scholarly journals Radiation Characteristics of 3D Resonant Cavity Antenna with Grid-Oscillator Integrated Inside

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
L. A. Haralambiev ◽  
H. D. Hristov
Keyword(s):  
Spectral Power ◽  
Resonant Cavity ◽  
Three Dimensional ◽  
Spectral Power Density ◽  
Measured Data ◽  
Radiation Characteristics ◽  
Power Combining ◽  
Radiated Power ◽  
Lateral Cavity ◽  
Directive Gain

A three-dimensional (3D) rectangular cavity antenna with an aperture size of 80 mm×80 mm and a length of 16 mm, integrated with a four-MESFET transistor grid-oscillator, is designed and studied experimentally. It is found that the use of 3D antenna resonant cavity in case of small or medium gain microwave active cavity antenna leads to effective and stable power combining and radiation. The lack of lateral cavity diffraction and radiation helps in producing a directive gain of about 17 dB and radiation aperture efficiency bigger than 75% at a resonance frequency of 8.62 GHz. Good DC to RF oscillator efficiency of 26%, effective isotropic radiated power (EIRP) of 5.2 W, and SSB spectral power density of −82 dBc/Hz are found from the measured data. The 3D antenna cavity serves also as a strong metal container for the solid-state oscillator circuitry.

scholarly journals The Changes of Ergonomic Engine Vibroacoustic Response Regarding Their Development

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4215
Author(s):  
Radosław Wróbel ◽  
Lech Sitnik ◽  
Monika Andrych-Zalewska ◽  
Łukasz Łoza ◽  
Radostin Dimitrov ◽  
...  
Keyword(s):  
Human Health ◽  
Power Density ◽  
High Speed ◽  
Internal Combustion Engines ◽  
Spectral Power ◽  
Spectral Power Density ◽  
Steering Wheel ◽  
Combustion Engines ◽  
Head Restraint ◽  
Vibroacoustic Response

The article presents the results of research on the vibroacoustic response of internal combustion engines mounted in a vehicle. The vehicles studied belong to popular models, which became available in successive versions. Each group included vehicles of the same model of an older generation (equipped with a naturally aspirated engine) and of a newer generation, including downsized (and turbocharged) engines. Tests in each group were carried out under repeatable conditions on a chassis-load dynamometer. The vibrations were measured using single-axis accelerometers mounted on the steering wheel, engine, and driver’s head restraint mounting. The primary purpose of the study was to verify whether the new generations of vehicles equipped with additional high-speed elements (compressors) generate additional harmonics (especially those within the range potentially affecting travel comfort and human health) and whether there are significant changes in the distribution of spectral power density in the new generations. As the study showed, new generations of vehicles are characterized by a different vibroacoustic response, and the trend of change is the same in each of the families studied.

Use of a three-dimensional model to predict heavy metal (copper) fluxes in the Oujiang estuary

2014 ◽  
Vol 69 (6) ◽  
pp. 1334-1343 ◽  
Author(s):  
Shasha Lu ◽  
Ruijie Li ◽  
Xiaoming Xia ◽  
Jun Zheng
Keyword(s):  
River Discharge ◽  
Water Surface ◽  
Three Dimensional ◽  
Measured Data ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Pollutant Concentrations ◽  
Suspended Sediment Concentrations ◽  
Adsorption Desorption ◽  
Good Agreement

Measuring pollutant concentrations in major tributaries is the standard method for establishing pollutant fluxes to the sea. However, this method is costly and difficult, and may be subject to a great deal of uncertainty due to the presence of unknown sources. This uncertainty presents challenges to managers and scientists in reducing contaminant discharges to water bodies. As one less costly method, a three-dimensional model was developed and used to predict pollutant fluxes to the sea. The sorptive contaminant model was incorporated into hydrodynamic and sediment models. Adsorption–desorption of copper by sediments in the Oujiang estuary were described using Henry's law. The model was validated using measured data for water surface elevations, flow velocity/direction, suspended sediment concentrations, and the proportion of copper sorbed to sediment. The validated model was then applied to predict fluxes of copper. Combined with the measured data, the copper concentration in the Oujiang River discharge was calculated as 13.0 μg/L and copper fluxes were calculated as 52 t in 2010. This copper flux prediction was verified using measured dissolved copper concentrations. Comparisons between the modeled and measured results showed good agreement at most stations, demonstrating that copper flux prediction in the Oujiang estuary was reasonably accurate.

scholarly journals Control and prediction protocol for bearing failure through spectral power density

2020 ◽  
Vol 22 (4) ◽  
pp. 651-657
Author(s):  
Javier Castilla-Gutiérrez ◽  
Juan Carlos Fortes ◽  
Jose Miguel Davila
Keyword(s):  
Power Density ◽  
Spectral Power ◽  
Spectral Power Density ◽  
Bearing Failure

BIOELECTRIC ACTIVITY OF THE BRAIN IN PATIENTS WITH ACUTE CEREBROVASCULAR ACCIDENT

Vestnik ◽  
2021 ◽  
pp. 29-34
Author(s):  
Д.А. Митрохин ◽  
М.М. Ибрагимов ◽  
Б.Р. Нурмухамбетова ◽  
Н.Ш. Буйракулова ◽  
В.В. Харченко ◽  
...  
Keyword(s):  
Ischemic Stroke ◽  
Hemorrhagic Stroke ◽  
Spectral Power ◽  
Spectral Power Density ◽  
Cerebral Stroke ◽  
Beta Activity ◽  
Bioelectric Activity ◽  
Early Recovery ◽  
Coherence Index ◽  
The Brain

