• Steel and Composite Structures
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• v.46 no.1
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• pp.1-13
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• 2023

Elastic bending of imperfect functionally graded sandwich plates (FGSPs) laying on the Winkler-Pasternak foundation and subjected to sinusoidal loads is analyzed. The analyses have been established using the quasi-3D sinusoidal shear deformation model. In this theory, the number of unknowns is condensed to only five unknowns using integral-undefined terms without requiring any correction shear factor. Moreover, the current constituent material properties of the middle layer is considered homogeneous and isotropic. But those of the top and bottom face sheets of the graded porous sandwich plate (FGSP) are supposed to vary regularly and continuously in the direction of thickness according to the trigonometric volume fraction's model. The corresponding equilibrium equations of FGSPs with simply supported edges are derived via the static version of the Hamilton's principle. The differential equations of the system are resolved via Navier's method for various schemes of FGSPs. The current study examine the impact of the material index, porosity, side-to-thickness ratio, aspect ratio, and the Winkler-Pasternak foundation on the displacements, axial and shear stresses of the sandwich structure.

• Steel and Composite Structures
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• v.45 no.1
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• pp.67-82
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• 2022

In this paper, buckling and free vibration of imperfect, functionally graded beams, including porosities, are investigated, using a higher order shear strain theory. Due to defects during the manufacturing process, micro porosities may appear in the material, hence the appearance of this imperfection in the structure. The material properties of the beams are assumed to vary regularly, with power and sigmoid law, in the direction of thickness. A novel porosity distribution affecting the functionally graded volume fraction is presented. For the compact formulation used for cementite-based materials and already used in P-FGM, we have adapted it for the distribution of S-FGM. The equations of motion in the FG beam are derived using Hamilton's principle. The boundary conditions for beam FG are assumed to be simply supported. Navier's solution is used to obtain the closed form solutions of the FG beam. The numerical results of this work are compared with those of other published research to verify accuracy and reliability. The comparisons of different shear shape functions, the influence of porosity, thickness and inhomogeneity parameters on buckling and free vibration of the FG beam are all discussed. It is established that the present work is more precise than certain theories developed previously.

• Journal of English Language & Literature
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• v.55 no.1
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• pp.3-24
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• 2009

The Harry Potter series is considered to represent the multicultural aspect of contemporary British society and to show critical perspectives of racism. This series, however, also includes many elements of British imperialism. This paper examines the ideas about education and Harry's role in relation to British imperialism. One of the main ideas prevalent in 19th century British boys' public schools was that people's blood origin is the most important element in determining their characteristics, ability and moral qualities. The students' inherited capacity and their family background are more highly regarded than their secondary learning and training. This reflects a 19th century concept that ultimately, inborn quality makes 'a hero', a truth presented in the educational policies of Hogwarts. Hogwarts' educational policies and systems can also be related to 'developmentalism', which defines children as imperfect, in-progress and incomplete, thus needing proper training and discipline. As this concept functioned to justify the control of children while educating them, Hogwarts adopts diverse controlling devices and oppressive policies, which are mainly justified in the name of education. On the one hand, child characters are controlled and oppressed by the school authorities, on the other hand, some of the students such as Harry have remarkable magic powers enough to resist the adult authority and even to save the magic society from the evil power. Harry plays dual roles, which the British boys of the Empire were assigned from their society; they are important heirs to conquer the 'evil' or 'barbarous' world but need to be obedient to a 'good' authority to achieve the mission. Harry's magic power and self-discipline ultimately contribute to fulfilling Dumbledore's mission, which mirrors 19th century British boys' roles as the heirs of the British Empire.

• Journal of The Korean Association For Science Education
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• v.28 no.6
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• pp.641-648
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• 2008

The purpose of this study is to analyze pre-service science teachers' pedagogical content knowledge. For this study, two senior education students were selected. The data of this study were collected through interviews, CoRe questionnaire, and classroom observation recordings during the period of student-teacher practice. Data were analyzed using the constant comparative method. The results indicated that the two pre-service science teachers had low level pedagogical content knowledge. Two pre-service science teachers' knowledges of science curriculum were different from each other. Orientations toward teaching science shifted to undesirable direction after the experience of a student-teacher's practice-teaching. Their subject matter knowledges were imperfect. They also had low levels of knowledge of students' understanding.

