Proper Feedback Research Articles

Revival of oscillation from mean-field-induced death: Theory and experiment.

The revival of oscillation and maintaining rhythmicity in a network of coupled oscillators offer an open challenge to researchers as the cessation of oscillation often leads to a fatal system degradation and an irrecoverable malfunctioning in many physical, biological, and physiological systems. Recently a general technique of restoration of rhythmicity in diffusively coupled networks of nonlinear oscillators has been proposed in Zou et al. [Nat. Commun. 6, 7709 (2015)], where it is shown that a proper feedback parameter that controls the rate of diffusion can effectively revive oscillation from an oscillation suppressed state. In this paper we show that the mean-field diffusive coupling, which can suppress oscillation even in a network of identical oscillators, can be modified in order to revoke the cessation of oscillation induced by it. Using a rigorous bifurcation analysis we show that, unlike other diffusive coupling schemes, here one has two control parameters, namely the density of the mean-field and the feedback parameter that can be controlled to revive oscillation from a death state. We demonstrate that an appropriate choice of density of the mean field is capable of inducing rhythmicity even in the presence of complete diffusion, which is a unique feature of this mean-field coupling that is not available in other coupling schemes. Finally, we report the experimental observation of revival of oscillation from the mean-field-induced oscillation suppression state that supports our theoretical results.

Optimal transient performance under output set‐point reset

SummaryThe purpose of this paper is to propose a new method for the optimization of the output transition in the case of set‐point reset for LTI, non‐minimum phase, possibly non‐hyperbolic plants. Assuming that the plant is stabilized by a proper feedback controller, the problem consists in finding a feedforward linear filter yielding a suitable reference trajectory for the closed‐loop system. The approach situates in the framework of model pseudo‐inversion because the external reference trajectory is computed starting from some desired features of the transient output between the two set points. A significant aspect of the new method is that the transition trajectory is not ‘ad hoc’ exactly prespecified by the designer. Rather, it is implicitly defined by the procedure for the minimization of a suitable multi‐objective quadratic cost functional. As no pre‐actuation is required, the method can be practically implemented on line and also works for the critical class of non‐hyperbolic systems. Copyright © 2015 John Wiley & Sons, Ltd.

Distilling the Wisdom of Crowds: Prediction Markets vs. Prediction Polls

We report the results of the first large-scale, long-term, experimental test between two crowdsourcing methods: prediction markets and prediction polls. More than 2,400 participants made forecasts on 261 events over two seasons of a geopolitical prediction tournament. Forecasters were randomly assigned to either prediction markets (continuous double auction markets) in which they were ranked based on earnings, or prediction polls in which they submitted probability judgments, independently or in teams, and were ranked based on Brier scores. In both seasons of the tournament, prices from the prediction market were more accurate than the simple mean of forecasts from prediction polls. However, team prediction polls outperformed prediction markets when forecasts were statistically aggregated using temporal decay, differential weighting based on past performance, and recalibration. The biggest advantage of prediction polls was at the beginning of long-duration questions. Results suggest that prediction polls with proper scoring feedback, collaboration features, and statistical aggregation are an attractive alternative to prediction markets for distilling the wisdom of crowds. This paper was accepted by Uri Gneezy, behavioral economics.

Redesigning incident reporting systems in the post-Mid-Staffordshire era.

Incident reporting systems are vital to safe health care. Existing systems should be made simpler and more accessible, proper feedback given to those who complete reports and lessons learned from investigations shared more widely. A major shift in culture is required so health-care professionals feel safe completing incident reports.

Anatomy of a negative feedback loop: the case of IκBα.

The magnitude, duration and oscillation of cellular signalling pathway responses are often limited by negative feedback loops, defined as an 'activator-induced inhibitor' regulatory motif. Within the NFκB signalling pathway, a key negative feedback regulator is IκBα. We show here that, contrary to current understanding, NFκB-inducible expression is not sufficient for providing effective negative feedback. We then employ computational simulations of NFκB signalling to identify IκBα molecular properties that are critical for proper negative feedback control and test the resulting predictions in biochemical and single-cell live-imaging studies. We identified nuclear import and nuclear export of IκBα and the IκBα-NFκB complex, as well as the free IκBα half-life, as key determinants of post-induction repression of NFκB and the potential for subsequent reactivation. Our work emphasizes that negative feedback is an emergent systems property determined by multiple molecular and biophysical properties in addition to the required 'activator-induced inhibitor' relationship.

