Boundary-Layer Transition on Hollow Cylinders in Supersonic Free Flight as Affected by Mach Number and a Screwthread Type of Surface Roughness

The effects of Mach number and surface-roughness variation on boundary-layer transition were studied using fin-stabilized hollow-tube models in free flight. The tests were conducted over the Mach number range from 2.8 to 7 at a nominally constant unit Reynolds number of 3 million per inch, and with heat transfer to the model surface. A screwthread type of distributed two-dimensional roughness was used. Nominal thread heights varied from 100 microinches to 2100 microinches. Transition Reynolds number was found to increase with increasing Mach number at a rate depending simultaneously on Mach number and roughness height. The laminar boundary layer was found to tolerate increasing amounts of roughness as Mach number increased. For a given Mach number an optimum roughness height was found which gave a maximum laminar run greater than was obtained with a smooth surface

USING COMMERCIAL 5G AND LEO TECHNOLOGIES TO ENHANCE NAVY-ARMY SENSOR-TO-SHOOTER NETWORKS

The emerging commercial technologies of 5G and low Earth orbit (LEO) satellite communications have the capability to provide links that send large amounts of data with low latency. As the DOD continues to explore how to best leverage these technologies, it is important to develop potential use cases within the military. This thesis describes a sensor-to-shooter operational scenario and the network transport links currently in use to move data from a Navy sensor to an Army shooter. The current sensor-to-shooter network transport links are then compared to the emerging commercial alternatives of 5G and LEO satellite communications in the categories of throughput, latency and range. This analysis demonstrates the comparative advantages and disadvantages of both 5G and LEO technologies over current links.Captain, United States ArmyLieutenant, United States NavyApproved for public release. Distribution is unlimited

DESIGNING WETLAND CONSERVATION STRATEGIES UNDER CLIMATE CHANGE

A methodology for evaluating public wetlands conservation investments that considers climate change is developed and applied to Virginia's Elizabeth River watershed. A revised cellular automaton (CA) model is applied to project future land use change. Discrete stochastic sequential programming (DSSP) is used to model a parcel-based discrete-time decision process.Environmental Economics and Policy,

Algorithm Development and Computer Graphic Simulation of an Articulated Transporter/ Manipulator System

The University of Florida is part of a multi-university research effort, sponsored by the U.S. Department of Energy, which is underway to develop and deploy an advanced semi-autonomous robotic system for use in nuclear power stations. The robotic system being designed by the Florida/Odetics team can be described . as an Articulated Transporter/Manipulator System (ATMS) which has several unique motion and transport capabilities. The ATMS will be capable of performing tasks in radioactive hazardous environments to reduce occupational radiation exposure of plant personnel and to increase the availability of the plant. This paper will describe the key design and control features of the ATMS with emphasis placed on the implementation of specific motion control algorithms

Online Meta-learning by Parallel Algorithm Competition

The efficiency of reinforcement learning algorithms depends critically on a few meta-parameters that modulates the learning updates and the trade-off between exploration and exploitation. The adaptation of the meta-parameters is an open question in reinforcement learning, which arguably has become more of an issue recently with the success of deep reinforcement learning in high-dimensional state spaces. The long learning times in domains such as Atari 2600 video games makes it not feasible to perform comprehensive searches of appropriate meta-parameter values. We propose the Online Meta-learning by Parallel Algorithm Competition (OMPAC) method. In the OMPAC method, several instances of a reinforcement learning algorithm are run in parallel with small differences in the initial values of the meta-parameters. After a fixed number of episodes, the instances are selected based on their performance in the task at hand. Before continuing the learning, Gaussian noise is added to the meta-parameters with a predefined probability. We validate the OMPAC method by improving the state-of-the-art results in stochastic SZ-Tetris and in standard Tetris with a smaller, 10$\times$10, board, by 31% and 84%, respectively, and by improving the results for deep Sarsa($\lambda$) agents in three Atari 2600 games by 62% or more. The experiments also show the ability of the OMPAC method to adapt the meta-parameters according to the learning progress in different tasks.Comment: 15 pages, 10 figures. arXiv admin note: text overlap with arXiv:1702.0311

