Recently, the development of highly active electrocatalysts with considerable, efficiency and moderate costs for application in the oxygen reduction reaction (ORR) has attracted a great deal of ...attention. In this work, an economic and easy approach has been evaluated for preparation of graphene doped with N, S, B and P. The source of graphene used in this study was grape leaves and N, S, P and B were then added thereto through a 2-hour pyrolysis reaction in N2 atmosphere at 900°C. The produced specimens were evaluated using XRD, FTIR, SEM, XPS ad TEM, as well as CV analyses using a rotating disk electrode (RDE). The morphology of doped graphene sample showed uniform dispersion of sulfur, nitrogen, boron and phosphorous in the carbon framework, which was obtained with elemental mapping distribution. The prepared samples show good selectivity to the 4 electron reaction pathway in an alkaline electrolyte as well as stable current density and great resistance against crossover effects of methanol. These indicate the considerable promise of these materials for use in oxygen reduction reaction as an electro-catalyst. Moreover, the onset potential of Gl300G-900 and GlG-900 samples (0.93 and 0.92 V vs. RHE) was found to be near that of Pt/C 20 wt.% (0.99 V vs RHE).
Explosively driven impact welding is a true example of multidisciplinary research as the phenomena associated with it fall under the various branches of engineering science. A great deal of the work ...in, and collaboration between various specialised fields have been expended on the subject. However, a comprehensive quantitative theory capable of giving an accurate description and prediction of the parameters and of the characteristic features of explosively welded components does not exist. Most of the investigators considered the welding process as a solid state welding process, but some believed that the process is a fusion welding process. Interfacial waves are the most discussed aspect of explosive welding. The presence of jet in the collision region, and the transient fluid-like behaviour under high pressure have led many investigators to seek an explanation and a characterisation of these waves in terms of a flow mechanics of one kind or another. In this study, part of the welding process was numerically analysed. A finite difference engineering package was used to model the oblique impact of a thin flyer plate on a relatively thick base. The results were validated by data from carefully controlled experiments using a pneumatic gun. Straight and wavy interfaces and jetting phenomena were modelled, and the magnitude of the waves and the velocity of jet predicted. The numerical analysis predicted a hump ahead of the collision point. Wave formation appears to be the result of variations in the velocity distribution at the collision point and periodic disturbances of the materials. Higher values of plastic strain were predicted in wavy interfaces. Bonding was found to be a solid state welding process. Phase changes which occur may be due to high temperatures (but less than the melting temperature) at the collision point.
In the present research, seismic performance of reduced beam section (RBS) moment connections in box-columns subjected to different loading protocols was evaluated through the experimental program ...and finite element study. The investigations performed in this research sought to explain the behavior and overall stability of the connection, strength degradation, panel zone performance, plasticity development at plastic hinges, and failure potentials. Also, since there are several loading protocols available in technical literature; another goal of this research was to investigate the difference and imposed demands by those protocols. In order to meet the research aims, laboratory specimens, along with the finite element models, were subjected to different loading protocols at the target value level, qualifying condition, and collapse threshold control. Based on the mentioned investigations, the performance parameters of the RBS moment connections in box-columns, as well as the demands and applied energies subjected to Western Asia, SAC, and ATC-24 loading protocols, were evaluated and compared.
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•Cyclicassessment of reduced beam section moment connection via experimental program and the finite element studies.•Comparative investigation of the RBS connection at target value level, qualifying condition, and collapse threshold control.•Effects of imposed demands on the specimens and the FEM models subjected to different cyclic loadings protocols.•Controlling the behavior of RBS moment connection at collapse threshold control.
This study was aimed to investigate Broiler chickens using PCR-RFLP (IGF1 and IGF2 genes). HinfI and Hsp92II restriction enzymes were used to amplify and digest 793-bp and 1146-bp fragments of the ...IGF1 gene, respectively. TT, TC, and CC genotypes were found in both genes in two different T and C allele subgroups. IGF1 had a higher prevalence of the C-allele (0.86) than IGF2, whereas IGF2 had a higher prevalence of the T-allele (0.5611).
