Universal fractional-order design of linear phase lead compensation multirate repetitive control for PWM inverters

Repetitive control (RC) with linear phase lead compensation provides a simple but very effective control solution for any periodic signal with a known period. Multirate repetitive control (MRC) with a downsampling rate can reduce the need of memory size and computational cost, and then leads to a more feasible design of the plug-in repetitive control systems in practical applications. However, with fixed sampling rate, both MRC and its linear phase lead compensator are sensitive to the ratio of the sampling frequency to the frequency of interested periodic signals: (1) MRC might fails to exactly compensate the periodic signal in the case of a fractional ratio; (2) linear phase lead compensation might fail to enable MRC to achieve satisfactory performance in the case of a low ratio. In this paper, a universal fractional-order design of linear phase lead compensation MRC is proposed to tackle periodic signals with high accuracy, fast dynamic response, good robustness, and cost-effective implementation regardless of the frequency ratio, which offers a unified framework for housing various RC schemes in extensive engineering application. An application example of programmable AC power supply is explored to comprehensively testify the effectiveness of the proposed control scheme

Virtual Delay Unit Based Digital nk ± m-order Harmonic Repetitive Controller for PWM Converter

Repetitive control (RC) scheme presents an attractive solution to achieve excellent steady-state tracking error and low total harmonic distortion (THD) for periodic signals. RC can produce extremely large gains at fundamental and each harmonic frequency of reference signal to achieve all harmonics suppression. However, a DC-AC inverter always has uneven THD distribution, e.g. THD concentrates at 4fc ± 1 orders for signal-phase inverter, and 6k ± 1 orders for three-phase inverter. Furthermore, a digital RC requires a integral ratio of the sampling frequency and the reference frequency, whereas the digital control system cannot always meet this requirement. For example, (e.g. 60 Hz reference signal with a 5 kHz sampling frequency, or grid-connected converter under grid frequency fluctuation, etc.). In this paper, virtual delay unit (VDU) based digital nk ± m-order harmonic RC is presented to solve the problems above. The VDU produces a different virtual RC sampling frequency from the system sampling frequency. The virtual sampling frequency for digital RC can be flexibly adjusted based on the integral ratio requirement. The advantage of VDU is that it does not vary the system sampling frequency and it is easy to be realized. Furthermore, nk ± m-order harmonic repetitive controller is selected to provide a selective harmonic compensation (SHC). Experimental results of VDU based nk±m-order harmonic RC for 60 Hz single-phase DC/AC inverter with 5 kHz system sampling frequency are provided to show the effectiveness of the proposed VDU-based SHC

A simple high-performance current control strategy for V2G three-phase four-leg inverter with LCL filter

Electric vehicles (EVs) can behave as distributed energy storage devices for providing on-demand smart grid support service, that is an emerging Vehicle-to-Grid (V2G) technology. A high-performance and easy-implementation current control strategy for V2G Three-phase four-leg inverter with LCL filter is proposed. It consists of a deadbeat (DB) controller and a paralleled repetitive controller (RC). The DB controller is based on weighted average inductor current (WAIC) scheme, which simplifies the third-order LCL filter to be an equivalent 1st order L filter. The stability of the DB controlled inverter with the unmodelled system time delay is analyzed. DB controller is of very fast response and easy implementation, but is not immune to system time delay and various uncertainties. To overcome the disadvantages, a plug-in RC is added to reinforce the DB controller to remove harmonic distortion from the feed-in current in the presence of parameter uncertainties. A lab prototype of 10kW grid-connected three-phase four-leg inverter has been built up to validate the proposed current control strategy. The simulations and experiments are provided to demonstrate the validity of the proposed control strategy

Virtual variable sampling discrete fourier transform based selective odd-order harmonic repetitive control of DC/AC converters

This paper proposes a frequency adaptive discrete Fourier transform (DFT) based repetitive control (RC) scheme for DC/AC converters. By generating infinite magnitude on the interested harmonics, the DFT-based RC offers a selective harmonic scheme to eliminate waveform distortion. The traditional DFT-based selective harmonic RC, however, is sensitive to frequency fluctuation since even very small frequency fluctuation leads to a severe magnitude decrease. To address the problem, virtual variable sampling method, which creates an adjustable virtual delay unit to closely approximate a variable sampling delay, is proposed to enable the DFT-based selective harmonic RC to be frequency adaptive. Moreover, a selective odd-order harmonic DFT filter is developed to deal with the dominant odd order harmonic. Because it halves the number of sampling delays in the DFT filter, the system transient response gets nearly 50% improvement. A comprehensive series of experiments of the proposed VVS DFT-based selective odd-order harmonic RC controlled programmable AC power source under frequency variations are presented to verify the effectiveness of the proposed method

Evaluation of MicroRNA 125b as a potential biomarker for postmenopausal osteoporosis

