Search

The digital model of airborne frequency selective surface radomes (AFSSRs) is the basis of design, simulation analysis, manufacturing, and other related research on AFSSRs. This paper proposes a rapid modeling method for AFSSRs based on dynamic customizable primitives. Firstly, a layered digital model construction scheme for AFSSRs is presented based on the typical radome wall structure. Then, according to the characteristics of various surface configurations and the complex wireframe information of AFSSRs, the dynamic primitives are raised to express the boundary and contour information of all kinds of radomes. Focusing on the undevelopable characteristics of the aerodynamic shape surface of the AFSSR, the arrangement solution and mapping method for frequency-selective elements on undevelopable surfaces are proposed. Furthermore, the implementation logic of this method for the creation of each layer model and the assembly of the whole machine model is introduced. Finally, a rapid modeling system (RMS) is established based on this method, enabling the automated creation of digital models of AFSSRs. Utilizing this system resulted in modeling time savings ranging from 20% to 97.5% compared to traditional methods, which verifies the feasibility and effectiveness of this method. [ABSTRACT FROM AUTHOR]

The digital model of airborne frequency selective surface radomes (AFSSRs) is the basis of design, simulation analysis, manufacturing, and other related research on AFSSRs. This paper proposes a rapid modeling method for AFSSRs based on dynamic customizable primitives. Firstly, a layered digital model construction scheme for AFSSRs is presented based on the typical radome wall structure. Then, according to the characteristics of various surface configurations and the complex wireframe information of AFSSRs, the dynamic primitives are raised to express the boundary and contour information of all kinds of radomes. Focusing on the undevelopable characteristics of the aerodynamic shape surface of the AFSSR, the arrangement solution and mapping method for frequency-selective elements on undevelopable surfaces are proposed. Furthermore, the implementation logic of this method for the creation of each layer model and the assembly of the whole machine model is introduced. Finally, a rapid modeling system (RMS) is established based on this method, enabling the automated creation of digital models of AFSSRs. Utilizing this system resulted in modeling time savings ranging from 20% to 97.5% compared to traditional methods, which verifies the feasibility and effectiveness of this method.

At present, the knowledge of cultural relics in cultural creative design is fragmented and fragmented, and lacks the support of a unified system. In this paper, firstly, with the help of a topological model to characterize the creative process of image thinking, effective reasoning is carried out on the objects, things and relations of cultural and creative products according to the expansion analysis of primitives. Then, a conceptual network of art design for cultural and creative products is constructed based on semantic association, and an identification model of art design elements for cultural and creative products is built based on quantitative theory. Finally, through the experiment of art design for cultural and creative products, the perception of cultural and creative products was analyzed in multiple dimensions. The results show that the maximum factor influencing the value of art design of cultural and creative products is 0.951, among which the cultural characteristics have a strong correlation with the color characteristics of 0.642, and the functional characteristics have a strong correlation with the cultural characteristics of 0.837. The results of this paper provide new ideas and methods for the development and maturation of artistic design of cultural and creative products.

The emergence of the Musée du quai Branly project and its inauguration in Paris in 2006 have sparked off many controversies and stimulated numerous debates about the politics of representation, the colonial heritage in museum collections, the influence of art dealers, the role of indigenous communities, but also and above all the often antagonistic relationship between ethnographic and aesthetic approaches. It is not our intention here to reopen the controversy of the origins or to settle the alternative between the End of Art and the end of museum ethnography. On the contrary, we wish to place ourselves in a historical perspective, and to take advantage of this contribution to lay down some milestones in an intellectual journey that began more than a century ago and which is still often written in the mode of discontinuity.

The emergence of the Musée du quai Branly project and its inauguration in Paris in 2006 have sparked off many controversies and stimulated numerous debates about the politics of representation, the colonial heritage in museum collections, the influence of art dealers, the role of indigenous communities, but also and above all the often antagonistic relationship between ethnographic and aesthetic approaches. It is not our intention here to reopen the controversy of the origins or to settle the alternative between the End of Art and the end of museum ethnography. On the contrary, we wish to place ourselves in a historical perspective, and to take advantage of this contribution to lay down some milestones in an intellectual journey that began more than a century ago and which is still often written in the mode of discontinuity. [ABSTRACT FROM AUTHOR]

