Power-Based Droop Control in DC Microgrids Enabling Seamless Disconnection From Upstream Grids

This paper proposes a local power-based droop controller for distributed energy resource converters in dc microgrids that are connected to upstream grids by grid-interface converters. During normal operation, the grid-interface converter imposes the microgrid bus voltage, and the proposed controller allows power flow regulation at distributed energy resource converters\u2019 output. On the other hand, during abnormal operation of the grid-interface converter (e.g., due to faults in the upstream grid), the proposed controller allows bus voltage regulation by droop control. Notably, the controller can autonomously convert from power flow control to droop control, without any need of bus voltage variation detection schemes or communication with other microgrid components, which enables seamless transitions between these two modes of operation. Considering distributed energy resource converters employing the power-based droop control, the operation modes of a single converter and of the whole microgrid are defined and investigated herein. The controller design is also introduced. Furthermore, the power sharing performance of this control approach is analyzed and compared with that of classical droop control. The experimental results from a laboratory-scale dc microgrid prototype are reported to show the final performances of the proposed power-based droop control

An Index of Biotic Integrity for Macroinvertebrate Stream Bioassessment Conducted by Community Scientists

Community science bioassessment has great potential to inform comprehensive stream management plans, but regional analytical tools are needed to evaluate macroinvertebrate data collected through community science programs. To this end, we modified a pre-existing professional index of biotic integrity (IBI) to create a community science IBI (CS-IBI), designed for stream macroinvertebrate data collected by community scientists with minimal training. We used data collected by both professional and community scientists to develop, calibrate, and validate the CS-IBI at 76 streamsites in the Puget Lowland andWillamette Valley ecoregions of the PacificNorthwest in theUnited States. Community science data were taxonomically coarser andmore variable than data generated by professionals; however, IBI scores and assemblage data were statistically similar between community science and professional data. Stream impairment categories classified by family-level CS-IBI scores matched genus-level professional classifications 65% of the time and never diverged by \u3e1 category. CS-IBI scores were negatively related to the percentage of agriculture and land development in the watershed, although this relationship was weaker than for professional IBI scores. Despite increased variability in data generated by community scientists, our findings suggest the CS-IBI performs similarly to a professional IBI across a gradient of human influence. Although we do not advocate using the CS-IBI in regulatory settings, we believe the development of community science IBIs enhances, expands, and strengthens public partnerships, thereby supporting environmental managers’ efforts to monitor and restore degraded streams and rapidly respond to pollution events. Our hope is that the CS-IBI will improve the applicability of community science bioassessment data and serve as a model for how agencies can develop regionalized macroinvertebrate IBIs for use in comprehensive watershed management plans. Key words: citizen science, community science, stream macroinvertebrates, stream bioassessment, index of biotic integrity, watershed stressor

A European study on decellularized homografts for pulmonary valve replacement: initial results from the prospective ESPOIR Trial and ESPOIR Registry data\u2020

