Bilgisayar Mühendisliği Bölümü Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12469/45

Browse

Now showing 1 - 18 of 18

Citation - WoS: 1
Citation - Scopus: 2
A Bayesian Approach To Developing a Strategic Early Warning System for the French Milk Market
(Halmstad University, 2017) Bisson, Christophe; Gürpınar, Furkan
A new approach is provided in our paper for creating a strategic early warning system allowing the estimation of the future state of the milk market as scenarios. This is in line with the recent call from the EU commission for tools that help to better address such a highly volatile market. We applied different multivariate time series regression and Bayesian networks on a pre-determined map of relations between macro-economic indicators. The evaluation of our findings with root mean square error (RMSE) performance score enhances the robustness of the prediction model constructed. Our model could be used by competitive intelligence teams to obtain sharper scenarios, leading companies and public organisations to better anticipate market changes and make more robust decisions.
Citation - WoS: 5
Citation - Scopus: 7
Biclustering Expression Data Based on Expanding Localized Substructures
(Springer-Verlag Berlin, 2009) Erten, Cesim; Sözdinler, Melih
Biclustering gene expression data is the problem of extracting submatrices of genes and conditions exhibiting significant correlation across both the rows and the columns of a data matrix of expression values. We provide a method LEB (Localize-and-Extract Biclusters) which reduces the search space into local neighborhoods within the matrix by first localizing correlated structures. The localization procedure takes its roots from effective use of graph-theoretical methods applied to problems exhibiting a similar structure to that of biclustering. Once interesting structures are localized the search space reduces to small neighborhoods and the biclusters are extracted from these localities. We evaluate the effectiveness of our method with extensive experiments both using artificial and real datasets.
Citation - WoS: 1
Citation - Scopus: 4
Channel Estimation in Underwater Cooperative Ofdm System With Amplify-And Relaying
(IEEE, 2012) Şenol, Habib; Panayırcı, Erdal; Erdoğan, Mustafa; Uysal, Murat
This paper is concerned with a challenging problem of channel estimation for amplify-and-forward cooperative relay based orthogonal frequency division multiplexing (OFDM) systems in the presence of sparse underwater acoustic channels and of the correlative non-Gaussian noise. We exploit the sparse structure of the channel impulse response to improve the performance of the channel estimation algorithm due to the reduced number of taps to be estimated. The resulting novel algorithm initially estimates the overall sparse channel taps from the source to the destination as well as their locations using the matching pursuit (MP) approach. The correlated non-Gaussian effective noise is modeled as a Gaussian mixture. Based on the Gaussian mixture model an efficient and low complexity algorithm is developed based on the combinations of the MP and the space-alternating generalized expectation-maximization (SAGE) technique to improve the estimates of the channel taps and their location as well as the noise distribution parameters in an iterative way. The proposed SAGE algorithm is designed in such a way that by choosing the admissible hidden data properly on which the SAGE algorithm relies a subset of parameters is updated for analytical tractability and the remaining parameters for faster convergence Computer simulations show that underwater acoustic (UWA) channel is estimated very effectively and the proposed algorithm has excellent symbol error rate and channel estimation performance.
Citation - WoS: 13
Characterization of Mps Capped Cds Quantum Dots and Formation Self-Assembled Quantum Dots Thin Films on a Glass Substrate
(Natl Inst R&D Materials Physics, 2011) Koç, Kenan; Tepehan, Fatma Zehra; Tepehan, Galip Gültekin
Colloidal powdered and thin film forms of MPS capped CdS quantum dots have been produced by combination of colloidal chemistry and sol-gel method. Nanoparticles were self-assembled directly on a glass substrate using spin coating method without introducing any matrix. Colloidal powdered and thin film forms were characterised by absorbance photolimunescence XRD FT-IR HRTEM and AFM measurements. The HRTEM images give a grain size of 2.5-3.0 nm and this is in agreement with the values found in the absorbance and XRD measurement. Average size of the quantum dots increase with increasing of heat treatment temperature due to Oswald ripening.
Citation - Scopus: 11
Competitive Intelligence and Information Technology Adoption of Smes in Turkey: Diagnosing Current Performance and Identifying Barriers
(Halmstad University, 2013) Wright, Sheila; Bisson, Christophe; Duffy, Alistair P.
