Characterization of the effective atomic number for first row transition elements by the ratio of coherent to compton scattering intensities obtained by wavelength dispersive X-ray fluorescence

The effective atomic numbers of compounds of the first row transition elements were determined experimentally by a scattering method using wavelength dispersive X-ray fluorescence spectrometer. A calibration curve was created by using the intensity ratios of coherent to Compton scattered peaks of pure elements from atomic number 13–48. This relationship was employed to determine the effective atomic numbers of the compounds. The effective atomic numbers were also calculated by using empirical formulas from the literature. Mass attenuation coefficients were calculated using software. The experimentally measured values of the effective atomic numbers with the calculated values by empirical formulas were comparable.     

SAR distribution in human beings when using body-worn RF transmitters

This study analyzes the exposure of the human torso to electromagnetic fields caused by wireless body-mounted or handheld devices. Because of the frequency and distance ranges from 30-5800 MHz and 10 to 200 mm, respectively, both near-field and far-field effects are considered. A generic body model and simulations of anatomical models are used to evaluate the worst case tissue composition with respect to the absorption of electromagnetic energy. Both standing wave effects and enhanced coupling of reactive near-field components can lead to a specific absorption rate (SAR) increase in comparison to homogeneous tissue. In addition, the exposure and temperature increase of different inner organs is assessed. With respect to compliance testing, the observed SAR enhancement may require the introduction of a multiplication factor for the spatial peak SAR measured in the liquid-filled phantom in order to obtain a conservative exposure assessment. The observed tissue heating at the body surface under adiabatic conditions can be significant, whereas the temperature increase in the inner organs turned out to be negligible for the cases investigated.     

Synthesis and thermal properties of poly(styrene-co-ally alcohol)-graft-stearic acid copolymers as novel solid–solid PCMs for thermal energy storage

A series of poly(styrene-co-allyalcohol)-graft-stearic acid copolymers were synthesized as novel polymeric solid–solid phase change materials (SSPCMs). The graft copolymerization reactions between poly(styrene-co-allyalcohol) and stearoyl chloride were verified by Fourier transform infrared (FT-IR) and Proton Nuclear Magnetic Resonance (¹H NMR) spectroscopy techniques. The crystal morphology of the SSPCMs was investigated using polarized optical microscopy (POM) technique. Thermal energy storage properties of the synthesized SSPCMs were measured using differential scanning calorimetry (DSC) analysis. The POM results showed that the crystalline phase of the copolymers transformed to amorphous phase above their phase transition temperatures. Thermal energy storage properties of the synthesized SSPCMs were investigated by differential scanning calorimetry (DSC) and found that they had typical solid–solid phase transition temperatures in the range of 27–30 °C and high latent heat enthalpy between 34 and 74 J/g. Especially, the copolymer with the mole ratio of 1/1 (poly(styrene-co-allyalcohol)/stearoyl chloride) is the most attractive one due to the highest latent heat storage capacity among them. The results of DSC and FT-IR analysis indicated that the synthesized SSPCMs had good thermal reliability and chemical stability after 5000 thermal cycles. Thermogravimetric (TG) analysis results suggested that the synthesized SSPCMs had high thermal resistance. In addition, thermal conductivity measurements signified that the synthesized PCMs had higher thermal conductivity compared to that of poly(styrene-co-allyalcohol). The synthesized copolymers as novel SSPCMs have considerable potential for thermal energy storage applications such as solar space heating and cooling in buildings and greenhouses.     

Energy and exergy utilization, and carbon dioxide emission in vegetable oil production

Energy and exergy utilization and carbon dioxide emission during production of soybean, sunflower, and olive oils are assessed. In all cases, agriculture is the most energy and exergy intensive process and emits most of the carbon dioxide, and diesel is the dominant energy and exergy source. The cumulative degree of perfection (CDP) for soybean and olive oil is 0.92 and 0.98, respectively, whereas the CDP for the sunflower oil is 2.36. Decreasing diesel consumption with good agricultural practices and substituting with biodiesel from renewable resources would decrease the cumulative exergy consumption, as a result, CDP of olive and soybean oil rises to 1.6 and sunflower oil to 2.9.Major contribution to the carbon dioxide emission is due to the excessive use of fertilizers. The most energy intensive process is olive oil production. However, since the fertilizer consumption here is limited, total carbon dioxide emission is less than those of the other two processes are. On the other hand, excessive fertilizer consumption during the soybean agriculture results in a rather large CO₂ emission.     

