Visualization of Flow Patterns in Closed Loop Flat Plate Pulsating Heat Pipe Acting as Hybrid Thermosyphons under Various Gravity Levels

A particular flat plate pulsating heat pipe (FPPHP), filled with FC72, is tested during the 62^th and 64^th ESA parabolic flight campaigns under vertical orientation. The FPPHP is made of a thin copper plate, in which a curved channel disposed with 11 U-turns is milled and closed on the top face by a transparent borosilicate plate. The particular characteristics is that the equivalent hydraulic diameter of the square channel (2.5 × 2.5 mm²) is above the working fluid capillary diameter on ground, inducing a stratification of the liquid/vapor phases under ground and hyper-gravity conditions, whatever the orientation. The energy transfer mode in such conditions is represented either by pure pool boiling inside the channels almost completely filled by the liquid phase or by an annular flow pattern inside the channels mostly filled by the refrigerant vapor. Instead, during the microgravity phases, the fluid regime naturally turns into a slug-plug flow pattern. During the transition from 1.8 g to 0 g a rapid dry-out may occur in some of the channels, followed by a similarly fast reaction of liquid plugs moving towards the evaporator from the condenser zone. Such stop-and-start motion events continue during the whole microgravity period, leading to strong temperature oscillations, but also to a still acceptable thermal performance of the device.     

A flexible framework for evaluating user and item fairness in recommender systems

User Modeling and User-Adapted Interaction - One common characteristic of research works focused on fairness evaluation (in machine learning) is that they call for some form of parity (equality)...     

Medieval glazed ceramic from Caesar's Forum (Rome,Italy): Production technology

This study is focused on Medieval Roman heavy lead-glazed ceramics from the archaeological site of the Caesar's Forum (Rome, Italy), dated from the 10th and not beyond the first decades of the 11th century. Optical microscopy (OM), X-ray powder diffraction (XRPD), scanning electron microscopy (SEM-EDS) and electron microprobe analysis (EMPA) have been used for the archaeometric characterization of the ceramics. Petrographic analysis of the body indicated the occurrence of three petro-fabrics, mainly composed by abundant quartz, feldspars, nodules of iron oxides, rare fragments of siliceous rocks, very rare fragments of calcareous rocks, pyroxene, biotite and olivine. This mineralogical assemblage suggests that the ceramics were fired in the range 950–1050 °C, under oxidizing conditions. SEM and EMP analysis show that the ceramic body was produced with non-or moderately calcareous clays and the heavy glaze with lead oxide, silica, alumina and alkalis. The microstructure of the glaze and the relationship with the body suggest that for the production of the ceramic repertoire of the Caesar's Forum either the single or the double firing techniques were used.     

Structure and properties of sugar beet fibres

Fibrous fractions were prepared from sugar beet pulp (RF) by sequential extractions with potassium oxalate, 0.05 M hydrochloric acid at 85°C and 0.05 m sodium hydroxide at 4°C. The overall composition, polysaccharide structure and some physico-chemical properties (cation exchange capacity, CEC; water holding capacity, WHC; swelling) of each fraction were determined. RF was mostly composed of carbohydrates (66.3 %) with minor amounts of ash, proteins and lignin. The main polysaccharides were highly methylated and acetylated pectins, cellulose and arabinans. The oxalate residue (82.1 % of RF) exhibited only minute differences from RF whereas the acidic and alkaline residues, accounting for 42.8 % and 35.5 % of RF, respectively, were enriched in cellulose and hemicelluloses (xylans, xyloglucans, mannans) and mostly devoid of pectins and arabinans. CEC and WHC of fractions were closely related to the content of unmethylated galacturonic acid residues. The influence of the ionic form of ionisable groups was demonstrated, the Na⁺ form giving the highest WHC. The ionic strength of the medium can reduce the WHC, especially in the case of the acid and alkali-extracted fibres.     

