The Effects of Doping on Crystal Structure, Magnetic and Microwave Properties of SrFe12−2x La x (Mn0.5Zr0.5) x O19 Nanoparticles

M-type hexagonal ferrite powders, SrFe_12?2x La _x (Mn_0.5Zr_0.5) _x O₁₉ (x=0.0, 0.2, 0.4, 0.6, 0.8), have been synthesized by the coprecipitation method. The X-ray diffraction, field emission scanning electron microscope, vibrating sample magnetometer and vector network analyzer all were used to characterize the structure of the samples, their magnetic and microwave properties. The value of the saturation magnetization increased up to x=0.2 and then slowly decreased with increasing doping. A decreasing trend was observed in the value of coercivity with increasing substitution degree, and its value reached a minimum of 2420 Oe for x=0.6 and then increased with further increasing x. The relative complex permittivity and permeability of the composite powders were investigated in the X-band frequency range (8.2–12.4 GHz).     

Assay of Total Mercury in Commercial Food Supplements of Marine Origin by Means of DLLME/ICP-AES

In this work, we have developed a sensitive and cost-effective preconcentration and quantification methodology for total mercury (Hg) at trace levels in food supplements of marine origin. Dispersive liquid–liquid microextraction was successfully employed for the preconcentration of mercury at trace levels prior to inductively coupled plasma atomic emission spectrometry. The mercury was extracted as mercury-1, 5-diphenyl-3-formazathiol complex, at pH 1.0 mediated by multidroplet formation of microextraction solvent assisted by disperser solvent. The lower limit of detection obtained under the optimal conditions was 0.24 μg L⁻¹. The calibration graphs were linear up to 500 μg L⁻¹. The precision of the method in terms of relative standard deviation was 4.8% for the concentration of 100 μg L⁻¹. In order to validate the proposed method, a certified reference material RTC-QCI-049 was analyzed with the proposed procedure. Moreover, potential interference by 20 species was also evaluated.     

Effect of pulsed plasma nitriding on mechanical and tribological performance of Ck45 steel

We studied the mechanical properties and wear performance of AISI 1045 (Ck45) carbon steel under the influence of pulsed plasma nitriding. The treatments were performed at temperatures of 500 and 550 degrees C in N2:H2 gas ratios of 1:3 and 3:1 and the working pressure of 10 mbar for 1 to 4 hours. Samples were examined by X-ray diffraction, optical, electron and atomic force microscopy, microhardness tests, roughness measurements and wear tests. Nitride layers were mainly composed of epsilon-(Fe2-3N) or gamma'-(Fe4N) depending on the gas ratio and/or temperature and time. When the nitriding time is increased, the composition of the compound layer varies from monophase gamma'-(Fe4N) to the two phase of epsilon-(Fe2-3N) and gamma'-(Fe4N). The highest thickness and hardness of the layers were obtained at 550 degrees C in the N2:H2 gas ratios of 3:1 for 4 h. The topographical evolution and surface roughness of the samples showed that all the roughness parameters increase with increasing the temperature. The friction coefficient of all samples was higher than that of untreated material. Wear performance of all nitrided samples was significantly better than that of untreated material.     

Effects of processing parameters on the convective heat transfer rate during ultrasound assisted low temperature immersion treatment of a stationary sphere

The effect of ultrasound irradiation, as a novel method, on the enhancement of convective heat transfer between a stationary copper sphere and cooling medium was experimentally studied at different Re and Pr numbers. The high thermal conductivity of copper allowed the application of lumped system analysis which led to more accurate results on convective heat transfer. The ultrasonic cooling system included a refrigerated circulator, a flow meter, an ultrasound generator (25 kHz) and an ultrasonic bath. The studied parameters were sphere diameter (0.01 or 0.02 m), flow rate (1.67 × 10⁻⁵, 2.5 × 10⁻⁵ m³ s⁻¹), fluid temperature (0, −5, −10, −15 and −20 °C) and ultrasound intensity (0, 190, 890 and 2800 W m⁻²), leading to Re range of 0.98–3.4 and Pr range of 68.3–188.9. The Nu number varied from 6.8 to 19 for non-irradiated samples. When ultrasound was irradiated (890 W m⁻²) the range of Nu number increased to 11–31. Enhancement factors from 30% to 119% were observed for the irradiated samples. The largest values of the enhancement factor were observed for low values of Re and Pr which demonstrated a better efficiency of ultrasound irradiation at higher viscosities and lower flow rates as a result of its mixing and cavitation effects. The results obtained in this study confirmed that ultrasound irradiation is able to enhance the convective heat transfer rate between the cooling medium and the submerged object. Irradiation effect was independent of sphere diameter and a linear relationship was detected between the ultrasound intensity and the Nu number. A correlation was suggested to predict the values of Nu at the presence or absence of ultrasound for different Re and Pr values with good agreement with the experimental data (R² = 0.90). The obtained data for copper can be generalized for food products with similar geometries and can be used for process design, as the convective heat transfer is mostly controlled by the cooling medium.     