OBJECTIVES: Decellularized pulmonary homografts (DPH) have shown excellent results for pulmonary valve replacement. However, controlled multicentre studies are lacking to date.METHODS: Prospective European multicentre trial evaluating DPH for pulmonary valve replacement. Matched comparison of DPH to bovine jugular vein (BJV) conduits and cryopreserved homografts (CH) considering patient age, type of heart defect and previous procedures.RESULTS: In total, 121 patients (59 female) were prospectively enrolled (August 2014-December 2016), age 21.3 +/- 14.4 years, DPH diameter 24.4 +/- 2.8 mm. No adverse events occurred with respect to surgical handling; there were 2 early deaths (30 + 59 years) due to myocardial failure after multi-valve procedures and no late mortality (1.7% mortality). After a mean follow-up of 2.2 +/- 0.6 years, the primary efficacy end points mean peak gradient (16.1 +/- 12.1 mmHg) and regurgitation (mean 0.25 +/- 0.48, grade 0-3) were excellent. One reoperation was required for recurrent subvalvular stenosis caused by a pericardial patch and 1 balloon dilatation was performed on a previously stented LPA. 100% follow-up for DPH patients operated before or outside the trial (n = 114) included in the ESPOIR Registry, age 16.6 +/- 10.4 years, diameter 24.1 +/- 4.2 mm, follow-up 5.1 +/- 3.0 years. The combined DPH cohort, n = 235, comprising both Trial and Registry data showed significantly better freedom from explantation (DPH 96.7 +/- 2.1%, CH 84.4 +/- 3.2%, P = 0.029 and BJV 82.7 +/- 3.2%, P = 0.012) and less structural valve degeneration at 10 years when matched to CH, n = 235 and BJV, n = 235 (DPH 61.4 +/- 6.6%, CH 39.9 +/- 4.4%, n.s., BJV 47.5 +/- 4.5%, P = 0.029).CONCLUSIONS: Initial results of the prospective multicentre ESPOIR Trial showed DPH to be safe and efficient. Current DPH results including Registry data were superior to BJV and CH.Thoracic Surger

5D gravity and the discrepant G measurements

It is shown that 5D Kaluza-Klein theory stabilized by an external bulk scalar field may solve the discrepant laboratory G measurements. This is achieved by an effective coupling between gravitation and the geomagnetic field. Experimental considerations are also addressed.Comment: 13 pages, to be published in: Proceedings of the 18th Course of the School on Cosmology and Gravitation: The gravitational Constant. Generalized gravitational theories and experiments (30 April-10 May 2003, Erice). Ed. by G. T. Gillies, V. N. Melnikov and V. de Sabbata, (Kluwer), 13pp. (in print) (2003

Excess of power during electrochemical loading : materials, electrochemical conditions and techniques

"Notes on The ENEA-University of Missouri NRL-SRI International Research Activities." ENEA, University of Missouri, NRL and SRI are cooperating within the frame of an International Program. The research field is on Metal Hydrogen Systems for Energy Applications and is oriented to develop nanostructured materials to be used into electrochemical devices and to study the Fleischmann and Pons Effect. Progress in material science and improvement in controlling the effect is presented

Development of a Testing and Analysis Framework for Validation of Rehabilitating Pipe-in-Pipe Technologies

Aging natural gas pipeline infrastructure needs rehabilitation, and trenchless, pipe-in-pipe (PIP) technologies offer a versatile solution. For example, legacy cast/wrought iron pipes have been subject to elevated incident rates for decades (www.phmsa.dot.gov). In an effort to accelerate innovation, the United States (U.S.) Department of Energy (DOE) has invested in a recently initiated, 3-year research program focused on pipeline “REPAIR”. To establish industry adoption of new technologies, a robust framework to evaluate and validate systems under in-service loading conditions is required. This paper introduces the approach taken by the Testing and Analysis team to develop a framework that confirms a 50-year design life for the PIP technologies. Testing protocols involve a comprehensive literature review, performance criteria, and relevant load cases and failure modes of PIP technologies. We use numerical and analytical modelling to investigate failure modes and severe conditions, thus informing testing protocols. In this paper, we discuss analytical frameworks and proposed model validation methods. We further discuss plans for test geometries (e.g., circumferentially cracked host pipe) and protocols (e.g., cyclic/dynamic traffic loading) to apply relevant load cases and probe failure modes in service. Modifications and enhancements are investigated in light of the insights gained from review and modelling. The testing and analysis framework for validating service life performance of trenchless PIP repair methods is intended to accelerate the development and adoption of new and safe repair technologies in the gas industry, as well as other critical lifeline systems.Patrick G. Dixon, Brad P. Wham, Jacob Klingaman, Allan Manalo, T. Tafsirojjaman, Khalid Farrag, Thomas D. O, Rourke, Mija H. Hubler, Shideh Dasht