• Journal of the Korea Society for Simulation
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• v.25 no.3
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• pp.117-123
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• 2016

This paper presents inference methods for inner operations of a multi-server queue when historical data are limited or system observation is restricted. In a queueing system analysis, autocorrelated arrival and service processes increase the complexity of modeling. Accordingly, numerous analysis methods have been developed. In this paper, we introduce an inference method for specific situations when external observations exhibit autocorrelated structure and and observations of internal operations are difficult. We release an assumption of the previous method and provide lemma and theorem to guarantee the correctness of our proposed inference method. Using only external observations, our proposed method deduces the internal operation of a multi-server queue via non-parametric approach even when the service times are autocorrelated. The main internal inference measures are waiting times and service times of respective customers. We provide some numerical results to verify that our method performs as intended.

• KIPS Transactions on Computer and Communication Systems
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• v.3 no.9
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• pp.279-292
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• 2014

Energy aware server cluster aims to reduce power consumption at maximum while keeping QoS(quality of service) as much as energy non-aware server cluster. In the existing methods of energy aware server cluster, they calculate the minimum number of active servers needed to handle current user requests and control server power mode in a fixed time interval to make only the needed servers ON. When loads change rapidly, QoS of the existing methods become degraded because they cannot increase the number of active servers so quickly. To solve this QoS problem, we classify load change situations into five types of rapid growth, growth, normal, decline, and rapid decline, and apply five different thresholds respectively in calculating the number of active servers. Also, we use a flexible scheme to adjust the above classification criterion for multi threshold, considering not only load change but also the remaining capacity of servers to handle user requests. We performed experiments with a cluster of 15 servers. A special benchmarking tool called SPECweb was used to generate load patterns with rapid change. Experimental results showed that QoS of the proposed method is improved up to the level of energy non-aware server cluster and power consumption is reduced up to about 50 percent, depending on the load pattern.

• Journal of Korea Multimedia Society
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• v.18 no.5
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• pp.620-630
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• 2015

This research suggests a load balancing method for a volume rendering system which supports concurrent users. When concurrent users use a volume rendering server system, the computational resources are occupied by a particular user by turns because each process consumes the computational resources as much as possible. In this case, the previous method shows acceptable throughput but the latency is increased for each user. In this research, we suggest a method to improve the latency without performance degradation. Each process makes concessions for taking the resources according to the number of users connected to the system. And we propose a load balancing method in the dynamic situation in which the number of users can vary. Using our methods, we can improve the latency time for each user.

• The Journal of Information Technology
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• v.12 no.2
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• pp.49-55
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• 2009

Currently the Web, multiple files in the Client to upload to the server of the multi-upload method, files are stored in specific folders on the server, the file name field in DB(Database Field) stored in a way that the process has been widely utilized. Therefore, a minimum number of file upload as many file names in the Database and the Table should be created in the field, but also a variable number of files can be uploaded has no limits. In this paper we proposed the new method that files to be uploaded to the server, you can upload a limited number of files, nor due to upload files to reduce load on the database to improve the processing speed of a single field using a multi-method file uploads using PHP directly implemented

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.775-778
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• 2002

In this paper, we've studied multi axis control system using embedded web server which is controlling and monitoring the state data of moors. NanoWit2 Board has been ported Linux Operating System and fabricated Web Sorrel by GCC. Motion controller is used MCS-40 of e-MOTION Tek Co., Ltd. which receiving control signal, controlling motors and sending the state data to Web Server.

• Journal of Korea Society of Industrial Information Systems
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• v.7 no.1
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• pp.16-26
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• 2002

A web based mail system consists of servers and clients. A server side takes charge of making rail accounts and service, a client side does interfacing with users. In this paper, we designed the mail system with multi-domain facility. Also we implemented both a ussr environment based on the internet explorer and management environment based on the windows server 2000. Using the service engine of rail system, we could provide the user efficiency through responding user absence, automatic mail sorting, verifying receipt and refusing messages, and implemented the rail system which provides the reliable system.

• IEMEK Journal of Embedded Systems and Applications
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• v.13 no.6
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• pp.329-335
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• 2018

Offline-first strategy is that it allows data to be saved while offline, and when connected online, data is synchronized to ensure that all devices have the same data. Multi-device is a term that shares data through synchronization on various platforms on Android, ios, etc. First, all of the data is stored in the local repository like SQLite and then on the server via HTTP communication. Then, the synchronization is completed by receiving the changed data from the server and storing it in the local repository at the time of the synchronization, and sending the changes to the server from the client. We proposed and implemented a database structure, APIs, and a illustrative application running on PC and Android phone.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.3
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• pp.911-931
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• 2021

Recently, most cloud services use Docker container environment to provide their services. However, there are no researches to evaluate the performance of communication libraries for multi-GPU based distributed deep learning in a Docker container environment. In this paper, we propose an efficient communication architecture for multi-GPU based deep learning in a Docker container environment by evaluating the performances of various communication libraries. We compare the performances of the parameter server architecture and the All-reduce architecture, which are typical distributed deep learning architectures. Further, we analyze the performances of two separate multi-GPU resource allocation policies - allocating a single GPU to each Docker container and allocating multiple GPUs to each Docker container. We also experiment with the scalability of collective communication by increasing the number of GPUs from one to four. Through experiments, we compare OpenMPI and MPICH, which are representative open source MPI libraries, and NCCL, which is NVIDIA's collective communication library for the multi-GPU setting. In the parameter server architecture, we show that using CUDA-aware OpenMPI with multi-GPU per Docker container environment reduces communication latency by up to 75%. Also, we show that using NCCL in All-reduce architecture reduces communication latency by up to 93% compared to other libraries.

• Journal of the military operations research society of Korea
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• v.23 no.2
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• pp.25-44
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• 1997

Internet users been rapidly increased due to the convenient GUI environment. Current Web-based HTTP/CGI client/server architecture has several problems such as the CGI bottleneck, no maintaince of state, and no load balancing. However, with Java and CORBA technologies called“Object Web technology”, we can solve them because Java is not only a mobile code but also a platform-independent code, and CORBA has ability to build distributed object and language-independent object model. The goal of “Object Web technology”is to create multivendor, multiOS, multilanguage“legoware”using objects. This paper implement“Book Search System”which is Web-based client/server architecture using distributed objects. Environments of this implementation are Hangul Windows NT(included IIS) server, Hangul Windows 95 client, Visigenic's VisiBroker for Java 1.2 which is a product of CORBA 2.0, HTTP protocol on TCP-IP-based, Sybase SQL Anywhere 5.0 database server, and the interface between application server and database is JDBC-ODBC bridge middleware.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.200-202
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• 2004

This paper deals with the real-time monitoring and control system using PC, PDA(Win CE embedded device) and PCS(based BREW platform). The camera attached to the server captures the moving target, and the captured frame of color image is encoded in JPEG for image compression at the server. The client(PC, PDA, PCS) receives the image data from the remote server and the received image is decoded from decompression. We use the TCP/IP protocol to send the image frames. The client can control the position of the camera by sending the control command to the server. Two DC servo motors for the camera are controlled in any directions, up-down and left-right, by the controller which is communicating with the server via the serial communication to get the control command. In this way, on the client we can monitor the moving images at the server and also control the position of the camera.