Thermodynamic analysis of load-leveling hyper energy converting and utilization system

Load-leveling hyper energy converting and utilization system (LHECUS) is a hybrid cycle which utilizes ammonia–water mixture as the working fluid in a combined power generation and refrigeration cycle. The power generation cycle functions as a Kalina cycle and an absorption refrigeration cycle is combined with it as a bottoming cycle. LHECUS is designed to utilize the waste heat from industry to produce cooling and power simultaneously. The refrigeration effect can be either transported to end-use sectors by means of a solution transportation absorption chiller (STA) as solution concentration difference or stored for demand load leveling.     

FINITE ELEMENT ANALYSIS OF A VERTICAL RECTANGULAR PLATE COUPLED WITH AN UNBOUNDED FLUID DOMAIN ON ONE SIDE USING A TRUNCATED FAR BOUNDARY

The dynamic pressure distribution on a rectangular plate attached to a rigid wall and supporting an infinitely large extent of fluid subjected to a harmonic ground excitation is evaluated in the time domain. Governing equations for the fluid domain are set considering the compressibility of the fluid with negligibly small change in density and a linearized free surface. A far boundary condition for the three-dimensional fluid domain is developed so that the far boundary is truncated at a closer proximity to the structure. The coupled problem is solved independently for the structure and the fluid domain by transferring the acceleration of the plate to the fluid and pressure of the fluid to the plate in sequence. Helmholtz equation for the three-dimensional fluid domain and Mindlin's theory for the two-dimensional plate are used for the solution of the interacting domains. Finite element technique is adopted for the solution of this problem with pressure as nodal variable for the fluid domain and displacement for the plate. The time dependent equations are solved in each of the interacting domain using Newmark-b method. The effectiveness of the technique is demonstrated and the influences of surface wave, exciting frequency and flexibility of the plate on dynamic pressure are investigated.     

Study of phase behavior and Congo red dye partitioning in aqueous two-phase systems composed of hydrophilic alcohols (1-propanol/ 1-butanol) and sodium salts

ABSTRACT

The partitioning of the Congo red dye in ATPSs formed by alcohols (1-butanol, 1-propanol)/sodium salts was considered. Binodal and the LLE data were experimentally determined at 298.15 K. The salting-out abilities of the salts follow the order Na₃C₆H₅O₇ > NaH₂PO₄ > C₂H₃ O₂Na. The phase-forming abilities of the alcohols follow the order: 1-butanol > 1-propanol. The four-parameter equation was applied to correlate the binodal curves data. Therefore, The Bancroft and Othmer-Tobias equations were used to prove the reliability of the corresponding LLE data. ATPS composed of 6.5% of 1-butanol and 20% of Na₃C₆H₅O₇ had the highest values of extraction by the yield of 98.54%.     

Effects of hysteretic damping on the seismic performance of tuned mass dampers

A tuned mass damper (TMD) as a convenient passive device in average to tall buildings has limitations specifically against broad band seismic excitations. According to evidences from the literature, this drawback can be dominated by using nonlinear stiffness in TMDs; however, past studies did not explore this issue, and observations are not sufficient to reach a conclusion about seismic performance of nonlinear TMDs. This paper considers seismic performance of a nonlinear TMD developed by adding a martensitic shape memory alloy spring with significant stable features to conventional TMDs. To this end, single degree of freedom structures (from short to large periods) equipped with the nonlinear TMD are investigated subjected to set of ground motions, and through numerical analyses, effects of hysteretic damping and energy absorption capacity of the nonlinear TMD are examined. In addition, features of the proposed TMD configuration and effects of the excitation properties have been scrutinized through graphing frequency response curves by the arc length continuation method. Results indicate that the proposed configuration can make the nonlinear TMD robust against variations of the loading properties. Moreover, due to significant hysteretic damping of the shape memory alloy, spring seismic performance of the nonlinear TMD is better than conventional TMDs.     

Side-Chain Engineering for High-Performance Conjugated Polymer Batteries

Conjugated polymers are attractive for energy storage but typically require significant amounts of conductive additives to successfully operate with thin electrodes. Here, side-chain engineering is used to improve the electrochemical performance of conjugated polymer electrodes. Naphthalene dicarboximide (NDI)-based conjugated polymers with ion-conducting ethylene glycol (EG) side chains ( PNDI-T2EG ) and non-ion-conducting 2-octyldodecyl side chains ( PNDI-T2 ) are synthesized, tested, and compared. For thick (20  µ m, 1.28 mg cm⁻²) electrodes with a 60 wt% polymer, the PNDI-T2EG electrodes exhibit 66% of the theoretical capacity at an ultrafast charge–discharge rate of 100C (72 s per cycle), while the PNDI-T2 electrodes exhibit only 23% of the theoretical capacity. Electrochemical impedance spectroscopy measurements on thin (5 µm, 0.32 mg cm⁻²), high-polymer-content (80 wt%) electrodes reveal that PNDI-T2EG exhibits much higher lithium-ion diffusivity (D_Li+  = 7.01 × 10⁻¹² cm² s⁻¹) than PNDI-T2 (D_Li+  = 3.96 × 10⁻¹² cm² s⁻¹). PNDI-T2EG outperforms most previously reported materials in thick, high-polymer-content electrodes in terms of rate performance. The results demonstrate that the rate performance and capacity are significantly improved through the incorporation of EG side chains, and this work demonstrates a route for increasing the rate of ion transport in conjugated polymers and improving the performance and capacity of conjugated-polymer-based electrodes.