Oxidation of ethyl alcohol in trickle bed reactors: Analysis of the conversion rate

The interpretation of results of a chemical reaction carried out in a trickle bed reactor is not immediate when the key reactants are volatile; in fact some authors state that the overall conversion rate increases at very low liquid flow rates, i.e. when the catalyst is unevenly wetted. In these conditions, the reactants may penetrate inside the catalyst pellets directly through the “dry” zones; therefore the mass transfer resistance is diminished and the conversion rate can be increased. To investigate this phenomenon tests on the catalytic oxidation of ethyl alcohol dissolved in water were performed at different operating conditions in a trickle bed reactor. An interpretation of the results was tried by using two different models based on partially wetted particles. This approach considers both the cases in which “dry” zones are active or not for mass transfer and mass transfer rates are affected or not by the chemical reaction.     

Near-recursive optical flow from weighted image differences.

This correspondence derives a formal link between temporally weighted frame differences, or disturbance fields, which carry limited information suitable for motion detection, and the optic flow (OF), which carries richer information on local image motion. We use this link to derive a novel, simple, near-recursive optic flow algorithm based on a recursive-filter formulation. Most quantities involved are computed recursively, using only data from the current and previous frame. We can limit expensive OF calculations to pixels where motion magnitude is sufficiently high using image differences which the algorithm computes anyway. Experimental results with well-known synthetic, ground-truthed test sequences and standard performance metrics indicate good quantitative performance. Tests with real sequences suggest similar or better performance than a well-known, similar algorithm due to Lucas and Kanade (LK).     

Surface Instability and Chemical Reactivity of ZrSiS and ZrSiSe Nodal‐Line Semimetals

Materials exhibiting nodal‐line fermions promise superb impact on technology for the prospect of dissipationless spintronic devices. Among nodal‐line semimetals, the ZrSiX (X = S, Se, Te) class is the most suitable candidate for such applications. However, the surface chemical reactivity of ZrSiS and ZrSiSe has not been explored yet. Here, by combining different surface‐science tools and density functional theory, it is demonstrated that the formation of ZrSiS and ZrSiSe surfaces by cleavage is accompanied by the washing up of the exotic topological bands, giving rise to the nodal line. Moreover, while the ZrSiS has a termination layer with both Zr and S atoms, in the ZrSiSe surface, reconstruction occurs with the appearance of Si surface atoms, which is particularly prone to oxidation. It is demonstrated that the chemical activity of ZrSiX compounds is mostly determined by the interaction of the Si layer with the ZrX sublayer. A suitable encapsulation for ZrSiX should not only preserve their surfaces from interaction with oxidative species, but also provide a saturation of dangling bonds with minimal distortion of the surface.     

Surface Reconstruction,Oxidation Mechanism,and Stability of Cd3As2

Cadmium arsenide (Cd₃As₂) has recently attracted considerable interest for the presence of 3D massless Dirac fermions with ultrahigh mobility and magnetoresistance. However, its surface properties are currently largely unexplored both theoretically and experimentally, due to the very large unit cell and the challenging growth of single‐crystal samples, respectively. Here, by combining ab initio calculations with surface‐science spectroscopic experiments, the presence of a surface reconstruction is unveiled in centimeter‐scale (112)‐oriented Cd₃As₂ single‐crystal foils produced by the self‐selecting vapor growth. Outermost Cd atoms descend into the As‐sublayer with a subsequent self‐passivation of the dangling bonds with As atoms, forming the triangle lattice previously imaged by scanning tunneling microscopy. Moreover, the oxidation mechanism of this reconstructed surface, dominated by the formation of As? O? Cd bonds, is revealed. Interestingly, it is found that the band structure of the reconstructed surface of Cd₃As₂ is quite robust against surface oxidation. Both computational and experimental findings point to a successful exploitation in technology of Cd₃As₂ single crystals.     

KIND‐DAMA: A modular middleware for Kinect‐like device data management

In the last decades, we have witnessed a growing interest toward touchless gestural user interfaces. Among other reasons, this is due to the large availability of different low‐cost gesture acquisition hardware (the so‐called “Kinect‐like devices”). As a consequence, there is a growing need for solutions that allow to easily integrate such devices within actual systems. In this paper, we present KIND‐DAMA, an open and modular middleware that helps in the development of interactive applications based on gestural input. We first review the existing middlewares for gestural data management. Then, we describe the proposed architecture and compare its features against the existing similar solutions we found in the literature. Finally, we present a set of studies and use cases that show the effectiveness of our proposal in some possible real‐world scenarios.