Experimental investigation of a two-dimensional shock-turbulent boundary layer interaction with bleed

The two-dimensional interaction of an oblique shock wave with a turbulent boundary layer that included the effect of bleed was examined experimentally using a shock generator mounted across a supersonic wind tunnel The studies were performed at Mach numbers 2.5 and 2.0 and unit Reynolds number of approximately 2.0 x 10 to the 7th/meter. The study includes surface oil flow visualization, wall static pressure distributions and boundary layer pitot pressure profiles. In addition, the variation of the local bleed rates were measured. The results show the effect of the bleed on the boundary layer as well as the effect of the flow conditions on the local bleed rate

Influence of climate change on storm surges in the Ariake sea

The influence of climate change on storm surges in the Ariake Sea was evaluated using the stochastic\ud typhoon model. The Ariake Sea is located in the middle of Kyushu Island, Japan and has been attacked by severe\ud typhoons many times. There are many lowland coastal farmlands along the coastline of the Ariake Sea as a result of\ud many reclamation projects since ancient times. These coastal farmlands are at risk of even more severe storm surges due\ud to typhoons caused by climate change. The deviations of tides due to storm surges were simulated by an experimental\ud typhoon model employing the Myers model. The stochastic typhoon model generated the tracks and attributes of\ud typhoons over the next 2,000 years. Meanwhile, the tracks of typhoons in the case of the climate after climate change\ud were generated by shifting the start points of typhoons 0.9 degrees further north and 1.9 degrees further east. The\ud number of typhoons after climate change was set to 0.79 times that of typhoons in the present climate. These changes in\ud the tracks and number of typhoons in the future were decided according to the results of numerical simulations of\ud climate change using the AGCM model based on the A1B scenario. The non-exceedance probabilities of the yearmaximum\ud anomaly rise were compared to evaluate the change due to climate change. The simulation suggested that the\ud height of the year-maximum anomaly rise due to storm surges in the future climate will be similar to or slightly lower\ud than the present height

Damages caused by 3/11 Great East Japan earthquake on coastal drainage pumping stations along Sendai bay

On March 11, 2011, a tsunami struck low-lying land along Sendai Bay, where no tsunami had hit in the past 200 years. These coastal lowlands were equipped with drainage pumping stations for paddy areas, but the pumping stations were destroyed by the tsunami, thus preventing drainage of the sea water inundation.There are two kinds of pumps, motor and diesel pumps. Even diesel pumps need electricity to start up and control their power. If a pump is inundated by salt water, all electric parts will be short-circuited. Although the diesel mechanisms can be reused after being washed by fresh water, the electric parts of both types of pump must be replaced. The switchboard for the pumps must also be replaced. If damages are caused only by salt inundation, the electric parts of both types of pump must be replaced. Temporary recovery was done by manually controlling the pumps because the automatic pump control system was difficult to restore. The mean recovery time was one month for electric pumps and two months for diesel pumps. For pumps that were broken by external force, quick recovery was abandoned.Past studies on tsunami have shown that concrete structures are strong enough to withstand tsunami surges. In the present study, a few concrete pumping stations located near the coast were damaged. The damages to buildings were mainly governed by the type of material and location on the coast. At some pumping stations, the tank for desorption prevented external forces from acting on the buildings.These results show that the tsunami safety of drainage pumping stations could be improved by increasing the resistance to salt inundation and appropriately locating the tank for desorption

Cooperative coupling of ultracold atoms and surface plasmons

Cooperative coupling between optical emitters and light fields is one of the outstanding goals in quantum technology. It is both fundamentally interesting for the extraordinary radiation properties of the participating emitters and has many potential applications in photonics. While this goal has been achieved using high-finesse optical cavities, cavity-free approaches that are broadband and easy to build have attracted much attention recently. Here we demonstrate cooperative coupling of ultracold atoms with surface plasmons propagating on a plane gold surface. While the atoms are moving towards the surface they are excited by an external laser pulse. Excited surface plasmons are detected via leakage radiation into the substrate of the gold layer. A maximum Purcell factor of $\eta_\mathrm{P}=4.9$ is reached at an optimum distance of $z=250~\mathrm{nm}$ from the surface. The coupling leads to the observation of a Fano-like resonance in the spectrum.Comment: 9 pages, 4 figure

