• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.12
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• pp.2891-2898
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• 2014

It is feasible to develop a fault tolerant system through module level redundancy on the Integrated Modular Avionics (IMA). However, its great implementation complexity is one of important challenges when asynchronous hardware environment is naturally assumed. To solve this problem, Physically Asynchronous Logically Synchronous (PALS) on IMA has been proposed. But, it has adaptation problem by not addressing specific architecture for IMA system. In the paper, we propose how to synchronize the input data on the IMA system under primary/secondary redundancy architecture by referring to existing PALS. In the proposed scheme, we introduce window frame by considering rate monotonic scheduling and analyze the adequate the synchronization time. Finally, we verify the feasibility of the proposed design pattern through the systematic experiments.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.12
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• pp.5622-5632
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• 2011

This paper presents the simulation design and analysis of Integrated Logistics System(ILS) which is operated by using the AGV(Automated Guided Vehicle). To maximize the operation performances of ILS with AGV, many parameters should be considered such as the number, velocity, and dispatching rule of AGV, part types, scheduling, and buffer sizes. We established the design of experiment in a way of Orthogonal Array in order to consider (1)maximizing the throughput; (2)maximizing the vehicle utilization; (3)minimizing the congestion; and (4)maximizing the Automated Storage and Retrieval System(AS/RS) utilization among various critical factors. Furthermore, we performed the optimization by using the simulation-based analysis and Evolution Strategy(ES). As a result, Orthogonal Array which is conducted far fewer than ES significantly saved not only the time but the same outcome when compared after validation test on the result from the two methods. Therefore, this approach ensures the confidence and provides better process for quick analysis by specifying exact experiment outcome even though it provides small number of experiment.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.5
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• pp.225-234
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• 2015

Nowadays a Virtual Power Plant (VPP) represents an aggregation of distributed energy resource such as Distributed Generation (DG), Combined Heat and Power generation (CHP), Energy Storage Systems (ESS) and load in order to operate as a single power plant by using Information and Communication Technologies, ICT. The VPP has been developed and verified based on a single virtual plant platform which is connected with a number of various distributed energy resources. As the VPP's distributed energy resources increase, so does the number of data from distributed energy. Moreover, it is obviously inefficient in the aspects of technique and cost that a virtual plant platform operates in a centralized manner over widespread region. In this paper the concept of the large-scale VPP which can reduce a error probability of system's load and increase the robustness of data exchange among distributed energy resources will be proposed. In addition, it can directly control and supervise energy resource by making small size's virtual platform which can make a optimal resource scheduling to consider of variable and sensitive load in the large-scale VPP. It makes certain the result is verified by simulation.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.7
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• pp.18-25
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• 2014

To increase wireless capacity, the concurrent use of multiple wireless interfaces on different frequency bands, called aggregation, can be considered. In this paper, we focus on aggregation of multiple Wi-Fi interfaces with packet-level traffic spreading between the interfaces. Two aggregation schemes, link bonding and multipath TCP (MPTCP), are tested and compared in a dualband Wi-Fi radio system with their Linux implementation. Various test conditions such as traffic types, network delay, locations, interface failures and configuration parameters are considered. Experimental results show that aggregation increases throughput performance significantly over the use of a single interface. Link bonding achieves lower throughput than MPTCP due to duplicate TCP acknowledgements (ACKs) resulting from packet reordering and filtering such duplicate ACKs out is considered as a possible solution. However, link bonding is fast responsive to links' status changes such as a link failure. It is shown that different combinations of interface weights for packet spread in link bonding result in different throughput performance, envisioning a spatio-temporal adaptation of the weights. We also develop a mathematical model of power consumption and compare the power efficiency of the schemes applying different power consumption profiles.

