Prediction of maritime pine boards modulus of elasticity by means of sonic testing on green timber

Timber buildings are experiencing a rapid diffusion due to their good performance and their sustainability; however, some steps of structural timber production process, such as drying, are energy-intensive and environmentally impactful, and many wood species are also affected by low yield. Therefore, it would be important to determine the quality of the green material, that is, in wet condition, before undergoing the most impactful and expensive production steps. This paper describes a research aimed at quantifying the variation of the dynamic modulus of elasticity MoEdyn, which is commonly used for structural timber mechanical grading, from wet to dry condition in Sardinian maritime pine boards to be used for the production of laminated timber, and to examine the relationship between wet and dry MoEdyn . The MoEdyn was determined from measurements of the velocity of sonic waves propagating through the boards. The results show that the dry MoEdyn can be estimated starting from boards sonic testing in the wet condition, so providing a basis for implementing Sardinian maritime pine pre-grading in order to obtain the reduction of manufacturing costs, the abatement of environmental impact, and the increase of structural grade yield

Feasibility of a Local Production Chain for Structural Timber in Sardinia, Italy

The construction sector is currently responsible for over 30% of the consumption of natural resources and the release of solid waste and pollution into the environment. This situation is even more serious in closed communities such as islands, economically highly dependent on the outside world. One of the possible interventions to reverse this trend is the use of eco-sustainable construction materials such as wood, produced through supply chains with a low environmental impact. This paper reports on a research activity that analyzed the feasibility of implementing a sustainable local supply chain in Sardinia to produce Cross-Laminated Timber (CLT) panels made of locally grown wood. This research has experimentally carried out the entire supply chain process: (i) choice and collection of the raw material in the forest for producing strength-graded boards to manufacture laminated timber, (ii) manufacturing of CLT panel prototypes, and (iii) determination of CLT panels’ mechanical performance through laboratory tests. This experimentation allowed, on the one hand, to evaluate the performance and competitiveness of CLT panels made of local wood, and on the other hand, to identify the criticalities that currently hinder the implementation of this supply chain in Sardinia, and to propose possible actions to solve them

Application of infrared thermography in civil engineering: Limits and drawbacks

Infrared thermography (IRT) is an effective diagnostic methodology for existing buildings monitoring, whose efficiency is however affected by the operator’s technical knowledge. This paper presents experimental research aimed at evaluating the accuracy of IRT temperature measurements with respect to the incorrect setting of five input parameters required to be set by the operator: emissivity, reflected apparent temperature, ambient temperature, relative humidity, and distance. The goal was to highlight how their accurate evaluation and setting affects the thermographic survey and the post-processing stage. To this end, IRT experimental investigations were carried out on materials characterized by different emissivity and surface roughness, such as concrete, granite and steel. The experimentation outcome has pointed out the factors that most affect the temperature measurement error and allowed to quantify the error on the temperature measurements deriving from the incorrect setting of these parameters during the acquisition phase of the thermogram

Deflection and Friction Performance of Waste-Wooden Block Pavements

The use of waste wood for road light pavements is essential for environmental and economic sustainability.The paper investigates the mechanical performance of pavements built with waste wood elements discarded from Sardinia manufacture (Italy). Without structural value, mainly Sardinian wood is used for combustion and heating due to the characteristics of dimensional irregularity, non-homogeneity, and the presence of defects. Even small urban and forest furniture comes from foreign markets. Landscape reasons, emissions reduction, and environmental integration with the local context could encourage its use if reliable techniques are available.The study first analyzed the structural response of a portion of pavementmade with waste wood bricks (pine and Eucalyptus). Subsequently, a Finite Element simulation of the pavement has been validated with the tests' results. The experimental pavement was created with Interlocked Block Pavement (IBP) technique, using brick elements 13 x 6 x 10 cm. The behavior of the pavement was analyzed in situ with dynamic deflection tests using the Falling Weight Deflectometer test (FWD). Further tests performed in the laboratory investigated the friction of the wood pavement surface. The simulation results show that the wooden pavement elements do not differ substantially from the classic concrete IBP and HMA cracked pavement. The mean deflections are greater than 19%, while the vertical stress on the foundation layer is equivalent. As with the classic concrete IBP, the results largely depend on the bearing capacity of the substrate and the degree of interlocking.Friction tests show good values with mean values of 53 divided by 64 BPN. The most significant values were observed in the elements eucalyptus. The direction of the wood fibers also influences the results: about 3 points in the case of pine and over 7 points in the case of Eucalyptus. The study shows how the use of wood for the pavement with elements is sustainable and practicable due to the minor and low-traffic roads while also guaranteeing permeability and low-cost maintenance

