2,927 research outputs found
Complex dynamics of elementary cellular automata emerging from chaotic rules
We show techniques of analyzing complex dynamics of cellular automata (CA)
with chaotic behaviour. CA are well known computational substrates for studying
emergent collective behaviour, complexity, randomness and interaction between
order and chaotic systems. A number of attempts have been made to classify CA
functions on their space-time dynamics and to predict behaviour of any given
function. Examples include mechanical computation, \lambda{} and Z-parameters,
mean field theory, differential equations and number conserving features. We
aim to classify CA based on their behaviour when they act in a historical mode,
i.e. as CA with memory. We demonstrate that cell-state transition rules
enriched with memory quickly transform a chaotic system converging to a complex
global behaviour from almost any initial condition. Thus just in few steps we
can select chaotic rules without exhaustive computational experiments or
recurring to additional parameters. We provide analysis of well-known chaotic
functions in one-dimensional CA, and decompose dynamics of the automata using
majority memory exploring glider dynamics and reactions
Cellular automaton supercolliders
Gliders in one-dimensional cellular automata are compact groups of
non-quiescent and non-ether patterns (ether represents a periodic background)
translating along automaton lattice. They are cellular-automaton analogous of
localizations or quasi-local collective excitations travelling in a spatially
extended non-linear medium. They can be considered as binary strings or symbols
travelling along a one-dimensional ring, interacting with each other and
changing their states, or symbolic values, as a result of interactions. We
analyse what types of interaction occur between gliders travelling on a
cellular automaton `cyclotron' and build a catalog of the most common
reactions. We demonstrate that collisions between gliders emulate the basic
types of interaction that occur between localizations in non-linear media:
fusion, elastic collision, and soliton-like collision. Computational outcomes
of a swarm of gliders circling on a one-dimensional torus are analysed via
implementation of cyclic tag systems
Housing bubbles and land planning corruption: evidence from Spain’s largest municipalities
Purpose: The purpose of this paper is to quantify to what extent the housing bubble in the early-to-mid 2000s in Spain exacerbated land planning corruption among Spain’s largest municipalities. Design/methodology/approach: The authors exploit plausibly exogenous variation in housing prices induced by changes in local mortgage market conditions; namely, the rapid expansion of savings banks (Cajas de Ahorros). Accounting for electoral competition in the 2003–2007 and 2007–2009 electoral cycles among Spanish municipalities larger than 25, 000 inhabitants, the authors estimate a positive relationship between housing prices and land planning corruption in municipalities with variation in savings bank establishments using instrumental variables techniques. Findings: A 1% increase in housing prices leads to a 3.9% points increase in the probability of land planning corruption. Moreover, absolute majority governments (not needing other parties’ support) are more susceptible to the incidence of corruption than non-majority ones. Two policy implications to address corruption emerge: enhance electoral competition and increase scrutiny over land planning decisions in sparsely populated. Originality/value: First empirical evidence of a formal link between the 2000s housing bubble in Spain and land planning corruption
Methanol to Gasoline (MTG): preparation, characterization and testing of HZSM-5 zeolite-based catalysts to be used in a fluidized bed reactor
The preparation of catalysts suitable for MTG processes in a fluidized bed reactor has been studied with emphasis on improving the textural, physico-chemical, morphological, structural and mechanical properties. A mixture of HZSM-5 zeolite (active material), boehmite or bentonite (binder) and alumina (inert filler) was used to prepare different catalysts. After preparation, characterization by physical adsorption of N2, XRF, XRD and SEM-EDX techniques was carried out. The screening of catalysts was performed in a fluidized bed reactor. The distribution of products was very similar in all cases, with the yield of light hydrocarbons always being higher than that of gasoline. Among the catalysts tested, the one containing boehmite as a binder (HZ_Boeh) was found as the most appropriate due to its high mechanical strength, high yield to aromatics and lower yield to durene
Methanol to gasoline (MTG): Parametric study and validation of the process in a two-zone fluidized bed reactor (TZFBR)
Methanol to Gasoline (MTG) process transforms methanol to hydrocarbons within the boiling point range of gasoline. The result is a wide spectrum of products (olefins, paraffins, aromatics and naphthenics, among others), with the total conversion of methanol to hydrocarbons and water. Catalyst deactivation by coke is a main problem in this process. This work aims to determine the feasibility of carrying out the production of gasoline from methanol in a two-zone fluidized bed reactor (TZFBR). The hypothesis is that the formation of carbonaceous deposits (coke) on the catalyst particles can be counteracted by its combustion in the regeneration zone that this novel reactor presents, thus achieving stable and continuous operation. In this way, both processes (reaction and regeneration) would be being carried out simultaneously in the same reactor (process intensification). The comparison of results between a conventional fluidized bed reactor and a TZFBR shows that the second one actually provides a better stability over time
