Study of complex heat exchange with account for phase transitions in secondary contour of the geothermal power plant

The numerical solution of complex heat exchange with account of phase transitions in secondary contour is obtained. Temperature, pressure and evaporation distributions along height of a heat exchanger and parametrical dependences of phase transitions boundaries on initial conditions are found.     

Improvement of adhesion of conductive polypyrrole coating on wool and polyester fabrics using atmospheric plasma treatment

In this paper wool and polyester fabrics were pretreated with atmospheric plasma glow discharge (APGD) to improve the ability of the substrate to bond with anthraquinone-2-sulfonic acid doped conducting polypyrrole coating. A range of APGD gas mixtures and treatment times were investigated. APGD treated fabrics were tested for surface contact angle, wettability and surface energy change. Effect of the plasma treatment on the binding strength was analyzed by studying abrasion resistance, surface resistivity and reflectance. Investigations showed that treated fabrics exhibited better hydrophilicity and increased surface energy. Surface treatment by an APGD gas mixture of 95% helium/5% nitrogen yielded the best results with respect to coating uniformity, abrasion resistance and conductivity.     

The workload-dependent MAP/PH/1 queue with infinite/finite workload capacity

We propose a numerical algorithm for finding the steady-state queue occupancy distribution for a workload-dependent MAP/PH/1 queue in which the arrival process and the service rate depend continuously on the instantaneous workload in the system. Both infinite and finite queue capacity scenarios are considered, including partial rejection and complete rejection policies for the latter. Using discretization, this system is approximately described by a multi-regime Markov fluid queue for which numerical algorithms are available. The computational complexity of the proposed method is linear in the number of regimes used for discretization. We provide numerical examples to validate the proposed approach.     

Investigation of heavy metal levels in economically important fish species captured from the Tuzla lagoon

Two hundred fish samples were collected seasonally from November 2000 to December 2001 from the Tuzla Lagoon. Heavy metal (Cd, Pb, Cu, Zn, and Fe) concentrations were measured in the muscle, gill, liver and gonad of three fish species (Sparus aurata, Dicentrarchus labrax and Mugil cephalus). The concentrations of heavy metals were determined by using flame atomic absorption spectrophotometry (FLAAS) and graphite furnace atomic absorption spectrophotometry (GFAAS) after wet digestion method.     

Crystal Structure and Optical Absorption Spectra of Ga0.5Fe0.5InS3 and Ga0.5Fe0.25In1.25S3 Crystals

Ga_0.5Fe_0.5InS₃ and Ga_0.5Fe_0.25In_1.25S₃ crystals are grown by chemical vapor transport and the Bridgman method, respectively. As determined by x-ray diffraction analysis, they have trigonal (sp. gr. P3m1, a= 3.796 × 2 Å, c = 12.210 Å) and rhombohedral (sp. gr. R3m, a= 3.786 × 2 Å, c = 36.606 Å) structures, respectively. From edge absorption data, the band gap is determined to be E _g = 1.885 eV in Ga_0.5Fe_0.5InS₃ and 1.843 eV in Ga_0.5Fe_0.25In_1.25S₃.     

Dielectric characterization of conducting textiles using free space transmission measurements: Accuracy and methods for improvement

The dielectric behaviour of in-situ polymerized thin polypyrrole (PPy) films on synthetic textile substrates were obtained in the 1–18 GHz region using free space transmission and reflection methods. The PPy/para-toluene-2-sulphonic acid (pTSA) coated fabrics exhibited an absorption dominated total shielding effectiveness (SE) of up to −7.34 dB, which corresponds to more than 80% of incident radiation. The permittivity response is significantly influenced by the changes in ambient conditions, sample size and diffraction around the sample. Mathematical diffraction removal, time-gating tools and high gain horns were utilized to improve the permittivity response. A narrow time-gate of 0.15 ns produced accurate response for frequencies above 6.7 GHz and the high gain horns further improved the response in the 7.5–18 GHz range. Errors between calculated and measured values of reflection were most commonly within 2%, indicating good accuracy of the method.     

Experimental assessment of energy storage via variable speed compressor

In this study, usage of a variable speed refrigeration system in latent heat thermal energy storage (LHTES) system is investigated to increase energy storage efficiency. Four different compressor speed control cases are compared to obtain a constant heat transfer fluid (HTF) temperature at the inlet of the energy storage tank. These control cases are (i) control with evaporation temperature, (ii) control with ethylene glycol temperature at the outlet section of evaporator, (iii) control with suction pressure of the compressor and (iv) on/off control. By means of the experimental analysis the best control strategy is obtained as control with Case (ii), in terms of stability of inlet temperature of heat transfer fluid, variations of energy efficiency of LHTES and coefficient of performance (COP) of the system. While the Case (ii) provides the most stabile inlet temperature of HTF, Case (iv) represents the worst stability. Besides, the highest energy efficiency (99.0%), exergy efficiency (87.0%) and COP (2.05) values observed in Case (ii). Additionally, the time period to reach the set value is nearly 50 min in Case (i), Case (iii) and Case (iv) on the other hand this unstable initial time period becomes nearly 25 min for Case (ii). As a result, variable speed compressor should be controlled with Case (ii) to stabilize ethylene glycol-water solution temperatures as well as increase efficiency and COP of the system.     

Blind-friendly user interfaces – a pilot study on improving the accessibility of touchscreen interfaces

Multimedia Tools and Applications - Touchscreen devices such as a smartphone, smartwatch, and tablets are essential assistive devices for visually impaired and blind people in performing activities...     

Structural diagram of the TlSeDySe system

The structural diagram of the TlSeDySe system has been constructed by the methods of differential thermal analysis and the results of microhardness measurements. At room temperature the solubility of DySe is TlSe is established to be 4 mol%. As a consequence of the investigations, TlDySe₂ compound (paramagnetic) is disclosed at peritectic reaction.