The need for SMEs to behave in a more concise and coherent competitive fashion is well recognised. This study reports on an empirical study of SMEs in Turkey. Their responses were applied to a behavioural and information technology adoption framework which enabled the identification of areas where changes would be required for these firms to begin operating at a higher level of competence. The findings revealed significant scope for improvements on all strands of the diagnostic framework: attitude gathering location technology support IT systems support and finally use of intelligence-based output by decision-makers. Through free form responses it was also possible to identify barrier to higher level adoption and performance inhibiters which were subsequently categorised and assessed for significance.
Citation - WoS: 10
Citation - Scopus: 12
Contraction Blockers for Graphs With Forbidden Induced Paths
(Springer-Verlag Berlin, 2015) Diner, Öznur Yaşar; Paulusma, Daniel; Picouleau, Christophe; Ries, Bernard
We consider the following problem: can a certain graph parameter of some given graph be reduced by at least d for some integer d via at most k edge contractions for some given integer k? We examine three graph parameters: the chromatic number clique number and independence number. For each of these graph parameters we show that when d is part of the input this problem is polynomial-time solvable on P-4-free graphs and NP-complete as well as W[1]-hard with parameter d for split graphs. As split graphs form a subclass of P-5-free graphs both results together give a complete complexity classification for P-l-free graphs. The W[1]-hardness result implies that it is unlikely that the problem is fixed-parameter tractable for split graphs with parameter d. But we do show on the positive side that the problem is polynomial-time solvable for each parameter on split graphs if d is fixed i.e. not part of the input. We also initiate a study into other subclasses of perfect graphs namely cobipartite graphs and interval graphs.
Citation - WoS: 1
Citation - Scopus: 2
Data-Aided Autoregressive Sparse Channel Tracking for Ofdm Systems
(IEEE, 2016) Buyuksar, Ayse Betul; Şenol, Habib; Erküçük, Serhat; Cirpan, Hakan Ali
In order to meet future communication system requirements channel estimation over fast fading and frequency selective channels is crucial. In this paper Space Alternated Generalized Expectation Maximization Maximum a Posteriori (SAGE-MAP) based channel estimation algorithm is proposed for Orthogonal Frequency Division Multiplexing (OFDM) systems for Autoregressive (AR) modeled time-varying sparse channels. Also an initialization algorithm has been developed from the widely used sparse approximation algorithm Orthogonal Matching Pursuit (OMP) since the performance of SAGE algorithm strictly depends on initialization. The results show that multipath delay positions can be tracked successfully for every time instant using the proposed SAGE-MAP based approach.
Citation - WoS: 1
Citation - Scopus: 3
Distributed Estimation With Channel Estimation Error Over Orthogonal Fading Channels
(IEEE, 2007) Şenol, Habib; Tepedelenlioğlu, Cihan
We study distributed estimation of a source corrupted by an additive Gaussian noise and observed by sensors which are connected to a fusion center with unknown orthogonal (parallel) flat Rayleigh fading channels. The fading communication channels are estimated with training. Subsequently source estimation given the channel estimates and transmitted sensor observations is performed. We consider a setting where the estimated channels are fed-back to the sensors for optimal power allocation which leads to a threshold behavior of sensors with bad channels being unused (inactive). We also show that at least half of the total power should be used for training. Simulation results corroborate our analytical findings.
Citation - WoS: 1
Citation - Scopus: 1
The Effects of Higher-Order Approximations in a Fluid-Filled Elastic Tube With Stenosis
(Verlag der Zeitschrift fur Naturforschung, 2006) Demiray, Hilmi
Treating arteries as thin-walled prestressed elastic tubes with a narrowing (stenosis) and blood as an inviscid fluid we study the propagation of weakly nonlinear waves in such a fluid-filled elastic tube by employing the reductive perturbation method in the long wave approximation. It is shown that the evolution equation of the first-order term in the perturbation expansion may be described by the conventional Korteweg-de Vries (KdV) equation. The evolution equation for the second-order term is found to be the linearized KdV equation with a nonhomogeneous term which contains the contribution of the stenosis. A progressive wave type solution is sought for the evolution equation and it is observed that the wave speed is variable which results from the stenosis. We study the variation of the wave speed with the distance parameter ? for various amplitude values of the stenosis. It is observed that near the center of the stenosis the wave speed decreases with increasing stenosis amplitude. However sufficiently far from the center of the stenosis stenosis amplitude becomes negligibly small. © 2006 Verlag der Zeitschrift für Naturforschung.
Citation - Scopus: 5
Fast Multi-View Face Trackingwith Pose Estimation
(2008) Meynet, Julien; Arsan, Taner; Mota, Javier Cruz; Thiran, Jean-Philippe Philippe H.
