Environmental impact reduction of precast multi-storey buildings by crescent-moon seismic dampers hidden in beam-column joints

The growing demand of sustainable precast structures for multi-storey con-structions is often driven by the optimisation of cross-sections and reinforcement volumes of the structural elements. The present paper describes a real building recently designed and assembled with the installation of crescent-moon hysteretic dampers in the beam-column joints, recently proposed and patented. The joint continuity allows for an optimisation of the lateral load resist-ing system, reducing the size of the columns with respect to the classical precast frame structural arrangement with hinged joints, whilst protecting columns and beams from the large actions deriving from the classical moment-resisting cast-in-situ or partially precast technological solu-tions. After the complete detailed design of the case study building employing the 3 solutions described above, the precast dissipative one being designed with dynamic non-linear analysis, the results of an environmental impact analysis are compared and discussed, confirming a reduced environmental impact for the dissipative solution, with respect to both precast with hinged beam-column joints and moment-resisting cast-in-situ alternatives

Cr segregation and impact fracture in a martensitic stainless steel

The fracture surfaces of a 10.5 wt.% Cr martensitic stainless steel broken in Charpy tests have been investigated through X-ray photoelectron spectroscopy (XPS). The specimens have been examined in two different conditions: as-quenched and heat treated for 10 h at 700°C. The trends of Fe/Cr ratio vs. test temperature are similar to the sigmoidal curves of absorbed energy and, after both ductile and quasi-cleavage brittle fractures, such ratio is always significantly lower than the nominal value of the steel chemical composition. Cr segregation does not occur on a macroscopic scale but takes place in microscopic zones which represent weaker spots in the steel matrix and a preferred path for moving cracks. Small area (diameter 300 μm) XPS measurements evidenced a higher density of such microscopic zones in the inner part of probes; this is explained by the different diffusion length of Cr atoms in the external and inner parts during quenching from austenitic field which has been calculated through FEM simulations. No significant differences of Cr concentration were observed in fracture surfaces of probes with and without heat treatment. The results highlight how Cr segregation plays a role not only in the intergranular mode of fracture but also in the quasi-cleavage and ductile ones

Otites externes nécrosantes: Apport de l’imagerie isotopique

Objective : the Necrotizing (malignant) External Otitis is a very serious, potentially lethal affection. It touches exclusively a debilitated population, where from the necessity of a premature and reliable diagnosis for a beam of cliniquo-biological, radiological and isotopic arguments. Its care as well as its treatment are heavy and require a better definition of themoment of cure. The purpose of our work is to specify the place of the isotopic explorations in the care of the NEO.Materials and methods : we report a retrospective study bringing together 29 patients hospitalized for suspicion of necrotizing external otitis of period going from 2003 till 2009.Résultats : the Middle Age of our population is 64.2 years, with a clear male prevalence. The majority of our patients are diabetics (90% of the cases) with a cardiac and hypertensive Co-morbidity among 19 patients. All our patients consulted, within 47 average days. An assessment of imagery was carried out, comprising a scanner for 16 of our patients. It wasnormal in 4 cases and had shown lesions of osteitis in 12 cases. The osseous scintigraphy marked in MDP-Tc99 was carried out among 24 patients, within 9.69 average day. It was positive for all our patients, objectifying an osseous hyperfixation. All our patients received an adapted treatment. After amendment of the clinico-biological signs, a scintigraphy in Ga67 was practiced for 16 patients within 74 average days. It confirmed the cure among 12 patients, at which one decided to stop the antibiotic therapy. In the other cases, it objectified an osseous hyperfixation translating the persistence of the active infectious process, from where prolongation of the treatment.Conclusion : it comes out from our work that the imagery is essential to confirm the diagnosis and to specify the extent of the osteitis. Indeed, the scanner and the MRI offer an excellent resolution and evaluate the extension of the infection perfectly. However, because of their poor sensitivity, they have little interest to the early phase of the diagnosis and for the therapeutic follow-up. The osseous scintigraphy has the advantage of an excellent sensitivity, approximately 100% in particular at the early stage, but is not specific. The tomographic techniques (SPECT) and the quantification improve however its specificity. The scintigraphy with gallium 67 seems quite as sensitive as and more specific than the osseousscintigraphy, especially if it is quantified, and appears essential with the therapeutic follow-up. Its standardization would have an excellent predictive value of cure, allowing the stop of the antibiotic therapyKeywords : Necrotizing External Otitis, scintigraphy with gallium, the osseous scintigraphy

Room-Temperature O3 Detection: Zero-Bias Sensors Based on ZnO Thin Films

ZnO thin films with a thickness of 300 nm were deposited on Si and Al2O3 substrates using an electron beam evaporation technique with the aim of testing them as low cost and low power consumption gas sensors for ozone (O3). Scanning electron microscopy and atomic force microscopy were used to characterize the film surface morphology and quantify the roughness and grain size, recognized as the primary parameters influencing the gas sensitivity due to their direct impact on the effective sensing area. The crystalline structure and elemental composition were studied through Raman spectroscopy and X-ray photoelectron spectroscopy. Gas tests were conducted at room temperature and zero-bias voltage to assess the sensitivity and response as a function of time of the films to O3 pollutant. The results indicate that the films deposited on Al2O3 exhibit promising characteristics, such as high sensitivity and a very short response time (<2 s) to the gas concentration. Additionally, it was observed that the films display pronounced degradation effects after a significant exposure to O3

