Parallel Feedback Research Articles

Fluid mediated communication among flexible micro-posts in chemically reactive solutions.

Communication in biological systems typically involves enzymatic reactions that occur within fluids confined between the soft, elastic walls of bio-channels and chambers. Through the inherent transformation of chemical to mechanical energy, the fluids can be driven to flow within the confined domains. Through fluid-structure interactions, the confining walls in turn are deformed by and affect this fluid flow. Imbuing synthetic materials with analogous feedback among chemo-mechanical, hydrodynamic and fluid-structure interactions could enable materials to perform self-driven communication and self-regulation. Herein, we develop computational models to determine how chemo-hydro-mechanical feedback affects interactions in biomimetic arrays of chemically active and passive micro-posts anchored in fluid-filled chambers. Once activated, the enzymatic reactions trigger the latter feedback, which generates a surprising variety of long-range, cooperative motion, including self-oscillations and non-reciprocal interactions, which are vital for propagating coherent, directional signals over net distances in fluids. In particular, the array propagates a distinct message; each post interprets the message; and the system responds with a specific mode of organized, collective behavior. This level of autonomous remote control is relatively rare in synthetic systems, particularly as this system operates without external electronics or power sources and only requires the addition of chemical reactants to function.

Discrete-Time Delta-Sigma Modulator with Successively Approximating Register ADC Assisted Analog Feedback Technique

Discrete-Time Delta-Sigma Modulator with Successively Approximating Register ADC Assisted Analog Feedback Technique

Range selective digital holographic imaging of vibrating objects using FMCW lidar

The use of frequency modulated continuous wave (FMCW) chirped transmit and reference waveforms in digital holographic (DH) imaging has enabled range selectivity. By frequency shifting the reference beam to compensate for the typical FMCW lidar beat frequency associated with a particular range, a temporally stable holographic image is formed for objects at the selected range and coherently integrates on a short wave infrared (SWIR) sensor. For vibrating objects, longitudinal movements of the object greater than half of an optical wavelength during the exposure time of the sensor array induce phase shifts that can wash out the hologram. An analog feedback system was designed and constructed whereby a lidar subassembly provides real time phase compensation information to a DH subassembly in order to stabilize the range selective digital holographic recording of the object. The design and characterization of the feedback system, as well as the results demonstrating the performance for vibrating objects that move over 17 wavelengths during the sensor exposure, are discussed.

Enhancing sound insulation performance with active constrained layer damping plates at low frequencies

In this paper, the normal incident sound transmission loss characteristics of active constrained layer damping (ACLD) plates are investigated numerically and experimentally. The sound insulation performance of the ACLD plate configuration with a centrally positioned 30 mm × 30 mm patch is initially examined in both passive and active control states. The analog feedback control strategy is employed to physically demonstrate that the ACLD treatment can effectively improve airborne sound insulation performance at low frequencies. To enhance control efficiency and mitigate control spillover effects, an edge-enhanced ACLD (EACLD) plate configuration is proposed, which enables a direct electrical connection between the PZT layer and base plate. Control mechanism is further analyzed from the perspectives of mean quadratic normal velocity and deformed modal shapes. Results show that, in the passive state, the formation of sound insulation peaks of the ACLD and EACLD plate configurations are attributed to structural anti-resonance effects. By applying active control, the shear deformation degree of the viscoelastic layer can be further increased, and the advantages of active and passive hybrid damping are formed. Therefore, the sound insulation performance of the EACLD plate configuration in the first-order resonance region around 190 Hz can be enhanced by approximately 20 dB. The proposed EACLD plate configuration demonstrates a broad low-frequency sound insulation bandwidth and holds strong potential for engineering applications.

Évaluation des échanges professionnels entre médecins généralistes et psychiatres

