Implementation Of Feedback Research Articles

On a New Paradigm for Stock Trading Via a Model-Free Feedback Controller

This paper describes a new paradigm for stock trading involving the use of classical feedback controllers which are “model free” in that they use neither parameterization nor estimation of stock price dynamics. At time $t$ , the control signal is the investment level $I(t)$ , obtained via a mapping on the so-called gain-loss function $g(t)$ . While such strategies fall under the umbrella of technical analysis, our approach differs from the literature in a fundamental way: Whereas existing work in finance involves statistical analysis via historical back-testing, our new control-theoretic paradigm aims to provide “certification theorems” giving conditions under which certain robustness properties are guaranteed with respect to benchmark classes for the time-varying stock price $p(t)$ . We demonstrate our ideas using a linear feedback implementation of a new stock-trading scheme called Simultaneous Long-Short. The analysis is carried out in a so-called idealized frictionless market first using smooth prices for pedagogical purposes and then using a more realistic benchmark involving Geometric Brownian Motion. Finally, simulations are given which include real-world implementation issues.

Z ~ 6 metal-line absorbers as a probe of galactic feedback models

AbstractObservations of metal absorption lines in the spectra of QSOs out to z > 6 are providing an important probe into the enrichment and ionization state of the intergalactic medium (IGM) at the tail end of reionization. Using simulations with four different feedback models, including the Illustris and Sherwood simulations, we investigate how the overall incidence rate and equivalent width distribution of metal-line absorbers varies with the galactic wind scheme. The low-ionization absorbers are reasonably insensitive to the feedback implementation, with all models reasonably close to the observed incidence rate of O i absorbers. However, all of our models struggle to reproduce the observations of C iv, which is probing overdensities close to the mean at z ~ 6, suggesting that the metals are not being transported out into the IGM efficiently enough in these simulations.

An empirical study of 360-degree feedback, organizational justice, and firm sustainability

The extensive efforts on soliciting organizational justice for employees and sustaining this justice throughout the organization have turned justice into a vital component of the organizational culture and structure. However, the conditions affecting the latter still lack research. This study tests the compound correlation between organizational justice and the application of 360-degree feedback while emphasizing the sustainability of a just and fair work environment in an organization. A sample of 400 employees occupying various positions in home appliances and electronics organizations contribute to this research. The results of the path analysis (PA) demonstrate that the implementation of 360-degree feedback in an organization not only gives rise to organizational justice, but also aids in sustaining this justice and making justice an integral part of the organizational culture.

Approximate and sampled-data predictors for control of nonlinear delay systems

This tutorial research article presents all recent advances on the use of approximate and sampled-data predictors for time-delay systems. The implementation of predictor feedback for delay systems requires the so-called predictor mapping, i.e., the prediction of the future value of the state vector. However, predictor mappings are rarely available for nonlinear systems. The approximate predictors allow us to overcome this challenge and implement predictor feedback safely for nonlinear time-delay systems even in the case of sampled measurements. The present article reviews the implementation schemes for predictor feedback and provides illustrative examples, which can help the reader to understand the importance of the topic.

Анализ существующих методов управления структурой металла сварного шва

Modern approaches to the management structure of the weld metal produced by arc, laser and electron beam welding. Analyzed various methods of modifying metal, including application of a mechanical treatment prior to welding, the introduction into the melt of various modifying additives, the implementation of an external periodic feedback and a repetitively pulsed heat input. The advantages of using pulsed-arc welding, providing a controlled heat input and control over micrometallurgical processes at intervals of formation and initial crystallization of the metal.

