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This paper describes an energy-efficient pulse-amplitude modulation (PAM)-4 digital receiver based on sequence detection. The proposed scheme exploits the pre-cursor ISI in the channel to reconstruct a time series of a 5-bit sequence including future MSB. The future MSB information is used to detect and correct error in the current symbol detection with minimal power and latency overhead. This concept is demonstrated with prototype implemented in a 28-nm fully-depleted silicon-on-insulator CMOS using 18-data comparators. Consuming only 82 mW at 28 Gb/s, the receiver can compensate up to 27-dB channel loss with bit error rate (BER) lower than 10−8. With error correction, the receiver can achieve BER lower than 10−10. [ABSTRACT FROM AUTHOR]

As the number of antenna elements increases in multiple-input multiple-output (MIMO) systems, an efficient feedback and beamforming strategy becomes more important to achieve the desired bandwidth efficiency required by the next-generation wireless systems. The authors investigate the statistical characteristics of the MIMO channel generated by the threedimensional spatial channel model to recognise some of the limitations inherent in the existing codebooks adopted by the current third generation partnership project specifications. Such limitations include unnecessary co-phasing combinations for cross-polarised (X-pol) antenna arrays and, in particular, long-term codevector selections, which are not best suited to the channel distributions. In this study, the observed shortcomings are improved by proposing a new multi-rank codebook applicable to the X-pol array of NT = 8 antenna elements supporting up to the quadruple rank. The proposed beamforming codevectors are presented using variable parameters so that they can be adapted to changing channel characteristics. The efficiency of the proposed codebook is further improved by eliminating redundant co-phasing values. The performance of the proposed codebook is evaluated using the TR 36.873 urban macro environment and its effectiveness is demonstrated by quantifying its gain over the existing codebooks. [ABSTRACT FROM AUTHOR]

The output synchronisation of two deterministic Boolean networks coupled in the master-slave configuration is studied. First, under the algebraic framework of logical systems, an auxiliary system is constructed. Second, core input-state cycles are generalised and an algorithm is given to calculate these cycles. Third, based on core input-state cycles of the newly constructed auxiliary system, a necessary and sufficient existence condition is derived for a synchronising state feedback controller. Furthermore, a constructive method is provided to get feasible state feedback controllers when the existence condition obtained above is satisfied. Finally, an illustrative example is provided to verify the effectiveness and superiority of the presented results. [ABSTRACT FROM AUTHOR]

Abstract This paper introduces an energy-efficient dynamic voltage scaler (DVS) based on charge- pump and binary-weighted capacitor digital to analog converter (BWC-DAC). Conventional DVS architectures suffer from long settling-time beside the limitation of coarse voltage resolution, so we propose DVS architecture based on BWC-DAC architecture. It takes advantage of DAC's reconfigurable structure to provide an output voltage scaled with high resolution of V IN /2N for input voltage V IN and N configuration bits; and Nano-second transition time. However, DAC inherently suffers from low power efficiency because it requires frequent reset to maintain the output voltage. To overcome this issue, a high efficiency charge-pump is employed to restore the charges in DAC's capacitors without the need to reset which results in improved power efficiency. The proposed DVS with a 6-bit DAC and a feedback controlled circuit have been implemented using a 130 nm CMOS process. The measurement results show an accurate 64 voltage levels of the 6-bit DAC from 0 V to 1.476 V, when supplied by an input voltage of 1.5 V. We achieved a peak efficiency of 84% for load current ranging from 1 μA–14.76 μA. Furthermore, it provides an extremely short settling time that is as short as 83.6 Nano second. [ABSTRACT FROM AUTHOR]

Abstract This paper presents two low cost methodologies for fault diagnosis and localization in digitally calibrated pipelined analog-to-digital converters (ADCs). A simple design for test (DFT) is proposed to generate the required test stimulus and to provide the required controllability to collect the code error (fault) signature, which is represented by the difference between the transfer characteristics of the device under test and a golden one. In the first method, the features of the code error-signature are modeled to differentiate between the fault types and fault locations. The main focus of the first method is to detect and localize the capacitance mismatch, gain degradation, reference voltage error and offset voltage error of the device under test (DUT). The modeled features of the code error signatures are the number of zero crossing and the number of jumps in its derivative. The number of zero crossing is utilized to diagnose and localize the capacitance mismatch and gain degradation faults, while the number of jumps is used to detect and localize the reference voltage and offset voltage faults. The faults are determined stage-wise. The second method needs longer diagnosing time, but is able to diagnose the multi-source faults. To verify the proposed methodologies, a ten-stage digitally-calibrated pipelined ADC is behaviorally modeled and simulated using MATLAB. Faults having different type and values are intentionally injected in different stages of the design. The simulation results show the effectiveness of the proposed methods in detecting the faulty portion and fault type. Therefore, the faulty (or even the weak) portion(s) of the DUT can be identified. Which is useful feedback information for the designer to enhance the reliability of the subsequent design generation. [ABSTRACT FROM AUTHOR]

In connection with their earlier contributions, addressing the issue of systemic approach to implementing management audit with regard to small and medium-sized enterprises, the authors intend to further pursue their effort and interest in this specific area of research with the following paper. Its main objectives are to introduce own comprehensive concept, which involves the use of a systemic approach and is expressed in the form of a specific model of "Systemic approach to management audit", and to propose both standardized and purposeful procedures related to such audit. In order to develop the concept, a questionnaire survey was conducted among a number of managers of small and medium-sized enterprises in the Czech Republic, along with structured interviews with auditors carrying out management audits in their professional practice as well. Based on their research, the authors found that the examined enterprises tend to perform management audits only on rare occasions and without using any systemic approach or particular procedures. This is mainly due to an absence of time schedules or lists of individual activities that are required in the audits according to a precisely and previously specified order, as suggested in this paper. [ABSTRACT FROM AUTHOR]

