Publications with Fulltext
Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/6
Browse
105 results
Search Results
Publication Open Access On the capacity of diffusion-based molecular communications with SiNW FET-based receiver(Institute of Electrical and Electronics Engineers (IEEE), 2016) Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Kuşcu, Murat; Akan, Özgür Barış; Faculty Member; College of EngineeringMolecular communication (MC) is a bio-inspired communication method based on the exchange of molecules for information transfer among nanoscale devices. Although MC has been extensively studied from various aspects, limitations imposed by the physical design of transceiving units have been largely neglected in the literature. Recently, we have proposed a nanobioelectronic MC receiver architecture based on the nanoscale field effect transistor-based biosensor (bioFET) technology, providing noninvasive and sensitive molecular detection at nanoscale while producing electrical signals at the output. In this paper, we derive analytical closed-form expressions for the capacity and capacity-achieving input distribution for a memoryless MC channel with a silicon nanowire (SiNW) FET-based MC receiver. The resulting expressions could be used to optimize the information flow in MC systems equipped with nanobioelectronic receivers.Publication Open Access Quantum state transfer among crystallographic groups of N-V centers in diamond(Society of Photo-optical Instrumentation Engineers (SPIE), 2011) Department of Physics; Department of Physics; Müstecaplıoğlu, Özgür Esat; Faculty Member; College of Sciences; 1674We investigate collections of Nitrogen-Vacancy (N-V) Centers in diamond crystals coupled to a circuit QED system of a coplanar waveguide (CPWG) resonator. Our analysis reveals that different symmetry axes oriented N-V centers in the diamond host can be grouped into bosonic modes of collective quasi-spin wave excitations so that the hybrid system can be described as an analog of an exciton-polariton type cavity QED model. We examine such model for quantum state transfer among distinct crystallographic groups of N-V centers in a single diamond as well as two spatially distant diamonds. Rabi oscillations, mode entanglement, possible use of N-V classes as spin ensemble qubits and an implementation of continuous-time quantum random walk are discussed.Publication Open Access Power performance of a continuous-wave Cr2+:ZnSe laser at 2.4 7 ?m(Optica Publishing Group, 2000) Pollock, C.R.; Department of Physics; Department of Physics; Sennaroğlu, Alphan; Konca, Ali Özgün; Faculty Member; Undergraduate Student; College of Sciences; 23851; N/AContinuous-wave power performance of a Cr2+:znSe laser was investigated at 2.474 ?m. End pumped by a 1.583-?m NaCl:OH- laser, the resonator with a 3% transmitting output coupler produced as high as 250 mW of output power with a slope efficiency of 24.2%. Analysis of the laser efficiency data shows that the magnitude of the excited-state absorption cross section is less than 5% of the emission cross section in agreement with spectroscopic results. Numerical calculations further predict the optimum crystal length and absorption coefficient to be 2.5 cm and 0.49 cm-1, respectively, for continuous-wave operation.Publication Open Access Minimum energy coding for wireless nanosensor networks(Institute of Electrical and Electronics Engineers (IEEE), 2012) Kocaoğlu, Murat; Akan, Özgür Barış; Faculty Member; College of EngineeringWireless nanosensor networks (WNSNs), which are collections of nanosensors with communication units, can be used for sensing and data collection with extremely high resolution and low power consumption for various applications. In order to realize WNSNs, it is essential to develop energy-efficient communication techniques, since nanonodes are severely energy-constrained. In this paper, a novel minimum energy coding scheme (MEC) is proposed to achieve energy-efficiency in WNSNs. Unlike the existing minimum energy codes, MEC maintains the desired Hamming distance, while minimizing energy, in order to provide reliability. It is analytically shown that, with MEC, codewords can be decoded perfectly for large code distance, if source set cardinality, M is less than inverse of symbol error probability, 1/ps. Performance analysis shows that MEC outperforms popular codes such as Hamming, Reed-Solomon and Golay in average energy per codeword sense.Publication Open Access Large-scale computational screening of MOF membranes and MOF-based polymer membranes for H2/N2 separations(American Chemical Society (ACS), 2019) Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Azar, Ayda Nemati Vesali; Velioğlu, Sadiye; Keskin, Seda; Graduate