A hierarchical learning control framework (HLF) has been validated on two affordable control laboratories: an active temperature control system (ATCS) and an electrical rheostatic braking system (EBS). The proposed HLF is data-driven and model-free, while being applicable on general control tracking tasks which are omnipresent. At the lowermost level, L1, virtual state-feedback control is learned from input–output data, using a recently proposed virtual state-feedback reference tuning (VSFRT) principle. L1 ensures a linear reference model tracking (or matching) and thus, indirect closed-loop control system (CLCS) linearization. On top of L1, an experiment-driven model-free iterative learning control (EDMFILC) is then applied for learning reference input–controlled outputs pairs, coined as primitives. The primitives' signals at the L2 level encode the CLCS dynamics, which are not explicitly used in the learning phase. Data reusability is applied to derive monotonic and safely guaranteed learning convergence. The learning primitives in the L2 level are finally used in the uppermost and final L3 level, where a decomposition/recomposition operation enables prediction of the optimal reference input assuring optimal tracking of a previously unseen trajectory, without relearning by repetitions, as it was in level L2. Hence, the HLF enables control systems to generalize their tracking behavior to new scenarios by extrapolating their current knowledge base. The proposed HLF framework endows the CLCSs with learning, memorization and generalization features which are specific to intelligent organisms. This may be considered as an advancement towards intelligent, generalizable and adaptive control systems. [ABSTRACT FROM AUTHOR]

We show how the Connes--Moscovici bialgebroid construction naturally provides universal objects for Lie algebras acting on non-commutative algebras. As a supplement, we see how these objects interact with the study of flat bimodule connections. [ABSTRACT FROM AUTHOR]

The apparently pessimistic implications of Spenglerian analysis have often appealed to others who foresaw the end of Western civilization, but Spengler himself was less discouraged. Even if no great art, music or literature could be expected in these latter days, great engineering projects were possible, and to be admired. Nor was Western ("Faustian") Culture and Civilization the only game in town: other Cultures, like the "Magian," had been embedded and distorted by the dominant regimes, both Classical and Western, and could still be an inspiring presence. A similarly distorted Culture might still be growing in Russia. And even when all present Cultures were exhausted there would be hope of some new, unpredictable, emergence, for which I offer some imaginable examples drawn from contemporary fantasy, as well as the abiding presence of what Spengler usually thought "pre-cultural," or "primitive" societies. [ABSTRACT FROM AUTHOR]

'If I were to toss a coin 1000 times, then it would land heads exactly n times'. Is there a specific value of n that renders this counterfactual true? According to an increasingly influential view, there is. A precursor of the view goes back to the Molinists; more recently it has been inspired by Stalnaker, and versions of it have been advocated by Hawthorne, Bradley, Moss, Schulz, and Stefánsson. More generally, I attribute to these authors what I call Counterfactual Plenitude: For any antecedent A, there is a world wisuch that A ☐→ wiis true. Moreover, some of these authors are also committed to Primitive Counterfacts Realism: There exist primitive modal facts that serve as truth-makers for counterfactual claims. Call the conjunction of these italicized theses counterfactism. I clarify it and suggest some of its virtues, while ultimately rejecting it. Stefánsson's counterfactism is motivated by and targeted at my "counterfactual skepticism"—I argue that most counterfactuals are false—and counterfactism has various other sources of support. I briefly defend that skepticism, and I seek to undercut those sources of support. I then argue more directly against counterfactism, especially on grounds of its ontological profligacy, and its leading to another kind of skepticism about counterfactuals that I believe is more problematic than my kind. In the process, I discuss how Bradley's multidimensional semantics bears on counterfactism; I offer some new considerations against some central theses regarding conditionals (Conditional Excluded Middle, Stalnaker's Thesis, and Skyrms' Thesis); and I reflect more generally on the epistemology of modality and the choice of primitives in our theorizing. [ABSTRACT FROM AUTHOR]

The human musculoskeletal system is highly complex mechanically. Its neural control must deal successfully with this complexity to perform the diverse, efficient, robust and usually graceful behaviors of which humans are capable. Most of those behaviors might be performed by many different subsets of its myriad possible states, so how does the nervous system decide which subset to use? One solution that has received much attention over the past 50 years would be for the nervous system to be fundamentally limited in the patterns of muscle activation that it can access, a concept known as muscle synergies or movement primitives. Another solution, based on engineering control methodology, is for the nervous system to compute the single optimal pattern of muscle activation for each task according to a cost function. This review points out why neither appears to be the solution used by humans. There is a third solution that is based on trial-and-error learning, recall and interpolation of sensorimotor programs that are good-enough rather than limited or optimal. The solution set acquired by an individual during the protracted development of motor skills starting in infancy forms the basis of motor habits, which are inherently low-dimensional. Such habits give rise to muscle usage patterns that are consistent with synergies but do not reflect fundamental limitations of the nervous system and can be shaped by training or disability. This habit-based strategy provides a robust substrate for the control of new musculoskeletal structures during evolution as well as for efficient learning, athletic training and rehabilitation therapy. [ABSTRACT FROM AUTHOR]