Fibrin promotes wound healing by serving as provisional extracellular matrix for fibroblasts that realign and degrade fibrin fibers, and sense and respond to surrounding substrate in a mechanical-feedback loop. We aimed to study mechanical adaptation of fibrin networks due to cell-generated forces at the micron-scale. Fibroblasts were elongated-shaped in networks with ≤ 2 mg/ml fibrinogen, or cobblestone-shaped with 3 mg/ml fibrinogen at 24 h. At frequencies f < 102 Hz, G′ of fibroblast-seeded fibrin networks with ≥ 1 mg/ml fibrinogen increased compared to that of fibrin networks. At frequencies f > 103 Hz, G″ of fibrin networks decreased with increasing concentration following the power-law in frequency with exponents ranging from 0.75 ± 0.03 to 0.43 ± 0.03 at 3 h, and of fibroblast-seeded fibrin networks with exponents ranging from 0.56 ± 0.08 to 0.28 ± 0.06. In conclusion, fibroblasts actively contributed to a change in viscoelastic properties of fibrin networks at the micron-scale, suggesting that the cells and fibrin network mechanically interact. This provides better understanding of, e.g., cellular migration in wound healing.Graphical abstract [ABSTRACT FROM AUTHOR]

Pointing gestures are our natural way of referencing distant objects and thus widely used in HCI for controlling devices. Due to current pointing models’ inherent inaccuracies, most of the systems using pointing gestures so far rely on visual feedback showing users where they point at. However, in many environments, e.g., smart homes, it is rarely possible to display cursors since most devices do not contain a display. Therefore, we raise the question of how to facilitate accurate pointing-based interaction in a cursorless context. In this paper we present two user studies showing that previous cursorless techniques are rather inaccurate as they lack important considerations about users’ characteristics that would help in minimizing inaccuracy. We show that pointing accuracy could be significantly improved by acknowledging users’ handedness and ocular dominance. In a first user study (n= 33), we reveal the large effect of ocular dominance and handedness on human pointing behavior. Current ray-casting techniques neglect both ocular dominance and handedness as effects onto pointing behavior, precluding them from accurate cursorless selection. With a second user study (n= 25), we show that accounting for ocular dominance and handedness yields to significantly more accurate selections compared to two previously published ray-casting techniques. This speaks for the importance of considering users’ characteristics further to develop better selection techniques to foster more robust accurate selections. [ABSTRACT FROM AUTHOR]

Background Direct observation can be valuable for learners' skill development in graduate medical education, but it is done infrequently. Information on how to optimize trainee learning from, and best practices of, direct observation interventions in the ambulatory setting is limited. Objective We explored the impact of a focused outpatient direct observation and coaching intervention on internal medicine residents. Methods Using a behavior checklist based on tenets of clinical excellence, 2 faculty preceptors observed outpatient primary care visits with 96% (46 of 48) of the internal medicine residents in 2017. Residents self-assessed their performance after the visit using the same checklist. Next, a focused coaching feedback session, emphasizing reflection, was structured to highlight areas of discrepancy between resident self-assessment and coach observation (blind spots), and residents were asked to identify goals for practice improvement. Results Common blind spots in resident self-assessment related to collaborating with patients while using the electronic health record (48%, 21 of 44), hand washing (43%, 20 of 46), and asking thoughtful questions (40%, 18 of 45). At 1-month follow-up, 93% (43 of 46) of responding residents reported change in practice toward goals often or sometimes. All residents reported that the intervention felt comfortable, and 98% (45 of 46) noted that it helped them identify new behaviors to incorporate into clinical practice. Conclusions Structured episodes of direct observation and coaching in the outpatient setting, with a behavior checklist, appear acceptable and useful for internal medicine residents' learning and development. [ABSTRACT FROM AUTHOR]

An admissible function constructed by orthogonal polynomials is presented to investigate the vibration and active flutter control of Honeycomb sandwich plate with general elastic support in a supersonic airflow. The control strategies based on the displacement feedback and LQR method are applied by means of pasting the piezoelectric material on the surface of the plate structure. Employing the first-order piston theory to describe the aerodynamic loads, the governing equation of plate system with the piezoelectric actuator is established based on the Hamilton principle. The mode shapes are obtained using the admissible functions, which are a set of characteristic orthogonal polynomials generated directly by employing the Gram-Schmidt process, and the general elastic constraint is modeled using the artificial spring technology. The frequency and mode shape under different boundary are calculated by Rayleigh-Ritz method. The validity of the proposed approach is confirmed by comparing the results with those obtained from FEM and literatures. The phenomenon of mode jumping is observed with the increase of the aerodynamic pressure. The study of active control shows that, the increasement of displacement feedback gain improves the critical dynamic pressure. [ABSTRACT FROM AUTHOR]

