2016 Cilt 21 Sayı 2

Permanent URI for this collectionhttps://hdl.handle.net/11452/11720

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Now showing 1 - 13 of 13

A DC~1.6 GHz distributed amplifier with GaAs MESFETs
(Uludağ Üniversitesi, 2016-08-31) Hiçdurmaz, Bahadır; Özzaim, Cengiz
In this study, a DC ~ 1.6 GHz bandwidth distributed amplifier (DA) is fabricated in printed circuit board (PCB). The scattering (S-) parameters of the distributed amplifier are measured and compared with simulated results. In characterization of the amplifier, small-signal microwave Sparameters given at some discrete frequencies of transistors are utilized. According to obtained results, it is observed that measured and simulated results are in relatively good agreement.
Analysis of signal-to-crosstalk ratio variations due to four-wave mixing in dense wavelength division multiplexing systems implemented with standard single-mode fibers
(Uludağ Üniversitesi, 2016-09-23) Karlık, Sait Eser; Uludağ Üniversitesi/Mühendislik Fakültesi/Elektrik-Elektronik Mühendisliği Bölümü.
In this paper, variation of the signal-to-crosstalk ratio (SXR) due to effects of four-wave mixing (FWM) has been analyzed on center channels of 5-, 7-, 9-channel dense wavelength division multiplexing (DWDM) systems implemented with G.652 standard single-mode fibers (SSMFs) for 12.5 GHz, 25 GHz, 50 GHz and 100 GHz equal channel spacing values. Center channels on such systems are the most severely impacted channels by FWM. Therefore, results obtained are the worst-case values for the DWDM system performance and important for system design. Simulations have been performed for systems using three different commercially available SMFs having different design parameter values for chromatic dispersion, dispersion slope, nonlinearity coefficient and attenuation coefficient which are all in the scope of the G.652 Recommendation of Telecommunication Standardization Sector of International Telecommunication Union (ITU-T) for SSMFs. In those simulations, under the impact of FWM, variation of SXR with variations in input powers, channel spacings and link lengths have been observed. Simulation results display the combined effect of the optical fiber and system design parameters on FWM performance of DWDM systems and give important clues for not only long-haul but also access network implementations of DWDM systems.
Computer-aided detection of brain tumors using morphological reconstruction
(Uludağ Üniversitesi, 2016-11-04) Doğan, Buket; Demir, Önder; Çalık, Seda Kazdal
Computer aided detection (CAD) systems helps the detection of abnormalities in medical images using advanced image processing and pattern recognition techniques. CAD has advantages in accelerating decision-making and reducing the human error in detection process. In this study, a CAD system is developed which is based on morphological reconstruction and classification methods with the use of morphological features of the regions of interest to detect brain tumors from brain magnetic resonance (MR) images. The CAD system consists of four stages: the preprocessing, the segmentation, region of interest specification and tumor detection stages. The system is evaluated on REMBRANDT dataset with 497 MR image slices of 10 patients. In the classification stage the performance of CAD has achieved accuracy of 93.36% with Decision Tree Algorithm, 94.89% with Artificial Neural Network (Multilayer Perceptron), 96.93% with K-Nearest Neighbour Algorithm and 96.93% with Meta-Learner (Decorate) Algorithm. These results show that the proposed technique is effective and promising for detecting tumors in brain MR images and enhances the classification process to be more accurate. The using morphological reconstruction method is useful and adaptive than the methods used in other CAD applications.
Design of an ann model trained by various learning algorithms to compute the operating frequency of e-shaped patch antennas
(Uludağ Üniversitesi, 2016-12-26) Kayabaşı, Ahmet; Toktaş, Abdurrahim; Akdağlı, Ali
An artificial neural network (ANN) trained by different learning algorithms implemented to computing the operating frequency of E-shaped patch antennas (EPAs) is designed in this study. The ANN model is built on a multilayered perceptron (MLP) based on feed forward back propagation (FFBP). A data pool is firstly constituted for training and testing the ANN model through 144 EPA simulations using the moment method-based HyperLynx® 3D EM software in terms of the operating frequency. The ANN model is then trained via 130 data, and the accuracy of the model is tested through 14 data of simulated EPAs. The ANN is trained by 8 different learning algorithms to achieve a robust model. A benchmark which compares the learning algorithms against each other according to percentage error is revealed. The validity of the ANN is corroborated by simulated and measured data reported in the literature. It shows that the ANN model trained by Levenberg–Marquardt learning algorithm computes the closest results. The proposed ANN model can be successfully exploited to analyze the EPAs in views of the operating frequency.
