• Structural Monitoring and Maintenance
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• 제2권4호
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• pp.399-418
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• 2015

Automated damage detection through Structural Health Monitoring (SHM) techniques has become an active area of research in the bridge engineering community but widespread implementation on in-service infrastructure still presents some challenges. In the meantime, visual inspection remains as the most common method for condition assessment even though collected information is highly subjective and certain types of damage can be overlooked by the inspector. In this article, a Frequency Response Functions-based model updating algorithm is evaluated using experimentally collected data from the University of Central Florida (UCF)-Benchmark Structure. A protocol for measurement selection and a regularization technique are presented in this work in order to provide the most well-conditioned model updating scenario for the target structure. The proposed technique is composed of two main stages. First, the initial finite element model (FEM) is calibrated through model updating so that it captures the dynamic signature of the UCF Benchmark Structure in its healthy condition. Second, based upon collected data from the damaged condition, the updating process is repeated on the baseline (healthy) FEM. The difference between the updated parameters from subsequent stages revealed both location and extent of damage in a "blind" scenario, without any previous information about type and location of damage.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2018년도 춘계학술발표대회
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• pp.69-72
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• 2018

최근 5G 네트워크의 출현은 전송속도의 진화에 따라 서비스를 확장하고 있는 추세이다. 네트워크에서 사용하는 단말의 수가 증가하며, 단말에서 사용하고 있는 서비스 수는 다양해지고 있다. 이러한 점은 이동성관리 연구가 필수적이며 다양한 기존 연구들이 있다. 하지만 기존 연구에서는 handover delay로 인한 QoE 저하 문제, 활성 링크 수 증가로 인한 패킷 손실 및 네트워크 자원 부족 문제점이 발생을 한다. 이러한 점을 해결하기 위해 단말에서 사용하는 flow 타입을 실시간과 비실시간 서비스로 구별한다. 이동성 요구사항을 필요로 하는 실시간 서비스 앵커를 설정하는 동작과정을 수행하여 라우팅의 경로를 최소화하여 네트워크에서 발생하는 여러 가지 문제점들을 해결한다. 본 논문에서는 수학적 수식을 통한 성능평가를 통해 기존 SDN 기반 이동성관리 보다 제안하는 아이디어가 handover delay 시간을 50% 줄일 수 있다는 점을 확인하였다.

• 한방재활의학과학회지
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• 제23권4호
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• pp.83-93
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• 2013

Objectives To present reviews of studies comparing surface-electromyography (SEMG) values between low back pain group and control group. Methods We searched 8 databases including KoreaMed, Google, KISS (Korean studies Information Service System), RISS (Research Information Sharing Service), OASIS (Oriental medicine Advanced Searching Integrated System), Pubmed, Ovid-MEDLINE and EMBASE. After searching, we conducted study selection by using inclusion and exclusion criteria and quality-assessment. We reviewed the selected studies concerning about the subject's measuring position, findings, sensitivities and specificities. Results 27 Studies were searched and reviewed. In static surface electromyography, more muscle activities observed in low back pain subjects than in controls. In dynamic surface electromyography, the low back pain subjects showed more muscle activites during flexion, while the control group showed more muscle activities during extension. Faster muscle fatigue observed in isometric muscle analysis. Conclusions Surface electromyography values will be able to be objective marker for evaluating low back pain. Further research is needed to determine additional unified protocol such as the type of SEMG and its directions.

• Journal of information and communication convergence engineering
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• 제10권3호
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• pp.231-236
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• 2012

For real-time wireless sensor network applications, it is essential to provide different levels of quality of service (QoS) such as reliability, low latency, and fault-tolerant traffic control. To meet these requirements, an (m,k)-firm based real-time routing protocol has been proposed in our prior work, including a novel local transmission status indicator called local DBP (L_DBP). In this paper, a fault recovery scheme for (m,k)-firm real-time streams is proposed to improve the performance of our prior work, by contributing a delay-aware forwarding candidates selection algorithm for providing restricted redundancy of packets on multipath with bounded delay in case of transmission failure. Each node can utilize the evaluated stream DBP (G_DBP) and L_DBP values as well as the deadline information of packets to dynamically define the forwarding candidate set. Simulation results show that for real-time service, it is possible to achieve both reliability and timeliness in the fault recovery process, which consequently avoids dynamic failure and guarantees meeting the end-to-end QoS requirement.

