• Proceedings of the Korea Society for Simulation Conference
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• 2003.11a
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• pp.185-192
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• 2003

Digital Manufacturing-based production could be very effective in shipbuilding in order to save costs and time, to increase safety for workers, and to prevent bottleneck processes in advance. Digital shipbuilding system, a simulation-based production tool, is being developed to achieve such aspects in Korea. To simulate material flow in a subassembly line at a shipyard, the product, process and resources was modeled for the subassembly process which consisted of several sub-processes such as tack welding, piece alignment, tack welding, and robot welding processes. The analysis and modeling were carried out by using the UML(Unified Modeling Language), an object-oriented modeling method as well as IDEF(Integration DEFinition), a functional modeling tool. Initially, the characteristics of the shop resources were analyzed using the shipyard data, and the layout of the subassembly line was designed with the resources. The production process modeling of the subassembly lines was performed using the discrete event simulation method. Using the constructed resource and process model, the productivity and efficiency of the line were investigated. The number of workers and the variations In the resource performance such as that of a new welding robot were examined to simulate the changes in productivity. The bottleneck process floated according to the performance of the new resources. The proposed model was viewed three-dimensionally in a digital environment so that interferences among objects and space allocations for the resources could be easily investigated

• Journal of the Korea Society for Simulation
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• v.2 no.1
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• pp.46-54
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• 1993

Analytic and simulation models for prioritized token ring are presented in this paper. Its protocol is based on prioritized token ring with reservation (R-PTR). Since the protocol of the R-PTR is simple and the performance of the R-PTR is not inferior to that of the IEEE-PTR under almost all traffic load environments, we use the R-PTR as our token ring model. By using the properties of Markovian process, the expressions for average throughput and average packet transmission delay are derived. The results obtained from the analytic model are compared with that of the discrete event simulation model.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1996.04a
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• pp.631-634
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• 1996

This paper describes an intelligent user interface to define simulation models from the process and resource models. It also explains an automatic program generator of discrete event simulation model for shop floor control in a flexible manufacturing system. Especially, the paper is focused on the design and development of methodology to automate simulation modeling from the system description. Describing a shop floor control system in simulation is not an easy task since it must resolve various decision problems such as deadlock resolution, part dispatching, resource conflict resolution, etc. The program generator should be capable of constructing a complete discrete simulation models for a multi-product and multi-stage flow shop containing the above mentioned problems.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.9
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• pp.4467-4486
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• 2016

Discrete cosine transform (DCT) based JPEG standard significantly improves the coding efficiency of image compression, but it is unacceptable event in serious blocking artifacts at low bit rate and low efficiency of high-definition image. In the light of all phase digital filtering theory, this paper proposes a novel transform based on discrete sine transform (DST), which is called all phase discrete sine biorthogonal transform (APDSBT). Applying APDSBT to JPEG scheme, the blocking artifacts are reduced significantly. The reconstructed image of APDSBT-JPEG is better than that of DCT-JPEG in terms of objective quality and subjective effect. For improving the efficiency of JPEG coding, the structure of JPEG is analyzed. We analyze key factors in design and evaluation of JPEG compression on the massive parallel graphics processing units (GPUs) using the compute unified device architecture (CUDA) programming model. Experimental results show that the maximum speedup ratio of parallel algorithm of APDSBT-JPEG can reach more than 100 times with a very low version GPU. Some new parallel strategies are illustrated in this paper for improving the performance of parallel algorithm. With the optimal strategy, the efficiency can be improved over 10%.

• Proceedings of the Safety Management and Science Conference
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• 2000.05a
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• pp.339-349
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• 2000

Inchon Port is the second largest import-export port of Korea, and has the point at issue such as the excessive logistics cost because of the limits of handling capacity and the chronic demurrage. There are few research activities on the analysis and improvement of the whole port operation, because Inchon Port not only has the dual dock system and various facilities but also handles a various kind of cargo. The purpose of this paper is to develop the simulation program as a long-term strategic support tool, considering the dual dock system and the TU(Terminal Operation Company) system executed since March, 1997 in Inchon Port. The basic input parameters such as arrival intervals, cargo tons, service rates are analyzed and the probability density functions for these parameters are estimated. The main mechanism of simulation model is the discrete event-driven simulation and the next-event time advancing. The program is executed based on the knowledge base and database. From the simulation model, it is possible to estimate the demurrage status through analyzing various scenarios and to establish the long-term port strategic plan.

