• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.2
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• pp.239-249
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• 2003

A lot many WWW sites are come into the world more and more as Web is considered as the unified Internet information tool. The location of each site or resource is usually specified by a physical URL, which is often too long to remember and tends to raise difficulty to show the aim of the site intuitively by seeing it. Since any person or organization can get his/her own domain name easily, it is more desirable to use a logical URL with the domain name which can be chosen more compact to remember and meaningful to represent the ultimate intention of the site. This paper presents an implementation of a URL forwarding server which forwards a URL to another, so that a WWW site can use a logical URL instead of a physical one. The server consists of a domain mapper which uses the redirection transaction of the HTTP protocol, and a name server based on the HIND. The paper shows how the interaction between the domain mapper and the name sever can make forwarding possible and describes its implementation in detail. Experimental results shows that the overhead incurred by URL forwarding is negligible compared to the typical delay of current Internet traffic condition.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.5
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• pp.529-539
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• 2000

This paper proposes a prefetch-based disk buffer management algorithm, which we call W2R (Veighingjwaiting Room). Instead of using elaborate prefetching schemes to decide which blockto prefetch and when, we simply follow the LRU-OBL (One Block Lookahead) approach and prefetchthe logical next block along with the block that is being referenced. The basic difference is that theW2R algorithm logically partitions the buffer into two rooms, namely, the Weighing Room and theWaiting Room. The referenced, hence fetched block is placed in the Weighing Room, while theprefetched logical next block is placed in the Waiting Room. By so doing, we alleviate some inherentdeficiencies of blindly prefetching the logical next block of a referenced block. Specifically, a prefetchedblock that is never used may replace a possibly valuable block and a prefetched block, thoughreferenced in the future, may replace a block that is used earlier than itself. We show through tracedriven simulation that for the workloads and the environments considered the W2R algorithm improvesthe hit rate by a maximum of 23.19 percentage points compared to the 2Q algorithm and a maximumof 10,25 percentage feints compared to the LRU-OBL algorithm.

• Journal of the Korea Society for Simulation
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• v.21 no.4
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• pp.35-46
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• 2012

As complexity of real-time systems is being increased ad hoc approaches to analysis of such systems would have limitations in completeness and coverability for states space search. Formal means using a model-based approach would solve such limitations. This paper proposes a model-based formal method for logical analysis, such as safety and liveness, of real-time systems at a discrete event system level. A discrete event model for real-time systems to be analyzed is specified by DEVS(Discrete Event Systems Specification) formalism, which specifies a discrete event system in hierarchical, modular manner. Analysis of such DEVS models is performed by Communicating DEVS (C-DEVS) formalism of a timed global state transition specification and an associated analysis algorithm. The C-DEVS formalism and an associated analysis algorithm guarantees that all possible states for a given system are visited in an analysis phase. A case study of a safety analysis for a rail road crossing system illustrates the effectiveness of the proposed method of the model-based approach.

• The Journal of Korean Association of Computer Education
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• v.16 no.4
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• pp.13-21
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• 2013

Recently, programming education is being actively performed in education field with development of educational programming language and teaching and learning methods for elementary students. However, programming education have limit to apply to the overall computer science curriculum, because it is performed by more than 5th grade and focused on the utilization of programming tools than problem-solving process. It is necessary to expand the range of students and educational content considered with problem-solving process for encouraging programming education in computer science. In this study, we suggest the easy-to-use programming tool for lower grade(1st grade) and robot programming task based on improvement of student's thinking ability. We use Tangible User Interface(TUI) for elementary student's(1st grade) convenience of programming and developed the robot programming task for improvement of logical thinking. As a result of this experiment, tangible programming tool can be used easily in elementary students(1st grade) and developed robot programming task is effective in improvement of logical thinking.

• Journal of Korean Elementary Science Education
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• v.33 no.1
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• pp.21-29
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• 2014

This study analyzed the inquiry activities in the 'matter' units from each science textbook for the fifth and the sixth graders developed by the 2007 revised national curriculum, using Practical Activity Analysis Inventory proposed by Millar(2009) to examine types of learning objectives, hands-on contents(what students have to do with objects and materials), minds-on contents(what students have to 'do' with ideas), and logical structure each activity had. The results of this study are as follows: First, most learning objectives of the inquiry activities seems to be suitable for the standards of 2007 revised national curriculum. Second, the standards of 2007 revised national curriculum are properly reflected in hands-on contents of inquiry activities. Third, minds-on contents of inquiry activities are well developed to meet the standards of 2007 revised national curriculum as a whole. Fourth, the logical structures of inquiry activities are mostly adequate for achieving the goals of the 2007 revised national curriculum. In the textbook for the fifth graders, however, all the activities are focusing too much on using students' current ideas to generate a prediction and collecting data to explore or test it. Based on these findings, this research has concluded that learning objectives, minds-on contents and logical structures of inquiry activities need to be designed carefully for students to be exposed to various activities when developing following textbooks.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.38 no.4
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• pp.10-21
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• 2001

This paper develops a logical simulation method for by dyversity of situations. Most existing systems, for example, games and infant tutoring systems lead users to virtual environment with unfolding situations, but are not designed to induce the change of the environment itself. In this paper, a logically simulated environment is created by defining situations and single events based on situation hierarchy structure. We elaborate the occurrence of events by classifying the causality. The occurrence or natural phenomena is dictated by physical laws and natural phenomena are expressed as the transition of the event based on event association. Specifically we define the source of the event for natural phenomena and we consider the existence of objects as a primary factor in event occurrence. The advantages of this approach include the reuse of events, that is, different events can be generated in the same flow with fresh conditions. This allows us to implement a more practical and logical environment. A drawback to this method is the difficulty in dividing a situation into events. The proposed method was implemented in the context of the change of season among natural phenomena.

