• The Journal of Korean Association of Computer Education
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• v.15 no.3
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• pp.37-47
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• 2012

One of the major goals in high school Informatics is for students to develop creative problem-solving abilities based on knowledge on computer science. Thus, the contents of the textbooks should be accurate and appropriate. However, we discovered that the current Informatics textbooks contain the untrue and/or inappropriate descriptions of main memory and virtual memory. The textbooks describe that main memory is composed of RAM and ROM. The virtual memory is described as a technique in which a part of the secondary storage is utilized as main memory to execute an application of which size is larger than that of main memory. In this study, we attempted to uncover the root causes of the fallacies, and suggest the accurate explanations by comparing with renowned books adopted in most schools worldwide including USA. Our study reveals that it is inappropriate to include ROM in main memory from the memory hierarchy perspective. Virtual memory is a technique that provides convenience to programmers, through which an operating system loads the necessary portion of a program from secondary storage to main memory. As for the advantages of virtual memory in the current computer systems, the focus should be on providing the effective multitasking capability, rather than on executing a larger program than the size of main memory. We suggest that it is appropriate to exclude virtual memory in textbooks considering its complexity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.12A
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• pp.1319-1332
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• 2004

Multicarrier direct sequence code-division multiple access CDMA(MC DS-CDMA) is an attractive technique for achieving high data rate transmission even if the potentially large peak-to-average power ratio(PAPR) is an important factor for its application. On the other hand, code select CDMA(CS-CDMA) is an attractive technique with constant amplitude transmission of multicode signal irregardless of subchannels by introducing code selection method. In this paper we propose a new multiple access scheme based on the combination of MC DS-CDMA and CS-CDMA. Proposed scheme, which we called MC CS-CDMA, includes the sutclasses of MC DS-CDMA and CS-CDMA as special cases. The performance of this system is investigated for multipath Sequency selective fading channel and maximal ratio combining with rake receiver. In addition the PAPR of proposed system is compare with that of both MC BS-CDMA and CS-CDMA. Simulation results show that proposed system improves PAPR reduction than MC DS-CDMA at the expense of the complexity of receiver and the number of available non. Also, the numerical result shows that the proposed system is better performance than MC DS-CDMA due to the increasing processing gain and the number of time diversity gain.

• Journal of the Korean earth science society
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• v.41 no.5
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• pp.459-468
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• 2020

In this study, the selection criteria for the occurrence of sea breezes in the Boseong area during the spring season (March-May) of 2016-2017 were prepared for the analysis of vertical weather characteristics. For this purpose, wind speed values were determined using the measured precipitation, cloud volume, wind direction, the difference between the ground and sea temperature, a wind Profiler at an altitude of 1 km, and numerical model data. The dates of the sea breezes in Boseong were classified according to the selection criteria, and the spatial and temporal characteristics of the sea breezes were identified by analyzing the time and altitude of the sea breeze and the size of the wind speed. Sea breezes occurred 23 out of 183 days (12%), and in Boseong, at least 1.2 out of 10 spring days exhibited sea breezes. Sea winds ranged from 1200 to 1800 LST, mainly from ground to 700 m altitude during the day. In addition, the maximum wind speed averaged 4.9 m s^-1, at an altitude of 40 m at 1600 LST, showing relatively lower values than those in a preceding study. This seems to be owing to the reduction in wind speed due to the complexity of the coastal terrain.

• Journal of The Korean Association For Science Education
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• v.35 no.3
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• pp.487-498
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• 2015

This research is for acquiring implications to science education based on learner's characteristics by analyzing the relationship between contents on science learning and cognitive domain of students in elementary schools through TIMSS 2011-based academic achievement test. Forty one multiple choice items from by TIMSS 2011 were used on 317 primary school students, fourth to sixth grade, and according to grade and achievement level of research targets, test results were analyzed. With these data, the relationship between contents on science learning and the score by cognitive domains, and through correlation by items, we drew static and negative correlations, and then compared the value. The result are as follows: First, other fields except for 'physical science' and 'inference' revealed meaningful differences by learners' grade, and the interrelationship between all contents domains and cognitive fields also appeared statically different. Second, both achievement level of contents and cognition of learners presented significant differences, but the correlation between scientific contents and cognitive field of learners showed different aspects. Third, in static and negative correlation by items, the complexity and their aspects could be classified by targets' academic achievement levels.

• Spatial Information Research
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• v.20 no.6
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• pp.109-118
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• 2012

Recent increasement of metropolitan infrastructure due to rapid expansion and development of urban areas which caused complexity and diversification of management system demands higher cost and effort to manage and maintain the facilities. The reason why it requires continuous and systematic management by national government is that the infrastructure facilities takes important role as it is directly related to public's living. Thus this study suggests an efficient management plan for increasement of work efficiency, cost reduction, and time saving by introducing 3D geospatial information system for water distribution reservoirs which is managed by the Office of Waterworks Seoul Metropolitan Government. This study evaluates and quantifies the range of work improvement using the 3D GIS technology through carrying out a survey targeting people in charge of the Office of Waterworks Seoul Metropolitan Government and other 8 offices. From the result of the research, applying the 3D-GIS improves by 90.32%, 93.55%, and 91.61% in the area of work efficiency, cost reduction, and time saving respectively. Consequently, using 3D GIS in future management of infrastructure could be used as a way of producing base data which supports administrative decision making through statistical and case analysis based on continuous data management. Also it would contribute to improving work efficiency by improving management system through preventing data omission.

