scholarly journals Frequency Estimation for Grid-Tied Inverters Using Resonant Frequency Estimator

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6513
Author(s):  
Dariusz Zieliński ◽  
Karol Fatyga
Keyword(s):  
Resonant Frequency ◽  
Frequency Estimation ◽  
Short Circuit ◽  
The Novel ◽  
Diesel Generator ◽  
Estimation Algorithms ◽  
New Strategy ◽  
Frequency Changes ◽  
Novel Strategy ◽  
Frequency Estimator

This paper introduces a new strategy of frequency estimation for grid-tied and stand-alone mode AC/DC power converters. Frequency stabilization is required, especially when operating in stand-alone mode with a Droop Control strategy, or in hybrid mode with a Diesel generator. It is also required to reduce or increase power output along with grid frequency changes. The novel strategy utilizes a resonant filter to estimate the frequency of the voltage grid and is referenced as a resonant-frequency-estimator (RFE). A mathematical background is presented for the proposed estimator and its performance is evaluated. It is compared with three common frequency estimation algorithms: SRF-FLL, DDSRF-FLL, and DSOGI-FLL. Results are presented for three cases: frequency swing, harmonics injection, and type B short-circuit. Results are analyzed and the conclusion shows that the proposed novel strategy has comparable parameters to commonly used frequency estimation algorithms while having a loopless structure.

Arousal Effects on Cognition: New Strategy Which Isolates Movement and Heart Rate Effects Inherent in Physical Work

1988 ◽  
Vol 32 (17) ◽  
pp. 1140-1144
Author(s):  
Tina Mihaly
Keyword(s):  
Heart Rate ◽  
Physical Work ◽  
The Novel ◽  
Validation Experiment ◽  
Rate Effects ◽  
New Strategy ◽  
Methodological Problems ◽  
Novel Strategy ◽  
Exercise Induced ◽  
Speed Accuracy

Most experiments which have sought to determine the effects of arousal, exercise and/or physical work on psychomotor performance have been tainted by methodological problems. This paper presents a strategy that was developed to overcome one methodological shortcoming inherent in many such studies: the confounding of movement and heart rate. The technique involves administering mental tests during both movement and non-movement intervals, at pre-selected exercise states. Results of a validation experiment, in which 11 subjects performed numerous psychomotor tasks with and without movement at four work intensities (rest, 30% VO2max, 60% VO2max, and post-exercise) on two testing days indicate that this method was sufficiently sensitive to identify previously undetected effects, e.g., movement slows index finger tapping rate and may impair an individual's ability to stabilize speed-accuracy tradeoff strategies in serial choice reaction time tasks. Inverted-U effects were also found, replicating some previous investigations. The novel strategy detailed herein, which isolates the relative effects of movement and elevated heart rate, appears appropriate for use in studies aimed at quantifying the effects of exercise-induced arousal (via cycle ergometry) on mental performance before, during, and after exercise. This work has implications for improving research methodologies and predicting which sorts of everyday speeded mental tasks will be affected when one is simultaneously engaged in physical work.

scholarly journals Wavelet Transform Based Fault Identification and Reconfiguration for a Reduced Switch Multilevel Inverter Fed Induction Motor Drive

Electronics ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 1023
Author(s):  
Arigela Satya Veerendra ◽  
Akeel A. Shah ◽  
Mohd Rusllim Mohamed ◽  
Chavali Punya Sekhar ◽  
Puiki Leung
Keyword(s):  
Wavelet Transform ◽  
Discrete Wavelet Transform ◽  
Multiresolution Analysis ◽  
Short Circuit ◽  
Open Circuit ◽  
Multilevel Inverter ◽  
Fault Identification ◽  
Discrete Wavelet ◽  
The Novel ◽  
Inverter Topology

