• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.4
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• pp.390-403
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• 2017

Smoothed Particle Hydrodynamics (SPH) method has a good adaptability for the simulation of free surface flow problems. There are two forms of SPH. One is weak compressible SPH and the other one is incompressible SPH (ISPH). Compared with the former one, ISPH method performs better in many cases. ISPH based on Rankine source solution can perform better than traditional ISPH, as it can use larger stepping length by avoiding the second order derivative in pressure Poisson equation. However, ISPH_R method needs to solve the sparse linear matrix for pressure Poisson equation, which is one of the most expensive parts during one time stepping calculation. Iterative methods are normally used for solving Poisson equation with large particle numbers. However, there are many iterative methods available and the question for using which one is still open. In this paper, three iterative methods, CGS, Bi-CGstab and GMRES are compared, which are suitable and typical for large unsymmetrical sparse matrix solutions. According to the numerical tests on different cases, still water test, dam breaking, violent tank sloshing, solitary wave slamming, the GMRES method is more efficient than CGS and Bi-CGstab for ISPH method.

• Environmental and Resource Economics Review
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• v.14 no.1
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• pp.201-220
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• 2005

Recently, we have been witnessing new records of crude oil price hikes. One question which naturally arises would be the possibility and accuracy of forecasting crude oil prices. This study tries to answer the relative predictability of futures prices compared to the forecasts based on experts system. Using WTI crude oil spot and futures prices, this study performs simple statistical comparisons in forecasting accuracy and a formal test of differences in forecasting errors. According to statistical results, WTI crude oil futures market turns out to be equally efficient relative to EIA experts system. Consequently, WTI crude oil futures market could be utilized as a market-based tool for price forecasting and/or resource allocation for both of petroleum producers and consumers.

• The Korean Journal of Rehabilitation Nursing
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• v.9 no.1
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• pp.72-80
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• 2006

Purpose: This study was conducted to examine the effect of multidimensional program on cognition, physical function and depression among institutionalized elderly and the relationship between study variables and resident's characteristics and health related variables. Method: This study involved a one group pre and post test, comparison of variables over a 12 month period. To investigate this research question, data of 114 residents of a nursing home were analyzed. Results: There was statistically significant difference in MMSE-K (t=-2.63, p=.010), ADL (t=-2.85, p=.005), and depression (t=4.66, p=.000) before and after program participation. Conclusion: These results indicate that, for a year their regular involvement in a broad spectrum of multidimensional program activities can improve in cognitive, physical and emotional perspectives, but the level of IADL decreased significantly (t=-6.72, p=.000). Further testing is required with the control group, to compare with community resident elders in order to explore the effects on social skill of elderly.

• Journal of Apiculture
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• v.34 no.4
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• pp.305-313
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• 2019

Honey bees (Apis mellifera) forage in agricultural areas, and are exposed to diverse pesticide poisoning. Toxic effects on Apis mellifera of different groups of pesticides were tested in the laboratory; fungicide (Metconazole), herbicide (Glyphosate), acaricide (Amitraz), organophosphate insecticide(Fenitrothion) and neonicotinoid insecticides(Thiacloprid, Thiamethoxam, Imidacloprid, Acetamiprid, Dinotefuran and Clothianidin). Commercial formulations were serially diluted from the recommended concentration (RC) to 10-6 times to carry out feeding and contact tests. Toxicity was transformed into lethal dose (LD50) and hazard question (HQ). The acute toxicity of pesticides showed similar patterns between feeding and contact tests. But feeding tests showed greater toxic to honey bee than contact test. The organophosphate and nitro-neonicotinoid insecticides were highly toxic with HQ values ranging greater than 1. However, cyano-neonicotinoids of Thiacloprid and Acetamiprid showed low toxicity. Even at the RC, 24 hr mortalities were 18 and 30%. The acaricide (Amitraz) showed intermediate level of toxicity at RC but negligible at the concentration lower than 10-1 times. A fungicide(Metconazole) and herbicide(Glyphosate) showed minimal impacts. The results imply that the selective use of pesticides could help conservation of pollinators in agricultural production systems.

• Nuclear Engineering and Technology
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• v.54 no.7
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• pp.2714-2719
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• 2022

The present paper proposes some new computational methods and results in the framework of flow computation through congested domains seen as porous media, as it can be found in the core of a Pressurized Water Reactor (PWR). The flow is thus mostly governed by the distribution of pressure losses, both through the porous structures, such as fuel assemblies, and in the thin fluid layers between them. The purpose of the present paper is to consider the question of the interaction of a flow and a rod bundle from an analytical point of view gathering all the contributions through a set of equations as simple and representative as possible. It aims at demonstrating a sound understanding of the relevant phenomena governing the flow establishment in the geometry of interest instead of relying mainly on a posteriori observations obtained both experimentally and numerically. Comparison with two set of experimental results showed good agreement. The model proposed being analytical it appears easily implementable for studies needing an expression of fluid forces in a rod array as for fuel assembly bowing issue. It would be interesting to test the reliability of the model on other geometry with different P/R ratios.