Learning from Errors

“Errare humanum est”, a well known and widespread Latin proverb which states that: to err is human, and that people make mistakes all the time. However, what counts is that people must learn from mistakes. On these grounds Steve Jobs stated: “Sometimes when you innovate, you make mistakes. It is best to admit them quickly, and get on with improving your other innovations.” Similarly, in learning new language, learners make mistakes, thus it is important to accept them, learn from them, discover the reason why they make them, improve and move on. The significance of studying errors is described by Corder as: “There have always been two justifications proposed for the study of learners' errors: the pedagogical justification, namely that a good understanding of the nature of error is necessary before a systematic means of eradicating them could be found, and the theoretical justification, which claims that a study of learners' errors is part of the systematic study of the learners' language which is itself necessary to an understanding of the process of second language acquisition” (Corder, 1982; 1). Thus the importance and the aim of this paper is analyzing errors in the process of second language acquisition and the way we teachers can benefit from mistakes to help students improve themselves while giving the proper feedback.

Compatibility of global environmental assessment methods of buildings with an Egyptian energy code

Several environmental assessment methods of buildings had emerged over the world to set environmental classifications for buildings, such as the American method “Leadership in Energy and Environmental Design” (LEED) the most widespread one. Several countries decided to put their own assessment methods to catch up with the previous orientation, such as Egypt. The main goal of putting the Egyptian method was to impose the voluntary local energy efficiency codes. Through a local survey, it was clearly noted that many of the construction makers in Egypt do not even know the local method, and whom are interested in the environmental assessment of buildings seek to apply LEED rather than anything else. Therefore, several questions appear about the American method compatibility with the Egyptian energy codes – that contain the most exact characteristics and requirements and give the outmost credible energy efficiency results for buildings in Egypt-, and the possibility of finding another global method that gives closer results to those of the Egyptian codes, especially with the great variety of energy efficiency measurement approaches used among the different assessment methods. So, the researcher is trying to find the compatibility of using non-local assessment methods with the local energy efficiency codes. Thus, if the results are not compatible, the Egyptian government should take several steps to increase the local building sector awareness of the Egyptian method to benefit these codes, and it should begin to enforce it within the building permits after a proper guidance and feedback.

Thorough subcells diagnosis in a multi-junction solar cell via absolute electroluminescence-efficiency measurements.

World-wide studies on multi-junction (tandem) solar cells have led to record-breaking improvements in conversion efficiencies year after year. To obtain detailed and proper feedback for solar-cell design and fabrication, it is necessary to establish standard methods for diagnosing subcells in fabricated tandem devices. Here, we propose a potential standard method to quantify the detailed subcell properties of multi-junction solar cells based on absolute measurements of electroluminescence (EL) external quantum efficiency in addition to the conventional solar-cell external-quantum-efficiency measurements. We demonstrate that the absolute-EL-quantum-efficiency measurements provide I–V relations of individual subcells without the need for referencing measured I–V data, which is in stark contrast to previous works. Moreover, our measurements quantify the absolute rates of junction loss, non-radiative loss, radiative loss, and luminescence coupling in the subcells, which constitute the “balance sheets” of tandem solar cells.

Notified or missed cases? An assessment of successful linkage for referred tuberculosis patients in South India

Background and Objectives: Although tuberculosis (TB) is a notifi able disease in India, most of the cases of TB are either not recorded or reported. Among diagnosed cases, for improving reporting, proper feedback on referral outcome needs to be ensured to all health care providers who refer cases to the public health system. Materials and Methods: All the received feedbacks for TB patients referred for treatment from July 2013 to December 2013 were analyzed. Feedback reports including referral date, the age and sex of patients, type of disease, and date of treatment initiation were examined. Results: Of the total 1,259 referred TB patients during the study period, feedback was received for 54% of them. Only 42.3% (n = 532) of the referred patients were successfully linked at the treatment facility. Seven (0.6%) referred patients died before the initiation of treatment while 3.7% migrated, 2.4% gave the wrong address, 1.0% started private treatment, and 0.6% were nontraceable; in 3.2% cases only was the TB number given. Feedback was signifi cantly associated with sex, age group, type of treatment, disease type, and place of residence. Conclusion: The feedback received for referred patients was poor and for improving the care of TB patients, there is a need to strengthen the feedback mechanism in Revised National Tuberculosis Control Programme (RNTCP) for referred patients.

