• School Mathematics
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• v.14 no.3
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• pp.275-296
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• 2012

This study investigated elementary school students' understanding of basic functional relationships. It analyzed the written responses from a total of 2087 students of second, fourth, and sixth graders using tests that examined their understanding of five types of functional relationships. The results of this study showed that students tended to be more successful as their grades went up with regard to all the problem types. There were statistically differences among the three grade levels. Even lower graders were quite successful in dealing with additive relation, direct proportion, and inverse proportion. However the items dealing with square relation and linear relation were difficult even to sixth graders. It was common that students were good at completing the table by looking for a pattern from the given numbers but that they had difficulties in anticipating the value of 'y' when the value of 'x' is given either as a big number or as a symbol. Given these results, this paper includes issues and implications on how to foster functional thinking ability at the elementary school.

• School Mathematics
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• v.11 no.2
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• pp.261-280
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• 2009

This study was motivated by recognizing the weakness of teaching and learning about the concepts of statements in high school mathematics curriculum. To report the reality of students' understanding about statements, this study investigated the 33 first-year undergraduate students' understanding about the concepts of statements by giving them 22 statement problems. The problems were selected based on the conceptual framework including five types of statement concepts which are considered as the key ideas for understanding mathematical reasoning and proof in college level mathematics. The analysis of the participants' responses to the statement problems found that their understanding about the concepts of prepositions are very limited and extremely based on the instrumental understanding applying an appropriate remembered rule to the solution of a preposition problem without knowing why the rule works. The results from this study will give the information for effective teaching and learning of statements in college level mathematics, and give the direction for the future reforming the unite of statements in high school mathematics curriculum as well.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.12
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• pp.5842-5861
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• 2019

A current autonomous vehicle determines its driving strategy by considering only external factors (Pedestrians, road conditions, etc.) without considering the interior condition of the vehicle. To solve the problem, this paper proposes "An Optimal Driving Support Strategy(ODSS) based on an Genetic Algorithm for Autonomous Vehicles" which determines the optimal strategy of an autonomous vehicle by analyzing not only the external factors, but also the internal factors of the vehicle(consumable conditions, RPM levels etc.). The proposed ODSS consists of 4 modules. The first module is a Data Communication Module (DCM) which converts CAN, FlexRay, and HSCAN messages of vehicles into WAVE messages and sends the converted messages to the Cloud and receives the analyzed result from the Cloud using V2X. The second module is a Data Management Module (DMM) that classifies the converted WAVE messages and stores the classified messages in a road state table, a sensor message table, and a vehicle state table. The third module is a Data Analysis Module (DAM) which learns a genetic algorithm using sensor data from vehicles stored in the cloud and determines the optimal driving strategy of an autonomous vehicle. The fourth module is a Data Visualization Module (DVM) which displays the optimal driving strategy and the current driving conditions on a vehicle monitor. This paper compared the DCM with existing vehicle gateways and the DAM with the MLP and RF neural network models to validate the ODSS. In the experiment, the DCM improved a loss rate approximately by 5%, compared with existing vehicle gateways. In addition, because the DAM improved computation time by 40% and 20% separately, compared with the MLP and RF, it determined RPM, speed, steering angle and lane changes faster than them.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.11
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• pp.3984-3996
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• 2014

Mobile social network can be seen as a specific application of the DTN (Delay Tolerant Network), in which the information propagation can be impacted by many social behaviors of the nodes. For a specific node, its social behaviors are various. For example, the node may not be interested in the information before receiving it and may also discard the information after getting it. On the other hand, people are more willing to forward the message to his friends. These interactive behaviors between nodes can be seen as social behaviors. It is easy to see that the impact of the social behaviors is related to the social ties, which can be manifested by the structure of the social network. State of the art works often simply assumes that the social networks can be divided into some communities. At present, some works find that the structure of some social networks is scale-free. To overcome this problem, this paper proposes a theoretical model to evaluate the impact of above social behaviors in the DTN-like scale-free network. Simulation shows the accuracy of the model. Numerical results show that both social behaviors and scale-free character have significant impact on information propagation. Moreover, the impact of social behaviors is related to the scale-free character of the networks.

• Journal of Internet Computing and Services
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• v.14 no.3
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• pp.23-33
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• 2013

Recently in the field of IT, cloud computing technology has been deployed rapidly in the current society because of its flexibility, efficiency and cost savings features. However, cloud computing system has a big problem of vulnerability in security. In order to solve the vulnerability of cloud computing systems security in this study, impact types of virtual machine about the vulnerability were determined and the priorities were determined according to the risk evaluation of virtual machine's vulnerability. For analyzing the vulnerability, risk measurement standards about the vulnerability were defined based on CVSS2.0, which is an open frame work; and the risk measurement was systematized by scoring for relevant vulnerabilities. Vulnerability risk standards are considered to suggest fundamental characteristics of vulnerability and to provide the degree of risks and consequently to be applicable to technical guides to minimize the vulnerability. Additionally, suggested risk standard of vulnerability is meaningful as the study content itself and could be used in technology policy project which is to be conducted in the future.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.11
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• pp.5338-5359
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• 2017

In-band full-duplex (IBFD) wireless communication supports symmetric dual transmission between two nodes and asymmetric dual transmission among three nodes, which allows improved throughput for distributed IBFD wireless networks. However, inter-node interference (INI) can affect desired packet reception in the downlink of three-node topology. The current Half-duplex (HD) medium access control (MAC) mechanism RTS/CTS is unable to establish an asymmetric dual link and consequently to suppress INI. In this paper, we propose a medium access control mechanism for use in distributed IBFD wireless networks, FD-DMAC (Full-Duplex Distributed MAC). In this approach, communication nodes only require single channel access to establish symmetric or asymmetric dual link, and we fully consider the two transmission modes of asymmetric dual link. Through FD-DMAC medium access, the neighbors of communication nodes can clearly know network transmission status, which will provide other opportunities of asymmetric IBFD dual communication and solve hidden node problem. Additionally, we leverage FD-DMAC to transmit received power information. This approach can assist communication nodes to adjust transmit powers and suppress INI. Finally, we give a theoretical analysis of network performance using a discrete-time Markov model. The numerical results show that FD-DMAC achieves a significant improvement over RTS/CTS in terms of throughput and delay.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.5
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• pp.2778-2791
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• 2017

