Control of a Mach reflection-induced interaction using an array of vane-type vortex generators.

An experimental investigation was conducted to control a Mach reflection (MR)-induced flow separation in a Mach 2.05 flow using a 18∘ shock generator (SG). The study was extended to four SG exit heights (g / w) of 0.87, 0.81, 0.725, and 0.66 primarily to study its effect on the extent of flow separation as well as on Mach stem height, with and without control. Two vane-type vortex generator configurations, namely the ramp vane (RV) with device heights h/δ=0.3,0.5,0.8, and 1.0 and the rectangular vane (RRV) with h/δ=0.3 and 0.5, were studied for control. Each control device array was implemented 10δ upstream of the separation location for no control. For stable MR interactions (i.e., g/w=0.87,0.81), the extent of separation and the reattachment shock strength are seen to decrease with increase in RV height (with h/δ=1.0 device showing 17% reduction). However, for unstable MR condition (i.e., g/w=0.725), RV devices of h/δ=0.8 and 1.0 become ineffective. The RRV2 device (h/δ=0.5), on the other hand, was found to be more effective in reducing the extent of separation in both the stable (31%) and unstable (24%) MR conditions. The effectiveness of each control device is also accompanied with an increase in height of the Mach stem. This is, however, not seen as a serious limitation since in such strong interactions it is more important to prevent or avert an intake unstart condition. The separation shock unsteadiness or the σmax/Pw value, on the other hand, is seen to increase considerably with controls and seems to be almost independent for h/δ≥0.5

Control of incident shock-induced separation using vane-type vortex-generating devices.

An experimental investigation was conducted to control an incident shock-induced boundary-layer separation associated with a 14 deg shock generator in a Mach 2.05 flow. Two vane-type configurations, namely the triangular (h/δ=0.3, 0.5, 0.8, 1.0) and the rectangular (h/δ=0.5) designs, were studied. An array of each control device was tested for three control locations of X/δ=5, 10, and 15. The control location of 5δ is seen to show the maximum reduction in separation length for each device tested. For the rectangular-vane device (h/δ=0.5), a maximum reduction of 38% in separation length is observed, followed by the triangular-vane devices of h/δ=0.8 and 1.0, each of which shows a 32% reduction, and finally, h/δ=0.5 with 18%. The effectiveness of these devices to control separation is, however, seen to decrease with increase in X/δ. In terms of separation shock unsteadiness, the maximum rms value for X/δ=5δ shows the highest value for each control device, and this value decreases with increase in control location. At X/δ=15, both the rectangular vane (h/δ=0.5) and triangular vane (h/δ=0.8,1.0) show a 50% reduction in maximum rms value, whereas it decreases to 30% at X/δ=10 for these devices

Base pressure fluctuations on typical missile configuration in presence of base cavity.

Pressure fluctuations in the base region of a typical missile configuration at a freestream Mach number of 0.7 are examined experimentally in the presence and absence of a base cavity. The objective was to characterize the pressure fluctuations and explain the influence of base cavities on their behavior. Experiments include unsteady pressure measurements at six azimuthal locations. Substantial variation in the characteristics of pressure fluctuations is noticed along the azimuthal direction due to the asymmetry of the model. The base cavities are seen to enhance the base pressure and reduce the root mean square of the pressure fluctuations. Higher-order moments show diminishing trend as the length of the base cavity is increased. Spectra in the absence of cavity exhibit three types of narrow-band tones based on the Strouhal number. Type I tones disapper from the spectra for small-length cavities, whereas type II tones get suppressed. On the other hand, for the large-length cavities, type I tones get enhanced, whereas type II tones disappear. Autocorrelation and cross-correlation plots exhibit a large-amplitude, low-frequency oscillation that exists even after large separation times for the larger-length cavities, and virtually no such oscillations are visible for the small-length-cavity models

A Multiclassifier Approach for Drill Wear Prediction

Classification methods have been widely used during last years in order to predict patterns and trends of interest in data. In present paper, a multiclassifier approach that combines the output of some of the most popular data mining algorithms is shown. The approach is based on voting criteria, by estimating the confidence distributions of each algorithm individually and combining them according to three different methods: confidence voting, weighted voting and majority voting. To illustrate its applicability in a real problem, the drill wear detection in machine-tool sector is addressed. In this study, the accuracy obtained by each isolated classifier is compared with the performance of the multiclassifier when characterizing the patterns of interest involved in the drilling process and predicting the drill wear. Experimental results show that, in general, false positives obtained by the classifiers can be slightly reduced by using the multiclassifier approach

Relationship between ecosystem productivity and photosynthetically active radiation for northern peatlands

