• 전기의세계
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• v.15 no.5
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• pp.6-12
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• 1966

As a power system gets complicated and the number of regulating points increases, the voltage reactive power control tends to be more complex and more difficult. In the past, we took only the voltage regulation into account for this voltage control problem. pay attention not only to the voltage regulation but also to the rational system operation which minimizes transmission losses. Considering the rehuirements mentioned above we aim developing a method of coordination of these regulating equipments and also present some preliminary discussions aboutcomputer control of power systems which is now frequently available with the progress of digital computer technique.

• Fire Science and Engineering
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• v.31 no.1
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• pp.81-88
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• 2017

This study analyzed chemical accidents each year according to the status, type of accident, accident place, business size, and chemical substance. The results of the chemical accident investigation were 16 cases in 2013, 27 cases in 2014, 46 cases in 2015, and 23 cases in 2016. According to the type of chemical accident, number of accidents, and casualty accidents, leakage was found to be the major cause. As a result of accidents and casualties caused by chemical accidents, workplaces had the highest numbers in all survey items. An examination of the top 10 accident materials revealed 9 substances to be hazardous chemicals. These materials were accident preparedness substances, and toxic substances.

• Journal of Communications and Networks
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• v.7 no.3
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• pp.313-324
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• 2005

The success of the IEEE 802.11 standard has prompted research into efficiency of the different medium access methods and their support for different traffic types. A modified version of the point coordination function (PCF) called modified PCF has been introduced as a way to improve the efficiency over the standard method. It has been shown through a simulation study and a mathematical analysis that channel utilization can be much improved compared to the standard, in case there is no so-called hidden station problem. However, under the hidden station problem, the efficiency of the modified PCF would obviously decrease. In this paper, some enhancements of the modified PCF are introduced. Firstly, we propose a retransmission process to allow frames involved in collisions to be retransmitted. Then, we propose a collision resolution mechanism to reduce the frame collision probability due to the hidden station problem. In addition, we propose a priority scheme to support prioritization for different traffic types such as interactive voice and video, and real-time data traffic in the modified PCF. To prevent the starvation of one low priority traffic, minimum transmission period is also guaranteed to each traffic type via an admission control algorithm. We study the performance of the modified PCF under the hidden station problem and the performance of the modified PCF with priority scheme through simulations. To illustrate the efficiency of the priority scheme, we therefore compare its simulation results with those of some standardized protocols: The distributed coordination function (DCF), the enhanced distributed channel access (EDCA), the PCF, and our previously proposed protocol: The modified PCF without priority scheme. The simulation results show that the increment of delay in the network due to the hidden station problem can be reduced using the proposed collision resolution mechanism. In addition, in a given scenario the modified PCF with priority scheme can provide better quality of service (QoS) support to different traffic types and also support a higher number of data stations than the previous proposals.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.6
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• pp.9-17
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• 2014

Heterogeneous network (HetNet) is a network consisting of macrocells overlaid with small cells. In HetNet, the interference from macrocell to small cell users is a major cause of performance degradation of small cell users and enhanced inter-cell interference coordination (eICIC) is needed to mitigate the interference. Previous works on eICIC gives limited performance gain because these works focus on maximizing long-term throughput and rarely consider varying channel conditions over frames. This paper proposes a new algorithm which dynamically coordinates interference and schedules users on each frame to maximize the total utility of the network with lower computational complexity than exhaustive search. Simulation results show that the proposed algorithm achieves higher total throughput than the throughput with the conventional algorithm, and has higher fairness index than the conventional algorithm when there large number of users.

• Education of Primary School Mathematics
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• v.23 no.2
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• pp.87-116
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• 2020

The purpose of this study is to explore how units-coordination ability is related to understanding fraction concepts. For this purpose, a teaching experiment was conducted with one fourth grade student, Eunseo for four months(2019.3. ~ 2019.6.). We analyzed in details how Eunseo's units-coordinating operations related to her understanding of fraction changed during the teaching experiment. At an early stage, Eunseo with a partitive fraction scheme recognized fractions as another kind of natural numbers by manipulating fractions within a two-levels-of-units structure. As she simultaneously recognized proper fraction and a referent whole unit as a multiple of the unit fraction, she became to distinguish fractions from natural numbers in manipulating proper fractions. Eunseo with a reversible partitive fraction scheme constructed a natural number greater than 1, as having an interiorized three-levels-of-units structure and established an improper fraction with three levels of units in activity. Based on the results of this study, conclusions and pedagogical implications were presented.

