• Structural Engineering and Mechanics
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• v.46 no.3
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• pp.387-402
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• 2013

A dynamic load protocol has been used to experimentally simulate fatigue behavior in cold-formed metal panels with screwed connections under wind loading. The specific protocol adopted is an adaptation of SIDGERS, originally developed for non-metallic membranes, which is composed of levels each under increasing load values. A total of 19 tests were performed on 3.35 m long by 0.91 m wide panels, identified as Type B-wide rib and Type E, both with screw connections at the edge and at the center, thus conforming two-span specimens. In some configurations the panels were fixed at the valleys, whereas crest-fixed connections were also investigated. Reinforcing the connections by means of washers was also investigated to evaluate their efficiency in improving fatigue capacity. The experimental results show maximum load capacities in improved connections with washers of approximately twice of those with classical connections.

• IEMEK Journal of Embedded Systems and Applications
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• v.1 no.1
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• pp.8-13
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• 2006

In mobile ad hoc networks, most of on demand routing protocols such as DSR and AODV do not deal with traffic load during the route discovery procedure. To achieve load balancing in networks, many protocols have been proposed. However, existing load balancing schemes do not consider the remaining available buffer size of the interface queue, which still results in buffer overflows by congestion in a certain node which has the least available buffer size in the route. To solve this problem, we propose a load balancing protocol called Dynamic Congestion Aware Routing Protocol (DCAR) which monitors the remaining buffer length of all nodes in routes and excludes a certain congested node during the route discovery procedure. We also propose two buffer threshold values to select an optimal route selection metric between the traffic load and the minimum hop count. Through simulation study, we compare DCAR with other on demand routing protocols and show that the proposed protocol is more efficient when a network is heavily loaded.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.868-870
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• 2004

ad-hoc 망에서 라우팅 프로토콜의 부하균등(load balancing)은 이동성과 전송 지연사이의 trade-off로 인하여 성능 관점에서 중요한 이슈가 되어왔다. 부하균등을 고려한 SLAP(Simple Load-balancing Ad-hoc routing Protocol)이 제안되었으나 혼잡이 발생하거나 망의 토폴로지가 변화하였을 때 유연하게 대처하지 못한다. 본 논문에서는 ad-hoc 망에서 트래픽 혼잡 제어와 망의 이동성에 적응하기 위하여 동적인 임계치를 사용하는 부하균등 라우팅 프로토콜을 제안하였다. 제안된 프로토콜은 성능은 GloMoSim으로 시뮬레이션을 수행하여 AODV, DSR, SLAP과 지연, 패킷 전송률 등을 비교하여 평가하였다.

• Journal of Information Processing Systems
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• v.7 no.1
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• pp.53-62
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• 2011

With the steady growth of mobile technology and applications, demand for more storage in mobile devices has also increased. A lightweight block-level protocol, Internet Advanced Technology Attachment (iATA), has been developed to deliver a cost-effective storage network solution for mobile devices to obtain more storage. This paper seeks to contribute to designing and implementing Load Balancing (LB), Network Monitoring (NM) and Write Replication (WR) modules to improve the protocol's scalability and data availability. LB and NM modules are invoked to collect system resources states and current network status at each associate node (server machine). A dynamic weight factor is calculated based on the collected information and sent to a referral server. The referral server is responsible to analyze and allocate the most ideal node with the least weight to serve the client. With this approach, the client can avoid connecting to a heavily loaded node that may cause delays in subsequent in-band I/O operations. Write replication is applied to the remaining nodes through a WR module by utilizing the Unison file synchronization program. A client initially connected to node IP A for write operations will have no hindrances in executing the relevant read operations at node IP B in new connections. In the worst case scenario of a node crashing, data remain recoverable from other functioning nodes. We have conducted several benchmark tests and our results are evaluated and verified in a later section.

• Journal of Information Processing Systems
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• v.6 no.3
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• pp.269-294
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• 2010

The interconnection of mobile devices in urban environments can open up a lot of vistas for collaboration and content-based services. This will require setting up of a network in an urban environment which not only provides the necessary services to the user but also ensures that the network is secure and energy efficient. In this paper, we propose a secure, energy efficient dynamic routing protocol for heterogeneous wireless sensor networks in urban environments. A decision is made by every node based on various parameters like longevity, distance, battery power which measure the node and link quality to decide the next hop in the route. This ensures that the total load is distributed evenly while conserving the energy of battery-constrained nodes. The protocol also maintains a trusted population for each node through Dynamic Trust Factor (DTF) which ensures secure communication in the environment by gradually isolating the malicious nodes. The results obtained show that the proposed protocol when compared with another energy efficient protocol (MMBCR) and a widely accepted protocol (DSR) gives far better results in terms of energy efficiency. Similarly, it also outdoes a secure protocol (QDV) when it comes to detecting malicious nodes in the network.

