Multi-vane expander performance: Breathing characteristics

The throttling of the working fluid flow at the inlet and exhaust port openings of multi-vane expanders leads to power losses. Therefore, a mathematical model has been developed to analyse their breathing characteristics. In particular two existing designs of multi-vane expanders, using refrigerant 113 as the working fluid, were considered. The results obtained indicate that multi-vane expanders exhibit easy-breathing behaviours. Improved breathing characteristics can be achieved by the wise selection of operating conditions for any existing design or by optimising the design parameters for a specific application.     

Control the corrosion of mild steel using synthesized polymers based on polyacrylamide

In this work polyacrylamide (PACM) was prepared by radical polymerization technique using ammonium persulfate (APS) as initiator under nitrogen atmosphere. The viscosity average molecular weight of the prepared PACM was found to be 177858. The free amino groups of PACM, poly(2-methoxyaniline) was grafted by the oxidation of 2-methoxyaniline using APS in acidic medium under nitrogen atmosphere. The grafting percent is found to be 96%. The morphology of the obtained PACM and PACM-g-P2-MeOANI was studied by X-ray diffraction and scanning electron microscope. The grafting process enhances the morphology of both PACM and poly(2-methoxyaniline). The inhibiting effect of the three polymers on the mild steel corrosion in the 1.0?M HCl as aggressive environments have been measured gravimetrically at three different temperatures 25, 40 and 55?°C and electrically at 25?°C. The inhibition efficiencies of the three tested polymers were found to increase with temperature. The poly(2-methoxyaniline) is the most effective one as a corrosion inhibitor at all tested temperatures. The adsorption behavior of the polymers was found to follow Villamil isotherm and the values of the change in free energy refer to a mixed chemical and physical adsorption on the steel surface. Tafel curves indicate that the tested polymers act as mixed anodic and cathodic inhibitor. The double layer capacitance was found to decrease with increasing the inhibitor concentration.     

BER improvement of PRCPM in mobile radio channels withdiscriminator detection using decision feedback equalization

The authors investigate the bit error rate (BER) improvement of partial-response continuous-phase modulation (PRCPM) signals in mobile radio channels, when decision feedback equalization (DFE) to cancel the effect of intersymbol interference (ISI) of one adjacent bit is added to the limiter discriminator. A closed-form expression for the average probability of error as a function of the Doppler shift is derived for discriminator detection with decision feedback. Numerical results are presented to compare the BER performance of discriminator detection with and without feedback equalization     

Tungsten Lamps as an Affordable Light Source for Testing of Photovoltaic Cells

An improved Tungsten light source system for photovoltaic cell testing made from low-cost, commercially available materials is presented as an alternative to standard expensive testing equipment. In this work, spectral correction of the Tungsten light source is achieved by increasing the color temperature to ??5200 K using inexpensive commercially available filters. Spectral measurements of the enhanced light source reveal that a better spectrum match towards the solar spectrum is achieved than what has been previously demonstrated. Specifically, the improved solar spectrum match is achieved by substantial filtering of the infrared range. The proposed setup is used to evaluate the performance of both silicon and organic based photovoltaic cells.     

Handover management based on user’s mobility specification

Considering the highly dynamic nature of wireless networks, the major challenge in this environment is the provision of QoS guarantees that different applications demand. Recent research is interested in advance resource reservation to provide the necessary QoS to the mobile terminals. Another way to obtain a better use of the resources in this environment is to determine the future locations of the mobile terminal. This paper describes a user’s mobility profile management based approach for advance resource reservation in wireless networks; it is based on theNsis signaling. This reservation is based on an objectMspec (Mobility Specification) which determines the future location of the mobile terminal. The mspec object is a part of a user’s mobility profile; this last is determined by the mobile terminal. Another applicability of our user’s mobility profile is in the 4G wireless systems, in this case; the mobile terminal supports various access technologies and the user’s mobility profile is used to adapt the vertical and the diagonal handover to the user’s needs.     