• Educational Technology International
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• v.13 no.1
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• pp.207-231
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• 2012

The purpose of this study is to analyze the effects of Critical Thinking Strategy supporting argumentation activities between learners. The research question is whether the form of Critical Thinking Strategy offered to support meaningful interaction of collaborative argumentation between learners influences the knowledge acquisition, learning outcome, and student satisfaction. For this, the collaboration outcome of the group, the level of individual knowledge acquisition, the level of students satisfaction were measured as outcome of argumentation activity and their differences analyzed. This study concludes the following: A comparison of the group that was provided with Critical Thinking Strategy (test group) and the group provided with general argumentation scaffolds (compared group) showed there wasn't statistically significant differences in the quality of the learning outcome of collaboration between the groups and in students satisfaction. But there was significant difference in the degree of individual acquisition depending on the offering of scaffolding for Critical Thinking. Therefore, as premised in this study, supporting meaningful mutual interaction between learners during collaborative argumentation using Critical Thinking Strategy has a positive influence on the individual acquisition of domain knowledge. The group provided with scaffolding for Critical Thinking gained higher effect in the degree of knowledge sharing and individual acquisition of domain knowledge compared to the group provided with general argumentation scaffolding.

• Geomechanics and Engineering
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• v.37 no.4
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• pp.371-382
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• 2024

Measurement or prediction of compression index (C_c) of soils is essential for assessment of total and differential settlement of structures. It is a well-known fact that this parameter is controlled by several index identifiers of soil including initial void ratio, Atterberg limits, overconsolidation ratio, specific gravity, etc. Many studies in the past proposed relationships for prediction of C_c based on different index properties. Therefore, this study aims to present a comparison of previously proposed equations for estimation of C_c. Data from literature was compiled, and a total of 90 and 623 test results on remolded and undisturbed specimens were used to question the validity of previously proposed equations. Nevertheless, the modeling ability of 7 and 12 equations for estimation of C_c of remolded and undisturbed soils were questioned by use of compiled data. Moreover, new empirical relationships based on initial void ratio and toughness limit for prediction of C_c was proposed by use of nonlinear multivariable regression and evolutionary based regression analyses. The results are promising-the performances of models established are quite acceptable, which are verified by statistical analyses.

• Journal of Gifted/Talented Education
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• v.22 no.1
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• pp.117-139
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• 2012

This study compared the cognitive conflict on peer instruction concerning the level of difficulty in question, between middle school science gifted students and non-gifted students. For the study, 35 the 7th grade science-gifted students in the organization affiliated with Science Education Institute for the Gifted in Seoul and Gyeong-gi province, and 14 the 8th grade science-gifted students, and 71 the 8th grade students. They performed peer instruction on propagation of straight light and composition of light and then, discussed three concept problems. After discussing the students took paper pencil test about changing levels of cognitive conflict. Regardless of the level of difficulty in question, the science-gifted students showed meaningful decreased figures on cognitive re-evaluation factors after peer-discussion. They trusted their peers, so during discussion, they explained their concepts. Furthermore discussion process enabled them to do reflective thinking. consequently, discord of students dropped, and total figures of cognitive conflict also declined. Science-gifted students have a tendency to worry lower than general students, though they felt anxiety as difficulty of the problems after peer-discussion. Through peer-discussion, science-gifted students presented statically decreased anxiety factors. By means of analyzed results of changing cognitive conflict of science-gifted students, developing and adapting strategies of cognitive conflict considering learner characteristics of science-gifted students is needed.

• Journal of the Korean Society of Earth Science Education
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• v.9 no.2
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• pp.123-138
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• 2016

The purpose of this study is to examine the effects of applying the Question-Answer Relationship (QAR)strategy on the attitude toward science of the elementary fifth grade students whose learning styles have beenidentified. The population of the study constitutes the total of 97 elementary fifth grade students who wereassigned into a comparison (n=48) or experimental group (n=49). To understandhow the QAR strategy potentially influencedscientific attitude, both groups were surveyedin the areas of scientific attitude before and after the experiment. TheKolb's Test was used to identifythe students' learning stylein the experimental group. According tothe learners' learning style, the results have been compared and analyzed. The results of this study are as follows:First, the findings revealed a significant difference in the experimental group students' attitude toward sciencecompared to the comparison group. Second, four learning styles were identified among the studentsin theexperimental group: a) Accommodators (46.9%), b) Convergers (24.5%), c) Divergers (20.4%), and d) Assimilator (8.2%). Following the data analysis, there was no meaningful statistical difference between four groups oflearning styles with respect to their scientific attitude.Applyingthe QAR strategy in a science class seemed toimprove the accommodators, convergers, and divergers' scientific attitude positively.

• Journal of The Korean Association For Science Education
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• v.32 no.3
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• pp.428-445
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• 2012

The objective of this study is developing an instrument for investigating views of the respondents on nature of science(NOS) by using experienced scientific knowledge, atomic model. It consists of total six questions and 36 detail items, and each question is reflected the aspects of different NOS which are 'recognition on the model', 'tentativeness of scientific knowledge', 'subjectivity in science', 'use of inference and imagination', 'myths of the scientific method', and 'comparison between science and art'. Particularly, 'comparison between science and art' is addressed almost for the first time in this questionnaire. In the class environment almost not to teach nature of science linking with concrete scientific knowledge, to inquire how the students recognize nature of science, relating to experienced scientific knowledge through this questionnaire will give the data of scientific knowledge based recognition on the nature of science and an important implication for nature of science teaching with concrete scientific knowledge. Developing processes have gone through four steps. In first step, we chose aspects of NOS and developed questions and details. In second step, we tested the draft into fifteen science teachers and, reflecting their opinions, corrected the form and contents of questionnaires. In third step, we tested the questionnaire included writing section for expressing thoughts of the respondents into 55 students in science high school and checked index of coincidence between Likert and open-ended responses which shows 88.2% degree of consensus. Furthermore, to identify the feature of using concrete scientific knowledge we applied this and views on science and education questionnaires together into six university students. We performed final test to 68 university students and measured Cronbach's, and ultimately completed final questionnaire in last step.