Simultaneous Feedback Research Articles

Designing and analysing parallel control for multifeed ternary systems

This paper explores a parallel control structure for improving the behaviour of a chemical plant having recycling and multiple feed streams; a ternary system is taken as an example, having an A+B→C second-order irreversible reaction. Material recycling dynamics can induce the so-called snowball effect in the presence of disturbance in the feed stream. The snowball effect can be prevented by distributing load through the parallel control scheme. A control structure was thus proposed where product composition was regulated by means of simultaneous feedback manipulation of final column vapour boilup rate and reactor temperature. An extension was made for one reactor, one distillation column and recycle stream configuration. Nonlinear simulations showed that effective composition control could be obtained with moderate vapour boilup control efforts.

Usability Evaluation of the Interactive Personal Patient Profile-Prostate Decision Support System With African American Men

The Personal Patient Profile-Prostate (P4) program is an interactive Web-based decision support system that provides men with localized prostate cancer customized education and coaching with which to make the best personal treatment decision. This study assessed functionality and usability of the P4 program and identified problems in user-computer interaction in a sample of African American men. Usability testing was conducted with 12 community-dwelling African American adult men. The health status of participants was not known or collected by the research team. Each participant worked with the P4 program and provided simultaneous feedback using the "think aloud" technique. Handwritten field notes were collated and assigned to 3 standard coded categories. Aspects of P4 program usability was made based on common issues in the assigned categories. Summary statistics were derived for types and frequency of usability issues noted in the coded data. Twelve participants reported a total of 122 usability comments, with a mean of 9 usability comments. The most common usability issue by participant was completeness of information content, which comprised 53 (43%) of the total issues. Comprehensibility of text and graphics was second, comprising 51 (42%) of the total issues. This study provided initial inventory of usability issues for community African American men that may potentially interfere with application of the P4 system in the community setting and overall system usability, confirming the need for usability testing of a culturally appropriate Internet-based decision support system before community application.

Capturing Cultural Glossaries: Case-study I *

This article is a presentation of a brief cultural glossary of Northern Sotho cooking terms. The glossary is mainly composed of names for utensils and ingredients, and action words for the processes involved in the preparation of cultural dishes. It also contains names of dishes tied to some idiomatic expressions in a way eliciting cultural experiences that can lead to an under-standing of indigenous knowledge systems. The article seeks to explore ways of capturing cultural glossaries to feed into the national dictionary corpora by using a case-study approach to investigate the processes that led to the generation of this specific school-based project. A number of issues that surfaced in this project, can possibly serve as models for the collection of authentic glossaries that can support dictionary making in African languages. Keywords: cultural glossary, indigenous knowledge systems, cultural terminology, corpus, authentic glossary, contextualisation, margin-alized languages, outcomes-based education, performance indicator, assessment criteria, range statement, traditional dishes, language val-orisation, simultaneous feedback, communicative approach, structural approach, metonymy

Online Dictionaries on the Internet: An Overview for the African Languages

The main purpose of this research article is rather bold, in that an attempt is made at a comprehensive overview of all currently available African-language Internet dictionaries. Quite surprisingly, a substantial number of such dictionaries is already available, for a large number of languages, with a relatively large number of users. The key characteristics of these dictionaries and various cross-language distributions are expounded on. In a second section the first South African online dictionary interface is introduced. Although compiled by just a small number of scholars, this dictionary contains a world's first in that lexicographic customisation is implemented on various levels in real time on the Internet. Keywords: lexicography, terminology, dictionaries, internet, online, look-up mode, browse mode, african languages, sesotho sa leboa, simultaneous feedback, fuzzy sf, customisation

Intraoperative neurophysiology for surgery in and around the brainstem: role of brainstem mapping and corticobulbar tract motor-evoked potential monitoring

New advancements of intraoperative neurophysiology for surgery in and around the brainstem have been described. NEUROPHYSIOLOGICAL TECHNIQUES: Brainstem mapping (BSM) is applied to locate cranial nerves and their motor nuclei (CMN) on the floor of the fourth ventricle. Corticobulbar tract (CBT) motor-evoked potential (MEP) monitoring is used to achieve on-line monitoring of the cranial motor nerves' functional integrity. Each of these procedures bears a specific role: BSM can help avoid direct damage to CMNs on the fourth ventricular floor; CBT-MEP can provide simultaneous feedback on the functional integrity of the CBT and CMN during surgery, eventually leading to "tailored" modifications of the surgical procedure, based upon neurophysiological responses. CBT-MEP monitoring has less restriction in terms of clinical indications, but a combination of both procedures is essential for functional preservation of CMNs during surgery in and around the brainstem.

