• Journal of Elementary Mathematics Education in Korea
• /
• v.19 no.4
• /
• pp.563-588
• /
• 2015

In elementary school, didactical transposition is inevitable due to several reasons. In mathematics, addition and multiplication are taught as binary operations, subtraction and division are taught as unary operations. But in elementary school, we try to teach all the four operations as binary operations by didactical transposition. In 'Mastering' the concepts of the four operations, the way of concept introduction is dealt importantantly. So it is different from understanding the four operations. In this study, we analyzed the four operations of natural numbers and fractions from two perspectives: concept understanding (how to introduce concepts and how to choose an operation) and connection between the operations. As a result, following implications were obtained. In division of fractions, students attempted a connection with multiplication of fractions right away without choosing an operation, based on the situation. Also, to understand division of fractions itself, integrate division of fractions presented from the second semester of the fifth grade to the first semester of the sixth grade are needed. In addition, this result can be useful in the future textbook development.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.39 no.4
• /
• pp.349-356
• /
• 1990

In order to control DC motors for electric cars by chopper system, four quadrant operations - forward powering, forward regenerative braking, reverse powering, reverse regenerative braking - are needed. For the four quadrant operations, the separately - excited DC motors are used in this study. The conversion of each quadrant operation has been obtained by 1) adopting the two phase chopper system with combined output for the armature control, and 2) the single phase chopper system for the field control.

• Journal of the Korean School Mathematics Society
• /
• v.13 no.3
• /
• pp.381-395
• /
• 2010

The purpose of this paper is to examine the competence and the methods of problem solving in four operations word problems based on the informal knowledges by five-year-old children. The numbers which are contained in problems consist of the numbers bigger than 5 and smaller than 10. The subjects were 21 five-year-old children who didn't learn four operations. The interview with observation was used in this research. Researcher gave the various materials to children and permitted to use them for problem solving. And researcher read the word problems to children and children solved the problems. The results are as follows: five-year-old children have the competence of problem solving in four operations word problems. They used mental computation or counting all materials strategy in addition problem. The methods of problem solving were similar to that of addition in subtraction, multiplication and division, but the rate of success was different. Children performed poor1y in division word problems. According to this research, we know that kindergarten educators should be interested in children's informal knowledges of four operations including shapes, patterns, statistics and probability. For this, it is needed to developed the curriculum and programs for informal mathematical experiences.

• Journal of the Chungcheong Mathematical Society
• /
• v.24 no.2
• /
• pp.253-266
• /
• 2011

We would like to generalize about trapezoidal fuzzy set and to calculate four operations based on the Zadeh's extension principle for two generalized trapezoidal fuzzy sets. And we roll up triangular fuzzy numbers and generalized triangular fuzzy sets into it. Since triangular fuzzy numbers and generalized triangular fuzzy sets are generalized trapezoidal fuzzy sets, we need no more the separate painstaking calculations of addition, subtraction, multiplication and division for two such kinds once the operations are done for generalized trapezoidal fuzzy sets.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.14 no.1
• /
• pp.1-15
• /
• 1989

Multistate survival data with censoring often arise in biomedical experiments. In particular, a four-state space is used for cancer clinical trials. In a four-state space, each patient may either respond to a given treatment and then relapse or may progress without responding. In this four-state space, a model which combines the Markov and semi-Markov models is proposed. In this combined model, the generalized maximum likelihood estimators of the Markov and semi-Markov hazard functions are derived. These estimators are illustrated for the data collected in a study of treatments for advanced breast cancer.

• Journal of the military operations research society of Korea
• /
• v.17 no.2
• /
• pp.16-30
• /
• 1991

Data from a series of four studies on leadership behavior are analyzed and compared to identify effective patterns of leadership behavior for platoon leaders and battalion commanders in ROK Army. Multiple-method research strategy is utilized in four studies to overcome some of the limitations of previous researches. Two of four studies employ a questionnaire method, and the rest use content analysis of critical incidents. Important behaviors for leadership effectiveness in both platoon leaders and battalion commanders include Supporting and Motivating Task Commitment. However, Developing and Monitoring Operations are only important in platoon level, and Planning & Organizing and Recognizing & Rewarding only in battalion level. Most discrepancies in results among studies can be explained in terms of either method effects or situational differences in role requirements for leaders.

• Journal of the Korean Society of Food Culture
• /
• v.15 no.2
• /
• pp.69-78
• /
• 2000

The purposes of this study were to : (a) investigate overall operating conditions of university residence hall foodservice, (b) compare them by the management systems. Questionnaires were hand delivered and mailed to 73 foodservice managers. A total of 56 were usable; resulting in 76.7% response rate. The survey was conducted between October, 1998 and May, 1999. Statistical data analysis was completed using the SAS/Win 6.12 for Descriptive Analysis, $x^2-test$. Sixty-four percent of the foodservice operations were 'self-operated'; 23% were 'contracted'; and 13% were 'rented'. Eighty-three percent of operations provided 'single menu'; forty-six percent of foodservice operations with 'partially self-service'; and forty-one percent with 'complete self-service'. Forty-four percent of overall foodservice operations provided 1,000-2,000 meals per day; thirty-one percent provided less than 1,000 meals per day, and twenty-four percent provided more than 2,000 meals per day. The highest meal price was 1,950 won and the lowest was 700 won with average of 1,295 won. The mean number of employees was 12.2; the number of working hours was 59.7 hours per week.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 1991.10a
• /
• pp.277-278
• /
• 1991

• The Mathematical Education
• /
• v.47 no.4
• /
• pp.519-543
• /
• 2008

The study has been conducted with 29 children from 4th to 6th grades to realize how they understand addition, subtraction, multiplication, and division of whole numbers, and how their understanding influences solving of one-step word problems. Children's understanding of operations was categorized into "adding" and "combination" for additions, "taking away" and "comparison" for subtractions, "equal groups," "rectangular arrange," "ratio," and "Cartesian product" for multiplications, and "sharing," "measuring," "comparison," "ratio," "multiplicative inverse," and "repeated subtraction" for divisions. Overall, additions were mostly understood additions as "adding"(86.2%), subtractions as "taking away"(86.2%), multiplications as "equal groups"(100%), and divisions as "sharing"(82.8%). This result consisted with the Fischbein's intuitive models except for additions. Most children tended to solve the word problems based on their conceptual structure of the four arithmetic operations. Even though their conceptual structure of arithmetic operations helps to better solve problems, this tendency resulted in wrong solutions when problem situations were not related to their conceptual structure. Children in the same category of understanding for each operations showed some common features while solving the word problems. As children's understanding of operations significantly influences their solutions to word problems, they needs to be exposed to many different problem situations of the four arithmetic operations. Furthermore, the focus of teaching needs to be the meaning of each operations rather than computational algorithm.

• Management Science and Financial Engineering
• /
• v.7 no.2
• /
• pp.1-11
• /
• 2001

Gouveia and Pires (European Journal of Operations Research 112(1999) 134-146) have proposed four extended formulations having precedence variables as extra variables and characterized the projections of three of the four formulations into the natural variable space. In Gouveia and Pires (Discrete Applied Mathematics 112 (2001)), they also have introduced some other extended formulations with the same extra variables and conjectured that the projection of one of the proposed formulations is equivalent to the one proposed by Dantzig, Fulkerson, and Johnson (Operations Research 2(1954) 393-410). In this paper, we provide a unifying framework based on which we give alternative proofs on the projections of three extended formulations and new proofs on those of two formulations appeared in Gouveia and Pires(1999, 2001).