Buffer-aided relays can improve the diversity of multi-hop networks, however, they increase packet delays. Thus, various delay-aware protocols have been developed, but without considering the transmission diversity. Moreover, most works adopt ideal assumptions, such as symmetric links, perfect channel state information (CSI), and error-free feedback channels. So, we propose a low-complexity (LoCo) link selection algorithm, herein called $\mathop {\mathrm {LoCo\!\!-\!\!Link}}$. The proposed algorithm may experience delays during CSI updates, and hence, by using outdated CSI its performance may deteriorate. To alleviate this issue, we next propose a distributed version of $\mathop {\mathrm {LoCo\!\!-\!\!Link}}$ ($\mathop {\mathrm {d\!\!-\!\!LoCo\!\!-\!\!Link}}$) dealing with outdated CSI. In both algorithms, the source performs broadcasting toward multiple relays; when the packets are transmitted by a relay to the destination, they are discarded from all other relays. This coordination relies on feedback channels. For non error-free feedback channels, we propose a scheme in which the relays listen to the transmission of the best relay and drop duplicate packets. Results show that $\mathop {\mathrm {LoCo\!\!-\!\!Link}}$ surpasses other algorithms, by decreasing the delay in asymmetric networks. Moreover, $\mathop {\mathrm {d\!\!-\!\!LoCo\!\!-\!\!Link}}$ avoids diversity losses due to outdated CSI, while the effect of non error-free feedback channels is mitigated by taking advantage of the inter-relay channels. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to analyze the link between manufacturing strategy formalization and manufacturing strategy implementation, considering the potential moderating role of shop-floor communication.Design/methodology/approach Multiple linear regression models considering main and interaction effects of strategy formulation and shop-floor communication on strategy implementation were performed using data from the fourth round of the international HPM Project. This includes plants with more than 100 employees in the automotive, machinery and electronics industries from 10 different countries. Unlike other research studies, this research takes into account plant management’s and plant supervisors’ perceptions.Findings The findings show that formal strategic planning positively influences manufacturing strategy implementation. Furthermore, both feedback and instructive communication practices moderate the manufacturing strategy process, resulting in successful manufacturing strategy embeddedness, and prompt adaptation to change.Practical implications This study provides a better understanding of the manufacturing strategy process for scholars and practitioners. In addition, the results suggest that the adoption of some shop-floor communication practices can benefit firms through the strengthening of strategy implementation.Originality/value This paper provides empirical evidence to the emerging discussion on whether formal strategic planning helps to adopt a strategy or on the contrary make decision making inflexible. [ABSTRACT FROM AUTHOR]

Vibration-based sensing modalities traditionally have relied upon monitoring small shifts in natural frequency in order to detect structural changes (such as those in mass or stiffness). In contrast, bifurcation-based sensing schemes rely on the detection of a qualitative change in the behavior of a system as a parameter is varied. This can produce easy-to-detect changes in response amplitude with high sensitivity to structural change, but requires resonant devices with specific dynamic behavior which is not always easily reproduced. Desirable behavior for such devices can be produced reliably via nonlinear feedback circuitry, but has in past efforts been largely limited to sub-MHz operation, partially due to the time delay limitations present in certain nonlinear feedback circuits, such as multipliers. This work demonstrates the design and implementation of a piecewise-linear resonator realized via diode- and integrated circuit-based feedback electronics and a quartz crystal resonator. The proposed system is fabricated and characterized, and the creation and selective placement of the bifurcation points of the overall electromechanical system is demonstrated by tuning the circuit gains. The demonstrated circuit operates at 16 MHz. Preliminary modeling and analysis is presented that qualitatively agrees with the experimentally-observed behavior. [ABSTRACT FROM AUTHOR]

An important property of negative feedback systems is the tendency to oscillate when feedback is delayed. This paper evaluated this phenomenon in a sustained phonation task, where subjects prolonged a vowel with 0–600 ms delays in auditory feedback. This resulted in a delay-dependent vocal wow: from 0.4 to 1 Hz fluctuations in fundamental frequency and intensity that increased in period and amplitude as the delay increased. A similar modulation in low-frequency oscillations was not observed in the first two formant frequencies, although some subjects did display increased variability. Results suggest that delayed auditory feedback enhances an existing periodic fluctuation in the voice, with a more complex, possibly indirect, influence on supraglottal articulation. These findings have important implications for understanding how speech may be affected by artificially applied or disease-based delays in sensory feedback. [ABSTRACT FROM AUTHOR]

We demonstrate the possibility of chaotic generation in a gyroklystron by introducing an external delayed feedback. It is shown that for the realization of “developed” chaos regimes with improved spectral uniformity, the region of the phase characteristic of a gyroklystron with rapid phase shift should be used. According to the time-domain-averaged model and direct particle-in-cell simulations with the parameters of the experimentally realized 93-GHz gyroklystron, the chaotic generation power can reach tens of kilowatts with a spectrum width of about 1 GHz. [ABSTRACT FROM AUTHOR]

Rare category identification is an important task in many application domains, ranging from network security, to financial fraud detection, to personalized medicine. These are all applications which require the discovery and characterization of sets of rare but structurally-similar data entities which are obscured within a larger but structurally different dataset. This paper introduces RCLens, a visual analytics system designed to support user-guided rare category exploration and identification. RCLens adopts a novel active learning-based algorithm to iteratively identify more accurate rare categories in response to user-provided feedback. The algorithm is tightly integrated with an interactive visualization-based interface which supports a novel and effective workflow for rare category identification. This paper (1) defines RCLens’ underlying active-learning algorithm; (2) describes the visualization and interaction designs, including a discussion of how the designs support user-guided rare category identification; and (3) presents results from an evaluation demonstrating RCLens’ ability to support the rare category identification process. [ABSTRACT FROM AUTHOR]

The proposed Compact Linear Collider (CLIC) uses a high intensity, low energy drive beam to produce the RF power needed to accelerate a lower intensity main beam with 100 MV/m gradient. This scheme puts stringent requirements on drive beam stability in terms of phase, energy and current. The consequent experimental work was carried out in CLIC Test Facility CTF3. In this paper, we present a novel analysis technique in accelerator physics to find beam drifts and their sources in the vast amount of the continuously gathered signals. The instability sources are identified and adequately mitigated either by hardware improvements or by implementation and commissioning of various feedbacks, mostly beam-based. The resulting drive beam stability is of 0.2°@ 3 GHz in phase, 0.08% in relative beam energy and about 0.2% beam current. Finally, we propose a stabilisation concept for CLIC to guarantee the main beam stability. [ABSTRACT FROM AUTHOR]

