bluuebunny/crossref_metadata_2025 huggingface dataset:
Selectivity of Mixed Iron-Cobalt Spinels Deposited on a N,S-Doped Mesoporous Carbon Support in the Oxygen Reduction Reaction in Alkaline Media
Authors: Kostuch Aldona , Gryboś Joanna , Wierzbicki Szymon , Sojka Zbigniew , Kruczała Krzysztof
Published: February 2021

One of the practical efforts in the development of oxygen reduction reaction (ORR) catalysts applicable to fuel cells and metal-air batteries is focused on reducing the cost of the catalysts production. Herein, we have examined the ORR performance of cheap, non-noble metal based catalysts comprised of nanosized mixed Fe-Co spinels deposited on N,S-doped mesoporous carbon support (N,S-MPC). The effect of the chemical and phase composition of the active phase on the selectivity of catalysts in the ORR process in alkaline media was elucidated by changing the iron content. The synthesized materials were thoroughly characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy (RS). Detailed S/TEM/EDX and Raman analysis of the phase composition of the synthesized ORR catalysts revealed that the dominant mixed iron-cobalt spinel is accompanied by minor fractions of bare cobalt and highly dispersed spurious iron oxides (Fe2O3 and Fe3O4). The contribution of individual phases and their degree of agglomeration on the carbon support directly influence the selectivity of the obtained catalysts. It was found that the mixed iron-cobalt spinel single phase gives rise to significant improvement of the catalyst selectivity towards the desired 4e− reaction pathway, in comparison to the reference bare cobalt spinel, whereas spurious iron oxides play a negative role for the catalyst selectivity.
Physical and Mechanical Performance of Coir Fiber-Reinforced Rendering Mortars
Authors: Maia Pederneiras Cinthia , Veiga Rosário , de Brito Jorge
Published: February 2021

Coir fiber is a by-product waste generated in large scale. Considering that most of these wastes do not have a proper disposal, several applications to coir fibers in engineering have been investigated in order to provide a suitable use, since coir fibers have interesting properties, namely high tensile strength, high elongation at break, low modulus of elasticity, and high abrasion resistance. Currently, coir fiber is widely used in concrete, roofing, boards and panels. Nonetheless, only a few studies are focused on the incorporation of coir fibers in rendering mortars. This work investigates the feasibility to incorporate coir fibers in rendering mortars with two different binders. A cement CEM II/B-L 32.5 N was used at 1:4 volumetric cement to aggregate ratio. Cement and air-lime CL80-S were used at a volumetric ratio of 1:1:6, with coir fibers were produced with 1.5 cm and 3.0 cm long fibers and added at 10% and 20% by total mortar volume. Physical and mechanical properties of the coir fiber-reinforced mortars were discussed. The addition of coir fibers reduced the workability of the mortars, requiring more water that affected the hardened properties of the mortars. The modulus of elasticity and the compressive strength of the mortars with coir fibers decreased with increase in fiber volume fraction and length. Coir fiber’s incorporation improved the flexural strength and the fracture toughness of the mortars. The results emphasize that the cement-air-lime based mortars presented a better post-peak behavior than that of the cementitious mortars. These results indicate that the use of coir fibers in rendering mortars presents a potential technical and sustainable feasibility for reinforcement of cement and cement-air-lime mortars.
Fabrication and Mechanical Properties of Cr2AlC MAX Phase Coatings on TiBw/Ti6Al4V Composite Prepared by HiPIMS
Authors: Qureshi Muhammad Waqas , Ma Xinxin , Tang Guangze , Miao Bin , Niu Junbo
Published: February 2021

The high-power impulse magnetron sputtering (HiPIMS) technique is widely used owing to the high degree of ionization and the ability to synthesize high-quality coatings with a dense structure and smooth morphology. However, limited efforts have been made in the deposition of MAX phase coatings through HiPIMS compared with direct current magnetron sputtering (DCMS), and tailoring of the coatings’ properties by process parameters such as pulse width and frequency is lacking. In this study, the Cr2AlC MAX phase coatings are deposited through HiPIMS on network structured TiBw/Ti6Al4V composite. A comparative study was made to investigate the effect of average power by varying frequency (1.2–1.6 kHz) and pulse width (20–60 μs) on the deposition rate, microstructure, crystal orientation, and current waveforms of Cr2AlC MAX phase coatings. X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to characterize the deposited coatings. The influence of pulse width was more profound than the frequency in increasing the average power of HiPIMS. The XRD results showed that ex situ annealing converted amorphous Cr-Al-C coatings into polycrystalline Cr2AlC MAX phase. It was noticed that the deposition rate, gas temperature, and roughness of Cr2AlC coatings depend on the average power, and the deposition rate increased from 16.5 to 56.3 nm/min. Moreover, the Cr2AlC MAX phase coatings produced by HiPIMS exhibits the improved hardness and modulus of 19.7 GPa and 286 GPa, with excellent fracture toughness and wear resistance because of dense and column-free morphology as the main characteristic.
The Effect of the Composition of a Concrete Mixture on Its Volume Changes
Authors: Ťažký Martin , Bodnárová Lenka , Ťažká Lucia , Hela Rudolf , Meruňka Milan , Hlaváček Petr
Published: February 2021