Pure hydrogen from biogas: Intensified methane dry reforming in a two-zone fluidized bed reactor using permselective membranes
Methane dry reforming of biogas can be a sustainable source of hydrogen but the development of this technology is hindered by limitations such as endothermicity and catalyst deactivation by coke. A two zone fluidized bed reactor coupling permselective Pd/Ag membranes counteracts them and allows to intensify the process obtaining a stable pure hydrogen production. Here we report the effect of operation variables (i.e., temperature, total bed height, nature and partial pressure of regenerative agent, relative height of the regeneration and reaction zones, and use of an activation period) on the yield to hydrogen and stability of the process. Hydrogen over-yields, compared with the conventional fluidized bed reactor, in the range of +200% to +100% were obtained for the entire interval of temperatures 475–575 °C whilst maintaining stable operation by continuous catalyst regeneration. Around 70% of it was pure hydrogen coming from the permeate side of the membranes. The proposed reactor configuration greatly increases both methane conversion and selectivity to hydrogen (expressed as H 2 /CO ratio), not only in relation to our own conventional reactor findings but also regarding other published results
Massive Parallel Current Power Amplifier Concept for Power Hardware in the Loop Applications
The development of the smartgrid increases the complexity of the current electric grid. To verify and validate the operation of the systems involved in it, Power Hardware-In-theLoop (PHIL) technique allows to test the complete system in an exhaustive way. But the reduced bandwidth of the overall test system can cause inaccuracies and instabilities, which can be harmful for the Hardware Under Test (HUT) or the people who are performing the test. To increase PHIL performance and tackle these problems, this paper proposes a new concept of high bandwidth current amplifier. It is based on a topology of massive parallel interleaved buck-boost converter, which distribute in an equal manner the total current in all the branches. This current reduction allows to use transistors with better switching behaviour, which increase the bandwidth of the converter. Furthermore, a Discontinuous Conduction Mode (DCM) is used, obtaining the nominal output current in only one switching cycle. Description of the concept and the design parameters are provided. Finally, the behaviour of the proposed Power Amplifier (PA) at high frequency setpoint currents is shown in a Matlab/Simulink simulation. © 2022, European Association for the Development of Renewable Energy, Environment and Power Quality (EA4EPQ). All rights reserved
SĂndrome doloroso del trocánter mayor.Resultados a corto plazo con el tratamiento artroscĂłpico
Objetivo
: Evaluar los resultados clĂnicos de la cirugĂa artroscĂłpica de cadera en el tratamiento del
sĂndrome doloroso del trocánter mayor tras fracaso del tratamiento conservador.
Material y MĂ©todo
: Estudio
prospectivo de 15 pacientes tratados mediante cirugĂa artroscĂłpica de cadera por sĂndrome doloroso del trocánter
mayor. Para valoracion clĂnica se utilizĂł la escala modificada de Harris.
Resultados
: La edad media de los pacien
-
tes fue de 53,2 años. Se detectó rotura del glúteo medio en el 73,3% de los casos. El seguimiento medio de los
pacientes fue de 16,3 meses. La puntuaciĂłn media de la escala modificada de Harris pasĂł de 55,4 puntos preope
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ratoriamente a 83,8 puntos al final del seguimiento.
DiscusiĂłn
: La artroscopia de cadera ha permitido la mejorĂa
clĂnica de los pacientes con sĂndrome doloroso del trocánter mayor que no responde al tratamiento conservador.
Un mayor seguimiento de los pacientes es preciso para confirmar la estabilidad de los resultados obtenidosObjective:
Evaluate the outcomes of hip arthroscopy as a treatment for greater throcanter pain
syndrome after conservative treatment failed.
Material and methods:
Prospective study with 15 patients under
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going hip arthroscopy for greater trochanter pain syndrome. Modified Harris Hip Score scale was used for clini
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cal assessment.
Results:
The mean age of patients was 53.2 years. Gluteus medium tears was detected in 73.3%.
The average follow-up was 16.3 months. The mean modified Harris Hip score increased from 55.4 points preop
to 83.8 points postoperative.
Discusion:
Hip arthroscopy resulted in improvement in hip functional outcome in
patients with greater trochanter pain syndrome after conservative treatment failed. Further follow-up is essential
to confirm the stability of the clinical outcome
CMB anisotropy: deviations from Gaussianity due to non-linear gravity
Non-linear evolution of cosmological energy density fluctuations triggers
deviations from Gaussianity in the temperature distribution of the cosmic
microwave background. A method to estimate these deviations is proposed. N-body
simulations -- in a CDM cosmology -- are used to simulate the strongly
non-linear evolution of cosmological structures. It is proved that these
simulations can be combined with the potential approximation to calculate the
statistical moments of the CMB anisotropies produced by non-linear gravity.
Some of these moments are computed and the resulting values are different from
those corresponding to Gaussianity.Comment: 6 latex pages with mn.sty, 3 eps figures. Accepted in MNRA
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