Previously-reported Methods Research Articles

Distributed Fault-Tolerant Voltage/Frequency Synchronization in Autonomous AC Microgrids

This paper proposes two new distributed fault-tolerant control (FTC) algorithms for the restoration of voltage and frequency in autonomous inverter-interfaced AC microgrids (MGs). The proposed control schemes give fault-tolerance capability to the system against different potential faults in sensors and actuators. In the first algorithm, a distributed adaptive fault-tolerant method is employed to compensate for the potential sensor faults. Then, to address both sensor and actuator faults simultaneously, a distributed H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> protocol is employed to guarantee the voltage and frequency synchronization for the closed-loop system. In the design of these algorithms, there is no need to know the amplitude or any quantitative information about fault signals. Additionally, there is no restriction on the number of faulty units. Finally, to evaluate the performance of the proposed distributed cooperative fault-tolerant control algorithms, simulation studies are carried out on a test MG system, including several distributed generation (DG) units in MATLAB/Simulink environment and also the results are compared with several previously-reported methods. Simulation results and comparison with previous works reveal the effectiveness and accuracy of the proposed method in regulating MG voltage and frequency and providing accurate proportional active power-sharing.

Chitosan-toluidine blue beads for purification of fucoidans

A simple and green method was developed to purify fucoidans from their crude extracts. The new method utilizes a genipin-crosslinked chitosan beads as a support matrix for toluidine blue (TB). The modification of the mostly composed of d-glucosamine polymer was performed in one-step reaction to improve its mechanical stability and affinity to fucoidans. The adsorption kinetics and isotherm were investigated, which showed a maximum loading capacity (qmax) of 137.8 mg fucoidans/g wet beads. Moreover, the modified chitosan-TB beads were applied for purification of fucoidans from Fucus vesiculosus crude extract at different pH values, pH 1.0 and pH 6.0, producing two fractions: FC_1 and FC_6, respectively. The fractions were then characterized in comparison with crude and Sigma-Aldrich® purified product by FTIR and elemental analysis. The new method produced beads with higher loading capacity and used a natural crosslinker compared to the previously-reported methods.

Cooperative Fault-Tolerant Control of Microgrids Under Switching Communication Topology

In this paper, to address the problem of multiple actuator faults in autonomous AC microgrids, a cooperative fault-tolerant control (CFTC) algorithm is designed. The proposed algorithm is responsible for the potential heterogeneous faults in units’ actuators, like loss of effectiveness (LOE) and unknown bias faults. Furthermore, the communication network is considered as a directed switching graph, which can be viewed as an unreliable network and makes the CFTC problem more challenging. Also, in addition to the distributed generation (DG) units, we consider the presence of distributed energy storage (DES) systems that operate in the islanded microgrid. In addition to the voltage and frequency regulation, it is required to balance the state of charge (SoC) of DESs to achieve accurate active power-sharing. Finally, to evaluate the performance of the proposed CFTC algorithm, simulation studies are carried out on a test microgrid system in MATLAB/Simulink environment, and the results are compared with several previously-reported methods. Simulation results and comparison with other previously-reported techniques reveal the effectiveness and accuracy of the proposed method in regulating microgrid voltage and frequency, balancing of SoC, and providing accurate proportional active power-sharing.

A Novel Method of Analysis for Prolonged-Standing Data: Accounting for Joint and Muscle Discomfort

