• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.5
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• pp.426-433
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• 1990

In this study, we propose a integrated type concentrator and compare with the separated type concentrating method, to accommodate 2B+D ISDN basic access traffic. This system's blocking probabilities are analyzed in terms of each class of bit rate, number of output channels, number of subscriber lines, and offered traffic. The result shows that the proposed method can significantly increase the maximum number of subscriber lines connecting to the system via a T1 carrier, compared with that of the "CCITT proposed" multiplexing scheme or the separated type concentrating method.ng method.

• Journal of the Korean Operations Research and Management Science Society
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• v.25 no.1
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• pp.85-92
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• 2000

Channel management is critical in designing a cellular mobile system that offers high capacity and high quality. In this paper, an integrated channel management scheme is proposed, which consists of a dynamic channel allocation scheme and an admission control scheme. The dynamic channel allocation scheme allocates a call request the channel which minimizes the impact on its interfering cell, and consists of two types of channel allocation strategies : nominal channel allocation strategy and non-nominal channel allocation strategy. The admission control scheme named the variable cutoff priority scheme reserves some frequency channels for handoff cells in each cell the number of which varies according to the blocking probability of handoff class in that cell. Computationl tests are performed to evaluate the performance of the proposed scheme in terms of overall blocking probability, defined by the weighted value of the blocking probabilities of new calls and handoff calls. The results show that the proposed scheme yields better performance than other compared schemes.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.2
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• pp.162-170
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• 2004

A 900MHz CMOS RF power amplifier with digitally controllable output power has been proposed and designed with 0.6${\mu}{\textrm}{m}$ standard CMOS technology. The designed power amplifier was composed of digitally controllable switch mode pre-amplifiers with an integrated 4nH spiral inductor load and class-C output stage. Especially, to compensate the 1ow Q of integrated spiral inductor, cascode amplifier with a Q-enhancement circuit is used. It has been shown that the proposed power control technique allows the output power to change from almost 3dBm to 13.5dBm. And it has a maximum PAE(Power Added Efficiency) of almost 55％ at 900MHz operating frequency and 3V power supply voltage.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7B
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• pp.771-779
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• 2011

It is expected that many heterogeneous wireless systems, such as 3GPP LTE systems, WiMAX systems and WLAN systems, will coexist in the next generation wireless communication environments. Integrated radio resource management and seamless vertical handoff (VHO) should be supported to provide integrated communication services over multi-radio access networks. A new class of adaptive VHO system that views the handoff problem as a pattern recognition problem is proposed. In this paper, we propose a unified radio resource management (URRM) architecture and Support Vector Machine (SVM) based vertical handoff decision system. Extensive simulation studies show the proposed VHO algorithm outperforms RSS based VHO algorithms in terms of throughput and service cost.

• Current Optics and Photonics
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• v.6 no.1
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• pp.10-14
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• 2022

Low-threshold optical bistability is essential for practical nonlinear optical applications. Many bistable optical devices based on high-quality-factor resonators have been proposed to reduce the threshold intensity. However, demonstrating high-quality-factor resonance requires complex fabrication techniques. In this work, we numerically demonstrate optical bistability with bound states in the continuum in a simple one-dimensional Si photonic crystal. The designed structure supports bound states in the continuum, producing an ultrahigh quality factor without tough fabrication conditions. The threshold intensity of the designed device is 150 MW/cm² at the optical communication wavelength. This scheme may lead to a new class of nonlinear photonics.

• English Language & Literature Teaching
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• v.17 no.3
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• pp.73-98
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• 2011

This study investigated the feasibility and effectiveness of incorporating oral corrective feedback into the content-based business English writing class. Two types of oral corrective feedback, recasts and metalinguistic feedback, were integrated into business English writing classes to help low intermediate-proficiency Korean university students improve the ability to use the simple past, present progressive, and present perfect tenses correctly in their written production. Prior to the treatments, the subjects had basic grammatical knowledge of the target verb tenses, but they had only limited control over them in their written production. Three groups were formed: recast group that received corrective recasting, metalinguistic group that received metalinguistic clues, and control group that received no oral corrective feedback. The study demonstrated that it was feasible to incorporate recasts and metalinguistic feedback into content-based business English writing classes and that metalinguistic feedback had greater and more endurable effects than recasts on promoting the correct use of the target verb tenses in written production. It can be concluded that oral corrective feedback, metalinguistic feedback in particular, can be used in the business English writing classroom to help students gain greater control over already partially acquired forms and therefore improve their writing accuracy.

