Enterprise Application Integration (EAI) e Beni Culturali: un’esperienza di gestione informatizzata assistita dalla radiofrequenza (RFId)

The Soprintendenza per i Beni Archeologici di Ostia is the Italian government office charged with the preservation of the ancient Roman city of Ostia and its surroundings. Ostia has been the object of excavations since the Middle Ages and has yielded an enormous quantity of finds of all kinds. The Soprintendenza today undertakes mostly preventive excavations, especially in connection with public works. These result in vast quantities of finds that need to be housed in the office’s stores. Since 2004 the management of the stores has availed itself of the use of Radio-Frequency Identification (RFId), an automatic identification method relying on storing and remotely retrieving data using devices called RFId tags or transponders. An advanced automatic identification technology based on the RFId technology has two values for inventory systems. First, the visibility provided by this technology allows an accurate knowledge on the inventory level by eliminating the discrepancy between inventory record and physical inventory. Second, the RFId technology can prevent or reduce the sources of errors. Benefits of using RFId include the reduction of labour costs, the simplification of business processes and the reduction of inventory inaccuracies

Crystal structure of the yellow 1:2 molecular complex lumiflavin–bisnaphthalene-2,3-diol

In the first molecular complex of the physiologically active neutral form of isoalloxazine studied, lumiflavin–bisnaphthalene-2,3-diol, each flavin is sandwiched between two naphthalenediol molecules with extensive overlap but a moderately large (3·44 Å) spacing, indicating at most weak charge-transfer interaction and in agreement with the yellow colour of the complex, nearly the same as that of the parent lumiflavin

Molecular simulations of hybrid cross-linked membranes for H₂S gas separation at very high temperatures and pressure:Binary 90%/10% N₂/H₂S and CH₄/H₂S, ternary 90%/9%/1% N₂/CO₂/H₂S and CH₄/CO₂/H₂S mixtures

Molecular dynamics (MD) simulations have previously identified four hybrid inorganic-organic membranes based on POSS or OAPS silsesquioxanes hyper-cross-linked with small PMDA or 6FDA imides, which are able to maintain reasonable CO2/N2 and CO2/CH4 permselectivities at very high temperatures (300 °C and 400 °C) and pressure (60 bar). Experimentally, the polyPOSS-imides are known to degrade above 300 °C while the polyOAPS-imides can resist up to above 400 °C. In the present work, the same four model polyOAPS/POSS-imide networks are further tested for their gas separation abilities of H2S-containing mixtures. Indeed, hydrogen sulfide is a hazardous gas present in many gas feeds, and, within the context of a toxic penetrant under harsh conditions, simulations are a useful task to perform before embarking on difficult experiments. The separations of H2S with respect to N2, CH4 and CO2 by the polyOAPS/POSS-imide matrices were studied at 300 °C, 400 °C and at 60 bar, firstly with H2S as a single-gas in order to obtain its ideal permselectivities, secondly as part of binary 90%/10% N2/H2S and CH4/H2S feeds and thirdly as part of ternary 90%/9%/1% N2/CO2/H2S and CH4/CO2/H2S feeds. They were compared to separations of binary 90%/10% N2/CO2 and CH4/CO2 feeds under exactly the same conditions. At 300 °C, H2S is much more soluble in the networks than the other three penetrants. It is the only one leading to a non-negligible volume swelling at 60 bar, although this does not happen for the mixed-gas feeds due to their low H2S partial pressures. Differences are attenuated at 400 °C because of the decrease in solubilities upon heating. The linear N2 and CO2 move faster than the non-linear CH4 and H2S penetrants, but the diffusion selectivities are moderate. As such, the ideal permselectivities under harsh conditions are mainly governed by the solubility selectivities. With binary 90%/10% N2/H2S, CH4/H2S, N2/CO2 and CH4/CO2 feeds, the transport parameters of the major N2 or CH4 components remain similar to their ideal values, whereas the solubilities of the minor H2S and CO2 components increase. This leads to some of the real separation factors for H2S being different from their ideal permselectivities, and approximately twice as high as those with CO2. In the ternary 90%/9%/1% N2/CO2/H2S and CH4/CO2/H2S mixtures, replacing 1% CO2 by 1% H2S in the feeds leads to small changes but, in pratice, these are not significant enough to make a difference. Under the conditions tested, the ternary separation factors are the same than for the 90%/10% binary mixtures. In all cases, the denser polyPOSS-imides show better sieving properties than the more open polyOAPS-imides. As such, the former should preferably be used in applications up to 300 °C, i.e. in the temperature range below their degradation. However, it is also possible to use the polyOAPS-imides at higher temperatures, since they still manage maintaining separation factors between 2 and 6 for CO2 and H2S at 400 °C, which is outstanding for polymer-based membranes at such high temperatures.</p

Numerical scheme for simulating multicomponent mass transport accompanied by reversible chemical reactions in porous media

A numerical scheme is presented for computer simulation of multicomponent gas transport possibly accompanied by reversible chemical reactions in a macroporous medium, based on the dusty gas model. Using analytical solutions for simple systems it is shown that the derivation of the scheme is mathematically correct and the implementation into Borland Dephi code is performed without vital programming errors. Simulations showed remarkable accuracy, robustness and efficiency

