Local Out-Tournaments with Upset Tournament Strong Components I: Full and Equal {0,1}-Matrix Ranks

A digraph D is a local out-tournament if the outset of every vertex is a tournament. Here, we use local out-tournaments, whose strong components are upset tournaments, to explore the corresponding ranks of the adjacency matrices. Of specific interest is the out-tournament whose adjacency matrix has boolean, nonnegative integer, term, and real rank all equal to the number of vertices, n. Corresponding results for biclique covers and partitions of the digraph are provided

Combined Visualization and Heat Transfer Measurements for Steam Flow Condensation in Hydrophilic and Hydrophobic Mini-Gaps

Citation: Chen X, Derby MM. Combined Visualization and Heat Transfer Measurements for Steam Flow Condensation in Hydrophilic and Hydrophobic Mini-Gaps. ASME. J. Heat Transfer. 2016;138(9):091503-091503-11. doi:10.1115/1.4033496.Condensation enhancement was investigated for flow condensation in mini-channels. Simultaneous flow visualization and heat transfer experiments were conducted in 0.952-mm diameter mini-gaps. An open loop steam apparatus was constructed for a mass flux range of 50–100 kg/m2s and steam quality range of 0.2–0.8, and validated with single-phase experiments. Filmwise condensation was observed in the hydrophilic mini-gap; pressure drop and heat transfer coefficients were compared to the (Kim and Mudawar, 2013, “Universal Approach to Predicting Heat Transfer Coefficient for Condensing Mini/Micro-Channel Flow,” Int. J. Heat Mass Transfer, 56(1–2), pp. 238–250) correlation and prediction was very good; the mean absolute error (MAE) was 20.2%. Dropwise condensation was observed in the hydrophobic mini-gap, and periodic cycles of droplet nucleation, coalescence, and departure were found at all mass fluxes. Snapshots of six typical sweeping cycles were presented, including integrated flow visualization quantitative and qualitative results combined with heat transfer coefficients. With a fixed average steam quality (x¯ = 0.42), increasing mass flux from 50 to 75 to 100 kg/m2s consequently reduced average sweeping periods from 28 to 23 to 17 ms and reduced droplet departure diameters from 13.7 to 12.9 to 10.3 μm, respectively. For these cases, condensation heat transfer coefficients increased from 154,700 to 176,500 to 194,800 W/m2 K at mass fluxes of 50, 75, and 100 kg/m2 s, respectively. Increased mass fluxes and steam quality reduced sweeping periods and droplet departure diameters, thereby reducing liquid thickness and increasing heat transfer coefficients

Optical-inertia space sextant for an advanced space navigation system, phase B

Optical-inertia space sextant for advanced space navigation syste

Numerical Optimization of the Thermal Field in Bridgman Detached Growth

The global modeling of the thermal field in two vertical Bridgman-like crystal growth configurations, has been performed to get optimal thermal conditions for a successful detached growth of Ge and CdTe crystals. These computations are performed using the CrysMAS code and expand upon our previous analysis [1] that propose a new mechanism involving the thermal field and meniscus position to explain stable conditions for dewetted Bridgman growth. The analysis of the vertical Bridgman configuration with two heaters, used by Palosz et al. for the detached growth of Ge, shows, consistent with their results, that the large wetting angle of germanium on boron nitride surfaces was an important factor to promote a successful detached growth. Our computations predict that by initiating growth much higher into the hot zone of the furnace, the thermal conditions will be favorable for continued detachment even for systems that did not exhibit high contact angles. The computations performed for a vertical gradient freeze configuration with three heaters representative of that used for the detached growth of CdTe, show favorable thermal conditions for dewetting during the entirely growth run described. Improved thermal conditions are also predicted for coated silica crucibles when the solid-liquid interface advances higher into the hot zone during the solidification process. The second set of experiments on CdTe growth described elsewhere has shown the reattachment of the crystal to the crucible after few centimeters of dewetted growth. The thermal modeling of this configuration shows a second solidification front appearing at the top of the sample and approaching the middle line across the third heater. In these conditions, the crystal grows detached from the bottom, but will be attached to the crucible in the upper part because of the solidification without gap in this region. The solidification with two interfaces can be avoided when the top of the sample is positioned below the middle position of the third furnace

Application of the CIRSSE cooperating robot path planner to the NASA Langley truss assembly problem