The evolution of the stellar mass versus halo mass relationship

We present an analysis of the predictions made by the Galform semi-analytic galaxy formation model for the evolution of the relationship between stellar mass and halo mass. We show that for the standard implementations of supernova feedback and gas reincorporation used in semi-analytic models, this relationship is predicted to evolve weakly over the redshift range 0<z<4. Modest evolution in the median stellar mass versus halo mass (SHM) relationship implicitly requires that, at fixed halo mass, the efficiency of stellar mass assembly must be almost constant with cosmic time. We show that in our model, this behaviour can be understood in simple terms as a result of a constant efficiency of gas reincorporation, and an efficiency of SNe feedback that is, on average, constant at fixed halo mass. We present a simple explanation of how feedback from active galactic nuclei (AGN) acts in our model to introduce a break in the SHM relation whose location is predicted to evolve only modestly. Finally, we show that if modifications are introduced into the model such that, for example, the gas reincorporation efficiency is no longer constant, the median SHM relation is predicted to evolve significantly over 0<z<4. Specifically, we consider modifications that allow the model to better reproduce either the evolution of the stellar mass function or the evolution of average star formation rates inferred from observations.

The distribution of atomic hydrogen in eagle galaxies: morphologies, profiles, and H i holes

We compare the mass and internal distribution of atomic hydrogen (HI) in 2200 present-day central galaxies with M_star > 10^10 M_Sun from the 100 Mpc EAGLE Reference simulation to observational data. Atomic hydrogen fractions are corrected for self-shielding using a fitting formula from radiative transfer simulations and for the presence of molecular hydrogen using an empirical or a theoretical prescription from the literature. The resulting neutral hydrogen fractions, M_(HI+H2)/M_star, agree with observations to better than 0.1 dex for galaxies with M_star between 10^10 and 10^11 M_Sun. Our fiducial, empirical H2 model based on gas pressure results in galactic HI mass fractions, M_HI/M_star, that agree with observations from the GASS survey to better than 0.3 dex, but the alternative theoretical H2 formula leads to a negative offset in M_HI/M_star of up to 0.5 dex. Visual inspection reveals that most HI disks in simulated HI-rich galaxies are vertically disturbed, plausibly due to recent accretion events. Many galaxies (up to 80 per cent) contain spuriously large HI holes, which are likely formed as a consequence of the feedback implementation in EAGLE. The HI mass-size relation of all simulated galaxies is close to (but 16 per cent steeper than) observed, and when only galaxies without large holes in the HI disc are considered, the agreement becomes excellent (better than 0.1 dex). The presence of large HI holes also makes the radial HI surface density profiles somewhat too low in the centre, at \Sigma_HI > 1 M_Sun pc^-2 (by a factor of <~ 2 compared to data from the Bluedisk survey). In the outer region (\Sigma_HI < 1 M_Sun pc^-2), the simulated profiles agree quantitatively with observations. Scaled by HI size, the simulated profiles of HI-rich (M_HI > 10^9.8 M_Sun) and control galaxies (10^9.1 M_Sun > M_HI > 10^9.8 M_Sun) follow each other closely, as observed. (Abridged)

A new method to quantify the effects of baryons on the matter power spectrum

Future large-scale galaxy surveys have the potential to become leading probes for cosmology provided the influence of baryons on the total mass distribution is understood well enough. As hydrodynamical simulations strongly depend on details in the feedback implementations, no unique and robust predictions for baryonic effects currently exist. In this paper we propose a baryonic correction model that modifies the density field of dark-matter-only N-body simulations to mimic the effects of baryons from any underlying adopted feedback recipe. The model assumes haloes to consist of 4 components: 1- hot gas in hydrostatical equilibrium, 2- ejected gas from feedback processes, 3- central galaxy stars, and 4- adiabatically relaxed dark matter, which all modify the initial dark-matter-only density profiles. These altered profiles allow to define a displacement field for particles in N-body simulations and to modify the total density field accordingly.The main advantage of the baryonic correction model is to connect the total matter density field to the observable distribution of gas and stars in haloes, making it possible to parametrise baryonic effects on the matter power spectrum. We show that the most crucial quantities are the mass fraction of ejected gas and its corresponding ejection radius. The former controls how strongly baryons suppress the power spectrum, while the latter provides a measure of the scale where baryonic effects become important. A comparison with X-ray and Sunyaev-Zel'dovich cluster observations suggests that baryons suppress wave modes above k∼0.5 h/Mpc with a maximum suppression of 10-25 percent around k∼ 2 h/Mpc. More detailed observations of the gas in the outskirts of groups and clusters are required to decrease the large uncertainties of these numbers.

