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41.
Engin Baysoy Dursun Korel Yildirim Cagla Ozsoy Senol Mutlu Ozgur Kocaturk 《Magma (New York, N.Y.)》2017,30(1):93-101
Objectives
A new microfabrication method to produce low profile radio frequency (RF) resonant markers on catheter shafts was developed. A semi-active RF resonant marker incorporating a solenoid and a plate capacitor was constructed on the distal shaft of a 5 Fr guiding catheter. The resulting device can be used for interventional cardiovascular MRI procedures.Materials and methods
Unlike current semi-active device visualization techniques that require rigid and bulky analog circuit components (capacitor and solenoid), we fabricated a low profile RF resonant marker directly on guiding the catheter surface by thin film metal deposition and electroplating processes using a modified physical vapor deposition system.Results
The increase of the overall device profile thickness caused by the semi-active RF resonant marker (130 µm thick) was lowered by a factor of 4.6 compared with using the thinnest commercial non-magnetic and rigid circuit components (600 µm thick). Moreover, adequate visibility performance of the RF resonant marker in different orientations and overall RF safety were confirmed through in vitro experiments under MRI successfully.Conclusion
The developed RF resonant marker on a clinical grade 5 Fr guiding catheter will enable several interventional congenital heart disease treatment procedures under MRI.42.
Christina Wildfire Engin Çiftyürek Katarzyna Sabolsky Edward M. Sabolsky 《Journal of Materials Science》2014,49(14):4735-4750
The incorporation of selective nanomaterials, such as common metal oxide semiconductor compositions, into resistive-type gas sensors has been shown by many researchers to lead to very high sensitivities and response rates, especially for micro-sized chemical sensors for room-temperature applications. The same strategy utilizing sensing nanomaterials has not been demonstrated for high-temperature sensors due to the intrinsic instability of typical metal oxide semiconductor nanomaterials at temperatures >500 °C. Within this work, doped Gd2Zr2O7 (GZO) nanomaterial compositions were investigated for H2 resistive-type sensors for applications between 600 and 1000 °C. This paper investigates the mechanism of H2 sensing for doped GZO nanomaterials and SnO2/GZO nanocomposites at the elevated temperatures. By integrating 10 vol.% nano-SnO2 into yttrium-doped GZO nanomaterials, a sensitivity of 4.15 % was retained for 4000 ppm H2 levels with a low signal drift of 0.42 %/h at 1000 °C in a 20 % O2/N2 gas stream. The signal drift was reduced by more than half of that compared to pure nano-SnO2 at the same conditions. The nano-GZO limited the grain growth of the nano-SnO2 particles and also prevented the nano-SnO2 from fully reducing to Sn at high temperatures in a low oxygen atmosphere. It is among the first resistive-type sensors operating at 1000 °C with sensing times of <5 min. This demonstration provided an example of a strategy of combining traditional metal oxide semiconductor and refractory nanomaterial compositions to form sensing nanocomposites with new sensing mechanisms, as well as, enhanced chemical and microstructural stabilities in high-temperature environments. 相似文献
43.
Yasin Varol Engin Avci Ahmet Koca Hakan F. Oztop 《International Communications in Heat and Mass Transfer》2007
Artificial Neural Network (ANN) and Adaptive-Network-Based Fuzzy Inference System (ANFIS) were used to predict the natural convection thermal and flow variables in a triangular enclosure which is heated from below and cooled from sloping wall while vertical wall is maintained adiabatic. Governing equations of natural convection were solved using finite difference technique by writing a FORTRAN code to generate database for ANN and ANFIS in the range of Rayleigh number from Ra = 104 to Ra = 106 and aspect ratio of triangle AR = 0.5 and AR = 1. Thus, the results obtained from numerical solutions were used for training and testing the ANN and ANFIS. A comparison was performed among the soft programming and Computational Fluid Dynamic (CFD) codes. It is observed that although both ANN and ANFIS soft programming codes can be used to predict natural convection flow field in a triangular enclosure, ANFIS method gives more significant value to actual value than ANN. 相似文献
44.
Engin A.E. John W. Sommer G. Mathis W. Reichl H. 《Advanced Packaging, IEEE Transactions on》2006,29(3):415-426
In this paper, a stripline model is presented for coupled signal lines routed between a power and a ground plane based on multiconductor transmission line (MTL) theory. Through a suitable diagonalization of the MTL equations for striplines, the transverse electromagnetic (TEM) parallel-plate mode is decoupled from the stripline mode. In this way, stripline models that are obtained assuming ideal planes at ground potential can be extended to take into account the nonideal behavior of the planes. The presented model is applied to represent mode conversion due to vias, holes in the reference planes, and terminations of the stripline. Influence of inhomogeneous media is discussed. 相似文献
45.
