Purifying and Reversible Physical Processes

Starting from the observation that reversible processes cannot increase the purity of any input state, we study deterministic physical processes, which map a set of states to a set of pure states. Such a process must map any state to the same pure output, if purity is demanded for the input set of all states. But otherwise, when the input set is restricted, it is possible to find non-trivial purifying processes. For the most restricted case of only two input states, we completely characterize the output of any such map. We furthermore consider maps, which combine the property of purity and reversibility on a set of states, and we derive necessary and sufficient conditions on sets, which permit such processes.Comment: 5 pages, no figures, v2: only minimal change

Design, construction, and testing of an aero-engine starter-generator for the more-electric aircraft

This study describes the design, construction, and testing of an aero-engine starter-generator and its associated power electronic converter. A high-speed, permanent magnet machine and a dual-channel machine-facing converter with an electrical power offtake rating of 95 kW have been developed for a small civil turbofan application. The study also describes the more-electric architecture into which the machine and converter are integrated and reviews the multi-faceted performance specification, which is a common feature of machines of this type

A manufacturing driven design methodology to lightweighting of the structural elements of a permanent magnet electrical machine rotor

It is common practice for electrical machines to be designed with a focus predominantly on the electromagnetic performance. The mechanical design is then subsequently undertaken to meet various mechanical performance criteria, with this finalised design then passed on for manufacture. In many cases, the manufacturing constraints have not been taken fully into consideration during the electromagnetic or more particularly the mechanical design and hence some changes are required to the design to make it manufacturable. This in turn can lead to a non-optimal machine being manufactured. If manufacturing constraints and opportunities are regarded as key quantitative inputs to the design process, not only can these post-design changes be minimised, but benefits of the manufacturing process can be exploited to produce a superior product. This paper proposes a methodology to fully integrate the mechanical design and manufacturing process routes into electrical machine design and illustrates its utility within the context of light-weighting of a permanent magnet rotor for an aerospace electrical machine. Within the proposed methodology, several alternative configurations of the rotor are considered with applicable manufacturing routes identified at the initial stages of design and an analytical design procedure to fulfil the application and performance criteria is developed. Different manufacturing materials and constraints as well as the impact of manufacturing process are identified to be embedded into the design procedures. Finally, the paper demonstrates an application of this methodology together with a discussion of the features which offer promise in achieving economically lighter weight design through integration of manufacturing into the design procedure

The Cholecystectomy As A Day Case (CAAD) Score: A Validated Score of Preoperative Predictors of Successful Day-Case Cholecystectomy Using the CholeS Data Set

Background Day-case surgery is associated with significant patient and cost benefits. However, only 43% of cholecystectomy patients are discharged home the same day. One hypothesis is day-case cholecystectomy rates, defined as patients discharged the same day as their operation, may be improved by better assessment of patients using standard preoperative variables. Methods Data were extracted from a prospectively collected data set of cholecystectomy patients from 166 UK and Irish hospitals (CholeS). Cholecystectomies performed as elective procedures were divided into main (75%) and validation (25%) data sets. Preoperative predictors were identified, and a risk score of failed day case was devised using multivariate logistic regression. Receiver operating curve analysis was used to validate the score in the validation data set. Results Of the 7426 elective cholecystectomies performed, 49% of these were discharged home the same day. Same-day discharge following cholecystectomy was less likely with older patients (OR 0.18, 95% CI 0.15–0.23), higher ASA scores (OR 0.19, 95% CI 0.15–0.23), complicated cholelithiasis (OR 0.38, 95% CI 0.31 to 0.48), male gender (OR 0.66, 95% CI 0.58–0.74), previous acute gallstone-related admissions (OR 0.54, 95% CI 0.48–0.60) and preoperative endoscopic intervention (OR 0.40, 95% CI 0.34–0.47). The CAAD score was developed using these variables. When applied to the validation subgroup, a CAAD score of ≤5 was associated with 80.8% successful day-case cholecystectomy compared with 19.2% associated with a CAAD score >5 (p < 0.001). Conclusions The CAAD score which utilises data readily available from clinic letters and electronic sources can predict same-day discharges following cholecystectomy