Performance assessment of an electrochemical hydrogen production and storage system for solar hydrogen refueling station

This paper investigates the performance of a hydrogen refueling system that consists of a polymer electrolyte membrane electrolyzer integrated with photovoltaic arrays, and an electrochemical compressor to increase the hydrogen pressure. The energetic and exergetic performance of the hydrogen refueling station is analyzed at different working conditions. The exergy cost of hydrogen production is studied in three different case scenarios; that consist of i) off-grid station with the photovoltaic system and a battery bank to supply the required electric power, ii) on-grid station but the required power is supplied by the electric grid only when solar energy is not available and iii) on-grid station without energy storage. The efficiency of the station significantly increases when the electric grid empowers the system. The maximum energy and exergy efficiencies of the photovoltaic system at solar irradiation of 850 W m-2 are 13.57% and 14.51%, respectively. The exergy cost of hydrogen production in the on-grid station with energy storage is almost 30% higher than the off-grid station. Moreover, the exergy cost of hydrogen in the on-grid station without energy storage is almost 4 times higher than the off-grid station and the energy and exergy efficiencies are considerably higher.     

Burst‐aware virtual machine migration for improving performance in the cloud

Burst is a common pattern in the user's requirements, which suddenly increases the workload of virtual machines (VMs) and reduces the performance and energy efficiency of cloud computing systems (CCS). Virtualization technology with the ability to migrate VMs attempts to solve this problem. By migration, VMs can be dynamically consolidated to the users' requests. Burst temporarily increases the workload. Ignoring this issue will lead to incorrect decisions regarding the migration of VMs. It increases the number of migrations and Service Level Agreement Violations (SLAVs) due to overload. This may cause waste of resources, increase in energy consumption, and misplaced VMs. Therefore, a burst‐aware method for these issues is proposed in this paper. The method consists of two algorithms: one for determining the migration time and the other for the placement of VMs. We use the PlanetLab real dataset and CloudSim simulator to evaluate the performance of the proposed method. The results confirm the advantages of the method regarding performance compared to benchmark methods.     

Microstructure and Multiwall Carbon Nanotube Partitioning in Polycarbonate/Acrylonitrile-Butadiene-Styrene/Multiwall Carbon Nanotube Nanocomposites

The multiwall carbon nanotube (MWNT) partitioning and its impact on morphology and electrical properties of Polycarbonate (PC)/Acrylonitrile-Butadiene-Styrene (ABS)/MWNT nanocomposites were studied. The rheological and TEM results indicated that the MWNT partitioning and state of dispersion of MWNT were determined by the affinity between MWNT and the blend components and MWNT concentration. In the PC/ABS (70/30: w/w)/2 wt.% MWNT sample the MWNTs were preferentially located in the ABS droplets and the interface due to the greater affinity between MWNT and ABS compared with PC. In the PC/ABS (30/70: w/w)/MWNT samples, however the MWNTs were mostly located in the ABS matrix.     

Synthesis,recognition and evaluation of molecularly imprinted polymer nanoparticle using miniemulsion polymerization for controlled release and analysis of risperidone in human plasma samples

We prepared high selective imprinted nanoparticle polymers by a miniemulsion polymerization technique, using risperidone as the template, MAA as the functional monomers, and TRIM as the cross-linker in acetonitrile as solvent. The morphology of the nanoparticles determined by scanning electron microscopy (SEM) images and drug release, binding properties and dynamic light scattering (DLS) of molecularly imprinted polymers (MIPs) were studied. Controlled release of risperidone from nanoparticles was investigated through in 1% wt sodium dodecyl sulfate aqueous solution and by measuring the absorbance by HPLC-UV. The results showed that the imprinted nanoparticles exhibited a higher binding level and slower release rate than non-imprinted nanoparticles, which contributed to interaction of risperidone with imprinted cavities within nanoparticles. Furthermore, the results from HPLC showed good precision (5% for 50.0 μg L^?1) and recoveries (between 86–91) using MIP from human plasma samples.     

