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Publication Metadata only 3D object matching via multivariate shape distributions(Institute of Electrical and Electronics Engineers (IEEE), 2005) Akgül, C.B.; Sankur, B.; Schmitt, F.; Department of Computer Engineering; Yemez, Yücel; Faculty Member; Department of Computer Engineering; College of Engineering; 1079073B nesne eşleştirme literatüründe, problemi şekil dağılımlarının karşılaştırılmasına indirgeyen yöntemler bulunmaktadır. Şekil dağılımı, 3B nesne yüzeyi üzerinde hesaplanan bir işlevin değerlerinin olasılık dağılımı olarak tanımlanır. Bu çalışmada varolan yöntemi, birden çok işlevin getirdiği şekil bilgisinden aynı anda yararlanacak şekilde genişletiyoruz. Çokboyutlu şekil dağılımları adını verdiğimiz bu 3B nesne betimleyicilerini, örnek bir 3B nesne veri tabanındaki nesneler için parametrik olmayan yaklaşımlarla kestiriyor, karşılaştırmaları alternatif metrikler yoluyla yapıyoruz. Elde edilen kesinlik-geri getirme eğrileri çokboyutlu şekil dağılımlarının karşılaştırılmasının yeni bir 3B nesne eşleştirme paradigması olabileceğini göstermektedir.Publication Open Access 3D-printed contact lenses: challenges towards translation and commercialization(Future Medicine, 2022) Yetişen, Ali K.; Department of Mechanical Engineering; Taşoğlu, Savaş; Özdalgıç, Berin; Faculty Member; PhD Student; Department of Mechanical Engineering; KU Arçelik Research Center for Creative Industries (KUAR) / KU Arçelik Yaratıcı Endüstriler Uygulama ve Araştırma Merkezi (KUAR); Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); College of Engineering; Graduate School of Sciences and Engineering; 291971; 323683NAPublication Metadata only A built-in vibration sensor using ARC-discharged reactive ion plated PZT(The Institute of Electrical Engineers of Japan, 2011) Tani, Masanao; Akamatsu, Masahiro; Yasuda, Yoshiaki; Fujita, Hiroyuk; Toshiyoshi, Hiroshi; N/A; Baran, Utku; Master Student; Graduate School of Sciences and Engineering; N/AA piezoelectrically excited micro cantilever with multiple electrode ports has been developed as a standard test device to investigate the piezoelectric oscillation sensing capability. A 5 μm thick PZT was deposited by the arc-discharge reactive ion plating on a 20-μm-thick and 2700-μm-long SOI cantilever, and its piezoelectrically measured vibration signal was correlated with the reference oscillation signal from the laser Doppler vibrometer to prove the feasibility as oscillation detector. An equivalent circuit expression for the sensing electrode has been found.Publication Metadata only A communication theoretical analysis of synaptic multiple-access channel in hippocampal-cortical neurons(IEEE-Inst Electrical Electronics Engineers Inc, 2013) N/A; N/A; Department of Electrical and Electronics Engineering; Malak, Derya; Akan, Özgür Barış; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 6647Communication between neurons occurs via transmission of neural spike trains through junctional structures, either electrical or chemical synapses, providing connections among nerve terminals. Since neural communication is achieved at synapses, the process of neurotransmission is called synaptic communication. Learning and memory processes are based on the changes in strength and connectivity of neural networks which usually contain multiple synaptic connections. In this paper, we investigate multiple-access neuro-spike communication channel, in which the neural signal, i.e., the action potential, is transmitted through multiple synaptic paths directed to a common postsynaptic neuron terminal. Synaptic transmission is initiated with random vesicle release process from presynaptic neurons to synaptic paths. Each synaptic channel is characterized by its impulse response and the number of available postsynaptic receptors. Here, we model the multiple-access synaptic communication channel, and investigate the information rate per spike at the postsynaptic neuron, and how postsynaptic rate is enhanced compared to single terminal synaptic communication channel. Furthermore, we analyze the synaptic transmission performance by incorporating the role of correlation among presynaptic terminals, and point out the postsynaptic rate improvement.Publication Metadata only A comparison of data representation types, feature types and fusion techniques for 3D face biometry(European Association for Signal Processing, 2006) Dutaǧaci, H.; Sankur, B.; Department of Computer Engineering; Yemez, Yücel; Faculty Member; Department of Computer Engineering; College of Engineering; 107907This paper focuses on the problems of person identification and authentication using registered 3D face data. The face surface geometry is represented alternately as a point cloud, a depth image or as voxel data. Various local or global feature sets are extracted, such as DFT/DCT coefficients, ICA- and NMF- projections, which results in a rich repertoire of representations/features. The identification and authentication performance of the individual schemes are compared. Fusion schemes are invoked, to improve the performance especially in the case when there are only few samples per subject.Publication Metadata only A cross-layer approach for minimum delay content adaptive video streaming over variable bitrate channels(European Association for Signal Processing, 2005) N/A; N/A; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Özçelebi, Tanır; Tekalp, Ahmet Murat; Civanlar, Mehmet Reha; Sunay, Mehmet Oğuz; PhD Student; Faculty Member; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; College of Engineering; N/A; 26207; 16372; N/AA novel cross-layer scheduling and stream switching algorithm for content and channel adaptive video streaming over 1xEV-DO (CDMA-HDR), where stream switching is done according to the receiver buffer level is presented. The instantaneous transmission rate to each user is determined by a multi-objective optimized scheduler, maximizing network throughput and individual receiver buffer levels simultaneously, while