Printed dipole array fed with parallel strip line for Ku-band applications

This paper presents the design procedure of a printed dipole antenna and 1D array configurations of the single dipole element in the Ku-Band with its metallic reflector plane parallel to the array plane. The proposed antenna has a natural beam tilt which is useful for some specific applications. Several array configurations in 1D are simulated and tested. The effect of mutual coupling among each array elements is also investigated. Required modifications on the individual array element and the feed structures due to the effect of mutual coupling are examined. The single dipole and array of dipole has measured VSWR values smaller than 2 in the Ku-Band with simulated gains of 5.7 dBi and 12 dBi, respectively. All the simulations are performed with ADS-2006A software and measurements are performed in an anechoic chamber

Governance in online communities of artistic cultural production

Thesis (D.B.A.)--Boston UniversityWhile scholars have brought much insight into the governance of online communities engaged in the production of goods with relatively established quality criteria, such as open source software, they paid less attention to the governance of online communities of artistic cultural production. In artistic cultural production, due to its drive for novelty and potential resistance to institutionalized norms, it is difficult to create agreements and shared routines among participants -particularly during initial emergence when participants are new to one another and new to their form of contributions. In this two-essay dissertation, I study arguably the largest online community of artistic production in Turkey, Sour Dictionary, and analyze the governance configurations during its initial emergence and ongoing growth. The first essay describes how coherence was achieved during the birth and early years of the Dictionary through the use of ambiguity in the two governance dimensions of vision and rules of production. I show that in this period, ambiguity was maintained in these dimensions not only to provide participants with the flexibility they needed for artistic expressions, but also to bring clarity to the recognition of participants' allegiances. The presence of a shared opposition among participants appears key to achieving coherence in an artistic community, and for such a community, ambiguity is an adaptive resource rather than something to eliminate as is often argued within an economic logic. The second essay follows a natural experiment where the founder's changing decisions on two other governance dimensions of quality assurance and member recruitment, along with his utilizations of IT for growth, resulted in different outcomes of coherence and popularity during the community's ongoing growth. As the founder switched the combination of his use of IT and member recruitment method from one that invited slow and incremental growth to one that brought sudden and massive growth, the community faced a variety of problems in both outcomes. I show that these problems arose as the founder responded to growth by implementing quality assurance methods that emphasized efficiency rather than flexibility, and thus failed to

Magneto Acoustic Spin Hall Oscillators

This paper introduces a novel oscillator that combines the tunability of spin Hall-driven nano oscillators with the high quality factor (Q) of high overtone bulk acoustic wave resonators (HBAR), integrating both reference and tunable oscillators on the same chip with CMOS. In such magneto acoustic spin Hall (MASH) oscillators, voltage oscillations across the magnetic tunnel junction (MTJ) that arise from a spin-orbit torque (SOT) are shaped by the transmission response of the HBAR that acts as a multiple peak-bandpass filter and a delay element due to its large time constant, providing delayed feedback. The filtered voltage oscillations can be fed back to the MTJ via a) strain, b) current, or c) magnetic field. We develop a SPICE-based circuit model by combining experimentally benchmarked models including the stochastic Landau-Lifshitz-Gilbert (sLLG) equation for magnetization dynamics and the Butterworth Van Dyke (BVD) circuit for the HBAR. Using the self-consistent model, we project up to $\sim$ 50X enhancement in the oscillator linewidth with Q reaching up to 52825 at 3 GHz, while preserving the tunability by locking the STNO to the nearest high Q peak of the HBAR. We expect that our results will inspire MEMS-based solutions to spintronic devices by combining attractive features of both fields for a variety of applications

One table to count them all: parallel frequency estimation on single-board computers