School of Sciences and Engineering; N/A; 200650; 40548Several thousands of metal organic frameworks (MOFs) have been reported to date, but the information on H-2/N-2 separation performances of MOF membranes is currently very limited in the literature. We report the first large-scale computational screening study that combines state-of-the-art molecular simulations, grand canonical Monte Carlo (GCMC) and molecular dynamics (MD), to predict H-2 permeability and H-2/N-2 selectivity of 3765 different types of MOF membranes. Results showed that MOF membranes offer very high H-2 permeabilities, 2.5 x 10(3) to 1.7 x 10(6) Barrer, and moderate H-2/N-2 membrane selectivities up to 7. The top 20 MOF membranes that exceed the polymeric membranes' upper bound for H-2/N-2 separation were identified based on the results of initial screening performed at infinite dilution condition. Molecular simulations were then carried out considering binary H-2/N-2 and quaternary H-2/N-2/CO2/CO mixtures to evaluate the separation performance of MOF membranes under industrial operating conditions. Lower H-2 permeabilities and higher N-2 permeabilities were obtained at binary mixture conditions compared to the ones obtained at infinite dilution due to the absence of multicomponent mixture effects in the latter. Structure performance relations of MOFs were also explored to provide molecular-level insights into the development of new MOF membranes that can offer both high H-2 permeability and high H-2/N-2 selectivity. Results showed that the most promising MOF membranes generally have large pore sizes (>6 A) as well as high surface areas (>3500 m(2)/g) and high pore volumes (>1 cm(3)/g). We finally examined H-2/N-2 separation potentials of the mixed matrix membranes (MMMs) in which the best MOF materials identified from our high-throughput screening were used as fillers in various polymers. Results showed that incorporation of MOFs into polymers almost doubles H-2 permeabilities and slightly enhances H-2/N-2 selectivities of polymer membranes, which can advance the current membrane technology for efficient H-2 purification.Publication Open Access Dimerization of pyrrole(TÜBİTAK, 1998) Yurtsever, Mine; Department of Chemistry; Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; College of Sciences; 7129Accurate ab-inito quantum mechanical calculations of pyrrole dimers are reported. The thermodynamical stabilities of dimers with alpha - alpha, alpha -beta, and beta - beta type linkages are compared in order to predict the possibilities of branching in polypyrroles. Calculations employing large basis sets and including electron correlation effects predict the alpha - alpha dimers as the most stable form. However, an alpha - beta type bonding requires only 1.5-2.0 kcal/mol, and the energy necessary to introduce a beta - beta type bond is 3.6-4.0 kcal/mol. These values show that a high degree of branching is possible even at room temperatures.Publication Open Access On the maximum coverage area of wireless networked control systems with maximum cost-efficiency under convergence constraint(Institute of Electrical and Electronics Engineers (IEEE), 2015) Kılınç, Deniz; Özger, Mustafa; Akan, Özgür Barış; PhD Student; College of EngineeringThe integration of wireless communication and control systems revealed wireless networked control systems (WNCSs). One fundamental problem in WNCSs is to have a wide coverage area. For the first time in the literature, we address this problem and we obtain the maximum coverage area by solving an optimization problem. In this technical note, we consider a WNCS where the output sensor measurements are transmitted over separate heterogeneous multi-hop wireless ad-hoc subnetworks. The observation process is divided into N parts and the system state is estimated using the Kalman filter. We present the critical arrival probability for a sensor measurement packet such that if the packet arrival probability is larger than the critical value, it is guaranteed that the estimator of the WNCS converges. We derive the maximum total coverage area of the heterogeneous wireless subnetworks having maximum cost-efficiency under the constraint of the convergence of the WNCS estimator.Publication Open Access Effects of force field selection on the computational ranking of MOFs for CO2 separations(American Chemical Society (ACS), 2018) Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Keskin, Seda; Dokur, Derya; Master Student; Graduate School of Sciences and Engineering; 40548; N/AMetal-organic frameworks (MOFs) have been considered as highly promising materials for adsorption-based CO2 separations. The number of synthesized MOFs has been increasing very rapidly. High-throughput molecular