Browsing by Author "Ayav, Tolga"

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Citation - WoS: 15
Citation - Scopus: 17
Achieving query performance in the cloud via a cost-effective data replication strategy
(Springer, 2021) Tos, Uras; Mokadem, Riad; Hameurlain, Abdelkader; Ayav, Tolga; Ayav, Tolga; Bilgisayar Mühendisliği Bölümü
Meeting performance expectations of tenants without sacrificing economic benefit is a tough challenge for cloud providers. We propose a data replication strategy to simultaneously satisfy both the performance and provider profit. Response time of database queries is estimated with the consideration of parallel execution. If the estimated response time is not acceptable, bottlenecks are identified in the query plan. Data replication is realized to resolve the bottlenecks. Data placement is heuristically performed in a way to satisfy query response times at a minimal cost for the provider. We demonstrate the validity of our strategy in a performance evaluation study.
Citation - Scopus: 9
Adaptive RTP rate control method
(2011) Tos, U.; Ayav, T.; Ayav, Tolga; Bilgisayar Mühendisliği Bölümü
In this paper, we present an adaptive method for maximizing network bandwidth utilization for the real-time applications. RTP protocol is chosen as the transport protocol and the network utilization is provided by increasing and decreasing the transmission rate of the RTP traffic. Our method employs a PID controller that keeps the RTP packet loss fraction at a predefined reference point. Packet loss fraction parameter is gathered from the RTCP receiver reports and fed into the PID controller that controls the transmission rate of the RTP traffic. Simulations are performed to demonstrate the effectiveness of the method under a bottleneck network configuration with background UDP traffic competing against the RTP traffic for the available bandwidth. © 2011 IEEE.
Assessment and certification of safety critical software
(Izmir Institute of Technology, 2018-07) Uzun Yenigün, Bengisu; Ayav, Tolga; Ayav, Tolga
Biomedical engineering which consists of combination of various dicipline such as chemical, biology etc. produces remedies to the challenges facing the globalizing world. Therefore, it covers a wide range of area from biosensor to surgical robots. Rapid development of biomedical engineering technology is aimed to research, diagnose and treatment to modern society for providing improved living conditions. Safety critical systems are interested with systems whose failure or malfunction could cause death, serious injury, damage to equipment and environmental harm. NeuRoboScope project is a safety-critical system which navigates the optical-camera system used in the endoscopic pituitary surgery by tracking the surgery tool that the surgeon uses. This thesis gives the information of how we scrutinize NeuRoboScope project depending on standards of medical device which are ISO 14971, IEC 62304, IEC 60601 and DO-178C.
Blackhole attacks in IoT networks
(01. Izmir Institute of Technology, 2020-12) Sokat, Barış; Ayav, Tolga; Ayav, Tolga; Erten, Yusuf Murat; 01. Izmir Institute of Technology
IoT technologies are very popular today, and they are used in almost every field. Therefore, the number of IoT devices used is increasing day by day. Like every field in computer networks, security is quite important in IoT networks. However, the resource-constrained nature of IoT devices makes the study of security measures for IoT networks very challenging. In the literature research conducted before this thesis study, it was seen that it can perform a wide variety of RPL-based attacks on IoT networks. One of these attacks is the blackhole attack. Although the black hole attack is functionally simple, the damage it causes in the network can be extremely destructive. As far as it is known, in addition to the limited number of studies in this field of attack, the black hole attack used in the studies in this field has also basic features. The basic feature mentioned here is that the attacker node that will perform a black hole attack drops all the packets that come to it. When the attacker node drops all incoming packets, it causes the topology to change in the network, the number of control messages to increase and the attacker node to be isolated from the network in a short time. However, blackhole attack can be combined with different attacks. Therefore, in this thesis, the node that will perform the black hole attack is designed to allow control messages to pass, while dropping all other packets. Here, it is aimed that the attacker node remains on the network for a longer time. As a result, as long as the attacker node is active, it will be able to drop more packets and the number of control messages in the network will be controlled since the topology does not change. With the black hole attack developed as a result of the simulation tests, the number of control messages released in the network was taken under control and it was observed that the attacker node could remain in the network throughout the simulation period. Thus, the effect of different types of black hole attacks on the network that can be developed has been revealed.
