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Item Open Access An adaptive speckle suppression filter for medical ultrasound imaging(Institute of Electrical and Electronics Engineers, 1995-06) Karaman, M.; Kutay, M. A.; Bozdagi, G.An adaptive smoothing technique for speckle suppression in medical B-scan ultrasonic imaging is presented. The technique is based on filtering with appropriately shaped and sized local kernels. For each image pixel, a filtering kernel, which fits to the local homogeneous region containing the processed pixel, is obtained through a local statistics based region growing technique. The performance of the proposed filter has been tested on the phantom and tissue images. The results show that the filter effectively reduces the speckle while preserving the resolvable details. The simulation results are presented in a comparative way with two existing speckle suppression methods.Item Restricted Afşin-Elbistan Termik Santralinin insan sağlığına ve doğaya olan etkileri(Bilkent University, 2020) Baltacı, Berk; Er, Erhan; Eraslan, Nur; Gezay, Mina; Turunç, FurkanAfşin-Elbistan A Termik Santrali 1984 yılında Çoğulhan mahallesinde kurulmuştur. 2006 yılında ise termik santralin B ünitesinin yapım aşaması tamamlanmıştır. Bugün her iki ünite de çalışmaya devam etmektedir. Araştırmada A santralinin çevre ve insan sağlığı üzerindeki etkileri incelenmiştir. Santral bacalarından NO2 ve SO2 gazlarının salınımının çevreye ve insan sağlığına etkileri mevcuttur. Kurulduğu günden bu yana termik santral Çoğulhan bölgesinde yaşayan insanlarda görülen çeşitli sağlık sorunlarıyla ilişkilendirilmiştir. Araştırmada ise bu sağlık sorunları istatistiklere dayanarak ortaya konulmuştur ve alınan önlemler ele alınmıştır.Item Open Access Analysis of the generation of amplitude-squeezed light with Gaussian-beam degenerate optical parametric amplifiers(OSA Publishing, 2001-06) Köprülü, K. G.; Aytür, O.We investigate the generation of amplitude-squeezed states with degenerate optical parametric amplifiers that are pumped by focused Gaussian beams. We present a model that facilitates the calculation of the squeezing level for an experimentally realistic cofiguration in which there is a Gaussian input signal beam that has the same confocal parameter and waist location as the Gaussian pump beam, with no restriction on the interaction length-to-confocal parameter ratio. We show that the 3-dB squeezing limit that was thought to be imposed by the Gaussian pump profile can be exceeded in the (previously uninvestigated) tight-focusing regime. We find the maximum possible amplitude squeezing in this regime to be 4.65 dB. However, it is possible to increase the squeezing level further by spatially filtering the tails of the output signal beam, resulting in squeezing levels in excess of 10 dB. (C) 2001 Optical Society of America.Item Open Access Automatic performance evaluation of Web search engines(Elsevier, 2004) Can, F.; Nuray, R.; Sevdik, A. B.Measuring the information retrieval effectiveness of World Wide Web search engines is costly because of human relevance judgments involved. However, both for business enterprises and people it is important to know the most effective Web search engines, since such search engines help their users find higher number of relevant Web pages with less effort. Furthermore, this information can be used for several practical purposes. In this study we introduce automatic Web search engine evaluation method as an efficient and effective assessment tool of such systems. The experiments based on eight Web search engines, 25 queries, and binary user relevance judgments show that our method provides results consistent with human-based evaluations. It is shown that the observed consistencies are statistically significant. This indicates that the new method can be successfully used in the evaluation of Web search engines. © 2003 Elsevier Ltd. All rights reserved.Item Restricted Item Open Access Bandwidth selection for kernel density estimation using fourier domain constraints(Institution of Engineering and Technology, 2016) Suhre, A.; Arıkan, Orhan; Çetin, A. EnisKernel density estimation (KDE) is widely-used for non-parametric estimation of an underlying density from data. The performance of KDE is mainly dependent on the bandwidth parameter of the kernel. This study presents an alternative method of estimating the bandwidth by incorporating sparsity priors in the Fourier transform domain. By using cross-validation (CV) together with an l1 constraint, the proposed method significantly reduces the under-smoothing effect of traditional CV methods. A solution for all free parameters in the minimisation is proposed, such that the algorithm does not need any additional parameter tuning. Simulation results indicate that the new approach is able to outperform classical and more recent approaches over a set of distributions of interest.Item Open Access ConceptMap: mining noisy web data for concept learning(Springer, 2014-09) Gölge, Eren; Duygulu, PınarWe attack the problem of learning concepts automatically from noisy Web image search results. The idea is based on discovering common characteristics shared among subsets of images by posing a method that is able to organise the data while eliminating irrelevant instances. We propose a novel clustering and outlier detection method, namely Concept Map (CMAP). Given an image collection returned for a concept query, CMAP provides clusters pruned from outliers. Each cluster is used to train a model representing a different characteristics of the concept. The proposed method outperforms the state-of-the-art studies on the task of learning from noisy web data for low-level attributes, as well as high level object categories. It is also competitive with the supervised methods in learning scene concepts. Moreover, results on naming faces support the generalisation capability of the CMAP framework