• Journal of the Korea Society for Simulation
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• v.23 no.4
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• pp.143-150
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• 2014

Cloud computing is fast becoming the wave of the future for both home and business computing. Because of this growing acceptance, we can expect an explosion of diverse cloud service providers in the coming years. However, the cloud is not a single entity, rather it is a set of many disconnected islands of application (SaaS), infrastructure (IaaS), and different platform (PaaS) services. Cloud brokering mechanisms are essential to transform the heterogeneous cloud market into a commodity-like service. Cloud service brokers (CSBs) are the new form of business entities to help to aggregate the scattered set of cloud services and make conveniently available to their diverse users. CSBs can reserve a certain percentage of their clients' (users') demand and satisfy the remaining portion in an on-demand basis. In doing so, they need to minimize cost of both reserved and on-demand instances as well as the distance of a link between the cloud service provider (CSP) and the user. The study proposes a reservation approach with a mixed integer model to optimizes the cloud service cost and quality.

• Journal of the Korea Society for Simulation
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• v.23 no.1
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• pp.1-10
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• 2014

A cloud computing is one of a parallel and distributed computing. The cloud computing provides some service for user with virtual resources. However, a user's service request does not show a time pattern. As a result, each resource also shows a different availability at the same time. This difference affects a quality of service (QoS) and a resource selection for users. Therefore, we propose the resource availability-based multi auction model for cloud service reservation and resource brokering system. The proposed system is to select the proper resource provider based on the users' request. The proposal adopts the multi phase of the auction to transact resources. The system evaluates the available factor of each resource on the auction phase, and finally reserves the service on the adaptive queue. The proposed model shows the better performance than other existing method.

• Journal of the Korea Society for Simulation
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• v.24 no.3
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• pp.27-35
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• 2015

We analyze an M/G/1/K queueing system with queue-length dependent service and arrival rates. There are a single server and a buffer with finite capacity K including a customer in service. The customers are served by a first-come-first-service basis. We put two thresholds $L_1$ and $L_2$($${\geq_-}L_1$$ ) on the buffer. If the queue length at the service initiation epoch is less than the threshold $L_1$, the service time of customers follows $S_1$ with a mean of ${\mu}_1$ and the arrival of customers follows a Poisson process with a rate of ${\lambda}_1$. When the queue length at the service initiation epoch is equal to or greater than $L_1$ and less than $L_2$, the service time is changed to $S_2$ with a mean of $${\mu}_2{\geq_-}{\mu}_1$$. The arrival rate is still ${\lambda}_1$. Finally, if the queue length at the service initiation epoch is greater than $L_2$, the arrival rate of customers are also changed to a value of $${\lambda}_2({\leq_-}{\lambda}_1)$$ and the mean of the service times is ${\mu}_2$. By using the embedded Markov chain method, we derive queue length distribution at departure epochs. We also obtain the queue length distribution at an arbitrary time by the supplementary variable method. Finally, performance measures such as loss probability and mean waiting time are presented.

• Journal of Korean Elementary Science Education
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• v.40 no.2
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• pp.162-174
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• 2021

The purpose of this study was to investigate the types of questions raised by pre-service elementary teachers when planning a science class utilizing smart technology and the characteristics of their lesson plans. For this purpose, lesson plans and questions written by the 96 pre-service teachers were collected. The results of this study can be summarized as follows: (1) Pre-service teachers used simulation apps, information offering apps, clicker evaluation apps, astronomical observation apps. Simulation apps and clicker evaluation apps were used the most in the introduction stage of the class, simulation apps in the development stage, and clicker evaluation apps in the finishing stage. (2) In the lesson plans, the activities that elementary school students use smart technology showed more than those used by teachers, and its characteristics were more prominent in the development stage of the class. (3) As for the content type of smart technology, experience type was the highest, followed by tool type and resource type. In comparison, there were relatively few interaction support types and learning opportunity extensions. (4) There were many cases in which pre-service teachers replaced elementary school students with virtual experiences using experience type instead of providing opportunities to experiment or experience directly. (5) Pre-service teachers asked various questions while planning science class utilizing smart technology, and a total of 25 question types appeared in 7 categories.