Turbulators have been developed as a capable passive technique for enhancing heat transfer through channels. The shape and arrangement of these geometries are the main factors in their performance. ...In the current analysis, three curved turbulators, i.e. circular (C), rectangular (R), and diamond (D), with four various arrangements, i.e. forward-vertical (FV), forward-horizontal (FH), backward-vertical (BV), and backward-horizontal (BH), inside a rectangular channel at the constant heat flux are examined. The thermal and aerodynamic characteristics are analyzed using the dimensional parameters of h and ∆p as well as the dimensionless parameters of Nu
enh
/Nu
smo
vs. f
enh
/f
smo
. Based on experimental data and their corresponding numerical results, the effects of both shape and arrangement on streamlines and contours of airflow are discussed. Also, a performance index (η) is applied to apprise overall thermal-aerodynamic performance at inlet velocities of 1, 2, and 3 m/s. The results show that the value of η has a deceasing trend with the inlet velocity, indicating a better performance is found at lower velocity for these turbulators. The best performance could be achieved by the C turbulators at the FV arrangement (CFV model with η between 1.36 and 1.52), followed the DFH model with η between 1.35 and 1.49.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
There is a critical need in orthopedic and orthodontic clinics for enhanced implant-bone interface contact to facilitate the quick establishment of a strong and durable connection. Surface ...modification by bioactive multifunctional materials is a possible way to overcome the poor osteoconductivity and the potential infection of Ti-based implants. Ti-25Zr biometallic alloy was prepared by powder metallurgy technique and then coated by Nano-composite fiber using electrospinning. Ceramic Nanocompound (CaTiO3, BaTiO3) was used as filler material and individually added to polymeric matrices constructed from the blend of polycaprolactone/chitosan. Using optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and wettability, respectively, the morphology, chemical analysis, surface roughness, and contact angle measurements of the samples were evaluated. The result shows a significant improvement in cell viability, proliferation, and ALP activity for coated samples compared to noncoated samples. PCL/Chitosan/Nano-CaTiO3 (CA1) recorded remarkable enhancement from the surface-coated samples, demonstrating a significantly higher cell viability value after seven days of MC3T3-E1 cell culture, reaching 271.56 ± 13.15%, and better cell differentiation with ALP activity reaching 5.61 ± 0.35 fold change for the same culture time. PCL/Chitosan/Nano-BaTiO3 (BA1) also shows significant improvement in cell viability by 181.63 ± 17.87% and has ALP activity of 3.97 ± 0.67 fold change. For coated samples, cell proliferation likewise exhibits a considerable temporal increase; the improvement reaches 237.53% for (CA1) and 125.16% for (BA1) in comparison with uncoated samples (bare Ti-25Zr). The coated samples resist bacteria in the antibacterial test compared to the noncoated samples with no inhibition zone. This behavior suggests that a Nanocomposite fiber coat containing an active ceramic Nanocompound (CaTiO3, BaTiO3) promotes cell growth and holds promise for orthodontic and orthopedic bioapplication.
•A novel design of microchannel is proposed for use in battery cooling.•The combination of chamber with pin is studied as enhanced techniques.•The reduction of total thermal resistance is analyzed ...and discussed numerically.•The highest values of h and Δp are recorded for the combined technique.•The maximum reduction of total thermal resistance is 43.6%.
The microchannel heat sink is an effective liquid cooling technique in thermal management of miniature systems. In the current work, to enhance the performance of a microchannel, the combination of rectangular pin with chamber is proposed and studied. A numerical study is carried out, and the governing equations are discretized by the finite volume method using the semi-implicit method for pressure linked equations algorithm. The reliability of the numerical results is verified based on the experimental section of this study. The deviations of the comparison fall in satisfactory ranges (maximum error of 8%). All the complex geometries have the same overall dimensions (height, width, and length) as the smooth microchannel, and a constant heat flux of 100 kW/m2 is applied. Water is used as working fluid, and all cases are examined in the Reynolds number ranging from 423 to 1990. The results illustrate that both the pin and the chamber boost the heat transfer coefficient of the microchannel with a penalty in the pressure drop. It is also found that in the case equipped with the rectangular pin and chamber, there is a 2.3%–53.1% increase in the heat transfer coefficient, and a 3.6%–681.4% increase in the pressure drop, compared with the reference model. Furthermore, the position of the pin and chamber affects the overall performance of the microchannel. It can be concluded that the enlargement in the length of the chamber improves the overall performance of the combined model, while the enlargement in the length of the pin has an inverse impact.
