Impact of an external electric field on grain growth in oxides: Comparison of flash sintered samples to field assisted grain growth

In the last years ample effort was done to investigate the effect of electric fields on matter. We investigated the effect of an external electric field on the oxide ceramic model system strontium titanate. More precisely, we observed that a non-contacting external electric field has an impact on the defect distribution and the grain growth. Oxygen vacancies are migrating towards the negative electrode yielding a higher oxygen vacancy concentration compared to the positive electrode. As a result, faster grain growth was observed on the negative electrode. Recent thermodynamic defect calculations revealed the mechanism for this relationship [1]: A high oxygen vacancy concentration results in less space charge and, as such, in less segregation of cationic defects. As less segregation requires less diffusion for grain boundary migration, faster grain growth occurs. We extended these findings to flash sintering of doped strontium titanate. TEM imaging and EDS analysis were used to investigate the microstructure and to map the dopant segregation at the grain boundaries. Observing different dopant species (acceptors and donors) gives insight on flash sintering for different defect concentration and types with different segregation properties. In addition, field assisted microstructure evolution experiments with titania (no current, insulating electrodes) allow to apply the gained knowledge to different material systems with different defect chemistry. [1] Work of Jana P Parras and Roger A. de Souz

Adubação nitrogenada em videiras jovens e em fase produtiva: recuperação e distribuição na planta do nitrogênio adicionado no solo.

bitstream/CNPUV/8144/1/cot060.pd

An Open-Source Data Manager for Network Models

Developing simulation and optimisation models for resource networks like water or energy systems increasingly involves integrating multiple data sources and software. Connecting multiple models and managing data accessed by different groups of analysts is a software challenge. Many resource systems are represented in computer models as networks of nodes and links, driven by a range of objectives and rules. We present a data storage platform, written in Python, which exploits the commonality of network representations to store data for multiple model types within a single deployment. This open-source platform provides a common source of data to multiple models using consistent data formats, reducing likelihood of error compared to file based data management. When deployed as a web service, it allows data to be shared securely among authorised users over the internet, facilitating collaboration. A case study describes the hosting of a water utility planning model, with an accompanying worked example

Soil physical properties affected by soil management and crop rotation in a long term experiment in Southern Brazil

The main objective of this work is to evaluate soil physical properties affected by cover crop rotations and soil management after 19 years of applying NoTill and Conventional Tillage systems with different winter species on a clayey Oxisol in South Brazil

Cobre em solos cultivados com a videira na Serra Gaúcha do Rio Grande do Sul.

O presente trabalho objetivou determinar as formas de cobre e a cinética de dessorção em solos cultivados com a videira e submetidos a sucessivas aplicações de fungicidas cúpricos.bitstream/CNPUV/10103/1/cot086.pd

Defect redistribution along grain boundaries in SrTiO3_3 by externally applied electric fields

During thermal annealing at 1425 °C nominal electric field strengths of 50 V/mm and 150 V/mm were applied along the grain boundary planes of a near 45° (100) twist grain boundary in SrTiO$_3$. Electron microscopy characterization revealed interface expansions near the positive electrode around 0.8 nm for either field strength. While the interface width decreased to roughly 0.4 nm after annealing at 50 V/mm, the higher field strength caused decomposition of the boundary structure close to the negative electrode. Electron energy-loss and X-ray photoelectron spectroscopies demonstrated an increased degree of oxygen sublattice distortion at the negative electrode side, and enhanced concentrations of Ti$^{3+}$ and Ti$^{2+}$ compared to bulk for both single crystals and bicrystals annealed with an external electric field, respectively. Oxygen migration due to the applied electric field causes the observed alteration of grain boundary structures. At sufficiently high field strength the agglomeration of anion vacancies may lead to the decomposition of the grain boundary

Deep soil water-use determines the yield benefit of long-cycle wheat

Wheat production in southern Australia is reliant on autumn (April-May) rainfall to germinate seeds and allow timely establishment. Reliance on autumn rainfall can be removed by sowing earlier than currently practiced and using late summer and early autumn rainfall to establish crops, but this requires slower developing cultivars to match life-cycle to seasonal conditions. While slow-developing wheat cultivars sown early in the sowing window (long-cycle), have in some cases increased yield in comparison to the more commonly grown fast-developing cultivars sown later (short-cycle), the yield response is variable between environments. In irrigated wheat in the sub-tropics, the variable response has been linked to ability to withstand water stress, but the mechanism behind this is unknown. We compared short- vs. long-cycle cultivars × time of sowing combinations over four seasons (2011, 2012, 2015, and 2016) at Temora, NSW, Australia. Two seasons (2011 and 2012) had above average summer fallow (December-March) rain, and two seasons had below average summer fallow rain (2015 and 2016). Initial plant available water in each season was 104, 91, 28, and 27 mm, respectively. Rainfall in the 30 days prior to flowering (approximating the critical period for yield determination) in each year was 8, 6, 14, and 190 mm, respectively. We only observed a yield benefit in long-cycle treatments in 2011 and 2012 seasons where there was (i) soil water stored at depth (ii) little rain during the critical period. The higher yield of long-cycle treatments could be attributed to greater deep soil water extraction (<1.0 m), dry-matter production and grain number. In 2015, there was little rain during the critical period, no water stored at depth and no difference between treatments. In 2016, high in-crop rainfall filled the soil profile, but high rainfall during the critical period removed crop reliance on deep water, and yields were equivalent. A simulation study extended our findings to demonstrate a median yield benefit in long-cycle treatments when the volume of starting soil water was increased. This work reveals environmental conditions that can be used to quantify the frequency of circumstances where long-cycle wheat will provide a yield advantage over current practice.The research undertaken as part of this project is made possible by the significant contributions of growers through both trial cooperation and the support of the GRDC (projects CSP00111, CSP00178, CSP00183, 9175069, and a GRDC Grains Industry Research Scholarship