• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 2000년도 춘계공동학술대회 논문집
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• pp.5-8
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• 2000

Vehicle travel time (empty travel time pius loaded travel time) is a key parameter for designing AGV-based material handling systems. Especially, the determination of empty vehicle travel time is difficult because of the stochastic nature of the empty vehicle locations. This paper presents a method to estimate vehicle travel times for AGV-based material transport systems. The model considers probabilistic aspects for the travel time and vehicle location under random vehicle selection rule and nearest vehicle selection rule. The estimation of empty travel time is of major effort. Simulation experiments are used to verify the proposed travel time model, and the simulation results show that the presented model provides reasonable travel time estimations.

• 제어로봇시스템학회논문지
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• 제18권4호
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• pp.302-307
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• 2012

Real-time systems perform periodic tasks and real-time aperiodic tasks such as alarm processing. Especially the periodic tasks included in control systems such as robots have precedence relationships among them. This paper proposes a new scheduling algorithm based on topological sort and residual time. The precedence relationships among periodic tasks are translated to the priorities of the tasks using topological sort algorithm. During the execution of the system the proposed scheduling algorithm decides on whether or not a newly arrived real-time aperiodic task is accepted based on residual time whenever the aperiodic task such as alarm is arrived. The proposed algorithm is validated using examples.

• 대한전기학회논문지:시스템및제어부문D
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• 제51권5호
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• pp.190-196
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• 2002

In this paper, the response characteristics of CAN-based feedback control system are analyzed when message time delays through the network are considered. The message time delays are composed of computation time delay and communication time delay. The application layer of CAN communication is modeled mathematically to analyze two time delays, and the communication time delay is redefined under several assumption conditions. The CAN-based feedback control system is proposed as a target system that is the machining system with the three axes. The response characteristics of time delays in the proposed system are analyzed through computer simulations, and can be improved by the compensation using the PID tuning method to satisfy the design specifications of the system.

• 한국전기전자재료학회논문지
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• 제15권11호
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• pp.946-952
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• 2002

The electrical and dielectric characteristics of ZPCCY-based varistor ceramics were investigated in the sintering time range of 1∼3 h. Increasing sintering time deteriorated the nonlinearity, in which nonlinear exponent is decreased from 51.2 to 23.8 and leakage current is increased from 1.3 to 5.6 $\mu$A. As sintering time increases, the donor concentration was decreased in the range of (1.25∼l.73)$\times$10$\^$18/cm$\^$-3/ and the density of interface states is (3.64∼94.19)$\times$10$\^$12/cm$\^$-2/ with increasing sintering time. The increase in sintering time caused tan $\delta$ to increase in the range of 0.043 to 0.062 and relaxation time to increase in the range of 1.55 to 2.23 ㎲.

• Communications for Statistical Applications and Methods
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• 제17권3호
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• pp.377-390
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• 2010

In the case of time-series analysis, it is often more convenient to rely on the frequency domain than the time domain. Spectral density is the core of the frequency-domain analysis that describes autocorrelation structures in a time-series process. Possible ways to estimate spectral density are to compute a periodogram or to average the periodogram over some frequencies with (un)equal weights. This can be an attractive tool to measure the similarity between time-series processes. We employ the metrics based on a smoothed periodogram proposed by Park and Kim (2008) for the classification of different classes of time-series processes. We consider several lag windows with unequal weights instead of a modified Daniel's window used in Park and Kim (2008). We evaluate the performance under various simulation scenarios. Simulation results reveal that the metrics used in this study split the time series into the preassigned clusters better than do the raw-periodogram based ones proposed by Caiado et al. 2006. Our metrics are applied to an economic time-series dataset.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2001년도 The Seoul International Simulation Conference
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• pp.484-484
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• 2001

The sophistication of current software applications results in the increasing cost fur software development time. The component-based software development framework is proposed to overcome the difficulty and time-consuming requirements by modularity and reusability. As is the general software case, a component-based simulation framework encourages the reusability of the real system model based on the modularity of the applied simulation methodology. This paper presents a component-based simulation environment that is based on the DEVS/COM run-time infrastructure. The DEVS (Discrete Event System Specification) formalism provides a formal modeling and simulation framework for the generic dynamic systems [1] and Microsoft's COM (Component Object Model) is one of the strongest competitor fur the component standard. The reusability by the DEVS/COM simulation environment saves model development time remarkably and component technology make simulator itself to be a subparts of real application.

• Journal of Information Processing Systems
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• 제15권6호
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• pp.1335-1349
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• 2019

Crowdsensing technologies can improve the efficiency of smart parking system in comparison with present sensor based smart parking system because of low install price and no restriction caused by sensor installation. A lot of sensing data is necessary to predict parking lot saturation in real-time. However in real world, it is hard to reach the required number of sensing data. In this paper, we model a saturation predication combining a time-based prediction model and a sensing data-based prediction model. The time-based model predicts saturation in aspects of parking lot location and time. The sensing data-based model predicts the degree of saturation of the parking lot with high accuracy based on the degree of saturation predicted from the first model, the saturation information in the sensing data, and the number of parking spaces in the sensing data. We perform prediction model learning with real sensing data gathered from a specific parking lot. We also evaluate the performance of the predictive model and show its efficiency and feasibility.

• 아동학회지
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• 제28권5호
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• pp.161-174
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• 2007

To analyze the effect of reminder type on the development of time-based prospective memory of children, 270(90 each 5-, 7-, and 9-year old) participants were randomly divided by age group into three subgroups : self-cued reminder, other-cued reminder, and control groups. Results showed that the performance of time-based prospective memory significantly increased with age, and the presentation of reminders was effective for improving the performance of time-based prospective memory. For younger children the presentation of other-cued reminder was more effective than self-cued reminder, but for the older children, presentation of self-cued reminder was more effective than other-cued reminder.

• 가정과삶의질연구
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• 제19권2호
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• pp.83-96
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• 2001

This study examined housework time management strategies between married female home-based workers and on-site workers, and found out the factors affecting the housework time management strategies. The data were collected from 165 married female home-based workers, and 292 married female on-site workers in Pusan and Kyungnam province, by self-administered questionnaire. Frequency distributions, Cronbachs alpha, t-tests, Pearsons correlations, and multiple regression analyses were conducted by SPSS/PC+. The major findings of this study were kas follows: 1) Married female home-based workers more used obtaining additional help and personal time reallocation than married female on-site workers. 2) For married female home-based workers, educational attainment and occupation were significant factors affecting housework time management strategies, and for married female on-site workers, employment hours per week and existence of elders/disability within the family were important variables.

• 한국정보과학회논문지:소프트웨어및응용
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• 제26권1호
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• pp.167-167
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• 1999

The majority of text categorization systems use the term-based classification method. However, because of too many terms, this method is not effective to classify the documents in areal-time environment. This paper presents a real-time concept-based text categorization system,which classifies texts using thesaurus. The system consists of a Korean morphological analyzer, athesaurus tool, and a probability-vector similarity measurer. The thesaurus tool acquires the meaningsof input terms and represents the text with not the term-vector but the concept-vector. Because theconcept-vector consists of semantic units with the small size, it makes the system enable to analyzethe text with real-time. As representing the meanings of the text, the vector supports theconcept-based classification. The probability-vector similarity measurer decides the subject of the textby calculating the vector similarity between the input text and each subject. In the experimentalresults, we show that the proposed system can effectively analyze texts with real-time and do aconcept-based classification. Moreover, the experiment informs that we must expand the thesaurustool for the better system.