NASTRAN modeling and analysis of rigid and flexible walled acoustic cavities

The acoustic slot elements, CSLOTi, are applied to analyze two-dimensional enclosures with fixed or moving boundaries. The capability utilized to compute (a) the acoustic natural modes and frequencies of a rigid walled enclosure and (b) the sound pressure at any point inside an enclosure when the surrounding walls are forced to vibrate. Applications to an automobile passenger compartment illustrate the technique. The axisymmetric fluid elements, CFLUIDi, are used in conjunction with a suitable choice of symmetry planes and a model of the surrounding structure to approximate a two-dimensional enclosure with flexible walls. The enclosure walls are modeled using finite elements or structural modes. Illustrative examples include a comparison of rectangular cavity modes with those calculated using the acoustic slot element and the free vibration modes of two enclosures coupled through a flexible rectangular panel

Probabilistic fatigue methodology for six nines reliability

Fleet readiness and flight safety strongly depend on the degree of reliability that can be designed into rotorcraft flight critical components. The current U.S. Army fatigue life specification for new rotorcraft is the so-called six nines reliability, or a probability of failure of one in a million. The progress of a round robin which was established by the American Helicopter Society (AHS) Subcommittee for Fatigue and Damage Tolerance is reviewed to investigate reliability-based fatigue methodology. The participants in this cooperative effort are in the U.S. Army Aviation Systems Command (AVSCOM) and the rotorcraft industry. One phase of the joint activity examined fatigue reliability under uniquely defined conditions for which only one answer was correct. The other phases were set up to learn how the different industry methods in defining fatigue strength affected the mean fatigue life and reliability calculations. Hence, constant amplitude and spectrum fatigue test data were provided so that each participant could perform their standard fatigue life analysis. As a result of this round robin, the probabilistic logic which includes both fatigue strength and spectrum loading variability in developing a consistant reliability analysis was established. In this first study, the reliability analysis was limited to the linear cumulative damage approach. However, it is expected that superior fatigue life prediction methods will ultimately be developed through this open AHS forum. To that end, these preliminary results were useful in identifying some topics for additional study

Flight testing and simulation of an F-15 airplane using throttles for flight control

Flight tests and simulation studies using the throttles of an F-15 airplane for emergency flight control have been conducted at the NASA Dryden Flight Research Facility. The airplane and the simulation are capable of extended up-and-away flight, using only throttles for flight path control. Initial simulation results showed that runway landings using manual throttles-only control were difficult, but possible with practice. Manual approaches flown in the airplane were much more difficult, indicating a significant discrepancy between flight and simulation. Analysis of flight data and development of improved simulation models that resolve the discrepancy are discussed. An augmented throttle-only control system that controls bank angle and flight path with appropriate feedback parameters has also been developed, evaluated in simulations, and is planned for flight in the F-15

Laparoscopic Transperitoneal Pyeloplasty

Laparoscopic pyeloplasty is a first-line option for the management of ureteropelvic junction obstruction. It has a greater success rate than endopyelotomy and is associated with a shorter and less intense convalescence than open surgical pyeloplasty. The technique is well established and reproducible, although the procedure is more difficult in certain situations, such as after a previous pyeloplasty. Because laparoscopic suturing is needed, it is considered an advanced laparoscopic procedure. Suturing devices can facilitate suturing, but they are not optimal for all repairs. This article and the accompanying video summarize the preoperative, intraoperative, and postoperative considerations for laparoscopic pyeloplasty.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90443/1/end-2E2010-2E0605.pd

Texas Business Review, October 1976

To Push or Not To Push; Tracking Intracity Changes; Killeen-Temple: Magnet AreaBureau of Business Researc

55 Local anaesthetic reduces postoperative analgesic requirements in laparoscopic urological surgery

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75011/1/j.1464-410X.2006.06085_55.x.pd

Convenient Creation and Use of Suturing Supplies for Laparoscopic Partial Nephrectomy

Abstract The closure of the renal defect is the most challenging part of laparoscopic partial nephrectomy when suturing is required. The author presents a method of creating and using suturing material for laparoscopic partial nephrectomy that has been developed over several hundred cases at the author's institution. These techniques can be used to simplify the task of suturing during laparoscopic partial nephrectomy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78109/1/end.2009.0006.pd

Hot forming of silicon sheet, silicon sheet growth development for the large area silicon sheet task of the low cost silicon solar array project

The hot workability of polycrystalline silicon was studied. Uniaxail stress-strain curves are given for strain rates in the range of .0001 to .1/sec and temperatures from 1100 to 1380 C. At the highest strain rates at 1380 C axial strains in excess of 20% were easily obtainable without cracking. After deformations of 36%, recrystallization was completed within 0.1 hr at 1380 C. When the recrystallization was complete, there was still a small volume fraction of unrecyrstallized material which appeared very stable and may degrade the electronic properties of the bulk materials. Texture measurements showed that the as-produced vapor deposited polycrystalline rods have a 110 fiber texture with the 110 direction parallel to the growth direction and no preferred orientation about this axis. Upon axial compression perpendicular to the growth direction, the former 110 fiber axis changed to 111 and the compression axis became 110 . Recrystallization changed the texture to 110 along the former fiber axis and to 100 along the compression axis