• IE interfaces
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• v.23 no.3
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• pp.229-238
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• 2010

Virtual metrology (VM), a critical component of semiconductor manufacturing, is an efficient way of assessing the quality of wafers not actually measured. This is done based on a model between equipment sensor data (obtained for all wafers) and the quality characteristics of wafers actually measured. This paper considers principal component regression (PCR), partial least squares regression (PLSR), kernel PCR (KPCR), and kernel PLSR (KPLSR) as VM models. For each regression model, two cases are considered. One utilizes all explanatory variables in developing a model, and the other selects significant variables using the genetic algorithm (GA). The prediction performances of 8 regression models are compared for the short- and long-term etch process data. It is found among others that the GA-KPLSR model performs best for both types of data. Especially, its prediction ability is within the requirement for the short-term data implying that it can be used to implement VM for real etch processes.

• Journal of Electrical Engineering and Technology
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• v.11 no.1
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• pp.157-166
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• 2016

In this paper, a new sag and peak voltage detector is proposed for a single-phase inverter using delta square operation. The conventional sag detector is from a single-phase digital phase-locked loop (DPLL) that is based on d-q transformations using an all-pass filter (APF). The d-q transformation is typically used in the three-phase coordinate system. The APF generates a virtual q-axis voltage component with a 90° phase delay, but this virtual phase cannot reflect a sudden change in the grid voltage at the instant the voltage sag occurs. As a result, the peak value is drastically distorted, and it settles down slowly. A modified APF generates the virtual q-axis voltage component from the difference between the current and the previous values of the d-axis voltage component in the stationary reference frame. However, the modified APF cannot detect the voltage sag and peak value when the sag occurs around the zero crossing points such as 0° and 180°, because the difference voltage is not sufficient to detect the voltage sag. The proposed algorithm detects the sag voltage through all regions including the zero crossing voltage. Moreover, the exact voltage drop can be acquired by calculating the q-axis component that is proportional to the d-axis component. To verify the feasibility of the proposed system, the conventional and proposed methods are compared using simulations and experimental results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.830-835
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• 1995

To quickly determine the effect of the substitute component on the machine's performance is very important in the defign and the manufacturing processes. And minimizing machine cost and maximizing machine quality mandata predictability of machine accuracy. In the study, in order to evaluate the effects of the component's geometric errors and dimensions on the machining accuracy of gantry-type 5-axis machining centers, a geometric error analysis and virtual manufacturing system is developed based on the mathematical model for the shape generation motion of machine tool considering the component's geometric errors and dimensions, the solid modeling techniques and so on.

• Journal of the Korea Society for Simulation
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• v.5 no.2
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• pp.13-24
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• 1996

Workflow is an ordered sequence of interdependent component data activities each of which can be executed on an integrated information system by accessing a remote information system. In our previous research [4], we proposed a distributed CIM Workflow system which consists of a workflow execution model called DAF-Net and an agent-based information systems called AIMIS. Given a component data activity, there needs an interaction protocol among agents which allocates the component data activity to a relevant information systems exist. The objective of this research is to propose and test two protocols: ARR(Asynchronous Request and Response)protocol and NCL(Negotiation with Case based Learning) protocol. To test the effectiveness of the protocols, we applied the PVM(Parallel Virtual Machine) software to simulate the distributed CIM Workflow system. PVM provides a distributed computing environment in which users can run different software processes in different computers while allowing communication among the processes.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.12
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• pp.65-73
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• 2014

In this paper, the detection scheme of the voltage variation using a two difference voltage is proposed. The conventional sag detector is from a single-phase digital phase-locked loop (DPLL) that is based on a d-q transformation using an all-pass filter (APF). The APF generates a virtual q-axis voltage component with $90^{\circ}$ phase delay but the APF cannot generate the virtual q-axis voltage depending on the phase of the grid voltage. To overcome the problem, q-axis voltage component is generated from difference between the current and previous value of d-axis voltage component in the stationary reference frame. However, the difference voltage around the zero crossing is not enough to detect the voltage sag. Therefore, the new detection scheme using the two difference voltage which can detect the sag around the zero crossing voltage is proposed.