The presented research aims to clarify the specific effect of the individual components of concrete with Portland cement CEM I 42.5 R on the volume changes of concrete. The effect of the filler component was evaluated from the point of view of the composition and type of aggregate (crushed versus mined) and from the point of view of the mineralogical composition of the aggregate. Concrete formulas with a maximum aggregate grain size of 16 and 22 mm were assessed. The effect of the binder component on the shrinkage of the concrete was monitored on the concrete mixtures produced using the same aggregate and maintaining the same strength class of concrete, C 45/55. The effect of the addition of finely ground limestone, finely ground granulated blast furnace slag and coal high-temperature fly ash was monitored. It was found that the maximum aggregate grain and the type of grading curve do not have a significant effect on the volume changes of concrete. Concretes with mined aggregates showed lower shrinkage than concretes with crushed aggregates. The most significant is the effect of the type of aggregate on the volume changes in the first 24 h. Mineral additives have a positive effect on the elimination of the volume changes of concrete, while the addition of high-temperature fly ash proved to be the most suitable.
Electrochemical Processing and Thermal Properties of Functional Core/Multi-Shell ZnAl/Ni/NiP Microparticles
Authors: Svetlizky David , Kazimierczak Honorata , Ovadia Bar , Sharoni Ariel , Eliaz Noam
Published: February 2021

Electroless deposition on zinc and its alloys is challenging because of the negative standard potential of zinc, the formation of poor surface layers during oxidation in aqueous solutions, and extensive hydrogen evolution. Therefore, there are only few reports of electroless deposition on Zn and its alloys, neither of them on micro/nano powders. Here, we propose a two-step process that allows the formation of compact, uniform, and conformal Ni/NiP shell on Zn-based alloy microparticles without agglomeration. The process utilizes controlled galvanic displacement of Ni deposition in ethanol-based bath, followed by NiP autocatalytic deposition in an alkaline aqueous solution. The mechanism and effect of deposition conditions on the shell formation are discussed. Thermal stability and functional analysis of core-shell powder reveal a thermal storage capability of 98.5% with an encapsulation ratio of 66.5%. No significant morphological change of the core-shell powder and no apparent leakage of the ZnAl alloy through the Ni shell are evident following differential scanning calorimetry tests. Our two-step process paves the way to utilize electroless deposition for depositing metallic-based functional coatings on Zn-based bulk and powder materials.
Terahertz Shielding Properties of Carbon Black Based Polymer Nanocomposites
Authors: Zeranska-Chudek Klaudia , Siemion Agnieszka , Palka Norbert , Mdarhri Ahmed , Elaboudi Ilham , Brosseau Christian , Zdrojek Mariusz
Published: February 2021

The majority of industry using high-speed communication systems is shifting towards higher frequencies, namely the terahertz range, to meet demands of more effective data transfer. Due to the rising number of devices working in terahertz range, effective shielding of electromagnetic interference (EMI) is required, and thus the need for novel shielding materials to reduce the electromagnetic pollution. Here, we show a study on optical and electrical properties of a series of ethylene co-butyl acrylate/carbon black (EBA/CB) composites with various CB loading. We investigate the transmittance, reflectance, shielding efficiency, absorption coefficient, refractive index and complex dielectric permittivity of the fabricated composites. Finally, we report a material that exhibits superior shielding efficiency (SE)—80 dB at 0.9 THz (14.44 vol% CB loading, 1 mm thick)—which is one of the highest SE values among non-metallic composite materials reported in the literature thus far. Importantly, 99% of the incoming radiation is absorbed by the material, significantly increasing its applicability. The absorption coefficient (α) reaches ~100 cm−1 for the samples with highest CB loading. The EBA/CB composites can be used as lightweight and flexible shielding packaging materials for electronics, as passive terahertz absorbers or as radiation shields for stealth applications.
Investigation on the Microporosity Formation of IN718 Alloy during Laser Cladding Based on Cellular Automaton
Authors: Lv Hao , Li Zhijie , Li Xudong , Yang Kun , Li Fei , Xie Hualong
Published: February 2021

Porosity is one of the most common defects in the laser cladding of Inconel 718 (IN718) alloy, which can reduce the strength and fatigue performance of the components. However, the dynamic formation of microporosity is challenging to observe through experiments directly. In order to explore the formation mechanism of porosities and dynamically reproduce the competitive growth between porosities and dendrite, a multi-scale numerical model was adopted, combined with a cellular automaton (CA) and finite element method (FEM). The decentered square algorithm was adopted to eliminate crystallographic anisotropy and simulate dendrite growth in different orientations. Afterward, based on the formation mechanism of microporosity during solidification, equiaxed and columnar dendrites with porosities were simulated, respectively. Dendrite morphology, porosity morphology, and distribution of solute concentration were obtained during the solidification process. The simulation results were reasonably compared with experimental data. The simulation results of the equiaxed crystal region are close to the experimental data, but the columnar crystal region has a relative error. Finally, the interaction effects of porosities and dendrites under different environmental conditions were discussed. The results suggested that with the increase in the cooling rate, the quantity of porosity nucleation increased and the porosity decreased.
The Effect of Refractory Wall Emissivity on the Energy Efficiency of a Gas-Fired Steam Cracking Pilot Unit
Authors: Vangaever Stijn , Van Thielen Joost , Hood Jeremy , Olver John , Honnerovà Petra , Heynderickx Geraldine J. , Van Geem Kevin M.
Published: February 2021

