Aergia number: A new non‐dimensional group for gas turbine power estimation

The work in this article defines an innovative approach to evaluate the performances of gas turbine based systems. This approach allows to link the thermodynamic and mechanical model of a gas turbine with its control system while bypassing the necessity to model the electrical generator. A non-dimensional group, called Aergia number, has been experimentally correlated with the measured electrical power output through a linear function. The Aergia number reproduces with accuracy the electrical power output during both steady state and transient operation. Furthermore, the proven linearity of the model implies that, in principle, its implementation requires the knowledge of just two data points during steady state operation. The model has been validated using two experimental facilities within the ENEA Casaccia Research Center, each equipped with a Turbec T100 S3 micro gas turbine, but characterized by different gas paths. Furthermore, the same linearity relation has been confirmed for aeroderivative and heavy duty single-, dual-, and triple-shaft gas turbines with power outputs ranging from 2 to 330 MWel. In light of these findings, the non-dimensional group Aergia positions itself, at least, as a rule of thumb for evaluating gas turbine off-design power output and, on a broader perspective, as a valid performance indicator in the definition of a gas turbine digital twin

Current status of liver surgery for non-colorectal non-neuroendocrine liver metastases: the NON.LI.MET. Italian Society for Endoscopic Surgery and New Technologies (SICE) and Association of Italian Surgeons in Europe (ACIE) collaborative international survey

Despite the increasing trend in liver resections for non-colorectal non-neuroendocrine liver metastases (NCNNLM), the role of surgery for these liver malignancies is still debated. Registries are an essential, reliable tool for assessing epidemiology, diagnosis, and therapeutic approach in a single hub, especially when data are dispersive and inconclusive, as in our case. The dissemination of this preliminary survey would allow us to understand if the creation of an International Registry is a viable option, while still offering a snapshot on this issue, investigating clinical practices worldwide. The steering committee designed an online questionnaire with Google Forms, which consisted of 37 questions, and was open from October 5th, 2022, to November 30th, 2022. It was disseminated using social media and mailing lists of the Italian Society of Endoscopic Surgery and New Technologies (SICE), the Association of Italian Surgeons in Europe (ACIE), and the Spanish Chapter of the American College of Surgeons (ACS). Overall, 141 surgeons (approximately 18% of the total invitations sent) from 27 countries on four continents participated in the survey. Most respondents worked in general surgery units (62%), performing less than 50 liver resections/year (57%). A multidisciplinary discussion was currently performed to validate surgical indications for NCNNLM in 96% of respondents. The most commonly adopted selection criteria were liver resectability, RECIST criteria, and absence of extrahepatic disease. Primary tumors were generally of gastrointestinal (42%), breast (31%), and pancreaticobiliary origin (13%). The most common interventions were parenchymal-sparing resections (51% of respondents) of metachronous metastases with an open approach. Major post-operative complications (Clavien-Dindo > 2) occurred in up to 20% of the procedures, according to 44% of respondents. A subset analysis of data from high-volume centers (> 100 cases/year) showed lower post-operative complications and better survival. The present survey shows that NCNNLM patients are frequently treated by surgeons in low-volume hospitals for liver surgery. Selection criteria are usually based on common sense. Liver resections are performed mainly with an open approach, possibly carrying a high burden of major post-operative complications. International guidelines and a specific consensus on this field are desirable, as well as strategies for collaboration between high-volume and low-volume centers. The present study can guide the elaboration of a multi-institutional document on the optimal pathway in the management of patients with NCNNLM