Process nonlinearities impose difficulties for model identification and control-system design. This paper presents a novel data-driven method for nonlinear control design based on the virtual-reference feedback tuning (VRFT) framework and block-oriented modeling of nonlinear systems. Control-design algorithms for Hammerstein, Wiener, and Hammerstein-Wiener systems were systematically developed. The proposed method can be applied to design a nonlinear controller for an unknown plant directly using one-shot input-output data generated by the plant. In the method, identifying a complete dynamic model of the nonlinear system is not necessary; and only the static non-linearity (or its inverse), represented by the B-spline series, requires estimation. Moreover, in the method, the non-linearity estimation and control design processes are performed simultaneously without the need for nonlinear optimization or iterative procedures. The effectiveness of the proposed control design method is demonstrated herein through several simulation examples, including two benchmark processes (namely, a distillation column and a pH-neutralization process). [ABSTRACT FROM AUTHOR]

We analyse the nonlinear behaviour of a third-order class-D amplifier, and demonstrate the remarkable effectiveness of the recently introduced ripple compensation (RC) technique in reducing the audio distortion of the device. The amplifier converts an input audio signal to a high-frequency train of rectangular pulses, whose widths are modulated according to the input signal (pulse-width modulation) and employs negative feedback. After determining the steady-state operating point for constant input and calculating its stability, we derive a small-signal model (SSM), which yields in closed form the transfer function relating (infinitesimal) input and output disturbances. This SSM shows how the RC technique is able to linearise the small-signal response of the device. We extend this SSM through a fully nonlinear perturbation calculation of the dynamics of the amplifier, based on the disparity in time scales between the pulse train and the audio signal. We obtain the nonlinear response of the amplifier to a general audio signal, avoiding the linearisation inherent in the SSM; we thereby more precisely quantify the reduction in distortion achieved through RC. Finally, simulations corroborate our theoretical predictions and illustrate the dramatic deterioration in performance that occurs when the amplifier is operated in an unstable regime. The perturbation calculation is rather general, and may be adapted to quantify the way in which other nonlinear negative-feedback pulse-modulated devices track a time-varying input signal that slowly modulates the system parameters. [ABSTRACT FROM AUTHOR]

We investigate the design of a prediction-based controller for a linear system subject to a time-varying input delay, not necessarily First-In/First-Out (FIFO). This means that the input signals can be reordered. The feedback law uses the current delay value in the prediction. It does not exactly compensate for the delay in the closed-loop dynamics but does not require to predict future delay values, contrary to the standard prediction technique. Modeling the input delay as a transport Partial Differential Equation, we prove asymptotic stabilization of the system state, that is, robust delay compensation, providing that the average ℒ 2 -norm of the delay time-derivative over some time-window is sufficiently small and that the average time between two discontinuities (average dwell time) is sufficiently large. [ABSTRACT FROM AUTHOR]

Digital pre-distortion (DPD) systems are employed to reduce intermodulation at the output of intrinsic non-linear RF power amplifiers. Typical DPD algorithms use time-domain linear regression to calculate the model coefficients used to compensate the amplifier’s distortion. This solution has high complexity and limited performance. This paper presents an innovative DPD system where the feedback information is a scalar measurement taken from the feedback signal. Different feedback information can be obtained from the distorted signal, e.g., the adjacent channel leakage rejection or the spectral mask margin. The DPD model coefficients estimation becomes a generic numerical optimization problem and is conducted iteratively in a coefficient-by-coefficient basis. A new coefficient orthogonalization algorithm removes the interaction between orders, resulting in a faster convergence time and lower output power variation across the iterations. The numerical optimization problem is simplified, since the nonlinear model becomes orthogonal in the intermodulation domain, i.e., the adjustment of given coefficient does not affect the others. Simulations and experimental results show that the proposed algorithm can effectively and efficiently compensate the nonlinear distortion and reduce the spectral regrowth. [ABSTRACT FROM AUTHOR]

The limited literature on online child grooming has focused mainly on studying the characteristics of perpetrators and victims that facilitate the sexual abuse of minors. Little attention has been given to the perceptions of the perpetrators about the abuse process and the strategies used to sustain it over time. In the present study, after identifying a sample of 12 men convicted of online grooming, we used qualitative grounded theory through in-depth interviews and comparisons with the proven facts of their convictions. The results show how aggressors actively study the structural environment, the needs and vulnerabilities of the minors). In this way, the aggressors adapt by using most effective strategies of persuasion at all times, so that the child feels like an active part of the plot. This allows the aggressors to have sexual interactions with minors either online or offline and in a sporadic or sustained manner. This process is maintained with some distorted perceptions about minors and the abuse process, which seem to feed back to the beginning of the cycle with other potential victims. The interaction between the persuasive processes and the distorted perceptions of the aggressor leads to a potential work focus for treatment as well as detection and prevention. Trying to visualize the complexity of the phenomenon could also help researchers to understand processes from this approach that may be applied with other types of vulnerable populations. [ABSTRACT FROM AUTHOR]

To tune the noise amplification in the feedback system caused by the waterbed effect effectively, an adaptive algorithm is proposed in this paper by replacing the scalar leaky factor of the leaky FxLMS algorithm with a real symmetric Toeplitz matrix. The elements in the matrix are calculated explicitly according to the noise amplification constraints, which are defined based on a simple but efficient method. Simulations in an ANC headphone application demonstrate that the proposed algorithm can adjust the frequency band of noise amplification more effectively than the FxLMS algorithm and the leaky FxLMS algorithm. [ABSTRACT FROM AUTHOR]