Block-chain based remote update for embedded devices
(Izmir Institute of Technology, 2019-12) Kaptan, Melike; Ayav, Tolga; Ayav, Tolga; Erten, Yusuf Murat
This research work is an attempt to devise a platform to send automatic remote updates for embedded devices. In this scenario there are Original Equipment Manufacturers (OEMs), Software suppliers, Block-Chain nodes, Gateways and embedded devices. OEMs and software suppliers are there to keep their software on IPFS (Inter Planetary File System) and send the meta-data and hashes of their software to the Block-Chain nodes in order to keep this information distributed and ready to be requested and used. There are also gateways which are also the members of the Block-Chain and IPFS network. Gateways are responsible for asking for a specific update for specific devices from IPFS database using the meta-data standing on the Block-Chain. And they will send those hashed secure updates to the devices. In order to provide a traceable data keeping platform gateway update operations are handled as a transactions in the second block-chain network which is the clock-chain of the gateways. In this study implementation of the two block chain shows us that, even though the calculation overhead of the member devices, with regulations specific to the applications block-chains provide applicable platforms.
A blockchain application for payment and traffic management in smart vehicles
(Izmir Institute of Technology, 2022-07) Yiğitbaşı, Boğaçhan; Ayav, Tolga; Ayav, Tolga
The proposed solution offers an alternative way to our current retail shopping of fuel fees. It can be applied to any retail shopping process but this phase of the project is considered an initiation of upcoming. The next phases of the project, include full integration with smart cars in order to handle all procedures automatically. In the traditional way, when you buy some gas from a station with your credit card, the station owner pays some fee to his bank and it has to wait for some time to be able to get that money. You as an individual have to expose your identity so they can track your shopping habits and follow your expenses. Sometimes they may offer some loyalty discounts or gifts but with really ridiculous rates. Our system offers a digital payment system based on the Ethereum blockchain. It has its own token called TRANT (Transport Token) and by this token, any client with a digital wallet (Metamask) is able to pay their gas fees without exposing their real identity -only their wallet address-, and get some rewards in terms of TRANT for their loyalties and using our DEX (Decentralized Exchange) exchange them into the ether which can be converted into real fiat money easily. On the other hand, the proposed solution also has some advantages for the other party in this equation such as gas station owners, they immediately get their money at that very first moment without any remittance.
Blockchain application on loyalty card
(Izmir Institute of Technology, 2020-04) Sönmeztürk, Osman; Ayav, Tolga; Ayav, Tolga; Erten, Yusuf Murat
Today, traditional loyalty systems are insufficient to meet the needs of users. The users need to stay within the loyalty system for a long time and accumulate points in order to win prizes and besides, the rewards they receive may be out of their interest. In addition, users usually forget the awards they have won in traditional loyalty systems and have difficulty in following up rewards. In addition to that, users usually do not prefer to share their personal information to join loyalty systems due to privacy concerns. Therefore, the number of customers in the loyalty systems is decreasing day by day. The designed loyalty program mentioned in this thesis works with IZTECH Tokens, which works on the Ethereum chain and are created by following ERC20 standards. Thanks to the new generation loyalty system, users can convert their earned tokens to Ethereum on the stock exchange without accumulating them or can receive services or products with the accumulated tokens according to their interests from a market that has been contracted by the manufacturer. Additionally, users in the designed system do not need to carry many cards, it is adequate to have only one Ethereum wallet. Furthermore, users do not need to share any personal data to join the loyalty system. Markets can request Ether from the manufacturer according to the number of tokens they have accumulated. The loyalty system mentioned in this thesis not only aims to establish a win-win relationship between the manufacturer, market, and client but also to find solutions to the customer problems mentioned above.
Citation - WoS: 3
Citation - Scopus: 9
Boolean Differentiation for Formalizing Myers' Cause-Effect Graph Testing Technique
(Ieee, 2015) Ayav, Tolga; Belli, Fevzi; Ayav, Tolga; Bilgisayar Mühendisliği Bölümü
Cause-Effect Graph Testing is a popular technique used for almost four decades. Based on Boolean algebra, this technique assists deriving test cases from a given specification informally written in a natural language. The present paper suggests Boolean differentiation for formalizing this technique. The new approach is applied to an example, borrowed from G. Myers, for demonstrating and analyzing its features. Evaluations show that the new approach outperforms Myers' approach in terms of the detected faults per test cases.
