• Journal of Dental Rehabilitation and Applied Science
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• v.27 no.2
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• pp.197-207
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• 2011

The study aimed at examining how different reline resins affect flexural strength and flexural modulus of denture base. A total of 80 specimens ($64{\times}10{\times}3.3$ mm, according to ISO 1567:1999) of heat-polymerized resin, 40 specimens for (Lucitone199(Dentsply Int., NewYork, USA), SR Ivocap(Ivoclar AG, Schaan, Liechtenstein)) respectively, were polymerized according to the manufacturer's instructions and divided into eight groups(n = 10). Control group specimens remained intact. Specimens in the other groups were abraded on both sides to 2 mm thickness, and were relined in 1.3 mm thickness with 3 types of resins (Lucitone199(Dentsply), SR Ivocap(Ivoclar), and Rebase II(Tokuyama Co., Ltd, Tokyo, Japan)). All specimens were preserved in distilled water at $37^{\circ}C$ for 50 hours, and then were subjected to flexural strength testing in a universal testing machine using 3-point loading. A crosshead speed of 5 mm/min was used, and the distance between the supports was 50 mm. Data analyses included one-way analysis of variance(ANOVA) and the Tukey Honestly Significant Difference test (p=.05). Both heat-polymerized resin groups and auto-polymerized resin groups showed statistically low flexural strength and flexural modulus than control groups. Specimens relined with Lucitone 199 showed significantly higher flexural strength and flexural modulus than those relined with SR-Ivocap. Specimens relined with auto-polymerized resin showed significantly lower flexural strength and flexural modulus than those relined with heat-polymerized resin. Relining with heat-polymerized resins showed superior mechanical properties to relining with an auto-polymerized resin. Relining with the same heat-polymerized resin as the denture base does not affect mechanical properties of a denture. Lucitone199 using a compression-mould technique resulted in the highest flexural strength.

• Journal of Dental Rehabilitation and Applied Science
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• v.31 no.2
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• pp.86-95
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• 2015

Purpose: The aim of the study was to evaluate the subjective symptoms and clinical signs through the TMD-questionnaire, clinical examination and radiography against the many instrumental performers and to investigate the association between playing instruments and TMDs. Materials and Methods: A total of 803 instrumental performers received TMD-related questionnaire and evaluations of prevalence and disease distribution were performed. Among those who reported at least one symptom of TMD, 70 volunteers visited in clinic then received clinical examination and radiography for diagnosis and evaluations of prevalence and disease distribution were performed. 70 subjects were divided into three groups as woodwind, brass wind, string. Comparative analysis of disease distribution was performed. Results: Among 803 instrumental performers, 610 people (75.97%) were reported to one or more symptoms of TMD. The most frequent symptom was click (29.68%).70 subjects underwent a clinical examination and radiography survey results, the most frequent symptom was a click (29.75%). Most commonly diagnosed disease was a myofacial pain (30.53%).Comparison of the three groups, a significant difference was not observed in the clinical sign. But among subject symptom, muscle pains howed significant differences in accordance with the Group (P = 0.024). During the 70 people who underwent clinical examination, 66 people (94.3%) showed moderate to severe attrition, mild to severe tongue ridging, mild to severe cheek ridging assigns of parafunction. Conclusion: Instrumental performers showed a high prevalence of TMD and the most of the musicians with temporomandibular disorder had bruxism or clenching habits.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.34 no.1
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• pp.25-35
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• 2008

In this study, the antioxidative effects and inhibitory effects on elastase and tyrosinase of Geranium nepalense extracts were investigated. The free radical(1,1-diphenyl-2-picrylhydrazyl, DPPH) scavenging activities ($FSC_{50}$) of extract/fractions of Geranium nepalense were in the order: 50% ethanol extract(15.0 ${\mu}g/mL$)${\mu}g/mL$). ${\mu}g/mL$). Reactive oxygen species (ROS) scavenging activities($OSC_{50}$) of some Geranium nepalense extracts on ROS generated in $Fe^{3+}-EDTA/H_2O_2$ system were investigated using the luminol-dependent chemiluminescense assay. The order of ROS scavenging activities were 50% ethanol extract($OSC_{50},\;0.23{\mu}g/mL$)${\mu}g/mL$)${\mu}g/mL$). Deglycosylated flavonoid fraction showed the most prominent scavenging activity. The protective effects of extract/fractions of Geranium nepalense on the rose-bengal sensitized photohemolysis of human erythrocytes were investigated. The Geranium nepalense extracts suppressed photohemolysis in a concentration dependent manner, particularly deglycosylated flavonoid fraction exhibited the most prominent celluar protective effect (${\tau}_{50}$, 676.7 min at 50 ${\mu}g/mL$). The inhibitory effect of aglycone fraction on tyrosinase($IC_{50}$, 70.0 ${\mu}g/mL$) and elastase ($IC_{50}$, 19.9 ${\mu}g/mL$) was very high. Aglycone fractions obtained from the deglycosylation reaction of ethyl-acetate fraction among the Geranium nepalense extracts, showed 2 bands in TLC and 2 peaks in HPLC experiments (370 nm). Two components were identified as quercetin(composition ratio, 15.3%), kaempferol(82.8%). These results indicate that extract/fractions of Geranium nepalense can function as antioxidants in biological systems, particularly skin exposed to UV radiation by scavenging $^1O_2$ and other ROS, and protect cellular membranes against ROS. And component analysis of Geranium nepalense extract and inhibitory activity on elastase of the aglycone fraction could be applicable to new functional cosmetics for smoothing wrinkles.

