• Journal of Engineering Education Research
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• v.13 no.6
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• pp.143-151
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• 2010

This paper presents a case study on the assessment of program outcomes using the capstone design course based on 16-year management experience and improvements of the school of mechanical design and automation engineering in the seoul national university of science and technology. First, the program outcomes related with the capstone design course are introduced, and the assessment methods and items are described. Based on them, the assessment results in 2008 were obtained and a strategy to improve the results were built after analyzation. As for the strategy, we revealed the assessment items and good examples in an internet web site in advance. As a result, we were able to obtain about 3.3% improved assessment results in 2009. Finally, the validity, efficiency, internal stability, and sustainability of the assessment of the program outcomes using the capstone design course are addressed in terms of a notion of the course-embedded assessment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.8
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• pp.5143-5151
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• 2015

This study desires to examine the factors of educational beliefs and child-care commitment of preservice child-care teachers affecting teacher efficacy. To achieve such study purpose, a questionnaire was used targeting 239 preservice child-care teachers in I City. For response results, first, preservice child-care teachers appreciated a belief for maturity in educational beliefs, educational love in child-care commitment, and teaching strategy and students' participation in teacher efficacy the most. Second, there is a statistically meaningful correlation in educational beliefs, child-care commitment, and teacher efficacy of preservice child-care teachers. Third, educational beliefs and child-care commitment of preservice child-care teachers have a positive effect on teacher efficacy. Through such study results, it is thought that role and importance of child-care teachers are appreciated, and various studies should be proceeded to ensure internal stability for professionalism awareness of child-care teachers for improvement of fine child-care service.

• The Journal of the Korea Contents Association
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• v.12 no.2
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• pp.505-516
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• 2012

The purpose of the this research is to find out what basic factors of aging for korean elderly(above 65years old). First of all, 90 preliminary questions were developed from 551 questionnaires. In addition, some practices of the composition factors were carried out from another 552 seniors and additional tests were tried for composition validity, certified validity and successful aging standards from other 399 elders. The survey showed that the standard of the successful aging for korean elderly, which was composed of 47 questions, displayed satisfaction of everyday life, off-spring's success, psychological support, positive activity. sense of self effectiveness, mental stability, satisfaction of spousal relationship and family support. The reliability of the Validation of Successful Aging for Korean Elderly showed high internal consistency of 0.932. It is also verified that the relationship between the factors and the questions has statistically meaningful, which makes it possible to confirm the reliability of the structure of the factors.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.4
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• pp.414-420
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• 2006

Purpose : The purpose of this study is to use finite element analysis to predict the fatigue life of an implant system subjected to fatigue load by mastication (chewing force). The reliability and the stability of implant system can be defined in terms of the fatigue strength. Not only an implant is expensive but also it is almost impossible to correct after it is inserted. From a bio-engineering standpoint, the fatigue strength of the dental implant system must be evaluated by simulation (FEA). Material and Methods Finite element analysis and fatigue test are performed to estimate the fatigue strength of the implant system. Mesh of implant is generated with the actual shape and size. In this paper, the fatigue strength of implant system is estimated. U-fit (T. Strong, Korea, internal type). The stress field in implant is calculated by elastic-plastic finite element analysis. The equivalent fatigue stress, considering the contact and preload stretching of a screw by torque for tightening an abutment, is obtained by means of Sine's method. To evaluate the reliability of the calculated fatigue strength, fatigue test is performed. Results: A comparison of the calculated fatigue strength with experimental data showed the validity and accuracy of the proposed method. The initiation points of the fatigue failure in the implant system exist in the region of high equivalent fatigue stress values. Conclusion: The above proposed method for fatigue life estimation tan be applied to other configurations of the differently designed and improved implant. In order to prove reliability of prototype implant, fatigue test should be executed. The proposed method is economical for the prediction of fatigue life because fatigue testing, which is time consuming and precision-dependent, is not required.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.5
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• pp.622-632
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• 2005

Statement of problem: Silicone Index Tooth Tray impression system which does not use gingicord has a shortcoming. It takes time to remove internal wall of Silicone Index Tooth Tray for space of wash impression material. Purpose: This study was to evaluate whether providing certain space to impression body can prevent from doing complicated laboratory work. Material and methods: After mounting metal dies with shoulder and chamfer margins arbiturarily, SITT was produced using $Blu-mousse^(R)$. In one experimental group, wash impression was taken using $Fit-tester^(R)$ without removing interior surface of SITT and in the other group, wash impression was taken using $Fit-tester^(R)$ providing 0.5mm space in the SITT and then compared the differences in two groups. Results: 1. There was no significant difference between a group which did not allow space and a group which granted equal 0.5mm space. 2. There was no significant difference between gingival diameter, occlusal diameter of metal die that has shoulder margin and gingival diameter, occlusal diameter of metal die that has chamfer margin. 3. There was no significant difference between a group which did not take pick-up impression and a group which took pick-up impression through relining method using SITT 4. There was no significant difference between a group that poured immediately after taking primary impression and a group that poured after removing poured stone die. Conclusions: When taking an impression of an abutment using SITT impression system, it is considered to obtain clinically identical results between a group that did not grant a 0.5mm space within SITT for wash impression and a group which invest a space. Furthermore, it is considered possible to produce an individual die through secondary pouring.