Business activity monitoring for logistics management systems
(Izmir Institute of Technology, 2013-07) Titiz, Dilek; Ayav, Tolga; Ayav, Tolga
Enterprises use different software for different purposes, such as accounting management, customer relationships, so that information technologies become an integral part of business processes. A business process turns out to be a combination of these different software, besides the received information/data by one of software tools that comes from another one. Different software systems cannot have been aware of each other directly. When the domain under consideration is container logistics, in addition to the different software, there are many relationships with other companies and so there are many different systems, variable types and file types that are being used. There are different transportation modes like highway, marine or airway, and by the expansion of intermodal transportation, tracking data is getting harder. For container logistics being a complicated business, tracking data is a necessity. The necessity is to track and to control the data that comes from outer systems and inner systems to an interoperable platform. This necessity enables trackable business processes and thus increases the business performance. In the scope of this thesis, a business activity monitoring environment is created in case of ARKAS Holding, which works on container logistics domain and Bimar Inc., which is the software provider of it. As it was mentioned above, this tracking needs cause to creation of the proposed and implemented monitoring environment for such a case of ARKAS Holding that does intermodal transportation, which has many endpoints in its business processes and there are too many data to be tracked. There are many different endpoints, such as marine, roadway and depot, in container logistics; also there are many different data types that are coming from different systems. Thus, the â€˜Business Activity Monitoringâ€™ environment is created as this thesisâ€™ subject to make these different systems talk to each other, also to enable gathering data directly and automatically to achieve real-time monitoring.
A dedicated server design for physical web applications
(Izmir Institute of Technology, 2019-07) Abdennebi, Anes; Ayav, Tolga; Ayav, Tolga
With the huge impressive technological improvements the world is witnessing where giants like Facebook, Google, Apple, Microsoft and other technology companies are offering different services to millions of clients, services which don’t take usually more than seconds to be within the users’ devices besides the Physical Web applications that makes things interacts, having entities and can be reached based on the proximity context without omitting the incoming IoT infrastructure that would make 20.4 billion devices connected by 2020, the amount of data transferred, and services provided will be enormous and along with that, the big energy consumer standing behind providing clients with the needed data and services instantly, the web servers. Although it has a magnificent performance and responds to billions of queries and requests, however, there is still a crucial point which must be highlighted, the remarkable amounts of energy consumption by these servers. Therefore, this work is proposing a new approach in order to reduce the energy consumption in such a scenario where the 18-core energy efficient computer Parallella board will be used in order to create an energy efficient server that can offer many services triggered by various devices or any ordinary web requests across any environment and to prove also that using a cluster of Parallella supercomputers may perform as other similar servers dealing with web content (e.g. Raspberry Pi server). We will show how would these boards work under low energy feeding where users can access a web content hosted on a Parallella cluster. The source codes of the project are available on GitHub.
Density grid based stream clustering algorithm
(Izmir Institute of Technology, 2019-11) Ahmed, Rowanda Daoud; Ayav, Tolga; Ayav, Tolga; Dalkılıç, Gökhan
Recently as applications produce overwhelming data streams, the need for strategies to analyze and cluster streaming data becomes an urgent and a crucial research area for knowledge discovery. The main objective and the key aim of data stream clustering is to gain insights into incoming data. Recognizing all probable patterns in this boundless data which arrives at varying speeds and structure and evolves over time, is very important in this analysis process. The existing data stream clustering strategies so far, all suffer from different limitations, like the inability to find the arbitrary shaped clusters and handling outliers in addition to requiring some parameter information for data processing. For fast, accurate, efficient and effective handling for all these challenges, we proposed DGStream, a new online-offline grid and density-based stream clustering algorithm. We conducted many experiments and evaluated the performance of DGStream over different simulated databases and for different parameter settings where a wide variety of concept drifts, novelty, evolving data, number and size of clusters and outlier detection are considered. Our algorithm is suitable for applications where the interest lies in the most recent information like stock market, or if the analysis of existing information is required as well as cases where both the old and the recent information are all equally important. The experiments, over the synthetic and real datasets, show that our proposed algorithm outperforms the other algorithms in efficiency.
Designing programmable logic controller for data acquisition and control
(Izmir Institute of Technology, 2010) Gözütok, Mehmet Emre; Baran, Yusuf; Ayav, Tolga
in this study, a new dsPIC microcontroller based PLC design for requirements of data acquisition, signal processing and control applications has been discussed. The aim of the study was to realize of today's automation applications with a more economic, convenient, and functional device other than PLC applications. This device is a general purpose product available in ali areas. it is used to determine the city power grid harmonics. The circuit schema of the device is drawn in Multisim environment. The design of the printed circuit board is implemented in Ultiboard. The Microchip IDE is used for writing the codes and programming the MCU. The C30 compiler is used for compiling the codes which is distributed free of charge by Microchip. To evaluate the performance of the product, the harmonics in the electricity netvvork are tested. The operating time of the two main functions which are used in the FFT algorithm that was used for determining those harmonics were observed and results were expressed visually. Further development that could be done, by other researchers, in the future, is also discussed in the final chapter.
