OTOC, complexity and entropy in bi-partite systems

There is a remarkable interest in the study of Out-of-time ordered correlators (OTOCs) that goes from many body theory and high energy physics to quantum chaos. In this latter case there is a special focus on the comparison with the traditional measures of quantum complexity such as the spectral statistics, for example. The exponential growth has been verified for many paradigmatic maps and systems. But less is known for multi-partite cases. On the other hand the recently introduced Wigner separability entropy (WSE) and its classical counterpart (CSE) provide with a complexity measure that treats equally quantum and classical distributions in phase space. We have compared the behavior of these measures in a system consisting of two coupled and perturbed cat maps with different dynamics: double hyperbolic (HH), double elliptic (EE) and mixed (HE). In all cases, we have found that the OTOCs and the WSE have essentially the same behavior, providing with a complete characterization in generic bi-partite systems and at the same time revealing them as very good measures of quantum complexity for phase space distributions. Moreover, we establish a relation between both quantities by means of a recently proven theorem linking the second Renyi entropy and OTOCs.Comment: 6 pages, 5 figure

Spatially distributed sea wave measurements

In recent years, there has been growing interest in remote and proximal observation of sea surface waves. This has been partially driven by new technologies allowing the characterization of wave fields in both their spatial and temporal aspects. Typical examples are radar systems and stereo-imaging that permit remote monitoring of oceanic waves (from satellites, platforms, or vessels) with remarkable accuracy and range of use. These new exciting possibilities usually come at the price of being relatively harder to master with respect to traditional “point-like” approaches providing measurements limited to a temporal perspective. This difficulty is not restricted to the technology itself (see, for example, the delicate camera-calibration process required in stereo-imaging) but also on how to properly process, analyze, and assimilate spatio-temporal data. Therefore, in this Special Issue, we decided to embrace a wide range of topics that have led a multitude of multi-disciplinary works in the recent past, including: Wave mechanics and sea surface dynamics; Analysis of the wave climate and its extremes; Data fusion and signal processing; Statistical and probabilistic methods; Assessment of wave models. We did our best to propose recent advancements, not only on the technological aspect of spatially distributed sea waves acquisition but also on the characterization of wave statistics from measured and assimilated data. For the former aspect, we included the work of Vieira et al. [1], proposing the first cheap and simple stereo-based technique to estimate the 3D sea surface elevation from inexpensive smartphones. For the latter, the paper of Serebryany et al. [2] investigates internal waves on a narrow steep shelf of the northeastern coast of the Black Sea using the spatial antenna of line temperature sensors. We also included a discussion on space-time wave extremes in the paper of Benetazzo et al. [3] and a comparison of assimilated coastal wave data by Yukiharu Hisaki [4]. Finally, the work of Ciurana and Aguilar [5] provides an overview of how an ensemble of meteorological buoys and citizen science data can help economic activities to achieve optimal performances (in a case study, to predict optimal surfing days in the Iberian Peninsula). We hope that these works will be interesting both for researchers already working on this topic and for those who want to embrace the new possibilities offered by modern sea wave acquisition techniques

Levantamento de modelos matemáticos aplicados à cana-de-açúcar.

Objetivos da construção de modelos matemáticos para cana-de-açúcar. Modelo, definição e classificaçào. Metodologia da modelagem matemática. Modelos matemáticos e software de simulação descritos para a cana-de açúcar.bitstream/CNPTIA/9209/1/DOCUMENTO1int.pdfAcesso em: 29 maio 2008

Kinematic design of a two contact points haptic interface for the thumb and index fingers of the hand.

This paper presents an integrated approach to the kinematic design of a portable haptic interface for the thumb and index fingers of the hand. The kinematics of the haptic interface was selected on the basis of constructive reasons, design constraints, and usability issues, and in order to guarantee the best level of performance with the lowest encumbrance and weight over the workspace of the hand. The kinematic dimensioning was the result of a multi-objective optimization of several performance parameters, such as minimum required torque at actuators and maximum reachable workspace, with the simultaneous fulfillment of design constraints, such as satisfactory mechanical stiffness at the end effector, global kinematic isotropy over the workspace, and limited bulk of the device. A geometric interpretation of singularities based on screw theory was formulated to point out both hand postures and movements associated with weaker performance. The results of the paper were used to build the prototype of a new portable haptic interface with two contact points, whose main design features are also specifically presented

Modelos de transferência de metal pesado na cana-de-açúcar adubada com composto de lixo urbano.

A pesquisa aborda a reciclagem do composto de lixo urbano (CLU) como fertilizante alternativo na cana-de-açúcar e como solução social e ambiental ao acúmulo de resíduos sólidos nos centros urbanos. Utilizou-se da modelagem matemática para conhecer a dinâmica dos metais pesados, visando ao estabelecimento de critérios e procedimentos para o uso seguro do CLU, limitado pela quantidade desses elementos. Foram construídos modelos compartimentais a partir de dados de experimentos em condições controladas e parcialmente validados com dados de campo. Esse modelo descreveu a transferência de metais pesados no sistema solo-raiz-parte aérea para a cana-de-açúcar. Pôde-se concluir, pelas condições desta pesquisa, que o metal mais preocupante foi o níquel, pois demora, aproximadamente, três anos para ser atenuado no solo e chega em maior quantidade na parte aérea. Quanto aos fatores argila, óxidos e pH do solo, notou-se que, nos solos de maior poder tampão, a passagem da maioria dos metais foi mais lenta. Esse modelo pode tornar-se importante aliado na definição de leis de utilização do CLU, visando à não-contaminação ambiental, redução no acúmulo de lixo e de custos de produção

