Sürdürülebilir Kalkınma Amaçları
Yazarlar
- Ashyralyyev, Charyyar(18)
- Ashyralyev, A.(15)
- Dogan, Ramazan Ozgur(15)
- Ashyralyev, A(10)
- Ekinci, Murat(9)
- Lukashov, A.(9)
- Kayikçioglu, Temel(8)
- Malkowsky, E(8)
- Özden, Talat(8)
- Akinoglu, Bulent G.(7)
- Memetoglu, M. E.(7)
- Albayrak, Cenk(6)
- Ashyralyev, Allaberen(6)
- Cakir, Zafer(6)
- Dogan, Hulya(6)
- Kayikcioglu, Temel(6)
- Bingol, Ozkan(5)
- Bingöl, Ozkan(5)
- Cakalli, H.(5)
- Canak, I.(5)
- Demir, S.(5)
- Gedikli, Eyup(5)
- Gurtug, O.(5)
- Harte, R.(5)
- Kalkan, A.(5)
- Kandemir, H.S.(5)
- Kocinac, L.D.R.(5)
- Ozden, Talat(5)
- Ozsahin, M(5)
- Sadybekov, M.(5)
- Sahin, H.(5)
- Simsek, Cemaleddin(5)
- Tez, M.(5)
- Turan, I.(5)
- Yildirim, Omer(5)
- Çakmak, Recep(5)
- Akay, K.U.(4)
- Akpulat, Murat(4)
- Aliyazicioglu, Y.(4)
- Altas, Ismail H.(4)
Yayınlar
- BildiriAçık Erişim2018Well-posedness of Neumann-type elliptic overdetermined problem with integral condition
Ashyralyyev, Charyyar; Çay, Aysel; Ashyralyev, A.; Sadybekov, M.; Lukashov, A.
The current paper is devoted to overdetermined elliptic problem with integral condition for derivatives. This overde-termined problem is converted to auxiliary nonlocal boundary value problem (ANBVP) with integral boundary condition. Well-posedness of abstract problem is established. Then, obtained results are used to obtain stability inequalities for solution of three Neumann-type inverse elliptic problems with integral condition to multidimensional differential equation.
AtıfScopus14WoS9OpenAlex16
İncele - BildiriAçık Erişim2018Performance and degradation analyses of two different pv modules in central anatolia
Ozden, Talat; Akinoglu, Bulent G.; Kurtz, Sarah
Ankara (latitude: around 40°N) is in Central Anatolia and the climate is dry continental. Due to the rapid transition to renewable energy policies of Turkey it is now a must to complete truthful feasibility analyses for solar power systems countrywide. Long term performance and degradation analyses have been carried out by the authors for three different arrays and many research results appearing in the literature are summarized. Present research analyzes the outdoor testing results of two PV modules monthly data. One of the modules has multi crystalline silicon (Poly-Si) cells and the other is thin film silicon (amorphous Si / microcrystalline Si tandem structure - a-Si/μc-Si) cells. The results showed that in five years the average yearly efficiency decreases from 14% to 11% for Poly-Si (14.72% is the nameplate Standard Test Condition (STC) efficiency) and from 8% to 6% for thin film modules (9.15% is STC efficiency). Our calculations are based on measured solar global-horizontal irradiance from which we calculated plane-of-array irradiation using an anisotropic sky model. We present the details of these analyses and degradation rates for the two types of modules to be used in long term feasibility analyses.
AtıfScopus11OpenAlex10İncele - BildiriAçık Erişim2018Stress Analysis and Fatigue Behaviour of PTFE-Bronze Layered Journal Bearing under Real-Time Dynamic Loading
Duman, M.S.; Kaplan, E.; Cuvalci, O.; Hamamci, M.; Gocer, A.; Karamis, M.B.; Nair, F.; Savas, S.
