With a view to achieving sustainable development and a circular economy, this work focused on the possibility to valorize a secondary waste stream of recycled carbon fiber (rCF) to produce a 3D ...printing usable material with a PA6,6 polymer matrix. The reinforcing fibers implemented in the research are the result of a double-recovery action: starting with pyrolysis, long fibers are obtained, which are used to produce non-woven fabrics, and subsequently, fiber agglomerate wastes obtained from this last process are ground in a ball mill. The effect of different amounts of reinforcement at 5% and 10% by weight on the mechanical properties of 3D-printed thermoplastic composites was investigated. Although the recycled fraction was successfully integrated in the production of filaments for 3D printing and therefore in the production of specimens via the fused deposition modeling technique, the results showed that fibers did not improve the mechanical properties as expected, due to an unsuitable average size distribution and the presence of a predominant dusty fraction ascribed to the non-optimized ball milling process. PA6,6 + 10 wt.% rCF composites exhibited a tensile strength of 59.53 MPa and a tensile modulus of 2.24 GPa, which correspond to an improvement in mechanical behavior of 5% and 21% compared to the neat PA6,6 specimens, respectively. The printed composite specimens loaded with the lowest content of rCF provided the greatest improvement in strength (+9% over the neat sample). Next, a prediction of the "optimum" critical length of carbon fibers was proposed that could be used for future optimization of recycled fiber processing.
To move toward eco-sustainable and circular composites, one of the most effective solutions is to create thermoplastic composites. The strong commitment of world organizations in the field of ...safeguarding the planet has directed the research of these materials toward production processes with a lower environmental impact and a strong propensity to recycle the polymeric part. Under its chemical properties, Nylon 6 is the polymer that best satisfies this specific trade-off. The most common production processes that use a thermosetting matrix are described. Subsequently, the work aimed at investigating the use of thermoplastics in the same processes to obtain comparable performances with the materials that are currently used. Particular attention was given to the in situ anionic polymerization process of Nylon 6, starting from the ε-caprolactam monomer. The dependencies of the process parameters, such as temperature, time, pressure, humidity, and concentration of initiators and activators, were therefore investigated with reference to the vacuum infusion technique, currently optimized only to produce thermosetting matrix composites, but promising for the realization of thermoplastic matrix composite; this is the reason why we chose to focus our attention on the vacuum infusion. Finally, three production processes of the polymeric matrix and glass fiber composites were compared in terms of carbon footprint and cumulative energy demand (CED) through life-cycle assessment (LCA).
The traditional choice of insulation material for liquefied natural gas (LNG) transportation with cryogenic tankers is the back-filled perlite-based system. However, aiming to further cut down the ...insulation cost, spare additional arrangement space, and provide safety in installation and maintenance, the requirement of looking for alternative materials still exists. Fiber-reinforced aerogel blankets (FRABs) could represent good candidates in designing insulation layers for LNG cryogenic storage because of their ability to ensure adequate thermal performance without the need to create deep vacuum conditions in the annular space of the tank. In this work, a finite element method (FEM) model was developed to study the thermal insulation performance of a commercial FRAB (Cryogel
Z) for application in cryogenic storage/transport LNG tanks, comparing it with the performance of traditional perlite-based systems. Within the reliability limits of the computational model, the analysis proved that FRAB insulation technology gave encouraging results and might be potentially scalable for transporting cryogenic liquid. In addition to demonstrating superior performance in terms of thermal insulating efficiency and boil-off rate over the perlite-based system, as far as a perspective of cost savings and space gain, FRAB technology allows for higher levels of insulation without vacuum and with lower thickness of the outer shell, which is therefore beneficial for storing more material and lightening the weight of the LNG transportation semitrailer.
BACKGROUND:Hemorrhoid laser procedure is a new laser procedure for outpatient treatment of hemorrhoids in which hemorrhoidal arterial flow feeding the hemorrhoidal plexus is stopped by means of ...Doppler-guided laser coagulation.
OBJECTIVE:Our aim was to compare the hemorrhoid laser procedure with rubber band ligation for outpatient treatment of symptomatic hemorrhoids with moderate mucosal prolapse.
DESIGN:This was a randomized controlled trial with balanced allocation to hemorrhoid laser procedure or rubber band ligation, with stratification by study center.
SETTING:This study was conducted at 2 teaching hospitals in Italy.
PATIENTS:Patients with symptomatic grade II or grade III hemorrhoids with minimal mucosal prolapse were eligible for the study.
INTERVENTIONS:In the hemorrhoid laser procedure operation, a Doppler probe was inserted into the anal canal through a dedicated disposable proctoscope to identify the terminal branches of superior hemorrhoidal arteries approximately 3 cm above the dentate line. Five pulsed laser shots were delivered to each identified artery through the proctoscope to close the terminal branches. The procedure was repeated for each artery through clockwise rotation of the proctoscope. Absence of a Doppler signal after treatment confirmed arterial coagulation. Rubber band ligation was performed by positioning rubber bands at the base of left lateral, right anterior, and right posterior piles. No anesthesia was given for either technique.
