• Structural Engineering and Mechanics
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• v.22 no.1
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• pp.17-32
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• 2006

The application of cellular materials in load-carrying and security-relevant structures requires the exact prediction of their mechanical behavior, which necessitates the development of robust simulation models and techniques based on appropriate experimental procedures. The determination of the yield surface requires experiments under multi-axial stress states because the yield behavior is sensitive to the hydrostatic stress and simple uniaxial tests aim only to determine one single point of the yield surface. Therefore, an experimental technique based on a uniaxial strain test for the description of the influence of the hydrostatic stress on the yield condition in the elastic-plastic transition zone at small strains is proposed and numerically investigated. Furthermore, this experimental technique enables the determination of a second elastic constant, e.g., Poisson's ratio.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3778-3787
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• 2022

The stress-assisted oxidation behaviour of Inconel 52 M/316 austenitic stainless-steel (SS) dissimilar weld joints (DMWJ) in a simulated pressurised water reactor environment was investigated. A corrosion galvanic couple formed between the Inconel 52 M and 316 SS due to differences in their nonferrous metal content. The electric field from the corrosion couple attracted metal cations (e.g. Fe²⁺, Cr³⁺) to the Inconel 52 M that were deposited as FeCr₂O₄. An additional corrosion galvanic couple was generated due to variations in the plastic deformation of the DMWJ. The superposition of electric fields from the different couples resulted in ridge-like oxide depositions in the fusion zone.

• Korean Journal of Soil Science and Fertilizer
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• v.25 no.2
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• pp.127-132
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• 1992

This experiment was conducted to find out the useful data for upland crop cultivation in the newly reclaimed tidal land. Poseung silty clay loam soil was selected, and cotton(Mogpo VII) and tall fescue were cultivated under different drainage systems and soil ameliorator applications. Soil hardness and bulk density were decreased by subsurface drainage and plastic film installed at 40cm depth of the soil. Red earth application was also effective to loosen the soil, but zeolite and gypsum made the subsoil compact. Water content of the soil was high in surface drain than that of subsurface drain or plastic film curtain plot during dry season. The water content was in order of plastic film curtain, surface drain and subsurface drain. Electrical conductivity(EC) was decreased to lower than 0.4 Simens $meter^{-1}$ ($SM^{-1}$) in the subsurface drain during rainy season, and the EC of subsurface drain was maintained a quater to an half of surface drain. The yield of cotton and tall fescue were high in order of subsurface drain, plastic film curtain and surface drain plot. The yields of cotton were increased to 36-73 % by ameliorator application, and the red earth application was more effective for tall fescue growth compare to gypsum and zeolite.

• Korean Journal of Soil Science and Fertilizer
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• v.38 no.6
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• pp.340-344
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• 2005

Salinity problems are caused from the accumulation of soluble salts in the root zone. These excess salts reduce plant growth and vigor by altering water uptake and causing ion-specific toxicities or imbalances. In this investigation, green pepper cultivation technique using mixture bed of soil and rice hull and surface drop fertigation system was examined to prolong the productivity of salt-affected plastic film house soils. Green pepper growth was better in the mixture bed of soil and rice hull comparing to the conventional soil cultivation. Especially root growth was much better and the root had more thin root system in the mixture bed of soil and rice hull. The better growth of root may be due to the better physical conditions and lower EC in the mixture bed of soil and rice hull where nutrient supply was well-managed with fertigation system. In the cultivation with mixture bed of soil and rice hull, fruit yield of green pepper was significantly higher; increased by 43% in comparison to the conventional soil cultivation. Pepper cultivation technique using mixture bed of soil and rice hull and surface drop fertigation system is expected to be a useful method for maintaining and prolonging the productivity of salt-affected plastic film house soils.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.11 no.1
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• pp.130-152
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• 1989

