Parasite-Drag Measurements of Five Helicopter Rotor Hubs

An investigation has been conducted in the Langley full-scale tunnel to determine the parasite drag of five production-type helicopter rotor hubs. Some simple fairing arrangements were attempted in an effort to reduce the hub drag. The results indicate that, within the range of the tests, changes in angle of attack, hub rotational speed, and forward speed generally had only a small effect on the equivalent flat-plate area representing parasite drag. The drag coefficients of the basic hubs, based on projected hub frontal area, increased with hub area and varied from 0.5 to 0.76 for the hubs tested

Elemental Relationships in Rock Varnish as Seen with Scanning Electron Microscopy and Energy Dispersive X-Ray Elemental Line Profiling

The heterogeneous nature of rock varnish requires a thorough understanding of elemental and mineralogic compositions before chemical variability of rock varnish may be confidently related to varnish age or to past geochemical environments. Elemental relationships in rock varnish were examined using scanning electron microscopy in conjunction with an elemental line profiling routine using semi-quantitative, energy-dispersive x-ray analysis. Results of our analyses suggest: 1) variations in cation concentrations used in varnish cation-ratio dating relate more specifically to variations in detritus concentration within the varnish than to element mobility as defined by weathering indices; 2) Mn:Fe ratios may be a poor indicator of paleoclimatic fluctuations; and 3) the Mn-oxide phase existing in varnish is most likely a Ba-enriched phase rather than birnessite. An examination of data collected from elemental line profiling offers great potential for gaining insights into geochemical processes affecting the deposition and diagenesis of rock varnish and for testing hypotheses relating to its chemical variability

Fault-tolerant quantum computation with high threshold in two dimensions

We present a scheme of fault-tolerant quantum computation for a local architecture in two spatial dimensions. The error threshold is 0.75% for each source in an error model with preparation, gate, storage and measurement errors.Comment: 4 pages, 4 figures; v2: A single 2D layer of qubits (simple square lattice) with nearest-neighbor translation-invariant Ising interaction suffices. Slightly improved threshol

Scanning Electron Microscopic Analysis of Rock Varnish Chemistry for Cation-Ratio Dating: An Examination of Electron Beam Penetration Depths

Rock varnish is a microns-thick manganese- and iron-rich coating that forms on exposed rock surfaces in arid and semi-arid environments, and empirical correlations of the varnish cation ratio (K+Ca):Ti with age have been used to estimate ages of geomorphic surfaces. One method of obtaining varnish chemistry for cation-ratio dating involves scanning electron microscope (SEM) energy dispersive x-ray (EDX) analysis of natural varnish surfaces. The chemical analyses of rock varnish with SEM/EDX utilize a sequence of accelerating voltages to vary penetration depths into the sample. Using elemental x-ray maps of natural varnish surfaces obtained by SEM/EDX analysis, penetration into the substrate can be recognized at accelerating voltages where contamination with substrate is inferred from SEM/EDX chemical analyses, illustrating the ability of the SEM method to obtain varnish chemistry with minimal inclusion of substrate. Calculations of theoretical x-ray depth-distribution (¢,(pz)) curves in varnish indicate that at an accelerating voltage of 10 kV most of the emitted x-rays are generated in the upper 0.5 µm of a sample. At a higher voltage of 30 kV most of the signal is still restricted to the upper 2 µm, representing a very small percentage of total varnish volume in many cases. The ability of the SEM method to obtain empirical correlations of the chemistry of the uppermost varnish with varnish age suggests that it is not necessary to average the entire varnish coat, and that surface-biased varnish analyses provide similar results as bulk varnish analyses

Non-Traditional Agriculture: Path to Future Food Production?

The world population is growing rapidly, and the amount of arable land is decreasing. This raises the issue of how to feed the 2050 projected population of nine billion people. Another issue is the presence of “food deserts.” Food deserts are defined as urban neighborhoods and rural towns without ready access to fresh, healthy, and affordable food. The purpose of this report is to examine possible alternatives for food production that are also located in close proximity to demand. Included in non-traditional production agriculture are several concepts currently in use, including greenhouses (covered agriculture), backyard gardens (called Victory Gardens during WW II), agriculture-designated land within urban areas, underground facilities (bomb shelters), urban agriculture in housing developments, and converted warehouses. Other production concepts are presented to demonstrate the breadth of discussion regarding meeting future food demand. In the several cases of unique, non-traditional agriculture, each is a new industry with few players in the market, suggesting time will be the final decision-maker on viability (agronomic and economic). Greenhouses have been a part of production agriculture for centuries, with the technology well-defined. But retrofitting abandoned warehouses or constructing high rise facilities, as well as production in high rise housing units, will take time to perfect the systems involved, including a water and reuse system, fertilization, pest and disease control, harvesting, overall quality control, and logistics. The necessary components of non-traditional food production facilities are resources, land, water, equipment and finances. Highly fertile land has for the most part been allocated to crop cultivation, and the quantity of high-quality water for irrigation is declining. Non-traditional systems typically have a much smaller land footprint and are highly efficient in water use. The implication is that non-traditional food production systems will provide society with more quantity, plus improved quality, of high-value food products per unit of land and per unit of water. This is a broad, brief review of actual production facilities, as well as projections for the future. Included are greenhouses, retrofitted warehouses, below-surface facilities, high rise facilities, and production near cities. This piece is intended to provide insight into the broad range of non-traditional food production facilities emerging and envisioned at this time. The mention of any business is not to be interpreted as endorsement or suggestion that it is viable