A model for the interaction of dislocations with planar defects based on Allen-Cahn type microstructure evolution coupled to strain gradient elasticity

In classical elasticity theory the stress-field of a dislocation is characterized by a $1/r$-type singularity. When such a dislocation is considered together with an Allen-Cahn-type phase-field description for microstructure evolution this leads to singular driving forces for the order parameter, resulting in non-physical (and discretization-dependent) predictions for the interaction between dislocations and phase-, twin- or grain-boundaries. We introduce a framework based on first strain gradient elasticity to regularize the dislocation core. It is shown that the use of strain energy density that is quadratic in the gradient of elastic deformation results in non-singular stresses but may result in singular driving forces, whereas a strain energy, which is quadratic in the gradient of the full deformation tensor, regularizes both stresses and driving forces for the order parameter and is therefore a suitable choice. The applicability of the framework is demonstrated using a comprehensive example

Dislocation structures and the role of grain boundaries in cyclically deformed Ni micropillars

Transmission electron microscopy and finite element-based dislocation simulations were combined to study the development of dislocation microstructures after cyclic deformation of single crystal and bicrystal Ni micropillars oriented for multi-slip. A direct correlation between large accumulation of plastic strain and the presence of dislocation cell walls in the single crystal micropillars was observed, while the presence of the grain boundary hampered the formation of wall-like structures in agreement with a smaller accumulated plastic strain. Automated crystallographic orientation and nanostrain mapping using transmission electron microscopy revealed the presence of lattice heterogeneities associated to the cell walls including long range elastic strain fields. By combining the nanostrain mapping with an inverse modelling approach, information about dislocation density, line orientation and Burgers vector direction was derived, which is not accessible otherwise in such dense dislocation structures. Simulations showed that the image forces associated with the grain boundary in this specific bicrystal configuration have only a minor influence on dislocation behavior. Thus, the reduced occurrence of “mature” cell walls in the bicrystal can be attributed to the available volume, which is too small to accommodate cell structures

OKULASI TANAMAN DURIAN “Durio zibethinus Murr.” DENGAN ASAL TUNAS BATANG ATAS DAN CARA PEMOTONGAN BATANG BAWAH

Durian memiliki prospek ekonomi yang bagus sebab pemasaran meningkat dari tahun ke tahun, akan tetapi ketersediaan benih bermutu masih terbatas. Penyediaan benih bermutu perlu dilakukan dengan cara gabungan (vegetatif dan generatif) salah satunya adalah okulasi. Pertumbuhan okulasi dipengaruhi oleh asal tunas yang menunjukkan tingkat ketuaan batang dan pemotongan batang bawah yang akan menekan pertumbuhan tunas lateral, sehingga perlu dilakukan pemotongan dengan ukuran yang tepat. Tujuan dari penelitian ini untuk mempelajari asal tunas dan mendapatkan panjang pemotongan batang bawah yang tepat untuk mempercepat pertumbuhan tunas okulasi serta mendapatkan kesesuaian antara asal tunas batang atas dengan pemotongan batang bawah terhadap pertumbuhan tunas okulasi. Penelitian dilaksanakan bulan Januari sampai Mei 2011 berdasarkan percobaan faktorial dengan rancangan acak lengkap, diulang empat kali, yang terdiri atas dua faktor yaitu asal entres (ujung, tengah, pangkal) dan pemotongan batang bawah (dipotong ½ batang, 10 cm dari ujung, 15 cm dan 5 cm di atas okulasi), sehingga diperoleh 12 kombinasi perlakuan. Variabel pengamatan meliputi jumlah keberhasilan okulasi, saat pecah mata entres, saat kemunculan daun pertama, tinggi tunas okulasi, jumlah daun, keberhasilan okulasi tumbuh. Hasil penelitian menunjukkan entres ujung diawal pertumbuhan tumbuh lebih cepat dibandingkan yang lain meskipun selanjutnya entres tengah memberikan pertumbuhan yang lebih baik. Panjang pemotongan batang bawah yang tepat adalah 10 cm dari ujung batang bawah. Secara keseluruhan perbanyakan vegetatif dengan okulasi menggunakan entres tengah dan pemotongan batang bawah 10 cm dari ujung menghasilkan pertumbuhan yang lebih baik. Unrestrict PDF - Trial Edition Website

The Helmholtz Digitization Ontology Representing Digital Assets in the Helmholtz Digital Ecosystem

The Helmholtz Association is actively digitizing research outcomes to drive progress and innovation. The vast volumes of digital data are diverse in terms of their formats and the semantic descriptions used in their interchange, and storage. Therefore, a semantic frame of reference is required to facilitate interoperability throughout the Helmholtz digital ecosystem. This paper presents the Helmholtz Digitization Ontology HDO , which is intended to serve that purpose. HDO is a mid level ontology that contains concepts representing digital assets relevant to the Helmholtz digital ecosystem, data creation, management, and exchange. It is developed within the framework of the Helmholtz Metadata Collaboration HMC with contributors from various scientific backgrounds. HDO serves as a harmonized semantic framework and machine actionable reference across all Helmholtz research field

Metadata schema to support FAIR data in scanning electron microscopy

The development and the adoption of metadata schemas and standards are a key aspect in data management. In this paper, we introduce our approach to a metadata model in the field of Materials Science. We present the specific use case of a metadata schema for Scanning Electron Microscopy, a characterization technique which is routinely used in Materials Science. This metadata schema is aiming to be a de-facto standard which will be openly available for reuse and further extension to other electron microscopy techniques

Consortium Proposal NFDI-MatWerk

This is the official proposal the NFDI-consortium NFDI-MatWerk submitted to the DFG within the request for funding the project. Visit www.dfg.de/nfdi for more infos on the German National Research Data Infrastructure (Nationale Forschungsdateninfrastruktur - NFDI) initiative. Visit www.nfdi-matwerk.de for last infos about the project NFDI-MatWerk