to different domains. CMAP is capable to work at large scale with no supervision through exploiting the available sources. © 2014 Springer International Publishing.Item Open Access Determinants of choosing withdrawal over modern contraceptive methods in Turkey(Taylor & Francis, 2008) Cindoglu, D.; Sirkeci, I.; Sirkeci, R. F.Objectives The determinants of the use of withdrawal in Turkey are examined using a multinomial logistic model. Methods Data were drawn from a nation-wide population-based cross-sectional study, the Turkish Demographic Health Surveys that took place in 1998 and 2003. Detailed interviews were conducted with 8576 women aged 15-49 and analysed using SPSS. Results Contextual, cultural and demographic characteristics define women's choice of withdrawal over modern methods. Socio-economic status, education, employment status, and past fertility behaviour are among key determinants. First-ever used contraception method has a very strong impact on later choices. Urban women, the more educated, those with better socioeconomic status, and those living in less crowded households resort less to withdrawal. Experience and empowerment positively linked to modern contraceptive use among women in Turkey. Conclusions The use of contraceptive methods in Turkey differs greatly. Empowerment of women in terms of better socioeconomic status, better education, modern and liberal attitudes towards women and family planning seem to reduce withdrawal use as the main method of contraception. The results suggest the need for education (particularly targeting young women and couples), information and provision of modern contraceptive services particularly for disadvantaged groups.Item Open Access Differences in the accumulation and distribution profile of heavy metals and metalloid between male and female crayfish (Astacus leptodactylus)(2013) Tunca, E.; Ucuncu, E.; Ozkan, A.D.; Ulger, Z.E.; Cansizoǧlu, A.E.; Tekinay, T.Concentrations of selected heavy metals and a metalloid were measured by ICP-MS in crayfish (Astacus leptodactylus) collected from Lake Hirfanli, Turkey. Aluminum (Al), chromium (52Cr, 53Cr), copper ( 63Cu, 65Cu), manganese (Mn), nickel (Ni) and arsenic (As) were measured in the exoskeleton, gills, hepatopancreas and abdominal muscle tissues of 60 crayfish of both genders. With the exception of Al, differences were determined between male and female cohorts for the accumulation trends of the above-mentioned elements in the four tissues. It was also noted that the accumulation rates of Ni and As were significantly lower in gill tissue of females compared to males and no significant difference was observed for Cu isotopes in female crayfish. Cluster Analysis (CA) recovered similar results for both genders, with links between accumulations of Ni and As being notable. Accumulation models were described separately for male and female crayfish using regression analysis, and are presented for models where R2 > 0.85. © 2013 Springer Science+Business Media New York.Item Open Access Effects of daylight savings time changes on stock market volatility(Sage Publications, Inc., 2010) Berument, Hakan; Dogan, N.; Onar, BaharThe presence of daylight savings time effects on stock returns and on stock volatility was investigated using an EGARCH specification to model the conditional variance. The evidence gathered from the major United States stock markets for the period between 1967 and 2007 did not support the existence of the daylight savings time effect on stock returns or on volatility. Returns on the first business day following daylight savings time changes were not lower nor was the volatility higher, as would be expected if there were an effect.Item Open Access Information retrieval on Turkish texts(John Wiley & Sons, Inc., 2008-02) Can, F.; Kocberber, S.; Balcik, E.; Kaynak, C.; Ocalan, H. C.; Vursavas, O. M.In this study, we investigate information retrieval (IR) on Turkish texts using a large-scale test collection that contains 408,305 documents and 72 ad hoc queries. We examine the effects of several stemming options and query-document matching functions on retrieval performance. We show that a simple word truncation approach, a word truncation approach that uses language-dependent corpus statistics, and an elaborate lemmatizer-based stemmer provide similar retrieval effectiveness in Turkish IR. We investigate the effects of a range of search conditions on the retrieval performance; these include scalability issues, query and document length effects, and the use of stop-word list in indexing. © 2007 Wiley Periodicals, Inc.Item Restricted Item Open Access On the Hajek projection for truncated and censored data(Scientific Publishers, 1993) Gürler, Ü.; Wang, J.-L.Large sample properties of the product-limit estimators for truncated or censored data are usually achieved via the empirical cumulative hazard function estimators. Hajek projection of the empirical cumulative hazard function estimator is derived for truncated data and expressed for censored data. It turns out that both projections are asymptotically ni-equivalent but not equal to the respective influence curves. Weak convergences of the empirical cumulative hazard processes are deduced accordingly.Item Open Access Optimal filtering in fractional Fourier domains(IEEE, 1995) Kutay, M. Alper; Onural, Levent; Özaktaş Haldun M.; Arıkan, OrhanThe ordinary Fourier transform is suited best for analysis and processing of time-invariant signals and systems. When we are dealing with time-varying signals and systems, filtering in fractional Fourier domains might allow us to estimate signals with smaller minimum-mean-square error (MSE). We derive the optimal fractional Fourier domain filter that minimizes the MSE for given non-stationary signal and noise statistics, and time-varying distortion kernel. We present an example for which the MSE is reduced by a factor of 50 as a result of filtering