A fast and light stream cipher for smartphones

We present a stream cipher based on a chaotic dynamical system. Using a chaotic trajectory sampled under certain rules in order to avoid any attempt to reconstruct the original one, we create a binary pseudo-random keystream that can only be exactly reproduced by someone that has fully knowledge of the communication system parameters formed by a transmitter and a receiver and sharing the same initial conditions. The plaintext is XORed with the keystream creating the ciphertext, the encrypted message. This keystream passes the NISTs randomness test and has been implemented in a videoconference App for smartphones, in order to show the fast and light nature of the proposed encryption system

A multi-method proposal to study the public space in the scale of neighborhood from a transactional approach

La perspectiva transaccional resulta muy atractiva para analizar y actuar sobre el espacio público en la escala de barrio. Sin embargo, las diferencias metodológicas y de lenguaje entre las distintas disciplinas implicadas lo hacen bastante complejo. En este artículo se presenta una estrategia cualitativa de análisis multimétodo, como una propuesta que integra los diferentes lenguajes gráficos y textuales que dominan en los análisis unidisciplinares del espacio público, a través de un trabajo de espacialización gráfica de resultados. Se triangularon diversas técnicas y se sometieron a un mismo proceso analítico (Grounded Theory), lo que apoyado por los programas de procesamiento Atlas/ti y Arcgis hicieron posible ligar aspectos gráficos (mapas e imágenes) con observaciones de los investigadores y narraciones biográficas de los participantes, asociando de esta manera, espacios físicos concretos con la evolución y construcción de significados y usos espaciales.The transactional perspective is very attractive in order to analyze and intervene in public space on neighborhood scale. However, language and methodological differences between the various disciplines involved make it quite complex. In this article we present a multi-method qualitative strategy of analysis, integrating various results graphically, in an attempt to bring together the graphic and textual languages that dominate single-discipline approaches of public space. Diverse techniques were triangulated and underwent the same analytical process (Grounded Theory), supported by Atlas / ti and Arcgis software. Using this techniques it was possible to link graphic aspects (maps and images) with comments from researchers and biographical accounts of the participants. So, specific physical spaces were associated with the development and construction of spatial meanings and uses

Complexity control in a synchronized complex system

We numerically analyze the problem of how to drive a synchronized state in a complex system to other state with diferent complexity, keeping synchronization. The complex system used is obtained by synchronizing two identical chaotic Takens-Bogdanov sub-systems specially coupled to recover in the global system the symmetries of each oscillator. The global state is adjusted to have an initial synchronized hyperchaotic state (with two positive Lyapunov exponents). This work is an attempt, using small amplitude external signals, to drive the global system to other complex state keeping the synchronized state. The method used to overcome the problems that we had to select a useful frequency value for the driving signal will be discussed, together with a possible experiment in a thermo-convective flow for validating the results obtained

Dynamics of two coupled chaotic systems driven by external signals

Setting-up a controlled or synchronized state in a space-time chaotic structure targeting an unstable periodic orbit is a key feature of many problems in high dimensional physical, electronics, biological and ecological systems (among others). Formerly, we have shown numerically and experimentally that phase synchronization [M.G. Rosenblum, A.S. Pikovsky, J. Kurths, Phys. Rev. Lett. 78, 4193 (1997)] can be achieved in time dependent hydrodynamic flows [D. Maza, A. Vallone, H.L. Mancini, S. Boccaletti, Phys. Rev. Lett. 85, 5567 (2000)]. In that case the flow was generated in a small container with inhomogeneous heating in order to have a single roll structure produced by a B´enard-Marangoni instability [E.L. Koshmieder, B´enard Cells and Taylor Vortices (Cambridge University Press, 1993)]. Phase synchronization was achieved by a small amplitude signal injected at a subharmonic frequency obtained from the measured Fourier temperature spectrum. In this work, we analyze numerically the effects of driving two previously synchronized chaotic oscillators by an external signal. The numerical system represents a convective experiment in a small container with square symmetry, where boundary layer instabilities are coupled by a common flow. This work is an attempt to control this situation and overcome some difficulties to select useful frequency values for the driving force, analyzing the influence of different harmonic injection signals on the synchronization in a system composed by two identical chaotic Takens-Bogdanov equations (TBA and TBB) bidirectionally coupled

