Guidelines for testing and release procedures

Guidelines and procedures are recommended for the testing and release of the types of computer software efforts commonly performed at NASA/Ames Research Center. All recommendations are based on the premise that testing and release activities must be specifically selected for the environment, size, and purpose of each individual software project. Guidelines are presented for building a Test Plan and using formal Test Plan and Test Care Inspections on it. Frequent references are made to NASA/Ames Guidelines for Software Inspections. Guidelines are presented for selecting an Overall Test Approach and for each of the four main phases of testing: (1) Unit Testing of Components, (2) Integration Testing of Components, (3) System Integration Testing, and (4) Acceptance Testing. Tools used for testing are listed, including those available from operating systems used at Ames, specialized tools which can be developed, unit test drivers, stub module generators, and the use of format test reporting schemes

A macroscale, phase-field model for shape memory alloys with non-isothermal effects: influence of strain-rate and environmental conditions on the mechanical response

A Ginzburg-Landau model for the macroscopic behaviour of a shape memory alloy is proposed. The model is one-dimensional in essence, in that we consider the effect of the martensitic phase transition in terms of a uniaxial deformation along a fixed direction and we use a scalar order parameter whose equilibrium values describe the austenitic phase and the two martensitic variants. The model relies on a Ginzburg-Landau free energy defined as a function of macroscopically measurable quantities, and accounts for thermal effects; couplings between the various relevant physical aspects are established according to thermodynamic consistency. The theoretical model has been implemented within a finite-element framework and a number of numerical tests are presented which investigate the mechanical behaviour of the model under different conditions; the results obtained are analysed in relation to experimental evidences available in literature. In particular, the influence of the strain-rate and of the ambient conditions on the response of the model is highlighted.Comment: 23 pages research article, 13 figure

Simulazione di transizioni di fase diffusive e deformative

Il calcolo degli organi di macchina richiede una descrizione molto accurata delle caratteristiche del materiale;ciò non può prescindere dalla descrizione dei trattamenti termici ai quali il pezzo è stato sottoposto.La simulazione dei trattamenti termici degli acciai viene normalmente affrontata mediante modelli di naturafenomenologica che fanno largo uso di leggi empiriche per descrivere l’evoluzione della microstrutturaall’interno del pezzo. Tuttavia, l’impiego di leggi empiriche richiede un’apposita taratura dei parametri delmodello; inoltre tali leggi, per loro natura, non chiariscono fino in fondo le ragioni fisiche per le quali ifenomeni in gioco avvengono. Ne consegue che tale metodo è fortemente limitato nella sua generalità.Il problema può essere affrontato nella sua globalità, ossia prendendo in considerazione gli effetti termici,meccanici e di transizione di fase, partendo da una descrizione della struttura interna del materiale a scalamicroscopica ed inserita in un contesto termodinamicamente consistente.In particolare, in questo lavoro viene proposto un modello a parametri di fase alla scala microscopica capacedi descrivere trasformazioni di fase sia diffusive sia deformative e dunque di modellare, rispettivamente, latrasformazione da austenite a perlite e quella da austenite a martensite. Il modello, per la formulazione e lasua natura, risulta consistente con i principi della termodinamica e permette una descrizione delletrasformazioni diffusiva e deformativa e dei fenomeni termici in un contesto unificato.Le equazioni sulle quali si basa sono: l’equazione del moto, il bilancio della massa di carbonio (che porta allaequazione di Cahn-Hilliard) e l’equazione del calore completa, che deriva dal bilancio di energia interna. Acausa della natura non-locale del modello e della presenza di equazioni differenziali alle derivate parziali finoal quarto ordine, la soluzione del problema così formulato risulta complessa da un punto di vistacomputazionale; per questo motivo è stato messo a punto uno strumento numerico sofisticato ma robusto.Sono stati inoltre condotti alcuni test numerici che mostrano le potenzialità dell’approccio. Il modello risultacapace di cogliere le principali caratteristiche esibite alla scala microscopica dalle transizioni di fase perliticae martensitica, le interazioni fra queste e l’influenza dei fenomeni meccanici e termici

