• Korean Journal of Computational Design and Engineering
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• v.6 no.4
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• pp.236-243
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• 2001

A key factor far realizing the internet-based virtual manufacturing system(VMS) and virtual enter-prise(VE) is how to precisely and effectively represent the machine elements and mechanics. In this paper, we present methods to represent the numerically controlled machine tools in the internet environment. The method is composed of: 1) geometrical modeling of the machine tools, 2) kinematic modeling for the movements of the machine tools, and 3) representing the developed model in the internet infrastructure. Based on the models. a web-based virtual machine tools (WVMT) is developed, and it can be accessed at hrrp://wvmt.postech.ac.kr. The WVMT can be used for various purposes: 1) web-based virtual manufacturing system, 2) web-based CAM system, and 3) CNC educational tools for the vocational school through internet.

• IE interfaces
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• v.14 no.2
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• pp.127-133
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• 2001

Virtual Manufacturing is a technology facilitating effective development and agile production of products via computer models representing physical and logical schema and the behavior of the real manufacturing systems. For the successful application of this technology, a virtual plant as a well-designed and integrated environment is essential. We propose a series of systematic approaches and effective methods for construction and operation of a virtual plant in this paper, such as a 3-D CAD modeling, cell and line simulations and databases. We developed key technologies for measuring and 3-D CAD modeling of many equipments, facilities and structures of the buildings. In order to study the benefit of virtual manufacturing, we constructed a sophisticated virtual plant model of a Korean automotive company's body shop, and conducted precise simulations of unit cell, lines and the whole plant. We could obtain the benefit of savings in time and cost in many manufacturing preparation activities in the new car development processes.

• Journal of Power Electronics
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• v.18 no.4
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• pp.1111-1126
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• 2018

In modern power systems, distributed generators (DGs) result in high stress on system frequency stability. Apart from the intermittent nature of DGs, most DGs do not contribute inertia or damping to systems. As a result, a new control method referred to as a virtual synchronous machine (VSM) has been proposed, which brought new characteristics to inverters such as synchronous machines (SM). DGs employing an energy storage system (ESS) provide inertia and damping through VSM control. Meanwhile, energy storage presents some physical constraints in the VSM implementation level. In this paper, a VSM mathematical model is built and analyzed. The dynamic responses of the output active power are presented when a step change in the frequency occurs. The influences of the inertia constant, damping factor and operating point on the ESS volume margins are investigated. In addition, physical constraints are proposed based on these analyses. The proposed physical constraints are simulated using PSCAD/EMTDC software and tested through RTDS experiment. Both simulation and RTDS test results verify the analysis.

• Proceedings of the Korea Society of Design Studies Conference
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• 2003.05a
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• pp.254-255
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• 2003

• Journal of Information Technology Applications and Management
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• v.14 no.1
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• pp.117-135
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• 2007

Globalization changes in market structures and consumer needs, as well as technology innovations force organizations to adopt new structures and collaborative networks to cope with rapidly changing environments. These Collaborative Networks are based on the Idea of virtual enterprise. A virtual enterprise(VE) is a temporary alliance of globally distributed independent enterprises that share core competencies and computer networks. This paper presents a proposal for a methodology to measure a key factor of success and risk First of all, we chose thirty experts' defines on virtual enterprise, fifteen are academic specialist and other fifteen are from industry. For this study we define twenty two factors determining VE's success and seventeen factors determining VE's risk using by Delphi method. And we built the influence model on virtual enterprise. A research model was established according to preceeding research and consensus on experts then the revised model of key factors on virtual enterprise. This survey was based on the Analytical Hierarchy Process (AHP). AHP is an approach to decision making that involves structuring multiple choice criteria into a hierarchy, the assessing the relative important of these criteria, comparing alternative for each criteria, and determining an overall ranking of the alternatives. A model was constructed as 3 level hierarchy. The hierarches are organizational, strategic, technical criteria. for success model on VE has 22 factors and 17 factors for risk model. They are selected by all 30 experts. 14 copies among 30 copies distributed to carry out on the Analytical Hierarchy Process (AHP). Consistency ratio confirm high validity and reliability of instrument and support theoretical model. The results of this study are summarized as follows. (1) This study presented success on VE influenced strategic criteria, and essential factor is Creating a value. Risk on VE influenced strategic criteria, and essential factor is Outcome/Distribution. (2) Its enable that ranking the criteria influence on VE. These are supported VE management and using guideline of VE.

