• The Mathematical Education
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• v.45 no.1 s.112
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• pp.61-74
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• 2006

The ability of understanding the number and number systems, grasping the properties of number systems, and manipulating number systems is the foundation to understand algebra. It is useful to deepen students' mathematical understanding of number systems and operations. The authentic understanding of numbers and operations can make it possible for the students to manipulate algebraic symbols, to represent relationship among sets of numbers, and to use variables to investigate the properties of sets of numbers. The high school students need to understand the number systems from more abstract perspective. The purpose of this study is to study on understanding and application ability of eleventh graders of basic properties of operations with real numbers.

• Korean Journal of Child Studies
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• v.30 no.1
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• pp.109-125
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• 2009

This study examined the effects of estimation activities on children's operation and measurement abilities. Subjects were 60 five-year-old children. This experiment used the untreated control group design with pretest and posttest. Instruments used to collect data were the Number and Operation and Measurement tests part of the Test of Mathematics Ability for Young Children (TMAYC) developed by Hong, Lee and Chung (2006). ANCOVA was employed for statistical analysis. Results of the posttest showed that children in the experimental group scored significantly higher on children's operation and measurement abilities than the control group. Results imply that an estimation program can be an effective teaching model for improving children's operation and measurement abilities.

• Journal of the Korean School Mathematics Society
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• v.8 no.4
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• pp.423-444
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• 2005

Despite the importance of number sense, computational skills have been emphasized in elementary mathematics curriculum. There is lack of research on number sense. Against this background, this study analyzed the way 137 sixth grade students coped with routine computation problems and with problems requiring number sense. Students performed better on the computation tasks than on the number sense tasks. With regard to the number sense tasks, many students had a tendency to implement direct computation rather than to use number sense appropriate to the given contexts. Students also had difficulties in making use of effective benchmarks or applying the knowledge of number and operation to various problem contexts. An implication is that students should explore multiple tasks requiring number sense as an integral part of their mathematics learning in order to develop number sense.

• Journal of Educational Research in Mathematics
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• v.19 no.4
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• pp.513-530
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• 2009

In this paper, We analyse the contents of the national mathematical curriculum, the handbook of the curriculum, and elementary school mathematics textbook for the elementary school grade 1-2 focusing on 'number sense'. At first, we identify the meaning and the elements of number sense through analysing studies which are related to number sense. Number sense includes understanding the meaning of number, operation, and estimation, and the ability of applying numbers, operation and estimation on the context. Number sense consists of the elements of the contents and the elements of the processes. Secondly, with the elements of number sense which we have identified, we analyse the contents of the national mathematical curriculum, the handbook of the curriculum, and elementary school mathematics textbooks, and then criticize the contents. We find some problems as a result of the analysis : the range of number sense is unclear, the word 'number sense' is not used consistently, the elements used are limited, and the contents of the textbook are materialized inconsistently and poorly.

• Korean Journal of Human Ecology
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• v.17 no.1
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• pp.35-43
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• 2008

The purpose of this study is to develop evaluation tools for young children's mathematical ability based on the content standards of NCTM and to verify the suitability of the tools. The tools consist of 5 sub-tests with 90 items, including number and operation, algebra, geometry, measurement, data analysis and probability. The tool analysis was examined with 300 three-to five-years-old children and 31 math education professionals. The results of this research are as follows : First, in order of age the passing rate increased. The gap between high and low score group reveals a statistically meaningful difference. Second, the internal consistency reliability coefficient, Cronbach ${\alpha}$, is .96. Test-retest reliability is around .90. The concurrent validity correlation between this tools and Choi Hye-Jin's test(2003) is .85. The analysis of the content validity was proved appropriately by math education professionals.

• Archives of Plastic Surgery
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• v.34 no.4
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• pp.436-440
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• 2007

Purpose: TRAM flap surgery has settled down as a common method for breast reconstruction after mastectomy. We investigated how TRAM flap surgery influences on the patients' physical movement capability by observing their capability of sit-ups as well as exercises they usually enjoy. Methods: A total of consecutive 375 patients were investigated who had breast reconstruction with unilateral pedicled TRAM flap surgery at Asan Medical Center from July 2001 to August 2005. The patients were asked to sit up right before the surgery and do it again 6 months later and 1 year later. 221 patients were followed up 6 month after the surgery. And 132 patients were followed up 1 year after the surgery. In addition, 155 patients who used to exercise before the surgery were also asked to show us the change in their physical movement capability one year after their surgery. Results: 139 patients showed decrease in the counted number of sit-ups, 48 increase, and 34 showed no change between 6 months in the first group of 221 patients. Among the second group of 132 patients, 64 showed decrease, 39 increase, and 29 no change a year later. There was a statistical significant decrease in the number of sit-ups between pre-operation and six months later and between pre-operation and one year later. According to the research on the exercise that 155 patients participated, 3 of them showed improvement in athletic ability, 7 showed decrease, while the rest, 145 patients, showed no change at all. Conclusion: Considering no difference in usual exercise ability, some patients' increase in the number of sit-ups and the effect of anticancer treatment, we found that the loss of abdominal wall function on this research is not too serious to exclude TRAM flap surgery in the field of breast reconstruction