• Journal of The Korean Association For Science Education
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• v.28 no.2
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• pp.159-168
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• 2008

The purpose of this study was to apply the coteaching to the teaching practice of the student-teachers and identify the distinctive characteristics of the communication processes appeared in coteaching. We developed the semiotic analyzing-frame and observed 7 classes of middle schools where the student-teachers cotaught one or two units. Then we analyzed the communication processes on the view of semiotics. We found three patterns of the communication processes. First, when there was a discontinuous communication between the student-teacher and the students, the communication was restarted by the other student-teacher leading to the complete meaning making. Second, when an insufficient communication took place by the student-teacher using inadequate interpretant, the other student-teacher modified the communication by selecting another interpretant including sufficient meaning towards the object. With this new interpretant, students could refine the imperfect private meanings and eventually establish the more objective meanings. Third, the communication was pre-planned between coteachers to help students understand the contents through the successful translation of interpretants. Coteaching provided positive implications to improve the communication processes in science lesson.

• Structural Engineering and Mechanics
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• v.90 no.1
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• pp.83-96
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• 2024

This paper suggests an analytical approach to investigate the free vibration and stability of functionally graded (FG) beams with both perfect and imperfect characteristics using a quasi-3D higher-order shear deformation theory (HSDT) with stretching effect. The study specifically focuses on FG beams resting on variable elastic foundations. In contrast to other shear deformation theories, this particular theory employs only four unknown functions instead of five. Moreover, this theory satisfies the boundary conditions of zero tension on the beam surfaces and facilitates hyperbolic distributions of transverse shear stresses without the necessity of shear correction factors. The elastic medium in consideration assumes the presence of two parameters, specifically Winkler-Pasternak foundations. The Winkler parameter exhibits variable variations in the longitudinal direction, including linear, parabolic, sinusoidal, cosine, exponential, and uniform, while the Pasternak parameter remains constant. The effective material characteristics of the functionally graded (FG) beam are assumed to follow a straightforward power-law distribution along the thickness direction. Additionally, the investigation of porosity includes the consideration of four different types of porosity distribution patterns, allowing for a comprehensive examination of its influence on the behavior of the beam. Using the virtual work principle, equations of motion are derived and solved analytically using Navier's method for simply supported FG beams. The accuracy is verified through comparisons with literature results. Parametric studies explore the impact of different parameters on free vibration and buckling behavior, demonstrating the theory's correctness and simplicity.

• Annals of Hepato-Biliary-Pancreatic Surgery
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• v.27 no.2
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• pp.195-200
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• 2023

Backgrounds/Aims: We aimed to build a machine learning tool to help predict low-grade intraductal papillary mucinous neoplasms (IPMNs) in order to avoid unnecessary surgical resection. IPMNs are precursors to pancreatic cancer. Surgical resection remains the only recognized treatment for IPMNs yet carries some risks of morbidity and potential mortality. Existing clinical guidelines are imperfect in distinguishing low-risk cysts from high-risk cysts that warrant resection. Methods: We built a linear support vector machine (SVM) learning model using a prospectively maintained surgical database of patients with resected IPMNs. Input variables included 18 demographic, clinical, and imaging characteristics. The outcome variable was the presence of low-grade or high-grade IPMN based on post-operative pathology results. Data were divided into a training/validation set and a testing set at a ratio of 4:1. Receiver operating characteristics analysis was used to assess classification performance. Results: A total of 575 patients with resected IPMNs were identified. Of them, 53.4% had low-grade disease on final pathology. After classifier training and testing, a linear SVM-based model (IPMN-LEARN) was applied on the validation set. It achieved an accuracy of 77.4%, with a positive predictive value of 83%, a specificity of 72%, and a sensitivity of 83% in predicting low-grade disease in patients with IPMN. The model predicted low-grade lesions with an area under the curve of 0.82. Conclusions: A linear SVM learning model can identify low-grade IPMNs with good sensitivity and specificity. It may be used as a complement to existing guidelines to identify patients who could avoid unnecessary surgical resection.

