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The problem of estimating time-varying harmonic components of a signal measured in noise is considered. The approach used is via state estimation. Two methods are proposed, one involving poleplacement of a state observer, the other using quadratic optimization techniques. The result is the development of a new class of filters, akin to recursive frequency-sampling filters, for inclusion in a parallel bank to produce sliding harmonic estimates. Kalman filtering theory is applied to effect the good performance in noise, and the class of filters is parameterized by the design tradeoff between noise rejection and convergence rate. These filters can be seen as generalizing the DFT. I. INTRODUCTION S HORT-TIME Fourier analysis has been a topic of considerable interest in digital signal processing [ 11, [ 2 ] , and is concerned with the evaluation of the slowly timevarying Fourier components of a quasi-periodic signal. This problem arises in many forms in signal processing, notably speech processing and recognition, vibration analysis, power system analysis, and general time series. For example, in a power system, one is frequently interested in studying the "harmonic pollution" of the fundamental mains frequency. The magnitudes and phases of the harmonics are of importance in determining the quality of supply and in identifying pollution sources. Equally, the efficiency of various thyristor motor control devices can best be determined and controlled by harmonic monitoring. The underlying signal model for situations such as these involves regularly sampled values of a continuous time signal. We presume that the period T of this signal is known or is predetermined and that there are 2N + 1 samples per period. The fundamental angular frequency is then wo = 2 r / T and we seek to determine all or part of the 2N + 1 harmonic components. The discrete-time signal model for the sampled data is

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The results presented herein are intended to aid in a fundamental understanding of conditioning water treatment residuals by the freeze/thaw process. Residuals were frozen such that the effects of freezing rate, solids content, and curing time were isolated. Residuals were frozen directionally on a copper surface maintained at subfreezing temperatures. In contrast to many of the results in the literature, freezing rate did not seem to affect the final dewaterability. However, the effects of initial solids content and curing time were noticeable. High solids content residuals yielded cake solids contents greater than 30% following freezing, thawing, and drainage under a vacuum. Samples cured at -10 °C for 1 h dewatered much more readily than uncured samples. The results will aid in the design of a mechanical freezing process; the cost optimum conditions for such a process appear to be fast freezing of a high solids content residual, followed by approximately 1 h of curing.

Background Bedside nurse turnover in the United States is 15.9%, representing a national challenge that has been attributed to poor work environments. Healthy work environments are associated with improved nurse satisfaction and retention as well as positive patient outcomes; unhealthy work environments have the opposite effects. Objectives To implement the American Association of Critical-Care Nurses (AACN) healthy work environment (HWE) framework in an intensive care unit and to evaluate staff satisfaction, turnover, and tenure 2 years later. Methods A pre-post study design was used to evaluate implementation of the HWE framework in an intensive care unit in a large academic medical facility. Interventions for each of the 6 HWE standards were performed. The AACN HWE assessment survey was used to measure skilled communication, true collaboration, effective decision-making, appropriate staffing, meaningful recognition, and authentic leadership in 2017 and in 2019. Results Nurse cohorts (n = 165 in 2017; n = 176 in 2019) had a mean age of 31 (median, 27; range, 23-63) years, were predominantly female (76%), and had a mean of 5 (median, 3) years of intensive care unit nursing experience. Statistically significant improvements were found in all standards except the skilled communication and overall measures. Registered nurse turnover remained stable and tenure increased by 79 days in this 2-year period. Conclusions Findings from this study suggest that interventions addressing the HWE standards are associated with improved staff satisfaction, turnover, and average tenure, further demonstrating the value of the HWE framework in improving retention.

The internet has become the chosen medium for professional learning. Completing professional learning can improve work performance; however, many individuals who begin online courses do not complete them. It is not well understood which influences keep individuals engaged in online professional learning. We address these issues with a systematic review. Our review of 51 studies and 9,583 participants includes a narrative synthesis and a meta-analysis that examined influences on user engagement in online professional learning. We found that course design and employers’ provision of time to complete learning are key for engaging learners. Other important influences were learners’ reasons for learning (e.g., intrinsic value and perceived usefulness), access to learning support, and opportunities for interaction during the learning experience.

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