• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.3
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• pp.39-47
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• 2002

This paper deals with study of a new framework for the traceback of distributed DoS(Denial of Service) attacks in the Internet, in which many sources flood "spoofed" IP packets towards a single victim. In our scheme, the destination host traces those anonymous packets' losses, and infers the logical end-to-end paths back towards the sources. This method is based on the fact that there is a strong correlation between packet losses when those packets traverse along a same route, and the simulation results show high probabilities of detecting the topology under a certain condition. Compared with previous approaches, our scheme has a number of distinct features: It can be performed in realtime or non-realtime, without any supports of routers or ISPs. Our results may be applied to the inference of physical topology and to support previous approaches.pproaches.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.6
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• pp.93-112
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• 2002

Since the multicast group which is composed of various members is dynamic, members of the group frequently join or leave. So, for a new session, group keys are efficiently updated and distributed. In this paper, we describe very simple and new efficient logical key hierarchy(ELKH) protocol which is based on an one-way function. In the previous schemes, when the group controller distributes new created keys or updated keys to the members the information is usally encryted and then transmited over a multicast channel. But ELKH secretes the multicast message by using the one-way function and XOR operator instead of encrypting it. Hence our main construction improves the computational efficiency required from the group controller and group memebers while doesn't increase size of re-keying message when compared to $EHBT^{[12]}$. Assuming the security of an underlying one-way function, we prove that our scheme satisfies forward secrecy and backward secrecy.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.38 no.6
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• pp.533-542
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• 2020

This study proposes the logical data model design of a spatial data model that complies with international standards for the waterworks of underground facilities. We conduct a preliminary study related to underground spatial data standards and data models, and review the status of the existing systems. Then, we defined the conceptual design direction of underground spatial data model based on the problems and issues. Next, we defined the terminology, classification, semantic relationships of waterworks. Next, for the conceptual design of the underground spatial data model, we defined the naming criteria for all data according to the waterworks classification. In addition, a logical model is drawn and described using UML (Unified Modeling Language) diagrams. Based on the results, it is expected that the accuracy related to underground facilities data will be improved.

• Journal of the Korean Society of Earth Science Education
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• v.9 no.3
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• pp.309-322
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• 2016

This study was conducted to investigate the effect of science based on question-centered Havruta learning on the logical thinking and the science related attitude of elementary students. The number of participants were 93, 4 classes of 4th graders in G elementary school in C city. The experimental group, 2 classes including 46 participants, took science lessons based on question centered Havruta learning while the comparative group, 2 classes including 47 participants, took teacher-driven lessons using teacher's guidebook. Pre and post tests were done before and after executing lessons to assess the changing in each group's logical thinking and the science related attitude. And targeting experimental group, a perception survey toward Havruta learning was carried out and the results were arranged. The results of this study can be summarized as follows: First, the pre and post test results of logical thinking revealed that the experimental group showed higher improvement compared to the comparative group and the difference was meaningful. This implies that question centered Havruta classe has the effect of improving students' logical thinking. Second, from the pre and post test results of the science related attitude, we saw that the experimental group showed higher improvement compared to the comparative group and the difference was meaningful. This confirms that question centered Havruta class has the effect of improving students' science related attitude. Third, the survey regarding perspectives of experimental group students toward Havruta learning showed that students had a high satisfaction level.

• Journal of the Korean Chemical Society
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• v.64 no.1
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• pp.19-29
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• 2020

We analyzed the representations of acid-base models in 4 kinds of Chemistry I and 4 kinds of Chemistry II textbooks of the 2009 revised curriculum, and 9 kinds of Chemistry I textbooks and 6 kinds of chemistry II textbooks of the 2015 revised curriculum in this study. The problems of the textbook were divided into the problems of definitions and the representations of the logical thinking. As a result of the study, the lack of the concept of chemical equilibrium had a problem with the representation of reversible reactions in the definition of the Brønsted-Lowry model in the Chemistry I textbooks of 2009 revised curriculum, it also appeared to persist in Chemistry I textbooks of 2015 revised curriculum which contains the concept of chemical equilibrium. The representations of logical thinking were related to particle kinds of conservation logic, combinational logic, particle number conservation logic, and proportion logic. There were few problems related to representation of logical thinking in Chemistry I textbook in 2009 revision curriculum, but more problems of representations related to logics are presented in Chemistry I textbooks in 2015 revision curriculum. Therefore, as the curriculum is revised, the representations of chemistry textbooks related to acid and base models need to be changed in a way that can help students' understanding.

• Journal of The Korean Association For Science Education
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• v.37 no.1
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• pp.39-48
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• 2017

In this study, we investigated the characteristics of analogs generated by high school students to explain ionic bonding in the perspectives of the number of analogs, the understanding of mapping, and the source and type of analogs. We also compared the results by students' conceptual understanding, logical thinking ability, and analogical reasoning ability. Participants in this study were 395 11th graders in Seoul. The results of the study showed that the higher the conceptual understanding, the logical thinking ability, and the analogical reasoning ability, the more the students generated the analogs. The understanding of mapping was related to logical thinking ability and analogical reasoning ability. It is noteworthy that the sources of analogs differed only depending on their conceptual understanding of the target concept among the cognitive variables studied. Students who had higher conceptual understanding also generated analogs from more diverse sources. Some types of the generated analogs were related to the cognitive variables. For examples, the students who had higher conceptual understanding and logical thinking ability generated more verbal/pictorial analogs. The types of analogs were not related to cognitive variables in terms of artificiality, abstraction, and systemicity. Educational implications of these findings were discussed.