OCCUPATIONAL APPLICATIONS Prolonged standing, often required in healthcare, factory, and retail jobs, is associated with adverse health effects. In the present study, we introduce a novel method for analyzing prolonged-standing data, which accounts for time-dependent strain characteristics of both cartilage and muscle tissue to identify two different types of weight distribution change events. Compared to existing methods for analyzing this type of data, our proposed method provides more information about the amplitude and temporal quality of the movements occurring. If a worker were to stand on a surface that measures postural sway during a typical work day, this analysis method could identify the types of movements an individual makes, and help infer sources of discomfort. By understanding the movement strategy utilized, the most appropriate work environment adaptations can be put into place to decrease discomfort. These environmental adaptations may have downstream effects on worker satisfaction and days on disability.TECHNICAL ABSTRACT Background: The typical American worker spends about two-thirds of their work day standing. Prolonged standing has been found to be associated with acute and chronic adverse health outcomes. There is considerable variability among existing methods of analysis for prolonged-standing data, and therefore difficulty interpreting and comparing results across studies. Purpose: The purpose of this study is to develop a bodyweight transfer analysis method that incorporates factors of both time and amplitude of loading. This method was then applied to actual prolonged-standing data, to understand how the results of this method are impacted by time spent standing, and how the results relate to previously-reported methods of analysis for weight shifting data. Methods: Seven subjects (six male, one female) stood with each foot on one of two force plates for 6 h with a 5-min seated rest break between hours. Our new method identified two different types of events: fidgets and weight shifts. Center-of-pressure data were analyzed with the proposed method and three existing methods of analysis. Results: Subjects utilized different quantities of fidgets and weight shifts over the course of the trials. Existing methods of analysis identified a wide range in number of events, with some methods consistently identifying more events than others. These existing methods significantly differed from the proposed method. Fidgets, weight shifts, and fidgets + weight shifts, as identified using the proposed method, had significant interactions with time, while only one of the existing methods showed a significant time interaction. Conclusions: The conclusions drawn from analysis of prolonged standing center-of-pressure data can differ significantly depending on the method of analysis used. The method proposed here accounts for the different sources of discomfort and the tissue characteristics of these sources. Future work should explore the relationships between physiologic parameters and fidgets and weight shifts, so that appropriate clinical interventions can be identified.

ANFIS-Based Peak Power Shaving/Curtailment in Microgrids Including PV Units and BESSs

One of the most crucial and economically-beneficial tasks for energy customers is peak load curtailment. On account of the fast response of renewable energy resources (RERs) such as photovoltaic (PV) units and battery energy storage system (BESS), this task is closer to be efficiently implemented. Depends on the customer peak load demand and energy characteristics, the feasibility of this strategy may vary. When adaptive neuro-fuzzy inference system (ANFIS) is exploited for forecasting, it can provide many benefits to address the above-mentioned issues and facilitate its easy implementation, with short calculating time and re-trainability. This paper introduces a data-driven forecasting method based on fuzzy logic (FL) for optimized peak load reduction. First, the amount of energy generated by PV is forecasted using ANFIS which conducts output trend, and then, the BESS capacity is calculated according to the forecasted results. The trend of the load power is then decomposed in Cartesian plane into two parts, namely left and right from load peak, for the sake of searching for equal BESS capacity. Network switching sequence over consumption is provided by a fuzzy logic controller (FLC) considering BESS capacity and PV energy output. Finally, to prove the effectiveness of the proposed ANFIS-based peak power shaving/curtailment method, offline digital time-domain simulations have been performed on a test microgrid system using the data gathered from a real-life practical test microgrid system in the MATLAB/Simulink environment and the results have been experimentally verified by testing on a practical microgrid system with real-life data obtained from smart meters and also, compared with several previously-reported methods.

Ultralow content silver densely-coated glass microsphere for high performance conducting polymer-matrix composites