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.40-40
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• 2009

Construction firms have long sought success in the global construction market through diversifying revenue sources and project portfolios. The volume of international contracts has contributed to firms' sustained growth by mitigating the impact of the domestic market's cyclical nature. In spite of the importance of international construction, the uncertainty and dynamic changes surrounding global construction pose serious threats to global contactors. Over the last decade, the international construction industry has changed drastically in many ways, particularly including financial resource diversity, competition rules for the selection of contractors, and the terms of delivery systems requiring more competent total service providers. This paper investigates the important changes for global contractors through various documentation analysis as well as in-depth interviews with industry experts. This paper then analyzes the common strategies and lessons obtained from the cases of leading global contractors that have sustained their growth in the competitive global construction during the last decade. In addition, the authors further analyzed the comparisons between those firms and Korean contractors to discern any difference in sustaining their growth in the competitive market. It was found that those leading firms were quite proactive and responsive to changing markets by diversifying their market revenues to stabilize their revenue structure and enhancing their competency through a wide range of 'business convergence'. In addition, they significantly increased their upstream/downstream functional capabilities; hence becoming more competent service providers, able to grow in these rapidly changing market conditions. Finally, this paper benchmarks the critical strategies that support growth, which in turn can provide a strategic guideline for expansion into the global construction market.

• 한국정보과학회논문지:시스템및이론
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• 제31권8호
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• pp.432-444
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• 2004

본 논문에서는 분산 환경에서 TMO(Time-triggered Message-triggered Object) 기반의 객체그룹 모델을 구축하고, 본 모델을 적용한 분산 실시간 옹용 시뮬레이터를 개발하여 제공된 객체그룹 모델의 분산 실시간 서비스에 대한 수행성을 분석 및 평가한다. TMO는 실시간 특성을 자체적으로 갖는 실시간 서버객체이다. TMO 객체그룹의 정의는 네트워크상에 물리적으로 분산된 하나 또는 그 이상의 TMO들을 주어진 분산응용에 따라 논리적으로 재구성한 객체들의 집합이다. 이들 서버객채들의 그룹관리를 지원하기 위해, 제안한 TMO 기반의 객체그룹 모델은 임의의 객체그룹에 서버객체를 그를 구성원으로 등록/탈퇴 및 클라이언트로부터 서버객체의 접근권한의 추가/삭제 기능을 제공한다. 또한, 우리 모델은 단일뿐 아니라 중복 TMO들에 대한 적정객체 선정 및 동적바인딩 서비스를 지원하고, 실시간 객체인 TMO로부터 서비스를 요청하는 클라이언트들에 대한 실시간 스케줄링 서비스를 지원하도록 설계 및 구현되었다. 마지막으로, 본 모델을 적용하여 분산 실시간 응용의 한 예인 적기침입방어시스템(Defence System against Invading Enemy Planes, DSIEP) 시뮬레이터를 개발하고, 이로부터 TMO 기반의 객체그룹 모델이 제공할 수 있는 그룹 구성요소들에 대한 분산 서비스 정책들의 적응성과 실시간 서비스의 수행성을 분석하였다.

• 방송공학회논문지
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• 제25권1호
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• pp.94-104
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• 2020

현재 유무선 인터넷을 통한 미디어 소비는 대부분 ISO/IEC MPEG(Moving Picture Experts Group)에 의해 표준화된 미디어 스트리밍 방식인 DASH(Dynamic Adaptive Streaming over HTTP) 또는 이와 유사한 형태의 적응형 미디어 스트리밍(adaptive media streaming) 기술에 의해 시행되고 있다. 이들은 모두 ISP(Internet Service Provider)가 웹서비스를 원활하게 제공하기 위해 충분히 설치할 수밖에 없는 HTTP 캐시(cache)에 크게 의존한다. 결과적으로 미디어 스트리밍 사용자 증가에 따라 CDN(Contents Delivery Network) 사업자의 서버 증설 부담 대신 ISP의 HTTP 캐시 증설 부담이 커지게 되었다. 이로 인해, ISP들은 이러한 HTTP 증설 비용을 보전하기 위해 CDN 사업자에게 미디어 트래픽 비용을 부과하게 되었다. 최근 이러한 비용을 줄이고자 P2P(Peer-to-Peer) 통신을 함께 사용하는(P2P-assisted) DASH 방식이 제안되었다. 또한 이러한 P2P 통신 병용 DASH 시스템의 효율을 극대화하여 CDN 사업자의 비용을 최대한 절감시키는 피어 선택 알고리듬도 연구되었다. 그러나 이 알고리듬은 선택된 피어에게 부담을 집중시키는 경향이 있다. 본 논문에서는 피어의 부담을 여러 피어들에게 분산시키면서도 CDN 사업자의 비용 절감 수준을 적절하게 유지하는 새로운 피어 선택 알고리듬을 제안하고, 이를 WebRTC(Web Real-Time Communication) 표준 API를 활용한 웹기반 스트리밍 시스템에 구현한 후, 실험을 통해 제안한 알고리듬의 효용성을 검증하였다.

