New neural circuits for robot phonotaxis

W. Grey Walter built robotic systems to improve understanding of biological systems. In that tradition, this paper reports ongoing work on a robot model of cricket sound localization. The main advances are the inclusion of a much larger range of neuroethological detail, and the investigation of multimodal influences on the behaviour. The former allows exploration of the functionality of identified neurons in the insect, including the possible roles of multiple sensory fibres, mutually inhibitory connections, and brain neurons with pattern-filtering properties. The latter focuses on the inclusion of an optomotor stabilization response, and how this might improve tracking, particularly under conditions of random disturbance.     

Theoretically-based algorithms for robustly tracking intersection curves of deforming surfaces

This paper applies singularity theory of mappings of surfaces to 3-space and the generic transitions occurring in their deformations to develop algorithms for continuously and robustly tracking the intersection curves of two deforming parametric spline surfaces, when the deformation is represented as a family of generalized offset surfaces. The set of intersection curves of two deforming surfaces over all time is formulated as an implicit 2-manifold I in an augmented (by time domain) parametric space R⁵. Hyperplanes corresponding to some fixed time instants may touchI at some isolated transition points, which delineate transition events, i.e. the topological changes to the intersection curves. These transition points are the 0-dimensional solution to a rational system of five constraints in five variables, and can be computed efficiently and robustly with a rational constraint solver using subdivision and hyper-tangent bounding cones. The actual transition events are computed by contouring the local osculating paraboloids. Away from any transition points, the intersection curves do not change topology and evolve according to a simple evolution vector field that is constructed in the Euclidean space in which the surfaces are embedded.     

Stiffness and Strength of Metal Bridge Deck Forms

Light gauge metal sheeting is often utilized in the building and bridge industries for concrete formwork. Although the in-plane stiffness and strength of the metal forms are commonly relied upon for stability bracing in buildings, the forms are generally not considered for bracing in steel bridge construction. The primary difference between the forming systems in the two industries is the method of connection between the forms and girders. In bridge construction, an eccentric support angle is incorporated into the connection details to achieve a uniform slab thickness along the girder length. While the eccentric connection is a benefit for slab construction, the flexible connection limits the amount of bracing provided by the forms. This paper presents results from the first phase of a research study investigating the bracing behavior of metal bridge deck forms. Shear diaphragm tests were conducted to determine the shear stiffness and strength of bridge deck forms, and modified connection details were developed that substantially improve the bracing behavior of the forms. The measured stiffness and strength of diaphragms with the modified connection often met or exceeded the values of diaphragms with conventional noneccentric connections. The experimental results for the diaphragms with the modified connection details dramatically improve the potential for bracing of steel bridge girders by metal deck forms.     

Thermal impact of an active 3-D microelectrode array implanted in the brain.

A chronically implantable, wireless neural interface device will require integrating electronic circuitry with the interfacing microelectrodes in order to eliminate wired connections. Since the integrated circuit (IC) dissipates a certain amount of power, it will raise the temperature in surrounding tissues where it is implanted. In this paper, the thermal influence of the integrated 3-D Utah electrode array (UEA) device implanted in the brain was investigated by numerical simulation using finite element analysis (FEA) and by experimental measurement in vitro as well as in vivo. The numerically calculated and experimentally measured temperature increases due to the UEA implantation were in good agreement. The experimentally validated numerical model predicted that the temperature increases linearly with power dissipation through the UEA, with a slope of 0.029 degree C/mW over the power dissipation levels expected to be used. The influences of blood perfusion, brain metabolism, and UEA geometry on tissue heating were also investigated using the numerical model.     

Reverse Phase-Controlled Dimmer for Incandescent Lighting

The reverse phase-controlled dimmer is an alternate method for varying the intensity of incandescent lights. Unlike conventional phase-controlled dimmers, the thyristors are triggered into conduction immediately following the zero crossing of the ac line rather than being delayed into the half-cycle. After an appropriate delay the silicon-controlled rectifiers (SCR's) are turned off by forced commutation. Manufacturers of conventional phase-controlled dimmers place a large inductor in series with the lamp load to reduce both lamp acoustical noise and radio-frequency interference (RFI) to acceptable levels. Instead of an inductor, reverse phase control connects a snubber capacitor in parallel with the main SCR's. The capacitor filters the output much like an inductor would, but without the inherent disadvantages. Eliminating the inductor makes more power available to the load since there is no reactive power loss in the main current path. Furthermore, without the inductor the dimmer will run quieter, because the inductor is a major source of acoustical noise. The control circuit incorporates an open loop scheme that provides line voltage regulation and fast response. A combination of analog and digital techniques tracks the amount of power available from the power line and meters out only the desired amount of the load. The dimmer responds to changes in control signal and line voltage within one half-cycle. Power levels are programmed by an 8 bit data word.     