Una propuesta multimétodo para un abordaje transaccional del espacio público en la escala de barrio

La perspectiva transaccional resulta muy atractiva para analizar y actuar sobre el espacio público en la escala de barrio. Sin embargo, las diferencias metodológicas y de lenguaje entre las distintas disciplinas implicadas lo hacen bastante complejo. En este artículo se presenta una estrategia cualitativa de análisis multimétodo, como una propuesta que integra los diferentes lenguajes gráficos y textuales que dominan en los análisis unidisciplinares del espacio público, a través de un trabajo de espacialización gráfica de resultados. Se triangularon diversas técnicas y se sometieron a un mismo proceso analítico (Grounded Theory), lo que apoyado por los programas de procesamiento Atlas/ti y Arcgis hicieron posible ligar aspectos gráficos (mapas e imágenes) con observaciones de los investigadores y narraciones biográficas de los participantes, asociando de esta manera, espacios físicos concretos con la evolución y construcción de significados y usos espaciales.The transactional perspective is very attractive in order to analyze and intervene in public space on neighborhood scale. However, language and methodological differences between the various disciplines involved make it quite complex. In this article we present a multi-method qualitative strategy of analysis, integrating various results graphically, in an attempt to bring together the graphic and textual languages that dominate single-discipline approaches of public space. Diverse techniques were triangulated and underwent the same analytical process (Grounded Theory), supported by Atlas / ti and Arcgis software. Using this techniques it was possible to link graphic aspects (maps and images) with comments from researchers and biographical accounts of the participants. So, specific physical spaces were associated with the development and construction of spatial meanings and uses

El espacio público en conflicto : coordenadas conceptuales y tensiones ideológicas

En este artículo aportamos herramientas conceptuales y argumentativas para pensar y problematizar la noción de "espacio público". Comenzamos esbozando los principales marcos discursivos desde los que se define "el espacio público" como objeto de reflexión en los estudios urbanos. Asumiendo la crítica neo-marxista al ideal normativo del espacio público como estándar ideológico mistificador de desigualdades sociales estructurales, subrayamos la inadecuación teórica y política resultante de ignorar la naturaleza contestada del espacio público como ámbito de territorialización de procesos y luchas sociales más amplios. Desarrollamos esta concepción crítica del espacio público como un lugar en el que se articula materialmente una disputa de orden ideológico en torno a la definición de los contornos de la publicidad legítima y la naturalización clasista del derecho a censurar y a excluir. Finalmente, señalamos algunas de las modalidades de conflicto urbano más prominentes que apuntalan esta visión desestabilizadora del espacio público normativo.In this article we provide conceptual and argumentative tools to think and to problematize the notion of "public space". We start outlining the main discursive frames that are usually used to define "the public space" as a research object in urban studies. Drawing on the neo-Marxist critique to the normative ideal of public space as an ideological standard that mystifies structural social inequalities, we underline the theoretical and political inadequacy that derives from ignoring the contested nature of public space as an arena for the territorialisation of broader social struggles. We develop this critical view of public space as a site in which an ideological dispute takes place, revolving around the definition of the boundaries of the legitimate publics and the classist naturalization of the right to exclude. Finally, we outline some of the most common modalities of urban conflict that underpin this destabilizing view of the normative public space

Модифицирование силумина электровзрывным методом

Осуществлено модифицирование поверхности силумина марки АК12 плазмой,формирующейся при электрическом взрыве фольги алюминия с помещенной в область взрыва навеской порошка оксида иттрия (метод электровзрывного легирования). Выполнен термодинамический анализ системы Al-Si-Y-O, выявлены фазы, формирующиеся в данной системе в равновесных условиях. Осуществлены трибологические испытания модифицированного материала и выявленырежимы обработки, позволяющие многократно повысить износостойкость силумина. The modification of the surface of the silumin of the AK12 grade by the plasma formed during the electrical explosion of the aluminum foil with the yttrium oxide powder placed in the explosion region (the method of electric explosive doping) was carried out. The thermodynamic analysis of the Al-Si- Y-O system was carried out, the phases formed in this system under equilibrium conditions were revealed. Tribological tests of the modified material have been carried out and processing regimes have been identified, which allow many times to increase the wear resistance of silumin