• The Journal of Advanced Prosthodontics
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• v.6 no.1
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• pp.46-52
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• 2014

PURPOSE. The aim of this study was to evaluate the interface accuracy of computer-assisted designed and manufactured (CAD/CAM) titanium abutments and implant fixture compared to gold-cast UCLA abutments. MATERIALS AND METHODS. An external connection implant system (Mark III, n=10) and an internal connection implant system (Replace Select, n=10) were used, 5 of each group were connected to milled titanium abutment and the rest were connected to the gold-cast UCLA abutments. The implant fixture and abutment were tightened to torque of 35 Ncm using a digital torque gauge, and initial detorque values were measured 10 minutes after tightening. To mimic the mastication, a cyclic loading was applied at 14 Hz for one million cycles, with the stress amplitude range being within 0 N to 100 N. After the cyclic loading, detorque values were measured again. The fixture-abutment gaps were measured under a microscope and recorded with an accuracy of ${\pm}0.1{\mu}m$ at 50 points. RESULTS. Initial detorque values of milled abutment were significantly higher than those of cast abutment (P<.05). Detorque values after one million dynamic cyclic loadings were not significantly different (P>.05). After cyclic loading, detorque values of cast abutment increased, but those of milled abutment decreased (P<.05). There was no significant difference of gap dimension between the milled abutment group and the cast abutment group after cyclic loading. CONCLUSION. In conclusion, CAD/CAM milled titanium abutment can be fabricated with sufficient accuracy to permit screw joint stability between abutment and fixture comparable to that of the traditional gold cast UCLA abutment.

• Geomechanics and Engineering
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• v.14 no.4
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• pp.307-314
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• 2018

Strength of loess that experienced cyclic freeze and thaw is of great significance for evaluating stability of slopes and foundations in loess regions. This paper takes the frequently encountered loess in the Northwestern China as the study object and carried out three kinds of laboratory tests including freeze-thaw test, direct shear test and SEM test to investigate the strength behaviors of loess after cyclic freeze and thaw, and the correlation with meso-level changes in soil structure. Results show that for loess specimens at four dry densities, the cohesion decreases with freeze-thaw cycles until a residual value is reached and thus an exponential equation is proposed. Besides, little change in the angle of internal friction was observed as freeze-thaw proceeds. This may depend on the varying of soil structure, based on which a clue can be found from the surface morphology and mesoscopic scanning of loess specimens. Clearly we observed significant changes in surface morphology of loess and it tends to aggravate at higher water contents or more cycles of freeze and thaw. Moreover, freeze-thaw cycling leads to obvious changes in the meso-structure of loess including lowering the particle aggregates and increasing both the proportion of fine particles and porosity area ratio. A damage variable dependent on the ratio of porosity area is introduced based on the continuum damage mechanics and its correlation with cohesion is discussed.

• Korean Journal of Remote Sensing
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• v.36 no.4
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• pp.573-586
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• 2020

PM (particulate matter) is of interest to everyone because it can have adverse effects on human health by the infiltration from respiratory to internal organs. To date, many studies have made efforts for the prediction of PM10 and PM2.5 concentrations. Unlike previous studies, we conducted the prediction of tomorrow's PM10 concentration for the Air Korea stations using Chinese PM10 data in addition to the satellite AOD and weather variables. We constructed 230,639 matchups from the raw data over 3 million and built an RF (random forest) model from the matchups to cope with the complexity and nonlinearity. The validation statistics from the blind test showed excellent accuracy with the RMSE (root mean square error) of 9.905 ㎍/㎥ and the CC (correlation coefficient) of 0.918. Moreover, our prediction model showed a stable performance without the dependency on seasons or the degree of PM10 concentration. However, part of coastal areas had a relatively low accuracy, which implies that a dedicated model for coastal areas will be necessary. Additional input variables such as wind direction, precipitation, and air stability should also be incorporated into the prediction model as future work.

• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3284-3288
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• 2013

This paper describes first development and validation of pentafluorophenylprophyl ligand-based liquid chromatography coupled to tandem mass spectrometry (PFPLC-MS/MS) method to determine metformin, a highly polar compound, in human plasma. Metformin and Phenformin (internal standard) were extracted from human plasma 50 ${\mu}L$ with a single-step protein precipitation. The chromatographic separation was performed using a linear gradient elution of mobile phase involving 5.0 mM ammonium formate solution with 0.1% formic acid (A) and acetonitrile (B) over 3.0 min of run time on a Phenomenex Luna PFP column. The detection was performed using a triple-quadrupole tandem mass spectrometer (Waters Quattro micro) with electrospray ionization in the mode of positive ionization and multiple-reaction monitoring (MRM). The developed method was validated with 5.0 ng/mL of lower limit of quantification (LLOQ). The calibration curve was linear over 5-3000 ng/mL of the concentration range ($R^2$ > 0.99). The specificity, selectivity, carry-over effect, precision, accuracy and stability of the method met the acceptance criteria. The method developed in this study had had rapidness, simplicity and ruggedness. The reliable method was successfully applied to high throughput analysis of real samples for a practical purpose of a pharmacokinetic study.

• Journal of the Korean Wood Science and Technology
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• v.37 no.4
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• pp.340-348
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• 2009

The recycled polyethylene was used for making wood-plastic composite panels. In this experiment, the sizes of wood particles used were 1/32", 1/4" and 1/2" in mesh number, and the contents of the recycled polyethylene were 10%, 30% and 50%. The physical and mechanical properties of the composite panels were investigated. At a given content of recycled polyethylene, the density of composite panel decreases with the increase of wood particle size. The thickness swelling and water adsorption decrease with the increase of recycled polyethylene, where significantly lower at 10%, compared with at 30%. In the water soaking experiment for 14 days, the dimensional stability of composite panel appeared good in the composite panel with recycled polyethylene content of 30% or higher. As the content of recycled polyethylene increases, the internal bonding strength and the modulus of rupture in bending strength increases. In SEM, the molten recycled polyethylene showed interlocking action through its penetration into tracheid openings including pits as well as binder between wood particles as the matrix material, thus increasing bonding strength and improving the physical and mechanical properties of composite panel.