• Restorative Dentistry and Endodontics
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• v.38 no.1
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• pp.21-25
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• 2013

Objectives: The aim of this study was to evaluate the shaping ability of newly marketed single-file instruments, Wave One (Dentsply-Maillefer) and Reciproc (VDW GmbH), in terms of maintaining the original root canal configuration and curvature, with or without a glide-path. Materials and Methods: According to the instruments used, the blocks were divided into 4 groups (n = 10): Group 1, no glide-path / Wave One; Group 2, no glide-path / Reciproc; Group 3, #15 K-file / Wave One; Group 4, #15 K-file / Reciproc. Pre- and post-instrumented images were scanned and the canal deviation was assessed. The cyclic fatigue stress was loaded to examine the cross-sectional shape of the fractured surface. The broken fragments were evaluated under the scanning electron microscope (SEM) for topographic features of the cross-section. Statistically analysis of the data was performed using one-way analysis of variance followed by Tukey's test (${\alpha}$ = 0.05). Results: The ability of instruments to remain centered in prepared canals at 1 and 2 mm levels was significantly lower in Group 1 (p < 0.05). The centering ratio at 3, 5, and 7 mm level were not significantly different. Conclusions: The Wave One file should be used following establishment of a glide-path larger than #15.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.189-194
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• 2020

This paper analyzes the gradient descent method, which is the one most used for learning neural networks. Learning means updating a parameter so the loss function is at its minimum. The loss function quantifies the difference between actual and predicted values. The gradient descent method uses the slope of the loss function to update the parameter to minimize error, and is currently used in libraries that provide the best deep learning algorithms. However, these algorithms are provided in the form of a black box, making it difficult to identify the advantages and disadvantages of various gradient descent methods. This paper analyzes the characteristics of the stochastic gradient descent method, the momentum method, the AdaGrad method, and the Adadelta method, which are currently used gradient descent methods. The experimental data used a modified National Institute of Standards and Technology (MNIST) data set that is widely used to verify neural networks. The hidden layer consists of two layers: the first with 500 neurons, and the second with 300. The activation function of the output layer is the softmax function, and the rectified linear unit function is used for the remaining input and hidden layers. The loss function uses cross-entropy error.

• The Korean Journal of Pain
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• v.30 no.3
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• pp.197-206
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• 2017

Background: Pain with neuropathic characteristics is generally more severe and associated with a lower quality of life compared to nociceptive pain (NcP). Short form of the Douleur Neuropathique en 4 Questions (S-DN4) is one of the most used and reliable screening questionnaires and is reported to have good diagnostic properties. This study was aimed to cross-culturally validate the Hindi version of the S-DN4 in patients with various chronic pain conditions. Methods: The S-DN4 is already translated into the Hindi language by Mapi Research Trust. This study assessed the psychometric properties of the Hindi version of the S-DN4 including internal consistency and test-retest reliability after 3 days' post-baseline assessment. Diagnostic performance was also assessed. Results: One hundred sixty patients with chronic pain, 80 each in the neuropathic pain (NeP) present and NeP absent groups, were recruited. Patients with NeP present reported significantly higher S-DN4 scores in comparison to patients in the NeP absent group (mean (SD), 4.7 (1.7) vs. 1.8 (1.6), P < 0.01). The S-DN4 was found to have an AUC of 0.88 with adequate internal consistency (Cronbach's ${\alpha}=0.80$) and a test-retest reliability (ICC = 0.92) with an optimal cut-off value of 3 (Youden's index = 0.66, sensitivity and specificity of 88.7% and 77.5%). The diagnostic concordance rate between clinician diagnosis and the S-DN4 questionnaire was 83.1% (kappa = 0.66). Conclusions: Overall, the Hindi version of the S-DN4 has good internal consistency and test-retest reliability along with good diagnostic accuracy.

• Journal of Korean Society of Forest Science
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• v.97 no.3
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• pp.316-325
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• 2008

This study was done to compare socio-economic characteristics and travel pattern, preferences for ecotourism facilities and programs of domestic and international tourists who visited to Jeju Island. On-site survey was carried out during July, 2006 and a total of five hundred and fifty five (555) individuals' data were analyzed. Survey results showed that there were significant differences between socioeconomic characteristics and travel patterns as well as preferences of both parties. Even among international tourists from countries with different languages showed different characteristics. These different characteristics among tourist groups imply that tour route design and program development should be accordingly considered to provide satisfactory experiences.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.1
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• pp.69-80
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• 2009

Purpose: We investigated validity of a monitor-based computer eye test program, Test Chart 2000 Pro (developed by Thomson Software Solutions, UK). Methods: We chose ten common eye tests of the Test Chart 2000 Pro and Korean Standard Eye Test, applying them to same subject groups each by each, followed by comparison and analyses of agreement degree of the results. Results: Among the ten eye tests, Snellen Chart, Cross-cyl target, Duochrome test, Fan and Block test, and Random dot stereograms showed statistically significant agreement between both the Korean standard eye test method and Test Chart 2000 Pro. On the other hand, some disagreements were found between the two eye test methods in LogMAR Chart, Single Letter Chart, Phoria Test, Fixation Disparity Test, and Worth 4 Dot Test. Conclusions: Comparing to the Korean Standard Eye Test that consists of Han eye chart and Phoroptor, validity of the Test Chart 2000 Pro is not so high. Further improvements of the Test Chart 2000 Pro in accuracy are required.

