Self-healing of cracks during ductile regime machining of silicon: Insights from molecular dynamics simulation

During nanoindentation and ductile-regime machining of silicon, a phenomenon known as “self-healing” takes place in that the microcracks, microfractures, and small spallings generated during the machining are filled by the plastically flowing ductile phase of silicon. However, this phenomenon has not been observed in simulation studies. In this work, using a long-range potential function, molecular dynamics simulation was used to provide an improved explanation of this mechanism. A unique phenomenon of brittle cracking was discovered, typically inclined at an angle of 45° to 55° to the cut surface, leading to the formation of periodic arrays of nanogrooves being filled by plastically flowing silicon during cutting. This observation is supported by the direct imaging. The simulated X-ray diffraction analysis proves that in contrast to experiments, Si-I to Si-II (beta tin) transformation during ductile-regime cutting is highly unlikely and solid-state amorphisation of silicon caused solely by the machining stress rather than the cutting temperature is the key to its brittle-ductile transition observed during the MD simulations

Spin and spatial dynamics in electron-impact scattering off S-wave He using R-matrix with Time-Dependence theory

R-matrix with time-dependence theory is applied to electron-impact ionisation processes for He in the S-wave model. Cross sections for electron-impact excitation, ionisation and ionisation with excitation for impact energies between 25 and 225 eV are in excellent agreement with benchmark cross sections. Ultra-fast dynamics induced by a scattering event is observed through time-dependent signatures associated with autoionisation from doubly excited states. Further insight into dynamics can be obtained through examination of the spin components of the time-dependent wavefunction.

The Democratic Dynamics of Government Consultations. Speaking Freely and Listening Properly

There is a growing use of consultation and e-consultation procedures by governments. This chapter seeks to examine the role of consultation as part of a new technology of government. Consultation on policy development can reinvigorate democratic engage- ment but often it can silence views through a sort of participatory disempowerment; it can loosen the democratic anchorage of the public service within the state. The chapter develops a governmentality perspective interrogating what participation, democratic engagement and free speech mean in this context, and how ideas of publicness are constructed, managed and controlled. The focus is on the nature of consultation, its relationship to ideas of free speech and speaking freely, and its potential to empower subaltern counterpublics which can formulate oppositional interpretations and urge alternative conclusions. The aim is to develop an idea of the democratic adequacy of the consultation process and draw out a sense of how democratic engagement here can be structured – for good or ill.