• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.3
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• pp.72-82
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• 1997

In all inelastic deformations time rate effects are always present to some degree. Whether or not their exclusion has a significant influence on the prediction of the material behaviour depends upon several factors. In the study of structural components under static loading conditions at normal temperature it is accepted that time rate effects are generally not important. However metals, especially under high temperatures, exhibit simultaneously the phenomena of creep and viscoplasticity. In this study, elastoplastic and elasto-viscoplastic models include nonlinear geometrical effects were developed and several numerical examples are also included to verify the computer programming work developed here in this work. Comparisons of the calculated results, for the elasto-viscoplastic analysis of an internally pressurised thick cylinder under plane strain condition, have shown that the model yields excellent results. The results obtained from the numerical examples for an elasto-viscoplastic analysis of the Nuclear Reinforced Concrete Containment Structure(NRCCS) subjected to an incrementally applied internal pressure were summarized as follows : 1. The steady state hoop stress distribution along the shell layer of dome and dome wall junction part of NRCCS were linearly behave and the stress in interior surfaces was larger than that in exterior. 2.However in the upper part of the wall of NRCCS the steady state hoop stress in creased linearly from its inner to outer surfaces, being the exact reverse to the previous case of dome/dome-wall junction part. 3.At the lower part of wall of NRCCS, the linear change of steady state hoop stress along its wall layer began to disturb above a certain level of load increase.

• Computational Structural Engineering
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• v.10 no.4
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• pp.217-228
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• 1997

The high precision analysis by the p-version of the finite element method are fairly well established as highly efficient method for linear elastic problems, especially in the presence of stress singularity. It has been noted that the merits of the p-version are accuracy, modeling simplicity, robustness, and savings in user's and CPU time. However, little has been done to exploit their benefits in elasto-plastic analysis. In this paper, the p-version finite element model is proposed for the materially nonlinear analysis that is based on the incremental theory of plasticity using the constitutive equation for work-hardening materials, and the associated flow rule. To obtain the solution of nonlinear equation, the Newton-Raphson method and initial stiffness method, etc are used. Several numerical examples are tested with the help of the square plates with cutout, the thick-walled cylinder under internal pressure, and the circular plate with uniformly distributed load. Those results are compared with the theoretical solutions and the numerical solutions of ADINA

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.9
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• pp.1562-1570
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• 2003

The prediction of the inelastic behavior of the structure is an essential part of reliability assessment procedure, because most of the failures are induced by the inelastic deformation, such as creep and plastic deformation. During decades, there has been much progress in understanding of the inelastic behavior of the materials and a lot of inelastic constitutive equations have been developed. The complexity of these constitutive equations generally requires a stable and accurate numerical method. The radial return mapping is one of the most robust integration scheme currently used. Nonlinear kinematic hardening model of Armstrong-Fredrick type has recovery term and the direction of kinematic hardening increment is not parallel to that of plastic strain increment. In this case, The conventional radial return mapping method cannot be applied directly. In this investigation, we expanded the radial return mapping method to consider the nonlinear kinematic hardening model and implemented this integration scheme into ABAQUS by means of UMAT subroutine. The solution of the non-linear system of algebraic equations arising from time discretization with the generalized midpoint rule is determined using Newton method and bisection method. Using dynamic yield condition derived from linearization of flow rule, the integration scheme for elastoplastic and viscoplastic constitutive model was unified. Several numerical examples are considered to demonstrate the efficiency and applicability of the present method.

• Restorative Dentistry and Endodontics
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• v.48 no.1
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• pp.7.1-7.10
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• 2023

Objectives: This study aimed to evaluate the surrounding and underlying shades' effect on the color adjustment potential (CAP) of a single-shade composite used in a thin layer. Materials and Methods: Cylinder specimens (1.0 mm thick) were built with the Vittra APS Unique composite, surrounded (dual specimens) or not (simple specimens) by a control composite (shade A1, A2, or A3). Simple specimens were also built only with the control composites. Each specimen's color was measured against white and black backgrounds or the simple control specimens with a spectrophotometer (CIELAB system). The whiteness index for dentistry (WI_D) and translucency parameters (TP₀₀) were calculated for simple specimens. Differences (ΔE₀₀) in color between the simple/dual specimens and the controls were calculated. The CAP was calculated based on the ratios between data from simple and dual specimens. Results: The Vittra APS Unique composite showed higher WID and TP₀₀ values than the controls. The highest values of ΔE₀₀ were observed among simple specimens. The color measurements of Vittra APS Unique (simple or dual) against the control specimens presented the lowest color differences. Only surrounding the single-shade composite with a shaded composite barely impacted the ΔE₀₀. The highest CAP values were obtained using a shaded composite under simple or dual specimens. Conclusions: The CAP of Vittra APS Unique was strongly affected by the underlying shade, while surrounding this composite with a shaded one barely affected its color adjustment.

