Department of Information Systems and Technologies

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Open Access
Task allocation onto a hypercube by recursive mincut bipartitioning
(Elsevier, 1990) Ercal, F.; Ramanujam, J.; Sadayappan, P.
An efficient recursive task allocation scheme, based on the Kernighan-Lin mincut bisection heuristic, is proposed for the effective mapping of tasks of a parallel program onto a hypercube parallel computer. It is evaluated by comparison with an adaptive, scaled simulated annealing method. The recursive allocation scheme is shown to be effective on a number of large test task graphs-its solution quality is nearly as good as that produced by simulated annealing, and its computation time is several orders of magnitude less
Open Access
Standard conformance test specification language TTCN
(Elsevier, 1992) Sarikaya, B.; Wiles, A.
The International Standards Organization (ISO) has defined a protocol test language called TTCN (Tree and Tabular Combined Notation) to specify abstract test suites for Open Systems Interconnection (OSI) protocols. TTCN combines a tree notation for dynamic behaviour description with a tabular representation of various language constructs. TTCN allows tabular constraints to enforce values on the Abstract Service Primitive (ASP) or Protocol Data Unit (PDU) parameters. For application layer protocols, Abstract Syntax Notation One (ASN.1) constraints are used. Dynamic behaviour description in TTCN is shown to address many important aspects of conformance testing such as modularity support in terms of test cases, steps and default behaviour tables and sophisticated timer management. TTCN has a machine processable form called TTCN-MP that defines all the TTCN syntax using BNF. Semantics of the tests specified in TTCN is operationally defined rendering TTCN almost a formal notation. © 1992.
Open Access
An animation system for rigid and deformable models
(1993) Güdükbay, Uğur; Özgüç, B.; Tokad, Y.
We describe a system for the animation of rigid and deformable models. The system uses the approaches from elasticity theory for animating the models. Two different formulations, namely the primal and the hybrid formulations, are implemented so that the user could select the suitable one for an animation depending on the rigidity of the models. Collision of the models with impenetrable obstacles and constraining model points to fixed positions in space are implemented for use in the animations.
Open Access
Computer aided frequency planning for the radio and TV broadcasts
(Institute of Electrical and Electronics Engineers, 1996-06) Altıntaş, Ayhan; Ocalı, O.; Topçu, Satılmış; Tanyer, S. G.; Köymen, Hayrettin
The frequency planning of the VHF and UHF broadcasts in Turkey is described. This planning is done with the aid of computer databases and digital terrain map. The frequency offset is applied whenever applicable to increase the channel capacity. The offset assignment is done through simulated annealing algorithm. The international rules and regulations concerning Turkey are also considered.
Open Access
Making peace with your multimedia
(1998) Adali, S.
[No abstract available]
Open Access
Electronic excited states of the CP29 antenna complex of green plants: a model based on exciton calculations
(Springer / Kluwer Academic Publishers, 2000) İşerı, E. İ.; Albayrak, D.; Gülen, D.
We have suggested a model for the electronic excited states of the minor plant antenna, CP29, by incorporating a considerable part of the current information offered by structure determination, site-directed mutagenesis, and spectroscopy in the modeling. We have assumed that the electronic excited states of the complex have been decided by the chlorophyll-chlorophyll (Chl) and Chl-protein interactions and have modeled the Coulombic interaction between a pair of Chls in the point-dipole approximation and the Chl-protein interactions are treated as empirical fit parameters. We have suggested the Qy dipole moment orientations and the site energies for all the chlorophylls in the complex through a simultaneous simulation of the absorption and linear dichroism spectra. The assignments proposed have been discussed to yield a satisfactory reproduction of all prominent features of the absorption, linear and circular dichroism spectra as well as the key spectral and temporal characteristics of the energy transfer processes among the chlorophylls. The orientations and the spectral assignments obtained by relatively simple exciton calculations have been necessary to provide a good point of departure for more detailed treatments of structure-function relationship in CP29. Moreover, it has been discussed that the CP29 model suggested can guide the studies for a better understanding of the structure-function relationship in the major plant antenna, LHCII.
