• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.7
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• pp.417-427
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• 2016

This paper is the first investigation of the steady flow characteristics of an SI engine with a semi-wedge combustion chamber as a function of the port shape. For this purpose, the planar velocity profiles were measured at the 1.75B position by particle image velocimetry. The flow patterns were examined with both a straight and a helical port. Two swirls were observed up to 4 mm valve lift with the straight port and up to 2 mm with the helical one; however, only one swirl was present after these lifts. The flow characteristics changed suddenly between 4 and 5 mm lift in the straight port; on the other hand, the change with lift was gradual with the helical port - the transition points between flow regimes were different with the port shapes. In addition, the centers of the swirls were relatively far from the cylinder center so that the effect of eccentricity may not be negligible at 1.75B, regardless the shape. The eccentricity values with the straight port were especially high - over 0.5 for all lifts. Finally, real velocities were found to be much lower than those predicted by the assumption of ISM evaluation, with the profiles differing qualitatively as well.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.3
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• pp.215-226
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• 2015

In this study, with variables the cross section area ($97m^2$, $58m^2$, $38m^2$) and the wind velocity(0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5 m/s), the time of getting off train dependent on the way of itself and the width of the evacuation route was analyzed, and also fire and evacuation characteristics is reviewed by cross section area of each wind velocity. As the result, if cross section become smaller, the density of harmful gases in the tunnel increased more than the ratio of decreasing cross section area. In the case of small cross sectional area, the surrounding environment from initial fire is indicated to exceed the limit criteria suggested in performance based design. In the analysis of effective evacuation time for evacuation characteristics, the effective evacuation time was the shortest in the case of evaluating effective evacuation time by the visibility. Also, there was significant difference between the effective evacuation time on the basis of performance based evaluation and the effective evacuation time obtained by analyzing FED (Fractional effective dose), one of the analysis method obtaining the point that deaths occur, against harmful gases.

• Journal of Nutrition and Health
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• v.47 no.6
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• pp.403-415
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• 2014

Purpose: This study was conducted in order to investigate the nutrient and food intake status, and dietary quality in Korean adults according to abdominal obesity based on waist circumference. Methods: We analyzed data from the combined 2010~2012 KNHANES (Korean National Health and Nutrition Examination Survey). The analysis included 6,974 adults aged 40 to 64 years. In this study, according to abdominal obesity based on waist circumference (male ${\geq}$ 90 cm, female ${\geq}$ 85 cm), we classified the subjects into the obesity group (male, n = 775, female, n = 1,113) and control group (male, n = 2,038, female, n = 3,048). The nutrient and food group intake, ND (nutrient density), NAR (nutrient adequacy ratio), MAR (mean adequacy ratio), INQ (index of nutritional quality), DDS (dietary diversity score), and DVS (dietary variety score) were analyzed using data from the 24-recall method. Results: For male, no significant difference in quality index of the diet was observed between the obesity group and the normal group. In female, in diet quality (ND, NAR, and INQ), vitamin $B_2$ (ND, NAR, and INQ) calcium (NAR), phosphorous (ND, INQ) and potassium (ND) of the obesity group was significantly lower than those of the control group. DDS and DVS in the obesity group (3.57, 30.95) were significantly lower than those of the control group (3.68, 32.84) (p = 0.0043, 0.0002). DVS (DVS ${\geq}$ 39.9) showed association with lower risk of waist obesity in a logistic regression model after adjustments for multiple confounding factors including age, education, income, alcohol intake frequency, smoking, physical activity, energy intake, and body mass index (OR: 0.616, 95% CI: 0.420-0.903). Conclusion: In conclusion, females with abdominal obesity had lower micronutrient intake quality, DVS than those of the control group. In Korean females, food intake variety can adversely affect waist circumference.