• Journal of Power Electronics
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• v.19 no.5
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• pp.1224-1234
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• 2019

Hybrid rotor position estimation methods that integrate a fundamental model and high frequency (HF) signal injection are widely used for the wide speed-range sensorless control of interior permanent-magnet synchronous machines (IPMSMs). However, the direct transition of two different schemes may lead to system fluctuations or system instability since two estimated rotor positions based on two different schemes are always unequal due to the effects of parameter variations, system delays and inverter nonlinearities. In order to avoid these problems, a seamless transition strategy to define and construct a virtual q-axis inductance is proposed in this paper. With the proposed seamless transition strategy, an estimated rotor position based on a fundamental model is forced to track that based on HF signal injection before the transition by adjusting the constructed virtual q-axis inductance. Meanwhile, considering that the virtual q-axis inductance changes with rotor position estimation errors, a new observer with a two-phase phase-locked loop (TP-PLL) is developed to accurately obtain the virtual q-axis inductance online. Furthermore, IPMSM sensorless control with maximum torque per ampere (MTPA) operations can be tracked automatically by selecting the proper virtual q-axis inductance. Finally, experimental results obtained from an IPMSM demonstrate the feasibility of the proposed seamless transition strategy.

• Journal of the Korea Society of Computer and Information
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• v.27 no.12
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• pp.111-119
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• 2022

The purpose of this paper is to examine the change in perception of 3D virtual fashion before and after COVID-19 using big data analysis. The data collection period is from January 1, 2017, before the outbreak of COVID-19, to October 30, 2022, after the outbreak. Big data was collected for key words related to 3D virtual fashion extracted from social media such as Naver, Daum, Google, and YouTube using Textom. After the collected words were refined, word cloud, word frequency, connection centrality, network visualization, and CONCOR analysis were performed. As a result of extracting and analyzing 32,461 words with 3D virtual fashion as a keyword, the frequency and centrality of fashion, virtual, and technology appeared the highest, and the frequency of appearance of digital, design, clothing, utilization, and manufacturing was also high. Through this, it was found that 3D virtual fashion is being used throughout the industry along with the development of technology. In particular, the key words that stand out the most after COVID-19 are metaverse and 3D education, which are in high demand in the fashion industry.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.32 no.5
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• pp.827-835
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• 2022

In order to use online financial services, user authentication technology is necessary. Password check through keyboard typing is the most common technique. However, since it became known that key stokes on the keyboard can be intercepted easily, many Internet banking services and easy payment services have adopted the virtual keyboard. However, contrary to the expectation that the virtual keyboard will be safe, there is a risk that key strokes on the virtual keyboard can be leaked. In this paper, we analyzed the possibility of password leaking on the virtual keyboard and presented a password leaking method using mouse event hooking and screen capture in PC operating system. In addition, we inspected the possibility of password leak attacks on several famous Korea Internet banking websites and simple payment services, and as a result, we verified that the password input method through the virtual keyboard in the PC operating system is not secure.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.62-63
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• 2003

We propose an improved image encryption and the shift-tolerance method in the Fourier space using a virtual phase image. The encrypted image is obtained by the Fourier transform of the product of a phase-encoded virtual image, not an original image, and a random phase image. We demonstrate the robustness to noise, to data loss and shift of the encrypted image or the Fourier decryption key in the proposed technique.

• Journal of the Korean housing association
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• v.12 no.2
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• pp.181-190
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• 2001

The purpose of this study is to analysis web sites which relate to housing environment on Internet and to suggest guidelines which are needed in digital life. Data are in 53 web sites searched by housing environmental word such as people, living, town and so on. The web sites are analyzed by key words. The results of this study were as follow: The web sites are divided into e-housing community, e-housing management, e-housing workplace and e-housing design. These are the digital life of new type. E-housing community sitess key words are 3D virtual world, chatting, information, service, community etc. E-housing community is related to making new wired community cross time and space. E-housing management sitess key words are guard management, apartment management, building management etc. E-housing management sites provide the useful information of housing management. E-housing workplace sitess key words are virtual office. conference etc. E-housing workplace sites enable us to work in cyberspace. E-housing design sitess key words are design, interior, furniture etc. E-housing design sites provide marketing, consulting and designing in relation to the house. The web life style on cyberspace is common and makes many changes happen in house life and environment.