• Journal of Elementary Mathematics Education in Korea
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• v.20 no.2
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• pp.193-213
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• 2016

This study has two goals. The First is to develop and apply a step-by-step program and the degree to which students' mathematical skills. The second is to analyze mathematical attitude change around the first grade students was done. The program for learning complement number is composed of series of 5 steps and 11 classes. Play for learning complement number, taking into account the difficulty of the learning steps 1-5 are organized. First step is composed of the classes which fragmented pieces of shapes to complete the entire geometry with fun activities for the entire part of the concept of learning and it maintenance concepts and can naturally learn by associating step. In second step, tools to take advantage of the real world and collecting the conservative concept. 3rd steps is to repair the mathematical concept of the parish in the learning stage of expansion. 4th step is halrigalri, number cards, making ten games etc. 5th step is to verify the concept of complement number and number operation ability. The concept of complement number through fun activities can improve students' mathematical skills, and mathematical attitude change. Early in the program, students use the finger to throw acid in the process. Simple addition and subtraction calculations may take a long time and error, but more and more we progress through the program using the fingers is eliminated and a more complex form calculations was not difficult to act out.

• Journal of Elementary Mathematics Education in Korea
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• v.16 no.2
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• pp.203-225
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• 2012

The purpose of this study is to suggest a program for improvement of the mathematical creativity of mathematical gifted children in the elementary gifted class and to examine the effect of developed program. Gifted education program is developed through analyzing relevant literatures and materials. This program is based on the operation bingo game related to the area of number and operation, which accounts for the largest portion in the elementary mathematics. According to this direction, the mathematically gifted educational program has been developed. According to the results which examine the effectiveness of the creative problem solving by the developed program, students' performance ability has been gradually improved by feeding back and monitoring their problem solving process continuously.

• Journal of National Security and Military Science
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• s.13
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• pp.1-41
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• 2016

US 8th Army in the attack on the Western Front was a situation that was frustrated by the 13th Corps Communist army. To this time support this, goals that have been granted to the US 1st Marine Division that initiated the attack in Mupyonri direction, lack the potential to achieve was not decisive. It was a operation specific erroneous judgment that occurred because there was no one accurately grasp the battlefield of the situation the wrong UN Forces Command. Tactical victory can be to maximize the operation outcomes. However, there is no possible failure of the operation is to expand the tactical success. This is because the failure of the operation, because directly linked to the success or failure of the war. Tactical victory can be to maximize the operation outcomes. However, operation specific failure is not it possible to expand the tactical victory. Therefore tactical success of the US 1st Marine Division, can not compensate for operation specific failure of the United Nations Forces Command. However, Chinese Communist Army 9th Corps is obsessed only victory of tactics to annihilate the US 1st Marine Division, by being fixation to the Chosin whole area, it was not possible to run a operational operation. Therefore tactical success df the US 1st Marine Division, Chinese Communist Army 9th Corps is to extinguish the ability to increase the number of the 13th Corps of the Western Front, 8th Army US have contributed to have escaped the crisis. In addition, the US 10th Corps while maintaining the combat force, by an important role to withdraw through the sea, was able to complement the misjudgment of the operation.

• The Journal of Korea Robotics Society
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• v.15 no.1
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• pp.39-47
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• 2020

This paper presents a control and operation system for a remotely operated vehicle (ROV). The ROV used in the study was equipped with a manipulator and is being developed for underwater exploration and autonomous underwater working. Precision position and attitude control ability is essential for underwater operation using a manipulator. For propulsion, the ROV is equipped with eight thrusters, the number of those are more than six degrees-of-freedom. Four of them are in charge of surge, sway, and yaw motion, and the other four are responsible for heave, roll, and pitch motion. Therefore, it is more efficient to integrate the management of the thrusters rather than control them individually. In this paper, a thrust allocation method for thruster management is presented, and the design of a feedback controller using sensor data is described. The software for the ROV operation consists of a robot operating system that can efficiently process data between multiple hardware platforms. Through experimental analysis, the validity of the control system performance was verified.