We analyzed the relationship between new ecosystem exchange of carbon dioxide (NEE) and irradiance (as photosynthetic photon flux density of PPFD), using published and unpublished data that have been collected during midgrowing season for carbon balance studies at seven peatlands in North America and Europe. NEE measurements included both eddy-correlation tower and clear, static chamber methods, which gave very similar results. Data were analyzed by site, as aggregated data set for all peatland type (bog, poor fen, rich fen, and all fens) and as a single aggregated data set for all peatlands. In all cases, a fit with a rectangular hyperbola (NEE = PPFD P max (PPFD + PMAX) + R) better described the NEE-PPFD relationships ,while bogs had lower respiration rates (R = -2.0 umol m-2 s-1 for bogs and -2.7 umol m-2 s-1 for fens) and lower NEE at moderate and high light levels (Pmax = 5.2 umol m-2 s-1) than the upland exosystems (closed canopy forest, grassland, and cropland) summarized by Ruimy et al. [1995]. Despite this low productivity, northern peatland soil carbon pools are generally 5-50 times larger than upland ecosystems because of slow rates of decomposition caused by litter quality and anaerobic, cold soils

Medicines in Pharmacy Students’ Residence and Self-medication Practices

This study was aimed at identifying the types of medicines in pharmacy students’ residence and to determine if a relationship exists between keeping medicines in students’ accommodation and self-medication practices. A cross-sectional survey of a random sample of 240 undergraduate pharmacy students of the University of Jos, Jos, Nigeria, was carried out. Participating students were given a self-administered questionnaire, and only 188 students returned their filled questionnaire. The data collected were entered and analyzed using SPSS 16, and the χ2-test was used to determine associations between the variables. The results revealed that 66.0% of respondents had medicines in their room. A total of 318 medicines items (2.56 items per student's room) of which 37.1% were leftover medicines were present in respondents’ rooms. Analgesics (34.3%) and antibiotics (25.2%) were the common classes of medicines present in respondents’ rooms. Respondents reported getting these medicines on prescription (25.8%) and self-medication (56.5%) or both (17.7%). Self-medication practice was common among respondents (53.2%); however, no significant relationship (P>0.05) existed between having medicine in students’ room and self-medication practices. Common reasons given by respondents for having medicines in their rooms were that they were leftover medicines and that they were keeping them for emergency use or for use in an event of a similar illness. Most respondents (72.2%) reported disposing of their unused medicines in a trash can/dust bin. This study demonstrated that the prevalence of medicine storage in students’ room and self-medication practice is high. Analgesics and antibiotics were the most common types of medicines present in students’ residence

Non-monotonic variation with salt concentration of the second virial coefficient in protein solutions

The osmotic virial coefficient $B_2$ of globular protein solutions is calculated as a function of added salt concentration at fixed pH by computer simulations of the ``primitive model''. The salt and counter-ions as well as a discrete charge pattern on the protein surface are explicitly incorporated. For parameters roughly corresponding to lysozyme, we find that $B_2$ first decreases with added salt concentration up to a threshold concentration, then increases to a maximum, and then decreases again upon further raising the ionic strength. Our studies demonstrate that the existence of a discrete charge pattern on the protein surface profoundly influences the effective interactions and that non-linear Poisson Boltzmann and Derjaguin-Landau-Verwey-Overbeek (DLVO) theory fail for large ionic strength. The observed non-monotonicity of $B_2$ is compared to experiments. Implications for protein crystallization are discussed.Comment: 43 pages, including 17 figure

Energy balance measurements over a banana orchard in the Semiarid region in the Northeast of Brazil

The objective of this work was to evaluate the reliability of eddy covariance measurements, analyzing the energy balance components, evapotranspiration and energy balance closure in dry and wet growing seasons, in a banana orchard. The experiment was carried out at a farm located within the irrigation district of Quixeré, in the Lower Jaguaribe basin, in Ceará state, Brazil. An eddy covariance system was used to measure the turbulent flux. An automatic weather station was installed in a grass field to obtain the reference evapotranspiration (ET0) from the combined FAO-Penman-Monteith method. Wind speed and vapor pressure deficit are the most important variables on the evaporative process in both growing seasons. In the dry season, the heat fluxes have a similar order of magnitude, and during the wet season the latent heat flux is the largest. The eddy covariance system had acceptable reliability in measuring heat flux, with actual evapotranspiration results comparing well with those obtained by using the water balance method. The energy balance closure had good results for the study area, with mean values of 0.93 and 0.86 for the dry and wet growing seasons respectively

Gravitational Radiation from Compact Binary Pulsars

An outstanding question in modern Physics is whether general relativity (GR) is a complete description of gravity among bodies at macroscopic scales. Currently, the best experiments supporting this hypothesis are based on high-precision timing of radio pulsars. This chapter reviews recent advances in the field with a focus on compact binary millisecond pulsars with white-dwarf (WD) companions. These systems - if modeled properly - provide an unparalleled test ground for physically motivated alternatives to GR that deviate significantly in the strong-field regime. Recent improvements in observational techniques and advances in our understanding of WD interiors have enabled a series of precise mass measurements in such systems. These masses, combined with high-precision radio timing of the pulsars, result to stringent constraints on the radiative properties of gravity, qualitatively very different from what was available in the past.Comment: Short review chapter to appear in "Gravitational Wave Astrophysics" by Springer-Verlag, edited by Carlos F. Sopuerta; v3: a few major corrections and updated references. Comments are welcome