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Conference Object Citation - WoS: 2Citation - Scopus: 3Design Considerations for Sub-Ghz Multilayer Microstrip Antenna for Near Ground Communication Links in Rural Areas(Ieee, 2017) Bilgin, Gulsima; Yilmaz, Vadi Su; Aydin, Elif; Kara, Ali; Department of Electrical & Electronics Engineering; Electrical-Electronics EngineeringThis paper presents some preliminary results of design and development of sub-GHz multilayer microstip antenna for use in near ground communication applications. In design stage of the antenna, iterative approach was applied. Firstly, a two layer microstrip antenna design process is presented. Next, the corners of the patch were cut, and a vertical wall on all sides of the antenna were introduced. In this way, both the size and resonant freqeuncy can be tuned. Moreover, as an application specific requirement, it is intended to embed this antenna into a metal box in order to protect it from man-made and natural environmental effects. This was also studied, and effects of the embedding ground on the antenna characteristics were examined. It is shown that the designed antenna provides -27dB resturn loss, and 7.3dB peak gain at 915MHz with the dimension of 150x200x13mm. Some preliminary measurements have proven the simulations.Conference Object Citation - WoS: 12Design of a Robotic Bicopter(Ieee, 2019) Albayrak, Ozge Beyza; Ersan, Yagmur; Bagbasi, Aysen Suheyla; Basaranoglu, Ahmet Turgut; Arikan, Kutluk BilgeThis article presents a Bicopter type of a flying robot with two rotary-wing units which are placed in a tandem form on the chassis. The rotors are tilted by the aid of the tilt mechanism. Cascaded type of PID controllers are designed on the dynamical models for the attitude and altitude dynamics. The simulated control systems are implemented and tuned on the Naze32 flight controller which is connected to a Raspberry Pi single board computer for real-time applications. The real-time performance is monitored and evaluated during the tests and it is seen that the system is suitable for indoor type of robotic applications.Conference Object Citation - WoS: 4Citation - Scopus: 6A Reinforcement Learning Algorithm for Data Collection in Uav-Aided Iot Networks With Uncertain Time Windows(Ieee, 2021) Cicek, Cihan TugrulUnmanned aerial vehicles (UAVs) have been considered as an efficient solution to collect data from ground sensor nodes in Internet-of-Things (IoT) networks due to their several advantages such as flexibility, quick deployment and maneuverability. Studies on this subject have been mainly focused on problems where limited UAV battery is introduced as a tight constraint that shortens the mission time in the models, which significantly undervalues the UAV potential. Moreover, the sensors in the network are typically assumed to have deterministic working times during which the data is uploaded. In this study, we revisit the UAV trajectory planning problem with a different approach and revise the battery constraint by allowing UAVs to swap their batteries at fixed stations and continue their data collection task, hence, the planning horizon can be extended. In particular, we develop a discrete time Markov process (DTMP) in which the UAV trajectory and battery swapping times are jointly determined to minimize the total data loss in the network, where the sensors have uncertain time windows for uploading. Due to the so-called curse-of-dimensionality, we propose a reinforcement learning (RL) algorithm in which the UAV is trained as an agent to explore the network. The computational study shows that our proposed algorithm outperforms two benchmark approaches and achieves significant reduction in data loss.Conference Object Microstrip Antennas For WiMAX Applications(Ieee, 2015) Demirci, Tugkan; Caliskan, Fatma; Aydin, ElifIn this paper, four different antenna types have been designed to be used for WiMAX applications. These antennas have been designed using HFSS simulation software. This paper has included the return loss and the radiation pattern of the designed antennas. Using the simulation results, it is shown that these four antennas are working on Wi-Fi and WiMAX frequency ranges.Conference Object Citation - WoS: 4A Layered Security Architecture for Corporate 802.11 Wireless Networks(Ieee, 2004) Erten, YM; Tomur, EIn this study we have investigated the security aspects of wireless local area networks and discussed the weaknesses associated with various conventional 802.11 security protocols such as WEP and 802.1x. We propose an architecture to control access to corporate 802.11 wireless networks, based on the privileges and location of users, using the tested wired network components such as VPNs and Firewalls. The presented architecture reduces the security risks in enterprise level deployment of wireless LANs.Conference Object Citation - WoS: 16Citation - Scopus: 30A Search-Based Approach for Cost-Effective Software Test Automation Decision Support and an Industrial Case Study(Ieee, 2014) Amannejad, Yasaman; Garousi, Vahid; Irving, Rob; Sahaf, ZahraTest automation is a widely-used approach to reduce the cost of manual software testing. However, if it is not planned or conducted properly, automated testing would not necessarily be more cost effective than manual testing. Deciding what parts of a given System Under Test (SUT) should be tested