KEYWORDS: Sensors, Sensor networks, Signal processing, Structural health monitoring, Sensing systems, Microcontrollers, Wireless communications, Data processing, Data storage, Structural monitoring
The traditional wired structural monitoring systems often suffer of various problems mainly related to the cabling which
limits their applicability. Then wireless monitoring system is needed. Most of the current wireless SHM systems are
mainly based on single-hop, and the network can only support a small number of nodes. For the realization of multi-hop,
low complexity and low power requirements, we introduce a system based on ZigBee protocol built on the
IEEE802.15.4, then design and implement the corresponding hardware and software of wireless sensor. The desired features are validated by experiments, including relatively high network capacity, low power consumption, and moderate data rate.
Now a day, cable plays a more and more important role in civil engineering. As an effective construction member, cable
is used in many long-span spatial structures. The cable tension measurement is required in the construction control,
assessment and long-term monitoring of cable-supported structures. Mostly, the detection uses the Fourier Transform to
get the frequencies of the cable, and then applies the vibration-based cable tension theory to evaluate the cable tension.
As a conventional method for cable tension measurement, the Fourier Transform can only be used in the static cable
tension force test, but not dynamic cable tension test. The cable dynamic tension describes the load-deformation behavior
of cables subjected to dynamic loading. It represents the intrinsic dynamic properties of cables. In order to get the
dynamic cable force, time-frequency analysis must be done. In this paper, wavelet transform tool is used to analyze the signal, and obtain the cable tension dynamic change along with the time.
KEYWORDS: Optical networks, Switches, Process control, Network architectures, Optical resolution, Switching, Packet switching, Control systems, Information science, Information technology
Good resource allocation strategy is able to alleviate the resource contention. Deflection routing is one of contention
resolution optical burst switching networks of good connectivity. But the offset time maybe not enough for reserve
resource if deflection routing adopted. Too much deflection adopted will deteriorate the network performance. Another
issue is how to determine if a contending burst will be deflected or discarded. In this paper, little Fiber Delay Lines
(FDL) is used to assure the offset time will be compensated in time, and an optimum scheme is proposed from three
aspects as if the network situation permits deflection, if contending burst is worthy to be hold continuously and the
impaction of alternative route on deflection. Numerical results show that our optimized deflection scheme can achieve
not only preferred deflection, but also to keep wavelength link from overloading. It balances the network load and
stabilizes the network performance some degree.
In this paper, we study the optimum configuration of FDL in OBS node, resource assignment ways of the node out-ports
and the allocation of optical buffer resource. We evaluate them in terms of burst loss probability. Through compare the
performance, the node port reserving modes and the use ways to FDLs are studied first. Analyze the impact of
granularity on performance in several resource assignment models. For the first time, void-filling and greedy reserving
are integrated investigated. Based on the results, the modified void-filling resource allocation scheme is proposed.
KEYWORDS: Optical networks, Switches, Process control, Network architectures, Switching, Packet switching, Control systems, Information science, Information technology, Civil engineering
Good resource allocation strategy is able to alleviate the resource contention. Deflection routing is one of contention
resolution of good connectivity optical burst switching networks. But the offset time maybe not enough for reserve
resource if deflection routing adopted. Too much deflection adopted will deteriorate the network performance, another
issue is how to determine if a contending burst will be deflected or discarded. In this paper, little Fiber Delay Lines
(FDL) is used to assure the offset time will be compensated in time, and an optimum scheme is proposed from three
aspects as if the network situation permits deflection, if contending burst is worthy to be hold continuously and the
impaction of alternative route on deflection. Numerical results show that our optimized deflection scheme can achieve
not only preferred deflection, but also to keep wavelength link from overloading. It balances the network load and
stabilizes the network performance some degree.
Damage detection is the core technique of structure health monitoring systems. Mostly, the detection is based on
comparison of initial signatures (frequency, mode shapes and so on) of intact structure with that of damaged structure.
The techniques based on the analysis of vibration data of structures have received great attention in recent years.
Generally, high-rise buildings have enough security under wind or some other natural conditions. Instances of damage
caused by routine work can be rarely found. But under earthquake, high-rise buildings damages may occur on some
weakness areas. In this paper, based on establishing the stiffness matrix of the columns and beams with joint damage, the
finite element model of the damaged frame structure is set up. Calculating the modal date by the finite element model
between the intact and damaged structure, simple and multi damages being imitated at the locations of the joints, the
curvature mode shape method is used to identify the damage. The numerical example shows that the structural damage
can be efficiency identified by using vibration characteristics of the building.
A new flexible broadcast optical switching structure (FBOSS) using tunable optical splitter is proposed. FBOSS supports both point-to-point and point-to-multipoint (broadcasting) connections, and any input optical signal can be broadcasted to any number of output optical ports without extra optical power loss. Its flexibilities of the optical port and optical wavelength help to enhance the capability of switching.
It has been proved that through burst segmenting, and thus dropping the segment of one burst that is overlapped with another burst, the packet loss probability will be significantly improved for optical burst switched networks. Based upon this, two main segment dropping strategies, head- and tail-dropping, can be used to resolve contention. In this paper, we point out that tail-dropping policy, which is adopted in most literatures, may not be a feasible solution, while head-dropping policy, even though it may make the packets to arrive out of order, is in deed a solution which can resolve the contention effectively. Moreover, with respect to tail-dropping policy, the increase of the disorder of packet arrivals for head-dropping policy is trivial. To support service differentiation and decrease the disorder of packet arrivals generated by contention resolution, we further propose a new threshold-based hybrid-assembly scheme. The most striking characteristic of the hybrid-assembly scheme is that the low and high packet classes are aggregated into one burst simultaneously. Once contention occurs, head-dropping policy is adopted to drop the overlapping packets. We describe the concrete implementation of QoS supporting, and the corresponding dropping strategy -- improved head-dropping policy, which aims at guaranteeing a better QoS support and a feasible implementation, is also detailed. Simulation results demonstrate that the proposed burst assembly scheme, together with the head-dropping policy, perform well in terms of performance metrics such as the average packet loss probability and service differentiation.
