• Korean Chemical Engineering Research
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• 제46권2호
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• pp.258-273
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• 2008

최근 고유가 시대를 맞이하여 에너지 다소비 공정인 건조 공정의 에너지 효율을 향상시키기 위한 방법으로 과열증기를 이용한 건조방식이 많은 관심의 대상이 되고 있다. 이 기술은 과열증기를 건조매체로 사용하여 피건조물을 건조하는 방식으로써 고온의 증발 증기를 재활용함으로써 에너지를 절약할 수 있고 건조된 제품의 품질이 향상되며 환경오염 물질의 배출을 최소화 할 수 있는 등의 장점이 있다. 본고에서는 과열증기를 이용한 건조기술의 원리와 관련 연구들을 소개한 후 건조기 형태에 따른 과열증기의 이용 사례 및 산업적 응용분야에 대하여 중점적으로 소개하고자 한다.

• 한국통신학회논문지
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• 제32권11A호
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• pp.1138-1145
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• 2007

In wireless communications, chaotic communications have been a field of interest due to its low complexity in hardware implementation and low power consumption in chaotic signal generation. Among the modulation schemes using the chaotic signal, Differential Chaos Shift Keying (DCSK) is a robust non coherent technique. As in the conventional communication systems, chaos-based systems are required to provide reasonable bit error performance in the presence of a narrow-band signal coming from any other systems. The frequency band of this foreign narrow band signal may lie within the bandwidth of the chaos-based systems. This situation may occur when chaotic signal transmission is done in the presence of other conventional communication system. This paper has evaluated the performance of the non coherent differential chaos shift keying (DCSK) system under the presence of conventional non-chaotic transmit reference system. Both systems are assumed to have same data rates. The mathematical expressions for the bit error rate (BER) are derived with computer simulations to verify the analytical results.

• 소음진동
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• 제10권4호
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• pp.610-614
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• 2000

Cellular Automata(CA)s are used as a simple mathematical model to investigate self-organization in statistical mechanics, which are originally introduced by von Neumann and S. Ulam at the end of the 1940s. CAs provide a framework for a large class of discrete models with homogeneous interactions, which are characterized by the following fundamental properties: 1) CAs are dynamical systems in which space and time are discrete. 2) The systems consist of a regular grid of cells. 3) Each cell is characterized by a state taken from a finite set of states and updated synchronously in discrete time steps according to a local, identical interaction rule. 4) The state of a cell is determined by the previous states of a surrounding neighborhood of cells. A cellular automaton has been attracted wide interest in modeling physical phenomena, which are described generally, partial differential equations such as diffusion and wave propagation. This paper describes one and two-dimensional analysis of wave propagation phenomena modeled by CA, where the local interaction rules were derived referring to the Lattice Gas Model reported by Chen et al., and also including finite difference scheme. Modeling processes by using CA are discussed and the simulation results of wave propagation with one wave source are compared with that by finite difference method.

• 상하수도학회지
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• 제22권4호
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• pp.437-444
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• 2008

Many other countries have investigated the new backwash water treatment process to save the existing water resource. There are various methods for reusing backwash water, but the membrane system has received the most interest for its efficiency. The objective of this study was to certify the application of membrane filtration system for the backwash water treatment. The experiment equipment was composed of Lab scale tubular membrane filtration system. Generally, cross-flow operation mode is used in the tubular membrane system but cross-flow operation mode demands high electric cost mainly for the pump energy. So to cut off electric cost, dead-end operation mode was used in this experiment. Filtration and bleed operation cycle was used in this membrane system. Backwash water was concentrated during the filtration process and when backwash water reached our target suspended solid concentration, it was discharged from this system. For efficient operation of filtration and bleed, mathematical matrix was drawn up and with this matrix we could simulate various sets of filtration and bleed time.

• 한국학교수학회논문집
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• 제8권4호
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• pp.459-480
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• 2005

이 연구의 목적은 수학영재아들의 행동 특성을 이해하는데 있다. 이를 위해, 대학 부설 영재교육원 수학분야에서 교육받고 있는 네 명의 수학영재아들을 관찰하여 관련 자료를 수집하였다. 수집된 자료를 분석하여, 우리는 다음을 확인하였다: 첫째, 수학영재아들은 자신의 수학적 재능에 자부심을 느끼면서도 스스로 영재성을 인정하려 하지 않는다. 둘째, 수학영재아들은 다양한 분야에 흥미를 갖는다. 특히, 그들은 독서량이 매우 많다. 셋째, 그들은 외재적 요인보다는 스스로 동기부여가 되며 고도의 도덕적 판단력을 지닌다.

