L’evoluzione di un grande classico The Evolution of a Great Classic

Il legno torna a proporsi come materiale da costruzione. Anche per i grattaciel

Creating China Visually: Collecting Chinese Propaganda Posters

Article / Letter to edito

Evaluation of the mechanical properties of self compacting concrete using current estimating models. Estimating the modulus of elasticity, tensile strength, and modulus of rupture of self compacting concrete

This study includes an analysis of the applicability of current models used for estimating the mechanical properties of conventional concrete to self-compacting concrete. The mechanical properties evaluated are: modulus of elasticity, tensile strength, and modulus of rupture. An extensive database which included the dosifications and the mechanical properties of 627 mixtures from 138 different references, was used. The models considered are: ACI, EC-2, NZS 3101:2006 (New Zealand code) and the CSA A23.3-04 (Canadian code). The precision in estimating the modulus of elasticity and tensile strength is acceptable for all models; however, all models are less precise in estimating the modulus of rupture

Development of boron calibration via hybrid comparator method in prompt gamma activation analysis

The prompt gamma activation analysis (PGAA) facility at the Nuclear Engineering Teaching Laboratory at The University of Texas at Austin was utilized to quantify boron concentrations in boron carbide semiconductor films deposited on silicon substrates. Calibration was complicated by the unique and varying sample geometries analyzed. In addition, there was a dearth of solid materials available with quantified boron concentrations having comparable or readily modifiable dimensions to exploit for calibration purposes. Therefore, a novel hybrid comparator method was developed for the quantification of boron utilizing aluminum as an inexpensive and easily machinable reference material. Aluminum samples were manufactured with high tolerances to match the geometry of each sample of interest. Each boron carbide film sample and its congruent aluminum sample were measured in the PGAA system. The measured aluminum responses and relevant nuclear parameters were used to standardize the measurements. A boron standard was created using a procedure derived from a similar approach used by the National Institute of Standards and Technology. Quality control measurements using this standard show that the method provided accuracy to within 5% for boron quantification

Locality and Nonlocality in the Interaction-Free Measurement

We present a paradox involving a particle and a mirror. They exchange a nonlocal quantity, modular angular momentum Lz mod 2ћ, but there seems to be no local interaction between them that allows such an exchange. We demonstrate that the particle and mirror do interact locally via a weak local current 〈Lz mod 2ћ〉w. In this sense, we transform the “interaction-free measurement” of Elitzur and Vaidman, in which two local quantities (the positions of a photon and a bomb in the two arms of a Mach-Zehnder interferometer) interact nonlocally, into a thought experiment in which two nonlocal quantities (the weak modular angular momentum of the particle and of the mirror) interact locally

Estudio sobre los modelos de cálculo de la retracción de la EHE y del Eurocódigo EC-2.

La retracción es una característica importante del hormigón para la evaluación de su comportamiento a largo plazo. Este trabajo ha consistido en la búsqueda y creación de una base de datos sobre la retracción en hormigón autocompactable (HAC) y hormigón convencional vibrado (HC) con el fin de evaluar la aplicabilidad de los modelos actuales también en el caso del HAC. Los modelos considerados son los incluidos en la EHE y en el Eurocódigo EC-2. Según los resultados obtenidos, cada modelo estima la retracción del HAC y HC con equivalente precisión, y no hace falta modificar estos modelos para su aplicación en HAC. Entre estos dos modelos, el Eurocódigo estima la retracción con mayor precisión