Subjects -> SCIENCES: COMPREHENSIVE WORKS (Total: 426 journals)
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 Communications Faculty of Sciences University of Ankara Series A2-A3 Physical Sciences and EngineeringNumber of Followers: 0     Open Access journal ISSN (Print) 1303-6009 - ISSN (Online) 2618-6462 Published by Ankara University  [5 journals]
• A study on non-linear discrete-time state-space models and adaptive
extended Kalman filter application on oscillatıon of an object tied to
the end of spring

• Authors: Fikri ÖZTÜRK; Levent ÖZBEK
Abstract: In this work, Adaptive Extended Kalman Filter (AEKF) is introduced and its use for oscillation of an object connected to the end of a spring is shown. As a new approach, an AEKF is used as a nonlinear estimation tool for online estimation of the states and parameters of an oscillating object attached to the end of a spring model. Parameter states that do not change with time were examined. The simulation results revealed that with proper selection of initial values of AEKF, AEKF is a very useful tool for this particular application.
PubDate: Wed, 30 Jun 2021 00:00:00 +030

• Enhanced boost converter with gan based power switches and
switched-capacitor

• Authors: Korhan CENGİZ
Abstract: To increase the voltage gain of power electronic circuits, several voltage converters have been designed by researchers. Especially, the boost based converters are used by designers for numerous devices and systems because of their reliability. Generally, in these studies, researchers propose to use high frequency transformers, silicon based diodes and inductance based sub-circuits. However, the improvement on new generation power transistors should be considered as an alternative way to provide these goals because of their lower inner resistances, lower switching losses and adoptability for new generation devices. Therefore, in this paper, usage of these kinds of semiconductors to improve the voltage gain performance of traditional boost converter is proposed. With this enhanced design and usage of new semiconductor switches, we obtain approximately 70% more output voltage gain than traditional boost converter. The proposed converter provides significant gain, high scalability in duty cycle vs output voltage usage and portability for weight restricted systems. The enhanced boost based converter is modelled in Simulink to verify the analytical voltage gain equations. Finally, the proposed model is compared with traditional boost converter in term of gain performance.
PubDate: Wed, 30 Jun 2021 00:00:00 +030

• Analysis of Bragg curve parameters and lateral straggle for proton and
carbon beams

• Authors: Fatih EKİNCİ; Gazi Erkan BOSTANCI, Özlem DAĞLI, Mehmet Serdar GÜZEL
Abstract: Heavy ions have varying effects on the target. The most important factor in comparing this effect is Linear Energy Transfer (LET). Protons and carbons are heavy ions with high LET. Since these ions lose energy through collisions as they move through the tissue, their range is not long. This loss of energy increases along the way, and the maximum energy loss is reached at the end of the range. This whole process is represented by the Bragg curve. The input dose of the Bragg curve, full width at half maximum (FWHM) value, Bragg peak amplitude and position, and Penumbra thickness are important factors in determining which particle is advantageous in tumor treatment. While heavy ions move through the tissue, small deviations occur in their direction of travel due to Coulomb collisions. These small deviations cause lateral straggle in the dose profile. Lateral straggle is important in determining the type and energy of the particle used in tumor treatments close to critical organs. In our study, when the water phantom of protons and carbon beams with different energies is taken into consideration, the input dose, FWHM value, peak amplitude and position, penumbra thickness and lateral straggle are calculated using the TRIM code and the results are compared with Monte Carlo (MC) simulation. It was found that the proton has an average of 63% more FWHM and 53% more Penumbra than the carbon ion. The carbon ion has an average of 28-45 times greater Bragg peak amplitude at the same Bragg peak location than the proton. It was observed that the proton scattered approximately 70% more in lateral straggle. The difference was found to be around 1.32 mm. In line with all these results, the most commonly used proton and carbon heavy ions in hadron therapy applications were compared.
PubDate: Wed, 30 Jun 2021 00:00:00 +030