• Education of Primary School Mathematics
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• v.16 no.2
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• pp.123-145
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• 2013

This study was expected to yield the meaningful conclusions from the experimental group who took lessons based on inductive activities using GeoGebra at the beginning of proof learning and the comparison one who took traditional expository lessons based on deductive activities. The purpose of this study is to give some helpful suggestions for teaching proof to mathematically gifted elementary students. To attain the purpose, two research questions are established as follows. 1. Is there a significant difference in proof abilities between the experimental group who took inductive lessons using GeoGebra and comparison one who took traditional expository lessons? 2. Is there a significant difference in proof attitudes between the experimental group who took inductive lessons using GeoGebra and comparison one who took traditional expository lessons? To solve the above two research questions, they were divided into two groups, an experimental group of 10 students and a comparison group of 10 students, considering the results of gift and aptitude test, and the computer literacy among 20 elementary students that took lessons at some education institute for the gifted students located in K province after being selected in the mathematics. Special lesson based on the researcher's own lesson plan was treated to the experimental group while explanation-centered class based on the usual 8th grader's textbook was put into the comparison one. Four kinds of tests were used such as previous proof ability test, previous proof attitude test, subsequent proof ability test, and subsequent proof attitude test. One questionnaire survey was used only for experimental group. In the case of attitude toward proof test, the score of questions was calculated by 5-point Likert scale, and in the case of proof ability test was calculated by proper rating standard. The analysis of materials were performed with t-test using the SPSS V.18 statistical program. The following results have been drawn. First, experimental group who took proof lessons of inductive activities using GeoGebra as precedent activity before proving had better achievement in proof ability than the comparison group who took traditional proof lessons. Second, experimental group who took proof lessons of inductive activities using GeoGebra as precedent activity before proving had better achievement in the belief and attitude toward proof than the comparison group who took traditional proof lessons. Third, the survey about 'the effect of inductive activities using GeoGebra on the proof' shows that 100% of the students said that the activities were helpful for proof learning and that 60% of the reasons were 'because GeoGebra can help verify processes visually'. That means it gives positive effects on proof learning that students research constant character and make proposition by themselves justifying assumption and conclusion by changing figures through the function of estimation and drag in investigative software GeoGebra. In conclusion, this study may provide helpful suggestions in improving geometry education, through leading students to learn positive and active proof, connecting the learning processes such as induction based on activity using GeoGebra, simple deduction from induction(i.e. creating a proposition to distinguish between assumptions and conclusions), and formal deduction(i.e. proving).

• Korean Journal of Materials Research
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• v.5 no.6
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• pp.690-698
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• 1995

The Poly-S $i_{1-x}$G $e_{x}$ thin films were deposited on oxidized Si wafer by RTCVD(rapid thermal chemical vapor deposition) using Si $H_4$and Ge $H_4$, at 450 ~5$50^{\circ}C$. The variation of Ge mole fraction and the deposition rate of S $i_{1-x}$G $e_{x}$ thin film were studied as a function of the deposition temperature and the Ge $H_4$/Si $H_4$input ratio, and the crystal phase and the surface roughness were studied by XRD and AFM(atomic force microscopy), respectively. The experimental results showed that the activation energy for the deposition of poly-S $i_{1-x}$G $e_{x}$ was about 32~37Kca /mol and the deposition rate of S $i_{1-x}$G $e_{x}$ thin films was increased with increasing the deposition temperature and the input ratio. From the analysis of composition, it was known that the Ge mole fraction within the poly-S $i_{1-x}$G $e_{x}$ thin film was decreased with decreasing the input ratio and increasing the deposition temperature. As-deposited S $i_{1-x}$G $e_{x}$ thin films were polycrystalline over the entire experimental range. But those were amorphous at the deposition temperature of 450, 475$^{\circ}C$ and the input ratio of 0.05. By adding the Ge $H_4$, poly-S $i_{1-x}$G $e_{x}$ thin film were deposited at relatively lower deposition temperatures($\leq$ 5$50^{\circ}C$) than those of conventional poly-Si(>$600^{\circ}C$). From surface roughness measurement of poly-S $i_{1-x}$G $e_{x}$ it was found that the surface roughness( $R_{i}$ ) increased with increasing the deposition temperature and input ratio.and input ratio.

