The First Spanish Short Wave Stations. Development of Radio & Tv Technology

In the thirties in Spain there were three big Short Wave Stations. One, belonging to Transradio Española in Aranjuez, 50 kilometers south of Madrid, which rendered radiotelegraphic services to the Canary Islands, Europe and America. Another, belonging to the Sociedad Anónima Radio Argentina (via Radiar), in Vallecas, on the outskirts of Madrid, also rendered radiotelegraphic services. The third belonged to the company Telefónica Nacional de España (CTNE), in Pozuelo del Rey, 50 kilometers east of Madrid provided radiotelephonic services to New York and Buenos Aires. In 1932, Aranjuez started broadcasting the programming of “EAQ-Madrid Radiodifusion Iberoamericana” directed to Spanish speaking countries. During the Civil War it became the Spanish Republican overseas broadcasting station. However, in 1937 as a result of the Battle of Jarama, Aranjuez became cut off from Madrid and the transmissions and call signs were transferred to the Vallecas transmitter EDZ using the call-sign EAQ-2

Boundary-layer turbulence in experiments of quasi-Keplerian flows

Most flows in nature and engineering are turbulent because of their large velocities and spatial scales. Laboratory experiments of rotating quasi-Keplerian flows, for which the angular velocity decreases radially but the angular momentum increases, are however laminar at Reynolds numbers exceeding one million. This is in apparent contradiction to direct numerical simulations showing that in these experiments turbulence transition is triggered by the axial boundaries. We here show numerically that as the Reynolds number increases turbulence becomes progressively confined to the boundary layers and the flow in the bulk fully relaminarizes. Our findings support that turbulence is unlikely to occur in isothermal constant density quasi-Keplerian flows.Comment: 16 pages, 8 figures. Accepted for publication in Journal of Fluid Mechanic

Two-point Taylor Expansions of Analytic Functions

Taylor expansions of analytic functions are considered with respect to two points. Cauchy-type formulas are given for coefficients and remainders in the expansions, and the regions of convergence are indicated. It is explained how these expansions can be used in deriving uniform asymptotic expansions of integrals. The method is also used for obtaining Laurent expansions in two points.Comment: 14 pages, 10 figure

Foreign entry into underwriting services: evidence from Japan's "Big Bang" deregulation

We examine the impact of foreign underwriting activity on bond markets using issue level data in the Japanese "Samurai" and euro-yen bond markets. Firms choosing Japanese underwriters tend to be Japanese, riskier, and smaller. We find that Japanese underwriting fees, while higher overall on average, are actually lower after conditioning for issuer characteristics. Moreover, firms tend to sort properly in their choice of underwriter, in the sense that a switch in underwriter nationality would be predicted to result in an increase in underwriting fees. Finally, we conduct a matching exercise to examine the 1995 liberalization of foreign access to the "Samurai" bond market, using yen-denominated issues in the euro-yen market as a control. Foreign entry led to a statistically and economically significant decrease in underwriting fees in the Samurai bond market, as spreads fell by an average of 23 basis points. Overall, our results suggest that the market for underwriting services is partially segmented by nationality, as issuers appear to have preferred habitats, but entry increases market competition.Japan

Exceeding the asymptotic limit of polymer drag reduction

The drag of turbulent flows can be drastically decreased by addition of small amounts of high molecular weight polymers. While drag reduction initially increases with polymer concentration, it eventually saturates to what is known as the maximum drag reduction (MDR) asymptote; this asymptote is generally attributed to the dynamics being reduced to a marginal yet persistent state of subdued turbulent motion. Contrary to this accepted view we will show in the following that for an appropriate choice of parameters polymers can reduce the drag beyond the suggested asymptotic limit, eliminating turbulence and giving way to laminar flow. However at higher polymer concentrations the laminar state becomes unstable, resulting in a fluctuating flow with the characteristic drag of the MDR asymptote. The asymptotic state is hence dynamically disconnected from ordinary turbulence.Comment: 6 pages, 6 figure

Dynamics of viscoelastic pipe flow in the maximum drag reduction limit

Polymer additives can substantially reduce the drag of turbulent flows and the upper limit, the so called "maximum drag reduction" (MDR) asymptote is universal, i.e. independent of the type of polymer and solvent used. Until recently, the consensus was that, in this limit, flows are in a marginal state where only a minimal level of turbulence activity persists. Observations in direct numerical simulations using minimal sized channels appeared to support this view and reported long "hibernation" periods where turbulence is marginalized. In simulations of pipe flow we find that, indeed, with increasing Weissenberg number (Wi), turbulence expresses long periods of hibernation if the domain size is small. However, with increasing pipe length, the temporal hibernation continuously alters to spatio-temporal intermittency and here the flow consists of turbulent puffs surrounded by laminar flow. Moreover, upon an increase in Wi, the flow fully relaminarises, in agreement with recent experiments. At even larger Wi, a different instability is encountered causing a drag increase towards MDR. Our findings hence link earlier minimal flow unit simulations with recent experiments and confirm that the addition of polymers initially suppresses Newtonian turbulence and leads to a reverse transition. The MDR state on the other hand results from a separate instability and the underlying dynamics corresponds to the recently proposed state of elasto-inertial-turbulence (EIT).Comment: 18 pages, 5 figure

On The Harmonic Oscillator Group

We discuss the maximum kinematical invariance group of the quantum harmonic oscillator from a view point of the Ermakov-type system. A six parameter family of the square integrable oscillator wave functions, which seems cannot be obtained by the standard separation of variables, is presented as an example. The invariance group of generalized driven harmonic oscillator is shown to be isomorphic to the corresponding Schroedinger group of the free particle.Comment: 11 pages, no figure