TREAT Neutronics Analysis of Water-Loop Concept Accommodating LWR 9-rod Bundle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hill, Connie M.; Woolstenhulme, Nicolas E.; Parry, James R.

Abstract. Simulation of a variety of transient conditions has been successfully achieved in the Transient Reactor Test (TREAT) facility during operation between 1959 and 1994 to support characterization and safety analysis of nuclear fuels and materials. A majority of previously conducted tests were focused on supporting sodium-cooled fast reactor (SFR) designs. Experiments evolved in complexity. Simulation of thermal-hydraulic conditions expected to be encountered by fuels and materials in a reactor environment was realized in the development of TREAT sodium loop experiment vehicles. These loops accommodated up to 7-pin fuel bundles and served to simulate more closely the reactor environment whilemore » safely delivering large quantities of energy into the test specimen. Some of the immediate TREAT restart operations will be focused on testing light water reactor (LWR) accident tolerant fuels (ATF). Similar to the sodium loop objectives, a water loop concept, developed and analyzed in the 1990’s, aimed at achieving thermal-hydraulic conditions encountered in commercial power reactors. The historic water loop concept has been analyzed in the context of a reactivity insertion accident (RIA) simulation for high burnup LWR 2-pin and 3-pin fuel bundles. Findings showed sufficient energy could be deposited into the specimens for evaluation. Similar results of experimental feasibility for the water loop concept (past and present) have recently been obtained using MCNP6.1 with ENDF/B-VII.1 nuclear data libraries. The old water loop concept required only two central TREAT core grid spaces. Preparation for future experiments has resulted in a modified water loop conceptual design designated the TREAT water environment recirculating loop (TWERL). The current TWERL design requires nine TREAT core grid spaces in order to place the water recirculating pump under the TREAT core. Due to the effectiveness of water moderation, neutronics analysis shows that removal of seven additional TREAT fuel elements to facilitate the experiment will not inhibit the ability to successfully simulate a RIA for the 2-pin or 3-pin bundle. This new water loop design leaves room for accommodating a larger fuel pin bundle than previously analyzed. The 7-pin fuel bundle in a hexagonal array with similar spacing of fuel pins in a SFR fuel assembly was considered the minimum needed for one central fuel pin to encounter the most correct thermal conditions. The 9-rod fuel bundle in a square array similar in spacing to pins in a LWR fuel assembly would be considered the LWR equivalent. MCNP analysis conducted on a preliminary LWR 9-rod bundle design shows that sufficient energy deposition into the central pin can be achieved well within range to investigate fuel and cladding performance in a simulated RIA. This is achieved by surrounding the flow channel with an additional annulus of water. Findings also show that a highly significant increase in TREAT to specimen power coupling factor (PCF) within the central pin can be achieved by surrounding the experiment with one to two rings of TREAT upgrade fuel assemblies. The experiment design holds promise for the performance evaluation of PWR fuel at extremely high burnup under similar reactor environment conditions.« less

Water cooling system for an air-breathing hypersonic test vehicle

NASA Technical Reports Server (NTRS)

Petley, Dennis H.; Dziedzic, William M.

1993-01-01

This study provides concepts for hypersonic experimental scramjet test vehicles which have low cost and low risk. Cryogenic hydrogen is used as the fuel and coolant. Secondary water cooling systems were designed. Three concepts are shown: an all hydrogen cooling system, a secondary open loop water cooled system, and a secondary closed loop water cooled system. The open loop concept uses high pressure helium (15,000 psi) to drive water through the cooling system while maintaining the pressure in the water tank. The water flows through the turbine side of the turbopump to pump hydrogen fuel. The water is then allowed to vent. In the closed loop concept high pressure, room temperature, compressed liquid water is circulated. In flight water pressure is limited to 6000 psi by venting some of the water. Water is circulated through cooling channels via an ejector which uses high pressure gas to drive a water jet. The cooling systems are presented along with finite difference steady-state and transient analysis results. The results from this study indicate that water used as a secondary coolant can be designed to increase experimental test time, produce minimum venting of fluid and reduce overall development cost.

Closed Loop Control of Automotive Engines

DOT National Transportation Integrated Search

1981-12-01

Internal combustion engine economy and emissions are known to be sensitive to changes in engine control variables. Two of the most important variables are fuel/air ratio (f/a) and spark advance. These variables are affected by environmental changes, ...

Closed Loop Short Rotation Woody Biomass Energy Crops

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brower, Michael

CRC Development LLC is pursuing commercialization of shrub willow crops to evaluate and confirm estimates of yield, harvesting, transportation and renewable energy conversion costs and to provide a diverse resource in its supply portfolio.The goal of Closed Loop Short Rotation Woody Biomass Energy Crops is supply expansion in Central New York to facilitate the commercialization of willow biomass crops as part of the mix of woody biomass feedstocks for bioenergy and bioproducts. CRC Development LLC established the first commercial willow biomass plantation acreage in North America was established on the Tug Hill in the spring of 2006 and expanded inmore » 2007. This was the first 230- acres toward the goal of 10,000 regional acres. This project replaces some 2007-drought damaged acreage and installs a total of 630-acre new planting acres in order to demonstrate to regional agricultural producers and rural land-owners the economic vitality of closed loop short rotation woody biomass energy crops when deployed commercially in order to motivate new grower entry into the market-place. The willow biomass will directly help stabilize the fuel supply for the Lyonsdale Biomass facility, which produces 19 MWe of power and exports 15,000 pph of process steam to Burrows Paper. This project will also provide feedstock to The Biorefinery in New York for the manufacture of renewable, CO2-neutral liquid transportation fuels, chemicals and polymers. This project helps end dependency on imported fossil fuels, adds to region economic and environmental vitality and contributes to national security through improved energy independence.« less

Effect of Intake Air Filter Condition on Light-Duty Gasoline Vehicles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas, John F; Huff, Shean P; West, Brian H

2012-01-01

Proper maintenance can help vehicles perform as designed, positively affecting fuel economy, emissions, and the overall drivability. This effort investigates the effect of one maintenance factor, intake air filter replacement, with primary focus on vehicle fuel economy, but also examining emissions and performance. Older studies, dealing with carbureted gasoline vehicles, have indicated that replacing a clogged or dirty air filter can improve vehicle fuel economy and conversely that a dirty air filter can be significantly detrimental to fuel economy. The effect of clogged air filters on the fuel economy, acceleration and emissions of five gasoline fueled vehicles is examined. Fourmore » of these were modern vehicles, featuring closed-loop control and ranging in model year from 2003 to 2007. Three vehicles were powered by naturally aspirated, port fuel injection (PFI) engines of differing size and cylinder configuration: an inline 4, a V6 and a V8. A turbocharged inline 4-cylinder gasoline direct injection (GDI) engine powered vehicle was the fourth modern gasoline vehicle tested. A vintage 1972 vehicle equipped with a carburetor (open-loop control) was also examined. Results reveal insignificant fuel economy and emissions sensitivity of modern vehicles to air filter condition, but measureable effects on the 1972 vehicle. All vehicles experienced a measured acceleration performance penalty with clogged intake air filters.« less

Active Control of Combustor Instability Shown to Help Lower Emissions

NASA Technical Reports Server (NTRS)

DeLaat, John C.; Chang, Clarence T.

2002-01-01

In a quest to reduce the environmental impact of aerospace propulsion systems, extensive research is being done in the development of lean-burning (low fuel-to-air ratio) combustors that can reduce emissions throughout the mission cycle. However, these lean-burning combustors have an increased susceptibility to thermoacoustic instabilities, or high-pressure oscillations much like sound waves, that can cause severe high-frequency vibrations in the combustor. These pressure waves can fatigue the combustor components and even the downstream turbine blades. This can significantly decrease the safe operating life of the combustor and turbine. Thus, suppression of the thermoacoustic combustor instabilities is an enabling technology for lean, low-emissions combustors. Under the Aerospace Propulsion and Power Base Research and Technology Program, the NASA Glenn Research Center, in partnership with Pratt & Whitney and United Technologies Research Center, is developing technologies for the active control of combustion instabilities. With active combustion control, the fuel is pulsed to put pressure oscillations into the system. This cancels out the pressure oscillations being produced by the instabilities. Thus, the engine can have lower pollutant emissions and long life.The use of active combustion instability control to reduce thermo-acoustic-driven combustor pressure oscillations was demonstrated on a single-nozzle combustor rig at United Technologies. This rig has many of the complexities of a real engine combustor (i.e., an actual fuel nozzle and swirler, dilution cooling, etc.). Control was demonstrated through modeling, developing, and testing a fuel-delivery system able to the 280-Hz instability frequency. The preceding figure shows the capability of this system to provide high-frequency fuel modulations. Because of the high-shear contrarotating airflow in the fuel injector, there was some concern that the fuel pulses would be attenuated to the point where they would not be effective for control. Testing in the combustor rig showed that open-loop pulsing of the fuel was, in fact, able to effectively modulate the combustor pressure. To suppress the combustor pressure oscillations due to thermoacoustic instabilities, it is desirable to time the injection of the fuel so that it interferes with the instability. A closed-loop control scheme was developed that uses combustion pressure feedback and a phase-shifting controller to time the fuel-injection pulses. Some suppression of the pressure oscillations at the 280-Hz instability frequency was demonstrated (see the next figure). However, the overall peak-to- peak pressure oscillations in the combustor were only mildly reduced. Improvements to control hardware and control methods are being continued to gain improved closed-loop reduction of the pressure oscillations.pulse the fuel at

Establishment of a Remotely Piloted Helicopter Test Flight Program for Higher Harmonic Control Research

DTIC Science & Technology

1990-06-01

amplitude of the l IC actuators are set manually with no feedback of airframe response. Closed loop contrl refers to a system which utilizes response...mixture being controlled by the all position diaphragm carburetor and fuel pump . Ignition spark is ac-.cvd using " OX I mm spark plg. 28 b. Drive

Perspectives for a better understanding of the metabolic integration of photorespiration within a complex plant primary metabolism network

USDA-ARS?s Scientific Manuscript database

Photorespiration is an important high flux metabolic pathway that is found in all oxygen-producing photosynthetic organisms. It is often viewed as a closed loop that recycles carbon to fuel the Calvin cycle. However, the photorespiratory cycle is known to interact with several primary metabolic path...

Process Model of A Fusion Fuel Recovery System for a Direct Drive IFE Power Reactor

NASA Astrophysics Data System (ADS)

Natta, Saswathi; Aristova, Maria; Gentile, Charles

2008-11-01

A task has been initiated to develop a detailed representative model for the fuel recovery system (FRS) in the prospective direct drive inertial fusion energy (IFE) reactor. As part of the conceptual design phase of the project, a chemical process model is developed in order to observe the interaction of system components. This process model is developed using FEMLAB Multiphysics software with the corresponding chemical engineering module (CEM). Initially, the reactants, system structure, and processes are defined using known chemical species of the target chamber exhaust. Each step within the Fuel recovery system is modeled compartmentally and then merged to form the closed loop fuel recovery system. The output, which includes physical properties and chemical content of the products, is analyzed after each step of the system to determine the most efficient and productive system parameters. This will serve to attenuate possible bottlenecks in the system. This modeling evaluation is instrumental in optimizing and closing the fusion fuel cycle in a direct drive IFE power reactor. The results of the modeling are presented in this paper.

Fuel cell stack arrangements

DOEpatents

Kothmann, Richard E.; Somers, Edward V.

1982-01-01

Arrangements of stacks of fuel cells and ducts, for fuel cells operating with separate fuel, oxidant and coolant streams. An even number of stacks are arranged generally end-to-end in a loop. Ducts located at the juncture of consecutive stacks of the loop feed oxidant or fuel to or from the two consecutive stacks, each individual duct communicating with two stacks. A coolant fluid flows from outside the loop, into and through cooling channels of the stack, and is discharged into an enclosure duct formed within the loop by the stacks and seals at the junctures at the stacks.

Relative position control design of receiver UAV in flying-boom aerial refueling phase.

PubMed

An, Shuai; Yuan, Suozhong

2018-02-01

This paper proposes the design of the relative position-keeping control of the receiver unmanned aerial vehicle (UAV) with the time-varying mass in the refueling phase utilizing an inner-outer loop structure. Firstly, the model of the receiver in the refueling phase is established. And then tank model is set up to analyze the influence of fuel transfer on the receiver. Subsequently, double power reaching law based sliding mode controller is designed to control receiver translational motion relative to tanker aircraft in the outer loop while active disturbance rejection control technique is applied to the inner loop to stabilize the receiver. In addition, the closed-loop stabilities of the subsystems are established, respectively. Finally, an aerial refueling model under various refueling strategies is utilized. Simulations and comparative analysis demonstrate the effectiveness and robustness of the proposed controllers. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Chemical-Looping Combustion and Gasification of Coals and Oxygen Carrier Development: A Brief Review

DOE PAGES

Wang, Ping; Means, Nicholas; Shekhawat, Dushyant; ...

2015-09-24

Chemical-looping technology is one of the promising CO 2 capture technologies. It generates a CO 2 enriched flue gas, which will greatly benefit CO 2 capture, utilization or sequestration. Both chemical-looping combustion (CLC) and chemical-looping gasification (CLG) have the potential to be used to generate power, chemicals, and liquid fuels. Chemical-looping is an oxygen transporting process using oxygen carriers. Recently, attention has focused on solid fuels such as coal. Coal chemical-looping reactions are more complicated than gaseous fuels due to coal properties (like mineral matter) and the complex reaction pathways involving solid fuels. The mineral matter/ash and sulfur in coalmore » may affect the activity of oxygen carriers. Oxygen carriers are the key issue in chemical-looping processes. Thermogravimetric analysis (TGA) has been widely used for the development of oxygen carriers (e.g., oxide reactivity). Two proposed processes for the CLC of solid fuels are in-situ Gasification Chemical-Looping Combustion (iG-CLC) and Chemical-Looping with Oxygen Uncoupling (CLOU). The objectives of this review are to discuss various chemical-looping processes with coal, summarize TGA applications in oxygen carrier development, and outline the major challenges associated with coal chemical-looping in iG-CLC and CLOU.« less

System identification from closed-loop data with known output feedback dynamics

NASA Technical Reports Server (NTRS)

Phan, Minh; Juang, Jer-Nan; Horta, Lucas G.; Longman, Richard W.

1992-01-01

This paper presents a procedure to identify the open loop systems when it is operating under closed loop conditions. First, closed loop excitation data are used to compute the system open loop and closed loop Markov parameters. The Markov parameters, which are the pulse response samples, are then used to compute a state space representation of the open loop system. Two closed loop configurations are considered in this paper. The closed loop system can have either a linear output feedback controller or a dynamic output feedback controller. Numerical examples are provided to illustrate the proposed closed loop identification method.

Analysis of flexible aircraft longitudinal dynamics and handling qualities. Volume 1: Analysis methods

NASA Technical Reports Server (NTRS)

Waszak, M. R.; Schmidt, D. S.

1985-01-01

As aircraft become larger and lighter due to design requirements for increased payload and improved fuel efficiency, they will also become more flexible. For highly flexible vehicles, the handling qualities may not be accurately predicted by conventional methods. This study applies two analysis methods to a family of flexible aircraft in order to investigate how and when structural (especially dynamic aeroelastic) effects affect the dynamic characteristics of aircraft. The first type of analysis is an open loop model analysis technique. This method considers the effects of modal residue magnitudes on determining vehicle handling qualities. The second method is a pilot in the loop analysis procedure that considers several closed loop system characteristics. Volume 1 consists of the development and application of the two analysis methods described above.

Dislocation dynamics simulations of interactions between gliding dislocations and radiation induced prismatic loops in zirconium

NASA Astrophysics Data System (ADS)

Drouet, Julie; Dupuy, Laurent; Onimus, Fabien; Mompiou, Frédéric; Perusin, Simon; Ambard, Antoine

2014-06-01

The mechanical behavior of Pressurized Water Reactor fuel cladding tubes made of zirconium alloys is strongly affected by neutron irradiation due to the high density of radiation induced dislocation loops. In order to investigate the interaction mechanisms between gliding dislocations and loops in zirconium, a new nodal dislocation dynamics code, adapted to Hexagonal Close Packed metals, has been used. Various configurations have been systematically computed considering different glide planes, basal or prismatic, and different characters, edge or screw, for gliding dislocations with -type Burgers vectors. Simulations show various interaction mechanisms such as (i) absorption of a loop on an edge dislocation leading to the formation of a double super-jog, (ii) creation of a helical turn, on a screw dislocation, that acts as a strong pinning point or (iii) sweeping of a loop by a gliding dislocation. It is shown that the clearing of loops is more favorable when the dislocation glides in the basal plane than in the prismatic plane explaining the easy dislocation channeling in the basal plane observed after neutron irradiation by transmission electron microscopy.

Fuel System Durability--U.S. Coast Guard

DTIC Science & Technology

2008-05-01

bypass rates at the rated operating condition to finalize the test loop design. Preliminary calculations suggest that because of the anticipated low...The other option was to allow greater speed variability and operate as close to full-rack as possible. 24 Wear Scar Approx. Activated Area...Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202- 4302

An optimal open/closed-loop control method with application to a pre-stressed thin duralumin plate

NASA Astrophysics Data System (ADS)

Nadimpalli, Sruthi Raju

The excessive vibrations of a pre-stressed duralumin plate, suppressed by a combination of open-loop and closed-loop controls, also known as open/closed-loop control, is studied in this thesis. The two primary steps involved in this process are: Step (I) with an assumption that the closed-loop control law is proportional, obtain the optimal open-loop control by direct minimization of the performance measure consisting of energy at terminal time and a penalty on open-loop control force via calculus of variations. If the performance measure also involves a penalty on closed-loop control effort then a Fourier based method is utilized. Step (II) the energy at terminal time is minimized numerically to obtain optimal values of feedback gains. The optimal closed-loop control gains obtained are used to describe the displacement and the velocity of open-loop, closed-loop and open/closed-loop controlled duralumin plate.

Round Trip Energy Efficiency of NASA Glenn Regenerative Fuel Cell System

NASA Technical Reports Server (NTRS)

Garcia, Christopher P.; Chang, Bei-jiann; Johnson, Donald W.; Bents, David J.; Scullin, Vincent J.; Jakupca, Ian J.; Scullin, Vincent J.; Jakupca, Ian J.

2006-01-01

NASA Glenn Research Center (GRC) has recently demonstrated a Polymer Electrolyte Membrane (PEM) based hydrogen/oxygen regenerative fuel cell system (RFCS) that operated for a charge/discharge cycle with round trip efficiency (RTE) greater than 50 percent. The regenerative fuel cell system (RFCS) demonstrated closed loop energy storage over a pressure range of 90 to 190 psig. In charge mode, a constant electrical power profile of 7.1 kWe was absorbed by the RFCS and stored as pressurized hydrogen and oxygen gas. In discharge mode, the system delivered 3 to 4 kWe of electrical power along with product water. Fuel cell and electrolyzer power profiles and polarization performance are documented in this paper. Individual cell performance and the variation of cell voltages within the electrochemical stacks are also reported. Fuel cell efficiency, electrolyzer efficiency, and the system RTE were calculated from the test data and are included below.

Fuel control for gas turbine with continuous pilot flame

DOEpatents

Swick, Robert M.

1983-01-01

An improved fuel control for a gas turbine engine having a continuous pilot flame and a fuel distribution system including a pump drawing fuel from a source and supplying a line to the main fuel nozzle of the engine, the improvement being a control loop between the pump outlet and the pump inlet to bypass fuel, an electronically controlled throttle valve to restrict flow in the control loop when main nozzle demand exists and to permit substantially unrestricted flow without main nozzle demand, a minimum flow valve in the control loop downstream of the throttle valve to maintain a minimum pressure in the loop ahead of the flow valve, a branch tube from the pilot flame nozzle to the control loop between the throttle valve and the minimum flow valve, an orifice in the branch tube, and a feedback tube from the branch tube downstream of the orifice to the minimum flow valve, the minimum flow valve being operative to maintain a substantially constant pressure differential across the orifice to maintain constant fuel flow to the pilot flame nozzle.

Closed-Loop Control Better than Open-Loop Control of Profofol TCI Guided by BIS: A Randomized, Controlled, Multicenter Clinical Trial to Evaluate the CONCERT-CL Closed-Loop System

PubMed Central

Zhang, Xuena; Wu, Anshi; Yao, Shanglong; Xue, Zhanggang; Yue, Yun

2015-01-01

Background The CONCERT-CL closed-loop infusion system designed by VERYARK Technology Co., Ltd. (Guangxi, China) is an innovation using TCI combined with closed-loop controlled intravenous anesthesia under the guide of BIS. In this study we performed a randomized, controlled, multicenter study to compare closed-loop control and open-loop control of propofol by using the CONCERT-CL closed-loop infusion system. Methods 180 surgical patients from three medical centers undergone TCI intravenous anesthesia with propofol and remifentanil were randomly assigned to propofol closed-loop group and propofol opened-loop groups. Primary outcome was global score (GS, GS = (MDAPE+Wobble)/% of time of bispectral index (BIS) 40-60). Secondary outcomes were doses of the anesthetics and emergence time from anesthesia, such as, time to tracheal extubation. Results There were 89 and 86 patients in the closed-loop and opened-loop groups, respectively. GS in the closed-loop groups (22.21±8.50) were lower than that in the opened-loop group (27.19±15.26) (p=0.009). The higher proportion of time of BIS between 40 and 60 was also observed in the closed-loop group (84.11±9.50%), while that was 79.92±13.17% in the opened-loop group, (p=0.016). No significant differences in propofol dose and time of tracheal extubation were observed. The frequency of propofol regulation in the closed-loop group (31.55±9.46 times/hr) was obverse higher than that in the opened-loop group (6.84±6.21 times/hr) (p=0.000). Conclusion The CONCERT-CL closed-loop infusion system can automatically regulate the TCI of propofol, maintain the BIS value in an adequate range and reduce the workload of anesthesiologists better than open-loop system. Trial Registration ChiCTR ChiCTR-OOR-14005551 PMID:25886041

Proximity Operations for Space Situational Awareness Spacecraft Rendezvous and Maneuvering using Numerical Simulations and Fuzzy Logic

NASA Astrophysics Data System (ADS)

Carrico, T.; Langster, T.; Carrico, J.; Alfano, S.; Loucks, M.; Vallado, D.

The authors present several spacecraft rendezvous and close proximity maneuvering techniques modeled with a high-precision numerical integrator using full force models and closed loop control with a Fuzzy Logic intelligent controller to command the engines. The authors document and compare the maneuvers, fuel use, and other parameters. This paper presents an innovative application of an existing capability to design, simulate and analyze proximity maneuvers; already in use for operational satellites performing other maneuvers. The system has been extended to demonstrate the capability to develop closed loop control laws to maneuver spacecraft in close proximity to another, including stand-off, docking, lunar landing and other operations applicable to space situational awareness, space based surveillance, and operational satellite modeling. The fully integrated end-to-end trajectory ephemerides are available from the authors in electronic ASCII text by request. The benefits of this system include: A realistic physics-based simulation for the development and validation of control laws A collaborative engineering environment for the design, development and tuning of spacecraft law parameters, sizing actuators (i.e., rocket engines), and sensor suite selection. An accurate simulation and visualization to communicate the complexity, criticality, and risk of spacecraft operations. A precise mathematical environment for research and development of future spacecraft maneuvering engineering tasks, operational planning and forensic analysis. A closed loop, knowledge-based control example for proximity operations. This proximity operations modeling and simulation environment will provide a valuable adjunct to programs in military space control, space situational awareness and civil space exploration engineering and decision making processes.

Reliable and Affordable Control Systems Active Combustor Pattern Factor Control

NASA Technical Reports Server (NTRS)

McCarty, Bob; Tomondi, Chris; McGinley, Ray

2004-01-01

Active, closed-loop control of combustor pattern factor is a cooperative effort between Honeywell (formerly AlliedSignal) Engines and Systems and the NASA Glenn Research Center to reduce emissions and turbine-stator vane temperature variations, thereby enhancing engine performance and life, and reducing direct operating costs. Total fuel flow supplied to the engine is established by the speed/power control, but the distribution to individual atomizers will be controlled by the Active Combustor Pattern Factor Control (ACPFC). This system consist of three major components: multiple, thin-film sensors located on the turbine-stator vanes; fuel-flow modulators for individual atomizers; and control logic and algorithms within the electronic control.

Design and development of the Waukesha Custom Engine Control Air/Fuel Module

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moss, D.W.

1996-12-31

The Waukesha Custom Engine Control Air/Fuel Module (AFM) is designed to control the air-fuel ratio for all Waukesha carbureted, gaseous fueled, industrial engine. The AFM is programmed with a personal computer to run in one of four control modes: catalyst, best power, best economy, or lean-burn. One system can control naturally aspirated, turbocharged, in-line or vee engines. The basic system consists of an oxygen sensing system, intake manifold pressure transducer, electronic control module, actuator and exhaust thermocouple. The system permits correct operation of Waukesha engines in spite of changes in fuel pressure or temperature, engine load or speed, and fuelmore » composition. The system utilizes closed loop control and is centered about oxygen sensing technology. An innovative approach to applying oxygen sensors to industrial engines provides very good performance, greatly prolongs sensor life, and maintains sensor accuracy. Design considerations and operating results are given for application of the system to stationary, industrial engines operating on fuel gases of greatly varying composition.« less

A multi-port power electronics interface for battery powered electric vehicles: Application of inductively coupled wireless power transfer and hybrid energy storage system

NASA Astrophysics Data System (ADS)

McDonough, Matthew Kelly

Climate change, pollution, and geopolitical conflicts arising from the extreme wealth concentrations caused by fossil fuel deposits are just a few of the side-effects of the way that we fuel our society. A new method to power our civilization is becoming more and more necessary. Research for new, more sustainable fuel sources is already underway due to research in wind, solar, geothermal, and hydro power. However this focus is mainly on stationary applications. A large portion of fossil fuel usage comes from transportation. Unfortunately, the transition to cleaner transportation fuels is being stunted by the inability to store adequate amounts of energy in electro-chemical batteries. The idea of charging while driving has been proposed by many researchers, however several challenges still exist. In this work some of these challenges are addressed. Specifically, the ability to route power from multiple sources/loads is investigated. Special attention is paid to adjusting the time constant of particular converters, namely the battery and ultra-capacitor converters to reduce the high frequency and high magnitude current components applied to the battery terminals. This is done by developing a closed loop model of the entire multi-port converter, including the state of charge of the ultra-capacitors. The development of closed loop models and two experimental testbeds for use as stationary vehicle charging platforms with their unique set of sources/loads are presented along-side an on-board charger to demonstrate the similarities and differences between stationary charging and mobile charging. Experimental results from each are given showing that it is not only possible, but feasible to utilize Inductively Coupled Wireless Power Transfer (ICWPT) to charge a battery powered electric vehicle while driving and still protect the life-span of the batteries under the new, harsher conditions generated by the ICWPT system.

Chemical Looping Technology: Oxygen Carrier Characteristics.

PubMed

Luo, Siwei; Zeng, Liang; Fan, Liang-Shih

2015-01-01

Chemical looping processes are characterized as promising carbonaceous fuel conversion technologies with the advantages of manageable CO2 capture and high energy conversion efficiency. Depending on the chemical looping reaction products generated, chemical looping technologies generally can be grouped into two types: chemical looping full oxidation (CLFO) and chemical looping partial oxidation (CLPO). In CLFO, carbonaceous fuels are fully oxidized to CO2 and H2O, as typically represented by chemical looping combustion with electricity as the primary product. In CLPO, however, carbonaceous fuels are partially oxidized, as typically represented by chemical looping gasification with syngas or hydrogen as the primary product. Both CLFO and CLPO share similar operational features; however, the optimum process configurations and the specific oxygen carriers used between them can vary significantly. Progress in both CLFO and CLPO is reviewed and analyzed with specific focus on oxygen carrier developments that characterize these technologies.

Airstart performance of a digital electronic engine control system in an F-15 airplane

NASA Technical Reports Server (NTRS)

Licata, S. J.; Burcham, F. W., Jr.

1983-01-01

The airstart performance of the F100 engine equipped with a digital electronic engine control (DEEC) system was evaluated in an F-15 airplane. The DEEC system incorporates closed-loop airstart logic for improved capability. Spooldown and jet fuel starter-assisted airstarts were made over a range of airspeeds and altitudes. All jet fuel starter-assisted airstarts were successful, with airstart time varying from 35 to 60 sec. All spooldown airstarts at airspeeds of 200 knots and higher were successful; airstart times ranged from 45 sec at 250 knots to 135 sec at 200 knots. The effects of altitude on airstart success and time were small. The flight results agreed closely with previous altitude facility test results. The DEEC system provided successful airstarts at airspeeds at least 50 knots lower than the standard F100 engine control system.

Posttest examination of Sodium Loop Safety Facility experiments. [LMFBR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Holland, J.W.

In-reactor, safety experiments performed in the Sodium Loop Safety Facility (SLSF) rely on comprehensive posttest examinations (PTE) to characterize the postirradiation condition of the cladding, fuel, and other test-subassembly components. PTE information and on-line instrumentation data, are analyzed to identify the sequence of events and the severity of the accident for each experiment. Following in-reactor experimentation, the SLSF loop and test assembly are transported to the Hot Fuel Examination Facility (HFEF) for initial disassembly. Goals of the HFEF-phase of the PTE are to retrieve the fuel bundle by dismantling the loop and withdrawing the test assembly, to assess the macro-conditionmore » of the fuel bundle by nondestructive examination techniques, and to prepare the fuel bundle for shipment to the Alpha-Gamma Hot Cell Facility (AGHCF) at Argonne National Laboratory.« less

Numerical Analysis of Combined Well and Open-Closed Loops Geothermal (CWG) Systems

NASA Astrophysics Data System (ADS)

Park, Yu-Chul

2016-04-01

Open-loop geothermal heat pump (GHP) system and closed-loop heat pump systems have been used in Korea to reduce emission of greenhouse gases such as carbon dioxide (CO2). The GHP systems have the pros and cons, for example, the open-loop GHP system is good energy-efficient and the closed-loop GHP system requires minimum maintenance costs. The open-loop GHP system can be used practically only with large amount of groundwater supply. The closed-loop GHP system can be used with high costs of initial installation. The performance and efficiency of the GHP system depend on the characteristics of the GHP system itself in addition to the geologic conditions. To overcome the cons of open-loop or closed-loop GHP system, the combined well and open-closed loops geothermal (CWG) system was designed. The open-loop GHP system is surrounded with closed-loop GHP systems in the CWG system. The geothermal energy in closed-loop GHP systems is supplied by the groundwater pumped by the open-loop GHP system. In this study, 2 different types of the CWG systems (small aperture hybrid CWG system and large aperture CWG system) are estimated using numerical simulation models in the aspect of energy efficiency. This work was supported by the New & Renewable Energy Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea. (No.20153030111120).

Mechanical-thermal noise in drive-mode of a silicon micro-gyroscope.

PubMed

Yang, Bo; Wang, Shourong; Li, Hongsheng; Zhou, Bailing

2009-01-01

A new closed-loop drive scheme which decouples the phase and the gain of the closed-loop driving system was designed in a Silicon Micro-Gyroscope (SMG). We deduce the system model of closed-loop driving and use stochastic averaging to obtain an approximate "slow" system that clarifies the effect of thermal noise. The effects of mechanical-thermal noise on the driving performance of the SMG, including the noise spectral density of the driving amplitude and frequency, are derived. By calculating and comparing the noise amplitude due to thermal noise both in the opened-loop driving and in the closed-loop driving, we find that the closed-loop driving does not reduce the RMS noise amplitude. We observe that the RMS noise frequency can be reduced by increasing the quality factor and the drive amplitude in the closed-loop driving system. The experiment and simulation validate the feasibility of closed-loop driving and confirm the validity of the averaged equation and its stablility criterion. The experiment and simulation results indicate the electrical noise of closed-loop driving circuitry is bigger than the mechanical-thermal noise and as the driving mass decreases, the mechanical-thermal noise may get bigger than the electrical noise of the closed-loop driving circuitry.

Dynamic Modeling, Model-Based Control, and Optimization of Solid Oxide Fuel Cells

NASA Astrophysics Data System (ADS)

Spivey, Benjamin James

2011-07-01

Solid oxide fuel cells are a promising option for distributed stationary power generation that offers efficiencies ranging from 50% in stand-alone applications to greater than 80% in cogeneration. To advance SOFC technology for widespread market penetration, the SOFC should demonstrate improved cell lifetime and load-following capability. This work seeks to improve lifetime through dynamic analysis of critical lifetime variables and advanced control algorithms that permit load-following while remaining in a safe operating zone based on stress analysis. Control algorithms typically have addressed SOFC lifetime operability objectives using unconstrained, single-input-single-output control algorithms that minimize thermal transients. Existing SOFC controls research has not considered maximum radial thermal gradients or limits on absolute temperatures in the SOFC. In particular, as stress analysis demonstrates, the minimum cell temperature is the primary thermal stress driver in tubular SOFCs. This dissertation presents a dynamic, quasi-two-dimensional model for a high-temperature tubular SOFC combined with ejector and prereformer models. The model captures dynamics of critical thermal stress drivers and is used as the physical plant for closed-loop control simulations. A constrained, MIMO model predictive control algorithm is developed and applied to control the SOFC. Closed-loop control simulation results demonstrate effective load-following, constraint satisfaction for critical lifetime variables, and disturbance rejection. Nonlinear programming is applied to find the optimal SOFC size and steady-state operating conditions to minimize total system costs.

Effect of Intake Air Filter Condition on Vehicle Fuel Economy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Norman, Kevin M; Huff, Shean P; West, Brian H

2009-02-01

The U.S. Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy and the U.S. Environmental Protection Agency (EPA) jointly maintain a fuel economy website (www.fueleconomy.gov), which helps fulfill their responsibility under the Energy Policy Act of 1992 to provide accurate fuel economy information [in miles per gallon (mpg)] to consumers. The site provides information on EPA fuel economy ratings for passenger cars and light trucks from 1985 to the present and other relevant information related to energy use such as alternative fuels and driving and vehicle maintenance tips. In recent years, fluctuations in the price of crude oilmore » and corresponding fluctuations in the price of gasoline and diesel fuels have renewed interest in vehicle fuel economy in the United States. (User sessions on the fuel economy website exceeded 20 million in 2008 compared to less than 5 million in 2004 and less than 1 million in 2001.) As a result of this renewed interest and the age of some of the references cited in the tips section of the website, DOE authorized the Oak Ridge National Laboratory (ORNL) Fuels, Engines, and Emissions Research Center (FEERC) to initiate studies to validate and improve these tips. This report documents a study aimed specifically at the effect of engine air filter condition on fuel economy. The goal of this study was to explore the effects of a clogged air filter on the fuel economy of vehicles operating over prescribed test cycles. Three newer vehicles (a 2007 Buick Lucerne, a 2006 Dodge Charger, and a 2003 Toyota Camry) and an older carbureted vehicle were tested. Results show that clogging the air filter has no significant effect on the fuel economy of the newer vehicles (all fuel injected with closed-loop control and one equipped with MDS). The engine control systems were able to maintain the desired AFR regardless of intake restrictions, and therefore fuel consumption was not increased. The carbureted engine did show a decrease in fuel economy with increasing restriction. However, the level of restriction required to cause a substantial (10-15%) decrease in fuel economy (such as that cited in the literature) was so severe that the vehicle was almost undrivable. Acceleration performance on all vehicles was improved with a clean air filter. Once it was determined how severe the restriction had to be to affect the carbureted vehicle fuel economy, the 2007 Buick Lucerne was retested in a similar manner. We were not able to achieve the level of restriction that was achieved with the 1972 Pontiac with the Lucerne. The Lucerne's air filter box would not hold the filter in place under such severe conditions. (It is believed that this testing exceeded the design limits of the air box.) Tests were conducted at a lower restriction level (although still considerably more severe than the initial clogged filter testing), allowing the air filter to stay seated in the air box, and no significant change was observed in the Lucerne's fuel economy or the AFR over the HFET cycle. Closed-loop control in modern fuel injected vehicle applications is sophisticated enough to keep a clogged air filter from affecting the vehicle fuel economy. However for older, open-loop, carbureted vehicles, a clogged air filter can affect the fuel economy. For the vehicle tested, the fuel economy with a new air filter improved as much as 14% over that with a severely clogged filter (in which the filter was so clogged that drivability was impacted). Under a more typical state of clog, the improvement with a new filter ranged from 2 to 6%.« less

AQUILA Remotely Piloted Vehicle System Technology Demonstrator (RPV-STD) Program. Volume 2. System Evolution and Engineering Testing

DTIC Science & Technology

1979-04-01

crosshead of the piston assembly. Shock transients at this location cause demagnetization of the magnet . This is being alleviated by in- stallation of magnets ...substantial structure, such as bulk - heads with edge cape. Soond, the wire-out foam *or* for the wing could not be sufficiently precise to preven the used for...characterize the power potential, fuel consumption, weight, bulk , and adaptability to closed loop control of candidate carburetion systems to be employed with

Active Pattern Factor Control for Gas Turbine Engines

NASA Technical Reports Server (NTRS)

May, James E.

1998-01-01

Small variations in fuel/air mixture ratios within gas turbine combustors can result in measurable, and potentially detrimental, exit thermal gradients. Thermal gradients can increase emissions, as well as shorten the design life of downstream turbomachinery, particularly stator vanes. Uniform temperature profiles are usually sought through careful design and manufacturing of related combustor components. However, small componentto-component variations as well as numerous aging effects degrade system performance. To compensate for degraded thermal performance, researchers are investigating active, closed-loop control schemes.

Airstart performance of a digital electronic engine control system on an F100 engine

NASA Technical Reports Server (NTRS)

Burcham, F. W., Jr.

1984-01-01

The digital electronic engine control (DEEC) system installed on an F100 engine in an F-15 aircraft was tested. The DEEC system incorporates a closed-loop air start feature in which the fuel flow is modulated to achieve the desired rate of compressor acceleration. With this logic the DEEC equipped F100 engine can achieve air starts over a larger envelope. The DEEC air start logic, the test program conducted on the F-15, and its results are described.

Evaluation of a Passive Heat Exchanger Based Cooling System for Fuel Cell Applications

NASA Technical Reports Server (NTRS)

Colozza, Anthony J.; Burke, Kenneth A.

2011-01-01

Fuel cell cooling is conventionally performed with an actively controlled, dedicated coolant loop that exchanges heat with a separate external cooling loop. To simplify this system the concept of directly cooling a fuel cell utilizing a coolant loop with a regenerative heat exchanger to preheat the coolant entering the fuel cell with the coolant exiting the fuel cell was analyzed. The preheating is necessary to minimize the temperature difference across the fuel cell stack. This type of coolant system would minimize the controls needed on the coolant loop and provide a mostly passive means of cooling the fuel cell. The results indicate that an operating temperature of near or greater than 70 C is achievable with a heat exchanger effectiveness of around 90 percent. Of the heat exchanger types evaluated with the same type of fluid on the hot and cold side, a counter flow type heat exchanger would be required which has the possibility of achieving the required effectiveness. The number of heat transfer units required by the heat exchanger would be around 9 or greater. Although the analysis indicates the concept is feasible, the heat exchanger design would need to be developed and optimized for a specific fuel cell operation in order to achieve the high effectiveness value required.

Closing loop base pairs in RNA loop-loop complexes: structural behavior, interaction energy and solvation analysis through molecular dynamics simulations.

PubMed

Golebiowski, Jérôme; Antonczak, Serge; Fernandez-Carmona, Juan; Condom, Roger; Cabrol-Bass, Daniel

2004-12-01

Nanosecond molecular dynamics using the Ewald summation method have been performed to elucidate the structural and energetic role of the closing base pair in loop-loop RNA duplexes neutralized by Mg2+ counterions in aqueous phases. Mismatches GA, CU and Watson-Crick GC base pairs have been considered for closing the loop of an RNA in complementary interaction with HIV-1 TAR. The simulations reveal that the mismatch GA base, mediated by a water molecule, leads to a complex that presents the best compromise between flexibility and energetic contributions. The mismatch CU base pair, in spite of the presence of an inserted water molecule, is too short to achieve a tight interaction at the closing-loop junction and seems to force TAR to reorganize upon binding. An energetic analysis has allowed us to quantify the strength of the interactions of the closing and the loop-loop pairs throughout the simulations. Although the water-mediated GA closing base pair presents an interaction energy similar to that found on fully geometry-optimized structure, the water-mediated CU closing base pair energy interaction reaches less than half the optimal value.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, J.L.; Jenkins, E.M.; Walthers, C.R.

Compound cryopumps have been added to the Tritium Systems Test Assembly (TSTA) integrated fusion fuel loop. Operations have been performed which closely simulate an actual fusion reactor pumping scenario. In addition, performance data have been taken that support the concept of using coconut charcoal as a sorbent at 4K for pumping helium. Later tests show that coconut charcoal may be used to co-pump D,T and He mixtures on a single 4K panel. Rotary spiral pumps have been used successfully in several applications at TSTA and have acquired more than 9000 hours of maintenance-free operation. Metal bellows pumps have been usedmore » to back the spiral pumps and have been relatively trouble free in loop operations. Bellows pumps also have more than 9000 hours of maintenance-free operation. 5 refs., 6 figs.« less

Microstructure evolution of recrystallized Zircaloy-4 under charged particles irradiation

NASA Astrophysics Data System (ADS)

Gaumé, M.; Onimus, F.; Dupuy, L.; Tissot, O.; Bachelet, C.; Mompiou, F.

2017-11-01

Recrystallized zirconium alloys are used as nuclear fuel cladding tubes of Pressurized Water Reactors. During operation, these alloys are submitted to fast neutron irradiation which leads to their in-reactor deformation and to a change of their mechanical properties. These phenomena are directly related to the microstructure evolution under irradiation and especially to the formation of -type dislocation loops. In the present work, the radiation damage evolution in recrystallized Zircaloy-4 has been studied using charged particles irradiation. The loop nucleation and growth kinetics, and also the helical climb of linear dislocations, were observed in-situ using a High Voltage Electron Microscope (HVEM) under 1 MeV electron irradiation at 673 and 723 K. In addition, 600 keV Zr+ ion irradiations were conducted at the same temperature. Transmission Electron Microscopy (TEM) characterizations have been performed after both types of irradiations, and show dislocation loops with a Burgers vector belonging to planes close to { 10 1 bar 0 } first order prismatic planes. The nature of the loops has been characterized. Only interstitial dislocation loops have been observed after ion irradiation at 723 K. However, after electron irradiation conducted at 673 and 723 K, both interstitial and vacancy loops were observed, the proportion of interstitial loops increasing as the temperature is increased. The loop growth kinetics analysis shows that as the temperature increases, the loop number density decreases and the loop growth rate tends to increase. An increase of the flux leads to an increase of the loop number density and a decrease of the loop growth rate. The results are compared to previous works and discussed in the light of point defects diffusion.

Human life support during interplanetary travel and domicile. III - Mars expedition system trade study

NASA Technical Reports Server (NTRS)

Seshan, P. K.; Ferrall, Joseph F.; Rohatgi, Naresh K.

1991-01-01

Several alternative configurations of life-support systems (LSSs) for a Mars missions are compared analytically on a quantitative basis in terms of weight, volume, and power. A baseline technology set is utilized for the illustrations of systems including totally open loop, carbon dioxide removal only, partially closed loop, and totally closed loop. The analytical model takes advantage of a modular, top-down hierarchical breakdown of LSS subsystems into functional elements that represent individual processing technologies. The open-loop systems are not competitive in terms of weight for both long-duration orbiters and short-duration lander vehicles, and power demands are lowest with the open loop and highest with the closed loop. The closed-loop system can reduce vehicle weight by over 70,000 lbs and thereby overcome the power penalty of 1600 W; the closed-loop variety is championed as the preferred system for a Mars expedition.

Electronic Warfare Closed Loop Laboratory (EWCLL) Antenna Motor Software and Hardware Development

DTIC Science & Technology

2016-09-01

ARL-TN-0779 ● SEP 2016 US Army Research Laboratory Electronic Warfare Closed Loop Laboratory (EWCLL) Antenna Motor Software and...Electronic Warfare Closed Loop Laboratory (EWCLL) Antenna Motor Software and Hardware Development by Neal Tesny Sensors and Electron Devices Directorate...TITLE AND SUBTITLE Electronic Warfare Closed Loop Laboratory (EWCLL) Antenna Motor Software and Hardware Development 5a. CONTRACT NUMBER 5b

Closed-loop spontaneous baroreflex transfer function is inappropriate for system identification of neural arc but partly accurate for peripheral arc: predictability analysis

PubMed Central

Kamiya, Atsunori; Kawada, Toru; Shimizu, Shuji; Sugimachi, Masaru

2011-01-01

Abstract Although the dynamic characteristics of the baroreflex system have been described by baroreflex transfer functions obtained from open-loop analysis, the predictability of time-series output dynamics from input signals, which should confirm the accuracy of system identification, remains to be elucidated. Moreover, despite theoretical concerns over closed-loop system identification, the accuracy and the predictability of the closed-loop spontaneous baroreflex transfer function have not been evaluated compared with the open-loop transfer function. Using urethane and α-chloralose anaesthetized, vagotomized and aortic-denervated rabbits (n = 10), we identified open-loop baroreflex transfer functions by recording renal sympathetic nerve activity (SNA) while varying the vascularly isolated intracarotid sinus pressure (CSP) according to a binary random (white-noise) sequence (operating pressure ± 20 mmHg), and using a simplified equation to calculate closed-loop-spontaneous baroreflex transfer function while matching CSP with systemic arterial pressure (AP). Our results showed that the open-loop baroreflex transfer functions for the neural and peripheral arcs predicted the time-series SNA and AP outputs from measured CSP and SNA inputs, with r2 of 0.8 ± 0.1 and 0.8 ± 0.1, respectively. In contrast, the closed-loop-spontaneous baroreflex transfer function for the neural arc was markedly different from the open-loop transfer function (enhanced gain increase and a phase lead), and did not predict the time-series SNA dynamics (r2; 0.1 ± 0.1). However, the closed-loop-spontaneous baroreflex transfer function of the peripheral arc partially matched the open-loop transfer function in gain and phase functions, and had limited but reasonable predictability of the time-series AP dynamics (r2, 0.7 ± 0.1). A numerical simulation suggested that a noise predominantly in the neural arc under resting conditions might be a possible mechanism responsible for our findings. Furthermore, the predictabilities of the neural arc transfer functions obtained in open-loop and closed-loop conditions were validated by closed-loop pharmacological (phenylephrine and nitroprusside infusions) pressure interventions. Time-series SNA responses to drug-induced AP changes predicted by the open-loop transfer function matched closely the measured responses (r2, 0.9 ± 0.1), whereas SNA responses predicted by closed-loop-spontaneous transfer function deviated greatly and were the inverse of measured responses (r, −0.8 ± 0.2). These results indicate that although the spontaneous baroreflex transfer function obtained by closed-loop analysis has been believed to represent the neural arc function, it is inappropriate for system identification of the neural arc but is essentially appropriate for the peripheral arc under resting conditions, when compared with open-loop analysis. PMID:21486839

Conditions for Stabilizability of Linear Switched Systems

NASA Astrophysics Data System (ADS)

Minh, Vu Trieu

2011-06-01

This paper investigates some conditions that can provide stabilizability for linear switched systems with polytopic uncertainties via their closed loop linear quadratic state feedback regulator. The closed loop switched systems can stabilize unstable open loop systems or stable open loop systems but in which there is no solution for a common Lyapunov matrix. For continuous time switched linear systems, we show that if there exists solution in an associated Riccati equation for the closed loop systems sharing one common Lyapunov matrix, the switched linear systems are stable. For the discrete time switched systems, we derive a Linear Matrix Inequality (LMI) to calculate a common Lyapunov matrix and solution for the stable closed loop feedback systems. These closed loop linear quadratic state feedback regulators guarantee the global asymptotical stability for any switched linear systems with any switching signal sequence.

Modeling Transients and Designing a Passive Safety System for a Nuclear Thermal Rocket Using Relap5

NASA Astrophysics Data System (ADS)

Khatry, Jivan

Long-term high payload missions necessitate the need for nuclear space propulsion. Several nuclear reactor types were investigated by the Nuclear Engine for Rocket Vehicle Application (NERVA) program of National Aeronautics and Space Administration (NASA). Study of planned/unplanned transients on nuclear thermal rockets is important due to the need for long-term missions. A NERVA design known as the Pewee I was selected for this purpose. The following transients were run: (i) modeling of corrosion-induced blockages on the peripheral fuel element coolant channels and their impact on radiation heat transfer in the core, and (ii) modeling of loss-of-flow-accidents (LOFAs) and their impact on radiation heat transfer in the core. For part (i), the radiation heat transfer rate of blocked channels increases while their neighbors' decreases. For part (ii), the core radiation heat transfer rate increases while the flow rate through the rocket system is decreased. However, the radiation heat transfer decreased while there was a complete LOFA. In this situation, the peripheral fuel element coolant channels handle the majority of the radiation heat transfer. Recognizing the LOFA as the most severe design basis accident, a passive safety system was designed in order to respond to such a transient. This design utilizes the already existing tie rod tubes and connects them to a radiator in a closed loop. Hence, this is basically a secondary loop. The size of the core is unchanged. During normal steady-state operation, this secondary loop keeps the moderator cool. Results show that the safety system is able to remove the decay heat and prevent the fuel elements from melting, in response to a LOFA and subsequent SCRAM.

Orbital Disturbance Analysis due to the Lunar Gravitational Potential and Deviation Minimization through the Trajectory Control in Closed Loop

NASA Astrophysics Data System (ADS)

Gonçalves, L. D.; Rocco, E. M.; de Moraes, R. V.

2013-10-01

A study evaluating the influence due to the lunar gravitational potential, modeled by spherical harmonics, on the gravity acceleration is accomplished according to the model presented in Konopliv (2001). This model provides the components x, y and z for the gravity acceleration at each moment of time along the artificial satellite orbit and it enables to consider the spherical harmonic degree and order up to100. Through a comparison between the gravity acceleration from a central field and the gravity acceleration provided by Konopliv's model, it is obtained the disturbing velocity increment applied to the vehicle. Then, through the inverse problem, the Keplerian elements of perturbed orbit of the satellite are calculated allowing the orbital motion analysis. Transfer maneuvers and orbital correction of lunar satellites are simulated considering the disturbance due to non-uniform gravitational potential of the Moon, utilizing continuous thrust and trajectory control in closed loop. The simulations are performed using the Spacecraft Trajectory Simulator-STRS, Rocco (2008), which evaluate the behavior of the orbital elements, fuel consumption and thrust applied to the satellite over the time.

Gas-engine-based, low-emission cogeneration units

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chellini, R.

1994-04-01

Continental Energy Systems (CES) of Westmalle, Belgium, has been specializing, since its foundation in 1983, in the supply of cogeneration packages in the 50-300 KW power range. CES activity is mainly concentrated in the transformation of Valmet, Scania, Iveco and MAN diesel engines into spark-ignited engines capable of running on natural gas, CNG, LPG, biogas, landfill gas, etc. In the upper power range they also package Waukesha gas engines supplied from the Dutch plant of the American engine manufacturer. The new closed-loop combustion control system allows engines in the naturally-aspirated or turbocharged configuration with catalytic converters to operate well belowmore » Euro 2 limits. In fact, these engines already comply with 1995 CARB (California Air Resources Board) emission limits and with those that will become mandatory in Europe with the 1996 step. The new system still makes use of conventional components for metering and mixing functions, but these are considered as three separate devices; the electronic control unit, the oxygen sensor and an actuator enabling closed loop air/fuel ratio control. 4 figs.« less

Fuel cycle cost, reactor physics and fuel manufacturing considerations for Erbia-bearing PWR fuel with > 5 wt% U-235 content

DOE Office of Scientific and Technical Information (OSTI.GOV)

Franceschini, F.; Lahoda, E. J.; Kucukboyaci, V. N.