Negative feedback is a powerful approach capable of improving several aspects of a system. In linear electronics, it has been critical for allowing device invariance. Negative feedback is also known to enhance linearity in amplification, which is one of the most important foundations of linear electronics. At the same time, thousands of transistors types have been made available, suggesting that these devices, in addition to their assumed variability of parameters, have distinguishing properties. The current work reports a systematic approach to quantifying the potential of negative feedback, with respect to bipolar transistors, as a means of providing device invariance and linearity. Several approaches, including concepts and methods from signal processing, multivariate statistics and complex systems, are applied at the theoretical as well as experimental levels, and a number of interesting results are obtained. For instance, it has been verified that transistor types have well-defined characteristics which clearly segregate them into groups. The addition of feedback at moderate and intense levels promoted uniformization of the properties of these transistors when used in a class A common emitter configuration. However, such effect occurred with different efficiencies regarding the considered device features, and even intense feedback was unable to completely eliminate device dependence. This indicates that it would be interesting to consider the device properties in linear design even when negative feedback is applied. We also verified that the linearization induced in the considered experiments is relatively modest, with effects that depend on type of transfer function of the original devices. [ABSTRACT FROM AUTHOR]

Due to the growing of electrical energy demand, wind energy is receiving much interest all over the world. This paper presents a new technique using fuzzy genetic algorithm, and ANFIS of the Optimization PI controller systems using different artificial Intelligent techniques is also included in this paper. The model using P&Q method and FB method is implemented in MATLAB/SIMULINK. Simulation results show the feasibility and robustness of the new proposed techniques. [ABSTRACT FROM AUTHOR]

Two-stage beamforming is a transmit strategy that uses two types of beamformers to reduce the feedback overhead of frequency-division-duplexing massive multiple-input multiple-output systems that are spatially correlated. In this paper, we present large system analysis of two-stage beamforming when a transmitter has limited channel information from feedback and when regularized-zero-forcing (RZF) is used as a second-stage beamformer. We consider two random-vector-quantization-based feedback schemes that can be respectively applied when users have perfect channel information or perfect effective channel information. For each feedback method, we analyze both expected signal-to-interference-plus-noise ratio (SINR) and expected rate loss and then characterize their bounds as a function of the number of feedback bits. From the characterization, we reveal that the sum rate of two-stage beamforming is very sensitive to the regularization parameter of RZF, especially when the number of feedback bits is limited. Motivated by this, we derive the optimal regularization parameter that maximizes the SINR of two-stage beamforming with limited feedback. Using simulations, we verify the tightness of the characterized bounds and quantify how the use of the optimal regularization parameter improves the sum rate of two-stage beamforming. [ABSTRACT FROM AUTHOR]

This paper proposes a combination of composite nonlinear feedback and integral sliding mode techniques for fast and accurate chaos synchronization of uncertain chaotic systems with Lipschitz nonlinear functions, time-varying delays and disturbances. The composite nonlinear feedback method allows accurate following of the master chaotic system and the integral sliding mode control provides invariance property which rejects the perturbations and preserves the stability of the closed-loop system. Based on the Lyapunov- Krasovskii stability theory and linear matrix inequalities, a novel sufficient condition is offered for the chaos synchronization of uncertain chaotic systems. This method not only guarantees the robustness against perturbations and time-delays, but also eliminates reaching phase and avoids chattering problem. Simulation results demonstrate that the suggested procedure leads to a great control performance. [ABSTRACT FROM AUTHOR]

This paper proposes a high performance tunable Voltage Differencing Inverting Buffered Amplifier (VDIBA) where transconductance of VDIBA is enhanced by using programmable positive feedback technique and bandwidth is enhanced by using resistive compensation technique. The enhanced performance of proposed VDIBA is demonstrated by presenting detailed frequency analysis. Furthermore, it is verified that transconductance of proposed VDIBA can be enhanced up to 10.6 mS at tuning current (Ic) of 100 µA. Moreover, resistive compensation technique enhance bandwidth of propose circuit up to 263 MHz. To illustrate the effectiveness of proposed circuit, voltage mode universal biquad filter is designed as an application example. The pole frequency of proposed filter is tunable in range of 10.5-83.4 MHz. The proposed VDIBA and its filter applications are designed and simulated using TSMC 0.18 µm CMOS technology in Cadence virtuoso schematic composer at ± 0.6 V supply voltage. [ABSTRACT FROM AUTHOR]

Summary: It is well known in the literature that delay‐adaptive control schemes for general linear systems with input delay, induced from predictor feedback, typically incorporate distributed terms in both the control law and the update law for the delay estimator, leading to the infinite‐dimension characteristic of the schemes. Furthermore, when the full actuator state is not employed, only local regulation has been achieved in the sense that the initial state has to be sufficiently small and, at the same time, the initial guess of the delay has to be sufficiently close to its actual value. In this paper, by restricting our attention to systems without exponentially unstable poles, we avoid implementational issues arising from typical infinite‐dimensional control schemes by developing a finite‐dimensional scheme inspired by the truncated predictor feedback (TPF) design technique. Our scheme achieves global regulation as long as a sufficiently small neighborhood of the actual delay is identified. An adaptation‐free version of the robust TPF, which is inferred from the delay‐adaptive control scheme, is also included to reveal a second level of robustness to the uncertainty in the value of the delay that appears in the state transition matrix of the TPF. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the impact of source correlation on the diversity and coding gains of a retransmission system, where we aim to recover $M$ erroneously received packets only by transmitting one helper packet utilizing the source correlation among the packets. This system is referred to as $M$-in-1 helper transmission. The helper packet is constructed simply by taking binary exclusive-OR of the $M$ erroneously received information packets, notified via the feedback channel. To identify the tradeoff between source correlation and performance gain due to coding and diversity, we start our investigation with in-depth analyses on rate regions and outage probabilities with $M=\lbrace 2, 3\rbrace$. We also evaluate the influence of unequal power and/or redundancy allocations between the helper and information packets. Finally, we provide the analytical results on achievable diversity order with arbitrary integer values of $M$. It is shown that $M$-in-1 helper transmission can always achieve $M$th-order diversity. Furthermore, $(M+1)$th-order diversity can be achieved with $M$ being odd when the source correlation is very high; however, it cannot be achieved with $M$ being even. [ABSTRACT FROM PUBLISHER]

