• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2000.05a
• /
• pp.41-45
• /
• 2000

Geotube is made of permeable but soil-tight geotextile, hydraulically filled with soil include dredged sand and mud, which has been successfully applied in hydraulic and coastal engineering projects. Ceotube method is getting popular and being used a lot in many countries of the world because of the simplicity of the placement and construction, cost effectiveness and minimum impact on the environment, and enable to store & isolate contaminated materials as obtained by harbor dredging. Laboratory tests and field construction were performed to determine the design methodology and construction procedures. From the results of laboratory and field construction, the retention ratio of solid particle is a minimum 86%. The minimum permeability and the tensile strength of geotextile are $\alpha$ x 10$^{-4}$ cm/sec and 20t/m, respectively Also, based on the environmental test results, it can be concluded that this method does meet the Korean EPA standards.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.37 no.4 s.112
• /
• pp.8-17
• /
• 2005

WCT (Wet compaction test) is a new fiber evaluation method developed recently by Seo and its test results can be used as a predictor for pulp quality and its paper property Bleached chemical pulps (SwBKP, HwBKP), recycled pulp (OCC), and mechanical pulp (BCTMP) were used for the furnishes to be tested by WCT We compared the WCT results to conventional fiber evaluation tests such as WRV (Water Retention Value), free ness, and fiber length in this study, and found that WCT always gave better regression coefficients in relation to pulp quality (drainage), and paper properties (density, tensile, tear, and burst strength). WCT may be used on-line in papermachine.

• Journal of Biomedical Engineering Research
• /
• v.17 no.3
• /
• pp.355-364
• /
• 1996

Construction of the stable monolayer of endothelial cells onto physicochemically modified polymeric surFace is one of the appropriate method to develop the small caliber vascular graft with the long-term patency. In this study, we constructed the monolayer of endothelial cells on the fibronectin rind the extracellular matrix-coated polyurethane surface derived from human fibroblast cells. To elucidate the adhesion strength of endothelial cells on the extracellular matrix-coated polyurethane, a laminar flow chamber apparatus was developed to exposure the shear stress on the apical membrane of ondothelial cells. Endothelial cells show the strongest adhesion after two days of seeding onto the fibronectin-coated polyurethane surface, whereas endothelial cells on the extracellular matrix derived from the human flbroblast cells show the minimal doubling time of cellular growth.

• Journal of Industrial Technology
• /
• v.22 no.A
• /
• pp.177-184
• /
• 2002

Reinforced concrete(R/C) is commonly used to structures because they have many merits that compressive strength, economy and so on. However, reinforced concrete has a crack at the tensile section which is due to the relatively lower tensile strength than its compressive strength Latex modified concrete(LMC) has higher tensile and flexural strength than the ordinary portland cement, due to the interconnections of hydrated cement and aggregates by a film of latex particles. The purpose of this study was to investigate the flexural behavior of reinforced concrete beam with latex modified concrete, having the main experimental variables such as concrete types(ordinary portland cement concrete, latex modified concrete), latex contents(0%, 15%), flexural steel ratios(0.012, 0.0235), and with/without shear reinforcement. The beam of LMC showed considerably higher initial cracking loads and ductility than that of OPC, but, similar to ultimate strength and deflection. This might be attributed to the interlocking of hydrated cement and aggregates by a film of latex particles, water retention due to hydrophobic, and colloidal properties of the latexes resulting in reduced water evaporation. The beam with latex modified concrete could be adopted at field for controlling and reducing the tensile crack due to its higher tensile strength.

• Computers and Concrete
• /
• v.4 no.3
• /
• pp.187-206
• /
• 2007

A rational three-dimensional nonlinear finite element model is described and implemented for evaluating the behavior of high strength concrete slabs under transverse load. The concrete was idealized by using twenty-nodded isoparametric brick elements with embedded reinforcements. The concrete material modeling allows for normal (NSC) and high strength concrete (HSC), which was calibrated based on experimental data. The behavior of concrete in compression is simulated by an elastoplastic work-hardening model, and in tension a suitable post-cracking model based on tension stiffening and shear retention models are employed. The nonlinear equations have been solved using the incremental iterative technique based on the modified Newton-Raphson method. The FE formulation and material modeling is implemented into a finite element code in order to carry out the numerical study and to predict the behavior up to ultimate conditions of various slabs under transverse loads. The validity of the theoretical formulations and the program used was verified through comparison with available experimental data, and the agreement has proven to be very good. A parametric study has been also carried out to investigate the influence of different material and geometric properties on the behavior of HSC slabs. Influencing factors, such as concrete strength, steel ratio, aspect ratio, and support conditions on the load-deflection characteristics, concrete and steel stresses and strains were investigated.

