• Journal of Advanced Navigation Technology
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• v.23 no.6
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• pp.577-583
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• 2019

A dynamic system is called positive if any trajectory of the system starting from non-negative initial states remains forever non-negative for non-negative controls. In this paper, we consider the new stability condition for the positive time-varying linear discrete interval systems with time-varying delay and unstructured uncertainty. The delay time is considered as time-varying within certain interval having minimum and maximum values and the system is subjected to nonlinear unstructured uncertainty which only gives information on uncertainty magnitude. The proposed stability condition is an improvement of the previous results which can be applied only to time-invariant systems or had no consideration of uncertainty, and they can be expressed in the form of a very simple inequality. The stability conditions are derived using the Lyapunov stability theory and have many advantages over previous results using the upper solution bound of the Lyapunov equation. Through numerical example, the proposed stability conditions are proven to be effective and can include the existing results.

• Journal of the Korea Concrete Institute
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• v.27 no.3
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• pp.265-272
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• 2015

In this study, a method to reduce temperature rise due to hydration in mass concrete is investigated. It is to use retarder (glucose) for reducing heat of hydration and to use calcium silicate hydrate (C-S-H) for compensating the retardation effect due to its role as a nucleation seed. For this purpose, the temperature rise of cement paste due to hydration was measured and the effect of using both C-S-H and glucose on setting and 28-day compressive strength of mortar specimens was investigated. According to the experimental results, using C-S-H and glucose caused the reduction in the maximum temperature but accelerated the time to reach the maximum temperature compared to that of retarded cement paste using glucose. In addition, using C-S-H and glucose did not show significant effect on 28-day compressive strength of mortar specimens, indicating that the method shown in this study can be a successful alternative to control maximum temperature rise in mass concrete.

• The KIPS Transactions:PartC
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• v.15C no.5
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• pp.419-428
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• 2008

IEEE 802.15.4 reserves transmission time to support real-time transport by sending GTS request packets to the PAN coordinator in advance. This paper introduces GTS-FAT technique to reduce the reservation time by giving a higher sending priority to GTS request packets than data packets. Differently from the conventional scheme where these two kinds of packets share a single transmission queue, GTS-FAT scheme allocates two queues with two different contention window sizes like IEEE 802.11e. This paper also proposes an analytical GTS delay model by combining the two legacy models for 802.15.4 and 802.11e to accurately predict the GTS-FAT delay over a given network topology. Our analysis shows that GTS-FAT reduces GTS service delay by up to 50% at the expense of the data delay by only up to 6.1% when GTS request packets four times outnumber data packets.

• Journal of Korea Game Society
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• v.16 no.4
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• pp.57-68
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• 2016

As the size of the data used in the game application increase gradually, the physical resources of game server grow. Accordingly, it is necessary to/it is required to introduce I/O virtualization in game server to improve I/O performance of the server. But it is difficult to ensure high responsiveness in game server where I/O delay change from time to time. To maximize the benefit of I/O virtualization, guaranteeing I/O response time is very important and it is necessary to have I/O scheduling techniques to manage the I/O latency in the order of priority of virtual machines. In this paper, we propose an efficient delay-constrained scheduling algorithm in a virtualization environment to ensure maximum I/O latency. In addition, a reduced amount of loss of the packet was found to increase the fairness of scheduling in the experiments with the proposed scheme.

• The KIPS Transactions:PartC
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• v.13C no.5 s.108
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• pp.567-574
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• 2006

VG-AnyLAN is a local area network standard developed by the IEEE 802.12 project. While preserving the frame format of IEEE 802.3, VG-AnyLAN adopts a new medium access control called Demand Priority where transmission requests of stations are arbitrated by a control hub in a round-robin manner. Unlike CSMA/CD which is the medium access control of IEEE 802.3, the Demand Priority, while providing the maximum bound on the packet delay, does not put the limit on the network segment size. In this paper, we analyze the delay and the channel utilization performances of the medium access control of IEEE 802.12 VG-AnyLAN. We develope an analytic model of the system under assumptions that each station generates traffic of the equal priority and that the packets are of fixed length. Using the analytic model, we obtain the recursive expression of the average channel utilization and the average access delay The numerical results obtained via analysis are compared to the simulation results of the system for a partial validation of our analysis.