Development of Closed-Loop Neural Interface Technology in a Rat Model: Combining Motor Cortex Operant Conditioning With Visual Cortex Microstimulation

Closed-loop neural interface technology that combines neural ensemble decoding with simultaneous electrical microstimulation feedback is hypothesized to improve deep brain stimulation techniques, neuromotor prosthetic applications, and epilepsy treatment. Here we describe our iterative results in a rat model of a sensory and motor neurophysiological feedback control system. Three rats were chronically implanted with microelectrode arrays in both the motor and visual cortices. The rats were subsequently trained over a period of weeks to modulate their motor cortex ensemble unit activity upon delivery of intra-cortical microstimulation (ICMS) of the visual cortex in order to receive a food reward. Rats were given continuous feedback via visual cortex ICMS during the response periods that was representative of the motor cortex ensemble dynamics. Analysis revealed that the feedback provided the animals with indicators of the behavioral trials. At the hardware level, this preparation provides a tractable test model for improving the technology of closed-loop neural devices.

Design and experimental evaluation of simultaneous fast output sampling feedback control for smart structures

This paper presents the design and experimental implementation of simultaneous fast output sampling feedback controller to minimise structural vibration using collocated piezoelectric actuator and sensor. The linear dynamic model of piezoelectric bonded cantilever beams is obtained using online recursive least square parameter estimation. A digital control system that consists of simulink modelling software and dSPACE 1104 controller board is used for identification and control. The performance of simultaneous controller is evaluated by considering three structure models. These models are obtained by introducing parameter variation in length and mass of a single cantilever beam structure. The effectiveness of the controller is demonstrated experimentally by exciting the structures at resonance.

Simultaneous Periodic Output Feedback Control for Piezoelectric Actuated Structures using Interval Methods

Abstract In this paper, the problem of modeling, output feedback control design and the experimental implementation for the vibration control of smart cantilever beam with parameter uncertainties represented in interval form is addressed. The interval model of the system is obtained by introducing variation in the parameter of the identified model. However, Uncertainties are assumed in the model, identified through on line recursive least square parameter estimation. The control and identification process is done by using Simulink modeling software and dSPACE DS 1104 controller board. The output feedback controller design for the interval model is carried out through simultaneous output feedback controller design methodology by considering lower, nominal and upper bound models. The controllers designed are periodic output feedback is experimentally evaluated for their performance in suppressing the first vibration mode.

Debriefing in Moodle: Written feedback on trust and knowledge sharing in a social dilemma game

This article describes a new approach to debriefing that uses the discussion forum feature of the Moodle open source course management system to debrief a simulation game with undergraduate business students. The simulation game allowed the students to experience the fragility of trust when sharing knowledge in a global virtual project team. I found using the Moodle forum for gathering written feedback on the task to be an improvement over verbal feedback sessions used with previous classes. The Moodle forum provides spontaneous and simultaneous rich feedback from a larger number of students and increases their awareness of the complexity of the task. It became clear to the students that there was no blueprint for success in the game but that participants each had to make sense of the experience in their own way.

Robust broadband nanopositioning: fundamental trade-offs, analysis, and design in atwo-degree-of-freedom control framework

This paper studies and analyses fundamental trade-offs between positioning resolution,tracking bandwidth, and robustness to modeling uncertainties in two-degree-of-freedom(2DOF) control designs for nanopositioning systems. The analysis of these systems isdone in optimal control setting with various architectural constraints imposedon the 2DOF framework. In terms of these trade-offs, our analysis shows thatthe primary role of feedback is providing robustness to the closed-loop devicewhereas the feedforward component is mainly effective in overcoming fundamentalalgebraic constraints that limit the feedback-only designs. This paper presents (1) anoptimal prefilter model matching design for a system with an existing feedbackcontroller, (2) a simultaneous feedforward and feedback control design in an optimalmixed sensitivity framework, and (3) a 2DOF optimal robust model matchingdesign. The experimental results on applying these controllers show a significantimprovement, as high as 330% increase in bandwidth for similar robustness andresolution over optimal feedback-only designs. Other performance objectives canbe improved similarly. We demonstrate that the 2DOF freedom design achievesperformance specifications that are analytically impossible for feedback-only designs.

