Showing papers by "Batman University published in 2009"

Determination of thermodynamic properties of an alternative refrigerant (R407c) using artificial neural network

Abstract: Thermodynamic analysis of the refrigeration systems is too complex because of thermodynamic properties equations of working fluids, involving the solution of complex differential equations. To simplify this complex process, this paper proposes a new approach (artificial neural network, ANN) to determine of thermodynamic properties of an environmentally friendly alternative refrigerant (R407c) for both saturated liquid-vapor region (wet vapor) and superheated vapor region. Instead of complex rules and mathematical routines, ANNs are able to learn the key information patterns within multidimensional information domain. Therefore, reducing the risk of experimental uncertainties and also removing the need for complex analytic equations requiring long computational time and efforts. R^2 values - which are errors known as absolute fraction of variance - in wet vapor region are 0.999706, 0.999949, 0.999909, 0.999988 and 0.999836 for specific volume, enthalpy, entropy, viscosity and thermal conductivity for training, respectively. Similarly, for superheated vapor, they are: 0.99992, 1, 0.99998, 0.99995 and 0.99996 for training data, respectively. Promising thermodynamics property results have been obtained for R407c within acceptable errors. PVTx properties predicted are in valid region for working conditions of the refrigeration systems in case of use to computer simulation programs.

Environmental radioactivity assessment for Bayburt, Turkey

Abstract: This study assesses the results of environmental radioactivity measurements for Bayburt Province in the Eastern Black Sea area of Turkey. Using γ-ray spectrometry, activity concentrations of the natural radionuclides 226Ra, 232Th and 40K and a fission product 137Cs were investigated in soil samples. The activity concentrations of 226Ra, 232Th and 40K in various building materials such as sand, cement and marble and in drinking waters were determined. The activity concentrations vary from 16 to 54 Bq kg−1 for 226Ra, from 10 to 21 Bq kg−1 for 232Th and from 113 to 542 Bq kg−1 for 40K in building materials. The mean specific activity concentrations of 226Ra, 232Th and 40K in drinking waters were 93, 30 and 504 mBq l−1, respectively. The concentrations of gross α and β radioactivity in drinking water samples collected from four different sampling stations have been determined. The results show that the gross α and β activities are lower than the screening levels given by the World Health Organization (WHO), which are a maximum contaminant level of 0.5 Bq l−1 and 1.0 Bq l−1 gross α and β radioactivity, respectively, in drinking water. Indoor radon measurements were made in 44 dwellings in Bayburt by using Cr-39 detectors. Radon concentrations in dwellings in Bayburt varied from 17 to 125 Bq m−3 and the average value was 56 Bq m−3. The results obtained in this study indicate that the region has a background radiation level that is within the typical natural range and shows no significant departures from other parts of the country.

Electrical Properties of Organic–Inorganic Semiconductor Device Based on Rhodamine-101

Abstract: Rhodamine-101 (Rh101) thin films on n-type Si substrates have been formed by means of evaporation, thus Sn/Rh101/n-Si heterojunctions have been fabricated. The Sn/Rh101/n-Si devices are rectifying. The optical energy gaps have been determined from the absorption spectra in the wavelength range of 400 nm to 700 nm. Rh101 has been characterized by direct optical absorption with an optical edge at 2.05 ± 0.05 eV and by indirect optical absorption with␣an optical edge at 1.80 ± 0.05 eV. It was demonstrated that trap-charge-limited current is the dominant transport mechanism at large forward bias. A␣mobility value of μ = 7.31 × 10−6 cm2 V−1 s−1 for Rh101 has been obtained from the forward-bias current–voltage characteristics.

Time-frequency analysis of snoring sounds in patients with simple snoring and OSAS

Abstract: In recent years variety of studies has been conducted towards the identification of correlation between Obstructive Sleep Apnea Syndrome (OSAS) and snoring. The features detected from time and frequency domain analysis of snores showed the differences between simple and OSAS patients. In this study the total episodes of 1500 snore records taken from 7 simple and 14 OSAS patients were evaluated through time-frequency analysis. From the time-frequency analysis the differences, particularly from the spectral bandwidth point of view, between the two groups were identified, and using this data the method was suggested as a cost effective and simple technique to be widely used in detection of OSAS from simple patients.