ObjectivesThere is in France a higher prevalence of psychiatric disorders and higher than average psychotropic consumption in the general population. Considering these elements and the need to involve two complementary medical specialities to manage these disorders, general practice and psychiatry, the necessity for optimal professional exchanges is a major public health concern. In the French public health system, primary care is overseen by self-employed general practitioners. The French psychiatric public sector is said to be “sectorised”, i.e. organised in specific sectors. These sectors include in-patient care entities and out-patient services. The private sector in psychiatry is not sectorised and is mainly composed of self-employed psychiatrists and private clinics. A 2004 law designed to govern who is authorized to refer patients to specialists, stipulated that general practitioners were the only authorized referring doctors for primary care. In the meantime, the number of general practitioners being consulted for cases of depression has doubled between 2005 and 2010. Less than a quarter of these patients were referred to a psychiatrist. Our main objective is to assess the satisfaction with and the efficiency of exchanges between psychiatrists and general practitioners. We also endeavour to identify the main channels through which collaborative care involving these two specialists can be improved. Materials and methodsOur work is an observational, transverse, monocentric and descriptive study carried out using analogous feedback forms mailed by post from June to September 2016. The feedback forms were designed to be analysed both separately and comparatively. Two hundred and ninety nine self-employed general practitioners and 46 psychiatrists employed in the public sector returned the forms. The psychiatric private sector was excluded. All of these doctors worked within three specific geographical treatment zones: Saint-Étienne, Ondaine and Pays de Gier (350,000 inhabitants). The results were treated anonymously via Microsoft Excel® and IBM Corporation SPSS Statistics®. This study was approved by the ethics committee of the university hospital center (CHU) of Saint-Étienne. The doctors’ registers were retrieved via the databases of the Departmental Council of Doctors (CDOM) of the Loire and that of the CHU of Saint-Étienne. ResultsOne hundred and twenty four general practitioners and 30 psychiatrists responded to the feedback form completely. Response rates were 41.4 % for the family physicians and 65.2 % for the psychiatrists. Respectively, 57 % and 70 % knew the identity of their counterpart. A public sector psychiatrist saw 91.9 % of the patients also treated by general practitioners. Of the attending doctors, 79.8 % reported a one third or less return rate of follow-up information from the psychiatrist for the patients they treated together. Similarly, 76.7 % of the psychiatrists reported a return rate of one third or less. One hundred percent (p<0.05) of the general practitioners who did not know the psychiatrists were dissatisfied with their collaboration. Likewise, 98.9% (p<0.05) of the general practitioners who rarely or never received correspondence from the psychiatrists were dissatisfied. Respectively, 77.7% (p>0.05) and 69.5% (p>0.05) of the psychiatrists were dissatisfied. In favor of participating in a standard addressing and return letter process, were 53.4% of the psychiatrists. On the contrary, 64.9% of the general practitioners were against such a process. Willing to receive additional medical training in the psychiatric field were 74.5 % of the family physicians. One out of five psychiatrists considered it a high priority for general practitioners to receive additional training in the psychiatric field. Sharing hospitalisation and consultation reports, along with general practitioners continuous medical training, were considered to be the top priorities for any approach for improving communication. ConclusionsWe observed a high level of dissatisfaction among the participants as a result of the lack of communication. As mentioned above, the field of psychiatry is compartmentalised, psychiatrists are less available for general practitioners. General practitioners are not sufficiently trained but are willing to take more training to improve their practice in the psychiatric field. The results of this study show that first and foremost there is a need to systematise mailings, to simplify phone-based opinion sharing, and to increase the frequency of cross-field training among general practitioners. All of the above could improve exchanges and the management of patients suffering from psychiatric disorders.

Stability analysis and vibration suppression in an overhung rotor system using active magnetic damper

The present work demonstrates the effectiveness of an active magnetic damper (AMD) in improving the vibration characteristics of an overhung rotor system (ORS) considering the effects of synchronous mass-unbalance, rotor bow, and viscous internal damping. A finite element-based rotordynamic analysis has been conducted to evaluate the system response using state-space formulation. MATLAB codes are developed for the numerical implementation of the rotordynamic model pertaining to the flexible ORS integrated with an AMD consisting of three parallel feedback loops. The internal damping is found to reduce the vibration amplitudes at the bearing and disk locations. However, it leads to system instability in the absence of AMD beyond the first critical speed (670 RPM) which is indicated by the change in the real part of eigenvalues. Under these circumstances, the use of AMD causes a remarkable improvement and the system stabilizes for almost the entire speed range considered here, 320–10,000 RPM. In addition, the AMD causes a maximum reduction of 95.8%, 96.5%, and 83.3% in the vibration amplitudes at the locations of Bearing 1, Bearing 2, and the overhung disk, respectively. Using an appropriate set of AMD parameters, the system characteristics can be altered effectively as per the requirement.

