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Effects of order of expansion for the exponential matrix and number of mathematical layers in the exact 3D static analysis of functionally graded plates and shells
No full textInfluence of the Facility Nozzle Design in the Unsteady Response of Direct-Connect Scramjet Combustors
No full textA numerical approach to the automatic design has been applied to the aerodynamic design of a device that acts as a facility nozzle and inlet distortion generator for a direct-connect scramjet combustor test-rig. The technique combines GA optimization and an inverse method based on a lightweight MoC solver for an efficient search of non-local extrema. The solution of the design problem is sought by using different approaches of CFD analysis and optimization tools. The initial design is based on the solution of an inverse problem coupled to optimization by genetic algorithms. The result of the optimization is then tested by CFD simulations of the direct-connect facility and the shock reflection patterns are compared with those of the in-flight configuration. The verification of nozzle design and the assessment of the prescribed flow distortion are then carried out by numerical simulations of the flowfield of the whole direct-connect facility by an URANS solver. Global effects of combustion dynamics have been included by using an heat-release model. The proposed procedure is checked by designing a facility nozzle and distortion generator system for a scramjet model available in the open literature
An experience of University Education on Occupational Safety and Health at Politecnico di Torino
No full textAccording to the European statistics on work related accidents and health impairments, the general situation still remains critical. In Italy approximately three fatalities/day are recorded. The causes are poor Hazard Iden-tification, uncritical Risk Assessment and, consequently, Risk Management lacking of a Quality approach. The Culture of Safety is a basic tool to support improvements of the situation. Its dissemination finds important al-location at the University education stage. Moreover, the cooperation programs involving Universities and top managers lay at the very base of Occupational Safety & Health (OS&H) improvements, particularly in critical NACE sectors. Politecnico di Torino provides Bachelor, Master Degree, Post-Graduate Master and PhD courses covering multidisciplinary aspects, with remarkable occupational success. The Authors provide infor-mation on organization and contents of a Master Degree course, whose applied part is based on Problem Based Learning, starting from in depth analyses of occurred work related fatalities, targeted to discuss suita-ble prevention measures
Localised sampling of myoelectric activity may provide biased estimates of cocontraction for gastrocnemius though not for soleus and tibialis anterior muscles
No full textProper muscle activity quantification is highly relevant to monitor and treat spastic cocontraction. As activity may distribute unevenly within muscle volumes, particularly for pennate calf muscles, surface electromyograms (EMGs) detected by traditional bipolar montage may provide biased estimations of muscle activity. We compared cocontraction estimates obtained using bipolar vs grids of electrodes (high-density EMG, HD-EMG). EMGs were collected from medial gastrocnemius, soleus and tibialis anterior during isometric plantar and dorsi-flexion efforts at three levels (30%, 70% and 100% MVC), knee flexed and extended. Cocontraction index (CCI) was estimated separately for each electrode pair in the grid. While soleus and tibialis anterior CCI estimates did not depend on the detection system considered, for gastrocnemius bipolar electrodes provided larger cocontraction estimates than HD-EMG at highest effort levels, at both knee angles (ANOVA; P <.001). Interestingly, HD-EMG detected greater gastrocnemius EMGs distally during plantar flexions, and greater CCI values proximally during dorsiflexions. These results suggest that bipolar electrodes: (i) provide reliable estimates of soleus and tibialis anterior cocontraction; (ii) may under-or overestimate gastrocnemius cocontraction, depending on their distal or proximal position
Packed hybrid silica nanoparticles as sorbents with thermo-switchable surface chemistry and pore size for fast extraction of environmental pollutants
No full textThermoresponsive poly(N-isopropylacrylamide)-grafted silica nanoparticles (SiNPs) have been synthesized and fully characterized by ATR-FTIR, TGA, HRTEM, BET and DLS analysis. Hybrid solid phase extraction (SPE) beds with tuneable pore size and switchable surface chemistry were prepared by packing the polymergrafted nanoparticles inside SPE cartridges. The cartridges were tested by checking the thermoregulated elution of model compounds, namely methylene blue, caffeine and amoxicillin. Extraction of the analytes and regeneration of the interaction sites on the sorbent surface was carried out entirely in water solution by changing the external temperature below and above the lower critical solution temperature (LCST) of the polymer. The results demonstrate that the elution of model compounds depends on the temperature-regulated size of the inter-particle voids and on the change of surface properties of the PNIPAM-grafted nanoparticles from hydrophilic to hydrophobic
Thermal-Hydraulic Analysis of the EU DEMO Helium-Cooled Pebble Bed Breeding Blanket Using the GETTHEM Code
No full textThe general tokamak thermal-hydraulic model (GETTHEM) has been updated to the most recent version of the EU DEMO helium-cooled pebble bed breeding blanket (BB) design. The GETTHEM results are first benchmarked in a controlled case against the results of 3-D computational fluid-dynamics computations, showing an acceptable accuracy despite the inherent simplifications in the GETTHEM model. GETTHEM is then applied to the evaluation of the poloidal hot spot temperature distribution in an entire BB segment, showing that the maximum temperature in the EUROFER structures overcomes the design limit of 550 °C by more than 50 °C in some blanket modules. A possible mitigation strategy is then proposed and analyzed, based on the idea of cooling the first wall in parallel with the breeding zone, showing that this solution would allow having the EUROFER in its working temperature range in the entire segment, although at the expense of a larger pressure drop
Insights on the role of β-Bi2O3/Bi5O7NO3 heterostructures synthesized by a scalable solid-state method for the sunlight-driven photocatalytic degradation of dyes
No full textA simple, solvent-free and scalable route for the synthesis of nanostructured Bi5O7NO3 and Bi2O3 polymorphs photocatalysts and their heterostructures is here presented. Morphology, porosity and crystal phases were tuned by controlling the thermal decomposition of Bi(NO3)3:5H2O, by using different calcination temperatures and cooling processes. Bi5O7NO3 layered nanosheets, highly porous β-Bi2O3/Bi5O7NO3 heterostructured nanoflakes and micrometric sheets of α-Bi2O3 were obtained at temperatures of 400 °C, 425-450 °C and 525 °C with a slow cooling rate, respectively. Moreover, in contrast to previous reports on Bi5O7NO3, the role on the visible-light driven photocatalytic activity of Bi5O7NO3 due to the formation of a stable heterojunction with β-Bi2O3, which here was identified to be also formed by a rapid cooling after calcination at 400 °C, was deeply investigated and demonstrated. All the samples were fully characterized by X-ray Diffraction, Field-emission scanning electron microscopy, UV-vis spectroscopy, N2 adsorption and X-ray Photoelectron Spectrometry analyses. The role of oxygen vacancies, which indicate structural defects and/or sub-stoichiometric forms of Bi5O7NO3 or Bi2O3 in the photocatalysts surface, was also analyzed and correlated to their photo-response. Simulated sunlight-driven degradation of organic dyes with different functionalities, i.e. a cationic dye (Rhodamine B) and an anionic one (Indigo Carmine), was investigated and proved to be optimized due to an efficient synergy between suitable amounts of Bi5O7NO3 and β-Bi2O3 in the heterostructured samples. An improved charge carriers separation at the heterojunction interphase and an enhanced formation of reactive oxygen species in these materials were additionally confirmed by both photocatalytic water oxidation experiments with O2 evolution and mineralization of a refractory anionic dye, i.e. Remazol Brilliant Blue R. The latter was reached with an optimum photocatalyst/ dye weight ratio of 33, which is about 2-3 times lower than previous literature results