• Journal of the Korean Society for Nondestructive Testing
• /
• v.27 no.1
• /
• pp.1-7
• /
• 2007

As fiber reinforced composite materials are widely used in aircraft, space structures and robot arms, the study on non-destructive testing methods has become an important research area for improving their reliability and safety. AE (acoustic emission) can evaluate the defects by detecting the emitting strain energy when elastic waves are generated by the initiation and growth of crack, plastic deformation, fiber breakage, matrix cleavage, or delamination. In the paper, AE signals generated under uniaxial tension were measured and analyzed using the $8{\times}8$ matrix piezo electric sensor. The electronic circuit to control the transmitting distance of AE signals was designed and constructed. The optical data storage system was also designed to store the AE signal of 64channels using LED (light emitting diode) elements. From the tests, it was shown that the source location and propagation path of AE signals in composite materials could be detected effectively by the $8{\times}8$ matrix piezo electric sensor.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.10 no.3
• /
• pp.27-36
• /
• 1986

The purpose of this study was, to estimate the detergency of commercial detergent and to examine the interrelationship between detergency and detergent characteristics, detergent concentration, fiber characteristics, and Rolling-up phenomenon which is the major removal mechanism of oily soil. A mixture of oleic acid-olive oil was used as oily soil. The detergency was estimated by analysis of oleic acid on cotton ana polyester fabrics before and after washing by means of liquid scintillation counting. The Rolling-up of oily soil from PET film was observed and change of contact angle and removal time were measured. The results were as follows ; 1. In the case of soaps and powder synthetic detergents, the optimum concentrations we-re about $0.2\~0.3\%$. And detergencies of liquid synthetic detergents were considerably low, and the detergency was continually increased up with increasing concentration to $0.5\%$, which seemed to be caused by the lower pH than that of soap and powder synthetic deter-gent solutions. 2. As the effect of external or internal fiber structure; the detergency of cotton was lower than that of polyester. 3. In the observation of Rolling-up, the contact angle increased and the Rolling-up time became shorter with increasing detergent concentrations ($0.05\~0.5\%$). And it was confirmed that detergency was increased with Rolling-up effect. In addition, the study on the actual laundry condition was studied using the questionaire. From the results, about $76\%$ of households used the concentration of detergent roughly or excessively and housewives were highly concerned on the recommended dose, but grade of practice were very low.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.21 no.3
• /
• pp.269-276
• /
• 2001

Ultrasonic testing of composite materials is much more difficult than that of isotropic materials, because of the beam skew phenomenon caused by their elastic anisotropy. An established analytical method exists for elastic wave propagation in anisotropic media as a result of previous research efforts. Yet, due to the complexity of the analytical method, solution of real problems must resort to the numerical method. In this work, analytical solutions have first been obtained for the wavefield due to a point source in a unidirectional fiber-reinforced composite, which may be modeled as transversely isotropic. Then, the corresponding numerical solutions have been obtained using the mass-spring lattice model(MSLM). The two solutions have agreed well with each other. Other problems such as reflection from free boundaries and scattering from cracks have also been solved numerically, and the results have been investigated from the viewpoint of wave mechanics. The numerical model whose validity has been confirmed by this work will be of great use in simulating ultrasonic testing of composite materials.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.31 no.1
• /
• pp.31-38
• /
• 1999

Adsorption of polymeric flocculants and dry strength agents onto the surface of papermaking fibers is critical for their effective utilization since the polymeric substances not adsorbed on fibers or fines keep recirculating in the papermaking system to cause various operational difficulties and loss of raw materials. Problems associated with the unadsorbed polymeric substances generate great attention because unprecedent interests in utilization of recycled papers and papermaking system closure. In this study, to understand the effects of recycling on the adsorption propensity of cationic polyacryamide (PAM) dry strength resin onto hardwood bleached kraft pulp fibers and fines a systematic approach was followed. Never dried bleached hardwood kraft pulp was recycled in two different ways. In mode one recycling experiment never dried pulp was beaten then recycled three times by employing simple drying and disintegrating steps. In mode two recycling experiment beating of the recycled pulp was carried out after each recycling step. Adsorption of cationic PAM on fibers and fines was evaluated employing Kjeldahl nitrogen analysis method. The influence of recycling on water retention value, carboxyl content, sheet density and tensile strength of the pulp was examined. As the number of recycling increased, water retention value of the fiber was reduced due to hornification and this in turn caused a decrease in adsorption of cationic PAM. On the other hand, the carboxyl content of the recycled fibers increased because of the oxidation of fibers occurred during drying, and this caused an increase in adsorption of cationic PAM. Because of these two opposing factors the adsorption of the cationic PAM on the recycled fibers decreased and then increased slightly at third recycling step. Increase of PAM adsorption, however, did not provide did not provide and strength improvement for the recycled pulp fibers indicating greater influence of the honification on interfiber bonding.