Strategy models for enabling offshore outsourcing: Russian short-cycle-time software development

Economic factors are driving software development projects onto globally dispersed models, as offshore outsourcing becomes more common. Software development companies in developing economies compete for lucrative, job-creating offshore contracts on the basis of industry maturity, labor skills, technology infrastructure, and government support. Diffusion of technology is a key aspect of each of these determinants of competitiveness. This paper analyzes the development of strategies for the diffusion of short-cycle-time software development into and within Russia. Short-cycle-time development is sometimes called agile development or Internet-speed development and uses a number of techniques to move software quickly into production. These techniques are spreading rapidly among software developers worldwide. The benefits of these techniques are well known and provide a credible explanation for why this rapid diffusion is occurring. This paper explains how these techniques are spreading in a borderless fashion. Using the Kline model of innovation diffusion and the Greiner model of evolution and growth of organizations, we analyze the enablers and barriers to diffusion of short-cycle-time software development techniques in Russia. This analysis reveals a complex interaction of political, economic, and technical elements enabling and inhibiting the development of knowledge that supports the innovation diffusion necessary for companies to compete for offshore contracts. © 2005 Wiley Periodicals, Inc.     

Continuous-time linear predictive control and flatness: A module-theoretic setting with examples

A general flatness-based framework for linear continuous-time predictive control is presented. The mathematical setting, which is valid for multivariable systems, is provided by the algebraic theory of modules where a controllable system corresponds to a finitely generated free module over a principal ideal ring. Any basis of this free module is a flat output which yields an easy calculation of the predicted trajectory. This formalism permits one to handle non-minimum phase systems, system constraints, and to deal with additive perturbations. Three concrete case studies, namely a dc motor, a flexible system, and a cement mill, are analysed and simulations are given. These examples are written in such a way that any reader who is not familiar with module theory may nevertheless grasp the proposed control strategy.     

Life is pleasant--and memory helps to keep it that way!

People's recollections of the past are often positively biased. This bias has 2 causes. The 1st cause lies in people's perceptions of events. The authors review the results of several studies and present several new comparative analyses of these studies, all of which indicate that people perceive events in their lives to more often be pleasant than unpleasant. A 2nd cause is the fading affect bias: The affect associated with unpleasant events fades faster than the affect associated with pleasant events. The authors review the results of several studies documenting this bias and present evidence indicating that dysphoria (mild depression) disrupts such bias. Taken together, this evidence suggests that autobiographical memory represents an important exception to the theoretical claim that bad is stronger than good. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dual approaches to strictly positive real controller synthesis with a performance using linear matrix inequalities

The synthesis of controllers that minimize a performance index subject to a strictly positive real (SPR) constraint is considered. Two controller synthesis methods are presented that are then combined into an iterative algorithm. Each method synthesizes optimal SPR controllers by posing a convex optimization problem where constraints are enforced via linear matrix inequalities. Additionally, each method fixes the controller state‐feedback gain matrix and finds an observer gain matrix such that an upper bound on the closed‐loop ‐norm is minimized and the controller is SPR. The first method retools the standard ‐optimal control problem by using a common Lyapunov matrix variable to satisfy both the criteria and the SPR constraint. The second method overcomes bilinear matrix inequality issues associated with the performance and the SPR constraint by employing a completing the square method and an overbounding technique. Both synthesis methods are used within an iterative scheme to find optimal SPR controllers in a sequential manner. Comparison of our synthesis methods to existing methods in the literature is presented. Copyright © 2012 John Wiley & Sons, Ltd.     

Verification of cardiac tissue electrophysiology simulators using an N-version benchmark

Ongoing developments in cardiac modelling have resulted, in particular, in the development of advanced and increasingly complex computational frameworks for simulating cardiac tissue electrophysiology. The goal of these simulations is often to represent the detailed physiology and pathologies of the heart using codes that exploit the computational potential of high-performance computing architectures. These developments have rapidly progressed the simulation capacity of cardiac virtual physiological human style models; however, they have also made it increasingly challenging to verify that a given code provides a faithful representation of the purported governing equations and corresponding solution techniques. This study provides the first cardiac tissue electrophysiology simulation benchmark to allow these codes to be verified. The benchmark was successfully evaluated on 11 simulation platforms to generate a consensus gold-standard converged solution. The benchmark definition in combination with the gold-standard solution can now be used to verify new simulation codes and numerical methods in the future.