A Stochastic Approach to Designing Affordable, Environmentally Acceptable Systems

Presented at the 1999 NSF Grantees Conference, Long Beach, CA, January 1999.The focus of the work being conducted under this grant is to create a virtual stochastic l environment that will enable designers to make decisions in the presence of uncertainty while considering all aspects relevant to the design at the earliest possible time. This paper describes a portion of this research involving the application of a probabilistic method which allows designers to make direct trades between probability of meeting design goals and product performance (such as specific fuel consumption). The example described here is focused on the cycle selection for a notional commercial aircraft engine such that the design merit can be quantified in terms of a probability of meeting a design target. Ultimately, this research will be extended to include environmental aspects such as acoustic noise and emissions requirements

Minimizing Vehicle Environmental and Economic Cost Via Thermodynamic Work Potential

Presented at the 2001 NSF DMII Grantees Conference, Tampa, FL, January 2001.The objective of this paper is to highlight several research opportunities currently being pursued at Georgia Tech to advance the state-of-the-art in vehicle design methods by applying the concept of thermodynamic work potential. The paper begins with a broad definition of thermodynamic work potential and describes several attributes that make it useful for vehicle design. Among these attributes are the ability to link aerothermodynamic performance and vehicle mass together in a "unified theory of vehicle design," as well as the ability to provide a means for explicitly calculating vehicle operating cost accountability. In addition, work potential methods are suggested as an excellent framework from which to conduct technology risk and benefit studies

Effectiveness of a national quality improvement programme to improve survival after emergency abdominal surgery (EPOCH): a stepped-wedge cluster-randomised trial

Background: Emergency abdominal surgery is associated with poor patient outcomes. We studied the effectiveness of a national quality improvement (QI) programme to implement a care pathway to improve survival for these patients. Methods: We did a stepped-wedge cluster-randomised trial of patients aged 40 years or older undergoing emergency open major abdominal surgery. Eligible UK National Health Service (NHS) hospitals (those that had an emergency general surgical service, a substantial volume of emergency abdominal surgery cases, and contributed data to the National Emergency Laparotomy Audit) were organised into 15 geographical clusters and commenced the QI programme in a random order, based on a computer-generated random sequence, over an 85-week period with one geographical cluster commencing the intervention every 5 weeks from the second to the 16th time period. Patients were masked to the study group, but it was not possible to mask hospital staff or investigators. The primary outcome measure was mortality within 90 days of surgery. Analyses were done on an intention-to-treat basis. This study is registered with the ISRCTN registry, number ISRCTN80682973. Findings: Treatment took place between March 3, 2014, and Oct 19, 2015. 22 754 patients were assessed for elegibility. Of 15 873 eligible patients from 93 NHS hospitals, primary outcome data were analysed for 8482 patients in the usual care group and 7374 in the QI group. Eight patients in the usual care group and nine patients in the QI group were not included in the analysis because of missing primary outcome data. The primary outcome of 90-day mortality occurred in 1210 (16%) patients in the QI group compared with 1393 (16%) patients in the usual care group (HR 1·11, 0·96–1·28). Interpretation: No survival benefit was observed from this QI programme to implement a care pathway for patients undergoing emergency abdominal surgery. Future QI programmes should ensure that teams have both the time and resources needed to improve patient care. Funding: National Institute for Health Research Health Services and Delivery Research Programme

Effectiveness of a national quality improvement programme to improve survival after emergency abdominal surgery (EPOCH): a stepped-wedge cluster-randomised trial

BACKGROUND: Emergency abdominal surgery is associated with poor patient outcomes. We studied the effectiveness of a national quality improvement (QI) programme to implement a care pathway to improve survival for these patients. METHODS: We did a stepped-wedge cluster-randomised trial of patients aged 40 years or older undergoing emergency open major abdominal surgery. Eligible UK National Health Service (NHS) hospitals (those that had an emergency general surgical service, a substantial volume of emergency abdominal surgery cases, and contributed data to the National Emergency Laparotomy Audit) were organised into 15 geographical clusters and commenced the QI programme in a random order, based on a computer-generated random sequence, over an 85-week period with one geographical cluster commencing the intervention every 5 weeks from the second to the 16th time period. Patients were masked to the study group, but it was not possible to mask hospital staff or investigators. The primary outcome measure was mortality within 90 days of surgery. Analyses were done on an intention-to-treat basis. This study is registered with the ISRCTN registry, number ISRCTN80682973. FINDINGS: Treatment took place between March 3, 2014, and Oct 19, 2015. 22 754 patients were assessed for elegibility. Of 15 873 eligible patients from 93 NHS hospitals, primary outcome data were analysed for 8482 patients in the usual care group and 7374 in the QI group. Eight patients in the usual care group and nine patients in the QI group were not included in the analysis because of missing primary outcome data. The primary outcome of 90-day mortality occurred in 1210 (16%) patients in the QI group compared with 1393 (16%) patients in the usual care group (HR 1·11, 0·96-1·28). INTERPRETATION: No survival benefit was observed from this QI programme to implement a care pathway for patients undergoing emergency abdominal surgery. Future QI programmes should ensure that teams have both the time and resources needed to improve patient care. FUNDING: National Institute for Health Research Health Services and Delivery Research Programme

