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Publication Metadata only Detecting motor bearing faults(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2004) Devaney, MJ; Eren, L; University of Missouri System; University of Missouri Columbia; Bahcesehir UniversityPublication Metadata only Sol-gel insulation coatings on Monel/Fe/MgB2 wires for coil development(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2008) Arda, L.; Boyraz, C.; Sacli, O. A.; Tomsic, M.; Hascicek, Y. S.; Bahcesehir University; Marmara University; State University System of Florida; Florida State UniversityIn this study, preparation, structure, morphology and thermal properties of ceramic insulation coating on Monel/Fe/MgB2 wires, which were fabricated by Hyper Tech Research Inc., using Continuous Tube Forming and Filling (CTFF) process were studied for coil development. Ceramic insulation coatings were prepared by reel-to-reel sol-gel method using solutions of Y and Zr based organometallic compounds. The coating thickness was controlled by number of coating, withdrawal speed and solution chemistry. 29 meter of Monel/Fe/MgB2 wire was insulated by Y2O3-ZrO2 using sol-gel method. Monel/Fe/MgB2 coil was layer wounded and impregnated with stycast. Sister samples of coil were tested between 4.2 K and 30 K with a Variable Temperature Insert (VTI) in a 20 T superconducting magnet using the analog DC pulse four-wire method with 1 (mu V/cm) criterion. The sample had a J(c) of 0.16 x 10(5) (A/cm(2)) at 4 T at 21 K. The surface morphologies and microstructure of sister samples of coil were characterized by ESEM, EDS, DTA, TGA and XRD. Resistance was measured by using HP 4339A High Resistance Meter.Publication Metadata only A NEW SPREADING CODE FOR MULTI-USER MC-SS COMMUNICATION SYSTEMS(ISTANBUL UNIV, FAC ENGINEERING, 2005) Cekic, Yalcin; Senay, Seda; Akan, Aydin; Chaparro, Luis F.; Bahcesehir University; Yeditepe University; Istanbul University; Pennsylvania Commonwealth System of Higher Education (PCSHE); University of PittsburghMulti-carrier spread spectrum (MCSS) communication systems are able to mitigate the effects of fading, interferences and Doppler frequency shifts as well as to support multiple access schemes. It is possible to get optimum performance from MCSS systems by carefully choosing the spreading sequences. However, due to inter-user interferences, performance degrades as the number of users increases unless the transmission channels are modeled and estimated. In this paper, we present a new spreading sequence obtained from a complex quadratic sequence multiplied by a pseudo random noise sequence, thus exploiting the properties of constant envelope and statistical independence. Our approach is based on the time-frequency characterization of the wireless communication channel by means of discrete evolutionary transform. The properties of the new spreading sequence enables us to estimate the parameters of multi-user channels, both for uplink and downlink transmission cases, and design a receiver that is robust to channel noise, inter-user interference and intentional jammers. The performance of the proposed system is illustrated by simulations.Publication Metadata only Preparation and Thermal Stress Analysis of Al2O3 Insulation Coatings on SS-304 Tape(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2009) Ataoglu, S.; Arda, L.; Kadioglu, N.; Cakiroglu, O.; Bulut, O.; Gulluoglu, A. N.; Belenli, I.; Istanbul Technical University; Bahcesehir University; Istanbul University; Marmara University; Abant Izzet Baysal University; Hakkari UniversityAl2O3 insulation coatings are grown on long-length stainless steel (SS) tapes using reel-to-reel sol-gel method for applications of HTS/LTS coils and magnets. Various ceramic solutions are prepared from Al based precursors, solvent and chelating agent, the coating are fabricated on SS substrates. Al2O3 solution was successfully obtained using Al-sec-butoxide precursor, and isopropanol and acetylacetone as solvent and chelating agents, respectively. In order to improve adhesion of Al2O3 on the SS-304 tapes, triethanolamine was used in the solution. The residual stresses are investigated at different temperature ranges, between (630, 600, 580, and 550 degrees C) and room temperature for different thicknesses (12, 10 and 7 mu m). The maximum stress values are obtained as 0.756 GPa as tension on substrate (SS) for the 12 mu m coating and 1.0 GPa as compression for the 7 mu m Al2O3 coating at 630 degrees C. The surface morphology and microstructure of samples are characterized by a scanning electron microscope (SEM). SEM observation revealed that Al2O3 coatings have crack and mosaic structure.Publication Metadata only Channel estimation and adaptive M-QAM in cognitive radio links(IEEE, 2008) Soysal, Alkan; Ulukus, Sennur; Clancy, Charles; Bahcesehir University; University System of Maryland; University of Maryland College Park; United States Department of DefenseCognitive radios have the ability to sense their RF environment and adapt their transmission parameters to perform optimally in any situation. Part of this involves selecting the best modulation type for a particular channel. In this paper we consider a variable-rate, variable-power, adaptive, M-ary Quadrature Amplitude Modulation (M-QAM) scheme in a single-user communication scenario. The channel between the transmitter and receiver is assumed to be a Rayleigh block-fading channel. Each block is divided into training and data phases. During the training phase, the receiver estimates the channel and feeds