Open Access
On Lempel-Ziv complexity of sequences
(Springer, Berlin, Heidelberg, 2006) Doǧanaksoy, A.; Göloǧlu, Faruk
We derive recurrences for counting the number a(n, r) of sequences of length n with Lempel-Ziv complexity r, which has important applications, for instance testing randomness of binary sequences. We also give algorithms to compute these recurrences. We employed these algorithms to compute a(n, r) and expected value. EPn, of number of patterns of a sequence of length n, for relatively large n. We offer a randomness test based on the algorithms to be used for testing randomness of binary sequences. We give outputs of the algorithms for some n. We also provide results of the proposed test applied to the outputs of contestant stream ciphers of ECRYPT's eSTREAM. © Springer-Verlag Berlin Heidelberg 2006.
Open Access
Exact expression and tight bound on pairwise error probability for performance analysis of turbo codes over Nakagami-m fading channels
(IEEE, 2007) Ali, S. A.; Kambo, N. S.; İnce, E. A.
This letter presents derivation for an exact and efficient expression on pairwise error probability over fully interleaved Nakagami-m fading channels under ideal channel state information at the decoder. As an outcome, this derivation also leads to a tight upper bound on pairwise error probability which is close to the exact expression. Pairwise error probability plots for different values of Nakagami parameter m along with an already existing numerically computable expression are provided. As an application of pairwise error probability, average union upper bounds for turbo codes having (1, 7/5, 7/5) and (1, 5/7, 5/7) generator polynomials employing transfer function approach are presented to illustrate the usefulness of the new efficient results. © 2007 IEEE.
Open Access
How content management problem of a remote laboratory system can be handled by integrating an open source learning management system? Problems and solutions
(IEEE, 2007) Özdoğru, Burcu; Cagıltay, N. E.
This paper represents the design and implementation of the integration process of an open source learning management system (LMS) to the remote laboratory platform. The reason of using a learning management system is to prevent the problems which can be seen in the learner side of the remote laboratory systems. However, since using a learning management system such as Moodle can handle the learner problems, since it is a separate system, there are still other problems to be handled such as integrating it with the other parts of remote laboratory systems. This study explores the background information of LMS, the problems faced while integrating Moodle to remote laboratory applications, the chosen content management systems' architecture, our architecture for integrating Moodle with the remote laboratory system and the solutions we propose for the problems.
Open Access
Performance analysis of turbo codes over Nakagami-m fading channels with impulsive noise
(IEEE, 2007) Ali, Syed Amjad; İnce, E. A.
The statistical characteristics of impulsive noise differ greatly from those of Gaussian noise. Hence, the performance of conventional decoders, optimized for AWGN channels is not promising in non-Gaussian environments. In order to achieve improved performance in impulsive environments the decoder structure needs to be adapted in accordance with the impulsive noise model. This paper provides performance analysis of turbo codes over fully interleaved Nakagami-m fading channels with Middleton's additive white Class-A impulsive noise (MAWCAIN). Simulation results for memoryless Nakagami-m fading channels under coherent BPSK signaling are provided for the cases of ideal channel state information (ICSI) and no channel state information (NCSI) at the decoder. As in the 3GPP UMTS forward link an eight state turbo encoder having (1, 13/15, 13/15) generator polynomial is used throughout the analysis. The novelty of this work lies in the fact that this is an initial attempt to provide a detailed analysis of turbo codes over Nakagami-m fading channels with impulsive noise rather than fading channels with AWGN. © 2007 IEEE.
Open Access
Gender and Tourism development: a case study of the Cappadoccia region of Turkey
(CABI Publishing, 2007) Elmas, Sermin; Pritchard, A.; Morgan, N.; Atelyevic, I.
Open Access
Performance analysis of turbo codes over Rician fading channels with impulsive noise
(IEEE, 2007) Ali, Syed Amjad; Ince, E.A.
