Tradeoffs between AC power quality and DC bus ripple for 3-phase 3-wire inverter-connected devices within microgrids

Visions of future power systems contain high penetrations of inverters which are used to convert power from dc (direct current) to ac (alternating current) or vice versa. The behavior of these devices is dependent upon the choice and implementation of the control algorithms. In particular, there is a tradeoff between dc bus ripple and ac power quality. This study examines the tradeoffs. Four control modes are examined. Mathematical derivations are used to predict the key implications of each control mode. Then, an inverter is studied both in simulation and in hardware at the 10 kVA scale, in different microgrid environments of grid impedance and power quality. It is found that voltage-drive mode provides the best ac power quality, but at the expense of high dc bus ripple. Sinusoidal current generation and dual-sequence controllers provide relatively low dc bus ripple and relatively small effects on power quality. High-bandwidth dc bus ripple minimization mode works well in environments of low grid impedance, but is highly unsuitable within higher impedance microgrid environments and/or at low switching frequencies. The findings also suggest that the certification procedures given by G5/4, P29 and IEEE 1547 are potentially not adequate to cover all applications and scenarios

SBMLToolbox: an SBML toolbox for MATLAB users

We present SBMLToolbox, a toolbox that facilitates importing and exporting models represented in the Systems Biology Markup Language (SBML) in and out of the MATLAB environment and provides functionality that enables an experienced user of either SBML or MATLAB to combine the computing power of MATLAB with the portability and exchangeability of an SBML model. SBMLToolbox supports all levels and versions of SBML

Systems Biology Markup Language (SBML) Level 2: Structures and Facilities for Model Definitions

Not applicabl

The Trouble with Ed Schools: A Book Review

American schools of education, whose two primary objectives are to prepare highly qualified teachers and to conduct valid and reliable education research, are often decried as “weak institutions” by many in academia and society in general. American schools of education are very often scorned by scholars and academia as intellectually inferior, referred to by teachers in the field as the “ivory tower” and considered to be out of touch and completely unrelated to what really transpires in schools, perceived by political leaders at all levels to be a primary contributing factor to the substandard state of contemporary public education. These are the observations and assertions of David Labaree, a professor in the school of education at Stanford University, who in The Trouble with Ed Schools employs critical sociological and historical analyses to analyze and examine the factors that have directly contributed to the lowly status of education schools in general, and the contemporary assumptions and perceptions that perpetuate this lowly status. If we as educators (and a society for that matter) are to achieve excellence in education we must be willing to engage in critical self reflection and analysis about the means by which we prepare teachers and engage in educational research and policy making. The Trouble with Ed Schools serves well as an impetus for such reflection and analysis

Guided Diffusion Monte Carlo Based On Bonding Environment: An Efficient Approach For Studying Molecular Vibrations In Pathological Systems

\par Diffusion Monte Carlo (DMC) is a technique that can be used to obtain the ground state energy and ground state wave function given a potential energy surface (PES) that fully describes the system of interest. However, one complication with this technique is that in order to obtain accurate results for molecular systems that have couplings between the high and low frequency vibrations, large ensemble sizes are needed. \footnote{Mallory, J. D. and Mandelshtam, V. A., {\it{J. Phys. Chem. A}} (2015), {\bf{119}}, 6504-6515.} One approach to combat these large ensemble sizes is to use a guiding function to describe the high-frequency vibrations. This approach has been applied to studies of neutral water clusters, protonated water clusters, and \chem{CH_5^+}, where a significant reduction in the ensemble sizes that were needed in the simulations was achieved. \footnote{Lee, V. G. M. and McCoy, A.B., {\it{J. Phys. Chem. A}} (2019), {\bf{123}}, 37, 8063-8070.} \footnote{Finney, J. M., DiRisio, R. J., McCoy, A.B., {\it{J. Phys. Chem. A}} (2020), {\bf{124}}, 45, 9567-9577.} An extension of this idea has been used to obtain excited state information in the coordinates described by the guiding functions. \par In this work, I will describe the applications of this approach to systems with large coupling among the vibrational degrees of freedom. The use of a guiding function that describes the ground state wave function of the high-frequency vibrations allow us to use smaller ensemble sizes, while producing ground state energies and wave functions that are as accurate or more accurate than those obtained using traditional DMC approaches. By using an excited state guiding function in the degrees of freedom that are being excited, we can obtain the excited state energy and wave functions through fixed-node DMC. With these wave functions in hand, we can also obtain overlaps between the ground state and first excited state, allowing us to evaluate intensities. This approach provides accurate representations of the excited state energy and the intensity of the transition from the ground state as long as the guiding functions for the ground and excited states provide fairly accurate representations of the wave functions along the excited degree of freedom

