Preparation of a LaNiO3/γ‐Al2O3 Catalyst and its Performance in Dry Reforming of Methane

LaNiO₃/γ‐Al₂O₃ catalysts containing 10, 15, 20, and 25 wt % Ni were prepared by a combination of sol gel with propionic acid as solvent and an impregnation method (LNA‐acid) as well as with ethanol as solvent and addition of acetic acid (LNA‐eth). Catalytic activities towards CO₂ reforming of CH₄ were tested in a fixed‐bed reactor at 700 °C, 750 °C, and 800 °C. LNA‐eth with 20 wt % Ni exhibited the best activities in dry reforming of methane and a good activity and stability, when it was tested at 800 °C during 75 h time‐on‐stream.     

Review of Heat Exchangers Enabled by Polymer and Polymer Composite Additive Manufacturing

ABSTRACT

This paper presents an overview of the most common polymer additive manufacturing processes, including vat photopolymerization, material jetting, sheet lamination, powder bed fusion, and fused filament fabrication. Next, the general strengths and challenges of the common methods are discussed and are followed by discussions on efforts to increase thermal performance of polymers used with the various manufacturing methods. Finally, heat exchangers enabled by polymer additive manufacturing are reviewed to show that novel designs in metal, ceramic, and polymer heat exchangers can be made possible by the unique properties of polymers and the advantages offered by additive manufacturing. By reporting what has been proven possible—and the associated challenges—we hope to stimulate the community and further development in a burgeoning field enabled by polymer additive manufacturing.     

Development of tri-layer breathable fluid barrier nonwoven fabrics for surgical gown applications

In this study, tri-layer fabrics for surgical gown applications were developed using polypropylene spunbond, polypropylene melt-blown and polyester/rayon spunlace (hydro-entangled) nonwoven layers with the aid of a fusing machine and polypropylene powder as the bonding agent. Weight, thickness, bending rigidity, grab tensile properties, bursting strength, air permeability, water vapour transmission rate, hydrostatic pressure, water resistance (impact penetration test), and synthetic blood repellency of the fabrics (unfinished and finished with water repellent polymethylhydrosiloxanes solution) were measured and the data was statistically analyzed. The results showed that the finished fabric composed of the spunbond outer layer, melt-blown middle layer, and spunlace inner layer, meets the blood repellency requirements of level 4 protection according to the barrier protection classification of Association for the Advancement of Medical Instrumentation (AAMI). The other samples, i.e. untreated type of abovementioned sample and treated and untreated tri-layer of spunbond, melt-blown, spunbond samples offer level 2 protection according to AAMI classification.     

The effect of nisin and garlic (Allium sativum L.) essential oil separately and in combination on the growth of Listeria monocytogenes

In the present study, the anti-listerial activity of the nisin and garlic (Allium sativum L.) essential oils (GO) alone and in combination was investigated at different temperatures (20 and 30 °C), pH (6.8, 5.6 and 4.8) and NaCl concentrations (0, 0.5, 2.5 and 4.5 g/100 mL). Minimum inhibitory concentrations (MICs) against Listeria monocytogenes were assessed for the nisin and essential oil. Furthermore, for combinations of the antimicrobials, the Differences in Population (DP) method were used to determine their effect. Both essential oil and nisin possessed considerable antimicrobial effects on the microorganism. The MICs for nisin and GO were 12.5 IU/mL and 100 μg/mL, respectively. Regardless of NaCl concentration and temperature, the anti-listerial activity of both GO and nisin was strongly influenced by pH. Moreover, at the same temperature, and regardless of pH value, the growth of the organism was also affected by increasing NaCl concentration. In combination, the DP was related strongly to the agent’s concentration and media pH. Meanwhile, among all combined systems, the effect of the combination (EC) of nisin with GO at 30 °C, pH 5.6 and 0 g/100 mL NaCl, showed significant anti-listerial activity (P ≤ 0.05).     

Catalytic dehydration of methanol to dimethyl ether over mordenite catalysts

The conversion of methanol to dimethyl ether was carried out over various commercial mordenite and ion-exchanged catalysts to evaluate the catalytic performance of mordenite catalysts with different pore structures and acidities. These catalysts were compared for their catalytic properties in a fixed-bed reactor at 1 atm, 573 K and LHSV of 2.84 h^− 1. The catalysts were characterized by BET, ICP, NH₃-TPD, XRD, TGA and FT-IR techniques. The ion-exchanged mordenite showed higher activity, selectivity and good stability in dehydration of methanol due to the addition of medium acid sites. Also, the effect of water on catalyst deactivation was investigated over two selected catalysts in order to develop a suitable catalyst for synthesis of dimethyl ether. It was found that the H-mordenite catalyst supplied by Süd-chemie Co., (MCDH-1) was more active and less deactivated than another one in a feed containing 20 wt.% water.     