• Journal of the Korea Furniture Society
• /
• v.10 no.2
• /
• pp.1-8
• /
• 1999

The use of structural wood based panels like plywood, OSB in many applications involves the use of nails, and data on the performance of panel-nail connection are needed for design and comparative purpose. This study was carried out to develop basic information on nail performance(withdrawal, embedding, nailhead push through) with water absorption in plywood and OSB. In withdrawal resistance test, initial stiffness of plywood performed better than OSB in 24hr soaked condition. The soaked condition reduced average nail withdrawal resistance value about 46% (12d mail), 53%(8d nail) in OSB, 17%(12d mail), 24%(8d mail) in plywood. The nail embedding strength of plywood also performed better than that of OSB and retention value(wet strength/dry strength) yielded similar in each nail types. The nail head push through capacity of OSB was higher than that of plywood in dry condition, but equal or lower in soaked condition. Therefore, critical consideration about structural panels is required in moist applications. The average values of nail withdrawal, nail embedding strength and nail head push through resistance of tested materials meet the minimum requirement of various specification and standards.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.6 no.4
• /
• pp.558-563
• /
• 1996

Fracture strength of $Si_{3}N_{4}/20$ vol% SiC nanocomposites with fifferent sintering additives was measured. Strength of nanocomposites with 6 wt% $Y_{2}O_{3}$ and 2 wt% $Al_{2}O_{3}$ as sintering additives was higher at room temperature but significant strength degradation at elevated temperature was occured due to the softening of grain boundary phase. Fracture strength of 8 wt% $Y_{2}O_{3}$ doped sample was higher than that of $Al_{2}O_{3}$ added sample at $1400^{\circ}C$. The retention of high temperature strength in 8 wt% $Y_{2}O_{3}$ doped sample can be attributed to high softening temperature and crystallization of grain boundary glassy phase.

• Journal of the Korean Society for Precision Engineering
• /
• v.10 no.4
• /
• pp.152-162
• /
• 1993

The purpose of this study is to investigate problems of residual bending strength and the impact damage experimentally when CFRP composite laminates are subjected to Foreign object damage. The specimens composed of four types of CR/EPOXY and a CF/PEEK composite laminates which involved difference of fiber stracking orientation and matrics. The result were summariged as follows : 1) It is found that both orthotropic and guasi-isotropic composite laminates are increasimg lineally between impact energy and damage delamination area. 2) Delamination devel- opment energy(mm$^{2}$J) OF cf/epoxy composite aminates is less than that of CF/PEEK. 3) When impact energy is applied to specimens within 3J, the residual strength of orthotropic is greater than guasi-isotropic composite laminates. On the other hand, it is predicted that residual bending strength of orthotropic composite laminates is less than that of quasi-isotropic when impact energy is more thaen 3J. 4) It is found in CF/PEEK that for the impact side compression, residual of bending strength versus impact energy is almost constant, while in case of impact side tension, residual bending strength is decreased rapidly near 1.2J. of impact energy due to the effect of delamination buckling.

• Journal of the Korean Home Economics Association
• /
• v.45 no.10
• /
• pp.73-81
• /
• 2007

The purpose of this study was to increase the ultraviolet-light (UV)-cut ability of cellulose fabrics (cotton, ramie, and rayon) dyed with safflower yellow colorants. For this purpose, samples treated with UV-cut agent and tannic-acid were compared with the untreated samples after UV exposure in terms of K/S value, color changes(${\Delta}E$), SEM, and strength retention. The K/S value rapidly decreased after 28 days exposure, whereas the K/S value of the samples treated with both UV-cut agent and tannic-acid decreased to less than that of the untreated samples. In color changes, $L^*$ increased while $a^*$ and $b^*$ decreased, indicating less red and yellow character in color. This induced a change in the hue, value and chroma values. However the color change(${\Delta}E$) of the samples treated with both UV-cut agent and tannic-acid was less than that of the untreated samples. Scanning electron microscopy (SEM) pictures showed a severe degradation by exposure in all samples. Tensile strength rapidly decreased after 28 days for cotton and rayon, and after 21 days for ramie. However, the strength retention of the samples treated with UV-cut agent and tannic-acid was higher than that of the untreated samples.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
• /
• 2006.06a
• /
• pp.85-90
• /
• 2006

Increasing the filler content of sheet improves the optical properties and printability of paper and provides an opportunity for saving production cost through fiber replacement with relatively low-priced filler. But increasing the filler content tends to decrease the strength of paper and filler retention. It also tends to deteriorate drainage on the paper machine. To overcome these problems, preflocculation technology of fillers may be employed. Many research efforts have been made on the properties of preflocculated filler, namely prefloc, whose size and size distribution were influenced by polymer type and shear level. But there is much to be investigated about the effect of the prefloc characteristics on the physical properties of paper. To evaluate the effect cationic polymers on the size and size distribution of preflocculated GCC and their shear stability, cationic PAM and cationic starch were used. The influence of the preflocculation on filler retention and its surface distribution, and the changes of physical and optical properties of handsheets affected by the characteristics of preflocs were examined. Filler distribution on sheet surface was also analyzed by EPMA. Results showed that cationic PAM formed large preflocs at low dosage. Cationic starch was required to add 15 times as much as cationic PAM to obtain the preflocs with similar size. But preflocs formed with cationic starch was superior in shear stability to those formed with cationic PAM. Filler preflocculation technology could provide an opportunity of increasing filler content significantly without loss in tensile strength. And increased filler contents could compensate brightness loss which often accompanies filler preflocculation. When excessively large preflocs were used, however, brightness loss rather than the improvement in tensile strength was predominant. Therefore it is of great importance to produce preflocs with proper size and shear stability for maximizing the improvement of physical properties of papers.