• The KIPS Transactions:PartD
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• v.8D no.5
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• pp.533-542
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• 2001

In this paper, we present a scheduling method for real-time mobile transaction manager in mobile computing environment. The proposed method checks whether a transaction is executable or not. It is able to by considering not only the deadline of real-time data in mobile hosts. And then, it schedules the real-time mobile transactions by making optimal execution window based on the priority queue, while considering transaction value and deadline. Disconnection with mobile hosts is monitored in selecting the transaction for execution. Using the proposed method reduces the number of restarting times after transaction aborts which is caused by the violation of the validity constraints of real-time data. And in has merits of maximizing the sum of values of real-time mobile transactions which meet the deadline. The performance evaluation demonstrates that the number of committed real-time transactions within the deadline is improved by 20%. This method can be used in real-time mobile transaction manager is such environments as cellular communications, emergency medicine information system and so on.

• Korean Journal of Environmental Agriculture
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• v.40 no.4
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• pp.260-269
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• 2021

BACKGROUND: Diquat dibromide is a fast-acting nonselective herbicide and plant growth regulator. In this study, in order to understand the possibility of unintentional pesticide contamination in the following crops, the phytotoxicity and transition of diquat dibromide residue in soil into the following crops such as pepper, radish, lettuce and corn have been assessed through phytotoxicity trial and residual evaluation in the unintentional contamination of the higher residual diquat dibromide. METHODS AND RESULTS: The pepper, radish, lettuce and corn were cultivated in the sandy soil and loam soil where the 35 mg/kg and 90 mg/kg diquat dibromide were applied, respectively. Mild growth inhibition symptoms were observed in radish, lettuce and corn crops at the 90 mg/kg- diquat dibromide treatment on the 30 day of cultivation. Diquat dibromide was analyzed using liquid chromatography QTRAP (LC-MS/MS). The recovery rates of diquat dibromide from soil and crop were determined within range from 89.1 to 116.4% with relative standard deviation less than 14.7%. Diquat dibromide residues in soil were found to be 23.90-30.22 and 69.59-82.57 mg/kg from the 35 mg/kg and 90 mg/kg of diquat dibromide-treated soil, respectively after 30 days of crop cultivation. This result implicates that diquat dibromide did not convert to metabolites and remained mostly in the soil, even though it was partially decomposed during crop cultivation. In addition, the diquat dibromide in pepper and radish that were grown for 47 days, and lettuce and corn that were cultivated for 30 days were detected to be 0.01 mg/kg or less in the sandy loam and loam soil where the 90 mg/kg diquat dibromide was applied. CONCLUSION(S): Diquat dibromide did not cause severe phytotoxicity in the following crops as well as it did not uptake and distribute to the following crops, even though it was considered to be residual in the soil.

• Journal of IKEEE
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• v.1 no.1 s.1
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• pp.31-46
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• 1997

In this paper, a parallel Optimal Best-First search Branch-and-Bound(B&B) algorithm(pobs) is designed and evaluated for MIN-based multiprocessor systems. The proposed algorithm decomposes a problem into G subproblems, where each subproblem is processed on a group of P processors. Each processor group uses tile sub-Global Best-First search technique to find a local solution. The local solutions are broadcasted through the network to compute the global solution. This broadcast provides not only the comparison of G local solutions but also the load balancing among the processor groups. A performance analysis is then conducted to estimate the speed-up of the proposed parallel B&B algorithm. The analytical model is developed based on the probabilistic properties of the B&B algorithm. It considers both the computation time and communication overheads to evaluate the realistic performance of the algorithm under the parallel processing environment. In order to validate the proposed evaluation model, the simulation of the parallel B&B algorithm on a MIN-based system is carried out at the same time. The results from both analysis and simulation match closely. It is also shown that the proposed Optimal Best-First search B&B algorithm performs better than other reported schemes with its various advantageous features such as: less subproblem evaluations, prefer load balancing, and limited scope of remote communication.

