• Journal of Information Technology Applications and Management
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• v.14 no.3
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• pp.227-236
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• 2007

Students in cyber universities can take every course because there are no physical constraints such as class rooms. On the other hand. cyber universities should take a heavy burden to schedule real-time exams in a designated time period. Any two courses a student takes must not be simultaneously allocated to a time slot in such a schedule. It is well known that the complexity of this kind of scheduling problem increases exponentially as the number of courses does. This research provides a heuristic method to make on-line real-time exam timetables with minimal exam time span. It considers the constraint of not allocating courses a student takes to simultaneous exam time and prioritizes courses by the number of students.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.27 no.1
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• pp.135-138
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• 2023

In this paper, we study real-time error in the context of monitoring a binary information source through a delay system. To derive the average real-time error, we model the delay system as a discrete time Geo/D/1/1 queueing model. Using a discrete time three-dimensional Markov chain with finite state space, we analyze the queueing model. We also perform some numerical analysis on various system parameters: state transition probabilities of binary information source; transmission times; and transmission frequencies. When the state changes of the information source are positively correlated and negatively correlated, we investigate the relationship between transmission time and transmission frequency.

• The KIPS Transactions:PartC
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• v.13C no.6 s.109
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• pp.669-676
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• 2006

In this paper, we present a new framework and stream synchronization mechanism to effectively support developing real-time multimedia streaming services by using a real-time object model named TMO (Time-triggered Message-triggered Object). The purpose of the framework is twofold. Firstly, the framework helps developers to design complex distributed real-time multimedia streaming services. Secondly, it supports timely streaming facilities. In order to achieve these goals, our framework is consist of Multimedia Streaming TMO, MMStreaming TMO Support Library and TMO Support Middleware. The time-triggered spontaneous feature of the MMStream TMO and a global-time based synchronization scheme is used as a regulator against the irregular deliveries and processing of media units caused by QoS non-guaranteed systems and communication channels. In conclusion, timely service capability of our framework is expected to contributed to overall enhancement of the real-time multimedia streaming.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.361-362
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• 2008

• Journal of Power System Engineering
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• v.13 no.2
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• pp.71-82
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• 2009

This paper presents a real-time haptic rendering method for a realistic force feedback in a remote environment with varying communication time-delay. The remote environment is assumed as a virtual environment based on a computer graphics, for example, on-line shopping mall, internet game and cyber-education. The properties of a virtual object such as stiffness and viscosity are assumed to be unknown because they are changed according to the contact position and/or a penetrated depth into the object. The DARMAX model based output estimator is proposed to trace the correct impedance of the virtual object in real-time. The output estimator is developed on the input-output relationship. It can trace the varying impedance in real-time by virtue of P-matrix resetting algorithm. And the estimator can trace the correct impedance by using a white noise that prevents the biased input-output information. Realistic output forces are generated in real-time, by using the inputs and the estimated impedance, even though the communication time delay and the impedance of the virtual object are unknown and changed. The generated forces trace the analytical forces computed from the virtual model of the remote environment. Performance is demonstrated by experiments with a 1-dof haptic device and a spring-damper-based virtual model.

• Journal of Korea Multimedia Society
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• v.21 no.2
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• pp.232-241
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• 2018

Operational Transformation (OT) algorithms for real-time collaborative editing systems are becoming increasingly important due to the increased demand for collaborative data processing. The operational transformation algorithm is a technique for real-time concurrency control and consistency maintenance with non-locking technique, and many studies have been conducted to overcome three issues of convergence, causality-prevention, and intention-prevention. However, previous work has the disadvantage of wasting memory by storing all operations that occurred during an edit operation in the history buffer to solve this problem. Therefore, we propose a memory-saving real-time collaborative editing system that maintains a constant memory space and concurrency control through a method of applying the valid-time to each user-generated operation in order to reduce memory waste. This system prevents long-term memory occupation of client-generated operations, thus it reduces the space and time complexity even with low-rate of collaboration work, so that the performance degradation avoids.

• Journal of Communications and Networks
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• v.15 no.1
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• pp.87-101
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• 2013

In industrial applications, sensor networks have to satisfy specified time requirements of exchanged messages. IEEE 802.15.4 defines the communication protocol of the physical and medium access control layers for wireless sensor networks, which support real-time transmission through guaranteed time slots (GTSs). In order to improve the performance of IEEE 802.15.4 in industrial applications, this paper proposes a new traffic scheduling algorithm for GTS. This algorithm concentrates on time-critical industrial periodic messages and determines the values of network and node parameters for GTS. It guarantees real-time requirements of periodic messages for industrial automation systems up to the order of tens to hundreds of milliseconds depending on the traffic condition of the network system. A series of simulation results are obtained to examine the validity of the scheduling algorithm proposed in this study. The simulation results show that this scheduling algorithm not only guarantees real-time requirements for periodic message but also improves the scalability, bandwidth utilization, and energy efficiency of the network with a slight modification of the existing IEEE 802.15.4 protocol.

• ETRI Journal
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• v.18 no.2
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• pp.61-74
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• 1996

We propose two new rate control schemes to improve MPEG-2 rate control in view of visual quality when scene changes happen. Two proposed schemes are characterized by real-time and non real-time improvement to reduce the impact of scene changes. We also propose a new target-bit prediction method using spatial activity of pictures and present a simple and efficient scene change detection scheme using signed difference of mean absolute difference (MAD). Computer simulation results show that the proposed real-time algorithm effectively alleviates visual quality degradation after scene changes. The proposed non real-time algorithm gives maximum 2 dB improvement in peak signal-to-noise ratio (PSNR) at a scene-changed picture, compared with MPEG-2 rate control scheme and it shows better quality than the real-time one.

• Journal of Information Technology Services
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• v.13 no.1
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• pp.209-220
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• 2014

Most of monitoring systems in logistics industry have limitations on monitoring container information in real-time. And customers only could check information gathered from certain points through web browser. That is why it is very hard to take actions in advance when emergency situation has happened. But if customers could check information such as position and status of freight in real-time through their mobile devices, they could take prompt actions. So, in this study, mobile application based on mobile devices is developed to monitor position and status information of the container in real-time. Entire devices monitoring container in aspect of logistics security are handled by workers in the field. So it is strongly required to develop monitoring system operated in mobile devices. For that reason this study aims to develop mobile application in order to monitor information related to container security and safety in real-time.

• Journal of Navigation and Port Research
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• v.35 no.9
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• pp.735-740
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• 2011

It is necessary to develop the one stop system in order to protect our marine environment rapidly from oil spill accident. The purpose of this study is to develop real time database for oil spill prediction modeling and implement real time prediction modelling with ESI and server-client GIS based user interface. The existing oil spill prediction model cannot provide one stop information system for public and government who should protect sea from oil spill accident. The development of multi user based information system permits integrated handling of real time meteorological data from external ftp. A server-client GIS based model is integrated on the basis of real time database and ESI map to provide the result of the oil spill prediction model. End users can access through the client interface and request analysis such as oil spill prediction and GIS functions on the network as their own purpose.