• Journal of the Korean Society for information Management
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• v.35 no.3
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• pp.101-121
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• 2018

This study proposes the analysis method in sentence semantics that can be automatically identified and processed as appropriate items in the system according to the composition of the sentences contained in the data corresponding to the logical semantic structure metadata of the research papers. In order to achieve the purpose, the structure of sentences corresponding to 'Research Objectives' and 'Research Outcomes' among the semantic structure metadata was analyzed based on the number of words, the link word types, the role of many-appeared words in sentences, and the end types of a word. As a result of this study, the number of words in the sentences was 38 in 'Research Objectives' and 212 in 'Research Outcomes'. The link word types in 'Research Objectives' were occurred in the order such as Causality, Sequence, Equivalence, In-other-word/Summary relation, and the link word types in 'Research Outcomes' were appeared in the order such as Causality, Equivalence, Sequence, In-other-word/Summary relation. Analysis target words like '역할(Role)', '요인(Factor)' and '관계(Relation)' played a similar role in both purpose and result part, but the role of '연구(Study)' was little different. Finally, the verb endings in sentences were appeared many times such as '~고자', '~였다' in 'Research Objectives', and '~었다', '~있다', '~였다' in 'Research Outcomes'. This study is significant as a fundamental research that can be utilized to automatically identify and input the metadata element reflecting the common logical semantics of research papers in order to support researchers' scholarly sensemaking.

• Journal of The Korean Association For Science Education
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• v.9 no.1
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• pp.19-37
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• 1989

The purpose of this study was to investigate the development of logical thinking and scientific reasoning pattern of Korean high school students. To carry out this study subjects were selected about 2,000 Junior high school students, and about 4,100 senior high school students throughout the nation. They were identified as concrete, transitional or formal operational stage with the use of TOLT(the Test of Logical Thinking) by Tobin and Capie(1980), and TOSR(the Test of Scientific Reasoning) by W.A Farmer(1986). This study turned out that more than 76% of Junior high school students were classified as the concrete operational stage and about 44% of senior high school students were classified as the formal operational stage, while about 26% of them were still in the concrete operational level. This study showed that the main factor of the intellectual development of students is learning by the gradual advancement of their grades and especially entrance into the senior high school rather than by the physical growth. This study also showed that there are the take-off stage of the development of logical thinking between fourteen and fifteen years of their ages. Less than 25% of junior high school students were in the formal operational stages which are capable of control of variables, probabilistic, correlation and combinational logic in problem-solving situation, while 33-54% of senior high school students were in the formal operational levels. 38% of junior high school students were in the formal operational stage which is capable of proportional logic, while about 55% of senior high school students were in the formal operational stage. Less than 20% of senior high school students were classified as group of highly capable of scientific reasoning, while more than 23% of them were classified as group of poor capability. It also turned out that there are differences or no differences between male and female students of each school in problem-solving situation regarding each logic approach. These differences were proved to be fluctuating depending on the situations and their grades. The other results of this study is similar to those of other researches such as Tomlinson-Keasey 1972, Coleman 1973, Lawson 1973, Lawson and Renner 1974, Neimark 1975, Han 1982, and Kim 1989.

• Journal of Radiation Protection and Research
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• v.45 no.2
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• pp.76-80
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• 2020

Background: To improve the measurement accuracy of liquid-scintillation counting for activity standardization, it is necessary to significantly reduce the background caused by thermal noise or after-pulses. We have therefore improved a movable 3 photomultiplier (3PM)-γ coincidence-counting method using the logical sum of three double coincidences for β events. Materials and Methods: We designed a new data-acquisition system in which β events are obtained by counting the logical sum of three double coincidences. The change in β-detection efficiency can be derived by moving three photomultiplier tubes sequentially from the liquid-scintillation vial. The validity of the method was investigated by activity measurement of ¹³⁴Cs calibrated at the Korea Research Institute of Standards and Science (KRISS) with 4π(PC)β-γ(NaI(Tl)) coincidence counting using a proportional counter (PC) for the β detector. Results and Discussion: Measurements were taken over 14 counting intervals for each liquidscintillation sample by displacing three photomultiplier tubes up to 45 mm from the sample. The dead time in each β- and γ-counting channel was adjusted to be a non-extending type of 20 ㎲. The background ranged about 1.2-3.3 s^-1, such that the contributions of thermal noise or after-pulses were negligible. As the β-detection unit was moved away from the sample, the β-detection efficiencies varied between 0.54 and 0.81. The result obtained by the method at the reference date was 396.3 ± 1.7 kBq/g. This is consistent with the KRISS-certified value of 396.0 ± 2.0 kBq/g within the uncertainty range. Conclusion: The movable 3PM-γ method developed in the present work not only succeeded in reducing background counts to negligible levels but enabled β-detection efficiency to be varied by a geometrical method to apply the efficiency extrapolation method. Compared with our earlier work shown in the study of Hwang et al. [2], the measurement accuracy has much improved. Consequently, the method developed in this study is an improved method suitable for activity standardization of β-γ emitters.

• School Mathematics
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• v.10 no.3
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• pp.357-374
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• 2008

The complex number system is supposed to introduce first chapter in the first grade of high school. When number system is expanded to complex numbers, the main aim is to understand preservation of algebraic structure with regard to the flow of curriculum and textbook. This research reviewed overall alternative articulation and treatment of textbooks from a logical viewpoint. Two research questions are developed below. First, in the structure of the current curriculum, when we consider student's 'level', how are the alternative articulation and treatment of textbooks in complex unit on a logical point of view? Second, What are more logical alternative articulation and treatment? What alternative articulation and treatment are suitable for a running goal? and what are the improvement which is definitive?