• Korean Journal of Heritage: History & Science
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• v.55 no.4
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• pp.138-164
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• 2022

The Neolithic shell midden in Daejuk-ri, Seosan, is distributed on the gentle slope of a low hill close to the west coast. The bedrock of the area consists mainly of schist with various mafic minerals, but shows a partial gneiss pattern. The site consists of loamy topsoil and clay loam subsoil, and the degree of siallization is relatively low. Although the pottery excavated from the shell midden shares mostly similar features, a variety of shapes and patterns coexist. The surface colors, thickness and physical properties are slightly different. The pottery can be subdivided into three types (IA, IB and II) according to the composition of the body clay, the temper and the existence of a black core. Types IA and IB are colorless mineral pottery with a non-black or black core respectively. TypeII is colored mineral pottery with a non-black core. Type I pottery also contains non-plastic colored minerals, but type II contains a large amount of biotite, chlorite, talc, amphibole, diopside and tremolite, which include a large amount of Mg and Fe. The studied pottery contains a small amount of organic matter. Considering the grain size and relatively poor sorting and roundness of the non-plastic particles, the pottery appears to be made by adding coarse non-plastic tempers for special purposes to the untreated weathered soil around the site. The three types of pottery seem to have been incompletely fired in general. While type IB has the lowest degree of oxidation, typeII shows the highest degree of redness and oxidation. It can be interpreted that these differences depend on the firing temperature and the ratio of non-plastic particles. Through a synthesis of the minerals, geochemical data and thermal history, it can be determined that the firing temperature ranged from 600 to 700℃. The pottery types of the Daejuk-ri Shell Midden have slightly different production conditions, mineral compositions, and physical properties, but have undergone similar production processes with basically the same clay materials. The clay is almost identical to the composition of the bedrock and weathered soil distributed in the Daejuk-ri area. Currently, there is an industrial complex in the area, so it is difficult to confirm the soil and geological distribution of the site. However, it is highly probable that the area around the site was self-sufficient for the clay and tempers required for the production of the Neolithic pottery. Therefore, it can be interpreted that the group that left the shell midden in Daejuk-ri lived near the site, visited the site for the purpose of collecting and processing shellfish, and discarded the broken pottery along with shells.

• Korean Journal of Agricultural Science
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• v.6 no.2
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• pp.166-184
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• 1979

In order to prevent the water loss in the irrigation canal constructed on the sandy gravel layer or on the other highly permeable ground layer, lining has been practiced. Many studies have been done so far on the lining method to prevent the water loss in the irrigation canal and recently studies on the lining with plastic film or polyethylene film were also reported. However, the plastic film or polyethylene film has low strength and is liable to break, and water loss from pin hole caused by contacting with sand or gravel is highly predicted. This study was then conducted to find proper lining and buring method in canal construction of polypropylene mat after coated with vinyl, as one way to overcome the shortcoming frequently observed when plastic or usual polyehtylene film were used. Eventhough rather longer periods of experiments are needed to attain reliable and accurate results on the variation of durability, the durability of asphalt coated area, or on the damage due to freeze after burial or exposure of polypropylene mat, the experiemental results obtained during one year of period are summarized as follows: 1. The curvature at the area between canal bottom and side slope had increased stability and saved consruction cost. The relationship among the variation of curvature, the reduction of polypropylene mat and the reduced amount of soil cutting at each side slope was presented in Fig. 7 through 9. 2. The depth of covering material to protect polypropylene mat was desired to be over 30cm, considering the water depth, side slope, canal cleaning practices, traffic, or back pressure of irrigation period. 3. In order to increase the canal stability and to prevent slope erosion, sandy soil was required, to be placed under ground, and coarse gravel should cover the surface area of canal. 4. The studies on the stability of side slope in the canal should consider the passive area on the bottom and the slope should be about 1 to 2, considering the slope stability, allowable velocity and tractive force. 5. When compared with earth lining, the lining with polypropylene mat coated with vinyl was responsible to save 28% and 37% of canal lining cost, when the soil carrying distances were 500 and 700m. respectively. 6. The water interception was almost completely attained when the polypropylene mat coated with vinyl was used for lining. But further studies were assumed to be necessary for the use of asphalt since the strength of polypropylene mat connected with asphalt will vary with duration.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.3
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• pp.353-359
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• 2012

