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Average Power (average + power)
Selected AbstractsAverage power handling capability of multilayer microstrip linesINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 6 2001Inder J. Bahl Abstract This article describes the average power handling capability (APHC) of multilayer microstrip lines, including the effect of mismatch at the terminations. The data presented herein are validated by considering an example of a 12-W monolithic microwave integrated circuit power amplifier fabricated using multilayer low-loss microstrip technology. The calculated value of APHC for a 50-, line of a 75-,m-thick GaAs substrate is 1445 W at 10 GHz, whereas the corresponding value for a multilayer microstrip that has 10-,m-thick polyimide is only 44 W. At 40 GHz, these values are reduced by a factor of 2. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 385,395, 2001. [source] The generalized Rice lognormal channel model,first and second order statistical characterization and simulationINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 1 2002F. Vatalaro Abstract The Rice-lognormal (RLN) channel model was recently generalized to include an additive scattering component having constant average power. The generalized Rice-lognormal (GRLN) model includes as limiting cases many well-known narrowband models such as, e.g. Rice, lognormal (and combinations), and Loo's. The paper provides the GRLN first-order statistical description of envelope and phase, and the second-order statistics in terms of level crossing rate. The paper then provides a fitting procedure to extract model parameters from experimental data. Finally, it presents a new simulation procedure and validates it through comparison with theoretical results. Copyright © 2002 John Wiley & Sons, Ltd. [source] Gold-Tip Electrodes,A New "Deep Lesion" Technology for Catheter Ablation?JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 7 2005In Vitro Comparison of a Gold Alloy Versus Platinum, Iridium Tip Electrode Ablation Catheter Radiofrequency (RF) catheter ablation is widely used to induce focal myocardial necrosis using the effect of resistive heating through high-frequency current delivery. It is current standard to limit the target tissue,electrode interface temperature to a maximum of 60,70°C to avoid char formation. Gold (Au) exhibits a thermal conductivity of nearly four times greater than platinum (Pt,Ir) (3.17 W/cm Kelvin vs 0.716 W/cm Kelvin), it was therefore hypothesized that RF ablation using a gold electrode would create broader and deeper lesions as a result of a better heat conduction from the tissue,electrode interface and additional cooling of the gold electrode by "heat loss" to the intracardiac blood. Both mechanisms would allow applying more RF power to the tissue before the electrode,tissue interface temperature limit is reached. To test this hypothesis, we performed in vitro isolated liver and pig heart investigations comparing lesion depths of a new Au-alloy-tip electrode to standard Pt,Ir electrode material. Mean lesion depth in liver tissue for Pt,Ir was 4.33 ± 0.45 mm (n = 60) whereas Au electrode was able to achieve significantly deeper lesions (5.86 ± 0.37 mm [n = 60; P < 0.001]). The mean power delivered using Pt,Ir was 6.95 ± 2.41 W whereas Au tip electrode delivered 9.64 ± 3.78 W indicating a statistically significant difference (P < 0.05). In vitro pig heart tissue Au ablation (n = 20) increased significantly the lesion depth (Au: 4.85 ± 1.01 mm, Pt,Ir: 2.96 ± 0.81 mm, n = 20; P < 0.001). Au tip electrode again applied significantly more power (P < 0.001). Gold-tip electrode catheters were able to induce deeper lesions using RF ablation in vitro as compared to Pt,Ir tip electrode material. In liver and in pig heart tissue, the increase in lesion depth was associated with a significant increase in the average power applied with the gold electrode at the same level of electrode,tissue temperature as compared to platinum material. [source] Role of various elliptical shapes for efficient microwave processing of materialsAICHE JOURNAL, Issue 6 2007Tanmay Basak Abstract A detailed theoretical analysis has been carried out to assess the role of various elliptical shapes/cross sections on microwave heating of 2-D cylinders for beef and oil samples. Two types of elliptical cross sections are considered as type A (ellipse with major axis along the horizontal plane), and type B (ellipse with minor axis along the horizontal plane.) A preliminary analysis on microwave heating of samples has been shown via average power within a sample vs. sample radius of circular cross section for beef and oil samples. Several regimes (I,III) based on small and large radius for circular cross sections have been selected. The effect of elliptical shapes for type A and B configurations has been studied initially via average power vs. aspect ratio distributions for various regimes. The grayscale images of power absorption have been analyzed further for elliptical cross section with varying aspect ratios for regimes I,III where aspect ratio and types of configuration are shown to influence spatial power absorptions. The detailed temperature profiles have also been shown to illustrate the role of elliptical shapes on uniform heating and thermal runaway. Depending on the material dielectric properties and sample dimension, either type A or B or both configuration has been recommended. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source] Mode-locked Yb-doped large-mode-area photonic crystal fiber laser operating in the vicinity of zero cavity dispersionLASER PHYSICS LETTERS, Issue 3 2010Y.-J. Song Abstract A passively mode-locked ytterbium-doped largemode-area photonic crystal fiber oscillator operating in the vicinity of zero cavity dispersion is demonstrated. The self-starting mode-locking operation is achieved by a high contrast saturable absorber mirror. Two mode-locking regimes with opposite signs of net cavity dispersion are investigated. At a net cavity dispersion of ,0.0035 ps2, the fiber laser directly generates 10-nJ laser pulses with an average power of 630 mW at 65.3 MHz repetition rate. The pulses can be dechirped to 78 fs by extracavity dispersion compensation. The pulse energy is scaled up to 18 nJ, yielding an average power of 1.2 W, when the cavity dispersion is set at 0.0035 ps2. In this regime, the laser output can be extracavitydechirped to 120 fs. Dynamics of pulse evolution in the fiber laser is illustrated by numerical simulation, which agrees well with experimental results. (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Experimental study of sealed off