A simulator for Timepix-like pixel front-ends

This work presents the development of a front-end simulation code for the Timepix3 readout chip [1], intended as digitizer stage in full detector simulation. The front-end electronics is modelled using an integrator stage and 3 parallel feedback loops with individually configurable time constants. The main feedback discharging the integrator consists of 3 low-pass filtered feedback loops. The leakage current compensation is approximated by an additional independent low-pass filtered feed-back loop. The system noise is modelled using independent bandwidth limited noise channels for pre-amplifier, feedback and threshold noise. The Timepix3 time of arrival (ToA) and time over threshold (ToT) measurement is implemented by a discriminator model with independent rise and fall times and 2 independent clock frequencies for ToA and ToT. The measured dependence of the ToT on the pre-amplifier input charge using test-pulses of a Timepix3 assembly is correctly reproduced for a wide range of discriminator settings.

Translingual Oral Corrective Feedback in an Arabic as a Heritage Language Classroom in the USA

Over the years, a sweeping interest in translanguaging practices and corrective feedback (CF) in parallel has received momentum in instructed SLA research. Whereas previous CF studies focused on CF interactions and factors affecting L2 learning, this study examined how translanguaging intertwined with CF in Arabic as a Heritage Language learning in a sixth-grade class at a K-12 school in the USA. The research data resulted from twenty hours of class observations, interviews with the class teacher, and ten randomly selected participating students. The data were coded based on Ranta and Lyster’s (2007) CF types and uptake moves taxonomy. The results showed that the teacher's translanguaging practices helped learners engage in pedagogical tasks and CF interactions, leading to effective Arabic language learning. The teacher provided five CF types—explicit correction, recast, metalinguistic feedback, elicitation, and multiple feedback. Metalinguistic feedback, recast, and multiple feedback accounted for 72% of CF, where recasts received the highest uptake and repair rates (95% and 87%, respectively), and the other types of CF also led to high uptake and repair moves. This study suggests that CF can be effective when teachers employ translanguaging during CF interactions, positively address learner errors, and motivate learners’ in-class participation.

Розробка цифрового інтерфейсу для керування імпульсним блоком живлення

Most switching power supplies are not designed to change their output voltage. However, situations arise where a different voltage from the power source is needed. The purpose of this article is to develop a practical interface scheme for digitally controlling the output voltage of a switching power supply with an analog feedback loop. The article presents the results of the research of isolated flyback switch-mode power supply (SMPS) circuits, determines the method of controlling the output voltage of the SMPS, and proposes a digital interface for controlling the output voltage of the power supply. The emphasis was on using readily available, inexpensive components with minimal modification to the existing design. The study revealed limitations in existing switching power supply designs regarding effective output voltage control. Modifying the internal reference source is often not an available option. Therefore, influencing the feedback circuit emerges as a simple and viable control method. All power supply feedback loops include a voltage divider measuring the output voltage of switching power supply. This research demonstrates that controlling output voltage can be achieved by injecting or draining current within or from output voltage divider of power supply. Draining current increases the output voltage, while injecting decreases it. The additional resistor only requires a single connection point within the existing circuit. The proposed method provides a linear dependence of the output voltage increase on the value of the injected/drained current. It is shown that the digital interface scheme depends on the number of discrete levels of the required output voltage. For a small number of levels, field-effect transistors controlled by a positional or binary code can be used to control the power supply, and with a significant number of levels, it is advisable to use ready-made digital-to-analog converters.

Robust multi‐loop control of a floating wind turbine

AbstractA principal challenge facing the control of floating offshore wind turbines (FOWTs) is the problem of instability, or “negative damping,” when using blade pitch feedback to control generator speed. This closed‐loop instability can be attributed to non‐minimum phase zeros in the transfer function from blade pitch to generator speed. Standard approaches to improving stability and performance include robust tuning of control gains and introducing multiple feedback loops to respond to platform motion. Combining these approaches is nontrivial because multiple control loops complicate the impact of coupling in the system dynamics. The single‐loop approach to analyzing stability robustness neglects inter‐loop coupling, while a simplistic multi‐loop approach is highly sensitive to dimensional scaling and overestimates the robustness of the single‐loop controller. This work proposes a sensitivity representation that separates some of the natural FOWT dynamic coupling into a parallel feedback loop in the sensitivity function loop to address both of these concerns. The modified robustness measure is used with a simplified linear FOWT model to optimize scheduled multi‐loop control parameters in an automated tuning procedure. This controller is implemented for the 10‐MW Ultraflexible Smart FLoating Offshore Wind Turbine (USFLOWT) and compared against conventional single‐ and multi‐loop controllers tuned using frequency‐domain analysis and high‐fidelity OpenFAST simulations. The multi‐loop robust controller shows the highest overall performance in generator speed regulation and tower load reduction, though consideration of power quality, actuator usage, and other structural loading leads to additional trade‐offs.

