Faculty of Engineering

Permanent URI for this communityhttps://hdl.handle.net/10679/10

Browse

Now showing 1 - 20 of 2213

Metadata only
A 130 nm CMOS receiver for visible light communication
(IEEE, 2022-06-15) Kısacık, Rıfat; Yagan, M. Y.; Uysal, Murat; Pusane, A. E.; Baykas, T.; Dundar, G.; Yalcinkaya, A. D.; Electrical & Electronics Engineering; UYSAL, Murat; Kısacık, Rıfat
Visible light communication (VLC) is an emerging technology that has been gaining attention over the last few years. Transmission of data at higher rates in a VLC system is mainly limited by the modulation bandwidth of the employed LED. To alleviate this limitation, equalization is frequently employed. This is usually achieved by either using discrete circuit elements or in digital form. In this paper, we present a power-efficient VLC receiver as a system-on-chip, implemented in 130 nm CMOS technology. The proposed receiver supports LEDs with different bandwidths thanks to the switchable equalizer. We tested the proposed receiver using phosphorescent white LEDs with different bandwidths on an experimental VLC link. For each tested LED, around 20 fold improvement in data rate was achieved compared to the original bandwidth of the LED. For the LED with a modulation bandwidth of 1.6 MHz, data rates of 32 Mbps and 50 Mbps at a BER of 102 were obtained at a distance of 2 meters without and with a blue filter, respectively.
Metadata only
The 13th international automated negotiating agent competition challenges and results
(Springer, 2023) Aydoğan, Reyhan; Baarslag, T.; Fujita, K.; Hoos, H. H.; Jonker, C. M.; Mohammad, Y.; Renting, B. M.; Computer Science; AYDOĞAN, Reyhan
An international competition for negotiating agents has been organized for years to facilitate research in agent-based negotiation and to encourage the design of negotiating agents that can operate in various scenarios. The 13th International Automated Negotiating Agents Competition (ANAC 2022) was held in conjunction with IJCAI2022. In ANAC2022, we had two leagues: Automated Negotiation League (ANL) and Supply Chain Management League (SCML). For the ANL, the participants designed a negotiation agent that can learn from the previous bilateral negotiation sessions it was involved in. In contrast, the research challenge was to make the right decisions to maximize the overall profit in a supply chain environment, such as determining with whom and when to negotiate. This chapter describes the overview of ANL and SCML in ANAC2022, and reports the results of each league, respectively.
Metadata only
15-15-0747-00-007a-tg7r1-cirs-channel-model-document-for-high-rate-pd-communications
(IEEE, 2015-11-14) Uysal, Murat; Baykas, T.; Miramirkhani, Farshad; Serafimovski, N.; Jungnickel, V.; Electrical & Electronics Engineering; UYSAL, Murat; Miramirkhani, Farshad
The LiFi channels developed by Prof. Murat Uysal and Mr. Miramirkhani were selected as the "LiFi Reference Channel Models" by the IEEE 802.15.7r Task Group during the IEEE's latest meeting held in Bangkok, Thailand, in September. Accordingly, all companies, universities and research institutions are required to use these channel models as reference for their performance assessments and comparative analysis in the standardization proposals they will submit over the coming months. The channel models developed by them are the most realistic models available in the literature and pointed out the significance of recognition and adoption of these models by industry.
Metadata only
16-elements helical antenna system integration with a solar cell powered IoT collector
(IEEE, 2019) Ullah, Naveed; Tekin, Ahmet; Electrical & Electronics Engineering; TEKİN, Ahmet; Ullah, Naveed
An 868MHz-915MHz 16-elements helical wire antenna array design with a solar-cell integration is presented. Each element is designed to be omni-directional with the corresponding tuning stubs and ground substrate. This is shared with distributed solar cell array, powering 16- Internet of Things (loT) transceivers operating at multiple Industrial Scientific and Medical (ISM) bands. 370mmx400mm design including the antennas, solar cells, and the tuning stubs can generate 8-watts solar power under direct sun, charging Lithium batteries. 1.6-mm thick planner design with horizontal radiation pattern resulted in average -15dB return loss at 868 MHz without using any external matching elements.