• Korean journal of food and cookery science
• /
• v.32 no.1
• /
• pp.1-8
• /
• 2016

This study aimed to enhance the applications of dates as a food material that can be utilized and stored easily by improving the inefficient process of the traditional cooking procedure. To this end, this study investigated the physico-chemical and nutritional properties of jujube pulp powder, and compared the traditional and newly developed methods of making yakbap, yakpyon, and jujube porridge. According to the analysis of physical and chemical properties, the jujube pulp powder contained 5.4% moisture, 2.6% crude ash, 6.6% crude protein, 0.35% crude fat, and 4.7% crude fiber. The water activity was 0.95% in jujube pulp while it was 0.24% in jujube pulp powder. In addition, the jujube pulp powder had a total sugar content of 70.4% and reducing sugar content of 6.3%. The vitamin C was content was estimated to be 68.5 mg/100 g in the jujube pulp powder and the jujube pulp contained 6.2 g/100 g of dietary fiber. Major minerals were K, Mg, and Ca. After appointing jujube pulp powder (new method) to a test group and jujube pulp (traditional method) to a control group, the sensory evaluation and acceptance testing were conducted for yakbap, yakpyon, and jujube porridge. As a result, there was no significant difference in any sensory factors tested (p<0.05). It was found that making and storing jujube pulp powder by drying jujube pulp is a useful way of utilizing jujube because Yakbab, Yakpyun and jujube porridge were found to have a relatively good appearance, color, flavor, taste, texture and overall acceptance.

• BMB Reports
• /
• v.29 no.5
• /
• pp.405-410
• /
• 1996

Previous studies have shown that transforming growth factor beta ($TGF-{\beta}$) is a potent regulator of cell growth and differentiation. To study the effects of $TGF-{\beta}$ on cell morphology and cytoskeleton reorganization, we conducted a survey using Mv1Lu mink lung epithelial cells with antibodies to cytoskeletal proteins and an extracellular matrix protein. While the untreated cells showed a cuboidal shape of typical epithelia, the Mv1Lu cells displayed a drastic shape change in the presence of $TGF-{\beta}$. This alteration was most prominent when near-confluent cells were treated with $TGF-{\beta}$. Since the morphology alteration is known to be accompanied by the reorganization of cytoskeletal proteins in other cell types, we investigated the intracellular distribution of the three major cytoskeletal structures: microfilaments, microtubules, and intermediate filaments. In the microfilament system, $TGF-{\beta}$ induced new stress fiber formation, which was caused primarily by the polymerization of cytoplasmic G-actin. However, $TGF-{\beta}$ appeared not to induce any significant changes in microtubular structures and vimentin filaments as determined by indirect fluorescence microscopy. Finally we confirmed the rapid accumulation of fibronectin by immunoblot analysis and chased the protein locations by immunofluorescence microscopy.

• Composites Research
• /
• v.16 no.2
• /
• pp.9-17
• /
• 2003

We have implemented a system of falling weight impact tester in order to evaluate the impact energy absorbing characteristics and impact strength of CFRP laminate plates. The absorbed energy of T-300 orthotropic composites is higher than that of quasi-isotropic specimen over impact energy 7J, but in case of using T700 fiber, much difference does not show. Also, absorbed energy of T-300 orthotropic composites, which are composed of the same stacking number and orientation became more than that of T700 fiber specimen however there was no big difference in case of quasi-isotropic specimens. Delamination area of impacted specimens was measured with ultrasonic C-scanner to find correlation between impact energy and delamination area. Delamination area and frequency responses were evaluated between impacted and unimpacted specimens. There is a strong correlation between frequency responses and impact-induced delamination. The presence and scale of damages have been investigated based on the variations of frequency responses.

• Composites Research
• /
• v.28 no.5
• /
• pp.327-332
• /
• 2015

In this research, a parametric study was carried out to design a metal-carbon fiber reinforced plastics (CFRP) hybrid pantograph for weight reduction of high speed train (KTX). To design a light-weight and high-stiffness pantograph, some parts of the original steel upper arm was replaced by CFRPs with appropriate stacking sequences. For the parametric study, steel was replaced by aluminium considering structure stiffness and weight of hybrid upperarm of a pantograph. Finite element analysis (FEA) was performed for checking the structure stiffness with varying design parameters. Static vertical load stiffness and weight changing ratio were derived from real CX-PG pantograph model analyses. From the FEA results, the geometries of high-stiffness, light-weight pantograph have been suggested.

• Composites Research
• /
• v.27 no.6
• /
• pp.254-259
• /
• 2014

In this study, a device and pressure press process that is able to substitute autoclave process is developed. This process complements disadvantages of autoclave process which are long process-time and high production cost. The developed device provides air pressure as well as the vacuum which are greatest feature of autoclave process. The device is sealed using hydraulic pressure to keep the air pressure inside the mold. The transfer of the heat is designed to be direct. The heating and pressure charging time are decreased by reducing the interior space. Tooling cost is reduced dramatically compared to autoclave process. Spring-back phenomenon is measured and compared. The temperatures of several parts of the mold during molding are measured. The fiber volume fraction of the parts molded by autoclave process and by the developed process are compared.

• Composites Research
• /
• v.23 no.4
• /
• pp.35-43
• /
• 2010

The purpose of this paper is to develop a Hybrid Fiber-reinforced High Strength Lightweight Cementitious Composite (HFSLCC) incorporated with lightweight filler and hybrid fibers for lightness and high ductility. Optimal ingredients and mixture proportion were determined on the basis of the micromechanical analysis and the steady-state cracking theory considering the fracture characteristics of matrix and the interfacial properties between fibers and matrix. Then 4 mixture proportions were determined according to the type and amount of fibers and the experiment was performed to evaluate the mechanical performance of those. The HFSLCC showed 3% of tensile strain, 4.2MPa of ultimate tensile stress, 57MPa of compressive strength and $1,660kg/m^3$ of bulk density. The mechanical performance of HFSLCC incorporated with PVA fibers of 1.0 Vol.% and PE fibers of 0.5 Vol.% is similar to those of the HFSLCC incorporated with fibers of 2.0 Vol.%.