• The Mathematical Education
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• v.51 no.1
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• pp.1-19
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• 2012

In this study, contents of 'the 2007 revised curriculum handbook' and 16 kinds of mathematics textbooks were analyzed first. The purpose of this study is to examine the understanding state of students at general high schools by making questionnaires to survey the understanding state on contents of chapter of complex number based on above analysis. Results of research can be summarized as follows. First, the content of chapter of complex number in textbook was not logically organized. In the introduction of imaginary number unit, two kinds of marks were presented without any reason and it has led to two kinds of notation of negative square root. There was no explanation of difference between delimiter symbol and operator symbol at all. The concepts were presented as definition without logical explanations. Second, students who learned with textbook in which problems were pointed out above did not have concept of complex number for granted, and recognized it as expansion of operation of set of real numbers. It meant that they were confused of operation of complex numbers and did not form the image about number system itself of complex number. Implications from this study can be obtained as follows. First, as we came over to the 7th curriculum, the contents of chapter of complex number were too abbreviated to have the logical configuration of chapter in order to remove the burden for learning. Therefore, the quantitative expansion and logical configuration fit to the level for high school students corresponding to the formal operating stage are required for correct configuration of contents of chapter. Second, teachers realize the importance of chapter of complex number and reconstruct the contents of chapter to let students think conceptually and logically.

• Journal of the Korean Society of Marine Environment & Safety
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• v.8 no.2
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• pp.71-78
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• 2002

For the first Maritime Accident Inquiry System in Korea, Central Marine Accidents Inquiry Committee were founded in Seoul and District Marine Accidents Inquiry Committee in Busan city In 1963 to determine the circumstances of the accidents and causes. At the present day, it was settled as Maritime Safety Tribunal tough several revision of the Law and regulations regarding the Maritime Accident Inquiry System. In Korea, there occurred about m cases of marine accident, and as a result, about 200 people were lost human lives in average per year. In accordance with the change of circumstances such as traffic increasing and being bigger in size, being faster in speed, etc., the causes of the marine accidents become complicated year by year. Accordingly, in this moment, it is meaningful that the introduction of the Research Official who assists the Judges probing the cases fair and square. In this Paper, with the consideration of the several kinds of Research Official System, such as the Research Official of the Korean Supreme Court, the Supreme Public Prosecutors' Office and the Constitutional Court, Japanese Supreme Court, Law Clerk in USA, etc., the selection, numbers, duty of the Research Official were studied. The results of the study are as follows; 1. The Research Official to be appointed among the person having long enough career as a Judge, Investigator engaged in the Maritime Safety Tribunal due to he sho띨d have capability to confirm perfectly logical judgement and to collect enough material for the conclusion of the causes of the case. The one who understands the foreign language is preferred for the study of the foreign cases; 2. It will be logical to post 3 joint Research Officials in Korea Maritime Safety Tribunal in Seoul after due consideration the cases treated a year; 3. It will be logical for the Research Official to perform the collection of material and inspection of the scene for the trial and inquiry of the cases, to attend the cases filed suit to the Supreme Court, to make commentarial papers regarding the judged cases, to collect statistics of marine accidents and to devise a reform measure through in-depth analysis of the accidents frequently occurred, to study for the improvement of the Maritime Accident Inquiry System;

• Journal of the Korean Chemical Society
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• v.45 no.4
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• pp.370-376
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• 2001

In this study, high school students' problem-solving strategy-performing ability was measured by an essay-type test. The relationship between students' logical thinking ability and strategy-performing ability was also investigated. Four classes (N=187) were selected from two high schools in Seoul, and the strategy performance ability test and the Group Assessment of Logical Thinking (GALT) were administered. Evaluation scheme for strategy-performing ability consists of 7 subcategories - understanding given of problems, recalling related law, setting up subgoals, deriving physical quantities, logical progress, mathematical execution, and reviewing. The intercoder agreement for scaling was .92, which indicated substantial strength of agreement. The results revealed that students' ability of understanding given of problems and mathematical execution was relatively high. However, their ability of setting up subgoals and reviewing was very low. The total scores of the strategy performance ability test and all of the scores of each subcategory were significantly correlated with the GALT scores.

• The Journal of Korean Association of Computer Education
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• v.18 no.5
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• pp.1-13
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• 2015

In recent domestic and international curriculum it is emphasized that students should acquire 'problem solving' competence as a member of knowledge information society and various programming educational methods of improving problem solving competence have been studied. But there is no difference between programming problems in related research and traditional programming courses. Most methods of solving problems are focused on acquiring specific languages rather than enhancing problem solving ability. In this research, we developed a suitable programming problems and curriculum for fostering problem solving competence and designed and developed teaching and learning contents based on PSA(Problem Solving Activities). Furthermore, we obtained meaningful results of improving learners' problem solving ability and logical thinking ability by operating curriculum with developed contents as learning materials. The results of this research are expected to be used as a reference model or basic teaching materials for developing and operating the programming teaching and learning contents or curriculum to enhance problem solving competence.