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

• Journal of the Korean Operations Research and Management Science Society
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• v.22 no.4
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• pp.17-35
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• 1997

This paper considers the efficient design of routing path and wavelength assignment in the single-hop WDM optical transport networks. The connection demands between node-pairs are given and a connection between a pair of nodes must be made by only one lightpath. It is assumed that no wavelength conversion is allowed and the physical topology of the network and the number of available wavelengths of a physical link are also given. This paper proposes the method to route a path and assign a wavelength to the path, which guarantees fairness to every node pair. In order to guarantee fairness and maximize connections, an optimization model is established, which successively maximizes minimum connection ratio to the demand of each node pair. A heuristic algorithm with polynomial iterations is developed for the problem since the problem is NP-hard. The heuristic algorithm is implemented and applied to the networks with real problem sizes. The results of the application are compared with GAMS/OSL.

• The Mathematical Education
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• v.45 no.3 s.114
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• pp.275-293
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• 2006

The purpose of this study was to analyze the connection between students' errors and prior knowledge as an attempt to design an efficient teaching method in decimal computation. A survey on decimal computations was conducted in two 6th grade elementary school classrooms. Error patterns on decimal computations were analyzed and clinical interviews were conducted with 8 students according to their error patterns. Main errors resulted from the insufficient understanding of prior knowledge such as place value, connection between decimals and fractions, meaning of operations, and computation principles of fractions. In order to help students overcome such obstacles, a teaching experiment was designed in a manner that strengthens a profound understanding of prior knowledge related to decimal computations, and connects such knowledge to actual decimal calculations. This study showed that well-designed lesson plans with base-ten blocks might decrease students' errors by helping them understand decimals and connect their prior knowledge to decimal operations.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2005.05a
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• pp.822-828
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• 2005

Customer satisfaction becomes one of the important managerial concerns associated with corporate competency in current competitive environment for Internet communication service companies. Hence, it is demanding to improve a company's customer satisfaction through the total quality management perspective. In practice, engineers as well as the management hope to find major quality characteristics with Internet communication network that is closely related to customer satisfaction, consequently aiming to the raise of their company's customer satisfaction. This paper presents an empirical relationship analysis between network quality characteristics and customer satisfaction on Internet communication. Methodologically, the relationship analysis framework is based on the regression variable selection procedures. In this framework, it is implemented that; 1) iterative model building; and 2) consistent criteria application to statistical tests for selecting significant variables. A case study shows that; 1) the customer satisfaction on the network connection seems to be more closely related to the network quality characteristics compared with the customer satisfaction on the network speed; and 2) the download disconnection rate has relatively evident relationship with the customer satisfaction on the network connection.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2008.10a
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• pp.348-352
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• 2008

KJCCS(Korean Joint Command & Control System) is a system that integrate each military tactics C4ISR into JCS(Joint Chiefs of Staff) level. It is established in major CP(Commanding Post) and provides all battlefield situation in real time by sharing that between connection troops. The objective of this study is to suggest a way for the measurement of force improvement effectiveness of KJCCS. C2 model is applied to measure force improvement effectiveness of KJCCS. This study will be also present a requirement logic for C4ISR system acquisition later.

• Journal of Chest Surgery
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• v.22 no.1
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• pp.25-31
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• 1989

Forty-five patients, aged 16 months to 15.5 years mean 69 months, with a wide variety of cardiac malformations underwent the modified Fontan operation between Sep. 1986 to Aug. 1988. Nineteen patients had previously undergone palliative operations mainly modified B-T shunt. Twenty patients had a mean pulmonary artery pressure greater than 15 mmHg, with nine operative deaths. Thirteen patients had anomalies of systemic venous connection and seven patients had anomalies of pulmonary venous connection. There were eighteen patients under the age 4 years and fifteen of them survived [83.3%]. Eighteen patients had a pulmonary vascular resistance [PVR] more than 2.5U/m, and nine died [50%] whereas two of twenty-three with a PVR less than 2.5U/m died[8.6%]. PVR and anomalies of pulmonary venous connection had a significant influence on survival, but age and anomalies of systemic venous connection did not. Amount of pleural effusion drained postoperatively and PVR had positive linear correlation. Pulmonary artery pressure was not an independent predictor of outcome and pulmonary artery pressure alone should not contraindicate a Fontan procedure if PVR is low. In general, the Fontan operation should be done at a younger age less than 4 year to avoid ventricular dysfunction due to long-standing exposure to hypoxia.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.7 s.361
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• pp.70-80
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• 2007