On the Analysis of the Effective Implementation of Peer Feedback in Non-English Majors’ Writing

For non-English majors, English writing is a difficult problem. As a key stage in writing process, peer feedback plays a very important role in writing. It has been proven to be an effective way to improve students’ writing. But its implementation can be affected and limited by some factors. In order to make better use of peer feedback, this paper first introduces peer feedback, and then analyzes the varied factors which may hinder the implementation of peer feedback, finally makes some suggestions to effectively implement peer feedback. By applying cooperative learning principles, making a checklist, combing peer feedback with teacher feedback and making students choosing the language freely, it can make students participate in the activities of peer feedback, ensure them to carry out peer feedback more actively and finally improve their writing ability.

Resolving flows around black holes: numerical technique and applications

Black holes are believed to be one of the key ingredients of galaxy formation models, but it has been notoriously challenging to simulate them due to the very complex physics and large dynamical range of spatial scales involved. Here we address a significant shortcoming of a Bondi-Hoyle-like prescription commonly invoked to estimate black hole accretion in cosmological hydrodynamic simulations of galaxy formation, namely that the Bondi-Hoyle radius is frequently unresolved. We describe and implement a novel super-Lagrangian refinement scheme to increase, adaptively and 'on the fly', the mass and spatial resolution in targeted regions around the accreting black holes at limited computational cost. While our refinement scheme is generically applicable and flexible, for the purpose of this paper we select the smallest resolvable scales to match black holes' instantaneous Bondi radii, thus effectively resolving Bondi-Hoyle-like accretion in full galaxy formation simulations. This permits us to not only estimate gas properties close to the Bondi radius much more accurately, but also allows us to improve black hole accretion and feedback implementations. We thus devise a more generic feedback model where accretion and feedback depend on the geometry of the local gas distribution and where mass, energy and momentum loading are followed simultaneously. We present a series of tests of our refinement and feedback methods and apply them to models of isolated disc galaxies. Our simulations demonstrate that resolving gas properties in the vicinity of black holes is necessary to follow black hole accretion and feedback with a higher level of realism and that doing so allows us to incorporate important physical processes so far neglected in cosmological simulations.

Intrinsic alignments of galaxies in the Horizon-AGN cosmological hydrodynamical simulation

The intrinsic alignments of galaxies are recognised as a contaminant to weak gravitational lensing measurements. In this work, we study the alignment of galaxy shapes and spins at low redshift ($z\sim 0.5$) in Horizon-AGN, an adaptive-mesh-refinement hydrodynamical cosmological simulation box of 100 Mpc/h a side with AGN feedback implementation. We find that spheroidal galaxies in the simulation show a tendency to be aligned radially towards over-densities in the dark matter density field and other spheroidals. This trend is in agreement with observations, but the amplitude of the signal depends strongly on how shapes are measured and how galaxies are selected in the simulation. Disc galaxies show a tendency to be oriented tangentially around spheroidals in three-dimensions. While this signal seems suppressed in projection, this does not guarantee that disc alignments can be safely ignored in future weak lensing surveys. The shape alignments of luminous galaxies in Horizon-AGN are in agreement with observations and other simulation works, but we find less alignment for lower luminosity populations. We also characterize the systematics of galaxy shapes in the simulation and show that they can be safely neglected when measuring the correlation of the density field and galaxy ellipticities.