The identification of effective root zone would clarify dynamics of plant available water and soil water balance. Using the relationship between soil properties and electrical resistivity (ER) the purpose of this research is to identify soil zone affected by a plant root activity using electrical resistivity tomography (ERT) technique. Four plastic containers were prepared for two different soil textures (clay and sandy loam) and one container for each texture was selected for planting four corn seedlings (Zea mays L.) and the others were prepared for the blank. For ERT monitoring, we prepared 0.8 m plastic sticks with 17 electrodes installed with 5 cm space. The Ministing (AGI Inc., Texas) instrument for electrical resistivity measurement and semi-auto converter of electrode arrangement were set up for dipole-dipole array. During 2 months of the corns growing, ERT monitoring was made 3 to 4 days after the irrigation practice. Despite of the same amount water supplied into soils, two textures showed very different apparent resistivity values due to different clay content. The apparent electrical resistivity is consistently lower in clay loam comparing to sandy loam soil implying that plant root does not significantly alter the overall trend of resistivity. When plant root system, however, is active both soils with plants showed 2-7 times higher electrical resistivity and higher coefficient variation than soils without plant, implying the effect of root system on the resistivity, in which may caused by. This result suggests plant root activities regulating the soil water dynamics mainly control the variation of electrical resistivity over soil textural difference. Therefore the identification of water uptake zone would highly be correlated to plant root activities, thus ERT will be feasible approach to identify spatial characteristics of a plant root activity.

• Computers and Concrete
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• v.11 no.2
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• pp.123-148
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• 2013

The nonlinear finite element method with eight noded isoparametric quadrilateral element for concrete and two noded element for reinforcement is used for the prediction of the behavior of reinforcement concrete structures. The disturbed state concept (DSC) including the hierarchical single surface (HISS) plasticity model with associated flow rule with modifications is used to characterize the constitutive behavior of concrete both in compression and in tension which is named DSC/HISS-CT. The HISS model is applied to shows the plastic behavior of concrete, and DSC for microcracking, fracture and softening simulations of concrete. It should be noted that the DSC expresses the behavior of a material element as a mixture of two interacting components and can include both softening and stiffening, while the classical damage approach assumes that cracks (damage) induced in a material treated acts as a void, with no strength. The DSC/HISS-CT is a unified model with different mechanism, which expresses the observed behavior in terms of interacting behavior of components; thus the mechanism in the DSC is much different than that of the damage model, which is based on physical cracks which has no strength and interaction with the undamaged part. This is the first time the DSC/HISS-CT model, with the capacity to account for both compression and tension yields, is applied for concrete materials. The DSC model allows also for the characterization of non-associative behavior through the use of disturbance. Elastic perfectly plastic behavior is assumed for modeling of steel reinforcement. The DSC model is validated at two levels: (1) specimen and (2) practical boundary value problem. For the specimen level, the predictions are obtained by the integration of the incremental constitutive relations. The FE procedure with DSC/HISS-CT model is used to obtain predictions for practical boundary value problems. Based on the comparisons between DSC/HISS-CT predictions, test data and ANSYS software predictions, it is found that the model provides highly satisfactory predictions. The model allows computation of microcracking during deformation leading to the fracture and failure; in the model, the critical disturbance, Dc, identifies fracture and failure.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.33 no.5
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• pp.385-391
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• 2011

