• The Journal of the Korea Contents Association
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• v.19 no.1
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• pp.132-140
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• 2019

Recently, many cities around the world introduced and operated shared bicycle system to reduce the traffic and air pollution. Seoul also provides shared bicycle service called as "Ddareungi" since 2015. As the use of shared bicycle increases, the demand for bicycle in each station is also increasing. In addition to the restriction on budget, however, there are managerial issues due to the different demands of each station. Currently, while bicycle rebalancing is used to resolve the huge imbalance of demands among many stations, forecasting uncertain demand at the future is more important problem in practice. In this paper, we develop forecasting model for demand for Seoul shared bicycle using statistical time series analysis and apply our model to the real data. In particular, we apply Holt-Winters method which was used to forecast electricity demand, and perform sensitivity analysis on the parameters that affect on real demand forecasting.

• Journal of KIISE:Computer Systems and Theory
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• v.30 no.3_4
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• pp.194-204
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• 2003

The performance of a shared memory multiprocessor system is dependent on the system software such as scheduling policy as well as hardware system. Most of existing simulators, however, do not support simulation for multi-programmed environment because they can execute only a single benchmark application at a time. We propose a multi-programmed simulation method on a program-driven simulator, which enables the concurrent executions of multiple parallel workloads contending for limited system resources. Using the proposed method, system developers can measure and analyze detailed effects of resource conflicts among the concurrent applications as well as the effects of scheduling policies on a program-driven simulator. As a result, the proposed multi-programmed simulation provides more accurate and realistic performance projection to design a multiprocessor system.

• The Transactions of the Korea Information Processing Society
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• v.3 no.3
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• pp.617-630
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• 1996

In this paper, a shared-concurrent file system (S-CFS) is designed and implemented using conventional disks as disk arrays on a Workstation Cluster which can be used as a small-scale server. Since it is implemented on UNIX operating systems, S_CFS is not only portable and flexible but also efficient in resource usage because it does not require additional I/O nodes. The result of the research shows that on small-scale systems with enough disks, the performance of the concurrent file system on transaction processing applications is bounded by the bottleneck of CPUs computing powers while the performance of the concurrent file system on massive data I/Os is bounded by the time required to copy data between buffers. The concurrent file system,which has been implemented on a Workstation Cluster with 8 disks,shows a throughput of 388 tps in case of transaction processing applications and can provide the bandwidth of 15.8 Mbytes/sec in case of massive data processing applications. Moreover,the concurrent file system has been dsigned to enhance the throughput of applications requirring high performance I/O by controlling the paralleism of the concurrent file system on user's side.

• ETRI Journal
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• v.10 no.3
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• pp.83-91
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• 1988

This paper describes the architecture and the performance analysis of a multiprocessor system, which is based on the shared memory and single system bus. The system bus provides the pended protocol for the multiprocessor environment. Analyzing the processor utilization, address/data bus utilization and memory conflicts, we use a simulation model. The hit ratio of private cache memory is a major factor on the linear increase of the performance of a shared memory based multiprocessor system.

• Journal of the Optical Society of Korea
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• v.18 no.5
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• pp.477-484
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• 2014

In this paper, we propose a new optical secret key sharing method based on the Diffie-Hellman key exchange protocol required in cipher system. The proposed method is optically implemented by using a free-space interconnected optical logic gate technique in order to process XOR logic operations in parallel. Also, we present a compact type of optical module which can perform the modified Diffie-Hellman key exchange for a cryptographic system. Schematically, the proposed optical configuration has an advantage of producing an open public key and a shared secret key simultaneously. Another advantage is that our proposed key exchange system uses a similarity to double key encryption techniques to enhance security strength. This can provide a higher security cryptosystem than the conventional Diffie-Hellman key exchange protocol due to the complexity of the shared secret key. Results of numerical simulation are presented to verify the proposed method and show the effectiveness in the modified Diffie-Hellman key exchange system.

