The Usability of Boric Acid as an Alternative Foaming Agent on the Fabrication of Al/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Composite Foams

Pure Al and alumina (2, 5, 10 wt.% Al₂O₃)-added Al composite foams were fabricated through powder metallurgy technique, where boric acid (H₃BO₃) is employed as a new alternative foaming agent. It is aimed to determine the effects of boric acid on the foaming behavior and cellular structure and also purposed to develop the mechanical properties of Al foams by addition of Al₂O₃. Al and Al composite foams with porosity fraction in the range of 46-53% were achieved by sintering at 620 °C for 2 h. Cell morphology was characterized using a combination of stereomicroscope equipped with image analyzer and scanning electron microscopy. Microhardness values were measured via using Vickers indentation technique. Quasi-static compression tests were performed at strain rate of 10^?3 s^?1. Compressive strength and energy absorption of the composite foams enhanced not only by the increasing weight fraction of alumina, but also by the usage of boric acid which leads to formation of boron oxide (B₂O₃) acting as a binder in obtaining dense cell walls. The results revealed that the boric acid has outstanding potential as foaming agent in the fabrication of Al and Al composite foams by providing improved mechanical properties.     

Hydrogen desorption kinetics of MgH2 synthesized from modified waste magnesium

In the present study, hydrogen desorption properties of magnesium hydride (MgH₂) synthesized from modified waste magnesium chips (WMC) were investigated. MgH₂ was synthesized by hydrogenation of modified waste magnesium at 320 °C for 90 min under a pressure of 6 × 10⁶ Pa. The modified waste magnesium was prepared by mixing waste magnesium with tetrahydrofuran (THF) and NaCl additions, applying mechanical milling. Next, it was investigated by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) techniques in order to characterize its structural properties. Hydrogen desorption properties were determined by differential scanning calorimetry (DSC) under nitrogen atmosphere at different heating rates (5, 10, and 15 °C/min). Doyle and Kissenger non-isothermal kinetic models were applied to calculate energy (E _a ) values, which were found equal to 254.68 kJ/mol and 255.88 kJ/mol, respectively.     

Degeneration of mechanical characteristics and performances with Zr nanoparticles inserted in Bi-2223 superconducting matrix and increment in dislocation movement and cracks propagation

This study explains the role of Zr concentration level on mechanical characteristics and performance belonging to the bulk Bi-2223 superconducting materials by means of standard Vickers microhardness (H _v ) measurements at different applied loads in the range of 0.245–2.940 N and evaluated theoretical calculations. The experimental measurement results obtained display that the mechanical performances regress with the increment of the Zr addition level due to the increased artificial disorders/damages/breaks/voids/cracks and irregular grain orientation distribution. In other words, the Zr addition accelerates both the dislocation movement and especially the cracks/voids propagation of as a consequence of the decrement in the Griffith critical crack length, being one of the most striking points deduced from this work. These vital findings are also favored by the extracted parameters of Young’s modulus, yield strength, fracture toughness and brittleness index. Nevertheless, it is found that every sample studied exhibit typical indentation size effect (ISE) behavior due to the production of the elastic and plastic deformations simultaneously in the system. Moreover, the load dependent microhardness values are theoretically analyzed with the aid of six available models such as six available approaches: Meyer’s law, proportional sample resistance model, modified proportional sample resistance model, elastic/plastic deformation, Hays–Kendall (HK) and indentation-induced cracking model for the first time. The results obtained show that the HK approach exhibits perfectly performance on the analysis of the mechanical characteristics of the superconducting materials exhibiting ISE behavior whereas the other models are inadequate to explain the load independent mechanical characteristics of the Bi-2223 system added by the Zr nanoparticles.     

Dimension‐Based Design of Melt Electrowritten Scaffolds

The electrohydrodynamic stabilization of direct‐written fluid jets is explored to design and manufacture tissue engineering scaffolds based on their desired fiber dimensions. It is demonstrated that melt electrowriting can fabricate a full spectrum of various fibers with discrete diameters (2–50 µm) using a single nozzle. This change in fiber diameter is digitally controlled by combining the mass flow rate to the nozzle with collector speed variations without changing the applied voltage. The greatest spectrum of fiber diameters was achieved by the simultaneous alteration of those parameters during printing. The highest placement accuracy could be achieved when maintaining the collector speed slightly above the critical translation speed. This permits the fabrication of medical‐grade poly(ε‐caprolactone) into complex multimodal and multiphasic scaffolds, using a single nozzle in a single print. This ability to control fiber diameter during printing opens new design opportunities for accurate scaffold fabrication for biomedical applications.     

Impacts of wind turbines on vegetation and soil cover: a case study of Urla,Cesme, and Karaburun Peninsulas,Turkey

Clean Technologies and Environmental Policy - The study presents a GIS- and RS-based diagnostic model to determine the changes in the existing vegetation in the Urla, Çeşme, and Karaburun...     