The effect of high emissivity coatings on the radiative heat transfer in steam cracking furnaces is far from understood. To start, there is a lack of experimental data describing the emissive properties of the materials encountered in steam cracking furnaces. Therefore, spectral normal emissivity measurements are carried out, evaluating the emissive properties of refractory firebricks before and after applying a high emissivity coating at elevated temperatures. The emissive properties are enhanced significantly after applying a high emissivity coating. Pilot unit steam cracking experiments show a 5% reduction in fuel gas firing rate after applying a high emissivity coating on the refractory of the cracking cells. A parametric study, showing the effect of reactor coil and furnace wall emissive properties on the radiative heat transfer inside a tube-in-box geometry, confirms that a non-gray gas model is required to accurately model the behavior of high emissivity coatings. Even though a gray gas model suffices to capture the heat sink behavior of a reactor coil, a non-gray gas model that is able to account for the absorption and re-emission in specific bands is necessary to accurately model the benefits of applying a high emissivity coating on the furnace wall.
Assessment of Mechanical and Thermal Properties of Hemp-Lime Mortar
Authors: Parcesepe Eliana , De Masi Rosa Francesca , Lima Carmine , Mauro Gerardo Maria , Pecce Maria Rosaria , Maddaloni Giuseppe
Published: February 2021

The use of renewable and natural materials characterized by the low environmental impact is nowadays a key issue for the sustainable development of the construction industry. For this reason, the interest for natural fibers, to be used as reinforcement in composites as an alternative to other fibers, is continuously growing. In this paper, the use of hemp for reinforcing lime mortar used as plaster is considered with a multidisciplinary approach, taking into consideration the structural and thermal performance. Natural fibers have several advantages compared to industrial ones, such as low cost, low environmental impact, biodegradability, renewable nature. Moreover, these can show remarkable mechanical performance in relation to specific weight, and sometimes, as in the case of hemp fibers, these can improve the thermal insulation capacity of the plaster. However, the experimental results on the mechanical features are still lacking, especially to assess their durability, and the variability of thermal parameters with the mechanical characteristics. Therefore, this paper proposes an experimental program, developed at Laboratory of Materials and Structures (LAMAS) of the University of Sannio (Italy), aimed at investigating the main mechanical properties (compression strength, flexural strength) of lime mortar reinforced by hemp fibers and subjected to various environmental exposures and aging processes. The characterization is completed with the measurement for the produced samples of the thermal conductivity by means of the standardized guarded hot plate technique.
A Comparative Study between Polymer and Metal Additive Manufacturing Approaches in Investigating Stiffened Hexagonal Cells
Authors: Laban Othman , Mahdi Elsadig , Samim Samahat , Cabibihan John-John
Published: February 2021

Recent polymer and metal additive manufacturing technologies were proven capable of building complex structures with high accuracy. Although their final products differ significantly in terms of mechanical properties and building cost, many structural optimization studies were performed with either one without systematic justification. Therefore, this study investigated whether the Direct Metal Laser Sintering (DMLS) and Fused Deposition Modelling (FDM) methodologies can provide similar conclusions when performing geometrical manipulations for optimizing structural crashworthiness. Two identical sets of four shapes of stiffened hexagonal cells were built and crushed under quasi-static loading. The results were compared in terms of collapsing behavior, load-carrying performance, and energy-absorption capability. Although the observed failure modes were different since the base-materials differ, similar improvement trends in performance were observed between both fabrication approaches. Therefore, FDM was recommended as a fabrication method to optimize thin-walled cellular hexagonal parameters since it was 80% more time-efficient and 53.6% cheaper than the DMLS technique.
Impact of Operating Time on Selected Tribological Properties of the Friction Material in the Brake Pads of Passenger Cars
Authors: Borawski Andrzej
Published: February 2021

Braking systems have a direct impact on the safety of road users. That is why it is crucial that the performance of brakes be dependable and faultless. Unfortunately, the operating conditions of brakes during their operating time are affected by many variables, which results in changes in their tribological properties. This article presents an attempt to develop a methodology for studying how the operating time affects the value of the coefficient of friction and the abrasive wear factor. The Taguchi method of process optimization was used to plan the experiment, which was based on tests using the ball-cratering method. The results clearly show that the degree of wear affects the properties of the friction material used in the production process of brakes.
Identification of Material Properties and Optimal Design of Magnetically Shielded Rooms
Authors: Canova Aldo , Freschi Fabio , Giaccone Luca , Repetto Maurizio , Solimene Luigi
Published: February 2021

In this paper, we propose an optimal design procedure for magnetically shielded rooms. Focusing on multi-layer ferromagnetic structures, where inner layers operate at very low magnetic field, we propose an identification method of the magnetic material characteristic in the Rayleigh region. A numerical model to simulate the shielding efficiency of a multi-layer ferromagnetic structure is presented and experimentally tested on different geometries and layer configurations. The fixed point iterative method is adopted to handle the nonlinearity of the magnetic material. In conclusion, the optimization of the design parameters of a MSR is discussed, using the Vector Immune System algorithm to minimize the magnetic field inside the room and the cost of the structure. The results highlight that a linear magnetic characteristic for the material is sufficient to identify the suitable geometry of the shield, but the nonlinear model in the Rayleigh region is of fundamental importance to determine a realistic shielding factor.
On the Canonical Foliation of an Indefinite Locally Conformal Kähler Manifold with a Parallel Lee Form
Authors: Barletta Elisabetta , Dragomir Sorin , Esposito Francesco
Published: February 2021

