MCNP6 simulation of light and medium nuclei fragmentation at intermediate energies

Fragmentation reactions induced on light and medium nuclei by protons and light nuclei of energies around 1 GeV/nucleon and below are studied with the Los Alamos transport code MCNP6 and with its CEM03.03 and LAQGSM03.03 event generators. CEM and LAQGSM assume that intermediate-energy fragmentation reactions on light nuclei occur generally in two stages. The first stage is the intranuclear cascade (INC), followed by the second, Fermi breakup disintegration of light excited residual nuclei produced after the INC. CEM and LAQGSM account also for coalescence of light fragments (complex particles) up to 4He from energetic nucleons emitted during INC. We investigate the validity and performance of MCNP6, CEM, and LAQGSM in simulating fragmentation reactions at intermediate energies and discuss possible ways of further improving these codesComment: 6 pages, 6 figures, proc. 12th Int. Conf. on Nucleus-Nucleus Collisions (NN2015), June 21-26, 2015, Catania, Ital

Chatter, process damping, and chip segmentation in turning: A signal processing approach

An increasing number of aerospace components are manufactured from titanium and nickel alloys that are difficult to machine due to their thermal and mechanical properties. This limits the metal removal rates that can be achieved from the production process. However, under these machining conditions the phenomenon of process damping can be exploited to help avoid self-excited vibrations known as regenerative chatter. This means that greater widths of cut can be taken so as to increase the metal removal rate, and hence offset the cutting speed restrictions that are imposed by the thermo-mechanical properties of the material. However, there is little or no consensus as to the underlying mechanisms that cause process damping. The present study investigates two process damping mechanisms that have previously been proposed in the machining literature: the tool flank/workpiece interference effect, and the short regenerative effect. A signal processing procedure is employed to identify flank/workpiece interference from experimental data. Meanwhile, the short regenerative model is solved using a new frequency domain approach that yields additional insight into its stabilising effect. However, analysis and signal processing of the experimentally obtained data reveals that neither of these models can fully explain the increases in stability that are observed in practice. Meanwhile, chip segmentation effects were observed in a number of measurements, and it is suggested that segmentation could play an important role in the process-damped chatter stability of these materials

Top-level design and local-level paralysis: Local politics in times of political centralisation

China’s leadership under Xi has reinforced the party’s hierarchical commandstructures, demonstrated through its top-down campaigns, focusing on austerity,anti-corruption efforts and party discipline. It has reinvigorated sanctioningand incentive mechanisms for local cadres, with unknown effects on theirlong-term performance and loyalty to the CCP.Re-centralising the intergovernmental financial system strengthens the overallsteering capacity of the central government temporarily, but does not alleviatethe fiscal stress on local governments. The central government is pushing forgreater market orientation at the local level, resulting, thus far, in short-sightedsolutions that will end up reducing transparency concerning local debt.Local leaders are abstaining from bold policy moves out of fear of demotion,exclusion from the party, or legal repercussions. Consequently, subnationalgovernments have ceased to act as independent actors of policy initiativeand innovation. Policy piloting and experimentation will remain an importantcomponent of the policy process, but will be employed only very selectivelyand under the auspices of the central government.These reconfigurations of central-local relations give the central leadershipmore tools to enforce local compliance, and they appear to be effective in theshort term. But they will suffocate subnational policy initiative, ultimatelyundermining the adaptive capacity of the Chinese state