El costo estándar en condiciones de máxima eficiencia : una meta a alcanzar

El costo estándar se calcula anticipadamente considerando la máxima eficiencia operativa. Como consecuencia, configura una meta a alcanzar. Toda la imaginación y el esfuerzo deben encausarse para lograr un costo de producción real muy cercano al estándar. Mientras menos diferencia se verifica entre el costo estándar y el real, más cerca se está del nivel óptimo de eficiencia. Ello estimula y entusiasma a los responsables de las diferentes áreas para alcanzar la meta fijada. El modelo que se presenta, no prevé consumos reales físicos inferiores a los estándares. Pero, es más flexible respecto a las magnitudes monetarias. Admite volúmenes de producción fluctuantes a lo largo del ejercicio económico y muestra un tratamiento novedoso de los costos indirectos de fabricación.Fil: Pellegrino, Antonio. Universidad Nacional de Cuyo. Facultad de Ciencias EconómicasFil: Costa, Marina. Universidad Nacional de Cuyo. Facultad de Ciencias Económica

Stress Concentration and Material Failure During Coiling of Ultra-Thin TRAC Booms

Ultra-thin TRAC booms are a promising technology for large deployable structures for space applications. A manufacturing process producing composites TRAC booms with flange thickness as low as 53 μm is proposed. Coiling behavior around hub with radii ranging from 19.1 mm to 31.8 mm is studied both experimentally and through finite element simulations. Due to the thinness of the TRAC boom, a buckle appears in the inner flange, in the transition region from the fully deployed to the coiled configurations. Material failure is observed at this location, and this correlates well with stresses computed in simulation, coupled with the fiber microbuckling failure criterion. Reducing the thickness, either by changing the laminate or by improving the manufacturing process, is shown to reduce stresses, allowing coiling around smaller hubs without material failure

Stress Concentration and Material Failure During Coiling of Ultra-Thin TRAC Booms

Ultra-thin TRAC booms are a promising technology for large deployable structures for space applications. A manufacturing process producing composites TRAC booms with flange thickness as low as 53 μm is proposed. Coiling behavior around hub with radii ranging from 19.1 mm to 31.8 mm is studied both experimentally and through finite element simulations. Due to the thinness of the TRAC boom, a buckle appears in the inner flange, in the transition region from the fully deployed to the coiled configurations. Material failure is observed at this location, and this correlates well with stresses computed in simulation, coupled with the fiber microbuckling failure criterion. Reducing the thickness, either by changing the laminate or by improving the manufacturing process, is shown to reduce stresses, allowing coiling around smaller hubs without material failure

A data-driven rate and temperature dependent constitutive model of the compression response of a syntactic foam

Polymeric syntactic foams are used in aerospace and marine applications requiring low density and low moisture absorption together with high specific strength and stiffness. Their mechanical response is highly sensitive to temperature and strain rate and such sensitivity must be modelled accurately. In this study, the uniaxial compressive response of a polymeric syntactic foam is measured at strain rates in the range [10−3, 2.5·103] /s and temperatures varying between −25°C and 100°C. The resulting dataset is used to train a neural network to predict the compressive response of the foam at arbitrary strain rates and temperatures. It is found that the surrogate model is highly effective in predicting the material response at temperature and rates not included in its training set. Finally, a stochastic version of the data-driven model to allow predictions of the variability in the stress versus strain response is proposed

Annoted provisional list of the Crambidae (Lepidoptera, Pyraloidea) of the Salento Peninsula (South Italy), second contribution

ItLa fauna entomologica della Penisola Salentina (Sud Italia) risulta essere scarsamente indagata, come affermato in Durante e Panzera (2004) e ribadito in diversi lavori (es., Durante e Potenza, 2016; Durante et al., 2021). I risultati di questo lavoro evidenziano, nell'area geografica investigata, la presenza di 18 specie della famiglia Crambidae (superfamiglia Pyraloidea), di cui 4 relative alla sottofamiglia Odontiinae, 7 relative alla sottofamiglia Crambinae, 1 relativa alla sottofamiglia Evergestinae, 1 relativa alla sottofamiglia Pyraustinae, 2 relative alla sottofamiglia Spilomelinae, 1 relativa alla sottofamiglia Glaphyriinae, 2 relative alla sottofamiglia Acentropinae. Inoltre, sulla base della bibliografia consultata, delle 18 specie di Crambidae rinvenute, 15 sono nuove segnalazioni per il Salento, di cui 6 risultano nuove per l'Italia meridionale, 6 per la Puglia e, di conseguenza, solo 3 erano già state segnalate nel territorio salentino. I dati esposti in questo lavoro non possono ancora considerarsi definitivi, in quanto si stanno esaminando ancora molti esemplari, ciò nondimeno si è ritenuto di un certo rilievo pubblicarne i risultati.EnAs pointed out in Durante and Panzera (2004) and various other works (e.g. Durante and Potenza, 2016; Durante et al., 2021), the entomological fauna of the Salento Peninsula (Southern Italy) has not been extensively investigated. The results of this study highlight, in the studied area, the presence of 18 species in the family Crambidae (superfamily Pyraloidea), of which 4 belong to the subfamily Odontiinae, 7 to the subfamily Crambinae, 1 to the subfamily Evergestinae, 1 to the subfamily Pyraustinae, 2 to the subfamily Spilomelinae, 1 to the subfamily Glaphyriinae, 2 to the subfamily Acentropinae. In addition, based on the consulted bibliography, of the 18 species of Crambidae discovered, 15 are new records for Salento, of which 6 are new for Southern Italy, 6 for Apulia and, accordingly, only 3 having already been reported for the Salento. The data presented in this paper are not to be considered definitive, as the authors are still examining the material. Nonetheless, the results achieved thus far are thought to be of some value

