Sürdürülebilir Yeşil Kampüs Koleksiyonu / Sustainable Green Campus Collection
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Article Citation - WoS: 10Citation - Scopus: 26Mobile Join Operators for Restricted Sources(Hindawi Publishing Corporation, 2005) Özakar, Belgin; Morvan, Franck; Hameurlain, AbdelkaderWe consider the problem of query execution when there is limited access to the relations, i.e. when binding patterns require values to be specified in order to get data from the relation. This problem is common in virtual data integration systems where there are heterogeneous sources with various restricted access patterns and query capabilities. Another problem is the lack of the statistical information about the sources and occurrence of unpredictable events. We introduce two mobile join operators, MDJoin and SMDJoin which are designed for restricted sources and implemented using ‘mobile agents’ in order to benefit from their autonomous and reactive characteristics. Mobile operators of restricted sources are capable to deal with restricted sources and react to the variations between the compile-time estimations and run-time computations of data during query execution. The difference between the two new query operators lies in their level of adaptation ability to the execution environment. Performance results show that mobile agent-based approach at operator level can lead to a significant reduction in response time with restricted sources.Conference Object Approximate Best Linear Unbiased Channel Estimation for Multi-Antenna Frequency Selective Channels With Applications To Digital Tv Systems(SPIE, 2004) Özen, Serdar; Pladdy, Christopher; Nerayanuru, Sreenivasa M.; Fimoff, Mark J.; Zoltowski, Michael D.We provide an iterative and a non-iterative channel impulse response (CIR) estimation algorithm for communication receivers with multiple-antenna. Our algorithm is best suited for communication systems which utilize a periodically transmitted training sequence within a continuous stream of information symbols, and the receivers for this particular system are expected work in a severe frequency selective multipath environment with long delay spreads relative to the length of the training sequence. The iterative procedure calculates the (semi-blind) Best Linear Unbiased Estimate (BLUE) of the CIR. The non-iterative version is an approximation to the BLUE CIR estimate, denoted by a-BLUE, achieving almost similar performance, with much lower complexity. Indeed we show that, with reasonable assumptions, a-BLUE channel estimate can be obtained by using a stored copy of a pre-computed matrix in the receiver which enables the use of the initial CIR estimate by the subsequent equalizer tap weight calculator. Simulation results are provided to demonstrate the performance of the novel algorithms for 8-VSB ATSC Digital TV system. We also provide a simulation study of the robustness of the a-BLUE algorithm to timing and carrier phase offsets.Article An Application With Webmathematica(Springer Verlag, 2003) Ufuktepe, ÜnalThere have been many technological dawns in the last 30 years, during which the desktop computer and the Internet have been developed. The importance of Internet in education, particularly using its Web is a well-recognized fact. A wealth of resources and techniques now exist which serve as a source both for exciting examples of new teaching practices, as well as easily accessible methods for adoption into various formats of teaching and learning. Internet technology allow teachers and students keep up with their minds. It let them try their ideas as soon as they come up with them. Generally, students appreciate the convenience, choice, and flexibility that an online courses offers. Instructional designers value the standardized framework and flexibility. WebMathematica is a web-based technology developed by Wolfram Research that allows the generation of dynamic web content with Mathematica. With this technology, the distance education students should be able to explore and experiment with the mathematical concepts. In this paper we will elucidate the pedagogical issues in the application of Hamiltonian systems in the webMathematica for the distance learning environment and the shape of the future "classroom" as well as relevant educational strategies towards improving mathematics education.Master Thesis B and Se Transport Modeling in Saturated/Unsaturated Zones(Izmir Institute of Technology, 2002) Yüreklitürk, O. Emin; Tayfur, GökmenThere has been renewed interest in the application of models to the transport of non-point source pollutants. However, very little work has been done to evaluate the performance of a functional transient-state model for the transport of a reactive solute over an extensive study period. This research consists of mathematical modeling to simulate water flow, boron and selenium transport through soil in tile-drained croplands.For Boron part a mathematical model was developed to simulate non-conservative boron transport. The dynamic two-dimensional finite element model simulates water flow and boron transport in saturated-unsaturated soil system, including boron sorption and boron uptake by root-water extraction. Two different models have been employed for the sorption of boron. Similarly, for selenium part a finite element model is developed to simulate species of selenium transport in two dimensions in saturated/unsaturated zones. The model considers water, selenate, selenite and selenomethionine uptake by plants. It also considers oxidation/reduction, volatilization, and chemical and biological transformations of selenate, selenite, and selenomethionine. Comparison of boron transport model results with observed data is satisfactory. The model employed with Langmuir isotherm was found to give slightly better simulation results when compared with the