High speed bidirectional dual-channel chaos secure communication based on semiconductor ring lasers

Chaos is a fascinating phenomenon of nonlinear dynamical systems, and optical chaos communication has been one of potential frontier techniques to implement secure transmission of information. In this paper a novel high-speed bidirectional dual-channel chaos secure communication system is proposed based on semiconductor ring lasers (SRLs). In this system, the time delay signatures in chaotic output of clockwise (CW) and counterclockwise (CCW) patterns from a driving SRL (D-SRL) are firstly suppressed by using the double optical cross-feedback frame. Then, the chaotic output of D-SRL is injected into two response SRLs (R-SRLs) to drive the corresponding CW and CCW patterns of R-SRLs that are synchronized and bandwidth enhanced simultaneously. Thus, a bidirectional dual-channel chaos communication could be built based on chaotic synchronization of the two R-SRLs. We theoretically investigated the chaotic characteristics of a D-SRL under double optical cross-feedback and the chaotic synchronization features between R-SRL1 and R-SRL2 under different driving conditions. Results show that the time delay signatures of CW and CCW patterns of D-SRL could be effectively hidden under proper feedback conditions. The bandwidths of CW and CCW patterns of the D-SRL could be enhanced significantly. Furthermore, high-quality isochronous synchronization between R-SRL1 and R-SRL2 can be realized by choosing appropriate injection strength and detuning frequency in D-SRL and R-SRLs. Finally, the communication performances of bidirectional dual-channel chaos secure communication based on this proposed system are preliminarily examined and discussed, and the simulated results demonstrate that for 10 Gbit/s message, the Q factor of decoded message could be maintained above 6 after 10 kilometers distance transmission.

Influence of feedback strength on the characteristics of the random number sequence extracted from an external-cavity feedback semiconductor laser

Under proper feedback strength, an external-cavity feedback semiconductor laser can operate at a chaos state, and its chaotic output can be used as a physical entropy source to generate a physical random number sequence. In this paper, we focus on the influence of feedback strength on the randomness of the obtained binary code sequence. The simulation results show that with the increase of feedback strength, the time delay characteristic peak of the chaotic signal from an external-cavity feedback semiconductor laser first decreases and then increases gradually, meanwhile, the permutation entropy characteristic value of chaotic signal first increases and then decreases gradually, namely, there exists an optimized feedback strength for obtaining the chaotic signal with the weakest time delay signature and high complexity. The randomness of binary code sequences, generated by the chaotic signal from the external-cavity feedback semiconductor laser under different feedback strengths, is tested by NIST Special Publication 800-22, and the influence of feedback strength on the test results is also discussed.

English

CONTEXT: Pharmacology is one of the most fundamental subjects in the field of medicine and a good grasp of this subject is vital for any clinical practitioner. The teaching of pharmacology in medical and dental colleges of India has evolved from mere didactic lectures to audio-visual aid based lectures and computer based learning. Evolution of teaching methods is an on- going process and a docent needs proper feedback from the pupils regarding their opinion on what is satisfactory and what needs improvement. AIMS: By way of this survey-based study we aim to grasp the MBBS and BDS students' opinion regarding the teaching practices in pharmacology and changes recommended for the betterment of the same. METHODS AND MATERIALS: After obtaining due approval of the Institutional Ethics Committee, the study was conducted amongst 2nd year exam going MBBS and BDS students of M R Medical College and S Nijalingappa Dental College, Gulbarga, Karnataka in the Department of Pharmacology M R Medical College. An exhaustive questionnaire based survey was prepared of 17 questions with choices ranging from 3-8 different options. RESULTS AND CONCLUSION: The result of our study favours the need for pharmacology as a subject to be more clinically oriented as well as being technologically sound. The students overall have a positive outlook of pharmacology (53%) and consider lectures as the most appropriate and helpful teaching method (62%). Introduction of group discussion is one change that is warranted by students overwhelmingly (41%), followed by introduction of clinical pharmacology exercises (31%). A vast majority of the students (70%) found the lectures in pharmacology to be interesting and want them to be more clinically oriented. The importance of pharmacology in clinical decision making is well understood by the majority of students and they aim to act in that behest. Also, we find that computer based learning is a new and important tool coming up in the arsenal of the pharmacology teacher.