• Restorative Dentistry and Endodontics
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• v.24 no.2
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• pp.310-321
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• 1999

In this in vitro study, confocal laser scanning microscopic morphology of dentin-resin interface and its relationship to shear bond strength were investigated after the exposed dentin surfaces were treated with 3 different kinds of dentin adhesive systems[three-step; Scotchbond Multi-Purpose Plus(SMPP), self-priming bonding resin; Single Bond(SB), self-etching primer; Clearfil Liner Bond 2(LB2)]. 52 extracted human molar teeth without caries and/or restorations. The experimental teeth were randomly divided into three groups of seventeen teeth each. In five teeth of each group, class V cavities(depth: 1.5mm) with 900 cavosurface angles were prepared at the cementoenamel junction on buccal and lingual surfaces. Bonding resins of each dentin adhesive system were mixed with rhodamine B. Primer of SMPP was mixed with fluorescein. In group 1. the exposed dentin was conditioned with etchant, applied with above primer and bonding resin of SMPP. In group 2, with etchant and self-priming bonding agent of SB. In group 3, with self-etching primer and bonding agent of LB2. After treatment with dentin adhesive systems, composite resin were applied and photocured. The experimental teeth were cut longitudinally through the center line of restoration and grounded so that about $90{\mu}m$-thick wafers of buccolingually orientated dentin were obtained. And, $70{\sim}80{\mu}m$-thick wafers sectioned horizontally, thus presenting a dentinal tubules at 900 to the cut surface of a remaining tooth, were obtained. Primer of SMPP mixed with rhodamine B was applied to these wafers. Confocal laser scanning microscopic investigations of these wafers were done within of 24 hours after treatment. To measure shear bond strength, the remaining twelve teeth of each group were grounded horizontally below the dentinoenamel junction, so that no enamel remained. After applying dentin adhesive systems on the dentin surface, composite was applied in the shape of cylinder. The cylinder was 5mm in diameter, and 2mm in thickness. Shear bond strength was measured using Instron with a cross-head speed of 0.5mm/min. It was concluded as follows ; 1. Hybrid layer of SMPP(mean: $4.56{\mu}m$) was thicker than that of any other groups. This value was not statistically significant thicker than that of SB(mean: $3.41{\mu}m$, p>0.05), and significant thicker than that of LB2(mean: $1.56{\mu}m$, p<0.05). There was a statistical difference between SB and LB2(p<0.05). 2. Although there were variations in the length of resin tag even in a sample, and in a group, most samples in SMPP and SB showed resin tags extending above $20{\mu}m$. But samples in LB2 showed resin tags of $10{\mu}m$ at best. 3. Besides primer's infiltration into demineralized peritubular dentin and dentinal tubules, fluorophore of primer was detected in the lateral branches of dentinal tubules. 4. All groups demonstrated statistically significant differences from one another(p<0.05), with shear bond strengths given in descending order as follows: SMPP(18.3MPa), SB(16.0MPa) and LB2(12.4MPa). 5. LB2 having thinnest hybrid layer($1.56{\mu}m$) showed the lowest shear bond strength(12.4MPa).

• Tunnel and Underground Space
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• v.19 no.6
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• pp.498-506
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• 2009

The stability assessment of a concrete liner of a compressed air storage tunnel should be performed by an approach which is different from that commonly used for the liners of road tunnels, since the liner is exposed to high air pressure. In this study, the stability analysis method for the liner of compressed air storage tunnel is proposed based on the elastic and elasto-plastic solutions of the thick-walled cylinder problem. In case of elastic analysis, the yield initiation condition at the inner boundary is considered as the failure condition of the liner, while the condition which results in the extension of yielding zone to a certain depth is taken as a failure indicator of the liner in the elasto-plastic analysis taking Mohr-Coulomb criterion. The application of the proposed method revealed that the influence of the relative magnitude of boundary loads on the stability of liner is considerable. In particular, noting that the estimation of the outer boundary load may be relatively difficult, it is thought that the precise prediction of outer boundary load is very important in the analysis. Accordingly, the emphasis is put on the selection of the liner installation time, which may govern the magnitude of outer boundary load.

