Experimental investigation of the steady state behaviour of Breathing Walls by means of a novel laboratory apparatus

Breathing Walls are envelope components, based on porous materials, crossed by a natural or forced airflow. Since they behave both as recovery heat exchangers and active insulation, reducing the conductive heat flux, they represent a promising envelope technology, allowing to reduce energy consumption in buildings. From the modeling point of view, an analytical model can be found in literature, describing heat and mass transfer across Breathing Walls in steady state conditions. However, to the best of the authors' knowledge, the model lacks an exhaustive experimental validation. Therefore, in this paper, the novel laboratory apparatus named Dual Air Vented Thermal Box developed at Politecnico of Milano is presented. The apparatus is used to experimentally investigate the steady state behaviour of a 1 m2 Air Permeable Concrete sample, crossed by an airflow at different velocities up to 12 mm/s. The temperature profile inside the sample, measured in different positions, is compared with the model predictions. While in the central portion of the wall a very good agreement is found, the experimental results at the top and at the bottom of the wall suggest a non-uniform velocity field entering the sample. A qualitative confirmation of this hypothesis is provided by CFD simulations on the apparatus, clearly showing a mixed convection regime on both sides of the wall. The results lead to state the validity of the one-dimensional analytical model in literature, although a careful application should take into account adjusted boundary conditions, consisting in an airflow velocity possibly variable with height

In Situ Measurement of Wall Thermal Properties: Parametric Investigation of the Heat Flow Meter Methods through Virtual Experiments Data

Energy retrofit of existing buildings is based on the assessment of the starting performance of the envelope. The procedure for the in situ measurement of thermal conductance is described in the ISO 9869-1:2014, which provides two techniques for data processing: the average method (AM) and the dynamic method (DM). This work studies their effectiveness using virtual data from numerical simulations based on a finite difference model applied to different wall kinds, considering winter and summer boundary conditions alternatively (Italian Milan-Linate TMY). The estimated thermal conductances are compared to the reference theoretical values. The main purposes are: (i) defining the shortest test duration that provides acceptable results; (ii) assess the reliability of the criteria provided by the standard to evaluate the measurement quality; (iii) evaluate the sensitivity of both methods to variables such as wall properties, boundary conditions and others more specific to the DM (namely, the number of time constants and linear equations). The AM always provides acceptable estimates in winter (-3.1% divided by 10% error), with better outcomes when indoor heat flux is considered, except for the highly insulated wall, but is not effective in summer, despite the fulfillment of the acceptance criteria for the highly insulated wall. The DM provides improvements in both seasons (0.05% divided by 8.6% absolute values of error), for most virtual samples, and requires shorter sampling periods, even below the 3 days limit suggested by the standard. The test on the confidence interval indicated by the ISO 9869-1:2014 is not reliable and measurements are sensitive to the number of linear equations, that is left to the user's discretion without strict indications. This work suggests a possible approach for overcoming this issue, which requires deeper future investigation

Numerical experiments for defining criteria for the use of LS-PIV based techniques in river monitoring.

The developing of new image-based techniques for environmental monitoring is opening new frontiers for remote streamflow measurements in natural environments, since they allow for non-intrusive measurements even in adverse circumstances, such as high flow conditions that often hinder the use of traditional approaches and instruments. Methods based on the acquisition, analysis and elaboration of images for streamflow observation, such as the large scale particle image velocimetry (LSPIV) and the particle tracking velocimetry (PTV) techniques, are rapidly evolving also in consideration of the growing availability of a new generation of optical sensors, digital cameras and methodologies. A number of free and easy software based on LSPIV and PTV allows for a complete characterization of the instantaneous surface velocity field of a river and the assessment of the discharge at specific cross-sections, when the cross-section geometry is known. This kind of software usually requires a sequence of images that can be captured by digital cameras, which can be permanent gauge-cams installed close to the river, mobile-devices with operators standing on the banks or on bridges, or even cams installed on unmanned aerial vehicle (UAV). Despite the great accessibility of cost-effective devices and the simplicity of the free availability of software for image processing, LSPIV and PTV techniques are rarely systematically implemented in practical applications, probably due to the lack of consistent image processing protocols. In this work the performance and the sensitivity of free software based on LSPIV to some factors, such as the seeding density, the frame to frame displacement of tracer, the number of elaborated frames, tracers geometry, are analyzed. In particular, difference sequences of images with known tracers (in size and density) moving at know velocity are created under different configurations (i.e. considering different combinations of the above mentioned factors) and the error in the evaluation of the instantaneous surface velocity field is assessed for each configuration. The different configurations are created considering three possible schemes: ideal (tracers constituted by white disks of equal size and uniformly distributed on a black background), semi-real (tracers constituted by disks of equal size, colored by a white color disturbed by a white noise, and uniformly distributed on a real background), real (real tracers on a real background). Real images, captured by a cam installed on UAV flying on a real river, have been used for the generation of the image-sequences generation under the schemes semi-real and real. Results can be considered extremely useful in defining criteria for guidelines for practical real applications

On the morphology of Anisakis pegreffii: a comparative analysis of three microscopic techniques used to build a new parasite atlas

