• Advances in aircraft and spacecraft science
• /
• v.5 no.4
• /
• pp.499-513
• /
• 2018

One of the major problems in glass fiber reinforced epoxy (GFRE) composite pipes is the durability under water absorption. This condition is generally recognized to cause degradations in strength and mechanical properties. Therefore, there is a need for an intelligent system for detecting the absorption rate and computing the mass of water absorption (M%) as a function of absorption time (t). The present work represents a new non-destructive evaluation (NDE) technique for detecting the water absorption rate by evaluating the dielectric properties of glass fiber and epoxy resin composite pipes subjected to internal hydrostatic pressure at room temperature. The variation in the dielectric signatures is employed to design an electrical capacitance sensor (ECS) with high sensitivity to detect such defects. ECS consists of twelve electrodes mounted on the outer surface of the pipe. Radius-electrode ratio is defined as the ratio of inner and outer radius of pipe. A finite element (FE) simulation model is developed to measure the capacitance values and node potential distribution of ECS electrodes on the basis of water absorption rate in the pipe material as a function of absorption time. The arrangements for positioning12-electrode sensor parameters such as capacitance, capacitance change and change rate of capacitance are analyzed by ANSYS and MATLAB to plot the mass of water absorption curve against absorption time (t). An analytical model based on a Fickian diffusion model is conducted to predict the saturation level of water absorption ($M_S$) from the obtained mass of water absorption curve. The FE results are in excellent agreement with the analytical results and experimental results available in the literature, thus, validating the accuracy and reliability of the proposed expert system.

• Journal of Welding and Joining
• /
• v.27 no.5
• /
• pp.74-80
• /
• 2009

The membrane of the LNG carriers consists of thin strips of INVAR(Fe-36%Ni) steel plates, and the junction between INVAR strips is fabricated by welding. Thousands of the raised edge joints, regularly spaced, are located around all the side of the tank corner near the transverse bulkhead, and TIG welding is manually made on the top of the raised edges. Since the thickness of all the laminated edge plies is extremely thin and the weld position is under a bad accessibility, highly skilled workers are required to perform welding relatively for a long welding time. An alternative scheme for the corner membrane fabrication is proposed in the study to improve the installation workability and thus productivity. The scheme replaces the welded edges with the preformed corrugation ones. A panel strip with regularly-spaced corrugations is installed at the corner instead of the individual flat strip of which edge is vertically raised to be welded with the adjacent strip. In the study, a series of the evaluation on the corrugated edge members was performed to assess the applicability to the real LNG carrier fabrication. Opening displacement at the raised edge was experimentally examined. Elastic stiffness regressed from the displacement was nearly same in both edge types. Edge displacement and local stresses were calculated under hydrostatic pressure and temperature change due to liquefied cargo. Fatigue test was performed on both corrugated and welded edge specimens consisting of two or five plies of invar strips. Fatigue strength of the corrugated specimens was not less than that of the welded specimens.

• Journal of the Korean Applied Science and Technology
• /
• v.8 no.1
• /
• pp.9-20
• /
• 1991

In the preparation of acrylic water repellent(EDLWC). quaternized 2-diethylarrunoethylmethacrylate-stearylmethacrylate copolymer (DSACC) and quaternized 1-Iaurovlbis(aminoethyl)-2-dodecylimidazoline(LDDIC) were selected as a basic resin and the improving agent such as softening effect and hydrostatic pressure of the water repellent. EDLWC was prepared by blending waxes and emulsifier for waxes with various ratio to DSACC and LDDIC. As the results of the measurement of water repellency, washable, tear strength and crease recovery to polyester-cotton(P/C) blended fabrics treated with EDLWC only or addition of textile finishing resin, the physical properties were increased. Sodium acetate was the most effective catalyst in the water repellency among the various kinds of catalyst. and the reasonable concentration of the catalyst was 1. 4 wt%. EDLWC was confirmed as durable water repellent with the results of making little difference of water repellency as ${\pm}5$ point after and before washing. The reaction mechanism between P/C blended fabrics and EDLWC in the presence of catalyst was proposed. And also, the longitudinal view of the P/C blended fabrics treated with water repellent was observed with scanning electron microscope.

• Journal of the Korean Institute of Gas
• /
• v.5 no.4 s.16
• /
• pp.49-55
• /
• 2001

This paper presents the design safety analysis of the inner tank structure, which is manufactured by 9 percent nickel steel sheets in the full containment type LNG storage tank. The FEM computed results indicate that top girder and several stiffener rings of the inner tank play an important role for controlling the deformation and stress intensity of the inner tank structure. The hydrostatic pressure due to cryogenic fluids gave more influential to the deformation of the inner tank wall compared with that of a cryogenic temperature of $-162^{\circ}C$. But, the deformation and stress of the inner tank. which is produced by the buckling loads, are very small because the external load is not applied to the top of the inner tank. This indicates the role of top girder and stiffener rings of the inner tank model is not important in full containment LNG storage tank.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.3
• /
• pp.309-316
• /
• 2011

Canoes are usually made from wood or FRP. However, today environment-friendly materials are preferred, and hulls made of FRP are prohibited in some countries. Polyethylene can be recycled and so is suitable for synthetic canoe construction. We used 3D Boat-Design to determine the hydrostatic properties of the canoe. Flow-structure coupled analysis was performed using ANSYS Workbench R12.1. The hull pressure and passenger weight were considered as canoe loading factors. The key parameters for the canoe are the design variables. The constraints are as follows: (1) The maximum stress must not exceed 50% of the polyethylene yield stress; and (2) the canoe weight must not exceed 50 kg. The optimal structural conditions were obtained by the response optimization process. The components of the canoe hull were manufactured from polyethylene pipes and joined by thermal fusion methods. Tests showed that the polyethylene canoe had better performance than existing canoes.

