSF hydrolyzates and 1.8-F/P PF prepolymers exhibited excellent adhesive strengths and formaldehyde emission. The tensile shear strength and formaldehyde emission of the plywood panels bonded with the formulate resins were satisfied with the minimum requirement of the KS standard for ordinary plywood panels (0.6 N/$mm^2$). In addition, formaldehyde emissions of the plywood panels approached to that of E0 specified in the KS standard (0.5 mg/${\ell}$), and even had much better than those of commercial UF glue mixes. Overall, the use of RSF-based adhesive resins for the production of plywood panels might provide durable adhesive properties and an environmentally friendly substitute for petroleum-based adhesive resins. However, further researches - the increase of solid content of RSF-based adhesives for reducing press time and the microscopic observation of plywood specimen for identifying the relationship between tensile shear strength and the penetration of adhesives into wood structure - are required to commercialize the RSF-based adhesives.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2011.05a
• /
• pp.14-14
• /
• 2011

W (tungsten)-alloys will be the most promising plasma facing armor materials in highly loaded plasma interactive components of the next step fusion reactors due to its high melting point, high sputtering resistance and low deuterium/tritium retention. The bonding technology of tungsten to Cu alloy was one of the key issues. In this paper, W/CuCrZr diffusion bonding has been performed successfully by inserting pure metal interlay. The joint microstructure, interfacial elements migration and phase composition were analyzed by SEM, EDS, XRD, and the joint shear strength and micro-hardness were investigated. The mock-ups were fabricated successfully with diffusion bonding and the cladding technology respectively, and the high heat flux test and thermal fatigue test were carried out under actively cooling condition. When Ni foil was used for the bonding of tungsten to CuCrZr, two reaction layers, Ni4W and Ni(W) layer, appeared between the tungsten and Ni interlayer with the optimized condition. Even though Ni4W is hard and brittle, and the strength of the joint was oppositely increased (217 MPa) due primarily to extremely small thicknesses (2~3 ${\mu}m$). When Ti foil was selected as the interlayer, the Ti foil diffused quickly with Cu and was transformed into liquid phase at $1,000^{\circ}C$. Almost all of the liquid was extruded out of the interface zone under bonding pressure, and an extremely thin residual layer (1~2 ${\mu}m$) of the liquid phase was retained between the tungsten and CuCrZr, which shear strength exceeded 160 MPa. When Ni/Ti/Ni multiple interlayers were used for bonding of tungsten to CuCrZr, a large number of intermetallic compound ($Ni_4W/NiTi_2/NiTi/Ni_3T$) were formed for the interdiffusion among W, Ni and Ti. Therefore, the shear strength of the joint was low and just about 85 MPa. The residual stresses in the clad samples with flat, arc, rectangle and trapezoid interface were estimated by Finite Element Analysis. The simulation results show that the flat clad sample was subjected maximum residual stress at the edge of the interface, which could be cracked at the edge and propagated along the interface. As for the rectangle and trapezoid interface, the residual stresses of the interface were lower than that of the flat interface, and the interface of the arc clad sample have lowest residual stress and all of the residual stress with arc interface were divided into different grooved zones, so the probabilities of cracking and propagation were lower than other interfaces. The residual stresses of the mock-ups under high heat flux of 10 $MW/m^2$ were estimated by Finite Element Analysis. The tungsten of the flat interfaces was subjected to tensile stresses (positive $S_x$), and the CuCrZr was subjected to compressive stresses (negative $S_x$). If the interface have a little microcrack, the tungsten of joint was more liable to propagate than the CuCrZr due to the brittle of the tungsten. However, when the flat interface was substituted by arc interfaces, the periodical residual stresses in the joining region were either released or formed a stress field prohibiting the growth or nucleation of the interfacial cracks. Thermal fatigue tests were performed on the mock-ups of flat and arc interface under the heat flux of 10 $MW/m^2$ with the cooling water velocity of 10 m/s. After thermal cycle experiments, a large number of microcracks appeared at the tungsten substrate due to large radial tensile stress on the flat mock-up. The defects would largely affect the heat transfer capability and the structure reliability of the mock-up. As for the arc mock-up, even though some microcracks were found at the interface of the regions, all microcracks with arc interface were divided into different arc-grooved zones, so the propagation of microcracks is difficult.