H Ertan Cetingül Yücel Yemez Engin Erzin A Murat Tekalp 《IEEE transactions on image processing》2006,15(10):2879-2891
There have been several studies that jointly use audio, lip intensity, and lip geometry information for speaker identification and speech-reading applications. This paper proposes using explicit lip motion information, instead of or in addition to lip intensity and/or geometry information, for speaker identification and speech-reading within a unified feature selection and discrimination analysis framework, and addresses two important issues: 1) Is using explicit lip motion information useful, and, 2) if so, what are the best lip motion features for these two applications? The best lip motion features for speaker identification are considered to be those that result in the highest discrimination of individual speakers in a population, whereas for speech-reading, the best features are those providing the highest phoneme/word/phrase recognition rate. Several lip motion feature candidates have been considered including dense motion features within a bounding box about the lip, lip contour motion features, and combination of these with lip shape features. Furthermore, a novel two-stage, spatial, and temporal discrimination analysis is introduced to select the best lip motion features for speaker identification and speech-reading applications. Experimental results using an hidden-Markov-model-based recognition system indicate that using explicit lip motion information provides additional performance gains in both applications, and lip motion features prove more valuable in the case of speech-reading application. 相似文献
46.
47.
Cebrail Çiflikli A. Tuncay Özşahin A. Çağrı Yapici 《Wireless Personal Communications》2009,51(2):221-229
The many advantages responsible for the widespread application of orthogonal frequency division multiplexing (OFDM) systems
are limited by the multipath fading. In OFDM systems, channel estimation is carried out by transmitting pilot symbols generally.
In this paper, we propose an artificial neural network (ANN) channel estimation technique based on levenberg-marquardt training
algorithm as an alternative to pilot based channel estimation technique for OFDM systems over Rayleigh fading channels. In
proposed technique, there are no pilot symbols which added to OFDM. Therefore, this technique is more bandwidth efficient
compared to pilot-based channel estimation techniques. Also, this technique is making full use of the learning property of
neural network. By using this feature, there is no need of any matrix computation and the proposed technique is less complex
than the pilot based techniques. Simulation results show that ANN based channel estimator gives better results compared to
the pilot based channel estimator for OFDM systems over Rayleigh fading channel. 相似文献
48.
In this work, undoped and Zn-doped copper oxide films were deposited on glass substrates at a substrate temperature of 250 ± 5°C
by using an ultrasonic spray pyrolysis technique. Electrical, optical, and structural properties of the films were investigated,
and the effect of Zn incorporation on these properties are presented. The variations of electrical conductivities and electrical
conduction mechanisms of all films were investigated in the dark and in the light. Optical properties of the produced films
were analyzed by transmission, linear absorption coefficient, and reflection spectra. The band gaps of the films were determined
by an optical method. The film structures were studied by x-ray diffraction. To obtain information about structural properties
in detail, the grain size (D), dislocation density (δ), and lattice parameters for preferential orientations were calculated. The elemental analyses were performed using energy-dispersive
x-ray spectroscopy. It was concluded that Zn has a strong effect, especially on the electrical and structural properties,
and the undoped and Zn-doped copper oxide (at 3%) films may be used as absorbing layers in solar cells due to their low resistivities
and suitable linear absorption coefficient values. 相似文献
49.
Nafion-clay hybrid membranes with a unique microstructure were synthesized using a fundamentally new approach. The new approach is based on depletion aggregation of suspended particles - a well-known phenomenon in colloids. For certain concentrations of clay and polymer, addition of Nafion solution to clay suspensions in water leads to a gel. Using Cryo-TEM we show that the clay particles in the hybrid gels form a network structure with an average cell size in the order of 500 nm. The hybrid gels are subsequently cast to produce hybrid Nafion-clay membranes. Compared to pure Nafion the swelling of the hybrid membranes in water and methanol is dramatically reduced while their selectivity (ratio of conductivity over permeability) increases. The small decrease of ionic conductivity for the hybrid membranes is more than compensated by the large decrease in methanol permeability. Lastly the hybrid membranes are much stiffer and can withstand higher temperatures compared to pure Nafion. Both of these characteristics are highly desirable for use in fuel cell applications, since a) they will allow the use of a thinner membrane circumventing problems associated with the membrane resistance and b) enable high temperature applications. 相似文献
50.
In this paper, instantaneous reactive power theory (IRP), also known as p–q theory based a new control algorithm is proposed for 3-phase 4-wire and 4-leg shunt active power filter (APF) to suppress harmonic currents, compensate reactive power and neutral line current and balance the load currents under unbalanced non-linear load and non-ideal mains voltage conditions. The APF is composed from 4-leg voltage source inverter (VSI) with a common DC-link capacitor and hysteresis–band PWM current controller. In order to show validity of the proposed control algorithm, compared conventional p–q and p–q–r theory, four different cases such as ideal and unbalanced and balanced-distorted and unbalanced-distorted mains voltage conditions are considered and then simulated. All simulations are performed by using Matlab-Simulink Power System Blockset. The performance of the 4-leg APF with the proposed control algorithm is found considerably effective and adequate to compensate harmonics, reactive power and neutral current and balance load currents under all non-ideal mains voltage scenarios. 相似文献