• Tuberculosis and Respiratory Diseases
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• v.56 no.1
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• pp.40-50
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• 2004

Background : Radiation pneumonitis(RP) is the major serious complication of thoracic irradiation treatment. In this study, we attempted to retrospectively evaluate the long-term prognosis of patients who experienced acute RP and to identify factor that might allow prediction of RP. Methods : Of the 114 lung cancer patients who underwent thoracic radiotherapy between December 2000 and December 2002, We performed analysis using a database of 90 patients who were capable of being evaluated. Results : Of the 44 patients(48.9%) who experienced clinical RP in this study, the RP was mild in 33(36.6%) and severe in 11(12.3%). All of severe RP were treated with corticosteroids. The median starting corticosteroids dose was 34 mg(30~40) and median treatment duration was 68 days(8~97). The median survival time of the 11 patients who experienced severe RP was significantly poorer than the mild RP group. (p=0.046) The higher total radiation dose(${\geq}60Gy$) was significantly associated with developing in RP.(p=0.001) The incidence of RP did not correlate with any of the ECOG performance, pulmonary function test, age, cell type, history of smoking, radiotherapy combined with chemotherapy, once-daily radiotherapy dose fraction. Also, serum albumin level, uric acid level at onset of RP did not influence the risk of severe RP in our study. Conclusion : Only the higher total radiation dose(${\geq}60Gy$) was a significant risk factor predictive of RP. Also severe RP was an adverse prognostic factor.

• Journal of Environmental Policy
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• v.7 no.4
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• pp.35-55
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• 2008

Assessing vulnerability to climate change is the first step to take when setting up appropriate adaptation strategies. Adaptive capacity to climate change is the important factor comprising vulnerability. An adaptive capacity index in agricultural water management system was developed considering agricultural water supply and demand for rice production in Jeolla-do, Korea. The agricultural water supply was assumed to be equal to the amount of water stored in the major agricultural reservoirs, while data on the agricultural water demand was obtained from the dynamic simulation results by Korea Agriculture Corporation(KAC). The spatial unit for analysis was conducted at the county(Si, Gun, Gu) level and temporal scale was based on every month from 1991-2003. Adaptive capacity for drought stress index(ACDS index) was calculated as the percentage of data points where the irrigated water supply was greater than the crop water demand. The ACDS index was compared with SWSCI(Standard Water Storage Capacity Index) and the relationship showed high degree of fit($R^2$=0.84) using the exponential function, indicating that the developed ACDS index is useful for evaluating the status of the balance between agricultural water supply and demand, especially for the small sized agricultural reservoirs. This study provided the methodological basis for developing climate change vulnerability index in agricultural water system which is projected to be more frequently exposed to drought condition in the future due to climate change. Further research should be extended to the study on the water demand of the crops other than rice and to the projection of the change in ACDS index in the future.

• KDI Journal of Economic Policy
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• v.12 no.2
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• pp.95-120
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• 1990