Effects of ecstasy/polydrug use on memory for associative information

Rationale Associative learning underpins behaviours that are fundamental to the everyday functioning of the individual. Evidence pointing to learning deficits in recreational drug users merits further examination. Objectives A word pair learning task was administered to examine associative learning processes in ecstasy/polydrug users. Methods After assignment to either single or divided attention conditions, 44 ecstasy/polydrug users and 48 non-users were presented with 80 word pairs at encoding. Following this, four types of stimuli were presented at the recognition phase: the words as originally paired (old pairs), previously presented words in different pairings (conjunction pairs), old words paired with new words, and pairs of new words (not presented previously). The task was to identify which of the stimuli were intact old pairs. Results Ecstasy/ploydrug users produced significantly more false-positive responses overall compared to non-users. Increased long-term frequency of ecstasy use was positively associated with the propensity to produce false-positive responses. It was also associated with a more liberal signal detection theory decision criterion value. Measures of long term and recent cannabis use were also associated with these same word pair learning outcome measures. Conjunction word pairs, irrespective of drug use, generated the highest level of false-positive responses and significantly more false-positive responses were made in the divided attention condition compared to the single attention condition. Conclusions Overall, the results suggest that long-term ecstasy exposure may induce a deficit in associative learning and this may be in part a consequence of users adopting a more liberal decision criterion value

Characterization of electrostatic shock in laser-produced optically-thin plasma flows using optical diagnostics

We present a method for evaluating the properties of electrostatic shock in laser-produced plasmas by using optical diagnostics. A shock is formed by a collimated jet in counter-streaming plasmas in nearly collisionless condition, showing the steepening of the transition width in time. In the present experiment, a streaked optical pyrometry was applied to evaluate the electron density and temperatures in the upstream and downstream regions of the shock so that the shock conditions are satisfied, by assuming thermal bremsstrahlung emission in optically thin plasmas. The derived electron densities are nearly consistent with those estimated from interferometry

TIME EVOLUTION of KELVIN-HELMHOLTZ VORTICES ASSOCIATED with COLLISIONLESS SHOCKS in LASER-PRODUCED PLASMAS

We report experimental results on Kelvin-Helmholtz (KH) instability and resultant vortices in laser-produced plasmas. By irradiating a double plane target with a laser beam, asymmetric counterstreaming plasmas are created. The interaction of the plasmas with different velocities and densities results in the formation of asymmetric shocks, where the shear flow exists along the contact surface and the KH instability is excited. We observe the spatial and temporal evolution of plasmas and shocks with time-resolved diagnostics over several shots. Our results clearly show the evolution of transverse fluctuations, wavelike structures, and circular features, which are interpreted as the KH instability and resultant vortices. The relevant numerical simulations demonstrate the time evolution of KH vortices and show qualitative agreement with experimental results. Shocks, and thus the contact surfaces, are ubiquitous in the universe; our experimental results show general consequences where two plasmas interact

Atomic Resolution Electron Holography

It has been demonstrated that electron holography is a very powerful tool to investigate an electromagnetic potential in medium resolution, since the phase of an electron wave is approximately proportional to the potential. Now, electron holography is at the second stage of development: to establish holography at atomic resolution and further to realize Gabor\u27s idea to improve the resolution restricted by the spherical aberration of the objective lens. We investigate the possibility of electron holography to get information at atomic resolution by computer simulations as well as by digital processing of electron holograms. We show that the phase distribution has more resemblance to the specimen structure than the amplitude distribution. We also compare electron holography with electron microscopy from an image processing point of view