Scattering of Elastic Waves in a Quasi-one-dimensional Cavity: Theory and Experiment

We study the scattering of torsional waves through a quasi-one-dimensional cavity both, from the experimental and theoretical points of view. The experiment consists of an elastic rod with square cross section. In order to form a cavity, a notch at a certain distance of one end of the rod was grooved. To absorb the waves, at the other side of the rod, a wedge, covered by an absorbing foam, was machined. In the theoretical description, the scattering matrix S of the torsional waves was obtained. The distribution of S is given by Poisson's kernel. The theoretical predictions show an excellent agreement with the experimental results. This experiment corresponds, in quantum mechanics, to the scattering by a delta potential, in one dimension, located at a certain distance from an impenetrable wall

Electromagnetic prompt response in an elastic wave cavity

A rapid, or prompt response, of an electromagnetic nature, is found in an elastic wave scattering experiment. The experiment is performed with torsional elastic waves in a quasi-one-dimensional cavity with one port, formed by a notch grooved at a certain distance from the free end of a beam. The stationary patterns are diminished using a passive vibration isolation system at the other end of the beam. The measurement of the resonances is performed with non-contact electromagnetic-acoustic transducers outside the cavity. In the Argand plane, each resonance describes a circle over a base impedance curve which comes from the electromagnetic components of the equipment. A model, based on a variation of Poisson's kernel is developed. Excellent agreement between theory and experiment is obtained.Comment: 4 pages, 5 figure

Origin and standing of Canary Black Pig

We summarize the historical information about origin of Canary Black Pig and standing in the Canary Islands. The presence of pig in Canary Islands is from 500 year b.C., where aborigines used its meat as food, its fat to preserve foods, its skin as clothing and its bones to produce tools and adornments. The census is constituted for 283 animals, 182 females and 101 males, with a major representation in Tenerife and Gran Canaria islands, 173 and 71 animals respectively.A través de la documentación histórica del Archipiélago Canario, se ha esbozado el origen del Cerdo Negro Canario, a la vez que se expone su estado actual en las diferentes islas del archipiélago. La presencia del cerdo data desde hace 2500 años en el Archipiélago Canario, donde los aborígenes utilizaron su carne como alimento, su manteca para conservas, su piel para vestimenta y sus huesos para fabricación de útiles y adornos. El censo lo constituyen unos 283 ejemplares, 182 hembras y 101 machos, y su mayor representación está en las islas de Tenerife y de Gran Canaria con 173 y 71 animales respectivamente

Materiales compuestos de cáscaras de maní y cemento. Influencia de diferentes tratamientos químicos sobre las propiedades mecánicas

An abundance of agri-food waste in the area around Cordoba, Argentina, has driven the development of new construction materials. This study explored the applicability of peanut shells as additions in cement blends and the suitability of the properties of the resulting mixes for use in construction materials. The mechanical properties of the specimens were observed to improve when the shells were previously treated with quicklime (CaO) or when sodium silicate and aluminium sulphate were added to the blend. While the resulting materials did not exhibit the same mechanical properties as traditional mortars and concretes, they do appear to be apt for use in lightweight and non-bearing structures.La abundante disponibilidad de residuos de la agroindustria local (Córdoba, Argentina), ha promovido el desarrollo de nuevos materiales para la construcción. Este trabajo de investigación se desarrolla a partir de la utilización de cáscara de maní como agregado en mezclas de cemento a fin de conocer las propiedades obtenidas en relación al tratamiento de dicho agregado, para la producción de materiales de construcción. Los ensayos demostraron mejoras en las propiedades mecánicas de las probetas realizadas con cemento y cáscaras previamente tratadas con cal viva (CaO), también en aquéllas aditivadas con silicato de sodio y sulfato de aluminio. Si bien los materiales resultantes no tienen las propiedades mecánicas de los morteros y hormigones tradicionales, parecen interesantes para ser aplicadas en componentes de construcción livianos y de uso no portante

Influence of the use of milk replacers and pH on the texture profiles of raw and cooked meat of suckling kids

The aim of this work was to study the texture profile of fresh and cooked longissimus thoracis et lumborum muscle from suckling kids raised with natural milk or milk replacers. Suckling Male kids from eight goat breeds (Florida, FL; Cabra del Guadarrama, GU; Majorera, MA; Palmera, PL; Payoya, PY; Retinta, RE; Tinerfeña, TI; Verata, VE), all of single parturition, were raised with milk replacers (MR) or with natural milk from the dams (NM). The meat pH, Warner-Bratzler shear force, texture profile analysis and chemical composition were determined. Kids were clustered based on their pH by k-means clustering. The effect of the rearing system on the textural profile was strongly modulated by breed. The values of Warner-Bratzler shear force and hardness found in these breeds under both rearing systems were very low. Hence, the toughness of very light suckling kids should not be a determining factor in choosing a breed or rearing system. Nevertheless, the use of milk replacers increased the presence of meat with high pH, which modified the textural parameters, decreasing the shear force but increasing cohesiveness and adhesiveness. Consequently, depending on the commercial strategy of the farm, the election of the breed and rearing system must be considered together