Changes in the turbulent boundary layer structure associated with net drag reduction by outer layer manipulators

A specially designed wind tunnel was used to examine the effects of tandemly arranged parallel plate manipulators (TAPPMs) on a turbulent boundary-layer structure and the associated drag. Momentum balances, as well as measurements of the local shear stress from the velocity gradient near the wall, were used to obtain the net drag and local skin friction changes. Two TAPPMs, identical except for the thickness of their plates, were used in the study. Results with .003 inch plates were a maximum net drag reduction of 10 percent at 58 beta sub o (using a momentum balance). At 20 beta sub o, simultaneous laser sheet flow visualization and hot-wire anemometry data showed that the Reynolds stress in the large eddies was significantly reduced, as were the streamwise and normal velocity components. Using space-time correlations the reductions were again identified. Furthermore, quantitative flow visualization showed that the outward normal velocity of the inner region was also significantly decreased in the region around 20 beta sub o. However, throughout the first 130 beta sub o, the measured sublayer thickness with the TAPPMs in place was 15 to 20 percent greater. The data showed that the skin friction, as well as the structure of the turbulence, was strongly modified in the first 35 beta sub o, but that they both significantly relaxed toward unmanipulated boundary layer values by 50 beta sub o

Reasons and opportunism control in public grants policies for development and innovations of businesses

In this paper we would to analyze the mechanism of public grants on economic growth. In particular this topic has been the subject of scientific interest by economists and, recently, also by business economics scholars. The studies of the economists focused on the motivations of the intervention itself; the business economic studies, on the other hand, have analyzed the impact both on the behavior of entrepreneurs and on the firms themselves by public grants. The studies examined so far highlight two basic conceptual dimensions, different, but also complementary to each other: on the one hand the economic-oriented to investigate the motivations and effectiveness of the public intervention; the second, business-oriented, focused on the firm’s behavior following public grant. Based on these arguments, our research question arises: could the effectiveness of public intervention for funding development and business innovation be influenced by the differences in the various socio-political and institutional contexts in which they are applied? The aim of paper is analyze the motivations of public grants policies and their influence on the behavior of firms. In this way we want to identify asolutions scheme able to recover efficiency and effectiveness of public actions to support development. It is therefore possible to identify some corrective mechanisms on public intervention policies. In particular with reference to the behaviors induced by the grants policies, the idea is to re-design the grants policies in consideration of the different forms of pre and post contractual opportunism. With reference, instead, to the motivations underlying the public grants policies, it is necessary to examine the relationship between the State (Principal) and the beneficiary firms (Agent) in relation to the respective dimensions of the contractual force

Positive or negative voting premium: what happened to private benefits in Italy?

A large body of research deals with voting premium as a proxy of private benefit of control. Almost all of them find positive voting premium, in particular in Italy. Therefore appears interesting to ask what is the current status of private benefits of control in Italy in the last decade (2007-2017). Surprisingly, we show three major findings: i) reduction of non-voting share in the Italian scenario; ii) prevalence of negative voting rights premium more than positive ones, thus conflicting with the assumption and the observations by other researchers; iii) limits of the voting premium method. Our aim is that this study, despite its limitations, may encourage further researches focused on the analysis of the improvement and the change in the Italian corporate governance. The article points out that interesting evidence already exists, although still much remains to do in the future

Conductive structures around Las Cañadas caldera, Tenerife (Canary Islands, Spain) : a structural control

External eastern areas of the Las Cañadas caldera (LCC) of Tenerife (Canary Islands, Spain) have been investigated using the audiomagnetotelluric (AMT) method with the aim to characterize the physical rock properties at shallow depth and the thickness of a first resistive layer. Using the results of 50 AMT tensors carried out in the period range of 0.001 s to 0.3 s, this study provides six unpublished AMT profiles distributed in the upper Orotava valley and data from the Pedro Gil caldera (Dorsal Ridge). Showing obvious 1-D behaviour, soundings have been processed through 1-D modeling and gathered to form profiles. Underlying a resistive cover (150-2000 Om), a conductive layer at shallow depth (18-140 Om, 250-1100 m b.g.l.) which is characterized by a "wavy-like" structure, often parallel to the topography, appears in all profiles. This paper points out the ubiquitous existence in Tenerife of such a conductive layer, which is the consequence of two different processes: a) according to geological data, the enhanced conductivity of the flanks is interpreted as a plastic breccia within a clayish matrix generated during huge lateral collapse; and b) along main tectonic structures and inside calderas, this layer is formed by hidrotermal alteration processes. In both areas, the conductive layer is thought to be related to major structural volcanic events (flank or caldera collapse) and can be seen as a temporal marker of the island evolution. Moreover, its slope suggests possible headwall locations of the giant landslides that affected the flanks of Tenerife