• The KIPS Transactions:PartA
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• v.8A no.3
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• pp.217-226
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• 2001

In this paper, for continuous media access operations performed by Clustered Continuous Media Storage Server (CCMSS) system, we present the analytical model based on the open queueing network, which considers simultaneously two critical delay factors, the disk I/O and the internal network, in the CCMSS system. And we derive by using the analytical model the stochastic model for the total service delay time in the system. Next, we propose the integrated stochastic admission control model for the CCMSS system, which estimate the maximum number of admittable service requests at the allowable service failure rate by using the derived stochastic model and apply the derived number of requests in the admission control operation. For the performance evaluation of the proposed model, we evaluated the deadline miss rates by means of the previous stochastic model considering only the disk I/O and the propose stochastic model considering the disk I/O and the internal network, and compared the values with the results obtained from the simulation under the real cluster-based distributed media server environment. The evaluation showed that the proposed admission control policy reflects more precisely the delay factors in the CCMSS system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.11 no.2
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• pp.137-145
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• 1986

The contention resolution algorithm with the limited packet delay time as well stable distribution as the packet delay time is proposed and implementes for improving the mean packet delay time in the network employing CSMA/CD as the access method. The implementation of node controller is based on IEEE 802.2 standard logical link control(LLC) and IEEE 802.3 standard medium access control(MAC). Some portion of IEEE 802.3 Standard MAC, and the Binary Exponential Back-off(BEB) algorithm is replaced by the proposed algorithm. From the view of normalized mean packet transmission delay time, the controller implemented here can be applicable to the office-automation system, and the factory-and laboratory-automation environment where the limited time criterion is very significant.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.24-26
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• 2005

광 간섭계는 광을 이용한 다양한 계측분야에 사용된다. 일반적인 광 간섭계의 지연단은 기계적인 광지연에 의해 저속이며, 시스템 구성상 안정성이 떨어지게 된다. 본 논문에서는 기존의 광간섭계 지연단의 기계적 방식을 배제한 광위상 변조기를 이용한 지연단을 설계하고 그 특성을 분석하였다. 제안된 광 간섭계는 1310nm 10GHz의 반복율을 갖는 광원과 광위상변조기를 이용한 전(全) 광섬유 형태로 안정한 구성을 하였다. 구성된 광간섭계는 광위상 변조기의 변조 전압, 변조 주파수의 변화에 의해 광지연시간의 쉬운 변조가 가능하였으며 최대 20ps 의 광지연시간을 얻을 수 있었다.

• Proceedings of the Korea Information Processing Society Conference
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• 2020.11a
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• pp.84-87
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• 2020

최근, 응용 프로그램의 이식성, 확장성, 낮은 오버헤드 및 관리의 용이성 등을 제공하는 컨테이너 기술을 고성능 컴퓨팅 (high performance computing, HPC) 환경에 접목하려는 다양한 연구들이 진행되고 있다. 본 논문에서는 멀티 프로그램화된 환경, 즉, 컨테이너 기반의 다수개의 HPC 워크로드들이 동시에 실행되는 환경에서 멀티 프로그래밍 수준, 통신 패턴 및 비율에 따른 HPC 워크로드들의 성능 특성을 분석하고, HPC 워크로드가 실행되는 동일한 컨테이너 그룹에 속한 컨테이너들의 스케쥴링 시간 부조화가 데이터 교환 지연 시간을 증가시키고 그 결과 응용 성능을 크게 저하시킬 수 있음을 확인한다. 또한 HPC 워크로드가 수행되는 동일 그룹 컨테이너들의 CPU 점유 가능값(CPU Shares)을 동적으로 조절하는 휴리스틱을 제안, 적용함으로써, HPC 워크로드의 성능(통신소비시간 최대 약 42.5%, 워크로드 실행시간 최대 약 23.6% 감소)을 크게 향상시킬 수 있음을 확인한다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2013.07a
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• pp.261-263
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• 2013

본 논문에서는 회로 구현 디바이스에 따른 저전력 알고리즘을 제안한다. 제안한 알고리즘은 회로를 구현할 디바이스의 면적과 동작 주파수를 고려하여 저전력의 회로를 구현할 수 있는 방법이다. 저전력의 회로를 구현하기 위해 우선 구현하고자 하는 회로를 구성하고 있는 라이브러리들 중에서 최소의 면적을 가지고 있는 라이브러리들을 선택한다. 선택된 라이브러리들의 면적과 지연시간을 이용하여 회로 구현 대상 소자의 면적에 따라 필수 라이브러리들의 면적을 제외한 나머지 면적에 대해 복제가 가능한 라이브러리들의 수를 구한다. 최대의 지연시간을 가지고 있는 라이브러리부터 면적에 따라 차례로 복제를 수행하여 회로 전체의 수행시간을 감소시킨다. 회로 구현의 라이브러리들과 수가 결정되면 회로 동작이 허용하는 범위내에서 주파수를 조절하여 최소의 소모 전력을 갖는 회로를 구현한다. 본 논문에서는 제안한 알고리즘의 효율성을 입증하기 위해 RT 라이브러리를 이용하여 회로를 구현하여 비교 실험을 수행하였다. 실험결과 8.3%의 소모 전력이 감소된 결과를 나타내어 제안한 알고리즘의 우수성이 입증되었다.