Microporous Carbon and Carbon/Metal Composite Materials Derived from Bio-Benzoxazine-Linked Precursor for CO2 Capture and Energy Storage Applications

There is currently a pursuit of synthetic approaches for designing porous carbon materials with selective CO₂ capture and/or excellent energy storage performance that significantly impacts the environment and the sustainable development of circular economy. In this study we prepared a new bio-based benzoxazine (AP-BZ) in high yield through Mannich condensation of apigenin, a naturally occurring phenol, with 4-bromoaniline and paraformaldehyde. We then prepared a PA-BZ porous organic polymer (POP) through Sonogashira coupling of AP-BZ with 1,3,6,8-tetraethynylpyrene (P-T) in the presence of Pd(PPh₃)₄. In situ Fourier transform infrared spectroscopy and differential scanning calorimetry revealed details of the thermal polymerization of the oxazine rings in the AP-BZ monomer and in the PA-BZ POP. Next, we prepared a microporous carbon/metal composite (PCMC) in three steps: Sonogashira coupling of AP-BZ with P-T in the presence of a zeolitic imidazolate framework (ZIF-67) as a directing hard template, affording a PA-BZ POP/ZIF-67 composite; etching in acetic acid; and pyrolysis of the resulting PA-BZ POP/metal composite at 500 °C. Powder X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller (BET) measurements revealed the properties of the as-prepared PCMC. The PCMC material exhibited outstanding thermal stability (T_d10 = 660 °C and char yield = 75 wt%), a high BET surface area (1110 m² g^–1), high CO₂ adsorption (5.40 mmol g^–1 at 273 K), excellent capacitance (735 F g^–1), and a capacitance retention of up to 95% after 2000 galvanostatic charge–discharge (GCD) cycles; these characteristics were excellent when compared with those of the corresponding microporous carbon (MPC) prepared through pyrolysis of the PA-BZ POP precursors with a ZIF-67 template at 500 °C.     

Heat transfer and fluid flow of nanofluids in laminar radial flow cooling systems

Nanofluids are considered as interesting alternatives to conventional coolants. It is well known that traditional fluids have limited heat transfer capabilities when compared to common metals. It is therefore quite conceivable that a small amount of extremely fine metallic particles placed in suspension in traditional fluids will considerably increase their heat transfer performances. A numerical investigation into the heat transfer enhancement capabilities of coolants with suspended metallic nanoparticles inside a radial, laminar flow cooling configuration is presented. Temperature dependant nanofluid properties are evaluated from experimental data available in recent literature. Results indicate that considerable heat transfer increases are possible with the use of relatively small volume fractions of nanoparticles. Generally, however, these are accompanied by considerable increases in wall shear-stress. Results also show that predictions obtained with temperature variable nanofluid properties yield greater heat transfer capabilities and lower wall shear stresses when compared to predictions using constant properties.     

Use of irradiation to control foodborne pathogens and extend the refrigerated market life of rabbit meat

This study set out to evaluate the microbiological status of rabbit meat and the possibility of using irradiation to control foodborne pathogenic bacteria and extend the refrigerated storage life of meat. Rabbit meat samples were γ irradiated at doses of 0, 1.5 and 3 kGy. The samples were stored at refrigeration temperature, then the effects of irradiation and storage on their microbiological, chemical and sensory properties were studied. Irradiation at 1.5 kGy significantly reduced the counts of Staphylococcus aureus, Listeria monocytogenes, Enterococcus faecalis and enterobacteriaceae but was not enough for complete elimination of Salmonella. However, 3 kGy dose reduced the counts of S. aureus, L. monocytogenes, E. faecalis and enterobacteriaceae by more than 3, 3, 1.4 and 4 log units, respectively, while Salmonella was not detected. On the other hand, irradiation at 1.5 and 3 kGy significantly reduced the counts of aerobic mesophilic bacteria, psychrophilic bacteria and molds and yeasts and prolonged the refrigerated shelf-life of samples to 12 and 21 days, respectively, compared to 6 days for non-irradiated controls. Irradiation of samples significantly increased their amounts of thiobarbituric acid reactive substances (TBARS) but had no significant effects on their total volatile nitrogen (TVN) contents, while storage significantly increased the TBARS and TVN for irradiated and non-irradiated samples. γ irradiation showed no significant effects on the sensory properties of raw meat. Moreover, fried burgers prepared from irradiated rabbit meat showed high sensory acceptability similar to those prepared from non-irradiated meat.