• Journal of Digital Contents Society
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• v.15 no.1
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• pp.19-27
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• 2014

In order to estimate the life of 2,5 inch HDD which is adopted by PC environment, make the test plan which reflect the failure mode of market, make the test model of accelerated life test which reflect the stress of temperature. after an analysis of the environment of PC using, test procedure was decided that operation was write 50 % and read 50 %, and then access method was sequential 50 % and random 50%. The acceleration life test was executed on condition that temperature was $50^{\circ}C$ and $60^{\circ}C$, performance was 95 % in max performance, test time was 1000 hours. by the test of goodness of fit of anderson-darling of the failure data during test, it was confirmed that the distribution of failure fellow weibull. test for shape and scale was equal, and shape parameter was 0.7177, characteristic life was 429434 hours at normal user condition($30^{\circ}C$) by the analysis of weibull-arrhenius modeling. It made no difference about the statistics when equality test was executed. The activation energy was 0.2775eV. In analyzing between the failure samples of acceleration test and the samples of market return even though there is detail difference about the share of failure mode, the rank of share was almost same. This study suggest the test procedure of acceleration test of 2.5 inch HDD in PC using environment, and help the life estimation at manufacture and user.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.6
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• pp.349-357
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• 2019

Finite element method (FEM) is utilized in the development of products to realistically analyze and predict the mechanical behavior of materials in various fields. However, the approach based on the numerical analysis of glass fiber reinforced plastic (GFRP) composites, for which the fiber orientation and strain rate affect the mechanical properties, has proven to be challenging. The purpose of this study is to define and evaluate the mechanical properties of glass fiber reinforced plastic composites using the numerical analysis models of Digimat, a linear, nonlinear multi-scale modeling program for various composite materials such as polymers, rubber, metal, etc. In addition, the aim is to predict the behavior of realistic polymeric composites. In this regard, the tensile properties according to the fiber orientation and strain rate of polybutylene terephthalate (PBT) with short fiber weight fractions of 30wt% among various polymers were investigated using references. Information on the fiber orientation was calculated based on injection analysis using Moldflow software, and was utilized in the finite element model for tensile specimens via a mapping process. LS-Dyna, an explicit commercial finite element code, was used for coupled analysis using Digimat to study the tensile properties of composites according to the fiber orientation and strain rate of glass fibers. In addition, the drawbacks and advantages of LS-DYNA's various anisotropic material models were compared and evaluated for the analysis of glass fiber reinforced plastic composites.

• Management & Information Systems Review
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• v.35 no.4
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• pp.141-153
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• 2016

This study estimates the productivity change of pharmaceutical industry and decompose the change into technical efficiency change and technological change to explore ways to improve the productive efficiency. Unlike most previous studies, this study employs the non-radial and non-oriented slacks-based Malmquist productivity index which can deals directly with the input excesses and output shortfalls. In addition a smoothed bootstrap method is applied to estimate statistical confidence intervals for the Malmquist Index and its components. For the empirical analysis a balanced panel data set is constructed covering ten years over the period from 2005 to 2014. The input variables used in this study are number of workers, tangible assets and major production cost. The gross production is selected as a main output variable. The empirical results suggest that the productivity of pharmaceutical industry has decreased due mainly to decline in the technological progress rather than improvements in technical efficiency. An analysis result shows that the scale efficiency outweighs the pure efficiency in determining the technical efficiency of pharmaceutical industry. Therefore, in order to enhance the competitiveness of domestic pharmaceutical industry, it is important to continue supporting policies to promote the technology innovation capability through efficient R&D investment and industry reform strategy.