Muscle synergy analysis is increasingly used in domains such as neurosciences, robotics, rehabilitation or sport sciences to analyze and better understand motor coordination. The analysis uses dimensionality reduction techniques to identify regularities in spatial, temporal or spatio-temporal patterns of multiple muscle activation. Recent studies have pointed out variability in outcomes associated with the different methodological options available and there was a need to clarify several aspects of the analysis methodology. While synergy analysis appears to be a robust technique, it remain a statistical tool and is, therefore, sensitive to the amount and quality of input data (EMGs). In particular, attention should be paid to EMG amplitude normalization, baseline noise removal or EMG filtering which may diminish or increase the signal-to-noise ratio of the EMG signal and could have major effects on synergy estimates. In order to robustly identify synergies, experiments should be performed so that the groups of muscles that would potentially form a synergy are activated with a sufficient level of activity, ensuring that the synergy subspace is fully explored. The concurrent use of various synergy formulations-spatial, temporal and spatio-temporal synergies- should be encouraged. The number of synergies represents either the dimension of the spatial structure or the number of independent temporal patterns, and we observed that these two aspects are often mixed in the analysis. To select a number, criteria based on noise estimates, reliability of analysis results, or functional outcomes of the synergies provide interesting substitutes to criteria solely based on variance thresholds. [ABSTRACT FROM AUTHOR]

Shape-driven approaches have been proposed as an effective strategy for the electrical impedance tomography (EIT) reconstruction problem in recent years. In order to augment the shape-driven approaches, we propose a new method that transforms the shape to be reconstructed as basic primitives directly modeled by using Fourier representations. To allow automatic topological changes between the basic primitives and surrounding objects simultaneously, Boolean operations are employed. The Boolean operations with direct representation of primitives can be utilized for dimensionality and ill-posedness reduction, enabling feasible shape and topology optimization with shape-driven approaches. As a proof of principle, we leverage the proposed method for two dimensional shape reconstruction in EIT with various conductivity distributions. We demonstrate that our method is able to improve EIT reconstructions by enabling accurate shape and topology optimization. [ABSTRACT FROM AUTHOR]

Radon transform based on complex shape detection is one of the most important challenges in the field of pattern recognition. Finding a robust transform for extracting and identifying complex shape is still an ongoing research issue. In this paper, aiming to simplify complex pattern recognition, we propose a new methodology of recognition flows. The proposed method is based on a decomposition of complex objects into elementary shapes and an evaluation of the pertinence of the generated primitives in recognizing the object. Accordingly, a series of the most pertinent primitives are selected. Then, the recognition step starts with a test on the most pertinent primitives. Our approach, called compound complex shape-invariant Radon transform, takes its importance in recognizing object class from a partial elementary scale and orientation-invariant Radon transforms, done on selected primitives. SVM classifier is then used for decision making based on obtained transforms. Validation of the proposed approach is done on the MPEG7 dataset, yielding a recognition rate of 98%. [ABSTRACT FROM AUTHOR]

To control unmanned aerial systems, we rarely have a perfect system model. Safe and aggressive planning is also challenging for nonlinear and under-actuated systems. Expert pilots, however, demonstrate maneuvers that are deemed at the edge of plane envelope. Inspired by biological systems, in this paper, we introduce a framework that leverages methods in the field of control theory and reinforcement learning to generate feasible, possibly aggressive, trajectories. For the control policies, Dynamic Movement Primitives (DMPs) imitate pilot-induced primitives, and DMPs are combined in parallel to generate trajectories to reach original or different goal points. The stability properties of DMPs and their overall systems are analyzed using contraction theory. For reinforcement learning, Policy Improvement with Path Integrals (PI2) was used for the maneuvers. The results in this paper show that PI2 updated policies are a feasible and parallel combination of different updated primitives transfer the learning in the contraction regions. Our proposed methodology can be used to imitate, reshape, and improve feasible, possibly aggressive, maneuvers. In addition, we can exploit trajectories generated by optimization methods, such as Model Predictive Control (MPC), and a library of maneuvers can be instantly generated. For application, 3-DOF (degrees of freedom) Helicopter and 2D-UAV (unmanned aerial vehicle) models are utilized to demonstrate the main results.

