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Technical-economic feasibility of CHP systems in large hospitals through the Energy Hub method: The case of Cagliari AOB
No full textMulti-energy systems satisfy different energy uses of a building such as space heating, space cooling, DHW, etc. by using different energy converters and energy sources simultaneously. These systems, if properly designed and operated, have high efficiency in the production of energy. This paper presents a method based on the Energy Hub model for the energy and economic analysis of a large hospital complex placed in Sardinia (Italy). The Energy Hub model allows dynamic simulations results and experimental data to be coupled. First of all, the model was calibrated according to real data and information obtained during an energy audit carried out by the University of Cagliari in collaboration with the Brotzu Hospital staff. Then, since cogeneration is recognised as one of the most effective ways to efficiently convert energy, the integration of a CHP system (internal combustion engine), within the multi-energy system of the hospital, was studied. The results obtained are useful to identify benefits that might be obtained by the CHP system, depending on its regulation and on the economic variables. The presented model represents a valuable tool to evaluate possible energy and economic savings and to design and to optimise every kind of multi-energy systems of a generic building
Bore Disruption: An Unusual Mechanical Failure of Two Hip Hemiarthroplasties
No full textWe report a case of two hemiarthroplasties (HAs) that underwent an unexpected mechanical failure. Two patients affected by femoral fractures were treated with an HA. At 5 and7 years after surgery, they showeda breakage of theHAat the head-stemjunction. We analyzed macroscopically and microscopically (by a scanning electron microscopy) the surfaces of the broken prostheses. In both cases, a fracture was detected starting at the joining point between the femoral head and the slot that receives the taper cone of the stem(the so-called bore),with the typicalmacroscopic and microscopic pattern of a fatigue fracture. The fatigue fracture resulted from repeated cycles of torsional stresses throughout the years. In literature, we did not find any other report of such HA failure
Proof of Concept for an Ultrasensitive Technique to Detect and Localize Sources of Elastic Nonlinearity Using Phononic Crystals
No full textThe appearance of nonlinear effects in elastic wave propagation is one of the most reliable and sensitive indicators of the onset of material damage. However, these effects are usually very small and can be detected only using cumbersome digital signal processing techniques. Here, we propose and experimentally validate an alternative approach, using the filtering and focusing properties of phononic crystals to naturally select and reflect the higher harmonics generated by nonlinear effects, enabling the realization of time-reversal procedures for nonlinear elastic source detection. The proposed device demonstrates its potential as an efficient, compact, portable, passive apparatus for nonlinear elastic wave sensing and damage detection
A Robust Multifunctional Sandwich Panel Design with Trabecular Structures by the Use of Additive Manufacturing Technology for a New De-Icing System
No full textBioactive glass coatings fabricated by laser cladding on ceramic acetabular cups: a proof-of-concept study
No full textDeposition of bioceramic coatings on medical implants is a valuable strategy to impart key added values, such as bioactivity. While flat coatings can be easily produced by enameling and similar techniques, applying a bioactive glass layer on surfaces with curved geometry is a great challenge from a technological viewpoint. In this work, for the first time we demonstrated the feasibility of bioactive glass coatings produced by laser cladding on alumina/zirconia ceramic acetabular cups for hip joint prosthesis. Laser-cladded glass coatings can be fabricated in a dense (pore-free) or porous form. Morphological analyses by scanning electron microscopy and micro-computed tomography revealed the good quality of joining at the coating/substrate interface and the good interconnectivity of the pores (size within 200-400 lm) in the outer porous layer. Indentation tests at the interface confirmed the excellent joining between glass and ceramic substrate. These coatings also exhibited a good bioactive behavior in vitro, as demonstrated by the formation of a surface apatite layer upon immersion studies in simulated body fluid
Artificial neural network assisted laser chip collimator assembly and impact on multi-emitter module beam parameter product
No full textA new tool based on artificial neural networks to assist in the accurate positioning of the lenses used to collimate the beams emitted by the individual chips forming multi-emitter diode laser modules is presented. An alternative expression for the evaluation of the obtained beam quality is disclosed and the impact of different choices on the overall module performance in terms of beam quality and coupling efficiency into a collecting fiber is analyzed. Experimental validations with different combinations of lenses are reported to prove the effectiveness of the proposed approach