We consider the primitive relay channel, where the source sends a message to the relay and to the destination, and the relay helps the communication by transmitting an additional message to the ...destination via a separate channel. Two well-known coding techniques have been introduced for this setting: decode-and-forward and compress-and-forward. In decode-and-forward, the relay completely decodes the message and sends some information to the destination; in compress-and-forward, the relay does not decode, and it sends a compressed version of the received signal to the destination using Wyner–Ziv coding. In this paper, we present a novel coding paradigm that provides an improved achievable rate for the primitive relay channel. The idea is to combine compress-and-forward and decode-and-forward via a chaining construction. We transmit over pairs of blocks: in the first block, we use compress-and-forward; and, in the second block, we use decode-and-forward. More specifically, in the first block, the relay does not decode, it compresses the received signal via Wyner–Ziv, and it sends only part of the compression to the destination. In the second block, the relay completely decodes the message, it sends some information to the destination, and it also sends the remaining part of the compression coming from the first block. By doing so, we are able to strictly outperform both compress-and-forward and decode-and-forward. Note that the proposed coding scheme can be implemented with polar codes. As such, it has the typical attractive properties of polar coding schemes, namely, quasi-linear encoding and decoding complexity, and error probability that decays at super-polynomial speed. As a running example, we take into account the special case of the erasure relay channel, and we provide a comparison between the rates achievable by our proposed scheme and the existing upper and lower bounds.
Biofunctionalization of an implant using functional ceramics with exceptional electrical characterization, such as BaTiO3 and SrTiO3, has gained considerable attention in creating a composite coating ...with bio-polymer to activate metal implant surfaces for bone tissue engineering applications and, at the same time, resist bacterial infection. A Ti–Zr alloy sample was created by powder technology, and then a coating was applied using the electrospinning technique. Individually, nanopowders of ceramic compounds such as nBaTiO3 and nSrTiO3 were added to a blend of polycaprolactone and chitosan to create composite solutions that could be converted into a nanofibrous coating layer using the electrospinning technique. The samples were analyzed for their morphology, chemical composition, surface roughness, dielectric constant, and wettability. The techniques employed were SEM, EDS, FTIR, an LCR meter, and a contact angle goniometer. The samples' cytocompatibility was assessed by examining the cell viability, ALP activity, proliferation, and attachment of MC3T3-E1 osteoblast cells on both coated and uncoated sample surfaces.The bacterial resistance assays were conducted against Staphylococcus aureus and Streptococcus mutans. The findings demonstrate a notable enhancement in the biocompatibility of the coated specimens following a week of cellular cultivation. The composite coating containing piezoelectric BaTiO3 has a dielectric constant Ɛr (16) close to dry human bone at 100HZ frequency. Cell proliferation increases dramatically with time in coated samples, and the improvement approaches 125.16% for (BA1) and 111.38% for (SR1) as compared to uncoated Ti–25Zr sample. Cell viability percentage for the coated samples is compared with bare Ti–25Zr, which has an 80.52 ± 1.97% crucial increase, while (BA1) has 181.63 ± 17.87 and (SR1) 170.09 ± 18.12%. No zone of inhibition was detected in the bacterial resistance test for the uncoated sample, while the samples with composite coating show an adequate and comparable inhibitory zone. The composite nano-fiber has a strong biocompatibility, and the coating process is simple and economical, holding potential for use in orthodontic and orthopedic bone regeneration applications.
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