2012-07-01

The efforts to reduce fuel cycle cost have driven LWR fuel close to the licensed limit in fuel fissile content, 5.0 wt% U-235 enrichment, and the acceptable duty on current Zr-based cladding. An increase in the fuel enrichment beyond the 5 wt% limit, while certainly possible, entails costly investment in infrastructure and licensing. As a possible way to offset some of these costs, the addition of small amounts of Erbia to the UO{sub 2} powder with >5 wt% U-235 has been proposed, so that its initial reactivity is reduced to that of licensed fuel and most modifications to the existingmore » facilities and equipment could be avoided. This paper discusses the potentialities of such a fuel on the US market from a vendor's perspective. An analysis of the in-core behavior and fuel cycle performance of a typical 4-loop PWR with 18 and 24-month operating cycles has been conducted, with the aim of quantifying the potential economic advantage and other operational benefits of this concept. Subsequently, the implications on fuel manufacturing and storage are discussed. While this concept has certainly good potential, a compelling case for its short-term introduction as PWR fuel for the US market could not be determined. (authors)« less

Review article: closed-loop systems in anesthesia: is there a potential for closed-loop fluid management and hemodynamic optimization?

PubMed

Rinehart, Joseph; Liu, Ngai; Alexander, Brenton; Cannesson, Maxime

2012-01-01

Closed-loop (automated) controllers are encountered in all aspects of modern life in applications ranging from air-conditioning to spaceflight. Although these systems are virtually ubiquitous, they are infrequently used in anesthesiology because of the complexity of physiologic systems and the difficulty in obtaining reliable and valid feedback data from the patient. Despite these challenges, closed-loop systems are being increasingly studied and improved for medical use. Two recent developments have made fluid administration a candidate for closed-loop control. First, the further description and development of dynamic predictors of fluid responsiveness provides a strong parameter for use as a control variable to guide fluid administration. Second, rapid advances in noninvasive monitoring of cardiac output and other hemodynamic variables make goal-directed therapy applicable for a wide range of patients in a variety of clinical care settings. In this article, we review the history of closed-loop controllers in clinical care, discuss the current understanding and limitations of the dynamic predictors of fluid responsiveness, and examine how these variables might be incorporated into a closed-loop fluid administration system.

Comparative assessment of the efficacy of closed helical loop and T-loop for space closure in lingual orthodontics-a finite element study.

PubMed

Chacko, Ajay; Tikku, Tripti; Khanna, Rohit; Maurya, Rana Pratap; Srivastava, Kamna

2018-05-28

Retraction in lingual orthodontics has biomechanical differences when compared to labial orthodontics, which is not yet established. Thus, we have intended to compare the biomechanical characteristics of closed helical loop and T-loop on 1 mm activation with 30° of compensatory curvatures during retraction in lingual orthodontics. STb lingual brackets were indirectly bonded to maxillary typhodont model that was scanned to obtain FEM model. Closed helical loop (2 × 7 mm) and T-loop (6 × 2 × 7 mm) of 0.016″ × 0.016″ TMA wire were modeled without preactivation bends. Preactivation bends at 30° were given in the software. Boundary conditions were set. The force (F) and moment (M) of both the loops were determined on 1 mm activation, using ANSYS software. M/F ratio was also calculated for both the loops. T-loop exerted less force, thus increased M/F ratio as compared to closed helical loop on 1 mm activation. When torque has to be preserved in the anterior segment during retraction in lingual orthodontics, T-loop can be preferred over closed helical loop.

Ground Source Heat Pumps vs. Conventional HVAC: A Comparison of Economic and Environmental Costs

DTIC Science & Technology

2009-03-26

of systems are surface water heat pumps (SWHPs), ground water heat pumps (GWHPs), and ground coupled heat pumps ( GCHPs ) (Kavanaugh & Rafferty, 1997...Kavanaugh & Rafferty, 1997). Ground Coupled Heat Pumps (Closed-Loop Ground Source Heat Pumps) GCHPs , otherwise known as closed-loop GSHPs, are the...Significant confusion has arisen through the use of GCHP and closed-loop GSHP terminology. Closed-loop GSHP is the preferred nomenclature for this

Closed-loop fiber optic gyroscope with homodyne detection

NASA Astrophysics Data System (ADS)

Zhu, Yong; Qin, BingKun; Chen, Shufen

1996-09-01

Interferometric fiber optic gyroscope (IFOG) has been analyzed with autocontrol theory in this paper. An open-loop IFOG system is not able to restrain the bias drift, but a closed-loop IFOG system can do it very well using negative feedback in order to suppress zero drift. The result of our theoretic analysis and computer simulation indicate that the bias drift of a closed-loop system is smaller than an open- loop one.

Low Speed and High Speed Correlation of SMART Active Flap Rotor Loads

NASA Technical Reports Server (NTRS)

Kottapalli, Sesi B. R.

2010-01-01

Measured, open loop and closed loop data from the SMART rotor test in the NASA Ames 40- by 80- Foot Wind Tunnel are compared with CAMRAD II calculations. One open loop high-speed case and four closed loop cases are considered. The closed loop cases include three high-speed cases and one low-speed case. Two of these high-speed cases include a 2 deg flap deflection at 5P case and a test maximum-airspeed case. This study follows a recent, open loop correlation effort that used a simple correction factor for the airfoil pitching moment Mach number. Compared to the earlier effort, the current open loop study considers more fundamental corrections based on advancing blade aerodynamic conditions. The airfoil tables themselves have been studied. Selected modifications to the HH-06 section flap airfoil pitching moment table are implemented. For the closed loop condition, the effect of the flap actuator is modeled by increased flap hinge stiffness. Overall, the open loop correlation is reasonable, thus confirming the basic correctness of the current semi-empirical modifications; the closed loop correlation is also reasonable considering that the current flap model is a first generation model. Detailed correlation results are given in the paper.

A Model for Developing Clinical Analytics Capacity: Closing the Loops on Outcomes to Optimize Quality.

PubMed

Eggert, Corinne; Moselle, Kenneth; Protti, Denis; Sanders, Dale

2017-01-01

Closed Loop Analytics© is receiving growing interest in healthcare as a term referring to information technology, local data and clinical analytics working together to generate evidence for improvement. The Closed Loop Analytics model consists of three loops corresponding to the decision-making levels of an organization and the associated data within each loop - Patients, Protocols, and Populations. The authors propose that each of these levels should utilize the same ecosystem of electronic health record (EHR) and enterprise data warehouse (EDW) enabled data, in a closed-loop fashion, with that data being repackaged and delivered to suit the analytic and decision support needs of each level, in support of better outcomes.

Two-loop controller for maximizing performance of a grid-connected photovoltaic - fuel cell hybrid power plant

NASA Astrophysics Data System (ADS)

Ro, Kyoungsoo

The study started with the requirement that a photovoltaic (PV) power source should be integrated with other supplementary power sources whether it operates in a stand-alone or grid-connected mode. First, fuel cells for a backup of varying PV power were compared in detail with batteries and were found to have more operational benefits. Next, maximizing performance of a grid-connected PV-fuel cell hybrid system by use of a two-loop controller was discussed. One loop is a neural network controller for maximum power point tracking, which extracts maximum available solar power from PV arrays under varying conditions of insolation, temperature, and system load. A real/reactive power controller (RRPC) is the other loop. The RRPC meets the system's requirement for real and reactive powers by controlling incoming fuel to fuel cell stacks as well as switching control signals to a power conditioning subsystem. The RRPC is able to achieve more versatile control of real/reactive powers than the conventional power sources since the hybrid power plant does not contain any rotating mass. Results of time-domain simulations prove not only effectiveness of the proposed computer models of the two-loop controller, but also their applicability for use in transient stability analysis of the hybrid power plant. Finally, environmental evaluation of the proposed hybrid plant was made in terms of plant's land requirement and lifetime COsb2 emissions, and then compared with that of the conventional fossil-fuel power generating forms.

A comparison of exhaust emissions from vehicles fuelled with petrol, LPG and CNG

NASA Astrophysics Data System (ADS)

Bielaczyc, P.; Szczotka, A.; Woodburn, J.

2016-09-01

This paper presents an analysis of THC, NMHC, CO, NOx and CO2 emissions during testing of two bi-fuel vehicles, fuelled with petrol and gaseous fuels, on a chassis dynamometer in the context of the Euro 6 emissions requirements. The analyses were performed on one Euro 5 bi-fuel vehicle (petrol/LPG) and one Euro 5 bi-fuel vehicle (petrol/CNG), both with SI engines equipped with MPI feeding systems operating in closed-loop control, typical three-way-catalysts and heated oxygen sensors. The vehicles had been adapted by their manufacturers for fuelling with LPG or CNG by using additional special equipment mounted onto the existing petrol fuelling system. The vehicles tested featured multipoint gas injection systems. The aim of this paper was an analysis of the impact of the gaseous fuels on the exhaust emission in comparison to the emission of the vehicles fuelled with petrol. The tests subject to the analyses presented here were performed in the Engine Research Department of BOSMAL Automotive Research and Development Institute Ltd in Bielsko-Biala, Poland, within a research programme investigating the influence of alternative fuels on exhaust emissions from light duty vehicle vehicles with spark-ignition and compression-ignition engines.

Singlet oxygen generator for a supersonic chemical oxygen iodine laser: parametric study and recovery of chemicals

NASA Astrophysics Data System (ADS)

Spalek, Otomar; Kodymova, Jarmila

1997-04-01

A jet singlet oxygen generator for a supersonic chemical oxygen-iodine laser was studied including singlet delta oxygen, O2(1(Delta) g), and residual chlorine concentration measurements. The investigation was intended mainly for a water vapor measurement in gas effluent of generator in dependence on properties of liquid jets: a chemical composition and temperature of the input liquid (alkaline solution of hydrogen peroxide), a liquid jets diameter and their geometrical arrangement. Effects of these parameters on output power of a small-scale supersonic laser were studied as well. Possible approaches to a chemical fuels management in a chemical oxygen-iodine laser for industrial applications are considered. An 'open loop' cycle with a possible use of sodium hydroxide, and a 'closed loop' cycle with a regeneration of both potassium hydroxide and hydrogen peroxide are discussed.

Strain actuated aeroelastic control

NASA Technical Reports Server (NTRS)

Lazarus, Kenneth B.

1992-01-01

Viewgraphs on strain actuated aeroelastic control are presented. Topics covered include: structural and aerodynamic modeling; control law design methodology; system block diagram; adaptive wing test article; bench-top experiments; bench-top disturbance rejection: open and closed loop response; bench-top disturbance rejection: state cost versus control cost; wind tunnel experiments; wind tunnel gust alleviation: open and closed loop response at 60 mph; wind tunnel gust alleviation: state cost versus control cost at 60 mph; wind tunnel command following: open and closed loop error at 60 mph; wind tunnel flutter suppression: open loop flutter speed; and wind tunnel flutter suppression: closed loop state cost curves.

Design and Calibration of the US Army Research Laboratory (ARL) Closed Loop Laboratory Radio Frequency (RF) Propagation Section

DTIC Science & Technology

2016-10-01

ARL-TR-7860 ● OCT 2016 US Army Research Laboratory Design and Calibration of the US Army Research Laboratory (ARL) Closed Loop ...ARL-TR-7860 ● OCT 2016 US Army Research Laboratory Design and Calibration of the US Army Research Laboratory (ARL) Closed Loop Laboratory...Design and Calibration of the US Army Research Laboratory (ARL) Closed Loop Laboratory Radio Frequency (RF) Propagation Section 5a. CONTRACT NUMBER

Hypoglycaemia incidence and recovery during home use of hybrid closed-loop insulin delivery in adults with type 1 diabetes.

PubMed

Ruan, Yue; Bally, Lia; Thabit, Hood; Leelarathna, Lalantha; Hartnell, Sara; Tauschmann, Martin; Wilinska, Malgorzata E; Evans, Mark L; Mader, Julia K; Kojzar, Harald; Dellweg, Sibylle; Benesch, Carsten; Arnolds, Sabine; Pieber, Thomas R; Hovorka, Roman

2018-03-25

Glucose excursion was assessed prior to and post hypoglycaemia to increase understanding of hypoglycaemia incidence and recovery during hybrid closed-loop insulin delivery. We retrospectively analysed data from 60 adults with type 1 diabetes who received, in a crossover randomized design, day-and-night hybrid closed-loop insulin delivery and insulin pump therapy, the latter with or without real-time continuous glucose monitoring. Over 4-week study periods, we identified hypoglycaemic episodes, defined as sensor glucose <3.0 mmol/L, and analysed sensor glucose relative to the onset of hypoglycaemia. We identified 377 hypoglycaemic episodes during hybrid closed-loop intervention vs 662 during control intervention (P < .001), with a predominant reduction of nocturnal hypoglycaemia. The slope of sensor glucose prior to hypoglycaemia was steeper during closed-loop intervention than during control intervention (P < .01), while insulin delivery was reduced (P < .01). During both day and night, participants recovered from hypoglycaemia faster when treated by closed-loop intervention. At 120 minutes post hypoglycaemia, sensor glucose levels were higher during closed-loop intervention compared to the control period (P < .05). In conclusion, closed-loop intervention reduces the risk of hypoglycaemia, particularly overnight, with swift recovery from hypoglycaemia leading to higher 2-hour post-hypoglycaemia glucose levels. © 2018 John Wiley & Sons Ltd.

Apparatus for and method of monitoring for breached fuel elements

DOEpatents

Gross, K.C.; Strain, R.V.

1981-04-28

This invention teaches improved apparatus for the method of detecting a breach in cladded fuel used in a nuclear reactor. The detector apparatus uses a separate bypass loop for conveying part of the reactor coolant away from the core, and at least three separate delayed-neutron detectors mounted proximate this detector loop. The detectors are spaced apart so that the coolant flow time from the core to each detector is different, and these differences are known. The delayed-neutron activity at the detectors is a function of the delay time after the reaction in the fuel until the coolant carrying the delayed-neutron emitter passes the respective detector. This time delay is broken down into separate components including an isotopic holdup time required for the emitter to move through the fuel from the reaction to the coolant at the breach, and two transit times required for the emitter now in the coolant to flow from the breach to the detector loop and then via the loop to the detector.

Combining Charge Couple Devices and Rate Sensors for the Feedforward Control System of a Charge Coupled Device Tracking Loop.

PubMed

Tang, Tao; Tian, Jing; Zhong, Daijun; Fu, Chengyu

2016-06-25

A rate feed forward control-based sensor fusion is proposed to improve the closed-loop performance for a charge couple device (CCD) tracking loop. The target trajectory is recovered by combining line of sight (LOS) errors from the CCD and the angular rate from a fiber-optic gyroscope (FOG). A Kalman filter based on the Singer acceleration model utilizes the reconstructive target trajectory to estimate the target velocity. Different from classical feed forward control, additive feedback loops are inevitably added to the original control loops due to the fact some closed-loop information is used. The transfer function of the Kalman filter in the frequency domain is built for analyzing the closed loop stability. The bandwidth of the Kalman filter is the major factor affecting the control stability and close-loop performance. Both simulations and experiments are provided to demonstrate the benefits of the proposed algorithm.

Solar Airplanes and Regenerative Fuel Cells

NASA Technical Reports Server (NTRS)

Bents, David J.

2007-01-01

A solar electric aircraft with the potential to "fly forever" has captured NASA's interest, and the concept for such an aircraft was pursued under Aeronautics Environmental Research Aircraft and Sensor Technology (ERAST) project. Feasibility of this aircraft happens to depend on the successful development of solar power technologies critical to NASA's Exploration Initiatives; hence, there was widespread interest throughout NASA to bring these technologies to a flight demonstration. The most critical is an energy storage system to sustain mission power during night periods. For the solar airplane, whose flight capability is already limited by the diffuse nature of solar flux and subject to latitude and time of year constraints, the feasibility of long endurance flight depends on a storage density figure of merit better than 400-600 watt-hr per kilogram. This figure of merit is beyond the capability of present day storage technologies (other than nuclear) but may be achievable in the hydrogen-oxygen regenerative fuel cell (RFC). This potential has led NASA to undertake the practical development of a hydrogen-oxygen regenerative fuel cell, initially as solar energy storage for a high altitude UAV science platform but eventually to serve as the primary power source for NASAs lunar base and other planet surface installations. Potentially the highest storage capacity and lowest weight of any non-nuclear device, a flight-weight RFC aboard a solar-electric aircraft that is flown continuously through several successive day-night cycles will provide the most convincing demonstration that this technology's widespread potential has been realized. In 1998 NASA began development of a closed cycle hydrogen oxygen PEM RFC under the Aeronautics Environmental Research Aircraft and Sensor Technology (ERAST) project and continued its development, originally for a solar electric airplane flight, through FY2005 under the Low Emissions Alternative Power (LEAP) project. Construction of the closed loop system began in 2002 at the NASA Glenn Research Center in Cleveland, Ohio. System checkout was completed, and testing began, in July of 2003. The initial test sequences were done with only a fuel cell or electrolyzer in the test rig. Those tests were used to verify the test apparatus, procedures, and software. The first complete cycles of the fully closed loop, regenerative fuel cell system were successfully completed in the following September. Following some hardware upgrades to increase reactant recirculation flow, the test rig was operated at full power in December 2003 and again in January 2004. In March 2004 a newer generation of fuel cell and electrolyzer stacks was substituted for the original hardware and these stacks were successfully tested at full power under cyclic operation in June of 2004.

Optimal Control of Distributed Energy Resources using Model Predictive Control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mayhorn, Ebony T.; Kalsi, Karanjit; Elizondo, Marcelo A.

2012-07-22

In an isolated power system (rural microgrid), Distributed Energy Resources (DERs) such as renewable energy resources (wind, solar), energy storage and demand response can be used to complement fossil fueled generators. The uncertainty and variability due to high penetration of wind makes reliable system operations and controls challenging. In this paper, an optimal control strategy is proposed to coordinate energy storage and diesel generators to maximize wind penetration while maintaining system economics and normal operation. The problem is formulated as a multi-objective optimization problem with the goals of minimizing fuel costs and changes in power output of diesel generators, minimizingmore » costs associated with low battery life of energy storage and maintaining system frequency at the nominal operating value. Two control modes are considered for controlling the energy storage to compensate either net load variability or wind variability. Model predictive control (MPC) is used to solve the aforementioned problem and the performance is compared to an open-loop look-ahead dispatch problem. Simulation studies using high and low wind profiles, as well as, different MPC prediction horizons demonstrate the efficacy of the closed-loop MPC in compensating for uncertainties in wind and demand.« less

A Closed-loop Brain Computer Interface to a Virtual Reality Avatar: Gait Adaptation to Visual Kinematic Perturbations

PubMed Central

Luu, Trieu Phat; He, Yongtian; Brown, Samuel; Nakagome, Sho; Contreras-Vidal, Jose L.

2016-01-01

The control of human bipedal locomotion is of great interest to the field of lower-body brain computer interfaces (BCIs) for rehabilitation of gait. While the feasibility of a closed-loop BCI system for the control of a lower body exoskeleton has been recently shown, multi-day closed-loop neural decoding of human gait in a virtual reality (BCI-VR) environment has yet to be demonstrated. In this study, we propose a real-time closed-loop BCI that decodes lower limb joint angles from scalp electroencephalography (EEG) during treadmill walking to control the walking movements of a virtual avatar. Moreover, virtual kinematic perturbations resulting in asymmetric walking gait patterns of the avatar were also introduced to investigate gait adaptation using the closed-loop BCI-VR system over a period of eight days. Our results demonstrate the feasibility of using a closed-loop BCI to learn to control a walking avatar under normal and altered visuomotor perturbations, which involved cortical adaptations. These findings have implications for the development of BCI-VR systems for gait rehabilitation after stroke and for understanding cortical plasticity induced by a closed-loop BCI system. PMID:27713915

Virtual grasping: closed-loop force control using electrotactile feedback.

PubMed

Jorgovanovic, Nikola; Dosen, Strahinja; Djozic, Damir J; Krajoski, Goran; Farina, Dario

2014-01-01

Closing the control loop by providing somatosensory feedback to the user of a prosthesis is a well-known, long standing challenge in the field of prosthetics. Various approaches have been investigated for feedback restoration, ranging from direct neural stimulation to noninvasive sensory substitution methods. Although there are many studies presenting closed-loop systems, only a few of them objectively evaluated the closed-loop performance, mostly using vibrotactile stimulation. Importantly, the conclusions about the utility of the feedback were partly contradictory. The goal of the current study was to systematically investigate the capability of human subjects to control grasping force in closed loop using electrotactile feedback. We have developed a realistic experimental setup for virtual grasping, which operated in real time, included a set of real life objects, as well as a graphical and dynamical model of the prosthesis. We have used the setup to test 10 healthy, able bodied subjects to investigate the role of training, feedback and feedforward control, robustness of the closed loop, and the ability of the human subjects to generalize the control to previously "unseen" objects. Overall, the outcomes of this study are very optimistic with regard to the benefits of feedback and reveal various, practically relevant, aspects of closed-loop control.

Load compensation in a lean burn natural gas vehicle

NASA Astrophysics Data System (ADS)

Gangopadhyay, Anupam

A new multivariable PI tuning technique is developed in this research that is primarily developed for regulation purposes. Design guidelines are developed based on closed-loop stability. The new multivariable design is applied in a natural gas vehicle to combine idle and A/F ratio control loops. This results in better recovery during low idle operation of a vehicle under external step torques. A powertrain model of a natural gas engine is developed and validated for steady-state and transient operation. The nonlinear model has three states: engine speed, intake manifold pressure and fuel fraction in the intake manifold. The model includes the effect of fuel partial pressure in the intake manifold filling and emptying dynamics. Due to the inclusion of fuel fraction as a state, fuel flow rate into the cylinders is also accurately modeled. A linear system identification is performed on the nonlinear model. The linear model structure is predicted analytically from the nonlinear model and the coefficients of the predicted transfer function are shown to be functions of key physical parameters in the plant. Simulations of linear system and model parameter identification is shown to converge to the predicted values of the model coefficients. The multivariable controller developed in this research could be designed in an algebraic fashion once the plant model is known. It is thus possible to implement the multivariable PI design in an adaptive fashion combining the controller with identified plant model on-line. This will result in a self-tuning regulator (STR) type controller where the underlying design criteria is the multivariable tuning technique designed in this research.

Bandwidth controller for phase-locked-loop

NASA Technical Reports Server (NTRS)

Brockman, Milton H. (Inventor)

1992-01-01

A phase locked loop utilizing digital techniques to control the closed loop bandwidth of the RF carrier phase locked loop in a receiver provides high sensitivity and a wide dynamic range for signal reception. After analog to digital conversion, a digital phase locked loop bandwidth controller provides phase error detection with automatic RF carrier closed loop tracking bandwidth control to accommodate several modes of transmission.

Iterative LQG Controller Design Through Closed-Loop Identification

NASA Technical Reports Server (NTRS)

Hsiao, Min-Hung; Huang, Jen-Kuang; Cox, David E.

1996-01-01

This paper presents an iterative Linear Quadratic Gaussian (LQG) controller design approach for a linear stochastic system with an uncertain open-loop model and unknown noise statistics. This approach consists of closed-loop identification and controller redesign cycles. In each cycle, the closed-loop identification method is used to identify an open-loop model and a steady-state Kalman filter gain from closed-loop input/output test data obtained by using a feedback LQG controller designed from the previous cycle. Then the identified open-loop model is used to redesign the state feedback. The state feedback and the identified Kalman filter gain are used to form an updated LQC controller for the next cycle. This iterative process continues until the updated controller converges. The proposed controller design is demonstrated by numerical simulations and experiments on a highly unstable large-gap magnetic suspension system.

Closed-loop carrier phase synchronization techniques motivated by likelihood functions

NASA Technical Reports Server (NTRS)

Tsou, H.; Hinedi, S.; Simon, M.

1994-01-01

This article reexamines the notion of closed-loop carrier phase synchronization motivated by the theory of maximum a posteriori phase estimation with emphasis on the development of new structures based on both maximum-likelihood and average-likelihood functions. The criterion of performance used for comparison of all the closed-loop structures discussed is the mean-squared phase error for a fixed-loop bandwidth.

Thermal Interface Evaluation of Heat Transfer from a Pumped Loop to Titanium-Water Thermosyphons

NASA Technical Reports Server (NTRS)

Jaworske, Donald A.; Sanzi, James L.; Gibson, Marc A.; Sechkar, Edward A.

2009-01-01

Titanium-water thermosyphons are being considered for use in the heat rejection system for lunar outpost fission surface power. Key to their use is heat transfer between a closed loop heat source and the heat pipe evaporators. This work describes laboratory testing of several interfaces that were evaluated for their thermal performance characteristics, in the temperature range of 350 to 400 K, utilizing a water closed loop heat source and multiple thermosyphon evaporator geometries. A gas gap calorimeter was used to measure heat flow at steady state. Thermocouples in the closed loop heat source and on the evaporator were used to measure thermal conductance. The interfaces were in two generic categories, those immersed in the water closed loop heat source and those clamped to the water closed loop heat source with differing thermal conductive agents. In general, immersed evaporators showed better overall performance than their clamped counterparts. Selected clamped evaporator geometries offered promise.

A comparative approach to closed-loop computation.

PubMed

Roth, E; Sponberg, S; Cowan, N J

2014-04-01

Neural computation is inescapably closed-loop: the nervous system processes sensory signals to shape motor output, and motor output consequently shapes sensory input. Technological advances have enabled neuroscientists to close, open, and alter feedback loops in a wide range of experimental preparations. The experimental capability of manipulating the topology-that is, how information can flow between subsystems-provides new opportunities to understand the mechanisms and computations underlying behavior. These experiments encompass a spectrum of approaches from fully open-loop, restrained preparations to the fully closed-loop character of free behavior. Control theory and system identification provide a clear computational framework for relating these experimental approaches. We describe recent progress and new directions for translating experiments at one level in this spectrum to predictions at another level. Operating across this spectrum can reveal new understanding of how low-level neural mechanisms relate to high-level function during closed-loop behavior. Copyright © 2013 Elsevier Ltd. All rights reserved.

Nuclear fuel element

DOEpatents

Meadowcroft, Ronald Ross; Bain, Alastair Stewart

1977-01-01

A nuclear fuel element wherein a tubular cladding of zirconium or a zirconium alloy has a fission gas plenum chamber which is held against collapse by the loops of a spacer in the form of a tube which has been deformed inwardly at three equally spaced, circumferential positions to provide three loops. A heat resistant disc of, say, graphite separates nuclear fuel pellets within the cladding from the plenum chamber. The spacer is of zirconium or a zirconium alloy.

Multiday Fully Closed Loop Insulin Delivery in Monitored Outpatient Conditions

ClinicalTrials.gov

2014-04-29

To Demonstrate That the Closed Loop System Can be Used Safely Over a Few Consecutive Days.; To Assess Effectiveness in Maintaining Patients' Glucose Levels in the Target Range of 70 to 180 mg/dl, Measured by Blood Glucose Sensor.; To Evaluate the User Experience With a Closed Loop System

Closed Loop Vibrational Control: Theory and Applications

DTIC Science & Technology

1993-10-01

the open loop system dynamics will be close to that of Bit. However, in general, in a closed loop system with a specified feedback co-’ - oller , for...Juang, and G. Rodriguez , "Formulations and Applications of Large Structure Actuator and Sensor Placements," Second VPI & SU/AIAA Symposium on Dynamics

Regenerable mixed copper-iron-inert support oxygen carriers for solid fuel chemical looping combustion process

DOEpatents

Siriwardane, Ranjani V.; Tian, Hanjing

2016-12-20

The disclosure provides an oxygen carrier for a chemical looping cycle, such as the chemical looping combustion of solid carbonaceous fuels, such as coal, coke, coal and biomass char, and the like. The oxygen carrier is comprised of at least 24 weight % (wt %) CuO, at least 10 wt % Fe2O3, and an inert support, and is typically a calcine. The oxygen carrier exhibits a CuO crystalline structure and an absence of iron oxide crystalline structures under XRD crystallography, and provides an improved and sustained combustion reactivity in the temperature range of 600.degree. C.-1000.degree. C. particularly for solid fuels such as carbon and coal.

Nuclear light bulb

NASA Technical Reports Server (NTRS)

Latham, Tom

1991-01-01

The nuclear light bulb engine is a closed cycle concept. The nuclear light bulb concept provides containment by keeping the nuclear fuel fluid mechanically suspended in a cylindrical geometry. Thermal heat passes through an internally cooled, fused-silica, transparent wall and heats hydrogen propellant. The seeded hydrogen propellant absorbs radiant energy and is expanded through a nozzle. Internal moderation was used in the configuration which resulted in a reduced critical density requirement. This result was supported by criticality experiments. A reference engine was designed that had seven cells and was sized to fit in what was then predicted to be the shuttle bay mass and volume limitations. There were studies done of nozzle throat cooling schemes to remove the radiant heat. Elements of the nuclear light bulb program included closed loop critical assembly tests done at Los Alamos with UF6 confined by argon buffer gas. It was shown that the fuel region could be seeded with constituents that would block UV radiation from the uranium plasma. A combination of calculations and experiments showed that internal moderation produced a critical mass reduction. Other aspects of the research are presented.

Subsonic flight test evaluation of a performance seeking control algorithm on an F-15 airplane

NASA Technical Reports Server (NTRS)

Gilyard, Glenn B.; Orme, John S.

1992-01-01

The subsonic flight test evaluation phase of the NASA F-15 (powered by F 100 engines) performance seeking control program was completed for single-engine operation at part- and military-power settings. The subsonic performance seeking control algorithm optimizes the quasi-steady-state performance of the propulsion system for three modes of operation. The minimum fuel flow mode minimizes fuel consumption. The minimum thrust mode maximizes thrust at military power. Decreases in thrust-specific fuel consumption of 1 to 2 percent were measured in the minimum fuel flow mode; these fuel savings are significant, especially for supersonic cruise aircraft. Decreases of up to approximately 100 degree R in fan turbine inlet temperature were measured in the minimum temperature mode. Temperature reductions of this magnitude would more than double turbine life if inlet temperature was the only life factor. Measured thrust increases of up to approximately 15 percent in the maximum thrust mode cause substantial increases in aircraft acceleration. The system dynamics of the closed-loop algorithm operation were good. The subsonic flight phase has validated the performance seeking control technology, which can significantly benefit the next generation of fighter and transport aircraft.

Effect of pole zero location on system dynamics of boost converter for micro grid

NASA Astrophysics Data System (ADS)

Lavanya, A.; Vijayakumar, K.; Navamani, J. D.; Jayaseelan, N.

2018-04-01

Green clean energy like photo voltaic, wind energy, fuel cell can be brought together by microgrid.For low voltage sources like photovoltaic cell boost converter is very much essential. This paper explores the dynamic analysis of boost converter in a continuous conduction mode (CCM). The transient performance and stability analysis is carried out in this paper using time domain analysis and frequency domain analysis techniques. Boost converter is simulated using both PSIM and MATLAB software. Furthermore, state space model obtained and the transfer function is derived. The converter behaviour when a step input is applied is analyzed and stability of the converter is analyzed from bode plot frequency for open loop. Effect of the locations of poles and zeros in the transfer function of boost converter and how the performance parameters are affected is discussed in this paper. Closed loop performance with PI controller is also analyzed for boost converter.

Model Predictive Control-based Optimal Coordination of Distributed Energy Resources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mayhorn, Ebony T.; Kalsi, Karanjit; Lian, Jianming

2013-01-07

Distributed energy resources, such as renewable energy resources (wind, solar), energy storage and demand response, can be used to complement conventional generators. The uncertainty and variability due to high penetration of wind makes reliable system operations and controls challenging, especially in isolated systems. In this paper, an optimal control strategy is proposed to coordinate energy storage and diesel generators to maximize wind penetration while maintaining system economics and normal operation performance. The goals of the optimization problem are to minimize fuel costs and maximize the utilization of wind while considering equipment life of generators and energy storage. Model predictive controlmore » (MPC) is used to solve a look-ahead dispatch optimization problem and the performance is compared to an open loop look-ahead dispatch problem. Simulation studies are performed to demonstrate the efficacy of the closed loop MPC in compensating for uncertainties and variability caused in the system.« less

Model Predictive Control-based Optimal Coordination of Distributed Energy Resources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mayhorn, Ebony T.; Kalsi, Karanjit; Lian, Jianming

2013-04-03

Distributed energy resources, such as renewable energy resources (wind, solar), energy storage and demand response, can be used to complement conventional generators. The uncertainty and variability due to high penetration of wind makes reliable system operations and controls challenging, especially in isolated systems. In this paper, an optimal control strategy is proposed to coordinate energy storage and diesel generators to maximize wind penetration while maintaining system economics and normal operation performance. The goals of the optimization problem are to minimize fuel costs and maximize the utilization of wind while considering equipment life of generators and energy storage. Model predictive controlmore » (MPC) is used to solve a look-ahead dispatch optimization problem and the performance is compared to an open loop look-ahead dispatch problem. Simulation studies are performed to demonstrate the efficacy of the closed loop MPC in compensating for uncertainties and variability caused in the system.« less

Open-cycle magnetohydrodynamic power plant based upon direct-contact closed-loop high-temperature heat exchanger

DOEpatents

Berry, G.F.; Minkov, V.; Petrick, M.

1981-11-02

A magnetohydrodynamic (MHD) power generating system is described in which ionized combustion gases with slag and seed are discharged from an MHD combustor and pressurized high temperature inlet air is introduced into the combustor for supporting fuel combustion at high temperatures necessary to ionize the combustion gases, and including a heat exchanger in the form of a continuous loop with a circulating heat transfer liquid such as copper oxide. The heat exchanger has an upper horizontal channel for providing direct contact between the heat transfer liquid and the combustion gases to cool the gases and condense the slag which thereupon floats on the heat transfer liquid and can be removed from the channel, and a lower horizontal channel for providing direct contact between the heat transfer liquid and pressurized air for preheating the inlet air. The system further includes a seed separator downstream of the heat exchanger.

Open-cycle magnetohydrodynamic power plant based upon direct-contact closed-loop high-temperature heat exchanger

DOEpatents

Berry, Gregory F.; Minkov, Vladimir; Petrick, Michael

1988-01-05

A magnetohydrodynamic (MHD) power generating system in which ionized combustion gases with slag and seed are discharged from an MHD combustor and pressurized high temperature inlet air is introduced into the combustor for supporting fuel combustion at high temperatures necessary to ionize the combustion gases, and including a heat exchanger in the form of a continuous loop with a circulating heat transfer liquid such as copper oxide. The heat exchanger has an upper horizontal channel for providing direct contact between the heat transfer liquid and the combustion gases to cool the gases and condense the slag which thereupon floats on the heat transfer liquid and can be removed from the channel, and a lower horizontal channel for providing direct contact between the heat transfer liquid and pressurized air for preheating the inlet air. The system further includes a seed separator downstream of the heat exchanger.

Open-cycle magnetohydrodynamic power plant based upon direct-contact closed-loop high-temperature heat exchanger

DOEpatents

Berry, Gregory F.; Minkov, Vladimir; Petrick, Michael

1988-01-01

A magnetohydrodynamic (MHD) power generating system in which ionized combustion gases with slag and seed are discharged from an MHD combustor and pressurized high temperature inlet air is introduced into the combustor for supporting fuel combustion at high temperatures necessary to ionize the combustion gases, and including a heat exchanger in the form of a continuous loop with a circulating heat transfer liquid such as copper oxide. The heat exchanger has an upper horizontal channel for providing direct contact between the heat transfer liquid and the combustion gases to cool the gases and condense the slag which thereupon floats on the heat transfer liquid and can be removed from the channel, and a lower horizontal channel for providing direct contact between the heat transfer liquid and pressurized air for preheating the inlet air. The system further includes a seed separator downstream of the heat exchanger.

Solar water-heating system for the Ingham County geriatric medical care facility, Okemos, Michigan. Operational and maintenance instruction manual

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

The objectives of the Ingham County Solar Project include: the demonstration of a major operational supplement to fossil fuels, thereby reducing the demand for non-renewable energy sources, demonstration of the economic and technical feasibility of solar systems as an important energy supplement over the expected life of the building, and to encourage Michigan industry to produce and incorporate solar systems in their own facility. The Ingham County solar system consists of approximately 10,000 square feet of solar collectors connected in a closed configuration loop. The primary loop solution is a mixture of water and propylene glycol which flows through themore » tube side of a heat exchanger connected to the primary storage tank. The heat energy which is supplied to the primary storage tank is subsequently utilized to increase the temperature of the laundry water, kitchen water, and domestic potable water.« less

INTESTINAL OBSTRUCTION

PubMed Central

Whipple, G. H.; Stone, H. B.; Bernheim, B. M.

1913-01-01

Closed duodenal loops may be made in dogs by ligatures placed just below the pancreatic duct and just beyond the duodenojejunal junction, together with a posterior gastro-enterostomy. These closed duodenal loop dogs die with symptoms like those of patients suffering from volvulus or high intestinal obstruction. This duodenal loop may simulate closely a volvulus in which there has been no vascular disturbance. Dogs with closed duodenal loops which have been washed out carefully survive a little longer on the average than animals with unwashed loops. The duration of life in the first instance is one to three days, with an average of about forty-eight hours. The dogs usually lose considerable fluid by vomiting and diarrhea. A weak pulse, low blood pressure and temperature are usually conspicuous in the last stages. Autopsy shows more or less splanchnic congestion which may be most marked in the mucosa of the upper small intestine. The peritoneum is usually clear and the closed loop may be distended with thin fluid, or collapsed, and contain only a small amount of pasty brown material. The mucosa of the loop may show ulceration and even perforation, but in the majority of cases it is intact and exhibits only a moderate congestion. Simple intestinal obstruction added to a closed duodenal loop does not modify the result in any manner, but it may hasten the fatal outcome. The liver plays no essential role as a protective agent against this poison, for a dog with an Eck fistula may live three days with a closed loop. A normal dog reacts to intraportal injection and to intravenous injection of the toxic substance in an identical manner. Drainage of this loop under certain conditions may not interfere with the general health over a period of weeks or months. Excision of the part of the duodenum included in this loop causes no disturbance. The material from the closed duodenal loops contains no bile, pancreatic juice, gastric juice, or split products from the food. It can be formed in no other way than by the activity of the intestinal mucosa and the growth of the intestinal bacteria. This material after dilution, autolysis, sterilization, and filtration produces a characteristic effect when introduced intravenously. When in toxic doses it causes a profound drop in blood pressure, general collapse, drop in temperature, salivation, vomiting, and profuse diarrhea, which is often blood-stained. Splanchnic congestion is the conspicuous feature at autopsy and shows especially in the villi of the duodenal and jejunal mucosæ. Adrenalin, during this period of low blood pressure and splanchnic congestion, will cause the usual reaction when given intravenously, but applied locally or given intravenously it causes no bleaching of the engorged intestinal mucosa. Secretin is not found in the duodenal loop fluid, and the loop material does not influence the pancreatic secretion. Intraportal injection of the toxic material gives a reaction similar to intravenous injection. Intraperitoneal and subcutaneous injections produce a relatively slow reaction which closely resembles the picture seen in the closed duodenal loop dog. In both cases there is a relatively slow absorption, but the splanchnic congestion and other findings, though less intense, are present in both groups. There seems, therefore, to be no escape from the conclusion that a poisonous substance is formed in this closed duodenal loop which is absorbed from it and causes intoxication and death. Injection of this toxic substance into a normal dog gives intoxication and a reaction more intense but similar to that developing in a closed-loop dog. PMID:19867644

A molten Salt Am242M Production Reactor for Space Applications

NASA Technical Reports Server (NTRS)

Emrich, William

2005-01-01

The use of Am242m holds great promise for increasing the efficiency nuclear thermal rocket engines. Because Am242m has the highest fission cross section of any known isotope (1000's of barns), its extremely high reactivity may be used to directly heat a propellant gas with fission fragments. Since this isotope does not occur naturally, it must be bred in special production reactors designed for that purpose. The primary advantage to using molten salt reactors for breeding Am242m is that the reactors can be reprocessed continually yielding a constant rate of production of the isotope. Once built and initially fueled, the reactor will continually breed the additional fuel it needs to remain critical. The only feedstock required is a salt of U238. No enriched fuel is required during normal operation and all fissile material, except the Am242m, is maintained in a closed loop. For a reactor operating at 200 MW several kilograms of Am242m may be bred each year.

Loop system for creating jet fuel vapor standards used in the calibration of infrared spectrophotometers and gas chromatographs.

PubMed

Reboulet, James; Cunningham, Robert; Gunasekar, Palur G; Chapman, Gail D; Stevens, Sean C

2009-02-01

A whole body inhalation study of mixed jet fuel vapor and its aerosol necessitated the development of a method for preparing vapor only standards from the neat fuel. Jet fuel is a complex mixture of components which partitions between aerosol and vapor when aspirated based on relative volatility of the individual compounds. A method was desired which could separate the vapor portion from the aerosol component to prepare standards for the calibration of infrared spectrophotometers and a head space gas chromatography system. A re-circulating loop system was developed which provided vapor only standards whose composition matched those seen in an exposure system. Comparisons of nominal concentrations in the exposure system to those determined by infrared spectrophotometry were in 92-95% agreement. Comparison of jet fuel vapor concentrations determined by infrared spectrophotometry compared to head space gas chromatography yielded a 93% overall agreement in trial runs. These levels of agreement show the loop system to be a viable method for creating jet fuel vapor standards for calibrating instruments.

78 FR 58535 - Hydropower Regulatory Efficiency Act of 2013; Supplemental Notice of Workshop

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-24

... license for hydropower development at non-powered dams and closed-loop pumped storage projects in... for licensing hydropower development at non-powered dams and closed-loop pumped storage projects... closed- loop pumped storage) affect the steps included in a two-year process? 3.9 Should there be a...

The Effects of Closed-Loop Medical Devices on the Autonomy and Accountability of Persons and Systems.

PubMed

Kellmeyer, Philipp; Cochrane, Thomas; Müller, Oliver; Mitchell, Christine; Ball, Tonio; Fins, Joseph J; Biller-Andorno, Nikola

2016-10-01

Closed-loop medical devices such as brain-computer interfaces are an emerging and rapidly advancing neurotechnology. The target patients for brain-computer interfaces (BCIs) are often severely paralyzed, and thus particularly vulnerable in terms of personal autonomy, decisionmaking capacity, and agency. Here we analyze the effects of closed-loop medical devices on the autonomy and accountability of both persons (as patients or research participants) and neurotechnological closed-loop medical systems. We show that although BCIs can strengthen patient autonomy by preserving or restoring communicative abilities and/or motor control, closed-loop devices may also create challenges for moral and legal accountability. We advocate the development of a comprehensive ethical and legal framework to address the challenges of emerging closed-loop neurotechnologies like BCIs and stress the centrality of informed consent and refusal as a means to foster accountability. We propose the creation of an international neuroethics task force with members from medical neuroscience, neuroengineering, computer science, medical law, and medical ethics, as well as representatives of patient advocacy groups and the public.

75 FR 16576 - Credit for Renewable Electricity Production, Refined Coal Production, and Indian Coal Production...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-01

..., open-loop biomass, geothermal energy, solar energy, small irrigation power, municipal solid waste... electricity produced from closed-loop biomass, open-loop biomass, geothermal energy, solar energy, small... electricity produced from the qualified energy resources of wind, closed-loop biomass, geothermal energy, and...

77 FR 21835 - Credit for Renewable Electricity Production, Refined Coal Production, and Indian Coal Production...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-11

..., open-loop biomass, geothermal energy, solar energy, small irrigation power, municipal solid waste... electricity produced from closed-loop biomass, open-loop biomass, geothermal energy, solar energy, small... electricity produced from the qualified energy resources of wind, closed-loop biomass, geothermal energy, and...

76 FR 21947 - Credit for Renewable Electricity Production, Refined Coal Production, and Indian Coal Production...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-19

..., open-loop biomass, geothermal energy, solar energy, small irrigation power, municipal solid waste... electricity produced from closed-loop biomass, open-loop biomass, geothermal energy, solar energy, small... electricity produced from the qualified energy resources of wind, closed-loop biomass, geothermal energy, and...

Loop-bed combustion apparatus

DOEpatents

Shang, Jer-Yu; Mei, Joseph S.; Slagle, Frank D.; Notestein, John E.

1984-01-01

The present invention is directed to a combustion apparatus in the configuration of a oblong annulus defining a closed loop. Particulate coal together with a sulfur sorbent such as sulfur or dolomite is introduced into the closed loop, ignited, and propelled at a high rate of speed around the loop. Flue gas is withdrawn from a location in the closed loop in close proximity to an area in the loop where centrifugal force imposed upon the larger particulate material maintains these particulates at a location spaced from the flue gas outlet. Only flue gas and smaller particulates resulting from the combustion and innerparticle grinding are discharged from the combustor. This structural arrangement provides increased combustion efficiency due to the essentially complete combustion of the coal particulates as well as increased sulfur absorption due to the innerparticle grinding of the sorbent which provides greater particle surface area.

Preliminary demonstration of a robust controller design method

NASA Technical Reports Server (NTRS)

Anderson, L. R.

1980-01-01

Alternative computational procedures for obtaining a feedback control law which yields a control signal based on measurable quantitites are evaluated. The three methods evaluated are: (1) the standard linear quadratic regulator design model; (2) minimization of the norm of the feedback matrix, k via nonlinear programming subject to the constraint that the closed loop eigenvalues be in a specified domain in the complex plane; and (3) maximize the angles between the closed loop eigenvectors in combination with minimizing the norm of K also via the constrained nonlinear programming. The third or robust design method was chosen to yield a closed loop system whose eigenvalues are insensitive to small changes in the A and B matrices. The relationship between orthogonality of closed loop eigenvectors and the sensitivity of closed loop eigenvalues is described. Computer programs are described.

A Review: Using Pyrolysis and its Bioproducts to Help Close the Loop in Sustainable Life Support Systems

NASA Technical Reports Server (NTRS)

McCoy, LaShelle E.

2013-01-01

The next step in human exploration of space is beyond low Earth orbit and possibly to sites such as the Moon and Mars. Resupply of critical life support components for missions such as these are difficult or impossible. Life support processes for closing the loop of water, oxygen and carbon have to be identified. Currently, there are many technologies proposed for terrestrial missions for waste, water, air processing. and the creation of consumables. There are a variety of different approaches, but few address all of these issues simultaneously. One candidate is pyrolysis; a method where waste streams can be heated in the absence of oxygen to undergo a thermochemical conversion producing a series of bioproducts. Bioproducts like biochar made from non-edible biomass and human solid waste can possibly provide valuable benefits such as waste reduction, regolith fertilization for increased food production, and become a consumable for water processing and air revitalization systems. Syngas containing hydrogen, carbon monoxide and carbon dioxide, can be converted to methane and dimethyl ether to create propellants. Bio-oils can be utilized as a heating fuel or fed to bioreactors that utilize oil-eating microbes.

Automated hybrid closed-loop control with a proportional-integral-derivative based system in adolescents and adults with type 1 diabetes: individualizing settings for optimal performance.

PubMed

Ly, Trang T; Weinzimer, Stuart A; Maahs, David M; Sherr, Jennifer L; Roy, Anirban; Grosman, Benyamin; Cantwell, Martin; Kurtz, Natalie; Carria, Lori; Messer, Laurel; von Eyben, Rie; Buckingham, Bruce A

2017-08-01

Automated insulin delivery systems, utilizing a control algorithm to dose insulin based upon subcutaneous continuous glucose sensor values and insulin pump therapy, will soon be available for commercial use. The objective of this study was to determine the preliminary safety and efficacy of initialization parameters with the Medtronic hybrid closed-loop controller by comparing percentage of time in range, 70-180 mg/dL (3.9-10 mmol/L), mean glucose values, as well as percentage of time above and below target range between sensor-augmented pump therapy and hybrid closed-loop, in adults and adolescents with type 1 diabetes. We studied an initial cohort of 9 adults followed by a second cohort of 15 adolescents, using the Medtronic hybrid closed-loop system with the proportional-integral-derivative with insulin feed-back (PID-IFB) algorithm. Hybrid closed-loop was tested in supervised hotel-based studies over 4-5 days. The overall mean percentage of time in range (70-180 mg/dL, 3.9-10 mmol/L) during hybrid closed-loop was 71.8% in the adult cohort and 69.8% in the adolescent cohort. The overall percentage of time spent under 70 mg/dL (3.9 mmol/L) was 2.0% in the adult cohort and 2.5% in the adolescent cohort. Mean glucose values were 152 mg/dL (8.4 mmol/L) in the adult cohort and 153 mg/dL (8.5 mmol/L) in the adolescent cohort. Closed-loop control using the Medtronic hybrid closed-loop system enables adaptive, real-time basal rate modulation. Initializing hybrid closed-loop in clinical practice will involve individualizing initiation parameters to optimize overall glucose control. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Recycling of carbon dioxide to methanol and derived products - closing the loop.

PubMed

Goeppert, Alain; Czaun, Miklos; Jones, John-Paul; Surya Prakash, G K; Olah, George A

2014-12-07

Starting with coal, followed by petroleum oil and natural gas, the utilization of fossil fuels has allowed the fast and unprecedented development of human society. However, the burning of these resources in ever increasing pace is accompanied by large amounts of anthropogenic CO2 emissions, which are outpacing the natural carbon cycle, causing adverse global environmental changes, the full extent of which is still unclear. Even through fossil fuels are still abundant, they are nevertheless limited and will, in time, be depleted. Chemical recycling of CO2 to renewable fuels and materials, primarily methanol, offers a powerful alternative to tackle both issues, that is, global climate change and fossil fuel depletion. The energy needed for the reduction of CO2 can come from any renewable energy source such as solar and wind. Methanol, the simplest C1 liquid product that can be easily obtained from any carbon source, including biomass and CO2, has been proposed as a key component of such an anthropogenic carbon cycle in the framework of a "Methanol Economy". Methanol itself is an excellent fuel for internal combustion engines, fuel cells, stoves, etc. It's dehydration product, dimethyl ether, is a diesel fuel and liquefied petroleum gas (LPG) substitute. Furthermore, methanol can be transformed to ethylene, propylene and most of the petrochemical products currently obtained from fossil fuels. The conversion of CO2 to methanol is discussed in detail in this review.

Method and apparatus for controlling fuel/air mixture in a lean burn engine

DOEpatents

Kubesh, John Thomas; Dodge, Lee Gene; Podnar, Daniel James

1998-04-07

The system for controlling the fuel/air mixture supplied to a lean burn engine when operating on natural gas, gasoline, hydrogen, alcohol, propane, butane, diesel or any other fuel as desired. As specific humidity of air supplied to the lean burn engine increases, the oxygen concentration of exhaust gas discharged by the engine for a given equivalence ratio will decrease. Closed loop fuel control systems typically attempt to maintain a constant exhaust gas oxygen concentration. Therefore, the decrease in the exhaust gas oxygen concentration resulting from increased specific humidity will often be improperly attributed to an excessive supply of fuel and the control system will incorrectly reduce the amount of fuel supplied to the engine. Also, the minimum fuel/air equivalence ratio for a lean burn engine to avoid misfiring will increase as specific humidity increases. A relative humidity sensor to allow the control system to provide a more enriched fuel/air mixture at high specific humidity levels. The level of specific humidity may be used to compensate an output signal from a universal exhaust gas oxygen sensor for changing oxygen concentrations at a desired equivalence ratio due to variation in specific humidity specific humidity. As a result, the control system will maintain the desired efficiency, low exhaust emissions and power level for the associated lean burn engine regardless of the specific humidity level of intake air supplied to the lean burn engine.

Direct-contact closed-loop heat exchanger

DOEpatents

Berry, Gregory F.; Minkov, Vladimir; Petrick, Michael

1984-01-01

A high temperature heat exchanger with a closed loop and a heat transfer liquid within the loop, the closed loop having a first horizontal channel with inlet and outlet means for providing direct contact of a first fluid at a first temperature with the heat transfer liquid, a second horizontal channel with inlet and outlet means for providing direct contact of a second fluid at a second temperature with the heat transfer liquid, and means for circulating the heat transfer liquid.