Piezo-driven clamp release for synchronisation and timing of combined direct-shear stress waves

We propose a novel double clamp Tension-Torsion Hopkinson bar (TTHB) technique for measuring material responses under combined direct-shear loading. The proposed method overcomes the limitations of the existing high rate loading techniques by allowing arbitrary loading paths of tension and torsion to be prescribed to the specimen. High speed piezo actuators were employed to enable the synchronisation of direct stress and shear stress waves. The system also allows flexibility of control on the arrival times of torsional and tensile waves, thus enabling the generation of different dynamic loading paths. Direct and shear stress pulses can be generated such a way to achieve synchronised loading, torsion loading followed by tensile loading, and vice versa. The stress pulse histories of three different loading paths are presented to illustrate and validate the technique

Optimal design, development and experimental analysis of a tension–torsion Hopkinson bar for the understanding of complex impact loading scenarios

Background Advanced testing methodologies and measurement techniques to identify complex deformation and failure at high strain rates have drawn increasing attention in recent years. Objective The objective of the current study is the development of a novel combined tension–torsion split Hopkinson bar (TTHB) conceived to generate a combination of tensile and torsional stress waves in a single loading case, and to measure material data representative of real case impact scenarios. Methods An energy store and release mechanism was employed to generate both the longitudinal and shear waves via the rapid release of a bespoke clamp assembly. A parametric study of the material and geometry of the clamp was implemented via numerical simulations to optimise critical aspects of the wave generation. Thin-walled tube specimens made of two metallic materials were utilised to examine the capability of the developed TTHB system by comparing the experimental measurements with those obtained from conventional split Hopkinson tension and torsion bars. Results The experimental results demonstrate that the synchronisation of the longitudinal and torsional waves was achieved within 15 microseconds. Different wave rise time were obtained via the controlled release of the clamp using fracture pins of various materials. The analysis indicates that the developed TTHB is capable of characterising the dynamic behaviour of materials under tension, torsion, as well as under a wide range of complex stress states. Conclusions The presented apparatus, testing and analysis methods allow for the direct population of the dynamic failure stress envelopes of engineering materials and for the accurate evaluation of existing and novel constitutive models

Documentary heritage: fungal deterioration in Compact Discs

AbstractIn recent years, there has been an exponential growth in the use of digital media for data storage and the creation of museums, libraries and digital archives. In particular, Compact Discs Recordable (CD-R) have become one of the most used tools for archiving documents related to cultural heritage. Many authors have investigated only the CD longevity, but very few studies have focused on their biological deterioration. The aim of this work was to examine the CD-R biodeterioration following two ways: (1) search badly preserved CD-R, showing clear degradation spots and verify that it is fungal deterioration; (2) fungal inoculation tests on blank CD-R to verify their bioreceptivity. The analysis of a badly preserved CD-R showed clear degradation spots, highlighting, after cultural and molecular analysis, the presence on the surface of three different fungi: Chaetomium globosum, Trichoderma atroviride e Coniochaeta sp. For the in vitro inoculation tests we used conidia suspensions of Cladosporium cladosporioides and Penicillium chrysogenum, and we observed the growth for 6 months. At the end of experiment, both fungi colonized the CD-R surface with hyphae and mycelia clearly visible, causing also loss of material and fractal structure presence. For the CD-R use as cultural heritage archiving, the correct storage is an essential phase and, in light of the results obtained, it will be necessary not only to consider the environmental factors (temperature, relative humidity) but also the biological deterioration caused by airborne fungi. Therefore, effort needs to be taken to regularly monitor temperature and relative humidity and it is essential to periodically conduct cleaning of optical media