The Role of Thermodynamic Work Potential in Aerospace Vehicle Design

Presented at 2003 ISABE Conference, Cleveland, OH.Thermodynamic performance is a prime consideration in the design of vehicles. This is because all vehicles operate by transforming the stored work potential contained in fuel into useful work. This work output is then used to overcome various loss mechanisms in the engine, drivetrain, and vehicle systems. A significant part of vehicle engineering is finding means to minimize losses integrated through the design mission in order to minimize costs. This paper discusses how thermodynamic work potential can be used as a vehicle analysis tool to minimize losses and improve performance. The foundation of this method is the second law of thermodynamics. This approach provides

A Method for Comprehensive Evaluation of Propulsion System Thermodynamic Performance and Loss

Presented at the 37th Joint Propulsion Conference and Exhibit, Salt Lake City, UT, July 2001.This paper develops a method to analyze usage and loss of thermodynamic work potential in vehicle propulsion systems. This method is then demonstrated on the Northrop F-5E propulsion system. The result is a thermodynamic 'loss deck' describing the partitioning of work potential usage (and loss) as a function of vehicle flight condition and engine power setting. Specifically, three loss deck formulations are demonstrated for the F-5E propulsion system: exergy, gas horsepower, and thrust work potential. Finally, these three loss decks are compared and contrasted to show their relative merits for propulsion system design and engine/airframe matching applications

A theoretical treatment of technical risk in modern propulsion system design

Ph.D.Dimitri Mavri

A Work Potential Perspective of Engine Component Performance

Presented at the 37th Joint Propulsion Conference and Exhibit, Salt Lake City, UT, July 2001.There is a strong interest within the propulsion community in applying the concept of thermodynamic work potential as a universal figure of merit for gauging the performance of prime-movers. In particular, exergy, gas horsepower, and thrust work potential have shown considerable promise as work potential figures of merit for propulsion system design. However, the relationships between these measures of work potential and the classical measures of component performance (component efficiencies) are not widely known. The objective of this paper is to derive a series of relationships linking classical efficiency-based performance metrics to modern measures of work potential. Derivations for the most common component efficiencies encountered in aircraft engine design are given in terms of all three work potential measures previously mentioned. Finally, the classical efficiency-based models are compared and contrasted with modern work potential methods to highlight the strengths and weaknesses of each

Geometric and algebraic approaches to quantum theory

We show how to formulate physical theory taking as a starting point the set of states (geometric approach). We discuss the relation of this formulation to the conventional approach to classical and quantum mechanics and the theory of complex systems. The equations of motion and the formulas for probabilities of physical quantities are analyzed. A heuristic proof of decoherence in our setting is used to justify the formulas for probabilities. We show that any physical theory theory can be obtained from classical theory if we restrict the set of observables. This remark can be used to construct models with any prescribed group of symmetries; one can hope that this construction leads to new interesting models that cannot be build in the conventional framework. The geometric approach can be used to formulate quantum theory in terms of Jordan algebras, generalizing the algebraic approach to quantum theory. The scattering theory can be formulated in geometric approach.Comment: New results are added, 30 page

Technology Evaluation Via Loss Management Models Formulated in Terms of Vehicle Weight

Presented at the 59th International Conference on Mass Properties Engineering, St. Louis, June 5-7, 2000.Mass properties engineering is today an established field and an indispensable part of the design process. Detailed bookkeeping schemes have been developed to track constituent component weights in extreme detail, down to the last rib and rivet. Given this situation, it may be more accurate to refer to this field as empty weights engineering because the focus has always been primarily on management and tracking of vehicle empty weight. Meanwhile, one of the largest weight fractions, fuel weight, is bookkept in a single lump and largely ignored (except inasmuch as it impacts vehicle size and growth factor). It is intuitively obvious that the aerothermodynamic losses due to the engine, airframe systems, and aerodynamic drag of the vehicle are the fundamental drivers on fuel weight and should therefore be expressible as increments in fuel weight chargeable to each loss mechanism. The sum of all chargeable fuel weights is equal to the total fuel weight required to complete a prescribed mission. The intent of this paper is to formulate a method for quantifying thermodynamic performance in terms of mission fuel chargeable to each thermodynamic loss mechanism. This is then used in conjunction with known vehicle zero fuel weight groups to estimate the gross weight chargeable to each functional component of the vehicle. The results show that chargeable vehicle gross weight can be used as a common figure of merit linking mass properties and performance aspects of vehicle design. This method is then demonstrated for a Northrop F-5E aircraft, and the fuel weight breakdown is analytically calculated for the design mission. The results of this analysis show that 37.3% of the F-5E subsonic mission fuel requirement is due to propulsion system losses, 36.8% is chargeable to aerodynamic drag, and 24.3% is chargeable to vehicle empty weight. This translates into a chargeable fuel cost of roughly $173.90,$171.76, and $113.53 for each of these three loss mechanisms, respectively. Finally, the usefulness of this technique as a means of technology evaluation is considered. The strengths of this method are that it allows quantification of both weight and performance aspects of technology benefits in a single figure of merit, and also enables one to ascertain the benefits of individual technologies even when applied as part of a suite of technologies