Browsing by Subject "Hierarchical systems"

Now showing 1 - 11 of 11

Open Access
An archiving model for a hierarchical information storage environment
(Elsevier, 2000) Moinzadeh, K.; Berk, E.
We consider an archiving model for a database consisting of secondary and tertiary storage devices in which the query rate for a record declines as it ages. We propose a `dynamic' archiving policy based on the number of records and the age of the records in the secondary device. We analyze the cases when the number of new records inserted in the system over time are either constant or follow a Poisson process. For both scenarios, we characterize the properties of the policy parameters and provide optimization results when the objective is to minimize the average record retrieval times. Furthermore, we propose a simple heuristic method for obtaining near-optimal policies in large databases when the record query rate declines exponentially with time. The e ectiveness of the heuristic is tested via a numerical experiment. Finally, we examine the behavior of performance measures such as the average record retrieval time and the hit rate as system parameters are varied.
Open Access
Distributed scheduling: a review of concepts and applications
(Taylor & Francis, 2010) Toptal, A.; Sabuncuoglu, I.
Distributed scheduling (DS) is an approach that enables local decision makers to create schedules that consider local objectives and constraints within the boundaries of the overall system objectives. Local decisions from different parts of the system are then integrated through coordination and communication mechanisms. Distributed scheduling attracts the interest of many researchers from a variety of disciplines, such as computer science, economics, manufacturing, and service operations management. One reason is that the problems faced in this area include issues ranging from information architectures, to negotiation mechanisms, to the design of scheduling algorithms. In this paper, we provide a survey and a critical analysis of the literature on distributed scheduling. While we propose a comprehensive taxonomy that accounts for many factors related to distributed scheduling, we also analyse the body of research in which the scheduling aspect is rigorously discussed. The focus of this paper is to review the studies that concern scheduling algorithms in a distributed architecture, not, for example, protocol languages or database architectures. The contribution of this paper is twofold: to unify the literature within our scope under a common terminology and to determine the critical design factors unique to distributed scheduling and in relation to centralised scheduling.
Open Access
Issues in commonsense set theory
(Springer/Kluwer Academic Publishers, 1994) Pakkan, M.; Akman, V.
The success of set theory as a foundation for mathematics inspires its use in artificial intelligence, particularly in commonsense reasoning. In this survey, we briefly review classical set theory from an AI perspective, and then consider alternative set theories. Desirable properties of a possible commonsense set theory are investigated, treating different aspects like cumulative hierarchy, self-reference, cardinality, etc. Assorted examples from the ground-breaking research on the subject are also given. © 1995 Kluwer Academic Publishers.
Open Access
Lossless image compression by LMS adaptive filter banks
(Elsevier, 2001) Öktem, R.; Çetin, A. Enis; Gerek, O. N.; Öktem, L.; Egiazarian, K.
A lossless image compression algorithm based on adaptive subband decomposition is proposed. The subband decomposition is achieved by a two-channel LMS adaptive filter bank. The resulting coefficients are lossy coded first, and then the residual error between the lossy and error-free coefficients is compressed. The locations and the magnitudes of the nonzero coefficients are encoded separately by an hierarchical enumerative coding method. The locations of the nonzero coefficients in children bands are predicted from those in the parent band. The proposed compression algorithm, on the average, provides higher compression ratios than the state-of-the-art methods.
Open Access
Novelty detection using soft partitioning and hierarchical models
(IEEE, 2017) Ergen, Tolga; Gökçesu, Kaan; Şimşek, Mustafa; Kozat, Süleyman Serdar
In this paper, we study novelty detection problem and introduce an online algorithm. The algorithm sequentially receives an observation, generates a decision and then updates its parameters. In the first step, to model the underlying distribution, algorithm constructs a score function. In the second step, this score function is used to make the final decision for the observed data. After thresholding procedure is applied, the final decision is made. We obtain the score using versatile and adaptive nested decision tree. We employ nested soft decision trees to partition the observation space in an hierarchical manner. Based on the sequential performance, we optimize all the components of the tree structure in an adaptive manner. Although this in time adaptation provides powerful modeling abilities, it might suffer from overfitting. To circumvent overfitting problem, we employ the intermediate nodes of tree in order to generate subtrees and we then combine them in an adaptive manner. The experiments illustrate that the introduced algorithm significantly outperforms the state of the art methods.