On the Efficiency of Packet Telephony

This paper presents a study on the efficiency of packet switching in providing toll quality telephone services. Packet switching is appealing for the implementation of a commercial telephone network because it features lower cost and higher manageability than circuit switching, and enables integration of real-time and non real-time services. This work compares the real-time efficiency of packet switching and circuit switching, i.e., the volume of voice traffic being guaranteed deterministic quality related to the amount of network resources used. For this purpose, we developed a call level simulator which allows a general topology network to be studied. The simulator performs call admission control according to the availability of the resources required to provide a deterministic delay bound for each call. Statistical data on accepted and rejected calls are the simulation output. Results show that packet size - possibly constrained by the protocol in use - is a key factor in determining the real-time efficiency. The packet size which maximizes real-time efficiency is devised analytically

One-Shot HDR Imaging via Stereo PFA Cameras

High Dynamic Range (HDR) imaging techniques aim to increase the range of luminance values captured from a scene. The literature counts many approaches to get HDR images out of low-range camera sensors, however most of them rely on multiple acquisitions producing ghosting effects when moving objects are present. In this paper we propose a novel HDR reconstruction method exploiting stereo Polarimetric Filter Array (PFA) cameras to simultaneously capture the scene with different polarized filters, producing intensity attenuations that can be related to the light polarization state. An additional linear polarizer is mounted in front of one of the two cameras, raising the degree of polarization of rays captured by the sensor. This leads to a larger attenuation range between channels regardless the scene lighting condition. By merging the data acquired by the two cameras, we can compute the actual light attenuation observed by a pixel at each channel and derive an equivalent exposure time, producing a HDR picture from a single polarimetric shot. The proposed technique results comparable to classic HDR approaches using multiple exposures, with the advantage of being a one-shot method

Cylinders extraction in non-oriented point clouds as a clustering problem

Finding geometric primitives in 3D point clouds is a fundamental task in many engineering applications such as robotics, autonomous-vehicles and automated industrial inspection. Among all solid shapes, cylinders are frequently found in a variety of scenes, comprising natural or man-made objects. Despite their ubiquitous presence, automated extraction and fitting can become challenging if performed ”in-the-wild”, when the number of primitives is unknown or the point cloud is noisy and not oriented. In this paper we pose the problem of extracting multiple cylinders in a scene by means of a Game-Theoretic inlier selection process exploiting the geometrical relations between pairs of axis candidates. First, we formulate the similarity between two possible cylinders considering the rigid motion aligning the two axes to the same line. This motion is represented with a unitary dual-quaternion so that the distance between two cylinders is induced by the length of the shortest geodesic path in SE(3). Then, a Game-Theoretical process exploits such similarity function to extract sets of primitives maximizing their inner mutual consensus. The outcome of the evolutionary process consists in a probability distribution over the sets of candidates (ie axes), which in turn is used to directly estimate the final cylinder parameters. An extensive experimental section shows that the proposed algorithm offers a high resilience to noise, since the process inherently discards inconsistent data. Compared to other methods, it does not need point normals and does not require a fine tuning of multiple parameters

Efeito do período de incubação e de doses de composto de lixo urbano na disponibilidade de metais pesados em diferentes solos.

Resumo – O uso do composto de lixo nas lavouras constitui alternativa econômica e ambiental viável, por ser fonte considerável de nutrientes e matéria orgânica. Este estudo, realizado em casa de vegetação, teve como objetivo avaliar a disponibilidade temporal dos metais pesados Cd, Co, Cr, Ni e Pb, por meio do extrator Mehlich-l, em cinco tipos de solos, incubados com 0, 25, 50 e 100 Mg ha-1 de composto de lixo, em períodos de 0, 16, 32, 64 e 150 dias. A maioria dos metais pesados teve sua disponibilidade reduzida nos primeiros períodos de incubação, sendo esse efeito dependente de textura, pH e teor de matéria orgânica do solo. O uso continuado de composto de lixo, principalmente nas doses mais elevadas, pode resultar em riscos de contaminação do ambiente pelo efeito cumulativo, em especial nos solos Latossolo Vermelho-Amarelo distrófico, Chernossolo Háplico órtico e Nitossolo Vermelho Vermelho eutroférrico, cujo período para redução da disponibilidade dos metais pesados varia de 6 a 12 meses

Disponibilidade de micronutrientes em cinco solos em função do tempo de incubação de um composto de lixo.

O uso agrícola do composto de lixo (CL) nas lavouras constitui a alternativa econômica e ambiental viável, por ser fonte de nutrientes e matéria orgânica. Este estudo foi conduzido em casa de vegetação e teve o objetivo de avaliar a disponibilidade temporal de micronutrientes (Cu, Fe, Mn e Zn) por Mehlich-1, em cinco solos (Latossolo Vermelho-Amarelo distrófico: LVd; Argissolo Vermelho-Amarelo distrófico: PVd; Chernossolo Haplico Órtico: MXo; Planossolo Hidromórfico distrófico: SGd, e Nitossolo Vermelho Eutroférrico: Nvef) incubados com diferentes doses de CL (0; 25; 50 e 100 Mg ha-1), em períodos de incubação (0; 16; 32; 64 e 150 dias). A maioria dos metais pesados teve sua disponibilidade reduzida nos primeiros períodos de incubação, sendo esse efeito dependente de textura, pH e teor de matéria orgânica do solo. O uso continuado de CL, principalmente nas doses mais elevadas, pode resultar em riscos de contaminação do ambiente pelo efeito cumulativo, em especial para o Mn e Zn nos solos Chernossolo e Nitossolo, cujo tempo de decaimento de sua disponibilidade é acima de seis meses