A Simplified Parametric Study on Occupant Comfort Conditions in Base Isolated Buildings under Wind Loading

Vibrations in buildings can cause occupant discomfort in the form of annoyance, headache, or sickness. While occupant comfort is considered in international standards regarding the design of high rise buildings against wind loading, it is neglected in the design of buildings with seismic protective base isolation systems. Nevertheless, due to their low flexibility, base isolated buildings can be prone to wind-induced vibrations, which makes occupant discomfort a potentially significant serviceability limit state. This paper presents a study on occupant comfort conditions in wind-excited base isolated buildings. A numerical simplified parametric procedure is proposed in order to evaluate the return period of wind events causing human discomfort. A parametric investigation is then presented to evaluate the effects of salient parameters on comfort conditions. The procedure is based on (i) the nonlinear dynamic analysis of the structure modeled as a single-degree-of-freedom oscillator with hysteretic base isolators, (ii) the digital generation of time histories of turbulent wind velocity, and (iii) comfort evaluations based on international standards. Results demonstrate that discomfort conditions can occur a few times in a year, depending upon the wind-exposure of the site, what suggests considering this serviceability limit state in the design of base isolated buildings

Low Electron Affinity Silicon/Nanocrystalline Diamond Heterostructures for Photon-Enhanced Thermionic Emission

Photon-enhanced thermionic emission (PETE) is a physical mechanism based on the electron’s emission from photon absorption and thermalization, which can be highly efficient to convert concentrated sunlight. Here, we demonstrate that nanocrystalline diamond thin films deposited on heavily doped p-type silicon absorbers can be potentially efficient PETE cathodes, showing a low χ value of ∼0.4 eV. A detailed analysis has been carried out as a function of the film thickness by correlating the PETE performance under concentrated sunlight with several chemical-physical measurements. The results highlight that grain boundaries are decisive to achieve the highest emission current density obtained with an 80 nm-thick emitter

CARATTERIZZAZIONE MICROCHIMICA DELL’ INTERFACCIA FIBRA-MATRICE NEL COMPOSITO TI6AL4V-SICf

Il materiale composito costituito da una matrice Ti6Al4V, rinforzato con fibre lunghe di SiC (tipo SCS-6), è stato caratterizzato sia allo stato di fabbricazione che dopo trattamenti termici in vuoto. Attraverso la microanalisi EDS e la spettroscopia di fotoemissione (XPS) e Auger (AES), è stata determinata la concentrazione dei principali elementi, operando su sezioni metallografiche. Le analisi sono state eseguite in varie posizioni: tra le interfaccie di fibra, nel rivestimento in carbonio e nella matrice. I dati sperimentali nella zona di reazione sono stati discussi e confrontati con andamenti teorici

Recycling of multilayer packaging waste with switchable anionic surfactants

Switchable Anionic Surfactants (SAS) were used for delaminating flexible packaging waste composed of various plastic layers and aluminium, thereby promoting the recycling of such waste streams from a circular economy perspective. The delamination protocol was optimized on de-pulped food and beverage cartons containing low-density polyethylene (LDPE) and aluminium, varying the carboxylic acid and its counterion constituting the SAS (C8[sbnd]C18 carboxylic acids as the anionic part; inorganic bases and primary, secondary and tertiary amines as the cationic one) their molar ratio (carboxylic acid: base molar ratio from 1:1 to 1:3), SAS concentration (0.15, 0.3 and 0.5 wt%), time (0.5–3 h) and material weight in input (1–10 wt%). High-quality LDPE and aluminium were separated and recovered by using a diluted solution of a surfactant based on lauric acid and triethanolamine (C12-TEA), with performances not achievable with other anionic or cationic surfactants available on the market. The C12-TEA solution was then applied to a large variety of multilayer waste materials composed of polypropylene and aluminium, polyolefins/polyethylene terephthalate/aluminium, giving a material separation dependant on the structure and composition of the material in input. At the end of the process, lauric acid was recovered from the aqueous solution used for washing the separated materials by tuning its water solubility with CO2

Charge transport mechanisms of black diamond at cryogenic temperatures

Black diamond is an emerging material for solar applications. The femtosecond laser surface treatment of pristine transparent diamond allows the solar absorptance to be increased to values greater than 90% from semi-transparency conditions. In addition, the defects introduced by fs-laser treatment strongly increase the diamond surface electrical conductivity and a very-low activation energy is observed at room temperature. In this work, the investigation of electronic transport mechanisms of a fs-laser nanotextured diamond surface is reported. The charge transport was studied down to cryogenic temperatures, in the 30–300 K range. The samples show an activation energy of a few tens of meV in the highest temperature interval and for T < 50 K, the activation energy diminishes to a few meV. Moreover, thanks to fast cycles of measurement, we noticed that the black-diamond samples also seem to show a behavior close to ferromagnetic materials, suggesting electron spin influence over the transport properties. The mentioned properties open a new perspective in designing novel diamond-based biosensors and a deep knowledge of the charge-carrier transport in black diamond becomes fundamental