• Journal of the Korea Society for Simulation
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• v.8 no.2
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• pp.29-43
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• 1999

As real-time processing of data with large storage space is required in the era of multimedia, disk arrays are generally used as storage subsystems which be able to provide improved I/O performance. To design the cost-effective disk array, it is important to develop performance models which evaluate the disk array performance. Both queueing theory and simulation are applicable as the method of performance evaluation through queueing modeling. But there is a limit to the analytical method using queueing theory due to the characteristics of disk array requests being serviced in the parallel and concurrent manner. So in this paper we evaluate the disk array performance using simulation method which abstract disk array systems in the low level. Performance results were evaluated through simulation, so that mean response time, mean queueing delay, mean service time, mean queue length for disk array requests and utilization, throughput for disk array systems, can be utilized for capacity planning in the phase of disk array design.

• Journal of the military operations research society of Korea
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• v.9 no.2
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• pp.23-30
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• 1983

A simulation study was conducted to determine optimum capacity of Navy drydock facility using GASP-IV, an advanced FORTRAN-based simulation language, under demands of regular overhauls and emergency repairs by ships of an hypothetical fleet composition. Three year dock usage data was analyzed to produce probability distributions underlying drydock repair demands. The present facility size of two drydocks was simulated and was found to be somewhat short of adequate service capability, showing excessive average waiting time and average queue length. The simulation model was then modified to include an additional drydock of similar size as the other two and a year's simulation was again conducted. All repair needs were quite satisfactorily met and all docks showed very high utilization factor (0.98). This contributed to an increase in the fleet's ship availability from 0.95 to 0.99. This study illustrates the usefulness of simulation technique as a tool for analyzing policy alternatives in military long-term investment areas.

• The Korean Journal of Emergency Medical Services
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• v.21 no.2
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• pp.71-78
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• 2017

Purpose: The purpose of the study was to investigate the satisfaction of paramedic students with simulation-based learning in an emergency intervention for bradycardia patients. Methods: Study participants were 72 paramedic students who experienced simulation-based learning. Data on satisfaction with the intervention were collected and analyzed using SPSS 18.0. Results: The mean satisfaction score for the simulation-based learning intervention was 4.28 by Likert 5 point scale. Conclusion: Simulation-based learning can facilitate adaptation to the scene of an emergency among paramedic students.

• Journal of the Korea Society for Simulation
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• v.9 no.2
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• pp.103-118
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• 2000

ITS(Intelligent Transportation System) is an advanced system which can effectively handle the current transportation problems. DSRC(Dedicated Short Range Communication) is considered as a promising technology since it has the capability of two-way communication and can serves to implement various ITS services. In this paper, we study DSRC based ITS telecommunication traffic analysis and suggest an architecture and network design of telecommunication network for DSRC services. We also perform a simulation study to validate the proposed network architecture and design for Metropolitan Seoul Area with various network alternatives. In this simulation, we use actual traffic data and road characteristics from Seoul area and use our DSRC service configuration.

• Journal of IKEEE
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• v.22 no.1
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• pp.136-142
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• 2018

Recently, as the development system has become larger, sequential simulation methods have become impossible to verify systems that take a long time or require real time results. Therefore, a study of a distributed simulation system that simulates several processes has been conducted. In order to simulate real-time systems, efficient data exchange between distributed systems is required. Data Distribution Service is a data-oriented communication middleware proposed by Object Management Group and provides efficient data exchange and various QoS. However, in a large-scale distributed simulation environment distributed over a wide area, there is a problem of Participant Discovery and QoS guarantee due to domain separation in data exchange. Therefore, in this paper, we propose a DDS/SDN architecture that can guaranteed QoS and effective Participant Discovery in an SDN-based network.

• Journal of the Korea Society for Simulation
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• v.28 no.2
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• pp.15-22
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• 2019

Simulation methods are being studied for various service models that can be used in industries as the development of web technology. DEVS is being used as a tool to simulate through scenarios using various information. In addition, DEVS/WS integrates web-based DEVS models through a distributed computing environment and can be used as tools for high-performance computing and data distribution. This paper describes a method for simulating an intelligent transportation system in DEVS/WS environment. This paper propose dynamic interest management model(DIMM) applied the genetic algorithm, manage efficiently road information of moving node. And, this paper evaluates performance of the dynamic interest management model in comparing to the none interest management model(NIMM). The transmitted messages and simulation time of the DIMM is saved than that of the NIMM.