In the age of big data, distributed data providers need to ensure the privacy, while data analysts need to mine the value of data. Therefore, how to find the privacy-utility tradeoff has become a research hotspot. Besides, the adversary may have the background knowledge of the data source. Therefore, it is significant to solve the privacy-utility tradeoff problem in the distributed environment with side information. This paper proposes a distributed privacy-utility tradeoff method using distributed lossy source coding with side information, and quantitatively gives the privacy-utility tradeoff region and Rate-Distortion-Leakage region. Four results are shown in the simulation analysis. The first result is that both the source rate and the privacy leakage decrease with the increase of source distortion. The second result is that the finer relevance between the public data and private data of source, the finer perturbation of source needed to get the same privacy protection. The third result is that the greater the variance of the data source, the slighter distortion is chosen to ensure more data utility. The fourth result is that under the same privacy restriction, the slighter the variance of the side information, the less distortion of data source is chosen to ensure more data utility. Finally, the provided method is compared with current ones from five aspects to show the advantage of our method.

• Journal of Embryo Transfer
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• v.24 no.1
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• pp.71-76
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• 2009

It is not easy for porcine embryos produced by in vitro systems to develop into blastocysts with high quality. To solve this problem, many researchers have developed novel culture methods. However, the formation of blastocysts with high quality is still low. In this study, we aimed to produce piglet following transfer of in vitro produced early embryos ($2{\sim}4$ cell stage embryos) or morula and blastocyst. The $2{\sim}4$ cell stage embryos were transferred to five estrus-synchronized recipients (200 embryos per recipient). One of the five sows farrowed three piglets, which contain two live piglets and one dead piglet, 114 days after embryo transfer. However, two recipients transferred with morula and blastocysts did not farrow. Microsatellite analysis confirmed that the genomic DNA of two live piglets were not genetically identical to that of the recipient. These results indicate that it is possible to obtain piglets by transfer of early embryos produced by in vitro production (IVP) systems.

• Journal of the Korean Society of Food Culture
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• v.20 no.6
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• pp.638-643
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• 2005

As Korea has approached the aging society, older Koreans have become an important force in restaurant sales today. To succeed with this silver market, it is important for restaurant managers to know who they are and what factors influence older Koreans' eating-out decision making process. The purpose of this study was to investigate the effect of the silver consumers' education level on eating-out decision making process. Data were collected from 178 older consumers above 55 years old and analyzed using the descriptive statistic analysis, MANOVA, and one-way ANOVA. The results showed that the elderly consumers' education level significantly influenced the decision making process in determining where to eat out. Significant differences were found in the Problem Recognition Step(Wilks' Lambda=0.817, F=2.991), Information Search Step(Wilks' Lambda=0828, F=2.218), Alternative Evaluation Step II(Wilks' Lambda=0.741, F=3.596), Purchase Decision Step(Wilks' Lambda=0.859, F=2.223), and the Post-Purchase Behavior(Wilks' Lambda=0.885, F=1.780). The higher education level was, the more directly involved in the eating out decision process. The elderly consumers with university education were likely to 'propose to eat out by themselves'(F=9.346), to obtain restaurant information from the 'printed materials'(F=7.452), to go to 'family restaurant'(F=9.057), 'Japanese restaurant'(F=8.7891) and 'fine dining restaurants'(F=3.936), and to directly express their emotion when they had complaints about restaurant service(F=3.206). In conclusion, older Koreans will become more healthy and wealthy which means the dining out activity will be an important part of their life to socialize with people. Therefore, food service operations should consider the elderly consumers' needs and expectation of restaurant services and actively position themselves for this new market segment.

• Asian Oncology Nursing
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• v.4 no.1
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• pp.62-70
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• 2004

The purpose of this study was to use as a basic data to develop suitable nursing intervention program and decide an appropriate intervention time after assessing shoulder range of motion in postmastectomy from 2 weeks to 3 month. 147 patients are chosen as study subject among patients who were in recovery of 2weeks, 1month, 2months and 3 months after surgical operation which is modified radical mastectomy. Data were collected at oncology medicine local and general surgery local in Seoul National University Hospital from May, 2003 to October, 2003. The range of motion of the shoulder(flexion, extension, abduction, internal rotation, external rotation) were examined. Analysis of data that shoulder range of motion average and standard deviation, percentage of the unaffected side and affected side compare with normal shoulder range of motion. Paired t-test was adopted to analyze the difference between affected side and unaffected side. Conclusion from this study is as following, 1. The most serious problem was external rotation (0.56%) and internal rotation is the next (19.9%) in 5 kinds of shoulder range of motion in 2 weeks after surgical operation 2. There was no difference in internal rotation after post operation 3 months but there were differences and shown to recover more than 90% in flexion and abduction. Also shoulder function incresed in flextion less than 80% and more than 80% in external rotation. As this study finding was shown that shoulder range of motion did not get back perfectly except of internal rotation and extension in point of 3 months after breast cancer surgical operation. External rotation was specially shown the lowest result so it is needed to exercise for improving their physical functioning recovery in postmastectomy patients. And it is suggested to study for helping to postmastectomy patients' physical and psycosocial functions with the early rehabilitation program which is based on these results.