Analysis of the Performance of MMC Under Fault Conditions in HVDC-Based Offshore Wind Farms

This paper analyzes the behavior of a modular multilevel converter-high-voltage direct-current (MMC-HVDC)-connected offshore wind power plant (WPP) during dc faults. For that purpose, detailed models of the dc cable, MMC stations, and transformers have been used in order to obtain reliable results. The influence of the WPP control method in the short-circuit behavior of the HVDC link has also been studied. Results show that the dynamics of the WPP contribution to pole-to-ground faults are slightly slower than those of the wind turbines current control loops. Therefore, the wind turbine front-end converters can be used to reduce the peak and average value of the fault current in such a system. Moreover, it has been found that ferroresonant oscillations can appear in the offshore ac grid when the WPP delivers constant power during faults.This work was supported in part by the Spanish Ministry of Economy funds under Grant DPI2014-53245-R, in part by Universitat Jaume I under Grants P1·1B2013-51 and E-2014-24, and in part by CONICYT/FONDAP/15110019 and Fondecyt/1151325. Paper no. TPWRD-01518-2014

Phonological prediction in speech processing

Auditory speech perception can be described as the task of mapping an auditory signal into meaning. We routinely perform this task in an automatic and effortless manner, which might conceal the complexity behind this process. It should be noted that the speech signal is highly variable, ambiguous and usually perceived in noise. One possible strategy the brain might use to handle this task is to generate predictions about the incoming auditory stream. Prediction occupies a prominent role in cognitive functions ranging from perception to motor control. In the specific case of speech perception, evidence shows that listeners are able to make predictions about incoming speech stimuli. Word processing, for example, is facilitated by the context of a sentence. Furthermore, electroencephalography studies have shown neural correlates that behave like error signals triggered when an unexpected word is encountered. But these examples of prediction in speech processing occur between words, and rely on semantic and or syntactic knowledge. Given the salient role of prediction in other cognitive domains, we hypothesize that prediction might serve a role in speech processing, even at the phonological level (within words) and independently from higher level information such as syntax or semantics. In other words, the brain might use the first phonemes of a word to anticipate which should be the following ones. To test this hypothesis, we performed three electroencephalography experiments with an oddball design. This approach allowed us to present individual words in a context that does not contain neither semantic nor syntactic information. Additionally, this type of experimental design is optimal for the elicitation of event related potentials that are well established marker of prediction violation, such as the Mismatch Negativity (MMN) and P3b responses. In these experiments, participants heard repetitions of standard words, among which, deviant words were presented infrequently. Importantly, deviant words were composed by the same syllables as standard words, although in different combinations. For example if in an experiment XXX and YYY were two standard words, XXY could be a deviant word. We expected that if as we proposed, the first phonemes of a word are used to predict which should be the following ones, encountering a deviant of this kind would elicit a prediction error signal. In Chapter 3, we establish that as we expected, the presentation of deviant words, composed of an unexpected sequence of phonemes, generates a chain of well established prediction error signals, which we take as evidence of the prediction of the forthcoming phonemes of a word. Furthermore, we show that the amplitude of these error signals can be modulated by the amount of congruent syllables presented before the point of deviance, which suggests that prediction strength can increase within a word as previous predictions prove to be successful. In Chapter 4, we study the modulating role of attentional set on the chain of prediction error signals. In particular we show that while high level prediction (indexed by the P3b response) is strategically used depending on the task at hand, early prediction error signals such as the MMN response are generated automatically, even when participants are simply instructed to listen to all the words. These results imply that phonological predictions are automatically deployed while listening to words, regardless of the task at hand. In Chapter 5, we extend our results to a more complex stimulus set that resemble natural speech more closely. Furthermore we show that the amplitude of the MMN and P3b prediction error signals is correlated with participant's reaction time in an on-line deviant detection task. This provides a strong argument in favor of a functional role of phonological predictions in speech processing. Taken together, this work shows that phonological predictions can be generated even in the absence higher level information such as syntax and semantics. This might help the human brain to complete the challenging task of mapping such a variable and noisy signal as speech, into meaning, in real time