• Nuclear Engineering and Technology
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• v.30 no.4
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• pp.298-307
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• 1998

In order to design mutual communication between a distributed control system and a function test facility, we used the Inter-Process Communication(IPC) in two systems and Transmission Control Protocol/Internet Protocol(TCP/IP) protocol. The data from the function test facility are put in the shared memory using an IPC, which is then accessed by the distributed control system through an Application Program Interface(API). The server in the function test facility includes two processes(one for sending and one for receiving), which are generated by the fork function from the client signal. The client in the distributed control system includes two separate programs(one for receiving and one for sending).

• Journal of Power Electronics
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• v.19 no.6
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• pp.1337-1350
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• 2019

This paper proposes a Phase-Shift Triple Full-Bridge (PSTB) Zero-Voltage Zero-Current-Switching (ZVZCS) converter with a high switching frequency and high efficiency. In the proposed converter, all three bridge legs are shared leading-legs, and all three transformers work in the Discontinuous Conduction Mode (DCM). Thus, all of the switches and diodes in the PSTB ZVZCS can be soft switched. Moreover, since all of the transformers can pass energy from the primary-side to the secondary-side when their primary-side currents are not zero, there is no circulating current. As a result, the PSTB ZVZCS converter can achieve a high efficiency at high operating frequencies. A theoretical analysis and the characteristics of the proposed converter are presented and verified on a 1MHz 200~300V/24V 1.2kW hardware prototype. The proposed converter can reach a peak efficiency of 96.6%.

• Informatization Policy
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• v.21 no.3
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• pp.33-55
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• 2014

Public Shared Service Centers (PSSC) consolidate functions such as human resources, information technology, financial management or accounting into one office to serve an organization. A prominent example from the United States is the Federal Information Technology Shared Services Strategy. It supports mission, administrative, and infrastructure-related IT functions through providing organizations in the Executive Branch of the Federal Government (Federal Agencies) with policy guidance on the full range and lifecycle of intra- and inter-agency information technology (IT) shared services. This study looks at the Federal Information Technology Shared Services Strategy in order to draw lessons for fostering collaborative government through the use of PSSC. It finds the following factors are critical for success when implementing IT shared services: (1) agency leadership must be solidly behind their IT shared service plan, or the needed changes will not happen at the business unit, program, or system levels; (2) there must be a move away from internally-centered, program-specific thinking, and a move toward a paradigm of consuming and providing IT shared services with multiple groups whenever possible; and (3) successfully managing "loss of control" issues is central, and optimizing business processes is essential to move from stove-piped workflows to processes that work across the agency enterprise and beyond. Therefore, the study suggests that a Korean model of PSSC implementation be introduced, and that good IT Governance is a crucial component of PSSC strategies.

• ETRI Journal
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• v.33 no.1
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• pp.136-139
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• 2011

A modular upgrade design for packet transport switch nodes is presented where packet loss is dramatically reduced by intra-module and inter-module buffer sharing. This modular design offers significant cost and power reduction in a high-data-rate system where buffers are highly costly and power-greedy.

• Proceedings of the Korea Multimedia Society Conference
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• 1998.10a
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• pp.208-213
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• 1998

멀티미디어 회의, 원격 교육, 원격 의료 등과 같이 다수가 참여하여 공동으로 작업을 하는 응용 서비스들이 컴퓨터와 네트워크의 발전에 따라 가능해지고 있다. 이와 같이 다수가 참여하여 객체를 공유하면서 공동 작업을 하여야 하는 응용들은 공유 작업 환경(shared work environment)을 필수적으로 요구한다. 또한 네트워크에서 다양한 응용 서비스들을 제공하고 관리하기 위해서는 서비스 세션에 대한 관리도 필요하다. 본 논문에서는 사용자가 여러 세션에 참여하여 공동 작업이 가능한 공유 작업 환경을 다자간 멀티미디어 서비스 세션의 제공, 제어 및 관리를 위한 메커니즘을 제공하는 CORBA(Common Object Request Broker Architecture)기반의 COMUS(CORBA based Multiparty Multimedia System)와 자바 언어의 객체 지향 특성을 이용하여 구현하였다.