• 한국정보과학회논문지:소프트웨어및응용
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• 제34권5호
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• pp.431-446
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• 2007

복합 웹 서비스 선택은 서비스의 기능만을 명시한 추상 워크플로우에 바인딩 정보를 추가하여 주어진 QoS 요구사항을 만족하는 복합 웹 서비스를 구성하는 과정이다. 웹 서비스의 급격한 증가와 QoS가 동적으로 변하는 웹 서비스 환경을 고려할 때 주어진 QoS 요구사항을 만족하는 복합 웹 서비스의 빠른 선택이 중요하다. 본 논문은 워크플로우 분할에 기반하여 복합 웹 서비스를 빠르게 선택하는 방법을 제안한다. 제안된 방법은 추상 워크플로우를 두 개의 서브 워크플로우로 분할하여 선택 과정에서 고려되는 후보 서비스의 수를 줄인다. 분할된 워크플로우의 QoS 요구사항은 원래의 QoS 요구사항을 분해함으로서 생성한다. QoS 요구사항의 분해는 휴리스틱에 기반하기 때문에 워크플로우 분할 시 적절한 복합 웹 서비스를 선택하지 못할 가능성이 있다. 이러한 실패를 줄이기 위해 주어진 QoS 요구사항의 제약정도를 정의하고 적절한 제약정도를 가지는 요구사항에 한해 워크플로우를 분할한다. 서비스 선택은 mixed integer linear programming을 이용하여 해결한다. 실험 결과 제안된 워크플로우 분할 방법은 99% 이상의 성공률을 보였다. 특히 워크플로우 분할 시 모든 경우에 대해서 복합 웹 서비스를 보다 빠르게 선택하였으며 이때 선택된 복합 웹 서비스의 QoS는 최적 서비스와 5%미만의 차이를 보였다.

• International Journal of Computer Science & Network Security
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• 제21권11호
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• pp.345-353
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• 2021

Cloud computing represent a new era of computing that's forms through the combination of service-oriented architecture (SOA), Internet and grid computing with virtualization technology. Virtualization is a concept through which every cloud is enable to provide on-demand services to the users. Most IT service provider adopt cloud based services for their users to meet the high demand of computation, as it is most flexible, reliable and scalable technology. Energy based performance tradeoff become the main challenge in cloud computing, as its acceptance and popularity increases day by day. Cloud data centers required a huge amount of power supply to the virtualization of servers for maintain on- demand high computing. High power demand increase the energy cost of service providers as well as it also harm the environment through the emission of CO₂. An optimization of cloud computing based on energy-performance tradeoff is required to obtain the balance between energy saving and QoS (quality of services) policies of cloud. A study about power usage of resources in cloud data centers based on workload assign to them, says that an idle server consume near about 50% of its peak utilization power [1]. Therefore, more number of underutilized servers in any cloud data center is responsible to reduce the energy performance tradeoff. To handle this issue, a lots of research proposed as energy efficient algorithms for minimize the consumption of energy and also maintain the SLA (service level agreement) at a satisfactory level. VM (virtual machine) consolidation is one such technique that ensured about the balance of energy based SLA. In the scope of this paper, we explore reinforcement with fuzzy logic (RFL) for VM consolidation to achieve energy based SLA. In this proposed RFL based active VM consolidation, the primary objective is to manage physical server (PS) nodes in order to avoid over-utilized and under-utilized, and to optimize the placement of VMs. A dynamic threshold (based on RFL) is proposed for over-utilized PS detection. For over-utilized PS, a VM selection policy based on fuzzy logic is proposed, which selects VM for migration to maintain the balance of SLA. Additionally, it incorporate VM placement policy through categorization of non-overutilized servers as- balanced, under-utilized and critical. CloudSim toolkit is used to simulate the proposed work on real-world work load traces of CoMon Project define by PlanetLab. Simulation results shows that the proposed policies is most energy efficient compared to others in terms of reduction in both electricity usage and SLA violation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권11호
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• pp.3565-3583
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• 2022

The task scheduling problem has received a lot of attention in recent years as a crucial area for research in the cloud environment. However, due to the difference in objectives considered by service providers and users, it has become a major challenge to resolve the conflicting interests of service providers and users while both can still take into account their respective objectives. Therefore, the task scheduling problem as a bi-objective game problem is formulated first, and then a task scheduling model based on the bi-objective game (TSBOG) is constructed. In this model, energy consumption and resource utilization, which are of concern to the service provider, and cost and task completion rate, which are of concern to the user, are calculated simultaneously. Furthermore, a many-objective evolutionary algorithm based on a partitioned collaborative selection strategy (MaOEA-PCS) has been developed to solve the TSBOG. The MaOEA-PCS can find a balance between population convergence and diversity by partitioning the objective space and selecting the best converging individuals from each region into the next generation. To balance the players' multiple objectives, a crossover and mutation operator based on dynamic games is proposed and applied to MaPEA-PCS as a player's strategy update mechanism. Finally, through a series of experiments, not only the effectiveness of the model compared to a normal many-objective model is demonstrated, but also the performance of MaOEA-PCS and the validity of DGame.