in an automated fashion and what parts should remain manual is a frequently-asked and challenging question for practitioner testers. In this study, we propose a search-based approach for deciding what parts of a given SUT should be tested automatically to gain the highest Return On Investment (ROI). This work is the first systematic approach for this problem, and significance of our approach is that it considers automation in the entire testing process (i.e., from test-case design, to test scripting, to test execution, and test result evaluation). The proposed approach has been applied in an industrial setting in the context of a software product used in the oil and gas industry in Canada. Among the results of the case study is that, when planned and conducted properly using our decision-support approach, test automation provides the highest ROI. In this study, we show that if automation decision is taken effectively, test-case design, test execution, and test evaluation can result in about 307%, 675%, and 41% ROI in 10 rounds of using automated test suites.Conference Object Citation - WoS: 3Citation - Scopus: 11Towards Modeling Patterns for Embedded Software Industry: Feedback From the Field(Ieee, 2018) Akdur, Deniz; Demirors, Onur; Say, BilgeThe analysis, design, implementation and testing of software for embedded systems are not trivial. Software modeling is a commonly used approach in the embedded software industry to manage complexity of these phases. The modeling approaches vary since the characteristics of modeling such as its purpose, the medium type used, the lifecycle phase used, differ among systems and industrial sectors. Our previous research identified and defined the modeling approach patterns in embedded software development projects based on quantitative data. In this paper, to validate and improve the pre-investigated pattern set, we present a series of semi-structured interviews over eight months with 53 embedded software professionals across a variety of target industrial sectors and roles. With the help of these interviews, the different modeling approach patterns in embedded software development were better understood and the hidden patterns not evident in the previous study were identified along with a documentation of personalized modeling experiences.Conference Object An Rfid Based Location Finding and Tracking With Guidance(Ieee, 2008) Oktem, Rusen; Aydin, Elif Uray; Cagiltay, Nergiz ErcilThis paper tackles an RFID based location finding and tracking system. The system is an integral part of a navigation aid being developed for guiding visually disabled people in a store. The aid is composed of a portable hardware interface unit, a standalone RFID unit, and a central processing unit. The units interact via wireless communication to locate the position of the user in a known indoor environment and tracking his/her movement. An active RFID tag helps to estimate the location of a user and the user is guided to follow a route accordingly, via a tactile compass. The system uses RF signal strengths and is based on Bayes Decision Theory. Initial simulation results with the system prove promising for location finding and tracking, especially when the tracked person is guided by a system.Conference Object Optimization of modeling parameters of of a direct dimethyl ether fuel cell (DDMEFC)(Ieee, 2019) Alpaydin, Guvenc Umur; Colpan, C. Ozgur; Devrim, YilserDirect alcohol fuel cells are one of the suitable candidates for sustainable power generation in portable applications. Among the different alcohol types that can be used in these fuel cells, DME, which is almost non-toxic at room temperature and easy to liquefy, and has a molecular structure similar to methanol, is one of the suitable options. For this reason, many studies have been carried out to develop direct dimethyl ether fuel cell (DDMEFC). Mathematical modeling studies also play an important role in the development of DDMEFC since they enable the understanding of the performance of the fuel cells more thoroughly. In this study, a model has been developed by using the principles of conservation chemical species and electrochemistry. A modeling study was performed using MATLAB. The values of some modeling parameters were estimated using the genetic algorithm optimization technique.Conference Object An Investigation About Process Matchmaking Performances of Unstructured and Decentralized Digital Environments(Ieee, 2007) Cakir, Bugra; Kilic, HurevrenEfficient matchmaking is an important problem in unstructured and decentralized digital environments. We report the results of simulations of these environments and provide measurements of match performance focusing on unstructured and decentralized environments. In the study, different environment models including P2P (Hypergrid, Gnutella with/without ultrapeer); small-world (Watts-Strogatz); heavy-tailed and random versions of Autonomous System Waxman model showing power-law distribution property; random and 2D-Grid are considered. The flooding mechanism enabling process encounters for match purposes is uninformed Breadth-First-Search. Simulations show that the matchmaking performance of random environment outperforms the others for almost all different problems and time-to-live settings. On the other hand, the total cost of small world environment model is the highest for almost all setups.