High‐speed adaptive analog filter based on fully analog artificial neural network

SummaryThis paper presents an innovative concept of a high‐speed and higher order adaptive filter. A fully analog artificial neural network handles the adaption by using a filter bank for filtering and learning through analog feedback inspired by backpropagation. There is no clock control used in this concept, which makes real‐time adaption possible even for high frequencies. Its functionality is shown by several electrical circuit simulations involving component inaccuracies as well as a commonly used filter example.

Design and Analysis of Analog Feedback Communication System with Rayleigh Fading Channel Model

In this work, we mathematically model a wireless Analog feedback communication system (AFCS) using a Rayleigh fading channel. AFCS system is a new research area and has promising applications, especially in low-power devices such as sensors. Compared to AWGN, Rayleigh fading channel more closely models the real wireless environment. In this work, AFCS Rayleigh fading channel is considered in forward transmission while AWGN is considered in the feedback channel. We evaluated the performance of the system which is mostly based on the minimization of mean square error (MSE) at the receiver. Even in presence of a wireless fading environment, the AFCS attains a 0 MSE value in 2-3 iterations if a noise power of 10dB is considered while in 10-15 iterations if a noise power of 20dB is considered.

Low-cost and miniaturized temperature compensation system for nuclear applications

Facilities using nuclear radiation and detectors require stability of detector response irrespective of the ambient conditions. This stability of radiation detector output is crucial for applications requiring precise monitoring of radiation. The paper presents the development and performance validation of an analogue feedback circuit designed to compensate for the effect of temperature variations in Silicon Photomultiplier (SiPM) based detectors and measurement systems. The presented circuit uses feedback from a temperature sensor to enable a linear compensation to control the bias voltage for the charge pump-based bias supply. The circuit was tested using a scintillator coupled to a 2 × 2 array of SiPMs and tested using a Caesium-137 radioactive source for checking the stability of the detector output. The system was tested over a temperature range from 5 to 55 °C. Considering this broad range, this circuit was calibrated for different temperature ranges allowing the user to set the compensation depending on the temperature range of interest.

A VCO-ADC Linearized by a Capacitive Frequency-to-Current Converter

In this brief we propose a technique to compensate the distortion of an open-loop VCO-based ADC. The VCO is linearized by placing an analog feedback loop based on a frequency-to-current converter which uses an asynchronous switched capacitor circuit. The feedback loop relies on the VCO gain to linearize the ADC without requiring additional amplifiers. This permits the use of a ring oscillator with small input range to efficiently encode a large signal. The proposed technique has been experimentally demonstrated in an audio ADC. The proof-of-concept chip was fabricated in 130nm CMOS and achieves 76.64 dBA of peak SNDR with a Dynamic Range of 90dB and a power consumption of 482μW in 20kHz.

Simple Internal Model-Based Robust Control Design for a Non-Minimum Phase Unmanned Aerial Vehicle

Robust control has been successful in enabling flight stability and performance for UAVs. This paper presents a simple explainable robust control design for UAV platforms with non-minimum phase (NMP) zero characteristics in their model. The paper contributes to economic (simple) robust control design by addressing the NMP model’s characteristics via Internal Model Control (IMC) and its impact on the UAV pitch response performance. The proposed design is compared with a Parallel Feedback Control Design (PFCD) scheme for the same vehicle platform, for fair comparison. Simulation results illustrate the achievement of the proposed control designs for the UAV platform; only the pitch control is addressed. A by-product of this work is the interpretation of different ways of manipulating the non-minimum phase plant model, so-called ‘modelling for control’, to enable the simple controller design. The work in this paper underpins the simplicity and robustness of the IMC technique for the NMP UAV platform, which further supports the explainability of the control structure relative to performance.