The present paper is based on experimental studies and numerical simulations on the surface fatigue failure of the PTFE-bronze layered journal bearings under real-time loading. 'Permaglide Plain Bearings P10' type journal bearings were experimentally tested under different real time dynamic loadings by using real time journal bearing test system in our laboratory. The journal bearing consists of a PTFE-bronze layer approximately 0.32 mm thick on the steel support layer with 2.18 mm thick. Two different approaches have been considered with in experiments: (i) under real- time constant loading with varying bearing widths, (ii) under different real-time loadings at constant bearing widths. Fatigue regions, micro-crack dispersion and stress distributions occurred at the journal bearing were experimentally and theoretically investigated. The relation between fatigue region and pressure distributions were investigated by determining the circumferential pressure distribution under real-time dynamic loadings for the position of every 10° crank angles. In the theoretical part; stress and deformation distributions at the surface of the journal bearing analysed by using finite element methods to determine the relationship between stress and fatigue behaviour. As a result of this study, the maximum oil pressure and fatigue cracks were observed in the most heavily loaded regions of the bearing surface. Experimental results show that PTFE-Bronze layered journal bearings fatigue behaviour is better than the bearings include white metal alloy.
AtıfScopus4WoS5OpenAlex5İncele - BildiriYalnız künye2018Power spectrum analysis of EEG for watching 2D & 3D videos and resting state
Manshouri, Negin; Maleki, Masoud; Kayikcioglu, Temel
Analysis of the brain waves has become useful over than 80 years. Along with the medical application, the brain signal is also used for other research works in the last fifteen years. In this study, by considering the depth factor in the image of a video, the effects of it are checked on EEG. A video is displayed in two-dimensional (2D) and three-dimensional (3D) format to the subjects. After recording the EEG signals in video watching, the resting state was recorded. Three states are considered for a better understanding of these effects on EEG. These states involve 2D&3D, 2D&resting and 3D&resting. Frequency analysis of the signals is evaluated by two methods. These methods are Fast Fourier Transform (FFT) and Welch method.
AtıfScopus2WoS1OpenAlex3İncele - BildiriAçık Erişim2018Daily and monthly module temperature variation for 9 different modules
Özden, Talat; Tolgay, Doga; Akinoglu, Bulent G.
One of the main parameter affecting the efficiency of PV modules is the module temperature. In this respect, outdoor testing of modules is very important to determine the temperature dependent performances and degradation rates. In this work, we analyzed the module temperatures of 9 different modules tested in the outdoor testing facility of METU-GUNAM, Ankara (latitude ∼40°N, in Central Anatolia and the climate is dry continental). The tested module types are two CIS (identical), one μc-Si/a-Si, one Poly-Si, three Mono-Si (two identical), one HIT and one bifacial. The module temperatures can reach up to 76°C while the ambient is around 39 °C during summer days. Monthly average module temperatures can reach up to 33.7°C (CIS) while the monthly average ambient is at 26.0°C and drops down to 1 °C while average ambient temperature is about the same as average module temperature. The results showed that the monthly averages of module temperatures differences are maximum during summer (∼3.5°C) and minimum during winter (1.1°C). It is interesting that the two CIS modules have the highest monthly average module temperature and although they are supposed to be identical their temperatures differ significantly. Bifacial and HIT module temperatures are lower than the Mono-Si modules. One of the two identical Mono-Si modules was not cleaned and its module temperature is always lower than the one that was cleaned periodically, as expected. In this work, we also present the results and discussions on the spatial variations of measured module temperatures of PV panels.
AtıfScopus6OpenAlex6İncele - BildiriYalnız künye2018Optimal scheduling of time shiftable loads in a task scheduling based demand response program by symbiotic organisms search algorithm
Cakmak, R.; Altas, I.H.
