• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.389-392
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• 2005

In the maskless photolithography based on the Digital Micromirror Device (DMD) by Texas Instruments Inc. (TI), the micromirror array works as a virtual photomask to write patterns directly onto Flat Panel Display (FPD) at high speed with low cost. However, it is neither simple to generate region-based patterns for the micromirror array nor easy to deliver sequences of patterns for the micromirror controller. Moreover, the quality of lithography yields the precise synchronization between generating sequence of patterns and irradiation rate off micromirrors. In this study, the region-based pattern generating system for maskless photolithography is devised. To verify salient features of devised functionalities, the prototype system is implemented and the system is evaluated with actual DMD based photolithography. The results show that proposed pattern generating method is proper and reliable. Moreover, the devised region-based pattern generating system is robust and precise enough to handle any possible user specified mandate and to achieve the quality of photolithography required by FPD manufacturer.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.70-73
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• 2003

Custom-tailored products are meant by the products having various sizes and shapes to meet the customer's different tastes or needs. Thus fabrication of custom-tailored products inherently involves inefficiency. To minimize this inefficiency, a new paradigm is proposed in this work. In this paradigm. different paris are grouped together according to their sizes and shapes. Then, representative shape of each group is derived and it will be used as the work-piece from which the parts in the group are machined. Once a new product is ordered, the optimal work-piece is selected through making similarity comparisons of new product and each representative shape. Then an effective NC tool-path is generated to machine only the different portions between the work-piece and the ordered product. The efficient machining conditions are also derived from this shape difference. By machining only the different portions between the work-piece and the ordered product, it saves time. Similarity comparison starts with the determination of the closest pose between two shapes in consideration. The closest pose is derived by comparing the ray distances while one shape is virtually rotated with respect to the other. Shape similarity value and overall similarity value calculated from ray distances are used for grouping. A prototype system based on the proposed methodology has been implemented and applied to the grouping and machining of the shoe lasts of various shapes and sizes.

• 한국공작기계학회논문집
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• 제16권5호
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• pp.211-217
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• 2007

A nano-imprinting stage has been widely used in various fields of nanotechnology. In this study, an analysis method of a nano-imprinting stage machine using FEM and flexible multi-body kinematics and dynamics has been presented. We have developed a virtual imprinting machine to evaluate the prototype design in the early design stage. The simulation using CAE for the imprinting machine is not only to analyze static and dynamic characteristics of the machine but also to determine design parameters of the components for the imprinting machine, such as dimensions and specifications of actuators and sensors. Structural components as the upper plate, the rotator, the shaft and the translator have been modeled with finite elements to analyze flexibility effects during the precision stage motion. In this paper flexible multi-body dynamic simulation is executed to support robust design of the precision stage mechanism. In addition, we made the 4-axis stage model to compare the dynamic behavior with that of 3-axis stage model.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권10호
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• pp.4640-4661
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• 2018

To cope with the explosive growth of Internet services, Service Function Chaining (SFC) based on Software-defined Networking (SDN) is an emerging and promising technology that has been suggested to meet this challenge. Determining the placement of Virtual Network Functions (VNFs) and routing paths that optimize the network utilization and resource consumption is a challenging problem, particularly without violating service level agreements (SLAs). This problem is called the optimal SFC placement problem and an Integer Linear Programming (ILP) formulation is provided. A greedy heuristic solution is also provided based on an improved two-step mapping algorithm. The obtained experimental results show that the proposed algorithm can automatically place VNFs at the optimal locations and find the optimal routing paths for each online request. This algorithm can increase the average request acceptance rate by about 17.6% and provide more than 20-fold reduction of the computational complexity compared to the Greedy algorithm. The feasibility of this approach is demonstrated via NetFPGA-10G prototype implementation.

• 천문학논총
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• 제19권1호
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• pp.109-119
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• 2004

As a core project of the Korean Astronomical Data Center (KADC) in Korea Astronomy Observatory (KAO), we have constructed a framework of astronomical database using MySQL and JSP. MySQL database server is a powerful open source database management system, and JSP technology provides a simplified, fast way to create dynamic web content. Combined together, MySQL and JSP enable us to develop server-independent web-based applications efficiently in a short amount of time. The MySQL tables and JSP programs embedded in our database are built/written in a way to benefit both users and managers. We plan to expand our database by supplementing additional data in the near future. Our newly constructed database is expected to be the prototype of the Korean Virtual Observatory (KVO).