In this paper, we investigate the somewhat untraditional approach of contention resolution in WDM optical packet switches. The most striking characteristics of the developed switch architecture are that (1) contention resolution is achieved by a combined sharing of fiber delay-lines (FDLs) and tunable optical wavelength converters (TOWCs); (2) FDLs used for contention resolution is in non-degenerate form, i.e., buffers are achieved by non-uniform distribution of the delay lines; (3) TOWCs just can achieve wavelength conversion in partial continuous wavelength channels, i.e., sparse wavelength conversion. We describe and analyze the concrete configuration of FDLs and TOWCs under non-bursty and bursty traffic scenarios. Simulation results demonstrate that for a prefixed packet loss probability constraint, e.g., 10-6, the developed architecture provides a different point of view in the optical packet switching (OPS) design. That is, combined sharing of FDLs and TOWCs can, effectively, obtain a good tradeoff between the switch size and the cost, and TOWCs which are achieved in sparse form can also decrease the implementing complexity.
This paper investigates the implementing techniques concerning 2-to-1 node receiver for all-optical packet switching. We point out that the state-of-the-art technologies introduced in the literatures are all associated with one main limitation, i.e., even if two incoming packets are directed to the different ports and thus no contention will occur, they can not be directed to the output ports simultaneously. To overcome this problem, a novel node receiver model is proposed in this paper. This work presents a solution that makes use of fiber delay-lines (FDLs) which allow multiple packets to be concurrently stored or transmitted. With a novel switch control, it is shown that this solution is very efficient to resolve contention, and overcomes the limitation existing in the current models (e.g., Quadro, M-Quadro and COD architectures). We describe and analyze the concrete scheduling of the switches. Simulation results based on bursty and non-bursty traffic scenarios demonstrate that the proposed node architecture (1) performs well in terms of performance metrics such as packet loss probability; (2) has a simple control requirement. In addition, we find that the required number of the recirculating time of the packets is minimal.
Integrated routing is a routing approach to support the peer interconnection model in IP over WDM networks. To have a better network link load distribution and network usage in IP over WDM networks, in which network nodes may have the ability to handle traffic in fine granularities, it is important to take into account the combined routing at the IP and WDM layers. Based upon this, this paper develops an algorithm for integrated dynamic routing of bandwidth guaranteed paths in IP over WDM networks. For newly dynamic arriving requests, as the developed algorithm takes into account the combined topology and resource usage information at the IP and WDM layers, and the routing procedure makes full use of the statistic information of the users’ bandwidth requirement and considers carefully both the routing cost and the corresponding length of the routing path, thus a better link load balancing and network usage can be achieved. Simulation results show that the developed scheme performs well in terms of performance metrics such as the number of rejected demands and the network link load balancing.
In this paper, two switch models -- MOD1, employs a set of nondegenerate fiber delay-lines (FDLs) shared among the input lines, and MOD2, employs a set of degenerate FDLs and tunable wavelength converters (TOWCs) shared among the input lines, are proposed to handle contention. We demonstrate that for a prefixed packet loss probability constraints, e.g., 10-6, and for nonbursty traffic, if the wavelengths per fiber is no less than 8, a very small number of FDLs is sufficient to obtain a reasonable packet loss probability for both models, i.e., without the need to use TOWCs for MOD2, used for MOD1 equals to those of the FDLs and TOWCs used for MOD2, MOD2 performs much better than MOD1 even if no TOWC is used. With the increase of the average burst length, the number of TOWCs needed by MOD2 needs to be increased so as to maintain a reasonable packet loss probability. However, even for the traffic with high degree of burstness, MOD2 is still a cost effective and robust solution.
This paper proposes a new 2x1 node receiver architecture for all-optical packet switched networks, whose basic principle can be extended to construct a larger buffer if more 2x2 switches and fiber delay lines (FDLs) are available. The most striking characteristic of the architecture is that the buffer is achieved by a combined use of feed-forward and feedback FDLs. We describe and analyze the concrete two-stage FDL architecture which is the cheapest and simplest multi-stage solution. As for control strategy, we demonstrate that bottom control strategy (BCS), which uses FDL that is arranged in the feed-forward form when both feed-forward and feedback FDLs are available, is a more robust solution against bursty and non-bursty traffic. Simulation results show that the developed scheme (1) performs well in terms of performance metrics such as packet loss probability; (2) has a simpler control requirement and a better packet loss probability than M-Quadro architecture.
In this paper, we analyze the drawback of tail-dropping contention resolution in optical burst switched networks. Once contention occurs, we adopt modified head-dropping policy to resolve contention. This policy drops the head of the contending burst only if the overlapping region of the two bursts is less than the whole contending burst size, otherwise drops the whole contending burst. In order to have a better support of differentiated service, a new burst assembly policy, namely, Priority-based Proportional Mixed Burst Assembly, is proposed. Simulation results show that the proposed scheme performs very well in terms of performance metrics such as the times of contention and packet loss probability.
A novel all-optical packet switching is presented. Adopting optical-controlled optical switch and multi-wavelength optical label technology, all the extraction of optical packet header, recognizing of route information and control of optical switch matrix can be processed in optical domain without O-E/E-O conversion. In this switching, the header label pulses are separated to different optical paths to control the optical-controlled optical switch matrix. According to different sequence and different wavelength of the header pulses, the different optical routes can be established, and a kind of all-optical packet switching is achieved.
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