• Journal of Korea Trade
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• v.23 no.5
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• pp.118-128
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• 2019

Purpose - This paper examines the international R&D contest in which the extent of intellectual property right (IPR) affects both the size of prize for the winning firm and the extent of positive spillover through cost of firms. Recognizing the possibility of incomplete protection of IPR, the present paper analyzes the effect of changes in the extent of IPR on payoffs to firms and social welfare. Design/methodology - This paper examines coordination of IPRs by countries in economic integration. The paper then develops a general model of international R&D contest with incomplete protection of IPR. An increase in the extent of IPR augments the share of the prize the winning firm can appropriate, while decreasing the positive cost externality. To derive sharper results, the paper considers the cases of linear and fixed spillovers. Findings - Under plausible assumptions, an increase in the IPR augments the payoff to each firm and the aggregate payoffs as well. The paper also shows that the number of firms participating in the R&D contest can be endogenously determined in the two-stage R&D contest. The higher the extent of cost spillover, and the larger the effective prize, the more firms participate in the international R&D contest. Originality/value - Existing studies assume that firms winning the R&D contest enjoy perfect IPR to the output of their R&D activities. This is a very restrictive assumption in that other firms can copy the new products or processes. By allowing for the incompleteness of the IPR, the present paper develops a more realistic model of R&D contest. The novelty of the present paper is to allow for the possibility that the higher extent of IPR increases the prize and decreases positive cost externality at the same time. The findings of the present paper can serve as a basis for government policy toward R&D activities of firms and protection of IPRs.

• The Mathematical Education
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• v.61 no.3
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• pp.441-456
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• 2022

The purpose of the current study is to report a part of our larger project whose focus is to understand a relationship between students' units coordination and K-12 school mathematics. In particular, in this paper we report how students who exhibit distinct levels of units coordinations used their knowledge of proportion to solve quadratic function problems of the form y = ax². To this end, three 7th grade students all of whom assimiliated whole number problem situations with three levels of units but showed different levels for fraction problems were chosen. We carried out clinical interviews not only to understand their ability to coordinate units but to understand their problem solving process of proportion and the quadratic function problems. The analysis suggest that their abilities to coordinate units influenced their ways to solving proportion problems, and in turn influenced their ways to solve the specific form of quadratic functions. We have finalized our study by discussing how students' ability to construct and coordinate units, their proportion knowledge, and their knowledge associated with expressing the specific type of quadractic functions could be related.

• Journal of the Korean Society of Costume
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• v.55 no.7 s.98
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• pp.76-88
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• 2005

The aim of this study is to define the concept of the matchless, and its social and cultural origins. I shall also define the different types of Matchless style, the respective characteristics of each style, and the distinguishing features of this style in domestic street fashion. In order to do this, 1 have referred to several published studies and a number of Web-sites of Korean fashion information companies for my research. The results of this study are the following; 1. The concept of matchless is a positive way of self-expression by coordination, created by consumers who attach great importance to their image and to developing their individual style. Also, this concept constitutes a new approach to code which reanalyzes existing styles with a new sensitivity. 2. The social & cultural origins of matchless are the expansion of fear of war and terror, and economic depression, the extension of the 5-day workweek, interest in 'Well-being', and the phenomena of cultural diversity. 3. The types of Matchless are Style Matchless, Theme Matchless, Texture Matchless, Season Matchless, and Complex-Layered Matchless. 4. The distinguishing features of Matchless in street fashion are the distinction of formal & Casual wear's Matchless, the creation of a new Look in Sports & Casual wear's Matchless, the development of a new coordinated, layered look, the immense popularity of Denim, the new fashionable versions of Military style, and the renaissance of the Romantic Feminine Look.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.751-756
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• 2001

Permanent-Form is one of system forms for reducing human labor, work costs, oscillation, noise, construction wastes and so on. Permanent-Form is made from precast method in facilities. and carried in construction site to assemble with no demolding. The biggest expense to produce Permanent-Form is about manufacturing mold. To satisfy various size of building member, the same number of manufacturing mold is needed. In this paper, studied about manufacturing mold module for acquiring economic merit and construction member safety. Permanent-Form is member stress and structural analyzed if temporary equipment were used. The result of this study is below. (1) Column sizes of Permanent-Form are 47 kinds of prototype that based on Modular coordination's basic module. 4 pieces or 6 pieces are composed basically. (2) For beam size modular coordination, standard height and width of beam are 150mm and 100mm. It brings 24 kinds of prototype. 4 pieces or 5 pieces are composed basically. (3) Structural analysis value of modular member is like this Column member shows 9.4 to 85kgf/$cm^{2}$ stress distribution and beam member shows 6.3 to 95kgf/$cm^{2}$ stress distribution. Constructing permanent form could have structural safety with use of temporary equipment

• Journal of the Korean Society of Clothing and Textiles
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• v.34 no.3
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• pp.540-552
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• 2010

This research forms preliminary data for the coordination of environmental color planning in industry through a color analysis of work clothes and the work environment. A digital camera was used to study the work environment of two major shipbuilding companies located in Geoje city and Goseong county. The picture data was analyzed as G (ground: environment) and F (figure: clothes), and analyzed hue, value, and the chroma value through a Muncell conversion 9.0.6 from the color cluster, number of pixel, and RGB value. The results are as follows: First, GY, Y color were mostly used in the shipbuilding environment and work clothes. The color value was used in a relatively wide range but very low chroma (0-3), dark grayish, grayish tone dominated both fields. Second, the use of limited colors cannot be secured for safety in attention of the shipbuilding field. Third, unclear and vogue colors lessened the optical tiredness of workers that helped in the prevention of industrial accidents. Color combination and color selection should be considered for a secure safety color coordination between work clothes and the work environment when it comes to complicated color principles.