Electron transport in Coulomb- and tunnel-coupled one-dimensional systems

We develop a linear theory of electron transport for a system of two identical quantum wires in a wide range of the wire length L, unifying both the ballistic and diffusive transport regimes. The microscopic model, involving the interaction of electrons with each other and with bulk acoustical phonons allows a reduction of the quantum kinetic equation to a set of coupled equations for the local chemical potentials for forward- and backward-moving electrons in the wires. As an application of the general solution of these equations, we consider different kinds of electrical contacts to the double-wire system and calculate the direct resistance, the transresistance, in the presence of tunneling and Coulomb drag, and the tunneling resistance. If L is smaller than the backscattering length l_P, both the tunneling and the drag lead to a negative transresistance, while in the diffusive regime (L >>l_P) the tunneling opposes the drag and leads to a positive transresistance. If L is smaller than the phase-breaking length, the tunneling leads to interference oscillations of the resistances that are damped exponentially with L.Comment: Text 14 pages in Latex/Revtex format, 4 Postscript figure

A multi-nodal ring finite element for analysis of pipe deflection

The main objective of this work is to present a numerical formulation to solve the problem of the deformation analysis ot thin-walled circular cylindrical pipes under concentred loads. The solutions is based on a displacement field entirely defined from a set of trigonometic functiobns where the amplitudes are assigned as a nodal paramenters in a multi-nodal finite element. With this formulation it is possible to provide an easy alternative tool when compared with a complex finite shell or solid element modelling for the same type of applications. The present work permits to examine the defection of pipe rings subjected to lateral (transverse) static loading conditions. Several case studies presented have been compared and discussed with numericalç analysisresults obtained with a shell element from Ansys programme

The deformation of cylindrical shells subjected to radial loads

Cylindrical shells have a simple geometry and application in pressure vessels and piping engineering. The development of calculation algorithms in structural project is impelled by a constant challenge in the search of more accurate and fast design tools in engineering. The objective of this work is to contribute with a simple and reliable numerical tool for the stress analysis of cylindrical vessels subjected to generalized forces. A hybrid formulation in the definition of forces and displacements is proposed for cylindrical shells subjected to radial loads. Variational techniques coupled with functional analysis are used to obtain an optimized solution for the shell displacement and further stress field evaluation. As it is not possible to obtain exact solutions for the displacements or deformation field whenever the external loads are either concentrate or locally distributed, the solution here proposed deals with the combination of unknown analytic functions combined with Fourier expansions, where the former depend on the axial shell coordinate and the trigonometric terms are dependent upon the cylinder circumferential polar angle. These functions are expanded in Fourier series where displacement amplitudes are combined with trigonometric terms. The result is a system of ordinary differential equations where the solution is analytic after evaluation of eigenvalues and eigenvectors. The boundary conditions are then used to reach the final solution. As an example a large cylindrical shell subjected to pinching loads is considered. The results for the radial displacement and section ovalization are analyzed where the solution was obtained with three terms (nq=6) for the accuracy is acceptable in this case. The transverse displacement presents important dependence on the shell thickness vs radius, as the shell can be a thin-walled one (this case is included in the presented example) up to a moderately thick one, where the surface displacement ranges until the extreme edges, which is not the case analyzed. The proposed method leads to accurate results with a relatively low complexity input data. For conclusions of this work it is remarked that the definitions of the load system and boundary conditions are easily processed as the method has pre-defined possibilities for each load case or edge boundary conditions. An analytic solution is obtained and a low number of terms in the Fourier series show good accuracy. A comparison with finite element methods is presented

Etching of random solids: hardening dynamics and self-organized fractality

When a finite volume of an etching solution comes in contact with a disordered solid, a complex dynamics of the solid-solution interface develops. Since only the weak parts are corroded, the solid surface hardens progressively. If the etchant is consumed in the chemical reaction, the corrosion dynamics slows down and stops spontaneously leaving a fractal solid surface, which reveals the latent percolation criticality hidden in any random system. Here we introduce and study, both analytically and numerically, a simple model for this phenomenon. In this way we obtain a detailed description of the process in terms of percolation theory. In particular we explain the mechanism of hardening of the surface and connect it to Gradient Percolation.Comment: Latex, aipproc, 6 pages, 3 figures, Proceedings of 6th Granada Seminar on Computational Physic

Blowin' in the Wind:The Musical Response to the War on Terror

Popular music was the most immediate way in which the cultural response to 9/11 manifested itself. Initially music offered a way of mourning and coping with grief. As the United States moved toward the invasion of Iraq, pop music also began to reflect the divisions in society between patriot-artists who supported the invasion, most notably in country music, and protest-artists who articulated critical attitudes to war. These anti-war songs did not attain the stature of those that characterized the era of protest during the Vietnam War, nor did they offer a musical accompaniment to a social movement with any enduring political significance. One little observed dissonance that a longitudinal survey of the musical response to political violence reveals, however, is that over time the attitudes of protest songwriters and the patriots transvalued. Ironically, interventionist “rednecks” became disillusioned with the endless wars of intervention, whilst the “protest” writers lost their voices after President Obama came to power. Ironically, icons of popular music instead turned their ire on those who voted for an anti-establishment President Trump who vowed not to involve the U.S. in further military adventures