The statistical characteristics of impulsive noise differ greatly from those of Gaussian noise. Hence, the performance of conventional decoders, optimized for additive white Gaussian noise (AWGN) channels is not promising in non-Gaussian environments. In order to achieve improved performance in impulsive environments the decoder structure needs to be modified in accordance with the impulsive noise model. This paper provides performance analysis of turbo codes over fully interleaved Rician fading channels with Middleton's additive white Class-A impulsive noise (MAWCAIN). Simulation results for the memoryless Rician fading channels using coherent BPSK signaling for both the cases of ideal channel state information (ICSI) and no channel state information (NCSI) at the decoder are provided. An eight state turbo encoder having (1, 13/15, 13/15) generator polynomial is used throughout the analysis. The novelty of this work lies in the fact that this is an initial attempt to provide a detailed analysis of turbo codes over Rician fading channels with impulsive noise rather than AWGN. ©2007 IEEE.
Open Access
Rule based segmentation and subject identification using fiducial features and subspace projection methods
(Academy Publisher, 2007) Ince, E. A.; Ali, S. A.
This paper describes a framework for carrying out face recognition on a subset of standard color FERET database using two different subspace projection methods, namely PCA and Fisherfaces. At first, a rule based skin region segmentation algorithm is discussed and then details about eye localization and geometric normalization are given. The work achieves scale and rotation invariance by fixing the inter ocular distance to a selected value and by setting the direction of the eye-to-eye axis. Furthermore, the work also tries to avoid the small sample space (S3) problem by increasing the number of shots per subject through the use of one duplicate set per subject. Finally, performance analysis for the normalized global faces, the individual extracted features and for a multiple component combination are provided using a nearest neighbour classifier with Euclidean and/or Cosine distance metrics.
Open Access
Teaching usage of equipments in a remote laboratory
(Sakarya Universitesi, 2008) Alparslan, N. C.; Cagiltay, N. E.; Ozen, M.; Aydin, E. U.
Remote laboratories are technologies that aim to increase the effectiveness of educational programs. European Remote Radio Laboratory (ERRL) is an e-learning project for students, teachers and technicians who will use very important devices of a radio frequency laboratory remotely. As a solution we have developed an e-learning system which aims to support the ERRL learners while studying on how to use equipments in the system. The system is developed according to the electronic performance support system (EPSS) approach. An EPSS is a computer-based, well-structured system which improves the performance of individuals. It is an electronic infrastructure that contains, stores and distributes personal (individual) or corporate knowledge to enable people to reach necessary levels of performance in the fastest possible time and with minimum teaching support of other people. This paper discusses how the content for such a system is developed and how this content is interactively used in the EPSS platform. The technical details of the developed EPSS are also discussed in this study. We believe that this paper will help instructional system designers for designing different alternatives to improve learners' performance.
Open Access
On determining cluster size of randomly deployed heterogeneous WSNs
(IEEE, 2008) Sevgi, C.; Koçyiğit, A.
Clustering is an efficient method to solve scalability problems and energy consumption challenges. For this reason it is widely exploited in Wireless Sensor Network (WSN) applications. It is very critical to determine the number of required clusterheads and thus the overall cost of WSNs while satisfying the desired level of coverage. Our objective is to study cluster size, i.e., how much a clusterhead together with sensors can cover a region when all the devices in a WSN are deployed randomly. Therefore, it is possible to compute the required number of nodes of each type for given network parameters.
Open Access
Tutorial services for students at Bilkent University an evaluation after five years
(Sense Publishers, 2008) Çelik, B. Keyik; Özdemir, B. Uslu; Verhoeven, John M
To realize our mission as academic coordinators for engineering students at Bilkent University, we facilitate in different ways tutorial services. These focus on the first year courses for physics, mathematics and computer science, which are courses that turn out to be difficult, as students' comments and grades often show. Most tutorial services are realized in cooperation with the Departments. Senior undergraduate students or graduate students are hired to work as laboratory assistants or as homework graders, or to offer recitation classes. During these classes questions are answered, difficult issues are explained, while many exercises are done to gain the necessary routine for applying the theory. Such classes can form together with theory classes and laboratory sessions a consistent unity of different working forms. Besides these services, which are scheduled regularly and for which participation often is included in the grading, we coordinate tutorials on demand, for students asking for them. Another idea behind the tutorial services is that they give the possibility for advanced students to practice their teaching and communication skills. We organize application procedures, hire the students accepted for the job, follow their work with duty reports to be submitted by them, try to coach them in different ways. By participating in workshops, where special attention is given to strategies for active learning, tutors can work for a teaching certificate. After they finished their job satisfactorily, tutors may ask for a 'thank you letter', as a useful academic reference. Everything considered, although the infrastructure for the tutorial services is quite challenging, they form a useful tool for our mission as student coordinators.