Potential predictors of outcome in patients with tissue loss who undergo infrainguinal vein bypass grafting

AbstractPurpose: Aggressive attempts at limb salvage in patients with ischemic tissue loss are justified by favorable initial results in most patients. The identification of patients whose conditions will not benefit from attempted revascularization remains difficult. Methods: This study was designed as a retrospective review of prospectively collected clinical data. The subjects were 210 consecutive patients who underwent infrainguinal vein bypass grafting for ischemic tissue loss in the setting of an academic medical center. Bypass grafting was to the popliteal artery in 56 patients, to the infrapopliteal arteries in 131 patients, and to the pedal arteries in 23 patients. The follow-up examination was complete in 209 of 210 patients. One hundred twenty-five patients underwent blinded review of duplex scan venous mapping and arteriography to determine simplified vein and run-off scores. The outcome measures were the influence of risk factors, venous conduit, and runoff on mortality, limb loss, and graft failure at the 6-month follow-up examination. Results: One hundred seventy patients (81%) were alive and had limb salvage. Nineteen patients (9.1%) died, with need for a simultaneous inflow procedure and end-stage renal disease being most commonly associated with mortality. Thirty-three patients (15.8%) had undergone amputation: 18 after graft failure, and 15 for progressive tissue loss despite a patent graft. Amputation was significantly more common in patients with diabetes (P = .05) and with poor runoff scores (poor runoff, 44.4% vs good runoff, 7.4%; P < .01). Amputation despite a patent graft also correlated with runoff (poor runoff, 41.7% vs good runoff, 4.3%; P < .01). Twenty-five patients had graft failure without amputation, so that only 145 patients (69.4%) were alive, had limb salvage, and had a patent graft. Run-off score was the strongest predictor of outcome, with 70% of patients with poor run-off scores having death, amputation, or graft failure. Conclusion: Aggressive use of infrainguinal vein bypass grafting in patients with ischemic tissue loss results in a high rate of initial limb salvage but significant morbidity and mortality. Arteriographically determined runoff scores appear to potentially identify patients at high risk for a poor initial outcome and may provide a method of selecting patients for primary amputation. (J Vasc Surg 1999;30:427-35.

A prospective evaluation of atherosclerotic risk factors and hypercoagulability in young adults with premature lower extremity atherosclerosis

Purpose: Fifty-one consecutive patients with premature lower extremity atherosclerosis were prospectively evaluated for atherogenic risk factors and primary or acquired hypercoagulability, which might contribute to early ischemia and revascularization failure.Methods: Laboratory tests included plasma assays of (1) natural anticoagulants (NAC), lipoprotein (a) (Lp[a]), and anticardiolipin antibodies, and (2) fibrinolytic activators and inhibitors at baseline and stimulated after 20 minutes of upper extremity venous occlusion.Results: Forty-six (90%) of these 51 patients had laboratory abnormalities. One or more NAC deficiencies were found in 15 (30%) patients and included antithrombin III (n=5), protein C (n=8), protein S (n=4), and heparin cofactor II (n=2). Hypofibrinolysis was identified as a deficiency of stimulated tissue plasminogen activator in 22 (45%) patients and elevated plasminogen activator inhibitor-1 (PAI-1) in 29 (59%). Elevated Lp(a) was found in 43 (86%) patients. Five (10%) patients had anticardiolipin antibodies. Ten patients had combined NAC deficiency and hypofibrinolysis. Five (10%) patients had no abnormality. NAC deficiencies, especially protein C deficiency, were associated with acute ischemia (p<0.01), prior vascular intervention (p<0.01), an increasing number of total vascular procedures (p<0.01), and major amputation (p<0.01). PAI-1 was associated with a history of heart disease (p<0.05) and prior vascular procedures (p<0.05). Elevated Lp(a) was associated with elevated PAI-1 (p<0.05). Retesting in 20 patients suggested that 80% of NAC deficiencies were acquired, but abnormalities persisted in 66% of patients with elevated PAI-1 and in 93% of those with elevated Lp(a).Conclusions: These data strongly support the hypothesis that the convergence of atherogenic risk factors and hypercoagulability play an important role in early ischemia and poor results reported for lower extremity vascular procedures in young adults