• Journal of The Korea Institute of Healthcare Architecture
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• v.24 no.2
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• pp.15-25
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• 2018

Purpose: The important things in space plan of a screening center are improving the spatial awareness by space systemization and minimizing the examination time for customers, and reducing the required time of screening work and maximizing the capacity for the screening center. Therefore, we tried to solve the problem of improving spatial awareness and reducing the examination time by using the pedestrian based discrete event simulation at the minimum cost. Methods: We have analyzed the drawbacks and the supplement points by comparing the floor plan at the time of opening and the current floor plan. Based on the analysis, we propose an improved plan which changes the location of the examination rooms and the number of services, and we also verify the improved plan based on simulation analyses. Results: 1) Through the analyses, we derived the drawbacks of the floor plan at the time of opening, and we realized that the current floor plan reflects the drawbacks. 2) The major reasons of the long examination time are the human traffic jam and the occurrence of queues due to unreasonable allocation of services. 3) Through the discrete event simulation analyses, it was possible to specify the place of the queues manually so as to use the given space fairly. 4) Using the discrete event simulation, it was possible to reduce the examination time and to improve the spatial awareness effectively at the minimum cost. Implications: Although the proposed simulation methodology in this paper is an analysis of the existing screening center, we expect that the proposed methodology will be used to develop a more efficient architectural design process by pre-applying the method to the course of designing a screening center and finding the suitability of the proposed method with the matched number of services.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.74-79
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• 1996

This paper describes a methodology for the development of models of discrete event system(DES). The methodology is based on transformation of continuous state space into discrete one to homomorphically represent dynamics of continuous processes in discrete events. This paper proposes a formal structure which can couple DES models within a framework. The structure employs the DEVS formalism for the DES models. The proposed formal structure has been applied to develop a DEVS model for the human cardiovascular system. For this, the cardiac cycle is partitioned into a set of phases based on events identified through VisSim simulation in the CS of the electrical analog model. VisSim is the simulation tool of visual environment for developing continuous, discrete, and hybrid system models and performing dynamic simulation. For each phase, a CS of the electrical analog model for the cardiovascular system has been simulated by VisSim 2.0. To validate this model, first develop the DEVS model, then simulate the model in the DEVSIM++ environment. It has same simulation results for the data obtained from the CS simulation using VisSim. The comparison shows that the DEVS model represents dynamics of the human heart system at each phase of cardiac cycle.

• Journal of Korea Multimedia Society
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• v.23 no.10
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• pp.1270-1285
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• 2020

As a representative concept of the fourth industrial revolution era where everything is digitized, digital twin means analyzing and optimizing a complex system using a simulation model synchronized with the system. In this paper, we propose a digital twin simulation model for the efficient operation of urban railways in Busan. Due to the geopolitical nature of Busan, where there are many mountains and narrow roads, the railways are more useful than other public transportation. However, this inversely results in a high level of congestion, which is an inconvenience to citizens and may be fatal to the spread of the virus, such as COVID19. Considering these characteristics, the proposed model analyzes the congestion level of the railways in Busan. The model is developed based on a mathematical formalism called discrete-event system specification and deduces the congestion level and the average waiting time of passengers depending on the train schedule. In addition, a new schedule to reduce the congestion level is derived through particle swarm optimization, which helps the efficient operation of the railways. Although the model is developed for the railways in Busan, it can also be used for railways in other cities where a high level of congestion is a problem.

• Journal of the Korea Society for Simulation
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• v.27 no.1
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• pp.91-99
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• 2018

Discrete event simulation environments often need to be modified because additional questions to systems may become apparent while observing the simulation results repeatedly. It leads to increasing development budget and depreciating the effectiveness of the environment. To avoid the modifications and to generate the altered results, this paper applies an Event Control Model (ECM) with control functions that modulate, delete and generate the events at the simulation time. In addition, this paper suggests an easier approach for domain-users, who do not want to program at source code level, by using ECM templates. The simulators with the ECMs can have better extensibility because it becomes more adaptable to possibly unanticipated changes. It prevents increasing development costs due to modifications or development of new models by M&S experts, and it provides a new alternative step to domain users. To support the effectiveness of this approach, this paper describes a relevant example, which is composed of an initial simulation model based on our empirical studies. It will show that there exist the uncountable benefits because the existing simulator is reused by domain users without new projects.

• Lingua Humanitatis
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• v.5
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• pp.221-264
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• 2003

This paper takes issue with the idea of language as a 'serial-time structure' as opposed to the 'real-time event' of speech, an idea entrenched in Chomskyan model of linguistic theory. The discussion centers around the leitmotif question: Is language constructed entirely from a finite set of apriori discrete symbol types, as the 'competence vs performance' dichotomy implies\ulcorner A set of linguistic patterns examined in this study, largely with regard to phonological considerations, points to the evidence to the contrary. That is, while the patterns may be said to be linguistically distinct, they are not discretely, different, i.e. not different enough to be reliably differentiated. It is demonstrated that much of current research in phonology, including the most recent Optimality Theory, is misdirected in that it falsely presupposes a discrete universal phonetic inventory. The main thrust of the present study is that there is no sharp boundary between 'competence' defined as the formal, symbolic, discrete time domain of language and human cognition on the one hand and 'performance' as the continuous, fuzzy, real-time domain of human physiology on the other.