Citation - WoS: 22
Citation - Scopus: 29
Dynamic replication strategies in data grid systems: a survey
(Springer, 2015) Tos, Uras; Mokadem, Riad; Hameurlain, Abdelkader; Ayav, Tolga; Bora, Sebnem; Ayav, Tolga; Bilgisayar Mühendisliği Bölümü
In data grid systems, data replication aims to increase availability, fault tolerance, load balancing and scalability while reducing bandwidth consumption, and job execution time. Several classification schemes for data replication were proposed in the literature, (i) static vs. dynamic, (ii) centralized vs. decentralized, (iii) push vs. pull, and (iv) objective function based. Dynamic data replication is a form of data replication that is performed with respect to the changing conditions of the grid environment. In this paper, we present a survey of recent dynamic data replication strategies. We study and classify these strategies by taking the target data grid architecture as the sole classifier. We discuss the key points of the studied strategies and provide feature comparison of them according to important metrics. Furthermore, the impact of data grid architecture on dynamic replication performance is investigated in a simulation study. Finally, some important issues and open research problems in the area are pointed out.
Effectiveness of using clustering for test case prioritization
(Izmir Institute of Technology, 2019-07) Günel, Can; Ayav, Tolga; Ayav, Tolga
Software testing is one of the most important processes in the software development life cycle. As software evolves, previous test cases need to be re-executed to make sure that there is no new bugs introduced and nothing is broken in the existing behaviours. However, re-execution of all test cases could be expensive. That is why, test case prioritization method can be used to detect faults earlier by prioritizing the test cases which could have the higher possibility than others to find faults. Studying different approaches, implementing different techniques or putting these techniques to test on different programs could make it easier to answer which technique should be used for which kind of programs or faults. We address this issue, focusing on selecting different test case prioritization approaches and calculating the average fault detection ratios of prioritized test suites. As a novelty, we propose to perform an optimization algorithm on one of the approaches called `Clustering` to increase its efficiency. To do that, our main objective is determined as maximizing the distance between each clusters by using the coverage information. The distance is measured as the difference of covered functions of test cases in a test suite. In the end, this study will give a hint about selection of test case prioritization technique to be used by checking the empirical results of the experiments.
Citation - WoS: 26
Citation - Scopus: 28
Ensuring performance and provider profit through data replication in cloud systems
(Springer, 2018) Tos, Uras; Mokadem, Riad; Hameurlain, Abdelkader; Ayav, Tolga; Bora, Sebnem; Ayav, Tolga; Bilgisayar Mühendisliği Bölümü
Cloud computing is a relatively recent computing paradigm that is often the answer for dealing with large amounts of data. Tenants expect the cloud providers to keep supplying an agreed upon quality of service, while cloud providers aim to increase profits as it is a key ingredient of any economic enterprise. In this paper, we propose a data replication strategy for cloud systems that satisfies the response time objective for executing queries while simultaneously enables the provider to return a profit from each execution. The proposed strategy estimates the response time of the queries and performs data replication in a way that the execution of any particular query is still estimated to be profitable for the provider. We show with simulations that how the proposed strategy fulfills these two criteria.
Evaluation of scheduling architectures for OSEK/VDX compliant hard real-time operating systems
(Izmir Institute of Technology, 2020-08) Saydam, Berkay; Ayav, Tolga; Ayav, Tolga
Technological advancements are reflected to the vehicles as well, but it brings the challenge of adding new functionalities to vehicles without compromising safety. Tasks are used to provide functionalities which are used in car. These tasks have different characterictics. Safety and performance are two main criteria to determine characterictic of tasks. Characteristics of tasks can be classified according to their safety levels which are known as Automotive Safety Integrity Levels. Designing of hardware and software and also testing them is a long progress in automotive industry. Any changes on the design of hardware is quite costly when an ECU began to be used in field. According to my hypothesis, scheduling algorithms which are used by Central Processing Unit to determine sequences of task executions, should be well known. Besides, designing of hardware and software should be done according to these characteristics and algorithms. If not, tasks will cause serious problem like missing deadline for safety-critical component. In this thesis, the scheduling architectures are evaluated and they are determined which scheduling architectures should be used for which purpose. Besides, the advantages and disadvantages are explained.
