• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.873-876
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• 2000

Characteristics of piezoelectric thick films prepared by screen printing method were investigated. The piezoelectric thick films were printed using Pb(Mg,Nb)O$_3$-Pb(Zr,Ti)O$_3$system. The lower electrodes were coated with various thickness of Ag-Pd by screen printing to investigate the effect as a diffusion barrier and deposited with Pt by sputtering on Ag-Pd. The ceramic paste was prepared by mixing powder and binder with various ratios using three roll miller. The fabricated thick films were burned out at 650$^{\circ}C$ and sintered at 950$^{\circ}C$ in the O$_2$condition for each 20, 60min after printing with 350mesh screen. The thickness of piezoelectric thick film was 15∼20 $\mu\textrm{m}$ and the Ag-Pd electrode acted as a diffusion barrier above 3 $\mu\textrm{m}$ thickness. When the lower electrode Ag-Pd was 6 $\mu\textrm{m}$ and the piezoelectric thick films were sintered by 2nd step (650$^{\circ}C$/20min and 950$^{\circ}C$/1h) using paste mixed Pb(Mg,Nb)O$_3$-Pb(Zr,Ti)O$_3$$.$ MnO$_2$+ Bi$_2$O$_3$. V$_2$O$\_$5/ and binder in the ratio of 70:30, the remnant polarization of thick film was 9.1 ${\mu}$C /cm$^2$.

• Structural Engineering and Mechanics
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• v.86 no.4
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• pp.519-533
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• 2023

This work focuses on the dynamic analysis of thermal barrier coated straight and curved turbine blades modelled as functionally graded sandwich panel under thermal environment. The pre- twisted straight/curved blade model is considered to be fixed to the hub and, the complete assembly of the hub and blade are assumed to be rotating. The functionally graded sandwich composite blade is comprised of functionally graded face-sheet material and metal alloy core. The constituents' material properties are assumed to be temperature-dependent, however, the overall properties are evaluated using Voigt's micromechanical scheme in conjunction with the modified power-law functions. The blade model kinematics is based on the equivalent single-layer shear deformation theory. The equations of motion are derived using the extended Hamilton's principle by including the effect of centrifugal forces, and further solved via 2D- isoparametric finite element approximations. The mesh refinement and validation tests are performed to illustrate the stability and accurateness of the present model. In addition, frequency characteristics of the pre-twisted rotating sandwich blades are computed under thermal environment at various sets of parametric conditions such as twist angles, thickness ratios, aspect ratios, layer thickness ratios, volume fractions, rotational velocity and blade curvatures which can be further useful for designing the blade type structures under turbine operating conditions.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.5
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• pp.523-533
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• 2015

A reactor containment acts as a final barrier to prevent leakage of radioactive material due to the possible reactor accidents into external environment. Because of the functional importance of the containment building, the SIT(Structural Integrity Test) for containments shall be performed to evaluate the structural acceptability and demonstrate the quality of construction. An initial numerical analysis was performed to simulate the results obtained from the SIT for a prestressed concrete(PSC) structure. But the analysis results by the initial model expected smaller displacements than the measured ones by 30% at some locations. Accordingly, the research and development to improve the initial model to corelate the measured results of the SIT more properly have been performed. In this paper, the effects of the loss of concrete due to duct for tendons and the contact of duct and tendons in un-bonded tendon system are mainly evaluated based on the preliminary analysis results. In addition, the importances of the proper definition of mesh connectivity among structural elements of concrete, liner plates, rebars and tendons are discussed.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.26 no.3
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• pp.244-253
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• 1990

For the purpose of the investigation on the selective action of trawl net, a series of fishing experiments carryed out in M. S. Pusan 402 during the years of 1986~1987, by using a set of trawl net with a few pocket nets in each part of the bagnet. The author analyzed these experimental data and derived the following results. 1. 58 species of aquatic animals were caught in totally 43 times of trawl operation and 33 species of them did not escape at all through the barrier of netting in the bagnet. 2. Sardinops melanosticta, Harengula zunasi, Thrisa kamalensis, Englausis japonicus, little size of Tracurus japonicus, Sphyraena pinguis, Trichirus lepturus, and Psenopsis anomala escaped easily through the barrier of netting after being caught inside of the codend. Especially, Englusis japonicus escaped well not only through the netting of the codend but also through the netting of the square and the baiting. 3. In the case of mesh size of 60mm in the codend, Pampus argentus, Doderleinia bercoides and Tracurus japonicus were caught all in the size of less than 10cm.

• Journal of computational fluids engineering
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• v.21 no.4
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• pp.61-70
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• 2016

Dong-tan Station, shared by high-speed railway and urban express railway, is a very complicated underground station having 6 tracks together with barrier and shafts between them, therefore it seems very hard to investigate the aerodynamic effects including the pressure variation and train gust in the station when a high-speed train runs through it. In this study, the aerodynamic effects on the structures and platform passengers when a high-speed train runs through an underground station have been studied using Computational Fluid Dynamics. STAR-CCM+ has been employed for numerical simulation based on Navier-Stokes equation and 2-equation turbulence model and moving mesh scheme supported by STAR-CCM+ has also been used to represent the relative motion between a train and station. Based on the simulation results, the unsteady flow fields in the underground station induced by the high-speed train have been analyzed and the pressures on the PSDs and pressure variation at the platform have quantitatively assessed.