For supporting various mobile networks, this paper proposes a framework of distributed connection admission control, named SmartCAC. Especially, intelligent CAC operations are adopted in terms of interoperation between mobile nodes and mobile networks. This scheme does not need to correct information between networks. Basically vertical handover call can use guard channel that was reserved for handoff, because SmartCAC addresses the identification between vertical handover call and new call, delay and reliability as requirement of QoS for efficient connection control. The scheme also uses mobile terminal speed for network filtering. Especially an extended protocol is proposed to give different network states information to mobile nodes because there have been no ways for mobile nodes to compare the states of different networks. Sophisticated simulation study is performed in order to evaluate SmartCAC in terms of signaling cost. As a result, signaling cost of ours is up to 96% better than that of the existing scheme.

• Convergence Security Journal
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• v.14 no.4
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• pp.55-60
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• 2014

In this study, we propose a cryptographic module quality evaluation system referenced by ISO/IEC 9000 quality system with Quality, Quality Factor, Quality Subfactor, Metric. Practical application process encryption algorithm based on the encryption algorithm to encrypt the pros and cons valuation of diagnosis, point selection algorithm, analysis, and quality items(quality factor), eliciting constraints derived, such as the cryptographic module design quality evaluation system is set to step 5. The five steps are examples of field-based diagnostic tool for cryptographic operations, the most essential work to be done in order to derive one will work. 2-Factor encryption module for connection between indicator items(quality factor) to identify and ensure the quality of the item the constraints of the environment are two kinds of cryptographic operations. This study is an encryption module and a practical field application system, it presents the standardized model. We have to meet the rapid changes in information technology. The environment, development and the encryption algorithm applied to model a wide variety of on-site development encryption will be able to expect the efficiency.

• Journal of the Korean Society for Library and Information Science
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• v.34 no.3
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• pp.5-23
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• 2000

The purpose of this study is to explore ways to imporve bookmobile operations by investigating bookmobiles' operating status and users' behavior in DaeJeon City. Concerning the bookmobiles operated in 32 areas of DaeJeon City, the suitability of visiting area and staying hours, the correlation between users' circumstances and lending aspects, the effects of bookloan shop in the same area, etc. are analyzed, and for the improvement of bookmobile operations, the utilization of volunteers, the connection with the main libraries' collection, the development of service programs, the strengthening of publicity activities, etc. are proposed.

• International Journal of Vascular Biomedical Engineering
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• v.1 no.2
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• pp.36-41
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• 2003

Both flow visualizations and computational fluid dynamics were performed to determine hemodynamics in a total cavopulmonary connection (TCPC) model for surgically correcting congenital heart defects. From magnetic resonance images, an anatomically correct glass model was fabricated to visualize steady flow. The total flow rates were 4, 6 and 8L/min and flow rates from SVC and IVC were 40:60. The flow split ratio between LPA and RPA was varied by 70:30, 60:40 and 50:50. A pressure-based finite-volume software was used to solve steady flow dynamics in TCPC models. Results showed that superior vena cava(SVC) and inferior vena cava(IVC) flow merged directly to the intra-atrial conduit, creating two large vortices. Significant swirl motions were observed in the intra-atrial conduit and pulmonary arteries. Flow collision or swirling flow resulted in energy loss in TCPC models. In addition, a large intra-atrial channel or a sharp bend in TCPC geometries could influence on energy losses. Energy conservation was efficient when flow rates in pulmonary branches were balanced. In order to increase energy efficiency in Fontan operations, it is necessary to remove a flow collision in the intra-atrial channel and a sharp bend in the pulmonary bifurcation.