Experimental study of operation performance for hydrocarbon fuel pump with low specific speed

NASA Astrophysics Data System (ADS)

Wu, Xianyu; Yang, Jun; Jin, Xuan

2017-10-01

In this paper, a small flow rate hydrocarbon turbine pump was used to pressurize the fuel supply system of scramjet engine. Some experiments were carried out to investigate the characteristics of turbine pump driven by nitrogen or combustion gas under different operating conditions. A experimental database with regard to the curves of the rotational speed, mass flow rate and net head with regard to centrifugal pump were plotted. These curves were represented as functions of the pressure and temperature at turbine inlet/outlet and the throttle diameter at downstream of centrifugal pump. A sensitivity study has been carried out based on design of experiments. The experimental was employed to analyze net head of centrifugal and throttle characteristics. The research results can accumulate foundations for the close loop control system of turbine pump.

Closed-Loop Control of Complex Networks: A Trade-Off between Time and Energy

NASA Astrophysics Data System (ADS)

Sun, Yong-Zheng; Leng, Si-Yang; Lai, Ying-Cheng; Grebogi, Celso; Lin, Wei

2017-11-01

Controlling complex nonlinear networks is largely an unsolved problem at the present. Existing works focus either on open-loop control strategies and their energy consumptions or on closed-loop control schemes with an infinite-time duration. We articulate a finite-time, closed-loop controller with an eye toward the physical and mathematical underpinnings of the trade-off between the control time and energy as well as their dependence on the network parameters and structure. The closed-loop controller is tested on a large number of real systems including stem cell differentiation, food webs, random ecosystems, and spiking neuronal networks. Our results represent a step forward in developing a rigorous and general framework to control nonlinear dynamical networks with a complex topology.

DC servomechanism parameter identification: a Closed Loop Input Error approach.

PubMed

Garrido, Ruben; Miranda, Roger

2012-01-01

This paper presents a Closed Loop Input Error (CLIE) approach for on-line parametric estimation of a continuous-time model of a DC servomechanism functioning in closed loop. A standard Proportional Derivative (PD) position controller stabilizes the loop without requiring knowledge on the servomechanism parameters. The analysis of the identification algorithm takes into account the control law employed for closing the loop. The model contains four parameters that depend on the servo inertia, viscous, and Coulomb friction as well as on a constant disturbance. Lyapunov stability theory permits assessing boundedness of the signals associated to the identification algorithm. Experiments on a laboratory prototype allows evaluating the performance of the approach. Copyright © 2011 ISA. Published by Elsevier Ltd. All rights reserved.

Closing the Feedback Loop Is Not Enough: The Assessment Spiral

ERIC Educational Resources Information Center

Wehlburg, Catherine M.

2007-01-01

For quite some time, the call to close the feedback loop has been heard throughout higher education. Faculty and administrators have paid attention, and now they can more easily than ever point to the fact that at their institution, the feedback loop is almost always closed. As reviewers from accreditation teams visit campuses, they often hear…

78 FR 62322 - Hydropower Regulatory Efficiency Act of 2013; Notice of Rescheduled Two-Year Licensing Process...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-10-16

... at non-powered dams and closed-loop pumped storage projects in compliance with section 6 of the... process for licensing hydropower development at non-powered dams and closed-loop pumped storage projects...-powered dam versus closed- loop pumped storage) affect the steps included in a two-year process? 3.9...

Conceptualization and validation of an open-source closed-loop deep brain stimulation system in rat.

PubMed

Wu, Hemmings; Ghekiere, Hartwin; Beeckmans, Dorien; Tambuyzer, Tim; van Kuyck, Kris; Aerts, Jean-Marie; Nuttin, Bart

2015-04-21

Conventional deep brain stimulation (DBS) applies constant electrical stimulation to specific brain regions to treat neurological disorders. Closed-loop DBS with real-time feedback is gaining attention in recent years, after proved more effective than conventional DBS in terms of pathological symptom control clinically. Here we demonstrate the conceptualization and validation of a closed-loop DBS system using open-source hardware. We used hippocampal theta oscillations as system input, and electrical stimulation in the mesencephalic reticular formation (mRt) as controller output. It is well documented that hippocampal theta oscillations are highly related to locomotion, while electrical stimulation in the mRt induces freezing. We used an Arduino open-source microcontroller between input and output sources. This allowed us to use hippocampal local field potentials (LFPs) to steer electrical stimulation in the mRt. Our results showed that closed-loop DBS significantly suppressed locomotion compared to no stimulation, and required on average only 56% of the stimulation used in open-loop DBS to reach similar effects. The main advantages of open-source hardware include wide selection and availability, high customizability, and affordability. Our open-source closed-loop DBS system is effective, and warrants further research using open-source hardware for closed-loop neuromodulation.

Conceptualization and validation of an open-source closed-loop deep brain stimulation system in rat

PubMed Central

Wu, Hemmings; Ghekiere, Hartwin; Beeckmans, Dorien; Tambuyzer, Tim; van Kuyck, Kris; Aerts, Jean-Marie; Nuttin, Bart

2015-01-01

Conventional deep brain stimulation (DBS) applies constant electrical stimulation to specific brain regions to treat neurological disorders. Closed-loop DBS with real-time feedback is gaining attention in recent years, after proved more effective than conventional DBS in terms of pathological symptom control clinically. Here we demonstrate the conceptualization and validation of a closed-loop DBS system using open-source hardware. We used hippocampal theta oscillations as system input, and electrical stimulation in the mesencephalic reticular formation (mRt) as controller output. It is well documented that hippocampal theta oscillations are highly related to locomotion, while electrical stimulation in the mRt induces freezing. We used an Arduino open-source microcontroller between input and output sources. This allowed us to use hippocampal local field potentials (LFPs) to steer electrical stimulation in the mRt. Our results showed that closed-loop DBS significantly suppressed locomotion compared to no stimulation, and required on average only 56% of the stimulation used in open-loop DBS to reach similar effects. The main advantages of open-source hardware include wide selection and availability, high customizability, and affordability. Our open-source closed-loop DBS system is effective, and warrants further research using open-source hardware for closed-loop neuromodulation. PMID:25897892

Performance constraints and compensation for teleoperation with delay

NASA Technical Reports Server (NTRS)

Mclaughlin, J. S.; Staunton, B. D.

1989-01-01

A classical control perspective is used to characterize performance constraints and evaluate compensation techniques for teleoperation with delay. Use of control concepts such as open and closed loop performance, stability, and bandwidth yield insight to the delay problem. Teleoperator performance constraints are viewed as an open loop time delay lag and as a delay-induced closed loop bandwidth constraint. These constraints are illustrated with a simple analytical tracking example which is corroborated by a real time, 'man-in-the-loop' tracking experiment. The experiment also provides insight to those controller characteristics which are unique to a human operator. Predictive displays and feedforward commands are shown to provide open loop compensation for delay lag. Low pass filtering of telemetry or feedback signals is interpreted as closed loop compensation used to maintain a sufficiently low bandwidth for stability. A new closed loop compensation approach is proposed that uses a reactive (or force feedback) hand controller to restrict system bandwidth by impeding operator inputs.

Using Pyrolysis and its Bioproducts to Help Close the Loop in Sustainable Life Support Systems

NASA Technical Reports Server (NTRS)

McCoy, LaShelle E.

2012-01-01

The next step in human exploration of space is beyond low Earth orbit and possibly to sites such as the Moon and Mars. Resupply of critical life support components for missions such as these are difficult or impossible. Life support processes for closing the loop of water, oxygen and carbon have to be identified .. Currently, there are many technologies proposed for terrestrial missions for waste, water, air processing and the creation of consumables. There are a variety of different approaches, but few address all of these issues simultaneously. One candidate is pyrolysis; a method where waste streams can be heated in the absence of oxygen to undergo a thermochemical conversion producing a series of bioproducts. Bioproducts like biochar made from non-edible biomass and human solid waste can possibly provide valuable benefits such as waste reduction, regolith fertilization for increased food production, and become a consumable for water processing and air revitalization systems. Syngas containing hydrogen, carbon monoxide and cbon dioxide, can be converted to methane and dimethyl ether to create propellants. Bio-oils can be utilized as a heating fuel or fed to bioreactors that utilize oil-eating microbes. Issues such as carbon sequestration and subsequent carbon balance of the closed system and identifying ideal process methods to achieve the highest quality products, whilst being energy friendly, will also be addressed.

Overnight closed-loop insulin delivery with model predictive control: assessment of hypoglycemia and hyperglycemia risk using simulation studies.

PubMed

Wilinska, Malgorzata E; Budiman, Erwin S; Taub, Marc B; Elleri, Daniela; Allen, Janet M; Acerini, Carlo L; Dunger, David B; Hovorka, Roman

2009-09-01

Hypoglycemia and hyperglycemia during closed-loop insulin delivery based on subcutaneous (SC) glucose sensing may arise due to (1) overdosing and underdosing of insulin by control algorithm and (2) difference between plasma glucose (PG) and sensor glucose, which may be transient (kinetics origin and sensor artifacts) or persistent (calibration error [CE]). Using in silico testing, we assessed hypoglycemia and hyperglycemia incidence during over-night closed loop. Additionally, a comparison was made against incidence observed experimentally during open-loop single-night in-clinic studies in young people with type 1 diabetes mellitus (T1DM) treated by continuous SC insulin infusion. Simulation environment comprising 18 virtual subjects with T1DM was used to simulate overnight closed-loop study with a model predictive control (MPC) algorithm. A 15 h experiment started at 17:00 and ended at 08:00 the next day. Closed loop commenced at 21:00 and continued for 11 h. At 18:00, protocol included meal (50 g carbohydrates) accompanied by prandial insulin. The MPC algorithm advised on insulin infusion every 15 min. Sensor glucose was obtained by combining model-calculated noise-free interstitial glucose with experimentally derived transient and persistent sensor artifacts associated with FreeStyle Navigator (FSN). Transient artifacts were obtained from FSN sensor pairs worn by 58 subjects with T1DM over 194 nighttime periods. Persistent difference due to FSN CE was quantified from 585 FSN sensor insertions, yielding 1421 calibration sessions from 248 subjects with diabetes. Episodes of severe (PG < or = 36 mg/dl) and significant (PG < or = 45 mg/dl) hypoglycemia and significant hyperglycemia (PG > or = 300 mg/dl) were extracted from 18,000 simulated closed-loop nights. Severe hypoglycemia was not observed when FSN CE was less than 45%. Hypoglycemia and hyperglycemia incidence during open loop was assessed from 21 overnight studies in 17 young subjects with T1DM (8 males; 13.5 +/- 3.6 years of age; body mass index 21.0 +/- 4.0 kg/m2; duration diabetes 6.4 +/- 4.1 years; hemoglobin A1c 8.5% +/- 1.8%; mean +/- standard deviation) participating in the Artificial Pancreas Project at Cambridge. Severe and significant hypoglycemia during simulated closed loop occurred 0.75 and 17.11 times per 100 person years compared to 1739 and 3479 times per 100 person years during experimental open loop, respectively. Significant hyperglycemia during closed loop and open loop occurred 75 and 15,654 times per 100 person years, respectively. The incidence of severe and significant hypoglycemia reduced 2300- and 200-fold, respectively, during stimulated overnight closed loop with MPC compared to that observed during open-loop overnight clinical studies in young subjects with T1DM. Hyperglycemia was 200 times less likely. Overnight closed loop with the FSN and the MPC algorithm is expected to reduce substantially the risk of hypoglycemia and hyperglycemia. 2009 Diabetes Technology Society.

Fundamental Physics and Practical Applications of Electromagnetic Local Flow Control in High Speed Flows (Rutgers)

DTIC Science & Technology

2010-02-16

field. Techniques utilizing this design use an open- loop control and no flow monitoring sensors are required. Conversely, reactive (or closed - loop ...and closed (dashed line) configuration. 38 closed configuration described above, the ambiguity in the critical limits of the transition...flow; a new vortex is then shed from the cavity leading edge, closing the feedback loop .[31] Open cavities with an L/D approximately greater than

Direct-contact closed-loop heat exchanger

DOEpatents

Berry, G.F.; Minkov, V.; Petrick, M.

1981-11-02

A high temperature heat exchanger is disclosed which has a closed loop and a heat transfer liquid within the loop, the closed loop having a first horizontal channel with inlet and outlet means for providing direct contact of a first fluid at a first temperature with the heat transfer liquid, a second horizontal channel with inlet and outlet means for providing direct contact of a second fluid at a second temperature with the heat transfer liquid, and means for circulating the heat transfer liquid.

Intraoperative stroke volume optimization using stroke volume, arterial pressure, and heart rate: closed-loop (learning intravenous resuscitator) versus anesthesiologists.

PubMed

Rinehart, Joseph; Chung, Elena; Canales, Cecilia; Cannesson, Maxime

2012-10-01

The authors compared the performance of a group of anesthesia providers to closed-loop (Learning Intravenous Resuscitator [LIR]) management in a simulated hemorrhage scenario using cardiac output monitoring. A prospective cohort study. In silico simulation. University hospital anesthesiologists and the LIR closed-loop fluid administration system. Using a patient simulator, a 90-minute simulated hemorrhage protocol was run, which included a 1,200-mL blood loss over 30 minutes. Twenty practicing anesthesiology providers were asked to manage this scenario by providing fluids and vasopressor medication at their discretion. The simulation program was also run 20 times with the LIR closed-loop algorithm managing fluids and an additional 20 times with no intervention. Simulated patient weight, height, heart rate, mean arterial pressure, and cardiac output (CO) were similar at baseline. The mean stroke volume, the mean arterial pressure, CO, and the final CO were higher in the closed-loop group than in the practitioners group, and the coefficient of variance was lower. The closed-loop group received slightly more fluid (2.1 v 1.9 L, p < 0.05) than the anesthesiologist group. Despite the roughly similar volumes of fluid given, the closed-loop maintained more stable hemodynamics than the practitioners primarily because the fluid was given earlier in the protocol and CO optimized before the hemorrhage began, whereas practitioners tended to resuscitate well but only after significant hemodynamic change indicated the need. Overall, these data support the potential usefulness of this closed-loop algorithm in clinical settings in which dynamic predictors are not available or applicable. Published by Elsevier Inc.

Assessing performance of closed-loop insulin delivery systems by continuous glucose monitoring: drawbacks and way forward.

PubMed

Hovorka, Roman; Nodale, Marianna; Haidar, Ahmad; Wilinska, Malgorzata E

2013-01-01

We investigated whether continuous glucose monitoring (CGM) levels can accurately assess glycemic control while directing closed-loop insulin delivery. Data were analyzed retrospectively from 33 subjects with type 1 diabetes who underwent closed-loop and conventional pump therapy on two separate nights. Glycemic control was evaluated by reference plasma glucose and contrasted against three methods based on Navigator (Abbott Diabetes Care, Alameda, CA) CGM levels. Glucose mean and variability were estimated by unmodified CGM levels with acceptable clinical accuracy. Time when glucose was in target range was overestimated by CGM during closed-loop nights (CGM vs. plasma glucose median [interquartile range], 86% [65-97%] vs. 75% [59-91%]; P=0.04) but not during conventional pump therapy (57% [32-72%] vs. 51% [29-68%]; P=0.82) providing comparable treatment effect (mean [SD], 28% [29%] vs. 23% [21%]; P=0.11). Using the CGM measurement error of 15% derived from plasma glucose-CGM pairs (n=4,254), stochastic interpretation of CGM gave unbiased estimate of time in target during both closed-loop (79% [62-86%] vs. 75% [59-91%]; P=0.24) and conventional pump therapy (54% [33-66%] vs. 51% [29-68%]; P=0.44). Treatment effect (23% [24%] vs. 23% [21%]; P=0.96) and time below target were accurately estimated by stochastic CGM. Recalibrating CGM using reference plasma glucose values taken at the start and end of overnight closed-loop was not superior to stochastic CGM. CGM is acceptable to estimate glucose mean and variability, but without adjustment it may overestimate benefit of closed-loop. Stochastic CGM provided unbiased estimate of time when glucose is in target and below target and may be acceptable for assessment of closed-loop in the outpatient setting.

Comparison of cardiac output optimization with an automated closed-loop goal-directed fluid therapy versus non standardized manual fluid administration during elective abdominal surgery: first prospective randomized controlled trial.

PubMed

Lilot, Marc; Bellon, Amandine; Gueugnon, Marine; Laplace, Marie-Christine; Baffeleuf, Bruno; Hacquard, Pauline; Barthomeuf, Felicie; Parent, Camille; Tran, Thomas; Soubirou, Jean-Luc; Robinson, Philip; Bouvet, Lionel; Vassal, Olivia; Lehot, Jean-Jacques; Piriou, Vincent

2018-01-27

An intraoperative automated closed-loop system for goal-directed fluid therapy has been successfully tested in silico, in vivo and in a clinical case-control matching. This trial compared intraoperative cardiac output (CO) in patients managed with this closed-loop system versus usual practice in an academic medical center. The closed-loop system was connected to a CO monitoring system and delivered automated colloid fluid boluses. Moderate to high-risk abdominal surgical patients were randomized either to the closed-loop or the manual group. Intraoperative final CO was the primary endpoint. Secondary endpoints were intraoperative overall mean cardiac index (CI), increase from initial to final CI, intraoperative fluid volume and postoperative outcomes. From January 2014 to November 2015, 46 patients were randomized. There was a lower initial CI (2.06 vs. 2.51 l min -1 m -2 , p = 0.042) in the closed-loop compared to the control group. No difference in final CO and in overall mean intraoperative CI was observed between groups. A significant relative increase from initial to final CI values was observed in the closed-loop but not the control group (+ 28.6%, p = 0.006 vs. + 1.2%, p = 0.843). No difference was found for intraoperative fluid management and postoperative outcomes between groups. There was no significant impact on the primary study endpoint, but this was found in a context of unexpected lower initial CI in the closed-loop group.Trial registry number ID-RCB/EudraCT: 2013-A00770-45. ClinicalTrials.gov Identifier NCT01950845, date of registration: 17 September 2013.

Dynamic simulation of perturbation responses in a closed-loop virtual arm model.

PubMed

Du, Yu-Fan; He, Xin; Lan, Ning

2010-01-01

A closed-loop virtual arm (VA) model has been developed in SIMULINK environment by adding spinal reflex circuits and propriospinal neural networks to the open-loop VA model developed in early study [1]. An improved virtual muscle model (VM4.0) is used to speed up simulation and to generate more precise recruitment of muscle force at low levels of muscle activation. Time delays in the reflex loops are determined by their synaptic connections and afferent transmission back to the spinal cord. Reflex gains are properly selected so that closed-loop responses are stable. With the closed-loop VA model, we are developing an approach to evaluate system behaviors by dynamic simulation of perturbation responses. Joint stiffness is calculated based on simulated perturbation responses by a least-squares algorithm in MATLAB. This method of dynamic simulation will be essential for further evaluation of feedforward and reflex control of arm movement and position.

Perception as a closed-loop convergence process.

PubMed

Ahissar, Ehud; Assa, Eldad

2016-05-09

Perception of external objects involves sensory acquisition via the relevant sensory organs. A widely-accepted assumption is that the sensory organ is the first station in a serial chain of processing circuits leading to an internal circuit in which a percept emerges. This open-loop scheme, in which the interaction between the sensory organ and the environment is not affected by its concurrent downstream neuronal processing, is strongly challenged by behavioral and anatomical data. We present here a hypothesis in which the perception of external objects is a closed-loop dynamical process encompassing loops that integrate the organism and its environment and converging towards organism-environment steady-states. We discuss the consistency of closed-loop perception (CLP) with empirical data and show that it can be synthesized in a robotic setup. Testable predictions are proposed for empirical distinction between open and closed loop schemes of perception.

Perception as a closed-loop convergence process

PubMed Central

Ahissar, Ehud; Assa, Eldad

2016-01-01

Perception of external objects involves sensory acquisition via the relevant sensory organs. A widely-accepted assumption is that the sensory organ is the first station in a serial chain of processing circuits leading to an internal circuit in which a percept emerges. This open-loop scheme, in which the interaction between the sensory organ and the environment is not affected by its concurrent downstream neuronal processing, is strongly challenged by behavioral and anatomical data. We present here a hypothesis in which the perception of external objects is a closed-loop dynamical process encompassing loops that integrate the organism and its environment and converging towards organism-environment steady-states. We discuss the consistency of closed-loop perception (CLP) with empirical data and show that it can be synthesized in a robotic setup. Testable predictions are proposed for empirical distinction between open and closed loop schemes of perception. DOI: http://dx.doi.org/10.7554/eLife.12830.001 PMID:27159238

Open-Loop HIRF Experiments Performed on a Fault Tolerant Flight Control Computer

NASA Technical Reports Server (NTRS)

Koppen, Daniel M.

1997-01-01

During the third quarter of 1996, the Closed-Loop Systems Laboratory was established at the NASA Langley Research Center (LaRC) to study the effects of High Intensity Radiated Fields on complex avionic systems and control system components. This new facility provided a link and expanded upon the existing capabilities of the High Intensity Radiated Fields Laboratory at LaRC that were constructed and certified during 1995-96. The scope of the Closed-Loop Systems Laboratory is to place highly integrated avionics instrumentation into a high intensity radiated field environment, interface the avionics to a real-time flight simulation that incorporates aircraft dynamics, engines, sensors, actuators and atmospheric turbulence, and collect, analyze, and model aircraft performance. This paper describes the layout and functionality of the Closed-Loop Systems Laboratory, and the open-loop calibration experiments that led up to the commencement of closed-loop real-time flight experiments.

Competition and quality in health care markets: a differential-game approach.

PubMed

Brekke, Kurt R; Cellini, Roberto; Siciliani, Luigi; Straume, Odd Rune

2010-07-01

We investigate the effect of competition on quality in health care markets with regulated prices taking a differential game approach, in which quality is a stock variable. Using a Hotelling framework, we derive the open-loop solution (health care providers set the optimal investment plan at the initial period) and the feedback closed-loop solution (providers move investments in response to the dynamics of the states). Under the closed-loop solution competition is more intense in the sense that providers observe quality in each period and base their investment on this information. If the marginal provision cost is constant, the open-loop and closed-loop solutions coincide, and the results are similar to the ones obtained by static models. If the marginal provision cost is increasing, investment and quality are lower in the closed-loop solution (when competition is more intense). In this case, static models tend to exaggerate the positive effect of competition on quality.

Probing the closed-loop model of mRNA translation in living cells

PubMed Central

Archer, Stuart K; Shirokikh, Nikolay E; Hallwirth, Claus V; Beilharz, Traude H; Preiss, Thomas

2015-01-01

The mRNA closed-loop, formed through interactions between the cap structure, poly(A) tail, eIF4E, eIF4G and PAB, features centrally in models of eukaryotic translation initiation, although direct support for its existence in vivo is not well established. Here, we investigated the closed-loop using a combination of mRNP isolation from rapidly cross-linked cells and high-throughput qPCR. Using the interaction between these factors and the opposing ends of mRNAs as a proxy for the closed-loop, we provide evidence that it is prevalent for eIF4E/4G-bound but unexpectedly sparse for PAB1-bound mRNAs, suggesting it primarily occurs during a distinct phase of polysome assembly. We observed mRNA-specific variation in the extent of closed-loop formation, consistent with a role for polysome topology in the control of gene expression. PMID:25826658

Guidance and Control strategies for aerospace vehicles

NASA Technical Reports Server (NTRS)

Hibey, J. L.; Naidu, D. S.; Charalambous, C. D.

1989-01-01

A neighboring optimal guidance scheme was devised for a nonlinear dynamic system with stochastic inputs and perfect measurements as applicable to fuel optimal control of an aeroassisted orbital transfer vehicle. For the deterministic nonlinear dynamic system describing the atmospheric maneuver, a nominal trajectory was determined. Then, a neighboring, optimal guidance scheme was obtained for open loop and closed loop control configurations. Taking modelling uncertainties into account, a linear, stochastic, neighboring optimal guidance scheme was devised. Finally, the optimal trajectory was approximated as the sum of the deterministic nominal trajectory and the stochastic neighboring optimal solution. Numerical results are presented for a typical vehicle. A fuel-optimal control problem in aeroassisted noncoplanar orbital transfer is also addressed. The equations of motion for the atmospheric maneuver are nonlinear and the optimal (nominal) trajectory and control are obtained. In order to follow the nominal trajectory under actual conditions, a neighboring optimum guidance scheme is designed using linear quadratic regulator theory for onboard real-time implementation. One of the state variables is used as the independent variable in reference to the time. The weighting matrices in the performance index are chosen by a combination of a heuristic method and an optimal modal approach. The necessary feedback control law is obtained in order to minimize the deviations from the nominal conditions.

Closed-Loop HIRF Experiments Performed on a Fault Tolerant Flight Control Computer

NASA Technical Reports Server (NTRS)

Belcastro, Celeste M.

1997-01-01

ABSTRACT Closed-loop HIRF experiments were performed on a fault tolerant flight control computer (FCC) at the NASA Langley Research Center. The FCC used in the experiments was a quad-redundant flight control computer executing B737 Autoland control laws. The FCC was placed in one of the mode-stirred reverberation chambers in the HIRF Laboratory and interfaced to a computer simulation of the B737 flight dynamics, engines, sensors, actuators, and atmosphere in the Closed-Loop Systems Laboratory. Disturbances to the aircraft associated with wind gusts and turbulence were simulated during tests. Electrical isolation between the FCC under test and the simulation computer was achieved via a fiber optic interface for the analog and discrete signals. Closed-loop operation of the FCC enabled flight dynamics and atmospheric disturbances affecting the aircraft to be represented during tests. Upset was induced in the FCC as a result of exposure to HIRF, and the effect of upset on the simulated flight of the aircraft was observed and recorded. This paper presents a description of these closed- loop HIRF experiments, upset data obtained from the FCC during these experiments, and closed-loop effects on the simulated flight of the aircraft.

Closed-Loop- and Decision-Assist-Guided Fluid Therapy of Human Hemorrhage.

PubMed

Hundeshagen, Gabriel; Kramer, George C; Ribeiro Marques, Nicole; Salter, Michael G; Koutrouvelis, Aristides K; Li, Husong; Solanki, Daneshvari R; Indrikovs, Alexander; Seeton, Roger; Henkel, Sheryl N; Kinsky, Michael P

2017-10-01

We sought to evaluate the efficacy, efficiency, and physiologic consequences of automated, endpoint-directed resuscitation systems and compare them to formula-based bolus resuscitation. Experimental human hemorrhage and resuscitation. Clinical research laboratory. Healthy volunteers. Subjects (n = 7) were subjected to hemorrhage and underwent a randomized fluid resuscitation scheme on separate visits 1) formula-based bolus resuscitation; 2) semiautonomous (decision assist) fluid administration; and 3) fully autonomous (closed loop) resuscitation. Hemodynamic variables, volume shifts, fluid balance, and cardiac function were monitored during hemorrhage and resuscitation. Treatment modalities were compared based on resuscitation efficacy and efficiency. All approaches achieved target blood pressure by 60 minutes. Following hemorrhage, the total amount of infused fluid (bolus resuscitation: 30 mL/kg, decision assist: 5.6 ± 3 mL/kg, closed loop: 4.2 ± 2 mL/kg; p < 0.001), plasma volume, extravascular volume (bolus resuscitation: 17 ± 4 mL/kg, decision assist: 3 ± 1 mL/kg, closed loop: -0.3 ± 0.3 mL/kg; p < 0.001), body weight, and urinary output remained stable under decision assist and closed loop and were significantly increased under bolus resuscitation. Mean arterial pressure initially decreased further under bolus resuscitation (-10 mm Hg; p < 0.001) and was lower under bolus resuscitation than closed loop at 20 minutes (bolus resuscitation: 57 ± 2 mm Hg, closed loop: 69 ± 4 mm Hg; p = 0.036). Colloid osmotic pressure (bolus resuscitation: 19.3 ± 2 mm Hg, decision assist, closed loop: 24 ± 0.4 mm Hg; p < 0.05) and hemoglobin concentration were significantly decreased after bolus fluid administration. We define efficacy of decision-assist and closed-loop resuscitation in human hemorrhage. In comparison with formula-based bolus resuscitation, both semiautonomous and autonomous approaches were more efficient in goal-directed resuscitation of hemorrhage. They provide favorable conditions for the avoidance of over-resuscitation and its adverse clinical sequelae. Decision-assist and closed-loop resuscitation algorithms are promising technological solutions for constrained environments and areas of limited resources.

Surface-reconstructed graphite nanofibers as a support for cathode catalysts of fuel cells.

PubMed

Gan, Lin; Du, Hongda; Li, Baohua; Kang, Feiyu

2011-04-07

Graphite nanofibers (GNFs), on which surface graphite edges were reconstructed into nano-loops, were explored as a cathode catalyst support for fuel cells. The high degree of graphitization, as well as the surface-reconstructed nano-loops that possess topological defects for uniform metal deposition, resulted in an improved performance of the GNF-supported Pt catalyst.

Predictive lethal proarrhythmic risk evaluation using a closed-loop-circuit cell network with human induced pluripotent stem cells derived cardiomyocytes

NASA Astrophysics Data System (ADS)

Nomura, Fumimasa; Hattori, Akihiro; Terazono, Hideyuki; Kim, Hyonchol; Odaka, Masao; Sugio, Yoshihiro; Yasuda, Kenji

2016-06-01

For the prediction of lethal arrhythmia occurrence caused by abnormality of cell-to-cell conduction, we have developed a next-generation in vitro cell-to-cell conduction assay, i.e., a quasi in vivo assay, in which the change in spatial cell-to-cell conduction is quantitatively evaluated from the change in waveforms of the convoluted electrophysiological signals from lined-up cardiomyocytes on a single closed loop of a microelectrode of 1 mm diameter and 20 µm width in a cultivation chip. To evaluate the importance of the closed-loop arrangement of cardiomyocytes for prediction, we compared the change in waveforms of convoluted signals of the responses in the closed-loop circuit arrangement with that of the response of cardiomyocyte clusters using a typical human ether a go-go related gene (hERG) ion channel blocker, E-4031. The results showed that (1) waveform prolongation and fluctuation both in the closed loops and clusters increased depending on the E-4031 concentration increase. However, (2) only the waveform signals in closed loops showed an apparent temporal change in waveforms from ventricular tachycardia (VT) to ventricular fibrillation (VF), which is similar to the most typical cell-to-cell conductance abnormality. The results indicated the usefulness of convoluted waveform signals of a closed-loop cell network for acquiring reproducible results acquisition and more detailed temporal information on cell-to-cell conduction.

Solid oxide fuel cell power plant having a bootstrap start-up system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lines, Michael T

The bootstrap start-up system (42) achieves an efficient start-up of the power plant (10) that minimizes formation of soot within a reformed hydrogen rich fuel. A burner (48) receives un-reformed fuel directly from the fuel supply (30) and combusts the fuel to heat cathode air which then heats an electrolyte (24) within the fuel cell (12). A dilute hydrogen forming gas (68) cycles through a sealed heat-cycling loop (66) to transfer heat and generated steam from an anode side (32) of the electrolyte (24) through fuel processing system (36) components (38, 40) and back to an anode flow field (26)more » until fuel processing system components (38, 40) achieve predetermined optimal temperatures and steam content. Then, the heat-cycling loop (66) is unsealed and the un-reformed fuel is admitted into the fuel processing system (36) and anode flow (26) field to commence ordinary operation of the power plant (10).« less

Fiber-Optic Determination of N2, O2, and Fuel Vapor in the Ullage of Liquid-Fuel Tanks

NASA Technical Reports Server (NTRS)

Nguyen, Quang-Viet

2008-01-01

A fiber-optic sensor system has been developed that can remotely measure the concentration of molecular oxygen (O2), nitrogen (N2), hydrocarbon vapor, and other gases (CO2, CO, H2O, chlorofluorocarbons, etc.) in the ullage of a liquid-fuel tank. The system provides an accurate and quantitative identification of the above gases with an accuracy of better than 1 percent by volume (for O2 or N2) in real-time (5 seconds). In an effort to prevent aircraft fuel tank fires or explosions similar to the tragic TWA Flight 800 explosion in 1996, OBIGGS are currently being developed for large commercial aircraft to prevent dangerous conditions from forming inside fuel tanks by providing an inerting gas blanket that is low in oxygen, thus preventing the ignition of the fuel/air mixture in the ullage. OBIGGS have been used in military aircraft for many years and are now standard equipment on some newer large commercial aircraft (such as the Boeing 787). Currently, OBIGGS are being developed for retrofitting to existing commercial aircraft fleets in response to pending mandates from the FAA. Most OBIGGS use an air separation module (ASM) that separates O2 from N2 to make nitrogen-enriched air from compressed air flow diverted from the engine (bleed air). Current OBIGGS systems do not have a closed-loop feedback control, in part, due to the lack of suitable process sensors that can reliably measure N2 or O2 and at the same time, do not constitute an inherent source of ignition. Thus, current OBIGGS operate with a high factor-of-safety dictated by process protocol to ensure adequate fuel-tank inerting. This approach is inherently inefficient as it consumes more engine bleed air than is necessary compared to a closed-loop controlled approach. The reduction of bleed air usage is important as it reduces fuel consumption, which translates to both increased flight range and lower operational costs. Numerous approaches to developing OBIGGS feedback-control sensors have been under development by many research groups and companies. However, the direct measurement of nitrogen (N2) is a challenge to most OBIGGS ullage sensors (such as tunable diode laser absorption) as they cannot measure N2 directly but depend on the measurement of oxygen (O2). The problem with a singular measure of O2, is that as the concentration (number density) of O2 decreases due to the inerting process or due to lower pressures from high altitudes, the precision and accuracy of the O2 measurement decreases. However, measuring O2 density in combination with N2 density (which is more abundant in air and in a N2-inerted fuel tank) can provide a much more accurate and reliable determination of the OBIGGS efficacy.

Closing the Loop: A Study of How the National Survey of Student Engagement (NSSE) Is Used for Decision-Making and Planning in Student Affairs

ERIC Educational Resources Information Center

McCaul, Jennifer Lee

2015-01-01

"Closing the loop" is a commonly used phrase in discussing cyclical processes, such as the area of outcomes assessment in higher education. Increased interest in accountability and a shift in accreditation focus have necessitated that higher education institutions are closing the assessment loop and creating a culture of evidence to…

Tonic accommodation predicts closed-loop accommodation responses.

PubMed

Liu, Chunming; Drew, Stefanie A; Borsting, Eric; Escobar, Amy; Stark, Lawrence; Chase, Christopher

2016-12-01

The purpose of this study is to examine the potential relationship between tonic accommodation (TA), near work induced TA-adaptation and the steady state closed-loop accommodation response (AR). Forty-two graduate students participated in the study. Various aspects of their accommodation system were objectively measured using an open-field infrared auto-refractor (Grand Seiko WAM-5500). Tonic accommodation was assessed in a completely dark environment. The association between TA and closed-loop AR was assessed using linear regression correlations and t-test comparisons. Initial mean baseline TA was 1.84diopter (D) (SD±1.29D) with a wide distribution range (-0.43D to 5.14D). For monocular visual tasks, baseline TA was significantly correlated with the closed-loop AR. The slope of the best fit line indicated that closed-loop AR varied by approximately 0.3D for every 1D change in TA. This ratio was consistent across a variety of viewing distances and different near work tasks, including both static targets and continuous reading. Binocular reading conditions weakened the correlation between baseline TA and AR, although results remained statistically significant. The 10min near reading task with a 3D demand did not reveal significant near work induced TA-adaptation for either monocular or binocular conditions. Consistently, the TA-adaptation did not show any correlation with AR during reading. This study found a strong association between open-loop TA and closed-loop AR across a variety of viewing distances and different near work tasks. Difference between the correlations under monocular and binocular reading condition suggests a potential role for vergence compensation during binocular closed-loop AR. Copyright © 2016 Elsevier Ltd. All rights reserved.

Double closed-loop cascade control for lower limb exoskeleton with elastic actuation.

PubMed

Zhu, Yanhe; Zheng, Tianjiao; Jin, Hongzhe; Yang, Jixing; Zhao, Jie

2015-01-01

Unlike traditional rigid actuators, the significant features of Series Elastic Actuator (SEA) are stable torque control, lower output impedance, impact resistance and energy storage. Recently, SEA has been applied in many exoskeletons. In such applications, a key issue is how to realize the human-exoskeleton movement coordination. In this paper, double closed-loop cascade control for lower limb exoskeleton with SEA is proposed. This control method consists of inner SEA torque loop and outer contact force loop. Utilizing the SEA torque control with a motor velocity loop, actuation performances of SEA are analyzed. An integrated exoskeleton control system is designed, in which joint angles are calculated by internal encoders and resolvers and contact forces are gathered by external pressure sensors. The double closed-loop cascade control model is established based on the feedback signals of internal and external sensor. Movement experiments are accomplished in our prototype of lower limb exoskeleton. Preliminary results indicate the exoskeleton movements with pilot can be realized stably by utilizing this double closed-loop cascade control method. Feasibility of the SEA in our exoskeleton robot and effectiveness of the control method are verified.

Closed-loop analysis and control of a non-inverting buck-boost converter

NASA Astrophysics Data System (ADS)

Chen, Zengshi; Hu, Jiangang; Gao, Wenzhong

2010-11-01

In this article, a cascade controller is designed and analysed for a non-inverting buck-boost converter. The fast inner current loop uses sliding mode control. The slow outer voltage loop uses the proportional-integral (PI) control. Stability analysis and selection of PI gains are based on the nonlinear closed-loop error dynamics incorporating both the inner and outer loop controllers. The closed-loop system is proven to have a nonminimum phase structure. The voltage transient due to step changes of input voltage or resistance is predictable. The operating range of the reference voltage is discussed. The controller is validated by a simulation circuit. The simulation results show that the reference output voltage is well-tracked under system uncertainties or disturbances, confirming the validity of the proposed controller.

Window-closing safety system

DOEpatents

McEwan, Thomas E.

1997-01-01

A safety device includes a wire loop embedded in the glass of a passenger car window and routed near the closing leading-edge of the window. The wire loop carries microwave pulses around the loop to and from a transceiver with separate output and input ports. An evanescent field only and inch or two in radius is created along the wire loop by the pulses. Just about any object coming within the evanescent field will dramatically reduce the energy of the microwave pulses received back by the transceiver. Such a loss in energy is interpreted as a closing area blockage, and electrical interlocks are provided to halt or reverse a power window motor that is actively trying to close the window.

Window-closing safety system

DOEpatents

McEwan, T.E.

1997-08-26

A safety device includes a wire loop embedded in the glass of a passenger car window and routed near the closing leading-edge of the window. The wire loop carries microwave pulses around the loop to and from a transceiver with separate output and input ports. An evanescent field only an inch or two in radius is created along the wire loop by the pulses. Just about any object coming within the evanescent field will dramatically reduce the energy of the microwave pulses received back by the transceiver. Such a loss in energy is interpreted as a closing area blockage, and electrical interlocks are provided to halt or reverse a power window motor that is actively trying to close the window. 5 figs.

Structural robustness with suboptimal responses for linear state space model

NASA Technical Reports Server (NTRS)

Keel, L. H.; Lim, Kyong B.; Juang, Jer-Nan

1989-01-01

A relationship between the closed-loop eigenvalues and the amount of perturbations in the open-loop matrix is addressed in the context of performance robustness. If the allowable perturbation ranges of elements of the open-loop matrix A and the desired tolerance of the closed-loop eigenvalues are given such that max(j) of the absolute value of Delta-lambda(j) (A+BF) should be less than some prescribed value, what is a state feedback controller F which satisfies the closed-loop eigenvalue perturbation-tolerance requirement for a class of given perturbation in A? The paper gives an algorithm to design such a controller. Numerical examples are included for illustration.

Method of Manufacturing Micro-Disperse Particles of Sodium Borohydride

DOEpatents

Kravitz, Stanley H.; Hecht, Andrew M.; Sylwester. Alan P.; Bell, Nelson S.

2008-09-23

A compact solid source of hydrogen gas, where the gas is generated by contacting water with micro-disperse particles of sodium borohydride in the presence of a catalyst, such as cobalt or ruthenium. The micro-disperse particles can have a substantially uniform diameter of 1-10 microns, and preferably about 3-5 microns. Ruthenium or cobalt catalytic nanoparticles can be incorporated in the micro-disperse particles of sodium borohydride, which allows a rapid and complete reaction to occur without the problems associated with caking and scaling of the surface by the reactant product sodium metaborate. A closed loop water management system can be used to recycle wastewater from a PEM fuel cell to supply water for reacting with the micro-disperse particles of sodium borohydride in a compact hydrogen gas generator. Capillary forces can wick water from a water reservoir into a packed bed of micro-disperse fuel particles, eliminating the need for using an active pump.

Method of generating hydrogen gas from sodium borohydride

DOEpatents

Kravitz, Stanley H.; Hecht, Andrew M.; Sylwester, Alan P.; Bell, Nelson S.

2007-12-11

A compact solid source of hydrogen gas, where the gas is generated by contacting water with micro-disperse particles of sodium borohydride in the presence of a catalyst, such as cobalt or ruthenium. The micro-disperse particles can have a substantially uniform diameter of 1-10 microns, and preferably about 3-5 microns. Ruthenium or cobalt catalytic nanoparticles can be incorporated in the micro-disperse particles of sodium borohydride, which allows a rapid and complete reaction to occur without the problems associated with caking and scaling of the surface by the reactant product sodium metaborate. A closed loop water management system can be used to recycle wastewater from a PEM fuel cell to supply water for reacting with the micro-disperse particles of sodium borohydride in a compact hydrogen gas generator. Capillary forces can wick water from a water reservoir into a packed bed of micro-disperse fuel particles, eliminating the need for using an active pump.

Compact solid source of hydrogen gas

DOEpatents

Kravitz, Stanley H.; Hecht, Andrew M.; Sylwester, Alan P.; Bell, Nelson S.

2004-06-08

A compact solid source of hydrogen gas, where the gas is generated by contacting water with micro-disperse particles of sodium borohydride in the presence of a catalyst, such as cobalt or ruthenium. The micro-disperse particles can have a substantially uniform diameter of 1-10 microns, and preferably about 3-5 microns. Ruthenium or cobalt catalytic nanoparticles can be incorporated in the micro-disperse particles of sodium borohydride, which allows a rapid and complete reaction to occur without the problems associated with caking and scaling of the surface by the reactant product sodium metaborate. A closed loop water management system can be used to recycle wastewater from a PEM fuel cell to supply water for reacting with the micro-disperse particles of sodium borohydride in a compact hydrogen gas generator. Capillary forces can wick water from a water reservoir into a packed bed of micro-disperse fuel particles, eliminating the need for using an active pump.

An Anomalous External Force on the MAP Spacecraft

NASA Technical Reports Server (NTRS)

Starin, Scott R.; Bay, P. Michael; Wollack, Edward J.; Fink, Dale R.; Ward, David K.; ODonnell, James R., Jr.; Bauer, Frank H. (Technical Monitor)

2002-01-01

A common theme in discussions of the Microwave Anisotropy Probe (MAP) is the attainment of mission goals for minimal cost. One area of cost savings was a reduction in the fuel budget required. To reach orbit around the L2 notation point of the Earth-Sun system, the MAP spacecraft was guided very close to the Moon, allowing a gravity-assisted trajectory out to L2. In order to property time the lunar swing-by, MAP followed a trajectory of three-and-a-half highly elliptical phasing loops. At each perigee of this trajectory MAP executed a thruster maneuver to increase orbit velocity; maneuvers were required at one or both clothe first two perigees (called P1 and P2) and at the third and final perigee (P-final). The preference was for successful maneuvers at all three perigees because this scheme provided a small, additional fuel savings.

Closed-loop endo-atmospheric ascent guidance for reusable launch vehicle

NASA Astrophysics Data System (ADS)

Sun, Hongsheng

This dissertation focuses on the development of a closed-loop endo-atmospheric ascent guidance algorithm for the 2nd generation reusable launch vehicle. Special attention has been given to the issues that impact on viability, complexity and reliability in on-board implementation. The algorithm is called once every guidance update cycle to recalculate the optimal solution based on the current flight condition, taking into account atmospheric effects and path constraints. This is different from traditional ascent guidance algorithms which operate in a simple open-loop mode inside atmosphere, and later switch to a closed-loop vacuum ascent guidance scheme. The classical finite difference method is shown to be well suited for fast solution of the constrained optimal three-dimensional ascent problem. The initial guesses for the solutions are generated using an analytical vacuum optimal ascent guidance algorithm. Homotopy method is employed to gradually introduce the aerodynamic forces to generate the optimal solution from the optimal vacuum solution. The vehicle chosen for this study is the Lockheed Martin X-33 lifting-body reusable launch vehicle. To verify the algorithm presented in this dissertation, a series of open-loop and closed-loop tests are performed for three different missions. Wind effects are also studied in the closed-loop simulations. For comparison, the solutions for the same missions are also obtained by two independent optimization softwares. The results clearly establish the feasibility of closed-loop endo-atmospheric ascent guidance of rocket-powered launch vehicles. ATO cases are also tested to assess the adaptability of the algorithm to autonomously incorporate the abort modes.

Bidirectional neural interface: Closed-loop feedback control for hybrid neural systems.

PubMed

Chou, Zane; Lim, Jeffrey; Brown, Sophie; Keller, Melissa; Bugbee, Joseph; Broccard, Frédéric D; Khraiche, Massoud L; Silva, Gabriel A; Cauwenberghs, Gert

2015-01-01

Closed-loop neural prostheses enable bidirectional communication between the biological and artificial components of a hybrid system. However, a major challenge in this field is the limited understanding of how these components, the two separate neural networks, interact with each other. In this paper, we propose an in vitro model of a closed-loop system that allows for easy experimental testing and modification of both biological and artificial network parameters. The interface closes the system loop in real time by stimulating each network based on recorded activity of the other network, within preset parameters. As a proof of concept we demonstrate that the bidirectional interface is able to establish and control network properties, such as synchrony, in a hybrid system of two neural networks more significantly more effectively than the same system without the interface or with unidirectional alternatives. This success holds promise for the application of closed-loop systems in neural prostheses, brain-machine interfaces, and drug testing.

Domain Hierarchy and closed Loops (DHcL): a server for exploring hierarchy of protein domain structure

PubMed Central

Koczyk, Grzegorz; Berezovsky, Igor N.

2008-01-01

Domain hierarchy and closed loops (DHcL) (http://sitron.bccs.uib.no/dhcl/) is a web server that delineates energy hierarchy of protein domain structure and detects domains at different levels of this hierarchy. The server also identifies closed loops and van der Waals locks, which constitute a structural basis for the protein domain hierarchy. The DHcL can be a useful tool for an express analysis of protein structures and their alternative domain decompositions. The user submits a PDB identifier(s) or uploads a 3D protein structure in a PDB format. The results of the analysis are the location of domains at different levels of hierarchy, closed loops, van der Waals locks and their interactive visualization. The server maintains a regularly updated database of domains, closed loop and van der Waals locks for all X-ray structures in PDB. DHcL server is available at: http://sitron.bccs.uib.no/dhcl. PMID:18502776

Novel imaging closed loop control strategy for heliostats

NASA Astrophysics Data System (ADS)

Bern, Gregor; Schöttl, Peter; Heimsath, Anna; Nitz, Peter

2017-06-01

Central Receiver Systems use up to thousands of heliostats to concentrate solar radiation. The precise control of heliostat aiming points is crucial not only for efficiency but also for reliable plant operation. Besides the calibration of open loop control systems, closed loop tracking strategies are developed to address a precise and efficient aiming strategy. The need for cost reductions in the heliostat field intensifies the motivation for economic closed loop control systems. This work introduces an approach for a closed loop heliostat tracking strategy using image analysis and signal modulation. The approach aims at the extraction of heliostat focal spot position within the receiver domain by means of a centralized remote vision system decoupled from the rough conditions close to the focal area. Taking an image sequence of the receiver while modulating a signal on different heliostats, their aiming points are retrieved. The work describes the methodology and shows first results from simulations and practical tests performed in small scale, motivating further investigation and deployment.

Fuel-cell engine stream conditioning system

DOEpatents

DuBose, Ronald Arthur

2002-01-01

A stream conditioning system for a fuel cell gas management system or fuel cell engine. The stream conditioning system manages species potential in at least one fuel cell reactant stream. A species transfer device is located in the path of at least one reactant stream of a fuel cell's inlet or outlet, which transfer device conditions that stream to improve the efficiency of the fuel cell. The species transfer device incorporates an exchange media and a sorbent. The fuel cell gas management system can include a cathode loop with the stream conditioning system transferring latent and sensible heat from an exhaust stream to the cathode inlet stream of the fuel cell; an anode humidity retention system for maintaining the total enthalpy of the anode stream exiting the fuel cell related to the total enthalpy of the anode inlet stream; and a cooling water management system having segregated deionized water and cooling water loops interconnected by means of a brazed plate heat exchanger.

The influence of visual feedback from the recent past on the programming of grip aperture is grasp-specific, shared between hands, and mediated by sensorimotor memory not task set.

PubMed

Tang, Rixin; Whitwell, Robert L; Goodale, Melvyn A

2015-05-01

Goal-directed movements, such as reaching out to grasp an object, are necessarily constrained by the spatial properties of the target such as its size, shape, and position. For example, during a reach-to-grasp movement, the peak width of the aperture formed by the thumb and fingers in flight (peak grip aperture, PGA) is linearly related to the target's size. Suppressing vision throughout the movement (visual open loop) has a small though significant effect on this relationship. Visual open loop conditions also produce a large increase in the PGA compared to when vision is available throughout the movement (visual closed loop). Curiously, this differential effect of the availability of visual feedback is influenced by the presentation order: the difference in PGA between closed- and open-loop trials is smaller when these trials are intermixed (an effect we have called 'homogenization'). Thus, grasping movements are affected not only by the availability of visual feedback (closed loop or open loop) but also by what happened on the previous trial. It is not clear, however, whether this carry-over effect is mediated through motor (or sensorimotor) memory or through the interference of different task sets for closed-loop and open-loop feedback that determine when the movements are fully specified. We reasoned that sensorimotor memory, but not a task set for closed and open loop feedback, would be specific to the type of response. We tested this prediction in a condition in which pointing to targets was alternated with grasping those same targets. Critically, in this condition, when pointing was performed in open loop, grasping was always performed in closed loop (and vice versa). Despite the fact that closed- and open-loop trials were alternating in this condition, we found no evidence for homogenization of the PGA. Homogenization did occur, however, in a follow-up experiment in which grasping movements and visual feedback were alternated between the left and the right hand, indicating that sensorimotor (or motor) memory can operate both within and between hands when the response type is kept the same. In a final experiment, we ruled out the possibility that simply alternating the hand used to perform the grasp interferes with motor or sensorimotor memory. We did this by showing that when the hand was alternated within a block of exclusively closed- or open-loop trials, homogenization of the PGA did not occur. Taken together, the results suggest that (1) interference from simply switching between task sets for closed or open-loop feedback or from switching between the hands cannot account homogenization in the PGA and that (2) the programming and execution of grasps can borrow not only from grasping movements executed in the past by the same hand, but also from grasping movements executed with the other hand. Copyright © 2015 Elsevier B.V. All rights reserved.

Experiment Needs and Facilities Study Appendix A Transient Reactor Test Facility (TREAT) Upgrade

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

The TREAT Upgrade effort is designed to provide significant new capabilities to satisfy experiment requirements associated with key LMFBR Safety Issues. The upgrade consists of reactor-core modifications to supply the physics performance needed for the new experiments, an Advanced TREAT loop with size and thermal-hydraulics capabilities needed for the experiments, associated interface equipment for loop operations and handling, and facility modifications necessary to accommodate operations with the Loop. The costs and schedules of the tasks to be accomplished under the TREAT Upgrade project are summarized. Cost, including contingency, is about 10 million dollars (1976 dollars). A schedule for execution ofmore » 36 months has been established to provide the new capabilities in order to provide timely support of the LMFBR national effort. A key requirement for the facility modifications is that the reactor availability will not be interrupted for more than 12 weeks during the upgrade. The Advanced TREAT loop is the prototype for the STF small-bundle package loop. Modified TREAT fuel elements contain segments of graphite-matrix fuel with graded uranium loadings similar to those of STF. In addition, the TREAT upgrade provides for use of STF-like stainless steel-UO{sub 2} TREAT fuel for tests of fully enriched fuel bundles. This report will introduce the Upgrade study by presenting a brief description of the scope, performance capability, safety considerations, cost schedule, and development requirements. This work is followed by a "Design Description". Because greatly upgraded loop performance is central to the upgrade, a description is given of Advanced TREAT loop requirements prior to description of the loop concept. Performance requirements of the upgraded reactor system are given. An extensive discussion of the reactor physics calculations performed for the Upgrade concept study is provided. Adequate physics performance is essential for performance of experiments with the Advanced TREAT loop, and the stress placed on these calculations reflects this. Additional material on performance and safety is provided. Backup calculations on calculations of plutonium-release limits are described. Cost and schedule information for the Upgrade are presented.« less

Time delay compensation for closed-loop insulin delivery systems: a simulation study.