In vivo evolution of lactic acid hyper-tolerant Clostridium thermocellum

Lactic acid (LA) has several applications in the food, cosmetics and pharmaceutical industries, as well as in the production of biodegradable plastic polymers, namely polylactides. Industrial production of LA is essentially based on microbial fermentation. Recent reports have shown the potential of the cellulolytic bacterium Clostridium thermocellum for direct LA production from inexpensive lignocellulosic biomass. However, C. thermocellum is highly sensitive to acids and does not grow at pH \u3c 6.0. Improvement of LA tolerance of this microorganism is pivotal for its application in cost-efficient production of LA. In the present study, the LA tolerance of C. thermocellum strains LL345 (wild-type fermentation profile) and LL1111 (high LA yield) was increased by adaptive laboratory evolution. At large inoculum size (10 %), the maximum tolerated LA concentration of strain LL1111 was more than doubled, from 15 g/L to 35 g/L, while subcultures evolved from LL345 showed 50–85 % faster growth in medium containing 45 g/L LA. Gene mutations (pyruvate phosphate dikinase, histidine protein kinase/phosphorylase) possibly affecting carbohydrate and/or phosphate metabolism have been detected in most LA-adapted populations. Although improvement of LA tolerance may sometimes also enable higher LA production in microorganisms, C. thermocellum LA-adapted cultures showed a yield of LA, and generally of other organic acids, similar to or lower than parental strains. Based on its improved LA tolerance and LA titer similar to its parent strain (LL1111), mixed adapted culture LL1630 showed the highest performing phenotype and could serve as a framework for improving LA production by further metabolic engineering

Possible Assessment of Calf Venous Pump Efficiency by Computational Fluid Dynamics Approach

Three-dimensional simulations of peripheral, deep venous flow during muscular exercise in limbs of healthy subjects and in those with venous dysfunction were carried out by a computational fluid-dynamics (CFD) approach using the STAR CCM + platform. The aim was to assess the effects of valvular incompetence on the venous calf pump efficiency. The model idealizes the lower limb circulation by a single artery, a capillary bed represented by a porous region and a single vein. The focus is on a segment of the circuit which mimics a typical deep vein at the level of the calf muscle, such as the right posterior tibial vein. Valves are idealized as ball valves, and periodic muscle contractions are given by imposing time-dependent boundary conditions to the calf segment wall. Flow measurements were performed in two cross-sections downstream and upstream of the calf pump. Model results demonstrate a reduced venous return for incompetent valves during calf exercise. Two different degrees of valvular incompetence are considered, by restricting the motion of one or both valves. Model results showed that only the proximal valve is critical, with a 30% reduction of venous return during calf exercise in case of valvular incompetence: the net flow volume ejected by the calf in central direction was 0.14 mL per working cycle, against 0.2 mL for simulated healthy limbs. This finding appeared to be consistent with a 25% reduction of the calf ejection fraction, experimentally observed in chronic venous disease limbs compared with healthy limbs

Imaging of the solar atmosphere in the centimetre-millimetre band through single-dish observations

Solar observations offer both a rich interdisciplinary laboratory on fundamental astrophysics and precious tools for Space Weather applications. The involved plasma processes determine a complex radio emission picture that could be efficiently explored through single-dish imaging at high frequencies. In particular, mapping the brightness temperature of the free-free radio emission in the centimetre and millimetre range is an effective tool to characterise the vertical structure of the solar atmosphere. We are performing continuum imaging of the solar chromosphere in K-band (18-26.5 GHz, spatial resolution ∼1 arcmin) with the 32-m diameter Medicina radio telescope and with the 64-m diameter Sardinia Radio Telescope (SRT), as a first scientific demonstration test for the potentialities of Italian single-dish antennas in this field. This will also be useful for the assessment of observation parameters aiming at studying in detail the chromospheric brightness temperature of the quiet Sun, the solar flares, active regions and the sunspots, at high radio frequencies. These early observations proved that our antennas and Kband receivers are stable during solar pointing and could provide full mapping of the solar disk in ∼1 hour exposure using state-of-the-art imaging techniques