A nonlinear damping controller using partial feedback linearization (PFL) technique is designed with an aim to mitigate subsynchronous resonance (SSR) in series-compensated doubly-fed induction generator (DFIG)-based wind farms, which is integrated to simplified Nordic power system. The controller using PFL technique is implementable into a partially linearized form of a system with DFIG wind farm that results in reduced system order and small computational burden. The derivation of control law does not also demand thorough knowledge of nonlinear and ambiguous system dynamics. The proposed controller design approach has four distinguished steps: 1) scrutinizing partial linearizability, 2) performing partial linearization, 3) assessing stability of internal system dynamics, and 4) obtaining control laws. Small-signal stability analysis is performed that includes electrical damping analysis and eigenvalue analysis. The controller is found to demonstrate a superior performance in SSR mitigation. Time-series simulation is carried out to confirm the veracity of the outcomes obtained from the small-signal stability analysis. [ABSTRACT FROM PUBLISHER]

Background: Out-of-hospital cardiac arrest is common in public locations, including public transportation sites. Feedback devices are increasingly being used to improve chest-compression quality. However, their performance during public transportation has not been studied yet.Objective: To test two CPR feedback devices representative of the current technologies (accelerometer and electromag- netic-field) in a long-distance train.Methods: Volunteers applied compressions on a manikin during the train route using both feedback devices. Depth and rate measurements computed by the devices were compared to the gold-standard values.Results: Sixty-four 4-min records were acquired. The accelerometer-based device provided visual help in all experiments. Median absolute errors in depth and rate were 2.4 mm and 1.3 compressions per minute (cpm) during conventional speed, and 2.5 mm and 1.2 cpm during high speed. The electromagnetic-field-based device never provided CPR feedback; alert messages were shown instead. However, measurements were stored in its internal memory. Absolute errors for depth and rate were 2.6 mm and 0.7 cpm during conventional speed, and 2.6 mm and 0.7 cpm during high speed.Conclusions: Both devices were accurate despite the accelerations and the electromagnetic interferences induced by the train. However, the electromagnetic-field-based device would require modifications to avoid excessive alerts impeding feedback. [ABSTRACT FROM AUTHOR]

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This paper proposes a new set-point control method for a musculoskeletal arm by combining muscular internal force feedforward control with feedback control including a large time delay. The proposed method accomplishes robust and rapid positioning with a relatively small muscular force. In the positioning by the muscular internal force feedforward controller, a large muscular force is required to achieve good performance. On the other hand, in the positioning by the feedback controller including the large time delay, the system can easily fall into an unstable state. A simple linear combination of these two controllers makes it possible to improve the control performance and to overcome the drawbacks of each controller in a complementary manner. First, a two-link six-muscle arm model is considered as a musculoskeletal system in this study. Second, the new set-point control method, which consists of the feedforward control signal and the feedback control signal including the time delay, is designed. Third, the stability of the proposed method is investigated using the Lyapunov-Razumikhin method. Finally, the results of numerical simulations and experiments are presented to demonstrate the advantages of the proposed method. [ABSTRACT FROM AUTHOR]

We examined how the provision of feedback affected two separate effects of retrieval practice: strengthening of practiced information and forgetting of related, unpracticed information. Feedback substantially increased recall of retrieval-practiced items. This unsurprising result shows once again that restudy opportunities boost the benefits of testing. In contrast, retrieval-induced forgetting was unaffected by the manipulation and occurred in equal size with or without feedback. These findings demonstrate strength independence of retrieval-induced forgetting and thus support a theoretical account assuming that an inhibitory mechanism causes retrieval-induced forgetting. According to this theory, inhibition resolves competition that arises during retrieval attempts but is unrelated to the consequences of retrieval practice concerning practiced items. The present results match these assumptions and contradict the theoretical alternative that blocking by strengthened information might explain retrieval-induced forgetting. We discuss our findings against the background of previous studies. [ABSTRACT FROM AUTHOR]

To cope with the interference problem in three-cell wireless relay systems, this paper proposes two schemes that perform interference suppression and multiuser detection. The proposed schemes do not require channel state information (CSI) feedback, and their computational complexity is much less than that of the maximum likelihood detection (MLD), which is considered in the optimal detection scheme. Of the two proposed schemes, the minimum mean-square error (MMSE)-based scheme estimates the weight coefficients for the interference suppression under the MMSE criterion. The other proposed scheme, the recursive least squares (RLS)-based scheme, directly estimates the weight coefficients using the RLS algorithm. The RLS-based scheme only requires two preamble sequences, whereas both the MMSE-based schemes and the MLD require the knowledge of all the three preamble sequences. Therefore, the RLS-based scheme can be considered more feasible. Moreover, computer simulations results and theoretical average bit error rate (BER) upper bounds of orthogonal frequency-division multiplexing transmission under three-cell and frequency-selective fading conditions were provided. It was observed that simulation results are consistent with theoretical upper bounds and that the RLS-based scheme achieves a BER performance that is identical to that of the MMSE-based scheme with perfect CSI while requiring much less computational complexity than the MLD. [ABSTRACT FROM AUTHOR]