• Journal of KIISE:Information Networking
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• v.35 no.2
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• pp.130-138
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• 2008

The scheme for recognizing the channel availability is one of the most important research issues in cognitive radio systems utilizing unused frequency bands. In this paper, we propose a novel scheme of selecting sensing channel in order to improve the sensing ability of frequency status in cognitive radio ad hoc networks. To fully exploit the sensing ability of each cognitive radio user, we adopt a master for a cluster which is made of several cognitive radio users. By gathering and analyzing the sensing information from cognitive radio users in the cluster, the cooperative sensing is realized. Since the transmission range of a licensed user is limited, it is possible that a master determines different sensing channels to each cognitive radio users based on their location. By making cognitive radio users sense different channels, the proposed scheme can recognize the state of wireless spectrum fast and precisely. Using the simulation, we compare the performance of the proposed scheme with those of two different compared schemes that one makes cognitive radio users recognize the frequency status based on their own sensing results and the other shares frequency status information but does not utilize the location information of licensed user. Simulation results show that the proposed scheme provides available channels as many as possible while detecting the activation of licensed user immediately.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.989-992
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• 1999

Battery로 작동되고, 소형인 제품들도 다양한 기능은 물론이고, 다양한 입출력 장치를 갖추고, 실시간으로 처리하는 시스템이 많이 요구되고 있는 실정이며, 점차 더욱 더 요구될 것으로 전망된다. 더욱이 포터블 기기는 일반적으로 MCU의 내부에 제한된 ROM type 메모리를 내장하게 되면, 데이터 메모리로 SRAM 및 flash memory를 갗추고 있다. 따라서 이러한 제한된 하드웨어 환경하에서 많은 기능을 수행해야 하는 경우가 많다. 여러 기능을 시간적인 간격으로 배분하거나, 기능 자체를 서로 배분하면서, 서로 융합하는 등의 여러 가지 기능을 수행하려다보면, 당연히 메인 소프트웨어 구조가 복잡해지며 대부분 어셈블리나 C와 같은 linear한 구조를 가지는 language로 개발되기 때문에 효과적인 프로그램 구조를 세우기는 쉽지 않다. 본 논문에서는 이를 위해 좀더 규격화된 방법을 제시하고자 한다. 보다 구체적인 구조를 연구할 목적으로 다양한 테스크를 수행하여야 하는 시스템이면서 프로세서가 필요한 포터블 기기의 한 응용 제품인 MP3 Player 에서 요구되는 job scheduling을 연구한다. 필요한 작업의 종류는 가장 부하가 많이 걸리는 압축된 MP3 file을 다시 복원시켜주는 codec 부분과 일정 시간 간격을 가지고 수행하여야 하는 외부 키보드 입력과 실시간으로 시간을 계산하는 타이머 기능, 그리고 LCD에 시간의 변화를 표시하여 주어야한다. 이와같이 수시로 작업이 발생하지만 시간 점유율이 중간 정도인 LCD 컨트롤과 메모리 컨트롤 등이다. 프로세서의 속도를 최소한으로 줄이면서 스케줄링에 의해 시간 문제를 해결하는 방법을 제시하도록 한다. 이는 기초과학 수준이 높은 북방권 국가들의 과학자들이 주로 활용되고 있다는 점에서도 잘 알 수 있으며 우리의 과학기술 약점을 보완하는 원천으로써 외국인 연구 인력이 대안이 되고 있음을 시사한다. 본 연구에서는 한국 연구 조직에서 일하는 외국인 연구자들의 동기 및 성과에 영향을 미치는 많은 요인들을 확인할 수 있었다. 상관관계, 분산분석, 회귀분석 등을 통해 활용 성과에 미치는 영향 요인들을 도출하였다. 설문 분석을 통하여 동기 및 성과 사이에는 강한 상관관계가 존재하는 것을 확인할 수 있었으며 이는 전통적인 동기 이론들과 부합한다. 대부분의 변수가 동기 및 성과에 동시에 영향을 미치는 것으로 조사되었으며 그중에서도 조직 협력 문화, 외국인 연구자의 의사소통 및 협력성, 외국인 연구자의 연구 능력 관련 변수들 및 연구 프로젝트의 기술수명주기, 외국인 연구자의 기존 기술지식의 흡수 등이 가장 중요한 변수로 나타났다. 이는 우리가 주로 중국 및 러시아 과학자들을 활용하여 상업화하는 외국인 연구인력 활용 패턴과도 일치하는 결과이다. 즉 우호적인 조직문화를 가지고 있는 연구 조직에서, 이미 과학기술 지식을 많이 가지고 있고 연구 능력도 높은 외국인 과학기술자를, 한국에서 기술이 태동 또는 성장하고 있는 연구 분야에서 활용하는 것이 가장 성과가 좋다는 사실을 확인시켜 주고 있다. 국내에서 최초로 수행된 본 연구는 외국인 연구 인력의 활용 성과가 매우 높으며, 우리의 과학기술혁신시스템을 보완하는 유효한 수단으로써 외국인 연구 인력이 중요한 대안이 될 수 있음을 발견하였다. 외국인 연구 인력을 잘 활용하기 위하여 문제점 및 개선방안을 활용 환경, 연구 인력이 중요한 대안이 될 수