Evaluation of a stakeholder advisory board for an adolescent mental health randomized clinical trial

IntroductionCommunity engagement in research is widely accepted as best practice, despite gaps in existing frameworks to evaluate its process, context, and impact on research. The Screening in High Schools to Identify, Evaluate, and Lower Depression (SHIELD) study evaluated the use of a school-based major depressive disorder screening tool in the identification of symptoms and treatment initiation among adolescents, and was developed, implemented, and disseminated in partnership with a Stakeholder Advisory Board (SAB). We summarize outcomes of the evaluation strategy applied through our partnership with the SAB and explore gaps in the available engagement evaluation tools for mixed stakeholder populations including youth.MethodsSHIELD study SAB members (n = 13; adolescents, parents, mental health and primary care providers, and professionals from education and mental health organizations) advised on study design, implementation, and dissemination over a three-year period. Both SAB members and study team members (i.e., clinician researchers, project managers) were invited to quantitatively and qualitatively evaluate stakeholder engagement after each project year. At the conclusion of the study, SAB members and study team members were asked to evaluate the application of engagement principles in overall stakeholder engagement across the study period, using portions of the Research Engagement Survey Tool (REST).ResultsSAB members and study team members responded similarly when evaluating engagement process (i.e., valued on team, voice represented); means ranged from 3.9 to 4.8 out of 5 points across all three project years. Reported engagement within study-specific engagement activities (i.e., meetings, study newsletter) varied from year to year, with some discrepancy between SAB member and study team evaluations. Using REST, SAB members reported the alignment of their experience with key engagement principles the same or higher than study team members. Qualitative feedback at the conclusion of the study generally matched quantitative measures; adolescent SAB members, however, reported disengagement from stakeholder activities that was not accurately or effectively captured in evaluation strategies employed across the study period.ConclusionsChallenges exist in effectively engaging stakeholders and evaluating their engagement, particularly among heterogenous groups that include youth. Evaluation gaps should be addressed through the development of validated instruments that quantify the process, context, and impact of stakeholder engagement on study outcomes. Consideration should be given to collecting parallel feedback from stakeholders and study team members to fully understand the application and execution of engagement strategy.

Spatial sigma-delta modulation for coarsely quantized linear, circular, and spherical arrays

Quantization noise shaping, also known as sigma-delta modulation, is widely used in analog-to-digital converters. Such converters oversample a signal in time, quantize it to one or a few bits of precision, and then use analog feedback to shape quantization noise outside the band of interest, producing a high-precision output. Similarly, if a sensor array is spatially oversampled so that its elements are much less than one-half wavelength apart, then quantization noise can be propagated between channels to shape its spatial distribution. A beamformer acts as a spatial filter, removing shaped quantization noise to produce a high-precision output even with coarsely quantized sensors. Spatial sigma-delta modulation has been explored primarily for radio-frequency applications using linear arrays. In this presentation, we apply spatial noise shaping to dense acoustic sensor arrays, including circular and spherical arrays. For immersive audio applications, we demonstrate how noise-shaping feedback can be used to push quantization noise into higher-order Ambisonic modes.

Steep resonance of parametrically excited active MEMS cantilevers for dynamic mode in Atomic Force Microscopy

AbstractOngoing developments in nanotechnology demand higher spatial resolution and thus, higher amplitude sensitivity in Atomic Force Microscopy (AFM). In this work, active cantilevers with integrated sensor and actuator systems are parametrically excited using a novel, analog feedback circuit. With that it is possible to adapt the strength and sign of a cubic nonlinearity which provides a bound to the amplitudes in resonance operation . The system response shows steeper resonance curves and therefore higher amplitude sensitivities compared to forced excited cantilevers. Theoretical findings are validated experimentally.

Focus on test, measurement, quantum metrology, and analytical equipment

Focus on test, measurement, quantum metrology, and analytical equipment

Компьютерный символьный анализ и исследование сигнальных характеристик СВЧ-интегрального трансимпедансного усилителя на КМОП-транзисторах

A technique is proposed for investigating and designing microwave transimpedance amplifiers (TIAs) based on the joint use of computer symbolic analysis and CMOS-transistors' linear equivalent circuits (ECs). The technique makes it possible to analyze the influence of various schematic parameters on TIA performances using automatically generated analytical expressions as well as to obtain recommendations for amplifier design. The investigation of the influence of devices' EC elements helps to choose CMOS-transistors' constructions and sizes when designing integrated TIAs. The approach proposed is applied to the input stage of microwave common source-common drain TIA with parallel feedback. The analysis of dependences of the main TIA characteristics (transimpedance, group delay, and input/output impedances) on circuit elements and transistor parameters is performed. Also, the amplifier stability is investigated. It is shown that, in contrast to the commonly used TIA analysis based on idealized models of active elements, the proposed approach provides sufficient accuracy in calculating amplifier performances up to the frequency of 30 GHz.