Forged in fire: cusps, cores and baryons in low-mass dwarf galaxies

We present ultra-high resolution cosmological hydrodynamic simulations of $M_*\simeq10^{4-6.3}M_{\odot}$ dwarf galaxies that form within $M_{v}=10^{9.5-10}M_{\odot}$ dark matter halos. Our simulations rely on the FIRE implementation of star formation feedback and were run with high enough force and mass resolution to directly resolve stellar and dark matter structure on the ~200 pc scales of interest for classical and ultra-faint dwarfs in the Local Group. The resultant galaxies sit on the $M_*$ vs. $M_{v}$ relation required to match the Local Group stellar mass function. They have bursty star formation histories and also form with half-light radii and metallicities that broadly match those observed for local dwarfs at the same stellar mass. We demonstrate that it is possible to create a large (~1 kpc) dark matter core in a cosmological simulation of an $M_*\simeq10^{6.5}M_{\odot}$ dwarf galaxy that resides within an $M_{v}=10^{10}M_{\odot}$ halo -- precisely the scale of interest for resolving the Too Big to Fail problem. However, these large cores are not ubiquitous and appear to correlate closely with the star formation histories of the dwarfs: dark matter cores are largest in systems that form their stars late ($z\lesssim2$), after the early epoch of cusp building mergers has ended. Our $M_*\simeq10^4M_{\odot}$ dwarf retains a cuspy dark matter halo density profile that matches almost identically that of a dark-matter only run of the same system. Despite forming in a field environment, this very low mass dwarf has observable properties that match closely to those of ultra-faint satellite galaxies of the Milky Way, including a uniformly old stellar population (>10 Gyr). Though ancient, most of the stars in our ultra-faint form after reionization; the UV field acts mainly to suppress fresh gas accretion, not to boil away gas that is already present in the proto-dwarf.

Patient-focused and feedback research in psychotherapy: Where are we and where do we want to go?

In the last 15 years feedback interventions have had a significant impact on the field of psychotherapy research and have demonstrated their potential to enhance treatment outcomes, especially for patients with an increased risk of treatment failure. This article serves as an introduction to the special issue on “Patient-focused and feedback research in psychotherapy: Where are we and where do we want to go?” Current investigations on feedback research are concerned with potential moderators and mediators of these effects, as well as the design and the implementation of feedback into routine care. This introduction summarizes the current state of feedback research and provides an overview of the three main research topics in this issue: (1) How to implement feedback systems into routine practice and how do therapist and patient attitudes influence its effects?, (2) How to design feedback reports and decision support tools?, and (3) What are the reasons for patients to become at risk of treatment failure and how should therapists intervene with these patients? We believe that the studies included in this special issue reflect the current state of feedback research and provide promising pathways for future endeavors that will enhance our understanding of feedback effects.

Does formative feedback on search behaviour help students in answering comprehension questions from an available text? / ¿Ayuda la retroalimentación formativa sobre el comportamiento de búsqueda a contestar preguntas de comprensión en lecturas con texto disponible?

This study analyses the efficacy of formative feedback to boost students’ search behaviour when answering comprehension questions in a with-text reading situation, which is a common reading situation in instructional and assessment settings. In these reading situations search strategies play an important role to predict students’ performance. Sixty-five high school students read two texts and answered eight multiple-choice comprehension questions per text using the software Read&Answer, which recorded all the students’ actions. After answering each question, students received either global-search-feedback or specific-search-feedback, which differed in the specificity of their information, or no-feedback. Participants who received any feedback had a second chance to correct their wrong answers. Specific-search-feedback increased students’ search decisions and improved their use of relevant information to repair wrong answers over global-search-feedback. Consequently, specific-search-feedback improved students’ performance when they corrected wrong answers over global-search-feedback. These results have implications for the design and implementation of formative feedback in computer-based systems aimed at improving students’ performance and teaching reading literacy skills.

Design and Simulation of Turbo Encoder in Quantum-Dot Cellular Automata

Quantum-dot cellular automata (QCA) is a potential nanoelectronic technology for information processing. To be considered as a suitable CMOS candidate, QCA must be able to implement complex real-time applications of bit-serial information processing, which lacks of enough investigation. Turbo encoding is one of such applications, which refers to three representative issues of bit-serial circuits: convolution computation, feedback, and serial data permutation. The inherent shift-register nature of QCA offers an advantage to performing convolution computation but poses handicaps to resolve the latter two issues. How to manage the ambivalent effects of shift-register nature is investigated in this paper, which determines the efficient design of Turbo encoder. A strobe scheme based on main-branch wire crossing is proposed to efficiently make data choosing that is the communally key procedure of the implementation of feedback and serial data permutation. On this basis, a method of implementing recursive convolutional encoder with multifeedback is proposed. A two-stage pipelining interleaver is presented. Finally, a Turbo encoder is implemented using QCA based on these approaches and simulation demonstrates that it performs well.