Fabrication of platinum coated nanoporous gold film electrode: A nanostructured ultra low-platinum loading electrocatalyst for hydrogen evolution reaction

The electrolytic hydrogen evolution reaction (HER) on platinum coated nanoporous gold film (PtNPGF) electrode is demonstrated. The deposition of platinum occurred as a spontaneous redox process in which a copper layer, obtained by underpotential deposition, was oxidized by platinum ions, which were reduced and simultaneously deposited. The present method could provide a very low Pt-loading electrode and the results demonstrated that ultra thin Pt coating effected efficiently and behaved as the nanostructured Pt for electrocatalytic hydrogen evolution reaction. The loading of Pt was calculated as 4.2 × 10⁻³ μg cm⁻² for PtNPGF electrode. The current density at −0.4 V and −0.8 V vs. Ag/AgCl was as high as 0.66 A μg⁻¹ Pt and 3 A μg⁻¹ Pt, respectively and the j₀ was evaluated as 0.03 mA cm⁻² or 8 mA μg⁻¹ Pt. The results indicated that increasing electrode area had no catalytic effect, but the nanostructure nature of as-fabricated electrode and submonolayer deposition of copper resulted in electrocatalytic activity for PtNPGF electrode.     

Security enhancements against UMTS–GSM interworking attacks

In this paper we first present three new attacks on Universal Mobile Telecommunication System (UMTS) in access domain. We exploit the interoperation of UMTS network with its predecessor, Global System for Mobile communications (GSMs). Two attacks result in the interception of the entire traffic of the victim UMTS subscriber in the GSM access area of UMTS network. These attacks are applicable, regardless of the strength of the selected GSM encryption algorithm. The third attack is an impersonation attack and allows the attacker to impersonate a genuine UMTS subscriber to a UMTS network and fool the network to provide services at the expense of the victim subscriber. Then, we propose some countermeasures to strengthen the UMTS network against the mentioned attacks with emphasis on the practicality in present networks. The proposed solutions require limited change of the network elements or protocols, insignificant additional computational load on the network elements and negligible additional bandwidth consumption on the network links.     

An electrochemical sensor based on V2O5 nanoparticles for the detection of ciprofloxacin

This research constructed and utilized a screen-printed electrode (SPE) modified with V₂O₅ nanoparticles (NPs) (V₂O₅/SPE) employed in order to sensitively and selectively quantify ciprofloxacin with exceptional accuracy in the phosphate buffer solution (PBS) with the use of differential pulse voltammetry (DPV). Moreover, electrochemical properties of this new V₂O₅/SPE sensor have been examined using diverse characterization procedures. Very good V₂O₅/SPE electrochemical features offered sensitive ciprofloxacin voltammetric determination with the reduced limit of detection (LOD?=?0.01 µM) toward electrocatalytic oxidation of ciprofloxacin in comparison with the bare SPE. Finally, this new disposable sensor exhibited higher sensitivity and thus has been efficiently utilized to determine ciprofloxacin in the real samples.

     

Evaluation of ‘green’ synthesis and biological activity of gold nanoparticles using Tragopogon dubius leaf extract as an antibacterial agent

Currently, the use of ‘green’ synthesised nanoparticles with environmentally friendly properties is considered a novel therapeutic approach in medicine. Here, the authors evaluated gold nanoparticles (AuNPs) conjugated with Tragopogon dubius leaf extract and their antibacterial activity in vitro and in vivo. Colour changes from yellow to dark brown and a peak at 560 nm on ultraviolet–visible spectroscopy confirmed the formation of nanoparticles. Additionally, transmission electron microscopy, X‐ray diffraction, and Fourier transform infrared spectroscopy analyses were performed to determine particle sizes and functional groups involved in gold reduction. Moreover, using standard micro‐dilution and disc‐diffusion assays against Klebsiella pneumoniae, Bacillus cereus, Escherichia coli, and Staphylococcus aureus, the antimicrobial properties of synthesised AuNPs were investigated. To confirm antibacterial activity, synthesised AuNPs were applied in a rat model on burn wounds infected with S. aureus, and the nanoparticles were as effective as tetracycline in bacterial reduction and wound healing. In conclusion, the synthesis of AuNPs with aqueous T. dubius extract was rapid, simple, and inexpensive, and the synthesised nanoparticles had significant antibacterial activity in vitro and in vivo.Inspec keywords: transmission electron microscopy, wounds, nanoparticles, ultraviolet spectra, reduction (chemical), particle size, nanofabrication, gold, X‐ray diffraction, antibacterial activity, microorganisms, visible spectra, nanomedicine, biomedical materials, Fourier transform infrared spectraOther keywords: biological activity, gold nanoparticles, antibacterial agent, therapeutic approach, colour changes, ultraviolet–visible spectroscopy, transmission electron microscopy, gold reduction, antimicrobial properties, Fourier transform infrared spectroscopy analyses, disc‐diffusion assay, green synthesis, Tragopogon dubius leaf, in vitro antibacterial activity, in vivo antibacterial activity, X‐ray diffraction, particle sizes, functional groups, standard microdilution assay, burn wounds, S. aureus, tetracycline, bacterial reduction, wound healing, wavelength 560.0 nm