Metadata only
A 2020 perspective on “A generalized stereotype learning approach and its instantiation in trust modeling”
(Elsevier, 2020-03) Fang, H.; Zhang, J.; Şensoy, Murat; Computer Science; ŞENSOY, Murat
Owing to the rapid increase of user data and development of machine learning techniques, user modeling has been explored in depth and exploited by both academia and industry. It has prominent impacts in e-commercerelated applications by facilitating users' experience in online platforms and supporting business organizations' decision-making. Among all the techniques and applications, user profiling and recommender systems are two representative and effective ones, which have also obtained growing attention. In view of its wide applications, researchers and practitioners should improve user modeling from two perspectives: (1) more effort should be devoted to obtain more user data via techniques like sensing devices and develop more effective ways to manage complex data; and (2) improving the ability of learning from a limited number of data samples (e.g., few-shot learning) has become an increasingly hot topic for researchers.
Metadata only
25th IFIP/IEEE conference on very large scale integration (VLSI-SoC 2017)
(IEEE, 2018-02) Elfadel, I. A. M.; Uğurdağ, Hasan Fatih; Electrical & Electronics Engineering; UĞURDAĞ, Hasan Fatih
The 25th IFIP/IEEE Conference on Very Large Scale Integration (VLSI-SoC 2017) was held between 23 and 25 October in the landmark Yas Viceroy Hotel, overlooking the Formula 1 Yas Marina racetrack in Yas Island, Abu Dhabi, United Arab Emirates (UAE). The conference was held under the overarching theme: “The Internet of Things: SoC Challenges and Opportunities,” and featured four keynote addresses on this topic by renowned leaders from industry and academia, including Dr. Yervant Zorian, Synopsys Fellow and President of Synopsys Armenia, Dr. Rafic Makki, Executive Fellow, GLOBALFOUNDRIES, Dr. Leon Stok, VP EDA, IBM, and Prof. Simha Sethumadhavan, Columbia University. Prof. Tod A. Laursen, President of Khalifa University of Science and Technology gave the Welcome Address at the Opening Session.
Metadata only
2D non-linear seismic response of the Dinar basin,TURKEY
(Elsevier, 2016-10) Khanbabazadeh, H.; Iyisan, R.; Ansal, Mustafa Atilla; Hasal, M. E.; Civil Engineering; ANSAL, Mustafa Atilla
Local geological conditions generate significant amplification of ground motion and concentrated damage during earthquakes. The highly concentrated damages at the edges of the Dinar basin during occurred earthquakes at regions close to rock outcrop bring up the effect of the inclined bedrock effect on the dynamic behavior of the basin with 2D geometry. In this study, first the idealized 2D model of the basin based on the results of the underground explorations and geologic investigations is proposed. Results show that Dinar basin has an asymmetric 2D geometry with two different bedrock angles at edges. Then, a numerical study using finite difference based nonlinear code which utilizes appropriate static and dynamic boundary conditions, and includes hysteresis damping formulation based on the user defined degradation curves is conducted using real earthquake motions of different strength and frequency content. The constructed model is subjected to the collection of 16 earthquakes with different PGA's of 0.1, 0.2, 0.3 and 0.4 g, four motions for each PGA. It was seen that the dynamic behavior of the basin is broadly affected by the two dimensional bedrock. The results indicates the higher effect of the 6° bedrock inclination at east part on the amplification with respect to the steeper 20° bedrock slope at the west. Also, the results show the insignificant effect of the bedrock at the depth more than 150 m on the amplification of the east edge. While the effect of the 6° bedrock angle at the east part continues until 1500 m from the outcrop, it affects the amplification until 700 m from the outcrop at the west part with 20° bedrock angle.
