Computer numerical control vertical machining centre feed drive modelling using the transmission line technique

This study presents a novel application of the Transmission Line Matrix Method (TLM) for the modelling of the dynamic behaviour of non-linear hybrid systems for CNC machine tool drives. The application of the TLM technique implies the dividing of the ball-screw shaft into a number of identical elements in order to achieve the synchronisation of events in the simulation, and to provide an acceptable resolution according to the maximum frequency of interest. This entails the use of a high performance computing system with due consideration to the small time steps being applied in the simulation. Generally, the analysis of torsion and axial dynamic effects on a shaft implies the development of independent simulated models. This study presents a new procedure for the modelling of a ball-screw shaft by the synchronisation of the axial and torsion dynamics into the same model. The model parameters were obtained with equipments such as laser interferometer, ball bar, electronic levels, signal acquisition systems etc. The MTLM models for single and two-axis configurations have been simulated and matches well with the measured responses of machines. The new modelling approach designated the Modified Transmission Line Method (MTLM) extends the TLM approach retaining all its inherent qualities but gives improved convergence and processing speeds. Further work since, not the subject of this paper, have identified its potential for real time application

On Eulers Rotation Theorem

Summary: It is well known that a rigid motion of the Euclidean plane can be written as the composition of at most three reflections. It is perhaps not so widely known that a rigid motion of n-dimensional Euclidean space can be written as the composition of at most n + 1 reflections. The purpose of the present article is, firstly, to present a natural proof of this result in dimension 3 by explicitly constructing a suitable sequence of reflections, and, secondly, to show how a careful analysis of this construction provides a quick and pleasant geometric path to Eulers rotation theorem, and to the complete classification of rigid motions of space, whether orientation preserving or not. We believe that our presentation will highlight the elementary nature of the results and hope that readers, perhaps especially those more familiar with the usual linear algebra approach, will appreciate the simplicity and geometric flavor of the arguments

The Sphaleron Rate in SU(N) Gauge Theory

The sphaleron rate is defined as the diffusion constant for topological number NCS = int g^2 F Fdual/32 pi^2. It establishes the rate of equilibration of axial light quark number in QCD and is of interest both in electroweak baryogenesis and possibly in heavy ion collisions. We calculate the weak-coupling behavior of the SU(3) sphaleron rate, as well as making the most sensible extrapolation towards intermediate coupling which we can. We also study the behavior of the sphaleron rate at weak coupling at large Nc.Comment: 18 pages with 3 figure

25 Anos: gerando e transferindo tecnologia.

Histórico da unidade; Missão; Negócio; Avanço em pesquisa e desenvolvimento; Principais publicações; Prêmios e honrarias recebidas; Registros importantes; Aunidade em números.bitstream/item/33315/1/CNPA-DOCUMENTOS-70-25-ANOS-GERANDO-E-TRANSFERINDO-TECNOLOGIA-02923.pd

Interpreting the Carbon Isotope Record of Mass Extinctions

Mass extinctions are global-scale environmental crises marked by the loss of numerous species from all habitats. They often coincide with rapid changes in the stable carbon isotope ratios (13C/12C) recorded in sedimentary carbonate and organic matter, ratios which can indicate substantial inputs to the surface carbon reservoirs and/or changes in the cycling of carbon. Models to explain these changes have provided much fuel for debate on the causes and consequences of mass extinctions. For example, the escape of methane from gas hydrate deposits or the emission of huge volumes of gaseous carbon from large-scale volcanic systems, known as large igneous provinces, may have been responsible for decreases of 13C/12C in sedimentary deposits. In this article, we discuss the challenges in distinguishing between these, and other, alternatives

Sistema de controle das pragas do algodoeiro para a região Centro-Sul do Brasil.

Broca do algodoeiro; Tripes do algodoeiro; Pulgao do algodoeiro; Curuquere do algodoeiro; Acaro; Rajado; Acaro branco; Lagarta das macas; Lagarta rosada; Lagarta falsa medideira; Percevejo.bitstream/item/33285/1/CIRCULAR-TECNICA-2.pd

Words and Deeds: From Incompatibilities to Outcomes in Anti-Government Disputes

Dissidents can choose among different tactics to redress political grievances, yet violent and nonviolent mobilization tend to be studied in isolation. We examine why some countries see the emergence of organized dissident activity over governmental claims, and why in some cases these organizational claims result in civil wars or nonviolent campaigns, while others see no large-scale collective action. We develop a two-stage theoretical framework examining the organized articulation of political grievance and then large-scale violent and nonviolent collective action. We test implications of this framework using new data on governmental incompatibilities in a random sample of 101 states from 1960- 2012. We show that factors such as demography, economic development and civil society have differential effects on these different stages and outcomes of mobilization. We demonstrate that the common finding that anocracies are more prone to civil war primarily stems from such regimes being more prone to see maximalist political demands that could lead to violent mobilization, depending on other factors conducive to creating focused military capacity We find that non-democracy generally promotes nonviolent campaigns as anocracies and autocracies are both more likely to experience claims and more prone to nonviolent campaigns, conditional on claims

Plasma photoemission from string theory

Leading 't Hooft coupling corrections to the photoemission rate of the planar limit of a strongly-coupled {\cal {N}}=4 SYM plasma are investigated using the gauge/string duality. We consider the full order \alpha'^3 type IIB string theory corrections to the supergravity action, including higher order terms with the Ramond-Ramond five-form field strength. We extend our previous results presented in arXiv:1110.0526. Photoemission rates depend on the 't Hooft coupling, and their curves suggest an interpolating behaviour from strong towards weak coupling regimes. Their slopes at zero light-like momentum give the electrical conductivity as a function of the 't Hooft coupling, in full agreement with our previous results of arXiv:1108.6306. Furthermore, we also study the effect of corrections beyond the large N limit.Comment: 36 pages, 5 figures, paragraph added in the conclusions, references added, typos correcte