• Journal of Information Processing Systems
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• 제19권5호
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• pp.702-712
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• 2023

Load balancing plays a crucial role in ensuring the stable operation of information management systems during periods of high user access requests; therefore, load balancing approaches should be reasonably selected. Moreover, appropriate load balancing techniques could also result in an appropriate allocation of system resources, improved system service, and economic benefits. Nginx is one of the most widely used loadbalancing software packages, and its deployment is representative of load-balancing application research. This study introduces Nginx into an educational administration system, builds a server cluster, and compares and sets the optimal cluster working strategy based on the characteristics of the system, Furthermore, it increases the stability of the system when user access is highly concurrent and uses the Nginx reverse proxy service function to improve the cluster's ability to resist illegal attacks. Finally, through concurrent access verification, the system cluster construction becomes stable and reliable, which significantly improves the performance of the information system service. This research could inform the selection and application of load-balancing software in information system services.

• Journal of Communications and Networks
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• 제15권1호
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• pp.102-110
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• 2013

This paper considers a cooperative orthogonal frequency division multiple access (OFDMA)-based cognitive radio network where the primary system leases some of its subchannels to the secondary system for a fraction of time in exchange for the secondary users (SUs) assisting the transmission of primary users (PUs) as relays. Our aim is to determine the cooperation strategies among the primary and secondary systems so as to maximize the sum-rate of SUs while maintaining quality-of-service (QoS) requirements of PUs. We formulate a joint optimization problem of PU transmission mode selection, SU (or relay) selection, subcarrier assignment, power control, and time allocation. By applying dual method, this mixed integer programming problem is decomposed into parallel per-subcarrier subproblems, with each determining the cooperation strategy between one PU and one SU. We show that, on each leased subcarrier, the optimal strategy is to let a SU exclusively act as a relay or transmit for itself. This result is fundamentally different from the conventional spectrum leasing in single-channel systems where a SU must transmit a fraction of time for itself if it helps the PU's transmission. We then propose a subgradient-based algorithm to find the asymptotically optimal solution to the primal problem in polynomial time. Simulation results demonstrate that the proposed algorithm can significantly enhance the network performance.

• Journal of Astronomy and Space Sciences
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• 제24권4호
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• pp.417-430
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• 2007

IGS(International GNSS Service) 산출물 생성에 사용되는 지상국의 선정은 산출물 정밀도에 영향을 미칠 수 있는 중요한 과정이다. 지상국 선정에 있어서 지상국 자료의 품질이 좋지 않은 지상국들은 제외시켜야 하며, 전 지구적으로 고른 분포를 갖도록 선정해야 한다. 이 연구에서는 12개의 지상국 망을 이용하여 GPS 위성의 궤도력을 산출하고 지상국 선정이 GPS 위성의 궤도력 산출에 미치는 영향을 분석하였다. 지상국의 성능을 판단하기 위해 자료의 품질을 조사하였으며, 관측개수, 사이클 슬립 개수 및 L1, L2에 대한 의사거리의 다중경로 오차를 고려하였다. 고른 지역분포를 갖는 지상국 선정을 위해서 SOD(Second Order Design) 방법을 사용하여 Taylor-Karman 구조로부터 정의되는 기준 행렬과 여행렬(cofactor matrix)의 차이가 가장 작도록 지상국들을 선정하였다.

• 한국정보과학회논문지:정보통신
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• 제33권2호
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• pp.183-192
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• 2006

이 논문은 QoS (Quality of Service) 네트워크 서비스를 위한 우선순위 방식의 스케줄링에서, 각 서비스 레벨의 가격을 정하는 문제를 분석한다. 특히 본 논문에서는 균형 분석 (equilibrium analysis)에 근거한 가격정책의 문제점을 파악하는 것에 중점을 둔다. 균형분석은 다음과 같은 두 가정하에 이루어진다. 첫째, 각각의 사용자들이 시스템 전체에 미치는 영향은 극히 미약하여 무시할 수 있다. 둘째, 사용자들은 전체 시스템 상태에 대한 최신의 정보를 알고 있다. 그러나 이러한 가정들은 실제 상황을 정확하게 반영하지 못하는 경우가 종종 있고, 따라서 균형분석에 의한 가격의 결정은 문제점이 있다고 본다. 본 논문에서는 시스템 작동상황을 분석하기 위해 '동적모델'을 개발하고, 이를 이용하여 현존하는 균형분석 방법의 정확성을 평가하였다. 연구결과에 의하면 균형분석은 실제적인 환경에서의 시스템의 작동 현황을 정확하게 반영하지 못하는 경우가 많은 것으로 나타났다.

• 산업경영시스템학회지
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• 제21권48호
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• pp.37-52
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• 1998

In many distribution systems important cost reductions and/or service improvements may be achieved by adopting an efficient inventory policy and proper selection of facilities. These efficiency improvements and service enhancements clearly require an integrated approach towards various logistical planning functions. The areas of inventory control and transportation planning need to be closely coordinated. The purpose of this paper is to construct an integrated model that can minimize the total cost of the transportation and inventory systems between multiple origin and destination points, where in origin point i has the supply of commodities and in destination point j requires the commodities. In this case, demands of the destination points are assumed random variables which have a known probability distribution. Using the lot-size reorder-point policy and the safety stock level that minimize total cost we find optimal distribution centers which transport the commodities to the destination points and suggest an optimal inventory policy to the selected distribution center. We also show if a demand greater than one unit will occur at a particular time, we describe the approximate optional replenishment policy from computational results of this lot-size reorder-point policy. This model is formulated as a 0-1 nonlinear integer programming problem. To solve the problem, this paper proposes heuristic computational procedures and a computer program with UNIX C language. In the usefulness review, we show the meaning and validity of the proposed model and exhibit the results of a comparison between our approach and the traditional approach, respectively.