Demand side management is one of the key issues in smart electrical grid studies. Power demand of consumers can be managed via demand response(DR) programs. Task scheduling (TS) based demand response is one of the DR schemes. Objective of the TS approach is to schedule activation time of the appropriate time-shiftable loads to reduce power consumption in peak-demand hours. Heuristic optimization methods can be used to provide this objective. Symbiotic Organisms Search (SOS) and Cuckoo Search (CS) algorithms are two of the most recent heuristic methods. In this paper, scheduling of the time-shiftable home appliances executed by SOS and CS algorithms. Time-shiftable home appliances of the consumers and run time tolerances of them aggregated by mini public survey to achieve results which close to reality. Obtained results are indicated the superiority of the SOS algorithm and demonstrated the positive effects of the demand side management on the electrical grid.
AtıfScopus20WoS12OpenAlex18İncele - BildiriYalnız künye2018On the Yearly Performance of a Bifacial PV Module in Central Anatolia - Turkey
Özden, Talat; Turan, Raşit; Aklnoǧlu, Bülent Gültekin; Zaz, Y.; Essaaidi, M.
With the tremendous increase in the photovoltaic (PV) power plants world-wide remarkable decreases in their installation prices per watt are attained mainly due to economic scale effect. This brings questioning to increase their energy yields by considering any possible way like fabricating bifacial solar modules. Present study is on the performance analysis of a bifacial PV module using one-year outdoor testing results in Ankara-Turkey. The module performed very well and reached a specific yield value of 1750 kWh/kWp. This value for Central Anatolia region is well above the values predicted (and suggested) by the local authorities. The efficiency and performance ratio variation with respect to ambient and module temperature are obtained. The calculated dependence of efficiency on the module temperature is found to be η=-0.073Tmod+18.05, and the maximum measured module temperature is about 70 °C. The results show that the bifacial modules have the potential to replace the mono facial modules that are now dominating the PV market.
AtıfScopus3OpenAlex2İncele - BildiriYalnız künye2018A third order of accuracy difference scheme for Bitsadze-Samarskii type elliptic overdetermined multi-point problem
Ashyralyyev, Charyyar; Akyüz, Gulzlpa; Ashyralyev, A.; Sadybekov, M.; Lukashov, A.
In this study, a third order of accuracy difference scheme for Bitsadze-Samarskii type multi-point elliptic overdetermined problem is studied. For solution of constructed difference problem stability, almost coercive stability and coercive stability estimates are established. The theoretical statements for the solution of this difference problem are supported by numerical results in test example by using Matlab.
- BildiriYalnız künye2018Experimental Channel Measurement for Indoor Office Visible Light Communication
Yazgan, Ayhan; Simsek, Cemaleddin; Albayrak, Cenk; Tugcu, Emin; Turk, Kadir; Herencsar, N.
Channel measurement for visible light communication (VLC) is theoretically and experimentally performed in a real office platform. Six armatures composed of phosphor based white LED arrays are fed by designed analog LED drivers. Measurements are taken in a 6m x 7.8m office room which is formed as 10×13 matrix with 60 cm grid distance for both simulation and experiment studies. The link distance between LED arrays and optical receiver is kept minimum 2.5 meters for each measurement. Experimental results are generally in good agreement with simulation results, which are obtained using Barry's theoretical channel model.
AtıfScopus3OpenAlex4İncele - BildiriYalnız künye2018Performance of Visible Light Communication with Colour Shift Keying Modulation and Polar Code
Simsek, Cemaleddin; Tugcu, Emin; Albayrak, Cenk; Yazgan, Ayhan; Turk, Kadir; Herencsar, N.
Visible light communication (VLC) is an emerging technology to fulfill both illumination and communication purposes considered as either an alternative or a support system for some of scenarios carried by RF communication systems. Colour shift keying (CSK) is the modulation given in IEEE 802.15.7 VLC standard which proposes Reed-Solomon as error correction code. Polar code is the first theoretically proven capacity achieving error correction code with low encoding and decoding complexities. Performance of Polar code with belief propagation decoder has not been studied under VLC CSK scheme. In this study we investigate performance of Polar code with belief propagation decoder under VLC CSK scheme and compare it with performance of Reed-Solomon code. Result show that Polar code with belief propagation decoder outperforms Reed-Solomon code by at least 1.5dB.