The purpose of this study was to observe the effect of intermaxillary fixation on the chondrocytes of the mandibular condyle under the light and the electron microscope. For this study, twenty rabbits were placed in maxillomandibular fixation, and two were used as a control group. The experimental group was subdivided into 3, 7, 14, 21 and 28 day group. After the experimental period of 3, 7, 14, 21 and 28 days, the animals were sacrificed with a vascular perfusion of 2.5% glutaraldehyde. The condylar processes were exenterated, and decalcified in 0.1M EDTA with 2.5% glutaraldehyde solution for two weeks. The specimens were rinsed with phosphate buffer solution and the post-fixation was carried out with 2% osmium tetroxide at $4^{\circ}C$ for two hours. Thereafter the specimens were dehydrated in alcohol series, cleared with propylene oxide and embedded in Epon 812 resin. Thin sections and ultra-thin sections were made, and the cellular structures of the condylar cartilages were observed with light and electron microscope. The results were as follows: 1. In the intermaxillary fixation group, the cartilaginous tissues of mandibular condyles showed a marked decrease in the thickness compared to the control group. 2. A remarkable change was noticed in the proliferating and the hypertrophic zone of the condylar cartilages in the experimental group. 3. An atrophic change of the condylar cartilage was appeared in the 3 day experimental group and degenerative change was observed in the 7 day experimental group, and recovery was seen in thereafter 14 day experimental group. 4. Calcification, degeneration and resorption of condylar cartilage were recognizable, and the cellular zone of the condylar cartilage was appeared indistinctly in 3 day and 7 day experimental group. The chondroblasts, however, were differentiated into chondrocytes and resumed mitosis, and then the cellular zones of the condylar cartilage were reorganized from the 14 day experimental group under the findings of light microscope. 5. Under the findings of electron microscope, atrophic changes and decrease in number of intracellular organelles, degenerative changes of cytoplasm, and pyknosis of nuclei were observed in early stage, however, a gradual regeneration and reorganization of the intracellular organelles were observed from 14 day experimental group.

• Magazine of the Korea Concrete Institute
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• v.6 no.1
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• pp.120-130
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• 1994

The purpose of this study is to propose the analytical model for the hysteretic behavior of Reinforced Concrete bearn-column joints under various loading history. Discrete line elernents , YVith inelastic rotational spring was adopted to consider the movement of plastic hinging zone influenced by the details of longitudinal reinforcements. Also hysteretic model was constructed by excluding such variables which can not be utilized in dynamic analysis of Reinforced Concrete. structure that it will be adoptable in two-dimensional inelastic frame ardysis with 6-DOF. From the analysis of previous test results, it was found that stiffness deterioration caused by inelastic hysteretic loadings can be predicted by the functron of basic pinching coefficients, ductility ratio.and yield strength ratio of members. Strength degradation coefficients were newly proposed to explain the difference of inelastic behavior of members caused by spacing ratio of transverse steel and sectlon aspect ratio. The energy dissipation capacities calculated using the analytical model proposed in thls paper show a good agreements w~lh test results by an error of 10~20%.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.33 no.4
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• pp.368-372
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• 2011

Progressive transformation of germinal centers (PTGC) is mostly a disease of young adults and it presents as unexplained, asymptomatic, localized or generalized lymphadenopathy that is usually persistent or recurrent over a period of many years. PTGCs are larger than regular germinal centers and they contain a variable proportion of small mantle zone lymphocytes and so they become progressively transformed and they may result in the loss of clear demarcation between them and the mantle zone. PTGC may resemble the nodules of nodular lymphocyte predominant Hodgkin's disease (NLPHD) and it may be mistaken for NLPHD. Histological and immunohistochemical studies are helpful in differentiating these diseases. Because of the relatively frequent recurrences of PTGC, follow-up and repeat biopsy are indicated. Although PTGC is not considered to be a premalignant condition, PTGC may occur prior to, concurrent with or following NLPHD. This emphasizes the need for ongoing follow-up and repeat biopsy. Although PTGC is reported in 3.5% to 10% of the cases of chronic nonspecific lymphadenopathy, oral & maxillofacial surgeons are not widely aware of this condition and its clinical implications. Herein, we present a case of PTGC. A 24-year-old male without any history of immunodeficiency or autoimmune disease was admitted to the Department of Oral & Maxillofacial surgery at Ulsan University Hospital for evaluation of a right submandibular swelling. He had another mass on the right thigh that was noticed about 1 year ago. The submandibular lesion was completely resected and biopsied. The histological findings and immunohistochemical stains (CD3, CD15, CD20, CD30, CD57, BCL-2, EMA) were consistent with PTGC. He was followed up without any other complaints for 9 months.

