• Journal of the Korean Statistical Society
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• v.26 no.3
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• pp.397-405
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• 1997

Recently maximum likelihood estimators using unconditional likelihood function are used for testing unit roots. When one wants to use this method the determinant term of initial values in the multivariate unconditional likelihood function produces a complicated function of the elements in the coefficient matrix and variance matrix. In this paper an approximation of the determinant term is calculated and based on this aproximation an approximated unconditional likelihood function is calculated. The approximated unconditional maximum likelihood estimators can be used to test for unit roots. When multivariate process has one unit root the limiting distribution obtained by this method and the limiting distribution using exact unconditional likelihood function are the same.

• Journal of the korean academy of Pediatric Dentistry
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• v.1 no.1
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• pp.19-29
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• 1974

Surveying the root resorption of the mandibular deciduous teeth in 967 children, (Male 493 Female 474) from 3 to 12 years old by orthopantomography, the author obtained the following results. 1) Female in the root resorption of the deciduous teeth was earlier than male. 2) The stages of initial resorption of the deciduous teeth were as follow. central incisor 4 years lateral incisor 4 years 2 months cuspid 6 years first decid uous molar 6 years second deciduous molar 6 years 5 months 3) The exfoliational stages ($R_5$) of the deciduous teeth were as follow. central incisor 6 years 8 months lateral incisor 7 years 2 months cuspid 9 years 10 months first deciduous molar 10 years 3 months second deciduous molar 11 years.

• Journal of Ginseng Research
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• v.20 no.2
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• pp.179-183
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• 1996

One exotherm was detected in the intact ginseng seeds containing more than 35% water, but in seeds with 20% there was no exotherm. The shapes of exotherm were remarkably uniform without relation to water content above 35%. The temperature at the initiation of freezing varied from -3.5$^{\circ}C$ to -9.6$^{\circ}C$ with the different water content in the seeds, and the Initial temperature of freezing delayed with the decrease of water content. The resistance damage at low temperature appeared in order of maln body, rhizome, lateral root of 3-year-old yearling rhizome, and fine root of 3-year-old. Ginseng roots didn't receive any damage at -5$^{\circ}C$ for 24 hours. Otherwise they received serious damage below -1$0^{\circ}C$ even for 5 hours'exposure. Hence, alternative low temperature gave more severe damage compared to constant low temperature. This result suggests that the Possibility of receiving injury at low temperature was higher during the thawing season of the early spring than in the winter.

• The korean journal of orthodontics
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• v.24 no.3 s.46
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• pp.631-648
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• 1994

The purpose of this study was to investigate the effects of different types of orthodontic force on the root resorption and repair in rat molar. 77 rats were divided into three groups; The control group was not equiped with orthodontic appliance between incisor and first molar. The experimental group was subdivided into closed coil spring subgroup and elastic chain subgroup by the application methods of orthodontic force. Initial orthodontic force between incisor and first molar was 100g. Experimental period was 8 weeks; for 4 weeks the appliance was acting and for another 4 weeks, removed. Root resorption and repair in the root of first molar was examined by light microscope for histologic changes and by inductively coupled plasma spectroscopy(ICP) for quantitative changes. The results were as follows: 1. In the closed coil spring subgroup odontoclasts and root resolution were appeared one week earlier. 2. One week after orthodontic force was eliminated the repair response in the resorptive lacuna was seen in both subgroups. Delayed resorption was seen on the periphery of resorptive lacunae whereas reparative response was seen in the center of lacunae. A new resorption was seen one week after orthodontic force was eliminated. Root contour was partially restored by repairing of resorbed root. 3. The weight ratios of calcium and phosphorous to the sample were decreased during resorptive process but increased during repair process in both the orthodontic groups, but not more than the control group. 4. By different types of orthodontic force (closed coil spring or elastic chain) resorption process was affected but repair process was not.

• Journal of Periodontal and Implant Science
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• v.24 no.3
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• pp.483-492
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• 1994

The purpose of this study was to assess the recolonization of the subgingival microflora following scaling and root planing on single and multiroot teeth with periodontal pockets which were above 5mm. 7 patients with deep pockets were selected for this study. They had not taken antibiotics for 6 months and no history of dental treatment for 6 months before the study. After initial clinical(plaque index, gingival index, probing pocket depth), microbiological and BANA test were determined, each subject received a single session of scaling and root planing, but they were not received oral hygiene instructions. Clinical indices, microbial parameters and BANA test were reassessed 1, 2, and 4 weeks after treatment. The results were as follows : 1. Plaue index, gingival index and pocket depth were not significantly when compared single root group with multiroot group, both groups were siginficantly reduced at 2weeks in plaque index and 2, 4 weeks in gingival index(P<0.05), probing pocket depth was siginificantly changed at 2, 4weeks in multiroot teeth group and 4 weeks in single root teeth group(P<0.05). 2. Percentage of cocci was significantly increased at 4weeks in single root teeth group(P<0.05), motile rod was significantly changed at 4weeks in both group(P<0.05), spirochetes and nonmotile rods were not significantly changed. 3. BANA test was significantly reduced at 1 and 2 weeks (P<0.05) in single root teeth group, multiroot teeth group was not significantly all weeks. This results were suggested that clinical and microbiological effect following scaling and root planing on periodontal disease.