RISE-Based Precision Motion Control of DC Motors With Continuous Friction Compensation

Continuous friction compensation along with other modeling uncertainties is concerned in this paper, to result in a continuous control input, which is more suitable for controller implementation. To accomplish this control task, a practical method, named as robust integral of the sign of the error controller, is synthesized with a continuous differentiable friction model for high-accuracy motion control of a dc motor. To reduce the noise sensitivity and further improve the tracking accuracy, a desired compensation technique is employed in the proposed controller, in which the model compensation term depends on the reference trajectory only, and its global stability is guaranteed by a proper robust feedback law. Furthermore, the proposed controller theoretically guarantees an asymptotic output tracking performance even in the presence of modeling uncertainties, which is very important for high-accuracy control of motion systems. Comparative experimental results are obtained for the motion control of a dc motor drive system to verify the high-performance nature of the proposed control strategy.

Exploring Effective Communication in District Education Offices in South Africa

Managers at district education offices in South Africa should be able to apply a variety of communication skills effectively in a range of management contexts for these district offices to be successful. This paper reports on a theoretical investigation into effective communication strategies and dimensions, as well as an empirical study of the perceptions of managers and staff at an educational district office regarding the effectiveness of the communication channels and strategies, as well as of the barriers to effective communication. The findings suggest that district managers may need training specifically with regard to the role and importance of communication and that the dissemination of proper feedback should be a consistent practice. While professional communication depends on both task and interpersonal orientation for its success, it is recommended that the latter should receive the greater emphasis in a people-oriented and pedagogical institution such as an education district office. * Address for correspondence

Climate drift of AMOC, North Atlantic salinity and arctic sea ice in CFSv2 decadal predictions

There are potential advantages to extending operational seasonal forecast models to predict decadal variability but major efforts are required to assess the model fidelity for this task. In this study, we examine the North Atlantic climate simulated by the NCEP Climate Forecast System, version 2 (CFSv2), using a set of ensemble decadal hindcasts and several 30-year simulations initialized from realistic ocean–atmosphere states. It is found that a substantial climate drift occurs in the first few years of the CFSv2 hindcasts, which represents a major systematic bias and may seriously affect the model’s fidelity for decadal prediction. In particular, it is noted that a major reduction of the upper ocean salinity in the northern North Atlantic weakens the Atlantic meridional overturning circulation (AMOC) significantly. This freshening is likely caused by the excessive freshwater transport from the Arctic Ocean and weakened subtropical water transport by the North Atlantic Current. A potential source of the excessive freshwater is the quick melting of sea ice, which also causes unrealistically thin ice cover in the Arctic Ocean. Our sensitivity experiments with adjusted sea ice albedo parameters produce a sustainable ice cover with realistic thickness distribution. It also leads to a moderate increase of the AMOC strength. This study suggests that a realistic freshwater balance, including a proper sea ice feedback, is crucial for simulating the North Atlantic climate and its variability.

Improved control strategy with grid‐voltage feedforward for LCL‐filter‐based inverter connected to weak grid

In grid-connected LCL-filtered inverters, the dual-loop current control is widely used. The LCL resonance is highly damped by proper feedback of the capacitor current. To suppress low-frequency current harmonics, a grid-voltage feedforward is commonly used. However, the system performance with such control is declined when connecting to a weak grid. Phase and gain margins are largely reduced while the proportional feedforward is used. The margins get worse and instability is aroused if the derivative feedforward is further implemented. Besides, a negative impact on the rejection of grid-voltage-induced harmonics is produced. To improve the control performance in the weak grid case, an adaptive control has been proposed. Adopting the estimated grid impedance, the signal for the grid-voltage feedforward is modified and the controller is adjusted with an adaptive rule to maintain a good phase margin or a high bandwidth. Performances of the inverter with the typical and the proposed methods are compared. Simulation and experimental results have demonstrated that the grid-connected LCL-filtered inverter with the proposed method produced a high-quality current while large grid impedance existed.

A force controlled grinding-milling technique for quartz-glass micromachining

This paper presents a novel approach to the micromachining of quartz glass using an intellectualized grinding-milling technique to overcome the difficulties in machining hard-brittle materials. A bench-type linear 3-axis CNC machine tool providing grinding-milling at depths of several nanometers is constructed to realize ductile-regime material removal during quartz-glass milling. Finite element analysis (FEA) is conducted on the deformation and resonant frequency of the developed machine tool. A micro-tipped grinding-tool made of boron-doped polycrystalline composite diamond (BD-PCD) and designed with a double-negative back rake angle (DN-BRA) to create compressive stress grinding-milling is proposed and employed. To sense the force at which grinding-milling is conducted and provide real-time feedback on the milling tool's feed-rate, load-cells are devised on 3 axes. Using an appropriate grinding-milling technique in combination with proper feedback to control the machining feed-rate, quartz glass is machined layer-by-layer under a ductile regime. A miniature 3-step-shaped pyramid made of quartz glass of 0.3mm in height and of Ra0.66μm surface roughness with very little brittle fracturing is achieved. The optimum grinding depth, milling speed and corresponding grinding-milling force are 1μm, 50–70m/min, and 0.4N, respectively. A comprehensive examination of the quantitative and qualitative properties of the BD-PCD tool was undertaken. Experimental confirmation of the proposed approach is presented. Additionally, the following aspects are discussed in detail: the spark erosion rate of the machined diamond tool, milling feed-rate, grinding depth, graphitization of diamond, and tool wear.

