14,501 research outputs found
An Author Writing to Remember and Celebrate Black Children
No full textWith an undergraduate degree in sociology from Morgan State University (Baltimore, MD) and a master’s degree in Library Science from the Catholic University of America (Washington, DC), Sharon Bell Mathis is a librarian and a multiple award-winning children’s and young adult book author [...
Report of A. P. Bell, Week of March 5-8, 1962
No full textReport of A. P. Bell, Week of March 5-8, 1962. Recorded attendance at the President\u27s Conference on Occupational Safety in Washington, DC
Report of A. P. Bell, Week of March 26-30, 1962
No full textReport of A. P. Bell, Week of March 26-30, 1962, which covers his attendance at the Inter-Regional Conference of Supervisors and Teacher-Trainers in Vocational Agriculture in Washington, DC
Loophole-free Bell test using electron spins in diamond: second experiment and additional analysis
No full textThis is the dataset that belongs to the experiment described in the article "Loophole-free Bell test using electron spins in diamond: second experiment and additional analysis", online preprint at arXiv:1603.05705
[Correspondence R. Hanson to: [email protected]
Common Mode Currents in DC Power Routers
No full textThe grid reinforcement and energy redirection needs have led to the emergence of Back-To-Back Voltage Source Converter (BTB-VSC) based dc power routers. This paper investigates the low frequency Common Mode Currents (CMCs) that arise in the system if the employed BTB-VSCs have an un-isolated ac path connected in parallel to their output ports. Simulation results are presented to show a sensitivity analysis of lower order harmonics in CMC with respect to the operating active and reactive power of the dc router, dc link voltage, link resistance, modulation method and pole capacitance. Experimental results are shared to show existance of lower order CMC in 3-wire ac link operating in parallel with the dc power router and these are mitigated using zero sequence controller
Modeling, Control, and Operation of an M-DAB DC-DC Converter for Interconnection of HVDC Grids
No full textFuture high-voltage direct-current (HVDC) networks based on voltage source converters (VSCs) will have different structures (asymmetric monopolar, bipolar, or symmetric monopolar), voltage levels, control, and protection schemes. Therefore, dc-dc converters are needed to interconnect those VSC-HVDC grids and several technical issues on their control and operational systems must be adequately addressed. A dc-dc converter based on a modular-dual active bridge (M-DAB) converter is suggested to reach a desirable interconnection of the HVDC grids and regulate power flow (PF) between them. A dynamic averaged model is proposed for the M-DAB converter and its stability is analyzed using the Lyapunov function. Moreover, a new local controller based on nonlinear control theory is proposed for the M-DAB. The new M-DAB local controller is integrated with the energy management system (EMS), by updating the PF equations, to create a complete control structure. Considering the CIGRE DCS3 HVDC test system and the studied M-DAB, static, dynamic simulation, and experimental studies are conducted and the dc-dc converter and the performance of the designed controllers and the EMS are examined and validated.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Intelligent Electrical Power Grid
REGCMPNT : A Fortran Program for Regression Models with ARIMA Component Errors
No full textRegComponent models are time series models with linear regression mean functions and error terms that follow ARIMA (autoregressive-integrated-moving average) component time series models. Bell (2004) discusses these models and gives some underlying theoretical and computational results. The REGCMPNT program is a Fortran program for performing Gaussian maximum likelihood estimation, signal extraction, and forecasting with RegComponent models. In this paper we briefly examine the nature of RegComponent models, provide an overview of the REGCMPNT program, and then use three examples to show some important features of the program and to illustrate its application to various different RegComponent models.
Restructuring the existing medium voltage distribution grids using DC systems
No full textGreen Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.DC systems, Energy conversion & Storag
Cold cracking in DC-cast high strength aluminum alloy ingots: An intrinsic problem intensified by casting process parameters
No full textFor almost half a century the catastrophic failure of direct chill (DC) cast high strength aluminum alloys has been challenging the production of sound ingots. To overcome this problem, a criterion is required that can assist the researchers in predicting the critical conditions which facilitate the catastrophic failure of the ingots. This could be achieved at first glance by application of computer simulations to assess the level and distribution of residual thermal stresses. However, the simulation results are only able to show the critical locations and conditions where and when high stresses may appear in the ingots. The prediction of critical void/crack size requires simultaneous application of fracture mechanics. In this paper, we present the thermo-mechanical simulation results that indicate the critical crack size distribution in several DC-cast billets cast at various casting conditions. The simulation results were validated upon experimental DC-casting trials and revealed that the existence of voids/cracks with a considerable size is required for cold cracking to occur.Materials Science & EngineeringMechanical, Maritime and Materials Engineerin
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