PubMed

Reboldi, G P; Home, P D; Calabrese, G; Fabietti, P G; Brunetti, P; Massi Benedetti, M

1991-06-01

Closed loop insulin therapy certainly represents the best possible approach to insulin replacement. However, present limitations preclude wider application of the so-called artificial pancreas. Therefore, a thorough understanding of these limitations is needed to design better systems for future long-term use. The present simulation study was design: to obtain better information on the impact of the measurement delay of currently available closed-loop devices both during closed-loop insulin delivery and blood glucose clamp studies, and to design and test a time delay compensator based on the method originally described by O.J. Smith. Simulations were performed on a Compaq Deskpro 486/25 personal computer under MS-DOS operating system using Simnon rel. 3.00 software. There was a direct relationship between measurement delay and amount of insulin delivered, i.e., the longer the delay the higher the insulin dose needed to control a rise in blood glucose; the closed-loop response in presence of a time delay was qualitatively impaired both during insulin delivery and blood glucose clamp studies; time delay compensation was effective in reducing the insulin dose and improving controller stability during the early phase of clamp studies. However, the robustness of a Smith's predictor-based controller should be carefully evaluated before implementation in closed-loop systems can be considered.

A review of implantable biosensors for closed-loop glucose control and other drug delivery applications.

PubMed

Scholten, Kee; Meng, Ellis

2018-06-15

Closed-loop drug delivery promises autonomous control of pharmacotherapy through the continuous monitoring of biomarker levels. For decades, researchers have strived for portable closed-loop systems capable of treating ambulatory patients with chronic conditions such as diabetes mellitus. After years of development, the first of these systems have left the laboratory and entered commercial use. This long-awaited advance reflects recent development of chronically stable implantable biosensors able to accurately measure biomarker levels in vivo. This review discusses the role of implantable biosensors in closed-loop drug delivery applications, with the intent to provide a resource for engineers and researchers studying such systems. We provide an overview of common biosensor designs and review the principle challenges in implementing long indwelling sensors: namely device sensitivity, selectivity, and lifetime. This review examines novel advances in transducer design, biological interface, and material biocompatibility, with a focus on recent academic and commercial work which provide successful strategies to overcome perennial challenges. This review focuses primarily on the topics of closed-loop glucose control and continuous glucose monitoring biosensors, which make up the overwhelming majority of published research in this area. We conclude with an overview of recent advances in closed-loop systems targeting applications outside blood glucose management. Copyright © 2018 Elsevier B.V. All rights reserved.

Pre-frontal control of closed-loop limbic neurostimulation by rodents using a brain-computer interface

NASA Astrophysics Data System (ADS)

Widge, Alik S.; Moritz, Chet T.

2014-04-01

Objective. There is great interest in closed-loop neurostimulators that sense and respond to a patient's brain state. Such systems may have value for neurological and psychiatric illnesses where symptoms have high intraday variability. Animal models of closed-loop stimulators would aid preclinical testing. We therefore sought to demonstrate that rodents can directly control a closed-loop limbic neurostimulator via a brain-computer interface (BCI). Approach. We trained rats to use an auditory BCI controlled by single units in prefrontal cortex (PFC). The BCI controlled electrical stimulation in the medial forebrain bundle, a limbic structure involved in reward-seeking. Rigorous offline analyses were performed to confirm volitional control of the neurostimulator. Main results. All animals successfully learned to use the BCI and neurostimulator, with closed-loop control of this challenging task demonstrated at 80% of PFC recording locations. Analysis across sessions and animals confirmed statistically robust BCI control and specific, rapid modulation of PFC activity. Significance. Our results provide a preliminary demonstration of a method for emotion-regulating closed-loop neurostimulation. They further suggest that activity in PFC can be used to control a BCI without pre-training on a predicate task. This offers the potential for BCI-based treatments in refractory neurological and mental illness.

Effect of closed-loop order processing on the time to initial antimicrobial therapy.

PubMed

Panosh, Nicole; Rew, Richardd; Sharpe, Michelle

2012-08-15

The results of a study comparing the average time to initiation of i.v. antimicrobial therapy with closed-versus open-loop order entry and processing are reported. A retrospective cohort study was performed to compare order-to-administration times for initial doses of i.v. antimicrobials before and after a closed-loop order-processing system including computerized prescriber order entry (CPOE) was implemented at a large medical center. A total of 741 i.v. antimicrobial administrations to adult patients during designated five-month preimplementation and postimplementation study periods were assessed. Drug-use reports generated by the pharmacy database were used to identify order-entry times, and medication administration records were reviewed to determine times of i.v. antimicrobial administration. The mean ± S.D. order-to-administration times before and after the implementation of the CPOE system and closed-loop order processing were 3.18 ± 2.60 and 2.00 ± 1.89 hours, respectively, a reduction of 1.18 hours (p < 0.0001). Closed-loop order processing was associated with significant reductions in the average time to initiation of i.v. therapy in all patient care areas evaluated (cardiology, general medicine, and oncology). The study results suggest that CPOE-based closed-loop order processing can play an important role in achieving compliance with current practice guidelines calling for increased efforts to ensure the prompt initiation of i.v. antimicrobials for severe infections (e.g., sepsis, meningitis). Implementation of a closed-loop order-processing system resulted in a significant decrease in order-to-administration times for i.v. antimicrobial therapy.

An investigation into closed-loop treatment of neurological disorders based on sensing mitochondrial dysfunction.

PubMed

Adams, Scott D; Kouzani, Abbas Z; Tye, Susannah J; Bennet, Kevin E; Berk, Michael

2018-02-13

Dynamic feedback based closed-loop medical devices offer a number of advantages for treatment of heterogeneous neurological conditions. Closed-loop devices integrate a level of neurobiological feedback, which allows for real-time adjustments to be made with the overarching aim of improving treatment efficacy and minimizing risks for adverse events. One target which has not been extensively explored as a potential feedback component in closed-loop therapies is mitochondrial function. Several neurodegenerative and psychiatric disorders including Parkinson's disease, Major Depressive disorder and Bipolar disorder have been linked to perturbations in the mitochondrial respiratory chain. This paper investigates the potential to monitor this mitochondrial function as a method of feedback for closed-loop neuromodulation treatments. A generic model of the closed-loop treatment is developed to describe the high-level functions of any system designed to control neural function based on mitochondrial response to stimulation, simplifying comparison and future meta-analysis. This model has four key functional components including: a sensor, signal manipulator, controller and effector. Each of these components are described and several potential technologies for each are investigated. While some of these candidate technologies are quite mature, there are still technological gaps remaining. The field of closed-loop medical devices is rapidly evolving, and whilst there is a lot of interest in this area, widespread adoption has not yet been achieved due to several remaining technological hurdles. However, the significant therapeutic benefits offered by this technology mean that this will be an active area for research for years to come.

Sensory feedback in prosthetics: a standardized test bench for closed-loop control.

PubMed

Dosen, Strahinja; Markovic, Marko; Hartmann, Cornelia; Farina, Dario

2015-03-01

Closing the control loop by providing sensory feedback to the user of a prosthesis is an important challenge, with major impact on the future of prosthetics. Developing and comparing closed-loop systems is a difficult task, since there are many different methods and technologies that can be used to implement each component of the system. Here, we present a test bench developed in Matlab Simulink for configuring and testing the closed-loop human control system in standardized settings. The framework comprises a set of connected generic blocks with normalized inputs and outputs, which can be customized by selecting specific implementations from a library of predefined components. The framework is modular and extensible and it can be used to configure, compare and test different closed-loop system prototypes, thereby guiding the development towards an optimal system configuration. The use of the test bench was demonstrated by investigating two important aspects of closed-loop control: performance of different electrotactile feedback interfaces (spatial versus intensity coding) during a pendulum stabilization task and feedforward methods (joystick versus myocontrol) for force control. The first experiment demonstrated that in the case of trained subjects the intensity coding might be superior to spatial coding. In the second experiment, the control of force was rather poor even with a stable and precise control interface (joystick), demonstrating that inherent characteristics of the prosthesis can be an important limiting factor when considering the overall effectiveness of the closed-loop control. The presented test bench is an important instrument for investigating different aspects of human manual control with sensory feedback.

Gait adaptation to visual kinematic perturbations using a real-time closed-loop brain-computer interface to a virtual reality avatar

NASA Astrophysics Data System (ADS)

Phat Luu, Trieu; He, Yongtian; Brown, Samuel; Nakagome, Sho; Contreras-Vidal, Jose L.

2016-06-01

Objective. The control of human bipedal locomotion is of great interest to the field of lower-body brain-computer interfaces (BCIs) for gait rehabilitation. While the feasibility of closed-loop BCI systems for the control of a lower body exoskeleton has been recently shown, multi-day closed-loop neural decoding of human gait in a BCI virtual reality (BCI-VR) environment has yet to be demonstrated. BCI-VR systems provide valuable alternatives for movement rehabilitation when wearable robots are not desirable due to medical conditions, cost, accessibility, usability, or patient preferences. Approach. In this study, we propose a real-time closed-loop BCI that decodes lower limb joint angles from scalp electroencephalography (EEG) during treadmill walking to control a walking avatar in a virtual environment. Fluctuations in the amplitude of slow cortical potentials of EEG in the delta band (0.1-3 Hz) were used for prediction; thus, the EEG features correspond to time-domain amplitude modulated potentials in the delta band. Virtual kinematic perturbations resulting in asymmetric walking gait patterns of the avatar were also introduced to investigate gait adaptation using the closed-loop BCI-VR system over a period of eight days. Main results. Our results demonstrate the feasibility of using a closed-loop BCI to learn to control a walking avatar under normal and altered visuomotor perturbations, which involved cortical adaptations. The average decoding accuracies (Pearson’s r values) in real-time BCI across all subjects increased from (Hip: 0.18 ± 0.31 Knee: 0.23 ± 0.33 Ankle: 0.14 ± 0.22) on Day 1 to (Hip: 0.40 ± 0.24 Knee: 0.55 ± 0.20 Ankle: 0.29 ± 0.22) on Day 8. Significance. These findings have implications for the development of a real-time closed-loop EEG-based BCI-VR system for gait rehabilitation after stroke and for understanding cortical plasticity induced by a closed-loop BCI-VR system.

Antenna Linear-Quadratic-Gaussian (LQG) Ccontrollers: Properties, Limits of Performance, and Tuning

NASA Technical Reports Server (NTRS)

Gawronski, Wodek K.

2004-01-01

The LQG controllers significantly improve antenna tracking precision, but their tuning is a trial-and-error process. A control engineer has two tools to tune an LQG controller: the choice of coordinate system of the controller, and the selection of weights of the LQG performance index. The paper selects the coordinates of the open-loop model that simplify the shaping of the closed-loop performance. and analyzes the impact of thc weights on the antenna closed-loop bandwidth, disturbance rejection properties, and antenna acceleration. Finally, it presents the LQG controller tuning procedure that rationally shapes the closed-loop performance.

Evaluation of Cathode Air Flow Transients in a SOFC/GT Hybrid System Using Hardware in the Loop Simulation.

PubMed

Zhou, Nana; Yang, Chen; Tucker, David

2015-02-01

Thermal management in the fuel cell component of a direct fired solid oxide fuel cell gas turbine (SOFC/GT) hybrid power system can be improved by effective management and control of the cathode airflow. The disturbances of the cathode airflow were accomplished by diverting air around the fuel cell system through the manipulation of a hot-air bypass valve in open loop experiments, using a hardware-based simulation facility designed and built by the U.S. Department of Energy, National Energy Technology Laboratory (NETL). The dynamic responses of the fuel cell component and hardware component of the hybrid system were studied in this paper.

A control system design approach for flexible spacecraft

NASA Technical Reports Server (NTRS)

Silverberg, L. M.

1985-01-01

A control system design approach for flexible spacecraft is presented. The control system design is carried out in two steps. The first step consists of determining the ideal control system in terms of a desirable dynamic performance. The second step consists of designing a control system using a limited number of actuators that possess a dynamic performance that is close to the ideal dynamic performance. The effects of using a limited number of actuators is that the actual closed-loop eigenvalues differ from the ideal closed-loop eigenvalues. A method is presented to approximate the actual closed-loop eigenvalues so that the calculation of the actual closed-loop eigenvalues can be avoided. Depending on the application, it also may be desirable to apply the control forces as impulses. The effect of digitizing the control to produce the appropriate impulses is also examined.

Geometrical criteria for characterizing open and closed states of WPD-loop in PTP1B

NASA Astrophysics Data System (ADS)

Shinde, Ranajit Nivrutti; Elizabeth Sobhia, M.

2012-06-01

Distinctive movement of WPD-loop occurs during the catalysis of phosphotyrosine by protein tyrosine phosphatase 1B (PTP1B). This loop is in the "open" state in apo-form whereas it is catalytically competent in the "closed" state. During the closure of this loop, unique hydrogen bond interactions are formed between different residues of the PTP1B. Present study examines such interactions from the available 118 crystal structures of PTP1B. It gives insights into the five novel hydrogen bonds essentially formed in the "closed" loop structures. Additionally, the study provides distance ranges between the atoms involved in the hydrogen bonds. This information can be used as a geometrical criterion in the characterization of conformational state of the WPD-loop especially in the molecular dynamics simulations.

78 FR 20176 - Credit for Renewable Electricity Production, Refined Coal Production, and Indian Coal Production...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-03

... electricity from closed-loop biomass, open-loop biomass, geothermal energy, solar energy, small irrigation..., geothermal energy, solar energy, small irrigation power, municipal solid waste, qualified hydropower... from the qualified energy resources of wind, closed-loop biomass, geothermal energy, and solar energy...

Enabling Medical Device Interoperability for the Integrated Clinical Environment

DTIC Science & Technology

2016-02-01

Pajic M, Mangharam R, Sokolsky O, Arney D, Goldman JM, Lee I. Model-Driven Safety Analysis of Closed - Loop Medical Systems. IEEE Transactions on...Manigel J, Osborn D, Roellike T, Weininger S, Westenskow D, “Development of a Standard for Physiologic Closed Loop Controllers in Medical Devices...3 2010. 27. Arney D, Pajic M, Goldman JM, Lee I, Mangharam R, Sokolsky O, “Toward Patient Safety in Closed - Loop Medical Device Systems,” In

Closed Loop Control of Oxygen Delivery and Oxygen Generation

DTIC Science & Technology

2017-08-01

AFRL-SA-WP-SR-2017-0024 Closed Loop Control of Oxygen Delivery and Oxygen Generation Dr. Jay Johannigman1, Richard Branson1...for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO...TITLE AND SUBTITLE Closed Loop Control of Oxygen Delivery and Oxygen Generation 5a. CONTRACT NUMBER FA8650-10-2-6140 5b. GRANT NUMBER

Closed-loop model identification of cooperative manipulators holding deformable objects

NASA Astrophysics Data System (ADS)

Alkathiri, A. A.; Akmeliawati, R.; Azlan, N. Z.

2017-11-01

This paper presents system identification to obtain the closed-loop models of a couple of cooperative manipulators in a system, which function to hold deformable objects. The system works using the master-slave principle. In other words, one of the manipulators is position-controlled through encoder feedback, while a force sensor gives feedback to the other force-controlled manipulator. Using the closed-loop input and output data, the closed-loop models, which are useful for model-based control design, are estimated. The criteria for model validation are a 95% fit between the measured and simulated output of the estimated models and residual analysis. The results show that for both position and force control respectively, the fits are 95.73% and 95.88%.

Sub-Poissonian light and photocurrent shot-noise suppression in closed opto-electronic loop

NASA Technical Reports Server (NTRS)

Masalov, A. V.; Putilin, A. A.; Vasilyev, Michael V.

1994-01-01

We examine experimentally photocurrent noise reduction in the opto-electronic closed loop. Photocurrent noise density 12.5 dB below the shot-noise was observed. So large suppression was not reached in previous experiments and cannot be explained in terms of an ordinary sub-Poissonian light in the loop. We propose the concept of anticorrelation state for the description of light in the loop.

Real-Time Closed Loop Modulated Turbine Cooling

NASA Technical Reports Server (NTRS)

Shyam, Vikram; Culley, Dennis E.; Eldridge, Jeffrey; Jones, Scott; Woike, Mark; Cuy, Michael

2014-01-01

It has been noted by industry that in addition to dramatic variations of temperature over a given blade surface, blade-to-blade variations also exist despite identical design. These variations result from manufacturing variations, uneven wear and deposition over the life of the part as well as limitations in the uniformity of coolant distribution in the baseline cooling design. It is proposed to combine recent advances in optical sensing, actuation, and film cooling concepts to develop a workable active, closed-loop modulated turbine cooling system to improve by 10 to 20 the turbine thermal state over the flight mission, to improve engine life and to dramatically reduce turbine cooling air usage and aircraft fuel burn. A reduction in oxides of nitrogen (NOx) can also be achieved by using the excess coolant to improve mixing in the combustor especially for rotorcraft engines. Recent patents filed by industry and universities relate to modulating endwall cooling using valves. These schemes are complex, add weight and are limited to the endwalls. The novelty of the proposed approach is twofold 1) Fluidic diverters that have no moving parts are used to modulate cooling and can operate under a wide range of conditions and environments. 2) Real-time optical sensing to map the thermal state of the turbine has never been attempted in realistic engine conditions.

Propulsion system performance resulting from an integrated flight/propulsion control design

NASA Technical Reports Server (NTRS)

Mattern, Duane; Garg, Sanjay

1992-01-01

Propulsion-system-specific results are presented from the application of the integrated methodology for propulsion and airframe control (IMPAC) design approach to integrated flight/propulsion control design for a 'short takeoff and vertical landing' (STOVL) aircraft in transition flight. The IMPAC method is briefly discussed and the propulsion system specifications for the integrated control design are examined. The structure of a linear engine controller that results from partitioning a linear centralized controller is discussed. The details of a nonlinear propulsion control system are presented, including a scheme to protect the engine operational limits: the fan surge margin and the acceleration/deceleration schedule that limits the fuel flow. Also, a simple but effective multivariable integrator windup protection scheme is examined. Nonlinear closed-loop simulation results are presented for two typical pilot commands for transition flight: acceleration while maintaining flightpath angle and a change in flightpath angle while maintaining airspeed. The simulation nonlinearities include the airframe/engine coupling, the actuator and sensor dynamics and limits, the protection scheme for the engine operational limits, and the integrator windup protection. Satisfactory performance of the total airframe plus engine system for transition flight, as defined by the specifications, was maintained during the limit operation of the closed-loop engine subsystem.

Multi-Objective Online Initialization of Spacecraft Formations

NASA Technical Reports Server (NTRS)

Jeffrey, Matthew; Breger, Louis; How, Jonathan P.

2007-01-01

This paper extends a previously developed method for finding spacecraft initial conditions (ICs) that minimize the drift resulting from J2 disturbances while also minimizing the fuel required to attain those ICs. It generalizes the single spacecraft optimization to a formation-wide optimization valid for an arbitrary number of vehicles. Additionally, the desired locations of the spacecraft, separate from the starting location, can be specified, either with respect to a reference orbit, or relative to the other spacecraft in the formation. The three objectives (minimize drift, minimize fuel, and maintain a geometric template) are expressed as competing costs in a linear optimization, and are traded against one another through the use of scalar weights. By carefully selecting these weights and re-initializing the formation at regular intervals, a closed-loop, formation-wide control system is created. This control system can be used to reconfigure the formations on the fly, and creates fuel-efficient plans by placing the spacecraft in semi-invariant orbits. The overall approach is demonstrated through nonlinear simulations for two formations a GEO orbit, and an elliptical orbit.

Testing of an Integrated Reactor Core Simulator and Power Conversion System with Simulated Reactivity Feedback

NASA Technical Reports Server (NTRS)

Bragg-Sitton, Shannon M.; Hervol, David S.; Godfroy, Thomas J.

2009-01-01

A Direct Drive Gas-Cooled (DDG) reactor core simulator has been coupled to a Brayton Power Conversion Unit (BPCU) for integrated system testing at NASA Glenn Research Center (GRC) in Cleveland, OH. This is a closed-cycle system that incorporates an electrically heated reactor core module, turbo alternator, recuperator, and gas cooler. Nuclear fuel elements in the gas-cooled reactor design are replaced with electric resistance heaters to simulate the heat from nuclear fuel in the corresponding fast spectrum nuclear reactor. The thermodynamic transient behavior of the integrated system was the focus of this test series. In order to better mimic the integrated response of the nuclear-fueled system, a simulated reactivity feedback control loop was implemented. Core power was controlled by a point kinetics model in which the reactivity feedback was based on core temperature measurements; the neutron generation time and the temperature feedback coefficient are provided as model inputs. These dynamic system response tests demonstrate the overall capability of a non-nuclear test facility in assessing system integration issues and characterizing integrated system response times and response characteristics.

Testing of an Integrated Reactor Core Simulator and Power Conversion System with Simulated Reactivity Feedback

NASA Technical Reports Server (NTRS)

Bragg-Sitton, Shannon M.; Hervol, David S.; Godfroy, Thomas J.

2010-01-01

A Direct Drive Gas-Cooled (DDG) reactor core simulator has been coupled to a Brayton Power Conversion Unit (BPCU) for integrated system testing at NASA Glenn Research Center (GRC) in Cleveland, Ohio. This is a closed-cycle system that incorporates an electrically heated reactor core module, turboalternator, recuperator, and gas cooler. Nuclear fuel elements in the gas-cooled reactor design are replaced with electric resistance heaters to simulate the heat from nuclear fuel in the corresponding fast spectrum nuclear reactor. The thermodynamic transient behavior of the integrated system was the focus of this test series. In order to better mimic the integrated response of the nuclear-fueled system, a simulated reactivity feedback control loop was implemented. Core power was controlled by a point kinetics model in which the reactivity feedback was based on core temperature measurements; the neutron generation time and the temperature feedback coefficient are provided as model inputs. These dynamic system response tests demonstrate the overall capability of a non-nuclear test facility in assessing system integration issues and characterizing integrated system response times and response characteristics.

ESCORT: A Pratt & Whitney nuclear thermal propulsion and power system for manned mars missions

NASA Astrophysics Data System (ADS)

Feller, Gerald J.; Joyner, Russell

1999-01-01

The purpose of this paper is to describe the conceptual design of an upgrade to the Pratt & Whitney ESCORT nuclear thermal rocket engine. The ESCORT is a bimodal engine capable of supporting a wide range of vehicle propulsive and electrical power requirements. The ESCORT engine is powered by a fast-spectrum beryllium-reflected CERMET-fueled nuclear reactor. In propulsive mode, the reactor is used to heat hot hydrogen to approximately 2700 K which is expanded through a converging/diverging nozzle to generate thrust. Heat pickup in the nozzle and the radial beryllium reflectors is used to drive the turbomachinery in the ESCORT expander cycle. In electrical mode, the reactor is used to heat a mixture of helium and xenon to drive a closed-loop Brayton cycle in order to generate electrical energy. This closed loop system has the additional function of a decay heat removal system after the propulsive mode operation is discontinued. The original ESCORT design was capable of delivering 4448.2 N (1000 lbf) of thrust at a vacuum impulse level of approximately 900 s. Design Reference Mission requirements (DRM) from NASA Johnson Space Center and NASA Lewis Research Center studies in 1997 and 1998 have detailed upgraded requirements for potential manned Mars missions. The current NASA DRM requires a nuclear thermal propulsion system capable of delivering total mission requirements of 200170 N (45000 lbf) thrust and 50 kWe of spacecraft electrical power. This is met assuming three engines capable of each delivering 66723 N (15000 lbf) of vacuum thrust and 25 kWe of electrical power. The individual engine requirements were developed assuming three out of three engine reliability for propulsion and two out of three engine reliability for spacecraft electrical power. The approximate target vacuum impulse is 925 s. The Pratt & Whitney ESCORT concept was upgraded to meet these requirements. The hexagonal prismatic fuel elements were modified to address the uprated power requirements while maintaining the peak fuel temperature below the 2880 K limit for W-UO2 CERMET fuels. A system integrated performance methodology was developed to assess the sensitivity to weight, thrust and impulse to the DRM requirements. Propellant tanks, shielding, and Brayton cycle power conversion unit requirements were included in this evaluation.

40 CFR 63.166 - Standards: Sampling connection systems.

Code of Federal Regulations, 2013 CFR

2013-07-01

... defined in 40 CFR part 261. (c) In-situ sampling systems and sampling systems without purges are exempt..., closed-loop, or closed-vent system, except as provided in § 63.162(b) of this subpart. Gases displaced...-purge, closed-loop, or closed-vent system as required in paragraph (a) of this section shall: (1) Return...

Solid oxide fuel cell power plant with an anode recycle loop turbocharger

DOEpatents

Saito, Kazuo; Skiba, Tommy; Patel, Kirtikumar H.

2015-07-14

An anode exhaust recycle turbocharger (100) has a turbocharger turbine (102) secured in fluid communication with a compressed oxidant stream within an oxidant inlet line (218) downstream from a compressed oxidant supply (104), and the anode exhaust recycle turbocharger (100) also includes a turbocharger compressor (106) mechanically linked to the turbocharger turbine (102) and secured in fluid communication with a flow of anode exhaust passing through an anode exhaust recycle loop (238) of the solid oxide fuel cell power plant (200). All or a portion of compressed oxidant within an oxidant inlet line (218) drives the turbocharger turbine (102) to thereby compress the anode exhaust stream in the recycle loop (238). A high-temperature, automotive-type turbocharger (100) replaces a recycle loop blower-compressor (52).

Solid oxide fuel cell power plant with an anode recycle loop turbocharger

DOEpatents

Saito, Kazuo; Skiba, Tommy; Patel, Kirtikumar H.

2016-09-27

An anode exhaust recycle turbocharger (100) has a turbocharger turbine (102) secured in fluid communication with a compressed oxidant stream within an oxidant inlet line (218) downstream from a compressed oxidant supply (104), and the anode exhaust recycle turbocharger (100) also includes a turbocharger compressor (106) mechanically linked to the turbocharger turbine (102) and secured in fluid communication with a flow of anode exhaust passing through an anode exhaust recycle loop (238) of the solid oxide fuel cell power plant (200). All or a portion of compressed oxidant within an oxidant inlet line (218) drives the turbocharger turbine (102) to thereby compress the anode exhaust stream in the recycle loop (238). A high-temperature, automotive-type turbocharger (100) replaces a recycle loop blower-compressor (52).

Small Reactor Designs Suitable for Direct Nuclear Thermal Propulsion: Interim Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruce G. Schnitzler

Advancement of U.S. scientific, security, and economic interests requires high performance propulsion systems to support missions beyond low Earth orbit. A robust space exploration program will include robotic outer planet and crewed missions to a variety of destinations including the moon, near Earth objects, and eventually Mars. Past studies, in particular those in support of both the Strategic Defense Initiative (SDI) and the Space Exploration Initiative (SEI), have shown nuclear thermal propulsion systems provide superior performance for high mass high propulsive delta-V missions. In NASA's recent Mars Design Reference Architecture (DRA) 5.0 study, nuclear thermal propulsion (NTP) was again selectedmore » over chemical propulsion as the preferred in-space transportation system option for the human exploration of Mars because of its high thrust and high specific impulse ({approx}900 s) capability, increased tolerance to payload mass growth and architecture changes, and lower total initial mass in low Earth orbit. The recently announced national space policy2 supports the development and use of space nuclear power systems where such systems safely enable or significantly enhance space exploration or operational capabilities. An extensive nuclear thermal rocket technology development effort was conducted under the Rover/NERVA, GE-710 and ANL nuclear rocket programs (1955-1973). Both graphite and refractory metal alloy fuel types were pursued. The primary and significantly larger Rover/NERVA program focused on graphite type fuels. Research, development, and testing of high temperature graphite fuels was conducted. Reactors and engines employing these fuels were designed, built, and ground tested. The GE-710 and ANL programs focused on an alternative ceramic-metallic 'cermet' fuel type consisting of UO2 (or UN) fuel embedded in a refractory metal matrix such as tungsten. The General Electric program examined closed loop concepts for space or terrestrial applications as well as open loop systems for direct nuclear thermal propulsion. Although a number of fast spectrum reactor and engine designs suitable for direct nuclear thermal propulsion were proposed and designed, none were built. This report summarizes status results of evaluations of small nuclear reactor designs suitable for direct nuclear thermal propulsion.« less

Irradiation performance of (Th,Pu)O2 fuel under Pressurized Water Reactor conditions

NASA Astrophysics Data System (ADS)

Boer, B.; Lemehov, S.; Wéber, M.; Parthoens, Y.; Gysemans, M.; McGinley, J.; Somers, J.; Verwerft, M.

2016-04-01

This paper examines the in-pile safety performance of (Th,Pu)O2 fuel pins under simulated Pressurized Water Reactor (PWR) conditions. Both sol-gel and SOLMAS produced (Th,Pu)O2 fuels at enrichments of 7.9% and 12.8% in Pu/HM have been irradiated at SCK·CEN. The irradiation has been performed under PWR conditions (155 bar, 300 °C) in a dedicated loop of the BR-2 reactor. The loop is instrumented with flow and temperature monitors at inlet and outlet, which allow for an accurate measurement of the deposited enthalpy.

Apparatus for and method of monitoring for breached fuel elements

DOEpatents

Gross, Kenny C.; Strain, Robert V.

1983-01-01

This invention teaches improved apparatus for the method of detecting a breach in cladded fuel used in a nuclear reactor. The detector apparatus uses a separate bypass loop for conveying part of the reactor coolant away from the core, and at least three separate delayed-neutron detectors mounted proximate this detector loop. The detectors are spaced apart so that the coolant flow time from the core to each detector is different, and these differences are known. The delayed-neutron activity at the detectors is a function of the dealy time after the reaction in the fuel until the coolant carrying the delayed-neutron emitter passes the respective detector. This time delay is broken down into separate components including an isotopic holdup time required for the emitter to move through the fuel from the reaction to the coolant at the breach, and two transit times required for the emitter now in the coolant to flow from the breach to the detector loop and then via the loop to the detector. At least two of these time components are determined during calibrated operation of the reactor. Thereafter during normal reactor operation, repeated comparisons are made by the method of regression approximation of the third time component for the best-fit line correlating measured delayed-neutron activity against activity that is approximated according to specific equations. The equations use these time-delay components and known parameter values of the fuel and of the part and emitting daughter isotopes.

"It Is Definitely a Game Changer": A Qualitative Study of Experiences with In-home Overnight Closed-Loop Technology Among Adults with Type 1 Diabetes.

PubMed

Hendrieckx, Christel; Poole, Lucinda A; Sharifi, Amin; Jayawardene, Dilshani; Loh, Margaret M; Horsburgh, Jodie C; Bach, Leon A; Colman, Peter G; Kumareswaran, Kavita; Jenkins, Alicia J; MacIsaac, Richard J; Ward, Glenn M; Grosman, Benyamin; Roy, Anirban; O'Neal, David N; Speight, Jane

2017-07-01

This qualitative study explored trial participants' experiences of four nights of in-home closed loop. Sixteen adults with type 1 diabetes, who completed a randomized crossover trial, were interviewed after four consecutive nights of closed-loop. Interviews were audio recorded, transcribed, and analyzed with a coding framework developed to identify the main themes. Participants had a mean age of 42 ± 10 years, nine were women; mean diabetes duration was 27 ± 7 years, and all were using insulin pumps. Overall, first impressions were positive. Participants found closed-loop easy to use and understand. Most experienced more stable overnight glucose levels, although for some these were similar to usual care or higher than they expected. Compared with their usual treatment, they noticed the proactive nature of the closed-loop, being able to predict trends and deliver micro amounts of insulin. Most reported technical glitches or inconveniences during one or more nights, such as transmission problems, problematic connectivity between devices, ongoing alarms despite addressing low glucose levels, and sensor inaccuracy. Remote monitoring by the trial team and their own hypoglycemic awareness contributed to feelings of trust and safety. Although rare, safety concerns were raised, related to feeling unsure whether the system would respond in time to falling glucose levels. This study provides relevant insights for implementation of closed-loop in the real world. For people with diabetes who are less familiar with technology, remote monitoring for the first few days may provide reassurance, strengthen their trust/skills, and make closed-loop an acceptable option for more people with type 1 diabetes.

Closed Loop Experiment Manager (CLEM)-An Open and Inexpensive Solution for Multichannel Electrophysiological Recordings and Closed Loop Experiments.

PubMed

Hazan, Hananel; Ziv, Noam E

2017-01-01

There is growing need for multichannel electrophysiological systems that record from and interact with neuronal systems in near real-time. Such systems are needed, for example, for closed loop, multichannel electrophysiological/optogenetic experimentation in vivo and in a variety of other neuronal preparations, or for developing and testing neuro-prosthetic devices, to name a few. Furthermore, there is a need for such systems to be inexpensive, reliable, user friendly, easy to set-up, open and expandable, and possess long life cycles in face of rapidly changing computing environments. Finally, they should provide powerful, yet reasonably easy to implement facilities for developing closed-loop protocols for interacting with neuronal systems. Here, we survey commercial and open source systems that address these needs to varying degrees. We then present our own solution, which we refer to as Closed Loop Experiments Manager (CLEM). CLEM is an open source, soft real-time, Microsoft Windows desktop application that is based on a single generic personal computer (PC) and an inexpensive, general-purpose data acquisition board. CLEM provides a fully functional, user-friendly graphical interface, possesses facilities for recording, presenting and logging electrophysiological data from up to 64 analog channels, and facilities for controlling external devices, such as stimulators, through digital and analog interfaces. Importantly, it includes facilities for running closed-loop protocols written in any programming language that can generate dynamic link libraries (DLLs). We describe the application, its architecture and facilities. We then demonstrate, using networks of cortical neurons growing on multielectrode arrays (MEA) that despite its reliance on generic hardware, its performance is appropriate for flexible, closed-loop experimentation at the neuronal network level.

Closed Loop Experiment Manager (CLEM)—An Open and Inexpensive Solution for Multichannel Electrophysiological Recordings and Closed Loop Experiments

PubMed Central

Hazan, Hananel; Ziv, Noam E.

2017-01-01

There is growing need for multichannel electrophysiological systems that record from and interact with neuronal systems in near real-time. Such systems are needed, for example, for closed loop, multichannel electrophysiological/optogenetic experimentation in vivo and in a variety of other neuronal preparations, or for developing and testing neuro-prosthetic devices, to name a few. Furthermore, there is a need for such systems to be inexpensive, reliable, user friendly, easy to set-up, open and expandable, and possess long life cycles in face of rapidly changing computing environments. Finally, they should provide powerful, yet reasonably easy to implement facilities for developing closed-loop protocols for interacting with neuronal systems. Here, we survey commercial and open source systems that address these needs to varying degrees. We then present our own solution, which we refer to as Closed Loop Experiments Manager (CLEM). CLEM is an open source, soft real-time, Microsoft Windows desktop application that is based on a single generic personal computer (PC) and an inexpensive, general-purpose data acquisition board. CLEM provides a fully functional, user-friendly graphical interface, possesses facilities for recording, presenting and logging electrophysiological data from up to 64 analog channels, and facilities for controlling external devices, such as stimulators, through digital and analog interfaces. Importantly, it includes facilities for running closed-loop protocols written in any programming language that can generate dynamic link libraries (DLLs). We describe the application, its architecture and facilities. We then demonstrate, using networks of cortical neurons growing on multielectrode arrays (MEA) that despite its reliance on generic hardware, its performance is appropriate for flexible, closed-loop experimentation at the neuronal network level. PMID:29093659

AQUILA Remotely Piloted Vehicle System Technology Demonstrator (RPV-STD) Program. Volume I. System Description and Capabilities

DTIC Science & Technology

1979-04-01

tools, simplification of equipment interfaces involved in manual operations to provide simple system preparation, closing flight control inner loops ...alti- tude, and heading rate. The closed loops operate in three primary modes: cruise, dead reckoning, and approach. The aircraft is stabilized by...onboard closed loops , so the operator is not required to maintain hands-on operation to keep it in the air. The operator is able to command airspeed

Closed loop problems in biomechanics. Part II--an optimization approach.

PubMed

Vaughan, C L; Hay, J G; Andrews, J G

1982-01-01

A closed loop problem in biomechanics may be defined as a problem in which there are one or more closed loops formed by the human body in contact with itself or with an external system. Under certain conditions the problem is indeterminate--the unknown forces and torques outnumber the equations. Force transducing devices, which would help solve this problem, have serious drawbacks, and existing methods are inaccurate and non-general. The purposes of the present paper are (1) to develop a general procedure for solving closed loop problems; (2) to illustrate the application of the procedure; and (3) to examine the validity of the procedure. A mathematical optimization approach is applied to the solution of three different closed loop problems--walking up stairs, vertical jumping and cartwheeling. The following conclusions are drawn: (1) the method described is reasonably successful for predicting horizontal and vertical reaction forces at the distal segments although problems exist for predicting the points of application of these forces; (2) the results provide some support for the notion that the human neuromuscular mechanism attempts to minimize the joint torques and thus, to a certain degree, the amount of muscular effort; (3) in the validation procedure it is desirable to have a force device for each of the distal segments in contact with a fixed external system; and (4) the method is sufficiently general to be applied to all classes of closed loop problems.

Closed-loop for type 1 diabetes - an introduction and appraisal for the generalist.

PubMed

Bally, Lia; Thabit, Hood; Hovorka, Roman

2017-01-23

Rapid progress over the past decade has been made with the development of the 'Artificial Pancreas', also known as the closed-loop system, which emulates the feedback glucose-responsive functionality of the pancreatic beta cell. The recent FDA approval of the first hybrid closed-loop system makes the Artificial Pancreas a realistic therapeutic option for people with type 1 diabetes. In anticipation of its advent into clinical care, we provide a primer and appraisal of this novel therapeutic approach in type 1 diabetes for healthcare professionals and non-specialists in the field. Randomised clinical studies in outpatient and home settings have shown improved glycaemic outcomes, reduced risk of hypoglycaemia and positive user attitudes. User input and interaction with existing closed-loop systems, however, are still required. Therefore, management of user expectations, as well as training and support by healthcare providers are key to ensure optimal uptake, satisfaction and acceptance of the technology. An overview of closed-loop technology and its clinical implications are discussed, complemented by our extensive hands-on experience with closed-loop system use during free daily living. The introduction of the artificial pancreas into clinical practice represents a milestone towards the goal of improving the care of people with type 1 diabetes. There remains a need to understand the impact of user interaction with the technology, and its implication on current diabetes management and care.

The effects of spaceflight on open-loop and closed-loop postural control mechanisms: human neurovestibular studies on SLS-2

NASA Technical Reports Server (NTRS)

Collins, J. J.; De Luca, C. J.; Pavlik, A. E.; Roy, S. H.; Emley, M. S.; Young, L. R. (Principal Investigator)

1995-01-01

Stabilogram-diffusion analysis was used to examine how prolonged periods in microgravity affect the open-loop and closed-loop postural control mechanisms. It was hypothesized that following spaceflight: (1) the effective stochastic activity of the open-loop postural control schemes in astronauts is increased; (2) the effective stochastic activity and uncorrelated behavior, respectively, of the closed-loop postural control mechanisms in astronauts are increased; and (3) astronauts utilized open-loop postural controls schemes for shorter time intervals and smaller displacements. Four crew members and two alternates from the 14-day Spacelab Life Sciences 2 Mission were included in the study. Each subject was tested under eyes-open, quiet-standing conditions on multiple preflight and postflight days. The subjects' center-of-pressure trajectories were measured with a force platform and analyzed according to stabilogram-diffusion analysis. It was found that the effective stochastic activity of the open-loop postural control schemes in three of the four crew members was increased following spaceflight. This result is interpreted as an indication that there may be in-flight adaptations to higher-level descending postural control pathways, e.g., a postflight increase in the tonic activation of postural muscles. This change may also be the consequence of a compensatory (e.g., "stiffening") postural control strategy that is adopted by astronauts to account for general feeling of postflight unsteadiness. The crew members, as a group, did not exhibit any consistent preflight/postflight differences in the steady-state behavior of their closed-loop postural control mechanisms or in the functional interaction of their open-loop and closed-loop postural control mechanisms. These results are interpreted as indications that although there may be in-flight adaptations to the vestibular system and/or proprioceptive system, input from the visual system can compensate for such changes during undisturbed stance.

Inverse spin Hall effect in a closed loop circuit

DOE Office of Scientific and Technical Information (OSTI.GOV)

Omori, Y.; Auvray, F.; Wakamura, T.

We present measurements of inverse spin Hall effects (ISHEs), in which the conversion of a spin current into a charge current via the ISHE is detected not as a voltage in a standard open circuit but directly as the charge current generated in a closed loop. The method is applied to the ISHEs of Bi-doped Cu and Pt. The derived expression of ISHE for the loop structure can relate the charge current flowing into the loop to the spin Hall angle of the SHE material and the resistance of the loop.

Insulin delivery and nocturnal glucose control in children and adolescents with type 1 diabetes.

PubMed

Tauschmann, Martin; Hovorka, Roman

2017-12-01

Nocturnal glucose control remains challenging in children and adolescents with type 1 diabetes due to highly variable overnight insulin requirements. The issue may be addressed by glucose responsive insulin delivery based on real-time continuous glucose measurements. Areas covered: This review outlines recent developments of glucose responsive insulin delivery systems from a paediatric perspective. We cover threshold-based suspend application, predictive low glucose suspend, and more advanced single hormone and dual-hormone closed-loop systems. Approaches are evaluated in relation to nocturnal glucose control particularly during outpatient randomised controlled trials. Expert opinion: Significant progress translating research from controlled clinical centre settings to free-living unsupervised home studies have been achieved over the past decade. Nocturnal glycaemic control can be improved whilst reducing the risk of hypoglycaemia with closed-loop systems. Following the US regulatory approval of the first hybrid closed-loop system in non-paediatric population, large multinational closed-loop clinical trials and pivotal studies including paediatric populations are underway or in preparation to facilitate the use of closed-loop systems in clinical practice.

Simulation of cortico-basal ganglia oscillations and their suppression by closed loop deep brain stimulation.

PubMed

Grant, Peadar F; Lowery, Madeleine M

2013-07-01

A new model of deep brain stimulation (DBS) is presented that integrates volume conduction effects with a neural model of pathological beta-band oscillations in the cortico-basal ganglia network. The model is used to test the clinical hypothesis that closed-loop control of the amplitude of DBS may be possible, based on the average rectified value of beta-band oscillations in the local field potential. Simulation of closed-loop high-frequency DBS was shown to yield energy savings, with the magnitude of the energy saved dependent on the strength of coupling between the subthalamic nucleus and the remainder of the cortico-basal ganglia network. When closed-loop DBS was applied to a strongly coupled cortico-basal ganglia network, the stimulation energy delivered over a 480 s period was reduced by up to 42%. Greater energy reductions were observed for weakly coupled networks, as the stimulation amplitude reduced to zero once the initial desynchronization had occurred. The results provide support for the application of closed-loop high-frequency DBS based on electrophysiological biomarkers.

NETL - Thermogravimetric Analysis Laboratory

ScienceCinema

Richards, George

2018-06-22

Researchers in NETL's Thermal Analysis Laboratory are investigating chemical looping combustion. As a clean and efficient fossil fuel technology, chemical looping combustion controls CO2 emissions and offers a promising alternative to traditional combustion.

Lidar-based wake tracking for closed-loop wind farm control

NASA Astrophysics Data System (ADS)

Raach, Steffen; Schlipf, David; Cheng, Po Wen

2016-09-01

This work presents two advancements towards closed-loop wake redirecting of a wind turbine. First, a model-based estimation approach is presented which uses a nacelle-based lidar system facing downwind to obtain information about the wake. A reduced order wake model is described which is then used in the estimation to track the wake. The tracking is demonstrated with lidar measurement data from an offshore campaign and with simulated lidar data from a SOWFA simulation. Second, a controller for closed-loop wake steering is presented. It uses the wake tracking information to set the yaw actuator of the wind turbine to redirect the wake to a desired position. Altogether, this paper aims to present the concept of closed-loop wake redirecting and gives a possible solution to it.

Closed-Loop and Activity-Guided Optogenetic Control

PubMed Central

Grosenick, Logan; Marshel, James H.; Deisseroth, Karl

2016-01-01

Advances in optical manipulation and observation of neural activity have set the stage for widespread implementation of closed-loop and activity-guided optical control of neural circuit dynamics. Closing the loop optogenetically (i.e., basing optogenetic stimulation on simultaneously observed dynamics in a principled way) is a powerful strategy for causal investigation of neural circuitry. In particular, observing and feeding back the effects of circuit interventions on physiologically relevant timescales is valuable for directly testing whether inferred models of dynamics, connectivity, and causation are accurate in vivo. Here we highlight technical and theoretical foundations as well as recent advances and opportunities in this area, and we review in detail the known caveats and limitations of optogenetic experimentation in the context of addressing these challenges with closed-loop optogenetic control in behaving animals. PMID:25856490

Study of the Open Loop and Closed Loop Oscillator Techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Imel, George R.; Baker, Benjamin; Riley, Tony

This report presents the progress and completion of a five-year study undertaken at Idaho State University of the measurement of very small worth reactivity samples comparing open and closed loop oscillator techniques.The study conclusively demonstrated the equivalency of the two techniques with regard to uncertainties in reactivity values, i.e., limited by reactor noise. As those results are thoroughly documented in recent publications, in this report we will concentrate on the support work that was necessary. For example, we describe in some detail the construction and calibration of a pilot rod for the closed loop system. We discuss the campaign tomore » measure the required reactor parameters necessary for inverse-kinetics. Finally, we briefly discuss the transfer of the open loop technique to other reactor systems.« less

Study of the open loop and closed loop oscillator techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baker, Benjamin; Riley, Tony; Langbehn, Adam

This paper presents some aspects of a five year study undertaken at Idaho State University of the measurement of very small worth reactivity samples comparing open and closed loop oscillator techniques. The study conclusively demonstrated the equivalency of the two techniques with regard to uncertainties in reactivity values, i.e., limited by reactor noise. As those results are thoroughly documented in recent publications, in this paper we will concentrate on the support work that was necessary. For example, we describe in some detail the construction and calibration of a pilot rod for the closed loop system. We discuss the campaign tomore » measure the required reactor parameters necessary for inverse-kinetics. Finally, we briefly discuss the transfer of the open loop technique to other reactor systems. (authors)« less

Closed-loop control of zebrafish response using a bioinspired robotic-fish in a preference test

PubMed Central

Kopman, Vladislav; Laut, Jeffrey; Polverino, Giovanni; Porfiri, Maurizio

2013-01-01

In this paper, we study the response of zebrafish to a robotic-fish whose morphology and colour pattern are inspired by zebrafish. Experiments are conducted in a three-chambered instrumented water tank where a robotic-fish is juxtaposed with an empty compartment, and the preference of live subjects is scored as the mean time spent in the vicinity of the tank's two lateral sides. The tail-beating of the robotic-fish is controlled in real-time based on feedback from fish motion to explore a spectrum of closed-loop systems, including proportional and integral controllers. Closed-loop control systems are complemented by open-loop strategies, wherein the tail-beat of the robotic-fish is independent of the fish motion. The preference space and the locomotory patterns of fish for each experimental condition are analysed and compared to understand the influence of real-time closed-loop control on zebrafish response. The results of this study show that zebrafish respond differently to the pattern of tail-beating motion executed by the robotic-fish. Specifically, the preference and behaviour of zebrafish depend on whether the robotic-fish tail-beating frequency is controlled as a function of fish motion and how such closed-loop control is implemented. PMID:23152102

A digital wireless system for closed-loop inhibition of nociceptive signals

NASA Astrophysics Data System (ADS)

Zuo, Chao; Yang, Xiaofei; Wang, Yang; Hagains, Christopher E.; Li, Ai-Ling; Peng, Yuan B.; Chiao, J.-C.

2012-10-01

Neurostimulation of the spinal cord or brain has been used to inhibit nociceptive signals in pain management applications. Nevertheless, most of the current neurostimulation models are based on open-loop system designs. There is a lack of closed-loop systems for neurostimulation in research with small freely-moving animals and in future clinical applications. Based on our previously developed analog wireless system for closed-loop neurostimulation, a digital wireless system with real-time feedback between recorder and stimulator modules has been developed to achieve multi-channel communication. The wireless system includes a wearable recording module, a wearable stimulation module and a transceiver connected to a computer for real-time and off-line data processing, display and storage. To validate our system, wide dynamic range neurons in the spinal cord dorsal horn have been recorded from anesthetized rats in response to graded mechanical stimuli (brush, pressure and pinch) applied in the hind paw. The identified nociceptive signals were used to automatically trigger electrical stimulation at the periaqueductal gray in real time to inhibit their own activities by the closed-loop design. Our digital wireless closed-loop system has provided a simplified and efficient method for further study of pain processing in freely-moving animals and potential clinical application in patients. Groups 1, 2 and 3 contributed equally to this project.

Antenna Linear-Quadratic-Gaussian (LQG) Controllers: Properties, Limits of Performance, and Tuning Procedure

NASA Technical Reports Server (NTRS)

Gawronski, W.

2004-01-01

Wind gusts are the main disturbances that depreciate tracking precision of microwave antennas and radiotelescopes. The linear-quadratic-Gaussian (LQG) controllers - as compared with the proportional-and-integral (PI) controllers significantly improve the tracking precision in wind disturbances. However, their properties have not been satisfactorily understood; consequently, their tuning is a trial-and-error process. A control engineer has two tools to tune an LQG controller: the choice of coordinate system of the controller model and the selection of weights of the LQG performance index. This article analyzes properties of an open- and closed-loop antenna. It shows that the proper choice of coordinates of the open-loop model simplifies the shaping of the closed-loop performance. The closed-loop properties are influenced by the LQG weights. The article shows the impact of the weights on the antenna closed-loop bandwidth, disturbance rejection properties, and antenna acceleration. The bandwidth and the disturbance rejection characterize the antenna performance, while the acceleration represents the performance limit set by the antenna hardware (motors). The article presents the controller tuning procedure, based on the coordinate selection and the weight properties. The procedure rationally shapes the closed-loop performance, as an alternative to the trial-and-error approach.

Thermodynamic analysis of in situ gasification-chemical looping combustion (iG-CLC) of Indian coal.

PubMed

Suresh, P V; Menon, Kavitha G; Prakash, K S; Prudhvi, S; Anudeep, A

2016-10-01

Chemical looping combustion (CLC) is an inherent CO 2 capture technology. It is gaining much interest in recent years mainly because of its potential in addressing climate change problems associated with CO 2 emissions from power plants. A typical chemical looping combustion unit consists of two reactors-fuel reactor, where oxidation of fuel occurs with the help of oxygen available in the form of metal oxides and, air reactor, where the reduced metal oxides are regenerated by the inflow of air. These oxides are then sent back to the fuel reactor and the cycle continues. The product gas from the fuel reactor contains a concentrated stream of CO 2 which can be readily stored in various forms or used for any other applications. This unique feature of inherent CO 2 capture makes the technology more promising to combat the global climate changes. Various types of CLC units have been discussed in literature depending on the type of fuel burnt. For solid fuel combustion three main varieties of CLC units exist namely: syngas CLC, in situ gasification-CLC (iG-CLC) and chemical looping with oxygen uncoupling (CLOU). In this paper, theoretical studies on the iG-CLC unit burning Indian coal are presented. Gibbs free energy minimization technique is employed to determine the composition of flue gas and oxygen carrier of an iG-CLC unit using Fe 2 O 3 , CuO, and mixed carrier-Fe 2 O 3 and CuO as oxygen carriers. The effect of temperature, suitability of oxygen carriers, and oxygen carrier circulation rate on the performance of a CLC unit for Indian coal are studied and presented. These results are analyzed in order to foresee the operating conditions at which economic and smooth operation of the unit is expected.

