Simulation of a Natural Gas Steam Reforming Reactor at Different Scales

The concept of sustainable energy is often associated to the so-called hydrogen economy. However, hydrogen cannot be regarded as an energy source, since it is not present in nature as free H2. Therefore, it must be produced using chemical processes. Among them, natural gas steam reforming (NGSR) is the most widespread and economically feasible process. Natural gas (NG) is a mixture with no well-defined and constant composition. However, methane is the prevailing component (around 85- 90%), but also higher hydrocarbons (i.e. ethane, propane, butane...) can be found. NGSR involves the proper endothermic reaction of reforming which produces syngas (a mixture of H2, CO and CO2). Then, the slight exothermic reaction of water gas shift, further converts CO in CO2 producing more hydrogen. The overall process is highly endothermic, so requires a large amount of heat. Therefore, the reactors are tubes placed in a furnace which provides direct heat to the tubes. Even though this process implements a well-established technology, it still presents some issues, such as carbon formation and deposition. Usually, a high steam to carbon (S/C) ratio allows to reduce carbon formation and its deposition: a value of S/C higher than 2.5 is generally believed to be safe for coke-free operation, nevertheless the problem of carbon formation and deposition is still not solved. The aim of the first part, is the development of an accurate model for these reactors. The mathematical model underlying the chemical and physical system is made of the mass and energy balances. The constitutive equations are then coupled with the kinetic equations for all the reaction involved in the process. The kinetic equations for the NGSR process are retrieved from the literature (i.e. Xu and Froment) but, with a simplified approach, they are adapted to our specific case. The overall set constitutes a partial differential and algebraic equation (PDAE) system which and requires boundary conditions which generally are chosen to be flowrate and composition of the feeding mixture. The resolution of the PDAE system needs the implementation of a numerical method through a finite element method (FEM), implemented through COMSOL Multiphysics\uae. The major problem which has shown up is the numerical method convergence. However, at the end of the simulation it is possible to obtain plots and maps of the main physical and chemical quantities of interest. Furthermore, an experimental analysis of end-of-life commercial catalyst coming from a full-scale industrial SMR reactor is carried out. This experimental analysis provides interesting results regarding catalyst structure and the eventual carbon deposition. Therefore, a possible qualitative explanation for the carbon formation can be given

Assessing SMEs’ cybersecurity organizational readiness: Findings from an Italian survey

The Small and Medium-sized Enterprises’ (SMEs) level of organizational cybersecurity readiness has been poorly investigated to date. Currently, all SMEs need to maintain an adequate level of cybersecurity to run their businesses, not only those wishing to fully exploit digitalization’s benefits. Unfortunately, due to their lack of resources, skills, and their low level of cyber awareness, SMEs often seem unprepared. It is essential that they address the digital threats that they face by using technology and complementary (and not alternative) factors, such as guidelines, formal policies, and training. All these elements trigger development processes regarding skills, awareness, the organizational cybersecurity culture, and the organizational resilience. This paper describes Italy’s first multidisciplinary attempt to assess its SMEs’ overall cybersecurity readiness level. We used a survey as its initial quantitative assessment approach, although SMEs can also use it as a cyber self-assessment tool, which prepares them better to navigate the digital ecosystem. Thereafter, we held semi-structured interviews to explore the critical points that had emerged from the study’s first phase. The overall results show that SMEs have not yet achieved high levels of organizational readiness. SMEs are currently starting to set the stage for their organizational cyber readiness and will, therefore, have to take many more proactive steps to address their cyber challenges

Clinical Relevance of Blood Glucose Concentration and Hyperglycemia Management in Neurocritical Care Patients