Discrete memoryless multicast network (DM-MN) is considered in this paper. We analyze the lower bounds of noisy network coding (NNC) and distributed decode-forward (DDF) for DM-MN, and show that both NNC and DDF ignore the channel output observed at the transmitter. Motivated by this observation, new coding schemes are proposed to improve NNC and DDF by exploiting the transmitter’s observation and applying hybrid relaying strategies. We first study a special case when the transmitter’s observation is rate-limited feedback signals, and propose a scheme that strictly improves NNC when feedback rates are sufficiently large. For the relay channel with perfect relay-transmitter feedback, our achievable rate reduces to Gabbai and Bross’s rate, which is strictly larger than NNC, DDF, and all known lower bounds on the achievable rates proposed for the setup without feedback. In our scheme, both relays and receivers compress their received signals like NNC, and the relays decode independent “common” and “private” parts of the source message. The generated compression indices are sent to the transmitter through feedback, from which the transmitter reconstructs the receivers’ and relays’ inputs and can thus cooperate with the receivers and relays. We then extend our idea to DM-MN without feedback. For this case, although the transmitter observes channel output, both NNC and DDF simply ignore it, while our new scheme has the transmitter utilize its channel output to decode a set of relays’ and receivers’ compression indices, which achieves some cooperation levels between the transmitter and the receivers and relays. An enhanced relay channel is introduced to show that our scheme strictly outperforms NNC and DDF. [ABSTRACT FROM AUTHOR]

We study the sum degrees of freedom (DoF) of the bursty MIMO X channel without feedback, where the four transmitter-receiver links are intermittently ON and OFF, controlled by four Bernoulli random sequences which may be arbitrarily correlated, subject to a symmetry assumption: The two direct-links have the same level of burstiness, modeled by \mathrm Ber(pd) , and so do the cross-links, modeled by \mathrm Ber(pc) . The sum DoF is fully characterized in the regime where (pc/{pd}) is small, i.e., below a certain threshold, and is partially characterized in the other regime where (pc/{pd}) is above the threshold. The achievability is proved with a combination of Han–Kobayashi strategy and interference alignment, which can achieve strictly higher DoF than interference alignment alone. The converse proof employs a channel-state-sequence pairing technique. We highlight that burstiness of the channel disrupts the network topology, turning the MIMO X channel into a network with time-varying topology. This fundamental difference has striking ramifications. In particular, various interference alignment schemes that achieve the DoF of non-bursty MIMO X channels become suboptimal on the bursty channels. The reciprocity between the forward and the reverse links is lost, and the sum DoF does not saturate when the ratio between the transmitter and the receiver antennas exceeds (2/3). [ABSTRACT FROM AUTHOR]

We characterize the fundamental limits of transmission of information over a Gaussian multiple access channel (MAC) with the use of variable-length feedback codes and under a non-vanishing error probability formalism. We develop new achievability and converse techniques to handle the continuous nature of the channel and the presence of expected power constraints. We establish the $\varepsilon $ -capacity regions and bounds on the second-order asymptotics of the Gaussian MAC with variable-length feedback with termination codes and stop-feedback codes. We show that the former outperforms the latter significantly. Due to the multi-terminal nature of the channel model, we leverage tools from renewal theory developed by Lai and Siegmund to bound the asymptotic behavior of the maximum of a finite number of stopping times. [ABSTRACT FROM AUTHOR]

Consider a target moving at a constant velocity on a unit-circumference circle, starting at an arbitrary location. To acquire the target, any region of the circle can be probed to obtain a noisy measurement of the target’s presence, where the noise level increases with the size of the probed region. We are interested in the expected time required to find the target to within some given resolution and error probability. For a known velocity and a given reliability, we provide an asymptotical characterization of the optimal tradeoff between time and resolution. Considering an asymptotically diminishing error probability, we derive the maximal targeting rate, and show that in contrast to the well-studied case of constant measurement noise, measurement dependent noise incurs a multiplicative gap in the maximal targeting rate between adaptive and non-adaptive search strategies. Moreover, for all rates below this maximal rate, our adaptive strategy attains the optimal rate-reliability tradeoff. We further show that accounting for a target moving at an unknown fixed velocity, the optimal non-adaptive search strategy incurs a factor of at least two in the maximal targeting rate. [ABSTRACT FROM AUTHOR]

This study tests a grounded theory that provides a pedagogical framework for instructors interested in facilitating student team project delivery. Since the theoretical model was developed with observations from the lived experience of virtual student teams delivering projects in an online course, this study advances previous findings by testing the model with feedback from a comparable on-campus course. The new findings affirm the model also applies for campus-based courses. In addition, findings about students' application of online collaboration tools, the role of culture and language in team productivity and the effectiveness of student peer evaluations in fostering accountability are also discussed. Finally, survey revisions for improved insights about team crises and team trust are suggested for a planned second study. [ABSTRACT FROM AUTHOR]

System dynamics (SD) and discrete event simulation (DES) follow two quite different modeling philosophies and can bring very different but, nevertheless, complimentary insights in understanding the same ‘real world’ problem. Thus, learning SD and DES approaches requires students to absorb different modeling philosophies usually through specific and distinct courses. We run a course where we teach model conceptualization for SD and DES in parallel and, then, the technical training on SD and DES software in sequential order. The ability of students to assimilate, and then put into practice both modeling approaches, was evaluated using simulation-based problems. While we found evidence that students can master both simulation techniques, we observed that they were better able to develop skills at representing the tangible characteristics of systems, the realm of DES, rather than conceptualizing the intangible properties of systems such as feedback processes, the realm of SD. Suggestions and reflections on teaching both simulation methods together are proposed. [ABSTRACT FROM PUBLISHER]

In this letter, we propose a sparsity promoting feedback acquisition and reconstruction scheme for sensing, encoding and subsequent reconstruction of spectrally sparse signals. In the proposed scheme, the spectral components are estimated utilizing a sparsity-promoting, sliding-window algorithm in a feedback loop. Utilizing the estimated spectral components, a level signal is predicted and sign measurements of the prediction error are acquired. The sparsity promoting algorithm can then estimate the spectral components iteratively from the sign measurements. Unlike many batch-based compressive sensing algorithms, our proposed algorithm gradually estimates and follows slow changes in the sparse components utilizing a sliding-window technique. We also consider the scenario in which possible flipping errors in the sign bits propagate along iterations (due to the feedback loop) during reconstruction. We propose an iterative error correction algorithm to cope with this error propagation phenomenon considering a binary-sparse occurrence model on the error sequence. Simulation results show effective performance of the proposed scheme in comparison with the literature. [ABSTRACT FROM AUTHOR]