AtıfScopus4WoS4OpenAlex4İncele - BildiriYalnız künye2018Fast and accurate classifier-based brain-computer interface system using single channel EEG data
Maleki, Masoud; Manshouri, Negin; Kayikcioglu, Temel
In brain-computer interface system (BCIs), direct communication between humans and computers is performed by analyzing neural signals and transforming them into digital signals. In the continuation of our previous works, in this paper, we advanced the proposed BCI system that was based on the gaze on rotating vanes. The speed of communication and convenience of the user are very important factors in BCI systems. Therefore, in this paper, for the convenience of the user, a single EEG channel was used. Also, for to increase the speed of the system, we tried to the classification of 0.5 sec epochs with a partial least squares regression (PLSR) as a fast classifier. In addition, we computed the information transfer rate (ITR) that has proved our proposed BCI system is fast and accurate. This system could be used in real-time implementations due to having high classification rate, speed and convenience of the user.
AtıfScopus6OpenAlex5İncele - BildiriAçık Erişim2018Finite difference approximations of first order derivatives of complex-valued functions
Ashyralyyev, Charyyar; Öztürk, Beyza; Ashyralyev, A.; Sadybekov, M.; Lukashov, A.
In this study, we generalize the well-known finite difference method to compute derivatives of a real-valued function to approximate complex derivatives wz and wz for complex-valued function w. Exploring different combinations of terms, we derive several approximations to compute the first order derivatives of complex-valued function. The first, second, third and fourth order of accuracy finite differences to calculate derivatives are studied. Error analysis in test examples are carried out by using Matlab program.
AtıfWoS1OpenAlex1İncele - BildiriYalnız künye2018The Relationship between Corruption and Tax Burden: The Moderator Effect of Strength of Auditing and Reporting Standards
Yesilcelebi, Gul; Keyifli, Nazli; Procházka, D.
The aim of this study is to examine the moderator effect of strength of auditing and reporting standards on the relationship between corruption and tax burden in the Organisation for Economic Co-operation and Development (OECD) countries. The study was conducted on annual data during the period 2011–2015 about the corruption, tax burden and strength of auditing and reporting standards of OECD member countries. In this context, data of corruption (Corruption Perceptions Index – CPI) were collected from Transparency International – the Global Coalition against Corruption; data of tax burden were collected from International Monetary Fund (IMF) database, and data of strength of auditing and reporting standards were collected from The Global Competitiveness Reports. The study analysed the relationship between corruption and tax burden and the moderator effect of strength of auditing and reporting standards on the relationship between two variables by the panel data analysis. The results of this analysis showed that have significantly and a negative relationship between corruption and tax burden; strength of auditing and reporting standards have significantly and a positive strengthen relationship between corruption and tax burden.
AtıfScopus1WoS1OpenAlex2İncele - BildiriAçık Erişim2018Tribological Behaviour of Ti:Ta-DLC Films under Different Tribo-Test Conditions
Efeoglu, İhsan; Keleş, Ayşenur; Totik, Yaşar; Cicek, Hikmet; Süküroglu, Ebru Emine; Hamamci, M.; Gocer, A.; Karamis, M.B.; Nair, F.; Savas, S.
Diamond-like carbon (DLC) films are suitable applicants for cutting tools due to their high hardness, low friction coefficient and wear rate. Doping metals in DLC films have been improved its tribological properties. In this study, titanium and tantalum doped hydrogenated DLC films were deposited by closed-field unbalanced magnetron sputtering system onto M2 high speed steels in Ar/N2/C2H2 atmosphere. The friction and wear properties of Ti:Ta-DLC film were investigated under different tribo-test conditions including in atmospheric pressure, distilled water, commercial oil and Ar atmosphere. The coated specimens were characterized by SEM and X-ray diffraction techniques. The bonding state of C-C (sp3) and C=C (sp2) were obtained with XPS. The tribological properties of Ti:Ta-DLC were investigated with pin-on-disc wear test. Hardness measurements performed by micro-indentation. Our results suggest that Ti:Ta-doped DLC film shows very dense columnar microstructure, high hardness (38.2 GPa) with low CoF (μ ≈0.02) and high wear resistance (0.5E-6 mm3/Nm).
