Search NASA⌕ Search

SEARCH · Search NASA

Results for “control”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Method for controlling fiber growth in a laser heated pedestal growth system by controlling a laser power output, a pedestal feedstock rate of motion, and a draw rate

One or more embodiments relate to a method for controlling fiber growth and fiber diameter in a laser heated pedestal growth (LHPG) system so as to provide long, continuous single-crystal optical fibers of uniform diameter. The method generally provides three independent parameter feedback controls to control the molten zone height, laser power, and fiber drawing rates simultaneously in order to reduce the mismatch between instantaneous diameter changes and current diameter. The method permits the growth of fibers with non-uniform diameters along the fiber's length. The method also provides the capability to stop the LHPG system, remove the exhausted pedestal feedstock with a second pedestal feedstock, and restart the LHPG system to provide a continuous fiber.

Buric, Michael P.↗
DOE OSTI2015

Anomalies of the fissile mass control inside a controlled geometry leading to important safety issues - 14298

This article focuses on the very usual case of the fissile mass control inside a controlled geometry, whatever the fissile density in the fissile-moderator mixture is. Although this case is very usual (maximal loading of fissile material in a transport cask, maximal fissile content in a 'geometrically favorable' tank, etc.), some unexpected behaviors ('anomalies') may be met, leading to important nuclear criticality safety issues. This article will show the three following anomalies and the associated safety issues: - the 'non-smooth' variation of the minimum critical mass for a small variation of the geometry size (a cylinder case is considered throughout this article), - the very important differences in critical values, for intermediate-size geometries, between two fissile media having very close minimum critical masses and dimensions, - the change in the hierarchy of different fissile media when the size of the geometry changes. The next part of the article will demonstrate that these anomalies are, from a physics point of view, due to the nature of the fissile material and, from a methodology point of view, due to the fact that this 'Mass- Geometry Control' problem is generally solved without looking at the critical mass for the whole range of geometries. The latter happens because this whole resolution is not trivial and requires either a lot of calculations or human effort to estimate the mass limits as a function of the geometry. Another article will discuss this question of the 'whole' resolution of the problem. (authors)

42 ENGINEERING↗
DOE OSTI2014

Heterogeneous recurrence monitoring and control of nonlinear stochastic processes

Recurrence is one of the most common phenomena in natural and engineering systems. Process monitoring of dynamic transitions in nonlinear and nonstationary systems is more concerned with aperiodic recurrences and recurrence variations. However, little has been done to investigate the heterogeneous recurrence variations and link with the objectives of process monitoring and anomaly detection. Notably, nonlinear recurrence methodologies are based on homogeneous recurrences, which treat all recurrence states in the same way as black dots, and non-recurrence is white in recurrence plots. Heterogeneous recurrences are more concerned about the variations of recurrence states in terms of state properties (e.g., values and relative locations) and the evolving dynamics (e.g., sequential state transitions). This paper presents a novel approach of heterogeneous recurrence analysis that utilizes a new fractal representation to delineate heterogeneous recurrence states in multiple scales, including the recurrences of both single states and multi-state sequences. Further, we developed a new set of heterogeneous recurrence quantifiers that are extracted from fractal representation in the transformed space. To that end, we integrated multivariate statistical control charts with heterogeneous recurrence analysis to simultaneously monitor two or more related quantifiers. Experimental results on nonlinear stochastic processes show that the proposed approach not only captures heterogeneous recurrence patterns in the fractal representation but also effectively monitors the changes in the dynamics of a complex system.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Recovery Act: Federspiel Controls (now Vigilent) and State of California Department of General Services Data Center Energy Efficient Cooling Control Demonstration. Final technical project report

Eight State of California data centers were equipped with an intelligent energy management system to evaluate the effectiveness, energy savings, dollar savings and benefits that arise when powerful artificial intelligence-based technology measures, monitors and actively controls cooling operations. Control software, wireless sensors and mesh networks were used at all sites. Most sites used variable frequency drives as well. The system dynamically adjusts temperature and airflow on the fly by analyzing real-time demands, thermal behavior and historical data collected on site. Taking into account the chaotic interrelationships of hundreds to thousands of variables in a data center, the system optimizes the temperature distribution across a facility while also intelligently balancing loads, outputs, and airflow. The overall project will provide a reduction in energy consumption of more than 2.3 million kWh each year, which translates to $240,000 saved and a reduction of 1.58 million pounds of carbon emissions. Across all sites, the cooling energy consumption was reduced by 41%. The average reduction in energy savings across all the sites that use VFDs is higher at 58%. Before this case study, all eight data centers ran the cooling fans at 100% capacity all of the time. Because of the new technology, cooling fans run at the optimum fan speed maintaining stable air equilibrium while also expending the least amount of electricity. With lower fan speeds, the life of the capital investment made on cooling equipment improves, and the cooling capacity of the data center increases. This case study depicts a rare technological feat: The same process and technology worked cost effectively in eight very different environments. The results show that savings were achieved in centers with diverse specifications for the sizes, ages and types of cooling equipment. The percentage of cooling energy reduction ranged from 19% to 78% while keeping temperatures substantially within the limits recommended by the American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) for data center facilities.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2017

User-Preference-Driven Model Predictive Control of Residential Building Loads and Battery Storage for Demand Response: Preprint

This paper presents a user-preference-driven home energy management system (HEMS) for demand response (DR) with residential building loads and battery storage. The HEMS is based on a multi-objective model predictive control algorithm, where the objectives include energy cost, thermal comfort, and carbon emission. A multi-criterion decision making method originating from social science is used to quickly determine user preferences based on a brief survey and derive the weights of different objectives used in the optimization process. Besides the residential appliances used in the traditional DR programs, a home battery system is integrated into the HEMS to improve the flexibility and reliability of the DR resources. Simulation studies have been performed on field data from a residential building stock data set. Appliance models and usage patterns were learned from the data to predict the DR resource availability. Results indicate the HEMS was able to provide a significant amount of load reduction with less than 20% prediction error in both heating and cooling cases.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