• Structural Engineering and Mechanics
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• v.91 no.6
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• pp.551-565
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• 2024

This study presents a methodical investigation into improving structural designs through the analytical examination of the dynamic behavior of functionally graded plates (FGPs) resting on viscoelastic foundations. By employing a four variable first-order shear deformation theory, the study computes non-dimensional frequencies for a variety of porous FGPs with diverse graded patterns and porosity distributions. Different gradient patterns of the plates are considered, and three distinct functions-sigmoid (S-FGM), exponential (E-FGM), and power-law (P-FGM)-are utilized to assess material performance in specific directions. The equations of motion are derived and solved using both Navier's method and Hamilton's principle. Analytical solutions for vibration frequency are provided to validate the proposed methodology against existing literature. Furthermore, a comprehensive parametric analysis is conducted, taking into account various factors such as ceramic material, porosity distribution, gradient index, length-to-thickness ratio, gradient pattern, and damping coefficient. The findings suggest that enhancing the damping coefficient of the viscoelastic foundation can significantly improve the free-vibrational response of functionally graded material plates.

• Korean Journal of Soil Science and Fertilizer
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• v.26 no.2
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• pp.72-77
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• 1993

This study was conducted to evaluate coated urea complex fertilizer (CUC) application for rice growth and its grain quality on clay loam (Deogpyeong series) and sandy loam (Gangseo series) in southern region of Korea, 1992. The coated urea complex fertilizer used in the experiment was CUC I and II. The CUC I is a complex fertilizer consisting of 18-12-13 for $N-P_2O_5-K_2O$ including 50% of coated urea as nitrogen source, and CUC II is the same complex fertilize as mentioned above but it contains 25% of coated urea. Seventy percent of conventional fertilizer for nitrogen level was applied as basal dose of side-band placement (SBP) and whole plowlayer placement (WPP). Greenish degree of rice leaf color at the late growth stage was high in CUC plots regardless of application method and soil series. Amount of nitrogen uptaken by the rice plant at harvesting stage was mush more in the CUC treatment compared to convential fertilizer, and also much more in CUC I than that of CUC II. In the WPP on clay loam, harvest index of CUC treatment was showed very low level, which was reduced more in CUC II plot. In the CUC treatments, perfect rice grain ratio decreased remarkably, and the notched-belly rice kernel ratios among imperfect rice grain increased drastically. In rice grain, Hon-value(Mg to K.N ratio) decreased, protein and amylose contents increased in CUC application plots in WPP. In addition, gel consitency and alkali spreading value related to eating quality in CUC plots were getting longer and lower, respectively. The yield in CUC plot was similar to conventional fertilizing, but significant decreased in SBP. As a result, the rice grain quality became poor with the coated urea complex fertilizer application, but it could be improved by incorporation with fast-release fertilizer.

• Korean Journal of Construction Engineering and Management
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• v.15 no.1
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• pp.101-110
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• 2014

The ministry of Land, Infrastructure and Transport announced that they launched the pilot project to offer Happy House built with modular construction as part of the major projects of incumbent government in 2013. The market size of modular construction is getting increasingly enlarged together with strong will of government. The major challenges that current modular construction encounters can be summed up as lack of standardization of material on the stage of design and fabrication. The portion of material costs in modular construction marks 16 to 17% higher than the existing other construction method, and account for 60 % of total construction cost, which is why material management is the most important factor. However, the imperfect standardization and specification on design causes high loss of materials on fabrication, which makes the construction wastes and total construction cost increasing in accordance with the increase of material costs. This study has been conducted to verify major modules by developing optimization algorithm on gypsum board material among wall finishing materials. It is expected that this paper contributes not only to eco-friendly construction by minimizing the waste factors of materials through these efforts, but also to removing high cost issues which had been recognized as a setback of current modular construction.