MAIN OUTCOME MEASURES:Operative time, complications, postoperative pain (visual analog scale), postoperative downgrading of hemorrhoids, resolution of symptoms, and quality of life were evaluated.
RESULTS:A total of 60 patients (35 women, 25 men; mean age, 46 years) entered the trial and were analyzed. No significant differences between rubber band ligation and hemorrhoid laser procedure were observed in operative time or intraoperative morbidity. The median postoperative pain score was 2.9 (range, 1–5) with rubber band ligation vs 1.1 (range, 0–2) for hemorrhoid laser procedure (P < .001). At 6 months, resolution of symptoms was observed in 16 patients (53%) with ligation vs 27 (90%) with hemorrhoid laser procedure (P < .001), and reduction of hemorrhoids by at least 1 grade was observed in 12 patients (40%) with ligation vs 24 (80%) with hemorrhoid laser procedure (P < .001). Significantly higher quality of life was seen in the hemorrhoid laser procedure group (P = .002).
LIMITATIONS:Follow-up was not longer than 1 year (median, 6 mo).
CONCLUSIONS:Despite higher cost, the hemorrhoid laser procedure technique was more effective than rubber band ligation in reducing postoperative pain, resolving symptoms, and improving quality of life in patients with grade II or III hemorrhoids with incomplete mucosal prolapse.
Blends based on high-density polyethylene (HDPE) and poly(lactic) acid (PLA) with different ratios of both polymers were produced: a blend with equal amounts of HDPE and PLA, hence 50 wt.% each, ...proved to be a useful compromise, allowing a high amount of bioderived charge without this being too detrimental for mechanical properties and considering its possibility to biodegradation behaviour in outdoor application. In this way, an optimal blend suitable for producing a composite with cellulosic fillers is proposed. In the selected polymer blend, wood flour (WF) was added as a natural filler in the proportion of 20, 30, and 40 wt.%, considering as 100 the weight of the polymer blend matrix. There are two compatibilizers to modify both HDPE-PLA blend and wood-flour/polymer interfaces, i.e., polyethylene-grafted maleic anhydride and a random copolymer of ethylene and glycidyl methacrylate. The most suitable percentage of compatibilizer for HDPE-PLA blends appears to be 3 wt.%, which was selected also for use with wood flour. In order to evaluate properties of blends and composites tensile tests, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analyses, and infrared spectroscopy have been performed. Wood flour seems to affect heavy blend behaviour in process production of material suggesting that future studies are needed to reduce defectiveness.
•The seismic behaviour of a shallow multi-propped underground structure is evaluated considering a sensitivity analysis.•Decoupled approach has been performed considering the soil deformations ...without taking into consideration the presence of the structure.•Coupled approach has been performed considering a Finite Difference Model through a fully-dynamic non-linear analysis.•The results of the two different methods have been compared in order to highlight the limits of the decoupled approach.
The evaluation of the seismic behaviour of shallow multi-propped underground structures (e.g. metro stations, parking, etc.) can be considered as one of the most important and actual research topics in structural earthquake engineering. Over the last decades, different types of analysis approaches have been proposed, but several issues are still open, especially for multi-propped structures embedded in granular soils. In this paper, the main limitations of the decoupled approach are investigated and discussed through a large set of numerical simulations involving: i) a multi-propped underground structure; ii) five natural and one synthetic accelerograms; iii) four different soil profiles characterized by the same mechanical properties but different values of the shear modulus that are related to the shear wave velocity ranging between 360 m/s and 750 m/s. The results, in terms of bending moment acting on RC retaining walls, obtained through the decupled approach are discussed in comparison with those obtained through the coupled approach (non-linear dynamic analysis), highlighting the main differences and limitations. This study shows that the decoupled approach provides consistent results only for soil profiles characterized by low values of stiffness due to the main assumptions underlying the approach.
A new hybrid fiber blend containing microfibrillated cellulose (MFC) gel and recycled carbon short fiber (RCSF) was implemented for designing fiber-reinforced cement mortars, to further improve the ...mechanical properties and enhance the sustainability of cement-based materials. The individual impact of single fibrous fillers as well as the synergistic effect of a hybrid fiber system (MFC + RCSF) were investigated in terms of the rheological properties, mechanical strength, and microstructure of the mortars. The results indicated that the workability of fresh mixtures slightly increased after fiber addition. The fibers incorporated alone improved the materials' performance in different ways. The addition of RCSF led to improvements of up to 76% in flexural strength and 13% in compression strength for a fiber content of 0.75 wt.%. However, the addition of carbon fibers led to slight deteriorations in terms of porosity and water absorption. On the other hand, the use of MFC induced a less significant growth in terms of mechanical strength (+14% in flexural strength for 0.75 wt.% of cellulose) but greatly improved the microstructural quality of the mortar, significantly reducing its water permeability. Considering the optimum MFC dosage, MFC+RCSF hybrid mixtures showed positive effects on the mechanical properties and microstructure of the mortar, displaying further improvements in strength, while preserving a lower porosity and water absorption than the control mix.