The multilevel inverter-based drive system is greatly affected by several faults occurring on switching elements. A faulty switch in the inverter can potentially lead to more losses, extensive downtime and reduced reliability. In this paper, a novel fault identification and reconfiguration process is proposed by using discrete wavelet transform and auxiliary switching cells. Here, the discrete wavelet transform exploits a multiresolution analysis with a feature extraction methodology for fault identification and subsequently for reconfiguration. For increasing the reliability, auxiliary switching cells are integrated to replace faulty cells in a proposed reduced-switch 5-level multilevel inverter topology. The novel reconfiguration scheme compensates open circuit and short circuit faults. The complexity of the proposed system is lower relative to existing methods. This proposed technique effectively identifies and classifies faults using the multiresolution analysis. Furthermore, the measured current and voltage values during fault reconfiguration are close to those under healthy conditions. The performance is verified using the MATLAB/Simulink platform and a hardware model.

scholarly journals Persistent SARS-CoV-2-positive over 4 months in a COVID-19 patient with CHB

Open Medicine ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. 749-753
Author(s):  
Wenyuan Li ◽  
Beibei Huang ◽  
Qiang Shen ◽  
Shouwei Jiang ◽  
Kun Jin ◽  
...  
Keyword(s):  
The Novel ◽  
Chain Reaction ◽  
Health Crisis ◽  
Public Health Crisis ◽  
Oxygen Inhalation ◽  
New Strategy ◽  
Polymerase Chain ◽  
Novel Coronavirus ◽  
Specific Symptoms

Abstract In recent months, the novel coronavirus disease 2019 (COVID-19) pandemic has become a major public health crisis with takeover more than 1 million lives worldwide. The long-lasting existence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has not yet been reported. Herein, we report a case of SARS-CoV-2 infection with intermittent viral polymerase chain reaction (PCR)-positive for >4 months after clinical rehabilitation. A 35-year-old male was diagnosed with COVID-19 pneumonia with fever but without other specific symptoms. The treatment with lopinavir-ritonavir, oxygen inhalation, and other symptomatic supportive treatment facilitated recovery, and the patient was discharged. However, his viral PCR test was continually positive in oropharyngeal swabs for >4 months after that. At the end of June 2020, he was still under quarantine and observation. The contribution of current antivirus therapy might be limited. The prognosis of COVID-19 patients might be irrelevant to the virus status. Thus, further investigation to evaluate the contagiousness of convalescent patients and the mechanism underlying the persistent existence of SARS-CoV-2 after recovery is essential. A new strategy of disease control, especially extending the follow-up period for recovered COVID-19 patients, is necessary to adapt to the current situation of pandemic.

scholarly journals Delayed improvement local search

2021 ◽  
Author(s):  
Heber F. Amaral ◽  
Sebastián Urrutia ◽  
Lars M. Hvattum
Keyword(s):  
Local Search ◽  
Heuristic Algorithms ◽  
Travelling Salesman Problem ◽  
Computation Time ◽  
The Novel ◽  
Local Optima ◽  
New Strategy ◽  
Max Cut Problem ◽  
Novel Method ◽  
Similar Solutions

AbstractLocal search is a fundamental tool in the development of heuristic algorithms. A neighborhood operator takes a current solution and returns a set of similar solutions, denoted as neighbors. In best improvement local search, the best of the neighboring solutions replaces the current solution in each iteration. On the other hand, in first improvement local search, the neighborhood is only explored until any improving solution is found, which then replaces the current solution. In this work we propose a new strategy for local search that attempts to avoid low-quality local optima by selecting in each iteration the improving neighbor that has the fewest possible attributes in common with local optima. To this end, it uses inequalities previously used as optimality cuts in the context of integer linear programming. The novel method, referred to as delayed improvement local search, is implemented and evaluated using the travelling salesman problem with the 2-opt neighborhood and the max-cut problem with the 1-flip neighborhood as test cases. Computational results show that the new strategy, while slower, obtains better local optima compared to the traditional local search strategies. The comparison is favourable to the new strategy in experiments with fixed computation time or with a fixed target.