• The Journal of Korean Academy of Prosthodontics
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• v.58 no.3
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• pp.185-192
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• 2020

Purpose: The purpose of this study is to investigate dental students' self-perception of clinical care ability after a denture treatment experience. Materials and methods: Of the 58 fourth-year students at the dental school in 2019, 50 students completed the questionnaire concerning their denture treatment session, including treatment planning and pre-prosthetic treatment (4 questions), clinical and laboratory procedures (20 questions), and students' opinions on clinical denture education (4 questions). Each question was answered on a five-point scale, of which points four and five, "agree" and "strongly agree" respectively, were classified as positive responses while points one and two, "disagree" and "strongly disagree" respectively, were classified as negative. Results: All the items on clinical and laboratory procedures received a positive response rate of over 60%, and the overall self-perception of the students appeared to be positive. However, the questions on the ability to perform denture treatment independently after graduation received only 48% of positive answer. Those on patient management, explanations of denture precautions, customized tray production, boxing, and work model production were answered with the highest positive response rate whereas those on treatment planning, final impression acquisition, and surveying, were the lowest in each session. Conclusion: The dental students with experience in denture treatment generally have a positive opinion of their clinical care ability, but further education may be necessary to improve their ability to treat their patients independently.

• Child Health Nursing Research
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• v.21 no.1
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• pp.37-45
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• 2015

Purpose: In this study, a comparison was done of the extent of health-related quality of life (HRQoL) for preterm and fullterm children during early childhood, and factors affecting HRQoL in the early childhood of premature children were analyzed. Methods: Eighty mothers of children born prematurely and 83 mothers of children born at fullterm listed on two Internet cafes were sampled for this study. The major instrument used for the study was the TNO-AZL Preschool Quality Of Life (TAPQOL) questionnaire. Results: Total score for HRQoL in the premature group was 80.5 (${\pm}9.9$) and for the full term group, 85.0 (${\pm}8.3$), on a 100-point scale. A comparison of the premature group and full term group showed that the domains which scored relatively lower with respect to HRQoL included the stomach, motor function, anxiety, liveliness and communication. Among the factors that have an impact on HRQoL were 'length of stay in neonatal intensive care unit (${\geq}7$ days)' and 'birth weight (<1,000 gm)'. The explanation power of the model was 17%, which was statistically significant. Conclusion: These findings indicate that a differentiated premature infant follow-up program for children who are hospitalized over 7 days in NICU or weighed under 1,000g at birth is urgently needed.

• Journal of the Korean Solar Energy Society
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• v.28 no.2
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• pp.58-63
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• 2008

This study has analysed power output characteristics of transparent thin-film PV module depending on incidence angle and azimuth. The experiment results showed power outputs of transparent thin-film PV module applied to full-scale mock up model on slope of $90^{\circ},\;30^{\circ},\;0^{\circ}$ to the south. The simulation results was evaluated power outputs of transparent thin-film PV module depending on incidence angle and azimuth after calibrating the experimental and computed data. As a result. the best power output performance of transparent thin-film PV module was obtained at slope of $30^{\circ}$ to the south, producing the annual power output of 977kWh/kWp. The annual power output data demonstrated that the PV module with a slope of $30^{\circ}$ could produce a 68 % higher power output than that with a slope of $90^{\circ}$ with respect to the inclined slope of the module, Furthermore, the PV module facing south showed a 22 % higher power output than that facing to the east in terms of the angle of the azimuth, Specipically. the varying power output with incidence angle of PV module can be resulted from the influence of incidence angle modifier of glass on PV module. That is, the solar energy transmission can be reduced as an increase of incidence angle of PV module. Therefore, when the inclined slope of the PV module was over $70^{\circ}$ there was a significant reduction of power output, and this was caused by the decrease of solar energy transmission in the transparent thin-film PV module.

• Journal of Korea Water Resources Association
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• v.48 no.2
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• pp.115-126
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• 2015