Detection of P53 consensus sequence: A novel string matching with classes algorithm
(Uludağ Üniversitesi, 2016-11-04) Özcan, Gıyasettin; Uludağ Üniversitesi/Mühendislik Fakültesi/Bilgisayar Mühendisliği Bölümü.
We present a novel fast string matching technique for special DNA pattern forms and compare performance of recent CPU architectures on the matching problem. In particular, we consider consensus P53 DNA-binding consensus sequence, which has an important contribution for cancer treatment. Based on biological findings, consensus P53 pattern may emerge in various sequence forms and its length is not deterministic. Therefore, classic string matching algorithms are not able to solve the problem. For efficient solution, we consider bitwise string matching algorithms with classes and present a novel search technique which is based on 64-bit packed variables. In order to prevent obstacles based on variable length of the pattern, we search right and left side indexes of P53 and reduce search space. For experimental analysis, we make use of mus musculus DNA sequences with approximately 2.3 billion nucleotides. We compare algorithm performance on three processors with distinct CPU architecture. Test results show that our search technique introduces at least 20% efficiency during P53 pattern search in each architecture platform. Due to its structure, the algorithm also introduces an efficient solution to similar string matching with class problems.
Effect of ethylene oxide, autoclave and ultra violet sterilizations on surface topography of pet electrospun fibers
(Uludağ Üniversitesi, 2016-10-21) Evke, Elif; Düzyer, Şebnem; Hockenberger, Aslı; Uguz, Agah; Kahveci, Zeynep; Uludağ Üniversitesi/Mühendislik Fakültesi/Tekstil Mühendisliği Bölümü.; Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.; Uludağ Üniversitesi/Tıp Fakültesi/Histoloji ve Embriyoloji Anabilim Dalı.
The aim of this study to investigate the effects of different sterilization methods on electrospun polyester. Ethylene oxide (EO), autoclave (AU) and ultraviolet (UV) sterilization methods were applied to electrospun fibers produced from polyethylene terephthalate (PET) solutions with concentrations of 10, 15 and 20 wt.%. The surface characteristics of the fibers were examined by scanning electron microscope (SEM), atomic force microscope (AFM), surface pore size studies and contact angle measurements. Differential scanning calorimetry (DSC) tests were carried out to characterize the thermal properties. Fourier Transform Infrared spectroscopy (FTIR) tests were performed to analyze the micro structural properties. SEM studies showed that different sterilization methods made significant changes on the surfaces of the fibers depending on the PET concentration. Although the effects were decreased with the increasing polymer concentration, the fiber structure was damaged especially with the EO sterilization. The contact angle values were decreased with the UV sterilization method the most.
Evaluation of empirical modelling techniques for the estimation of sediment amount in rivers
(Uludağ Üniversitesi, 2016-11-17) Güven, Başak; Akdoğan, Zeynep
The sediment transport processes of streams have been the subject of research for many years. Sediment amount carried by a river is strongly correlated with the river’s flow rate and sediment concentration. This study aims to represent this correlation and to estimate the sediment amount using four different modelling techniques: MLR, PLS, SVM, and ANN. Records of river flow, sediment concentration and sediment amount obtained from the Göksu River, located in the Eastern Mediterranean region of Turkey, are used as input data in the models. The aim of is this study is to evaluate the effectiveness of ANN modelling in the estimation of sediment amount carried by river flow. Fifty percent of the data are used as training set to develop the models. The other half of the data is used for verification set. The performance of the four models is evaluated by determination coefficient of prediction set (r 2 pred). The results indicate that ANN is the most effective method (r2 pred = 0.94), followed by SVM (r 2 pred = 0.72). MLR and PLS methods are the least effective techniques (r 2 pred = 0.67) for estimating sediment amount in the Göksu River. Therefore, ANN approach is further studied to propose the best configuration for the prediction of river sediment amount.
The evaluation of physical space quality in education buildings in regard to user satisfaction
(Uludağ Üniversitesi, 2016-07-04) Sezer, Filiz Şenkal; Arslan, Tülin Vural; Uludağ Üniversitesi/Mimarlık Fakültesi/Mimarlık Bölümü.
In this study, physical space quality of two different engineering department buildings in Uludag University Gorukle Campus, Bursa, Turkey are analyzed in regard to user evaluations about the physical space quality. In the analysis of these evaluations, criteria about physical space quality are predetermined by the authors. In the method of the study, the below phases are implemented. In first, the literature review about the physical space quality is done and then a questionnaire is prepared with regard to the key themes in literature review in order to evaluate the user satisfaction. The key themes in user satisfaction questionnaire is accessibility, ergonomics, thermal comfort, audible comfort, visual comfort, inner space air quality, service spaces, socialization. The aim of this study is first to understand which criteria are important for the students and then to improve the physical space quality in regard to the dissatisfaction.
