Reducing Occupational Noise Propagated from Centrifugal Fan through Dissipative Silencers: A Field Study

Acoustic performance of dissipative silencer was evaluated to determine the effectiveness of perforated duct porosity and absorbent material density in reducing occupational noise exposure propagated from centrifugal fan. Design charts were applied to predict noise reduction and length of a dissipative silencer. Dissipative silencers with various punched duct porosity (14%, 30% and 40%) and sound absorbent density (80 Kg/m³, 120 Kg/m³, and 140 Kg/m³) were designed and fabricated. According to ISO9612 and ISO11820, noise level was measured before and after installing all nine test silencers at fixed workstations around the discharge side of a centrifugal fan in a manufacturing plant. On average, the noise level at the discharge side of a fan without silencer was measured to be 93.6 dBA, whereas it was significantly mitigated by 67.4 dBA to 70.1 dBA after installing all silencers. Dynamic insertion loss for a dissipative silencer with 100 cm length was predicted to be 27.9 dB, which was in agreement with experimental ones. Although, there was no significant differences between insertion loss of silencers, the one with 30% porosity and 120 Kg/m³ rock wool density had the highest insertion loss of 26.2 dBA. Dissipative silencers noticeably reduced centrifugal fan noise exposures. Increasing sound absorbent density and duct porosity up to a certain limit could probably be effective in noise reduction of dissipative silencers.     

Synthesis,characterization and application of a novel nanorod-structured organic–inorganic hybrid material as an efficient catalyst for the preparation of aminouracil derivatives

Research on Chemical Intermediates - In this work, a novel nanorod-structured organic–inorganic hybrid material namely nanorod-[SiO2-Pr-Im-SO3H][TFA] (N-[SPIS][TFA]) has been synthesized, and...     

Special chaotic systems

The European Physical Journal Special Topics - This topical issue collects contributions related to recent achievements and scientific progress in special chaotic systems. The individual papers...     

Highly efficacious preparation of 3,3′-(arylmethylene)-bis(2-hydroxynaphthoquinone) derivatives catalyzed by a nanorod-structured organic–inorganic hybrid material

Research on Chemical Intermediates - A nanorod-structured organic–inorganic hybrid material namely nanorod-[SiO2–Pr–Im–SO3H][CF3CO2] (N-[SPIS][TFA]) has been applied as a...     

Green synthesis,characterization, and biological activities of saffron leaf extract-mediated zinc oxide nanoparticles: A sustainable approach to reuse an agricultural waste

To increase the profitability and sustainability of agricultural waste, a facile green approach was established to synthesize zinc oxide nanoparticles (ZnO NPs) using saffron leaf extract as a reducing and stabilizing agent. Structural characteristics of NPs were investigated by X-ray diffraction (XRD), Fourier-transform infrared (FTIR), field emission scanning electron microscopy (FESEM), and UV–Visible (UV–Vis) spectroscopy. Characterization results revealed that ZnO NPs is highly crystalline with a hexagonal wurtzite structure and spherical particles with diameter less than 50 nm, as confirmed by XRD and FESEM techniques. UV–Vis absorption spectra depicted an absorption peak at 370 nm, which confirms the formation of ZnO NPs. FTIR spectral analysis confirmed the presence of functional groups and metal oxygen groups. The biological activities of ZnO NPs were also investigated. The antibacterial effect of ZnO NPs was investigated against selected food pathogens (Salmonella Typhimurium, Listeria monocytogenes, and Enterococcus faecalis). The study results prove that the green synthesized ZnO NPs show enhanced antibacterial activity against S. Typhimurium when compared with other strains. A dose-dependent free radical scavenging activity was observed for ZnO NPs in both 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) and fluorescence recovery after photobleaching (FRAP) assays. The ZnO NPs were evaluated for their photocatalytic activity during the degradation of methylene blue (MB) dye in aqueous solutions. The maximum removal of MB achieved was 64% with an initial ZnO NP concentration of 12 mg/mL under UV light. The present study revealed that the agricultural waste (saffron leaf) provides a simple and eco-friendly option to sustainably synthesize ZnO NPs for use as a photocatalyst. In addition, this is the first report on saffron leaf-mediated synthesis of ZnO NPs.     

Dynamical behavior and network analysis of an extended Hindmarsh–Rose neuron model

Nonlinear Dynamics - In this paper, the extended Hindmarsh–Rose neuron model, which considers the slow intracellular exchange of calcium ions between its store and the cytoplasm, is studied....     

Syntheses of Isoquinoline and Substituted Quinolines in Charged Microdroplets

A Pomeranz–Fritsch synthesis of isoquinoline and Friedländer and Combes syntheses of substituted quinolines were conducted in charged microdroplets produced by an electrospray process at ambient temperature and atmospheric pressure. In the bulk phase, all of these reactions are known to take a long time ranging from several minutes to a few days and to require very high acid concentrations. In sharp contrast, the present report provides clear evidence that all of these reactions occur on the millisecond timescale in the charged microdroplets without the addition of any external acid. Decreasing the droplet size and increasing the charge of the droplet both strongly contribute to reaction rate acceleration, suggesting that the reaction occurs in a confined environment on the charged surface of the droplet.     

Preparation and Characterization of Functionalized Polyaniline-Based Nanocomposite as an Antibacterial Agent

Polyaniline-co-phenylenediamine (PAn/PDA) nanocomposite has been prepared in the aqueous medium using sodium dodecyl benzene sulfonate (DBSNa) and hydroxypropylcellulose (HPC) as a surfactant. The tests used in this research to characterize the products were SEM, TEM, FTIR, UV–Visible and TGA for morphology, particle size, chemical structure and stability. The results confirm that the spherical nanocomposites (40–90 nm) were formed with high thermal stability. It is shown in the results that the physicochemical properties of poly(alkyl substituted anilines) are depended on the substituent groups that are bonded to N-position. The prepared nanocomposites were then tested for the antibacterial properties against three pathogenic strains. The antibacterial properties of nanocomposites were investigated by disk diffusion, minimum inhibitory concentration (MIC), minimum bactericidal concentrations (MBC), and bactericidal kinetic methods. The disk diffusion result indicated that the diameter of the inhibition zones of PAn/PDA–HPC nanocomposite was 9, 11, and 10 mm against E. coli, P. aeruginosa, and S. aureus respectively. It was found that the value of MIC of PAn/PDA–HPC nanocomposite against E. coli, P. aeruginosa and S. aureus were 2.5, 1.25 and 2.5 mg/mL respectively. The evaluation results revealed the PAn/PDA–HPC nanocomposite exhibited excellent inhibitory activity against both gram-negative and gram-positive bacteria.