Open Access
An optimal network dimensioning and initial energy assignment minimizing the monetary cost of a heterogeneous WSN
(IEEE, 2009) Sevgi, Cüneyt; Kocyigit, A.
In this paper, a novel method is proposed to dimension a randomly deployed heterogeneous Wireless Sensor Network (WSN) of minimum monetary cost satisfying minimum coverage and minimum lifetime requirements. We consider WSNs consisting of two different types of nodes clusterheads and ordinary sensor nodes, randomly deployed over a sensing field. All devices are assumed to be stationary and have identical sensing capabilities. However, the clusterheads are more energetic and powerful in terms of processing and communication capabilities compared to sensor nodes. For such a network, finding minimum cost WSN problem is not a trivial one, since the distribution of the mixture of two different types of devices and the batteries with different initial energies in each type of device primarily determine the monetary cost of a WSN. Therefore, we formulated an optimization problem to minimize the monetary cost of a WSN for given coverage and lifetime requirements. The proposed optimization problem is solved for a certain scenario and the solution is validated by computer simulations. © 2009 IEEE.
Open Access
Solutions to challenges of teaching "systems analysis and design" for undergraduate software engineers
(IGI Global, 2009) Albayrak, Ö.
This study is an enhancement of previous research presented at the 2nd AIS SIGSAND European Symposium on Systems Analysis and Design and its improved version presented at the 3rd National Software Engineering Symposium (UYMS) 2007. The AIS-SIGSAND 2007 study, the first phase, was part of on-going research by which systems analysis and design-teaching experiences related to course evaluation items were enlightened. This study summarizes previous studies and introduces new findings suggested by those studies that relate to teaching challenges on systems analysis and design in software engineering. The first challenge studied is to decide a suitable evaluation item set in undergraduate level system analysis and design courses for software engineers. The second challenge relates to implicit assumptions made by software engineers during the analysis phase. Based on pre-interview, test, and post-interview data, the study presents a snapshot of an analysis in software engineering regarding implicit assumptions made by analysts. Related to these challenges, the study concludes with proposals on systems analysis and design education.
Open Access
An experiment to observe the impact of UML diagrams on the effectiveness of software requirements inspections
(IEEE, 2009) Albayrak, Özlem
Software inspections aim to find defects early in the development process and studies have found them to be effective. However, there is almost no data available regarding the impact of UML diagram utilization in software requirements specification documents on inspection effectiveness. This paper addresses this issue by investigating whether inclusion of UML diagrams impacts the effectiveness of requirements inspection. We conducted an experiment in an academic environment with 35 subjects to empirically investigate the impact of UML diagram inclusion on requirements inspections' effectiveness and the number of reported defects. The results show that including UML diagrams in requirements specification document significantly impacts the number of reported defects, and there is no significant impact on the effectiveness of individual i nspections. © 2009 IEEE.
Open Access
Are software engineers' responses to incomplete requirements related to project characteristics?
(IEEE, 2009) Albayrak, Özlem; Albayrak, Duygu; Kiliç, T.
Software requirements quality affects software product quality. For high-quality software products, software requirements must be complete. When faced with incomplete requirements, software engineers attempt to fill the requirements' gaps differently, either by getting feedback from the user or by making assumptions. Assumptions may be explicit or implicit. Explicit assumptions are preferable to implicit assumptions as explicit assumptions can be validated. We conduct an empirical study to determine whether the number of explicit assumptions made by software engineers is related to a project's characteristics. Using data from two CMMI Level 3 companies and 16 projects, we investigated the responses of 92 software engineers to the same incomplete software requirement. Our findings show possible relationships between projects' characteristics and the number of explicit assumptions. ©2009 IEEE.