Experimental demonstration of the supersonic-subsonic bifurcation in the circular jump: A hydrodynamic white hole

We provide an experimental demonstration that the circular hydraulic jump represents a hydrodynamic white hole or gravitational fountain (the time-reverse of a black hole) by measuring the angle of the Mach cone created by an object in the "supersonic" inner flow region. We emphasise the general character of this gravitational analogy by showing theoretically that the white hole horizon constitutes a stationary and spatial saddle-node bifurcation within dynamical-systems theory. We also demonstrate that the inner region has a "superluminal" dispersion relation, i.e., that the group velocity of the surface waves increases with frequency, and discuss some possible consequences with respect to the robustness of Hawking radiation. Finally, we point out that our experiment shows a concrete example of a possible "transplanckian distortion" of black/white holes.Comment: 5 pages, 5 figures. New "transplanckian effect" described. Several clarifications, additional figures and references. Published versio

Almacén y centro de distribución de materiales de construcción, en Bussigny (Suiza)

Centre for storage and distribution of construction material at Bussigny, Switzerland Owing to the cost and small area of the site the building has been extended upwards. The ground floor has access ramps to the various floors, a hall, offices, retail sales department, loading wharfs, etc. The second floor is level with the railway, and on the south east there is a loading platform for heavy trucks. The third floor serves mainly as storage of stocks of light weight materials. Finally, on the top floor, in addition to a car park, there are management offices. The sober and sincerely expressive design and use of materials constitute outstanding aspects of this building.<br><br>El edificio se ha desarrollado en vertical, debido al elevado precio de los solares y al poco espacio disponible. La planta baja contiene, además de las rampas de acceso a las diferentes plantas, el hall; oficinas; sección de venta al detall; muelles de carga; etc. La primera planta, situada al nivel de la vía férrea, dispone al sudeste de un muelle de carga accesible a los vehículos pesados. La segunda planta sirve principalmente para el almacenaje y formación de los stocks de materiales ligeros. Y finalmente, la planta de cubierta, además del parking para los coches, alberga las oficinas de la administración, etc. El tratamiento sobrio del edificio y la sinceridad expresiva de los materiales son las notas destacadas de esta construcción

Almacén y centro de distribución de materiales de construcción, en Bussigny (Suiza)

Centre for storage and distribution of construction material at Bussigny, Switzerland Owing to the cost and small area of the site the building has been extended upwards. The ground floor has access ramps to the various floors, a hall, offices, retail sales department, loading wharfs, etc. The second floor is level with the railway, and on the south east there is a loading platform for heavy trucks. The third floor serves mainly as storage of stocks of light weight materials. Finally, on the top floor, in addition to a car park, there are management offices. The sober and sincerely expressive design and use of materials constitute outstanding aspects of this building.El edificio se ha desarrollado en vertical, debido al elevado precio de los solares y al poco espacio disponible. La planta baja contiene, además de las rampas de acceso a las diferentes plantas, el hall; oficinas; sección de venta al detall; muelles de carga; etc. La primera planta, situada al nivel de la vía férrea, dispone al sudeste de un muelle de carga accesible a los vehículos pesados. La segunda planta sirve principalmente para el almacenaje y formación de los stocks de materiales ligeros. Y finalmente, la planta de cubierta, además del parking para los coches, alberga las oficinas de la administración, etc. El tratamiento sobrio del edificio y la sinceridad expresiva de los materiales son las notas destacadas de esta construcción

Horizon effects for surface waves in wave channels and circular jumps

Surface waves in classical fluids experience a rich array of black/white hole horizon effects. The dispersion relation depends on the characteristics of the fluid (in our case, water and silicon oil) as well as on the fluid depth and the wavelength regime. In some cases, it can be tuned to obtain a relativistic regime plus high-frequency dispersive effects. We discuss two types of ongoing analogue white-hole experiments: deep water waves propagating against a counter-current in a wave channel and shallow waves on a circular hydraulic jump.Comment: 4 pages, 2 figs. To appear in: Proceedings of the Spanish Relativity Meeting (ERE2010

Status of the low beta 0.07 cryomodules for SPIRAL2

International audienceThe status of the low beta cryomodules for SPIRAL2, supplied by the Irfu institute of CEA Saclay, is reported in this paper. We summarise in three parts the RF tests performed on the cavities in vertical cryostat, the RF power tests of the qualifying cryomodule performed in 2010 and the RF power tests performed in 2011 on the first cryomodule of the serie

SPIRAL2 RFQ prototype - First results

JACoW web site MOPCH103International audienceThe SPIRAL2 RFQ is designed to accelerate either 5 mA deuteron beam (Q/A=1/2) or a 1 mA of q/A=1/3 particle up to 0.75 MeV/A at 88 MHz. It is a CW machine which has to show stable operation, provide the required availability and reduce losses to a minimum in order to minimize the activation constraints. Extensive modelisation was done to ensure a good vane position under RF. The prototype of this 4-vane RFQ was built and tested in INFN-LNS Catania and then in IN2P3-LPSC Grenoble. It allowed us to measure the vacuum quality, the RF field by X-ray measurements, the cavity displacement and the real vane displacement during the RF injection. Different techniques were used, including an innovative CCD measurement with a 0.8 μm precision. This paper outlines the different results

The known unknowns of hydraulic engineering

Hydraulic engineers and researchers deal with scientific challenges involving turbulent flow motion and its interactions with the surroundings. Turbulent flows are characterised by unpredictable behaviour, and little systematic research has yet been conducted in natural systems. This paper discusses the implications of recent developments in affordable instrumentation previously characterised by intrinsic weaknesses that adversely affect the quality of the signal outputs. A challenging application is the unsteady turbulence field in tidal bores. The interactions between open channel flows and movable boundaries and atmosphere illustrate another aspect of our limited knowledge. Rapid siltation of reservoirs and air entrainment in turbulent free-surface flows are discussed. In both applications, hydraulic engineers require some broad-based expertise. In turn the education of future hydraulic engineers is of vital importance

Finite Theories and the SUSY Flavor Problem

We study a finite SU(5) grand unified model based on the non-Abelian discrete symmetry A_4. This model leads to the democratic structure of the mass matrices for the quarks and leptons. In the soft supersymmetry breaking sector, the scalar trilinear couplings are aligned and the soft scalar masses are degenerate, thus solving the SUSY flavor problem.Comment: 17 pages, LaTeX, 1 figur

The GANIL control system as seen from the control room

http://accelconf.web.cern.ch/AccelConf/c81/papers/fp-08.pdfInternational audienc

Corporate political activity in less developed countries:The Volta River Project in Ghana, 1958-66

The article expands existing categorisations of political and economic governance by including literature on less developed countries (LDCs). In four consecutive negotiations between the US multinational Kaisers and the US and Ghana governments in the early 1960s, it is argued that the company reached levels of influence that are at odds with existing explanations. In order to understand corporate political activities in LDCs, analysis needs to go beyond static factors (political risk) and include dynamic factors such as diplomatic relations and 'arenas of power', and consider the role of the investor's home country relative to the host economy