We study the semi-Riemannian geometry of the foliation F of an indefinite locally conformal Kähler (l.c.K.) manifold M, given by the Pfaffian equation ω=0, provided that ∇ω=0 and c=∥ω∥≠0 (ω is the Lee form of M). If M is conformally flat then every leaf of F is shown to be a totally geodesic semi-Riemannian hypersurface in M, and a semi-Riemannian space form of sectional curvature c/4, carrying an indefinite c-Sasakian structure. As a corollary of the result together with a semi-Riemannian version of the de Rham decomposition theorem any geodesically complete, conformally flat, indefinite Vaisman manifold of index 2s, 0<s<n, is locally biholomorphically homothetic to an indefinite complex Hopf manifold CHsn(λ), 0<λ<1, equipped with the indefinite Boothby metric gs,n.
New from Old: Thorectandrin Alkaloids in a Southern Australian Marine Sponge, Thorectandra choanoides (CMB-01889)
Authors: Khushi Shamsunnahar , Salim Angela A. , Elbanna Ahmed H. , Nahar Laizuman , Capon Robert J.
Published: February 2021

Thorectandra choanoides (CMB-01889) was prioritized as a source of promising new chemistry from a library of 960 southern Australian marine sponge extracts, using a global natural products social (GNPS) molecular networking approach. The sponge was collected at a depth of 45 m. Chemical fractionation followed by detailed spectroscopic analysis led to the discovery of a new tryptophan-derived alkaloid, thorectandrin A (1), with the GNPS cluster revealing a halo of related alkaloids 1a–1n. In considering biosynthetic origins, we propose that Thorectandrachoanoides (CMB-01889) produces four well-known alkaloids, 6-bromo-1′,8-dihydroaplysinopsin (2), 6-bromoaplysinopsin (3), aplysinopsin (4), and 1′,8-dihydroaplysinopsin (10), all of which are susceptible to processing by a putative indoleamine 2,3-dioxygenase-like (IDO) enzyme to 1a–1n. Where the 1′,8-dihydroalkaloids 2 and 10 are fully transformed to stable ring-opened thorectandrins 1 and 1a–1b, and 1h–1j, respectively, the conjugated precursors 3 and 4 are transformed to highly reactive Michael acceptors that during extraction and handling undergo complete transformation to artifacts 1c–1g, and 1k–1n, respectively. Knowledge of the susceptibility of aplysinopsins as substrates for IDOs, and the relative reactivity of Michael acceptor transformation products, informs our understanding of the pharmaceutical potential of this vintage marine pharmacophore. For example, the cancer tissue specificity of IDOs could be exploited for an immunotherapeutic response, with aplysinopsins transforming in situ to Michael acceptor thorectandrins, which covalently bind and inhibit the enzyme.
Establishing a Smartphone Ambulatory ECG Service for Patients Presenting to the Emergency Department with Pre-Syncope and Palpitations
Authors: Reed Matthew J. , Muir Alexandra , Cullen Julia , Murphy Ross , Pollard Valery , Zangana Goran , Krupej Sean , Askham Sylvia , Holdsworth Patricia , Davies Lauren
Published: February 2021

Background and Objectives: The Investigation of Palpitations in the ED (IPED) study showed that a smartphone-based event recorder increased the number of patients in whom an electrocardiogram (ECG) was captured during symptoms over five-fold to more than 55% at 90 days compared to standard care and concluded that this safe, non-invasive and easy-to-use device should be considered part of on-going care to all patients presenting acutely with unexplained palpitations or pre-syncope. This study reports the process of establishing a smartphone palpitation and pre-syncope ambulatory care Clinic (SPACC) service. Materials and Methods: A clinical standard operating procedure (SOP) was devised, and funding was secured through a business case for the purchase of 40 AliveCor devices in the first instance. The clinic was launched on 22 July 2019. Results: Between 22 July 2019 and 31 October 2019, 68 patients seen in the emergency departments (EDs) with palpitations or pre-syncope were referred to SPACC. Of those, 30 were male and 38 were female, and the mean age was 45.8 years old (SD 15.1) with a range from 18 years old to 80 years old. A total of 50 (74%) patients underwent full investigation. On the first assessment, seven (10%) patients were deemed to have non-cardiac palpitations and were not fitted with the device. All patients who underwent full investigation achieved symptomatic rhythm correlation most with sinus rhythm, ventricular ectopics, or bigeminy. A symptomatic cardiac dysrhythmia was detected in six (8.8%) patients. Three patients had supraventricular tachycardia (4%), two had atrial fibrillation (3%), and one had atrial flutter (2%). Qualitative feedback from the SPACC team suggested several areas where improvement to the clinic could be made. Conclusion: We believe a smartphone palpitation service based on ambulatory care is simple to implement and is effective at detecting cardiac dysrhythmia in ED palpitation patients.
Protocol for Prevention and Monitoring of Surgical Site Infections in Implant-Based Breast Reconstruction: Preliminary Results
Authors: Papa Giovanni , Frasca Andrea , Renzi Nadia , Stocco Chiara , Pizzolato Giuseppe , Ramella Vittorio , Arnež Zoran Marij
Published: February 2021

