Scheduling of continuous and discontinuous material flows with intermediate storage restrictions

This paper deals with scheduling batch (i.e., discontinuous), continuous, and semicontinuous production in process industries (e.g., chemical, pharmaceutical, or metal casting industries) where intermediate storage facilities and renewable resources (processing units and manpower) of limited capacity have to be observed. First, different storage configurations typical of process industries are discussed. Second, a basic scheduling problem covering the three above production modes is presented. Third, (exact and truncated) branch-and-bound methods for the basic scheduling problem and the special case of batch scheduling are proposed and subjected to an experimental performance analysis. The solution approach presented is flexible and in principle simple, and it can (approximately) solve relatively large problem instances with sufficient accuracy.

A nonparametric method of comparing the partial areas under two correlated receiver operating characteristic curves

A non-parametric method was developed and tested to compare the partial areas under two correlated Receiver Operating Characteristic curves. Based on the theory of generalized U-statistics the mathematical formulas have been derived for computing ROC area, and the variance and covariance between the portions of two ROC curves. A practical SAS application also has been developed to facilitate the calculations. The accuracy of the non-parametric method was evaluated by comparing it to other methods. By applying our method to the data from a published ROC analysis of CT image, our results are very close to theirs. A hypothetical example was used to demonstrate the effects of two crossed ROC curves. The two ROC areas are the same. However each portion of the area between two ROC curves were found to be significantly different by the partial ROC curve analysis. For computation of ROC curves with large scales, such as a logistic regression model, we applied our method to the breast cancer study with Medicare claims data. It yielded the same ROC area computation as the SAS Logistic procedure. Our method also provides an alternative to the global summary of ROC area comparison by directly comparing the true-positive rates for two regression models and by determining the range of false-positive values where the models differ. ^

Impact of Team Familiarity in the Operating Room on Surgical Complications

BACKGROUND: The quality of surgical performance depends on the technical skills of the surgical team as well as on non-technical skills, including teamwork. The present study evaluated the impact of familiarity among members of the surgical team on morbidity in patients undergoing elective open abdominal surgery. METHODS: A retrospective analysis was performed to compare the surgical outcomes of patients who underwent major abdominal operations between the first month (period I) and the last month (period II) of a 6-month period of continuous teamwork (stable dyads of one senior and one junior surgeon formed every 6 months). Of 117 patients, 59 and 58 patients underwent operations during period I and period II, respectively, between January 2010 and June 2012. Team performance was assessed via questionnaire by specialized work psychologists; in addition, intraoperative sound levels were measured. RESULTS: The incidence of overall complications was significantly higher in period I than in period II (54.2 vs. 34.5 %; P = 0.041). Postoperative complications grade <3 were significantly more frequently diagnosed in patients who had operations during period I (39.0 vs. 15.5 %; P = 0.007), whereas no between-group differences in grade ≥3 complications were found (15.3 vs. 19.0 %; P = 0.807). Concentration scores from senior surgeons were significantly higher in period II than in period I (P = 0.033). Sound levels during the middle third part of the operations were significantly higher in period I (median above the baseline 8.85 dB [range 4.5-11.3 dB] vs. 7.17 dB [5.24-9.43 dB]; P < 0.001). CONCLUSIONS: Team familiarity improves team performance and reduces morbidity in patients undergoing abdominal surgery.

"Let's Talk Cash": Cantons' Interests and the Reform of Swiss Federalism

In 2004 the Swiss people accepted a new equalization scheme and a new distribution of competences between the federal state and the cantons. It was argued that the reform was successful because of the capacity of veto-players to overcome their interests and adopt a ‘problem-solving’ interaction mode. We propose a different interpretation and argue that distributive issues and the accommodation of actors' interests crucially mattered. We identify three mechanisms that contribute to a successful reform, i.e. package-deals, side-payments and the downsizing of the reform. Our in-depth, mainly qualitative study of both the content of the reform and related decision-making process supports the pertinence of these strategies for the explanation of the successful reform of Swiss federalism.

Laminar and turbulent nozzle-jet flows and their acoustic near-field

We investigate numerically the effects of nozzle-exit flow conditions on the jet-flow development and the near-field sound at a diameter-based Reynolds number of Re D = 18 100 and Mach number Ma = 0.9. Our computational setup features the inclusion of a cylindrical nozzle which allows to establish a physical nozzle-exit flow and therefore well-defined initial jet-flow conditions. Within the nozzle, the flow is modeled by a potential flow core and a laminar, transitional, or developing turbulent boundary layer. The goal is to document and to compare the effects of the different jet inflows on the jet flow development and the sound radiation. For laminar and transitional boundary layers, transition to turbulence in the jet shear layer is governed by the development of Kelvin-Helmholtz instabilities. With the turbulent nozzle boundary layer, the jet flow development is characterized by a rapid changeover to a turbulent free shear layer within about one nozzle diameter. Sound pressure levels are strongly enhanced for laminar and transitional exit conditions compared to the turbulent case. However, a frequency and frequency-wavenumber analysis of the near-field pressure indicates that the dominant sound radiation characteristics remain largely unaffected. By applying a recently developed scaling procedure, we obtain a close match of the scaled near-field sound spectra for all nozzle-exit turbulence levels and also a reasonable agreement with experimental far-field data.

Magnitude-frequency aspects of alpine debris flows

Based on historic documents the event history for 17 mountain torrents in the Swiss Alps was evaluated. Four classes could be determined for the recurrence interval of the debris flow events. The magnitude is not necessarily dependent on the recurrence interval. The characteristics of the catchment basin (disposition) are mainly controlling the magnitude. In order to evaluate the effects of climatic change on the debris flow activity, knowledge about the magnitude and the frequency are necessary.

The 1987 debris flows in Switzerland: documentation and analysis

A great number of debris flows occurred during the flood catastrophes of the summer of 1987 in the Swiss Alps. Aerial photography, field investigations and eyewitness accounts documented and analysed the events. As an example of the reconstructed major events, the large debris flow in the Varuna valley involved an estimated peak discharge between 400 and 800 m3/s and an event magnitude of 200,000 m3. Several single pulses were observed; the duration of each of them appeared to be not more than a few minutes. Apart from incision into weak bedrock, the maximum erosion depth seemed to depend on the channel gradient. Based on approximately 600 events, typical starting zones and rainfall conditions are discussed with regard to the triggering conditions. Existing and new empirical formulae are proposed to estimate the most important flow parameters. These values are compared to debris flow data from Canada and Japan.