Sweating the small stuff: simulating dwarf galaxies, ultra-faint dwarf galaxies, and their own tiny satellites

We present FIRE/Gizmo hydrodynamic zoom-in simulations of isolated dark matter halos, two each at the mass of classical dwarf galaxies ($M_{\rm vir} \simeq 10^{10} M_{\odot}$) and ultra-faint galaxies ($M_{\rm vir} \simeq 10^9 M_{\odot}$), and with two feedback implementations. The resultant central galaxies lie on an extrapolated abundance matching relation from $M_{\star} \simeq 10^6$ to $10^4 M_{\odot}$ without a break. Every host is filled with subhalos, many of which form stars. Our dwarfs with $M_{\star} \simeq 10^6 M_{\odot}$ each have 1-2 well-resolved satellites with $M_{\star} = 3-200 \times 10^3 M_{\odot}$. Even our isolated ultra-faint galaxies have star-forming subhalos. If this is representative, dwarf galaxies throughout the universe should commonly host tiny satellite galaxies of their own. We combine our results with the ELVIS simulations to show that targeting $\sim 50~ \rm kpc$ regions around nearby isolated dwarfs could increase the chances of discovering ultra-faint galaxies by $\sim 35\%$ compared to random halo pointings, and specifically identify the region around the Phoenix dwarf galaxy as a good potential target. The well-resolved ultra-faint galaxies in our simulations ($M_{\star} \simeq 3 - 30 \times 10^3 M_{\odot}$) form within $M_{\rm peak} \simeq 0.5 - 3 \times 10^9 M_{\odot}$ halos. Each has a uniformly ancient stellar population ($ > 10~ \rm Gyr$) owing to reionization-related quenching. More massive systems, in contrast, all have late-time star formation. Our results suggest that $M_{\rm halo} \simeq 5 \times 10^9 M_{\odot}$ is a probable dividing line between halos hosting reionization "fossils" and those hosting dwarfs that can continue to form stars in isolation after reionization.

The implementation of best practice in medication administration across a health network: a multisite evidence-based audit and feedback project.

Medication errors present a significant risk to patient safety. The "rights" of medication administration represent one approach to potentially reducing this risk. The aim of this project was to implement an evidence-based audit and feedback project to improve compliance with best practice in this area across a health network. A baseline audit was conducted to determine compliance with evidence-based standards by trained observers. The results of this audit were analysed and fed back to staff. An analysis of barriers to compliance was undertaken by key staff within the organization, which was followed by the implementation of targeted strategies to improve compliance. A follow-up audit was conducted and the results compared to the baseline audit. There were improvements in the percentage of compliance across all of the eight criteria audited, with statistically significant improvements found in six of the eight. In general, compliance with the criteria was high in both the baseline and follow-up audits. This audit and feedback implementation project was successful in increasing compliance and knowledge in this area and providing future direction for sustaining evidence-based practice change. It is now planned to use this approach for rolling out future implementation projects within this health system.

Conjugate adaptive optics in widefield microscopy with an extended-source wavefront sensor

Subsurface microscopy is often limited by poor image quality due to sample-induced aberrations. Adaptive optics (AO) can counter such aberrations, though generally over limited fields of view. In most applications, AO is either slow or requires a “guide star” in the sample to serve as a localized reference target. We describe a fast closed-loop feedback implementation of AO that requires no guide stars, where the sample itself serves as the reference. Several features of our implementation are new. First, it is based on a high-resolution, single-shot wavefront sensor that is compatible with extended samples. Second, it is applied to widefield (i.e., nonscanning) microscopy in a conjugate AO configuration that increases field of view. Third, it makes use of a fast algorithm to identify sample-induced aberrations using illumination from an arbitrarily shaped source. We present the principle of our technique and proof-of-concept experimental demonstrations.

Implementation of improvement strategies in palliative care: an integrative review.