Значимость биоэлектрической активности головного мозга в оценке функционального состояния нервной системы при цереброваскулярных заболеваниях широко известна. В настоящей работе показана характеристика биоэлектрической активности головного мозга у больных, перенесших острое нарушение мозгового кровообращения. В данной статье приведены данные о том, что у больных в остром и раннем восстановительном периодах церебрального инсульта биоэлектрическая активность головного мозга характеризовалась, в основном, десинхронным и дезорганизованным типами электроэнцефалограммы. Вместе с тем, отмечались, выраженная дельта и тета активность, а также единичные острые волны, спайки, преимущественно в пораженном полушарии головного мозга, реже в контралатеральном полушарии, межполушарная асимметрия, повышение мощности спектров в сторону преобладания медленных волн. Показатели индекса когерентности по всем отведениям были снижены, что свидетельствует о нарушении функциональных межполушарных взаимосвязей. Более значительное повышение индекса когерентности в дельта и тета диапазонах у пациентов, перенесших геморрагический инсульт, может указывать на более грубые межполушарные нарушения, в сравнении с ишемическим инсультом. Результаты исследования относительной спектральной плотности мощности диапазонов показали, что при геморрагическом инсульте отмечена более высокая дельта и бета активность, а также более значительное снижение мощности альфа ритма, в сравнении с ишемическим инсультом. В тоже время, отмечается повышение интегрального индекса диапазона низкочастотной медленно-волновой активности, особенно выраженное у больных с геморрагическим инсультом р<0,05. The significance of bioelectric activity of the brain in assessing the functional state of the nervous system in cerebrovascular diseases is widely known. In this paper, the characteristics of the bioelectric activity of the brain in patients with acute cerebral circulatory disorders are shown. This article presents data that in patients with acute and early recovery periods of cerebral stroke , the bioelectric activity of the brain was characterized mainly by desynchronous and disorganized types of electroencephalogram. At the, same time, pronounced delta and theta activity was noted , as well as single acute waves, spikes, mainly in the affected hemisphere of the brain, less often in the contralateral hemisphere, interhemispheric asymmetry, increased spectral power in the direction of predominance of slow waves. The coherence index values for all leads were reduced, which indicates a violation of functional interhemispheric relationships. A more significant increase in the coherence index in the delta and theta ranges in patients who have had a hemorrhagic stroke may indicate more severe interhemispheric disorders compared to ischemic stroke. The results of the study of the relative spectral power density of the ranges showed, that in hemorrhagic stroke, there was a higher delta and beta activity, as well as a more significant decrease in the power of the alpha rhythm, in comparison with ischemic stroke. At the same time, there is an increase in the integral index of the range of low-frequency slow-wave activity, especially pronounced in patients with hemorrhagic stroke p < 0.05.

scholarly journals The Spectral Power Density and Shadowing Function of a Glacial Microrelief at the Decimetre Scale

1979 ◽  
Vol 23 (89) ◽  
pp. 57-66 ◽  
Author(s):  
J.-P. Benoist
Keyword(s):  
Power Density ◽  
Gaussian Distribution ◽  
Spectral Power ◽  
Spectral Power Density ◽  
Total Length ◽  
Theoretical Function ◽  
Significant Difference ◽  
Longitudinal Profiles ◽  
Non Gaussian

Abstract Longitudinal profiles of roches moutonnées have been measured once every centimetre over a total length of more than 100 m. Only wavelengths in the range 3.6 cm &lt; λ &lt; 40 cm have been kept and analysed. Levels and their slopes have a symmetrical, non-Gaussian distribution. The spectral power density varies roughly as γ 0 ν–n (ν ═ wavenumber ═ 1/λ); n being the same for all the profiles (n ═ 2.36) and γ 0 being dependent on the studied area. No significant difference has been found for the shadowing function of the different studied areas. It differs consistently from Smith’s theoretical function.

scholarly journals Effects of Diazepam on Low-Frequency and High-Frequency Electrocortical γ-Power Mediated by α1- and α2-GABAA Receptors

2019 ◽  
Vol 20 (14) ◽  
pp. 3486 ◽  
Author(s):  
Julian I. Hofmann ◽  
Cornelius Schwarz ◽  
Uwe Rudolph ◽  
Bernd Antkowiak
Keyword(s):  
Power Density ◽  
Gabaa Receptors ◽  
Barrel Cortex ◽  
Spectral Power ◽  
Low Frequency ◽  
Electric Activity ◽  
Spectral Power Density ◽  
Wild Type ◽  
Potential Activity ◽  
Α2 Receptors

Patterns of spontaneous electric activity in the cerebral cortex change upon administration of benzodiazepines. Here we are testing the hypothesis that the prototypical benzodiazepine, diazepam, affects spectral power density in the low (20–50 Hz) and high (50–90 Hz) γ-band by targeting GABAA receptors harboring α1- and α2-subunits. Local field potentials (LFPs) and action potentials were recorded in the barrel cortex of wild type mice and two mutant strains in which the drug exclusively acted via GABAA receptors containing either α1- (DZα1-mice) or α2-subunits (DZα2-mice). In wild type mice, diazepam enhanced low γ-power. This effect was also evident in DZα2-mice, while diazepam decreased low γ-power in DZα1-mice. Diazepam increased correlated local LFP-activity in wild type animals and DZα2- but not in DZα1-mice. In all genotypes, spectral power density in the high γ-range and multi-unit action potential activity declined upon diazepam administration. We conclude that diazepam modifies low γ-power in opposing ways via α1- and α2-GABAA receptors. The drug’s boosting effect involves α2-receptors and an increase in local intra-cortical synchrony. Furthermore, it is important to make a distinction between high- and low γ-power when evaluating the effects of drugs that target GABAA receptors.

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