Survivability Performance Evaluation of WDM Networks with Wavelength Converters

Network Survivability is defined as the ability of a network to support the committed Quality of Services (QoS) continuously in the presence of different failure scenarios. Both availability and performance degradation of a system in presence of failure are integral components of survivability evaluation. Therefore, a composite model is presented for network survivability that includes system availability analysis to find out the cost due to system downtime, and system failure impact analysis to find out the transient performance degradation when failure occurs. A new analytical technique is presented to evaluate the excess loss due to failure (ELF) as the transient performance degradation when the system is operating in gracefully degraded states. Single and multiple link failures as well as node failures are considered. An algorithm is proposed to carry out the steady state availability analysis of a network even when the available paths between a pair of nodes are non-disjoint. A recursive generalized form of the availability algorithm when there are multiple paths available between a pair of nodes is presented. The availability model and the performance model are combined to construct a hierarchical model to evaluate the network survivability performance. Simulation results are used to validate the proposed model. A WDM network with wavelength conversion is considered as an example for this evaluation.     

Microstructural Evolution,Powder Characteristics,Compaction Behavior and Sinterability of Al 6061–B<Subscript>4</Subscript>C Composites as a Function of Reinforcement Content and Milling Times

Al 6061_100–x–x wt % B₄C (x = 0, 5, 10, 20, 30 and 40) composites, prepared by mechanical alloying and compacted at room temperature, have been used for the present investigation. The effects of B₄C content and milling time on the powder morphology, powder particle size, and other powder characteristics such as the apparent density, tap density, flow rate, cohesiveness, and hausner ratio are systematically investigated. The steady state of milling process is determined by observing the correlation between apparent densities and milling time explained by the morphological evolution of the powder particles during the milling process. The Hausner ratio (HR), estimated to evaluate friction between the particles, decreases with an increase in milling duration and B₄C content due to the changes in morphology and hardness of the powders. The compressibility behavior of post-compacts as a function of compaction pressure and the B₄C content was analyzed by using several linear and non-linear powder compaction equations. The linear Panelli and Ambrozio Filho, and non-linear Van Der Zwan and Siskens equations give the highest regression coefficients. The results are explained in terms of the plastic deformation capacity and plastic deformation coefficient of the powders, which are influenced by the hardness and the morphology of the powder. After compaction, the supersolidus liquid phase sintering was performed at various temperatures (585, 610 and 630°C) under high purity nitrogen atmosphere. The results revealed that the sinterability was degraded by increasing the reinforcement content, particularly above 10 wt % B₄C. Neutron radiography measurements conducted on the rolled composite sheet have revealed the uniform distribution of B₄C particles in the composite.     

Energy analysis of a trigeneration plant based on solid oxide fuel cell and organic Rankine cycle

In this study, energy analysis of a trigeneration plant based on solid oxide fuel cell (SOFC) and organic Rankine cycle (ORC) is conducted. The physical and thermodynamic elements of the plant include an SOFC, an ORC, a heat exchanger for the heating process and a single-effect absorption chiller for cooling. The results obtained from this study show that there is at least a 22% gain in efficiency using the trigeneration plant compared with the power cycle (SOFC and ORC). The study also shows that the maximum efficiency of the trigeneration plant is 74%, heating cogeneration is 71%, cooling cogeneration is 57% and net electricity is 46%. Furthermore, it is found that the highest net power output that can be provided by the trigeneration plant considered in this study is 540 kW and, the highest SOFC-AC power is 520 kW. The study reveals that the inlet pressure of the turbine has an insignificant effect on the efficiency. The study also examines the effect of both the SOFC current density and the SOFC inlet flow temperature on the cell voltage and voltage loss.     

Recent progress in synthesis of antifogging agents and their application to agricultural films: a review

Antifogging agents are very important for use on agricultural films. Fogging reduces crop yield and causes other negative effects. To overcome fogging problems on agricultural films, several approaches including surface coating and reactive extrusion methods have been used. To date, researchers have designed a variety of agents to prepare antifogging films. The mechanism and rules for the composition of such agents have also been reported. However, reported antifogging films do not exhibit satisfactory results. Therefore, antifogging methods require further improvement. In this review, different preparation methods for antifogging agents and films are summarized, along with the advantages and disadvantages of each method. Moreover, test methods for antifogging performance are introduced.     