In this paper a fast and an effective multi-view face tracking algorithm with head pose estimation is introduced. For modeling the face pose we employ a tree of boosted classifiers built using either Haar-like filters or Gauss filters. A first classifier extracts faces of any pose from the background. Then more specific classifiers discriminate between different poses. The tree of classifiers is trained by hierarchically sub-sampling the pose space. Finally Condensation algorithm is used for tracking the faces. Experiments show large improvements in terms of detection rate and processing speed compared to state-of-the-art algorithms.
Citation - WoS: 6
Citation - Scopus: 8
Gpu Accelerated Molecular Docking Simulation With Genetic Algorithms
(Springer International Publishing Ag, 2016) Altuntaş, Serkan; Bozkuş, Zeki; Fraguela, Basilio B.
Receptor-Ligand Molecular Docking is a very computationally expensive process used to predict possible drug candidates for many diseases. A faster docking technique would help life scientists to discover better therapeutics with less effort and time. The requirement of long execution times may mean using a less accurate evaluation of drug candidates potentially increasing the number of false-positive solutions which require expensive chemical and biological procedures to be discarded. Thus the development of fast and accurate enough docking algorithms greatly reduces wasted drug development resources helping life scientists discover better therapeutics with less effort and time. In this article we present the GPU-based acceleration of our recently developed molecular docking code. We focus on offloading the most computationally intensive part of any docking simulation which is the genetic algorithm to accelerators as it is very well suited to them. We show how the main functions of the genetic algorithm can be mapped to the GPU. The GPU-accelerated system achieves a speedup of around similar to 14x with respect to a single CPU core. This makes it very productive to use GPU for small molecule docking cases.
Citation - WoS: 19
Citation - Scopus: 19
Influence of Ph on the Optical and Structural Properties of Spin Coated Ceo2-Tio2 Thin Films Prepared by Sol-Gel Process
(Elsevier Science Bv, 2007) Ghodsi, Farhad E.; Tepehan, Fatma Zehra; Tepehan, Galip Gültekin
Optical and structural properties of mixed CeO2-TiO2 thin films have been investigated by varying the pH of the coating sol. The films were prepared by sol-gel process using spin-coating technique with a spin speed of 2500 rpm. The optical and structural properties of films were examined by a spectrophotometer AFM and XRD. Optical constants and thickness of the CeO2-TiO2 thin films have been determined with respect to the pH of the coating bath before deposition. The refractive index at 550 nm wavelength increases from 1.49 to 1.60 when the pH of the sol increases from 2.22 to 2.92. The thickness increases from 46.6 nm to 96.1 nm in this pH range. The XRD measurements show that the films have amorphous structure. The AFM analysis shows that the pH of sol prior to deposition changes the uniformity and porosity of the films. (C) 2007 Elsevier B.V. All rights reserved.
Citation - WoS: 11
Citation - Scopus: 13
Lsb Image Steganography Based on Blocks Matrix Determinant Method
(KSII-KOR SOC Internet Information, 2019) Shehzad, Danish; Dağ, Tamer
Image steganography is one of the key types of steganography where a message to be sent is hidden inside the cover image. The most commonly used techniques for image steganography rely on LSB steganography. In this paper, a novel image steganography technique based on blocks matrix determinant method is proposed. Under this method, a cover image is divided into blocks of size 2 x 2 pixels and the determinant of each block is calculated. The comparison of the determinant values and corresponding data bits yields a delicate way for the embedment of data bits. The main aim of the proposed technique is to ensure concealment of secret data inside an image without affecting the cover image quality. When the proposed steganography method is compared with other existing LSB steganography methods, it is observed that it not only provides higher PSNR, lower MSE but also guarantees better quality of the stego image.