• Journal of the Korean Wood Science and Technology
• /
• v.38 no.4
• /
• pp.323-332
• /
• 2010

Petroleum-based adhesive resins have extensively been used for the production of wood panels. However, it is necessary to develop environmentally friendly adhesive resins due to the increase of manufacturing cost and the environmental issue, such as the emission of volatile organic compounds, of the pertroleum-based adhesive resins. This study was conducted to formulate environmentally friendly adhesive resins using by rapeseed flour (RSF), which is the by-product of bio-diesel produced from rapeseed, for replacing petroleum-based adhesives with them. To formulate RSF-based adhesive resins, RSF was hydrolyzed in de-ionized water, 1% and 3% sodium hydroxide solutions. As a crosslinking agent, PF prepolymers were prepared with 1.8, 2.1 and 2.4 mol formaldehyde and 1 mol phenol (1.8-, 2.1- and 2.4-PF), and then mixed with RSF hydrolyzates to complete the formulation of RSF-based adhesive resins. The RSF-based adhesive resins were applied to fabricate 3-ply plywood panels. The solid content of RSF-based adhesive resins were ranged from 26.08% to 36.12% depending on the hydrolysis condition of RSF and PF prepolymer type with a high viscosity. The tensile shear strength and wood failure of plywood fabricated with RSF-based adhesive resins exceeded a minimum requirement of KS standard for ordinary plywood regardless of the hydrolysis condition of RSF and PF prepolymer type. Formaldehyde emissions of the plywood panels fabricated with 1.8-PF and RSF hydrolyzates were lower than that of E0 specified in the KS standard. Based on the results, RSF might be used as a raw material of environmentally friendly adhesives for the production of plywood panels, but further researches - the increase of solid content of RSF-based adhesives for reducing press time and the microscopic observation of plywood specimen for identifying the relationship between tensile shear strength and the penetration of adhesives into wood structure - are required to commercialize the RSF-based adhesives.

• The Journal of the Petrological Society of Korea
• /
• v.13 no.4
• /
• pp.179-190
• /
• 2004

Precambrian metamorphic rocks of Yeongyang-Uljin area, which is located in the eastern part of Sobaegsan Massif, Korea, are composed of Pyeonghae, Giseong, Wonnam Formations and Hada leuco granite gneisses. These show a zonal distribution of WNW-ESE trend, and are intruded by Mesozoic igneous rocks and are unconformably overlain by Mesozoic sedimentary rocks. This study clarifies the deformation history of Precambrian metamorphic rocks after the formation of gneissosity or schistosity on the basis of the geometric and kinematic features and the forming sequence of multi-deformed rock structures, and suggests that the geological structures of this area experienced at least four phases of deformation i.e. ductile shear deformation, one deformation before that, at least two deformations after that. (1) The first phase of deformation formed regional foliations and WNW-trending isoclinal folds with subhorizontal axes and steep axial planes dipping to the north. (2) The second phase of deformation occurred by dextral ductile shear deformation of top-to-the east movement, forming stretching lineations of E-W trend, S-C mylonitic structure foliations, and Z-shaped asymmetric folds. (3) The third phase deformation formed I-W trending open- or kink-type recumbent folds with subhorizontal axes and gently dipping axial planes. (4) The fourth phase deformation took place under compression of NNW-SSE direction, forming ENE-WSW trending symmetric open upright folds and asymmetric conjugate kink folds with subhorizontal axes, and conjugate faults thrusting to the both NNW and SSE with drag folds related to it. These four phases of deformation are closely connected with the orientation of regional foliation in the Yeongyang-Uljin area. 1st deformation produced regional foliation striking WNW and steeply dipping to the north, 2nd deformation locally change the strike of regional foliation into N-S direction, and 3rd and 4th deformations locally change dip-angle and dip-direction of regional foliation.