Surgical site infection in implant-based breast reconstruction is a complication with variable incidence reported in the literature. Due to potential loss of implant and reconstruction, it can have a strong psychological impact on patients. Background and objectives: This study aimed primarily at analyzing the current status of the surgical site infection (SSI), (type, time of onset, clinical presentation, pathogens and management) in patients who underwent implant-based breast reconstruction at our Breast Unit. Secondarily, we wanted to establish whether introduction of a new, updated evidence-based protocol for infection prevention can reduce SSI in implant-based breast reconstruction. Materials and Methods: A single-center retrospective study was performed primarily to evaluate the incidence and features of SSI after implant-based breast reconstruction from 2007 to 2020. In June 2020, a protocol for prevention of SSI in implant-based breast reconstruction was introduced in clinical practice. Secondarily, a data analysis of all patients who underwent implant-based breast reconstruction in compliance with this protocol was performed after preliminarily assessing its efficacy. Results: 756 women were evaluated after mastectomy and implant-based breast reconstruction for breast cancer. A total of 26 surgical site infections were detected. The annual incidence of SSI decreased over time (range 0–11.76%). Data relating to infections’ features, involved pathogens and implemented treatments were obtained. Since the introduction of the protocol, 22 patients have been evaluated, for a total of 29 implants. No early infections occurred. Conclusions: Surgical site infection rates at our Breast Unit are comparable to those reported in the literature. The SSI rates have shown a decreasing trend over the years. No SSI has occurred since the introduction of the prevention protocol for surgical site infection in June 2020.
Associations between Physical Function, Bone Density, Muscle Mass and Muscle Morphology in Older Men with Sarcopenia: A Pilot Study
Authors: Mastavičiūtė Asta , Kilaitė Justina , Petroška Donatas , Laurinavičius Arvydas , Tamulaitienė Marija , Alekna Vidmantas
Published: February 2021

Background and Objectives: It is thought that muscle and bone interact only on a biomechanical level, however, some research is now emerging that links bone and muscle on a cellular level. The aim of this study was to explore associations between physical function, muscle mass and bone density in community-dwelling elderly men with sarcopenia. A secondary goal was to analyze if muscle morphology was associated with bone density and physical functioning. Materials and Methods: Body composition was measured by dual-energy X-ray absorptiometry (DXA). Bone density was evaluated according to WHO criteria. Sarcopenia was diagnosed according to European Working Group on Sarcopenia in Older People (EWGSOP) criteria: low muscle mass and low muscle strength or low physical performance. Microbiopsy of musculus vastus lateralis was performed with a disposable muscle microbiopsy system. The perimeter and cross-sectional area of muscle fibers were calculated using image analysis software in whole slide images; type of fibers and their distribution were evaluated as well. Results: A total of 151 men, 60 years or older were included in this study. Mean age of the subjects was 72.9 ± 8.02 years. Sarcopenia was diagnosed in 45 (29.8%) men. Multiple significant correlations were found between bone mineral density, lean mass, appendicular lean mass, arm and leg lean mass, gait speed, balance test and handgrip strength in sarcopenic men. Lean mass was associated with femoral neck BMD (bone mineral density; r = 0.418, p = 0.006) and handgrip strength (r = 0.553, p < 0.001). In the sarcopenia group, 25 muscle biopsies were examined. In 9 sarcopenic men with T-scores equal or below −2.5, the muscle fiber area had a significant correlation with the balance test (r = 0.73, p = 0.025). Conclusions: In men with sarcopenia, low lean muscle mass was associated with low femoral neck BMD and low muscle strength. In sarcopenic men with osteoporosis, low muscle fiber area was associated with low scores in a balance test.
Microscopic Polyangiitis Presenting with Splenic Infarction: A Case Report
Authors: Chung Sang Wan
Published: February 2021

Microscopic polyangiitis (MPA) is an anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). The splenic involvement in AAV is known to be rare, and that in MPA has not been reported to date. A 74-year-old woman was admitted owing to left arm numbness and weakness. The patient was diagnosed as MPA with vasculitic neuropathy. Her abdominal computed tomography (CT) revealed splenic infarction incidentally. The splenic infarction had been resolved at follow-up CT after treatment. If splenic involvement of MPA was not considered, treatment may have been delayed in order to differentiate other diseases. Herein, I report the first case of splenic involvement of MPA.
Kinetic and Isotherm Study of As(III) Removal from Aqueous Solution by PET Track-Etched Membranes Loaded with Copper Microtubes
Authors: Russakova Alyona V. , Altynbaeva Liliya Sh. , Barsbay Murat , Zheltov Dmitriy A. , Zdorovets Maxim V. , Mashentseva Anastassiya A.
Published: February 2021

This paper reports on the synthesis and structure elucidation of track-etched membranes (TeMs) with electrolessly deposited copper microtubes (prepared in etched-only and oxidized polyethylene terephthalate (PET) TeMs), as well as on the comparative testing of arsenic (III) ion removal capacities through bath adsorption experiments. The structure and composition of composites were investigated by X-ray diffraction technique and scanning electron and atomic force microscopies. It was determined that adsorption followed pseudo-second-order kinetics, and the adsorption rate constants were calculated. A comparative study of the applicability of the adsorption models of Langmuir, Freundlich, and Dubinin–Radushkevich was carried out in order to describe the experimental isotherms of the prepared composite TeMs. The constants and parameters of all of the above equations were determined. By comparing the regression coefficients R2, it was shown that the Freundlich model describes the experimental data on the adsorption of arsenic through the studied samples better than others. Free energy of As(III) adsorption on the samples was determined using the Dubinin–Radushkevich isotherm model and was found to be 17.2 and 31.6 kJ/mol for Cu/PET and Cu/Ox_PET samples, respectively. The high EDr value observed for the Cu/Ox_PET composite indicates that the interaction between the adsorbate and the composite is based on chemisorption.
The Removal of Selected Inorganics from Municipal Membrane Bioreactor Wastewater Using UF/NF/RO Membranes for Water Reuse Application: A Pilot-Scale Study
Authors: Aziz Mujahid , Kasongo Godwill
Published: February 2021