Design and experimental evaluation of simultaneous periodic output feedback control for piezoelectric actuated beam structure

This paper presents the design and experimental implementation of a simultaneous periodic output feedback controller to minimize structural vibration using collocated piezoelectric actuator and sensor. The linear dynamic model of piezoelectric-bonded cantilever beams is obtained using online recursive least-square parameter estimation. A digital control system that consists of simulink modelling software and dSPACE 1104 controller board is used for identification and control. The performance of simultaneous controller is evaluated by considering a cantilever beam structure of three different lengths and mass. The effectiveness of the controller is demonstrated experimentally by exciting the structures at resonance. The advantage of the simultaneous periodic output feedback controller implemented in this paper is unique in the sense that the common controller gain reduces the first two vibration modes of three plants, which is not commonly shown in the literature with other feedback controllers. From the experimental results it is observed that with the simultaneous output feedback controller the vibration reduction is approximately 75% for the first mode and 60% for the second mode for all the three plants. Copyright © 2008 John Wiley & Sons, Ltd.

Providing simultaneous visual feedback may ameliorate speech disruptions caused by exposure to delayed auditory feedback

Speakers exposed to delayed auditory feedback (DAF) are often dysfluent. We investigated the possibility that providing visual feedback in addition to DAF would reduce speech disruption. Participants repeated sentences while they heard their auditory feedback delayed with and without simultaneous visual feedback. Replicating previous work, DAF led to increased sentence durations and an increased number of speech disruptions. Results showed that visual feedback did not reduce DAF effects on duration, however, a nonsignificant trend was observed that indicated fewer speech disruptions occurred when visual feedback was provided. This trend was significant in speakers who were overall less affected by DAF. These results suggest the possibility that speakers can strategically use alternative sources of feedback.

Integrated IPMC/PVDF sensory actuator and its validation in feedback control

Position and/or force feedback is critical in ensuring precise and safe operation of ionic polymer–metal composite (IPMC) actuators in bio/micromanipulation. In this paper the design of an integrated sensory actuator is presented, where polyvinylidene fluoride (PVDF) films are used to provide simultaneous feedback of bending and force outputs of the IPMC actuator. The design adopts differential configurations for sensing, which eliminates corruption of sensing signals by feedthrough of actuation signal or by thermal drift. Experimental results are presented to demonstrate closed-loop control of IPMC bending output based upon the integrated PVDF sensor, together with simultaneous tip force measurement with μ N resolution.

The Impact of Human Capital on Regional Labor Productivity in Europe

This paper employs a spatial Durbin model for analyzing the impact of human capital on regional productivity using for 198 NUTS-2 European regions for the sample period from 1995 to 2004. The study provides evidence for the existence of spatial externalities and interactions of the sort as emphasized by new growth theory. To interpret results meaningfully, we calculate summary measures that account for the simultaneous feedback nature of the underlying model. By sampling from the parameter distribution we present measures of dispersion, revealing that it is relative regional advantages in human capital that matter most for productivity growth.

Invited Paper: Surface‐emitting‐diode lasers and laser arrays for displays

Abstract— High‐power red, green, and blue laser light sources made from vertically emitting arrays of intracavity doubled IR lasers is reported. The emitted infrared light from a monolithic array of large‐aperture vertical cavity lasers is converted into visible light using a PPLN doubling crystal in an external cavity. A volume Bragg grating provides simultaneous feedback for all emitters in the array and sets the laser wavelength. Increased diffraction losses for higher‐order modes result in quasi‐Gaussian beams with excellent conversion efficiency. Green 532‐nm lasers with more than 5.8‐W visible power have been demonstrated at a base temperature of 40°C. Blue 465‐nm lasers with 4.4‐W power at 40°C are unmatched in performance and wavelength when compared to competing GaN‐based edge emitters. Typical wall‐plug efficiencies are higher than 8%. We have measured single‐emitter operating lifetimes to be more than 28,000 hours. Red lasers based on highly strained InGaAs achieve record laser powers of 2.0W at 618 nm in the same form factor as the green and blue lasers. Red single‐emitter lifetimes of more than 10,000 hours have been attained. The technology described in this paper delivers on a full suite of cost efficient and reliable red, green, and blue lasers that meet the demands of the display markets.

