Mode I steady crack growth is analyzed to determine the toughening due to domain switching in poled ferroelectric ceramics. A multi-axial, electromechanically coupled, incremental constitutive theory is applied to model the material behavior of the ferroelectric ceramic. The constitutive law is then implemented within the finite element method to study steady crack growth. The effects of poling direction, either out of plane or in plane, and poling magnitude on the fracture toughness are investigated. Results for the predicted fracture toughness, remanent strain and remanent polarization distributions, and domain switching zone shapes and sizes are presented. Finally, the model predictions are discussed in comparison to experimental observations.
Deflection routing is one of contention resolution of 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.
A Differentiated Service (Diffserv) model is proposed to support Differentiated Services end-to-end and several function terms are explained in detail in this paper. In order to implement Diffserv for Optical Burst Switched (OBS) networks, we present a kind of Diffserv code-point in control packet. A series of Diffserv rules are studied in detail, including the overwriting and update of Diffserv code-point and the scalability of Diffserv model. Also several issues which need to be improved are proposed.
Accurate phenomenological constitutive laws for ferroelectric ceramics that can be rapidly integrated are required for finite element models aiming to resolve the complex fields in ferroelectric devices. At best, phenomenological theories can provide a framework within which thermodynamic restrictions are satisfied and undetermined functions exist for "fitting" material behavior. The ultimate challenge in deriving a final constitutive law is to capture the physics of the material deformation and polarization processes within these undetermined functions. A number of micro-electromechanical models exist in the literature. These models are bases on domain switching events at the domain/grain level and then are generalized to polycrystalline behavior by averaging over many different domain/grain orientations. In this work it will be shown how information obtained from these micro-electromechanical models can be incorporated directly into the undetermined functions of a phenomenological theory.
In Optical Burst Switched (OBS) networks, the requirements on packet loss probability vary for different class users. In order to meet different packet loss probability demands, besides the traditional methods to support Differentiated services (DiffServ) by resource allocation and contention resolution, the scheduling of control
packets should also support DiffServ. A new type of scheduling strategy, Priority-based Weight Fair Queuing (PWFQ) scheduling strategy, is proposed. An equivalent analysis model is also presented to simplify the solving process of scheduling weight of each class. We also define a parameter, normalized deviation factor, to evaluate
the validity of our analysis model as well as the fairness of scheduling strategy on supporting DiffServ. Numerical results confirm that, it is feasible to analyze queue system, in which PWFQ scheduling strategy is adopted, with our equivalent model. At the same time, it confirms that our scheduling strategy performs well on providing fair DiffServ in terms of packet loss probability.
Optical Burst Switching combines the advantages of circuit switching and package switching, and it can improve the efficiency of system resource with high speed transmission and Qos. Now the rationale of OBS has been discussed a lot, and many schemes have been given. While there are still some key problems need to be resolved, such as in the model of IP over WDM, how to assemble the IP packages into burst that will be transmitted in the optical networks; and how to set the offset time between payload and its control package. In this paper, we provide a part randomized offset-time method to calculate the offset time upon the basis of: the network condition of the optical path that the payload will pass, the shaping scheme which is introduced to reduce the drop probability. At the same time, although there are many factors should be considered when setting the offset time, too sophisticated algorithm will be discarded. Because our ultimate end is to get equilibrium between the control complexity and bandwidth efficiency even some redundancy will be introduced in this method. We also consider a balance between end-to-end delay and blocking probability introduced by the new offset-time determination algorithm. At last, we will analyze the improvement in the network performance if the offset time has been set properly, especially when associated with delayed reservation technology.
The realization technology of a new kind of multi-wavelengths label optical packet switching technology is discussed. In this switching, optical header is labeled by several optical pulses at different wavelengths in the same optical communication channel band as optical payload. The optical transmitter with header generation and packet formation, receiver with data restoration and switching node with route processing are introduced. The switching principle is verified by a simplified experiment.
Optical label switching is a promising optical packet switching technology to ease the process of getting the route information from the packet label in optical domain. In this paper, a promising kind of multi-wavelength label is adopted and to which a simple label extraction and recognition technology through a array of tunable Fiber Bragg Gratings (FBGs) is presented.
Several tunable optical splitter techniques and some of their applications, including some prospective schemes, are discussed in this paper. It is explained by specific examples that all the variable transmission/reflection film technology, variable fiber couple length technology, acousto-optic/electro-optic deflection technology, and Mach-Zehnder interference technology are the capable technologies to realize tunable optical splitter, and tunable splitter technology to be applied to optical transmission networks, other devices and optical measurements.
Optical label switching is a promising optical packet switching technology to ease the process of getting the route information from the packet label in optical domain. In this paper, a promising kind of multi-wavelength label is adopted and to which a simple label extraction and recognition technology through a array of tunable Fiber Bragg Gratings (FBGs) is presented.
A kind of multi-wavelength labeled optical packet switching technology is presented, in which optical header is consisted of several optical pulses in different wavelength that are in the same WDM optical channel band as optical signal payload. A probable scheme to realize such optical switching as well as an optical switching node structure is proposed. A simplify principle experiment has proved the possibility of such switching method.
The basic technology of adaptive optical amplifier is introduced in this paper. How the performance of optical amplifier may meet the needs of application system is discussed according to the amplitude and shape of the input optical signal, the amplifier automatically adjusting the operating parameters. Taking the EDFA as an example, the feasibility to be realized technology of adaptive amplifier is investigated.
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