Feedforward

This text describes the design and implementation of high-performance feedback controllers for engineering systems. It emphasizes the frequency-domain design and methods based on Bode integrals, loop shaping and nonlinear dynamic compensation. The book also supplies numerous problems with practcal applications, illustrations and plots, together with MATLAB simulation and design examples.

This book has been possible thanks to the research carried out in the field of the linearization techniques applied to digital communication systems, particularly to those with high spectral efficient modulation techniques. It merges in the need of developing frequency efficient modulations with widespread codification techniques. The book puts into practice the Feedforward linearization technique, aimed at improving either the linearity or efficiency parameters of power amplifiers.

The visual system consists of hierarchically organized distinct anatomical areas functionally specialized for processing different aspects of a visual object (Felleman & Van Essen, 1991). These visual areas are interconnected through ascending feedforward projections, descending feedback projections, and projections from neural structures at the same hierarchical level (Lamme et al., 1998). Accumulating evidence from anatomical, functional and theoretical studies suggests that these three projections play fundamentally different roles in perception. However, their distinct functional roles in visual processing are still subject to debate (Lamme & Roelfsema, 2000). The focus of this Research Topic is the roles of feedforward and feedback projections in vision. Even though the notions of feedforward, feedback, and reentrant processing are widely accepted, it has been found difficult to distinguish their individual roles on the basis of a single criterion. We welcome empirical contributions, theoretical contributions and reviews that fit into any one (or a combination) of the following domains: 1) their functional roles for perception of specific features of a visual object 2) their contributions to the distinct modes of visual processing (e.g., pre-attentive vs. attentive, conscious vs. unconscious) 3) recent techniques/methodologies to identify distinct functional roles of feedforward and feedback projections and corresponding neural signatures. We believe that the current Research Topic will not only provide recent information about feedforward/feedback processes in vision but also contribute to the understanding fundamental principles of cortical processing in general.

This short comic of Feedforward will eliminate your usage of feedback which rehashes a past that cannot be changed, and will encourage you to spend your time giving Feedforward to create the future.

This decade has seen an explosive growth in computational speed and memory and a rapid enrichment in our understanding of artificial neural networks. These two factors provide systems engineers and statisticians with the ability to build models of physical, economic, and information-based time series and signals. This book provides a thorough and coherent introduction to the mathematical properties of feedforward neural networks and to the intensive methodology which has enabled their highly successful application to complex problems.

Now in its Third Edition, this text clearly and concisely presents the physiological principles that are essential to clinical medicine. Outstanding pedagogical features include Active Learning Objectives that emphasize problem-solving applications of basic principles; conceptual diagrams that help students visualize complex processes; case studies, Clinical Focus boxes, and From Bench to Bedside boxes; a comprehensive glossary; and online USMLE-style questions with answers and explanations. This edition features a new Immunology and Organ Function chapter and a completely rewritten and reorganized cardiovascular section. A companion Website will include the fully searchable text, an interactive question bank, case studies with practice questions, animations of complex processes, an image bank, and links for further study.

Locomotion involves many different muscles and the need of controlling several degrees of freedom. Despite the Central Nervous System can finely control the contraction of individual muscles, emerging evidences indicate that strategies for the reduction of the complexity of movement and for compensating the sensorimotor delays may be adopted. Experimental evidences in animal and lately human model led to the concept of a central pattern generator (CPG) which suggests that circuitry within the distal part of CNS, i.e. spinal cord, can generate the basic locomotor patterns, even in the absence of sensory information. Different studies pointed out the role of CPG in the control of locomotion as well as others investigated the neuroplasticity of CPG allowing for gait recovery after spinal cord lesion. Literature was also focused on muscle synergies, i.e. the combination of (locomotor) functional modules, implemented in neuronal networks of the spinal cord, generating specific motor output by imposing a specific timing structure and appropriate weightings to muscle activations. Despite the great interest that this approach generated in the last years in the Scientific Community, large areas of investigations remain available for further improvement (e.g. the influence of afferent feedback and environmental constrains) for both experimental and simulated models. However, also supraspinal structures are involved during locomotion, and it has been shown that they are responsible for initiating and modifying the features of this basic rhythm, for stabilising the upright walking, and for coordinating movements in a dynamic changing environment. Furthermore, specific damages into spinal and supraspinal structures result in specific alterations of human locomotion, as evident in subjects with brain injuries such as stroke, brain trauma, or people with cerebral palsy, in people with death of dopaminergic neurons in the substantia nigra due to Parkinson’s disease, or in subjects with cerebellar dysfunctions, such as patients with ataxia. The role of cerebellum during locomotion has been shown to be related to coordination and adaptation of movements. Cerebellum is the structure of CNS where are conceivably located the internal models, that are neural representations miming meaningful aspects of our body, such as input/output characteristics of sensorimotor system. Internal model control has been shown to be at the basis of motor strategies for compensating delays or lacks in sensorimotor feedbacks, and some aspects of locomotion need predictive internal control, especially for improving gait dynamic stability, for avoiding obstacles or when sensory feedback is altered or lacking. Furthermore, despite internal model concepts are widespread in neuroscience and neurocognitive science, neurorehabilitation paid far too little attention to the potential role of internal model control on gait recovery. Many important scientists have contributed to this Research Topic with original studies, computational studies, and review articles focused on neural circuits and internal models involved in the control of human locomotion, aiming at understanding the role played in control of locomotion of different neural circuits located at brain, cerebellum, and spinal cord levels.

Coinciding with the evolution of new standards for mobile communications systems and wireless multimedia services, this text provides an introduction and analysis of linear feedforward power amplifiers. It guides the reader through the feedforward design process, starting with the initial system specifications and continuing with a detailed look at the practical implementation of feedforward. The linearity and bandwidth demands on power amplifiers are explained in relation to the use of spectrally efficient linear modulation schemes and wide operating bandwidths for high data rate applications such as multimedia and Internet. The book includes numerous examples and analyses the advantages and disadvantages of different implementations, radio standards and system configurations. Future design trends are discussed and a review of alternative linearization techniques is also included.