• Journal of the Korean Society for Precision Engineering
• /
• v.29 no.4
• /
• pp.461-468
• /
• 2012

Silo is a warehouse for storing granular materials such as grain, cement, petroleum compound and coal. When compared to other warehouses, the silo can use space efficiently. The coal silo are consists of silo, tunnel and extractor. Of these, there are not sufficient study and design data on tunnel. It depends heavily upon trial and error method by field engineers with several years of experience. Recently, silos are constructed with a large size, and tunnel becomes to be in danger of severe cracking and collapse by a huge load of coal. So it is necessary to analyze structural safety for tunnel. In this study, the problems of the tunnel are analyzed by field data, and reinforcement of structural weak area using FE analysis has been carried out to design the tunnel satisfying structural safety. From FE Analysis, the reinforced model which does not exceed the yield strength of the material has been proposed.

• Journal of Physiology & Pathology in Korean Medicine
• /
• v.27 no.4
• /
• pp.367-373
• /
• 2013

The purpose of this study was to analyze the patent application trend in the processing technology for medicinal herbs. Recently, in processing technology for medicinal herbs, experimental researches have frequently been published through papers in journals. However, the research results about the patent area were fewer than the others. We tried to analyze the patent application trend in nonthermal processing technologies for medicinal herbs by country as Korea, Japan, U.S.A. and Europe. The detailed technologies consisted of pulsed electric field, oscillatory magnetic field, intense pulsed light, ultrasonification, high hydrostatic pressure, microwave, radiation, Ohmic heating, and supercritical extraction. As a result we found that patents of nonthermal processing technologies has been growing steadily in quantity from 1980s and growing quickly since 2000s. The number of patent in Korea is larger than others as making up 70% in that whole. The number of patent in ultrasonification field was larger than others in portfolio analysis. Patent application trend in nonthermal processing technologies for ingestion occupies high share compared to other usage applications. In conclusion, patent trends of nonthermal processing technologies for medicinal herbs belong to the period in the development.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.13 no.2
• /
• pp.253-265
• /
• 1993

This paper presents a numerical method for implementing a nonlinear constitutive material model developed by Lade, into a finite element computer program. The techniques used are based on the displacement method for the solution of axial symmetric and plane strain nonlinear boundary value problems. Laboratory behaviour of Baekma river sand(#40-60) is used to illustrate the determination of the parameters and verification of the model. Computer procedure is developed to determine the material parameters for the nonlinear model from the raw laboratory test data. The model is verified by comparing its predictions with observed data used for the determination of the parameters and then with observed data not used for the determination. Three categories of tests are carried out in the back-prediction exercise; (1) A hydrostatic test including loading and unloading response, (2) Conventional triaxial drained compression tests at three different confining pressure and (3) A model strip footing test not including in the evaluation of material parameters. Pertinent observations are discussed based on the comparison of predicted response and experimental data.

• Journal of the Korean Applied Science and Technology
• /
• v.11 no.2
• /
• pp.69-74
• /
• 1994

Durable softening water repellents for nylon fiber were synthesized, using two compounds: quaternized octadecyl methacrylate-2-diethylaminoethyl methacrylate copolymer as a mother resin of water repellent and quaternized fatty carbamide for improving softness and hydrostatic pressure, of which syntheses were studied in the previous papers. They were blended with waxes and emulsifiers in a variety of ratios and synthesized into water repellent PADWC, and it was nylon taffeta treated with and without textile finishing resin. The synthesized water repellents can be used either or without resin. The optimum curing temperature was 150 to 160$^{\circ}C$ and the optimum concentration was 3 to 5wt%. In the independent and conjunct treatment, the water repellency of nylon taffeta samples have no remarkable changes between initial value and that after three times washing, so these prove that the synthesized compounds are durable water repellent. The water repellency of PADWC-3 and -4 were around 90. Also, comparison of crease recovery and tear strength after repelling treatment showed that the synthesized water repellents have a very high softening effect.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.25 no.2
• /
• pp.268-276
• /
• 1998

Dentigerous cyst is a cyst arising by a seperation of follicles from around the anatomical crown of an unerupted tooth within the jaws. The dentigerous cyst is seen during routine radiographic examination. It is detected radiographically as a sharply delineated, round or oval, unilocular, homogeneous, and radiolucent area within which there is the crown of an unerupted tooth. The histological appearance of the dentigerous cyst is usually attached to the tooth at the cementoenamel junction and the sac lined by a thin, regular. stratified squamous epithelium. The dentigerous cyst can be treated by two surgical procedures: enucleation or marsupialization. The size and location of the lesion usually dictates the surgical procedures. The marsupialization consists of the removal of only a portion of the wall of the cyst to make the remaining cystic lining continous with the oral mucosa. The cyst, deprived of its supporting hydrostatic pressure, gradually shrinks until it is obliterated. The marsupialization is the best way to conserve the tooth affected by a dentigerous cyst and to permit its eruption. especially in a young person. Main advantages of the marsupialization are its relative simplicity and its conservation with respect to adjacent important structures. In marsupialization technique, a plugger can be constructed, if necessary, to maintain the opening and prevent food debris from entering the cystic cavity. However, the disadvantage is the potentiality of leaving pathologic tissues. Therefore frequent recall appointments are advisable.