Endogenous fields enhanced stochastic resonance in a randomly coupled neuronal network

Endogenous field, evoked by structured neuronal network activity in vivo, is correlated with many vital neuronal processes. In this paper, the effects of endogenous fields on stochastic resonance (SR) in a randomly connected neuronal network are investigated. The network consists of excitatory and inhibitory neurons and the axonal conduction delays between neurons are also considered. Numerical results elucidate that endogenous field feedback results in more rhythmic macroscope activation of the network for proper time delay and feedback coefficient. The response of the network to the weak periodic stimulation can be notably enhanced by endogenous field feedback. Moreover, the endogenous field feedback delay plays a vital role in SR. We reveal that appropriately tuned delays of the feedback can either induce the enhancement of SR, appearing at every integer multiple of the weak input signal’s oscillation period, or the depression of SR, appearing at every integer multiple of half the weak input signal’s oscillation period for the same feedback coefficient. Interestingly, the parameters of low-passed filter which is used in obtaining the endogenous field feedback signal play a subtle role in SR.

Implementation of sequential logic circuits using the Mach–Zehnder interferometer structure based on electro-optic effect

The electro-optic effect is one of the most important phenomena in Mach–Zehnder (MZI) interferometer structure. The Mach–Zehnder interferometer structure working on the principle of electro-optic effect behaves as the powerful optical switching device. The paper contains the discussion of electro-optic effect based MZI structure. The proper feedback mechanism with the delay unit provides the responses of optical clocked D flip-flop. The paper includes the detailed mathematical description of optical clocked D flip-flops with the MATLAB simulation result. Based on the proposed optical D-flip flop, it is possible to construct some sequential circuits such as synchronous shift registers and ripple counters. Finally, the paper includes the detailed discussion of optical sequential circuits such as synchronous shift register and ripple counter and its implementation using the MATLAB simulation. However, the concept of proposed optical clocked D flip-flop is implemented using the OptiBPM software for the proper verification of the discussed schemes. The Basic building block structures are analyzed to check the optimum performance parameters such as crosstalk, power imbalance, extinction ratio and transition losses, in order to obtain the appropriate Ti-thickness and switching voltage.

Early Intervention With Intranasal NPY Prevents Single Prolonged Stress-Triggered Impairments in Hypothalamus and Ventral Hippocampus in Male Rats

Intranasal administration of neuropeptide Y (NPY) is a promising treatment strategy to reduce traumatic stress-induced neuropsychiatric symptoms of posttraumatic stress disorder (PTSD). We evaluated the potential of intranasal NPY to prevent dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis, a core neuroendocrine feature of PTSD. Rats were exposed to single prolonged stress (SPS), a PTSD animal model, and infused intranasally with vehicle or NPY immediately after SPS stressors. After 7 days undisturbed, hypothalamus and hippocampus, 2 structures regulating the HPA axis activity, were examined for changes in glucocorticoid receptor (GR) and CRH expression. Plasma ACTH and corticosterone, and hypothalamic CRH mRNA, were significantly higher in the vehicle but not NPY-treated group, compared with unstressed controls. Although total GR levels were not altered in hypothalamus, a significant decrease of GR phosphorylated on Ser232 and increased FK506-binding protein 5 mRNA were observed with the vehicle but not in animals infused with intranasal NPY. In contrast, in the ventral hippocampus, only vehicle-treated animals demonstrated elevated GR protein expression and increased GR phosphorylation on Ser232, specifically in the nuclear fraction. Additionally, SPS-induced increase of CRH mRNA in the ventral hippocampus was accompanied by apparent decrease of CRH peptide particularly in the CA3 subfield, both prevented by NPY. The results show that early intervention with intranasal NPY can prevent traumatic stress-triggered dysregulation of the HPA axis likely by restoring HPA axis proper negative feedback inhibition via GR. Thus, intranasal NPY has a potential as a noninvasive therapy to prevent negative effects of traumatic stress.