Cascade photocaging of diazeniumdiolate: a novel strategy for one and two photon triggered uncaging with real time reporting

2017 ◽  
Vol 53 (68) ◽  
pp. 9470-9473 ◽  
Author(s):  
Krishna Kalyani Behara ◽  
Y. Rajesh ◽  
Yarra Venkatesh ◽  
Bhaskar Rao Pinninti ◽  
Mahitosh Mandal ◽  
...  
Keyword(s):  
Real Time ◽  
Two Photon ◽  
New Strategy ◽  
Novel Strategy

We report a new strategy, viz. cascade photocaging, for protecting diethylamine diazeniumdiolate (O2-position), a light sensitive molecule.

scholarly journals New Strategy for Analog Circuit Performance Evaluation under Disturbance and Fault Value

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Aihua Zhang ◽  
Yongchao Wang ◽  
Chen Chen ◽  
Hamid Reza Karimi
Keyword(s):  
Performance Evaluation ◽  
Support Vector Regression ◽  
Analog Circuit ◽  
Support Vector ◽  
Training Set ◽  
Circuit Performance ◽  
New Strategy ◽  
Indirect Evaluation ◽  
Novel Strategy ◽  
Fuzzy Learning

Focus on this issue of disturbance and fault value is inevitable in data collection about analog circuit. A novel strategy is developed for analog circuit online performance evaluation based on fuzzy learning and double weighted support vector machine (DWMK-FSVM). First, the double weighted support vector regression machine is employed to be the indirect evaluation means, relied on the college analog electronic technology experiment to evaluate analog circuit. Second, the superiority of fuzzy learning also is addressed to realize active suppression to the fault values and disturbance parameters. Moreover, the multikernel RBF is employed by support vector regression machine to realize more flexibility online such as the bandwidths tuning. Numerical results, supported by the college analog circuit experiments, adopted OTL performance eight indexes, which were obtained via precision instrument evaluation in two years to construct training set and are then to be evaluated online based on DWMK-FSVM. Simulation results presented not only highlight precision of the evaluation strategy derived here but also illustrate its great robustness.

A Frequency-Tunable Comb Resonator Using Spring Tension and Compression Effects

2004 ◽  
Author(s):  
Ki Bang Lee ◽  
Albert P. Pisano ◽  
Liwei Lin
Keyword(s):  
Resonant Frequency ◽  
Bias Voltage ◽  
Frequency Tuning ◽  
Electrostatic Force ◽  
Voltage Change ◽  
Tension And Compression ◽  
Frequency Tunable ◽  
Frequency Changes ◽  
Compression Effects ◽  
First Time

A 2μm-thick frequency-tunable microresoantor capable of either increasing or decreasing its resonant frequency by a combination of Joule heating and electrostatic force has been successfully demonstrated for the first time. For the heating voltage increase from 0 to 2V under fixed bias voltage of 40V, the resonant frequency changes from 22.2kHz to 16.2kHz, resulting in the 27% reduction in the resonant frequency. For the bias voltage change from 20V to 40V under the heating voltage of 0V, the resonant frequency increase from 19.0kHz to 23.6kHz, resulting in the 24.2% increase in the resonant frequency. As such, this surface-micromachined microactuator could assist complicated frequency tuning for applications of microsensors and microactuators.

scholarly journals Epilepsy, Forgetting, and Convalescence in Ondaatje’s Warlight

2021 ◽  
Vol 13 (2) ◽  
Author(s):  
Jan Gresil S. Kahambing ◽  
Keyword(s):  
Medical Humanities ◽  
Short Circuit ◽  
Epileptic Seizures ◽  
Close Reading ◽  
The Novel ◽  
Health Humanities ◽  
Do So

Michael Ondaatje’s Warlight (2018), his latest novel to-date, contains nostalgic elements of strangeness and cartography. In this paper, I short-circuit such themes with health under medical humanities, which heeds a Nietzschean counsel of close reading in literature. To do so, I explore the case of Rachel’s illness, namely her epileptic seizures, as an instance that drives her impetus for active forgetting and eventual convalescence. A close hermeneutical reading of the novel can reveal that both of Nietzsche’s ideas on active forgetting and convalescence provide traction in terms of what this paper constructs as Rachel’s pathography or narration of illness. Shifting the focus from the main narrator, Nathaniel, I argue that it is not the novel’s reliance on memory but the subplot events of Nathaniel’s sister and her epilepsy that form a substantial case of medical or health humanities.

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