Low temperature pyrolysis of thin film composite polyphosphazene membranes for hot gas separation

Highly selective thin-film composite membranes for hot hydrogen sieving are prepared via the pyrolysis of thin cyclomatric polyphenoxy phosphazene films that are prepared via a non-conventional interfacial polymerization of hexachlorocyclotriphosphazene with 1,3,5-trihydroxybenzene or m-dihydroxybenzene. The presence of the cyclic phosphazene ring within the weakly branched polymer films gives rise to a distinct thermal degradation evolution, with an onset temperature of around 200 °C. For the trihydroxybenzene derived material, the hydrogen permselectivity of the films shows a maximum pyrolysis temperature of around 450 °C. At this temperature a compact atomic structure is obtained that comprises mostly disordered carbon and accommodates P–O–C and P–O–P bonds. During thermal treatment, these films reveal molecular sieving with permselectivities exceeding 100 for H2/N2, H2/CH4, and H2/CO2, and a hydrogen permeance of 2 × 10−10 to 1.5 × 10−8 mol/m2/s/Pa (0.6-44.8GPU), at 200 °C. At ambient temperatures, thin films are very effective barriers for small gas molecules. Because of the inexpensive facile synthesis and low- temperature pyrolysis, the polyphosphazene films have the potential for use in high-temperature industrial gas separations, as well as for use as barriers such as liners in high- pressure hydrogen storage vessels at ambient temperature.</p

Tensile stress in a porous mediumdue to gas expansion

Stress profiles develop in a porous material due to a gas-phase pressure difference and subsequent gas flow. If stresses become tensile, material failure (explosion and blistering) can occur. Stress profiles are calculated for an asymmetric inorganic porous disk-like membrane material placed in a pressure vessel, which is depressurized. The stress that develops in the membrane material depends on the gas-phase pressure and the porosity. The gas-phase pressure is a function of place, time and characteristics of the membrane, the vessel and the valve. Two regimes are identified for membrane depressurization, and a critical initial pressure is defined below which tensile stresses cannot develop. The theory presented combines the dusty gas model with balances for mass, momentum, and mechanical energy

Comparison of Eight Classical Lennard-Jones-Based H₂ Molecular Models in the Gas Phase at Temperatures and Pressures Relevant to Hydrogen On-Board Storage Tanks

This work compares eight classical H2 molecular models in the gas phase taken from the existing literature. All models are based on Lennard-Jones (LJ) 12-6 terms for the van der Waals interactions and hence easier to transfer to multiphase molecular simulations than more sophisticated potentials. The H2 potentials tested include one-site, two-site, three-site, and five-site models, with the sites being either the H atoms, the center-of-mass of the H2 molecule, or massless sites. For the multisite models, high-frequency H-H stretching modes can lead to poor equipartition of the kinetic energy, and the timestep for molecular dynamics (MD) simulations should be reduced to maintain a stable numerical integration of the equations of motion. As such, only those models with rigid bonds are considered. In the present case, 600 MD simulations of H2 gas were carried out over a large range of temperatures (−50 to +90 °C) and at densities corresponding to a pressure range of 50 to 2000 bar, which include the operating conditions of on-board storage tanks in hydrogen-fueled vehicles. Most of the models under study were found to reproduce reasonably well the experimental pVT phase diagram as well as the solubility. Discrepancies only became significant at the highest densities tested, and these could be used to rank the different models. All model diffusion coefficients were essentially indistinguishable from experimental results, and as such, kinetically dominated dynamic properties could not be used as a criterion for the choice of model. Among the eight models tested, two of them, i.e., the two-site model of Yang and Zhong and the one-site model derived from Buch performed very well over the range of conditions tested. They represent a good compromise between realism, simplicity, and computational efficiency.</p

Nonaqueous Interfacial Polymerization-Derived Polyphosphazene Films for Sieving or Blocking Hydrogen Gas

A series of cyclomatrix polyphosphazene films have been prepared by nonaqueous interfacial polymerization (IP) of small aromatic hydroxyl compounds in a potassium hydroxide dimethylsulfoxide solution and hexachlorocyclotriphosphazene in cyclohexane on top of ceramic supports. Via the amount of dissolved potassium hydroxide, the extent of deprotonation of the aromatic hydroxyl compounds can be changed, in turn affecting the molecular structure and permselective properties of the thin polymer networks ranging from hydrogen/oxygen barriers to membranes with persisting hydrogen permselectivities at high temperatures. Barrier films are obtained with a high potassium hydroxide concentration, revealing permeabilities as low as 9.4 × 10-17 cm3 cm cm-2 s-1 Pa-1 for hydrogen and 1.1 × 10-16 cm3 cm cm-2 s-1 Pa-1 for oxygen. For films obtained with a lower concentration of potassium hydroxide, single gas permeation experiments reveal a molecular sieving behavior, with a hydrogen permeance of around 10-8 mol m-2 s-1 Pa-1 and permselectivities of H2/N2 (52.8), H2/CH4 (100), and H2/CO2 (10.1) at 200 °C.</p