A general control system tracking learning framework is proposed, by which an optimal learned tracking behavior called ‘primitive’ is extrapolated to new unseen trajectories without requiring relearning. This is considered intelligent behavior and strongly related to the neuro-motor cognitive control of biological (human-like) systems that deliver suboptimal executions for tasks outside of their current knowledge base, by using previously memorized experience. However, biological systems do not solve explicit mathematical equations for solving learning and prediction tasks. This stimulates the proposed hierarchical cognitive-like learning framework, based on state-of-the-art model-free control: (1) at the low-level L1, an approximated iterative Value Iteration for linearizing the closed-loop system (CLS) behavior by a linear reference model output tracking is first employed; (2) an experiment-driven Iterative Learning Control (EDILC) applied to the CLS from the reference input to the controlled output learns simple tracking tasks called ‘primitives’ in the secondary L2 level, and (3) the tertiary level L3 extrapolates the primitives’ optimal tracking behavior to new tracking tasks without trial-based relearning. The learning framework relies only on input-output system data to build a virtual state space representation of the underlying controlled system that is assumed to be observable. It has been shown to be effective by experimental validation on a representative, coupled, nonlinear, multivariable real-world system. Able to cope with new unseen scenarios in an optimal fashion, the hierarchical learning framework is an advance toward cognitive control systems.

We present a formalisation of the theory of finite fields, from basic axioms to their classification, both existence and uniqueness, in HOL4 using the notion of subfields. The tools developed are applied to the characterisation of subfields of finite fields, and to the cyclotomic factorisation of polynomials of the form , with coefficients over a finite fields. [ABSTRACT FROM AUTHOR]

Many have written about trope ontology, but relatively few have considered its implications for some of the ontological conditions needed for us to have knowledge. I explore the resources of trope ontology to meet those conditions. With J. P. Moreland, I argue that, being simple, we can eliminate tropes' qualitative contents without ontological loss, resulting in bare individuators. Then I extend Moreland's argument, arguing that tropes undermine some of the needed ontological conditions for knowledge. Yet, we do know many things, and trope nominalists presuppose that too. Therefore, I consider three counter-arguments, starting with David Lewis's rebuttal based on appeal to brute facts. Second, I explore Jeffrey Brower's recent proposal as a possible solution. Last, I consider Robert Garcia's recent distinction between module and modifier tropes, to see if it can be of assistance. I conclude, however, that trope nominalism cannot preserve some of the needed ontology to have knowledge. [ABSTRACT FROM AUTHOR]

Copyright of Revista de Pesquisa: Cuidado é Fundamental is the property of Revista de Pesquisa: Cuidado e Fundamental Online and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

At the heart of the creation of modern cryptographic systems is the use of cryptographic primitives. This has as its main goal of providing high security created cryptographic primitives and cryptosystem. For the development of cryptographic primitives used various mathematical transformations. To evaluate the security of cryptographic primitives are used very different approaches. The paper proposes a universal approach to the assessment of security of any cryptographic primitives. Cryptographic primitive - algorithms of reversible transformation of the block of the data of the fixed size with use of a set of key parameters of the fixed size is offered. It shown that substitution is a base cryptographic primitive through which it is possible to express all the others. At the heart of the offered approach lies the theorem of C. Shannon that defines perfect secrecy for secret-key systems and shows that they exist. For perfect security receive it is necessary, that the size of a key was not less than size of the converted data and the key was in regular intervals distributed. Matrix representation of similar system is a Latin square - rectangular table, in each line and each column all elements are various. For maximum security of cryptographic primitives defined optimal parameters of the substitutions table. For a number of cryptographic primitives obtained analytical and prognostic assessment of their security based on proximity to the Latin square.

The increasing heterogeneity of the underlying hardware forces modern database system engineers to implement multiple variants of a single database operator (e.g., join, selection). With increasing heterogeneity, these variants become too complex to maintain and tune for different devices. To overcome these disadvantages, developers use an alternative, primitive-based operator design. This design paradigm splits the database operators into granular functions or primitives and executes a given operator by combing the necessary primitives. Hence, we require only a limited set of these primitives as we reuse them for multiple database operations. Thus, tuning a single primitive improves efficiency of all the database operations using it.In this survey, we provide an overview of a primitive-based database engine. First, we list different primitives from literature and place them in a hierarchy from the finest granular level to a complete database operator. Second, for each of primitive we list its possible tuning opportunities. Finally, we discuss the significance of primitive-based execution on the query engine. Overall, this survey aims to serve as a general reference for implementing a primitive-based query engine and possible strategies to tune it for specific processors. [ABSTRACT FROM AUTHOR]