BACKGROUND: Human anisakidosis is a parasitic anthropozoonosis caused by larval nematodes of the family Anisakidae. Here, we report a detailed description of the morphology of Anisakis pegreffii third-stage larva performed using a conventional light and confocal microscopy, and scanning electron microscopy (SEM) that provide a basis for both phenotypic studies and genetic mutations. METHODS: The collected larvae from fish were morphologically identified as Anisakis larvae Type I, and they were characterized by PCR-RFLP to identify the Anisakis pegreffii specie. Using NC5/NC2 primers, ribosomal genomic regions ITS1, 5.8 SrRNA and ITS2 of DNA were amplified and PCR products were sequenced. Fifteen larvae belonging to Anisakis pegreffii were fixed, sectioned, and examined with a light and confocal microscope and by SEM. RESULTS: In our studies, have been acquired detailed ultrastructural images, which have been integrated with those derived from the dissection of the parasite, obtained with light and confocal microscopy. The structural and ultrastructural images concerning the third stage larvae of Anisakis pegreffii have been studied, analyzed and compared among them. The derived overall view has allowed detecting new interesting details of a well-known parasite and has been schematically showed. CONCLUSIONS: The aim of this study is to furnish an updated atlas of Anisakis pegreffii. Confocal microscopy, as well as the light and electron microscopy have played a pivotal role in the accumulation of new scientific data regarding the anatomical structures of this nematode. This work is the result of one year of engagement by the Authors and the outcome is a comprehensive atlas on Anisakis pegreffii microscopy

Sulfur-based copolymeric polyamidoamines as efficient flame-retardants for cotton

The polyamidoamine derived from N,N'-methylenebisacrylamide (M) and glycine (G), M-G, has been shown to be an effective flame-retardant (FR) for cotton in horizontal flame spread tests (HFST), extinguishing the flame at 5% add-on. Its activity was attributed to its intrinsic intumescence. In vertical flame spread tests (VFST), M-G failed to extinguish the flame even at 30% add-on. Conversely, in VFST, the polyamidoamine derived from M and cystine (C), M-C, inhibited cotton combustion at 16% add-on, but in HFST failed to extinguish the flame below 12% add-on. Its activity was ascribed to the release of sulfur-containing volatiles acting as radical scavengers. In this work, the FR effectiveness of M-Gm-Cn copolymers with different G/C ratio was compared with that of the M-G and M-C homopolymers and of M-G/M-C blends of the same compositions. In HFST, both copolymers and blends extinguished the flame. In particular, M-G50-C50 and (M-G/M-C)50/50 extinguished the flame, even at 7% add-on. In VFST, the copolymers with 6550% M-C units, similar to M-C, inhibited cotton combustion at 16% add-on. At the same add-on, the M-G/M-C blends failed to extinguish the flame. It may be concluded that, in contrast to blends, copolymers combined the merits of both homopolymers in all tests

Polyamidoamines derived from natural α-amino acids as effective flame retardants for cotton

In this paper, bioinspired polyamidoamines (PAAs) were synthesized from N,N′-methylene bisacrylamide and nine natural α-amino acids: L-alanine, L-valine, L-leucine (M-LEU), L-histidine, L-serine, L-asparagine, L-glutamine (M-GLN), L-aspartic acid and L-glutamic acid (M-GLU) and their performance as flame retardants (FRs) for cotton were determined. The aim was to ascertain if the ability to protect cotton from fire by the process of intumescing, previously found for the glycine-derived M-GLY, was a general feature of α-amino acid-derived PAAs. None of the PAAs ignited by flame impingement, apart from M-LEU, which burned for a few seconds leaving 93% of residue. All of them formed carbon-and oxygen-rich, porous chars with a graphitic structure in the air at 350◦C, as revealed by X-ray photoelectron spectroscopy. All samples were tested as FRs for cotton by horizontal flame spread tests. At a 5% add-on, M-GLU and M-GLN extinguished the flame. The same results were obtained with all the other PAAs at a 7% add-on. The α-amino acid residues influenced the FR performance. The most effective were those that, by heating, were most suitable for producing thermally stable cyclic aromatic structures. All PAA-treated cotton samples, even when burning, left significant residues, which, according to scanning electron microscopy analysis, maintained the original cotton texture

Highlight on the Mechanism of Linear Polyamidoamine Degradation in Water

This paper aims at elucidating the degradation mechanism of linear polyamidoamines (PAAs) in water. PAAs are synthesized by the aza-Michael polyaddition of prim-monoamines or bis-sec-amines with bisacrylamides. Many PAAs are water-soluble and warrant potential for biotechnological applications and as flame-retardants. PAAs have long been known to degrade in water at pH 65 7, but their degradation mechanism was never explored in detail. Filling this gap was necessary to assess the suitability of PAAs for the above applications. To this aim, a small library of nine PAAs was expressly synthesized and their degradation mechanism in aqueous solution studied by 1H-NMR in different conditions of pH and temperature. The main degradation mechanism was in all cases the retro-aza-Michael reaction triggered by dilution but, in some cases, hints were detected of concurrent hydrolytic degradation. Most PAAs were stable at pH 4.0; all degraded at pH 7.0 and 9.0. Initially, the degradation rate was faster at pH 9.0 than at pH 7.0, but the percent degradation after 97 days was mostly lower. In most cases, at pH 7.0 the degradation followed first order kinetics. The degradation rates mainly depended on the basicity of the amine monomers. More basic amines acted as better leaving groups

Nonlinear models of the bump cepheid HV 905 and the distance modulus to the large magellanic cloud

Nonlinear pulsation models have been used to simulate the light curve of the LMC bump Cepheid HV 905. In order to reproduce the light curve accurately, tight constraints on the input parameters M, L, and T-eff are required. The results, combined with accurate existing V and I photometry, yield an LMC distance modulus of 18.51 +/- 0.05, and they show that the luminosity of HV 905 is much higher than expected from the mass-luminosity relation of stellar evolution theory. If we assume that the pulsation models are accurate, this suggests that there is a larger amount of convective core overshoot during the main-sequence evolution of stars with M similar to 5 M. than is usually assumed