model employed with Freundlich. The sensitivity analysis results indicate that the irrigation scheduling and the irrigation water quality are very important parameters for boron accumulation in the soil. Also the adsorption isotherm parameters, which reflect us the soil properties, are found to be important for the boron movement in the soil. Comparison of selenium transport model with observed data is not quite satisfactory in accuracy when compared with the model for boron transport. This may be the result of the complexity of the mechanisms affecting the selenium transport in soil. There are too many parameters, and due to the errors depending on the parameters, the total error for the estimation of the total selenium increases.Article Citation - WoS: 31Citation - Scopus: 41Metadata-Based Heritage Sites Modeling With E-Learning Functionality(Elsevier Ltd., 2009) Styliadis, Athanasios D.; Akbaylar, İpek; Papadopoulou, Despoina A.; Hasanagas, Nikolaos D.; Roussa, Sotiria A.; Sexidis, Lazaros A.Nowadays, cultural heritage is under threat and danger (pollution, natural disasters, wars, etc.). In this domain, cultural heritage management (CHM) as the art, vocation and practice of managing cultural heritage resources and as a multi-discipline research area has a vital role. In recent years, the innovations, improvements and rapid advances in traditional and geographic (GIS) databases, design computing, digital architecture and archaeology, imaging sensors and scanners, computer modeling software, haptic equipments and e-learning technology, as well as the affordability and availability of many powerful graphics workstations make metadata and 3D modeling techniques for CHM with e-learning and haptic rendering (virtual reality) functionality feasible. This paper addresses the application research issue of incorporating metadata and modeling in a CHM case study and discusses the related e-learning functionality. So, in this article, a practical project is used to demonstrate the functionality and the performance of the proposed 3D modeling metadata based CHM methodology. In particular, the processing steps from image acquisition to the 3D geometric and semantic description of the Galerius Palace "Octagonon" (Thessaloniki, Greece) in a 3D digital environment are presented. Also, emphasis is put on documenting the new term 3D modeling metadata for CHM and on discussing as an open issue the concept personalized e-learning CHM scenarios. The proposed methodology has 10-2 modeling accuracy (i.e. 1% relative inaccuracy) and it is of interest for archaeology, architecture, virtual reality, e-learning, e-culture and virtual tourism.Article Citation - WoS: 20Citation - Scopus: 23Estimation of Suspended Sediment Concentration in Rivers Using Acoustic Methods(Springer Verlag, 2009) Elçi, Şebnem; Aydın, Ramazan; Work, Paul A.Acoustic Doppler current meters (ADV, ADCP, and ADP) are widely used in water systems to measure flow velocities and velocity profiles. Although these meters are designed for flow velocity measurements, they can also provide information defining the quantity of particulate matter in the water, after appropriate calibration. When an acoustic instrument is calibrated for a water system, no additional sensor is needed to measure suspended sediment concentration (SSC). This provides the simultaneous measurements of velocity and concentration required for most sediment transport studies. The performance of acoustic Doppler current meters for measuring SSC was investigated in different studies where signal-to-noise ratio (SNR) and suspended sediment concentration were related using different formulations. However, these studies were each limited to a single study site where neither the effect of particle size nor the effect of temperature was investigated. In this study, different parameters that affect the performance of an ADV for the prediction of SSC are investigated. In order to investigate the reliability of an ADV for SSC measurements in different environments, flow and SSC measurements were made in different streams located in the Aegean region of Turkey having different soil types. Soil samples were collected from all measuring stations and particle size analysis was conducted by mechanical means. Multivariate analysis was utilized to investigate the effect of soil type and water temperature on the measurements. Statistical analysis indicates that SNR readings ob tained from the ADV are affected by water temperature and particle size distribution of the soil, as expected, and a prediction model is presented relating SNR readings to SSC mea surements where both water temperature and sediment characteristics type are incorporated into the model. The coefficients of the suggested model were obtained using the multivariate anal ysis. Effect of high turbidity conditions on ADV performance was also investigated during and after rain events.Article Citation - WoS: 19Citation - Scopus: 22Optimization of the Associative Growth of Novel Yoghurt Cultures in the Production of Biomass, Ss-Galactosidase and Lactic Acid Using Response Surface Methodology(Elsevier Ltd., 2009) Tarı, Canan; Üstok, Fatma Işık; Harsa, Hayriye ŞebnemThe associative growth of Streptococcus thermophilus 95/2 (St 95/2) and Lactobacillus delbrueckii ssp. bulgaricus 77 (Lb 77) isolated from the Toros mountain region of Turkey was investigated with respect to lactic acid, biomass and β-galactosidase enzyme production using response surface methodology (RSM). The ratio (St 95/2:Lb 77) of the strains and media formulation had significant effect on all responses (p < 0.001). The predicted enzyme activity (2.14 U mL-1), lactic acid (22.50 g L-1) and biomass (7.11 g L-1) production at optimum conditions were very close to the actual experimental values (2.14 U mL-1, 22.94 g L-1 and 7.86 g L-1, respectively). The optimum conditions were