Quantitative Feedback Technique (QFT): Bridging the Gap

DTIC Science & Technology

2003-05-01

with Eq. (2) illustrates: (a) the effect of changes of the uncertainty set P(s) upon the output of the closed -loop control system is reduced by the...Bridging the Gap root-locus technique the dominant closed -loop poles are determined for a ζ= 0.45. Table 3 presents the required value of Kx and...degree of decoupling will have been enhanced. Method 1 is then more readily applicable, with the additional benefit of reduced closed -loop BW. E.R.2

An Investigation Relating Longitudinal Pilot-Induced Oscillation Tendency Rating to Describing Function Predictions for Rate-Limited Actuators

DTIC Science & Technology

2004-03-01

2-15 2-10. Pitch Tracking Closed Loop System for Gap Criterion...................................... 2-16 2-11. Four Resulting Gap ...Level 1 Minimize Resonance Closed Loop Bode Diagram ( ) ( ) s sCommand θ θ ( ) ( ) s sCommand θ θ         BWω 2-16 Gap Criterion...System for Gap Criterion In modern fly-by-wire aircraft, feedback is an integral part of obtaining more desirable closed loop flying qualities

Parameter estimation in linear models of the human operator in a closed loop with application of deterministic test signals

NASA Technical Reports Server (NTRS)

Vanlunteren, A.; Stassen, H. G.

1973-01-01

Parameter estimation techniques are discussed with emphasis on unbiased estimates in the presence of noise. A distinction between open and closed loop systems is made. A method is given based on the application of external forcing functions consisting of a sun of sinusoids; this method is thus based on the estimation of Fourier coefficients and is applicable for models with poles and zeros in open and closed loop systems.

A training rule which guarantees finite-region stability for a class of closed-loop neural-network control systems.

PubMed

Kuntanapreeda, S; Fullmer, R R

1996-01-01

A training method for a class of neural network controllers is presented which guarantees closed-loop system stability. The controllers are assumed to be nonlinear, feedforward, sampled-data, full-state regulators implemented as single hidden-layer neural networks. The controlled systems must be locally hermitian and observable. Stability of the closed-loop system is demonstrated by determining a Lyapunov function, which can be used to identify a finite stability region about the regulator point.

Rationale for evaluating a closed food chain for space habitats

NASA Technical Reports Server (NTRS)

Modell, M.; Spurlock, J. M.

1980-01-01

Closed food cycles for long duration space flight and space habitation are examined. Wash water for a crew of six is economically recyclable after a week, while a total closed loop water system is effective only if the stay exceeds six months' length. The stoichiometry of net plant growth is calculated and it is shown that the return of urine, feces, and inedible plant parts to the food chain, along with the addition of photosynthesis, closes the food chain loop. Scenarios are presented to explore the technical feasibility of achieving a closed loop system. An optimal choice of plants is followed by processing, waste conversion, equipment specifications, and control requirements, and finally, cost-effectiveness.

Development of near real time performance measurements for closed-loop signal systems (CLS) using historical traffic data from existing loop detectors and signal timing data.

DOT National Transportation Integrated Search

2014-10-01

The overarching goal of this research project was to investigate the potential for the NCDOT Central Office Signal Timing : (COST) Section to monitor and assess the quality of field deployed closed-loop signal system plans using the data inherent in ...

A closed loop wireless power transmission system using a commercial RFID transceiver for biomedical applications.

PubMed

Kiani, Mehdi; Ghovanloo, Maysam

2009-01-01

This paper presents a standalone closed loop wireless power transmission system that is built around a commercial off-the-shelf (COTS) radio frequency identification (RFID) transceiver (MLX90121) operating at 13.56 MHz. It can be used for inductively powering implantable biomedical devices in a closed loop fashion. Any changes in the distance and misalignment between transmitter and receiver coils in near-field wireless power transmission can cause a significant change in the received power, which can cause either malfunction or excessive heat dissipation. RFID transceivers are often used open loop. However, their back telemetry capability can be utilized to stabilize the received voltage on the implant. Our measurements showed that the delivered power to the transponder was maintained at 1.48 mW over a range of 6 to 12 cm, while the transmitter power consumption changed from 0.3 W to 1.21 W. The closed loop system can also oppose voltage variations as a result of sudden changes in load current.

An RFID-Based Closed-Loop Wireless Power Transmission System for Biomedical Applications.

PubMed

Kiani, Mehdi; Ghovanloo, Maysam

2010-04-01

This brief presents a standalone closed-loop wireless power transmission system that is built around a commercial off-the-shelf (COTS) radio-frequency identification (RFID) reader (TRF7960) operating at 13.56 MHz. It can be used for inductively powering implantable biomedical devices in a closed loop. Any changes in the distance and misalignment between transmitter and receiver coils in near-field wireless power transmission can cause a significant change in the received power, which can cause either a malfunction or excessive heat dissipation. RFID circuits are often used in an open loop. However, their back telemetry capability can be utilized to stabilize the received voltage on the implant. Our measurements showed that the delivered power to the transponder was maintained at 11.2 mW over a range of 0.5 to 2 cm, while the transmitter power consumption changed from 78 mW to 1.1 W. The closed-loop system can also oppose voltage variations as a result of sudden changes in the load current.

Electrical crosstalk-coupling measurement and analysis for digital closed loop fibre optic gyro

NASA Astrophysics Data System (ADS)

Jin, Jing; Tian, Hai-Ting; Pan, Xiong; Song, Ning-Fang

2010-03-01

The phase modulation and the closed-loop controller can generate electrical crosstalk-coupling in digital closed-loop fibre optic gyro. Four electrical cross-coupling paths are verified by the open-loop testing approach. It is found the variation of ramp amplitude will lead to the alternation of gyro bias. The amplitude and the phase parameters of the electrical crosstalk signal are measured by lock-in amplifier, and the variation of gyro bias is confirmed to be caused by the alternation of phase according to the amplitude of the ramp. A digital closed-loop fibre optic gyro electrical crosstalk-coupling model is built by approximating the electrical cross-coupling paths as a proportion and integration segment. The results of simulation and experiment show that the modulation signal electrical crosstalk-coupling can cause the dead zone of the gyro when a small angular velocity is inputted, and it could also lead to a periodic vibration of the bias error of the gyro when a large angular velocity is inputted.

Closed Loop System Identification with Genetic Algorithms

NASA Technical Reports Server (NTRS)

Whorton, Mark S.

2004-01-01

High performance control design for a flexible space structure is challenging since high fidelity plant models are di.cult to obtain a priori. Uncertainty in the control design models typically require a very robust, low performance control design which must be tuned on-orbit to achieve the required performance. Closed loop system identi.cation is often required to obtain a multivariable open loop plant model based on closed-loop response data. In order to provide an accurate initial plant model to guarantee convergence for standard local optimization methods, this paper presents a global parameter optimization method using genetic algorithms. A minimal representation of the state space dynamics is employed to mitigate the non-uniqueness and over-parameterization of general state space realizations. This control-relevant system identi.cation procedure stresses the joint nature of the system identi.cation and control design problem by seeking to obtain a model that minimizes the di.erence between the predicted and actual closed-loop performance.

Experimental diagnostics and modeling of inductive phenomena at low frequencies in impedance spectra of proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Pivac, Ivan; Šimić, Boris; Barbir, Frano

2017-10-01

Representation of fuel cell processes by equivalent circuit models, involving resistance and capacitance elements representing activation losses on both anode and cathode in series with resistance representing ohmic losses, cannot capture and explain the inductive loop that may show up at low frequencies in Nyquist diagram representation of the electrochemical impedance spectra. In an attempt to explain the cause of the low-frequency inductive loop and correlate it with the processes within the fuel cell electrodes, a novel equivalent circuit model of a Proton Exchange Membrane (PEM) fuel cell has been proposed and experimentally verified here in detail. The model takes into account both the anode and the cathode, and has an additional resonant loop on each side, comprising of a resistance, capacitance and inductance in parallel representing the processes within the catalyst layer. Using these additional circuit elements, more accurate and better fits to experimental impedance data in the wide frequency range at different current densities, cell temperatures, humidity of gases, air flow stoichiometries and backpressures were obtained.

Gait adaptation to visual kinematic perturbations using a real-time closed-loop brain computer interface to a virtual reality avatar

PubMed Central

Luu, Trieu Phat; He, Yongtian; Brown, Samuel; Nakagame, Sho; Contreras-Vidal, Jose L.

2017-01-01

Objective The control of human bipedal locomotion is of great interest to the field of lower-body brain computer interfaces (BCIs) for gait rehabilitation. While the feasibility of closed-loop BCI systems for the control of a lower body exoskeleton has been recently shown, multi-day closed-loop neural decoding of human gait in a BCI virtual reality (BCI-VR) environment has yet to be demonstrated. BCI-VR systems provide valuable alternatives for movement rehabilitation when wearable robots are not desirable due to medical conditions, cost, accessibility, usability, or patient preferences. Approach In this study, we propose a real-time closed-loop BCI that decodes lower limb joint angles from scalp electroencephalography (EEG) during treadmill walking to control a walking avatar in a virtual environment. Fluctuations in the amplitude of slow cortical potentials of EEG in the delta band (0.1 – 3 Hz) were used for prediction; thus, the EEG features correspond to time-domain amplitude modulated (AM) potentials in the delta band. Virtual kinematic perturbations resulting in asymmetric walking gait patterns of the avatar were also introduced to investigate gait adaptation using the closed-loop BCI-VR system over a period of eight days. Main results Our results demonstrate the feasibility of using a closed-loop BCI to learn to control a walking avatar under normal and altered visuomotor perturbations, which involved cortical adaptations. The average decoding accuracies (Pearson’s r values) in real-time BCI across all subjects increased from (Hip: 0.18 ± 0.31; Knee: 0.23 ± 0.33; Ankle: 0.14 ± 0.22) on Day 1 to (Hip: 0.40 ± 0.24; Knee: 0.55 ± 0.20; Ankle: 0.29 ± 0.22) on Day 8. Significance These findings have implications for the development of a real-time closed-loop EEG-based BCI-VR system for gait rehabilitation after stroke and for understanding cortical plasticity induced by a closed-loop BCI-VR system. PMID:27064824

Home Use of Day-and-Night Hybrid Closed-Loop Insulin Delivery in Suboptimally Controlled Adolescents With Type 1 Diabetes: A 3-Week, Free-Living, Randomized Crossover Trial.

PubMed

Tauschmann, Martin; Allen, Janet M; Wilinska, Malgorzata E; Thabit, Hood; Acerini, Carlo L; Dunger, David B; Hovorka, Roman

2016-11-01

This study evaluated the feasibility, safety, and efficacy of day-and-night hybrid closed-loop insulin delivery in adolescents with type 1 diabetes under free-living conditions. In an open-label randomized crossover study, 12 suboptimally controlled adolescents on insulin pump therapy (mean ± SD age 14.6 ± 3.1 years; HbA 1c 69 ± 8 mmol/mol [8.5 ± 0.7%]; duration of diabetes 7.8 ± 3.5 years) underwent two 21-day periods in which hybrid closed-loop insulin delivery was compared with sensor-augmented insulin pump therapy in random order. During the closed-loop intervention, a model predictive algorithm automatically directed insulin delivery between meals and overnight. Participants used a bolus calculator to administer prandial boluses. The proportion of time that sensor glucose was in the target range (3.9-10 mmol/L; primary end point) was increased during the closed-loop intervention compared with sensor-augmented insulin pump therapy by 18.8 ± 9.8 percentage points (mean ± SD; P < 0.001), the mean sensor glucose level was reduced by 1.8 ± 1.3 mmol/L (P = 0.001), and the time spent above target was reduced by 19.3 ± 11.3 percentage points (P < 0.001). The time spent with sensor glucose levels below 3.9 mmol/L was low and comparable between interventions (median difference 0.4 [interquartile range -2.2 to 1.3] percentage points; P = 0.33). Improved glucose control during closed-loop was associated with increased variability of basal insulin delivery (P < 0.001) and an increase in the total daily insulin dose (53.5 [39.5-72.1] vs. 51.5 [37.6-64.3] units/day; P = 0.006). Participants expressed positive attitudes and experience with the closed-loop system. Free-living home use of day-and-night closed-loop in suboptimally controlled adolescents with type 1 diabetes is safe, feasible, and improves glucose control without increasing the risk of hypoglycemia. Larger and longer studies are warranted. © 2016 by the American Diabetes Association.

Gait adaptation to visual kinematic perturbations using a real-time closed-loop brain-computer interface to a virtual reality avatar.

PubMed

Luu, Trieu Phat; He, Yongtian; Brown, Samuel; Nakagame, Sho; Contreras-Vidal, Jose L

2016-06-01

The control of human bipedal locomotion is of great interest to the field of lower-body brain-computer interfaces (BCIs) for gait rehabilitation. While the feasibility of closed-loop BCI systems for the control of a lower body exoskeleton has been recently shown, multi-day closed-loop neural decoding of human gait in a BCI virtual reality (BCI-VR) environment has yet to be demonstrated. BCI-VR systems provide valuable alternatives for movement rehabilitation when wearable robots are not desirable due to medical conditions, cost, accessibility, usability, or patient preferences. In this study, we propose a real-time closed-loop BCI that decodes lower limb joint angles from scalp electroencephalography (EEG) during treadmill walking to control a walking avatar in a virtual environment. Fluctuations in the amplitude of slow cortical potentials of EEG in the delta band (0.1-3 Hz) were used for prediction; thus, the EEG features correspond to time-domain amplitude modulated potentials in the delta band. Virtual kinematic perturbations resulting in asymmetric walking gait patterns of the avatar were also introduced to investigate gait adaptation using the closed-loop BCI-VR system over a period of eight days. Our results demonstrate the feasibility of using a closed-loop BCI to learn to control a walking avatar under normal and altered visuomotor perturbations, which involved cortical adaptations. The average decoding accuracies (Pearson's r values) in real-time BCI across all subjects increased from (Hip: 0.18 ± 0.31; Knee: 0.23 ± 0.33; Ankle: 0.14 ± 0.22) on Day 1 to (Hip: 0.40 ± 0.24; Knee: 0.55 ± 0.20; Ankle: 0.29 ± 0.22) on Day 8. These findings have implications for the development of a real-time closed-loop EEG-based BCI-VR system for gait rehabilitation after stroke and for understanding cortical plasticity induced by a closed-loop BCI-VR system.

A LabVIEW model incorporating an open-loop arterial impedance and a closed-loop circulatory system.

PubMed

Cole, R T; Lucas, C L; Cascio, W E; Johnson, T A

2005-11-01

While numerous computer models exist for the circulatory system, many are limited in scope, contain unwanted features or incorporate complex components specific to unique experimental situations. Our purpose was to develop a basic, yet multifaceted, computer model of the left heart and systemic circulation in LabVIEW having universal appeal without sacrificing crucial physiologic features. The program we developed employs Windkessel-type impedance models in several open-loop configurations and a closed-loop model coupling a lumped impedance and ventricular pressure source. The open-loop impedance models demonstrate afterload effects on arbitrary aortic pressure/flow inputs. The closed-loop model catalogs the major circulatory waveforms with changes in afterload, preload, and left heart properties. Our model provides an avenue for expanding the use of the ventricular equations through closed-loop coupling that includes a basic coronary circuit. Tested values used for the afterload components and the effects of afterload parameter changes on various waveforms are consistent with published data. We conclude that this model offers the ability to alter several circulatory factors and digitally catalog the most salient features of the pressure/flow waveforms employing a user-friendly platform. These features make the model a useful instructional tool for students as well as a simple experimental tool for cardiovascular research.

An Environmental for Hardware-in-the-Loop Formation Navigation and Control

NASA Technical Reports Server (NTRS)

Burns, Rich; Naasz, Bo; Gaylor, Dave; Higinbotham, John

2004-01-01

Recent interest in formation flying satellite systems has spurred a considerable amount of research in the relative navigation and control of satellites. Development in this area has included new estimation and control algorithms as well as sensor and actuator development specifically geared toward the relative control problem. This paper describes a simulation facility, the Formation Flying Test Bed (FFTB) at NASA Goddard Space Flight Center, which allows engineers to test new algorithms for the formation flying problem with relevant GN&C hardware in a closed loop simulation. The FFTB currently supports the inclusion of GPS receiver hardware in the simulation loop. Support for satellite crosslink ranging technology is at a prototype stage. This closed-loop, hardware inclusive simulation capability permits testing of navigation and control software in the presence of the actual hardware with which the algorithms must interact. This capability provides the navigation or control developer with a perspective on how the algorithms perform as part of the closed-loop system. In this paper, the overall design and evolution of the FFTB are presented. Each component of the FFTB is then described. Interfaces between the components of the FFTB are shown and the interfaces to and between navigation and control software are described. Finally, an example of closed-loop formation control with GPS receivers in the loop is presented.

Recovery Act: Novel Oxygen Carriers for Coal-fueled Chemical Looping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Wei-Ping; Cao, Yan

2012-11-30

Chemical Looping Combustion (CLC) could totally negate the necessity of pure oxygen by using oxygen carriers for purification of CO{sub 2} stream during combustion. It splits the single fuel combustion reaction into two linked reactions using oxygen carriers. The two linked reactions are the oxidation of oxygen carriers in the air reactor using air, and the reduction of oxygen carriers in the fuel reactor using fuels (i.e. coal). Generally metal/metal oxides are used as oxygen carriers and operated in a cyclic mode. Chemical looping combustion significantly improves the energy conversion efficiency, in terms of the electricity generation, because it improvesmore » the reversibility of the fuel combustion process through two linked parallel processes, compared to the conventional combustion process, which is operated far away from its thermo-equilibrium. Under the current carbon-constraint environment, it has been a promising carbon capture technology in terms of fuel combustion for power generation. Its disadvantage is that it is less mature in terms of technological commercialization. In this DOE-funded project, accomplishment is made by developing a series of advanced copper-based oxygen carriers, with properties of the higher oxygen-transfer capability, a favorable thermodynamics to generate high purity of CO{sub 2}, the higher reactivity, the attrition-resistance, the thermal stability in red-ox cycles and the achievement of the auto-thermal heat balance. This will be achieved into three phases in three consecutive years. The selected oxygen carriers with final-determined formula were tested in a scaled-up 10kW coal-fueled chemical looping combustion facility. This scaled-up evaluation tests (2-day, 8-hour per day) indicated that, there was no tendency of agglomeration of copper-based oxygen carriers. Only trace-amount of coke or carbon deposits on the copper-based oxygen carriers in the fuel reactor. There was also no evidence to show the sulphidization of oxygen carriers in the system by using the high-sulfur-laden asphalt fuels. In all, the scaled-up test in 10 kW CLC facility demonstrated that the preparation method of copper-based oxygen carrier not only help to maintain its good reactivity, also largely minimize its agglomeration tendency.« less

Indirect Identification of Linear Stochastic Systems with Known Feedback Dynamics

NASA Technical Reports Server (NTRS)

Huang, Jen-Kuang; Hsiao, Min-Hung; Cox, David E.

1996-01-01

An algorithm is presented for identifying a state-space model of linear stochastic systems operating under known feedback controller. In this algorithm, only the reference input and output of closed-loop data are required. No feedback signal needs to be recorded. The overall closed-loop system dynamics is first identified. Then a recursive formulation is derived to compute the open-loop plant dynamics from the identified closed-loop system dynamics and known feedback controller dynamics. The controller can be a dynamic or constant-gain full-state feedback controller. Numerical simulations and test data of a highly unstable large-gap magnetic suspension system are presented to demonstrate the feasibility of this indirect identification method.

77 FR 55416 - Drawbridge Operation Regulations; Long Island, New York Inland Waterway From East Rockaway Inlet...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-10

...: The Loop Parkway Bridge, mile 0.7, across Long Creek has a vertical clearance in the closed position... deviation the Loop Parkway Bridge and the Meadowbrook Parkway Bridge may remain in the closed position... operation of the Loop Parkway Bridge, mile 0.7, across Long Creek, and the Meadowbrook Parkway Bridge, mile...

Pulsatile desynchronizing delayed feedback for closed-loop deep brain stimulation

PubMed Central

Lysyansky, Borys; Rosenblum, Michael; Pikovsky, Arkady; Tass, Peter A.

2017-01-01

High-frequency (HF) deep brain stimulation (DBS) is the gold standard for the treatment of medically refractory movement disorders like Parkinson’s disease, essential tremor, and dystonia, with a significant potential for application to other neurological diseases. The standard setup of HF DBS utilizes an open-loop stimulation protocol, where a permanent HF electrical pulse train is administered to the brain target areas irrespectively of the ongoing neuronal dynamics. Recent experimental and clinical studies demonstrate that a closed-loop, adaptive DBS might be superior to the open-loop setup. We here combine the notion of the adaptive high-frequency stimulation approach, that aims at delivering stimulation adapted to the extent of appropriately detected biomarkers, with specifically desynchronizing stimulation protocols. To this end, we extend the delayed feedback stimulation methods, which are intrinsically closed-loop techniques and specifically designed to desynchronize abnormal neuronal synchronization, to pulsatile electrical brain stimulation. We show that permanent pulsatile high-frequency stimulation subjected to an amplitude modulation by linear or nonlinear delayed feedback methods can effectively and robustly desynchronize a STN-GPe network of model neurons and suggest this approach for desynchronizing closed-loop DBS. PMID:28273176

Comparison of the Shack-Hartmann and plenoptic sensor in closed-loop adaptive optics system

NASA Astrophysics Data System (ADS)

Jiang, Pengzhi; Xu, Jieping; Liang, Yonghui; Mao, Hongjun

2016-03-01

The wavefront sensor is used in adaptive optics (AO) to detect the atmospheric distortion, which feeds back to the deformable mirror to compensate for this distortion. While the Shack-Hartmann sensor has been widely used, the plenoptic sensor was proposed in recent years. The two different wavefront sensing methods have different interpretations and numerical consequences, though they are both slope-based. The plenoptic sensor is compared with the Shack-Hartmann sensor in a closed-loop AO system. Simulations are performed to investigate their performances under closed-loop conditions. The plenoptic sensors both without and with modulation are discussed. The results show that the closed-loop performance of the plenoptic sensor without modulation is worse than that of the Shack-Hartmann sensor when the star for observation is brighter than magnitude 7, but better when the star is fainter. The closed-loop performance of the plenoptic sensor could be improved by modulation, except for the faint star. In summary, the limiting magnitude of the astronomical AO system may be improved by using the plenoptic sensor instead of the Shack-Hartmann sensor, and the modulation of the plenoptic sensor is more suitable for the bright star.

A closed-loop photon beam control study for the Advanced Light Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Portmann, G.; Bengtsson, J.

1993-05-01

The third generation Advanced Light Source (ALS) will produce extremely bright photon beams using undulators and wigglers. In order to position the photon beams accurate to the micron level, a closed-loop feedback system is being developed. Using photon position monitors and dipole corrector magnets, a closed-loop system can automatically compensate for modeling uncertainties and exogenous disturbances. The following paper will present a dynamics model for the perturbations of the closed orbit of the electron beam in the ALS storage ring including the vacuum chamber magnetic field penetration effects. Using this reference model, two closed-loop feedback algorithms will be compared --more » a classical PI controller and a two degree-of-freedom approach. The two degree-of-freedom method provides superior disturbance rejection while maintaining the desired performance goals. Both methods will address the need to gain schedule the controller due to the time varying dynamics introduced by changing field strengths when scanning the insertion devices.« less

Application of frequency domain handling qualities criteria to the longitudinal landing task

NASA Technical Reports Server (NTRS)

Sarrafian, S. K.; Powers, B. G.

1985-01-01

Three frequency-domain handling qualities criteria have been applied to the observed data to correlate the actual pilot ratings assigned to generic transport configurations with stability augmentation during the longitudinal landing task. The criteria are based on closed-loop techniques using pitch attitude, altitude rate at the pilot station, and altitude at the pilot station as dominating control parameters during this task. It is found that most promising results are obtained with altitude control performed by closing an inner loop on pitch attitude and closing an outer loop on altitude.

Non-polynomial closed string field theory: loops and conformal maps

NASA Astrophysics Data System (ADS)

Hua, Long; Kaku, Michio

1990-11-01

Recently, we proposed the complete classical action for the non-polynomial closed string field theory, which succesfully reproduced all closed string tree amplitudes. (The action was simultaneously proposed by the Kyoto group). In this paper, we analyze the structure of the theory. We (a) compute the explicit conformal map for all g-loop, p-puncture diagrams, (b) compute all one-loop, two-puncture maps in terms of hyper-elliptic functions, and (c) analyze their modular structure. We analyze, but do not resolve, the question of modular invariance.

Closed-loop systems for drug delivery.

PubMed

Fields, Aaron M; Fields, Kevin M; Cannon, Jeremy W

2008-08-01

To discuss closed-loop systems, the engineering behind them, and the application of these systems. The literature demonstrates that closed-loop systems can be used for controlling the depth of anesthesia, muscle relaxation, blood pressure, intravascular volume, and blood glucose levels. The future anesthesiologist may devote less time to easily delegated tasks when in the operating room. The ability of computers to maintain variables in a set range allows some tasks to be automated. Although monitoring of these systems will never be completely eliminated, the necessity for minute-to-minute intervention may.

Closed loop biomass in Puerto Rico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schroeder, R.M.

1995-11-01

Kenetech Energy Systems, Inc., began to explore the opportunities for power generation in Puerto Rico in 1993. Among the projects investigated was the development of a power plant that uses biomass for fuel. Through the assistance of a grant from the National Renewable Energy Laboratory, a preliminary study was undertaken to explore various possibilities in biomass production and conversion. The existing sugar cane industry was examined, and various species and regimes of cane species, grass species, and other types of crops were studied. Among the other issues were the political and economic situation, and the uncertainty of the sugar industrymore » in Puerto Rico. A current status of the project is provided.« less

Advanced Ignition in Supersonic Airflow by Tunable Plasma System

NASA Astrophysics Data System (ADS)

Firsov, A. A.; Dolgov, E. V.; Leonov, S. B.; Yarantsev, D. A.

2017-10-01

The plasma-based technique was studied for ignition and flameholding in a supersonic airflow in different laboratories for a long time. It was shown that flameholding of gaseous and liquid hydrocarbon fuel is feasible by means of surface DC discharge without employing mechanical flameholders in a supersonic combustion chamber. However, a high power consumption may limit application of this method in a real apparatus. This experimental and computational work explores a distributed plasma system, which allows reducing the total energy consumption and extending the life cycle of the electrode system. Due to the circuit flexibility, this approach may be potentially enriched with feedbacks for design of a close loop control system.

Orbiter integrated active thermal control subsystem test

NASA Technical Reports Server (NTRS)

Jaax, J. R.

1980-01-01

Integrated subsystem level testing of the systems within the orbiter active thermal chamber capable of simulating ground, orbital, and entry temperature and pressure profiles. The test article was in a closed loop configuration that included flight type and functionally simulated protions of all ATCS components for collecting, transporting, and rejecting orbiter waste heat. Specially designed independently operating equipment simulated the transient thermal input from the cabin, payload, fuel cells, freon cold plates, hydraulic system, and space environment. Test team members using data, controls, and procedures available to a flight crew controlled the operation of the ATCS. The ATCS performance met or exceeded all thermal and operational requirements for planned and contingency mission support.

Day-and-Night Hybrid Closed-Loop Insulin Delivery in Adolescents With Type 1 Diabetes: A Free-Living, Randomized Clinical Trial.

PubMed

Tauschmann, Martin; Allen, Janet M; Wilinska, Malgorzata E; Thabit, Hood; Stewart, Zoë; Cheng, Peiyao; Kollman, Craig; Acerini, Carlo L; Dunger, David B; Hovorka, Roman

2016-07-01

To evaluate feasibility, safety, and efficacy of day-and-night hybrid closed-loop insulin delivery in adolescents with type 1 diabetes under free-living conditions without remote monitoring or supervision. In an open-label, randomized, free-living, crossover study design, 12 adolescents receiving insulin pump therapy (mean [±SD] age 15.4 ± 2.6 years; HbA1c 8.3 ± 0.9%; duration of diabetes 8.2 ± 3.4 years) underwent two 7-day periods of sensor-augmented insulin pump therapy or hybrid closed-loop insulin delivery without supervision or remote monitoring. During the closed-loop insulin delivery, a model predictive algorithm automatically directed insulin delivery between meals and overnight; prandial boluses were administered by participants using a bolus calculator. The proportion of time when the sensor glucose level was in the target range (3.9-10 mmol/L) was increased during closed-loop insulin delivery compared with sensor-augmented pump therapy (72 vs. 53%, P < 0.001; primary end point), the mean glucose concentration was lowered (8.7 vs. 10.1 mmol/L, P = 0.028), and the time spent above the target level was reduced (P = 0.005) without changing the total daily insulin amount (P = 0.55). The time spent in the hypoglycemic range was low and comparable between interventions. Unsupervised day-and-night hybrid closed-loop insulin delivery at home is feasible and safe in young people with type 1 diabetes. Compared with sensor-augmented insulin pump therapy, closed-loop insulin delivery may improve glucose control without increasing the risk of hypoglycemia in adolescents with suboptimally controlled type 1 diabetes. © 2016 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.

Closing the Referral Loop: an Analysis of Primary Care Referrals to Specialists in a Large Health System.

PubMed

Patel, Malhar P; Schettini, Priscille; O'Leary, Colin P; Bosworth, Hayden B; Anderson, John B; Shah, Kevin P

2018-05-01

Ideally, a referral from a primary care physician (PCP) to a specialist results in a completed specialty appointment with results available to the PCP. This is defined as "closing the referral loop." As health systems grow more complex, regulatory bodies increase vigilance, and reimbursement shifts towards value, closing the referral loop becomes a patient safety, regulatory, and financial imperative. To assess the ability of a large health system to close the referral loop, we used electronic medical record (EMR)-generated data to analyze referrals from a large primary care network to 20 high-volume specialties between July 1, 2015 and June 30, 2016. The primary metric was documented specialist appointment completion rate. Explanatory analyses included documented appointment scheduling rate, individual clinic differences, appointment wait times, and geographic distance to appointments. Of the 103,737 analyzed referral scheduling attempts, only 36,072 (34.8%) resulted in documented complete appointments. Low documented appointment scheduling rates (38.9% of scheduling attempts lacked appointment dates), individual clinic differences in closing the referral loop, and significant differences in wait times and distances to specialists between complete and incomplete appointments drove this gap. Other notable findings include high variation in wait times among specialties and correlation between high wait times and low documented appointment completion rates. The rate of closing the referral loop in this health system is low. Low appointment scheduling rates, individual clinic differences, and patient access issues of wait times and geographic proximity explain much of the gap. This problem is likely common among large health systems with complex provider networks and referral scheduling. Strategies that improve scheduling, decrease variation among clinics, and improve patient access will likely improve rates of closing the referral loop. More research is necessary to determine the impact of these changes and other potential driving factors.

A theory of how active behavior stabilises neural activity: Neural gain modulation by closed-loop environmental feedback

PubMed Central

2018-01-01

During active behaviours like running, swimming, whisking or sniffing, motor actions shape sensory input and sensory percepts guide future motor commands. Ongoing cycles of sensory and motor processing constitute a closed-loop feedback system which is central to motor control and, it has been argued, for perceptual processes. This closed-loop feedback is mediated by brainwide neural circuits but how the presence of feedback signals impacts on the dynamics and function of neurons is not well understood. Here we present a simple theory suggesting that closed-loop feedback between the brain/body/environment can modulate neural gain and, consequently, change endogenous neural fluctuations and responses to sensory input. We support this theory with modeling and data analysis in two vertebrate systems. First, in a model of rodent whisking we show that negative feedback mediated by whisking vibrissa can suppress coherent neural fluctuations and neural responses to sensory input in the barrel cortex. We argue this suppression provides an appealing account of a brain state transition (a marked change in global brain activity) coincident with the onset of whisking in rodents. Moreover, this mechanism suggests a novel signal detection mechanism that selectively accentuates active, rather than passive, whisker touch signals. This mechanism is consistent with a predictive coding strategy that is sensitive to the consequences of motor actions rather than the difference between the predicted and actual sensory input. We further support the theory by re-analysing previously published two-photon data recorded in zebrafish larvae performing closed-loop optomotor behaviour in a virtual swim simulator. We show, as predicted by this theory, that the degree to which each cell contributes in linking sensory and motor signals well explains how much its neural fluctuations are suppressed by closed-loop optomotor behaviour. More generally we argue that our results demonstrate the dependence of neural fluctuations, across the brain, on closed-loop brain/body/environment interactions strongly supporting the idea that brain function cannot be fully understood through open-loop approaches alone. PMID:29342146

A theory of how active behavior stabilises neural activity: Neural gain modulation by closed-loop environmental feedback.

PubMed

Buckley, Christopher L; Toyoizumi, Taro

2018-01-01

During active behaviours like running, swimming, whisking or sniffing, motor actions shape sensory input and sensory percepts guide future motor commands. Ongoing cycles of sensory and motor processing constitute a closed-loop feedback system which is central to motor control and, it has been argued, for perceptual processes. This closed-loop feedback is mediated by brainwide neural circuits but how the presence of feedback signals impacts on the dynamics and function of neurons is not well understood. Here we present a simple theory suggesting that closed-loop feedback between the brain/body/environment can modulate neural gain and, consequently, change endogenous neural fluctuations and responses to sensory input. We support this theory with modeling and data analysis in two vertebrate systems. First, in a model of rodent whisking we show that negative feedback mediated by whisking vibrissa can suppress coherent neural fluctuations and neural responses to sensory input in the barrel cortex. We argue this suppression provides an appealing account of a brain state transition (a marked change in global brain activity) coincident with the onset of whisking in rodents. Moreover, this mechanism suggests a novel signal detection mechanism that selectively accentuates active, rather than passive, whisker touch signals. This mechanism is consistent with a predictive coding strategy that is sensitive to the consequences of motor actions rather than the difference between the predicted and actual sensory input. We further support the theory by re-analysing previously published two-photon data recorded in zebrafish larvae performing closed-loop optomotor behaviour in a virtual swim simulator. We show, as predicted by this theory, that the degree to which each cell contributes in linking sensory and motor signals well explains how much its neural fluctuations are suppressed by closed-loop optomotor behaviour. More generally we argue that our results demonstrate the dependence of neural fluctuations, across the brain, on closed-loop brain/body/environment interactions strongly supporting the idea that brain function cannot be fully understood through open-loop approaches alone.

Miniature Fourier transform spectrometer with a dual closed-loop controlled electrothermal micromirror.

PubMed

Han, Fengtian; Wang, Wei; Zhang, Xiaoyang; Xie, Huikai

2016-10-03

A large piston-displacement electrothermal micromirror with closed-loop control of both piston scan and tilting of the mirror plate is demonstrated for use in a miniature Fourier transform spectrometer. Constant scan velocity in an ultra large piston scan range has been demonstrated by the proposed closed-loop piston control scheme which can be easily implemented without considerably increasing system complexity. The experimental results show that the usable linear scan range generated by the micromirror has been extended up to 505 μm. The measured spectral resolution in a compact spectrometer reaches 20 cm^-1, or 0.57 nm at 532 nm wavelength. Compared to other presented systems, this microspectrometer will benefit from the closed-loop thermal actuator approach utilizing both the piston servo and tilt control to provide more consistent spectral response, improved spectral resolution and enhanced robustness to disturbances.

Robust fast controller design via nonlinear fractional differential equations.

PubMed

Zhou, Xi; Wei, Yiheng; Liang, Shu; Wang, Yong

2017-07-01

A new method for linear system controller design is proposed whereby the closed-loop system achieves both robustness and fast response. The robustness performance considered here means the damping ratio of closed-loop system can keep its desired value under system parameter perturbation, while the fast response, represented by rise time of system output, can be improved by tuning the controller parameter. We exploit techniques from both the nonlinear systems control and the fractional order systems control to derive a novel nonlinear fractional order controller. For theoretical analysis of the closed-loop system performance, two comparison theorems are developed for a class of fractional differential equations. Moreover, the rise time of the closed-loop system can be estimated, which facilitates our controller design to satisfy the fast response performance and maintain the robustness. Finally, numerical examples are given to illustrate the effectiveness of our methods. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Similarity Metrics for Closed Loop Dynamic Systems

NASA Technical Reports Server (NTRS)

Whorton, Mark S.; Yang, Lee C.; Bedrossian, Naz; Hall, Robert A.

2008-01-01

To what extent and in what ways can two closed-loop dynamic systems be said to be "similar?" This question arises in a wide range of dynamic systems modeling and control system design applications. For example, bounds on error models are fundamental to the controller optimization with modern control design methods. Metrics such as the structured singular value are direct measures of the degree to which properties such as stability or performance are maintained in the presence of specified uncertainties or variations in the plant model. Similarly, controls-related areas such as system identification, model reduction, and experimental model validation employ measures of similarity between multiple realizations of a dynamic system. Each area has its tools and approaches, with each tool more or less suited for one application or the other. Similarity in the context of closed-loop model validation via flight test is subtly different from error measures in the typical controls oriented application. Whereas similarity in a robust control context relates to plant variation and the attendant affect on stability and performance, in this context similarity metrics are sought that assess the relevance of a dynamic system test for the purpose of validating the stability and performance of a "similar" dynamic system. Similarity in the context of system identification is much more relevant than are robust control analogies in that errors between one dynamic system (the test article) and another (the nominal "design" model) are sought for the purpose of bounding the validity of a model for control design and analysis. Yet system identification typically involves open-loop plant models which are independent of the control system (with the exception of limited developments in closed-loop system identification which is nonetheless focused on obtaining open-loop plant models from closed-loop data). Moreover the objectives of system identification are not the same as a flight test and hence system identification error metrics are not directly relevant. In applications such as launch vehicles where the open loop plant is unstable it is similarity of the closed-loop system dynamics of a flight test that are relevant.

Feasibility of outpatient fully integrated closed-loop control: first studies of wearable artificial pancreas.

PubMed

Kovatchev, Boris P; Renard, Eric; Cobelli, Claudio; Zisser, Howard C; Keith-Hynes, Patrick; Anderson, Stacey M; Brown, Sue A; Chernavvsky, Daniel R; Breton, Marc D; Farret, Anne; Pelletier, Marie-Josée; Place, Jérôme; Bruttomesso, Daniela; Del Favero, Simone; Visentin, Roberto; Filippi, Alessio; Scotton, Rachele; Avogaro, Angelo; Doyle, Francis J

2013-07-01

To evaluate the feasibility of a wearable artificial pancreas system, the Diabetes Assistant (DiAs), which uses a smart phone as a closed-loop control platform. Twenty patients with type 1 diabetes were enrolled at the Universities of Padova, Montpellier, and Virginia and at Sansum Diabetes Research Institute. Each trial continued for 42 h. The United States studies were conducted entirely in outpatient setting (e.g., hotel or guest house); studies in Italy and France were hybrid hospital-hotel admissions. A continuous glucose monitoring/pump system (Dexcom Seven Plus/Omnipod) was placed on the subject and was connected to DiAs. The patient operated the system via the DiAs user interface in open-loop mode (first 14 h of study), switching to closed-loop for the remaining 28 h. Study personnel monitored remotely via 3G or WiFi connection to DiAs and were available on site for assistance. The total duration of proper system communication functioning was 807.5 h (274 h in open-loop and 533.5 h in closed-loop), which represented 97.7% of the total possible time from admission to discharge. This exceeded the predetermined primary end point of 80% system functionality. This study demonstrated that a contemporary smart phone is capable of running outpatient closed-loop control and introduced a prototype system (DiAs) for further investigation. Following this proof of concept, future steps should include equipping insulin pumps and sensors with wireless capabilities, as well as studies focusing on control efficacy and patient-oriented clinical outcomes.

Control of a flexible link by shaping the closed loop frequency response function through optimised feedback filters

NASA Astrophysics Data System (ADS)

Del Vescovo, D.; D'Ambrogio, W.

1995-01-01

A frequency domain method is presented to design a closed-loop control for vibration reduction flexible mechanisms. The procedure is developed on a single-link flexible arm, driven by one rotary degree of freedom servomotor, although the same technique may be applied to similar systems such as supports for aerospace antennae or solar panels. The method uses the structural frequency response functions (FRFs), thus avoiding system identification, that produces modeling uncertainties. Two closed-loops are implemented: the inner loop uses acceleration feedback with the aim of making the FRF similar to that of an equivalent rigid link; the outer loop feeds back displacements to achieve a fast positioning response and null steady state error. In both cases, the controller type is established a priori, while actual characteristics are defined by an optimisation procedure in which the relevant FRF is constrained into prescribed bounds and stability is taken into account.

Enhanced Performance Controller Design for Stochastic Systems by Adding Extra State Estimation onto the Existing Closed Loop Control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Yuyang; Zhang, Qichun; Wang, Hong

To enhance the performance of the tracking property , this paper presents a novel control algorithm for a class of linear dynamic stochastic systems with unmeasurable states, where the performance enhancement loop is established based on Kalman filter. Without changing the existing closed loop with the PI controller, the compensative controller is designed to minimize the variances of the tracking errors using the estimated states and the propagation of state variances. Moreover, the stability of the closed-loop systems has been analyzed in the mean-square sense. A simulated example is included to show the effectiveness of the presented control algorithm, wheremore » encouraging results have been obtained.« less

An Environment for Hardware-in-the-Loop Formation Navigation and Control Simulation

NASA Technical Reports Server (NTRS)

Burns, Rich

2004-01-01

Recent interest in formation flying satellite systems has spurred a considerable amount of research in the relative navigation and control of satellites. Development in this area has included new estimation and control algorithms as well as sensor and actuator development specifically geared toward the relative control problem. This paper describes a simulation facility, the Formation Flying Testbed (FFTB) at NASA's Goddard Space Flight Center, which allows engineers to test new algorithms for the formation flying problem with relevant GN&C hardware in a closed loop simulation. The FFTB currently supports the injection of GPS receiver hardware into the simulation loop, and support for satellite crosslink ranging technology is at a prototype stage. This closed-loop, hardware inclusive simulation capability permits testing of navigation and control software in the presence of the actual hardware with which the algorithms must interact. This capability provides the navigation or control developer with a perspective on how the algorithms perform as part of the closed-loop system. In this paper, the overall design and evolution of the FFTB are presented. Each component of the FFTB is then described in detail. Interfaces between the components of the FFTB are shown and the interfaces to and between navigation and control software are described in detail. Finally, an example of closed-loop formation control with GPS receivers in the loop is presented and results are analyzed.

Study of advanced fuel system concepts for commercial aircraft

NASA Technical Reports Server (NTRS)

Coffinberry, G. A.

1985-01-01

An analytical study was performed in order to assess relative performance and economic factors involved with alternative advanced fuel systems for future commercial aircraft operating with broadened property fuels. The DC-10-30 wide-body tri-jet aircraft and the CF6-8OX engine were used as a baseline design for the study. Three advanced systems were considered and were specifically aimed at addressing freezing point, thermal stability and lubricity fuel properties. Actual DC-10-30 routes and flight profiles were simulated by computer modeling and resulted in prediction of aircraft and engine fuel system temperatures during a nominal flight and during statistical one-day-per-year cold and hot flights. Emergency conditions were also evaluated. Fuel consumption and weight and power extraction results were obtained. An economic analysis was performed for new aircraft and systems. Advanced system means for fuel tank heating included fuel recirculation loops using engine lube heat and generator heat. Environmental control system bleed air heat was used for tank heating in a water recirculation loop. The results showed that fundamentally all of the three advanced systems are feasible but vary in their degree of compatibility with broadened-property fuel.

Operation of a cascade air conditioning system with two-phase loop

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Yinshan; Wang, Jinliang; Zhao, Futao

A method of operating a heat transfer system includes starting operation of a first heat transfer fluid vapor/compression circulation loop including a fluid pumping mechanism, a heat exchanger for rejecting thermal energy from a first heat transfer fluid, and a heat absorption side of an internal heat exchanger. A first conduit in a closed fluid circulation loop circulates the first heat transfer fluid therethrough. Operation of a second two-phase heat transfer fluid circulation loop is started after starting operation of the first heat transfer fluid circulation loop. The second heat transfer fluid circulation loop transfers heat to the first heatmore » transfer fluid circulation loop through the internal heat exchanger and includes a heat rejection side of the internal heat exchanger, a liquid pump, and a heat exchanger evaporator. A second conduit in a closed fluid circulation loop circulates a second heat transfer fluid therethrough.« less

Dynamics of the active site loops in catalyzing aminoacylation reaction in seryl and histidyl tRNA synthetases.

PubMed

Dutta, Saheb; Kundu, Soumya; Saha, Amrita; Nandi, Nilashis

2018-03-01

Aminoacylation reaction is the first step of protein biosynthesis. The catalytic reorganization at the active site of aminoacyl tRNA synthetases (aaRSs) is driven by the loop motions. There remain lacunae of understanding concerning the catalytic loop dynamics in aaRSs. We analyzed the functional loop dynamics in seryl tRNA synthetase from Methanopyrus kandleri ( mk SerRS) and histidyl tRNA synthetases from Thermus thermophilus ( tt HisRS), respectively, using molecular dynamics. Results confirm that the motif 2 loop and other active site loops are flexible spots within the catalytic domain. Catalytic residues of the loops form a network of interaction with the substrates to form a reactive state. The loops undergo transitions between closed state and open state and the relaxation of the constituent residues occurs in femtosecond to nanosecond time scale. Order parameters are higher for constituent catalytic residues which form a specific network of interaction with the substrates to form a reactive state compared to the Gly residues within the loop. The development of interaction is supported from mutation studies where the catalytic domain with mutated loop exhibits unfavorable binding energy with the substrates. During the open-close motion of the loops, the catalytic residues make relaxation by ultrafast librational motion as well as fast diffusive motion and subsequently relax rather slowly via slower diffusive motion. The Gly residues act as a hinge to facilitate the loop closing and opening by their faster relaxation behavior. The role of bound water is analyzed by comparing implicit solvent-based and explicit solvent-based simulations. Loops fail to form catalytically competent geometry in absence of water. The present result, for the first time reveals the nature of the active site loop dynamics in aaRS and their influence on catalysis.

Shifting the closed-loop spectrum in the optimal linear quadratic regulator problem for hereditary systems

NASA Technical Reports Server (NTRS)

Gibson, J. S.; Rosen, I. G.

1985-01-01

In the optimal linear quadratic regulator problem for finite dimensional systems, the method known as an alpha-shift can be used to produce a closed-loop system whose spectrum lies to the left of some specified vertical line; that is, a closed-loop system with a prescribed degree of stability. This paper treats the extension of the alpha-shift to hereditary systems. As infinite dimensions, the shift can be accomplished by adding alpha times the identity to the open-loop semigroup generator and then solving an optimal regulator problem. However, this approach does not work with a new approximation scheme for hereditary control problems recently developed by Kappel and Salamon. Since this scheme is among the best to date for the numerical solution of the linear regulator problem for hereditary systems, an alternative method for shifting the closed-loop spectrum is needed. An alpha-shift technique that can be used with the Kappel-Salamon approximation scheme is developed. Both the continuous-time and discrete-time problems are considered. A numerical example which demonstrates the feasibility of the method is included.

Shifting the closed-loop spectrum in the optimal linear quadratic regulator problem for hereditary systems

NASA Technical Reports Server (NTRS)

Gibson, J. S.; Rosen, I. G.

1987-01-01

In the optimal linear quadratic regulator problem for finite dimensional systems, the method known as an alpha-shift can be used to produce a closed-loop system whose spectrum lies to the left of some specified vertical line; that is, a closed-loop system with a prescribed degree of stability. This paper treats the extension of the alpha-shift to hereditary systems. As infinite dimensions, the shift can be accomplished by adding alpha times the identity to the open-loop semigroup generator and then solving an optimal regulator problem. However, this approach does not work with a new approximation scheme for hereditary control problems recently developed by Kappel and Salamon. Since this scheme is among the best to date for the numerical solution of the linear regulator problem for hereditary systems, an alternative method for shifting the closed-loop spectrum is needed. An alpha-shift technique that can be used with the Kappel-Salamon approximation scheme is developed. Both the continuous-time and discrete-time problems are considered. A numerical example which demonstrates the feasibility of the method is included.

Environmental Impacts of a Multi-Borehole Geothermal System: Model Sensitivity Study

NASA Astrophysics Data System (ADS)

Krol, M.; Daemi, N.

2017-12-01

Problems associated with fossil fuel consumption has increased worldwide interest in discovering and developing sustainable energy systems. One such system is geothermal heating, which uses the constant temperature of the ground to heat or cool buildings. Since geothermal heating offers low maintenance, high heating/cooling comfort, and a low carbon footprint, compared to conventional systems, there has been an increasing trend in equipping large buildings with geothermal heating. However, little is known on the potential environmental impact geothermal heating can have on the subsurface, such as the creation of subsurface thermal plumes or changes in groundwater flow dynamics. In the present study, the environmental impacts of a closed-loop, ground source heat pump (GSHP) system was examined with respect to different system parameters. To do this a three-dimensional model, developed using FEFLOW, was used to examine the thermal plumes resulting from ten years of operation of a vertical closed-loop GSHP system with multiple boreholes. A required thermal load typical of an office building located in Canada was calculated and groundwater flow and heat transport in the geological formation was simulated. Consequently, the resulting thermal plumes were studied and a sensitivity analysis was conducted to determine the effect of different parameters like groundwater flow and soil type on the development and movement of thermal plumes. Since thermal plumes can affect the efficiency of a GSHP system, this study provides insight into important system parameters.

Closed-loop assisted versus manual goal-directed fluid therapy during high-risk abdominal surgery: a case-control study with propensity matching.

PubMed

Rinehart, Joseph; Lilot, Marc; Lee, Christine; Joosten, Alexandre; Huynh, Trish; Canales, Cecilia; Imagawa, David; Demirjian, Aram; Cannesson, Maxime

2015-03-19

Goal-directed fluid therapy strategies have been shown to benefit moderate- to high-risk surgery patients. Despite this, these strategies are often not implemented. The aim of this study was to assess a closed-loop fluid administration system in a surgical cohort and compare the results with those for matched patients who received manual management. Our hypothesis was that the patients receiving closed-loop assistance would spend more time in a preload-independent state, defined as percentage of case time with stroke volume variation less than or equal to 12%. Patients eligible for the study were all those over 18 years of age scheduled for hepatobiliary, pancreatic or splenic surgery and expected to receive intravascular arterial blood pressure monitoring as part of their anesthetic care. The closed-loop resuscitation target was selected by the primary anesthesia team, and the system was responsible for implementation of goal-directed fluid therapy during surgery. Following completion of enrollment, each study patient was matched to a non-closed-loop assisted case performed during the same time period using a propensity match to reduce bias. A total of 40 patients were enrolled, 5 were ultimately excluded and 25 matched pairs were selected from among the remaining 35 patients within the predefined caliper distance. There was no significant difference in fluid administration between groups. The closed-loop group spent a significantly higher portion of case time in a preload-independent state (95 ± 6% of case time versus 87 ± 14%, P =0.008). There was no difference in case mean or final stroke volume index (45 ± 10 versus 43 ± 9 and 45 ± 11 versus 42 ± 11, respectively) or mean arterial pressure (79 ± 8 versus 83 ± 9). Case end heart rate was significantly lower in the closed-loop assisted group (77 ± 10 versus 88 ± 13, P =0.003). In this case-control study with propensity matching, clinician use of closed-loop assistance resulted in a greater portion of case time spent in a preload-independent state throughout surgery compared with manual delivery of goal-directed fluid therapy. ClinicalTrials.gov Identifier: NCT02020863. Registered 19 December 2013.