Purpose: The periosteum is a well-known source of osteogenic precursor cells for tissue-engineered bone formation. However, cultured endothelial or endothelial-like cells derived from periosteum have not yet been investigated. This study focused on endothelial-like cell culture from the periosteum. Methods: Periosteal tissues were harvested from the mandible during surgical extraction of lower impacted third molars. The tissues were treated with 0.075% type I collagenase in phosphate-buffered saline (PBS) for 1 hr at $37^{\circ}C$ to release cellular fractions. The collagenase was inactivated with an equal volume of DMEM/10% fetal bovine serum (FBS) and the infranatant was centrifuged for 10 min at 2,400 rpm. The cellular pellet was filtered through a $100{\mu}m$ nylon cell strainer, and the filtered cells were centrifuged for 10 min at 2,400 rpm. The resuspended cells were plated into T25 flasks and cultured in endothelial cell basal medium (EBM)-2. Results: Among the hematopoietic markers, CD146 was more highly expressed than CD31 and CD34. The periosteal-derived cells also expressed CD90 and CD166, mesenchymal stem cell markers. Considering that the expression of CD146 was constant and that the expression of CD90 was lower at passage 5, respectively, the CD146 positive cells in passage 5 were isolated using the magnetic cell sorting (MACS) system. These CD146 sorted, periosteal-derived cells formed tube-like structures on Matrigel. The uptake of acetylated, low-density lipoprotein, labeled with 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI-Ac-LDL) was also examined in these cells. Conclusion: These results suggest that the CD146-sorted positive cells can be referred to as periosteal-derived CD146 positive endothelial-like cells. In particular, when a co-culture system with endothelial and osteoblastic cells in a three-dimensional scaffold is used, the use of periosteum as a single cell source would be strongly beneficial for bone tissue engineering.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.31 no.3
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• pp.229-236
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• 2009

Purpose: Some recent literatures report that it is possible to recover defected areas caused by enucleation of relatively large jaw cysts without using bone grafts. The aim was to find out whether spontaneous recovery of defected area with time occurred and what the contributing factors were. Materials and methods: In total, 194 patients were considered as patients. Out of these 194 patients, 74 patients who had no wound dehiscence and who were available for follow-up studies were selected. They were classified into two groups according to the size of radiolucent area in the preoperative panoramic radiographs: in one group, it was larger than $3{\times}4cm$, while in the other group, it was smaller than $3{\times}4cm$. Follow-up panoramic radiographs were taken immediately after the surgery, then after 3, 6, 9 and 12 months. On those radiographs, changes in size and density of the defected areas were observed using the Gray-level histogram of Adobe photoshop v7.0. Correlation between bone regeneration and factors such as the type and size of the cysts, age, sex, site of the cysts and systemic disease was evaluated using the General repeated measure and Mann-Whitney Test. Results: Analyses of panoramic radiographs showed that the recovery of radiopacity after 12 months was more than 97% on average in defected areas that were smaller than $3{\times}4cm$. in the defected areas that were larger than $3{\times}4cm$, considerable portion showed recovery of radiopacity. No statistically significant change was observed in bone density according to the type of cysts. Young patients under 20 years of age with highly active metabolism presented more significant bone regeneration than patients over 20 years of age. Bone regeneration was more hampered in patients who had medical disease, compared with patients who didn’t have any medical problem. No statistically significant change was seen in bone density according to sex. Changes in bone density according to the site of cysts such as maxilla, mandible, anterior or posterior region were not considered to be significant. Conclusion: Analyses of panoramic radiographs suggest that in approximately 12 months after the enucleation of cysts, clinically acceptable spontaneous bone regeneration can be observed even though normal bone graft procedures have not been applied.