•A novel heuristic to detect Move Method refactoring opportunities based on static dependencies.•The implementation of the proposed heuristic as an Eclipse plug-in, named JMove.•Two evaluations ...including (i) 10 open-source systems and (ii) two industrial-strength systems.•A comparative study with three state-of-the-art techniques (JDeodorant, inCode, and Methodbook).•JMove overcomes state-of-the-art techniques when providing recommendations for large methods.
This paper presents a recommendation approach that suggests Move Method refactorings using the static dependencies established by methods. This approach, implemented in a publicly available tool called JMove, compares the similarity of the dependencies established by a method with the dependencies established by the methods in possible target classes. We first evaluate JMove using 195 Move Method refactoring opportunities, synthesized in 10 open-source systems. In this evaluation, JMove precision ranges from 21% (small methods) to 32% (large methods) and its median recall ranges from 21% (small methods) to 60% (large methods). In the same scenario, JDeodorant, which is a state-of-the-art Move Method recommender, has a maximal precision of 15% (large methods) and a maximal median recall of 40% (small methods). Therefore, we claim that JMove is specially useful to provide recommendations for large methods. We reinforce this claim by means of two other studies. First, by investigating the overlapping of the recommendations provided by JMove and three other recommenders (JDeodorant, inCode, and Methodbook). Second, by validating JMove and JDeodorant recommendations with experts in two industrial-strength systems.
The preservation (in terms of inhibition of failures and collapses) of architectural heritage against horizontal loads (such as earthquakes) requires an accurate assessment of the non-linear response ...up to failure: to this aim, the use of advanced numerical tools to perform three-dimensional non-linear dynamic analyses is fundamental. This paper investigates the performance (up to the activation of local failures and under horizontal loads) of three historical masonry palaces of the outstanding cultural heritage in Mantua (Northern Italy) after the 2012 Emilia earthquake. Despite the unquestionable importance of the three case studies, until now these palaces have not been studied with advanced numerical simulations; moreover, the recent seismic sequence and the consequent significant cracks patterns observed in the post-earthquake survey phase have pointed out their vulnerability even to small seismic actions. The first part of the study was addressed to an accurate knowledge of the three palaces, focusing especially on the information gathered during on-site surveys, bibliographical and historical research: the data collected were employed to detect the complex three-dimensional geometry of the palaces under study and to define the cracks patterns. In the second part of the study, detailed and representative three-dimensional finite element (FE) models of the structures were developed and non-linear dynamic analyses were carried out to obtain a deep numerical insight into the seismic response of the three palaces, identifying the most vulnerable elements for each structure. The comparison between the numerical results and the damage survey showed that the numerical approach used in this study may be an adequate tool to properly evaluate the seismic response of historical masonry buildings. A comparative assessment of the results obtained for the different palaces was performed in terms of predicted damage distributions, energy density dissipated by tensile damage and maximum displacements registered for the different macro-elements.
•Evaluation of failure risk with advanced numerical FE computing on outstanding historical palaces•Utilization of full 3D FE Non-linear dynamic analyses NLADA method to reproduce damage•Detailed reproduction of crack patterns observed during surveys•Damage-plasticity with softening in tension and compression material used to model masonry•Incremental PGA analyses to investigate the level of PGA needed to activate failure mechanisms
Cellulose nitrate (CN) has been used in the past as support for photographic negatives and cinematographic films. This material is particularly unstable and can undergoes severe degradation due to ...thermal, photocatalytic and hydrolytic loss of nitro groups from the lateral chain. Thus, to prevent the disappearance of the movies, their scanning and digitalization become a priority.
However, CN bases degradation may prevent the scanning of the films. The decrease in pH, for instance, lowers the viscosity of gelatin, which becomes softer. This causes the formation of gelatin residues which stick on the back of the superimposed frames inside the reels creating a deposit.
Traditional approaches to clean gelatin residues from the surface of CN bases include the mechanical removal with scalpels and the use of organic solvents (such as isopropyl alcohol). However, these methods are either slow and ineffective or could potentially damage the degraded CN supports.
To overcome these drawbacks, we have evaluated the performance of three choline chloride and betaine-based Deep Eutectic Solvent (DES) formulations as alternative for the removal of gelatine residues from CN supports. These solvents are inexpensive (when compared to traditional solvents), easy to prepare, green (non volatile, safe towards the operators and the environment, and potentially recyclable), non flammable and have been previously proposed for the extraction of proteinaceous materials, but their use for the restoration of photographic negatives or cinematographic films has not been reported yet.
Selected areas over the frames of a real deteriorated CN cinematographic film were cleaned comparing the DES performances with the ones obtained using isopropyl alcohol as an example of a traditional method.
In particular, the tested DES formulations showed superior cleaning power compared to isopropyl alcohol and, at the selected application times, resulted capable to remove the gelatin residues without affecting the CN film supports.
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