Application of the aerodynamic energy concept to flutter suppression and gust alleviation by use of active controls

The effects of active controls on flutter suppression and gust alleviation of the Arava twin turboprop STOL transport and the Westwind twinjet business transport are investigated. The active control surfaces are introduced in pairs which include, in any chosen wing strip, a 20-percent chord leading-edge control and a 20-percent chord trailing-edge control. Each control surface is driven by a combined linear-rotational sensor system located on the activated strip. The control law is based on the concept of aerodynamic energy and utilizes previously optimized control law parameters based on two-dimensional aerodynamic theory. The best locations of the activated system along the span of the wing are determined for bending-moment alleviation, reduction in fuselage accelerations, and flutter suppression. The effectiveness of the activated system over a wide range of maximum control deflections is also determined. Two control laws are investigated. The first control law utilizes both rigid-body and elastic contributions of the motion. The second control law employs primarily the elastic contribution of the wing and leads to large increases in the activated control effectiveness as compared with the basic control law. The results indicate that flutter speed can be significantly increased (over 70 percent increase) and that the bending moment due to gust loading can be almost totally eliminated by a control system of about 10 to 20 percent span with reasonable control-surface rotations

Greater Omentectomy Improves Insulin Sensitivity in Nonobese Dogs

Visceral adiposity is strongly associated with insulin resistance; however, little evidence directly demonstrates that visceral fat per se impairs insulin action. Here, we examine the effects of the surgical removal of the greater omentum and its occupying visceral fat, an omentectomy (OM), on insulin sensitivity (SI) and β-cell function in nonobese dogs. Thirteen male mongrel dogs were used in this research study; animals were randomly assigned to surgical treatment with either OM (n = 7), or sham-surgery (SHAM) (n = 6). OM failed to generate measurable changes in body weight (+2%; P = 0.1), or subcutaneous adiposity (+3%; P = 0.83) as assessed by magnetic resonance imaging (MRI). The removal of the greater omentum did not significantly reduce total visceral adipose volume (−7.3 ± 6.4%; P = 0.29); although primary analysis showed a trend for OM to increase SI when compared to sham operated animals (P = 0.078), further statistical analysis revealed that this minor reduction in visceral fat alleviated insulin resistance by augmenting SI of the periphery (+67.7 ± 35.2%; P = 0.03), as determined by the euglycemic-hyperinsulinemic clamp. Insulin secretory response during the hyperglycemic step clamp was not directly influenced by omental fat removal (presurgery 6.82 ± 1.4 vs. postsurgery: 6.7 ± 1.2 pmol/l/mg/dl, P = 0.9). These findings provide new evidence for the deleterious role of visceral fat in insulin resistance, and suggest that a greater OM procedure may effectively improve insulin sensitivity