Process and formulation variables of pregabalin microspheres prepared by w/o/o double emulsion solvent diffusion method and their clinical application by animal modeling studies

Pregabalin is an anticonvulsant drug used for neuropathic pain and as an adjunct therapy for partial seizures with or without secondary generalization in adults. In conventional therapy recommended dose for pregabalin is 75?mg twice daily or 50?mg three times a day, with maximum dosage of 600?mg/d. To achieve maximum therapeutic effect with a low risk of adverse effects and to reduce often drug dosing, modified release preparations; such as microspheres might be helpful. However, most of the microencapsulation techniques have been used for lipophilic drugs, since hydrophilic drugs like pregabalin, showed low-loading efficiency and rapid dissolution of compounds into the aqueous continous phase. The purpose of this study was to improve loading efficiency of a water-soluble drug and modulate release profiles, and to test the efficiency of the prepared microspheres with the help of animal modeling studies. Pregabalin is a water soluble drug, and it was encapsulated within anionic acrylic resin (Eudragit S 100) microspheres by water in oil in oil (w/o/o) double emulsion solvent diffusion method. Dichloromethane and corn oil were chosen primary and secondary oil phases, respectively. The presence of internal water phase was necessary to form stable emulsion droplets and it accelerated the hardening of microspheres. Tween 80 and Span 80 were used as surfactants to stabilize the water and corn oil phases, respectively. The optimum concentration of Tween 80 was 0.25% (v/v) and Span 80 was 0.02% (v/v). The volume of the continous phase was affected the size of the microspheres. As the volume of the continous phase increased, the size of microspheres decreased. All microsphere formulations were evaluated with the help of in vitro characterization parameters. Microsphere formulations (P1–P5) exhibited entrapment efficiency ranged between 57.00?±?0.72 and 69.70?±?0.49%; yield ranged between 80.95?±?1.21 and 93.05?±?1.42%; and mean particle size were between 136.09?±?2.57 and 279.09?±?1.97?µm. Pregabalin microspheres having better results among all formulations (Table 3) were chosen for further studies such as differential scanning calorimetry, Fourier transform infrared analysis and dissolution studies. In the last step, the best pregabalin microsphere formulation (P3) was chosen for in vivo animal studies. The pregabalin-loaded microspheres (P3) and conventional pregabalin capsules were applied orally in rats for three days, resulted in clinical improvement of cold allodynia, an indicator of peripheral neuropathy. This result when evaluated together with the serum pregabalin levels and in vitro release studies suggests that the pregabalin microspheres prepared with w/o/o double emulsion solvent diffusion method can be an alternative form for neuropathic pain therapy. Conclusively, a drug delivery system successfully developed that showed modified release up to 10?h and could be potentially useful to overcome the frequent dosing problems associated with pregabalin conventional dosage form.     

Immobilization of 2,2'-dipyridyl onto bentonite and its adsorption behavior of copper(II) ions

In this study, the immobilization of 2,2'-dipyridyl onto bentonite was firstly carried out and it was then used for the adsorption of copper(II) ions from aqueous solutions. The variation of the parameters of pH, contact time, initial copper(II) concentration and temperature were investigated in the adsorption experiments. The XRD, FTIR, elemental and thermal analyses were performed to observe the immobilization of 2,2'-dipyridyl onto natural bentonite. The adsorption data obtained were well described by the Langmuir adsorption isotherm model at all studied temperatures. The results indicated that the maximum adsorption capacity was 54.07 mg g(-1) from the Langmuir isotherm model at 50 degrees C. The thermodynamic parameters indicated that the adsorption process is spontaneous, endothermic and chemical in nature. The kinetic parameters of the adsorption were calculated from the experimental data. According to these parameters, the best-fit was obtained by the pseudo-second-order kinetic model. The results showed that 2,2'-dipyridyl-immobilized bentonite can be used as the effective adsorbent for the removal of heavy metal contaminants.     

Content-based copy detection by a subspace learning based video fingerprinting scheme

We propose a video copy detection scheme that employs a transform domain global video fingerprinting method. Video fingerprinting has been performed by the subspace learning based on nonnegative matrix factorization (NMF). It is shown that the binary video fingerprints extracted from the basis and gain matrices of the NMF representation enable us to efficiently represent the spatial and temporal content of a video segment respectively. An extensive performance evaluation has been carried out on the query and reference dataset of CBCD task of TRECVID 2011. Our results are compared with the average and the best performance reported for the task. Also NDCR and F1 rates are reported in comparison to the performance achieved via the global methods designed by the TRECVID 2011 participants. Results demonstrate that the proposed method achieves higher correct detection rates with good localization capability for the transformation of text/logo insertion, strong re-encoding, frame dropping, noise addition, gamma change or their mixtures; however there is still potential for improvement to detect copies with picture-in-picture transformations. It is also concluded that the introduced binary fingerprinting scheme is superior to the existing transform based methods in terms of the compactness.     

Thermoeconomic analysis of a trigeneration system

In this study a trigeneration plant which produces electrical power with a natural gas fed reciprocating engine and which yields absorption cooling by making use of exhaust gases of the system has been examined. In order to use both energy and financial resources most efficiently, the thermoeconomic analysis method which gives the most accurate and easy results have been applied on the system and its components. Using this method, the amount of available energy (exergy) gained, lost and destroyed have been calculated separately for each component of the system. Taking investment and operation costs of the system into account, recommendations have been given on the subject of which parameters have to be changed in what way so that the system works more efficiently.