Further studies of stall flutter and nonlinear divergence of two-dimensional wings

An experimental investigation is made of the purely torsional stall flutter of a two-dimensional wing pivoted about the midchord, and also of the bending-torsion stall flutter of a two-dimensional wing pivoted about the quarterchord. For the purely torsional flutter case, large amplitude limit cycles ranging from + or - 11 to + or - 160 degrees were observed. Nondimensional harmonic coefficients were extracted from the free transient vibration tests for amplitudes up to 80 degrees. Reasonable nondimensional correlation was obtained for several wing configurations. For the bending-torsion flutter case, large amplitude coupled limit cycles were observed with torsional amplitudes as large as + or - 40 degrees. The torsion amplitudes first increased, then decreased with increasing velocity. Additionally, a small amplitude, predominantly torsional flutter was observed when the static equilibrium angle was near the stall angle

Centre Commissioned External Review (CCER) of the IWMI-TATA Water Policy Research Program

Agricultural research / Research projects / Project appraisal / Financing / Institutional development / Evaluation / Water policy / Water management / Irrigation management / Groundwater

Passivity-Based Control of Human-Robotic Networks with Inter-Robot Communication Delays and Experimental Verification

In this paper, we present experimental studies on a cooperative control system for human-robotic networks with inter-robot communication delays. We first design a cooperative controller to be implemented on each robot so that their motion are synchronized to a reference motion desired by a human operator, and then point out that each robot motion ensures passivity. Inter-robot communication channels are then designed via so-called scattering transformation which is a technique to passify the delayed channel. The resulting robotic network is then connected with human operator based on passivity theory. In order to demonstrate the present control architecture, we build an experimental testbed consisting of multiple robots and a tablet. In particular, we analyze the effects of the communication delays on the human operator's behavior

Thermal design improvements for 30kWe arcjet engine

Two thermal design improvements for 30 kWe arcjet engines are described. A ZrB2 high temperature coating was used to increase the surface emissivity of the nozzle radiating surface, enabling lower temperature operation, which should lead to longer nozzle life. The ZrB2-coated engine operated 120 C cooler than the uncoated baseline engine indicating a 30 percent increase in the surface emissivity. An engine design which has fewer active seals than previous designs and operates at lower overall component temperatures is described. The nozzle on the engine operated at 1950 C at 30 kWe while the baseline engine nozzle reached 2000 C at 23 kWe. The back of the engine was more than a factor of two cooler when compared to the baseline engine

Psychosocial Effects of a Holistic Ayurvedic Approach to Well-being in Health and Wellness Courses.

BackgroundAs individuals are increasingly attending health and wellness courses outside of the conventional medical system, there is a need to obtain objective data on the effects of those programs on well-being.MethodsIn total, 154 men and women (mean age 54.7 years; range 25-83) participated in 3 different holistic wellness programs based on Ayurvedic Medicine principles (Seduction of Spirit, Journey into Healing, and Perfect Health) or a vacation control group. Psychosocial outcomes included spirituality (Delaney Spirituality Scale), mindful awareness (Mindful Attention Awareness Scale), psychological flexibility (Acceptance and Action Questionnaire), mood (Center for Epidemiology Studies-Depression), and anxiety (Patient-Reported Outcomes Measurement System Anxiety Scale).ResultsParticipants in the Seduction of Spirit (P < .004), Journey into Healing (P < .05), and Perfect Health (P < .004) courses showed significant increases in spirituality as compared to vacation controls. Participants in Seduction of Spirit (P < .007) also showed significant increases in mindfulness as compared to vacation controls. Participants in the Seduction of Spirit (P < .001) and Journey into Healing (P < .05) courses showed significant decreases in depressed mood as compared to those in the Perfect Health and vacation control groups. All study participants showed similar increases in psychological flexibility (P < .01) and decreases in anxiety (P < .01).ConclusionParticipation in wellness courses that incorporate a mind-body-spirit approach to health improves multiple domains of psychosocial well-being, which persists even after course participation

The 30-kW ammonia arcjet technology

The technical results are summarized of a 30 kW class ammonia propellant arcjet technology program. Evaluation of previous arcjet thruster performance, including materials analysis of used thruster components, led to the design of an arcjet with improved performance and thermal characteristics. Tests of the new engine demonstrated that engine performance is relatively insensitive to cathode tip geometry. Other data suggested a maximum sustainable arc length for a given thruster configuration, beyond which the arc may reconfigure in a destructive manner. A flow controller calibration error was identified. This error caused previously reported values of specific impulse and thrust efficiency to be 20 percent higher than the real values. Corrected arcjet performance data are given. Duration tests of 413 and 252 hours, and several tests 100 hours in duration, were performed. The cathode tip erosion rate increased with increasing arc current. Elimination of power source ripple did not affect cathode tip whisker growth. Results of arcjet modeling, diagnostic development and mission analyses are also discussed. The 30 kW ammonia arcjet may now be considered ready for development for a flight demonstration, but widespread application of 30 kW class arcjet will require improved efficiency and lifetime

Packing Fractions and Maximum Angles of Stability of Granular Materials

In two-dimensional rotating drum experiments, we find two separate influences of the packing fraction of a granular heap on its stability. For a fixed grain shape, the stability increases with packing fraction. However, in determining the relative stability of different grain shapes, those with the lowest average packing fractions tend to form the most stable heaps. We also show that only the configuration close to the surface of the pile figures prominently.Comment: 4 pages, 4 figure