Effectiveness of Motor Imagery Versus Mirror Therapy to Improve Upper Limb Training in Stroke Subjects: A Comparative study

BACKGROUND: Stroke rehabilitation helps to restore lost function and reintegrates the stroke survivors into the society. Based on mirror neuron system, mental practice (MP) does cognitive rehearsal of activities that involves same cortical changes as physical practice in stroke survivors. OBJECTIVE: To determine the comparative efficacy of a mental practice (MP) intervention versus a mirror therapy (MT) intervention on upper limb motor function after stroke. METHODOLOGY: A thirty acute stroke subjects were assigned to the mental practice (MP; n-15) or to the mirror therapy (MT; n-15) group. Subjects were assessed before and after 7 weeks of intervention using Action Research Arm Test (ARAT). MP group was administered functional activity based visual motor imagery training and MT group was administered functional activity based mirror therapy training. Both groups had five tasks of real life rehearsal strategies and each session consisted of 60 minutes, 3 days in a week. RESULTS: After the intervention, means of ARAT using an ‘independent t-test’ showed subjects in the mental practice (MP) group were significantly higher than those of subjects in the mirror therapy (MT) group. There is a statistically significant difference in grasp, gross, pinch, grip and total score between the groups. CONCLUSION: Mental practice is a promising adjuvant therapy to physiotherapy practice with minimal direct supervision and minimal expense. It’s feasible to self-administer in virtually any environment with no specialized equipment

A variational approach to assess reaction coordinates for two-step crystallization

Molecule- and particle-based simulations provide the tools to test, in microscopic detail, the validity of classical nucleation theory. In this endeavor, determining nucleation mechanisms and rates for phase separation requires an appropriately defined reaction coordinate to describe the transformation of an out-of-equilibrium parent phase for which myriad options are available to the simulator. In this article, we describe the application of the variational approach to Markov processes to quantify the suitability of reaction coordinates to study crystallization from supersaturated colloid suspensions. Our analysis indicates that collective variables (CVs) that correlate with the number of particles in the condensed phase, the system potential energy, and approximate configurational entropy often feature as the most appropriate order parameters to quantitatively describe the crystallization process. We apply time-lagged independent component analysis to reduce high-dimensional reaction coordinates constructed from these CVs to build Markov State Models (MSMs), which indicate that two barriers separate a supersaturated fluid phase from crystals in the simulated environment. The MSMs provide consistent estimates for crystal nucleation rates, regardless of the dimensionality of the order parameter space adopted; however, the two-step mechanism is only consistently evident from spectral clustering of the MSMs in higher dimensions. As the method is general and easily transferable, the variational approach we adopt could provide a useful framework to study controls for crystal nucleation

The Standardization of the Surgeon

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The actin binding proteins cortactin and HS1 are dispensable for platelet actin nodule and megakaryocyte podosome formation

A dynamic, properly organised actin cytoskeleton is critical for the production and haemostatic function of platelets. The Wiskott Aldrich Syndrome protein (WASp) and Actin-Related Proteins 2 & 3 Complex (Arp2/3 complex) are critical mediators of actin polymerisation and organisation in many cell types. In platelets and megakaryocytes, these proteins have been shown to be important for proper platelet production and function. The cortactin family of proteins (Cttn & HS1) are known to regulate WASp-Arp2/3-mediated actin polymerisation in other cell types and so here we address the role of these proteins in platelets using knockout mouse models. We generated mice lacking Cttn and HS1 in the megakaryocyte/platelet lineage. These mice had normal platelet production, with platelet number, size and surface receptor profile comparable to controls. Platelet function was also unaffected by loss of Cttn/HS1 with no differences observed in a range of platelet function assays including aggregation, secretion, spreading, clot retraction or tyrosine phosphorylation. No effect on tail bleeding time or in thrombosis models was observed. In addition, platelet actin nodules, and megakaryocyte podosomes, actin-based structures known to be dependent on WASp and the Arp2/3 complex, formed normally. We conclude that despite the importance of WASp and the Arp2/3 complex in regulating F-actin dynamics in many cells types, the role of cortactin in their regulation appears to be fulfilled by other proteins in platelets