Machine Learning Approaches for Predicting Protein Complex Similarity
(Mary Ann Liebert Inc Publ, 2017) Farhoodi, Roshanak; Akbal-Delibas, Bahar; Haspel, Nurit
Discriminating native-like structures from false positives with high accuracy is one of the biggest challenges in protein-protein docking. While there is an agreement on the existence of a relationship between various favorable intermolecular interactions (e.g. Van der Waals electrostatic and desolvation forces) and the similarity of a conformation to its native structure the precise nature of this relationship is not known. Existing protein-protein docking methods typically formulate this relationship as a weighted sum of selected terms and calibrate their weights by using a training set to evaluate and rank candidate complexes. Despite improvements in the predictive power of recent docking methods producing a large number of false positives by even state-of-the-art methods often leads to failure in predicting the correct binding of many complexes. With the aid of machine learning methods we tested several approaches that not only rank candidate structures relative to each other but also predict how similar each candidate is to the native conformation. We trained a two-layer neural network a multilayer neural network and a network of Restricted Boltzmann Machines against extensive data sets of unbound complexes generated by RosettaDock and PyDock. We validated these methods with a set of refinement candidate structures. We were able to predict the root mean squared deviations (RMSDs) of protein complexes with a very small often less than 1.5 angstrom error margin when trained with structures that have RMSD values of up to 7 angstrom. In our most recent experiments with the protein samples having RMSD values up to 27 angstrom the average prediction error was still relatively small attesting to the potential of our approach in predicting the correct binding of protein-protein complexes.
Citation - WoS: 1
Citation - Scopus: 3
Outage Diversity for Distributed Estimation Over Parallel Fading Channels
(IEEE, 2008) Bai, Kai; Tepedelenlioğlu, Cihan; Şenol, Habib
In this paper we study the outage diversity in distributed estimation over parallel fading channels. We find tight upper and lower bounds on the diversity order and show that they are arbitrarily close under certain conditions. Our results show that the diversity order does not always equal to the number of sensors but also depends on sensing quality of the sensors.
Citation - WoS: 3
Performance Improvement of Threshold Based Audio Steganography Using Parallel Computation
(Science & Information SAI Organization Ltd, 2016) Shoaib, Muhammad; Shehzad, Danish; Umar, Arif Iqbal; Khan, Zakir; Dağ, Tamer; Ul Amin, Noor
Audio steganography is used to hide secret information inside audio signal for the secure and reliable transfer of information. Various steganography techniques have been proposed and implemented to ensure adequate security level. The existing techniques either focus on the payload or security but none of them has ensured both security and payload at same time. Data Dependency in existing solution was reluctant for the execution of steganography mechanism serially. The audio data and secret data pre-processing were done and existing techniques were experimentally tested in Matlab that ensured the existence of problem in efficient execution. The efficient least significant bit steganography scheme removed the pipelining hazard and calculated Steganography parallel on distributed memory systems. This scheme ensures security focuses on payload along with provisioning of efficient solution. The result depicts that it not only ensures adequate security level but also provides better and efficient solution.
Citation - WoS: 6
Citation - Scopus: 6
Slow Release of Trapped Homopolymers From a Swelling Polymeric Gel: a Fluorescence Study
(Taylor & Francis Inc, 2008) Erdoğan, Matem; Yağcı, Yusuf; Pekcan, Önder
In-situ steady-state fluorescence experiments were performed for studying slow release of pyrene-labeled polystyrene chains from polystyrene gels formed by free-radical crosslinking copolymerization. Atom transfer radical polymerization was used to produce the pyrene end-capped polystyrene chains. In order to load the pyrene end-capped polystyrene chains into the gel disc-shaped gels were left in toluene solutions of pyrene end-capped polystyrene chains of various molecular weights. These swollen gels were redried in air and then immersed in pure toluene solution for monitoring slow release from the gel. These reswelling experiments were performed at room temperature in real time by monitoring the pyrene emission intensity using steady-state fluorescence measurements. Slow-release diffusion coefficients were measured and found to decrease as the crosslink density of the gels increased. It was observed that higher molecular weight pyrene end-capped polystyrene chains released much faster than low molecular ones during the slow-release process.
Citation - WoS: 6
Citation - Scopus: 9
Three-fast-searchable graphs
(Elsevier Science Bv, 2013) Dereniowski, Dariusz; Diner, Öznur Yaşar; Dyer, Danny
In the edge searching problem searchers move from vertex to vertex in a graph to capture an invisible fast intruder that may occupy either vertices or edges. Fast searching is a monotonic internal model in which at every move a new edge of the graph G must be guaranteed to be free of the intruder. That is once all searchers are placed the graph G is cleared in exactly vertical bar E(G)vertical bar moves. Such a restriction obviously necessitates a larger number of searchers. We examine this model and characterize graphs for which 2 or 3 searchers are sufficient. We prove that the corresponding decision problem is NP-complete. (C) 2013 Elsevier B.V. All rights reserved.

Browse

Browsing Bilgisayar Mühendisliği Bölümü Koleksiyonu by Scopus Q "Q3"