AtıfScopus7WoS5OpenAlex8İncele - BildiriAçık Erişim2018OBJECT BASED BUILDING EXTRACTION and BUILDING PERIOD ESTIMATION from UNMANNED AERIAL VEHICLE DATA
Comert, Resul; Kaplan, Onur; Honkavaara, E.; Komp, K.; Stilla, U.; Jiang, J.; Zhang, H.; Peled, A.; Soergel, U.; Scaioni, M.
The aim of this study is to examine whether it is possible to estimate the building periods with respect to the building heights in the urban scale seismic performance assessment studies by using the building height retrieved from the unmanned aerial vehicle (UAV) data. For this purpose, a small area, which includes eight residential reinforced concrete buildings, was selected in Eskisehir (Turkey) city center. In this paper, the possibilities of obtaining the building heights that are used in the estimation of building periods from UAV based data, have been investigated. The investigations were carried out in 3 stages; (i) Building boundary extraction with Object Based Image Analysis (OBIA), (ii) height calculation for buildings of interest from nDSM and accuracy assessment with the terrestrial survey. (iii) Estimation of building period using height information. The average difference between the periods estimated according to the heights obtained from field measurements and from the UAV data is 2.86 % and the maximum difference is 13.2 %. Results of this study have shown that the building heights retrieved from the UAV data can be used in the building period estimation in the urban scale vulnerability assessments.
AtıfScopus9OpenAlex10İncele - BildiriYalnız künye2018Seasonal Variation of the Monthly Efficiencies of Thin Film PV Modules
Özden, Talat; Turan, Raşit; Akmoǧlu, Bülent Gültekin; Zaz, Y.; Essaaidi, M.
Outdoor testing of solar photovoltaic (PV) modules must be carried out at different climates as PV power plants nowadays are installed and continues to be installed in many countries. Present study is outdoor testing results and analyses of 5 thin film modules in Ankara, Turkey. The analyses are carried out using monthly efficiencies of the modules that are derived using the energy yield and input. The average efficiencies of the CIS, CIGS and μc-Si/a-Si thin film modules are. We present the monthly and average efficiencies and discuss their variations with the parameter: input, ambient temperature and relative humidity. We also carried out seasonal analyses using Pearson's correlation coefficient and find out that the efficiencies are differently dependent on the above mentioned parameters. This arose a new open question on differentiation of the strength of the effect of each parameter on the monthly efficiencies.
AtıfScopus1WoS1OpenAlex1İncele - BildiriAçık Erişim2018Determining photovoltaic module performance and comparisons
Karaveli, Abdullah Bugrahan; Ozden, Talat; Akinoglu, Bulent G.
Knowing electricity production potential of a photovoltaic (PV) system prior to installation is very beneficial for the investor to see the feasibility of the investment. There are three procedures that can be followed to calculate the potential electricity production of any system under different conditions. These are installation of sample systems and gathering data over time, the use of some databases/software programs to reach the performances and developing new model/methodology to make these estimations. It is obvious that installation of PV systems everywhere is neither technically nor economically conceivable. On the other hand, global software programs may not reflect local conditions to calculations. Consequently, there is a need to develop methodology that is able to derive location specific equations and coefficients and make accurate estimations. Its accuracy can be controlled by validating the results for some locations with the measured values from already installed PV power plants (PV PP). So, in this study we initially develop a methodology to calculate efficiency and electricity production performance of some modules for Ankara and compare the results with the measured values owing to the system installed on the roof of the Middle East Technical University Solar Energy Research Center (METU GUNAM) in Ankara/Turkey. The methodology initially calculates solar irradiation falling on the modules that is the input. Then the performance of the module is calculated by using developed methodology. There are also some online software programs to calculate the performances, such as EU PVGIS and PV WATTS. We analyzed and used these software programs and compare their results with the results of newly developed methodology. As proven through mean-bias error (MBE), root-mean-square error (RMSE) and mean absolute error (MAE) statistical comparison methods, the methodology of this study has given the most accurate results.