Citation - Scopus: 0
Evaluation of Scheduling Architectures for OSEK/VDX Compliant Hard Real-Time Operating Systems
(Institute of Electrical and Electronics Engineers Inc., 2020) Saydam, B.; Ayav, T.; Ayav, Tolga; Bilgisayar Mühendisliği Bölümü
Developing technology is reflected to the vehicles as well. But it brings the challenge of adding new functionalities to vehicles without compromising safety. The chips, which are used to provide the functionalities, are determined in the first step of ECU design. This decision will effect the remaining part of the development. Designing hardware and software together with testing phase is a long process in automotive industry. Changing the design of the hardware is quite costly after an ECU begins to be used in field. For these reasons, the selection of chips is directly related to cost and the functionality which should be provided to customer. Tasks, which fulfill desired functionality, provide a balance between performance and safety. These were evaluated for an OSEK/VDX certified OS and results are presented from the scheduling algorithms point of view. © 2020 IEEE.
Citation - WoS: 0
Evaluation of Scheduling Architectures for OSEK/VDX Compliant Hard Real-Time Operating Systems
(Ieee, 2020) Saydam, Berkay; Ayav, Tolga; Ayav, Tolga; Bilgisayar Mühendisliği Bölümü
Developing technology is reflected to the vehicles as well. But it brings the challenge of adding new functionalities to vehicles without compromising safety. The chips, which are used to provide the functionalities, are determined in the first step of ECU design. This decision will effect the remaining part of the development. Designing hardware and software together with testing phase is a long process in automotive industry. Changing the design of the hardware is quite costly after an ECU begins to be used in field. For these reasons, the selection of chips is directly related to cost and the functionality which should be provided to customer. Tasks, which fulfill desired functionality, provide a balance between performance and safety. These were evaluated for an OSEK/VDX certified OS and results are presented from the scheduling algorithms point of view.
An exact approach with minimum side-effects for association rule hiding
(Izmir Institute of Technology, 2014) Leloğlu, Engin; Ayav, Tolga; Ayav, Tolga
Concealing sensitive relationships before sharing a database is of utmost importance in many circumstances. This implies to hide the frequent itemsets corresponding to sensitive association rules by removing some items of the database. Research efforts generally aim at finding out more effective methods in terms of convenience, execution time and side-effect. This paper presents a practical approach for hiding sensitive patterns while allowing as much nonsensitive patterns as possible in the sanitized database. We model the itemset hiding problem as integer programming whereas the objective coefficients allow finding out a solution with minimum loss of nonsensitive itemsets. We evaluate our method using three real datasets from FIMI repository and compared the results with previous exact solution and the heuristic study whose procedures are imposed by new approach. The results show that information loss is dramatically minimized without sacrificing so many modifications on databases.
Exploring house price dynamics: An agent-based simulation with behavioral heterogeneity
(İzmir Institute of Technology, 2016-07) Özbakan, Ahmet Tolga; Ayav, Tolga; Kale, Serdar
In contemporary capitalist economies, housing is not only a shelter that satisfies a basic human need. It is also a commodity produced for exchange in markets and an asset for storing and enhancing wealth. As such, its mispricing can have repercussions for individuals, firms, industries, nationwide economies, and for the global economy. The purpose of this dissertation is to explore the price dynamics of this complex entity in an analytically tractable framework. In agreement with a recent but growing body of literature, the study shares the view that incorporating insights from behavioral economics can be valuable in such an undertaking. To support this statement, the dissertation first presents a theoretical framework that situates differing views on house prices in a wider split between neoclassical and behavioral economists. Then, the study proposes an agent-based simulation by extending a prominent real estate market model known as the Four Quadrant Model. Specifically, the extended model seeks to explore the extent to which behavioral heterogeneity and dynamic market behavior enhance the existing explanations of house price dynamics. The dissertation validates the proposed model by running a set of experiments with empirical data obtained from Istanbul’s housing market between January 2010 and September 2015. The results suggest that both the inclusion of behavioral heterogeneity and dynamic behavior are relevant in the exploration of house price dynamics. Based on the theoretical framework and the simulation results, the dissertation calls for action on the part of policy makers, researchers, and members of civic and professional organizations.