Metadata only
3-D extension of chemical mechanical polishing for nano-structuring applications on alternative technologies
(The Electrochemical Society, 2016) Özdemir, Zeynep; Başım, Gül Bahar; Mechanical Engineering; BAŞIM DOĞAN, Gül Bahar; Özdemir, Zeynep
In this study we tune the chemical mechanical polishing process to a 3-D level to generate controlled nanostructures on functional metallic surfaces such as titanium implants and steel based heating elements. The chemical passivation action of the CMP process on metallic surfaces enables the formation of inert interfaces resistant to corrosion and degradation while the induced nanostructures help tune the surface attachment/detachment ability as these surfaces interact with alternative external elements.
Metadata only
3B kamera takibi için eylemsizlik algılayıcılarının birleştirilmesi
(IEEE, 2012) Özer, N.; Erdem, Tanju; Ercan, Ali Özer; Eroğlu Erdem, Ç.; Electrical & Electronics Engineering; Computer Science; ERDEM, Arif Tanju; ERCAN, Ali Özer
It is well known in a Bayesian filtering framework, the use of inertial sensors such as accelerometers and gyroscopes improves 3D tracking performance compared to using camera measurements only. The performance improvement is more evident when the camera undergoes a high degree of motion. However, it is not well known whether the inertial sensors should be used as control inputs or as measurements. In this paper, we present the results of an extensive set of simulations comparing different combinations of using inertial sensors as control inputs or as measurements. We show that it is better use a gyroscope as a control input while an accelerometer can be used as a measurement or control input. We also derive and present the extended Kalman filter (EKF) equations for a specific case of fusing accelerometer and gyroscope data that has not been reported before.
Metadata only
3D simulation of droplet impact on static and moving walls
(Begell House Inc., 2022) Yılmaz, Anıl; Kayansalçik, Gökhan; Ertunç, Özgür; Mechanical Engineering; ERTUNÇ, Özgür; Yılmaz, Anıl; Kayansalçik, Gökhan
In the present study, the contact angle model and the origin of the parasitic current, precisely, the relation of the parasitic current with grid distribution, have been studied to accurately predict droplet impact on static and moving walls in the volume of fluid (VOF) framework. The authors have quantitatively shown that the number of neighboring cells of the central cell influences the gradient calculations regarding the generation and spatial distribution of parasitic current. Accordingly, the polyhedral cell structure provides smoother interface gradient distribution than the Cartesian grid structure. After implementing a modified Kistler contact angle model in OpenFOAM and using the polyhedral grid for the simulations, we could accurately validate transient droplet shapes formed upon impact with those obtained from experiments. Droplet outcomes obtained, such as deposition, partial rebound, and split deposition on stationary and moving smooth surfaces, are consistent with experimental results.
Metadata only
Absorption and plasmon resonance of bi-metallic core-shell nanoparticles on a dielectric substrate
(Begell House Inc., 2019-06) Avşar, D.; Ertürk, H.; Mengüç, Mustafa Pınar; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
Numerical investigation of absorption efficiency profiles and localized surface plasmon resonance (LSPR) wavelengths are performed for metallic core-shell nanoparticles (NPs) placed over a BK7 glass substrate. Gold (Au) and silver (Ag) metallic components are used in two different coreshell structures. This numerical study is performed with vectorized version of the discrete dipole approximation with surface interactions (DDA-SI-v). Absorption enhancement and the hybrid modes of plasmon resonances of the core-shell structures are compared by using a metric that defines a size configuration. It is observed that small volume fraction of the core sizes results in shell domination over the plasmon response. Moreover, an additional study is conducted to discern the sensitivity of the refractive index of nanoparticles in different surrounding environments. With a selected core-shell size configuration of Ag-Au pairs, a significant absorption enhancement with a redshift of LSPR wavelength is observed for both Ag core-Au shell and Au core-Ag shell NPs. These findings show the possible targeted uses of metallic core-shell nanoparticles in local heating, bio-sensing, and material detection applications.
Metadata only
Absorption suppression of silver nanoparticles in the presence of an AFM tip: A harmonic oscillator model
(AIP, 2012) Huda, G. M.; Mengüç, Mustafa Pınar; Hastings, J. T.; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
We numerically calculated the optical absorption of silver nanoparticles (AgNP) in the presence of metallic and dielectric AFM probes, illuminated by transverse magnetic (TM) polarized, total internal reflected waves. Nanoscale probes localize and enhance the field between the apex of the tip and the particle. However, such probes can actually suppress the optical absorption of the AgNP. To better understand this phenomenon, we fitted the numerical absorption data with the equation of a driven damped harmonic oscillator (HO), and we found that the AFM tip modifies both the driving force and increases the overall damping of the oscillator by introducing an additional radiative decay path. For a 50 nm diameter AgNP the introduction of either a metallic or dielectric AFM probe suppresses absorption.