Open Access
PHR: A parallel hierarchical radiosity system with dynamic load balancing
(Springer, 2005) Sinop, A.; Abacı, T.; Akkuş Ü.; Gürsoy, A.; Güdükbay, Uğur
In this paper, we present a parallel system called PHR for computing hierarchical radiosity solutions of complex scenes. The system is targeted for multi-processor architectures with distributed memory. The system evaluates and subdivides the interactions level by level in a breadth first fashion, and the interactions are redistributed at the end of each level to keep load balanced. In order to allow interactions freely travel across processors, all the patch data is replicated on all the processors. Hence, the system favors load balancing at the expense of increased communication volume. However, the results show that the overhead of communication is negligible compared with total execution time. We obtained a speed-up of 25 for 32 processors in our test scenes. © 2005 Springer Science + Business Media, Inc.
Open Access
Retrieval of Ottoman documents
(ACM, 2006-10) Ataer, Esra; Duygulu, Pınar
There is a growing need to access historical Ottoman documents stored in large archives and therefore managing tools for automatic searching, indexing and transcription of these documents is required. In this paper, we present a method for the retrieval of Ottoman documents based on word matching. The method first successfully segments the documents into word images and then uses a hierarchical matching technique to find the similar instances of the word images. The experiments show that even with simple features promising results can be achieved. Copyright 2006 ACM.
Open Access
Reusability and schema evolution in object - oriented query models
(ASME, New York, NY, United States, 1996) Polat, F.; Alhajj, R.
In this paper, we have benefited from having an object algebra maintaining closure that makes it possible to have the output from a query persistent in the hierarchy. Based on this, it is possible to maximize reusability in object-oriented databases. Furthermore, we show how the object algebra is utilized to handle basic schema evolution functions without requiring any special set of built-in functions to serve the purpose. The invariants and the conflict resolving rules are specified. It is also shown how other schema functions are derivable from the basic ones.
Open Access
Scheduling of automated guided vehicles in a decision making hierarchy
(Taylor & Francis, 1996) Aktürk, M. S.; Yılmaz, H.
Scheduling efforts made without considering the special limitations of the material handling system might lead to infeasible results. An analytical model is proposed, first, to incorporate the automated guided vehicle (AGV) system into the overall decision making hierarchy. A mathematical formulation is developed to include interaction between the AGV module and other modules in the system by considering the restrictions of the material handling system. A micro-opportunistic approach is then proposed to solve the AGV scheduling problem. Finally, the proposed method is compared with a number of dispatching rules.
Open Access
Tracking motion and intensity variations using hierarchical 2-D mesh modeling for synthetic object transfiguration
(1996-11) Toklu, C.; Erdem, A. T.; Sezan, M. I.; Tekalp, A. M.
We propose a method for tracking the motion and intensity variations of a 2-D mildly deformable image object using a hierarchical 2-D mesh model. The proposed method is applied to synthetic object transfiguration, namely, replacing an object in a real video clip with another synthetic or natural object via digital postprocessing. Successful transfiguration requires accurate tracking of both motion and intensity (contrast and brightness) variations of the object-to-be-replaced so that the replacement object can be rendered in exactly the same way from a single still picture. The proposed method is capable of tracking image regions corresponding to scene objects with nonplanar and/or mildly deforming surfaces, accounting for intensity variations, and is shown to be effective with real image sequences.
Open Access
Use of intuitive tools to enhance student learning and user experience
(ACM, 2009) Altın, Rukiye; Bektik, Mustafa; Ekşioǧlu, Nuray; Koray, Can; Öner, Ömer Canbek; Sadetaş, Merve; Şener, Hilal; Şimşek, D.; Ma, C. C.; Price, C.; Routh, C. R.
Most user interfaces today present system functions by use of verbal or iconic symbols on static 2D menu pages organized in a hierarchical system [1]. This is unnatural to all human beings and must be learned, thus being a barrier between the full use and understanding of computer systems. With this problem in mind we set out to build a website and collaborative application for International Childrens Center (ICC) which could be used not only across languages but across ages as well. This effort was tested on a daily basis by a multinational team consisting of students from the United States and Turkey as well as children from the respective countries. This attention to usability will not only lead to an intuitive tool for the client but also teach the students in the course how to build intuitive user interfaces.