in the fractional Fourier domain, as compared to filtering in the conventional Fourier or time domains. We also discuss how the fractional Fourier transformation can be computed in O(N log N) time, so that the improvement in performance is achieved with little or no increase in computational complexity.Item Open Access Ordering translation templates by assigning confidence factors(Springer Verlag, 1998) Öz, Zeynep; Çiçekli, İlyasTTL (Translation Template Learner) algorithm learns lexical level correspondences between two translation examples by using analogical reasoning. The sentences used as translation examples have similar and different parts in the source language which must correspond to the similar and different parts in the target language. Therefore these correspondences are learned as translation templates. The learned translation templates are used in the translation of other sentences. However, we need to assign confidence factors to these translation templates to order translation results with respect to previously assigned confidence factors. This paper proposes a method for assigning confidence factors to translation templates learned by the TTL algorithm. Training data is used for collecting statistical information that will be used in confidence factor assignment process. In this process, each template is assigned a confidence factor according to the statistical information obtained from training data. Furthermore, some template combinations are also assigned confidence factors in order to eliminate certain combinations resulting bad translation. © Springer-Verlag Berlin Heidelberg 1998.Item Open Access Pre-service elementary teachers' understandings of graphs(Eurasia Publishing House, 2011) Alacaci, C.; Lewis, S.; O'Brien G. E.; Jiang, Z.Choosing graphs to display quantitative information is a component of graph sense. An important aspect of pre-service elementary teachers' content knowledge; ability to choose appropriate graphs in applied contexts is investigated in this study. They were given three scenarios followed by four graphs representing the same quantitative data. They rated the appropriateness of each graph and indicated the reasons for their choices. Results showed that pre-service elementary teachers can recognize the situations appropriate for bar graphs, pie charts, and line graphs and match the suitable graphs to these situations. However, they had limited knowledge of scatterplots and did not recognize the situations for which they are typically used. Implications of findings for elementary pre-service teacher education programs are drawn.Item Open Access Snippet based trajectory statistics histograms for assistive technologies(Springer, 2014-09) İscen, Ahmet; Wang Y.; Duygulu, Pınar; Hauptmann, A.Due to increasing hospital costs and traveling time, more and more patients decide to use medical devices at home without traveling to the hospital. However, these devices are not always very straight-forward for usage, and the recent reports show that there are many injuries and even deaths caused by the wrong use of these devices. Since human supervision during every usage is impractical, there is a need for computer vision systems that would recognize actions and detect if the patient has done something wrong. In this paper, we propose to use Snippet Based Trajectory Statistics Histograms descriptor to recognize actions in two medical device usage problems; inhaler device usage and infusion pump usage. Snippet Based Trajectory Statistics Histograms encodes the motion and position statistics of densely extracted trajectories from a video. Our experiments show that by using Snippet Based Trajectory Statistics Histograms technique, we improve the overall performance for both tasks. Additionally, this method does not require heavy computation, and is suitable for real-time systems. © Springer International Publishing Switzerland 2015.Item Open Access Soccer and stock market risk: empirical evidence from the Istanbul stock exchange(Sage Publications, Inc., 2013) Berument, Hakan; Ceylan, N. B.There is an emerging but important literature on the effects of sport events such as soccer on stock market returns. After a soccer team's win, agents discount future events more favorably and increase risk tolerance. Similarly, after a loss, risk tolerance decreases. This paper directly assesses risk tolerance after a sports event by using daily data from the three major soccer teams in Turkey (Beşiktaş, Fenerbahçe and Galatasaray). Results provide evidence that risk tolerance increases after a win, but similar patterns were not found after a loss. © Psychological Reports 2013.Item Open Access Synthetic TEC mapping with ordinary and universal kriging(IEEE, 2007-06) Sayın, I.; Arıkan, F.; Arıkan, OrhanSpatiotemporal variations in the ionosphere affects the HF and satellite communications and navigation systems. Total Electron Content (TEC) is an important parameter since it can be used to analyze the spatial and temporal variability of the ionosphere. In this study, the performance of the two widely used Kriging algorithms, namely Ordinary Kriging (OrK) and Universal Kriging (UnK), is compared over the synthetic data set. In order to represent various ionospheric states, such as quiet and disturbed days, spatially correlated residual synthetic TEC data with different variances is generated and added to trend functions. Synthetic data sampled with various type of sampling patterns and for a wide range of sampling point numbers. It is observed that for small sampling numbers and with higher variability, OrK gives smaller errors. As the sample number increases, UnK errors decrease faster. For smaller variances in the synthetic surfaces, UnK gives better results. For increasing variance and decreasing range values, usually, the errors increase for both OrK and UnK. © 2007 IEEE.Item Restricted Türk yazarının halklaşması(1967)