• A new astronomical parameter from remote sensing data: Astronomical
clearness index (ACI)

• Authors: Kazım KABA; Cahit YEŞİLYAPRAK, Onur ŞATIR
Abstract: Eastern Anatolia Observatory (DAG) project was initiated in Erzurum/Turkey in 2011. DAG will have Turkey’s largest (4 m) and first infrared telescope. The installation process is planned to be by taking its first light in the end of 2021. This study was focused on a new analysis method about the atmospheric properties of DAG site in terms of the cloudiness as known the most vital atmospheric parameter for ground-based astronomical observatories. In this regard, the cloudiness for DAG site is comprehensively examined using the “Cloud Mask” (CMa) and “Cloud Type” (CT) products from Satellite Application Facility on Support to Nowcasting and Very Short-Range Forecasting (NWC SAF). Firstly, the cloudiness and the cloud types over DAG site were determined. Secondly, NWC SAF CMa and CT data have been redefined for astronomical purposes, and the pixel values/meanings in CMa and CT images have been reduced from 6 to 4 and from 21 to 4 pixels, respectively. Thirdly, these new data were used to define a new index named as “Astronomical Clearness Index” (ACI), and finally, the observable days for DAG site were determined using this newly defined index.
PubDate: Wed, 30 Jun 2021 00:00:00 +030

• Impurity effects on activation energy, structure and physical properties
of Ybco superconductor

• Authors: Murat ÖZABACI
Abstract: The influence of separately added 0.3 wt%, CdO, Bi2O3, BeO and SiO2 on the phase formation, microstructure, magnetic and transport properties of Y1Ba2Cu3O(7-$\delta$)  (Y-123 or YBCO) fabricated by conventional solid state reaction method has been analyzed. The results reveal a very low solubility limit for bismuth and silicon in the Y-123 phase, leading to precipitation phases located within intergranular regions. BeO addition suppresses the granular nature of the structure by probably incorporating into the host matrix. CdO does not have a remarkable effect both on structural and superconducting properties of the Y-123 at this doping ratio. Attractive infield transition behavior was obtained in the Bi2O3 added sample with a narrower transition width and an increase of transition temperatures approximately 1 K. The activation energy (U0), a potential energy barrier to prevent flux flow, of the samples was estimated by taking into account Arrhenius law. The best U0 value was computed to be 1.11 eV belonging to the Bi2O3 added sample which implies the contribution of 3-5 µm sized Bi containing precipitation regions on the flux pinning capability of the Y-123.
PubDate: Wed, 30 Jun 2021 00:00:00 +030

• A new distributed denial-of-service detection system in cloud environment
by using deep belief networks

• Authors: Ibrahim IBRAHİM; Sefer KURNAZ
Abstract: This study presents new method to detect DDOS attacks by using Deep Belief Networks (DBN). The input data which represented the DDoS features in cloud environment are first analyzed by using DBN to extracted high level and sensitive features. The output of the DBN wired to the classifier (SoftMax and SVM). The aim of using the DBN is to extracted features that have ability to present the best classification results and to speed up the processing time by reducing the dimension of features. In the last stage, the Classifier trained in supervised method to classify the features into two labels there is attack or not. The obtained results compared with well-known studies presented in this field.
PubDate: Wed, 30 Jun 2021 00:00:00 +030

• Determining the most relevant input parameter set by using extreme
learning machine

• Authors: Semra GÜNDÜÇ; Recep ERYİGİT
Abstract: In this work, Extreme Learning Machine (ELM) algorithm is used to estimate the GDP per capita. The amount of electricity production, from four different sources, is chosen as input parameters. To find out the most relevant input data for a reasonable estimation of GDP, different sources introduced separately to ELM. By following the coefficient of determination of estimation, by trial and error, results are obtained. The residuals are also given to show that model perform well. Renewable energy sources produce the best results in the estimation of GDP.
PubDate: Wed, 30 Jun 2021 00:00:00 +030

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