• 천문학회지
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• 제40권4호
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• pp.165-169
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• 2007

The numerical simulations associated with the interaction of High Velocity Clouds (HVC) with the Magnetized Galactic Interstellar Medium (ISM) are a powerful tool to describe the evolution of the interaction of these objects in our Galaxy. In this work we present a new project referred to as Theoretical Virtual i Observatories. It is oriented toward to perform numerical simulations in real time through a Web page. This is a powerful astrophysical computational tool that consists of an intuitive graphical user interface (GUI) and a database produced by numerical calculations. In this Website the user can make use of the existing numerical simulations from the database or run a new simulation introducing initial conditions such as temperatures, densities, velocities, and magnetic field intensities for both the ISM and HVC. The prototype is programmed using Linux, Apache, MySQL, and PHP (LAMP), based on the open source philosophy. All simulations were performed with the MHD code ZEUS-3D, which solves the ideal MHD equations by finite differences on a fixed Eulerian mesh. Finally, we present typical results that can be obtained with this tool.

• 한국해양공학회지
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• 제32권4호
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• pp.222-227
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• 2018

Most underwater acoustic arrays for low frequency operation are deployed vertically, but a mid-range frequency horizontal array system is being developed by the Korea Research Institute of Ships and Ocean Engineering (KRISO). The horizontal array platform is deployed underwater and kept in place by weather vaning mooring. This is essential because it is nearly impossible to keep a submerged body at a given position in the water without any external force. Hence, the horizontal array platform can maintain the desired position in the presence of a weak tidal current. The objective of this study is to design an underwater platform that can maintain its horizontal position in a weak current. First, the authors investigated various virtual models, selected one of the models, and performed a small model test of the selected model at a basin. We calculated the external forces associated with the 2D motion, and then we conducted a large basin test followed by a circulation water channel test for the manufactured array platform. The results of the simplified 2D motion calculation essentially matched the results of the underwater test.

• Journal of Information Processing Systems
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• 제12권3호
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• pp.511-524
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• 2016

The Virtual Local Area Network (VLAN) has been used for a long time in campus and enterprise networks as the most popular network virtualization solution. Due to the benefits and advantages achieved by using VLAN, network operators and administrators have been using it for constructing their networks up until now and have even extended it to manage the networking in a cloud computing system. However, their configuration is a complex, tedious, time-consuming, and error-prone process. Since Software Defined Networking (SDN) features the centralized network management and network programmability, it is a promising solution for handling the aforementioned challenges in VLAN management. In this paper, we first introduce a new architecture for campus and enterprise networks by leveraging SDN and OpenFlow. Next, we have designed and implemented an application for easily managing and flexibly troubleshooting the VLANs in this architecture. This application supports both static VLAN and dynamic VLAN configurations. In addition, we discuss the hybrid-mode operation where the packet processing is involved by both the OpenFlow control plane and the traditional control plane. By deploying a real test-bed prototype, we illustrate how our system works and then evaluate the network latency in dynamic VLAN operation.

• 한국소음진동공학회논문집
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• 제20권11호
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• pp.995-1000
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• 2010

With the development of the auto industry, the automobile manufacturers demand to shorten development period and reduce the cost. Compared with the traditional method, applying the virtual prototype is more economical. This paper presents a method for parameters sensitivity analysis and optimizing the performance of vehicle noise and vibration. The existing design processes were repeatedly analyzed with a focus on vehicle performance to decide the design parameters of dimension, thickness, mounting type of body and chassis systems in the vehicle development period. This paper describes the prediction technique of vehicle performance using L18 orthogonal array layout, quality deviation analysis and parameter sensitivity analysis for robust design. This paper analyzed the performance correlation equation through the frequency and sensitivity database according to a design factor change. The new concept is that the performance prediction is possible without repeated activities of test and analysis. This paper described the parameter analysis applications such as bush dynamic stiffness and bush void direction of rear suspension. Design engineer could efficiently decide the design variable using parameter analysis database in early design stage. These improvements can reduce man hour and test development period as well as to achieve stable NVH performance.

• Journal of Power Electronics
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• 제16권6호
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• pp.2221-2230
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• 2016

Voltage and frequency stability issues occur in existing centralized power system due to the high penetration of renewable energy sources, which decrease grid absorptive capacity of them. The grid-connected inverter that mimics synchronous generator characteristics with inertia characteristic is beneficial to electric power system stability. This paper proposed a novel three-phase four-wire grid-connected inverter with an independent neutral line module that mimics synchronous generators. A mathematical model of the synchronous generator and operation principles of the synchronverter are introduced. The main circuit and control parameters design procedures are also provided in detail. A 10 kW prototype is built and tested for further verification. The primary frequency modulation and primary voltage regulation characteristics of the synchronous generator are emulated and automatically adjusted by the proposed circuit, which helps to supports the grid.