Hydrothermal treatment of cellulose in hotpressurized water for the production of levulinic acid
(Uludağ Üniversitesi, 2016-12-15) Yüksel, Aslı
In this paper, hot-pressurized water, operating above boiling point and below critical point of water (374. 15 °C and 22.1 MPa), was used as a reaction medium for the decomposition of cellulose to high-value chemicals, such levulinic acid. Effects of reaction temperature, pressure, time, external oxidant type and concentration on the cellulose degradation and product distribution were evaluated. In order to compare the cellulose decomposition and yields of levulinic acid, experiments were performed with and without addition of oxidizing agents (H2SO4 and H2O2). Analysis of the liqueur was monitored by HPLC and GC-MS at different temperatures (150 - 280 °C), pressures (5-64 bars) and reaction times (30 - 120 mins). Levulinic acid, 5-HMF and formic acid were detected as main products. 73% cellulose conversion was achieved with 38% levulinic acid yield when 125 mM of sulfuric acid was added to the reaction medium at 200 °C for 60 min reaction time.
Investigation of the effects of the magnetic circuit design parameters on the electromechanical valve actuators
(Uludağ Üniversitesi, 2016-12-18) Kocabıçak, Zeliha Kamış; Topçu, Elif Erzan; Uludağ Üniversitesi/Mühendislik Fakültesi/Otomotiv Mühendisliği Bölümü.; Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.
The paper describes the suitable type of magnetic circuits used in the electromechanical valve actuators (EVAs). Two different types of EVA models with the disc type of magnetic circuits were designed and the effects of various design parameters such as spring constant, moving mass, supply voltage, holding force on the system were investigated. The static and dynamic equations of the system were derived and their numerical solutions were obtained with MATLAB/Simulink program. The detailed theoretical analysis and experimental tests were carried out on the manufactured different prototypes of the EVAs. Simulation and experimental results showed a good agreement with each other.
Low temperature solid-state synthesis and characterization of LaBo3
(Uludağ Üniversitesi, 2016-01-21) Kıpçak, Azmi Seyhun
Rare earth (lanthanide series) borates, possess high vacuum ultraviolet (VUV) transparency, large electronic band gaps, chemical and environmental stability and exceptionally large optical damage thresholds. For this properties, they are used in the development of plasma display panels (PDPs). In this study the synthesis of lanthanum borates via solid-state method is studied. For this purpose, lanthanum oxide (La2O3) and boric acid (H3BO3) are used for as lanthanum and boron sources, respectively. Different elemental molar ratios of La to B (between 3:1 to 1:6 as La2O3:H3BO3) were reacted by solidstate method at the reaction temperatures between 500°C - 700°C with the constant reaction time of 4 h. Following the synthesis, characterizations of the synthesized products are conducted by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy and scanning electron microscope (SEM). From the results of the experiments, three types of lanthanum borates of; La3BO6, LaBO3 and La(BO2)3 were observed at different reaction parameters. Among these three types of lanthanum borates LaBO3 phase were obtained as a major phase.
Microwave energy-assisted fabrication of hierarchically structured carbon nanotube/carbon fiber composites
(Uludağ Üniversitesi, 2016-07-04) Poyraz, Selçuk
Through a facile, simple, yet efficient, affordable and ultrafast (30 s) microwave (MW) energy heating process, hierarchical composites made up of carbon fibers (CFs) decorated with multi-walled carbon nanotube (MWCNT) forest were produced at ambient conditions in one-step. Morphological features of the as-produced composites were characterized in details by using scanning and transmission electron microscopy (SEM, TEM) and the elemental analysis (EDX) techniques. Both the composite material characterization results and the versatile and easily controllable nature of the above mentioned process strongly support its promising success for the fabrication of such hierarchical composites that could be effectively used for the next generation advanced engineering applications.
On the calibration of multigene genetic programming to simulate low flows in the Moselle River
(Uludağ Üniversitesi, 2016-11-27) Mehr, Ali Danandeh; Demirel, Mehmet C.
The aim of this paper is to calibrate a data-driven model to simulate Moselle River flows and compare the performance with three different hydrologic models from a previous study. For consistency a similar set up and error metric are used to evaluate the model results. Precipitation, potential evapotranspiration and streamflow from previous day have been used as inputs. Based on the calibration and validation results, the proposed multigene genetic programming model is the best performing model among four models. The timing and the magnitude of extreme low flow events could be captured even when we use root mean squared error as the objective function for model calibration. Although the model is developed and calibrated for Moselle River flows, the multigene genetic algorithm offers a great opportunity for hydrologic prediction and forecast problems in the river basins with scarce data issues.

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