An atomic commit protocol for gigabit-networked distributed database systems

In the near future, different database sites will be interconnected via gigabit networks, forming a very powerful distributed database system. In such an environment, the propagation latency will be the dominant component of the overall communication cost while the migration of large amounts of data will not pose a problem. Furthermore, computer systems are expected to become even more reliable than today’s systems with long mean time between failures and short mean time to repair. In this paper, we present implicit yes-vote (IYV), a one-phase atomic commit protocol, that exploits these new domain characteristics to minimize the cost of distributed transaction commitment. IYV eliminates the explicit voting phase of the two-phase commit protocol, hence reducing the number of sequential phases of message passing during normal processing. In the case of a participant’s site failure, IYV supports the option of forward recovery by enabling partially executed transactions that are still active in the system to resume their execution when the failed participant is recovered.     

Boron removal by membrane contactors: the water that purifies water

The potential of membrane contactors for treating boron containing waters were investigated. In particular, experimental tests at lab scale on flat membrane modules with 40 cm² of membrane area were carried out, to identify the effect of different parameters, such as temperature, flow rate, boron concentration, etc. on the efficiency of the process. Water was chosen as the extractant in order to avoid the pollution of the feed stream and two symmetric microporous hydrophilic flat membranes with different pore size and porosity were used. From these tests, it results that the boron removal increases with the extractant temperature and with the operating flow rates. However, it is independent on the initial boron concentration in the feed water. Moreover, higher removals are obtained with the membrane with larger pore size and higher porosity. Based on the experimental results, an integrated reverse osmosis-membrane contactor system, where the membrane contactor works on the reverse osmosis permeate, was proposed and designed for a 100 m³/h fresh water production (with a boron content ≤0.4 ppm). In particular, membranes with higher porosity and lower thickness than those used in the experimental tests were considered for the calculations, in order to work at 25°C (so, there is no need of heating the extractant stream) with reasonable membrane areas. The comparison of the proposed plant to that actually used, has shown that the proposed one appears to be more effective in terms of size, energy and chemical consumption, flexibility and modularity.     

Ubiquitous knowledge empowers the Smart Factory: The impacts of a Service-oriented Digital Twin on enterprises' performance

While the Industry 4.0 is idolizing the potential of an artificial intelligence embedded into ``things", it is neglecting the role of the human component, which is still indispensable in different manufacturing activities, such as a machine setup or maintenance operations. The present research study first proposes an Industrial Internet pyramid as emergent human-centric manufacturing paradigm within Industry 4.0 in which central is the role of a Ubiquitous Knowledge about the manufacturing system intuitively accessed and used by the manufacturing employees. Second, the prototype of a Service-oriented Digital Twin, which leverage on a flexible ontology-oriented knowledge structure and on augmented reality combined to a vocal interaction system for an intuitive knowledge retrieval and fruition, has been designed and developed to deliver this manufacturing knowledge. Two test-beds, complimentary for the problems in practice (the former on the maintenance-production interface in a large enterprise, the latter majorly focused in production and setups in a small and medium enterprise), show the significant benefits in terms of time, costs and process quality, thus validating the approach proposed. This research shows that a human-centric and knowledge-driven approach can drive the performance of Industry 4.0 initiatives and lead a Smart Factory towards its full potential.     

The Se–S Bond Formation in the Covalent Inhibition Mechanism of SARS-CoV-2 Main Protease by Ebselen-like Inhibitors: A Computational Study

The inhibition mechanism of the main protease (M^pro) of SARS-CoV-2 by ebselen (EBS) and its analog with a hydroxyl group at position 2 of the benzisoselenazol-3(2H)-one ring (EBS-OH) was studied by using a density functional level of theory. Preliminary molecular dynamics simulations on the apo form of M^pro were performed taking into account both the hydrogen donor and acceptor natures of the Nδ and Nε of His41, a member of the catalytic dyad. The potential energy surfaces for the formation of the Se–S covalent bond mediated by EBS and EBS-OH on M^pro are discussed in detail. The EBS-OH shows a distinctive behavior with respect to EBS in the formation of the noncovalent complex. Due to the presence of canonical H-bonds and noncanonical ones involving less electronegative atoms, such as sulfur and selenium, the influence on the energy barriers and reaction energy of the Minnesota hybrid meta-GGA functionals M06, M06-2X and M08HX, and the more recent range-separated hybrid functional wB97X were also considered. The knowledge of the inhibition mechanism of M^pro by the small protease inhibitors EBS or EBS-OH can enlarge the possibilities for designing more potent and selective inhibitor-based drugs to be used in combination with other antiviral therapies.     