An emerging approach to design locomotion assistive devices deals with reproducing desirable biological principles of human locomotion. In this paper, we present a bio-inspired controller for locomotion assistive devices based on the concept of motor primitives. The weighted combination of artificial primitives results in a set of virtual muscle stimulations. These stimulations then activate a virtual musculoskeletal model producing reference assistive torque profiles for different locomotion tasks (i.e., walking, ascending stairs, and descending stairs). The paper reports the validation of the controller through a set of experiments conducted with healthy participants. The proposed controller was tested for the first time with a unilateral leg exoskeleton assisting hip, knee, and ankle joints by delivering a fraction of the computed reference torques. Importantly, subjects performed a track involving ground-level walking, ascending stairs, and descending stairs and several transitions between these tasks. These experiments highlighted the capability of the controller to provide relevant assistive torques and to effectively handle transitions between the tasks. Subjects displayed a natural interaction with the device. Moreover, they significantly decreased the time needed to complete the track when the assistance was provided, as compared to wearing the device with no assistance. [ABSTRACT FROM AUTHOR]

Interest in and appreciation of medieval and early Renaissance art developed in Britain throughout the 1800s, reaching an apogee in the second half of the nineteenth century. Women who participated in the culture of connoisseurship played an important role in this shift in taste. This article traces how, through developing her first-hand knowledge of and familiarity with such art, author and editor Maria Callcott (1785–1842) made important early contributions to scholarship on the primitives. It then explores the links between Callcott and Queen Victoria (1819–1901), and assesses the influence exerted by the latter on the appreciation of early Renaissance art through her collecting activities. [ABSTRACT FROM PUBLISHER]

Movement generation has been hypothesized to rely on a modular organization of muscle activity. Crucial to this hypothesis is the ability to perform reliably a variety of motor tasks by recruiting a limited set of modules and combining them in a task-dependent manner. Thus far, existing algorithms that extract putative modules of muscle activations, such as Nonnegative Matrix Factorization (NMF), identify modular decompositions that maximize the reconstruction of the recorded EMG data. Typically, the functional role of the decompositions, i.e. task accomplishment, is only assessed a posteriori. However, as motor actions are defined in task space, we suggest that motor modules should be computed in task space too. In this study, we propose a new module extraction algorithm, named DsNM3F, that uses task information during the module identification process. DsNM3F extends our previous space-by-time decomposition method (the so-called sNM3F algorithm, which could assess task performance only after having computed modules) to identify modules gauging between two complementary objectives: reconstruction of the original data and reliable discrimination of the performed tasks. We show that DsNM3F recovers the task dependence of module activations more accurately than sNM3F. We also apply it to electromyographic signals recorded during performance of a variety of arm pointing tasks and identify spatial and temporal modules of muscle activity that are highly consistent with previous studies. DsNM3F achieves perfect task categorization without significant loss in data approximation when task information is available and generalizes as well as sNM3F when applied to new data. These findings suggest that the space-by-time decomposition of muscle activity finds robust task-discriminating modular representations of muscle activity and that the insertion of task discrimination objectives is useful for describing the task modulation of module recruitment.

The current literature on Intra-Spinal Micro-Stimulation (ISMS) for motor prostheses is reviewed in light of neurobiological data on spinal organization, and a neurobiological perspective on output motor modularity, ISMS maps, stimulation combination effects, and stability. By comparing published data in these areas, the review identifies several gaps in current knowledge that are crucial to the development of effective intraspinal neuroprostheses. Gaps can be categorized into a lack of systematic and reproducible details of: (a) Topography and threshold for ISMS across the segmental motor system, the topography of autonomic recruitment by ISMS, and the coupling relations between these two types of outputs in practice. (b) Compositional rules for ISMS motor responses tested across the full range of the target spinal topographies. (c) Rules for ISMS effects' dependence on spinal cord state and neural dynamics during naturally elicited or ISMS triggered behaviors. (d) Plasticity of the compositional rules for ISMS motor responses, and understanding plasticity of ISMS topography in different spinal cord lesion states, disease states, and following rehabilitation. All these knowledge gaps to a greater or lesser extent require novel electrode technology in order to allow high density chronic recording and stimulation. The current lack of this technology may explain why these prominent gaps in the ISMS literature currently exist. It is also argued that given the "known unknowns" in the current ISMS literature, it may be prudent to adopt and develop control schemes that can manage the current results with simple superposition and winner-take-all interactions, but can also incorporate the possible plastic and stochastic dynamic interactions that may emerge in fuller analyses over longer terms, and which have already been noted in some simpler model systems. [ABSTRACT FROM AUTHOR]