• Journal of Korean Institute of Industrial Engineers
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• v.34 no.2
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• pp.140-150
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• 2008

Point Coordination Function (PCF) of the IEEE 802.11 protocol providing a centrally-controlled polling-based multiple access to a wireless channel is very efficient in high load conditions. However, its performance degrades with increasing the number of terminals and decreasing the load, because of wastes related to unsuccessful polling attempts. To solve the problem, we propose and study analytically the generic dynamic polling policy using backoff concept. For this aim, we develop Markov models describing the network queues changes, what allows us to estimate such performance measures as the average MAC service time and the average MAC sojourn time, to show the dynamic polling efficiency and to tune optimally the backoff rule.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.12
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• pp.1-8
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• 1994

In this paper, we hve compare the performance of DAR(Dynamic Adaptive Routing) with that of FSR(Flooding Search Routing) to select an adequate routing protocol in circuit-switched networs. As a performance factor, we have considered call setup time, which is the key factor of performance evaluation in circuit switched networks. We have evaluated the performance of two methods in grid topology circuit-switched networks using a commn channel signaling scheme, as application examples. As results, FSR method shows better performance than DAR method under light traffic load, when the number of links by which call has passed increases, but DAR method represents better performance than FSR method under heavy traffic load or large networks because of redundant packets.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.10
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• pp.2171-2180
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• 1997

In this paper, we proposed a MAC protocol called P/S-DCA that using dynamci channel allocation scheme for supports the multimedia traffic in wireless ATM, and analysis theoretically the throughput and delay of up/down link according to varying the down traffic load. To evaluate and the dynamic channel allocation scheme, simulations are executed with varying down traffic load. The results are proved that system capacity is improved better than PRMA and C-PRAM. The system capacity, denoting by $M_{0.01}$, is defined as the maximum number of conversations which can be supported under constraint of packet dropping probability no more than 1%. It is shown that the values of $M_{0.01}$ for ${\lambda}_{d}=0.5,\;{\lambda}_{d}=0.2\;{\lambda}_{d}=0.1\;{\lambda}_{d}=0.001$ are about 43, 69, 77 and 83, respectively. This indicates that P/S-DCA protocol achieves a significant improvement in system capacity relative to PRMA and C-PRMA protocol.

• Structural Engineering and Mechanics
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• v.49 no.2
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• pp.237-259
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• 2014

Wind-induced failure around screwed connections has been documented in roof and wall cladding systems made with steel sheet cold-formed panels during high wind events. Previous research has found that low cycle fatigue caused by stress concentration and fluctuating wind loads is responsible for most such failures. A dynamic load protocol was employed in this work to represent fatigue under wind effects. A finite element model and fatigue criteria were implemented and compared with laboratory experiments in order to predict the fatigue failure associated with fluctuating wind loads. Results are used to develop an analytical model which can be employed for the fatigue analysis of steel cold-formed cladding systems. Existing three dimensional fatigue criteria are implemented and correlated with fatigue damage observed on steel claddings. Parametric studies are used to formulate suitable yet simple fatigue criteria. Fatigue failure is predicted in different configurations of loads, types of connections, and thicknesses of steel folded plate cladding. The analytical model, which correlated with experimental results reported in a companion paper, was validated for the fatigue life prediction and failure mechanism of different connection types and thicknesses of cold-formed steel cladding.

• Journal of the Korea Society of Computer and Information
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• v.14 no.3
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• pp.113-119
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• 2009

In this paper, we proposed an efficient TDMA scheduling algorithm for a clustered Wireless Sensor Network. Since some previous algorithms used unnecessary idle period and schedule period in each frame. It became an overhead that might consume unexpected energy and delay data transmission. To solve this problem, a dynamic scheduling algorithm according to the number of member nodes and node traffic load within a cluster was suggested. Our proposed DS-MAC(Dynamic Scheduling MAC) could save energy and reduce transmission delay Then DS-MAC was analyzed mathematically to compare with the previous algorithms.