• The Journal of the Korea Contents Association
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• v.19 no.5
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• pp.187-193
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• 2019

Key-value storage engines are an essential component of growing demand in many computing environments, including social networks, online e-commerce, and cloud services. Recent key-value storage engines offer many features such as transaction, versioning, and replication. In a key-value storage engine, transaction processing provides atomicity through Write-Ahead-Logging (WAL), and a synchronous commit method for transaction processing flushes log data before the transaction completes. According to our observation, flushing log data to persistent storage is a performance bottleneck for key-value storage engines due to the significant overhead of fsync() calls despite the various optimizations of existing systems. In this article, we propose a group synchronization method to improve the performance of the key-value storage engine. We also design and implement a transaction scheduling method to perform other transactions while the system processes fsync() calls. The proposed method is an efficient way to reduce the number of frequent fsync() calls in the synchronous commit while supporting the same level of transaction provided by the existing system. We implement our scheme on the WiredTiger storage engine and our experimental results show that the proposed system improves the performance of key-value workloads over existing systems.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.10
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• pp.2935-2944
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• 2009

This paper proposes Dual DBR(Drum-Buffer-Rope) system for a small-to-medium-sized PCB(Printed Circuit Board) manufacturing line. DBR method of TOC(Theory of Constraints) is an effective system for a small-to-medium-sized company to build production scheduling system. But to apply it to PCB line, it needs more technical consideration because of multiple constraints, looping process line and complex buffer management. This paper proposes an answer of these problems using Dual DBR to build production scheduling system more successfully. And it was confirmed that lead time was reduced more than 20% applying Dual DBR system to a domestic PCB manufacturing line actually.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.42 no.1
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• pp.9-26
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• 2005

In the pursuit of ever higher levels of performance, recent computer systems have made use of deep pipeline, dynamic scheduling and multi-issue superscalar processor technologies. In this situations, branch prediction schemes are an essential part of modem microarchitectures because the penalty for a branch misprediction increases as pipelines deepen and the number of instructions issued per cycle increases. In this paper, we propose a novel branch prediction scheme, direction-gshare(d-gshare), to improve the prediction accuracy. At first, we model a neural network with the components that possibly affect the branch prediction accuracy, and analyze the variation of their weights based on the neural network information. Then, we newly add the component that has a high weight value to an original gshare scheme. We simulate our branch prediction scheme using Simple Scalar, a powerful event-driven simulator, and analyze the simulation results. Our results show that, compared to bimodal, two-level adaptive and gshare predictor, direction-gshare predictor(d-gshare. 3) outperforms, without additional hardware costs, by up to 4.1% and 1.5% in average for the default mont of embedded direction, and 11.8% in maximum and 3.7% in average for the optimal one.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.8
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• pp.432-444
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• 2004

In this paper, we construct the TMO-based object group model on distributed environment, and analyze and evaluate the executability for distributed real-time service of our object group model by developing the distributed real-time application simulator applying the model. The Time-triggered Message-triggered Object(TMO) is a real-time server object having real-time property itself. The TMO-based object group is defined as a set of objects which logically reconfigured the physically distributed one or more TMOs on network by a given distributed application. For supporting group management of the server objects, the TMO-based object group we suggested provides the functions which register and withdraw the solver objects as a group member to an arbitrary object group, and also provides the functions which insert and delete the access rights of server objects from clients. Also, our model was designed and implemented to support the appropriate object selection and dynamic binding service for a single TMO as well as the duplicated TMOs, and to support the real-time scheduling service for the clients which are requesting the service. Finally, we developed the Defence System against Invading Enemy Planes(DSIEP) simulator as a practical example of distributed real-time application by applying our model, and evaluated the adaptability of distributed service strategies for the group components and the executability of real-time services that the TMO-based object group model provides.