1,721,454 research outputs found
The Hyper-Kamiokande detector: R&D studies of a new generation of photosensors
No full textHyper-Kamiokande is a large water Cherenkov detector which, just like the successful Super-Kamiokande, requires large aperture, high sensitivity photosensors able to detect the weak Cherenkov light generated by neutrino interactions or proton decay. The capability of a water Cherenkov detector largely relies on the performance of its photosensors. Currently the photosensors used in Super-Kamiokande, characterised by the 50 cm diameter photocathode, are the world's largest photomultiplier tubes. The ambitious physics program of Hyper-Kamiokande will be possible only by using a new generation of photosensors whose performances are considerably improved with respect to those currently available. In this paper the current status of development of Hyper-Kamiokande photodetectors will be reviewed
On the validity of Clauser and Horne factorizability
No full textThe Clauser-Horne approach used to derive experimentally measurable quantities for performing experiments on EPR paradox based on Type-I Spontaneous Parametric Down Conversion (SPDC) sources is discussed. It is proved that in this case the deduced Bell's type inequality does not correctly express separability and causality. A deeper analysis of the problem shows that the Clauser-Horne hypothesis of factorizability of joint detection probability cannot be considered so general as to describe this physical situation
Experimental and Analytical Investigation of the Shear Fracture Behavior of Bonded Joints
No full textThe demand of adhesive bonding as technique for the strengthening of existing structures is currently increasing in many engineering fields. Therefore, the prediction of bonded joints fracture behavior is an open issue for the structural safety of repairs. With this aim, a cohesive zone approach is adopted to determine the shear fracture behavior of epoxy resin interface layer of end notched flexure (ENF) specimen. Experimental tangential slip displacements of adherends are evaluated by digital image correlation (DIC) analysis. The identified traction-separation law can be implemented in a finite element (FE) code to predict the decohesion of adhesively bonded joints
Mass minimization approach for the optimal preliminary design of CMC inner liners in rocket thrust chambers
No full textIn the past decade, the world has witnessed a new space race, driven by a growing commitment to reducing the environmental impact of space missions. This has led to the widespread adoption of liquid-propellant rocket engines, which offer several advantages over their solid-propellant counterparts. One key advantage is their reusability, which not only helps to reduce the generation of space debris but also makes space exploration cheaper. To further enhance the performance of liquid rocket engines, researchers have been exploring innovative cooling techniques and advanced materials. Among these materials, Ceramic Matrix Composites (CMCs) have shown great potential in reducing the overall engine weight when used instead of high-tech metal alloys, resulting in lower fuel consumption and emissions during launches. This paper focuses on the mass minimization of inner liners made of CMCs in rocket thrust chambers. At this aim, a computationally efficient preliminary design approach, based on an analytical one-dimensional thermo-mechanical model, is proposed. A case study of mass minimization of an inner liner of rocket thrust chamber is also presented and discussed, by considering five different CMC materials
Effects of recycled PET fibres on the mechanical properties and seawater curing of Portland cement-based concretes
No full textThis paper deals with an experimental study on the mechanical properties of recycled polyethylene terephthalate fibre-reinforced concrete (RPETFRC) and its durability in an aggressive seawater environment. A Portland limestone cement-based concrete with a 0.38 water/cement ratio is used to cast cubic and prismatic specimens, in association with two different PET fibres obtained through extrusion of recycled PET flakes (R-PET). Some of these specimens were conditioned in the Salerno harbour seawater for a period of 6/12 months. Compressive strength and four-point bending tests are performed in order to investigate the mechanical properties of such RPETFRCs. Comparison of the present results and those in the literature for air-cured RPETRCs highlights the influence of the analysed R-PET fibres on the mechanical properties of concretes showing different water/cement ratios and binders. The given results for seawater-cured specimens demonstrate that such a curing condition slightly modifies the first-crack strength and markedly reduces the toughness of the RPETFRCs examined in the present work. © 2014 Elsevier Ltd. All rights reserved
Experimental analysis on the time-dependent bonding of FRP laminates under sustained loads
No full textFiber reinforced composite materials are frequently used in the rehabilitation or upgrading of existing structures. From a design point of view, current international guidelines on FRP strengthening applications do not give rules based on rigorous approaches to evaluate the reliability and durability of strengthening interventions with respect to long-term behavior. In order to give a contribution on this topic, the authors have carried out a creep experimental program on retrofitting systems, either of carbon or glass fibers and subject to different stress values in regime of constant temperature. The tests have been carried out by means of a dedicated test device that provided a pure bending stress state in the strengthened beam, being the external loads held constant over time. In this paper the results of their investigation and critical analysis are presented. © 2012 Elsevier Ltd. All rights reserved
Correlation functions in EPR-type experiments: the low-detection-efficiency loophole
No full textIn this paper we derive a general approach using correlation functions for interpreting the results of measurements on two-particle entangled states. In our analysis we explicitly take into account the detector efficiency. We show that all Bell-type inequalities have bounds depending on both the losses in the apparatus and the supplementary assumptions about the statistical distribution of the losses themselves. Moreover. our approach enables us to include in the causal and local theory the same assumptions as used in the quantum mechanical analysis of an experiment, and to deduce the inequality which has to be satisfied by any local realistic model incorporating these assumptions. We show that, although the most recent experiments on Bell's inequality can be considered to be a remarkable step in the direction of testing quantum mechanics predictions, the loophole of the low quantum efficiency of the detector is not yet solved. In fact, using the quantum mechanical assumption of random nondetection in the causal and local approach, we deduce a generalized Bell-type inequality which includes no-count events and whose upper hound can be violated by the quantum mechanical predictions only if the detector quantum efficiency is >0.811. RI Berardi, Vincenzo/H-4550-201
Mode I Fracture Toughness Evaluation of Adhesively Bonded Joints via J-Integral and DIC
No full textAmorphous polymers, such as epoxy resins, are commonly used in the realization of adhesively bonded joints. In this paper an evaluation of mode I fracture toughness of bonded joints is presented. Moreover, an identification of cohesive zone model parameters via Rice's J-integral is described. Experimental tests are performed on double cantilever beam specimens and relative displacements between adherends are acquired by using the digital image correlation technique. The obtained interface law can be implemented in a finite element code for simulating the decohesion process of complex bonded structures
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