Metadata only
Achievable data rates and power allocation for frequency-selective fading relay channels with imperfect channel estimation
(Springer Science+Business Media, 2012-12) Ding, Y.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
In this article, we investigate the information-theoretical performance of a cooperative orthogonal frequency division multiplexing (OFDM) system with imperfect channel estimation. Assuming the deployment of training-aided channel estimators, we derive a lower bound on the achievable rate for the cooperative OFDM system with amplify-and-forward relaying over frequency-selective Rayleigh fading channels. The bound is later utilized to allocate power among the training and data transmission phases. Numerical results demonstrate that the proposed power allocation scheme brings between 5 and 19% improvement depending on the level of signal-to-noise ratio and relay locations.
Metadata only
Acoustic analysis of an axial fan
(IEEE, 2017) Hashım, Hafız Muhammad; Dogruoz, M. B.; Arık, Mehmet; Mechanical Engineering; ARIK, Mehmet; Hashım, Hafız Muhammad
Axial fans are often used in cooling electronic enclosures where low noise levels are highly demanded. Therefore, methods for predicting the noise emitted by an application including single or multiple fans are desirable to improve, stimulate and reduce the cost of low-noise design. The prediction of sound generated from fluid flow has been difficult due to the non-linear form of the governing equations, however, recent developments in computational fluid dynamics (CFD) and computational acoustics allow us to determine sound pressure levels (SPL) in a fluid flow. In this study, time dependent flow field produced by an axial fan is computed via Large Eddy Simulations (LES), and the consequent sound pressure map is determined using the Ffowcs Williams-Hawkings (FW-H) model. Since an axial fan is a complex source of sound, for engineering design purposes, simplifications are needed when modelling its acoustic characteristics, therefore, the sound radiation of an axial fan in free space is examined by expanding the generated sound pressure field into spherical harmonics. In addition, acoustic measurements are carried out in a semi-anechoic chamber to validate the aforementioned computational models and make necessary comparisons. Comparison of the numerical results against the experimental data shows that, despite some discrepancies, the former is able to capture the trends observed in the measurements.
Metadata only
Acoustics and heat transfer characteristics of piezoelectric driven central orifice synthetic jet actuators
(Taylor & Francis, 2022-09-19) Ikhlaq, M.; Yasir, M.; Ghaffari, O.; Arık, Mehmet; Mechanical Engineering; ARIK, Mehmet
Growth in computational capacity combined with a decrease in the size of digital devices has led to increasing demand for more active and efficient cooling of electronics. In this study, an experimental investigation into two different sizes of central orifice Synthetic Jet Actuators (SJAs) is conducted to evaluate their heat transfer as well as noise generation characteristics. Two SJAs (40 mm and 20 mm) are examined, covering a distinct span of frequencies ranging from low to medium (<5500 Hz) in regards to the effect of SJA size over performance. The SJAs’ disk deflection, structural frequency, and jet exit velocity were measured to fully characterize the jet performance. The maximum Nusselt number for the largest SJA was 3 times more than the smallest SJA, where the evaluation of stroke length suggests no effective synthetic jet formation for the smallest SJA. The noise from the SJAs was measured in an anechoic chamber using three microphones, Fast Fourier Transform (FFT) of the sound pressure levels provide contributions to different tones in the resulting noise. 1/3 Octave Constant Percentage Bandwidth (CPB) analysis was performed to identify the frequency bands making the largest contribution to the noise. The largest SJA showed the highest heat transfer at acceptable noise levels during the operation below resonance frequency.