Tractor accelerated test on test rig

The experimental tests performed to validate a tractor prototype before its production, need a substantial financial and time commitment. The tests could be reduced using accelerated tests able to reproduce on the structural part of the tractor, the same damage produced on the tractor during real life in a reduced time. These tests were usually performed reproducing a particular harsh condition a defined number of times, as for example using a bumpy road on track to carry out the test in any weather condition. Using these procedures the loads applied on the tractor structure are different with respect to those obtained during the real use, with the risk to apply loads hard to find in reality. Recently it has been demonstrated how, using the methodologies designed for cars, it is possible to also expedite the structural tests for tractors. In particular, automotive proving grounds were recently successfully used with tractors to perform accelerated structural tests able to reproduce the real use of the machine with an acceleration factor higher than that obtained with the traditional methods. However, the acceleration factor obtained with a tractor on proving grounds is in any case reduced due to the reduced speed of the tractors with respect to cars. In this context, the goal of the paper is to show the development of a methodology to perform an accelerated structural test on a medium power tractor using a 4 post test rig. In particular, several proving ground testing conditions have been performed to measure the loads on the tractor. The loads obtained were then edited to remove the not damaging portion of signals, and finally the loads obtained were reproduced in a 4 post test rig. The methodology proposed could be a valid alternative to the use of a proving ground to reproduce accelerated structural tests on tractors

Monitoring of the tractor working parameters from the Can-Bus.

The analysis of the tractor mission profile is one of the main objectives for tractor manufacturers. The mission profile has usually been estimated through the use of questionnaires submitted to consumers. This procedure is time-consuming and not totally reliable due to the trustworthiness in the questionnaire compilation. In all the high power tractors numerous transducers are fitted to monitor some parameters to optimise the operation of the machines. All of these transducers are connected to an electronic central unit or with the tractor CAN-Bus. In this context, a system able to monitor the working parameters of the machines capitalising the existing transducers could represent the optimal solution for monitoring tractors distributed in different regions. The high number of signals are in any case difficult to memorise without a high quantity of memory. The goal of the paper is to define a methodology to memorise the operation parameters useful to define the mission profile of a tractor using a small memory. A tractor of a nominal power of 230 kW was selected and a system able to measure the signals acquired by the transducers fitted on the tractor was connected to the CAN Bus of the tractor. After a detailed analysis of the parameters measured on the tractor, the useful parameters were defined and acquired in different working conditions. The analysis of the parameters stored in the memory has allowed a detailed analysis of the operational parameters of the tractor in different applications. These parameters could be used by engineers to design tractors with a higher quality and reliability and also to define predictive maintenance criteria and reduce unexpected tractor failures

CO₂ leakage can cause loss of benthic biodiversity in submarine sands

One of the options to mitigate atmospheric CO2 increase is CO2 Capture and Storage in sub-seabed geological formations. Since predicting long-term storage security is difficult, different CO2 leakage scenarios and impacts on marine ecosystems require evaluation. Submarine CO2 vents may serve as natural analogues and allow studying the effects of CO2 leakage in a holistic approach. At the study site east of Basiluzzo Islet off Panarea Island (Italy), gas emissions (90–99% CO2) occur at moderate flows (80–120 L m−2 h−1). We investigated the effects of acidified porewater conditions (pHT range: 5.5–7.7) on the diversity of benthic bacteria and invertebrates by sampling natural sediments in three subsequent years and by performing a transplantation experiment with a duration of one year, respectively. Both multiple years and one year of exposure to acidified porewater conditions reduced the number of benthic bacterial operational taxonomic units and invertebrate species diversity by 30–80%. Reduced biodiversity at the vent sites increased the temporal variability in bacterial and nematode community biomass, abundance and composition. While the release from CO2 exposure resulted in a full recovery of nematode species diversity within one year, bacterial diversity remained affected. Overall our findings showed that seawater acidification, induced by seafloor CO2 emissions, was responsible for loss of diversity across different size-classes of benthic organisms, which reduced community stability with potential relapses on ecosystem resilience