AbstractIn patients admitted to a neurocritical care (NCC) unit, management of blood glucose concentration (BGC) is a challenging clinical task. Several studies have shown that episodes of hypo- and hyperglycemia and high BGC variability are associated with poor short- and long-term outcomes. Optimal BGC target-range and BGC management in NCC patients have dramatically evolved in the past decades and new insulin infusion and adequate nutrition protocols are now available. The aim of this narrative review is to report the state-of-the-art on clinical relevance on BGC and hyperglycemia management in NCC patients

Cell Death Induced by the Herpes Simplex Virus-1 Thymidine Kinase Delivered by Human Immunodeficiency Virus-1-Based Virus-like Particles

HIV-1 Nef incorporates into virions at low levels, likely about 10 molecules per viral particle. Here, we describe a Nef mutant (Nef7) apparently showing more than 100-fold higher efficiency of virion incorporation. Interestingly, Nef7 can act as a cargo molecule for protein delivery into the cells, as its virion incorporation appeared conserved even upon C-terminal fusion with proteins of up to 30 kDa. This was demonstrated first by assessing the intracellular fluorescence of cells challenged with lentivirus-based virus-like particles (VLPs) pseudotyped with the vesicular stomatitis virus envelope glycoprotein (VSV-G) and incorporating Nef7 fused with the green fluorescent protein. Furthermore, the biologic activity of products delivered by Nef7-based VLPs was demonstrated by tagging Nef7 with the herpes simplex virus-1 thymidine kinase (HSV-1 TK). In fact, we observed that both cell lines and primary human macrophages challenged with (VSV-G) Nef7/TK VLPs died after 5 to 7 days of treatment with ganciclovir (GCV). In sum, our findings support the notion that Nef7-based VLPs can be considered platforms for original systems of protein delivery. In particular, the here- described Nef7/TK VLPs represent a first applicative example opening the way toward new HSV-1 TK/GCV-based cell suicide therapies circumventing cell gene engineering procedures

Integration and Optimization of Voltage Active Filtering Functionality in a PV Park

The stringent regulations on the power quality declared in the standard IEEE 519-2014 push the companies and the power producers to install active filters to compensate the voltage harmonics distortion in the point of common coupling (PCC). However, in the case of a Photovoltaic (PV) park, the cost for an additional active filter converter can be saved by using the PV converters themselves as active filter. This solution is very attractive, but reserves several challenges. In fact, the harmonic current injection by the PV converters can generate ripples in the DC link which increases the stress on the converter components and affects the MPPT. Moreover, the overcurrent protection of the PV converter must be taken into account. In this paper a centralized optimized strategy to share the harmonic current injection among all the converters in a PV park is investigated. The optimization is formulated as a quadratic programming (QP) problem: the active power consumed by the PV park for the active filtering and the DC link ripple of the PV converters caused by the harmonic currents injection are minimized. The limit on the maximum injectable harmonic current by each PV converter are respected

Analysis of Overmodulation in Power Synchronization-based Voltage Source Converters

Low power system inertia in power electronics-dominated grids is a widely discussed problem. Power synchronization allows to emulate inertia by means of the active power low-pass filter, slowing down the grid frequency excursions. Nevertheless, inertia emulation during grid disturbances results in high energy exchange with the dc-link, which brings large dc voltage excursions. When the dc voltage dips below the ac line voltage peak, the modulation index can become too high and make the converter unable to produce the requested ac voltage. The consequent saturation of the voltage can cause current control wind-up, harmonic distortion and loss of controllability. Moreover, when the reference voltage is saturated, the converter does not behave anymore according to the power synchronization control law, making the conventional stability analyses not valid. Despite the relevance of these issues, a systematic analysis about the voltage saturation induced by grid disturbances in power converters is still missing. For that, this paper proposes a mathematical tool based on Bode plots. The target of this tool is to properly chose the converter parameters in order to tolerate grid disturbances without reaching the voltage saturation. Simulations and experiments are provided

The use of x-ray CT and MRI in the study of sacroiliac joints in patients with Behcet disease and acute anterior uveitis

