1,721,192 research outputs found
Evaluation of the arrhythmic risk in the 21st century: is multi-tracer nuclear imaging the answer?
No full textA micro gas turbine one-dimensional model: approach description, calibration with a vector optimization methodology and validation
No full textBased on recent studies, it is mandatory to match energy supply with user demand with the aim of achieving a
significant primary energy saving. In order to ensure an efficient matching, the power plant must be capable to
follow the energy demand fluctuation of specific users. The paper deals with the one-dimensional modeling,
calibration and validation of a micro gas turbine plant which performs a regenerative Brayton cycle. Compressor
and turbine have been outlined with performance maps, the combustor behavior is simulated by a 0D block and
the recuperator is defined by a steady-state block; seven pipes have been modeled as 1D unsteady flow, and they
connect the main components of the power plant. Although a micro gas turbine is substantially a steady plant,
the application of a one-dimensional approach allows the accurate investigation of transient and stable part-load
working conditions. The model has been calibrated using a multi-variable multi-objective methodology in which
a genetic algorithm was coupled with the model and was capable to find out the optimal model settings. The
model has been validated through the comparison between calculated and experimental data at part-load
working conditions. The novelty of the paper is the modeling approach and its validation methodology
Dynamic ultrafast CZT imaging: Time for a paradigm change in myocardial perfusion imaging
No full textDetection of ischemia with early myocardial perfusion imaging: You see more if you watch before
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Radial artery access for invasive coronary angiography: Is going distal the new frontier?
No full textStress Protocol and Myocardial Perfusion Imaging Accuracy
No full textPurpose of Review: To evaluate the most recent evolutions in the field of single photon emission computed tomography (SPECT) nuclear cardiac imaging (NCI), particularly regarding the influence of stress protocol specifics on test accuracy. Recent Findings: The substantial improvement in both software and hardware SPECT settings may allow a drastic redefinition of the acquisition parameters, with a radical reduction of scanning time. Moreover, recent evidence has identified novel (contra)-indications to the different cardiac stressors, defining the categories of patients in which a specific stressor is most appropriate. Summary: Whilst exercise stress is favoured in the majority of patients submitted to SPECT NCI, in patients with atrial fibrillation or diabetes mellitus, a vasodilator stress may be preferred because of a significantly higher specificity. Moreover, the use of non-perfusion variables, such as post-stress diastolic left ventricular parameters or eccentricity index, is favoured to increase the accuracy of SPECT imaging. Finally, the quantification of myocardial blood flow through dynamic scans with cadmium-zinc-telluride cameras is gaining its way in clinical practice, possibly further increasing NCI accuracy in the most difficult patients
Performance assessment of a 15 kW Micro-CHCP plant through the 0D/1D thermo-fluid dynamic characterization of a double water circuit waste heat recovery system
No full textThe exploitation of renewable energy sources and the use of primary energy saving techniques have been
recognized as key solutions to face climate changes. The consequent energy policies are pushing the
transition from a centralized power generation system to a distributed polygeneration system able to
meet simultaneous heating, cooling and electricity demand. However, small scale polygeneration plants
do not ensure any primary energy and cost saving without a proper sizing and operation of the plant.
Furthermore, a flexible configuration of the waste heat recovery system (WHRS) adopted for polygeneration
purposes can be equally important. Therefore, starting from the experimental data concerning
a 15 kW micro-CHP plant previously designed and prototyped, the paper addresses the
performance assessment of a CHCP plant configuration based on the same basic engine-electric generator
system through the 1D thermo-fluid dynamic characterization of an alternative double water circuit
WHRS. This configuration, delivering thermal power at different temperature level, could be useful to
meet thermal and cooling demand from different user or when seasonal energy demand occurs. This
paper also provides an effective approach for the design of WHRS which are capable to ensure a
reasonable matching between the temperature level required by the user and that provided by the plant.
In this way, being the energy saving dependent on the thermal power recovered and actually exploited,
and so on the temperature level which characterizes the user's heat demand, primary energy savings are
more easily achievable even when small scale polygeneration applications are considered. Results shows
the possibility of supplying an absorption chiller and obtaining a coolling capacity of about 10.5 kW from
the resulting CHCP plant configuration
Myocardial perfusion years after radiation therapy for left-sided breast cancer: Normal or abnormal? This is the question
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