On-site calibration system for trace humidity sensors

A portable device for calibration of trace humidity sensors and an adopted calibration procedure have been developed. The calibration device is based on humidity generation by permeating water through polymeric membrane tubes. Water vapour transmission rates for various polymers were experimentally determined in order to select the most suitable polymeric material. The developed trace humidity generator consists of a gas-flow polymeric hose immersed in a water reservoir thermostated by a sensor-controlled heater. Mole fractions of water vapour between 1 μmol mol⁻¹ and 350 μmol mol⁻¹ (equivalent to frost-point temperatures from −76 °C to −31 °C) were generated by varying either the operating temperature or gas flow. The operating temperature can be varied from 20 °C to 60 °C and kept stable within 0.1 K. Uncertainty analysis indicated that the trace humidity generator produces gas flows of constant humidity amounts with a relative expanded uncertainty less than 3.4% (k = 2) of the generated value.     

Effects of prong-wire interferences in dual hot-wire probes on the measurements of unsteady flows and turbulence in low-speed axial fans

Support needles of Dual Hot Wire (DHW) anemometers induce significant inaccuracies for flow angle and turbulence measurements in the case of X-array probes with prongs perpendicular to the flow plane. At certain angular ranges of the incident flow, a wake interference is established between the sensors which leads to a practical limitation of the device. In the case of turbomachinery environments, this is even more critical due to the inherent unsteadiness of the flow direction rotor downstream.In the present work, the measurement deviation caused by hot-wire probes operated under interference effects has been studied and evaluated, in both steady and unsteady conditions, especially for turbomachinery flows. New designs of DHW probes without prong-wire interference effects in their operative angular ranges were developed for validation. In particular, both V-type and Z-type interference-free probes are compared to a classic X-type probe susceptible for prong-wire interferences. Firstly, a steady calibration is performed to show the baseline deviation of the X-array probe in the measurement of the velocity magnitude, the flow angle and the turbulence intensity. Typical errors up to 10–13% in velocity, 5.5–7 deg in angle and 1.5–2.5 points overestimation in turbulence levels are observed. Also, unacceptable inaccuracies are found in the turbulence spectra of the measurements.Following, the impact of the interference for unsteady flow measurements is highlighted comparing the performance of the three probes within the single stage of a low-speed axial fan. The unsteady measurements of the X-array probe have revealed similar averaged discrepancies to those observed in the steady performance, but the instantaneous deviations can be as high as a 20% in velocity and 16–18 deg in flow angle in those regions (rotor wakes) with large unsteady velocity gradients and turbulence generation. Turbulence intensity measured in the rotor wakes is also excessively higher.     

The instrumental resolution of a moire extensometer in light of its recent automatisation

This paper assesses the instrumental resolution of a mechanical extensometer in light of its recent automatisation. The instrument takes advantage of the moire phenomenon of optical interference to measure angular rotation in two perpendicular planes and displacement in three dimensions. Our assessment systematically defines an analytical solution for the complete interpretation of a generic moire pattern and a set of mathematical approximations for the moire patterns used to measure rotation and displacement. The ultimate sensitivity of the automated instrument is determined on the basis of a generic least square differences fitting procedure while the instrumental resolution is defined on the basis of realistic, rather than optimal, scenarios: the resolution of the rotation measurements are in the order of 8.7 1 10⁻⁵ rad while the resolution of the displacement measurements are better than 5 μm. This assessment represents the first step towards a global numerical repository for processed data recorded by the automated extensometers.     

The numerical method for the coverage interval determination in the conducted emission measurements

This paper presents a numerical method for the coverage interval determination of the output variable while knowing the probability density functions of two non-dependent input variables. The coverage interval is derived from distribution function. In order to obtain the probability density function of the output variable, which is of mixed distribution type, the numerical combined method is applied, consisted of the Monte Carlo method and the modified least-squares method. The proposed method is applied for the symmetric distributions in the conducted emission measurements. The validation of the combined method showed its satisfactory level of accuracy.