Objective: It's controversial if Behcet Disease (BD) must be included in the group of seronegative spondyloarthropathy (SpA). Our aim was to establish the prevalence of sacroiliitis (SI) in patients with BD using X-Ray, CT and MRI, in comparison with patients with Acute Anterior Uveitis (AAU), that is known to belong to the subgroups of SpA. Methods: We considered, in the period from 04/2006 to 04/2009, 21 consecutive patients with BD, positive for HLA B51 and 28 consecutive patients with AAU, positive for HLA B27. These patients were previously selected by our Rheumatological Ward. Altogether we evaluated 98 sacroiliac joints (SIJ); each side of any patient was graded separately. Results: X-ray of the pelvis showed advanced SI (grade 4) in 14% of the cases in patients with AAU; in BD group only 7% CT showed advanced SI in 14% within AAU patients versus 6-12% of advanced SI (right to left) within BD patients. MR showed 14% of advanced SI (bilateral) within AAU versus 6-11% of advanced SI (right to left) in BD patients. Conclusions: This study supports the trend to not consider BD within the SpA, being the prevalence of SI in BD patients not very different from general population and anyway lower than that observed in patients with AAU. On the other side the prevalence of SI in AAU patients is higher than in BD patients and very similar to the one observed in patients with seronegative arthritis, and anyway high enough to consider joint involvement as an important feature of the disease

Design and Manufacturing of a Nd-Doped Phosphate Glass-Based Jewel

This paper reports the results of the designing, manufacturing and characterization of a jewel obtained by means of coupling the dogmas of industrial design to the analytical engineering approach. The key role in the design of the jewel was played by an in-house synthesized Neodymium (Nd)-doped phosphate glass, selected due to its easy handling and capability to change color according to the incident light wavelength. The glass core was covered by a metal alloy to mitigate its relatively high fragility and sensitivity to thermal shock and, at the same time, to highlight and preserve its beauty. The selection of the proper metal alloy, having thermo-mechanical properties compatible with those exhibited by the glass, was carried out by means of Ashby’s maps, a powerful tool commonly adopted in the field of industrial design

Clinical predictive factors of pathologic complete response in locally advanced rectal cancer

Background: Predictive factors of pathologic complete response (pCR) after neoadjuvant chemoradiotherapy (nCRT) in locally advanced rectal cancer (LARC) are still not identified. The purpose of this study was to define them. Materials and Methods: Data from consecutive LARC patients treated between January 2008 and June 2014 at our Institution were included in the analysis. All patients were treated with a long course of nCRT. Demographics, initial diagnosis and tumor extension details, as well as treatment modalities characteristics were included in the univariate and logistic regression analysis. Results: In total 99 patients received nCRT, of whom 23 patients (23.2%) achieved pCR. Patients with and without pCR were similar in term of age, sex, comobidities, BMI and tumor characteristics. Multivariate logistic regression indicated that pre-treatment tumor size <= 5 cm was a significant predictor for pCR (p = 0.035), whereas clinical N stage only showed a positive trend (p = 0.084). Conclusions: Tumor size at diagnosis could be used to predict pCR, and thus to individualize therapy in LARC patients management. Validation in other studies is needed

Specification and analysis of SOC systems using COWS: a finance case study

Service-oriented computing, an emerging paradigm for distributed computing based on the use of services, is calling for the development of tools and techniques to build safe and trustworthy systems, and to analyse their behaviour. Therefore many researchers have proposed to use process calculi, a cornerstone of current foundational research on specification and analysis of concurrent and distributed systems. We illustrate this approach by focussing on COWS, a process calculus expressly designed for specifying and combining services, while modelling their dynamic behaviour. We present the calculus and one of the analysis techniques it enables, that is based on the temporal logic SocL and the associated model checker CMC. We demonstrate applicability of our tools by means of a large case study, from the financial domain, which is first specified in COWS, and then analysed by using SocL to express many significant properties and CMC to verify them