Membrane technology has advanced substantially as a preferred choice for the exclusion of widespread pollutants for reclaiming water from various treatment effluent. Currently, little information is available about Ultrafiltration (UF)/Nanofiltration (NF)/Reverse Osmosis (RO) performance at a pilot scale as a practical engineering application. In this study, the effluent from a full-scale membrane bioreactor (MBR) municipal wastewater treatment works (MWWTWs) was treated with an RO pilot plant. The aim was to evaluate the effect of operating conditions in the removal of selected inorganics as a potential indirect water reuse application. The influent pH, flux, and membrane recovery were the operating conditions varied to measure its influence on the rejection rate. MBR/RO exhibited excellent removal rates (>90%) for all selected inorganics and met the standard requirements for reuse in cooling and irrigation system applications. The UF and NF reduction of inorganics was shown to be limited to meet water standards for some of the reuse applications due to the high Electron Conductivity (EC > 250 μS·cm−1) levels. The MBR/NF was irrigation and cooling system compliant, while for the MBR/UF, only the cooling system was compliant.
Efficient Facilitated Transport Polymer Membrane for CO2/CH4 Separation from Oilfield Associated Gas
Authors: Zhang Chunwei , Sheng Menglong , Hu Yaoqiang , Yuan Ye , Kang Yulong , Sun Xiao , Wang Tao , Li Qinghua , Zhao Xisen , Wang Zhi
Published: February 2021

CO2 enhanced oil recovery (CO2-EOR) technology is a competitive strategy to improve oil field economic returns and reduce greenhouse gas emissions. However, the arbitrary emissions or combustion of the associated gas, which mainly consists of CO2 and CH4, will cause the aggravation of the greenhouse effect and a huge waste of resources. In this paper, the high-performance facilitated transport multilayer composite membrane for CO2/CH4 separation was prepared by individually adjusting the membrane structure of each layer. The effect of test conditions on the CO2/CH4 separation performance was systematically investigated. The membrane exhibits high CO2 permeance of 3.451 × 10−7 mol·m−2·s−1·Pa−1 and CO2/CH4 selectivity of 62 at 298 K and 0.15 MPa feed gas pressure. The cost analysis was investigated by simulating the two-stage system. When the recovery rate and purity of CH4 are 98%, the minimum specific cost of separating CO2/CH4 (45/55 vol%) can be reduced to 0.046 $·Nm−3 CH4. The excellent short-to-mid-term stability indicates the great potential of large industrial application in the CH4 recovery and CO2 reinjection from oilfield associated gas.
Desalination of Municipal Wastewater Using Forward Osmosis
Authors: Ezugbe Elorm , Kweinor Tetteh Emmanuel , Rathilal Sudesh , Asante-Sackey Dennis , Amo-Duodu Gloria
Published: February 2021

Membrane technology has gained much ground in water and wastewater treatment over the past couple of decades. This is timely, as the world explores smart, eco-friendly, and cheap water and wastewater treatment technologies in its quest to make potable water and sanitation commonplace in all parts of the world. Against this background, this study investigated forward osmosis (FO) in the removal of salts (chlorides, sulphates, and carbonates) and organics (chemical oxygen demand (COD), turbidity, total suspended solids (TSS), and color) from a synthetic municipal wastewater (MWW), mimicking secondary-treated industrial wastewater, at very low feed and draw solution flow rates (0.16 and 0.14 L/min respectively), using 70 g/L NaCl solution as the draw solution. The results obtained showed an average of 97.67% rejection of SO42− and CO32− while Cl− was found to enrich the feed solution (FS). An average removal of 88.92% was achieved for the organics. A permeation flux of 5.06 L/m2.h was obtained. The kinetics of the ions transport was studied, and was found to fit the second-order kinetic model, with Pearson’s R-values of 0.998 and 0.974 for Cl− and CO32− respectively. The study proves FO as a potential technology to desalinate saline MWW.
Hydrodynamic and Performance Evaluation of a Porous Ceramic Membrane Module Used on the Water–Oil Separation Process: An Investigation by CFD
Authors: Oliveira Neto Guilherme L. , Oliveira Nívea G. N. , Delgado João M. P. Q. , Nascimento Lucas P. C. , Magalhães Hortência L. F. , Oliveira Paloma L. de , Gomez Ricardo S. , Farias Neto Severino R. , Lima Antonio G. B.
Published: February 2021

