1,167 research outputs found
Experimental investigation and 2D mathematical modelling of copper foams packed with Rh-Al2O3 catalysts for the intensification of methane steam reforming
Get PDFEfficient heat transfer is a crucial factor in the design of compact methane steam reformers for delocalized hydrogen production. The use of copper packed foams was proposed few years ago by our group to strongly intensify heat transfer in these systems, allowing the design of small-scale units with minimal radial temperature gradients. In this study, a new experimental campaign was performed to demonstrate the concept potential under industrially relevant heat fluxes and to establish an experimental foundation for validating a 2D mathematical model of the process. Copper open-cell foams were packed with a Rh/Al2O3 egg-shell catalyst and loaded into a 29.5 mm diameter tubular reactor, which was heated using a lab-scale oven. By leveraging the combined benefits of enhanced heat transfer, granted by the copper foam, and the high activity of the Rh-based eggshell catalyst, experiments were successfully performed at gas hourly space velocities (GHSV) ranging from 10 to 30 Nm^3/h/kg cat, with heat duties of up to 9 MW/m^3. These experiments lead to a methane conversion close to thermodynamic equilibrium while maintaining limited radial gradients within the system (maximum 20 °C across the mid-radius). A predictive pseudo-heterogeneous 2D reactor model was developed and validated against experimental data. The model accurately captured the observed trends in temperature profiles and outlet concentrations, and can be utilized for optimized design, paving the way for the development of efficient small-scale hydrogen production units
Experimental and theoretical study of gas/solid mass transfer in metallic filters as supports for micro-structured catalysts
No full textExperimental and theoretical study of gas/solid mass transfer in metallic filters as supports for micro-structured catalysts
No full textDoes hip osteoarthritis have a protective effect against proximal femoral fractures? A retrospective study
No full textThe inverse relationship between proximal femoral fracture incidence and hip osteoarthritis remains controversial. However, femoral neck fractures rarely occur in patients with hip osteoarthritis, suggesting a protective effect of osteoarthritis. We sought to determine if the severity of osteoarthritis influenced fracture type. We examined the radiographs of 190 consecutive patients treated at our institution after hip trauma. They were divided into three groups according to the outcome of the trauma: femoral neck fracture; trochanteric fracture; and no fracture. We then analysed the severity of osteoarthritis within these groups. No relationship between the grade of hip osteoarthritis and the presence of a proximal femoral fracture was found. However, the grade of osteoarthritis was related both to the outcome of the trauma (p<0.0001) and to the location of the fracture (p<0.0001). Patients with osteoarthritis of the hip had a three-fold increased likelihood of trochanteric fracture compared to femoral neck fracture. Osteoarthritis does not protect against proximal femoral fractures, but strongly affects the location of the fracture in the proximal femur, increasing the possibility of a trochanteric location. © 2014 Wichtig Publishing
Giulia Veronica Varisco
No full textThe headword explains the biography and the contribution of the author Giulia Varisco to the children's literatur
Semitendinosus Tendon Transfer Associated With Distal Alignment for Patella Alta in a Patient With Recurrent Dislocations
No full textPatellofemoral instability is characterized by pain during normal daily activities and frequent dislocation events. In the reported case, an adolescent girl, aged 15 years, affected by left patellofemoral instability, underwent surgery with a double technique comprising tibial tubercle distalization and medial patellofemoral ligament reconstruction. In case of patella alta associated with patellofemoral instability, surgical treatment should focus on medial patellofemoral ligament repair and on recurrent instability prevention
Gamma nailTM in pertrochanteric fractures in elderly patients: Is anatomical reduction necessary? A preliminary study
No full textAim of the work: This study analyzes the clinical and radiographic results of 100 patients who underwent osteosynthesis with Gamma nailTM, following fracture of the pertrochanteric region. Methods: These patients were divided into 2 groups: A, those without anatomical reduction of the fracture and B, those with anatomical reduction. All patients were classified according to the ASA system, pre-injury and follow-up Harris Hip Score and pre-operative/post-operative radiographic evaluation. An univariate analysis has been performed comparing pre-injury and final follow-up Harris Hip Score. Moreover a multivariate analysis has been completed including: age, ASA classification, anticoagulant therapy, cognitive impairment, length of surgical procedure, type of surgical result, length of hospitalization, timing between trauma and surgical procedure. Results: The univariate analysis documented no statistical significance (p=0.541). At multivariate analysis resulted as statistically significant only the age, the ASA classification and the timing between trauma and surgical procedure. Patients of group A have obtained rehabilitation time, fracture healing time and long-term functional results similar to patients of group B. Conclusions: It is suggested that, compared with anatomic reduction, preoperative ASA, age and the time interval between trauma and surgery are more predictive criteria of patient mortality in the months following the intervention. (www.actabiomedica.it)
Experimental and theoretical study of mass-transfer in open-cell foams and other filamentous media
No full textYtterbium Disilicate/Monosilicate Multilayer Environmental Barrier Coatings: Influence of Atmospheric Plasma Spray Parameters on Composition and Microstructure
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Ytterbium Disilicate/Monosilicate Multilayer Environmental Barrier Coatings: Influence of Atmospheric Plasma Spray Parameters on Composition and Microstructure
by Giulia Di Iorio,Laura Paglia *ORCID,Giulia PedrizzettiORCID,Virgilio GenovaORCID,Francesco MarraORCID,Cecilia BartuliORCID andGiovanni PulciORCID
INSTM Reference Laboratory for Materials and Surface Engineering, Sapienza University of Rome, Eudossiana 18, 00184 Rome, Italy
*
Author to whom correspondence should be addressed.
Coatings 2023, 13(9), 1602; https://doi.org/10.3390/coatings13091602
Original submission received: 10 August 2023 / Revised: 31 August 2023 / Accepted: 11 September 2023 / Published: 13 September 2023
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Abstract
SiC/SiC ceramic matrix composites (SiCf/SiC CMCs) are regarded as the new materials for the hot-section components of aircraft gas turbine engines, since they have one-third of the density of metallic superalloys, a higher temperature capability, good mechanical strength, and excellent thermal shock resistance. However, high-temperature water-vapor-rich combustion gases can induce severe surface recession phenomena in SiC/SiC leading to component failure. For this reason, it is necessary to design protective coatings, i.e., environmental barrier coatings (EBCs), able to protect the SiC/SiC surface in combustion environments. In the present work, ytterbium monosilicate (Yb2SiO5), stable when exposed to water vapor at high temperatures, and ytterbium disilicate (Yb2Si2O7), characterized by a thermal expansion coefficient closer to that of the substrate, were selected for a multilayer EBC system. EBCs were processed using the atmospheric plasma spray (APS) technique. A set of deposition parameters were tested, varying the power of the torch, and the composition and microstructure of the deposited coatings were studied in terms of porosity, crack density, and post-deposition phase retention by performing SEM, EDS, and XRD analysis. The results allow for the definition of the influence of deposition parameters on the final properties of multilayer EBC coatings
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