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Yayın A survey of algorithms and architectures for H.264 sub-pixel motion estimation(World Scientific, 2012-05) Fatemi, Mohammad Reza Hosseiny; Ateş, Hasan Fehmi; Salleh, Rosli BinThis paper reviews recent state-of-the-art H. 264 sub-pixel motion estimation (SME) algorithms and architectures. First, H.264 SME is analyzed and the impact of its functionalities on coding performance is investigated. Then, design space of SME algorithms is explored representing design problems, approaches, and recent advanced algorithms. Besides, design challenges and strategies of SME hardware architectures are discussed and promising architectures are surveyed. Further perspectives and future prospects are also presented to highlight emerging trends and outlook of SME designs.Yayın Achievable rates for two user cooperative OFDMA(IEEE, 2010) Bakım, İsmail Sezi; Kaya, OnurWe propose two encoding strategies for a two user cooperative Orthogonal Frequency Division Multiple Access (OFDMA) system, based on block Markov superposition encoding. We obtain the expressions for the resulting achievable rate regions for both encoding strategies, and evaluate them through simulations. We show that, by allowing for re-partitioning and re-encoding of the cooperative messages across subchannels, it is possible to better exploit the diversity created by OFDMA, and higher rates can be achieved.Yayın VC-dimension of univariate decision trees(IEEE-INST Electrical Electronics Engineers Inc, 2015-02-25) Yıldız, Olcay TanerIn this paper, we give and prove the lower bounds of the Vapnik-Chervonenkis (VC)-dimension of the univariate decision tree hypothesis class. The VC-dimension of the univariate decision tree depends on the VC-dimension values of its subtrees and the number of inputs. Via a search algorithm that calculates the VC-dimension of univariate decision trees exhaustively, we show that our VC-dimension bounds are tight for simple trees. To verify that the VC-dimension bounds are useful, we also use them to get VC-generalization bounds for complexity control using structural risk minimization in decision trees, i.e., pruning. Our simulation results show that structural risk minimization pruning using the VC-dimension bounds finds trees that are more accurate as those pruned using cross validation.Yayın Monitoring of a laboratory-scale inland-delta formation using a structured-light system(Blackwell Publishing Ltd, 2016-06) Akça, Mehmet Devrim; Seybold, Hansjörg J.A reduced complexity model, which simulates the process of fluvial inland-delta formation, has been developed in a previous study. The results have been compared and validated with a laboratory experiment. This work elaborates the laboratory investigation in which an experimental inland delta is generated and its eroding topography is measured using a structured-light 3D scanner. The least squares 3D (LS3D) co-registration and comparison method is used for alignment as well as for comparing data epochs both spatially and temporally. A spatial precision value of around ±50 ?m (1/20 000) is achieved. A series of high-quality digital elevation models (DEMs) are generated and the space-time evolution of the inland delta is monitored and analysed, in terms of slope and topography dynamics, in the consecutive DEM layers. The combination of high-resolution scanning together with high-precision co-registration techniques allows investigation of the details of the space-time variability of the sedimentation-deposition patterns to be used for geomorphological analysis.Yayın Tracing back the signs of complexity thinking in management: Mary Parker Follett re-visited(PressAcademia, 2015-09-29) Yüksel, Ahmet HakanThe modernist stream of thought had immensely influenced the theories of organizational management in the early twentieth century. Equilibriumoriented and universally valid reductionist approaches viewed organizations as machines that could be broken down into pieces, hence, behavior of the whole could be understood from the knowledge of its parts. Mary Parker Follett, owing to her valuable contribution ahead of her time, emerges as a prominent figure in the history of management thought and organizational studies. Most of what is written and discussed today in the field of organization studies and management such as power, authority, group dynamics, leadership, coordination and governance have been derived from Mary Parker Follett’s corpus. She had built the bridge between complexity thinking and management almost four decades before the introduction of nonlinear dynamics to scientific research. Although the actual terminology of nonlinear dynamics was not employed in her postulations Mary Parker Follett’s works provide profound insights for the field of management under the prevailing global circumstances where the impact of repeated attempts to design the ‘whole’ seems to have been neutralized since it is barely enough to predict the outcomes of the upward-causality from the knowledge of the parts. A thorough analysis of her writings reveals that she had accurately anticipated the problems associated with the contemporary organizational settings as well as incorporating nonlinear dynamics into management thinking. This conceptual paper intends to draw inspiration from Mary Parker Follett’s works with special emphasis on the links between her conceptions and complexity thinking in the field of management.Yayın Breaking free from the linear: In search for Innoveaders(Elsevier Science Inc, 2015-07-03) Yüksel, Ahmet HakanThe characteristics of the global business environment in which the organizations are expected to sense-and-respond to the target customers’ preferences constantly on the move have drastically changed for the last four decades. The impact of repeated