• Information Systems Review
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• v.17 no.3
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• pp.19-38
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• 2015

Utilization of information increases not only individual performance but also the welfare of whole society including social trust, efficiency, and communication. This study examines the effects of the utilization of mobile information on social trust, efficiency, and communication using a survey data responding 2,000 people from Korea, China, USA, and Japan. As the results, the higher uses mobile information, the higher perceives social trust, efficiency, communication, and welfare. In addition the effects of utilization of mobile information on the perception of social trust, efficiency, communication, and welfare are different among 4 countries. Cross-cultural implications of IT are suggested based on the results.

• Korean Journal of Food Science and Technology
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• v.52 no.2
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• pp.172-176
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• 2020

Recently, it has been reported that the positive emotional responses from previously consumed food could be transferred to the new food, affecting the acceptance of the food. This study was conducted to develop emotional lexicons for evaluating consumers' emotional responses to the food. Focus group interviews were conducted using 15 Koreans and 23 Chinese consumers to elicit emotional terms for Korean food HMR products. Using 23 Chinese participants who did not participate in the previous interview, emotional terms were screened through discussions in an interview setting. An online survey among 50 Koreans and 50 Chinese was carried out to evaluate and verify the valence and arousal potential of the selected terms. Elicited emotional terms in these two countries had similar valence and arousal potentials. However, cross-cultural differences were also found, mostly in arousal potential. Therefore, interpretation should be done carefully when comparing emotional responses between Korean and Chinese subjects.

• Nuclear Engineering and Technology
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• v.47 no.7
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• pp.791-803
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• 2015

The effective cross sections (XSs) in the direct whole core calculation code nTRACER are evaluated by the equivalence theory-based resonance-integral-table method using the WIMS-based library as an alternative to the subgroup method. The background XSs, as well as the Dancoff correction factors, were evaluated by the enhanced neutron-current method. A method, with pointwise microscopic XSs on a union-lethargy grid, was used for the generation of resonance-interference factors (RIFs) for mixed resonant absorbers. This method was modified by the intermediate-resonance approximation by replacing the potential XSs for the non-absorbing moderator nuclides with the background XSs and neglecting the resonance-elastic scattering. The resonance-escape probability was implemented to incorporate the energy self-shielding effect in the spectrum. The XSs were improved using the proposed method as compared to the narrow resonance infinite massbased method. The RIFs were improved by 1% in $^{235}U$, 7% in $^{239}Pu$, and >2% in $^{240}Pu$. To account for thermal feedback, a new feature was incorporated with the interpolation of pre-generated RIFs at the multigroup level and the results compared with the conventional resonance-interference model. This method provided adequate results in terms of XSs and k-eff. The results were verified first by the comparison of RIFs with the exact RIFs, and then comparing the XSs with the McCARD calculations for the homogeneous configurations, with burned fuel containing a mixture of resonant nuclides at different burnups and temperatures. The RIFs and XSs for the mixture showed good agreement, which verified the accuracy of the RIF evaluation using the proposed method. The method was then verified by comparing the XSs for the virtual environment for reactor applicationbenchmark pin-cell problem, as well as the heterogeneous pin cell containing burned fuel with McCARD. The method works well for homogeneous, as well as heterogeneous configurations.

• Journal of the Korean Society of School Health
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• v.34 no.1
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• pp.1-12
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• 2021

Purpose: Growing evidence indicates that adolescents from multicultural families are more vulnerable to drug use than those from non-multicultural families. This study aimed to compare the factors associated with the habitual drug use among adolescents from multicultural and non-multicultural families. Methods: A descriptive cross-sectional design was employed. Data were obtained from the 14~15th (2018~2019) Korea Youth Risk Behavior Web-based Survey. Overall, 91,443 multicultural (n=1,725) and non-multicultural adolescents (n=89,718) were included. Data were analyzed using descriptive statistics, univariate analysis, and logistic regression analysis. Results: The multicultural adolescents engaged in more habitual drug use than did non-multicultural adolescents. In both groups, those who currently drank, experienced violent victimization, had sexual experiences, and did not live with their family were at greater risk of engaging in habitual drug use. The odds ratios of these factors were higher in multicultural adolescents than in non-multicultural adolescents. In non-multicultural adolescents, those who were boys, had experienced depression and suicidal ideation, perceived their body image as normal, overweight, or obese, and had poor subjective health status were at greater risk of engaging in habitual drug use. Conclusion: These results highlight the need to develop customized strategies for adolescents from both multicultural and non-multicultural families to reduce and prevent their habitual drug use.

• Journal of Environmental Science International
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• v.31 no.1
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• pp.61-76
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• 2022

In this study, surface particulate matter (PM_2.5) concentrations were calculated based on empirical equations using measurements of ceilometer backscatter intensities and meteorological variables taken over 19 months. To quantify the importance of meteorological conditions on the calculations of surface PM_2.5 concentrations, eight different meteorological conditions were considered. For each meteorological condition, the optimal upper limit height for an integration of ceilometer backscatter intensity and coefficients for the empirical equations were determined using cross-validation processes with and without considering meteorological variables. The results showed that the optimal upper limit heights and coefficients depended heavily on the meteorological conditions, which, in turn, exhibited extensive impacts on the estimated surface PM_2.5 concentrations. A comparison with the measurements of surface PM_2.5 concentrations showed that the calculated surface PM_2.5 concentrations exhibited better results (i.e., higher correlation coefficient and lower root mean square error) when considering meteorological variables for all eight meteorological conditions. Furthermore, applying optimal upper limit heights for different weather conditions revealed better results compared with a constant upper limit height (e.g., 150 m) that was used in previous studies. The impacts of vertical distributions of ceilometer backscatter intensities on the calculations of surface PM_2.5 concentrations were also examined.