High Temperature Crystallization Process of a-Si Thin-films on Aluminum Nitride Substrates

Crystallization of silicon (Si) from amorphous silicon (a-Si) on foreign substrates has been studied by various research institutes. Crystallization of silicon thin-films on foreign substrates acts as an active layer in silicon thinfilm solar cells. In this research, due to the compatibility of thermal stability and expansion coefficient with Si, we used an aluminum nitride (AIN) substrate as an alternative candidate to glass and other ceramic substrates. P-type amorphous Si 5 μm thin-film was deposited using an ebeam evaporator directly on AIN substrates. The deposited layer was annealed at high temperature (°C) with N2 environment in a conventional tube furnace. Optical characterization was done using an optical microscope to investigate the surface morphology of as-grown and annealed samples. A smoother surface with an average grain size of about 3–4 μm was formed after annealing. Reflectance parameters were measured by UV-vis spectrometry. UV-vis-NIR was studied on as-grown and annealed samples to calculate the quality factor of the Si thin-film which was about 84.4 %. X-ray diffraction (XRD) was used to determine the phase direction of the Si thin-film before and after thermal annealing. It was observed that FWHM varied from 7.73 to 9.30 cm?1, Raman shift was from 520 to 522 cm^?1, and the stressed level also changed from 180 to 540 Mpa after annealing at high temperature for a long time. Interestingly, a crystallinity fraction was achieved of about 90 % at 1100 °C.     

The Effect of Lithium Disilicate Ceramic Surface Neutralization on Wettability of Silane Coupling Agents and Adhesive Resin Cements

This in vitro study was aimed to evaluate the possible changes in wettability of an etched glass ceramic surface to silane primers, adhesive resin and resin cement when the surface had been neutralized by a special neutralizing agent after etching. Rectangular shaped specimens were cut from the CAD blocks of an e-max lithium disilicate glass ceramic, cut specimens were sequentially polished and ultrasonically cleaned. All the specimens were etched for 20 s with 5% hydrofluoric acid and ultrasonically cleaned. Specimens were randomly assigned to one control group (without neutralization) and one treatment group (with neutralization) having 20 specimens each. The specimens of each group were further divided into two subgroups having 10 specimens each and tested to determine the effect of neutralizing agent on wettability of experimental and commercial silanes. Each subgroup specimen was tested for wettability to adhesive resin and commercial resin cement. Data were analyzed using two-way ANOVA. Neutralizing the ceramic surface did not show a significant effect on wettability to the silanes and the resin based materials, but the experimental silane showed better wettability than the commercial silane. The adhesive resin had statistically significant lower contact angle (high wettability) values than the commercial resin cement. The results of the current study suggested that the neutralizing agent did not have an impact on the wettability of the etched ceramic. However, there were differences in wetting properties of the silane primers, and adhesive resin versus resin composite luting cements.     

Monocytes Expose Factor XIII-A and Stabilize Thrombi against Fibrinolytic Degradation

Factor XIII (FXIII) is a transglutaminase that promotes thrombus stability by cross-linking fibrin. The cellular form, a homodimer of the A subunits, denoted FXIII-A, lacks a classical signal peptide for its release; however, we have shown that it is exposed on activated platelets. Here we addressed whether monocytes expose intracellular FXIII-A in response to stimuli. Using flow cytometry, we demonstrate that FXIII-A antigen and activity are up-regulated on human monocytes in response to stimulation by IL-4 and IL-10. Higher basal levels of the FXIII-A antigen were noted on the membrane of the monocytic cell line THP-1, but activity was significantly enhanced following stimulation with IL-4 and IL-10. In contrast, treatment with lipopolysaccharide did not upregulate exposure of FXIII-A in THP-1 cells. Quantification of the FXIII-A activity revealed a significant increase in THP-1 cells in total cell lysates following stimulation with IL-4 and IL-10. Following fractionation, the largest pool of FXIII-A was membrane associated. Monocytes were actively incorporated into the fibrin mesh of model thrombi. We found that stimulation of monocytes and THP-1 cells with IL-4 and IL-10 stabilized FXIII-depleted thrombi against fibrinolytic degradation, via a transglutaminase-dependent mechanism. Our data suggest that monocyte-derived FXIII-A externalized in response to stimuli participates in thrombus stabilization.