• Journal of Energy Engineering
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• v.18 no.4
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• pp.246-257
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• 2009

Regarding climate change, the most significant challenge the world faces is achieving the goal of stabilizing the global concentration of greenhouse gases. However, this cannot be accomplished by greenhouse gas reduction efforts of developed countries alone. In this context, a "sectoral approach" has been brought up as a way to overcome the limit of the Kyoto Protocol and induce the participation of developing countries. This paper focuses on the different types of sectoral approaches that have been suggested so far, and their criteria, scope and effectiveness. It therefore explores the potential each approach has as a policy alternative under the post-2012 scheme. On top of that, with the possibility of these sectoral approaches becoming strong future policy alternatives in mind, this paper also analyzes their applicability to the Korean industry. For the steel, petrochemical and oil industries - in which energy efficiency exceeds the world average- a technology-based approach is proposed as an alternative. For the cement, paper and power generation industries - in which energy efficiency is about the same as the global average - a sectoral crediting mechanism or an index-based approach or a sector-wide transnational approach are proposed as alternatives. Lastly, this paper suggests a future research direction for their adoption and implementation.

• The Journal of the Convergence on Culture Technology
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• v.9 no.1
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• pp.339-345
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• 2023

Pre-service teachers have established and developed their own teaching strategies and professional language teaching skills based on their pedagogical and learning experiences. In this regard, it is conceivable that pre-service teachers' feedback may have distinct viewpoints and focuses. Therefore, the purpose of this study is to analyze pre-service teachers' feedback to microteaching demonstrations. Participants in the study were 40 prospective elementary school teachers. They were invited to offer feedback on microteachings video-recorded by their peers. According to the findings, we identified a total of 708 comments. The majority of feedback was categorized as teacher talk(40.1%) , followed by teaching and learning activity (20.9%), interaction (12.6%), teaching materials (11.4%), classroom atmosphere and learning environment (8.9%), lesson flow (3.7%), review and evaluation (1.3%), and introduction and objectives (1.1%). The most frequent types of feedback were the teacher's use of appropriate speaking rate, tone, and intonation. This finding reflects the fact that English teachers realize the importance of the teacher's English proficiency, therefore we suggest that teacher education institutions need raise awareness not just of teachers' English skills but also of their diverse perspectives.

• Communications of Mathematical Education
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• v.24 no.3
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• pp.563-585
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• 2010

The major goals of this study are to find the factors that enhance self-directed math learning in college math classes and to provide the students with the opportunities to check and develop their self-directed math learning attitude. For these research goals, we prepared the questionnaires that asked about their learning motivations, basic learning ability, self-discipline strategies, and self-directed learning strategies. Another purpose of the questionnaires was to give them the chances to check and improve their attitude toward those learning strategies, motivation and ability. From the research results, we find that the important factors for self-directed learning are internal & external motivations, concentration ability, and the goal-setting and plan-making abilities. In addition, concentration ability, good habit, stress-control, recognition of math value, and self-directing ability are found to be necessary for the desirable learning environment. On the other hand, we find that the ability to perform note-taking, class preparation and review, time-control, and test-control is required for the selection and practice of self-fitting learning strategies. Finally, we provided our own self-directed math learning model. Our model, containing the necessary factors for self-directed math learning, is the revised and modified one of Knowles(1975)'s 5 stage self-directed learning model that comprises diagnosis of learning desire, setting learning goals, grasping human&material resources, selection and practice of proper learning strategies, and evaluation of learning results.

• The Journal of the Convergence on Culture Technology
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• v.9 no.4
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• pp.95-103
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• 2023

This paper proposes an artificial intelligence convergence education program for teaching the main concept and principle of Support Vector Machines(SVM) at elementary schools. The developed program, based on Jeju's natural environment theme, explains the decision boundary and margin of SVM by vertical and parallel from 4th grade mathematics curriculum. As a result of applying the developed program to 3rd and 5th graders, most students intuitively inferred the location of the decision boundary. The overall performance accuracy and rate of reasonable inference of 5th graders were higher. However, in the self-evaluation of understanding, the average value was higher in the 3rd grade, contrary to the actual understanding. This was due to the fact that junior learners had a greater tendency to feel satisfaction and achievement. On the other hand, senior learners presented more meaningful post-class questions based on their motivation for further exploration. We would like to find effective ways for artificial intelligence convergence education for elementary school students.