Sketches are probabilistic data structures that can provide approx- imate results within mathematically proven error bounds while using orders of magnitude less memory than traditional approaches. They are tailored for streaming data analysis on architectures even with limited memory such as single-board computers that are widely exploited for IoT and edge computing. Since these devices offer multiple cores, with efficient parallel sketching schemes, they are able to manage high volumes of data streams. However, since their caches are relatively small, a careful parallelization is required. In this work, we focus on the frequency estimation problem and evaluate the performance of a high-end server, a 4-core Raspberry Pi and an 8-core Odroid. As a sketch, we employed the widely used Count-Min Sketch. To hash the stream in parallel and in a cache-friendly way, we applied a novel tabulation approach and rearranged the auxiliary tables into a single one. To parallelize the process with performance, we modified the workflow and applied a form of buffering between hash computations and sketch updates. Today, many single-board computers have heterogeneous processors in which slow and fast cores are equipped together. To utilize all these cores to their full potential, we proposed a dynamic load-balancing mechanism which signif- icantly increased the performance of frequency estimation

Gold(i)/Zn(ii) catalyzed tandem hydroamination/annulation reaction of 4-yne-nitriles

The tandem hydroamination-annulation reaction of 4-pentyne-nitriles in the presence of amine nucleophiles and a cooperatively operating catalyst system, consisting of Ph3PAuCl and Zn(ClO4)2, provides an efficient route to 2-aminopyrroles. Two regioisomeric 2-aminopyrroles were formed in moderate to good yields. © 2010 The Royal Society of Chemistry.TÜBİTAK; TÜBA and MET

Essays on nonlinear dynamics in optimal growth models

Ankara : Department of Economics İhsan Doğramacı Bilkent University, 2014.Thesis (Ph. D.) -- Bilkent University, 2014.Includes bibliographical references leaves 79-84.Economic models with time delay have long been considered in economic theory. It is considered that delay forces the economic system into persistent cycles which can be interpreted as intrinsic crises of the capitalist economy. The e§ect of delay on economic dynamics is analyzed by Hopf bifurcation according to the recent developments in economics and mathematics. Hopf bifurcation depends on the existence of a pair of pure imaginary eigenvalues of the Jacobian matrix evaluated at the steady state. However, recent studies are inconsistent in a determinate way to decide whether the optimal growth model with investment lags admits persistent cycles or not. In the second chapter of this thesis, the author tries to sharpen the analysis of one sector optimal growth model with one control and one state variables and time delay. We Örstly give a brief outline of the mathematical history and ëknow-howíof delays in economic models, as well as its interpretation, and then, we further the analysis set of the model of Asea and Zak (1999) and try to introduce of a new technique for the exposition of the eigenvalues of the characteristic equation of these type of models in a generalized framework. In the third chapter we introduce a new technique (see Louisell, 2001) to the study of economic models with delays and incorporate this technique to evaluate the cycleinducing e§ects of capital dependent population growth in economic models with time delay. We employ the Solow-Kalecki framework and show that the presence of capital dependent population growth induces cycles. Other than the introduction of a new technique into the area of economics, one particular contribution of this chapter is that the results clearly shows that delay is not su¢ cient in inducing cycles even in the most simple economic models. In the forth chapter, we show that Hopf bifurcation may emerge in an overlapping generations resource economy through a feedback mechanism between population and resource availability. In overlapping generations resource economy models, the cycle inducing factor is mainly the nonlinearity of the regeneration of the resources. On the contrary, we assume linear regeneration and yet, endogenize the population growth rate. We show that the interaction between instantenous population growth and regeneration rate triggers persistent cycles in the economy. In the Öfth chapter, we employ a continuous delay structure in the process of recruitment in the population growth in an optimal growth model and hence obtain cyclic solutions. We exploit Erlangian process in the population growth mechanism. As far as we know, the incorporation of Erlangian process in optimal growth models is handled in this chapter for the Örst time in economic literature. Through this mechanism, not only the population is considered as a function of per capita capital, or in other words, population growth is endogenized, but also the current level of population growth is linked with those of older generations. We Önd out that the interaction between the e§ect of older generationsífertility choices and the accumulation of capital induces cyclic behaviour in the economy. The sixth and the last chapter concludes with future research agenda. Overall, the thesis considers the e§ects of delay and endogenized population on the economies of interest (Solow, overlapping generations, optimal growth model) economically and tries to introduce the existing methods and develop new ones to investigate the e§ects of delay and endogenized population on the eigenvalues of the Jacobians that the drive the economies of interest at their steady states.Yüksel, Mustafa KeremPh.D

