• Journal of The Korean Association For Science Education
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• v.41 no.4
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• pp.339-358
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• 2021

This study explores the agency of a student leader, expressed through efforts to distribute power and encourage participation in elementary scientific modeling classes. The study also analyzes the context in which the leader's agency was expressed and the context in which the development of a collective agency was constrained. The participants were 22 fifth-grade students. The leader's agency was analyzed by examining his words and actions. As a result, at the outset of the study, the leader had the most power, performing all the activities as the sole authority in a non-cooperative participation pattern. However, with reflection and help from the researcher, the leader recognized the problem and facilitated the participation of other students. He developed an identity as a teacher and demonstrated the agency. The leader's agentic behaviors can be categorized into three aspects. First, regarding the cognitive aspect, the leader helped other students participate in modeling by sharing his knowledge. Second, regarding the normative aspect, he made rules to give all students an equal voice. Third, regarding the emotional aspect, the leader acknowledged the contribution of the students, increasing their confidence. The leader's agency temporarily helped the group to overcome the student hierarchy, facilitating a cooperative participation pattern. However, the development of a collective agency was constrained. The power of the leader was partially redistributed, and the other students did not position themselves as equal to the leader. To support the leader's agency to develop into a collective agency, it is necessary to redistribute the power of the leader more equally and to change the recognition of students.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.11
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• pp.911-923
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• 2013

Multipath routing is one of challenging issues for improving the reliability of end-to-end data delivery in wireless sensor networks. Recently, a disjointedness and management of path have been studying to enhance the robustness and efficiency of the multipath routing. However, previous multipath routing protocols exploit the disjointed multipath construction method that is not to consider the wireless communication environment. In addition, if a path failures is occurred due to the node or link failures in the irregular network environment, they maintain the multipath through the simple method that to construct a new extra path. Even some of them have no a method. In order to cope with the insufficiency of path management, a hole detouring scheme, to bypass the failures area and construct the new paths, was proposed. However, it also has the problem that requires a heavy cost and a delivery suspension to the some or all paths in the hole detouring process due to the centralized and inflexible path management. Due to these limitations and problems, the previous protocols may lead to the degradation of data delivery reliability and the long delay of emergency data delivery. Thus, we propose a flexible disjoint multipath routing protocol which constructs the radio disjoint multipath by considering irregular and constrained wireless sensor networks. It also exploits a localized management based on the path priority in order to efficiently maintain the flexible disjoint multipath. We perform the simulation to evaluate the performance of the proposed method.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.44 no.2 s.314
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• pp.1-11
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• 2007

H.264/AVC uses variable block sizes to achieve significant coding gain. It has 7 different coding modes having different motion compensation block sizes in Inter slice, and 2 different intra prediction modes in Intra slice. This fine-tuned new coding feature has achieved far more significant coding gain compared with previous video coding standards. However, extremely high computational complexity is required when rate-distortion optimization (RDO) algorithm is used. This computational complexity is a major problem in implementing real-time H.264/AVC encoder on computationally constrained devices. Therefore, there is a clear need for complexity reduction algorithm of H.264/AVC such as fast mode decision. In this paper, we propose a fast mode decision with early $P8\times8$ mode rejection based on block size activity using large block history map (LBHM). Simulation results show that without any meaningful degradation, the proposed method reduces whole encoding time on average by 53%. Also the hybrid usage of the proposed method and the early SKIP mode decision in H.264/AVC reference model reduces whole encoding time by 63% on average.

• Journal of Broadcast Engineering
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• v.13 no.6
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• pp.892-904
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• 2008

As a video encoding in resource constrained environments such as sensor networks has become an important issue, DVC(Distributed Video Coding) has been intensively investigated as a solution for light weighted video encoding problem. Known as one of the representative schemes of DVC, the Wyner-Ziv coding generates side information of current frame only at decoder, using correlation among frames, and reconstructs video through noise elimination on the side information using channel code. Accordingly, the better quality of side information brings less channel noise, thus attains better coding performance of the Wyner-Ziv coder. However, since it is hard for decoder to generate an accurate side information without any information of original frame, a method to successively improve side information using successively decoded original frame, based on decoding reliability, was previously developed. However, to improve side information from decoding results, not only an error rate of the decoding result as a reliability, but also the amount of reliable information from the decoding result is important. Therefore, we propose TDWZ(Transform-domain Wyner-Ziv coding) with successively improving side information based on decoding reliability considering not only an error rate but also the amount of reliable information of the decoding results. Our experiment shows the proposed method gains average PSNR up to 1.7 dB over the previous TDWZ, that is without successive side information improvement.

• The Journal of the Acoustical Society of Korea
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• v.15 no.2
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• pp.21-32
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• 1996

The performance of the energy density control algorithm for controlling a broadband noise is evaluated in a one-dimensional enclosure. To avoid noncausality problem of a control filter, which often happens in a frequency domain optimization, analyses presented in this paper are undertaken in the time domain. This approach provides the form of the causally constrained optimal controller. Numerical results are presented to predict the performance of the active noise control system, and indicate that imp개ved global attenuation of the broadband noise can be achieved by minimizing the energy density, rather than the squared pressure. It is shown that minimizing the energy density at a single location yields global attenuation results that are comparable to minimizing the potential energy. Furthermore, unlike the squared pressure control, the energy density control does not demonstrate any dependence on the error sensor location for this one-dimensional field. A practical implementation of the energy-based control algorithm is presented. Results show that the energy density control can be implemented using the two sensor technique with a tolerable margin of performance degradation.