Molecular dynamics and mutational analysis of the catalytic and translocation cycle of RNA polymerase

PubMed Central

2012-01-01

Background During elongation, multi-subunit RNA polymerases (RNAPs) cycle between phosphodiester bond formation and nucleic acid translocation. In the conformation associated with catalysis, the mobile “trigger loop” of the catalytic subunit closes on the nucleoside triphosphate (NTP) substrate. Closing of the trigger loop is expected to exclude water from the active site, and dehydration may contribute to catalysis and fidelity. In the absence of a NTP substrate in the active site, the trigger loop opens, which may enable translocation. Another notable structural element of the RNAP catalytic center is the “bridge helix” that separates the active site from downstream DNA. The bridge helix may participate in translocation by bending against the RNA/DNA hybrid to induce RNAP forward movement and to vacate the active site for the next NTP loading. The transition between catalytic and translocation conformations of RNAP is not evident from static crystallographic snapshots in which macromolecular motions may be restrained by crystal packing. Results All atom molecular dynamics simulations of Thermus thermophilus (Tt) RNAP reveal flexible hinges, located within the two helices at the base of the trigger loop, and two glycine hinges clustered near the N-terminal end of the bridge helix. As simulation progresses, these hinges adopt distinct conformations in the closed and open trigger loop structures. A number of residues (described as “switch” residues) trade atomic contacts (ion pairs or hydrogen bonds) in response to changes in hinge orientation. In vivo phenotypes and in vitro activities rendered by mutations in the hinge and switch residues in Saccharomyces cerevisiae (Sc) RNAP II support the importance of conformational changes predicted from simulations in catalysis and translocation. During simulation, the elongation complex with an open trigger loop spontaneously translocates forward relative to the elongation complex with a closed trigger loop. Conclusions Switching between catalytic and translocating RNAP forms involves closing and opening of the trigger loop and long-range conformational changes in the atomic contacts of amino acid side chains, some located at a considerable distance from the trigger loop and active site. Trigger loop closing appears to support chemistry and the fidelity of RNA synthesis. Trigger loop opening and limited bridge helix bending appears to promote forward nucleic acid translocation. PMID:22676913

Tri-metallic ferrite oxygen carriers for chemical looping combustion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siriwardane, Ranjani V.; Fan, Yueying

The disclosure provides a tri-metallic ferrite oxygen carrier for the chemical looping combustion of carbonaceous fuels. The tri-metallic ferrite oxygen carrier comprises Cu.sub.xFe.sub.yMn.sub.zO.sub.4-.delta., where Cu.sub.xFe.sub.yMn.sub.zO.sub.4-.delta. is a chemical composition. Generally, 0.5.ltoreq.x.ltoreq.2.0, 0.2.ltoreq.y.ltoreq.2.5, and 0.2.ltoreq.z.ltoreq.2.5, and in some embodiments, 0.8.ltoreq.x.ltoreq.1.2, y.ltoreq.1.2, and z.gtoreq.0.8. The tri-metallic ferrite oxygen carrier may be used in various applications for the combustion of carbonaceous fuels, including as an oxygen carrier for chemical looping combustion.

Phase-lock loop frequency control and the dropout problem

NASA Technical Reports Server (NTRS)

Attwood, S.; Kline, A. J.

1968-01-01

Technique automatically sets the frequency of narrow band phase-lock loops within automatic lock-in-range. It presets a phase-lock loop to a desired center frequency with a closed loop electronic frequency discriminator and holds the phase-lock loop to that center frequency until lock is achieved.

The Concept and Analytical Investigation of CO2 and Steam Co-Electrolysis for Resource Utilization in Space Exploration

NASA Technical Reports Server (NTRS)

McKellar, Michael G.; Stoots, Carl M.; Sohal, Manohar S.; Mulloth, Lila M.; Luna, Bernadette; Abney, Morgan B.

2010-01-01

CO2 acquisition and utilization technologies will have a vital role in designing sustainable and affordable life support and in situ fuel production architectures for human and robotic exploration of Moon and Mars. For long-term human exploration to be practical, reliable technologies have to be implemented to capture the metabolic CO2 from the cabin air and chemically reduce it to recover oxygen. Technologies that enable the in situ capture and conversion of atmospheric CO2 to fuel are essential for a viable human mission to Mars. This paper describes the concept and mathematical analysis of a closed-loop life support system based on combined electrolysis of CO2 and steam (co-electrolysis). Products of the coelectrolysis process include oxygen and syngas (CO and H2) that are suitable for life support and synthetic fuel production, respectively. The model was developed based on the performance of a co-electrolysis system developed at Idaho National Laboratory (INL). Individual and combined process models of the co-electrolysis and Sabatier, Bosch, Boudouard, and hydrogenation reactions are discussed and their performance analyses in terms of oxygen production and CO2 utilization are presented.

Classical and adaptive control of ex vivo skeletal muscle contractions using Functional Electrical Stimulation (FES)

PubMed Central

Shoemaker, Adam; Grange, Robert W.; Abaid, Nicole; Leonessa, Alexander

2017-01-01

Functional Electrical Stimulation is a promising approach to treat patients by stimulating the peripheral nerves and their corresponding motor neurons using electrical current. This technique helps maintain muscle mass and promote blood flow in the absence of a functioning nervous system. The goal of this work is to control muscle contractions from FES via three different algorithms and assess the most appropriate controller providing effective stimulation of the muscle. An open-loop system and a closed-loop system with three types of model-free feedback controllers were assessed for tracking control of skeletal muscle contractions: a Proportional-Integral (PI) controller, a Model Reference Adaptive Control algorithm, and an Adaptive Augmented PI system. Furthermore, a mathematical model of a muscle-mass-spring system was implemented in simulation to test the open-loop case and closed-loop controllers. These simulations were carried out and then validated through experiments ex vivo. The experiments included muscle contractions following four distinct trajectories: a step, sine, ramp, and square wave. Overall, the closed-loop controllers followed the stimulation trajectories set for all the simulated and tested muscles. When comparing the experimental outcomes of each controller, we concluded that the Adaptive Augmented PI algorithm provided the best closed-loop performance for speed of convergence and disturbance rejection. PMID:28273101

Efficiently computing exact geodesic loops within finite steps.

PubMed

Xin, Shi-Qing; He, Ying; Fu, Chi-Wing

2012-06-01

Closed geodesics, or geodesic loops, are crucial to the study of differential topology and differential geometry. Although the existence and properties of closed geodesics on smooth surfaces have been widely studied in mathematics community, relatively little progress has been made on how to compute them on polygonal surfaces. Most existing algorithms simply consider the mesh as a graph and so the resultant loops are restricted only on mesh edges, which are far from the actual geodesics. This paper is the first to prove the existence and uniqueness of geodesic loop restricted on a closed face sequence; it contributes also with an efficient algorithm to iteratively evolve an initial closed path on a given mesh into an exact geodesic loop within finite steps. Our proposed algorithm takes only an O(k) space complexity and an O(mk) time complexity (experimentally), where m is the number of vertices in the region bounded by the initial loop and the resultant geodesic loop, and k is the average number of edges in the edge sequences that the evolving loop passes through. In contrast to the existing geodesic curvature flow methods which compute an approximate geodesic loop within a predefined threshold, our method is exact and can apply directly to triangular meshes without needing to solve any differential equation with a numerical solver; it can run at interactive speed, e.g., in the order of milliseconds, for a mesh with around 50K vertices, and hence, significantly outperforms existing algorithms. Actually, our algorithm could run at interactive speed even for larger meshes. Besides the complexity of the input mesh, the geometric shape could also affect the number of evolving steps, i.e., the performance. We motivate our algorithm with an interactive shape segmentation example shown later in the paper.

Experience using individually supplied heater rods in critical power testing of advanced BWR fuel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Majed, M.; Morback, G.; Wiman, P.

1995-09-01

The ABB Atom FRIGG loop located in Vasteras Sweden has during the last six years given a large experience of critical power measurements for BWR fuel designs using indirectly heated rods with individual power supply. The loop was built in the sixties and designed for maximum 100 bar pressure. Testing up to the mid eighties was performed with directly heated rods using a 9 MW, 80 kA power supply. Providing test data to develop critical power correlations for BWR fuel assemblies requires testing with many radial power distributions over the full range of hydraulic conditions. Indirectly heated rods give largemore » advantages for the testing procedure, particularly convenient for variation of individual rod power. A test method being used at Stern Laboratories (formerly Westinghouse Canada) since the early sixties, allows one fuel assembly to simulate all required radial power distributions. This technique requires reliable indirectly heated rods with independently controlled power supplies and uses insulated electric fuel rod simulators with built-in instrumentation. The FRIGG loop was adapted to this system in 1987. A 4MW power supply with 10 individual units was then installed, and has since been used for testing 24 and 25 rod bundles simulating one subbundle of SVEA-96/100 type fuel assemblies. The experience with the system is very good, as being presented, and it is selected also for a planned upgrading of the facility to 15 MW.« less

Modeling and control of fuel cell based distributed generation systems

NASA Astrophysics Data System (ADS)

Jung, Jin Woo

This dissertation presents circuit models and control algorithms of fuel cell based distributed generation systems (DGS) for two DGS topologies. In the first topology, each DGS unit utilizes a battery in parallel to the fuel cell in a standalone AC power plant and a grid-interconnection. In the second topology, a Z-source converter, which employs both the L and C passive components and shoot-through zero vectors instead of the conventional DC/DC boost power converter in order to step up the DC-link voltage, is adopted for a standalone AC power supply. In Topology 1, two applications are studied: a standalone power generation (Single DGS Unit and Two DGS Units) and a grid-interconnection. First, dynamic model of the fuel cell is given based on electrochemical process. Second, two full-bridge DC to DC converters are adopted and their controllers are designed: an unidirectional full-bridge DC to DC boost converter for the fuel cell and a bidirectional full-bridge DC to DC buck/boost converter for the battery. Third, for a three-phase DC to AC inverter without or with a Delta/Y transformer, a discrete-time state space circuit model is given and two discrete-time feedback controllers are designed: voltage controller in the outer loop and current controller in the inner loop. And last, for load sharing of two DGS units and power flow control of two DGS units or the DGS connected to the grid, real and reactive power controllers are proposed. Particularly, for the grid-connected DGS application, a synchronization issue between an islanding mode and a paralleling mode to the grid is investigated, and two case studies are performed. To demonstrate the proposed circuit models and control strategies, simulation test-beds using Matlab/Simulink are constructed for each configuration of the fuel cell based DGS with a three-phase AC 120 V (L-N)/60 Hz/50 kVA and various simulation results are presented. In Topology 2, this dissertation presents system modeling, modified space vector PWM implementation (MSVPWM) and design of a closed-loop controller of the Z-source converter which utilizes L and C components and shoot-through zero vectors for the standalone AC power generation. The fuel cell system is modeled by an electrical R-C circuit in order to include slow dynamics of the fuel cells and a voltage-current characteristic of a cell is also considered. A discrete-time state space model is derived to implement digital control and a space vector pulse-width modulation (SVPWM) technique is modified to realize the shoot-through zero vectors that boost the DC-link voltage. Also, three discrete-time feedback controllers are designed: a discrete-time optimal voltage controller, a discrete-time sliding mode current controller, and a discrete-time PI DC-link voltage controller. Furthermore, an asymptotic observer is used to reduce the number of sensors and enhance the reliability of the system. To demonstrate the analyzed circuit model and proposed control strategy, various simulation results using Matlab/Simulink are presented under both light/heavy loads and linear/nonlinear loads for a three-phase AC 208 V (L-L)/60 Hz/10 kVA.

Failure Analysis of Network Based Accessible Pedestrian Signals in Closed-Loop Operation

DOT National Transportation Integrated Search

2011-03-01

The potential failure modes of a network based accessible pedestrian system were analyzed to determine the limitations and benefits of closed-loop operation. The vulnerabilities of the system are accessed using the industry standard process known as ...

Analysis and design of a 3rd order velocity-controlled closed-loop for MEMS vibratory gyroscopes.

PubMed

Wu, Huan-ming; Yang, Hai-gang; Yin, Tao; Jiao, Ji-wei

2013-09-18

The time-average method currently available is limited to analyzing the specific performance of the automatic gain control-proportional and integral (AGC-PI) based velocity-controlled closed-loop in a micro-electro-mechanical systems (MEMS) vibratory gyroscope, since it is hard to solve nonlinear functions in the time domain when the control loop reaches to 3rd order. In this paper, we propose a linearization design approach to overcome this limitation by establishing a 3rd order linear model of the control loop and transferring the analysis to the frequency domain. Order reduction is applied on the built linear model's transfer function by constructing a zero-pole doublet, and therefore mathematical expression of each control loop's performance specification is obtained. Then an optimization methodology is summarized, which reveals that a robust, stable and swift control loop can be achieved by carefully selecting the system parameters following a priority order. Closed-loop drive circuits are designed and implemented using 0.35 μm complementary metal oxide semiconductor (CMOS) process, and experiments carried out on a gyroscope prototype verify the optimization methodology that an optimized stability of the control loop can be achieved by constructing the zero-pole doublet, and disturbance rejection capability (D.R.C) of the control loop can be improved by increasing the integral term.

Camera Based Closed Loop Control for Partial Penetration Welding of Overlap Joints

NASA Astrophysics Data System (ADS)

Abt, F.; Heider, A.; Weber, R.; Graf, T.; Blug, A.; Carl, D.; Höfler, H.; Nicolosi, L.; Tetzlaff, R.

Welding of overlap joints with partial penetration in automotive applications is a challenging process, since the laser power must be set very precisely to achieve a proper connection between the two joining partners without damaging the backside of the sheet stack. Even minor changes in welding conditions can lead to bad results. To overcome this problem a camera based closed loop control for partial penetration welding of overlap joints was developed. With this closed loop control it is possible to weld such configurations with a stable process result even under changing welding conditions.

Closed loop models for analyzing the effects of simulator characteristics. [digital simulation of human operators

NASA Technical Reports Server (NTRS)

Baron, S.; Muralidharan, R.; Kleinman, D. L.

1978-01-01

The optimal control model of the human operator is used to develop closed loop models for analyzing the effects of (digital) simulator characteristics on predicted performance and/or workload. Two approaches are considered: the first utilizes a continuous approximation to the discrete simulation in conjunction with the standard optimal control model; the second involves a more exact discrete description of the simulator in a closed loop multirate simulation in which the optimal control model simulates the pilot. Both models predict that simulator characteristics can have significant effects on performance and workload.

A novel Cs-(129)Xe atomic spin gyroscope with closed-loop Faraday modulation.

PubMed

Fang, Jiancheng; Wan, Shuangai; Qin, Jie; Zhang, Chen; Quan, Wei; Yuan, Heng; Dong, Haifeng

2013-08-01

We report a novel Cs-(129)Xe atomic spin gyroscope (ASG) with closed-loop Faraday modulation method. This ASG requires approximately 30 min to start-up and 110 °C to operate. A closed-loop Faraday modulation method for measurement of the optical rotation was used in this ASG. This method uses an additional Faraday modulator to suppress the laser intensity fluctuation and Faraday modulator thermal induced fluctuation. We theoretically and experimentally validate this method in the Cs-(129)Xe ASG and achieved a bias stability of approximately 3.25 °∕h.

Variability of Insulin Requirements Over 12 Weeks of Closed-Loop Insulin Delivery in Adults With Type 1 Diabetes.

PubMed

Ruan, Yue; Thabit, Hood; Leelarathna, Lalantha; Hartnell, Sara; Willinska, Malgorzata E; Dellweg, Sibylle; Benesch, Carsten; Mader, Julia K; Holzer, Manuel; Kojzar, Harald; Evans, Mark L; Pieber, Thomas R; Arnolds, Sabine; Hovorka, Roman

2016-05-01

To quantify variability of insulin requirements during closed-loop insulin delivery. We retrospectively analyzed overnight, daytime, and total daily insulin amounts delivered during a multicenter closed-loop trial involving 32 adults with type 1 diabetes. Participants applied hybrid day-and-night closed-loop insulin delivery under free-living home conditions over 12 weeks. The coefficient of variation was adopted to measure variability of insulin requirements in individual subjects. Data were analyzed from 1,918 nights, 1,883 daytime periods and 1,564 total days characterized by closed-loop use over 85% of time. Variability of overnight insulin requirements (mean [SD] coefficient of variation 31% [4]) was nearly twice as high as variability of total daily requirements (17% [3], P < 0.001) and was also higher than variability of daytime insulin requirements (22% [4], P < 0.001). Overnight insulin requirements were significantly more variable than daytime and total daily amounts. This may explain why some people with type 1 diabetes report frustrating variability in morning glycemia. © 2016 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.

Closed-Loop Neuromorphic Benchmarks

PubMed Central

Stewart, Terrence C.; DeWolf, Travis; Kleinhans, Ashley; Eliasmith, Chris

2015-01-01

Evaluating the effectiveness and performance of neuromorphic hardware is difficult. It is even more difficult when the task of interest is a closed-loop task; that is, a task where the output from the neuromorphic hardware affects some environment, which then in turn affects the hardware's future input. However, closed-loop situations are one of the primary potential uses of neuromorphic hardware. To address this, we present a methodology for generating closed-loop benchmarks that makes use of a hybrid of real physical embodiment and a type of “minimal” simulation. Minimal simulation has been shown to lead to robust real-world performance, while still maintaining the practical advantages of simulation, such as making it easy for the same benchmark to be used by many researchers. This method is flexible enough to allow researchers to explicitly modify the benchmarks to identify specific task domains where particular hardware excels. To demonstrate the method, we present a set of novel benchmarks that focus on motor control for an arbitrary system with unknown external forces. Using these benchmarks, we show that an error-driven learning rule can consistently improve motor control performance across a randomly generated family of closed-loop simulations, even when there are up to 15 interacting joints to be controlled. PMID:26696820

Non-linear control of a hydraulic piezo-valve using a generalised Prandtl-Ishlinskii hysteresis model

NASA Astrophysics Data System (ADS)

Stefanski, Frederik; Minorowicz, Bartosz; Persson, Johan; Plummer, Andrew; Bowen, Chris

2017-01-01

The potential to actuate proportional flow control valves using piezoelectric ceramics or other smart materials has been investigated for a number of years. Although performance advantages compared to electromagnetic actuation have been demonstrated, a major obstacle has proven to be ferroelectric hysteresis, which is typically 20% for a piezoelectric actuator. In this paper, a detailed study of valve control methods incorporating hysteresis compensation is made for the first time. Experimental results are obtained from a novel spool valve actuated by a multi-layer piezoelectric ring bender. A generalised Prandtl-Ishlinskii model, fitted to experimental training data from the prototype valve, is used to model hysteresis empirically. This form of model is analytically invertible and is used to compensate for hysteresis in the prototype valve both open loop, and in several configurations of closed loop real time control system. The closed loop control configurations use PID (Proportional Integral Derivative) control with either the inverse hysteresis model in the forward path or in a command feedforward path. Performance is compared to both open and closed loop control without hysteresis compensation via step and frequency response results. Results show a significant improvement in accuracy and dynamic performance using hysteresis compensation in open loop, but where valve position feedback is available for closed loop control the improvements are smaller, and so conventional PID control may well be sufficient. It is concluded that the ability to combine state-of-the-art multi-layer piezoelectric bending actuators with either sophisticated hysteresis compensation or closed loop control provides a route for the creation of a new generation of high performance piezoelectric valves.

Microgyroscope with closed loop output

NASA Technical Reports Server (NTRS)

Challoner, A. Dorian (Inventor); Gutierrez, Roman C. (Inventor); Tang, Tony K. (Inventor); Cargille, Donald R. (Inventor)

2002-01-01

A micro-gyroscope (10) having closed loop operation by a control voltage (V.sub.TY), that is demodulated by an output signal of the sense electrodes (S1, S2), providing Coriolis torque rebalance to prevent displacement of the micro-gyroscope (10) on the output axis (y-axis). The present invention provides wide-band, closed-loop operation for a micro-gyroscope (10) and allows the drive frequency to be closely tuned to a high Q sense axis resonance. A differential sense signal (S1-S2) is compensated and fed back by differentially changing the voltage on the drive electrodes to rebalance Coriolis torque. The feedback signal is demodulated in phase with the drive axis signal (K.sub..omega..crclbar..sub.x) to produce a measure of the Coriolis force.

Hippocampal closed-loop modeling and implications for seizure stimulation design

NASA Astrophysics Data System (ADS)

Sandler, Roman A.; Song, Dong; Hampson, Robert E.; Deadwyler, Sam A.; Berger, Theodore W.; Marmarelis, Vasilis Z.

2015-10-01

Objective. Traditional hippocampal modeling has focused on the series of feedforward synapses known as the trisynaptic pathway. However, feedback connections from CA1 back to the hippocampus through the entorhinal cortex (EC) actually make the hippocampus a closed-loop system. By constructing a functional closed-loop model of the hippocampus, one may learn how both physiological and epileptic oscillations emerge and design efficient neurostimulation patterns to abate such oscillations. Approach. Point process input-output models where estimated from recorded rodent hippocampal data to describe the nonlinear dynamical transformation from CA3 → CA1, via the schaffer-collateral synapse, and CA1 → CA3 via the EC. Each Volterra-like subsystem was composed of linear dynamics (principal dynamic modes) followed by static nonlinearities. The two subsystems were then wired together to produce the full closed-loop model of the hippocampus. Main results. Closed-loop connectivity was found to be necessary for the emergence of theta resonances as seen in recorded data, thus validating the model. The model was then used to identify frequency parameters for the design of neurostimulation patterns to abate seizures. Significance. Deep-brain stimulation (DBS) is a new and promising therapy for intractable seizures. Currently, there is no efficient way to determine optimal frequency parameters for DBS, or even whether periodic or broadband stimuli are optimal. Data-based computational models have the potential to be used as a testbed for designing optimal DBS patterns for individual patients. However, in order for these models to be successful they must incorporate the complex closed-loop structure of the seizure focus. This study serves as a proof-of-concept of using such models to design efficient personalized DBS patterns for epilepsy.

The impact of closed-loop electronic medication management on time to first dose: a comparative study between paper and digital hospital environments.

PubMed

Austin, Jodie A; Smith, Ian R; Tariq, Amina

2018-01-22

Closed-loop electronic medication management systems (EMMS) are recognised as an effective intervention to improve medication safety, yet evidence of their effectiveness in hospitals is limited. Few studies have compared medication turnaround time for a closed-loop electronic versus paper-based medication management environment. To compare medication turnaround times in a paper-based hospital environment with a digital hospital equipped with a closed-loop EMMS, consisting of computerised physician order entry, profiled automated dispensing cabinets packaged with unit dose medications and barcode medication administration. Data were collected during 2 weeks at three private hospital sites (one with closed-loop EMMS) within the same organisation network in Queensland, Australia. Time between scheduled and actual administration times was analysed for first dose of time-critical and non-critical medications located on the ward or sourced via pharmacy. Medication turnaround times at the EMMS site were less compared to the paper-based sites (median, IQR: 35 min, 8-57 min versus 120 min, 30-180 min, P < 0.001). For time-critical medications, 77% were administered within 60 min of scheduled time at the EMMS site versus 38% for the paper-based sites. Similar difference was observed for non-critical medications, 80% were administered within 60 min of their scheduled time at the EMMS site versus 41% at the paper-based facilities. The study indicates medication turnaround times utilising a closed-loop EMMS are less compared to paper-based systems. This improvement may be attributable to increased accessibility of medications using automated dispensing cabinets and electronic medication administration records flagging tasks to nurses in real time. © 2018 Royal Pharmaceutical Society.

Applying Computer Models to Realize Closed-Loop Neonatal Oxygen Therapy.

PubMed

Morozoff, Edmund; Smyth, John A; Saif, Mehrdad

2017-01-01

Within the context of automating neonatal oxygen therapy, this article describes the transformation of an idea verified by a computer model into a device actuated by a computer model. Computer modeling of an entire neonatal oxygen therapy system can facilitate the development of closed-loop control algorithms by providing a verification platform and speeding up algorithm development. In this article, we present a method of mathematically modeling the system's components: the oxygen transport within the patient, the oxygen blender, the controller, and the pulse oximeter. Furthermore, within the constraints of engineering a product, an idealized model of the neonatal oxygen transport component may be integrated effectively into the control algorithm of a device, referred to as the adaptive model. Manual and closed-loop oxygen therapy performance were defined in this article by 3 criteria in the following order of importance: percent duration of SpO2 spent in normoxemia (target SpO2 ± 2.5%), hypoxemia (less than normoxemia), and hyperoxemia (more than normoxemia); number of 60-second periods <85% SpO2 and >95% SpO2; and number of manual adjustments. Results from a clinical evaluation that compared the performance of 3 closed-loop control algorithms (state machine, proportional-integral-differential, and adaptive model) with manual oxygen therapy on 7 low-birth-weight ventilated preterm babies, are presented. Compared with manual therapy, all closed-loop control algorithms significantly increased the patients' duration in normoxemia and reduced hyperoxemia (P < 0.05). The number of manual adjustments was also significantly reduced by all of the closed-loop control algorithms (P < 0.05). Although the performance of the 3 control algorithms was equivalent, it is suggested that the adaptive model, with its ease of use, may have the best utility.

Hippocampal closed-loop modeling and implications for seizure stimulation design.

PubMed

Sandler, Roman A; Song, Dong; Hampson, Robert E; Deadwyler, Sam A; Berger, Theodore W; Marmarelis, Vasilis Z

2015-10-01

Traditional hippocampal modeling has focused on the series of feedforward synapses known as the trisynaptic pathway. However, feedback connections from CA1 back to the hippocampus through the entorhinal cortex (EC) actually make the hippocampus a closed-loop system. By constructing a functional closed-loop model of the hippocampus, one may learn how both physiological and epileptic oscillations emerge and design efficient neurostimulation patterns to abate such oscillations. Point process input-output models where estimated from recorded rodent hippocampal data to describe the nonlinear dynamical transformation from CA3 → CA1, via the schaffer-collateral synapse, and CA1 → CA3 via the EC. Each Volterra-like subsystem was composed of linear dynamics (principal dynamic modes) followed by static nonlinearities. The two subsystems were then wired together to produce the full closed-loop model of the hippocampus. Closed-loop connectivity was found to be necessary for the emergence of theta resonances as seen in recorded data, thus validating the model. The model was then used to identify frequency parameters for the design of neurostimulation patterns to abate seizures. Deep-brain stimulation (DBS) is a new and promising therapy for intractable seizures. Currently, there is no efficient way to determine optimal frequency parameters for DBS, or even whether periodic or broadband stimuli are optimal. Data-based computational models have the potential to be used as a testbed for designing optimal DBS patterns for individual patients. However, in order for these models to be successful they must incorporate the complex closed-loop structure of the seizure focus. This study serves as a proof-of-concept of using such models to design efficient personalized DBS patterns for epilepsy.

Hippocampal Closed-Loop Modeling and Implications for Seizure Stimulation Design

PubMed Central

Sandler, Roman A.; Song, Dong; Hampson, Robert E.; Deadwyler, Sam A.; Berger, Theodore W.; Marmarelis, Vasilis Z.

2016-01-01

Objective Traditional hippocampal modeling has focused on the series of feedforward synapses known as the trisynaptic pathway. However, feedback connections from CA1 back to the hippocampus through the Entorhinal Cortex (EC) actually make the hippocampus a closed-loop system. By constructing a functional closed-loop model of the hippocampus, one may learn how both physiological and epileptic oscillations emerge and design efficient neurostimulation patterns to abate such oscillations. Approach Point process input-output models where estimated from recorded rodent hippocampal data to describe the nonlinear dynamical transformation from CA3→CA1, via the Schaffer-Collateral synapse, and CA1→CA3 via the EC. Each Volterra-like subsystem was composed of linear dynamics (Principal Dynamic Modes) followed by static nonlinearities. The two subsystems were then wired together to produce the full closed-loop model of the hippocampus. Main Results Closed-loop connectivity was found to be necessary for the emergence of theta resonances as seen in recorded data, thus validating the model. The model was then used to identify frequency parameters for the design of neurostimulation patterns to abate seizures. Significance DBS is a new and promising therapy for intractable seizures. Currently, there is no efficient way to determine optimal frequency parameters for DBS, or even whether periodic or broadband stimuli are optimal. Data-based computational models have the potential to be used as a testbed for designing optimal DBS patterns for individual patients. However, in order for these models to be successful they must incorporate the complex closed-loop structure of the seizure focus. This study serves as a proof-of-concept of using such models to design efficient personalized DBS patterns for epilepsy. PMID:26355815

Production test IP-544-A, irradiation of 1.6% enriched thick walled single tube elements in KER-1 and 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kratzer, W.K.; Wise, M.J.

1962-12-12

The objective of this production test is to authorize the irradiation of coextruded Zr-2 jacketed thick walled 1.6% enriched tubular elements in KER loops 1 and 2 to evaluate the swelling behavior of fuel elements at high uranium temperatures Coextruded Zr-2 jacketed 1.6% enriched tubular fuel elements 1.79 inch OD, 0.97 inch ID, and 12 inches long will be irradiated KER loops 1 and 2 to exposures no greater than 2500 MWD/T.

Closed-loop conductance scanning tunneling spectroscopy: demonstrating the equivalence to the open-loop alternative.

PubMed

Hellenthal, Chris; Sotthewes, Kai; Siekman, Martin H; Kooij, E Stefan; Zandvliet, Harold J W

2015-01-01

We demonstrate the validity of using closed-loop z(V) conductance scanning tunneling spectroscopy (STS) measurements for the determination of the effective tunneling barrier by comparing them to more conventional open-loop I(z) measurements. Through the development of a numerical model, the individual contributions to the effective tunneling barrier present in these experiments, such as the work function and the presence of an image charge, are determined quantitatively. This opens up the possibility of determining tunneling barriers of both vacuum and molecular systems in an alternative and more detailed manner.

High Torque-to-Inertia Servo System for Stabilizing Sensor Systems. Candidate Systems Include Missile Guidance, Surveillance, and Tracking

DTIC Science & Technology

1980-04-01

specifications ... 3-10 25. Typical isolation curve ... 3-12 26. Servo amp/motor/load frequency response (inner gimbal) ... 4-3 27. Slave loop ( open loop...slave loop ( open loop) frequency response (inner gimbal) . . . 4-4 30. Slave loop (closed loop) frequency response (inner gimbal) ... 4-5 3 . Slave...loop inner gimbal time response ... 4-5 32. Servo amp/motor/load frequency response (outer gimbal) ... 4-6 33. Slave loop ( open loop) uncompensated

Closing the Loop Sampler.

ERIC Educational Resources Information Center

California Integrated Waste Management Board, Sacramento.

Closing the Loop (CTL) is a science curriculum designed to introduce students to integrated waste management through awareness. This document presents five lesson plans focusing on developing an understanding of natural resources, solid wastes, conservation, and the life of landfills. Contents include: (1) "What Are Natural Resources?"; (2)…

Nonlinear predictive control for adaptive adjustments of deep brain stimulation parameters in basal ganglia-thalamic network.

PubMed

Su, Fei; Wang, Jiang; Niu, Shuangxia; Li, Huiyan; Deng, Bin; Liu, Chen; Wei, Xile

2018-02-01

The efficacy of deep brain stimulation (DBS) for Parkinson's disease (PD) depends in part on the post-operative programming of stimulation parameters. Closed-loop stimulation is one method to realize the frequent adjustment of stimulation parameters. This paper introduced the nonlinear predictive control method into the online adjustment of DBS amplitude and frequency. This approach was tested in a computational model of basal ganglia-thalamic network. The autoregressive Volterra model was used to identify the process model based on physiological data. Simulation results illustrated the efficiency of closed-loop stimulation methods (amplitude adjustment and frequency adjustment) in improving the relay reliability of thalamic neurons compared with the PD state. Besides, compared with the 130Hz constant DBS the closed-loop stimulation methods can significantly reduce the energy consumption. Through the analysis of inter-spike-intervals (ISIs) distribution of basal ganglia neurons, the evoked network activity by the closed-loop frequency adjustment stimulation was closer to the normal state. Copyright © 2017 Elsevier Ltd. All rights reserved.

Closed-Loop Process Control for Electron Beam Freeform Fabrication and Deposition Processes

NASA Technical Reports Server (NTRS)

Taminger, Karen M. (Inventor); Hofmeister, William H. (Inventor); Martin, Richard E. (Inventor); Hafley, Robert A. (Inventor)

2013-01-01

A closed-loop control method for an electron beam freeform fabrication (EBF(sup 3)) process includes detecting a feature of interest during the process using a sensor(s), continuously evaluating the feature of interest to determine, in real time, a change occurring therein, and automatically modifying control parameters to control the EBF(sup 3) process. An apparatus provides closed-loop control method of the process, and includes an electron gun for generating an electron beam, a wire feeder for feeding a wire toward a substrate, wherein the wire is melted and progressively deposited in layers onto the substrate, a sensor(s), and a host machine. The sensor(s) measure the feature of interest during the process, and the host machine continuously evaluates the feature of interest to determine, in real time, a change occurring therein. The host machine automatically modifies control parameters to the EBF(sup 3) apparatus to control the EBF(sup 3) process in a closed-loop manner.

Closed loop insulin delivery in diabetes.

PubMed

Battelino, Tadej; Omladič, Jasna Šuput; Phillip, Moshe

2015-06-01

The primary goal of type 1 diabetes treatment is attaining near-normal glucose values. This currently remains out of reach for most people with type 1 diabetes despite intensified insulin treatment in the form of insulin analogues, educational interventions, continuous glucose monitoring, and sensor augmented insulin pump. The main remaining problem is risk of hypoglycaemia, which cannot be sufficiently reduced in all patient groups. Additionally, patients' burn-out often develops with years of tedious day-to-day diabetes management, rendering available diabetes-related technology less efficient. Over the past 40 years, several attempts have been made towards computer-programmed insulin delivery in the form of closed loop, with faster developments especially in the past decade. Automated insulin delivery has reduced human error in glycaemic control and considerably lessened the burden of routine self-management. In this chapter, data from randomized controlled trials with closed-loop insulin delivery that included type 1 diabetes population are summarized, and an evidence-based vision for possible routine utilization of closed loop is provided. Copyright © 2015 Elsevier Ltd. All rights reserved.

Fiber-optic projected-fringe digital interferometry

NASA Technical Reports Server (NTRS)

Mercer, Carolyn R.; Beheim, Glenn

1990-01-01

A phase-stepped projected-fringe interferometer was developed which uses a closed-loop fiber-optic phase-control system to make very accurate surface profile measurements. The closed-loop phase-control system greatly reduces phase-stepping error, which is frequently the dominant source of error in digital interferometers. Two beams emitted from a fiber-optic coupler are combined to form an interference fringe pattern on a diffusely reflecting object. Reflections off of the fibers' output faces are used to create a phase-indicating signal for the closed-loop optical phase controller. The controller steps the phase difference between the two beams by pi/2 radians in order to determine the object's surface profile using a solid-state camera and a computer. The system combines the ease of alignment and automated data reduction of phase-stepping projected-fringe interferometry with the greatly improved phase-stepping accuracy of our closed-loop phase-controller. The system is demonstrated by measuring the profile of a plate containing several convex surfaces whose heights range from 15 to 25 micron high.

Design of multivariable feedback control systems via spectral assignment using reduced-order models and reduced-order observers

NASA Technical Reports Server (NTRS)

Mielke, R. R.; Tung, L. J.; Carraway, P. I., III

1984-01-01

The feasibility of using reduced order models and reduced order observers with eigenvalue/eigenvector assignment procedures is investigated. A review of spectral assignment synthesis procedures is presented. Then, a reduced order model which retains essential system characteristics is formulated. A constant state feedback matrix which assigns desired closed loop eigenvalues and approximates specified closed loop eigenvectors is calculated for the reduced order model. It is shown that the eigenvalue and eigenvector assignments made in the reduced order system are retained when the feedback matrix is implemented about the full order system. In addition, those modes and associated eigenvectors which are not included in the reduced order model remain unchanged in the closed loop full order system. The full state feedback design is then implemented by using a reduced order observer. It is shown that the eigenvalue and eigenvector assignments of the closed loop full order system rmain unchanged when a reduced order observer is used. The design procedure is illustrated by an actual design problem.

Linear state feedback, quadratic weights, and closed loop eigenstructures. M.S. Thesis

NASA Technical Reports Server (NTRS)

Thompson, P. M.

1979-01-01

Results are given on the relationships between closed loop eigenstructures, state feedback gain matrices of the linear state feedback problem, and quadratic weights of the linear quadratic regulator. Equations are derived for the angles of general multivariable root loci and linear quadratic optimal root loci, including angles of departure and approach. The generalized eigenvalue problem is used for the first time to compute angles of approach. Equations are also derived to find the sensitivity of closed loop eigenvalues and the directional derivatives of closed loop eigenvectors (with respect to a scalar multiplying the feedback gain matrix or the quadratic control weight). An equivalence class of quadratic weights that produce the same asymptotic eigenstructure is defined, sufficient conditions to be in it are given, a canonical element is defined, and an algorithm to find it is given. The behavior of the optimal root locus in the nonasymptotic region is shown to be different for quadratic weights with the same asymptotic properties.

Design of multivariable feedback control systems via spectral assignment using reduced-order models and reduced-order observers

NASA Technical Reports Server (NTRS)

Mielke, R. R.; Tung, L. J.; Carraway, P. I., III

1985-01-01

The feasibility of using reduced order models and reduced order observers with eigenvalue/eigenvector assignment procedures is investigated. A review of spectral assignment synthesis procedures is presented. Then, a reduced order model which retains essential system characteristics is formulated. A constant state feedback matrix which assigns desired closed loop eigenvalues and approximates specified closed loop eigenvectors is calculated for the reduced order model. It is shown that the eigenvalue and eigenvector assignments made in the reduced order system are retained when the feedback matrix is implemented about the full order system. In addition, those modes and associated eigenvectors which are not included in the reduced order model remain unchanged in the closed loop full order system. The fulll state feedback design is then implemented by using a reduced order observer. It is shown that the eigenvalue and eigenvector assignments of the closed loop full order system remain unchanged when a reduced order observer is used. The design procedure is illustrated by an actual design problem.

First Results from a Hardware-in-the-Loop Demonstration of Closed-Loop Autonomous Formation Flying

NASA Technical Reports Server (NTRS)

Gill, E.; Naasz, Bo; Ebinuma, T.

2003-01-01

A closed-loop system for the demonstration of formation flying technologies has been developed at NASA s Goddard Space Flight Center. Making use of a GPS signal simulator with a dual radio frequency outlet, the system includes two GPS space receivers as well as a powerful onboard navigation processor dedicated to the GPS-based guidance, navigation, and control of a satellite formation in real-time. The closed-loop system allows realistic simulations of autonomous formation flying scenarios, enabling research in the fields of tracking and orbit control strategies for a wide range of applications. A sample scenario has been set up where the autonomous transition of a satellite formation from an initial along-track separation of 800 m to a final distance of 100 m has been demonstrated. As a result, a typical control accuracy of about 5 m has been achieved which proves the applicability of autonomous formation flying techniques to formations of satellites as close as 50 m.

Edge-on dislocation loop in anisotropic hcp zirconium thin foil

NASA Astrophysics Data System (ADS)

Wu, Wenwang; Xia, Re; Qian, Guian; Xu, Shucai; Zhang, Jinhuan

2015-10-01

Edge-on dislocation loops with 〈 a 〉 -type and 〈 c 〉 -type of Burgers vectors can be formed on prismatic or basel habit planes of hexagonal close-packed (hcp) zirconium alloys during in-situ ion irradiation and neutron irradiation experiments. In this work, an anisotropic image stress method was employed to analyze the free surface effects of dislocation loops within hcp Zr thin foils. Calculation results demonstrate that image stress has a remarkable effect on the distortion fields of dislocation loops within infinite medium, and the image energy becomes remarkable when dislocation loops are situated close to the free surfaces. Moreover, image forces of the 1 / 2 〈 0001 〉 (0001) dislocation loop within (0001) thin foil is much stronger than that of the 1 / 3 〈 11 2 bar 0 〉 (11 2 bar 0) dislocation loop within (11 2 bar 0) thin foil of identical geometrical configurations. Finally, image stress effect on the physical behaviors of loops during in-situ ion irradiation experiments is discussed.

Equilibrium Moisture Content of Common Fine Fuels in Southeastern Forests

Treesearch

W.H. Blackmarr

1971-01-01

Nine different kinds of forest litter found in ground fuel complexes of southeastern forests were subjected to step-wise changes in relative humidity to determine their equilibrium moisture content (EMC) at different levels of relative humidity. The adsorption and desorption EMC curves for these fuels exhibited the typical hysteresis loop...

Falcon: a highly flexible open-source software for closed-loop neuroscience.

PubMed

Ciliberti, Davide; Kloosterman, Fabian

2017-08-01

Closed-loop experiments provide unique insights into brain dynamics and function. To facilitate a wide range of closed-loop experiments, we created an open-source software platform that enables high-performance real-time processing of streaming experimental data. We wrote Falcon, a C++ multi-threaded software in which the user can load and execute an arbitrary processing graph. Each node of a Falcon graph is mapped to a single thread and nodes communicate with each other through thread-safe buffers. The framework allows for easy implementation of new processing nodes and data types. Falcon was tested both on a 32-core and a 4-core workstation. Streaming data was read from either a commercial acquisition system (Neuralynx) or the open-source Open Ephys hardware, while closed-loop TTL pulses were generated with a USB module for digital output. We characterized the round-trip latency of our Falcon-based closed-loop system, as well as the specific latency contribution of the software architecture, by testing processing graphs with up to 32 parallel pipelines and eight serial stages. We finally deployed Falcon in a task of real-time detection of population bursts recorded live from the hippocampus of a freely moving rat. On Neuralynx hardware, round-trip latency was well below 1 ms and stable for at least 1 h, while on Open Ephys hardware latencies were below 15 ms. The latency contribution of the software was below 0.5 ms. Round-trip and software latencies were similar on both 32- and 4-core workstations. Falcon was used successfully to detect population bursts online with ~40 ms average latency. Falcon is a novel open-source software for closed-loop neuroscience. It has sub-millisecond intrinsic latency and gives the experimenter direct control of CPU resources. We envisage Falcon to be a useful tool to the neuroscientific community for implementing a wide variety of closed-loop experiments, including those requiring use of complex data structures and real-time execution of computationally intensive algorithms, such as population neural decoding/encoding from large cell assemblies.

Falcon: a highly flexible open-source software for closed-loop neuroscience

NASA Astrophysics Data System (ADS)

Ciliberti, Davide; Kloosterman, Fabian

2017-08-01

Objective. Closed-loop experiments provide unique insights into brain dynamics and function. To facilitate a wide range of closed-loop experiments, we created an open-source software platform that enables high-performance real-time processing of streaming experimental data. Approach. We wrote Falcon, a C++ multi-threaded software in which the user can load and execute an arbitrary processing graph. Each node of a Falcon graph is mapped to a single thread and nodes communicate with each other through thread-safe buffers. The framework allows for easy implementation of new processing nodes and data types. Falcon was tested both on a 32-core and a 4-core workstation. Streaming data was read from either a commercial acquisition system (Neuralynx) or the open-source Open Ephys hardware, while closed-loop TTL pulses were generated with a USB module for digital output. We characterized the round-trip latency of our Falcon-based closed-loop system, as well as the specific latency contribution of the software architecture, by testing processing graphs with up to 32 parallel pipelines and eight serial stages. We finally deployed Falcon in a task of real-time detection of population bursts recorded live from the hippocampus of a freely moving rat. Main results. On Neuralynx hardware, round-trip latency was well below 1 ms and stable for at least 1 h, while on Open Ephys hardware latencies were below 15 ms. The latency contribution of the software was below 0.5 ms. Round-trip and software latencies were similar on both 32- and 4-core workstations. Falcon was used successfully to detect population bursts online with ~40 ms average latency. Significance. Falcon is a novel open-source software for closed-loop neuroscience. It has sub-millisecond intrinsic latency and gives the experimenter direct control of CPU resources. We envisage Falcon to be a useful tool to the neuroscientific community for implementing a wide variety of closed-loop experiments, including those requiring use of complex data structures and real-time execution of computationally intensive algorithms, such as population neural decoding/encoding from large cell assemblies.

Identifiability and Performance Analysis of Output Over-sampling Approach to Direct Closed-loop Identification

NASA Astrophysics Data System (ADS)

Sun, Lianming; Sano, Akira

Output over-sampling based closed-loop identification algorithm is investigated in this paper. Some instinct properties of the continuous stochastic noise and the plant input, output in the over-sampling approach are analyzed, and they are used to demonstrate the identifiability in the over-sampling approach and to evaluate its identification performance. Furthermore, the selection of plant model order, the asymptotic variance of estimated parameters and the asymptotic variance of frequency response of the estimated model are also explored. It shows that the over-sampling approach can guarantee the identifiability and improve the performance of closed-loop identification greatly.

Closed-Loop Analysis of Soft Decisions for Serial Links

NASA Technical Reports Server (NTRS)

Lansdowne, Chatwin A.; Steele, Glen F.; Zucha, Joan P.; Schlensinger, Adam M.

2012-01-01

Modern receivers are providing soft decision symbol synchronization as radio links are challenged to push more data and more overhead through noisier channels, and software-defined radios use error-correction techniques that approach Shannon s theoretical limit of performance. The authors describe the benefit of closed-loop measurements for a receiver when paired with a counterpart transmitter and representative channel conditions. We also describe a real-time Soft Decision Analyzer (SDA) implementation for closed-loop measurements on single- or dual- (orthogonal) channel serial data communication links. The analyzer has been used to identify, quantify, and prioritize contributors to implementation loss in real-time during the development of software defined radios.

Artificial intelligence programming with LabVIEW: genetic algorithms for instrumentation control and optimization.

PubMed

Moore, J H

1995-06-01

A genetic algorithm for instrumentation control and optimization was developed using the LabVIEW graphical programming environment. The usefulness of this methodology for the optimization of a closed loop control instrument is demonstrated with minimal complexity and the programming is presented in detail to facilitate its adaptation to other LabVIEW applications. Closed loop control instruments have variety of applications in the biomedical sciences including the regulation of physiological processes such as blood pressure. The program presented here should provide a useful starting point for those wishing to incorporate genetic algorithm approaches to LabVIEW mediated optimization of closed loop control instruments.

Development of closed loop roll control for magnetic balance systems

NASA Technical Reports Server (NTRS)

Covert, E. E.; Haldeman, C. W.; Ramohalli, G.; Way, P.

1982-01-01

This research was undertaken with the goal of demonstrating closed loop control of the roll degree of freedom on the NASA prototype magnetic suspension and balance system at the MIT Aerophysics Laboratory, thus, showing feasibility for a roll control system for any large magnetic balance system which might be built in the future. During the research under this grant, study was directed toward the several areas of torque generation, position sensing, model construction and control system design. These effects were then integrated to produce successful closed loop operation of the analogue roll control system. This experience indicated the desirability of microprocessor control for the angular degrees of freedom.

On the feasibility of closed-loop control of intra-aortic balloon pumping

NASA Technical Reports Server (NTRS)

Clark, J. W., Jr.; Bourland, H. M.; Kane, G. R.

1973-01-01

A closed-loop control scheme for the control of intra-aortic balloon pumping has been developed and tested in dog experiments. A performance index reflecting the general objectives of balloon-assist pumping is developed and a modified steepest ascent control algorithm is utilized for the selection of a proper operating point for the balloon during its pumping cycle. This paper attempts to indicate the feasibility of closed-loop control of balloon pumping, and particularly its flexibility in achieving both diastolic augmentation of mean aortic pressure and control of the level of end-diastolic pressure (EDP) an important factor in reducing heart work.

Explicit knowledge about the availability of visual feedback affects grasping with the left but not the right hand.

PubMed

Tang, Rixin; Whitwell, Robert L; Goodale, Melvyn A

2014-01-01

Previous research (Whitwell et al. in Exp Brain Res 188:603-611, 2008; Whitwell and Goodale in Exp Brain Res 194:619-629, 2009) has shown that trial history, but not anticipatory knowledge about the presence or absence of visual feedback on an upcoming trial, plays a vital role in determining how that feedback is exploited when grasping with the right hand. Nothing is known about how the non-dominant left hand behaves under the same feedback regimens. In present study, therefore, we compared peak grip aperture (PGA) for left- and right-hand grasps executed with and without visual feedback (i.e., closed- vs. open-loop conditions) in right-handed individuals under three different trial schedules: the feedback conditions were blocked separately, they were randomly interleaved, or they were alternated. When feedback conditions were blocked, the PGA was much larger for open-loop trials as compared to closed-loop trials, although this difference was more pronounced for right-hand grasps than left-hand grasps. Like Whitwell et al., we found that mixing open- and closed-loop trials together, compared to blocking them separately, homogenized the PGA for open- and closed-loop grasping in the right hand (i.e., the PGAs became smaller on open-loop trials and larger on closed-loop trials). In addition, the PGAs for right-hand grasps were entirely determined by trial history and not by knowledge of whether or not visual feedback would be available on an upcoming trial. In contrast to grasps made with the right hand, grasps made by the left hand were affected both by trial history and by anticipatory knowledge of the upcoming visual feedback condition. But these effects were observed only on closed-loop trials, i.e., the PGAs of grasps made with the left hand on closed-loop trials were smaller when participants could anticipate the availability of feedback on an upcoming trial (alternating trials) than when they could not (randomized trials). In contrast, grasps made with the left hand on open-loop trials exhibited the same large PGAs under all feedback schedules: blocked, random, or alternating. In other words, there was no evidence for homogenization. Taken together, these results suggest that in addition to the real-time demands of the task, such as the target's size and position and the availability of visual feedback, the initial (i.e., pre-movement) programming of right-hand grasping relies on what happened on the previous trial, whereas the programming of left-hand grasping is more cognitively supervised and exploits explicit information about trial order to prepare for an upcoming trial.

A Method for Precision Closed-Loop Irrigation Using a Modified PID Control Algorithm

NASA Astrophysics Data System (ADS)

Goodchild, Martin; Kühn, Karl; Jenkins, Malcolm; Burek, Kazimierz; Dutton, Andrew

2016-04-01

The benefits of closed-loop irrigation control have been demonstrated in grower trials which show the potential for improved crop yields and resource usage. Managing water use by controlling irrigation in response to soil moisture changes to meet crop water demands is a popular approach but requires knowledge of closed-loop control practice. In theory, to obtain precise closed-loop control of a system it is necessary to characterise every component in the control loop to derive the appropriate controller parameters, i.e. proportional, integral & derivative (PID) parameters in a classic PID controller. In practice this is often difficult to achieve. Empirical methods are employed to estimate the PID parameters by observing how the system performs under open-loop conditions. In this paper we present a modified PID controller, with a constrained integral function, that delivers excellent regulation of soil moisture by supplying the appropriate amount of water to meet the needs of the plant during the diurnal cycle. Furthermore, the modified PID controller responds quickly to changes in environmental conditions, including rainfall events which can result in: controller windup, under-watering and plant stress conditions. The experimental work successfully demonstrates the functionality of a constrained integral PID controller that delivers robust and precise irrigation control. Coir substrate strawberry growing trial data is also presented illustrating soil moisture control and the ability to match water deliver to solar radiation.

Relative stability of the open and closed conformations of the active site loop of streptavidin

NASA Astrophysics Data System (ADS)

Ignacio J., General; Meirovitch, Hagai

2011-01-01

The eight-residue surface loop, 45-52 (Ser, Ala, Val, Gly, Asn, Ala, Glu, Ser), of the homotetrameric protein streptavidin has a "closed" conformation in the streptavidin-biotin complex, where the corresponding binding affinity is one of the strongest found in nature (ΔG ˜ -18 kcal/mol). However, in most of the crystal structures of apo (unbound) streptavidin, the loop conformation is "open" and typically exhibits partial disorder and high B-factors. Thus, it is plausible to assume that the loop structure is changed from open to closed upon binding of biotin, and the corresponding difference in free energy, ΔF = Fopen - Fclosed in the unbound protein, should therefore be considered in the total absolute free energy of binding. ΔF (which has generally been neglected) is calculated here using our "hypothetical scanning molecular-dynamics" (HSMD) method. We use a protein model in which only the atoms closest to the loop are considered (the "template") and they are fixed in the x-ray coordinates of the free protein; the x-ray conformation of the closed loop is attached to the same (unbound) template and both systems are capped with the same sphere of TIP3P water. Using the force field of the assisted model building with energy refinement (AMBER), we carry out two separate MD simulations (at temperature T = 300 K), starting from the open and closed conformations, where only the atoms of the loop and water are allowed to move (the template-water and template-loop interactions are considered). The absolute Fopen and Fclosed (of loop + water) are calculated from these trajectories, where the loop and water contributions are obtained by HSMD and a thermodynamic integration (TI) process, respectively. The combined HSMD-TI procedure leads to total (loop + water) ΔF = -27.1 ± 2.0 kcal/mol, where the entropy TΔS constitutes 34% of ΔF, meaning that the effect of S is significant and should not be ignored. Also, ΔS is positive, in accord with the high flexibility of the open loop observed in crystal structures, while the energy ΔE is unexpectedly negative, thus also adding to the stability of the open loop. The loop and the 250 capped water molecules are the largest system studied thus far, which constitutes a test for the efficiency of HSMD-TI; this efficiency and technical issues related to the implementation of the method are also discussed. Finally, the result for ΔF is a prediction that will be considered in the calculation of the absolute free energy of binding of biotin to streptavidin, which constitutes our next project.