• Korean Journal Plant Pathology
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• v.2 no.3
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• pp.193-198
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• 1986

Bottom rot of Chinese cabbage (Brassica pekinensis Rupr) hitherto undescribed in Korea is caused by Rhizoctonia solani Kuhn. Development of bottom rot in fall crops was observed and the efficiencies of fungiciial control in naturally infested field in Southern region were studied. Bottom rot symptom started to develop 20 days after transplanting 20 day old seedlings, which corresponded to the middle growing stage. At the reading stage, the infection rate increased substantially, which progressed upto an average of $52\%$ at harvesting time. The overall infection rate was about $30\%$ in Chinese cabbage field under plastic film house cultivation. However, disease intensity of fall crops was less severe than that of crops in plastic film house. where plants infested earlier, stunted and their growth was extremely poor. Optimum temperature for mycelial growth of bottom rot isolates of R. solani was $20\~25^{\circ}C$ on potato-sucrose agar. This fungus was highly pathogenic on seedlings of Chinese cabbage, radish, sesame and rape resulting in high percentage of damping-off. For other crops, such as lettuce, tomato the cucumber, the germination was delayed for 2-3 days and the percentage damping-off was lower. Anastomosis group of this fungus was idenlfied as AG II-I. Soil drenching of fungicide pencycr WP., three applications at 10 day interval, was effective; indicating the most promising one with control value $80\%$.

• Journal of Powder Materials
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• v.9 no.6
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• pp.394-408
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• 2002

Nanostructured high strength metastable Al-, Mg- and Ti-based alloys containing different amorphous, quasicrystalline and nanocrystalline phases are synthesized by non-equilibrium processing techniques. Such alloys can be prepared by quenching from the melt or by powder metallurgy techniques. This paper focuses on one hand on mechanically alloyed and ball milled powders containing different volume fractions of amorphous or nano-(quasi)crystalline phases, consolidated bulk specimens and, on the other hand. on cast specimens containing different constituent phases with different length-scale. As one example. $Mg_{55}Y_{15}Cu_{30}$- based metallic glass matrix composites are produced by mechanical alloying of elemental powder mixtures containing up to 30 vol.% $Y_2O_3$ particles. The comparison with the particle-free metallic glass reveals that the nanosized second phase oxide particles do not significantly affect the glass-forming ability upon mechanical alloying despite some limited particle dissolution. A supercooled liquid region with an extension of about 50 K can be maintained in the presence of the oxides. The distinct viscosity decrease in the supercooled liquid regime allows to consolidate the powders into bulk samples by uniaxial hot pressing. The $Y_2O_3$ additions increase the mechanical strength of the composites compared to the $Mg_{55}Y_{15}Cu_{30}$ metallic glass. The second example deals with Al-Mn-Ce and Al-Cu-Fe composites with quasicrystalline particles as reinforcements, which are prepared by quenching from the melt and by powder metallurgy. $Al_{98-x}Mn_xCe_2$ (x =5,6,7) melt-spun ribbons containing a major quasicrystalline phase coexisting with an Al-matrix on a nanometer scale are pulverized by ball milling. The powders are consolidated by hot extrusion. Grain growth during consolidation causes the formation of a micrometer-scale microstructure. Mechanical alloying of $Al_{63}Cu_{25}Fe_{12}$ leads to single-phase quasicrystalline powders. which are blended with different volume fractions of pure Al-powder and hot extruded forming $Al_{100-x}$$(Al_{0.63}Cu_{0.25}Fe_{0.12})_x$ (x = 40,50,60,80) micrometer-scale composites. Compression test data reveal a high yield strength of ${\sigma}_y{\geq}$700 MPa and a ductility of ${\varepsilon}_{pl}{\geq}$5% for than the Al-Mn-Ce bulk samples. The strength level of the Al-Cu-Fe alloys is ${\sigma}_y{\leq}$550 MPa significantly lower. By the addition of different amounts of aluminum, the mechanical properties can be tuned to a wide range. Finally, a bulk metallic glass-forming Ti-Cu-Ni-Sn alloy with in situ formed composite microstructure prepared by both centrifugal and injection casting presents more than 6% plastic strain under compressive stress at room temperature. The in situ formed composite contains dendritic hcp Ti solid solution precipitates and a few $Ti_3Sn,\;{\beta}$-(Cu, Sn) grains dispersed in a glassy matrix. The composite micro- structure can avoid the development of the highly localized shear bands typical for the room temperature defor-mation of monolithic glasses. Instead, widely developed shear bands with evident protuberance are observed. resulting in significant yielding and homogeneous plastic deformation over the entire sample.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.18 no.4
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• pp.652-672
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• 1996