the instantaneous coding rate for each user is determined according to buffer status feedback. The transmitter always switches to the most suitable pre-optimized bitstream with minimum delay and visual distortion calculated for various channel capacity values and under constant bitrate assumption. The main target of the proposed framework is to guarantee continuous playout of the transmitted content at all user devices while providing maximum system throughput, minimum overall distortion and minimum pre-roll delay. Experimental results show that decoder buffer overflows and underflows that cause pauses in the playout are prevented as opposed to the case without stream switching.Publication Open Access A DASH7-based power metering system(Institute of Electrical and Electronics Engineers (IEEE), 2015) Çetinkaya, Oktay; Akan, Özgür Barış; Researcher; College of EngineeringConsidering the inability of the existing energy resources to satisfy the current needs, the right and efficient. use of the energy has become compulsory. To make energy sustainability permanent, management and planning activities should be carried out by arranging the working hours and decreasing the energy wasting. For all these, power metering, managing and controlling systems or plugs has been proposed in recent efforts. Starting from this point, a new DASH7-based Smart Plug (D7SP) is designed and implemented to achieve a better structure compared to ZigBee equipped models and reduce the drawbacks of current applications. DASH7 technology reaches nearly 6 times farther distances in comparison with 2.4 GHz based protocols and provides multi-year battery life as a result of using limited energy during transmission. Performing in the 433 MHz band prevents the possible interference from overcrowded 2.4 GHz and the other frequencies which helps to gather a more reliable working environment. To shorten the single connection delays and human oriented failures, the MCU was shifted directly into the plug from the rear-end device. Working hours arrangement and standby power cutting off algorithms are implemented in addition to these energy saving targeted improvements to enhance more efficient systems. With the collaboration of the conducted hardware and software oriented adjustments and DASH7-based improvements, a more reliable, mobile and efficient system has been obtained in this work.Publication Metadata only A deformation-based approach to tuning of magnetic micromechanical resonators(2018) Yalçınkaya, Arda D.; Department of Mechanical Engineering; N/A; Department of Mechanical Engineering; Biçer, Mahmut; Esfahani, Mohammad Nasr; Alaca, Burhanettin Erdem; Researcher; PhD Student; Faculty Member; Department of Mechanical Engineering; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 115108Resonance frequency tuning in magnetic micromechanical resonators remains a primary field of study for frequency reference applications. The use of magnetic micromechanical resonators for innovative timing, oscillator and sensing applications necessitates a platform for the precise control of the resonance frequency. The present work addresses a deformation based technique for tuning the resonance frequency of nickel micromechanical resonators. Frequency response is measured through magnetic actuation and optical readout. The tuning approach is based on a combination of flexural deformation and uniaxial strain. The bending deformation is achieved by using a DC current through the microbeam. This magnetomotive mechanism reduces the resonance frequency by about 13% for a maximum DC current of 80 mA. A substrate bending method is used for applying uniaxial strain to increase the resonance frequency by about 8%. A bidirectional frequency modulation is thus demonstrated by utilizing both deformation techniques. The interpretation of results is carried out by finite element analysis and electromechanical analogy in an equivalent circuit. Using deformation techniques, this study provides a rigorous approach to control the resonance frequency of magnetic micromechanical resonators.Publication Open Access A diversity combination model incorporating an inward bias for interaural time-level difference cue integration in sound lateralization(Multidisciplinary Digital Publishing Institute (MDPI), 2020) N/A; Department of Computer Engineering; Mojtahedi, Sina; Erzin, Engin; Ungan, Pekcan; Faculty Member; Faculty Member; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Engineering; School of Medicine; N/A; 34503; N/AA sound source with non-zero azimuth leads to interaural time level differences (ITD and ILD). Studies on hearing system imply that these cues are encoded in different parts of the brain, but combined to produce a single lateralization percept as evidenced by experiments indicating trading between them. According to the duplex theory of sound lateralization, ITD and ILD play a more significant role in low-frequency and high-frequency stimulations, respectively. In this study, ITD and ILD, which were extracted from a generic head-related transfer functions, were imposed on a complex sound consisting of two low- and seven high-frequency tones. Two-alternative forced-choice behavioral tests were employed to assess the accuracy in identifying a change in lateralization. Based on a diversity combination model and using the error rate data obtained from the tests, the weights of the ITD and ILD cues in their integration were determined by incorporating a bias observed for inward shifts. The weights of the two cues were found to change with the azimuth of the sound source. While the ILD appears to be the optimal cue for the azimuths near the midline, the ITD and ILD weights turn to be balanced for the azimuths far from the midline.Publication Open Access A fast, accurate, and separable method for fitting a Gaussian function(Institute of Electrical and Electronics Engineers (IEEE), 2019) Al-Nahhal Ibrahim; Dobre Octavia A.; Moloney Cecilia; Ikki Salama; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 149116