An Optimal Medium Access Control with Partial Observations for Sensor Networks

We consider medium access control (MAC) in multihop sensor networks, where only partial information about the shared medium is available to the transmitter. We model our setting as a queuing problem in which the service rate of a queue is a function of a partially observed Markov chain representing the available bandwidth, and in which the arrivals are controlled based on the partial observations so as to keep the system in a desirable mildly unstable regime. The optimal controller for this problem satisfies a separation property: we first compute a probability measure on the state space of the chain, namely the information state, then use this measure as the new state on which the control decisions are based. We give a formal description of the system considered and of its dynamics, we formalize and solve an optimal control problem, and we show numerical simulations to illustrate with concrete examples properties of the optimal control law. We show how the ergodic behavior of our queuing model is characterized by an invariant measure over all possible information states, and we construct that measure. Our results can be specifically applied for designing efficient and stable algorithms for medium access control in multiple-accessed systems, in particular for sensor networks

FHJ: A Formal Model for Hierarchical Dispatching and Overriding

Multiple inheritance is a valuable feature for Object-Oriented Programming. However, it is also tricky to get right, as illustrated by the extensive literature on the topic. A key issue is the ambiguity arising from inheriting multiple parents, which can have conflicting methods. Numerous existing work provides solutions for conflicts which arise from diamond inheritance: i.e. conflicts that arise from implementations sharing a common ancestor. However, most mechanisms are inadequate to deal with unintentional method conflicts: conflicts which arise from two unrelated methods that happen to share the same name and signature. This paper presents a new model called Featherweight Hierarchical Java (FHJ) that deals with unintentional method conflicts. In our new model, which is partly inspired by C++, conflicting methods arising from unrelated methods can coexist in the same class, and hierarchical dispatching supports unambiguous lookups in the presence of such conflicting methods. To avoid ambiguity, hierarchical information is employed in method dispatching, which uses a combination of static and dynamic type information to choose the implementation of a method at run-time. Furthermore, unlike all existing inheritance models, our model supports hierarchical method overriding: that is, methods can be independently overridden along the multiple inheritance hierarchy. We give illustrative examples of our language and features and formalize FHJ as a minimal Featherweight-Java style calculus

Damage investigation on welded tubes of a reforming furnace

In this work the creep damage of radiant tubes of a reforming furnace has been investigated. The considered furnacecontains a battery of tubes constructed by butt welding three spun cast pieces, made of ASTM 608 HP-Nb alloy.They are designed to operate at temperatures of about 900°C, pressures of about 30 bars and times of the order of100000 h. Tubes were inspected during the plant stops scheduled every two years, in order to identify and replacethe damaged ones with the aim to ensure conditions of safe operation in the furnace. They were selected though acriterion based on measures of the internal diameter deformation performed in situ by Laser Optic Tube InspectionSystem (LOTIS). For a verification of this method, optical and scanning electron microscopy observation, Vickersmicroharndess and creep tests have been carried out on samples taken from tubes put out of service

hedgehog pathway influence in the immune escape of tumor cells through pdl 1 modulation

n/

FOLFIRINOX after first-line gemcitabine-based chemotherapy in advanced pancreatic cancer: a retrospective comparison with FOLFOX and FOLFIRI schedules

Background: Pancreatic adenocarcinoma is the fourth leading cause of cancer-related death. In cases with metastasis, the combination of 5-fluorouracil, irinotecan, and oxaliplatin (FOLFIRINOX) or gemcitabine-based chemotherapy regimens are considered the standard of care. However, the optimal sequence of these regimens is unclear. Methods: This retrospective study initially evaluated 186 patients with locally advanced/metastatic pancreatic cancer at three Italian institutions between February 2013 and October 2019. All patients had progressed after receiving gemcitabine-based first-line chemotherapy and were subsequently offered second-line FOLFIRINOX, FOLFOX-6, or FOLFIRI treatment. This study evaluated progression-free survival (PFS), overall survival from the start of second-line treatment (OS2), overall survival from the start of first-line treatment (OS1), and safety outcomes. Results: A total of 77 patients received ⩾4 cycles of second-line chemotherapy and were considered eligible: 15 patients received FOLFIRINOX, 32 patients received FOLFOX-6, and 30 patients received FOLFIRI. The FOLFIRINOX group had median PFS of 26.29 weeks and median OS2 of 47.86 weeks, while the FOLFIRI group had median PFS of 10.57 weeks and median OS2 of 25.00 weeks (p = 0.038). No significant differences were observed between the FOLFIRINOX and FOLFOX-6 groups in terms of PFS (26.29 weeks versus 23.07 weeks) or OS2 (47.86 weeks versus 42.00 weeks). The most common grade 3–4 toxicities were anemia, neutropenia, and thrombocytopenia, which occurred more frequently in the FOLFIRINOX and FOLFOX-6 groups. Conclusion: Relative to the FOLFIRI regimen, the FOLFIRINOX regimen had a favorable toxicity profile and better survival outcomes. No significant differences were observed relative to the FOLFOX-6 regimen

Fitness for service assessment of defected welded structural details by experimental evaluation of the fatigue resistance S-N curve

During the fabrication of two different structures (a ship, a bridge) some unacceptable anomalies were detected; the structures were almost completely fabricated and a repair of the defected structural details was impractical, due to the extent of the defected zones. As far as the ship was concerned the anomalies were represented by a large number of welded joints, judged unacceptable according to the Design and Fabrication Code, while in the case of the bridge, the anomalies were represented by planar flaws in the plates forming the girder web, subjected to outof-plane loads for effect of fillet welded connections of bracing. A fitness for service assessment has therefore been carried out, in both cases, by performing fatigue tests on representative samples, cut-off from the structure, and by evaluating the fatigue resistance curve. A re-assessment of the structural details in question was undertaken, on the basis of the experimental S-N curve, evaluating the fitness for service of the \u201cdefected details\u201d. The experimental program has also given the opportunity to compare different methodologies for fatigue assessment: the Effective Notch Stress Method, the Fracture Mechanics Method and the Peak Stress Method. The different procedures have been applied to the tested specimens, and the expected fatigue life was compared with the experimental one