A method for autonomously planning collision free paths for two cooperating robots in a static environment was developed at the Center for Intelligent Robotic Systems for Space Exploration (CIRSSE). The method utilizes a divide-and-conquer type of heuristic and involves non-exhaustive mapping of configuration space. While there is no guarantee of finding a solution, the planner was successfully applied to a variety of problems including two cooperating 9 degrees of freedom (dof) robots. Although developed primarily for cooperating robots the method is also applicable to single robot path planning problems. A single 6 dof version of the planner was implemented for the truss assembly east, at NASA Langley's Automated Structural Assembly Lab (ASAL). The results indicate that the planner could be very useful in addressing the ASAL path planning problem and that further work along these lines is warranted

WHOOPING CRANE AND SANDHILL CRANE MONITORING AT FIVE WIND ENERGY FACILITIES

Biologists have expressed concern that individuals of the Aransas-Wood Buffalo Population of the federally endangered whooping crane (Grus americana), numbering about 300, may be injured or killed by wind turbines during migration. To help address this concern and curtail (stop) turbine operations when whooping cranes approached turbines, we monitored the area around 5 wind energy facilities in North and South Dakota during spring and fall migration for whooping cranes and sandhill cranes (G. canadensis). Observers monitored cranes for 3 years at each facility from 2009 to 2013 (1,305 total days of monitoring), recording 14 unique observations for a total of 45 whooping cranes for which curtailment occurred during portions of 9 days. Observers also searched for dead cranes at the base of every turbine each day of monitoring. This resulted in approximately 92,022 cumulative individual inspections, during which no dead or injured cranes were detected. Based on our results and monitoring efforts at other wind energy facilities in the migration corridor, no whooping crane fatalities have been documented. Although migrating cranes use areas near turbines, they do not appear to be overly susceptible to collisions with wind turbines

Permeability Analysis of Additively-Manufactured Wick Structures with Heat Exchanger Applications

Heat pipes and other heat transfer applications use capillary-driven liquid motion to enhance performance. This research uses water and a low surface tension fluid FC-40 to test additive-manufactured polymer wicks using a rateof-rise test. The rate-of-rise tests give a measure of the wicks’ performance capabilities as well as being able to calculate the wicks’ permeability and effective pore radius. Four wicks were measured having two different internal structures (i.e., 1.0 mm triangle and 1.75 mm square) and two external structures (i.e., layered and column). The 1.0 mm Triangle wicks performed better than their 1.0 mm Square counterparts for both water and FC-40. Both 1.0 mm Triangle wicks performed similarly for both water and FC-40, with the column wick (11.0 mm) performing better than the layered wick (8.98 mm). Using a least squares method from the rate-of-rise results, the permeability and effective pore radius of each wick were calculated for the 1.0 mm triangle layered wick, the 1.75 mm square layered wick, and the 1.0 mm triangle column wick. The 1.75 mm square column wick was unable to wick either liquid, so the permeability and effective pore radius were not able to be calculated. The permeability and effective pore radius for each wick were 3.00 um2 and 130.1 um, 0.95 um2 and 221.1 um, and 77.8 um2 and 1099 um, respectively. Some challenges involved with polymer additive manufacturing design and creation were also discussed

Droplet ejection and sliding on a flapping film

Citation: X. Chen, N. Doughramaji, A.R. Betz, M.M. Derby, Droplet departure and ejection on flapping films, AIP Advances, 7, 035014.Water recovery and subsequent reuse are required for human consumption as well as industrial, and agriculture applications. Moist air streams, such as cooling tower plumes and fog, represent opportunities for water harvesting. In this work, we investigate a flapping mechanism to increase droplet shedding on thin, hydrophobic films for two vibrational cases (e.g., ± 9 mm and 11 Hz; ± 2 mm and 100 Hz). Two main mechanisms removed water droplets from the flapping film: vibrational-induced coalescence/sliding and droplet ejection from the surface. Vibrations mobilized droplets on the flapping film, increasing the probability of coalescence with neighboring droplets leading to faster droplet growth. Droplet departure sizes of 1–2 mm were observed for flapping films,compared to 3–4 mm on stationary films, which solely relied on gravity for droplet removal. Additionally, flapping films exhibited lower percentage area coverage by water after a few seconds. The second removal mechanism, droplet ejection was analyzed with respect to surface wave formation and inertia. Smaller droplets (e.g., 1-mm diameter) were ejected at a higher frequency which is associated with a higher acceleration. Kinetic energy of the water was the largest contributor to energy required to flap the film, and low energy inputs (i.e., 3.3 W/m2) were possible. Additionally, self-flapping films could enable novel water collection and condensation with minimal energy input