In recent years, debris flow disaster has occurred in multiple locations between high and low mountainous areas simultaneously with a flooding disaster in urban areas caused by heavy and torrential rainfall due to the changing global climate and environment. As a result, these disasters frequently lead to large-scale destruction of infrastructures or individual properties and cause psychological harm or human death. In order to mitigate these disasters more effectively, it is necessary to investigate what causes the damage with an integrated model of both disasters at once. The objectives of this study are to analyze the mechanism of debris flow for real basin, to determine the PMP and run-off discharge due to the DAD analysis, and to estimate the influence range of debris flow for fan area according to the scenario. To analyse the characteristics of debris flow at the real basin, the parameters such as the deposition pattern, deposit thickness, approaching velocity, occurrence of sediment volume and travel length are estimated from DAD analysis. As a results, the peak time precipitation is estimated by 135 mm/hr as torrential rainfall and maximum total amount of rainfall is estimated by 544 mm as typhoon related rainfall.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.28 no.4
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• pp.449-454
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• 2010

Lately, airborne digital camera and airborne laser scanner in field of airborne surveying are used to build geography information such as digital ortho photo map and DEM(Digital Elevation Model). In this study, 3D position accuracy is compared medium format CCD camera RCD105 with airborne digital camera DMC. For this, test area was decided for aerial photograph. And using 1/1,000 scale digital map, ground control points were selected for aerial triangulation and check points were selected for horizontal/vertical accuracy analysis using softcopy stereoplotter. Accuracy of RCD105 and DMC was estimated by result of aerial triangulation and result of check points measurement of using softcopy stereoplotter. In result of aerial triangulation, RMSE(Root Mean Square Error) X, Y, Z of RCD105 is 2.1, 2.2, 1.3 times larger than DMC. In result of check point measurement using softcopy stereoplotter, horizontal/ vertical RMSE of RCD105 is 2.5, 4.3 times larger than DMC. Even though accuracy of RCD105 is lower than DMC, it is maybe possible to make digital map and ortho photo using RCD105.

• Journal of Korea Water Resources Association
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• v.53 no.11
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• pp.929-938
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• 2020

In this study, we estimated missing evapotranspiration (ET) data at a eddy-covariance flux tower in the Cheongmicheon farmland site using the Artificial Neural Network (ANN). The ANN showed excellent performance in numerical analysis and is expanding in various fields. To evaluate the performance the ANN-based gap-filling, ET was calculated using the existing gap-filling methods of Mean Diagnostic Variation (MDV) and Food and Aggregation Organization Penman-Monteith (FAO-PM). Then ET was evaluated by time series method and statistical analysis (coefficient of determination, index of agreement (IOA), root mean squared error (RMSE) and mean absolute error (MAE). For the validation of each gap-filling model, we used 30 minutes of data in 2015. Of the 121 missing values, the ANN method showed the best performance by supplementing 70, 53 and 84 missing values, respectively, in the order of MDV, FAO-PM, and ANN methods. Analysis of the coefficient of determination (MDV, FAO-PM, and ANN methods followed by 0.673, 0.784, and 0.841, respectively.) and the IOA (The MDV, FAO-PM, and ANN methods followed by 0.899, 0.890, and 0.951 respectively.) indicated that, all three methods were highly correlated and considered to be fully utilized, and among them, ANN models showed the highest performance and suitability. Based on this study, it could be used more appropriately in the study of gap-filling method of flux tower data using machine learning method.

• Journal of the Korean Geotechnical Society
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• v.28 no.12
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• pp.5-15
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• 2012

In this study, a series of CFD (Computational Fluid Dynamics) numerical analyses were performed in order to evaluate the thermal performance of six full-scale closed-loop vertical ground heat exchangers constructed in a test bed located in Wonju. The circulation HDPE pipe, borehole and surrounding ground formation were modeled using FLUENT, a finite-volume method (FVM) program, for analyzing the heat transfer process of the system. Two user-defined functions (UDFs) accounting for the difference in the temperatures of the circulating inflow and outflow fluid and the variation of the surrounding ground temperature with depth were adopted in the FLUENT model. The relevant thermal properties of materials measured in laboratory were used in the numerical analyses to compare the thermal efficiency of various types of the heat exchangers installed in the test bed. The simulation results provide a verification for the in-situ thermal response test (TRT) data. The CFD numerical back-analysis with the ground thermal conductivity of 4 W/mK yielded better agreement with the in-situ thermal response tests than with the ground thermal conductivity of 3 W/mK.