ABSTRACT
Purpose: In this study an evaluation of the imaging performance of an electronic portal imaging device (EPID) is presented. The evaluation performed employing the QC-3V image quality phantom. Methods: An EPID system of a 6 MV LINAC, was used to obtain images of a QC-3V EPID phantom. The X-ray source to phantom distance was 100 cm and the field size was 15x15 cm2. The irradiation conditions comprised Dose Rates (DR) of 200, 400 and 600 for a 2 MU-100 MU range. The Contrast Transfer Function (CTF), the Noise Power Spectrum (NPS), the Normalized Noise Power Spectrum (NNPS) and the Contrast-to-Noise Ratio (CNR) were studied. In addition, an alternative factor showing a frequency related output signal-to-noise ratio (SNR), the Signal-to-Noise-Frequency Response (SNFR), has been introduced. SNFR is a comprehensive quality index, easily determined in clinical environment. Results: The CTF curves were found comparable to each other. The lowest values were measured at 2 MU and 200 MU/min. Concerning the NPS and NNPS graphs it was found that the values decrease up to approximately 0.3 lp/mm and demonstrate a white noise shape afterwards. SNFR values were found reducing with spatial frequency. Highest CNR were found between the region 7 and 11 of the phantom. Conclusions: The influence of MU and DR on EPID performance were investigated. Image quality was assessed using the QC-3V phantom. The presented results can lead to image quality amelioration and act supportively to current image quality control routine protocols.
ABSTRACT
Our work analyzes the biophysical and economic foundations of the Sherwood Plot (SP). In general, the SP depicts the theoretical relationship between the cost of recovering a target material or an identified Value Added Compound (VAC) from a waste matrix and its dilution in the waste matrix; specifically suggesting that the recovery cost is reverse proportional to the VAC's dilution in it. We further utilize the SP as a scientifically consistent and economically coherent analytical framework for measuring resource recovery performance. Initially, we analyze the SP's fundamental physical properties, as well as its many potential economic extensions. Specifically, we substantiate the relation between a VAC's Entropy, Dilution and Recovery Cost. On these grounds we present the SP's remarkable and numerous economic properties that make it consistent to its physical foundations; thus integrating concisely its physical and economic aspects and postulate a generalized SP function. We further test econometrically the validity of an SP based on both deterministic and stochastic real data from a small-scale industrial unit of polyphenols' recovery from natural fruit juice production residual wastewater. In turn, based on the fusion of our theoretical argumentation and empirical findings we dive into the epistemological extensions of the SP. Specifically, we study how the recovery cost structure at the single industry level is revealed by the SP and can be useful for postulating cost structure ontologies. Cost ontologies are in turn useful as a diagnostic of the formation process of VAC recovery markets as well as their structure and concentration, defining the industrial shares when many industries operate in the recovery of the same VAC.
ABSTRACT
We present data and code for visualizing the electrical energy data and weather-, climate-related and socioeconomic variables in the time domain in Greece. The electrical energy data include hourly demand, weekly-ahead forecasted values of the demand provided by the Greek Independent Power Transmission Operator and pricing values in Greece. We also present the daily temperature in Athens and the Gross Domestic Product of Greece. The code combines the data to a single report, which includes all visualizations with combinations of all variables in multiple time scales. The data and code were used in Tyralis et al. (2017) [1].