Wastewater from the oil industry can be considered a dangerous contaminant for the environment and needs to be treated before disposal or re-use. Currently, membrane separation is one of the most used technologies for the treatment of produced water. Therefore, the present work aims to study the process of separating oily water in a module equipped with a ceramic membrane, based on the Eulerian–Eulerian approach and the Shear-Stress Transport (SST k-ω) turbulence model, using the Ansys Fluent® 15.0. The hydrodynamic behavior of the water/oil mixture in the filtration module was evaluated under different conditions of the mass flow rate of the fluid mixture and oil concentration at the entrance, the diameter of the oil particles, and membrane permeability and porosity. It was found that an increase in the feed mass flow rate from 0.5 to 1.5 kg/s significantly influenced transmembrane pressure, that varied from 33.00 to 221.32 kPa. Besides, it was observed that the particle diameter and porosity of the membranes did not influence the performance of the filtration module; it was also verified that increasing the permeability of the membranes, from 3 × 10−15 to 3 × 10−13 m2, caused transmembrane pressure reduction of 22.77%. The greater the average oil concentration at the permeate (from 0.021 to 0.037 kg/m3) and concentrate (from 1.00 to 1.154 kg/m3) outlets, the higher the average flow rate of oil at the permeate outlets. These results showed that the filter separator has good potential for water/oil separation.
Bone Regeneration Assessment of Polycaprolactone Membrane on Critical-Size Defects in Rat Calvaria
Authors: Bassi Ana , Bizelli Vinícius , Francatti Tamires , Rezende de Moares Ferreira Ana , Carvalho Pereira Járede , Al-Sharani Hesham , de Almeida Lucas Flavia , Faverani Leonardo
Published: February 2021

Biomaterials for use in guided bone regeneration (GBR) are constantly being investigated and developed to improve clinical outcomes. The present study aimed to comparatively evaluate the biological performance of different membranes during the bone healing process of 8 mm critical defects in rat calvaria in order to assess their influence on the quality of the newly formed bone. Seventy-two adult male rats were divided into three experimental groups (n = 24) based on the membranes used: the CG—membrane-free control group (only blood clot, negative control), BG—porcine collagen membrane group (Bio-Guide®, positive control), and the PCL—polycaprolactone (enriched with 5% hydroxyapatite) membrane group (experimental group). Histological and histometric analyses were performed at 7, 15, 30, and 60 days postoperatively. The quantitative data were analyzed by two-way ANOVA and Tukey’s test (p < 0.05). At 7 and 15 days, the inflammatory responses in the BG and PCL groups were significantly different (p < 0.05). The PCL group, at 15 days, showed a large area of newly formed bone. At 30 and 60 days postoperatively, the PCL and BG groups exhibited similar bone healing, including some specimens showing complete closure of the critical defect (p = 0.799). Thus, the PCL membrane was biocompatible, and has the potential to help with GBR procedures.
Monitoring the Damage Evolution in Rolling Contact Fatigue Tests Using Machine Learning and Vibrations
Authors: Provezza Luca , Bodini Ileana , Petrogalli Candida , Lancini Matteo , Solazzi Luigi , Faccoli Michela
Published: February 2021

This study shows the application of a system to monitor the state of damage of railway wheel steel specimens during rolling contact fatigue tests. This system can make continuous measurements with an evaluation of damage without stopping the tests and without destructive measurements. Four tests were carried out to train the system by recording torque and vibration data. Both statistical and spectral features were extracted from the sensors signals. A Principal Component Analysis (PCA) was performed to reduce the volume of the initial dataset; then, the data were classified with the k-means algorithm. The results were then converted into probabilities curves. Metallurgical investigations (optical micrographs, wear curves) and hardness tests were carried out to assess the trends of machine learning analysis. The training tests were used to train the proposed algorithm. Three validation tests were performed by using the real-time results of the k-means algorithm as a stop condition. Metallurgical analysis was performed also in this case. The validation tests follow the results of the training test and metallurgical analysis confirms the damage found with the machine learning analysis: when the membership probability of the cluster corresponding to the damage state reaches a value higher than 0.5, the metallurgical analysis clearly shows the cracks on the surface of the specimen due to the rolling contact fatigue (RCF) damage mechanism. These preliminary results are positive, even if reproduced on a limited set of specimens. This approach could be integrated in rolling contact fatigue tests to provide additional information on damage progression.
The Development of WC-Based Composite Tools for Friction Stir Welding of High-Softening-Temperature Materials
Authors: Ahmed Mohamed M. Z. , Barakat Waheed S. , Y. A. Mohamed Abdelkarim , A. Alsaleh Naser , Elkady Omayma A.
Published: February 2021

This work presents a detailed investigation for the effect of Y2O3 and Ni additions on the densification behavior, microstructural evolution and mechanical properties of a WC-Co-TaC-NbC composite. With the aim of obtaining WC-based composites with improved fracture toughness, to be used in severe conditions of high-temperature deformation, different concentrations of Y2O3 were incorporated with and without 5 wt% Ni addition. The consolidated composites were characterized using density measurement, XRD, SEM, hardness, fracture toughness, transverse rupture strength and compression testing. Fully dense composites were obtained through the applied consolidation regime of cold compaction and sintering at 1450 °C for 1.5 h under vacuum with a relative density up to 97%. The addition of 2.5 wt% Y2O3 to the base WC composite increased the relative density and then slightly decreased with the increase of the Y2O3 content. The addition of 5 wt% Ni to the base composites significantly increased the relative density to 97%. The XRD results indicated the existence of the Co3W3C η-phase after sintering, and the intensity of its peaks was reduced with the addition of 5 wt% Ni. The microstructure of the consolidated composites consisted of three phases: WC, Co3W3C and Y2O3. The area fraction of the Y2O3 phase increased as its weight fraction increased. In terms of the fracture toughness, the transverse-rupture strength (TRS) and the compressive strength were significantly improved by the addition of 5 wt% Ni with the 2.5 wt% Y2O3. Accordingly, this composition was used to manufacture the tools for the friction stir welding of the high-softening-temperature materials, which was successfully used for 25 plunges and about 500 cm of butt joints in nickel-based and carbon–steel alloys.
Hydrometallurgical Recovery of Cu and Zn from a Complex Sulfide Mineral by Fe3+/H2SO4 Leaching in the Presence of Carbon-Based Materials
Authors: Álvarez María Luisa , Fidalgo José Manuel , Gascó Gabriel , Méndez Ana
Published: February 2021