• International Journal of Advanced Culture Technology
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• 제10권1호
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• pp.230-235
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• 2022

This study is to select an optimal object detection algorithm for designing a self-checkout counter to improve the inconvenience of payment systems for products without existing barcodes. To this end, a performance comparison analysis of YOLO v2, Tiny YOLO v2, and the latest YOLO v5 among deep learning-based object detection algorithms was performed to derive results. In this paper, performance comparison was conducted by forming learning data as an example of 'donut' in a bakery store, and the performance result of YOLO v5 was the highest at 96.9% of mAP. Therefore, YOLO v5 was selected as the artificial intelligence object detection algorithm to be applied in this paper. As a result of performance analysis, when the optimal threshold was set for each donut, the precision and reproduction rate of all donuts exceeded 0.85, and the majority of donuts showed excellent recognition performance of 0.90 or more. We expect that the results of this paper will be helpful as the fundamental data for the development of an automatic payment system using AI self-service technology that is highly usable in the non-face-to-face era.

• ETRI Journal
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• 제40권3호
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• pp.291-302
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• 2018

The deployment of an incremental hybrid decode-amplify and forward relaying scheme is a promising and superior solution for cellular networks to meet ever-growing network traffic demands. However, the selection of a suitable relaying protocol based on the signal-to-noise ratio threshold is important in realizing an improved quality of service. In this paper, an incremental hybrid relaying protocol is proposed using polar codes. The proposed protocol achieves a better performance than existing turbo codes in terms of capacity. Simulation results show that the polar codes through an incremental hybrid decode-amplify-and-forward relay can provide a 38% gain when ${\gamma}_{th(1)}$ and ${\gamma}_{th(2)}$ are optimal. Further, the channel capacity is improved to 17.5 b/s/Hz and 23 b/s/Hz for $2{\times}2$ MIMO and $4{\times}4$ MIMO systems, respectively. Monte Carlo simulations are carried out to achieve the optimal solution.

• 물과 미래
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• 제28권1호
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• pp.133-144
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• 1995

본 연구의 목적은 실시간 자료수집 시스템의 일환으로서 어떤 유역에 존재하는 기존의 강우관측지점으로로부터 유역평균강우량을 산정할 때나 이를 강우-유출 모형의 입력치로 사용할 때 필요한 강우관측지점의 수와 위치를 선정하는 방법을 제시하였다. 유역평균강우량 산정방법은 미국 국립기상청이 제안한 가중치방법을 사용하였다. 강우관측지점 수에 따른 국부적인 최적위치선정은 서로 다른 두가지 방법으로 추적되었다. 유량예측을 위한 강우관측지점의 최적위치와 수를 결정하기 위하여 실제 실무에서 적용하고 있는 강우-유출 모형을 사용하였다.

• 한국통신학회논문지
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• 제30권5A
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• pp.370-375
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• 2005

인터넷 및 통신망 국제표준 단체들은 자신들의 망에서 서비스 품질 보장형 기능을 제공하기 위한 방안으로써 공통적으로 리키버킷에 의한 입력 트래픽 정의 방법을 채택하고 있다. 반면, 그동안 연구결과는 멀티미디어 트래픽의 버스트특성이 시간적으로 광범위한 준위에 걸쳐 있음을 확인하고 있다. 이러한 두개의 상반되는 현실을 해결하기 위하여 본 논문에서는 임계 시준위 개념을 사용한 표준적 트래픽 기술자계산 방법을 제안하고 이를 시뮬레이션을 통하여 분석하였다. 제안된 알고리듬은 지연치가 주어진 상태에서 최상의 성능을 얻음을 수학적으로 증명하였고, 실제 시스템 응용에 대하여 제안하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권4호
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• pp.1911-1930
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• 2017

Overlay routing has emerged as a promising approach to improve reliability and efficiency of the Internet. The key to overlay routing is the placement and maintenance of the overlay infrastructure, especially, the selection and placement of key relay nodes. Spurred by the observation that a few relay nodes with high betweenness centrality can provide more optimal routes for a large number of node pairs, we propose a resilient routing overlay network construction method by introducing Super-Relay nodes. In detail, we present the K-Minimum Spanning Tree with Super-Relay nodes algorithm (SR-KMST), in which we focus on the selection and connection of Super-Relay nodes to optimize the routing quality in a resilient and scalable manner. For the simultaneous path failures between the default physical path and the overlay backup path, we also address the selection of recovery path. The objective is to select a proper one-hop recovery path with minimum cost in path probing and measurement. Simulations based on a real ISP network and a synthetic Internet topology show that our approach can provide high-quality overlay routing service, while achieving good robustness.