On the existence of Hopf cycles in optimal growth models with time delay

Ankara : The Department of Economics and the Institute of Economics and Social Sciences of Bilkent University, 2008.Thesis (Master's) -- Bilkent University, 2008.Includes bibliographical refences.In this thesis, we analyzed the existence of cycles `a la Poincar´e-AndronovHopf in optimal growth models with time delay. The analysis builds upon a new method developed, which investigates the number of pure imaginary roots of the characteristic equation. The method was applied to the time-tobuild models of Asea and Zak (1999) and Winkler (2004).Yüksel, Mustafa KeremM.S

Automatic License Plate Location and Recognition Algorithm for Color Images

An automatic car license plate location and recognition system has a great importance in today's industrial world for intelligent transport systems. Any automatic license plate location and recognition system has two main stages: (1) the license plate location and (2) the license plate recognition (LPR). The license plate location is the most important stage in the LPR systems which affects the system's accuracy, directly. Most of the previous methods are based on gray images but the color information is also an important factor to locate the license plate. In this project, we propose a novel license plate location algorithm for color images. The proposed algorithm is based on the brake lights and headlights of car. At the recognition stage, a well known and accepted character recognition algorithm has been used

A Comparison of Local Site Conditions with Passive and Active Surface Wave Methods

This study encompasses dynamic soil characterization and seismic hazard mapping of the Plio-Quaternary and especially Quaternary alluvial sediments of the Çubuk district and its close vicinity that is situated towards the north of Ankara. The project site is located at a region which has a potential of being seriously affected by a possible earthquake occurring along the Çubuk Fault Zone that is thought to be a continuation of the Dodurga Fault Zone and a sub-fault belt of the North Anatolian Fault System that is one of the most prominent fault systems in Turkey with significant earthquake potential. Non-invasive seismic methods were used to obtain a 1-D shear wave velocity profile of the subsurface at 41 sites and two measurements were taken at each site for passive and active surface wave methods. The Multichannel Analysis of Surface Wave Method (MASW) and the Microtremor Array Method (MAM) were used as active and passive surface wave methods, respectively. By combining these two techniques, the shear wave velocity profiles of the sites were obtained. Based on the results, site classes were assigned for seismic hazard assessment studies followed by a preparation of a seismic zonation map of the site utilizing GIS software

Predicting NOx emissions in diesel engines via sigmoid NARX models using a new experiment design for combustion identification

Diesel engines are still widely used in heavy-duty engine industry because of their high energy conversion efficiency. In recent decades, governmental institutions limit the maximum acceptable hazardous emissions of diesel engines by stringent international regulations, which enforces engine manufacturers to find a solution for reducing the emissions while keeping the power requirements. A reliable model of the diesel engine combustion process can be quite useful to search for the best engine operating conditions. In this study, nonlinear modeling of a heavy-duty diesel engine NOx emission formation is presented. As a new experiment design, air-path and fuel-path input channels were excited by chirp signals where the frequency profile of each channel is different in terms of the number and the direction of the sweeps. This method is proposed as an alternative to the steady-state experiment design based modeling approach to substantially reduce testing time and improve modeling accuracy in transient operating conditions. Sigmoid based nonlinear autoregressive with exogenous input (NARX) model is employed to predict NOx emissions with given input set under both steady-state and transient cycles. Models for different values of parameters are generated to analyze the sensitivity to parameter changes and a parameter selection method using an easy-to-interpret map is proposed to find the best modeling parameters. Experimental results show that the steady-state and the transient validation accuracies for the majority of the obtained models are higher than 80% and 70%, respectively