Outlining the mission profile of agricultural tractors through CAN-BUS data analytics

Tractor manufacturers need to know how farmers use their agricultural tractors for an optimal machine design. Tractor usage is not easy to assess due to the large variability of field operations. However, modern tractors embed sensors integrated into the CAN-BUS network and their data is accessible through the ISO 11,783 protocol. Even though this technology has been available for a long time, the use of CAN-BUS data for outlining the tractor usage is still limited, because a proper post-processing method is lacking. This study aimed to present a novel classification scheme of CAN-BUS data which permits to outline the tractor usage. On a tractor, a CAN-BUS data logger and a GNSS receiver were installed, and real-world data were recorded for 579 h. Thus, data was obtained in the most realistic condition. Tractor positions were classified using GIS layers while operating conditions were classified depending on the usage of the tractor's subsystems. The method highlights that showed to be able to detect the 97% of the logged data and that the tractor operated on the field in working, on idle, and moving duties for 65%, 18% and 16% of the time, respectively. The method allows a far more precise outline of tractor usage opening opportunities to obtain large benefits from massively collected CAN-BUS data

Active metal-cycling microbial communities of polymetallic nodules from the Eastern Pacific Ocean

The rising demand for minerals and metals is encouraging the great international interest for alternative sources in the deep sea. Deposits of deep-sea polymetallic nodules attracted the attention for a long time because they are rich in nickel, copper, cobalt, and rare earth elements. The environmental consequences of large-scale mining of polymetallic nodules are currently less known. In 2019 the Belgian and German licence area in the Clarion-Clipperton Zone (Eastern Pacific) were studied to obtain further baseline characteristics of the 4000 m deep polymetallic nodule fields. Here, we present: i) diversity and distribution of the present & active microbial communities of polymetallic nodules and ii) abundance and activity of relevant metal-cycling microorganisms by quantification of extracellular enzyme activity and 16S rRNA amplicon sequencing. Further we aim to enrich potential metal-cycling microorganisms and investigate microbial metabolisms by metagenomic/-transcriptomic from polymetallic nodules. Our results may provide a new set of tools for monitoring ecosystem impacts associated with deep-sea polymetallic nodule mining. New regulations are required to protect these areas from irreversible anthropogenic impacts

Persistence of plastic debris and its colonization by bacterial communities after two decades on the abyssal seafloor

The fate of plastic debris entering the oceans is largely unconstrained. Currently, intensified research is devoted to the abiotic and microbial degradation of plastic floating near the ocean surface for an extended period of time. In contrast, the impacts of environmental conditions in the deep sea on polymer properties and rigidity are virtually unknown. Here, we present unique results of plastic items identified to have been introduced into deep-sea sediments at a water depth of 4150 m in the eastern equatorial Pacific Ocean more than two decades ago. The results, including optical, spectroscopic, physical and microbial analyses, clearly demonstrate that the bulk polymer materials show no apparent sign of physical or chemical degradation. Solely the polymer surface layers showed reduced hydrophobicity, presumably caused by microbial colonization. The bacterial community present on the plastic items differed significantly (p < 0.1%) from those of the adjacent natural environment by a dominant presence of groups requiring steep redox gradients (Mesorhizobium, Sulfurimonas) and a remarkable decrease in diversity. The establishment of chemical gradients across the polymer surfaces presumably caused these conditions. Our findings suggest that plastic is stable over extended times under deep-sea conditions and that prolonged deposition of polymer items at the seafloor may induce local oxygen depletion at the sediment-water interface