AtıfScopus2OpenAlex4İncele - BildiriAçık Erişim2018Impacts of a photovoltaic power plant for possible heat island effect
Demirezen, Emre; Ozden, Talat; Akinoglu, Bulent G.
Today, solar energy conversion technologies take a significant place within the efforts of obtaining renewable and sustainable energy around the world, and show a rapid progress. One of the most common technologies is photovoltaic power plants (PVPP) which are built using PV modules that provide electricity directly from sunlight. These plants are qualified as one of the pioneering applications among clean energy production methods. However, as the modules cover large areas and as they are produced by mostly dark-colored solar cells, an environmental debate has already been opened via some recent studies in the literature: Do they alter the solar reflectivity (albedo) of the region's surface where they are installed, and in turn affect the typical microclimate characteristics of that region such as the local air temperatures, humidity, pressure and wind speed? Considering also the additional heat that the modules radiate while producing electricity, the main probable result should be expected as Heat Island Effect (HIE). HIE has been particularly discussed for about last 10 years. Basically, this effect defines the day-night and inter-seasonal variations of local temperatures due to artificial changes on the natural land surface. Accordingly, when an urbanized area is compared with the neighboring rural areas, the difference is specifically named as Urban Heat Island (UHI) effect. In the present work, we are conducting a field research with in-situ measurements taken by the two weather monitoring stations inside and outside a PVPP in the district Tavsanli (Kutahya, Turkey). We also provide the meteorological data of Tavsanli station from Turkish State Meteorological Service (TSMS), which is the nearest weather monitoring station to the PVPP under inspection. These stations have been collecting the data of air temperature, relative humidity, average wind speed and atmospheric pressure every 10 minutes since October 2017. We used two statistical methods to compare and interpret the first 8-month data of all the three stations. We considered the statistical significance tests for both the first 8 months as a whole and dividing it into two 4 months before and after the PVPP becomes operational. We found that the measurements of the three stations differ significantly for most of the weather parameters. We also carried out pairwise tests and showed that each pair has significant differences for most parameters.
AtıfScopus2WoS3OpenAlex6İncele - BildiriYalnız künye2018Generalized beta parameters for a SVEIR-type random model of Polio transmission
Bekiryazici, Zafer; Merdan, Mehmet; Kesemen, Tulay; Tosun, M.
In this study, a SVEIR-type compartmental model of Poliomyelitis transmission is examined under random effects. We introduce Generalized Beta and normal distributed random parameters into the equation system to investigate the random dynamics of the disease. The approximate analytical solution of the model under random effects is obtained by using Random Differential Transformation Method (RDTM). Results from simulations and RDTM are analyzed to comment on the randomness of the compartments and disease transmission. It is seen that the random model successfully provides similar results that can be obtained through the deterministic model while providing additional information on the random behavior of the disease, such as the standard deviations and the variation coefficients.
AtıfScopus1WoS1İncele - BildiriYalnız künye2017Real Time Sending and Monitoring Electronic Health Records
Dogan, Ramazan Ozgur; Kayikçioglu, Temel; Yagci, Yavuz
Innovations in the field of health increase with the developing technology nowadays. These technological advances in the health field have enabled us to meet with telemedicine applications. Telemedicine is the use of computer technologies and the Internet infrastructure so that we can access health services without going to the hospital. In telemedicine applications, patients can access past electronic health records of patients can be accessed as well as access real-time instant electronic health records is provided. Real-time telemedicine applications usually aim to provide remote access to the biological signs of the patient and to diagnose them through these signals. In this study, it is mentioned how a real time telemedicine application can be performed, which features should be provided, and which performance criteria should be taken into consideration while developing. In addition, performance values are examined for a sample implementation.