Innovative design of closing loops producing an optimal force system applicable in the 0.022-in bracket slot system.

PubMed

Sumi, Mayumi; Koga, Yoshiyuki; Tominaga, Jun-Ya; Hamanaka, Ryo; Ozaki, Hiroya; Chiang, Pao-Chang; Yoshida, Noriaki

2016-12-01

Most closing loops designed for producing higher moment-to-force (M/F) ratios require complex wire bending and are likely to cause hygiene problems and discomfort because of their complicated configurations. We aimed to develop a simple loop design that can produce optimal force and M/F ratio. A loop design that can generate a high M/F ratio and the ideal force level was investigated by varying the portion and length of the cross-sectional reduction of a teardrop loop and the loop position. The forces and moments acting on closing loops were calculated using structural analysis based on the tangent stiffness method. An M/F ratio of 9.3 (high enough to achieve controlled movement of the anterior teeth) and an optimal force level of approximately 250 g of force can be generated by activation of a 10-mm-high teardrop loop whose cross-section of 0.019 × 0.025 or 0.021 × 0.025 in was reduced in thickness by 50% for a distance of 3 mm from the apex, located between a quarter and a third of the interbracket distance from the canine bracket. The simple loop design that we developed delivers an optimal force and an M/F ratio for the retraction of anterior teeth, and is applicable in a 0.022-in slot system. Copyright © 2016 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

A platform for dynamic simulation and control of movement based on OpenSim and MATLAB.

PubMed

Mansouri, Misagh; Reinbolt, Jeffrey A

2012-05-11

Numerical simulations play an important role in solving complex engineering problems and have the potential to revolutionize medical decision making and treatment strategies. In this paper, we combine the rapid model-based design, control systems and powerful numerical method strengths of MATLAB/Simulink with the simulation and human movement dynamics strengths of OpenSim by developing a new interface between the two software tools. OpenSim is integrated with Simulink using the MATLAB S-function mechanism, and the interface is demonstrated using both open-loop and closed-loop control systems. While the open-loop system uses MATLAB/Simulink to separately reproduce the OpenSim Forward Dynamics Tool, the closed-loop system adds the unique feature of feedback control to OpenSim, which is necessary for most human movement simulations. An arm model example was successfully used in both open-loop and closed-loop cases. For the open-loop case, the simulation reproduced results from the OpenSim Forward Dynamics Tool with root mean square (RMS) differences of 0.03° for the shoulder elevation angle and 0.06° for the elbow flexion angle. MATLAB's variable step-size integrator reduced the time required to generate the forward dynamic simulation from 7.1s (OpenSim) to 2.9s (MATLAB). For the closed-loop case, a proportional-integral-derivative controller was used to successfully balance a pole on model's hand despite random force disturbances on the pole. The new interface presented here not only integrates the OpenSim and MATLAB/Simulink software tools, but also will allow neuroscientists, physiologists, biomechanists, and physical therapists to adapt and generate new solutions as treatments for musculoskeletal conditions. Copyright © 2012 Elsevier Ltd. All rights reserved.

A platform for dynamic simulation and control of movement based on OpenSim and MATLAB

PubMed Central

Mansouri, Misagh; Reinbolt, Jeffrey A.

2013-01-01

Numerical simulations play an important role in solving complex engineering problems and have the potential to revolutionize medical decision making and treatment strategies. In this paper, we combine the rapid model-based design, control systems and powerful numerical method strengths of MATLAB/Simulink with the simulation and human movement dynamics strengths of OpenSim by developing a new interface between the two software tools. OpenSim is integrated with Simulink using the MATLAB S-function mechanism, and the interface is demonstrated using both open-loop and closed-loop control systems. While the open-loop system uses MATLAB/Simulink to separately reproduce the OpenSim Forward Dynamics Tool, the closed-loop system adds the unique feature of feedback control to OpenSim, which is necessary for most human movement simulations. An arm model example was successfully used in both open-loop and closed-loop cases. For the open-loop case, the simulation reproduced results from the OpenSim Forward Dynamics Tool with root mean square (RMS) differences of 0.03° for the shoulder elevation angle and 0.06° for the elbow flexion angle. MATLAB’s variable step-size integrator reduced the time required to generate the forward dynamic simulation from 7.1 s (OpenSim) to 2.9 s (MATLAB). For the closed-loop case, a proportional–integral–derivative controller was used to successfully balance a pole on model’s hand despite random force disturbances on the pole. The new interface presented here not only integrates the OpenSim and MATLAB/Simulink software tools, but also will allow neuroscientists, physiologists, biomechanists, and physical therapists to adapt and generate new solutions as treatments for musculoskeletal conditions. PMID:22464351

Sensing mode coupling analysis for dual-mass MEMS gyroscope and bandwidth expansion within wide-temperature range

NASA Astrophysics Data System (ADS)

Cao, Huiliang; Li, Hongsheng; Shao, Xingling; Liu, Zhiyu; Kou, Zhiwei; Shan, Yanhu; Shi, Yunbo; Shen, Chong; Liu, Jun

2018-01-01

This paper presents the bandwidth expanding method with wide-temperature range for sense mode coupling dual-mass MEMS gyro. The real sensing mode of the gyroscope is analyzed to be the superposition of in-phase and anti-phase sensing modes. The mechanical sensitivity and bandwidth of the gyroscope structure are conflicted with each other and both governed by the frequency difference between sensing and drive modes (min {Δω1, Δω2}). The sensing mode force rebalancing combs stimulation method (FRCSM) is presented to simulate the Coriolis force, and based on this method, the gyro's dynamic characteristics are tested. The sensing closed- loop controller is achieved by operational amplifier based on phase lead method, which enable the magnitude margin and phase margin of the system to reach 7.21 dB and 34.6° respectively, and the closed-loop system also expands gyro bandwidth from 13 Hz (sensing open-loop) to 102 Hz (sensing closed-loop). What's more, the turntable test results show that the sensing closed-loop works stably in wide-temperature range (from -40 °C to 60 °C) and the bandwidth values are 107 Hz @-40 °C and 97 Hz @60 °C. The results indicate that the higher temperature causes lower bandwidth, and verify the simulation results are 103 Hz @-40 °C and 98.2 Hz @60 °C. The new bottleneck of the closed loop bandwidth is the valley generated by conjugate zeros, which is formed by superposition of sensing modes.

Smart Braid Feedback for the Closed-Loop Control of Soft Robotic Systems.

PubMed

Felt, Wyatt; Chin, Khai Yi; Remy, C David

2017-09-01

This article experimentally investigates the potential of using flexible, inductance-based contraction sensors in the closed-loop motion control of soft robots. Accurate motion control remains a highly challenging task for soft robotic systems. Precise models of the actuation dynamics and environmental interactions are often unavailable. This renders open-loop control impossible, while closed-loop control suffers from a lack of suitable feedback. Conventional motion sensors, such as linear or rotary encoders, are difficult to adapt to robots that lack discrete mechanical joints. The rigid nature of these sensors runs contrary to the aspirational benefits of soft systems. As truly soft sensor solutions are still in their infancy, motion control of soft robots has so far relied on laboratory-based sensing systems such as motion capture, electromagnetic (EM) tracking, or Fiber Bragg Gratings. In this article, we used embedded flexible sensors known as Smart Braids to sense the contraction of McKibben muscles through changes in inductance. We evaluated closed-loop control on two systems: a revolute joint and a planar, one degree of freedom continuum manipulator. In the revolute joint, our proposed controller compensated for elasticity in the actuator connections. The Smart Braid feedback allowed motion control with a steady-state root-mean-square (RMS) error of [1.5]°. In the continuum manipulator, Smart Braid feedback enabled tracking of the desired tip angle with a steady-state RMS error of [1.25]°. This work demonstrates that Smart Braid sensors can provide accurate position feedback in closed-loop motion control suitable for field applications of soft robotic systems.

Inverted Pendulum Standing Apparatus for Investigating Closed-Loop Control of Ankle Joint Muscle Contractions during Functional Electrical Stimulation.

PubMed

Tan, John F; Masani, Kei; Vette, Albert H; Zariffa, José; Robinson, Mark; Lynch, Cheryl; Popovic, Milos R

2014-01-01

The restoration of arm-free standing in individuals with paraplegia can be facilitated via functional electrical stimulation (FES). In developing adequate control strategies for FES systems, it remains challenging to test the performance of a particular control scheme on human subjects. In this study, we propose a testing platform for developing effective control strategies for a closed-loop FES system for standing. The Inverted Pendulum Standing Apparatus (IPSA) is a mechanical inverted pendulum, whose angular position is determined by the subject's ankle joint angle as controlled by the FES system while having the subject's body fixed in a standing frame. This approach provides a setup that is safe, prevents falling, and enables a research and design team to rigorously test various closed-loop controlled FES systems applied to the ankle joints. To demonstrate the feasibility of using the IPSA, we conducted a case series that employed the device for studying FES closed-loop controllers for regulating ankle joint kinematics during standing. The utilized FES system stimulated, in able-bodied volunteers, the plantarflexors as they prevent toppling during standing. Four different conditions were compared, and we were able to show unique performance of each condition using the IPSA. We concluded that the IPSA is a useful tool for developing and testing closed-loop controlled FES systems for regulating ankle joint position during standing.

Inverted Pendulum Standing Apparatus for Investigating Closed-Loop Control of Ankle Joint Muscle Contractions during Functional Electrical Stimulation

PubMed Central

Tan, John F.; Masani, Kei; Vette, Albert H.; Zariffa, José; Robinson, Mark; Lynch, Cheryl; Popovic, Milos R.

2014-01-01

The restoration of arm-free standing in individuals with paraplegia can be facilitated via functional electrical stimulation (FES). In developing adequate control strategies for FES systems, it remains challenging to test the performance of a particular control scheme on human subjects. In this study, we propose a testing platform for developing effective control strategies for a closed-loop FES system for standing. The Inverted Pendulum Standing Apparatus (IPSA) is a mechanical inverted pendulum, whose angular position is determined by the subject's ankle joint angle as controlled by the FES system while having the subject's body fixed in a standing frame. This approach provides a setup that is safe, prevents falling, and enables a research and design team to rigorously test various closed-loop controlled FES systems applied to the ankle joints. To demonstrate the feasibility of using the IPSA, we conducted a case series that employed the device for studying FES closed-loop controllers for regulating ankle joint kinematics during standing. The utilized FES system stimulated, in able-bodied volunteers, the plantarflexors as they prevent toppling during standing. Four different conditions were compared, and we were able to show unique performance of each condition using the IPSA. We concluded that the IPSA is a useful tool for developing and testing closed-loop controlled FES systems for regulating ankle joint position during standing. PMID:27350992

Learning from ISS-modular adaptive NN control of nonlinear strict-feedback systems.

PubMed

Wang, Cong; Wang, Min; Liu, Tengfei; Hill, David J

2012-10-01

This paper studies learning from adaptive neural control (ANC) for a class of nonlinear strict-feedback systems with unknown affine terms. To achieve the purpose of learning, a simple input-to-state stability (ISS) modular ANC method is first presented to ensure the boundedness of all the signals in the closed-loop system and the convergence of tracking errors in finite time. Subsequently, it is proven that learning with the proposed stable ISS-modular ANC can be achieved. The cascade structure and unknown affine terms of the considered systems make it very difficult to achieve learning using existing methods. To overcome these difficulties, the stable closed-loop system in the control process is decomposed into a series of linear time-varying (LTV) perturbed subsystems with the appropriate state transformation. Using a recursive design, the partial persistent excitation condition for the radial basis function neural network (NN) is established, which guarantees exponential stability of LTV perturbed subsystems. Consequently, accurate approximation of the closed-loop system dynamics is achieved in a local region along recurrent orbits of closed-loop signals, and learning is implemented during a closed-loop feedback control process. The learned knowledge is reused to achieve stability and an improved performance, thereby avoiding the tremendous repeated training process of NNs. Simulation studies are given to demonstrate the effectiveness of the proposed method.

Demonstration of a vectorial optical field generator with adaptive close loop control.

PubMed

Chen, Jian; Kong, Lingjiang; Zhan, Qiwen

2017-12-01

We experimentally demonstrate a vectorial optical field generator (VOF-Gen) with an adaptive close loop control. The close loop control capability is illustrated with the calibration of polarization modulation of the system. To calibrate the polarization ratio modulation, we generate 45° linearly polarized beam and make it propagate through a linear analyzer whose transmission axis is orthogonal to the incident beam. For the retardation calibration, circularly polarized beam is employed and a circular polarization analyzer with the opposite chirality is placed in front of the CCD as the detector. In both cases, the close loop control automatically changes the value of the corresponding calibration parameters in the pre-set ranges to generate the phase patterns applied to the spatial light modulators and records the intensity distribution of the output beam by the CCD camera. The optimized calibration parameters are determined corresponding to the minimum total intensity in each case. Several typical kinds of vectorial optical beams are created with and without the obtained calibration parameters, and the full Stokes parameter measurements are carried out to quantitatively analyze the polarization distribution of the generated beams. The comparisons among these results clearly show that the obtained calibration parameters could remarkably improve the accuracy of the polarization modulation of the VOF-Gen, especially for generating elliptically polarized beam with large ellipticity, indicating the significance of the presented close loop in enhancing the performance of the VOF-Gen.

Development of a closed-loop system for tremor suppression in patients with Parkinson's disease.

PubMed

Xu, F L; Hao, M Z; Xu, S Q; Hu, Z X; Xiao, Q; Lan, N

2016-08-01

More than 70% of patients suffering Parkinson's disease (PD) exhibit resting tremor in their extremities, hampering their ability to perform daily activities. Based on our earlier studies on corticospinal transmission of tremor signals [10,11], we hypothesize that cutaneous afferents evoked by surface stimulation can produce an inhibitory effect on propriospinal neurons (PN), which in turn will suppress tremor signals passing through the PN. This paper presents the development of a closed-loop system for tremor suppression by transcutaneous electrical nerve stimulation (TENS) of sensory fibers beneath the skin. The closed-loop system senses EMGs of forearm muscles, and detects rhythmic bursting in the EMG signal. When a tremor is detected by the system, a command signal triggers a stimulator to output a train of bi-phasic, current regulated pulses to a pair of surface electrodes. The stimulation electrode is placed on the dorsal hand skin near the metacarpophalangeal joint of index finger, which is innervated by the superficial radial nerve that projects an inhibitory afferent to PNs of forearm muscles. We tested the closed-loop system in 3 normal subjects to verify the algorithm and in 2 tremor dominated PD subjects for feasibility of tremor detecting and suppression. Preliminary results indicate that the closed-loop system can detect tremor in all subjects, and tremor in PD patients was suppressed significantly by electrical stimulation of cutaneous afferents.

Rational Design of Mixed-Metal Oxides for Chemical Looping Combustion of Coal via Coupled Computational-Experimental Studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mishra, Amit; Li, Fanxing; Santiso, Erik

Energy and global climate change are two grand challenges to the modern society. An urgent need exists for development of clean and efficient energy conversion processes. The chemical looping strategy, which utilizes regenerable oxygen carriers (OCs) to indirectly convert carbonaceous fuels via redox reactions, is considered to be one of the more promising approaches for CO2 capture by the U.S. Department of Energy (USDOE). To date, most long-term chemical looping operations were conducted using gaseous fuels, even though direct conversion of coal is more desirable from both economics and CO2 capture viewpoints. The main challenges for direct coal conversion residemore » in the stringent requirements on oxygen carrier performances. In addition, coal char and volatile compounds are more challenging to convert than gaseous fuels. A promising approach for direct conversion of coal is the so called chemical looping with oxygen uncoupling (CLOU) technique. In the CLOU process, a metal oxide that decomposes at the looping temperature, and releases oxygen to the gas phase is used as the OC. The overarching objective of this project was to discover the fundamental principles for rational design and optimization of oxygen carriers (OC) in coal chemical looping combustion (CLC) processes. It directly addresses Topic Area B of the funding opportunity announcement (FOA) in terms of “predictive description of the phase behavior and mechanical properties” of “mixed metal oxide” based OCs and rational development of new OC materials with superior functionality. This was achieved through studies exploring i) iron-containing mixed-oxide composites as oxygen carriers for CLOU, ii) Ca1-xAxMnO3-δ (A = Sr and Ba) as oxygen carriers for CLOU, iii) CaMn1-xBxO3-δ (B=Al, V, Fe, Co, and Ni) as oxygen carrier for CLOU and iv) vacancy creation energy in Mn-containing perovskites as an indicator chemical looping with oxygen uncoupling.« less

Accessibility, stabilizability, and feedback control of continuous orbital transfer.

PubMed

Gurfil, Pini

2004-05-01

This paper investigates the problem of low-thrust orbital transfer using orbital element feedback from a control-theoretic standpoint, concepts of controllability, feedback stabilizability, and their interaction. The Gauss variational equations (GVEs) are used to model the state-space dynamics. First, the notion of accessibility, a weaker form of controllability, is presented. It is then shown that the GVEs are globally accessible. Based on the accessibility result, a nonlinear feedback controller is derived that asymptotically steers a vehicle from an initial elliptic Keplerian orbit to any given elliptic Keplerian orbit. The performance of the new controller is illustrated by simulating an orbital transfer between two geosynchronous Earth orbits. It is shown that the low-thrust controller requires less fuel than an impulsive maneuver for the same transfer time. Closed-form, analytic expressions for the new orbital transfer controller are given. Finally, it is proved, based on a topological nonlinear stabilizability test, that there does not exist a continuous closed-loop controller that can transfer a spacecraft to a parabolic escape trajectory.

A model for technology assessment as applied to closed loop infusion systems. Technology Assessment Task Force of the Society of Critical Care Medicine.

PubMed

Jastremski, M; Jastremski, C; Shepherd, M; Friedman, V; Porembka, D; Smith, R; Gonzales, E; Swedlow, D; Belzberg, H; Crass, R

1995-10-01

To test a model for the assessment of critical care technology on closed loop infusion control, a technology that is in its early stages of development and testing on human subjects. A computer-assisted search of the English language literature and reviews of the gathered data by experts in the field of closed loop infusion control systems. Studies relating to closed loop infusion control that addressed one or more of the questions contained in our technology assessment template were analyzed. Study design was not a factor in article selection. However, the lack of well-designed clinical outcome studies was an important factor in determining our conclusions. A focus person summarized the data from the selected studies that related to each of the assessment questions. The preliminary data summary developed by the focus person was further analyzed and refined by the task force. Experts in closed loop systems were then added to the group to review the summary provided by the task force. These experts' comments were considered by the task force and this final consensus report was developed. Closed loop system control is a technological concept that may be applicable to several aspects of critical care practice. This is a technology in the early stages of evolution and much more research and data are needed before its introduction into usual clinical practice. Furthermore, each specific application and each device for each application (e.g., nitroprusside infusion, ventilator adjustment), although based on the same technological concept, are sufficiently different in terms of hardware and computer algorithms to require independent validation studies. Closed loop infusion systems may have a role in critical care practice. However, for most applications, further development is required to move this technology from the innovation phase to the point where it can be evaluated so that its role in critical car practice can be defined. Each application of closed loop infusion systems must be independently validated by appropriately designed research studies. Users should be provided with the clinical parameters driving each closed loop system so that they can ensure that it agrees with their opinion of acceptable medical practice. Clinical researchers and leaders in industry should collaborate to perform the scientifically valid, outcome-based research that is necessary to evaluate the effect of this new technology. The original model we developed for technology assessment required the addition of several more questions to produce a complete analysis of an emerging technology. An emerging technology should be systematically assessed (using a model such as the model developed by the Society of Critical Care Medicine), before its introduction into clinical practice in order to provide a focus for human outcome validation trials and to minimize the possibility of widespread use of an unproven technology.

Fully probabilistic control design in an adaptive critic framework.

PubMed

Herzallah, Randa; Kárný, Miroslav

2011-12-01

Optimal stochastic controller pushes the closed-loop behavior as close as possible to the desired one. The fully probabilistic design (FPD) uses probabilistic description of the desired closed loop and minimizes Kullback-Leibler divergence of the closed-loop description to the desired one. Practical exploitation of the fully probabilistic design control theory continues to be hindered by the computational complexities involved in numerically solving the associated stochastic dynamic programming problem; in particular, very hard multivariate integration and an approximate interpolation of the involved multivariate functions. This paper proposes a new fully probabilistic control algorithm that uses the adaptive critic methods to circumvent the need for explicitly evaluating the optimal value function, thereby dramatically reducing computational requirements. This is a main contribution of this paper. Copyright © 2011 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Snepvangers, J.J.M.

Equipment and results are described connected with irradiation studies of UO/sub 2/ fuels, fuel element testing in pressurized water loops, graphite irradiation, and steel irradiations with and without temperature control. The apparatus described is associated with a 20-Mw pool-type research reactor. (T.F.H.)

Closed Loop Software Control of the MIDEX Power System

NASA Technical Reports Server (NTRS)

Castell, Karen; Hernandez-Pellerano, Amri; Wismer, Margaret

1998-01-01

The Microwave Anisotropy Probe (MAP) is a follow-on to the Differential Microwave Radiometer (DMR) instrument on the Cosmic Background Explorer (COBE) spacecraft. The design and analysis of the MAP attitude control system (ACS) have been refined since work previously reported. The full spacecraft and instrument flexible model was developed in NASTRAN, and the resulting flexible modes were plotted and reduced with the Modal Significance Analysis Package (MSAP). The reduced-order model was used to perform the linear stability analysis for each control mode, the results of which are presented in this paper. Although MAP is going to a relatively disturbance-free Lissajous orbit around the Earth-Sun L2 Lagrange point, a detailed disturbance-torque analysis is required because there are only a small number of opportunities for momentum unloading each year. Environmental torques, including solar pressure at L2, and aerodynamic and gravity gradient during phasing-loop orbits, were calculated and simulated. A simple model of fuel slosh was derived to model its effect on the motion of the spacecraft. In addition, a thruster mode linear impulse controller was developed to meet the accuracy requirements of the phasing loop burns. A dynamic attitude error limiter was added to improve the performance of the ACS during large attitude slews. The result of this analysis is a stable ACS subsystem that meets all of the mission's requirements.

[Closed-loop management model of clinical investigational product for new drug of traditional Chinese medicine].

PubMed

Wu, Ping; Zhang, Jian-Wu

2013-09-01

This paper discussed the management regulations and technical requirements of clinical investigational product for new drug of traditional Chinese medicine, analyzed some common problems on the management of them, and proposed the establishment of closed-loop management model and management requirements in various aspects.

Disaggregating Assessment to Close the Loop and Improve Student Learning

ERIC Educational Resources Information Center

Rawls, Janita; Hammons, Stacy

2015-01-01

This study examined student learning outcomes for accelerated degree students as compared to conventional undergraduate students, disaggregated by class levels, to develop strategies for then closing the loop with assessment. Using the National Survey of Student Engagement, critical thinking and oral and written communication outcomes were…

Flight Engineer Donald R. Pettit looks closely at Sodium Chloride within a 50-millimeter metal loop

NASA Image and Video Library

2003-03-12

ISS006-E-39142 (12 March 2003) --- Astronaut Donald R. Pettit, Expedition Six NASA ISS science officer, looks closely at a water bubble within a 50-millimeter metal loop. The experiment took place in the Destiny laboratory on the International Space Station (ISS).

Simulating closed- and open-loop voluntary movement: a nonlinear control-systems approach.

PubMed

Davidson, Paul R; Jones, Richard D; Andreae, John H; Sirisena, Harsha R

2002-11-01

In many recent human motor control models, including feedback-error learning and adaptive model theory (AMT), feedback control is used to correct errors while an inverse model is simultaneously tuned to provide accurate feedforward control. This popular and appealing hypothesis, based on a combination of psychophysical observations and engineering considerations, predicts that once the tuning of the inverse model is complete the role of feedback control is limited to the correction of disturbances. This hypothesis was tested by looking at the open-loop behavior of the human motor system during adaptation. An experiment was carried out involving 20 normal adult subjects who learned a novel visuomotor relationship on a pursuit tracking task with a steering wheel for input. During learning, the response cursor was periodically blanked, removing all feedback about the external system (i.e., about the relationship between hand motion and response cursor motion). Open-loop behavior was not consistent with a progressive transfer from closed- to open-loop control. Our recently developed computational model of the brain--a novel nonlinear implementation of AMT--was able to reproduce the observed closed- and open-loop results. In contrast, other control-systems models exhibited only minimal feedback control following adaptation, leading to incorrect open-loop behavior. This is because our model continues to use feedback to control slow movements after adaptation is complete. This behavior enhances the internal stability of the inverse model. In summary, our computational model is currently the only motor control model able to accurately simulate the closed- and open-loop characteristics of the experimental response trajectories.

Feasibility study on an energy-saving desiccant wheel system with CO2 heat pump

NASA Astrophysics Data System (ADS)

Liu, Yefeng; Meng, Deren; Chen, Shen

2018-02-01

In traditional desiccant wheel, air regeneration process occurs inside an open loop, and lots of energy is consumed. In this paper, an energy-saving desiccant wheel system with CO2 heat pump and closed loop air regeneration is proposed. The general theory and features of the desiccant wheel are analysed. The main feature of the proposed system is that the air regeneration process occurs inside a closed loop, and a CO2 heat pump is utilized inside this loop for the air regeneration process as well as supplying cooling for the process air. The simulation results show that the proposed system can save significant energy.

A closed expression for the UV-divergent parts of one-loop tensor integrals in dimensional regularization

NASA Astrophysics Data System (ADS)

Sulyok, G.

2017-07-01

Starting from the general definition of a one-loop tensor N-point function, we use its Feynman parametrization to calculate the ultraviolet (UV-)divergent part of an arbitrary tensor coefficient in the framework of dimensional regularization. In contrast to existing recursion schemes, we are able to present a general analytic result in closed form that enables direct determination of the UV-divergent part of any one-loop tensor N-point coefficient independent from UV-divergent parts of other one-loop tensor N-point coefficients. Simplified formulas and explicit expressions are presented for A-, B-, C-, D-, E-, and F-functions.

Motor-sensory confluence in tactile perception.

PubMed

Saig, Avraham; Gordon, Goren; Assa, Eldad; Arieli, Amos; Ahissar, Ehud

2012-10-03

Perception involves motor control of sensory organs. However, the dynamics underlying emergence of perception from motor-sensory interactions are not yet known. Two extreme possibilities are as follows: (1) motor and sensory signals interact within an open-loop scheme in which motor signals determine sensory sampling but are not affected by sensory processing and (2) motor and sensory signals are affected by each other within a closed-loop scheme. We studied the scheme of motor-sensory interactions in humans using a novel object localization task that enabled monitoring the relevant overt motor and sensory variables. We found that motor variables were dynamically controlled within each perceptual trial, such that they gradually converged to steady values. Training on this task resulted in improvement in perceptual acuity, which was achieved solely by changes in motor variables, without any change in the acuity of sensory readout. The within-trial dynamics is captured by a hierarchical closed-loop model in which lower loops actively maintain constant sensory coding, and higher loops maintain constant sensory update flow. These findings demonstrate interchangeability of motor and sensory variables in perception, motor convergence during perception, and a consistent hierarchical closed-loop perceptual model.

High Impulse Gun Airborne Demonstration. GAU-13/A Weapon, Feed System, Gun Drive and Electronic Controls.

DTIC Science & Technology

1981-05-01

made to provide mounting bosses for the closed loop conveyor chute . Ten small round bosses were welded onto the housing to provide this support...became necessary to depart from previous closed loop feeder designs . The original feed system consisted of a series of conveyor elements in a flexible...The flexible chuting has been replaced with rigid chuting forming a loop around the gun housing. This design affords the maximum stiffness and hence

THE ARMOUR DUST FUELED REACTOR (ADFR). Quarterly Progress Report No. 2 For the Period May 21, 1958 to August 21, 1958

DOE Office of Scientific and Technical Information (OSTI.GOV)

Loewe, W.E.; Krucoff, D.

1958-10-31

Study of the ADFR concept included experimental work on fuel dust suspension stability and redispersibility, erosion, and dust deposition using the fuel dust circulation loop. Some theoretical work was done in the areas of reactor safety and breeding. (For preceding period -see AECU-3827.) (auth)

Fuel cell tubes and method of making same

DOEpatents

Borglum, Brian P.

1999-11-30

A method of manufacturing porous ceramic tubes for fuel cells with improved properties and higher manufacturing yield is disclosed. The method involves extruding a closed end fuel cell tube, such as an air electrode of a solid oxide fuel cell, in which the closed end also functions as the sintering support. The resultant fuel cell tube has a superior porosity distribution which allows improved diffusion of oxygen at the closed end of the tube during operation of the fuel cell. Because this region has the highest current density, performance enhancement and improved reliability of the fuel cell tube result. Furthermore, the higher manufacturing yield associated with the present method decreases the overall fuel cell cost. A method of manufacturing porous ceramic tubes for fuel cells with improved properties and higher manufacturing yield is disclosed. The method involves extruding a closed end fuel cell tube, such as an air electrode of a solid oxide fuel cell, in which the closed end also functions as the sintering support. The resultant fuel cell tube has a superior porosity distribution which allows improved diffusion of oxygen at the closed end of the tube during operation of the fuel cell. Because this region has the highest current density, performance enhancement and improved reliability of the fuel cell tube result. Furthermore, the higher manufacturing yield associated with the present method decreases the overall fuel cell cost.

Model-Driven Safety Analysis of Closed-Loop Medical Systems

PubMed Central

Pajic, Miroslav; Mangharam, Rahul; Sokolsky, Oleg; Arney, David; Goldman, Julian; Lee, Insup

2013-01-01

In modern hospitals, patients are treated using a wide array of medical devices that are increasingly interacting with each other over the network, thus offering a perfect example of a cyber-physical system. We study the safety of a medical device system for the physiologic closed-loop control of drug infusion. The main contribution of the paper is the verification approach for the safety properties of closed-loop medical device systems. We demonstrate, using a case study, that the approach can be applied to a system of clinical importance. Our method combines simulation-based analysis of a detailed model of the system that contains continuous patient dynamics with model checking of a more abstract timed automata model. We show that the relationship between the two models preserves the crucial aspect of the timing behavior that ensures the conservativeness of the safety analysis. We also describe system design that can provide open-loop safety under network failure. PMID:24177176

Model-Driven Safety Analysis of Closed-Loop Medical Systems.

PubMed

Pajic, Miroslav; Mangharam, Rahul; Sokolsky, Oleg; Arney, David; Goldman, Julian; Lee, Insup

2012-10-26

In modern hospitals, patients are treated using a wide array of medical devices that are increasingly interacting with each other over the network, thus offering a perfect example of a cyber-physical system. We study the safety of a medical device system for the physiologic closed-loop control of drug infusion. The main contribution of the paper is the verification approach for the safety properties of closed-loop medical device systems. We demonstrate, using a case study, that the approach can be applied to a system of clinical importance. Our method combines simulation-based analysis of a detailed model of the system that contains continuous patient dynamics with model checking of a more abstract timed automata model. We show that the relationship between the two models preserves the crucial aspect of the timing behavior that ensures the conservativeness of the safety analysis. We also describe system design that can provide open-loop safety under network failure.

A Review of Control Strategies in Closed-Loop Neuroprosthetic Systems

PubMed Central

Wright, James; Macefield, Vaughan G.; van Schaik, André; Tapson, Jonathan C.

2016-01-01

It has been widely recognized that closed-loop neuroprosthetic systems achieve more favorable outcomes for users then equivalent open-loop devices. Improved performance of tasks, better usability, and greater embodiment have all been reported in systems utilizing some form of feedback. However, the interdisciplinary work on neuroprosthetic systems can lead to miscommunication due to similarities in well-established nomenclature in different fields. Here we present a review of control strategies in existing experimental, investigational and clinical neuroprosthetic systems in order to establish a baseline and promote a common understanding of different feedback modes and closed-loop controllers. The first section provides a brief discussion of feedback control and control theory. The second section reviews the control strategies of recent Brain Machine Interfaces, neuromodulatory implants, neuroprosthetic systems, and assistive neurorobotic devices. The final section examines the different approaches to feedback in current neuroprosthetic and neurorobotic systems. PMID:27462202

Design and simulation of a sensor for heliostat field closed loop control

NASA Astrophysics Data System (ADS)

Collins, Mike; Potter, Daniel; Burton, Alex

2017-06-01

Significant research has been completed in pursuit of capital cost reductions for heliostats [1],[2]. The camera array closed loop control concept has potential to radically alter the way heliostats are controlled and installed by replacing high quality open loop targeting systems with low quality targeting devices that rely on measurement of image position to remove tracking errors during operation. Although the system could be used for any heliostat size, the system significantly benefits small heliostats by reducing actuation costs, enabling large numbers of heliostats to be calibrated simultaneously, and enabling calibration of heliostats that produce low irradiance (similar or less than ambient light images) on Lambertian calibration targets, such as small heliostats that are far from the tower. A simulation method for the camera array has been designed and verified experimentally. The simulation tool demonstrates that closed loop calibration or control is possible using this device.

Inadequate interaction between open- and closed-loop postural control in phobic postural vertigo.

PubMed

Wuehr, M; Pradhan, C; Novozhilov, S; Krafczyk, S; Brandt, T; Jahn, K; Schniepp, R

2013-05-01

Phobic postural vertigo (PPV) is characterized by a subjective dizziness and postural imbalance. Changes in postural control strategy may cause the disturbed postural performance in PPV. A better understanding of the mechanisms behind this change in strategy is required to improve the diagnostic tools and therapeutic options for this prevalent disorder. Here we apply stabilogram diffusion analysis (SDA) to examine the characteristics and modes of interaction of open- and closed-loop processes that make up the postural control scheme in PPV. Twenty patients with PPV and 20 age-matched healthy controls were recorded on a stabilometer platform with eyes open and with eyes closed. Spatio-temporal changes of the center of pressure (CoP) displacement were analyzed by means of SDA and complementary CoP amplitude measures. (1) Open-loop control mechanisms in PPV were disturbed because of a higher diffusion activity (p < 0.001). (2) The interaction of open- and closed-loop processes was altered in that the sensory feedback threshold of the system was lowered (p = 0.010). These two changes were comparable to those observed in healthy subjects during more demanding balance conditions such as standing with eyes closed. These data indicate that subjective imbalance in PPV is associated with characteristic changes in the coordination of open- and closed-loop mechanisms of postural control. Patients with PPV use sensory feedback inadequately during undisturbed stance, and this impairs postural performance. These changes are compatible with higher levels of anti-gravity muscle activity and co-contraction during the conscious concentration on control of postural stability.

Modulation of critical brain dynamics using closed-loop neurofeedback stimulation.

PubMed

Zhigalov, Alexander; Kaplan, Alexander; Palva, J Matias

2016-08-01

EEG long-range temporal correlations (LRTCs) are a significant for both human cognition and brain disorders, but beyond suppression by sensory disruption, there are little means for influencing them non-invasively. We hypothesized that LRTCs could be controlled by engaging intrinsic neuroregulation through closed-loop neurofeedback stimulation. We used a closed-loop-stimulation paradigm where supra-threshold α-waves trigger visual flash stimuli while the subject performs the standard eyes-closed resting-state task. As a "sham" control condition, we applied similar stimulus sequences without the neurofeedback. Over three sessions, a significant difference in the LRTCs of α-band oscillations (U=89, p<0.028, Wilcoxon rank sum test) and their scalp topography (T=-2.92, p<0.010, T-test) emerged between the neurofeedback and sham conditions so that the LRTCs were stronger during neurofeedback than sham. No changes (F=0.16, p>0.69, ANOVA test) in the scalp topography of α-band power were observed in either condition. This study provides proof-of-concept for that EEG LRTCs, and hence critical brain dynamics, can be modulated with closed-loop stimulation in an automatic, involuntary fashion. We suggest that this modulation is mediated by an excitation-inhibition balance change achieved by the closed-loop neuroregulation. Automatic LRTC modulation opens novel avenues for both examining the functional roles of brain criticality in healthy subjects and for developing novel therapeutic approaches for brain disorders associated with abnormal LRTCs. Copyright © 2016 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Evaluation of tantalum-alloy-clad uranium mononitride fuel specimens from 7500-hour, 1040 C pumped-lithium-loop test

NASA Technical Reports Server (NTRS)

Watson, G. K.

1974-01-01

Simulated nuclear fuel element specimens, consisting of uranium mononitride (UN) fuel cylinders clad with tungsten-lined T-111, were exposed for up to 7500 hr at 1040 C (1900 F) in a pumped-lithium loop. The lithium flow velocity was 1.5 m/sec (5 ft/sec) in the specimen test section. No evidence of any compatibility problems between the specimens and the flowing lithium was found based on appearance, weight change, chemistry, and metallography. Direct exposure of the UN to the lithium through a simulated cladding crack resulted in some erosion of the UN in the area of the defect. The T-111 cladding was ductile after lithium exposure, but it was sensitive to hydrogen embrittlement during post-test handling.

Space Station evolution study oxygen loop closure

NASA Technical Reports Server (NTRS)

Wood, M. G.; Delong, D.

1993-01-01

In the current Space Station Freedom (SSF) Permanently Manned Configuration (PMC), physical scars for closing the oxygen loop by the addition of oxygen generation and carbon dioxide reduction hardware are not included. During station restructuring, the capability for oxygen loop closure was deferred to the B-modules. As such, the ability to close the oxygen loop in the U.S. Laboratory module (LAB A) and the Habitation A module (HAB A) is contingent on the presence of the B modules. To base oxygen loop closure of SSF on the funding of the B-modules may not be desirable. Therefore, this study was requested to evaluate the necessary hooks and scars in the A-modules to facilitate closure of the oxygen loop at or subsequent to PMC. The study defines the scars for oxygen loop closure with impacts to cost, weight and volume and assesses the effects of byproduct venting. In addition, the recommended scenarios for closure with regard to topology and packaging are presented.

SLSF in-reactor local fault safety experiment P4. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thompson, D. H.; Holland, J. W.; Braid, T. H.

The Sodium Loop Safety Facility (SLSF), a major facility in the US fast-reactor safety program, has been used to simulate a variety of sodium-cooled fast reactor accidents. SLSF experiment P4 was conducted to investigate the behavior of a "worse-than-case" local fault configuration. Objectives of this experiment were to eject molten fuel into a 37-pin bundle of full-length Fast-Test-Reactor-type fuel pins form heat-generating fuel canisters, to characterize the severity of any molten fuel-coolant interaction, and to demonstrate that any resulting blockage could either be tolerated during continued power operation or detected by global monitors to prevent fuel failure propagation. The designmore » goal for molten fuel release was 10 to 30 g. Explusion of molten fuel from fuel canisters caused failure of adjacent pins and a partial flow channel blockage in the fuel bundle during full-power operation. Molten fuel and fuel debris also lodged against the inner surface of the test subassembly hex-can wall. The total fuel disruption of 310 g evaluated from posttest examination data was in excellent agreement with results from the SLSF delayed neutron detection system, but exceeded the target molten fuel release by an order of magnitude. This report contains a summary description of the SLSF in-reactor loop and support systems and the experiment operations. results of the detailed macro- and microexamination of disrupted fuel and metal and results from the analysis of the on-line experimental data are described, as are the interpretations and conclusions drawn from the posttest evaluations. 60 refs., 74 figs.« less

Laboratory demonstrations on a pyramid wavefront sensor without modulation for closed-loop adaptive optics system.

PubMed

Wang, Shengqian; Rao, Changhui; Xian, Hao; Zhang, Jianlin; Wang, Jianxin; Liu, Zheng

2011-04-25

The feasibility and performance of the pyramid wavefront sensor without modulation used in closed-loop adaptive optics system is investigated in this paper. The theory concepts and some simulation results are given to describe the detection trend and the linearity range of such a sensor with the aim to better understand its properties, and then a laboratory setup of the adaptive optics system based on this sensor and the liquid-crystal spatial light modulator is built. The correction results for the individual Zernike aberrations and the Kolmogorov phase screens are presented to demonstrate that the pyramid wavefront sensor without modulation can work as expected for closed-loop adaptive optics system.

Closed loop control of penetration depth during CO₂ laser lap welding processes.

PubMed

Sibillano, Teresa; Rizzi, Domenico; Mezzapesa, Francesco P; Lugarà, Pietro Mario; Konuk, Ali Riza; Aarts, Ronald; Veld, Bert Huis In 't; Ancona, Antonio

2012-01-01

In this paper we describe a novel spectroscopic closed loop control system capable of stabilizing the penetration depth during laser welding processes by controlling the laser power. Our novel approach is to analyze the optical emission from the laser generated plasma plume above the keyhole, to calculate its electron temperature as a process-monitoring signal. Laser power has been controlled by using a quantitative relationship between the penetration depth and the plasma electron temperature. The sensor is able to correlate in real time the difference between the measured electron temperature and its reference value for the requested penetration depth. Accordingly the closed loop system adjusts the power, thus maintaining the penetration depth.

Closed Loop Control of Penetration Depth during CO2 Laser Lap Welding Processes

PubMed Central

Sibillano, Teresa; Rizzi, Domenico; Mezzapesa, Francesco P.; Lugarà, Pietro Mario; Konuk, Ali Riza; Aarts, Ronald; Veld, Bert Huis in 't; Ancona, Antonio

2012-01-01

In this paper we describe a novel spectroscopic closed loop control system capable of stabilizing the penetration depth during laser welding processes by controlling the laser power. Our novel approach is to analyze the optical emission from the laser generated plasma plume above the keyhole, to calculate its electron temperature as a process-monitoring signal. Laser power has been controlled by using a quantitative relationship between the penetration depth and the plasma electron temperature. The sensor is able to correlate in real time the difference between the measured electron temperature and its reference value for the requested penetration depth. Accordingly the closed loop system adjusts the power, thus maintaining the penetration depth. PMID:23112646

Fault Detection and Safety in Closed-Loop Artificial Pancreas Systems

PubMed Central

2014-01-01

Continuous subcutaneous insulin infusion pumps and continuous glucose monitors enable individuals with type 1 diabetes to achieve tighter blood glucose control and are critical components in a closed-loop artificial pancreas. Insulin infusion sets can fail and continuous glucose monitor sensor signals can suffer from a variety of anomalies, including signal dropout and pressure-induced sensor attenuations. In addition to hardware-based failures, software and human-induced errors can cause safety-related problems. Techniques for fault detection, safety analyses, and remote monitoring techniques that have been applied in other industries and applications, such as chemical process plants and commercial aircraft, are discussed and placed in the context of a closed-loop artificial pancreas. PMID:25049365

A dynamic flare with anomalously dense flare loops

NASA Technical Reports Server (NTRS)

Svestka, Z.; Fontenla, J. M.; Machado, M. E.; Martin, S. F.; Neidig, D. F.

1986-01-01

The dynamic flare of November 6, 1980 developed a rich system of growing loops which could be followed in H-alpha for 1.5 hours. Throughout the flare, these loops, near the limb, were seen in emission against the disk. Theoretical computations of b-values for a hydrogen atom reveal that this requires electron densities in the loops to be close to 10 to the 12th per cu cm. From measured widths of higher Balmer lines the density at the tops of the loops was found to be 4 x 10 to the 12th per cu cm if no nonthermal motions were present. It is now general knowledge that flare loops are initially observed in X-rays and become visible in H-alpha only after cooling. For such a high density a loop would cool through radiation from 10 to the 7th K to 10 to the 4th K within a few minutes so that the dense H-alpha loops should have heights very close to the heights of the X-ray loops. This, however, contradicts the observations obtained by the HXIS and FCS instruments on board SMM which show the X-ray loops at much higher altitudes than the loops in H-alpha. Therefore, the density must have been significantly smaller when the loops were formed and the flare loops were apparently both shrinking and becoming denser while cooling.

Evaluation of an Active Clearance Control System Concept

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M.; Lattime, Scott B.; DeCastro, Jonathan A.; Oswald, Jay; Melcher, Kevin J.

2005-01-01

Reducing blade tip clearances through active tip clearance control in the high pressure turbine can lead to significant reductions in emissions and specific fuel consumption as well as dramatic improvements in operating efficiency and increased service life. Current engines employ scheduled cooling of the outer case flanges to reduce high pressure turbine tip clearances during cruise conditions. These systems have relatively slow response and do not use clearance measurement, thereby forcing cold build clearances to set the minimum clearances at extreme operating conditions (e.g., takeoff, reburst) and not allowing cruise clearances to be minimized due to the possibility of throttle transients (e.g., step change in altitude). In an effort to improve upon current thermal methods, a first generation mechanically-actuated active clearance control (ACC) system has been designed and fabricated. The system utilizes independent actuators, a segmented shroud structure, and clearance measurement feedback to provide fast and precise active clearance control throughout engine operation. Ambient temperature performance tests of this first generation ACC system assessed individual seal component leakage rates and both static and dynamic overall system leakage rates. The ability of the nine electric stepper motors to control the position of the seal carriers in both open- and closed-loop control modes for single and multiple cycles was investigated. The ability of the system to follow simulated engine clearance transients in closed-loop mode showed the system was able to track clearances to within a tight tolerance (0.001 in. error).

Evaluation of an Active Clearance Control System Concept

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M.; Lattime, Scott B.; Taylor, Shawn; DeCastro, Jonathan A.; Oswald, Jay; Melcher, Kevin J.

2005-01-01

Reducing blade tip clearances through active tip clearance control in the high pressure turbine can lead to significant reductions in emissions and specific fuel consumption as well as dramatic improvements in operating efficiency and increased service life. Current engines employ scheduled cooling of the outer case flanges to reduce high pressure turbine tip clearances during cruise conditions. These systems have relatively slow response and do not use clearance measurement, thereby forcing cold build clearances to set the minimum clearances at extreme operating conditions (e.g., takeoff, reburst) and not allowing cruise clearances to be minimized due to the possibility of throttle transients (e.g., step change in altitude). In an effort to improve upon current thermal methods, a first generation mechanically-actuated active clearance control (ACC) system has been designed and fabricated. The system utilizes independent actuators, a segmented shroud structure, and clearance measurement feedback to provide fast and precise active clearance control throughout engine operation. Ambient temperature performance tests of this first generation ACC system assessed individual seal component leakage rates and both static and dynamic overall system leakage rates. The ability of the nine electric stepper motors to control the position of the seal carriers in both open- and closed-loop control modes for single and multiple cycles was investigated. The ability of the system to follow simulated engine clearance transients in closed-loop mode showed the system was able to track clearances to within a tight tolerance ( 0.001 in. error).

Real-time control of hind limb functional electrical stimulation using feedback from dorsal root ganglia recordings

NASA Astrophysics Data System (ADS)

Bruns, Tim M.; Wagenaar, Joost B.; Bauman, Matthew J.; Gaunt, Robert A.; Weber, Douglas J.

2013-04-01

Objective. Functional electrical stimulation (FES) approaches often utilize an open-loop controller to drive state transitions. The addition of sensory feedback may allow for closed-loop control that can respond effectively to perturbations and muscle fatigue. Approach. We evaluated the use of natural sensory nerve signals obtained with penetrating microelectrode arrays in lumbar dorsal root ganglia (DRG) as real-time feedback for closed-loop control of FES-generated hind limb stepping in anesthetized cats. Main results. Leg position feedback was obtained in near real-time at 50 ms intervals by decoding the firing rates of more than 120 DRG neurons recorded simultaneously. Over 5 m of effective linear distance was traversed during closed-loop stepping trials in each of two cats. The controller compensated effectively for perturbations in the stepping path when DRG sensory feedback was provided. The presence of stimulation artifacts and the quality of DRG unit sorting did not significantly affect the accuracy of leg position feedback obtained from the linear decoding model as long as at least 20 DRG units were included in the model. Significance. This work demonstrates the feasibility and utility of closed-loop FES control based on natural neural sensors. Further work is needed to improve the controller and electrode technologies and to evaluate long-term viability.

Real-time control of hind limb functional electrical stimulation using feedback from dorsal root ganglia recordings

PubMed Central

Bruns, Tim M; Wagenaar, Joost B; Bauman, Matthew J; Gaunt, Robert A; Weber, Douglas J

2013-01-01

Objective Functional electrical stimulation (FES) approaches often utilize an open-loop controller to drive state transitions. The addition of sensory feedback may allow for closed-loop control that can respond effectively to perturbations and muscle fatigue. Approach We evaluated the use of natural sensory nerve signals obtained with penetrating microelectrode arrays in lumbar dorsal root ganglia (DRG) as real-time feedback for closed-loop control of FES-generated hind limb stepping in anesthetized cats. Main results Leg position feedback was obtained in near real-time at 50 ms intervals by decoding the firing rates of more than 120 DRG neurons recorded simultaneously. Over 5 m of effective linear distance was traversed during closed-loop stepping trials in each of two cats. The controller compensated effectively for perturbations in the stepping path when DRG sensory feedback was provided. The presence of stimulation artifacts and the quality of DRG unit sorting did not significantly affect the accuracy of leg position feedback obtained from the linear decoding model as long as at least 20 DRG units were included in the model. Significance This work demonstrates the feasibility and utility of closed-loop FES control based on natural neural sensors. Further work is needed to improve the controller and electrode technologies and to evaluate long-term viability. PMID:23503062

Detailed ADM-based Modeling of Shock Retreat and X-ray Emission of τ Sco

NASA Astrophysics Data System (ADS)

Fletcher, C. L.; Petit, V.; Cohen, D. H.; Townsend, R. H.; Wade, G. A.

2018-01-01

Leveraging the improvement of spectropolarimeters over the past few decades, surveys have found that about 10% of OB-type stars host strong (˜ kG) and mostly dipolar surface magnetic fields. One B-type star, τ Sco, has a more complex surface magnetic field than the general population of OB stars. Interestingly, its X-ray luminosity is an order of magnitude higher than predicted from analytical models of magnetized winds. Previous studies of τ Sco's magnetosphere have predicted that the region of closed field loops should be located close to the stellar surface. However, the lack of X-ray variability and the location of the shock-heated plasma measured from forbidden-to-intercombination X-ray line ratios suggest that the hot plasma, and hence the closed magnetic loops, extend considerably farther from the stellar surface, implying a significantly lower mass loss rate than initially assumed. We present an adaptation of the Analytic Dynamical Magnetosphere model, describing the magnetic confinement of the stellar wind, for an arbitrary field loop configuration. This model is used to predict the shock-heated plasma temperatures for individual field loops, which are then compared to high resolution grating spectra from the Chandra X-ray Observatory. This comparison shows that larger closed magnetic loops are needed.

Closing the Feedback Loop: Ensuring Effective Action from Student Feedback

ERIC Educational Resources Information Center

Watson, Sarah

2003-01-01

Feedback from students can inform improvement in higher education institutions and be part of the students' role in university management. To be effective it is important to"close the loop": from student views, through identifying issues and delegating responsibility for action, to informing students of the action resulting from their expressed…

Close-up view of sugar crystals in a water bubble within a metal loop on Expedition Six

NASA Image and Video Library

2003-03-15

ISS006-E-39299 (15 March 2003) --- A close up view of sugar crystals in a water bubble within a 50-millimeter (mm) metal loop was photographed by an Expedition Six crewmember. The experiment took place in the Destiny laboratory on the International Space Station (ISS).