• Journal of Broadcast Engineering
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• v.14 no.6
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• pp.661-675
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• 2009

The carelessly and illegally copied contents are raising serious social problem as internet and multimedia technologies are advancing. Therefore, development of video copy detection system must be settled without delay. In this paper, we propose the hierarchical video copy detection method that estimates similarity using statistical characteristics between original video and manipulated(transformed) copy video. We rank according to luminance value of video to be robust to spacial transformation, and choose similar videos categorized as candidate segments in huge amount of database to reduce processing time and complexity. The copy videos generally insert black area in the edge of the image, so we remove rig black area and decide copy or not by using statistical characteristics of original video and copied video with center part of frame that contains important information of video. Experiment results show that the proposed method has similar keyframe accuracy to reference method, but we use less memory to save feature information than reference's, because the number of keyframes is less 61% than that of reference's. Also, the proposed method detects if the video is copied or not efficiently despite expansive spatial transformations such as blurring, contrast change, zoom in, zoom out, aspect ratio change, and caption insertion.

• Journal of Bio-Environment Control
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• v.17 no.2
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• pp.83-89
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• 2008

A wind tunnel test was conducted at Protected Horticulture Experiment Station of National Horticultural Research Institute in Busan to find the aerodynamic resistance and quadratic resistance coefficient of chrysanthemum in greenhouse. The internal plants of the CFD model has been designed as a porous media because of the complexity of its physical shapes. Then the aerodynamic resistance value should be input for analyzing CFD model that crop is considered while the value varies by crops. In this study, the aerodynamic resistance value of chrysanthemum canopy was preliminarily found through wind tunnel test. The static pressure at windward increased as wind velocity and planting density increased. The static pressure at leeward decreased as wind velocity increased but was not significantly affected by planting density. The difference of static pressure between windward and leeward increased as wind velocity and planting density increased. The aerodynamic resistance value of chrysanthemum canopy was found to be 0.22 which will be used later as the input data of Fluent CFD model. When the planting distances were $9{\times}9\;cm$, $11{\times}11\;cm$, and $13{\times}13\;cm$, the quadratic resistance coefficients of porous media were found to be 2.22, 1.81, and 1.07, respectively. These values will be used later as the input data of CFX CFD model.

• Information Systems Review
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• v.9 no.2
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• pp.41-66
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• 2007

The e-marketplace is a virtual marketplace where buyers and sellers meet in order to conduct transactions through the intermediation of market-makers. For the success of an e-marketplace, it is crucial for the market-maker to induce both buyers and sellers to make active transactions in it. However, their participation is frequently deterred by potential risk factors caused mainly by the inherent, structural complexity of the e-marketplace. Therefore, it is a critical challenge for the market-maker to identify and manage the transactional risk perceived by both the buyers and sellers. In this paper, we investigate the sources of buyers' and sellers' perceived risks and their mitigating factors in the e-marketplace. Specifically, we derive an analysis framework based on the economic theory of agency relationship. The framework includes four sources of the risks(perceived information asymmetry, fears of seller opportunism, fears of buyer opportunism, and concerns about market-maker's role incompleteness) and five mitigators of the risks(website informativeness, trust in market-maker, trust in seller, product diagnosticity, and social presence). Then, we empirically verify the framework through a case study on four successful e-marketplaces, and provide implications and strategies for the market-maker to effectively manage the transactional risks.

• Journal of Gifted/Talented Education
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• v.24 no.1
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• pp.113-147
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• 2014

This study is a case study of the process of emerging for creative products to lead world science and technology. The aim of the study is to understand the emerging process of scientific creative products, and is to provide the direction of gifted education that discovers and trains globally competitive science talents through this. To discuss the emerging process of creative products, this study has academically discussed the creativity of the complexity of dealing with theory of evolution, the real life settings, and self-organization of experience etc., and has methodologically adopted the qualitative research method through a case study to look at the structures and processes. Data collection has been formed through a discussion with 12 Korean scientists who have created selected creative products, greatly contributed for the world science and technology(12 areas). The analysis has been carried out by the latter part positivist methods. As a result, the emerging process of creative products in the field of science and technology were separated into four steps: (1)the foundation stage of knowledge, (2)the exploration stage of knowledge, (3)the construction stage of knowledge, and (4)the emerging stage of knowledge. Each stage has been revealed growing up through the macro-system and the self-organization of each micro-systems.

• Journal of Internet Computing and Services
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• v.14 no.4
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• pp.25-33
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• 2013

The procedure of the arbitration which is the tag collision is essential because the multiple tags response simultaneously in the same frequency to the request of the Reader. This procedure is known as Anti-collision and it is a key technology in the RFID system. In this paper, we propose the 4-Bit Pattern Slot Allocation(4-BPSA) algorithm for the high-speed identification of the multiple tags. The proposed algorithm is based on the tree algorithm using the time slot and identify the tag quickly and efficiently through accurate prediction using the a slot as a 4-bit pattern according to the slot allocation scheme. Through mathematical performance analysis, We proved that the 4-BPSA is an O(n) algorithm by analyzing the worst-case time complexity and the performance of the 4-BPSA is improved compared to existing algorithms. In addition, we verified that the 4-BPSA is performed the average 0.7 times the query per the Tag through MATLAB simulation experiments with performance evaluation of the algorithm and the 4-BPSA ensure stable performance regardless of the number of the tags.