Browsing by Subject "Detection performance"
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Item Open Access Bağlamsal çıkarımla nesne sezimi(IEEE, 2009-04) Kalaycılar, Fırat; Aksoy, SelimBu bildiride, sezim başarımını arttırmada tek tek sezilmiş nesneler arasındaki bağlamsal ilişkilerden yararlanan bir nesne sezim sistemi tanıtılmaktadır. Bu çalışmadaki ilk katkı, iki boyutlu görüntü uzayında yapılan ölçümlerden olasılıksal çıkarım yaparak nesneler arası gerçek dünya ilişkilerinin (çevresinde, yakınında, üzerinde vb.) modellenmesidir. Diğer bir katkı ise, bireysel nesne etiketlerine ve nesne ikilileri arasındaki ilişkilere bağlı olan sahne olasılık fonksiyonunun enbüyütülerek, nesnelerin en son etiketlerinin atanmasıdır. En tutarlı sahne duzenleşimini bulmak için bu enbüyütme problemi, doğrusal eniyileme kullanılarak çözülmüştür. Ofis görüntüleri içeren iki farklı veri kümesinde yapılan deneylerde, gerçek dünya uzamsal ilişkileri bağlamsal bilgi olarak kullanıldığında genel sezim başarımının arttığı gözlemlenmiştir. In this paper, an object detection system that utilizes contextual relationships between individually detected objects to improve the overall detection performance is introduced. The first contribution in this work is the modelling of real world object relationships (beside, on, near etc.) that can be probabilistically inferred using measurements in the 2D image space. The other contribution is the assignment offinol lobe/s to the detected objects by maximizing a scene probability function that is defined jointly using both individual object labels and their pairwise spatial relationships. The most consistent scene configuration is obtained by solving the maximization problem using linear optimization. Experiments on two different office data sets showed that incorporation of the real world spatial relationships as can textual information improved the overall detection performance. ©2009 IEEE.Item Open Access Covariance matrix-based fire and flame detection method in video(Springer, 2011-09-17) Habiboğlu, Y. H.; Günay, O.; Çetin, A. EnisThis paper proposes a video-based fire detection system which uses color, spatial and temporal information. The system divides the video into spatio-temporal blocks and uses covariance-based features extracted from these blocks to detect fire. Feature vectors take advantage of both the spatial and the temporal characteristics of flame-colored regions. The extracted features are trained and tested using a support vector machine (SVM) classifier. The system does not use a background subtraction method to segment moving regions and can be used, to some extent, with non-stationary cameras. The computationally efficient method can process 320×240 video frames at around 20 frames per second in an ordinary PC with a dual core 2.2 GHz processor. In addition, it is shown to outperform a previous method in terms of detection performance.Item Open Access Optimal signaling and detector design for power constrained on-off keying systems in Neyman-Pearson framework(IEEE, 2011) Dulek, Berkan; Gezici, SinanOptimal stochastic signaling and detector design are studied for power constrained on-off keying systems in the presence of additive multimodal channel noise under the Neyman-Pearson (NP) framework. The problem of jointly designing the signaling scheme and the decision rule is addressed in order to maximize the probability of detection without violating the constraints on the probability of false alarm and the average transmit power. Based on a theoretical analysis, it is shown that the optimal solution can be obtained by employing randomization between at most two signal values for the on-signal (symbol 1) and using the corresponding NP-type likelihood ratio test at the receiver. As a result, the optimal parameters can be computed over a significantly reduced optimization space instead of an infinite set of functions using global optimization techniques. Finally, a detection example is provided to illustrate how stochastic signaling can help improve detection performance over various optimal and sub-optimal signaling schemes. © 2011 IEEE.Item Open Access Range resolution improvement in passive bistatic radars using nested FM channels and least squares approach(SPIE, 2015) Arslan, Musa Tunç; Tofighi, Muhammad; Sevimli, Rasim Akın; Çetin, A. EnisOne of the main disadvantages of using commercial broadcasts in a Passive Bistatic Radar (PBR) system is the range resolution. Using multiple broadcast channels to improve the radar performance is offered as a solution to this problem. However, it suffers from detection performance due to the side-lobes that matched filter creates for using multiple channels. In this article, we introduce a deconvolution algorithm to suppress the side-lobes. The two-dimensional matched filter output of a PBR is further analyzed as a deconvolution problem. The deconvolution algorithm is based on making successive projections onto the hyperplanes representing the time delay of a target. Resulting iterative deconvolution algorithm is globally convergent because all constraint sets are closed and convex. Simulation results in an FM based PBR system are presented.Item Open Access A smartphone based surface plasmon resonance imaging (SPRi) platform for on-site biodetection(Elsevier, 2017) Guner, H.; Ozgur, E.; Kokturk, G.; Celik, M.; Esen, E.; Topal, A. E.; Ayas, S.; Uludag, Y.; Elbuken, C.; Dana, A.We demonstrate a surface plasmon resonance imaging platform