• The Journal of Engineering Geology
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• v.23 no.3
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• pp.283-292
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• 2013

A calcareous rock slope failed during excavation of the slope for construction of a tunnel entrance. The slope is located at the construction site for widening highway in Yeongwol, Korea. Field surveys, laboratory tests, and numerical analyses were performed to determine the reason for the slope failure. The numerical analysis revealed that the safety factor of the slope before construction of the entrance was less than 1, and that this decreased after construction. After construction of the entrance, the sliding zone of the slope increased and slope stability decreased because the shear strain and plastic zone in the slope over the tunnel entrance showed an increase relative to the lower part of the slope. To enhance the stability of the slope for construction of the tunnel entrance, countermeasures such as rock bolts, rock anchors, and FRP (Fiber glass Reinforced Plastic) grouting were adopted in light of the field conditions. Serial field monitoring performed to confirm the reinforcing effects of the adopted countermeasures revealed a small amount of horizontal deformation of the slope soils, most of the elastic deformation that can regain its former value. In addition, the axial forces of the rock bolt and anchor were more strongly affected by slope excavation during construction of the tunnel entrance than by tunnel excavation or the rainy season, and the axial forces tended to converge after excavation of the tunnel. Therefore, we can confirm that the slope is currently safe.

• Journal of the Korean GEO-environmental Society
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• v.6 no.2
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• pp.5-14
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• 2005

In the present study, the liquefaction potential in the area of the Incheon international airport was assessed by applying the data of both standard penetration tests and laboratory tests to the modified Seed & Idriss method. The analysis was performed against the non-plastic silty soil layer and silty sand soil layer existing within the depth of 20m and under the ground water level, having the standard penetration value(N) of below 20. Also, each set of data was mapped using the GIS(Geographic Information System) and the safety factor against the liquefaction potential ($FS_{liquefaction}$) was obtained by overlapping those layers. Throughout the analysis, it was found that there exists a potential hazard zone for the liquefaction, showing partially that the safety factor against the liquefaction potential is 1.0 to 1.5 below the standard safety factor criterion. It is further thought to be necessary that the liquefaction potential for the corresponding hazard zone be additionally assessed in detail.

• Tunnel and Underground Space
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• v.31 no.6
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• pp.480-493
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• 2021

Since the generalized Hoek-Brown criterion (GHB) provides an efficient way of identifying its strength parameter values with the consideration of in-situ rock mass condition via Geological Strength Index (GSI), this criterion is recognized as one of the standard rock mass failure criteria in rock mechanics community. However, the nonlinear form of the GHB criterion makes its mathematical treatment inconvenient and limits the scope of its application. As an effort to overcome this disadvantage of the GHB criterion, the explicit approximate analytical equations for the minimum principal stress, which is associated with the maximum principal stress at failure, are formulated based on the Taylor polynomial approximation of the original GHB criterion. The accuracy of the derived approximate formula for the minimum principal stress is verified by comparing the resulting approximate minimum principal stress with the numerically calculated exact values. To provide an application example of the approximate formulation, the equivalent friction angle and cohesion for the expected plastic zone around a circular tunnel in a GHB rock mass are calculated by incorporating the formula for the approximate minimum principal stress. It is found that the simultaneous consideration of the values of mi, GSI and far-field stress is important for the accurate calculation of equivalent Mohr-Coulomb parameter values of the plastic zone.