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Yayın Monitoring diffusion of reptating polymer chains by a direct energy transfer method: A Monte Carlo simulation(Wiley-Blackwell, 2002-07-29) Tüzel, Erkan; Kısacıkoğlu, Kemal Batuhan; Pekcan, Mehmet ÖnderA kinetic Monte Carlo method was used to simulate the diffusion of reptating polymer chains across an interface. A time-resolved fluorescence technique in conjunction with a direct energy transfer method was used to measure the extent of diffusion of dye-labeled reptating polymer chains. The diffusion of donor- and acceptor-labeled polymer chains between adjacent compartments was randomly generated. The fluorescence decay profiles of donor molecules were simulated at several diffusion steps to produce mixing of the polymer chains. Mixing ratios of donor- and acceptor-labeled polymer chains in compartments were measured at various stages (snap-shots) of diffusion. It was observed that for a given molecular weight, the average interpenetration contour length was found to be proportional to the mixing ratio. Monte Carlo analysis showed that the curvilinear diffusion coefficient is inversely proportional to the weight of polymer chains during diffusion.Yayın Effects of annealing on morphology of polymer/polymer (PS/PMMA) blend; a fluorescence study(John Wiley& Sons Inc, 2006-05-05) Uğur, Şaziye; Pekcan, Mehmet ÖnderSteady state fluorescence (SSF) technique conjunction with optical microscopy were used to study the morphology of polystyrene (PS)/poly(methyl methacrylate) (PMMA) blend upon annealing above glass transition in elevated time intervals. The PS/PMMA blends were prepared from dissolution of pyrene (P) and naphthalene (N) labeled PS and PMMA particles, respectively. Monte Carlo Simulations were performed to model the N and P fluorescence intensities (I-N and I-P), Using photon diffusion theory. Number of N and P photons (N-N and N-P) emerging from the front surface of the blend are calculated when only N is excited, where N-P photons are combined of photons from radiative (N-PR) and nonradiative (N-PNR) energy transfer processes. Optical microscopy images were taken at each annealing step to Support Our findings from fluorescence measurements.Yayın Termination transformation theorem for microwave power transfer networks(World Scientific Publishing Co. Pte Ltd, 2020-03-15) Köprü, RamazanTermination transformation theorem (TTT) proposed in this work transforms a doubly complex terminated microwave power transfer network (PTN) to an equivalent doubly resistively terminated termination transformed network (TTN) which is essentially a filter network. In this work, the transducer power gain (TPG) formula, Tgen, based on S and transmission (ABCD) parameters for the PTN have been restudied from the classical literature. Then, a new TPG formula, Tgen1, based on the newly proposed TTT has been derived using the transformed TTN network. To be able to show the validity of the proposed TTT, the newly derived TPG formula Tgen1 and the classical TPG formula Tgen have been computed within the scope of an example PTN design. The theorem has been proved mathematically, and experimentally as well with the aid of a Matlab code. The performance plots yielded from the Matlab code have clearly shown that both TPG formulae, i.e., Tgen and Tgen1, are in complete agreement with each other. In that sense, the proposed TTT might be considered as an alternative and helpful technique to be used in microwave engineering.Yayın Energy and data cooperation in energy harvesting multiple access channel(Institute of Electrical and Electronics Engineers Inc., 2016-08-26) Gürakan, Berk; Şişman, Berrak; Kaya, Onur; Ulukuş, SennurWe consider the energy harvesting two user Gaussian multiple access channel (MAC), where both users harvest energy from nature. The users cooperate at the physical layer (data cooperation) by establishing common messages through overheard signals and then cooperatively sending them. In addition, the users cooperate at the battery level (energy cooperation) by wirelessly transferring energy to each other. We find the jointly optimal offline transmit power and rate allocation policy together with the energy transfer policy that maximizes the departure region. We provide necessary conditions for energy transfer, and prove some properties of the optimal transmit policy, thereby shedding some light on the interplay between energy and data cooperation.Yayın Energy efficient transmission scheduling for channel-adaptive wireless energy transfer(Institute of Electrical and Electronics Engineers Inc, 2018) Bacinoǧlu, Baran Tan; Kaya, Onur; Uysal Bıyıkoğlu, ElifWe consider a fading communication link where the transmitter is powered by the receiver through wireless energy transfer (WET). A typical application scenario for this is the transmitter being a simple sensor while the demand for data is created by an application running at the receiver side and pulled from the transmitter as needed. We formulate two offline transmission scheduling problems: the transmitter-centric WET transmission optimization problem, where the schedule is computed by the transmitter, and the receiver-centric WET transmission optimization problem, where the receiver computes the schedule. We provide explicit solutions of both problems and propose online policies that rely on using the estimated water level values for each case. Our formulation allows direct optimization of energy efficiency in contrast to other EH transmission scheduling formulations in the literature. We prove some equivalence results under the special case of fixed channels.Yayın When to pull data for minimum age penalty(IEEE, 2021-10-18) Yavaşcan, Orhan Tahir; Ceran, Elif Tuğçe; Cakir, Zeynep; Uysal, Elif; Kaya, OnurA communication receiver that wants to pull data from a remote sensor by exploiting wireless energy transfer is considered. The receiver has a long-term average energy budget for this operation, and its goal is to keep the time average of a general age penalty function as small as possible. The channel from the source to the receiver is a two-state (ON/OFF) communication link whose state is IID or Markovian, and known instantaneously by the receiver. Modeling the problem as a constrained Markov decision problem, we obtain a randomized threshold-based decision policy that achieves the minimum possible average age penalty. We determine the optimal time average Age of Information and age violation probabilities by exploiting the optimality of the derived policy.