Coca, Clausewitz, and Colombia:The Inadequacy of Micro-level Studies in Explaining FARC Violence Against Civilians During the Colombian Civil War

Studies of micro-level violence make various claims to universality: namely, that there are patterns of violence in civil wars that are observable across time and space. The analysis of rebel violence against civilians constitutes one of the enduring themes of these studies. By evaluating the actions of the Revolutionary Armed Forces of Colombia (FARC) during the latter half of the Colombian civil war, this paper demonstrates that the claims of micro-level studies are unable to account for FARC’s violence against civilians. In response, this study provides an alternative framework for understanding FARC’s violence. Informed by the theories of Carl von Clausewitz it is possible to comprehend the logic of FARC’s violence against civilians within a strategic framework that aimed to advance the movement’s political goals. However, it also illustrates that FARC was influenced heavily by its involvement in the drugs trade. The main findings are a) that whilst FARC’s acts of violence may have contained similarities to that of other drugs cartels FARC did not become a narco-guerrilla organization, b) the case of FARC demonstrates that ultimately there are no reproducible patterns in war, micro-level or otherwise.</p

Intelligent collaborative decision-making models, methods, and tools

[Excerpt] Problems in engineering are usually hard to be modeled and solved through mathematical approaches, due to the complex nature of these problems and the need for specifying efective, efcient, and proper models to consider and approach reallife or empirical and emulated problem scenarios. Many proposals are constantly being put forward, based on diferent kind of models, specially referring to mathematical models, and formalization approaches, in the context of this journal, ranging from purely linear programming models, algebra or diferential equations based models to artifcial intelligent (AI) oriented models or based on agents or neural networks. These include a great number of AI tools, such as fuzzy theory, grey theory, neural network model, Genetic Algorithms, and expert systems. [...

How environment dynamics affects production scheduling: requirements for development of CPPS models

Production scheduling can be affected by many disturbances in the manufacturing system, and consequently, the feasible schedules previously defined became obsolete. Emerging of new technologies associated with Industry 4.0, such as Cyber-Physical Production Systems, as a paradigm of implementation of control and support in decision making, should embed the capacity to simulate different environment scenarios based on the data collected by the manufacturing systems. This paper presents the evaluation of environment dynamics effect on production scheduling, considering three scheduling models and three environment scenarios, through a case study. Results show that environment dynamics affect production schedules, and a very strong or strong positive correlation between environment dynamics scenarios and total completion time with delay, over three scheduling paradigms. Based on these results, the requirement for mandatory inclusion of a module for different environment dynamics scenarios generation and the corresponded simulations, of a Cyber-Physical Production Systems architecture, is confirmed.This work has been supported by FCT -Fundacao para a Ciencia e Tecnologia within the R&D Units Project Scope: UIDB/00319/2020

Iconoclasm and Strategic Thought:Islamic State and Strategic Thought

This paper analyses the way in which Islamic State manages cultural heritage sites under its control. Drawing on three different case studies – Sufi, Shi’a and Sunni heritage sites, Palmyra and Mosul – it examines the manner in which the logic of Islamic State’s destruction can be considered a strategy. It is argued that for it to be considered as such evidence of three things need to be present: the degradation and delegitimisation of the existing societal fabric, the removal of all reference to the previous society and an attempt to reconstruct society in keeping with a new ideology. When these three elements are present and interlocking then iconoclasm as a strategy can be said to be manifest.<br/

The concept of collaborative engineering: a systematic literature review

Collaborative engineering is not a new subject but it assumes a new importance in the Industry 4.0 (I4.0). There are other concepts frequently mismatched with collaboration. Thus, the main objective of this paper is to put forward a collaborative engineering concept, along its sub concepts, supported by an extensive systematic literature review. A critical analysis and discussion about the fundamental importance of learning, and the central human role in collaboration, in the I4.0, is presented, based on the main insights brought through the literature review. This study also enables to realize about the importance of collaboration in the current digitalization era, along with the importance of recent approaches and technology for enabling or promoting collaboration. Main current practices of human centered and autonomous machine-machine approaches and applications of collaboration in engineering, namely in manufacturing and management, are presented, along with main difficulties and further open research opportunities on collaboration.This work was supported by the Fundação para a Ciência e a Tecnologia [UIDB/00319/2020, UIDB/50014/2020, and EXPL/EME-SIS/1224/2021]