the estimate back to the transmitter. During the data phase, the transmitter sends its message by adapting the size of the M-QAM constellation. We first find a closed-form expression that relates the Bit Error Rate (BER) to the constellation size of the M-QAM, and therefore to the data rate of our system. Then, for a given target BER, we maximize the data rate over the training parameters, which are the training signal, the training duration, and the training power. When these optimum parameters are used in a MATLAB implementation, we find that the target BER is matched to within an order of magnitude, and the resulting data rate is close to the theoretical limit.Publication Metadata only MIMO Multiple Access Channels with Noisy Channel Estimation and Partial CSI Feedback(IEEE, 2008) Soysal, Alkan; Ulukus, Sennur; Bahcesehir University; University System of Maryland; University of Maryland College ParkWe consider correlated MIMO multiple access channels with block fading, where each block is divided into training and data transmission phases. We find the channel estimation and data transmission parameters that jointly optimize the achievable data rate of the system. Our results for the training phase are particularly interesting, where we show that the optimum training signals of the users should be non-overlapping in time. For the data transmission phase, we propose an iterative algorithm that updates the parameters of the users in a round-robin fashion. In particular, the algorithm updates the training and data transmission parameters of a user, when those of the rest of the users are fixed, in a way to maximize the achievable sum-rate in a multiple access channel, and iterates over users in a round-robin fashion.Publication Metadata only Optimizing the rate of a correlated MIMO link jointly over channel estimation and data transmission parameters(IEEE, 2008) Soysal, Alkan; Ulukus, Sennur; Bahcesehir University; University System of Maryland; University of Maryland College ParkWe consider a single-user correlated MIMO channel with block fading, where each block is divided into training and data transmission phases. The receiver has a noisy CSI that it obtains through a channel estimation process, while the transmitter has partial CSI in the form of covariance feedback. We optimize the achievable rate jointly over the parameters of the training and data transmission phases. In particular, we first choose the training signal to minimize the channel estimation error, and then, develop an iterative algorithm to solve for the optimum training duration, the optimum allocation of power between training and data transmission phases, and the optimum allocation of power over the antennas during the data transmission phase.Publication Metadata only Adjustable-Speed Drive Bearing-Fault Detection Via Wavelet Packet Decomposition(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2009) Teotrakool, Kaptan; Devaney, Michael J.; Eren, Levent; University of Missouri System; University of Missouri Columbia; Bahcesehir UniversityAdjustable-speed drives perform many vital control functions in the industry, serving in such diverse applications as rolling mills, variable-speed compressors, fans, and pumps. When an adjustable-speed drive fails due to a bearing failure, it is usually catastrophic. Bearing defects introduce vibration anomalies that alter the current characteristic frequencies. This paper addresses the application of motor current signature analysis using wavelet packet decomposition to detect bearing faults in adjustable-speed drives.Publication Metadata only Bearing fault detection via wavelet packet decomposition with spectral post processing(IEEE, 2007) Eren, Levent; Teotrakool, Kaptan; Devaney, Michael J.; Bahcesehir University; University of Missouri System; University of Missouri ColumbiaWe present a method for detecting motor bearing fault conditions via wavelet packet decomposition (WPD) of induction motor current. This method involves the decomposition of motor current into equally spaced frequency bands by using all pass implementation of Elliptic IIR half-band filters in the filter bank structure to obtain wavelet packet coefficients (WPC). Then, the bias in WPCs for each frequency band is removed to suppress leakage from adjacent frequency bands. Fourier analysis is applied to wavelet packet coefficients to provide higher frequency resolution within each frequency band. The changes in the energy levels of frequency bands in which motor fault related current frequencies lie are monitored to detect motor fault conditions.Publication Metadata only On state reduction of incompletely specified finite state machines(PERGAMON-ELSEVIER SCIENCE LTD, 2007) Goren, Sezer; Ferguson, F. Joel; Bahcesehir University; University of California System; University of California Santa CruzState reduction of incompletely specified finite state machines (ISFSMs) is an important task in optimization of sequential circuit design and known as an NP-complete problem. Removal of redundant states reduces the logic, because of this, chip area decreases. In addition, test generation is easier when the sequential circuit is irredundant. In this paper, we present a heuristic for state reduction of ISFSMs. The proposed heuristic is based on a branch-and-bound search technique and identification of sets of compatible states of a given ISFSM specification. We have obtained results as good as the best exact method in the literature but with significantly better run-times. (c) 2006 Elsevier Ltd. All rights reserved.