Device measures fluid drag on test vehicles

Electromechanical drag balance device measures the aerodynamic drag force acting on a vehicle as it moves through the atmosphere and telemeters the data to a remote receiving station. This device is also used for testing the hydrodynamic drag characteristics of underwater vehicles

Air frame drag balance Patent

Device for measuring drag forces in flight test

Detecting periodicity in experimental data using linear modeling techniques

Fourier spectral estimates and, to a lesser extent, the autocorrelation function are the primary tools to detect periodicities in experimental data in the physical and biological sciences. We propose a new method which is more reliable than traditional techniques, and is able to make clear identification of periodic behavior when traditional techniques do not. This technique is based on an information theoretic reduction of linear (autoregressive) models so that only the essential features of an autoregressive model are retained. These models we call reduced autoregressive models (RARM). The essential features of reduced autoregressive models include any periodicity present in the data. We provide theoretical and numerical evidence from both experimental and artificial data, to demonstrate that this technique will reliably detect periodicities if and only if they are present in the data. There are strong information theoretic arguments to support the statement that RARM detects periodicities if they are present. Surrogate data techniques are used to ensure the converse. Furthermore, our calculations demonstrate that RARM is more robust, more accurate, and more sensitive, than traditional spectral techniques.Comment: 10 pages (revtex) and 6 figures. To appear in Phys Rev E. Modified styl

Oviposition deterrents for Aedes aegypti in extracts of Lemna minor

Dual choice bioassays demonstrated that water and methanolic extracts of <i>Lemna minor</i> L., in aqueous solution, deterred oviposition by <i>Aedes aegypti</i> L. The methanolic extracts were active at concentrations of 1000 and 10,000 PPM but were inactive at 1, 10, and 100 PPM. Pentane extracts and L. minor culture water showed no activity. None of the extracts bioassayed were biologically active against <i>Culex pipiens</i> L. Experiments in which physical contact with the extracts was prevented, provide evidence that a volatile chemical emanating from the extract is responsible for the deterrency

The cost of a small membrane bioreactor

The individual cost contributions to the mechanical components of a small membrane bioreactor (MBR) (100–2,500 m3/d flow capacity) are itemised and collated to generate overall capital and operating costs (CAPEX and OPEX) as a function of size. The outcomes are compared to those from previously published detailed cost studies provided for both very small containerised plants (<40 m3/day capacity) and larger municipal plants (2,200–19,000 m3/d). Cost curves, as a function of flow capacity, determined for OPEX, CAPEX and net present value (NPV) based on the heuristic data used indicate a logarithmic function for OPEX and a power-based one for the CAPEX. OPEX correlations were in good quantitative agreement with those reported in the literature. Disparities in the calculated CAPEX trend compared with reported data were attributed to differences in assumptions concerning cost contributions. More reasonable agreement was obtained with the reported membrane separation component CAPEX data from published studies. The heuristic approach taken appears appropriate for small-scale MBRs with minimal costs associated with installation. An overall relationship of net present value = (a tb)Q(−c lnt+d) was determined for the net present value where a = 1.265, b = 0.44, c = 0.00385 and d = 0.868 according to the dataset employed for the analysis

Effects of Glycol on Leachability and Efficacy of Boron Wood Preservatives

Although boron has many advantages as a wood preservative, this chemical performs poorly in leaching exposures. In this study, we investigated the potential for decreasing the leachability of boron preservatives with polyethylene glycol (PEG). Southern pine (Pinus spp.) test samples impregnated with combinations of sodium borate or boric acid and PEG were subjected to both leaching and decay tests. Samples treated sequentially with sodium borate or boric acid and then with PEG-400 or PEG-600 showed a significantly increased resistance to boron leaching. However, decay tests indicated that blocks treated with sodium borate or boric acid and PEG experienced slightly higher weight losses at nearly all retention levels, possibly as a result of PEG depletion. Thus, although the results suggest that bulking agents may enhance the resistance of boron to leaching, the enhanced leach resistance may be a temporary effect

Cold atoms near superconductors: Atomic spin coherence beyond the Johnson noise limit

We report on the measurement of atomic spin coherence near the surface of a superconducting niobium wire. As compared to normal conducting metal surfaces, the atomic spin coherence is maintained for time periods beyond the Johnson noise limit. The result provides experimental evidence that magnetic near field noise near the superconductor is strongly suppressed. Such long atomic spin coherence times near superconductors open the way towards the development of coherently coupled cold atom / solid state hybrid quantum systems with potential applications in quantum information processing and precision force sensing.Comment: Major revisions of the text for submission to New Journal of Physics 8 pages, 4 figure

The impact of mechanical shear on membrane flux and energy demand

The use of forced mechanical shear for both disc membranes (rotating and vibrating disc filtration, RDF and VDF respectively) and hollow fibres (vibrating HF membranes, VHFM) is reviewed. These systems have been extensively studied and, in the case of the disc membranes, have reached commercialisation and proven effective in achieving transmembrane pressure (TMP) control for various challenging feed waters. The effects of operating conditions, namely shear rate as enhanced by rotation and vibration speed and TMP, and feed water quality on the filtration flux and specific energy consumption are quantified as part of the review. A new relationship is revealed between the two empirical constants governing the classical relationship between membrane flux and shear rate, and a mathematical correlation proposed accordingly. A study of available information on energy reveals that operation at lower shear rates (i.e. rotation or vibration speeds) and more conservative fluxes leads to lower specific energy demands in kWh m−3 permeate, albeit with a larger required membrane area

Comparative power demand of mechanical and aeration imposed shear in an immersed membrane bioreactor

The power demanded for the application of mechanically-imposed shear on an immersed flat sheet (iFS) membrane bioreactor (MBR) has been compared to that of conventional membrane air scouring. Literature correlations based on the Ostwald model were used to define the rheological characteristics of an MBR sludge. The correlation of specific power demand (, in Watts per m2 membrane area) with shear rate γ in s-1 was developed from first principles through a consideration of the force balance on the system in the case of mechanically-imposed shear. The corresponding aeration imposed shear correlation was interpreted from literature information. The analysis revealed the energy required to impose a shear mechanically through oscillation (or reciprocation) of the membrane to be between 20 and 70% less than that demanded for providing the same shear by conventional aeration of the immersed membrane. The energy saving increases with decreasing shear in accordance with a power demand ratio (aeration:mechanical) of 1400γ-1.4 for a specific sludge rheology. Whilst the absolute value is dependent on the sludge rheology, the aeration:mechanical power demand ratio is determined by the difference in the two exponents in the respective correlations between and γ. Consequently, aeration-imparted shear becomes energetically favoured beyond some threshold shear rate value (∼180 s-1, based on the boundary conditions applied in the current study). The outcomes qualitatively corroborate findings from the limited practical measurement of energy demand in MBRs fitted with reciprocating immersed membranes