and prolonged attempts to design the whole (system) has been neutralized since it is barely enough to predict the outcomes of the upward-causality from the knowledge of the parts. Innovativeness, under these circumstances, cannot be reified as something done to organizations via deliberate managerial interventions. Traditional leadership approaches fail to grasp the very insight regarding the creation of ingenious organizations in which emergence is giving rise to innovation. This conceptual paper intends to delve into the relationship between innovation-driven organizations and the right context of leadership to be instilled through incorporation of complexity science into management and coins the term innoveadership to identify the characteristics of such context.Yayın Power control for two user cooperative OFDMA channels(IEEE-INST Electrical Electronics Engineers Inc, 2013-01) Bakım, İsmail Sezi; Kaya, OnurFor a two user cooperative orthogonal frequency division multiple access (OFDMA) system with full channel state information (CSI), we obtain the optimal power allocation (PA) policies which maximize the rate region achievable by a channel adaptive implementation of inter-subchannel block Markov superposition encoding (BMSE), used in conjunction with backwards decoding. We provide the optimality conditions that need to be satisfied by the powers associated with the users' codewords and derive the closed form expressions for the optimal powers. We propose two algorithms that can be used to optimize the powers to achieve any desired rate pair on the rate region boundary: a projected subgradient algorithm, and an iterative waterfilling-like algorithm based on Karush-Kuhn-Tucker (KKT) conditions for optimality, which operates one user at a time and converges much faster. We observe that, utilization of power control to take advantage of the diversity offered by the cooperative OFDMA system, not only leads to a remarkable improvement in achievable rates, but also may help determine how the subchannels have to be instantaneously allocated to various tasks in cooperation. Simulations show that the gain from power allocation is still significant even when the CSI feedback is limited.Yayın Rate-distortion and complexity optimized motion estimation for H.264 video coding(IEEE-INST Electrical Electronics Engineers Inc, 2008-02) Ateş, Hasan Fehmi; Altunbaşak, Yücel11.264 video coding standard supports several inter-prediction coding modes that use macroblock (MB) partitions with variable block sizes. Rate-distortion (R-D) optimal selection of both the motion vectors (MVs) and the coding mode of each MB is essential for an H.264 encoder to achieve superior coding efficiency. Unfortunately, searching for optimal MVs of each possible subblock incurs a heavy computational cost. In this paper, in order to reduce the computational burden of integer-pel motion estimation (ME) without sacrificing from the coding performance, we propose a R-D and complexity joint optimization framework. Within this framework, we develop a simple method that determines for each MB which partitions are likely to be optimal. MV search is carried out for only the selected partitions, thus reducing the complexity of the ME step. The mode selection criteria is based on a measure of spatiotemporal activity within the MB. The procedure minimizes the coding loss at a given level of computational complexity either for the full video sequence or for each single frame. For the latter case, the algorithm provides a tight upper bound on the worst case complexity/execution time of the ME module. Simulation results show that the algorithm speeds up integer-pel ME by a factor of up to 40 with less than 0.2 dB loss in coding efficiency.Yayın Re-mining item associations: Methodology and a case study in apparel retailing(Elsevier Science BV, 2011-12) Demiriz, Ayhan; Ertek, Gürdal; Atan, Sabri Tankut; Kula, UfukAssociation mining is the conventional data mining technique for analyzing market basket data and it reveals the positive and negative associations between items. While being an integral part of transaction data, pricing and time information have not been integrated into market basket analysis in earlier studies. This paper proposes a new approach to mine price, time and domain related attributes through re-mining of association mining results. The underlying factors behind positive and negative relationships can be characterized and described through this second data mining stage. The applicability of the methodology is demonstrated through the analysis of data coming from a large apparel retail chain, and its algorithmic complexity is analyzed in comparison to the existing techniques.Yayın Leaders as enablers creating ecologies of innovation within organizations(Sawyer Business School, 2013-06) Yüksel, Ahmet HakanOrganizations are expected to devise adroit actions in the face of prevailing complexity in business environment. Under the circumstances of intensive competition in global markets, dealing with the concept of innovation entails to embrace a more profound coverage than generally ascribed. Innovation is about building capabilities that will eventually be materialized into novel ways of doing things. The very essence of innovation lies in its ability to carry a work process to a superior level of value generation. Therefore, leaders (leadership) are supposed to be reengineered as enablers who function as catalyst for the transformation of organizations into ecologies of innovation where building capabilities and creation of knowledge are continuous endeavors. This conceptual paper aims to tap into the heart of this matter and deal with the relationship between becoming innovative and the appropriate context of leadership that should be instilled in contemporary organizations.