operation of a high repetition rate TEA CO2 laserLASER PHYSICS LETTERS, Issue 10 2006M. J. Torkamany Abstract Design and construction of a high repetition rate low average power TEA CO2 laser with ultra violet pre ionization is presented. Replacing thyratron with a high voltage semiconductor switch and magnetic pulse compressor considering the highest peak power achievable is investigated. When using semiconductors as main switch of laser excitation circuit the output energy and laser power is lower about 5,10% relative to thyratron excitation circuit but the sealed off operation of laser is more uniform. (© 2006 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] 20-W average power, high repetition rate, nanosecond pulse with diffraction limit from an all-fiber MOPA systemMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2008Songtao Du Abstract In this article, we report an all-fiber master oscillator power amplifier (MOPA) system, which can provide high repetition rate and nanosecond pulse with diffraction-limit. The system was constructed using a (2 + 1) × 1 multimode combiner. The Q-Switched, LD pumped Nd:YVO4 solid-state laser was used as master oscillator. The 976-nm fiber-coupled module is used as pump source. A 10-m long China-made Yb3+ -doped D-shape double-clad large-mode-area fiber was used as amplifier fiber. The MOPA produced as much as 20-W average power with nanosecond pulse and near diffraction limited. The pulse duration is maintained at about 15 ns during 50,175 kHz. The system employs a simple and compact architecture and is therefore suitable for the use in practical applications such as scientific and military airborne LIDAR and imaging. Based on this system, the amplification performances of the all-fiber amplifier is investigated. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2546,2549, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23770 [source] Quenching cluster cooling flows with recurrent hot plasma bubblesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2004Claudio Dalla Vecchia ABSTRACT The observed cooling rate of hot gas in clusters is much lower than that inferred from the gas density profiles. This suggests that the gas is being heated by some source. We use an adaptive-mesh refinement code (flash) to simulate the effect of multiple, randomly positioned, injections of thermal energy within 50 kpc of the centre of an initially isothermal cluster with mass M200= 3 × 1014 M, and kT= 3.1 keV. We have performed eight simulations with spherical bubbles of energy generated every 108 yr, over a total of 1.5 Gyr. Each bubble is created by injecting thermal energy steadily for 107 yr; the total energy of each bubble lies in the range (0.1,3) ×1060 erg, depending on the simulation. We find that 2 × 1060 erg per bubble (corresponding to an average power of 6.3 × 1044 erg s,1) effectively balances energy loss in the cluster and prevents the accumulation of gas below kT= 1 keV from exceeding the observational limits. This injection rate is comparable to the radiated luminosity of the cluster, and the required energy and periodic time-scale of events are consistent with observations of bubbles produced by central active galactic nuclei in clusters. The effectiveness of this process depends primarily on the total amount of injected energy and the initial location of the bubbles, but is relatively insensitive to the exact duty cycle of events. [source] The sensitivity of human event-related potentials and reaction time to mobile phone emitted electromagnetic fieldsBIOELECTROMAGNETICS, Issue 4 2006D.L. Hamblin Abstract There is some evidence to suggest that exposure to mobile phones (MPs) can affect neural activity, particularly in response to auditory stimuli. The current investigation (n,=,120) aimed to test recent findings in this area, namely that N100 amplitude and latency would decrease, and that P300 latency and reaction time (RT) would increase under active relative to sham exposure during an auditory task. Visual measures were also explored. A double blind, counterbalanced, crossover design was employed where subjects attended two sessions 1 week apart. In both sessions participants (1) performed auditory and visual oddball tasks while electroencephalogram (EEG) was recorded with a MP set to sham exposure mounted over the temporal region, and (2) performed the same tasks while the handset was set to active/sham. When active, the MP transmitted for 30 min at 895 MHz (average power 250 mW, pulse modulated at 217 Hz, average SAR 0.11 W/kg). Paired t -tests compared difference scores from the sham/sham session to those from the sham/active condition. The study was designed to detect differences of of a standard deviation with a power of 0.80. There was no significant difference between exposure conditions for any auditory or visual event related potential (ERP) component or RT. As previous positive findings were not replicated, it was concluded that there is currently no evidence that acute MP exposure affects these indices of brain activity. Bioelectromagnetics 27:265,273, 2006. © 2006 Wiley-Liss, Inc. [source] Reduction in DNA Synthesis During Two-photon Microscopy of Intrinsic Reduced Nicotinamide Adenine Dinucleotide Fluorescence,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2005Michael G. Nichols ABSTRACT Two-photon laser scanning microscopy (TPLSM) of endogenous reduced nicotinamide adenine dinucleotide (NAD(P)H) provides important information regarding the cellular metabolic state. When imaging the punctate mitochondrial fluorescence originating from NAD(P)H in a rat basophilic leukemia (RBL) cell at low laser powers, no morphological changes are evident, and photobleaching is not observed when many images are taken. At higher powers, mitochondrial NAD(P)H fluorescence bleaches rapidly. To assess the limitations of this technique and to quantify the extent of photodamage, we have measured the effect of TPLSM on DNA synthesis. Although previous reports have indicated a threshold power for "safe" two-photon imaging, we find the laser power to be an insufficient indicator of photodamage. A more meaningful metric is a two-photon-absorbed dose that is proportional to the number of absorbed photon paris. A temporary reduction of DNA synthesis in RBL cells occurs whenever a threshold dose of approximately 2 × 1053 photon2 cm,4 s,1 is exceeded. This threshold is independent of laser intensity when imaging with average powers ranging from 5 to 17 mW at 740 nm. Beyond this threshold, the extent of the reduction is intensity dependent. DNA synthesis returns to control levels after a recovery period of several hours. [source] | ||||||||||||||||