Metadata only
Action and language mechanisms in the brain: data, models and neuroinformatics
(Springer Science+Business Media, 2014-01) Arbib, M. A.; Bonaiuto, J. J.; Bornkessel-Schlesewsky, I.; Kemmerer, D.; MacWhinney, B.; Årup Nielsen, F.; Öztop, Erhan; Computer Science; ÖZTOP, Erhan
We assess the challenges of studying action and language mechanisms in the brain, both singly and in relation to each other to provide a novel perspective on neuroinformatics, integrating the development of databases for encoding – separately or together – neurocomputational models and empirical data that serve systems and cognitive neuroscience.
Metadata only
An active brace for controlled transdermal drug delivery for adjustable physical therapy
(IEEE, 2014) Erol, Levent; Bebek, Özkan; Karagöz, Ayşe; Başım, Gül Bahar; Mechanical Engineering; BEBEK, Özkan; BAŞIM DOĞAN, Gül Bahar; Erol, Levent; Karagöz, Ayşe
This study presents an active brace which is a cost efficient precision-controlled advanced therapy medicinal product for time and rate controlled transdermal drug delivery (TDD) through the use of drug containing nanoparticles and electronics. The active brace is designed to adjust the pressure at the contact area where the medication is applied. The drug is contained in the nanoparticles produced and takes effect when the nanoparticles burst under pressure. The brace is designed to be compact and wearable which can be preprogrammed by a specialist to continue treatment sessions outside the medical facilities providing convenience and comfort to the patient.
Metadata only
Adapted infinite kernel learning by multi-local algorithm
(World Scientific Publishing Co, 2016-05) Özöğür Akyüz, S.; Üstünkar, Gürkan; Weber, G. W.
The interplay of machine learning (ML) and optimization methods is an emerging field of artificial intelligence. Both ML and optimization are concerned with modeling of systems related to real-world problems. Parameter selection for classification models is an important task for ML algorithms. In statistical learning theory, cross-validation (CV) which is the most well-known model selection method can be very time consuming for large data sets. One of the recent model selection techniques developed for support vector machines (SVMs) is based on the observed test point margins. In this study, observed margin strategy is integrated into our novel infinite kernel learning (IKL) algorithm together with multi-local procedure (MLP) which is an optimization technique to find global solution. The experimental results show improvements in accuracy and speed when comparing with multiple kernel learning (MKL) and semi-infinite linear programming (SILP) with CV.
Metadata only
Adaptive 6.78-MHz ISM band wireless charging for small form factor receivers
(IEEE, 2017) Abouzeid, Mohamed Osama Hussein Soliman; Tekin, Ahmet; Electrical & Electronics Engineering; TEKİN, Ahmet; Abouzeid, Mohamed Osama Hussein Soliman
This paper presents a low cost wireless power transfer system tailored particularly for size limited insulation sealed wearable devices. The 5-V USB input system features a crystal oscillator as reference signal source, a class-E power stage, a transmit coil with tunable series resonance and a feedback path to tune the resonance for peak power transmission. Regardless of the receive coil, load, component variations or any external blockers, the system continuously targets peak power at the strict center frequency of 6.78 MHz for compliance with international frequency regulations. Design choices and experimental measurement results were presented along with detailed circuit diagrams. The design can transfer around 50mW power to a 15mm × 17mm × 1mm 40-turn receive coil in a charging pad area of as wide as 9cm × 9cm.
Metadata only
Adaptive bit loading for multi-relay cooperative orthogonal frequency division multiple with imperfect channel estimation
(IEEE, 2012-08-14) Amin, O.; Ikki, S. S.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
In this study, the authors introduce an adaptive bit loading scheme for an amplify-and-forward orthogonal frequency division multiple cooperative system with relay selection. The proposed bit loading scheme maximises the throughput for a target error rate taking into account the quality of imperfect channel estimation. It relies on estimated channel state information (CSI) at the destination node and partial CSI (which involves the number of loaded bits) at the source node. The authors provide extensive Monte Carlo simulation results to demonstrate the throughput and the no-transmission probability performance of the proposed scheme and discuss the effect of various system and channel parameters on the performance.

Browse

Browsing by Rights "info:eu-repo/semantics/restrictedAccess"