Dysfunction of the inferior alveolar nerve may result from trauma, diseases or iatrogenic injury. The development and refinement of an objective method to evaluate this clinical problem is highly desirable and needed, especially concerning for an increasing medico-legal issue. Evoked potential techniques have attracted considerable attention as a means of assessing the function and integrity of nerve pathways. The purpose of this study was to characterize the Sensory Evoked Potentials(SEPs) and Somatosensory Evoked Potentials(SSEPs) elicited by electrical stimulation of mental nerve. SEPs and SSEPs were measured and analyzed statistically before and after needle injury on the inferior alveolar nerve of Sprague-Dawalye rats. Measuring SEPs was more sensitive in evaluation of the recovery of sensory function from inferior alveolar nerve injury then measuring SSEPs but we measured SSEPs in the hope of providing a safe, simple and objective test to check oral and facial sensibility, which is acceptable to the patient. We stimulated mental nerve after needle injury on the inferior alveolar nerve and SEPS on the level of mandibular foramen and SSEPs on the level of cerebral cortex were recorded. Threshold, amplitude, and latency of both of SEPs and SSEPs were analyzed. The results were as follows ; 1. Threshold of SEPs and SSEPs were $184{\pm}14{\mu}A$ and $164{\pm}14{\mu}A$ respectively. 2 SEPs were composed of 2 waves, i.e., N1 N2 in which N1 was conducted by II fibers and N2 was conducted by III fibers. 3. SSEPS were composed of 5 waves, of which N1 and N2 shower statistically significant changes(p<0.01, unpaired t-test). 4. SEPs and SSEPs were observed to be abolished immediately after local anesthesia and recovered 30 minutes later. 5. SEPs were abolished immediately after injury. N1 of SSEPs was abolished immediately and amplitued of N2 was decreased($20.7{\pm}12.2%$) immediately after 23G needle injury, but N3, N4 and N5 did not change significantly. Recovery of waveform delayed 30 minutes in SEPs and 45 minutes in SSEPs. 6. The degree of decrease in amplitude of SEPs and SSEPs, after 30G needle injury was smaller than those with 23G. SEPs recorded on the level of mandibular foramen were though to be reliable and useful in the assessment of the function of the inferior alveolar nerve after injury. Amplitude of SSEPs reflected the function and integrity of nerve and measuring them provided a safe, simple and abjective test to check oral and facial sensibility. These results suggest that measuring SEPs and SSEPs are meaningful methods for objective assessment in the diagnosis of nerve injury. N1 and N2 of SSEPs can be useful parameters for the evaluation of the nerve function following a needle injury.

• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.133-144
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• 2003

Horizontal consolidation characteristics of Busan marine clay were investigated by computing coefficient of horizontal consolidation from Piezocone data and comparing their results with those of standard consolidation test. It is well known that current prediction models of $c_h$ for high plastic soils have large uncertainties, and show a great difference between the predicted and the measured values. However, the spherical models and expanding cavity theory of Torstensson(1977), and Burns & Mayne(1998) based on modified Cam-Clay model with critical limit state concepts have relative reliability in estimating $c_h$ and good applicability in highly plasticity soils. In this paper, a normalization technique was used to evaluate $c_h$ using the Burns and Mayne's method based on the dissipation test, and their normalized consolidation curves give 0.015 of time factor($T_{50}$) when 50% degree of consolidation is completed. Comparison study using Piezocone data obtained at other similar ground site shows 1.5 times less systematicality than that of standard consolidation test, which indicates considerable approximation with the measured values because standard consolidation test gives the difference of three to few times compared with the measured values. In addition, design chart for estimating $c_h$ based on the chart from Robertson et al.(1992) and using the other method of the direct prediction from the of dissipation test was newly proposed. It is judged that new proposed chart is very applicable to Korean marine soils, especially in very high plastic soils.