Hydrodesulfurization‐Supported Catalysts: Effect of the Preparation Method

Hydrodesulfurization (HDS) of dibenzothiophene in a batch reactor was performed at 5.5 MPa and 320 °C on CoMoS/Al₂O₃‐TiO₂ using trans‐1,2‐cyclohexanediamine‐N,N,N′,N′‐tetraacetic acid (CYDTA) as a complexing agent for the preparation method. The effects of titania, concentration of CYDTA, and preparation procedure were investigated by using X‐ray diffraction, BET, Fourier transform infrared spectroscopy, and temperature‐programmed desorption of ammonia experiments. The catalyst prepared by impregnation with γ‐alumina and titanium isopropoxide as raw materials and a CYDTA/Co mole ratio of 1.2 provided an HDS activity (on a pseudo‐first‐order kinetic constant basis) value ～3.8 times higher compared to that of a CoMo/Al₂O₃ catalyst.     

Evaluation of the Heliosat-II method using daily irradiation data for four stations in Iran

Efficient use of solar radiation needs detailed knowledge of its spatial and temporal variations. Such information can be achieved using interpolating measured irradiance by ground stations. But more reliable results can be obtained by processing geostationary satellite images. Heliosat is an algorithm which has been developed to estimate global horizontal irradiance at ground level from images taken in the visible band by the Meteosat satellites.The aim of this study was to evaluate the Heliosat-II model by using daily global solar irradiation data measured at the four radiometric stations in Iran as well as Meteosat-5 images which are recorded by a spacecraft over 63°E. Mean RMSD% and MBD% for all stations were 11.7% and 1.9%, respectively. The mean values of intercept, slope and correlation coefficient were 0.82 (kWh m⁻²), 1.05 and 0.93, respectively. Seasonally, the maximum RMSD occurs in autumn (22.1%) and the minimum is experienced in spring (8.4%). This accuracy is a great achievement for producing a high quality solar radiation atlas in a country such as Iran with very sparse radiometric network and frequently unreliable measured irradiation data.     

Analytical solution of non-Fourier and Fourier bioheat transfer analysis during laser irradiation of skin tissue

The thermal wave and the Pennes bioheat transfer models are solved analytically by employing the Laplace transform method for small and large values of reflection power (albedo) during laser irradiation. Most of the previous studies have been based on the infinite heat diffusion velocity, but non-Fourier thermal behavior has been observed experimentally in biological tissue. At low initial albedo values, the temperature in the skin depth that directly results from conduction heat transfer process is caused by the lengthy thermal relaxation time in skin tissue. This condition generates a big difference between the thermal wave and Pennes results at the beginning of the heating process. This difference increases under short-time heating condition and high heat flux. However, with high initial albedo, the temperature distribution in the skin depth becomes negligible because of the skin absorption of laser beams. The non-Fourier effect should be considered during laser heating with low albedo, because errors in the predicted temperature values may occur.

     

Suppression of nonlinear regenerative chatter in milling process via robust optimal control

During the milling process, self-excited vibration or chatter adversely affects tool life, surface quality and productivity rate. In this paper, nonlinear cutting forces of milling process are considered as a function of chip thickness with a complete third order polynomial (instead of the common linear dependency). An optimal control strategy is developed for chatter suppression of the system described through nonlinear delay differential equations. Counterbalance forces exerted by actuators in x and y directions are the control inputs. For optimal control problem, an appropriate performance index is defined such that the regenerative chatter is suppressed while control efforts are minimized. Optimal control law is determined based on variation of extremals algorithm. Results show that under unstable machining conditions, regenerative chatter is suppressed effectively after applying the optimal control strategy. In addition, optimal controller guarantees robust performance of the process in the presence of model parametric uncertainties.     

Solvatochromism, tautomerism and dichroism of some azoquinoline dyes in liquids and liquid crystals

Absorption and emission spectra of three hetarylazoquinoline compounds with different substituents were examined in liquids and liquid crystalline solvents for the first time. The spectral features of the hetarylazoquinoline dyes were explained according to azo/hydrazone tautomerism in conjunction with the solvatochromic characteristic of the preferred tautomer. The nature and extent of solute-solvent interactions were described using Kamlet-Taft and Katritzky multiparameter polarity scales. It was observed that solvatochromic azo/hydrazone tautomerism depend on multiple solute-solvent interactions, in particular on specific interactions and the solvent ability to transport the hydrogen atom through the media. In addition, it was concluded that anisotropic hosts prevent shift of the tautomeric equilibrium toward the hydrazone form.