Chalcopyrite, the main ore of copper, is refractory in sulfuric media with slow dissolution. The most commonly employed hydrometallurgical process for the oxidation of chalcopyrite and copper extraction is the sulfuric acid ferric sulfate system The main objective of the present work is to study the use of cheap carbon-based materials in the leaching of copper and zinc from a sulfide complex mineral from Iberian Pyrite Belt (IPB). The addition effect of commercial charcoal (VC) and two magnetic biochars (BM and HM) that were obtained by pyrolysis of biomass wastes was compared to that of commercial activated carbon (AC). The experimental results performed in this work have shown that the presence of carbon-based materials significantly influences the kinetics of chalcopyrite leaching in the sulfuric acid ferric sulfate media at 90 °C. The amount of copper and zinc extracted from IPB without the addition of carbon-based material was 63 and 72%, respectively. The highest amount of extracted zinc (>90%) was obtained with the addition of VC and AC in IPB/carbon-based material ratio of 1/0.25 w/w. Moreover, it is possible to recover more than 80% of copper with the addition of VC in a ratio 1/0.25 w/w. Moreover, an optimization of the properties of the carbon-based material for its potential application as catalyst in the leaching of metals from sulfide is necessary.
Fatigue Performance of High- and Low-Strength Repaired Welded Steel Joints
Authors: Schubnell Jan , Ladendorf Phillip , Sarmast Ardeshir , Farajian Majid , Knödel Peter
Published: February 2021

Large portions of infrastructure buildings, for example highway- and railway bridges, are steel constructions and reach the end of their service life, as a reason of an increase of traffic volume. As lifetime extension of a commonly used weld detail (transverse stiffener) of these structures, a validated approach for the weld repair was proposed in this study. For this, welded joints made of S355J2+N and S960QL steels were subjected to cyclic loading until a pre-determined crack depth was reached. The cracks were detected by non-destructive testing methods and repaired by removal of the material around the crack and re-welding with the gas metal arc welding (GMAW). Then, the specimens were subjected to cyclic loading again. The hardness, the weld geometry, and the residual stress state was investigated for both the original- and the repaired conditions. It was determined that nearly all repaired specimens reached at least the fatigue life of the original specimen.
Efficient Recovery of Rare Earth Elements (Pr(III) and Tm(III)) From Mining Residues Using a New Phosphorylated Hydrogel (Algal Biomass/PEI)
Authors: He Chunlin , Salih Khalid A.M. , Wei Yuezhou , Mira Hamed , Abdel-Rahman Adel A.-H. , Elwakeel Khalid Z. , Hamza Mohammed F. , Guibal Eric
Published: February 2021

With the target of recovering rare earth elements (REEs) from acidic leachates, a new functionalized hydrogel was designed, based on the phosphorylation of algal/polyethyleneimine beads. The functionalization strongly increased the sorption efficiency of the raw material for Pr(III) and Tm(III). Diverse techniques were used for characterizing this new material and correlating the sorption performances and mechanisms to the physicochemical structure of the sorbent. First, the work characterized the sorption properties from synthetic solutions with the usual procedures (study of pH effect, uptake kinetics, sorption isotherms, metal desorption and sorbent recycling, and selectivity from multi-element solutions). Optimum pH was found close to 5; sorption isotherms were fitted by the Langmuir equation (maximum sorption capacities close to 2.14 mmol Pr g−1 and 1.57 mmol Tm g−1). Fast uptake kinetics were modeled by the pseudo-second order rate equation. The sorbent was highly selective for REEs against alkali-earth and base metals. The sorbent was remarkably stable for sorption and desorption operation (using 0.2 M HCl/0.5 M CaCl2 solutions). The sorbent was successfully applied to the leachates of Egyptian ore (pug leaching) after a series of pre-treatments (precipitation steps), sorption, and elution. The selective precipitation of REEs using oxalic acid allows for the recovery of a pure REE precipitate.
GPU-Accelerated Cellular Automaton Model for Grain Growth during Directional Solidification of Nickel-Based Superalloy
Authors: Zhang Yongjia , Zhou Jianxin , Yin Yajun , Shen Xu , Shehabeldeen Taher A. , Ji Xiaoyuan
Published: February 2021

To accelerate the large-scale cellular automaton (CA) simulation for grain growth, a parallel CA model for grain growth was developed. The model was implemented based on the compute unified device architecture (CUDA) parallel computing platform. The model was verified by the grain growth of a single crystal and the columnar-to-equiaxed transition (CET) of an Al-7wt% Si specimen of uniform undercooling with a constant cooling rate. The grid independence of the model was verified. The grain growth of a plate-like casting of nickel-based superalloy during directional solidification process was simulated and the obtained results of grain density at each section with different heights were compared with the experimental data. The CET transition of directional solidified Al-7wt% Si cylindrical ingot was simulated. The grain texture and cooling curves were in good agreement with experimental results from the literature. Finally, high parallel performance of the CA model was obtained and evaluated.