SCHOLARLY PUBLICATION

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Now showing 1 - 20 of 3089

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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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The 39th international conference of the EURO working group on operational research applied to health services: ORAHS 2013 special issue
(Springer Science+Business Media, 2015-09) Çayırlı, Tuğba; Gunal, M. M.; Gunes, E.; Ormeci, L.; Business Administration; ÇAYIRLI, Tuğba
The healthcare sector is facing major challenges worldwide in terms of higher demands for efficiency, quality and equity. Operational Research (OR) techniques offer valuable tools for improving the design and delivery of healthcare services (e.g., inpatient and outpatient care, admission processes, emergency services, home healthcare, etc.), as well as improving the decision-making processes and implementation of public health policies.
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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.
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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.
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40th anniversary editorial: Looking backwards to move forward in management research
(Elsevier, 2022-08) Robinson, S.; Muratbekova-Touron, M.; Linder, C.; Bouncken, R. B.; Fındıkoğlu, Melike Nur; Garbuio, M.; Hartner-Tiefenthaler, M.; Thanos, I. C.; Aharonson, B. S.; Strobl, A.; Zhang, H.; Erz, A.; von Wallpach, S.; Karapinar, P. B.; Diedrich, A.; Saint-Germes, E.; Cole, R.; Management Information Systems; FINDIKOĞLU, Melike Nur
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6098 sayılı Türk Borçlar Kanununa göre sorumluluk sebeplerinin yarışması
(Seçkin Yayıncılık, 2016-10) Kaya, Asım; Kaya, Asım
Sorumluluk sebeplerinin yarışması için sorumluluğun birden çok sebebe dayanması gerekir. Bu sebepler, haksız fiil sorumluluğu, sözleşmesel sorumluluk, sebepsiz zenginleşme olarak değerlendirilir. Sorumluluk sebeplerinin yarışması hali uygulamada sıkça karşılaşılan bir durumdur. Önceleri içtihatlarla geliştirilen bu kurum 6098 sayılı Türk Borçlar Kanun’un 60. maddesinde “Sebeplerin Yarışması” başlığı altında düzenlenmiştir. Bu maddeye göre, bir kişinin sorumluluğu, birden çok sebebe dayandırılabiliyorsa hâkim, zarar gören aksini istemiş olmadıkça veya kanunda aksi öngörülmedikçe, zarar görene en iyi giderim imkânı sağlayan sorumluluk sebebine göre karar verir. Bu durumda zamanaşımı da farklı uygulanabilecektir. Sebeplerin yarışması; seçimlik illiyet, yarışan illiyet ve ortak illiyetten farklı kavramlardır.
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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.
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Absorption and plasmon resonance of Bi-metallic core-shell nanoparticles on a dielectric substrate near an external tip
(Elsevier, 2020-01) Avsar, D.; Erturk, H.; Mengüç, Mustafa Pınar; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
Absorption efficiency profiles and localized surface plasmon resonance (LSPR) wavelengths are reported for metallic core-shell nanoparticles (NPs) placed over a BK7 glass substrate. A numerical study is performed with the vectorized version of the discrete dipole approximation with surface interactions (DDA-Sl-v). Gold (Au) and silver (Ag) metallic components are used for the simulations of two different core-shell structures. Absorption enhancement and the hybrid modes of plasmon resonances of the core-shell structures are compared by using a measure that defines a size configuration. It is observed that a small volume fraction of the core sizes results in shell domination over the plasmon response. 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. The absorption behavior of the bare metallic NPs and selected core-shell pairs in proximity to an external probe's tip is also analyzed. The gallium phosphide (GaP) and silicon (Si) tip usage are investigated with transverse electric (TE) and transverse magnetic (TM) wave polarizations. It is observed that the dominance of light polarization on the absorption enhancement of the NPs switches at different wavelengths, where the dielectric transition for tip materials occurs. These findings show the possible targeted uses of metallic core-shell nanoparticles in several areas such as nanomanufacturing, localized heating, bio-sensing, and material detection applications.
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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.
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Accelerated learning of user profiles
(Informs, 2011-02) Atahan, Pelin; Sarkar, S.; Sectoral Education and Professional Development; DEMİRCİLER, Pelin Atahan
Websites typically provide several links on each page visited by a user. Whereas some of these links help users easily navigate the site, others are typically used to provide targeted recommendations based on the available user profile. When the user profile is not available (or is inadequate), the site cannot effectively target products, promotions, and advertisements. In those situations, the site can learn the profile of a user as the user traverses the site. Naturally, the faster the site can learn a user's profile, the sooner the site can benefit from personalization. We develop a technique that sites can use to learn the profile as quickly as possible. The technique identifies links for sites to make available that will lead to a more informative profile when the user chooses one of the offered links. Experiments conducted using our approach demonstrate that it enables learning the profiles markedly better after very few user interactions as compared to benchmark approaches. The approach effectively learns multiple attributes simultaneously, can learn well classes that have highly skewed priors, and remains quite effective even when the distribution of link profiles at a site is relatively homogeneous. The approach works particularly well when a user's traversal is influenced by the most recently visited pages on a site. Finally, we show that the approach is robust to noise in the estimates for the probability parameters needed for its implementation.
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Accounting for age in marital search decisions
(Elsevier, 2016-06) Akın, Şerife Nuray; Platt, B. C.; Economics; DURAN, Şerife Nuray
Spouse quality, measured by educational attainment, varies significantly with the age at which an individual marries, peaking in the mid-twenties then declining through the early-forties. Interestingly, this decline is much sharper for women than men, meaning women increasingly marry less educated men as they age. Moreover, quality has worsened for educated women over several decades, while it has improved for men. Using a non-stationary sequential search model, we identify and quantify the search frictions that generate these age-dependent marriage outcomes. We find that single-life utility is typically the dominant friction, though college women in the 1950 and 1970 cohorts are affected even more by deteriorating suitor quality. Regardless of educational status, individual choice (as opposed to pure luck) is pivotal in explaining marriage market outcomes earlier in life.
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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.
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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.

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