• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.2
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• pp.165-170
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• 2013

This paper presents the iron loss prediction of rotating electric machines taking account of the vector hysteretic properties of electrical steel sheet. The E&S vector hysteresis model is adopted to describe the vector hysteretic properties of a non-oriented electrical steel sheet, and incorporated into finite element analysis (FEA) for magnetic field analysis and iron loss prediction. A permanent magnet synchronous generator is taken as a numerical model, and the analyzed magnetic field distribution and predicted iron loss by using the proposed method is compared with those from a conventional method which employs an empirical iron loss formula with FEA based on a non-linear B-H curve. Through the comparison the effectiveness of the presented method for the iron loss prediction of the rotating machine is verified.

• Steel and Composite Structures
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• v.48 no.5
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• pp.485-498
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• 2023

The need for carbon neutrality in the world strives the construction industry to reduce the use of construction materials. Aiming to this, recycled aggregate concrete (RAC) could be used as it reduces the carbon dioxide emissions. Currently, RAC is mainly used in non-structural members of civil constructions, seldom used in structural members. To broaden its structural use, a new type of composite column, i.e., the square and rectangular RAC filled FRP tubes (CFFTs), has been concerned in this study. The investigation on their axial compressive behavior through physical test and numerical analysis demonstrated that the load-carrying capacity of such column is reduced with the increase of replacement ratio of recycled aggregate and aspect ratio of section but can be improved by the increase of FRP confining stiffness and corner radius, said capacity can be equivalent to their steel reinforced concrete counterparts. At failure, the hoop strain at corner of tube is unexpectedly smaller than that at flat side of the tube although the FRP tube ruptured at its corner first, revealing a premature failure. Besides, a design-oriented stress-strain model of concrete and an analysis-oriented finite element model are proposed to predict the load-strain response of square and rectangular CFFT columns, which facilitates the engineering use of RAC in load-carrying structural members.

• Korean Management Science Review
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• v.14 no.1
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• pp.131-149
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• 1997

Software cost estimation is an important both for buyers and sellers(developers). We reviewed domestic and foreign researches and practices on software cost estimation with function point method comprehensively, In this paper, we derived four promising alternative function point models. They are an IFPUG(International Function Point User Group)-based model(Model I), a shorthand model for client/sever software systems(Model II), a data-oricnted model for relatively large software projects(Model III), and a general- purpose function point model for non business application softwares as well as business applications(Model IV). Empirical data shows that Model I, II, and IV are very useful function point models. In particular, model II and IV look very useful models since they are concise and accurate. These models can be incorporated in a new improved guideline for software cost estimation. General opinion survey shows that Model I, II and IV are preferable. There are no significant differences in preference between buyers and sellers. The survey also shows that users think function point method is better than step(line of code)-oriented cost estimation methods in many ways including objectivity and estimation accuracy.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.10
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• pp.523-529
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• 1999

In the case of the large power transformer, the grain-oriented material is usually used. So, to obtain more accurate results, anisotropy and non-linearity of the material must be considered. The Newton-Raphson(NR) method is generally used for analyzing these non-linear properties, but it consumes so much time, especially when the number of nodes is large or the shape of the model is complex. The transmission line modeling (TLM) method is successfully adopted to the analysis of non-linear properties with FEM, but it has not been adopted to the analysis of the anisotropic material. In this paper, the formulation of the TLM method considering anisotropy is developed and the adoption to the 3-phase transformer is presented.

• Journal of Power Electronics
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• v.14 no.2
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• pp.369-382
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• 2014

A growing dynamic electrical demand has created an increasing interest in utilizing nonconventional energy sources like Photovoltaic (PV), wind power, etc. In this context, this paper focuses on the design and development of a composite power controller (CPC) in the decoupled double synchronous reference frame (DDSRF) combining the advantages of direct power control (DPC) and voltage oriented control (VOC) for a PV sourced grid connected inverter. In addition, a controller with the inherent active filter configuration is tested with nonlinear and unbalanced loads at the point of common coupling in both grid connected and autonomous modes of operation. Furthermore, the loss and reactive power compensation due to a non-fundamental component is also incorporated in the design, and the developed DDSRF model subsequently allows independent active and reactive power control. The proposed developed model of the controller is also implemented using MATLAB-Simulink-ISE and a Xilinx system generator which evaluate both the simulated and experimental setups. The simulation and experimental results confirm the validity of the developed model. Further, simulation results for the DPC are also presented and compared with the proposed CPC to further bring out the salient features of the proposed work.