This paper presents a low voltage variable gain low noise amplifier (VG-LNA) for ultra-wideband (UWB) applications. The design consists of a folded cascode input stage and a common source second stage while a noise cancellation technique is employed to reduce the noise contribution of the input stage. The gain is continuously controlled by a feedback loop at the second stage. The proposed VG-LNA is designed and simulated using RF-TSMC 0.18 µm CMOS technology. Simulation results show a maximum flat power gain (S21) of 14 dB with a noise figure (NF) lower than 4 dB and an input and output impedance matching (S11 and S22) less than -10 dB over 3 to 5 GHz bandwidth. Its power consumption is 8 mW with low power supply of 0.75 V. The power gain ranges from -4 to 14 dB at the center frequency of 4 GHz. [ABSTRACT FROM AUTHOR]

This paper presents a two-phase process consisting of advantage distillation (AD) and information reconciliation for achieving secret sharing over a wiretap channel. By using the feedback bits from the legitimate receiver to transmitter, we propose a novel AD scheme for multiple-input multiple-output (MIMO) wiretap (MIMO-WT) channels. We first generalize the extended orthogonal space-time block codes (EO-STBCs). Then, based on the generalized EO-STBCs (GEO-STBCs) and channel state information (CSI), the feedback bits transmitted from the legitimate receiver to the transmitter are generated to increase the signal-to-noise ratio (SNR) gap between the legitimate receiver and the eavesdropper. Simulation results show that the feedback performance gain of the proposed AD scheme increases rapidly with the number of transmit antennas and the value of SNR. A bit error rate (BER) performance gain up to 5.5 dB is obtained by the legitimate receiver over the eavesdropper at the BER of 10^-5. Moreover, it is also shown that the secrecy capacity of two-way MIMO-WT channels with feedback grows rapidly in low SNR regime and grows slowly in high SNR regime. [ABSTRACT FROM AUTHOR]

This paper presents an ultra-low-power, bulk-driven, source-degenerated fully differential transconductor (FD-OTA), operating in subthreshold region. The source-degeneration (SD) and bulk-drive ensure linearity and rail-to-rail input swing. The flipped voltage follower and SD resistor perform V–I conversion in input core with power efficient class AB mode of operation. The reduction in open loop gain and gain bandwidth (GBW) of bulk-drive is compensated by applying partial positive feedback at diode connected MOSFET pair. The current gain from input core to output load side is set (1:1) in OTA1 and (1:4) in OTA2. The OTA2 offers increased transconductance and GBW whereas self-cascode load increases the output impedance and overall gain of the FD-OTAs. Both the input core and common source self-cascode load operate in class AB mode so these FD-OTAs provide enhanced slew rates. These OTAs have been employed to implement Biquadratic low-frequency Gm-C filter suitable for bio-signal applications. The proposed OTA2 has used dual supply voltage of ± 0.3 V and dissipates around 70 nW power and provides 62 dB FD-open loop gain with GBW of 7.73 kHz while driving the FD-load of 2 × 15 pF. The Cadence VIRTUOSO environment using UMC 0.18 µm CMOS process technology has been used to simulate the proposed circuit. The Simulation results verified fully differential total harmonic distortion of − 72 dB, for 1.2 Vp–p signal at 200 Hz frequency in unity gain configuration with resistive degeneration of 1 MΩ for OTA1. [ABSTRACT FROM AUTHOR]

This paper proposes a feedback time difference amplifier (FTDA) that achieves linear, controllable gain and changeable input range for different time difference gains. The proposed FTDA consists of two identical feedback output generators. The feedback output generator achieves a linear input–output transfer characteristic by employing two p-type keepers for time gain feedback control. Its validity was demonstrated using 0.13μm SiGe BiCMOS process. The power consumption is 91.54μW for the highest gain with input signals at 2MHz. The gain can be controlled from 25.06 to 734.9s/s within 40ps input time interval. [ABSTRACT FROM AUTHOR]

In adaptive feedback cancellation, the feedback path must bemodeled precisely using as few adaptive parameters as possible to reduce computational complexity and enable rapid convergence. To reduce the number of adaptive parameters, the feedback path is usually modeled with a transfer function composed of an invariant component and a variable component using all-pole, allzero, and pole-zero filters. These filters may be inefficient, requiring a large number of parameters for their specification, particularly in reverberant environments. In this letter, we present a weighted least-squares algorithm to precisely estimate the common poles of feedback paths, and we then model the invariant basis functions employing a Kautz filter. The Kautz filter is defined by a set of the fixed poles and a corresponding set of tap output weights. The fixed poles are associated with prominent peaks that are common to the measured feedback path frequency responses. The algorithm guarantees unconditionally the stability of the estimated poles of the inferred model. The experimental results using measured acoustic feedback paths from a two-microphone, behind-the-ear hearing aid show that the proposed method provides an accurate model of the feedback paths for a variety of acoustic environments that were not employed in estimating the common poles. [ABSTRACT FROM AUTHOR]

This study proposes a stationary coordinate system-based virtual-multilevel model predictive control strategy with error feedback for the control of the modular multilevel converter (MMC). In order to reduce the number of considered states for the ac-side current control, a cost function is established according to the mathematical model of the MMC in the two-phase stationary coordinate system. The selection of the output voltage levels is optimised with the introduction of the virtual-multilevel algorithm. By using real-time submodule (SM) capacitor voltages in current prediction, the circulating current control is combined with the SM capacitor voltage sorting to improve the control accuracy of the circulating current. This study also proposes an error feedback correction method to eliminate the steady-state error in current control and avoid parameter sensitivity of the control performance. The simulation results and experimental results from a down-scaled MMC prototype are provided to verify the validity and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]