Solution combustion synthesis for the preparation of structured catalysts: a mini-review on process intensification for energy applications and pollution control
No full textSolution combustion synthesis (SCS) is a preparation technique that can be used to synthesize a variety of inorganic nanomaterials and structured catalysts. It is based on a self-propagating, exothermic, redox reaction between organic salts and a fuel, mixed together in an aqueous solution, which results in the formation of nanocrystalline and highly pure solid nanomaterials. SCS can be considered as an attractive synthesis method for catalysts due to the simple nature of the synthetic route and short reaction times. The process is easily scaled up to any kind of application which makes it economically attractive. This mini-review provides a short overview on the synthesis of structured catalysts by SCS and their recent applications for energy applications and pollution control
Effect of State Feedback Coupling on the Design of Voltage Source Inverters for Standalone Applications
No full textThis Ph.D. thesis aims at investigating the effect of state feedback cross‐coupling decoupling of the capacitor voltage on the dynamics performance of Voltage Source Inverters for standalone microgrids/Uninterruptible Power Supply systems. Computation and PWM delays are the main factors which limit the achievable bandwidth of current regulators in digital implementations. In particular, the performance of state feedback decoupling is degraded because of these delays. Two decoupling techniques aimed at improving the transient response of voltage and current regulators are investigated, named nonideal and ideal capacitor voltage decoupling respectively. In particular, the latter solution consists in leading the capacitor voltage on the state feedback decoupling path in order to compensate for system delays. Practical implementation issues are discussed with reference to both the decoupling techniques. Moreover, different resonant regulators structures for the inner current loop are analysed and compared to investigate which is the most suitable for standalone microgrid applications. A design methodology for the voltage loop, which considers the closed loop transfer functions developed for the inner current loop, is also provided. Proportional resonant voltage controllers tuned at specific harmonic frequencies are designed according to the Nyquist criterion taking into account application requirements. For this purpose, a mathematical expression based on root locus analysis is proposed to find the minimum value of the resonant gain at the fundamental frequency. The exact model of the output LC filter of a three‐phase inverter is derived in the z‐domain. The devised formulation allows the comparison of two techniques based on a lead compensator and Smith predictor structure. These solutions permit the bandwidth of the current regulator to be widened while still achieving good dynamic performance. As a consequence, the voltage regulator can be designed for a wide bandwidth and even mitigates odd harmonics arising with unbalance loads supply. Discrete‐time domain implementation issues of an anti‐wind up scheme are discussed as well, highlighting the limitations of some discretization methods. Experimental tests performed in accordance to Uninterruptible Power Supply standards verify the theoretical analysis
Assessment of risk to human health due to intake of chromium in the groundwater of the Aosta Valley region, Italy
No full textThe aim of this study is to assess the risk to human health presented by total chromium (CrT) and hexavalent chromium (Cr(VI)) due to the intake of the groundwater (shallow aquifer) in the Aosta Valley region. One hundred and fifty-three groundwater samples were collected from seventeen locations in the Aosta Valley region during the years 2007-2015 to determine the CrT and Cr(VI) concentrations. The cancer risk (CR) and non-cancer risk, reflected by the hazard quotient (HQ) were estimated using the United States Environmental Protection Agency methods. The concentrations of CrT exceeded the limit for drinking water established by Italian legislative decree at the sampling location Ao23 in all the years studied. Moreover, Cr(VI) concentrations exceeded the limit for drinking water at many sampling locations in the study area. The estimated HQ values for non-cancer risk suggested that all the sampling locations were well within the safe zone during all the years except for location Ao23 in many years considered. The CR levels were very low to high risk in the groundwater of the study area. The results of this analysis suggest that a suitable treatment of the groundwater is required before its utilization for drinking purposes. This study could be of great value for the prevention of risk to human health and for groundwater resource management