to use these cultures in a ratio of 1.66:1.62 (St 95/2:Lb 77) in a medium containing whey (5%), corn steep liquor (4%), potassium phosphate (2%) and peptone (2%) at 43 °C for 8 h. The associative growth provided 6.4% and 39% more β-galactosidase activity and 8.73% and 44% more lactic acid compared with the results obtained using pure St 95/2 and Lb 77 strains, respectively.Article Citation - WoS: 15Citation - Scopus: 17Genetic Algorithm-Based Discharge Estimation at Sites Receiving Lateral Inflows(American Society of Civil Engineers (ASCE), 2009) Tayfur, Gökmen; Barbetta, Silvia; Moramarco, TommasoThe genetic algorithm (GA) technique is applied to obtain optimal parameter values of the standard rating curve model (RCM) for predicting, in real time, event-based flow discharge hydrographs at sites receiving significant lateral inflows. The standard RCM uses the information of discharge and effective cross-sectional flow area at an upstream station and effective cross-sectional flow area wave travel time later at a downstream station to predict the flow rate at this last site. The GA technique obtains the optimal parameter values of the model, here defined as the GA-RCM model, by minimizing the mean absolute error objective function. The GA-RCM model was tested to predict hydrographs at three different stations, located on the Upper Tiber River in central Italy. The wave travel times characterizing the three selected river branches are, on the average, 4, 8, and 12h. For each river reach, seven events were employed, four for the model parameters' calibration and three for model testing. The GA approach, employing 100 chromosomes in the initial gene pool, 75% crossover rate, 5% mutation rate, and 10,000 iterations, made the GA-RCM model successfully simulate the hydrographs observed at each downstream section closely capturing the trend, time to peak, and peak rates with, on the average, less than 5% error. The model performance was also tested against the standard RCM model, which uses, on the contrary to the GA-RCM model, different values for the model parameters and wave travel time for each event, thus, making the application of the standard RCM for real time discharge monitoring inhibited. The comparative results revealed that the RCM model improved its performance by using the GA technique in estimating parameters. The sensitivity analysis results revealed that at most two events would be sufficient for the GA-RCM model to obtain the optimal values of the model parameters. A lower peak hydrograph can also be employed in the calibration to predict a higher peak hydrograph. Similarly, a shorter travel time hydrograph can be used in GA to obtain optimal model parameters that can be used to simulate floods characterized by longer travel time. For its characteristics, the GA-RCM model is suitable for the monitoring of discharge in real time, at river sites where only water levels are observed.Article Citation - WoS: 28Citation - Scopus: 30Hydrochemical and Isotopic Composition of Tuzla Geothermal Field (canakkale-Turkey) and Its Environmental Impacts(Taylor and Francis Ltd., 2009) Baba, Alper; Yüce, Galip; Deniz, Ozan; Yasin, DidemTuzla is an active geothermal area located in northwestern Turkey, 80 km south of the city of Canakkale and 5 km from the Aegean Coast. Geothermal brine, deriving from this area, contains an abundance of NaCl and a water temperature of 173°C (T1 well at 814 m depth) is typically encountered. The aim of this study was to determine the hydrogeochemical properties of the geothermal brine using both chemical and isotopic data, and to investigate the origin of the geothermal brine in the Tuzla area and the environmental impacts of Tuzla Geothermal Field (TGF). Both geothermal brine and shallow groundwater in the area are of meteoric origin. Isotope results indicate that the hot saline waters (brine) in the Tuzla geothermal field originate from connate water along faults. As the saline water rises to the surface, it mixes with shallow groundwaters in various ratios. In addition, the high sodium (Na) and chloride (Cl) content in the Tuzla Stream, fed from the Tuzla geothermal brine during the dry season, cause an increase in sodium and chloride concentrations in the shallow groundwaters by infiltration into the aquifer. Moreover, salt accumulation on the surface is observed due to the uncontrolled artesian flow of geothermal brine, which adversely affects the salinity of shallow groundwater.Article Citation - WoS: 59Citation - Scopus: 59Interfacial and Structural Properties of Sputtered Hfo2 Layers(American Institute of Physics, 2009) Özyüzer, Gülnur Aygün; Yıldız, İlkerMagnetron sputtered HfO2 layers formed on a heated Si substrate were studied by spectroscopic ellipsometer (SE), x-ray diffraction (XRD), Fourier transform infrared (FTIR), and x-ray photoelectron spectroscopy (XPS) depth profiling techniques. The results show that the formation of a SiO x suboxide layer at the HfO2 /Si interface is unavoidable. The HfO2 thickness and suboxide formation are highly affected by the growth parameters such as sputtering power, O2 /Ar gas ratio during sputtering, sputtering time, and substrate temperature. XRD spectra show that the deposited film has (111) monoclinic phase of HfO2, which is also supported by FTIR spectra. The atomic concentration and chemical environment of Si, Hf, and O have been measured as a function of depth starting from the surface of the sample by XPS technique. It shows that HfO2 layers of a few nanometers are formed at the top surface. Below this thin layer, Si-Si bonds are detected just before the Si suboxide layer, and then the Si substrate is reached during the depth profiling by XPS. It is clearly understood that the highly reactive sputtered Hf atoms consume some of the oxygen atoms from the underlying SiO2 to form HfO2, leaving Si-Si bonds behind.