• Journal of the Korea Society of Computer and Information
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• v.18 no.10
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• pp.141-148
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• 2013

This paper proposes an EMS algorithm designed to determine the optimal locations for Emergency Medical Service centers that both satisfy the maximum ambulance response time T in case of emergency and cover the largest possible number of residents given a limited number of emergency medical services p in a city divided into different zones. This methodology generally applies integer programming whereby cases are categorized into 1 if the distance between two zones is within the response time and 0 if not and subsequently employs linear programming to obtain the optimal solution. In this paper, where p=1, the algorithm determines a node with maximum coverage. In cases where $p{\geq}2$, the algorithm selects top 5 nodes with maximum coverage. Based on inclusion-exclusion method, this selection entails repeatedly selecting a node with the maximum coverage when nodes with lower numbers are deleted. Among these 5 selected nodes, the algorithm selects a single node set with the greatest coverage and thereby as the optimal EMS location. The proposed algorithm has proven to accurately and expeditiously obtain the optimal solutions for 12-node network, 21-node network, and Swain's 55-node network.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.45 no.1
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• pp.11-21
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• 2008

In conventional video coding, the complexity of encoder is much higher than that of decoder. However, as more needs arises for extremely simple encoder in environments having constrained energy such as sensor network, much investigation has been carried out for eliminating motion prediction/compensation claiming most complexity and energy in encoder. The Wyner-Ziv coding, one of the representative schemes for the problem, reconstructs video at decoder by correcting noise on side information using channel coding technique such as turbo code. Since the encoder generates only parity bits without performing any type of processes extracting correlation information between frames, it has an extremely simple structure. However, turbo decoding errors occur in noisy side information. When there are high-motion or occlusion between frames, more turbo decoding errors appear in reconstructed frame and look like Salt & Pepper noise. This severely deteriorates subjective video quality even though such noise rarely occurs. In this paper, we propose a computationally extremely light encoder based on symbol-level Wyner-Ziv coding technique and a new corresponding decoder which, based on a decision whether a pixel has error or not, applies median filter selectively in order to minimize loss of texture detail from filtering. The proposed method claims extremely low encoder complexity and shows improvements both in subjective quality and PSNR. Our experiments have verified average PSNR gain of up to 0.8dB.

• Journal of KIISE:Information Networking
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• v.30 no.1
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• pp.75-81
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• 2003

User authentication, including confidentiality, integrity over untrusted networks, is an important part of security for systems that allow remote access. Using human-memorable Password for remote user authentication is not easy due to the low entropy of the password, which constrained by the memory of the user. This paper presents a new password authentication and key agreement protocol suitable for authenticating users and exchanging keys over an insecure channel. The new protocol resists the dictionary attack and offers perfect forward secrecy, which means that revealing the password to an attacher does not help him obtain the session keys of past sessions against future compromises. Additionally user passwords are stored in a form that is not plaintext-equivalent to the password itself, so an attacker who captures the password database cannot use it directly to compromise security and gain immediate access to the server. It does not have to resort to a PKI or trusted third party such as a key server or arbitrator So no keys and certificates stored on the users computer. Further desirable properties are to minimize setup time by keeping the number of flows and the computation time. This is very useful in application which secure password authentication is required such as home banking through web, SSL, SET, IPSEC, telnet, ftp, and user mobile situation.

• Journal of The Korean Association For Science Education
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• v.39 no.3
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• pp.427-439
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• 2019

In this study, we investigated how scientists and teachers engaged in mentoring program are conducting research ethics education and how they are creating an ethical educational environment. A questionnaire survey was given to 32 scientists and 44 teachers conducting mentoring programs for gifted high school students. In the content of research ethics education, most of the respondents opined that they should teach against falsification, plagiarism, and fabrication. Teachers were most likely to teach ethical decision-making in each step of the research process. Most of the scientists said that they should teach how to write research note. For the difficulties, the teachers pointed out the challenging system that focuses only on college entrance exams while the scientists answered that it was difficult to recognize research ethics as the problem of the students themselves. For the teachers, the most affective factor in creating an ethical research environment is the amount of time to teach research ethics while for the scientists, it is the ethics of the mentors. For creating an ethical research environment, the teachers responded with making an atmosphere wherein failure is tolerated, and the scientists responded with increasing the degrees of freedom in results. For the difficulties of creating an ethical research environment, the teachers were constrained by research time while the scientists were pressured about the results. These results provide implications for ways to teach research ethics and for ways to create an ethical research environment in the mentoring program for science-gifted students.

• The Journal of the Korea Contents Association
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• v.19 no.5
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• pp.553-561
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• 2019

In this study, the method of quality measurement for the statistical usefulness of de-identified data was examined in terms of prediction accuracy by statistical modeling. In the era of the 4th industrial revolution, effective use of big data is essential to innovation through information and communication technology, but personal information issues are constrained to actively utilize big data. In order to solve this problem, de-identification guidelines have been established and the possibility of actual re-identification of personal information has become very low due to the utilization of various de-identification methods. On the other hand, strong de-identification can have side effects that degrade the usefulness of the data. We have studied the quality of statistical usefulness of the de-identified data by KLT model which is a representative de-identification method, A case study was conducted to see how statistical accuracy of prediction is degraded by de-identification. We also proposed a new measure of data usefulness of the de-identified data by quantifying how much data is added to the de-identified data to restore the accuracy of the predictive model.