The underpricing of new shares of a firm that are offered to the public for the first time (initial offerings) is well known and has puzzled financial economists for a long time since it seems at odds with the optimal behavior of the owners of issuing firms. Past attempts by financial economists to explain this phenomenon have not been successful in the sense that the explanations given by them are either inconsistent with the equilibrium theory or implausible. Approaches by such authors as Welch or Allen and Faulhaber are no exceptions. In this paper, we develop a signalling model of capital investment to explain the underpricing phenomenon and also analyze the efficiency of investment. The model focuses on the information asymmetry between the owners of issuing firms and general investors. We consider a firm that has been owned and operated by a single owner and that has a profitable project but has no capital to develop it. The profit from the project depends on the capital invested in the project as well as a profitability parameter. The model also assumes that the financial market is represented by a single investor who maximizes the expected wealth. The owner has superior information as to the value of the firm to investors in the sense that it knows the true value of the parameter while investors have only a probability distribution about the parameter. The owner offers the representative investor a fraction of the ownership of the firm in return for a certain amount of investment in the firm. This offer condition is equivalent to the usual offer condition consisting of the number of issues to sell and the unit price of a share. Thus, the model is a signalling game. Using Kreps' criterion as the solution concept, we obtained an essentially unique separating equilibrium offer condition. Analysis of this separating equilibrium shows that the owner of the firm with high profitability chooses an offer condition that raises an amount of capital that is short of the amount that maximizes the potential profit from the project. It also reveals that the fraction of the ownership of the firm that the representative investor receives from the owner of the highly profitable firm in return for its investment has a value that exceeds the investment. In other words, the initial offering in the model is underpriced when the profitability of the firm is high. The source of underpricing and underinvestment is the signalling activity by the owner of the highly profitable firm who attempts to convince investors that his firm has a highly profitable project by choosing an offer condition that cannot be imitated by the owner of a firm with low profitability. Thus, we obtained two main results. First, underpricing is a result of a signalling activity by the owner of a firm with high profitability when there exists information asymmetry between the owner of the issuing firm and investors. Second, such information asymmetry also leads to underinvestment in a highly profitable project. Those results clearly show the underpricing entails underinvestment and that information asymmetry leads to a social cost as well as a private cost. The above results are quite general in the sense that they are based upon a neoclassical profit function and full rationality of economic agents. We believe that the results of this paper can be used as a basis for further research on the capital investment process. For instance, one can view the results of this paper as a subgame equilibrium in a larger game in which a firm chooses among diverse ways to raise capital. In addition, the method used in this paper can be used in analyzing a wide range of problems arising from information asymmetry that the Korean financial market faces.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.28 no.3
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• pp.114-121
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• 2010

Traditional temples in Korea are the important cultural heritage because of artistic traditonal buildings and structures, paintings, sculptures, and big forest areas which are most ecological and beautiful in Korea. Since traditional temples still function as religious places for very long time, the sense of places intrinsic to the temples are very strong and vivid. The sense of place is very closely related to the conservation of the original landscape type. Recently however, there is a strong tendency to use solar energy in traditional temples because of the low energy efficiency of the old traditional architecture which may have negative impact on landscape which again in turn may lead to the destruction of the sense of place. The purpose of this study was to suggest some landscape design guidelines to protect the sense of place of traditional temple by investigating the impact of solar energy facility on the landscape experience of traditional temple. In order to do perform this purpose, Tongdosa was selected as a study site and four kinds of measurement tools(landscape image, temple identity, landscape satisfaction, degree of landscape improvement) were used as questionnaire items. 180 college students participated in the questionnaire survey. The analysis showed that the solar energy facility had very negative impact on landscape experience such as three landscape image factors(scenic beauty, openness, complexity), landscape satisfaction, temple identity, and landscape improvement. Based on the results, three landscape improvement plans were suggested. First, solar energy facility should be built in the forest in order not to be exposed to visitors, if possible. Second, the landscape management of traditional temple should emphasize on sustaining scenic beauty and temple identity along with the provision of openness. Lastly, detailed landscape guideline should be prepared to regulate the scale, ratio, and the form of the artificial buildings and structures to protect the sense of place of traditional temple.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.2
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• pp.109-120
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• 2017

A discounted cost model for preventive maintenance of armor units of rubble-mound breakwaters is mathematically derived by combining the deterioration model based on a discrete-time stochastic process of shock occurrence with the cost model of renewal process together. The discounted cost model of condition-based maintenance proposed in this paper can take into account the nonlinearity of cumulative damage process as well as the discounting effect of cost. By comparing the present results with the previous other results, the verification is carried out satisfactorily. In addition, it is known from the sensitivity analysis on variables related to the model that the more often preventive maintenance should be implemented, the more crucial the level of importance of system is. However, the tendency is shown in reverse as the interest rate is increased. Meanwhile, the present model has been applied to the armor units of rubble-mound breakwaters. The parameters of damage intensity function have been estimated through the time-dependent prediction of the expected cumulative damage level obtained from the sample path method. In particular, it is confirmed that the shock occurrences can be considered to be a discrete-time stochastic process by investigating the effects of uncertainty of the shock occurrences on the expected cumulative damage level with homogeneous Poisson process and doubly stochastic Poisson process that are the continuous-time stochastic processes. It can be also seen that the stochastic process of cumulative damage would depend directly on the design conditions, thus the preventive maintenance would be varied due to those. Finally, the optimal periods and scale for the preventive maintenance of armor units of rubble-mound breakwaters can be quantitatively determined with the failure limits, the levels of importance of structure, and the interest rates.