Thermodynamics of a Bose-Einstein Condensate with Weak Disorder

We consider the thermodynamics of a homogeneous superfluid dilute Bose gas in the presence of weak quenched disorder. Following the zero-temperature approach of Huang and Meng, we diagonalize the Hamiltonian of a dilute Bose gas in an external random delta-correlated potential by means of a Bogoliubov transformation. We extend this approach to finite temperature by combining the Popov and the many-body T-matrix approximations. This approach permits us to include the quasi-particle interactions within this temperature range. We derive the disorder-induced shifts of the Bose-Einstein critical temperature and of the temperature for the onset of superfluidity by approaching the transition points from below, i.e., from the superfluid phase. Our results lead to a phase diagram consistent with that of the finite-temperature theory of Lopatin and Vinokur which was based on the replica method, and in which the transition points were approached from above.Comment: 11 pages, 5 figure

Microlensing of the Lensed Quasar SDSS0924+0219

We analyze V, I and H band HST images and two seasons of R-band monitoring data for the gravitationally lensed quasar SDSS0924+0219. We clearly see that image D is a point-source image of the quasar at the center of its host galaxy. We can easily track the host galaxy of the quasar close to image D because microlensing has provided a natural coronograph that suppresses the flux of the quasar image by roughly an order of magnitude. We observe low amplitude, uncorrelated variability between the four quasar images due to microlensing, but no correlated variations that could be used to measure a time delay. Monte Carlo models of the microlensing variability provide estimates of the mean stellar mass in the lens galaxy (0.02 Msun < M < 1.0 Msun), the accretion disk size (the disk temperature is 5 x 10^4 K at 3.0 x 10^14 cm < rs < 1.4 x 10^15 cm), and the black hole mass (2.0 x 10^7 Msun < MBH \eta_{0.1}^{-1/2} (L/LE)^{1/2} < 3.3 x 10^8 Msun), all at 68% confidence. The black hole mass estimate based on microlensing is consistent with an estimate of MBH = 7.3 +- 2.4 x 10^7 Msun from the MgII emission line width. If we extrapolate the best-fitting light curve models into the future, we expect the the flux of images A and B to remain relatively stable and images C and D to brighten. In particular, we estimate that image D has a roughly 12% probability of brightening by a factor of two during the next year and a 45% probability of brightening by an order of magnitude over the next decade.Comment: v.2 incorporates referee's comments and corrects two errors in the original manuscript. 28 pages, 10 figures, published in Ap

The Rewards of Patience: An 822 Day Time Delay in the Gravitational Lens SDSS J1004+4112

We present 107 new epochs of optical monitoring data for the four brightest images of the gravitational lens SDSS J1004+4112 observed between October 2006 and June 2007. Combining this data with the previously obtained light curves, we determine the time delays between images A, B and C. We confirm our previous measurement finding that A leads B by dt_BA=40.6+-1.8 days, and find that image C leads image A by dt_CA=821.6+-2.1 days. The lower limit on the remaining delay is that image D lags image A by dt_AD>1250 days. Based on the microlensing of images A and B we estimate that the accretion disk size at a rest wavelength of 2300 angstrom is 10^{14.8+-0.3} cm for a disk inclination of cos{i}=1/2, which is consistent with the microlensing disk size-black hole mass correlation function given our estimate of the black hole mass from the MgII line width of logM_BH/M_sun=8.44+-0.14. The long delays allow us to fill in the seasonal gaps and assemble a continuous, densely sampled light curve spanning 5.7 years whose variability implies a structure function with a logarithmic slope of gamma = 0.35+-0.02. As C is the leading image, sharp features in the C light curve can be intensively studied 2.3 years later in the A/B pair, potentially allowing detailed reverberation mapping studies of a quasar at minimal cost.Comment: Submitted to ApJ, 12 pages, 3 figure