• Journal of Pharmaceutical Investigation
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• v.32 no.2
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• pp.103-106
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• 2002

A method that describes the determination of the in vitro release of ketoprofen from gels was suggested. The experimental system of the method consists of a Franz diffusion cell, which contains a pH 7.4 phosphate buffer as a receptor medium, and a $70\;{\mu}m$ mesh woven nylon membrane as a diffusion barrier. Under the given condition of the system, the diffusion of ketoprofen across the membrane was rapid enough that the apparent release profile of ketoprofen obtained from the present method could represent the release of the drug from gel preparations. The release of ketoprofen in the present method was reproducible, and the rate increased in proportion to the concentration of ketoprofen in the gel. These suggest that the present method is applicable to the quality evaluation of gel preparations containing ketoprofen.

• Journal of Periodontal and Implant Science
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• v.25 no.2
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• pp.192-209
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• 1995

The purpose of this study was to evaluate drug-loaded biodegradable membranes for guided tissue regeneration(GTR). The membranes were made by coating mesh of polyglycolic acid(PGA) with polylactic acid(PLA) containing 10% flurbiprofen or tetracycline. The thickness of membrane was $150{\pm}30{\mu}m$, and the pore size of surface was about $8{\mu}m$ in diameter. The release of drugs from the membrane was measured in vitro. Cytotoxity test for the membrane was performed by gingival fibroblast cell culture, and the tissue response was observed after implant of membrane into the dorsal skin of the rat for 8 wks. Ability to guided tissue regeneration of membranes were tested by measuring new bone in the calvarial defects(5mm in diameter) of the rat for 5 weeks. The amount of flurbiprofen and tetracycline released from membrane were about 30-60% during 7 days. Minimal cytotoxity was observed in the membrane except 20% drug containing membrane. In histologic finding of rat dorsal skin, many inflammatory cells were observed around e-PTFE, polyglactin 910 and PLAPGA membrane after 1 or 2 weeks. PLA-PGA membrane was perforated by connective tissue after 4 or 6 weeks, and divided as a segment at 8 weeks. In bone regeneration guiding potential test, tetracycline loaded membrane was most effective (p

• Elastomers and Composites
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• v.44 no.4
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• pp.384-390
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• 2009

Roll-to-roll forming process is one of important metal processing technology because the process is simple and economical. These days, with these merits, roll-to-roll forming process is tried to be employed in manufacturing the circuit board, barrier ribs and solar cell plate. The solar cell plate may have millions of patterns, and the analysis of forming considering all the patterns is impossible due to the computational costs. In this study, analyses are carried out for various numbers of patterns and the results are compared. It is shown that the analyses results with four row patterns and twelve row patterns are same. So, it is considered that the analysis can be carried out for only four rows of pattern for the design of incremental roll-to-roll forming process. Also formability is analysed for various number of mesh, protrusion shapes and forming temperature.

• Korean Journal of Ecology and Environment
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• v.49 no.3
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• pp.187-196
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• 2016

This study was performed to improve the foaming generated in the effluent of wastewater treatment plant from March 2015 to July 2016. The main cause of foaming was air entrainment by an impinging jet and the internal accumulation by the diffusion barrier. Particularly, the foam growth was most active when there is low tide and larger discharge. To solve this problem, we experimented after installing fine mesh screen and the artificial channel device with underwater discharging outlet in the treated wastewater discharge channel and the outlet, respectively. As a result, the effects of foam reduction by devices ranged 85.0~92.0% and 70.7~85.6%, respectively. In addition, the foam and the noise were easily solved, first of all look to contribute to the prevention of complaints. Our device studies were applied to a single wastewater treatment plant. However, it is considered to be able to apply in other similar cases of domestic sewage treatment plants.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.6
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• pp.804-811
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• 2010

The lower portion of sloping paddy fields normally contains excessive moisture and the higher water table caused by the inflow of ground water from the upper part of the field resulting in non-uniform water content distribution. Four drainage methods namely Open Ditch, Vinyl Barrier, Pipe Drainage and Tube Bundle for multiple land use were installed within 1-m position from the lower edge of the upper embankment of sloping alluvial paddy fields. Knowledge of the spatial variability of soil water properties is of primary importance for management of agricultural lands. This study was conducted to evaluate the effect of drainage in the soil on spatial variability of soil water content using the geostatistical analysis. The soil water content was collected by a TDR (Time Domain Reflectometry) sensor after the installation of subsurface drainage on regular square grid of 80 m at 20 m paddy field located at Oesan-ri, Buk-myeon, Changwon-si in alluvial slopping paddy fields ($35^{\circ}22^{\prime}$ N, $128^{\circ}35^{\prime}$). In order to obtain the most accurate field information, the sampling grid was divided 3 m by 3 m unit mesh by four drainage types. The results showed that spatial variance of soil water content by subsurface drainage was reduced, though yield of soybean showed the same trends. Value of "sill" of soil water content with semivariogram was 9.7 in Pipe Drainage, 86.2 in Open Ditch, and 66.8 in Vinyl Barrier and 15.7 in Tube Bundle.