• The Journal of the Korea Contents Association
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• v.14 no.2
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• pp.387-395
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• 2014

The authors reviewed research related to nursing organizational culture in order to determine the direction for future research, as well as the current status of nursing organizational culture. Research that analyzed nursing organizational culture were selected from journal articles in Korea and were reviewed. A total of 30 articles were collected. The number of studies on nursing organizational culture has shown a rapid increase since the late 1990s. Most research studies used a non-experimental design. The most frequently used organizational culture model and instrument was the competing values model defining culture pattern, which consists of relation-oriented, innovation-oriented, hierarch-oriented, and task-oriented culture. Other factors showing correlation with nursing organizational culture included job satisfaction, effectiveness, and so on. These results will be used to provide basic data for nursing leaders. In Korea, the next phase of research on organizational culture will require use of various approaches and research methods.

• Journal of Digital Convergence
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• v.16 no.2
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• pp.27-36
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• 2018

Financial IT evaluation methods have been unable to satisfy firms' requirements. There has been a growing demand for more comprehensively and non-financially measuring the IT performance. We developed a process-based approach in evaluating impacts of IT on primary activities. In this research we proposed a model that uses the corporate objective of IT and strategic fitt as the core independent variables in measuring the IT effect. Based on the data collected from the management variables of the 125 companies located in Korea, the companies were classified into the 4 different groups according to their corporate objective for IT: un-oriented, operations oriented, market oriented and dual oriented. Through the empirical analysis, we were able to demonstrate that the management of the companies showing a higher orientation level perceives a better IT investment performance, and this shows that the corporate objective for IT serves as a useful index for measuring the IT investment effect. In this research, it was also demonstrated that the strategic alignment has a positive influence on perceiving the IT investment effect.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.38 no.6
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• pp.1-17
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• 2001

Nowadays, spatiotemporal data models deal with objects which can be potentially useful for wide range applications in order to describe complex objects with spatial and/or temporal facilities. However, the information needed by each application usually varies, specially in the geographic information which depends on the kind of time oriented views, as defined in the modeling phase of the spatiotemporal geographic data design. To be able to deal with such diverse needs, geographic information systems must offer features that manipulate geometric, space-dependent(i.e, thematic), and spatial relationship positions with multiple time oriented views. This paper addresses problems of the formal definition of relationships among spatiotemporal objects and their properties on geographic information systems. The geographical data are divided in two main classes : geo-objects and geo-fields, which describe discrete and continuous representations of the spatial reality. I study semantics and syntax about the temporal changes of attributes and the relationship roles on geo-objects and non-geo-objects, This result will contribute on the design of object oriented spatiotemporal data model which is distinguishied from the recent geographic information system of the homogeneously anchored spatial objects

• Journal of Digital Convergence
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• v.17 no.10
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• pp.23-35
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• 2019

In order to cultivate talented people who have problem solving ability due to computational thinking according to the trend of the fourth industrial revolution, each university is actively promoting software education. This study suggests that understanding-oriented SW curriculum is needed for non-majors students to improve computational thinking. In order to achieve the purpose of the study, this study designed the basic education program based on the understanding of the SW with the backward design model. The SW Basic Education Program was applied to 15 weeks of instruction and conducted three surveys. The positive effects of the understanding-oriented SW basic education on the computational thinking efficacy and the computer perception were verified. In addition, it was found that the understanding-oriented computational thinking and programming education are effective when they are linked to one process. It is expected that understanding-based SW based education, which uses the backward design model, can be applied as one of the efficient ways to improve computational thinking in the education field.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4D
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• pp.467-472
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• 2009

Even if Seoul City administration improved its public transportation service, transportation model share in seoul has not been increased. Subway user is also decreasing. Therefore, policy transition into TOD(Transit Oriented Development) should be applied in oder to enhance subway modal share. This paper develops a influencing model by using variables of transportation demand and supply. In addition, it provides major influencing factors for users in subway station area and level of transportation supply based on the analysis results. The results show that: first, cluster analysis presents that traffic pattern is proved to be different according to land use characteristics(residence, non-residence); second, main transportation variables such as transferring distance, the number of bus stop, the number of short distant bus lines, and the number of bicycle are more supplied in residential area compared to non-residential areas; third, the number of lines, bus dispatching interval, operating time, and distance between subway stations are more supplied in non-residential areas than residential areas. All in all, the results will be useful for providing priority of considerations in case of decision-making on public transportation policy in subway station area.