Antennas for the detection of radio emission pulses from cosmic-ray induced air showers at the Pierre Auger Observatory

The Pierre Auger Observatory is exploring the potential of the radio detection technique to study extensive air showers induced by ultra-high energy cosmic rays. The Auger Engineering Radio Array (AERA) addresses both technological and scientific aspects of the radio technique. A first phase of AERA has been operating since September 2010 with detector stations observing radio signals at frequencies between 30 and 80 MHz. In this paper we present comparative studies to identify and optimize the antenna design for the final configuration of AERA consisting of 160 individual radio detector stations. The transient nature of the air shower signal requires a detailed description of the antenna sensor. As the ultra-wideband reception of pulses is not widely discussed in antenna literature, we review the relevant antenna characteristics and enhance theoretical considerations towards the impulse response of antennas including polarization effects and multiple signal reflections. On the basis of the vector effective length we study the transient response characteristics of three candidate antennas in the time domain. Observing the variation of the continuous galactic background intensity we rank the antennas with respect to the noise level added to the galactic signal

From Pabst to Pepsi: The Deinstitutionalization of Social Practices and the Creation of Entrepreneurial Opportunities

In this paper, we examine the dual role that social movement organizations can play in altering organizational landscapes by undermining existing organizations and creating opportunities for the growth of new types of organizations. Empirically, we investigate the impact of a variety of tactics employed by the Woman’s Christian Temperance Union (WCTU), the leading organizational representative of the American temperance movement, on two sets of organizations: breweries and soft drink producers. By delegitimating alcohol consumption, altering attitudes and beliefs about drinking, and promoting temperance legislation, the WCTU contributed to brewery failures. These social changes, in turn, created opportunities for entrepreneurs to found organizations producing new kinds of beverages by creating demand for alternative beverages, providing rationales for entrepreneurial action, and increasing the availability of necessary resources.Tolbert13_From_Pabst_to_Pepsi.pdf: 3878 downloads, before Oct. 1, 2020

Factors influencing the production rate and quality of lead sinter

The sintering characteristics of a typical Missouri lead concentrate were determined for two types of raw sinter mix: conventionally prepared and pelletized. The important sintering characteristics are sulfur elimination, sinter strength, production rate of sinter, permeability of the sinter bed, and bed temperature. These characteristics were analyzed statistically, and are described by an empirical model, in which proportion of returns, moisture content, air flow, bed height, size distribution of returns, and ignition time are the independent variables. The characteristics of a conventionally prepared sinter mix are most strongly affected by the moisture content of the raw mix. The characteristics of a pelletized sinter mix are not strongly affected by any of the independent variables. However, a pelletized charge gave a much higher production rate and a higher sinter quality as compared to a conventionally prepared charge. Recycle of off gas has a large deleterious effect on sinter production rate and quality. The results provide suggestions for improved operation of sinter plants. © 1982 American Society for Metals and the Metallurgical Society of AIME