• 한국학교수학회논문집
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• 제2권1호
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• pp.167-179
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• 1999

The aim of this study is to improve the basic learning ability of those who make poor progress in mathematics and to keep positive and active learning attitudes in class afterward by using problems whith both make them advance their basic learning ability and supplement lack of previous learning in class or after school. supplementary problems were developed by focusing the ability of basic calculation, the comprehension of concepts, principles, and rules by analyzing necessary contents precisely each domain after itemizing learning contents each unit. the results of the study are this: 1) The students who solved the problems, that were developed to improve the basic learning ability and to supplement the earlier learning during their classes or giving homework, made significant progress in their scholastic achievement; more than those who were not involved. 2) Meaningful changes were demonstrated in the motivation for achievement among the domains of learning attitudes before and after the experiment but, not in their interest, the consciousness of purpose, attention, voluntary and efficient learning as shown in their learning habits. In this study, therefore, the problems which were developed to improve the basic learning ability and to supplement the earlier learning by focusing on the competence for basic calculation, and the comprehension of concepts, principles and rules were effective positively only in the area of motivation for achievement. there were no meaningful differences in the other domains.

• 한국정보과학회논문지:소프트웨어및응용
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• 제26권10호
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• pp.1167-1167
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• 1999

Although spatial databases support an efficient spatial management on objects in the real world, they have a characteristic that process only spatial information valid at current time, So in case of change in the spatial domain, it is very hard to support an efficient historical management for time-varying spatial information because they delete an old value and then replace with new value that is valid at current time. To solve these problems, there are rapidly increasing of interest for spatiotemporal databases, which serve historical functions for spatial information as well as spatial management functions for an object. However most of them presented in an abstract time-varying spatial phenomenon, but have not presented a concrete policy in spatiotemporal databases. In this paper, we propose a spatiotemporal data model that supports bitemporal time concepts in three dimensional architecture. In the proposed model, not only data types and their operation for object of spatiotemporal databases have been classified, but also mathematical expressions using formal semantics for them have been given. Then, the data structures and their operations based on relational database model as well as object-oriented database model are presented.

• Smart Structures and Systems
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• 제2권3호
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• pp.209-224
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• 2006

The use of smart dampers to optimally control the response of structures is on the increase. To maximize the potential use of such damper systems, their accurate modeling and assessment of their performance is of vital interest. In this study, the performance of a controllable fluid dashpot damper, in terms of damper forces, damper dynamic range and damping force hysteretic loops, respectively, is studied mathematically. The study employs a damper Bingham-Maxwell (BingMax) model whose mathematical formulation is developed using a Fourier series technique. The technique treats this one-dimensional Navier-Stokes's momentum equation as a linear superposition of initial-boundary value problems (IBVPs): boundary conditions, viscous term, constant Direct Current (DC) induced fluid plug and fluid inertial term. To hold the formulation applicable, the DC current level to the damper is supplied as discrete constants. The formulation and subsequent simulation are validated with experimental results of a commercially available magneto rheological (MR) dashpot damper (Lord model No's RD-1005-3) subjected to a sinusoidal stroke motion using a 'SCHENK' material testing machine in the Materials Laboratory at the University of Technology, Sydney.

• 수산해양교육연구
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• 제25권1호
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• pp.233-245
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• 2013

The purpose of this study is to analyse the effects on the academic achievement and learning motive in mathematics class by use of Cornell-note method at an elementary school. Thus, Cornell-mathematic note is designed for the experiment in order to recognize the effects how the Cornell-note influences students' mathematics academic achievement and learning motive. This experiment was carried out for 13 weeks and the target was 28 students. The group was consisted of 6rd grade students in elementary school located in Busan. To see the effects of Cornell-note method after experiment, post-test was carried out about mathematics academic achievement and learning motive. The results of this study are as follows: There was meaningful difference before and after test about mathematics academic achievement and learning motive. The academic achievement and learning motive in mathematics were improved after Cornell-note applied. Improvement of learning motive caused progress of academic achievement in mathematics class. The Cornell-note way is not appropriate, however, to reinforce mathematical communication ability and to attract students' interest. Therefore, systematic symbol is necessary and consider about adoption of story-telling way.

• 한국비블리아학회지
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• 제4권1호
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• pp.23-48
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• 1980

Libraries are social apparatuses made by social needs and functions, each class of services and technology in them were changed and developed variously adapting to chronological conditions. There is reaching the interest about development in the information system to deal with it's all materials effectively, but most of libraries are interfacing from the limit of materials and manpower. Some obstacle factors restrained in the attainment of purposes and is made Sufficiently services by librarians through the information networks for libraries, they devise the utilization of materials widely in libraries and information centers. As the pre-condition of library networks, the mathematical model of organization and it's formular, 29 universities and 7 public libraries in seoul are to make the non-directed and the directed networks, and then the former has 5 groups, the latter has 1 group by the switching center. I studied for the switching centers from 6 groups experimentally. Organization, finances, cataloging and Situation that are some obstacle factors of the information networks for libraries were studied the alternatives of them. When we can have supports of the nation actively for the making networks in geographical and various libraries and get grants of it, many agencies and industries, we can achieve the purpose by social apparatuses in the information society.