Speech disruption during delayed auditory feedback with simultaneous visual feedback

Delayed auditory feedback (DAF) regarding speech can cause dysfluency. The purpose of this study was to explore whether providing visual feedback in addition to DAF would ameliorate speech disruption. Speakers repeated sentences and heard their auditory feedback delayed with and without simultaneous visual feedback. DAF led to increased sentence durations and an increased number of speech disruptions. Although visual feedback did not reduce DAF effects on duration, a promising but nonsignificant trend was observed for fewer speech disruptions when visual feedback was provided. This trend was significant in speakers who were overall less affected by DAF. The results suggest the possibility that speakers strategically use alternative sources of feedback.

Stability and control of resistive wall modes in high beta, low rotation DIII-D plasmas

Recent high-β DIII-D (Luxon J.L. 2002 Nucl. Fusion 42 64) experiments with the new capability of balanced neutral beam injection show that the resistive wall mode (RWM) remains stable when the plasma rotation is lowered to a fraction of a per cent of the Alfvén frequency by reducing the injection of angular momentum in discharges with minimized magnetic field errors. Previous DIII-D experiments yielded a high plasma rotation threshold (of order a few per cent of the Alfvén frequency) for RWM stabilization when resonant magnetic braking was applied to lower the plasma rotation. We propose that the previously observed rotation threshold can be explained as the entrance into a forbidden band of rotation that results from torque balance including the resonant field amplification by the stable RWM. Resonant braking can also occur naturally in a plasma subject to magnetic instabilities with a zero frequency component, such as edge localized modes. In DIII-D, robust RWM stabilization can be achieved using simultaneous feedback control of the two sets of non-axisymmetric coils. Slow feedback control of the external coils is used for dynamic error field correction; fast feedback control of the internal non-axisymmetric coils provides RWM stabilization during transient periods of low rotation. This method of active control of the n = 1 RWM has opened access to new regimes of high performance in DIII-D. Very high plasma pressure combined with elevated qmin for high bootstrap current fraction, and internal transport barriers for high energy confinement, are sustained for almost 2 s, or 10 energy confinement times, suggesting a possible path to high fusion performance, steady-state tokamak scenarios.

Simultaneous feedback control of plasma rotation and stored energy on the DIII-D tokamak

A major modification made recently to the DIII-D tokamak was the rotation of one of the four neutral beam systems to allow injection of power in the opposite direction of the usual plasma current (counter-injection). Mixing the usual co-injection beams with the counter-injection beams provides a new capability that allows, for the first time, a partial decoupling of the injected energy and momentum during neutral beam heating experiments. To implement this capability, we have developed within the plasma control system (PCS) [B.G. Penaflor, et al., Fusion Eng. Design 71 (2004) 47] a model-based control algorithm for simultaneous regulation of plasma rotation and beta. The present work describes the development of the model, discusses its validation using actual experimental data, and presents the details of the implementation of the model within the PCS to allow simultaneous control of both plasma rotation and stored energy.

Spatial Growth Regressions: Model Specification, Estimation and Interpretation

This paper uses Bayesian model comparison methods to simultaneously specify both the spatial weight structure and explanatory variables for a spatial growth regression involving 255 NUTS 2 regions across 25 European countries. In addition, a correct interpretation of the spatial regression parameter estimates that takes into account the simultaneous feedback nature of the spatial autoregressive model is provided. Our findings indicate that incorporating model uncertainty in conjunction with appropriate parameter interpretation decreased the importance of explanatory variables traditionally thought to exert an important influence on regional income growth rates.

Design of Simultaneous Periodic Output Feedback Control for Smart Structures

This paper presents the problem of modelling simultaneous periodic output feedback control design to control the first two vibration modes of a flexible smart cantilever beam. The entire structure is modeled by finite element method using a piezoelectric beam element which includes a piezoelectric sensor and actuator dynamics. Simulation results demonstrate that a single controller can be employed to control the first two vibration modes for six different sensor/actuator locations along the beam. Application of simultaneous control introduces a redundancy in smart structure control.