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AbstractSlender structures with circular cylindrical cross-sections are very common in civil engineering, industrial equipment and bridge engineering. Such long cylinders subjected to wind are columns, piles, long cables, chimney, pylons and others. On long cables, an instability called dry galloping has been recently theorized to be linked to an unpredictable jump state occurring once the boundary layers of the circular cylinder changes from laminar to turbulent. With a non-stationary character, the force generated at the critical flow regime is named bi-stable activity. In this work, the birth of bi-stable flow activity around a circular cylinder made of high-density polyethylene is studied experimentally in a wind tunnel. The pressure pattern is linearly decomposed and geometric modes governing the bi-stable activity as a function of circularity defect are created. The results show that the energy of the non-stationary load observed at the critical flow regime depends strongly on the circularity defect. Furthermore, the inclination angle of 60° confers a significant increase in the energy of the bi-stable flow mode when an unsteady asymmetric reattachment event occurs. The paper also highlights the variability of the mean drag coefficient as a function of the macroscopic defect.

Byline: Gilles A Orliaguet, Pierre A Carli, Alain Rozenberg, Daniel Janniere, Patrick Sauval, Philippe Delpech Abstract: Study objectives: To compare the maximal end-tidal carbon dioxide pressure (ETCO.sub.2 peak) values obtained during standard (S-CPR) and active compression-decompression CPR (ACD-CPR) during prolonged resuscitation in out-of-hospital cardiac arrest. Design: Prospective, randomized crossover study. Setting: City with a population of 3.5 million, served by an emergency medical service system providing advanced cardiac life support. Participants: Patients with nontraumatic out-of-hospital cardiac arrest. Interventions: Patients were randomly assigned to receive first, for a period of 3 minutes, either ACD-CPR or S-CPR; then the two methods were alternated. ETCO.sub.2 was continuously monitored and computed. Measurements and Results: Sixteen patients (48[+ or -]20 years old) were included; in 12, return of spontaneous circulation was achieved, and 5 were admitted alive to the hospital. A statistically significant increase in ETCO.sub.2 peak was obtained with ACD-CPR (27.6[+ or -]3 mm Hg) compared with S-CPR (15.6[+ or -]2.2 mm Hg). No major adverse effect possibly related to ACD-CPR was observed. Conclusion: This prospective study suggests that ACD-CPR may improve cardiac output compared with S-CPR. [Orliaguet GA, Carli PA, Rozenberg A, Janniere D, Sauval P, Delpech P: End-tidal carbon dioxide during out-of-hospital cardiac arrest resuscitation: Comparison of active compression-decompression and standard CPR. Ann Emerg Med January 1995;25:48-51.] Article History: Received 6 April 1994; Revised 8 July 1994; Accepted 13 July 1994 Article Note: (footnote) [star] From the Service d'Aide Medicale Urgente 9SAMU) de Paris, Department of Anesthesiology, HA[acute accent]spital Necker., [star][star] No financial support for this study was provided by Ambu International, nor are any of the authors affiliated with this company., a Address for reprints: Professor Pierre A Carli, SAMU de Paris, Department of Anesthesiology, HA[acute accent]pital Necker, 149 rue de Sevres, 75015 Paris, France, 33-1-44-49-23-23, Fax 33-1-44-49-24-24, aa Reprint no. 47/1/60938