Improving the Reliability of Software-Defined Networks with Distributed Controllers Through Leader Election Algorithm and Colored Petri-Net

Wireless Personal Communications - Software-Defined Networks (SDNs) are developed to compensate the complicated function of the controlling parts of the given network elements and making the...     

Decision Making for Reduction of Nonproductive Time through an Integrated Lost Circulation Prediction

Abstract

An increase in world energy demand forces oil and gas companies to drill deeper in order to produce more oil and gas. This requires drilling layers with various characteristics and results in drilling problems as drilling progresses. Lost circulation and stuck pipes are the most common drilling problems, which are always challenging. Mechanical pipe sticking is likely to occur after complete loss. Time that is spent dealing with such problems is called nonproductive time. It is also defined as time during which drilling is ceased or the penetration rate is very low. This definition includes consequences of lost circulation.

Lost circulation is likely to take place throughout drilling operations and even during primary cementing due to direct contact of the drilling fluid with the formation along with severe pressure pulses due to pipe movement or onset of circulation after connection, which sometimes goes over hundreds of psi. Lost circulation results in a loss of money, especially when severe losses are experienced. Partial mud loss, or even complete mud loss, can occur in low fluxes, which can lead to well blowout or severe pipe sticking. Freeing the pipes may involve a week or even more time from the rig. Thus, accurate information on returned fluid and recording mud loss rate can help prevent drilling problems. A recent solution to dealing with lost circulation is an underbalanced drilling technique, although this is not applicable in some countries due to lack of technology or great expenses. Thus, prediction of loss severity can bring the opportunity of decision making true for adjusting drilling fluid content and operational parameters. Several factors while drilling will govern how severe mud loss would occur. These make analytical modeling of lost circulation complicated. Employing artificial intelligence can be a leeway with proven capability and accuracy. In this article, the operational parameters in a Middle Eastern oilfield are used for prediction of the mud loss severity along different sectors of the oilfield. Cross-validation showed fairly good compatibility with reality.     

Improving the reliability of Byzantine fault‐tolerant distributed software‐defined networks

This paper presents a method to improve the reliability and fault tolerance of distributed software‐defined networks. This method is called “BIRDSDN (Byzantine‐Resilient Improved Reliable Distributed Software‐Defined Networks).” In BIRDSDN, a group communication is implemented among the controllers of the whole clusters. This method can detect the crash failure and Byzantine failure of any controller and undertakes a fast detection and recovery scheme to select the controllers to take over the orphan switches. BIRDSDN takes into account the reliability of the nodes considering the failure probability of intracluster and intercluster links, topology, load, and latency. The numerical results show that this approach performs better than the other approaches regarding failure detection, recovery, latency, throughput, reliability, and packet loss.     

Kinetics of murine decidual dendritic cells

Dendritic cells (DCs) are professional antigen presenting cells (APC) capable of induction of primary immune responses as well as immunologic tolerance. Myeloid and lymphoid subsets of murine DCs are able to shift cytokine responses of T cells toward Th2 and Th1 profiles respectively. Thus, DCs would be suitable candidates to mediate the balance of maternal immune responses to conception. We analyzed pregnancy-related variations in uterus and splenic DCs in a murine model. C57BL/6-mated Balb/c female mice with vaginal plugs were scarified at early, middle, and late pregnancy. Frozen sections of uterus and spleen at each stage of pregnancy were immunostained with CD11c- and MHC-II-specific antibodies. Two-color immunohistochemistry was also carried out using anti-CD11c and one of the antibodies against CD11b, CD8alpha, CD86, and DEC-205. Using morphometric analysis, the average density of DCs and relative percentage of myeloid (CD11c+, CD11b+) and lymphoid DCs (CD11c+, CD8a+) were determined at each stage. Our results showed that DCs are present throughout the pregnancy in decidua. The average density of decidual DCs at early pregnancy was significantly higher relative to middle and late gestation or to those of endometrial DCs of non-pregnant mice. Interestingly, the average density of decidual and splenic DCs, followed the same variations at different stages of pregnancy. The relative percentage of decidual lymphoid DCs (LDC) was significantly higher at mid-gestation when compared with other stages of pregnancy or non-pregnant mice. Inversely, the frequency of myeloid DCs (MDC) and the MDC/LDC ratio were statistically lower at the middle stage of pregnancy. A majority of decidual DCs expressed MHC-II and CD86. At early pregnancy, DCs were more concentrated subadjacent to the luminal epithelial layers, whereas at mid-or late gestation, DCs were randomly distributed in the stroma and around the epithelium. Mid-pregnancy period was a critical point with regard to splenic DCs kinetics, as both the average density of DCs and the frequency of MDCs decreased significantly when compared with early or late pregnancy, although the relative percentage of splenic LDCs did not change. Our data suggest that the balance of MDC and LDC is finely tuned throughout pregnancy, pointing an eminent immunoregulatory role of DCs in the maintenance of pregnancy.     

Sunlight photodecolorization of a mixture of Methyl Orange and Bromocresol Green by CuS incorporated in a clinoptilolite zeolite as a heterogeneous catalyst

Photocatalytic activity of CuS incorporated into an Iranian clinoptilolite (CuS-Cp) was studied for decolorization of a mixture of Methyl Orange and Bromocresol Green under sunlight irradiation. All samples were characterized by XRD, FTIR, DRS and TG/DTG techniques. The effect of some key experimental parameters such as: amount of the catalyst (0.05–5 g L^?1), initial concentration of dyes (5–30 mg L^?1), solution pH (1–11) and also dosage of H₂O₂ and KBrO₃ was studied on the decolorization extent. The extent of decolorization was estimated from the residual concentration by spectrophotometrically and it was confirmed by the reduction of chemical oxygen demand (COD).     

Optimizing the power-sensitivity trade-off in TRF receivers

There is an inevitable trade-off between the sensitivity of an RF receiver and its total power consumption, meaning that in order to design a receiver with a high sensitivity, more power must be dissipated. Ultra-low power receivers in general and wake-up receivers in particular require a sensitivity of better than ?70 dBm while the power consumption should be as low as possible at the same time. Therefore, obtaining an optimum point where these two design specifications are met is of great interest. In this work, we present a design methodology for the tuned radio frequency (TRF) receiver topology, which yields an optimum power-sensitivity product for given design parameters. The most interesting outcome of this study is finding an optimum number of amplifier stages at the front-end of the receiver that leads to a minimum power-sensitivity product. It is shown through analytical/graphical approach in Matlab that the optimum number of stages resulting in the minimum power-sensitivity product can be different from the optimum number of amplifier stages leading to the maximum overall gain-bandwidth product. These results are also verified through circuit-level simulation with Cadence Spectre for practical design parameters. According to our study, the minimum power-sensitivity product occurs for a two-stage amplifier with moderate gain at the front-end of the TRF receiver.