integrated with a smartphone to be used in the field with high-throughput biodetection. Inexpensive and disposable SPR substrates are produced by metal coating of commercial Blu-ray discs. A compact imaging apparatus is fabricated using a 3D printer which allows taking SPR measurements from more than 20.000 individual pixels. Real-time bulk refractive index change measurements yield noise equivalent refractive index changes as low as 4.12 × 10−5 RIU which is comparable with the detection performance of commercial instruments. As a demonstration of a biological assay, we have shown capture of mouse IgG antibodies by immobilized layer of rabbit anti-mouse (RAM) IgG antibody with nanomolar level limit of detection. Our approach in miniaturization of SPR biosensing in a cost-effective manner could enable realization of portable SPR measurement systems and kits for point-of-care applications.Item Open Access Sparse delay-Doppler image reconstruction under off-grid problem(IEEE, 2014-06) Teke, Oğuzhan; Gürbüz, A. C.; Arıkan, OrhanPulse-Doppler radar has been successfully applied to surveillance and tracking of both moving and stationary targets. For efficient processing of radar returns, delay-Doppler plane is discretized and FFT techniques are employed to compute matched filter output on this discrete grid. However, for targets whose delay-Doppler values do not coincide with the computation grid, the detection performance degrades considerably. Especially for detecting strong and closely spaced targets this causes miss detections and false alarms. Although compressive sensing based techniques provide sparse and high resolution results at sub-Nyquist sampling rates, straightforward application of these techniques is significantly more sensitive to the off-grid problem. Here a novel and OMP based sparse reconstruction technique with parameter perturbation, named as PPOMP, is proposed for robust delay-Doppler radar processing even under the off-grid case. In the proposed technique, the selected dictionary parameters are perturbed towards directions to decrease the orthogonal residual norm. A new performance metric based on Kull-back-Leibler Divergence (KLD) is proposed to better characterize the error between actual and reconstructed parameter spaces. © 2014 IEEE.Item Open Access Stochastic resonance in binary composite hypothesis-testing problems in the Neyman-Pearson framework(Elsevier, 2012-02-20) Bayram, S.; Gezici, SinanPerformance of some suboptimal detectors can be enhanced by adding independent noise to their inputs via the stochastic resonance (SR) effect. In this paper, the effects of SR are studied for binary composite hypothesis-testing problems. A Neyman-Pearson framework is considered, and the maximization of detection performance under a constraint on the maximum probability of false-alarm is studied. The detection performance is quantified in terms of the sum, the minimum, and the maximum of the detection probabilities corresponding to possible parameter values under the alternative hypothesis. Sufficient conditions under which detection performance can or cannot be improved are derived for each case. Also, statistical characterization of optimal additive noise is provided, and the resulting false-alarm probabilities and bounds on detection performance are investigated. In addition, optimization theoretic approaches to obtaining the probability distribution of optimal additive noise are discussed. Finally, a detection example is presented to investigate the theoretical results.Item Open Access Tarım alanlarında doğrusal odunsu bitki gruplarının otomatik sezimi(IEEE, 2009-04) Akçay, H. Gökhan; Aksoy, SelimTarım alanlarının otomatik haritalanması ve izlenmesi önemli bir araştırma konusudur. Bu bildiride, çok yüksek çözünürlükteki uydu görüntülerinde doğrusal şeritler halindeki odunsu bitki gruplarının otomatik olarak sezilmesi için bir yöntem sunulmaktadır. Yötem, öznitelik çıkarma ve karar verme adımlarını sıradüzensel bir şekilde uygulayarak spektral, doku ve nesne şekil bilgisini bir arada kullanmaktadır. Farklı özellikte alanlardan elde edilen Quickbird görüntüleri üzerinde yapılan deneyler tatmin edici başarım göstermektedir. Automatic mapping and monitoring of agricultural landscapes is an important research problem. In this paper, we present a method for automatic mapping of linear strips of woody vegetation in very high-resolution imagery. The method combines spectral, textural and object shape information using hierarchical feature extraction and decision making steps. Experiments on Quickbird imagery from different sites show promising detection performance. ©2009 IEEE.Item Open Access An underwater acoustic communications scheme with inherent scale diversity for multiple users(IEEE, 2013) Zhou, M.; Zhang J.J.; Papandreou-Suppappola, A.; Duman, Tolga M.Wideband underwater acoustic communication channels can cause undesirable multipath and Doppler scaling distortions to propagating acoustic signals. In this paper, we propose to exploit a time-scale canonical representation for wideband time-varying channels to achieve joint multipath-scale diversity. We design a signaling scheme with hyperbolic time-frequency signatures that is matched to the underwater acoustic environment to achieve scale diversity. The signaling scheme, combined with code-division multiple-access, is extended to multiple user transmission to improve multiuser detection performance, as demonstrated with simulations. © 2013 MTS.