BackgroundThe European population is ageing, and as a consequence, an increasing number of patients are in need of palliative care, including those with dementia. Although a growing number of new insights and best practices in palliative care have been published, they are often not implemented in daily practice. The aim of this integrative review is to provide an overview of implementation strategies that have been used to improve the organisation of palliative care.MethodsUsing an integrative literature review, we evaluated publications with strategies to improve the organisation of palliative care. Qualitative analysis of the included studies involved categorisation of the implementation strategies into subgroups, according to the type of implementation strategy.ResultsFrom the 2379 publications identified, 68 studies with an experimental or quasi-experimental design were included. These studies described improvements using educational strategies (n = 14), process mapping (n = 1), feedback (n = 1), multidisciplinary meetings (n = 1) and multi-faceted implementation strategies (n = 51). Fifty-three studies reported positive outcomes, 11 studies reported mixed effects and four studies showed a limited effect (two educational and two multi-faceted strategies).ConclusionsThis review is one of the first to provide an overview of the available literature in relation to strategies used to improve the organisation of palliative care. Since most studies reported positive results, further research is needed to identify and improve the effects of strategies aiming to improve the organisation of palliative care.Electronic supplementary materialThe online version of this article (doi:10.1186/s13012-015-0293-2) contains supplementary material, which is available to authorized users.

Evaluation of a continuous monitoring and feedback initiative to improve quality of anaesthetic care: a mixed-methods quasi-experimental study

BackgroundThis study evaluated the impact of a continuous quality monitoring and feedback initiative in anaesthesia.ObjectivesTo conduct a quasi-experimental evaluation of the feedback initiative and its effect on quality of anaesthetic care and perioperative efficiency. To understand the longitudinal effects of passive and active feedback and investigate the mechanisms and interactions underpinning those effects.DesignMixed-methods evaluation with analysis and synthesis of data from longitudinal qualitative interviews, longitudinal evaluative surveys and an interrupted time series study.InterventionContinuous measurement of a range of anaesthetic quality indicators was undertaken in a London teaching hospital alongside monthly personal feedback from case summary data to a cohort of anaesthetists, with follow-up roll-out to the whole NHS trust. Basic feedback consisted of the provision of passive monthly personalised feedback reports containing summary case data. In the enhanced phase, data feedback consisted of more sophisticated statistical breakdown of data, comparative and longitudinal views, and was paired with an active programme of dissemination and professional engagement.MethodsBaseline data collection began in March 2010. Implementation of basic feedback took place in October 2010, followed by implementation of the enhanced feedback protocol in July 2012. Weekly aggregated quality indicator data, coupled with surgical site infection and mortality rates, was modelled using interrupted time series analyses. The study anaesthetist cohort comprised 50,235 cases, performed by 44 anaesthetists over the course of the study, with 22,670 cases performed at the primary site. Anaesthetist responses to the surveys were collected pre and post implementation of feedback at all three sites in parallel with qualitative investigation. Seventy anaesthetists completed the survey at one or more time points and 35 health-care professionals, including 24 anaesthetists, were interviewed across two time points.ResultsResults from the time series analysis of longitudinal variation in perioperative indicators did not support the hypothesis that implementation of basic feedback improved quality of anaesthetic care. The implementation of enhanced feedback was found to have a significant positive impact on two postoperative pain measures, nurse-recorded freedom from nausea, mean patient temperature on arrival in recovery and Quality of Recovery Scale scores. Analysis of survey data demonstrated that anaesthetists value perceived credibility of data and local relevance of quality indicators above other criteria when assessing utility of feedback. A significant improvement in the perceived value of quality indicators, feedback, data use and overall effectiveness was observed between baseline and implementation of feedback at the primary site, a finding replicated at the two secondary sites. Findings from the qualitative research elucidated processes of interaction between context, intervention and user, demonstrating a positive response by clinicians to this type of initiative and willingness to interact with a sustained and comprehensive feedback protocol to understand variations in care.ConclusionsThe results support the potential of quality monitoring and feedback interventions as quality improvement mechanisms and provide insight into the positive response of clinicians to this type of initiative, including documentation of the experiences of anaesthetists that participated as users and codesigners of the feedback. Future work in this area might usefully investigate how this type of intervention may be transferred to other areas of clinical practice and further explore interactions between local context and the successful implementation of quality monitoring and feedback systems.FundingThe National Institute for Health Research Health Services and Delivery Research programme.