A synergistic electroless Ag plating using binary reductants of NaBH4 and glucose is demonstrated to fabricate high conducting silver-coated glass microsphere composite particles (GM@AgCPs) with ultralow Ag content (WAg) of 5.1 wt% for high performance conducting polymer-matrix composites (CPMCs). In this approach, NaBH4, as strong reductant, plays an important role in the nucleation while glucose, as weak one, is responsible for the growth of nuclei, indicating the synergistic effect between the binary reductants. Furthermore, the nucleation and growth are dexterously separated by our experimental design. First, the addition of a small amount of NaBH4 solution results in a large driving force of redox reaction, and favors nucleation burst. Meanwhile, homogeneous nucleation is effectively inhibited at a low T. Second, glucose at an elevated T results in fast and uniform growth rate of nuclei, which tends to form compact nanoshell on glass microsphere. Consequently, CPMCs of as-synthesized GM@AgCPs exhibit lower resistivity, smaller percolation threshold and stronger shielding effectiveness than those of composite particles with same WAg synthesized by the previously-reported methods, originating from denser silver nanoshell. More importantly, as-obtained CPMCs show the most excellent reliability for electronic device interconnect among all available commercial Ag-containing CPMCs with the comparative resistivity, owing to the lowest WAg. Additionally, the as-synthesized composite particles or their CPMCs exhibit perfect environmental adaptability and mechanical performance. Our results promise important applications in conducting or electromagnetic interference shielding polymer-matrix composites.

An efficient route to Cu2O nanorod array film for high-performance Li-ion batteries

Fabrication of well-organized one-dimensional nanostructured arrays on conducting substrates as binder free electrodes allows us to synergize and integrate multi-functionalities into lithium ion batteries. In this contribution, we report a metal-induced thermal reduction (MITR) method to prepare free-standing Cu2O nanorod array film with average diameters of 400±100nm and lengths of several microns on copper substrates by direct thermal reduction of Cu(OH)2 nanorod arrays on copper foils in nitrogen atmosphere at 500°C. The presence of Cu substrates reduces the Cu(OH)2 to Cu2O and decreases the reduction temperature significantly through changing the reaction Gibbs energy. Compared with some previously-reported methods about thermal reduction, the MITR method is facile, controllable, efficient and low energy consumption. The free-standing Cu2O nanorod array film on Cu substrates as anode can achieve high rate capability (315mAhg−1 at 10 C) and good cyclability (358mAhg−1 after 200cycles at 1 C), demonstrating their excellent electrochemical performance in lithium ion batteries, which results from relatively faster electron and ion transport, easier electrolyte diffusion and better accommodation of strains from the repeated conversion reactions based on their one-dimensional nanostructured arrays.

On the vacuum Einstein equations along curves with a discrete local rotation and reflection symmetry

We discuss the possibility of a dimensional reduction of the Einstein equations in S3 black-hole lattices. It was reported in previous literature that the evolution of spaces containing curves of local, discrete rotation and reflection symmetry (LDRRS) can be carried out via a system of ODEs along these curves. However, 3+1 Numerical Relativity computations demonstrate that this is not the case, and we show analytically that this is due to the presence of a tensorial quantity which is not suppressed by the symmetry. We calculate the term analytically, and verify numerically for an 8-black-hole lattice that it fully accounts for the anomalous results, and thus quantify its magnitude in this specific case. The presence of this term prevents the exact evolution of these spaces via previously-reported methods which do not involve a full 3+1 integration of Einstein's equation.

Single-feature polymorphism discovery by computing probe affinity shape powers

BackgroundSingle-feature polymorphism (SFP) discovery is a rapid and cost-effective approach to identify DNA polymorphisms. However, high false positive rates and/or low sensitivity are prevalent in previously described SFP detection methods. This work presents a new computing method for SFP discovery.ResultsThe probe affinity differences and affinity shape powers formed by the neighboring probes in each probe set were computed into SFP weight scores. This method was validated by known sequence information and was comprehensively compared with previously-reported methods using the same datasets. A web application using this algorithm has been implemented for SFP detection. Using this method, we identified 364 SFPs in a barley near-isogenic line pair carrying either the wild type or the mutant uniculm2 (cul2) allele. Most of the SFP polymorphisms were identified on chromosome 6H in the vicinity of the Cul2 locus.ConclusionThis SFP discovery method exhibits better performance in specificity and sensitivity over previously-reported methods. It can be used for other organisms for which GeneChip technology is available. The web-based tool will facilitate SFP discovery. The 364 SFPs discovered in a barley near-isogenic line pair provide a set of genetic markers for fine mapping and future map-based cloning of the Cul2 locus.