simulations are very useful to screen large numbers of MOFs in order to identify the most promising adsorbents prior to extensive experimental studies. Results of molecular simulations depend on the force field used to define the interactions between gas molecules and MOFs. Choosing the appropriate force field for MOFs is essential to make reliable predictions about the materials' performance. In this work, we performed two sets of molecular simulations using the two widely used generic force fields, Dreiding and UFF, and obtained adsorption data of CO2/H-2, CO2/N-2, and CO2/CH4 mixtures in 100 different MOF structures. Using this adsorption data, several adsorbent evaluation metrics including selectivity, working capacity, sorbent selection parameter, and percent regenerability were computed for each MOF. MOFs were then ranked based on these evaluation metrics, and top performing materials were identified. We then examined the sensitivity of the MOF rankings to the force field type. Our results showed that although there are significant quantitative differences between some adsorbent evaluation metrics computed using different force fields, rankings of the top MOF adsorbents for CO2 separations are generally similar: 8, 8, and 9 out of the top 10 most selective MOFs were found to be identical in the ranking for CO2/H-2, CO2/N-2, and CO2/CH4 separations using Dreiding and UFF. We finally suggested a force field factor depending on the energy parameters of atoms present in the MOFs to quantify the robustness of the simulation results to the force field selection. This easily computable factor will be highly useful to determine whether the results are sensitive to the force field type or not prior to performing computationally demanding molecular simulations.Publication Open Access Optical scanners for high resolution RSD systems(Society of Photo-optical Instrumentation Engineers (SPIE), 2002) DeWitt, F.; Luanava, S.; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Ürey, Hakan; Faculty Member; College of Engineering; 8579This paper outlines the design trade-offs and measured results of scanner architectures for use in high resolution Retinal Scanning Displays: Mechanical resonant for horizontal scanning, and MEMS-based pinch correction and vertical linear scanners. Analysis steps and techniques used to model and minimize dynamic deformations are covered. This paper also discusses two types of scanners and associated mirror flatness issues. Dynamic flatness modeling and performance results are presented, followed by thermally induced deformations and possible athermalize solutions for MEMS-type scanning mirrors. Theory, FEA dynamic and thermal analysis, experimental results, and methods to reduce mirror deformation are discussed.Publication Open Access On the physical design of molecular communication receiver based on nanoscale biosensors(Institute of Electrical and Electronics Engineers (IEEE), 2016) Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Kuşcu, Murat; Akan, Özgür Barış; Faculty Member; College of EngineeringMolecular communications, where molecules are used to encode, transmit, and receive information, are a promising means of enabling the coordination of nanoscale devices. The paradigm has been extensively studied from various aspects, including channel modeling and noise analysis. Comparatively little attention has been given to the physical design of molecular receiver and transmitter, envisioning biological synthetic cells with intrinsic molecular reception and transmission capabilities as the future nanomachines. However, this assumption leads to a discrepancy between the envisaged applications requiring complex communication interfaces and protocols, and the very limited computational capacities of the envisioned biological nanomachines. In this paper, we examine the feasibility of designing a molecular receiver, in a physical domain other than synthetic biology, meeting the basic requirements of nanonetwork applications. We first review the state-of-the-art biosensing approaches to determine whether they can inspire a receiver design. We reveal that the nanoscale field effect transistor-based electrical biosensor technology (bioFET) is particularly a useful starting point for designing a molecular receiver. Focusing on bioFET-based molecular receivers with a conceptual approach, we provide a guideline elaborating on their operation principles, performance metrics, and design parameters. We then provide a simple model for signal flow in silicon nanowire FET-based molecular receiver. Finally, we discuss the practical challenges of implementing the receiver and present the future research avenues from a communication theoretical perspective.