• Textile Coloration and Finishing
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• v.5 no.4
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• pp.29-41
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• 1993

In order to surface Hydrophobilization of Poly(ethylene terephthalate) (PET) fiber samples were treated in the atmosphere of CF$_{4}$ or $C_{2}$F$_{6}$glow discharge. The sample used in this study was PET film which is 75$\mu$m thick made by Teijin, O-Type(Japan). The cleaned samples were placed in plasma reactor made of pyrex glass cylinder, and plasma processing was carried out by glow discharge of CF$_{4}$ or $C_{2}$F$_{6}$ gas, being continuously fed by gas flow and continuously pumped out by a vacuum system. Electric power source for generate plasma state was sustained alternating current(60Hz) and voltage was sustained 600 volt. The duration of plasma treatment varied from 15 to 120 seconds except special case, the monomer gase pressure varied from 0.02 to 0.3 Torr and power range was 10 to 90 watts. The hydrophobic features of changed PET surface were evaluated by contact angle measurement and surface chemical characteristics were analyzed by ESCA. Results can be summerized as follows. 1. The most favorable setting position of substrate was the center area between the two electrodes. 2. $C_{2}$F$_{6}$ discharge current was lower than that of CF$_{4}$ when same voltage was sustained. Treated efficiency between CF$_{4}$ and $C_{2}$F$_{6}$ did not revealed significant differences under same electric power(wattage). 3. When monomer pressure is very low below 0.02 torr, as though substrate is exposed to CF$_{4}$ or $C_{2}$F$_{6}$ plasma, it tend to be hydrophilic through a little of fluorine bond and a great deal of oxidizing reaction. 4. There brought good hydrophobilization when monomer pressure was more 0.1 torr and duration of glow discharge treatment was over 45 seconds. When monomer pressure was too high, discharge current became low. Although prolong the duration, there was no more high hydrophobilization. 5. According to ESCA analysis, there were a little CF bond and a prevailing CF$_{2}$ bond in CF$_{4}$-treated substrate. There were CF$_{3}$, a little CF and a prevailing CF$_{2}$ bond in $C_{2}$F$_{6}$-treated substrate.d substrate.

• Korean Journal of Agricultural Science
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• v.9 no.1
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• pp.284-302
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• 1982

Development of protein resources as food has been a big issue especially in Southeast Asia region, and intake of protein is also insufficient in Korea. To cope with this shortage of protein resources and its improvement together with increased production of high nutritive animal protein, studies were carried out on feeding of Korean native goats. In the experiments were made absorption of carbohydrate and volatile fatty acid in miniature rumen, and absorption of amino acid in rumen as in vivo were conducted as part of studies on nutritional absorption in rumen. Those nutritional for improvement of feeding and management as described above are summarized as following. 1. According to the result of test on the nutritional absorption of native goat by means of miniature rumen method, absorption ratio of VFA measured at 0.5, 1 and 2 hours after injection of nutrition showed propionic acid 70-86%, acetic acid 74-87%, and lactic acid 76-89%. In the absorption of organic substances, ethyl alcohol of 0.5% showed 29-87% and lactic acid of 0.1M showed 12-27% of absorption ratio. 2. Result of absorption measurement in rumen from L-type free amino acid injection in the content of rumen vein showed lower rate at menthionine-free group compared to whole-egg amino acid injection in the content of rumen vein showed lower rate at methioine-free group compared to whole-egg amino acid group, and high absorption ratio was observed at methionine 3 times group and urea added group. Deficiency of methionine caused no change of the content in mucous membranes. 3. Absorption of amino acid in rumen muscular layer showed equal tendency as in the mucous membrane without exerting any influence of methionine deficiency. At the methionine3-times group, content of methionine and glutamine were increased by 14.7 and 4.4 times as compared to whole-egg amino acid group, an absorption ratio of glutamine, proline and valine were increased at urea added group. 4. In general, concentration of amino acid in rumen vein plasma was lower than in rumen mucous membrane and muscular layer. Absorption ratio of amino acid is decreased due to methionine deficiency, and tripling of methionine or urea adding caused increment of amino acid. Absorption pattern is thus varied depending on the composition of amino acid. 5. At the urea added group, content of ammonia-N, amino-N and urea were increased in rumen muscular layer. As the inside of goat's rumen was unable to clean thoroughly, investigation was made on remaining bacteria, however, variation of ammonia-N was affected by these bacterial content. 6. Variation in rumen structure by differential absorption of amino acid was observed by general microscope and fluorescent microscope. According to the result of observation in the methionine 3 times group, single cylinder epithelium of mucous membrane showed rather thin, and it was thick at urea added group though no significant differences existed among test groups in submucous membrane and muscular layer.