Alternating Direction Method of Multipliers-Based Constant Modulus Waveform Design for Dual-Function Radar-Communication Systems.

In this paper, we design constant modulus waveforms for dual-function radar-communication (DFRC) systems based on a multi-input multi-output (MIMO) configuration of sensors for a far-field scenario. At first, we formulate a non-convex optimization problem subject to waveform synthesis for minimizing the interference power while maintaining a constant modulus constraint. Next, we solve this non-convex problem, iteratively, using the alternating direction method of multipliers (ADMM) algorithm. Importantly, the designed waveforms approximate a desired beampattern in terms of a high-gain radar beam and a slightly high gain communication beam while maintaining a desired low sidelobe level. The designed waveforms ensure an improved detection probability and an improved bit error rate (BER) for radar and communications parts, respectively. Finally, we demonstrate the effectiveness of the proposed method through simulation results.

Sensor Fault-Tolerant Control of Microgrid Using Robust Sliding-Mode Observer.

This work investigates sensor fault diagnostics and fault-tolerant control for a voltage source converter based microgrid (model) using a sliding-mode observer. It aims to provide a diagnosis of multiple faults (i.e., magnitude, phase, and harmonics) occurring simultaneously or individually in current/potential transformers. A modified algorithm based on convex optimization is used to determine the gains of the sliding-mode observer, which utilizes the feasibility optimization or trace minimization of a Ricatti equation-based modification of H-Infinity (H∞) constrained linear matrix inequalities. The fault and disturbance estimation method is modified and improved with some corrections in previous works. The stability and finite-time reachability of the observers are also presented for the considered faulty and perturbed microgrid system. A proportional-integral (PI) based control is utilized for the conventional regulations required for frequency and voltage sags occurring in a microgrid. However, the same control block features fault-tolerant control (FTC) functionality. It is attained by incorporating a sliding-mode observer to reconstruct the faults of sensors (transformers), which are fed to the control block after correction. Simulation-based analysis is performed by presenting the results of state/output estimation, state/output estimation errors, fault reconstruction, estimated disturbances, and fault-tolerant control performance. Simulations are performed for sinusoidal, constant, linearly increasing, intermittent, sawtooth, and random sort of often occurring sensor faults. However, this paper includes results for the sinusoidal nature voltage/current sensor (transformer) fault and a linearly increasing type of fault, whereas the remaining results are part of the supplementary data file. The comparison analysis is performed in terms of observer gains being estimated by previously used techniques as compared to the proposed modified approach. It also includes the comparison of the voltage-frequency control implemented with and without the incorporation of the used observer based fault estimation and corrections, in the control block. The faults here are considered for voltage/current sensor transformers, but the approach works for a wide range of sensors.

Low serum 25-hydroxyvitamin D (25D) levels in patients hospitalised with COVID-19 are associated with greater disease severity: results of a local audit of practice.

ObjectivesTo audit implementation of a local protocol for the treatment of vitamin D deficiency (VDD) among patients hospitalized for Coronavirus Disease 2019 (COVID-19), including an assessment of the prevalence of VDD in these patients, and of potential associations with disease severity and fatality. DesignThis was not a study or clinical trial, but rather a retrospective interim audit (Newcastle-upon-Tyne Hospitals Registration No. 10075) of a local clinical care pathway for hospitalized patients with COVID-19-related illness. The Information (Caldicott) Guardian permitted these data to be shared beyond the confines of our institution. SettingA large tertiary academic NHS Foundation Trust in the North East of England, UK, providing care to COVID-19 patients. ParticipantsOne hundred thirty-four hospitalized patients with documented COVID-19 infection. Main outcome measuresAdherence to local investigation and treatment protocol; prevalence of VDD, and relationship of baseline serum 25(OH)D with markers of COVID-19 severity and inpatient fatality versus recovery. Results55.8% of eligible patients received Colecalciferol replacement, albeit not always loaded as rapidly as our protocol suggested, and no cases of new hypercalcaemia occurred following treatment. Patients admitted to ITU were younger than those managed on medical wards (61.1 years {+/-} 11.8 vs. 76.4 years {+/-} 14.9, p<0.001), with greater prevalence of hypertension, and higher baseline respiratory rate, National Early Warning Score-2 and C-reactive protein level. While mean serum 25(OH)D levels were comparable [i.e. ITU: 33.5 nmol/L {+/-} 16.8 vs. Non-ITU: 48.1 nmol/L {+/-} 38.2, mean difference for Ln-transformed-25(OH)D: 0.14, 95% Confidence Interval (CI) (-0.15, 0.41), p=0.3], only 19% of ITU patients had 25(OH)D levels greater than 50 nmol/L vs. 39.1% of non-ITU patients (p=0.02). However, we found no association with fatality, potentially due to small sample size, limitations of no-trial data and, potentially, the prompt diagnosis and treatment of VDD. ConclusionsSubject to the inherent limitations of observational (non-trial) audit data, analysed retrospectively, we found that patients requiring ITU admission were more frequently vitamin D deficient than those managed on medical wards, despite being significantly younger. Larger prospective studies and/or clinical trials are needed to elucidate the role of vitamin D as a preventive and/or therapeutic strategy for mitigating the effects of COVID-19 infection in patients with VDD. What is already known on this topicO_LIVitamin D deficiency (VDD) is associated with increased risk for acute respiratory tract infections C_LIO_LIA link between VDD and severity of COVID-19 pathophysiology has been proposed C_LIO_LITwo recent (non-peer-reviewed) studies have reported crude associations between VDD in defined geographic populations and COVID-19 severity and mortality C_LI What this study addsO_LIThese data do not arise from a clinical study; rather from an audit of a local replacement protocol for VDD in COVID-19 inpatients in a large UK centre, which found a significantly higher prevalence of VDD among ITU patients compared to non-ITU patients, despite the ITU patients being significantly younger. C_LIO_LIPrompt treatment of VDD following a local protocol did not result in any adverse events, such as hypercalcaemia. C_LIO_LIWhilst by no means conclusive, these data suggest an important association between VDD and COVID-19 severity; hence our report of interim findings in advance of achieving completed outcomes (fatality vs. recovery) for all patients. C_LIO_LIThere is an urgent need for larger studies exploring vitamin D as a potential preventative measure and/or treatment of Covid-19-related illness among individuals with VDD. C_LI