• Water Engineering Research
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• v.3 no.4
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• pp.259-267
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• 2002

South Africa has developed a policy and law that calls and provides for the equitable and sustainable use of water resources. Sustainable resource use is dependent on effective resource protection. Rivers are the most important freshwater resources in the country, and there is a focus on developing and applying methods to quantify what rivers need in terms of flow and water quality. These quantified and descriptive objectives are then related to specified levels of ecological health in a classification system. This paper provides an overview of an integrated and systematic methodology, where, fer each river, and each river reach, the natural condition and the present ecological condition are described, and a level/class of ecosystem health is selected. The class will define long term management goals. This procedure requires each ecosystem component to be quantified, starting with the abiotic template. A modified flow regime is modelled for each ecosystem health class, and the resultant fluvial geomorphology and hydraulic habitats are described. Then the water chemistry is described, and the water quality changes that are likely to occur as a consequence of altered flows are predicted. Finally, the responses to the stress imposed on the biota (fish, invertebrates and vegetation) by modified flow and water quality are predicted. All of the predicted responses are translated into descriptive and/or quantitative management objectives. The paper concludes with the recognition of active method development, and the enormous challenge of applying the methods, implementing the law, and achieving river protection and sustainable resource-use.

• Journal of The Korea Institute of Healthcare Architecture
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• v.15 no.2
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• pp.51-58
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• 2009

These days the trend of special education is changing from special school-based education to special class room based education, and from separated education to integrated education. In accordance with this change, special classes should be planned for multi purposes so that the class room can be used for the place of teaching and learning, guidance, job education. This research surveyed the special teachers working for 937 schools which have special classes(elementary 631, middle 217 high school 89). The result of this survey shows the different responses according to the level of the schools. For education activities, elementary and middle schools put emphasis on curriculum rather than guidance. High education, elementary school should have the places for teaching and learning, student management, play ground. Middle schools give priority to the places for individual learning, computer and practical training. High schools value the places for job education and practical training above for learning.

• Cross-Cultural Studies
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• v.20
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• pp.67-111
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• 2010

This paper examined the role of intermediate texts in the writing process in the context of an EFL composition class. From the tradition of teacher research, this study examined how the Korean college students in different proficiency groups created intermediate texts and used them while composing their own writing. The students produced various types of intermediate texts during the compositing process, which could serve as a basis of their writing. However, the patterns of using these intermediate texts differed widely across the proficiency groups. A writing cycle for the low proficiency group, or "surface reading-few intermediate texts-writing," indicates that less proficient students tended to engage in reading in separation of writing practices and thus produced few intermediate texts through their literacy practices. On the other hand, the students in the higher proficiency groups revealed the more integrated pattern (i.e., purpose reading/intermediate texts/writing), indicating that they often engaged in reading with specific writing purposes, practiced reading in connection to other writing practices, and elaborated written intermediate texts produced. This study argues that, to shift our student writers to a higher level category, we as teachers need to help them engage in reading and writing practices in the way they produce and use intermediate texts appropriate to their specific writing purposes.

• (The)Korea Educational Review
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• v.15 no.1
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• pp.107-132
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• 2009

What is good instruction? The term "instruction" means the essential activity of school education, a precondition for good school, and the starting point of reforming school education. The purpose of this study is to investigate the meaning of "good instruction" by examining the difference of perception between in-service teachers and pre-service teachers who encompass the viewpoint of both teacher and student using open-ended questionnaires asking the type of instruction that they have to avoid and the undesirable instruction. This study was carried out with 150 teachers who were working in the schools and 160 students who were in college of education to be teacher in the future. Collected data was analyzed using the QSR Nvivo qualitative program. The findings of this study indicates the followings: First, the most undesirable class cited by in-service teachers was the class that applies uniform instructional strategy, followed by class based on directions instruction, unsystematic class, class characterized by lack of teaching competency, class that emphasizes test scores and competition, class that are not interactive enough, class that does not consider the level of students, class in which students are not respected, class that have poor educational environment, and the class in which little support is provided. Second, the most undesirable class cited by pre-service teachers was the class that applies uniform instructional strategy, followed by unsystematic class, class characterized by lack of teaching competency, class based on directions instruction, class in which students are not respected, class that emphasizes test scores and competition, class that does not consider the level of students, class that are not interactive enough, class that have poor educational environment, and the class in which little support is provided. Third, this study examined the difference of perception between in-service teachers and pre-service teachers toward the undesirable class that they have to avoid. In terms of the integrated rank that is common among in-service teachers and pre-service teachers, the most undesirable class that they have to avoid was the class that applies uniform instructional strategy, unsystematic class, class based on directions instruction, and class characterized by lack of teaching competency. The findings of this study may be used as a basis for in-service teachers to reflect on their professionalism of instruction that they provide and examine the attitude of students toward instruction, while providing a practical guideline for pre-service teachers to design and ensure systematic instruction in the future.