• Journal of Periodontal and Implant Science
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• v.38 no.2
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• pp.231-236
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• 2008

Purpose: The treatment of gingival recessions is needed to reduce root sensitivity and improve esthetical satisfaction. Several surgical techniques have been proposed to achieve these goals. The use of connective tissue grafts has made esthetic root coverage a predictable procedure. Numerous clinical studies have represented that using connective tissue grafts to cover exposed root surface showed high success rates. This is a case report which demonstrates the technique to obtain root coverage of a buccal recession defect. Materials and Methods: A 35-year-old patient with a high level of oral hygiene was selected for the study. This patient had one Class I Miller recession defect in the mandible. A coronally advanced flap in combination with the connective tissue graft was chosen for the treatment. After surgery, the patient was told to visit the hospital once a week for his oral management and professional prophylaxis. The depth of initial recession was 4.0 mm. Result: After three months, it reduced to 0.0 mm, and the average recession reduction was 4.0 mm. The average root coverage was 100%. Conclusion: The connective tissue graft is both effective and predictable way to produce root coverage in increasing the width of CAL and KT of various adjacent gingival recessions.

• Advances in concrete construction
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• v.9 no.4
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• pp.413-421
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• 2020

For steel-concrete girders made composite using shear studs, initial damage on studs induced by weld defect, unexpected overloading, fatigue and others might degrade the service performance and even threaten the structural safety. This paper conducted a numerical study to investigate the static behavior of damaged stud shear connectors that were embedded in ultra high performance concrete (UHPC). Parameters included damage degree and damage location. The material nonlinear behavior was characterized by multi-linear stress-strain relationship and damage plasticity model. The results indicated that the shear strength was not sensitive to the damage degree when the damage occurred at 2/3d (d is the stud diameter) from the stud root. An increased stud area would be engaged in resisting shear force as the distance of damage location from stud root increased and the failure section becomes inclined, resulting in a less reduction in the shear strength and shear stiffness. The reduction factor was proposed to consider the degradation of the shear strength of the damaged stud. The reduction factor can be calculated using two approaches: a linear relationship and a square relationship with the damage degree corresponding to the shear strength dominated by the section area and the nominal diameter of the damaged stud. It was found that the proposed method is preferred to predict the shear strength of a stud with initial damage.

• Journal of Periodontal and Implant Science
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• v.18 no.1
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• pp.118.3-118.3
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• 1988

• Restorative Dentistry and Endodontics
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• v.46 no.3
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• pp.33.1-33.12
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• 2021

Objectives: This study aimed to investigate the efficacy of ionic and non-ionic-based contrast media (in vitro study) and the combinatorial effect of chitosan-based endo-radiopaque solution (CERS) (in vivo study) for visualization of the root canal anatomy. Materials and Methods: In vitro study (120 teeth): The root canal of maxillary premolars and molars (in vitro group 1 and 2 respectively, n = 60 each) were analyzed using 4 different contrast media (subgroups: Omnipaque 350, Iopamidol, Xenetix 350, and Urografin 76; n = 15 each) in combination with 5.25% sodium hypochlorite (NaOCl). Based on the results of the in vitro study, in vivo study (80 teeth) was done to compare Xenetix 350 + 5.25% NaOCl with CERS (in vivo group 1 and 2 respectively, n = 40 each) on maxillary and mandibular premolars and molars. Two endodontists used radiovisiography to assess the depth of ingress and identify the aberrant root anatomy after access cavity preparation, and after initial cleaning and shaping of canals. Kruskal-Wallis test was used for in vitro comparison (p < 0.05), and Wilcoxon signed-rank test and Mann-Whitney U test for in vivo analysis (p < 0.01). Results: In vitro study, Xenetix 350 + 5.25% NaOCl facilitated a significant higher visualization (p < 0.05). For in vivo study, CERS had a statistically significant depth of ingress (p < 0.01), and was efficient in identifying the aberrant root canal anatomy of premolars and molars. Conclusions: CERS facilitates better visualization of the root canal anatomy of human premolars and molars.

• 한국생태학회:학술대회논문집
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• 2002.08a
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• pp.101-105
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• 2002

Fine root decomposition and nutrient release patterns were examined using in situ buried fine root (< 2mm in diameter) bags inserted vertically into the mineral soil to a depth of the top 15 cm in a sawtooth oak (Quercus acutissima) and a Korean pine (Pinus korainesis) stands in the Jungbu Forest Experiment Station, Kyonggi-do, Korea. The pine roots compared with the oak roots showed rapid mass loss in early stages of decomposition, but decomposed similarly after 12 months of incubation. Decomposition rates of fine roots were about 33%/yr for the oak roots and 37%/yr for the pine roots. Nutrients except for calcium and phosphorus showed similar concentrations between the oak and the pine roots during the study period. However, calcium concentration was significantly higher in the oak than in the pine roots. Nutrient concentrations in both stands except for nitrogen decreased during the study period. In addition, potassium compared with other nutrients was the most mobile ion and about 70% of initial amount was released during the first 3 months of incubation. The results indicate that tree species influence mass loss and nutrient dynamics of fine roots on similar site conditions.