• Journal of the Korea Society for Simulation
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• v.12 no.1
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• pp.1-10
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• 2003

Recently, various network protocols have been developed to keep step with the rapid growth of Internet users. For the education of students in the computer networks classes, there have been many attempts to allow students experiment routers setting, operations and management of networks by themselves, in addition to the classroom lectures based on textbooks. One of the attempts is to install expensive real router experiment sets in laboratories for students, and one another is using router and network simulators for virtual experiments. This paper presents the design and implementation of NetSim, a scalable, component-based simulator environment for the network experimentation. NetSim expands the existing component-based JavaSim simulation tool for the education purpose, and it allows the design and experiment of various networks and protocols. For the evaluation of NetSim, it is shown that the network design and RIP-based router setting process is possible in NetSim.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.1
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• pp.96-104
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• 2014

The all pass filter generates a virtual q-axis voltage component with $90^{\circ}$ phase delay but the virtual q-axis voltage cannot detect the voltage depending on the phase of the grid voltage. To overcome the problem, q-axis voltage component is generated from difference between the current and previous value of d-axis voltage component in the stationary reference frame. However, the difference voltage between the current and previous value around the zero crossing voltage is not enough to detect the voltage sag. Therefore, the new detection scheme which can detect the sag around the zero crossing voltage is proposed.

• International Journal of Contents
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• v.11 no.1
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• pp.21-30
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• 2015

A simulated realistic virtual environment is inhabited by autonomous cyber-humans who play the roles of agents in events. A key element, which enables this realism, is the historical context formed by time and space. A knowledge-representation scheme, composed of both spatial and temporal aspects needed by the agent to respond to dynamically changing situations, is essential for the design of a realistic virtual agent. In this work, spatial and temporal aspects of dynamic situations in the virtual environment have been formalized as a key component of our knowledge-representation scheme. This scheme provides a mathematical framework to construct realistic virtual situations that change with time, and background knowledge for agents in the simulated environment to deduce new pieces of information and plan against changing situations.

• Journal of the Korea Society for Simulation
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• v.8 no.1
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• pp.1-18
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• 1999

Current CIM systems need to correspond flexibly to the frequent change of demands of the customers and the fast changing informations about the production environment. The demands have brought forth CIM systems developed using object-oriented technology, with reusability, expansibility, and flexibility for the system components. Due to the fact that the OO-CIM system has been developed based on an incomplete data, the constructed system must be implemented to the actual surroundings to see how pertinent it is. Hence, this paper presents an OO-simulator as a means to evaluate the pertinency and the efficiency of the developed CIM system. The OO-simulator can determine the problems likely to occur when a developed CIM system is implemented to the actual site and evaluate the efficiency beforehand. Such properties will decrease the cost of CIM system development and increase the reliability of the system. This paper presents a framework for an OO-simulator composed of a virtual factory component embodying the characteristics of a virtual factory, a connector component for the interface between the CIM system and the simulator, a configuration component for modeling the constituent structure of the CIM system, and a timer component in charge of the time advance for the simulation.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.478-483
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• 2000

In this study to cope with the decreasing product's life-cycle a virtual simulator to realize the simulation environment similar to a real manufacturing line is developed. The developed simulator plays a role in reducing the product conversion time by alternating manufacturing components and work plans on the simulation as manufacturing lines change and actuating a virtual manufacturing lines change and actuating a virtual manufacturing line before a real production. The developed simulator realized a virtual manufacturing line on the simulation using various manipulators and work cells as manufacturing components. Also It can be shown that the simulator can cope with rapid change of a manufacturing line by developing a interface that a separate process is managed for each manufacturing module and a manipulator component and a work cell are changed for a user to become convenient to teach tasks of each work module. using Microsoft Visual C++ 6.0 and OpenGL of Silicon Graphics for libraries to realize 3-dimensional graphic and constructing a database system, a hybrid type of hierachical and relational model to develop a progra that has efficiency and standardization.