An observing system for the collection of fishery and oceanographic data

Fishery Observing System (FOS) was developed as a first and basic step towards fish stock abundance nowcasting/forecasting within the framework of the EU research program Mediterranean Forecasting System: Toward an Environmental Prediction (MFSTEP). The study of the relationship between abundance and environmental parameters also represents a crucial point towards forecasting. Eight fishing vessels were progressively equipped with FOS instrumentation to collect fishery and oceanographic data. The vessels belonged to different harbours of the Central and Northern Adriatic Sea. For this pilot application, anchovy (&lt;I&gt;Engraulis encrasicolus&lt;/I&gt;, L.) was chosen as the target species. Geo-referenced catch data, associated with in-situ temperature and depth, were the FOS products but other parameters were associated with catch data as well. MFSTEP numerical circulation models provide many of these data. In particular, salinity was extracted from re-analysis data of numerical circulation models. Satellite-derived sea surface temperature (SST) and chlorophyll were also used as independent variables. Catch and effort data were used to estimate an abundance index (CPUE &amp;ndash; Catch per Unit of Effort). Considering that catch records were gathered by different fishing vessels with different technical characteristics and operating on different fish densities, a standardized value of CPUE was calculated. A spatial and temporal average CPUE map was obtained together with a monthly mean time series in order to characterise the variability of anchovy abundance during the period of observation (October 2003&amp;ndash;August 2005). In order to study the relationship between abundance and oceanographic parameters, Generalized Additive Models (GAM) were used. Preliminary results revealed a complex scenario: the southern sector of the domain is characterised by a stronger relationship than the central and northern sector where the interactions between the environment and the anchovy distribution are hidden by a higher percentage of variability within the system which is still unexplained. &lt;br&gt;&lt;br&gt; GAM analysis showed that increasing the number of explanatory variables also increased the portion of variance explained by the model. Data exchange and interdisciplinary efforts will therefore be crucial for the success of this research activity

Localized states and interaction induced delocalization in Bose gases with quenched disorder

Very diluted Bose gas placed into a disordered environment falls into a fragmented localized state. At some critical density the repulsion between particles overcomes the disorder. The gas transits into a coherent superfluid state. In this article the geometrical and energetic characteristics of the localized state at zero temperature and the critical density at which the quantum phase transition from the localized to the superfluid state proceeds are found.Comment: 17 pages, 5 figur

A Black Hole of > 6 Solar Masses in the X-ray Nova XTE J1118+480

Observations of the quiescent X-ray nova XTE J1118+480 with the new 6.5-m MMT have revealed that the velocity amplitude of the dwarf secondary is 698 +/- 14 km/s and the orbital period of the system is 0.17013 +/- 0.00010 d. The implied value of the mass function, f(M) = 6.00 +/- 0.36 solar masses, provides a hard lower limit on the mass of the compact primary that greatly exceeds the maximum allowed mass of a neutron star. Thus we conclude that the compact primary is a black hole. Among the eleven dynamically established black-hole X-ray novae, the large mass function of XTE J1118+480 is rivaled only by that of V404 Cyg. We estimate that the secondary supplies 34% +/- 8% of the total light at 5900A and that its spectral type is in the range K5V to M1V. A double-humped I-band light curve is probably due to ellipsoidal modulation, although this interpretation is not entirely secure because of an unusual 12-minute offset between the spectroscopic and photometric ephemerides. Assuming that the light curve is ellipsoidal, we present a provisional analysis which indicates that the inclination of the system is high and the mass of the black hole is correspondingly modest. The broad Balmer emission lines (FWHM = 2300-2900 km/s) also suggest a high inclination. For the range of spectral types given above, we estimate a distance of 1.8 +/- 0.6 kpc.Comment: 4 pages, 2 figures, to appear in ApJ Letters; Minor changes to Fig 1