Purpose: To identify significant dysregulated miRNAs in postmenopausal  osteoporosis in Chinese women and to test whether any of these miRNAs have diagnostic potential as circulatory biomarkers for postmenopausal osteoporosis.Methods: Thirty osteoporotic patients and 30 non-osteoporotic healthy individuals were recruited, and blood and bone tissue samples were collected from them. miRNA expression profiling and quantitative real-time polymerase chain reaction  (qRT-PCR) were used to identify and substantiate dysregulated miRNAs in blood sera and bone tissue from osteoporotic patients. Receiver operating characteristic curve (ROC) analysis was carried out to assess the diagnostic potential of significantly dysregulated miRNAs.Results: Based on profiling and qRT-PCR, miR-125b, miR-30 and miR-5914 were significantly upregulated in the blood sera and bone tissues of patients with postmenopausal osteoporosis. In all the experiments carried out, miR-125b showed the highest levels of upregulation both in the blood sera and bone tissue compared to other upregulated miRNAs in osteoporotic patients. ROC analysis indicate that the AUC of miR-125b was the highest amongst the upregulated miRNAs.Conclusion: miR-125b is the highest significantly upregulated miRNA in  postmenopausal osteoporosis. Furthermore, circulating miR-125b has the potential of a non-invasive biomarker for postmenopausal osteoporosis.Keywords: Postmenopausal osteoporosis, Profiling, Up-regulation, miR-125b,  Biomarke

Effect of Seed Morph and Light Level on Growth and Reproduction of the Amphicarpic Plant \u3cem\u3eAmphicarpaea edgeworthii\u3c/em\u3e (Fabaceae)

Amphicarpic plants produce aerial and subterranean fruits on an individual plant, and these heteromorphic diaspores give rise to plants that differ in growth and ecology. Amphicarpaea edgeworthii is a summer annual amphicarpic species that grows over a range of light levels. We aimed to compare the response to shading intensity of plants of A. edgeworthii grown throughout their life cycle from aerial seeds (ASP) and from subterranean seeds (SSP). We hypothesized that vegetative and reproductive growth of plants from ASP and SSP respond differently to light. Plants were grown from ASP and SSP under 0, 46, 71 and 90% shading intensities. With plant height as a covariate, vegetative biomass of ASP and SSP did not differ. Leaf area and seed production of SSP were greater and internode length less than they were for ASP in all shading intensities. Aerial and subterranean seed yield, seed mass and number for both ASP and SSP were highest in full light. Aerial seed yield was affected more than subterranean seed yield by shading intensity. The growth and reproductive responses of ASP and SSP of A. edgeworthii may be adaptive to the range of low to high light environments in which this species grows

Deep Reinforcement Learning Framework for Thoracic Diseases Classification via Prior Knowledge Guidance

The chest X-ray is often utilized for diagnosing common thoracic diseases. In recent years, many approaches have been proposed to handle the problem of automatic diagnosis based on chest X-rays. However, the scarcity of labeled data for related diseases still poses a huge challenge to an accurate diagnosis. In this paper, we focus on the thorax disease diagnostic problem and propose a novel deep reinforcement learning framework, which introduces prior knowledge to direct the learning of diagnostic agents and the model parameters can also be continuously updated as the data increases, like a person's learning process. Especially, 1) prior knowledge can be learned from the pre-trained model based on old data or other domains' similar data, which can effectively reduce the dependence on target domain data, and 2) the framework of reinforcement learning can make the diagnostic agent as exploratory as a human being and improve the accuracy of diagnosis through continuous exploration. The method can also effectively solve the model learning problem in the case of few-shot data and improve the generalization ability of the model. Finally, our approach's performance was demonstrated using the well-known NIH ChestX-ray 14 and CheXpert datasets, and we achieved competitive results. The source code can be found here: \url{https://github.com/NeaseZ/MARL}

New Polysaccharide Compounds Derived from Submerged Culture of Ganoderma lucidum and Lycium barbarum

Biljka Lycium barbarum i gljiva Ganoderma lucidum sve se više istražuju u Kini zbog njihove antitumorske aktivnosti, pri čemu se drži da su polisaharidi njihovi najvažniji funkcionalni sastojci. U ovom je radu istražen postupak dobivanja novih polisaharida, izoliranih iz sušenih plodova L. barbarum i dobivenih submerznim uzgojem G. lucidum. Podaci pokazuju da novodobiveni fermentirani polisaharidi i smjesa polisaharida u odgovarajućim omjerima i koncentracijama imaju veću sposobnost uklanjanja slobodnih radikala od izvornih polisaharida, te da sadrže slične frakcije. Zaključeno je da novi polisaharidi imaju veću bioaktivnost, a mogu se lakše dobiti fermentacijom.Lycium barbarum and Ganoderma lucidum, highly valued Chinese medicinal fruit and mushroom, have attracted more and more attention because of the antitumour activities they have shown, and polysaccharides are considered their most important functional constituent. Forming new compounds of L. barbarum polysaccharides, isolated from dried L. barbarum fruits, and G. lucidum polysaccharides, derived from a submerged culture of G. lucidum, has been investigated in this paper. Our data illustrate that two polysaccharide compounds, fermented polysaccharides and mixed polysaccharides, at the appropriate ratio and concentration have stronger free radical scavenging ability than the single polysaccharide. Ion exchange chromatography and high-performance liquid chromatography (HPLC) analyses indicated that the components of the new polysaccharide compounds had changed compared to those of the single polysaccharide. In addition, similar fractions were shared with the two polysaccharide compounds. Hence, the findings demonstrate that these new polysaccharide compounds might have stronger bioactivity than a single polysaccharide and could be obtained more easily by fermentation