Soil-Steel Interaction of Long-Span Box Culverts—Performance during Backfilling

The paper presents the performance of four long-span deep-corrugated steel box culverts with spans of 8- and 14-m during backfilling, as well as comparisons with finite-element modeling and design codes. Two of the culverts were stiffened at the crown arch. The test results show that the stiffening applied on the culverts is quite effective. The crown rises of the respective stiffened culverts were found to be half those of the not-stiffened culverts. The influence of the structure geometry on the soil-passive earth pressure was confirmed, as well as the sensitivity of box culverts to soil loads with increasing spans. The results showed that the influence of the size and shape of the box culverts on the amount of thrusts must be better implemented in the design method. The finite-element analysis results were conservative when live loading was concerned but the crown displacements and thrust during backfilling were underestimated.     

A new catalyst of AlCu@ZnO for hydrogen evolution reaction

Thin films of undoped ZnO, Al-doped ZnO, Cu-doped ZnO, and AlCu@ZnO deposited on indium tin oxide were performed by the sol-gel spin coating method. The prepared ZnO thin films were investigated for their structural and electrical properties after annealing at 500 °C for 1 h. ZnO thin films were characterized by electrochemical impedance spectroscopy, linear sweep voltammetry, scanning electron microscopy, Fourier transform infrared spectroscopy and Mott Schottky. According to the results obtained from the Nyquist diagrams of the ZnO thin films, the resistance value was found to decrease with binary doping and the resistance value was found to be lowest in AlCu@ZnO doped thin film containing 0.01 M Al and 0.1 M Cu. As ZnO thin films go to cathodic potentials, it is seen that the cathodic current value of ZnO with undoped is the lowest. It has been found that only Al and Cu doping showed less cathodic current than double doping.     

Thickness-Dependent Permanent Magnet Properties of Zr $$_{2}$$ Co $$_{11}$$ Thin Films Grown on Si with Pt Underlayer

Metallurgical and Materials Transactions A - Zr-Co is one of the essential magnetic materials due to its interesting magnetic and structural properties. In this work, we studied the magnetic and...     

Measurements of Thermal Conductivity Variations with Temperature for the Organic Analog of the Nonmetal–Nonmetal System: Urea–4-Bromo-2-Nitroaniline

Thermal conductivity variations with temperature for solid phases in the Urea (U)–[X] mol pct 4-bromo-2-nitroaniline (BNA) system (X = 0, 2, 45, 89.9, and 100) were measured using the radial heat flow method. From graphs of thermal conductivity variations with temperature, the thermal conductivities of the solid phases at their melting temperature and temperature coefficients for the U–[X] mol pct BNA system (X  =  0, 2, 45, 89.9, and 100) were found to be 0.26, 0.55, 0.46, 0.38, and 0.23 W/Km and 0.007781, 0.005552, 0.002058, 0.002188, and 0.002811 K^?1, respectively. The ratios of thermal conductivity of the liquid phase to thermal conductivity of the solid phase in the U–[X] mol pct BNA system (X  =  0, 2, 45, 89.9, and 100) were also measured to be 0.30, 0.44, 0.46, 0.49, and 0.51, respectively, with a Bridgman-type directional solidification apparatus at their melting temperature.     

Ultrasonic-assisted pH Swing Method for the Synthesis of Highly Efficient TiO2 Nano-size Photocatalysts

A new route for the preparation of nanocrystalline TiO₂ particles based on the pH swing method assisted by ultrasonic irradiation in the presence of a surfactant (Pluronic P-123) has been successfully achieved. The prepared TiO₂ catalysts were calcined from 400 to 800 °C and characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transformed infra-red spectroscopy (FTIR), gas adsorption measurements (BET) and thermogravimetirc measurements (TAG/DTA) analyses. Characterization results revealed that the enhancement in the particle size of TiO₂ by the pH swing method could be controlled by combining the pH swing with ultrasonic irradiation. Increasing the calcination temperatures led to an increase in both the particle and pore size, whereas the surface area and pore volume gradually decreased. A synergistic effect was observed in the combined process of pH swing with ultrasonication, yielding small TiO₂ particles as well as high surface area, pore volume, pore diameter, and crystalline anatase phase. The activity of the catalysts was investigated for the oxidation of 4-chlorophenol (4-CP). TiO₂ prepared with 15 times pH swing and calcined at 700 °C was found to show the highest rate for the oxidative degradation of 4-CP when compared to the TiO₂ sample prepared with just 1 time pH swing and to the commercial P-25 TiO₂ Degussa photocatalyst. Thus, a novel approach in controlling the various physico-chemical parameters of TiO₂ nanoparticles was developed.