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Öğe Analysis of the Effects of Gsm Bands to the Electromagnetic Pollution in the Rf Spectrum(E M W Publishing, 2010) Genç, Ö.; Bayrak, M.; Yaldız, E.In this study, electromagnetic (EM) pollution measurements in crowded residential areas were performed, and statistical analysis of values recorded for the EM sources causing pollution was carried out. The actual measurement values and estimated values by the analysis model obtained through the statistical analysis were compared. Also, amplitude fluctuations of the electromagnetic radiations from EM pollution sources were detected for a long time, and statistical analyses were made. EM field levels were measured in the districts of Turkish capital, Ankara where cellular base stations and TV/Radio stations are densely populated . EM radiation levels were measured for the GSM900, GSM1800, FM, UHF4, VHF4 and VHF5 stations for certain spectrum ranges under far-field conditions by utilizing isotropic field probe and selective spectrum analyzer. The measurements were fulfilled by using NARDA SRM3000 radiation meter with isotropic antenna that can be utilized in 75 MHz-3 GHz frequency range. The obtained measurement levels were compared with the limit values given by International Commission for Non-Ionizing Radiation Protection (ICNIRP). The measurement results for each pollution sources were compared,and their contributions to the combined radiation were analyzed. The values for the EM pollution in the measurement regions were embedded over the digital maps created for the related places. During this process, comparisons of the pollution maps were made by utilizing Natural Neighbour (NN) interpolation technique.Öğe Designs and Analyses of Some Rf/microwave Passive Elements on Cylindrical Cpws(Electromagnetics Academy, 2009) Akan, V.; Duyar, M.; Yazgan, E.; Bayrak, M.In this article, designs and analyses of several CCPW (Cylindrical CPW) discontinuities have been realized as microwave reactive elements. The quasi-TEM characteristic parameters of CCPWs have been obtained by CMT (Conformal Mapping Techniques) which provide satisfactory accuracy at microwave frequencies and lead to closed-form analytical solutions suitable for CAD software packages. Then these discontinuities have been simulated in CST Microwave Studio 2006 in order to obtain inductance, capacitance and also input impedance versus frequency and physical dimensions of the elements. The results show that CCPW discontinuities can be used successfully as reactive elements for related applications.Öğe Effects of Microstrip Feed Line Width on 1 x 4 Rectangular Microstrip Antenna Array Electrical Parameters and Estimation with Artificial Neural Networks(ELECTROMAGNETICS ACAD, 2012) Dundar, O.; Uzer, D.; Gultekin, S. S.; Bayrak, M.In this study, 1 x 4 rectangular microstrip array antennas are designed at 16 GHz resonant frequency for KU Band usage on Duroid 5880 substrate that has a thickness of 0.254 mm and a dielectric constant of 2.2. Designs are simulated using HFSS v12. At these designs, by changing the feed line widths systematically, for each antenna, electrical parameters like Sit response, directivity, gain, radiation efficiency etc. are investigated for 26 array antennas in simulation media. Also, directivity and gain values are predicted with an Artificial Neural Network model. The network has four inputs as dielectric substrate thickness, resonant frequency and dielectric constant of the substrate and three outputs as directivity, gain and radiation efficiency. Multi layer perceptron structure for Artificial Neural Network model and Levenberg-Marquart learning algorithm for training the network are used. The network model is trained with 20 of 26 design data and is tested with the rest 6 ones. It is seen that the results from simulations and the neural network model are compatible with similar studies in the literature.Öğe Effects of Microstrip Feed Line Width on 1 £4 Rectangular Microstrip Antenna Array Electrical Parameters and Estimation with Artificial Neural Networks(2012) Dündar, O.; Uzer, D.; Gültekin, S. S.; Bayrak, M.In this study, 1 £ 4 rectangular microstrip array antennas are designed at 16 GHz resonant frequency for KU Band usage on Duroid 5880 substrate that has a thickness of 0.254mm and a dielectric constant of 2.2.Designs are simulated using HFSS v12.At these designs, by changing the feed line widths systematically, for each antenna, electrical parameters like S 11 response, directivity, gain, radiation efficiency etc.are investigated for 26 array antennas in simulation media.Also, directivity and gain values are predicted with an Artificial Neural Network model.The network has four inputs as dielectric substrate thickness, resonant frequency and dielectric constant of the substrate and three outputs as directivity, gain and radiation efficiency.Multilayer perceptron structure for Artificial Neural Network model and Levenberg- Marquart learning algorithm for training the network are used.The network model is trained with 20 of 26 design data and is tested with the rest 6 ones.It is seen that the results from simulations and the neural network model are compatible with similar studies in the literature.Öğe The Results of Surgical Techniques in Hepatic Hydatidosis: Treatment with Drainage Versus Treatment Without Drainage - A 6-Year Experience(BLACKWELL SCIENCE LTD, 1998) Kama, N. A.; Şahin, M.; Göçmen, E.; Bayrak, M.; Kulaçoğlu, H.; Akat, A. Z.Fifty-nine consecutive patients who underwent surgery for hepatic hydatid cysts between 1 March 1988 and 31 July 1994, were included in this study. The aim was to compare the results of surgical techniques with respect to post-operative complications, morbidity and recurrence of the disease. Patients were divided into two groups. The first group, (1) of patients (n = 30)were treated surgically without drainage and the second group (2) of patients (n = 29) were treated surgically with tube drainage of the cystic cavity. In the study, there were 12 (20.33%) male and 47 (79.66%) female patients, with an age range of between 16 and 85 years. In five of the patients a communication between the cyst and the biliary system was documented. 11.8% of the cysts were localized extrahepatically. Post-operative morbidity was 10% in group 1 and 44.7% in group 2 (P < 0.05). Average post-operative hospital stay was 8.5 days in group 1 and 18.6 days in group 2 (P < 0.05). During the follow-up period, which lasted from 1 to 6 years, recurrence rates were not significantly different in the two groups (P < 0.05).Öğe VNA Calibration by Random Neural Network(2002) Danacı, E.; Uçan, O. N.; Bayrak, M.A new calibration method is investigated for conventional VNA calibration. It is based on teaching the error terms of VNA to a Neural Network (NN). A well-known two ports calibration standard is adequate VNA calibration for this method. Experimental results are presented and compared to data obtained with traditional techniques.