Closed-Loop Neuromodulation Systems: Next-Generation Treatments for Psychiatric Illness

PubMed Central

Lo, Meng-Chen; Widge, Alik S.

2017-01-01

Despite deep brain stimulation’s positive early results in psychiatric disorders, well-designed clinical trials have yielded inconsistent clinical outcomes. One path to more reliable benefit is closed-loop therapy: stimulation that is automatically adjusted by a device or algorithm in response to changes in the patient’s electrical brain activity. These interventions may provide more precise and patient-specific treatments. In this article, we first introduce the available closed-loop neuromodulation platforms, which have shown clinical efficacy in epilepsy and strong early results in movement disorders. We discuss the strengths and limitations of these devices in the context of psychiatric illness. We then describe emerging technologies to address these limitations, including pre-clinical developments such as wireless deep neurostimulation and genetically targeted neuromodulation. Finally, we discuss ongoing challenges and limitations for closed-loop psychiatric brain stimulation development, most notably the difficulty of identifying meaningful biomarkers for titration. We consider this in the recently-released Research Domain Criteria (RDoC) framework and describe how neuromodulation and RDoC are jointly very well suited to address the problem of treatment-resistant illness. PMID:28523978

Disturbance rejection performance analyses of closed loop control systems by reference to disturbance ratio.

PubMed

Alagoz, Baris Baykant; Deniz, Furkan Nur; Keles, Cemal; Tan, Nusret

2015-03-01

This study investigates disturbance rejection capacity of closed loop control systems by means of reference to disturbance ratio (RDR). The RDR analysis calculates the ratio of reference signal energy to disturbance signal energy at the system output and provides a quantitative evaluation of disturbance rejection performance of control systems on the bases of communication channel limitations. Essentially, RDR provides a straightforward analytical method for the comparison and improvement of implicit disturbance rejection capacity of closed loop control systems. Theoretical analyses demonstrate us that RDR of the negative feedback closed loop control systems are determined by energy spectral density of controller transfer function. In this manner, authors derived design criteria for specifications of disturbance rejection performances of PID and fractional order PID (FOPID) controller structures. RDR spectra are calculated for investigation of frequency dependence of disturbance rejection capacity and spectral RDR analyses are carried out for PID and FOPID controllers. For the validation of theoretical results, simulation examples are presented. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

Adaptive optics for peripheral vision

NASA Astrophysics Data System (ADS)

Rosén, R.; Lundström, L.; Unsbo, P.

2012-07-01

Understanding peripheral optical errors and their impact on vision is important for various applications, e.g. research on myopia development and optical correction of patients with central visual field loss. In this study, we investigated whether correction of higher order aberrations with adaptive optics (AO) improve resolution beyond what is achieved with best peripheral refractive correction. A laboratory AO system was constructed for correcting peripheral aberrations. The peripheral low contrast grating resolution acuity in the 20° nasal visual field of the right eye was evaluated for 12 subjects using three types of correction: refractive correction of sphere and cylinder, static closed loop AO correction and continuous closed loop AO correction. Running AO in continuous closed loop improved acuity compared to refractive correction for most subjects (maximum benefit 0.15 logMAR). The visual improvement from aberration correction was highly correlated with the subject's initial amount of higher order aberrations (p = 0.001, R 2 = 0.72). There was, however, no acuity improvement from static AO correction. In conclusion, correction of peripheral higher order aberrations can improve low contrast resolution, provided refractive errors are corrected and the system runs in continuous closed loop.

Eigenvalue sensitivity of sampled time systems operating in closed loop

NASA Astrophysics Data System (ADS)

Bernal, Dionisio

2018-05-01

The use of feedback to create closed-loop eigenstructures with high sensitivity has received some attention in the Structural Health Monitoring field. Although practical implementation is necessarily digital, and thus in sampled time, work thus far has center on the continuous time framework, both in design and in checking performance. It is shown in this paper that the performance in discrete time, at typical sampling rates, can differ notably from that anticipated in the continuous time formulation and that discrepancies can be particularly large on the real part of the eigenvalue sensitivities; a consequence being important error on the (linear estimate) of the level of damage at which closed-loop stability is lost. As one anticipates, explicit consideration of the sampling rate poses no special difficulties in the closed-loop eigenstructure design and the relevant expressions are developed in the paper, including a formula for the efficient evaluation of the derivative of the matrix exponential based on the theory of complex perturbations. The paper presents an easily reproduced numerical example showing the level of error that can result when the discrete time implementation of the controller is not considered.

Efficacy of different types of self-expandable stents in carotid artery stenting for carotid bifurcation stenosis.

PubMed

Liu, Ya-min; Qin, Hao; Zhang, Bo; Wang, Yu-jing; Feng, Jun; Wu, Xiang

2016-02-01

Both open and closed loop self-expandable stents were used in carotid artery stenting (CAS) for carotid bifurcation stenosis. We sought to compare the efficacy of two types of stents in CAS. The data of 212 patients treated with CAS (42 and 170 cases implanted with closed and open loop stents, respectively) for carotid bifurcation stenosis and distal filtration protection devices were retrospectively analyzed. Between closed and open loop stents, there were no significant differences in hospitalization duration, NIHSS score before and after the treatment, stenosis at 12th month, and cumulative incidence of primary endpoint events within 30 days or from the 31st day to the 12th month; while there were significant differences in hemodynamic changes and rate of difficulty in recycling distal filtration protection devices. Use of open vs. closed loop stents for carotid bifurcation stenosis seems to be associated with similar incidence of complications, except for greater rate of hemodynamic changes and lower rate of difficulty in recycling the distal filtration protection devices.

An estimator-predictor approach to PLL loop filter design

NASA Technical Reports Server (NTRS)

Statman, Joseph I.; Hurd, William J.

1990-01-01

The design of digital phase locked loops (DPLL) using estimation theory concepts in the selection of a loop filter is presented. The key concept, that the DPLL closed-loop transfer function is decomposed into an estimator and a predictor, is discussed. The estimator provides recursive estimates of phase, frequency, and higher-order derivatives, and the predictor compensates for the transport lag inherent in the loop.

Loop equations and bootstrap methods in the lattice

DOE PAGES

Anderson, Peter D.; Kruczenski, Martin

2017-06-17

Pure gauge theories can be formulated in terms of Wilson Loops by means of the loop equation. In the large-N limit this equation closes in the expectation value of single loops. In particular, using the lattice as a regulator, it becomes a well defined equation for a discrete set of loops. In this paper we study different numerical approaches to solving this equation.

Hardware-in-the-Loop Rendezvous Tests of a Novel Actuators Command Concept

NASA Astrophysics Data System (ADS)

Gomes dos Santos, Willer; Marconi Rocco, Evandro; Boge, Toralf; Benninghoff, Heike; Rems, Florian

2016-12-01

Integration, test and validation results, in a real-time environment, of a novel concept for spacecraft control are presented in this paper. The proposed method commands simultaneously a group of actuators optimizing a given set of objective functions based on a multiobjective optimization technique. Since close proximity maneuvers play an important role in orbital servicing missions, the entire GNC system has been integrated and tested at a hardware-in-the-loop (HIL) rendezvous and docking simulator known as European Proximity Operations Simulator (EPOS). During the test campaign at EPOS facility, a visual camera has been used to provide the necessary measurements for calculating the relative position with respect to the target satellite during closed-loop simulations. In addition, two different configurations of spacecraft control have been considered in this paper: a thruster reaction control system and a mixed actuators mode which includes thrusters, reaction wheels, and magnetic torqrods. At EPOS, results of HIL closed-loop tests have demonstrated that a safe and stable rendezvous approach can be achieved with the proposed GNC loop.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Verkerk, B.

In 1959 a fuel development program was undertaken based on UO/sub 2/ in which it was intended to study all variables that could influence the quality of fabricated UO/sub 2/-pellets. Later this program was extended to a study of electrolytic UO/sub 2/ with the fabrication of swaged or vibratory compacted fuel elements in mind, and recently the study of the UO/sub 2/-PuO/sub 2/ system was incorporated in it. In order to obtain a better knowledge of the UO/sub 2/- powders that can be used for sintering purposes, an extensive study was made of various preparation methods. A small plutonium laboratorymore » containing equipment for the preparation of UO/sub 2/-- PuO/sub 2/ pellets containing 1 to 10% PuO/sub 2/ was set up and preliminary experiments were performed. Work on a small scale was done on pressing and sintering of UO/sub 2/ made along various routes. The reduction process was also studied. For the regeneration of scrap, especially for the case of enriched material, a 5-kg batch dissolution and precipitation plant was built. This installation is also used for various precipitation studies on a larger scale. Within the scope of tue fuel development program the study of canning materials is also of great importance. For the ship-propulsion reactor Zircaloy-2 was chosen as canning material. Various welding experiments were done in an argon-arc welding chamber and it was found that under well selected conditions very satisfactory end-cap welds could be obtained. 1n the corrosion program it became clear that proper conditioning is of utmost importance. Means of pre-operation treatment are being studied. In the HFR a low-temperature, low-pressure loop for the irradiation of capsules is in regular operation. The pressurized loop now under construction was designed for testing of fuel rods and clusters as planned for the ship-propulsion reactor, under conditions close to those of the actual reactor. The facilities for the post- irradiation measurements consist of two lead cells. (auth)« less

Automated Droplet Manipulation Using Closed-Loop Axisymmetric Drop Shape Analysis.

PubMed

Yu, Kyle; Yang, Jinlong; Zuo, Yi Y

2016-05-17

Droplet manipulation plays an important role in a wide range of scientific and industrial applications, such as synthesis of thin-film materials, control of interfacial reactions, and operation of digital microfluidics. Compared to micron-sized droplets, which are commonly considered as spherical beads, millimeter-sized droplets are generally deformable by gravity, thus introducing nonlinearity into control of droplet properties. Such a nonlinear drop shape effect is especially crucial for droplet manipulation, even for small droplets, at the presence of surfactants. In this paper, we have developed a novel closed-loop axisymmetric drop shape analysis (ADSA), integrated into a constrained drop surfactometer (CDS), for manipulating millimeter-sized droplets. The closed-loop ADSA generalizes applications of the traditional drop shape analysis from a surface tension measurement methodology to a sophisticated tool for manipulating droplets in real time. We have demonstrated the feasibility and advantages of the closed-loop ADSA in three applications, including control of drop volume by automatically compensating natural evaporation, precise control of surface area variations for high-fidelity biophysical simulations of natural pulmonary surfactant, and steady control of surface pressure for in situ Langmuir-Blodgett transfer from droplets. All these applications have demonstrated the accuracy, versatility, applicability, and automation of this new ADSA-based droplet manipulation technique. Combining with CDS, the closed-loop ADSA holds great promise for advancing droplet manipulation in a variety of material and surface science applications, such as thin-film fabrication, self-assembly, and biophysical study of pulmonary surfactant.

Carbon deposition and sulfur poisoning during CO2 electrolysis in nickel-based solid oxide cell electrodes

NASA Astrophysics Data System (ADS)

Skafte, Theis Løye; Blennow, Peter; Hjelm, Johan; Graves, Christopher

2018-01-01

Reduction of CO2 to CO and O2 in the solid oxide electrolysis cell (SOEC) has the potential to play a crucial role in closing the CO2 loop. Carbon deposition in nickel-based cells is however fatal and must be considered during CO2 electrolysis. Here, the effect of operating parameters is investigated systematically using simple current-potential experiments. Due to variations of local conditions, it is shown that higher current density and lower fuel electrode porosity will cause local carbon formation at the electrochemical reaction sites despite operating with a CO outlet concentration outside the thermodynamic carbon formation region. Attempts at mitigating the issue by coating the composite nickel/yttria-stabilized zirconia electrode with carbon-inhibiting nanoparticles and by sulfur passivation proved unsuccessful. Increasing the fuel electrode porosity is shown to mitigate the problem, but only to a certain extent. This work shows that a typical SOEC stack converting CO2 to CO and O2 is limited to as little as 15-45% conversion due to risk of carbon formation. Furthermore, cells operated in CO2-electrolysis mode are poisoned by reactant gases containing ppb-levels of sulfur, in contrast to ppm-levels for operation in fuel cell mode.

Analysis of alkaline exchange membrane fuel cells performance at different operating conditions using DC and AC methods

NASA Astrophysics Data System (ADS)

Reshetenko, Tatyana; Odgaard, Madeleine; Schlueter, Debbie; Serov, Alexey

2018-01-01

Membrane electrode assemblies (MEAs) for anion exchange membrane fuel cells (AEMFCs) were manufactured from commercial materials: Pt/C catalyst, A201 AEM and AS4 ionomer by using an industrial mass-production digital printing method. The MEA designs selected are close to those recommended by US Department of Energy, including low loading of platinum on the cathode side (0.2 mg cm-2). Polarization curves and electrochemical impedance spectroscopy (EIS) were applied for MEA evaluation in fuel cell conditions with variation of gas humidification and oxygen partial pressure (air vs oxygen). The typical impedance curves recorded at H2/O2 gas configuration consist of high- and medium-frequency arcs responsible for hydrogen oxidation and oxygen reduction, respectively. Operation with air as a cathode feed gas resulted in a decrease in AEMFC performance due to possible CO2 poisoning and mass transfer losses. At the same time, EIS demonstrated formation of a low frequency loop due to diffusion limitations. Despite the low loading of platinum on the cathode (0.2 mg cm-2), a peak power density of ∼330 mW cm-2 was achieved (at 50/50% of RH on anode and cathode), which is substantially higher performance than for AEMFC MEAs tested at similar conditions.

Fuel loading of PeBR for a long operation life on the lunar surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schriener, T. M.; Chemical and Nuclear Engineering Dept., Univ. of New Mexico, Albuquerque, NM; El-Genk, M. S.

2012-07-01

The Pellet Bed Reactor (PeBR) power system could provide 99.3 kW e to a lunar outpost for 66 full power years and is designed for no single point failures. The core of this fast energy spectrum reactor consists of three sectors that are neutronically and thermally coupled, but hydraulically independent. Each sector has a separate Closed Brayton Cycle (CBC) loop for energy conversion and separate water heat-pipes radiator panels for heat rejection. He-Xe (40 g/mole) binary gas mixture serves as the reactor coolant and CBC working fluid. On the lunar surface, the emplaced PeBR below grade is loaded with sphericalmore » fuel pellets (1-cm in dia.). It is launched unfueled and the pellets are launched in separate subcritical canisters, one for each core sector. This paper numerically simulates the transient loading of a core sector with fuel pellets on the Moon. The simulation accounts for the dynamic interaction of the pellets during loading and calculates the axial and radial distributions of the volume porosity in the sector. The pellets pack randomly with a volume porosity of 0.39 - 0.41 throughout most of the sector, except near the walls the local porosity is higher. (authors)« less

Orbiter fuel cell performance constraints. STS/OPS Pratt Whitney fuel cells. Operating limits for mission planning

NASA Technical Reports Server (NTRS)

Kolkhorst, H. E.

1980-01-01

The orbiter fuel cell powerplant (FCP) performance constraints listed in the Shuttle Operational Data Book (SODB) were analyzed using the shuttle environmental control requirements evaluation tool. The effects of FCP lifetime, coolant loops, and FCP voltage output were considered. Results indicate that the FCP limits defined in the SODB are not valid.

Initial experimental evaluation of crud-resistant materials for light water reactors

NASA Astrophysics Data System (ADS)

Dumnernchanvanit, I.; Zhang, N. Q.; Robertson, S.; Delmore, A.; Carlson, M. B.; Hussey, D.; Short, M. P.

2018-01-01

The buildup of fouling deposits on nuclear fuel rods, known as crud, continues to challenge the worldwide fleet of light water reactors (LWRs). Crud causes serious operational problems for LWRs, including axial power shifts, accelerated fuel clad corrosion, increased primary circuit radiation dose rates, and in some instances has led directly to fuel failure. Numerous studies continue to attempt to model and predict the effects of crud, but each assumes that it will always be present. In this study, we report on the development of crud-resistant materials as fuel cladding coatings, to reduce or eliminate these problems altogether. Integrated loop testing experiments at flowing LWR conditions show significantly reduced crud adhesion and surface crud coverage, respectively, for TiC and ZrN coatings compared to ZrO2. The loop testing results roughly agree with the London dispersion component of van der Waals force predictions, suggesting that they contribute most significantly to the adhesion of crud to fuel cladding in out-of-pile conditions. These results motivate a new look at ways of reducing crud, thus avoiding many expensive LWR operational issues.

Development of Passive Fuel Cell Thermal Management Technology

NASA Technical Reports Server (NTRS)

Burke, Kenneth A.; Jakupca, Ian; Colozza, Anthony

2011-01-01

The NASA Glenn Research Center is developing advanced passive thermal management technology to reduce the mass and improve the reliability of space fuel cell systems for the NASA exploration program. The passive thermal management system relies on heat conduction within the cooling plate to move the heat from the central portion of the cell stack out to the edges of the fuel cell stack rather than using a pumped loop cooling system to convectively remove the heat. Using the passive approach eliminates the need for a coolant pump and other cooling loop components which reduces fuel cell system mass and improves overall system reliability. Previous analysis had identified that low density, ultra-high thermal conductivity materials would be needed for the cooling plates in order to achieve the desired reductions in mass and the highly uniform thermal heat sink for each cell within a fuel cell stack. A pyrolytic graphite material was identified and fabricated into a thin plate using different methods. Also a development project with Thermacore, Inc. resulted in a planar heat pipe. Thermal conductivity tests were done using these materials. The results indicated that lightweight passive fuel cell cooling is feasible.

Antimisting kerosene: Low temperature degradation and blending

NASA Technical Reports Server (NTRS)

Yavrouian, A.; Parikh, P.; Sarohia, V.

1988-01-01

The inline filtration characteristics of freshly blended and degraded antimisting fuels (AMK) at low temperature are examined. A needle valve degrader was modified to include partial recirculation of degraded fuel and heat addition in the bypass loop. A pressure drop across the needle valve of up to 4,000 psi was used. The pressure drop across a 325 mesh filter screen placed inline with the degrader and directly downstream of the needle valve was measured as a function of time for different values of pressure drop across the needle valve. A volume flux of 1 gpm/sq in was employed based on the frontal area of the screen. It was found that, at ambient temperatures, freshly blended AMK fuel could be degraded using a single pass degradation at 4,000 psi pressure drop across the needle valve to give acceptable filterability performance. At fuel temperatures below -20 C, degradation becomes increasingly difficult and a single pass technique results in unacceptable filtration performance. Recirculation of a fraction of the degraded fuel and heat addition in the bypass loop improved low temperature degradation performance. The problem is addressed of blending the AMK additive with Jet A at various base fuel temperatures.

Safe Glycemic Management during Closed-Loop Treatment of Type 1 Diabetes: The Role of Glucagon, Use of Multiple Sensors, and Compensation for Stress Hyperglycemia

PubMed Central

Ward, W Kenneth; Castle, Jessica R; Youssef, Joseph El

2011-01-01

Patients with type 1 diabetes mellitus (T1DM) must make frequent decisions and lifestyle adjustments in order to manage their disorder. Automated treatment would reduce the need for these self-management decisions and reduce the risk for long-term complications. Investigators in the field of closed-loop glycemic control systems are now moving from inpatient to outpatient testing of such systems. As outpatient systems are developed, the element of safety increases in importance. One such concern is the risk for hypoglycemia, due in part to the delayed onset and prolonged action duration of currently available subcutaneous insulin preparations. We found that, as compared to an insulin-only closed-loop system, a system that also delivers glucagon when needed led to substantially less hypoglycemia. Though the capability of glucagon delivery would mandate the need for a second hormone chamber, glucagon in small doses is tolerated very well. People with T1DM often develop hyperglycemia from emotional stress or medical stress. Automated closed-loop systems should be able to detect such changes in insulin sensitivity and adapt insulin delivery accordingly. We recently verified the adaptability of a model-based closed-loop system in which the gain factors that govern a proportional-integral-derivative-like system are adjusted according to frequently measured insulin sensitivity. Automated systems can be tested by physical exercise to increase glucose uptake and insulin sensitivity or by administering corticosteroids to reduce insulin sensitivity. Another source of risk in closed-loop systems is suboptimal performance of amperometric glucose sensors. Inaccuracy can result from calibration error, biofouling, and current drift. We found that concurrent use of more than one sensor typically leads to better sensor accuracy than use of a single sensor. For example, using the average of two sensors substantially reduces the proportion of large sensor errors. The use of more than two allows the use of voting algorithms, which can temporarily exclude a sensor whose signal is outlying. Elements such as the use of glucagon to minimize hypoglycemia, adaptation to changes in insulin sensitivity, and sensor redundancy will likely increase safety during outpatient use of closed-loop glycemic control systems. PMID:22226254

Simulations of Solar Jets Confined by Coronal Loops

NASA Technical Reports Server (NTRS)

Wyper, P. F.; De Vore, C. R.

2016-01-01

Coronal jets are collimated, dynamic events that occur over a broad range of spatial scales in the solar corona. In the open magnetic field of coronal holes, jets form quasi-radial spires that can extend far out into the heliosphere, while in closed-field regions the jet outflows are confined to the corona. We explore the application of the embedded-bipole model to jets occurring in closed coronal loops. In this model, magnetic free energy is injected slowly by footpoint motions that introduce twist within the closed dome of the jet source region, and is released rapidly by the onset of an ideal kink-like instability. Two length scales characterize the system: the width (N) of the jet source region and the footpoint separation (L) of the coronal loop that envelops the jet source. We find that both the conditions for initiation and the subsequent dynamics are highly sensitive to the ratio L/N. The longest-lasting and most energetic jets occur along long coronal loops with large L/N ratios, and share many of the features of open-field jets, while smaller L/N ratios produce shorter-duration, less energetic jets that are affected by reflections from the far-loop footpoint. We quantify the transition between these behaviors and show that our model replicates key qualitative and quantitative aspects of both quiet Sun and active-region loop jets. We also find that there connection between the closed dome and surrounding coronal loop is very extensive: the cumulative reconnected flux at least matches the total flux beneath the dome for small L/N, and is more than double that value for large L/N.

SIMULATIONS OF SOLAR JETS CONFINED BY CORONAL LOOPS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wyper, P. F.; DeVore, C. R., E-mail: peter.f.wyper@nasa.gov, E-mail: c.richard.devore@nasa.gov

Coronal jets are collimated, dynamic events that occur over a broad range of spatial scales in the solar corona. In the open magnetic field of coronal holes, jets form quasi-radial spires that can extend far out into the heliosphere, while in closed-field regions the jet outflows are confined to the corona. We explore the application of the embedded-bipole model to jets occurring in closed coronal loops. In this model, magnetic free energy is injected slowly by footpoint motions that introduce twist within the closed dome of the jet source region, and is released rapidly by the onset of an idealmore » kink-like instability. Two length scales characterize the system: the width (N) of the jet source region and the footpoint separation (L) of the coronal loop that envelops the jet source. We find that both the conditions for initiation and the subsequent dynamics are highly sensitive to the ratio L/N. The longest-lasting and most energetic jets occur along long coronal loops with large L/N ratios, and share many of the features of open-field jets, while smaller L/N ratios produce shorter-duration, less energetic jets that are affected by reflections from the far-loop footpoint. We quantify the transition between these behaviors and show that our model replicates key qualitative and quantitative aspects of both quiet Sun and active-region loop jets. We also find that the reconnection between the closed dome and surrounding coronal loop is very extensive: the cumulative reconnected flux at least matches the total flux beneath the dome for small L/N, and is more than double that value for large L/N.« less

Downlink Training Techniques for FDD Massive MIMO Systems: Open-Loop and Closed-Loop Training With Memory

NASA Astrophysics Data System (ADS)

Choi, Junil; Love, David J.; Bidigare, Patrick

2014-10-01

The concept of deploying a large number of antennas at the base station, often called massive multiple-input multiple-output (MIMO), has drawn considerable interest because of its potential ability to revolutionize current wireless communication systems. Most literature on massive MIMO systems assumes time division duplexing (TDD), although frequency division duplexing (FDD) dominates current cellular systems. Due to the large number of transmit antennas at the base station, currently standardized approaches would require a large percentage of the precious downlink and uplink resources in FDD massive MIMO be used for training signal transmissions and channel state information (CSI) feedback. To reduce the overhead of the downlink training phase, we propose practical open-loop and closed-loop training frameworks in this paper. We assume the base station and the user share a common set of training signals in advance. In open-loop training, the base station transmits training signals in a round-robin manner, and the user successively estimates the current channel using long-term channel statistics such as temporal and spatial correlations and previous channel estimates. In closed-loop training, the user feeds back the best training signal to be sent in the future based on channel prediction and the previously received training signals. With a small amount of feedback from the user to the base station, closed-loop training offers better performance in the data communication phase, especially when the signal-to-noise ratio is low, the number of transmit antennas is large, or prior channel estimates are not accurate at the beginning of the communication setup, all of which would be mostly beneficial for massive MIMO systems.

A study on single lane-change manoeuvres for determining rearward amplification of multi-trailer articulated heavy vehicles with active trailer steering systems

NASA Astrophysics Data System (ADS)

Wang, Qiushi; He, Yuping

2016-01-01

The Society of Automotive Engineers issued a test procedure, SAE-J2179, to determine the rearward amplification (RA) of multi-trailer articulated heavy vehicles (MTAHVs). Built upon the procedure, the International Organization for Standardization released the test manoeuvres, ISO-14791, for evaluating directional performance of MTAHVs. For the RA measures, ISO-14791 recommends two single lane-change manoeuvres: (1) an open-loop procedure with a single sine-wave steering input; and (2) a closed-loop manoeuvre with a single sine-wave lateral acceleration input. For an articulated vehicle with active trailer steering (ATS), the RA measure in lateral acceleration under the open-loop manoeuvre was not in good agreement with that under the closed-loop manoeuvre. This observation motivates the research on the applicability of the two manoeuvres for the RA measures of MTAHVs with ATS. It is reported that transient response under the open-loop manoeuvre often leads to asymmetric curve of tractor lateral acceleration [Winkler CB, Fancher PS, Bareket Z, Bogard S, Johnson G, Karamihas S, Mink C. Heavy vehicle size and weight - test procedures for minimum safety performance standards. Final technical report, NHTSA, US DOT, contract DTNH22-87-D-17174, University of Michigan Transportation Research Institute, Report No. UMTRI-92-13; 1992]. To explore the effect of the transient response, a multiple cycle sine-wave steering input (MCSSI) manoeuvre is proposed. Simulation demonstrates that the steady-state RA measures of an MTAHV with and without ATS under the MCSSI manoeuvre are in excellent agreement with those under the closed-loop manoeuvre. It is indicated that between the two manoeuvres by ISO-14791, the closed-loop manoeuvre is more applicable for determining the RA measures of MTAHVs with ATS.

Neutron Tomography Using Mobile Neutron Generators for Assessment of Void Distributions in Thermal Hydraulic Test Loops

NASA Astrophysics Data System (ADS)

Andersson, P.; Bjelkenstedt, T.; Sundén, E. Andersson; Sjöstrand, H.; Jacobsson-Svärd, S.

Detailed knowledge of the lateral distribution of steam (void) and water in a nuclear fuel assembly is of great value for nuclear reactor operators and fuel manufacturers, with consequences for both reactor safety and economy of operation. Therefore, nuclear relevant two-phase flows are being studied at dedicated thermal-hydraulic test loop, using two-phase flow systems ranging from simplified geometries such as heated circular pipes to full scale mock-ups of nuclear fuel assemblies. Neutron tomography (NT) has been suggested for assessment of the lateral distribution of steam and water in such test loops, motivated by a good ability of neutrons to penetrate the metallic structures of metal pipes and nuclear fuel rod mock-ups, as compared to e.g. conventional X-rays, while the liquid water simultaneously gives comparatively good contrast. However, these stationary test loops require the measurement setup to be mobile, which is often not the case for NT setups. Here, it is acknowledged that fast neutrons of 14 MeV from mobile neutron generators constitute a viable option for a mobile NT system. We present details of the development of neutron tomography for this purpose at the division of Applied Nuclear Physics at Uppsala University. Our concept contains a portable neutron generator, exploiting the fusion reaction of deuterium and tritium, and a detector with plastic scintillator elements designed to achieveadequate spatial and energy resolution, all mounted in a light-weight frame without collimators or bulky moderation to allow for a mobile instrument that can be moved about the stationary thermal hydraulic test sections. The detector system stores event-to-event pulse-height information to allow for discrimination based on the energy deposition in the scintillator elements.

Day-and-night glycaemic control with closed-loop insulin delivery versus conventional insulin pump therapy in free-living adults with well controlled type 1 diabetes: an open-label, randomised, crossover study.

PubMed

Bally, Lia; Thabit, Hood; Kojzar, Harald; Mader, Julia K; Qerimi-Hyseni, Jehona; Hartnell, Sara; Tauschmann, Martin; Allen, Janet M; Wilinska, Malgorzata E; Pieber, Thomas R; Evans, Mark L; Hovorka, Roman

2017-04-01

Tight control of blood glucose concentration in people with type 1 diabetes predisposes to hypoglycaemia. We aimed to investigate whether day-and-night hybrid closed-loop insulin delivery can improve glucose control while alleviating the risk of hypoglycaemia in adults with HbA 1c below 7·5% (58 mmol/mol). In this open-label, randomised, crossover study, we recruited adults (aged ≥18 years) with type 1 diabetes and HbA 1c below 7·5% from Addenbrooke's Hospital (Cambridge, UK) and Medical University of Graz (Graz, Austria). After a 2-4 week run-in period, participants were randomly assigned (1:1), using web-based randomly permuted blocks of four, to receive insulin via the day-and-night hybrid closed-loop system or usual pump therapy for 4 weeks, followed by a 2-4 week washout period and then the other intervention for 4 weeks. Treatment interventions were unsupervised and done under free-living conditions. During the closed-loop period, a model-predictive control algorithm directed insulin delivery, and prandial insulin delivery was calculated with a standard bolus wizard. The primary outcome was the proportion of time when sensor glucose concentration was in target range (3·9-10·0 mmol/L) over the 4 week study period. Analyses were by intention to treat. This study is registered with ClinicalTrials.gov, number NCT02727231, and is completed. Between March 21 and June 24, 2016, we recruited 31 participants, of whom 29 were randomised. One participant withdrew during the first closed-loop period because of dissatisfaction with study devices and glucose control. The proportion of time when sensor glucose concentration was in target range was 10·5 percentage points higher (95% CI 7·6-13·4; p<0·0001) during closed-loop delivery compared with usual pump therapy (65·6% [SD 8·1] when participants used usual pump therapy vs 76·2% [6·4] when they used closed-loop). Compared with usual pump therapy, closed-loop delivery also reduced the proportion of time spent in hypoglycaemia: the proportion of time with glucose concentration below 3·5 mmol/L was reduced by 65% (53-74, p<0·0001) and below 2·8 mmol/L by 76% (59-86, p<0·0001). No episodes of serious hypoglycaemia or other serious adverse events occurred. Use of day-and-night hybrid closed-loop insulin delivery under unsupervised, free-living conditions for 4 weeks in adults with type 1 diabetes and HbA 1c below 7·5% is safe and well tolerated, improves glucose control, and reduces hypoglycaemia burden. Larger and longer studies are warranted. Swiss National Science Foundation (P1BEP3_165297), JDRF, UK National Institute for Health Research Cambridge Biomedical Research Centre, and Wellcome Strategic Award (100574/Z/12/Z). Copyright © 2017 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY license. Published by Elsevier Ltd.. All rights reserved.

A neural network-based estimator for the mixture ratio of the Space Shuttle Main Engine

NASA Astrophysics Data System (ADS)

Guo, T. H.; Musgrave, J.

1992-11-01

In order to properly utilize the available fuel and oxidizer of a liquid propellant rocket engine, the mixture ratio is closed loop controlled during main stage (65 percent - 109 percent power) operation. However, because of the lack of flight-capable instrumentation for measuring mixture ratio, the value of mixture ratio in the control loop is estimated using available sensor measurements such as the combustion chamber pressure and the volumetric flow, and the temperature and pressure at the exit duct on the low pressure fuel pump. This estimation scheme has two limitations. First, the estimation formula is based on an empirical curve fitting which is accurate only within a narrow operating range. Second, the mixture ratio estimate relies on a few sensor measurements and loss of any of these measurements will make the estimate invalid. In this paper, we propose a neural network-based estimator for the mixture ratio of the Space Shuttle Main Engine. The estimator is an extension of a previously developed neural network based sensor failure detection and recovery algorithm (sensor validation). This neural network uses an auto associative structure which utilizes the redundant information of dissimilar sensors to detect inconsistent measurements. Two approaches have been identified for synthesizing mixture ratio from measurement data using a neural network. The first approach uses an auto associative neural network for sensor validation which is modified to include the mixture ratio as an additional output. The second uses a new network for the mixture ratio estimation in addition to the sensor validation network. Although mixture ratio is not directly measured in flight, it is generally available in simulation and in test bed firing data from facility measurements of fuel and oxidizer volumetric flows. The pros and cons of these two approaches will be discussed in terms of robustness to sensor failures and accuracy of the estimate during typical transients using simulation data.

A neural network-based estimator for the mixture ratio of the Space Shuttle Main Engine

NASA Technical Reports Server (NTRS)

Guo, T. H.; Musgrave, J.

1992-01-01

In order to properly utilize the available fuel and oxidizer of a liquid propellant rocket engine, the mixture ratio is closed loop controlled during main stage (65 percent - 109 percent power) operation. However, because of the lack of flight-capable instrumentation for measuring mixture ratio, the value of mixture ratio in the control loop is estimated using available sensor measurements such as the combustion chamber pressure and the volumetric flow, and the temperature and pressure at the exit duct on the low pressure fuel pump. This estimation scheme has two limitations. First, the estimation formula is based on an empirical curve fitting which is accurate only within a narrow operating range. Second, the mixture ratio estimate relies on a few sensor measurements and loss of any of these measurements will make the estimate invalid. In this paper, we propose a neural network-based estimator for the mixture ratio of the Space Shuttle Main Engine. The estimator is an extension of a previously developed neural network based sensor failure detection and recovery algorithm (sensor validation). This neural network uses an auto associative structure which utilizes the redundant information of dissimilar sensors to detect inconsistent measurements. Two approaches have been identified for synthesizing mixture ratio from measurement data using a neural network. The first approach uses an auto associative neural network for sensor validation which is modified to include the mixture ratio as an additional output. The second uses a new network for the mixture ratio estimation in addition to the sensor validation network. Although mixture ratio is not directly measured in flight, it is generally available in simulation and in test bed firing data from facility measurements of fuel and oxidizer volumetric flows. The pros and cons of these two approaches will be discussed in terms of robustness to sensor failures and accuracy of the estimate during typical transients using simulation data.

High-altitude closed magnetic loops at Mars observed by MAVEN

NASA Astrophysics Data System (ADS)

Xu, Shaosui; Mitchell, David; Luhmann, Janet; Ma, Yingjuan; Fang, Xiaohua; Harada, Yuki; Hara, Takuya; Brain, David; Webber, Tristan; Mazelle, Christian; DiBraccio, Gina A.

2017-10-01

With electron and magnetic field data obtained by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, we have identified closed magnetic field lines, with both footpoints embedded in the dayside ionosphere, extending up to 6200 km altitude (2.8 $R_m$) into the Martian tail. This topology is deduced from photoelectrons produced in the dayside ionosphere being observed in both parallel and anti-parallel directions along the magnetic field line. At perpendicular pitch angles, cases with either solar wind electrons or photoelectrons have been found, indicative of different formation mechanisms of these closed loops. These large closed loops are predicted by MHD simulations. The case with field-aligned photoelectrons mixed with perpendicular solar wind electrons is likely to be associated with reconnection, while the case with photoelectrons in all directions are probably due to closed field lines being pulled back down tail. We have developed an automated algorithm for distinguishing photoelectrons from solar wind electrons in pitch angle resolved energy spectra. This allows us to systematically analyze the MAVEN database and map the spatial distribution and occurrence rate of these closed magnetic loops, ranging from a few percent to a few tens percent outside of the optical shadow and less than one percent within the wake. These observations can be used to investigate the general magnetic topology in the tail, which is relevant to ion escape, reconnection, and flux ropes.

Closed Brayton cycle power conversion systems for nuclear reactors :

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wright, Steven A.; Lipinski, Ronald J.; Vernon, Milton E.

2006-04-01

This report describes the results of a Sandia National Laboratories internally funded research program to study the coupling of nuclear reactors to gas dynamic Brayton power conversion systems. The research focused on developing integrated dynamic system models, fabricating a 10-30 kWe closed loop Brayton cycle, and validating these models by operating the Brayton test-loop. The work tasks were performed in three major areas. First, the system equations and dynamic models for reactors and Closed Brayton Cycle (CBC) systems were developed and implemented in SIMULINKTM. Within this effort, both steady state and dynamic system models for all the components (turbines, compressors,more » reactors, ducting, alternators, heat exchangers, and space based radiators) were developed and assembled into complete systems for gas cooled reactors, liquid metal reactors, and electrically heated simulators. Various control modules that use proportional-integral-differential (PID) feedback loops for the reactor and the power-conversion shaft speed were also developed and implemented. The simulation code is called RPCSIM (Reactor Power and Control Simulator). In the second task an open cycle commercially available Capstone C30 micro-turbine power generator was modified to provide a small inexpensive closed Brayton cycle test loop called the Sandia Brayton test-Loop (SBL-30). The Capstone gas-turbine unit housing was modified to permit the attachment of an electrical heater and a water cooled chiller to form a closed loop. The Capstone turbine, compressor, and alternator were used without modification. The Capstone systems nominal operating point is 1150 K turbine inlet temperature at 96,000 rpm. The annular recuperator and portions of the Capstone control system (inverter) and starter system also were reused. The rotational speed of the turbo-machinery is controlled by adjusting the alternator load by using the electrical grid as the load bank. The SBL-30 test loop was operated at the manufacturers site (Barber-Nichols Inc.) and installed and operated at Sandia. A sufficiently detailed description of the loop is provided in this report along with the design characteristics of the turbo-alternator-compressor set to allow other researchers to compare their results with those measured in the Sandia test-loop. The third task consisted of a validation effort. In this task the test loop was operated and compared with the modeled results to develop a more complete understanding of this electrically heated closed power generation system and to validate the model. The measured and predicted system temperatures and pressures are in good agreement, indicating that the model is a reasonable representation of the test loop. Typical deviations between the model and the hardware results are less than 10%. Additional tests were performed to assess the capability of the Brayton engine to continue to remove decay heat after the reactor/heater is shutdown, to develop safe and effective control strategies, and to access the effectiveness of gas inventory control as an alternative means to provide load following. In one test the heater power was turned off to simulate a rapid reactor shutdown, and the turbomachinery was driven solely by the sensible heat stored in the heater for over 71 minutes without external power input. This is an important safety feature for CBC systems as it means that the closed Brayton loop will keep cooling the reactor without the need for auxiliary power (other than that needed to circulate the waste heat rejection coolant) provided the heat sink is available.« less

Crystal structure analysis, covalent docking, and molecular dynamics calculations reveal a conformational switch in PhaZ7 PHB depolymerase.

PubMed

Kellici, Tahsin F; Mavromoustakos, Thomas; Jendrossek, Dieter; Papageorgiou, Anastassios C

2017-07-01

An open and a closed conformation of a surface loop in PhaZ7 extracellular poly(3-hydroxybutyrate) depolymerase were identified in two high-resolution crystal structures of a PhaZ7 Y105E mutant. Molecular dynamics (MD) simulations revealed high root mean square fluctuations (RMSF) of the 281-295 loop, in particular at residue Asp289 (RMSF 7.62 Å). Covalent docking between a 3-hydroxybutyric acid trimer and the catalytic residue Ser136 showed that the binding energy of the substrate is significantly more favorable in the open loop conformation compared to that in the closed loop conformation. MD simulations with the substrate covalently bound depicted 1 Å RMSF higher values for the residues 281-295 in comparison to the apo (substrate-free) form. In addition, the presence of the substrate in the active site enhanced the ability of the loop to adopt a closed form. Taken together, the analysis suggests that the flexible loop 281-295 of PhaZ7 depolymerase can act as a lid domain to control substrate access to the active site of the enzyme. Proteins 2017; 85:1351-1361. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Innovative hybrid pile oscillator technique in the Minerve reactor: open loop vs. closed loop

NASA Astrophysics Data System (ADS)

Geslot, Benoit; Gruel, Adrien; Bréaud, Stéphane; Leconte, Pierre; Blaise, Patrick

2018-01-01

Pile oscillator techniques are powerful methods to measure small reactivity worth of isotopes of interest for nuclear data improvement. This kind of experiments has long been implemented in the Mineve experimental reactor, operated by CEA Cadarache. A hybrid technique, mixing reactivity worth estimation and measurement of small changes around test samples is presented here. It was made possible after the development of high sensitivity miniature fission chambers introduced next to the irradiation channel. A test campaign, called MAESTRO-SL, took place in 2015. Its objective was to assess the feasibility of the hybrid method and investigate the possibility to separate mixed neutron effects, such as fission/capture or scattering/capture. Experimental results are presented and discussed in this paper, which focus on comparing two measurements setups, one using a power control system (closed loop) and another one where the power is free to drift (open loop). First, it is demonstrated that open loop is equivalent to closed loop. Uncertainty management and methods reproducibility are discussed. Second, results show that measuring the flux depression around oscillated samples provides valuable information regarding partial neutron cross sections. The technique is found to be very sensitive to the capture cross section at the expense of scattering, making it very useful to measure small capture effects of highly scattering samples.

Is the kinetoplast DNA a percolating network of linked rings at its critical point?

NASA Astrophysics Data System (ADS)

Michieletto, Davide; Marenduzzo, Davide; Orlandini, Enzo

2015-05-01

In this work we present a computational study of the kinetoplast genome, modelled as a large number of semiflexible unknotted loops, which are allowed to link with each other. As the DNA density increases, the systems shows a percolation transition between a gas of unlinked rings and a network of linked loops which spans the whole system. Close to the percolation transition, we find that the mean valency of the network, i.e. the average number of loops which are linked to any one loop, is around three, as found experimentally for the kinetoplast DNA (kDNA). Even more importantly, by simulating the digestion of the network by a restriction enzyme, we show that the distribution of oligomers, i.e. structures formed by a few loops which remain linked after digestion, quantitatively matches experimental data obtained from gel electrophoresis, provided that the density is, once again, close to the percolation transition. With respect to previous work, our analysis builds on a reduced number of assumptions, yet can still fully explain the experimental data. Our findings suggest that the kDNA can be viewed as a network of linked loops positioned very close to the percolation transition, and we discuss the possible biological implications of this remarkable fact.

Pumped lithium loop test to evaluate advanced refractory metal alloys and simulated nuclear fuel elements

NASA Technical Reports Server (NTRS)

Brandenburf, G. P.; Hoffman, E. E.; Smith, J. P.

1974-01-01

The performance was determined of refractory metal alloys and uranium nitride fuel element specimens in flowing 1900F (1083C) lithium. The results demonstrate the suitability of the selected materials to perform satisfactorily from a chemical compatibility standpoint.

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2012-04-03

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Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-09

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An error criterion for determining sampling rates in closed-loop control systems

NASA Technical Reports Server (NTRS)

Brecher, S. M.

1972-01-01

The determination of an error criterion which will give a sampling rate for adequate performance of linear, time-invariant closed-loop, discrete-data control systems was studied. The proper modelling of the closed-loop control system for characterization of the error behavior, and the determination of an absolute error definition for performance of the two commonly used holding devices are discussed. The definition of an adequate relative error criterion as a function of the sampling rate and the parameters characterizing the system is established along with the determination of sampling rates. The validity of the expressions for the sampling interval was confirmed by computer simulations. Their application solves the problem of making a first choice in the selection of sampling rates.

Spiral vane bioreactor

NASA Technical Reports Server (NTRS)

Morrison, Dennis R. (Inventor)

1991-01-01

A spiral vane bioreactor of a perfusion type is described in which a vertical chamber, intended for use in a microgravity condition, has a central rotating filter assembly and has flexible membranes disposed to rotate annularly about the filter assembly. The flexible members have end portions disposed angularly with respect to one another. A fluid replenishment medium is input from a closed loop liquid system to a completely liquid filled chamber containing microcarrier beads, cells and a fluid medium. Output of spent medium is to the closed loop. In the closed loop, the output and input parameters are sensed by sensors. A manifold permits recharging of the nutrients and pH adjustment. Oxygen is supplied and carbon dioxide and bubbles are removed and the system is monitored and controlled by a microprocessor.

Closing the loops in biomedical informatics from theory to daily practice.

PubMed

Gaudinat, A

2009-01-01

This article presents the 2009 selection of the best papers in the special section dedicated to biomedical informatics and cybernetics. Synopsis of the articles selected for the IMIA yearbook 2009 Five papers from international peer reviewed journals where selected for this section. Most of the papers have a strong practical orientation in clinical care. And this selection gives a good overview of what is done with "closing loop" approach, particularly during the year 2008. While quite mature for some clinical applications such as mechanical ventilation, it remains a challenge where rules for the decision system could be difficult to identify due to the number of variables. More complex systems with greater Artificial Intelligence approaches will certainly be the next trend for closed-loop applications.

Design of dissipative low-authority controllers using an eigensystem assignment technique

NASA Technical Reports Server (NTRS)

Maghami, P. G.; Gupta, S.; Joshi, S. M.

1992-01-01

A novel method for the design of dissipative, low-authority controllers has been developed. The method uses a sequential approach along with eigensystem assignment to compute rate and position gain matrices that assign a number of closed-loop poles of the system to desired locations. Because the feedback gain matrices are symmetric and nonnegative definite, the closed-loop stability is always guaranteed regardless of the model order or parameter inaccuracies. The resulting (nominal) closed-loop system can have specified damping ratios for m modes, which makes the plant amenable to high-authority controller design, using methods such as LQG/LTR or H-infinity. A numerical example is worked out for a flexible structure in order to demonstrate the proposed technique.

Automatic control of finite element models for temperature-controlled radiofrequency ablation.

PubMed

Haemmerich, Dieter; Webster, John G

2005-07-14

The finite element method (FEM) has been used to simulate cardiac and hepatic radiofrequency (RF) ablation. The FEM allows modeling of complex geometries that cannot be solved by analytical methods or finite difference models. In both hepatic and cardiac RF ablation a common control mode is temperature-controlled mode. Commercial FEM packages don't support automating temperature control. Most researchers manually control the applied power by trial and error to keep the tip temperature of the electrodes constant. We implemented a PI controller in a control program written in C++. The program checks the tip temperature after each step and controls the applied voltage to keep temperature constant. We created a closed loop system consisting of a FEM model and the software controlling the applied voltage. The control parameters for the controller were optimized using a closed loop system simulation. We present results of a temperature controlled 3-D FEM model of a RITA model 30 electrode. The control software effectively controlled applied voltage in the FEM model to obtain, and keep electrodes at target temperature of 100 degrees C. The closed loop system simulation output closely correlated with the FEM model, and allowed us to optimize control parameters. The closed loop control of the FEM model allowed us to implement temperature controlled RF ablation with minimal user input.

Predictive Lateral Logic for Numerical Entry Guidance Algorithms

NASA Technical Reports Server (NTRS)

Smith, Kelly M.

2016-01-01

Recent entry guidance algorithm development123 has tended to focus on numerical integration of trajectories onboard in order to evaluate candidate bank profiles. Such methods enjoy benefits such as flexibility to varying mission profiles and improved robustness to large dispersions. A common element across many of these modern entry guidance algorithms is a reliance upon the concept of Apollo heritage lateral error (or azimuth error) deadbands in which the number of bank reversals to be performed is non-deterministic. This paper presents a closed-loop bank reversal method that operates with a fixed number of bank reversals defined prior to flight. However, this number of bank reversals can be modified at any point, including in flight, based on contingencies such as fuel leaks where propellant usage must be minimized.

Optimal thrust level for orbit insertion

NASA Astrophysics Data System (ADS)

Cerf, Max

2017-07-01

The minimum-fuel orbital transfer is analyzed in the case of a launcher upper stage using a constantly thrusting engine. The thrust level is assumed to be constant and its value is optimized together with the thrust direction. A closed-loop solution for the thrust direction is derived from the extremal analysis for a planar orbital transfer. The optimal control problem reduces to two unknowns, namely the thrust level and the final time. Guessing and propagating the costates is no longer necessary and the optimal trajectory is easily found from a rough initialization. On the other hand the initial costates are assessed analytically from the initial conditions and they can be used as initial guess for transfers at different thrust levels. The method is exemplified on a launcher upper stage targeting a geostationary transfer orbit.

Development of variable-width ribbon heating elements for liquid-metal and gas-cooled fast breeder reactor fuel-pin simulators

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCulloch, R.W.; Post, D.W.; Lovell, R.T.

1981-04-01

Variable-width ribbon heating elements that provide a chopped-cosine variable heat flux profile have been fabricated for fuel pin simulators used in test loops by the Breeder Reactor Program Thermal-Hydraulic Out-of-Reactor Safety test facility and the Gas-Cooled Fast Breeder Reactor-Core Flow Test Loop. Thermal, mechanical, and electrical design considerations are used to derive an analytical expression that precisely describes ribbon contour in terms of the major fabrication parameters. These parameters are used to generate numerical control tapes that control ribbon cutting and winding machines. Infrared scanning techniques are developed to determine the optimum transient thermal profile of the coils and relatemore » this profile to that generated by the coils in completed fuel pin simulators.« less

Efficient dynamic modeling of manipulators containing closed kinematic loops

NASA Astrophysics Data System (ADS)

Ferretti, Gianni; Rocco, Paolo

An approach to efficiently solve the forward dynamics problem for manipulators containing closed chains is proposed. The two main distinctive features of this approach are: the dynamics of the equivalent open loop tree structures (any closed loop can be in general modeled by imposing some additional kinematic constraints to a suitable tree structure) is computed through an efficient Newton Euler formulation; the constraint equations relative to the most commonly adopted closed chains in industrial manipulators are explicitly solved, thus, overcoming the redundancy of Lagrange's multipliers method while avoiding the inefficiency due to a numerical solution of the implicit constraint equations. The constraint equations considered for an explicit solution are those imposed by articulated gear mechanisms and planar closed chains (pantograph type structures). Articulated gear mechanisms are actually used in all industrial robots to transmit motion from actuators to links, while planar closed chains are usefully employed to increase the stiffness of the manipulators and their load capacity, as well to reduce the kinematic coupling of joint axes. The accuracy and the efficiency of the proposed approach are shown through a simulation test.

Robust fuel- and time-optimal control of uncertain flexible space structures

NASA Technical Reports Server (NTRS)

Wie, Bong; Sinha, Ravi; Sunkel, John; Cox, Ken

1993-01-01

The problem of computing open-loop, fuel- and time-optimal control inputs for flexible space structures in the face of modeling uncertainty is investigated. Robustified, fuel- and time-optimal pulse sequences are obtained by solving a constrained optimization problem subject to robustness constraints. It is shown that 'bang-off-bang' pulse sequences with a finite number of switchings provide a practical tradeoff among the maneuvering time, fuel consumption, and performance robustness of uncertain flexible space structures.

Fuel cell gas management system

DOEpatents

DuBose, Ronald Arthur

2000-01-11

A fuel cell gas management system including a cathode humidification system for transferring latent and sensible heat from an exhaust stream to the cathode inlet stream of the fuel cell; an anode humidity retention system for maintaining the total enthalpy of the anode stream exiting the fuel cell equal to the total enthalpy of the anode inlet stream; and a cooling water management system having segregated deionized water and cooling water loops interconnected by means of a brazed plate heat exchanger.

Can composite digital monitoring biomarkers come of age? A framework for utilization.

PubMed

Kovalchick, Christopher; Sirkar, Rhea; Regele, Oliver B; Kourtis, Lampros C; Schiller, Marie; Wolpert, Howard; Alden, Rhett G; Jones, Graham B; Wright, Justin M

2017-12-01

The application of digital monitoring biomarkers in health, wellness and disease management is reviewed. Harnessing the near limitless capacity of these approaches in the managed healthcare continuum will benefit from a systems-based architecture which presents data quality, quantity, and ease of capture within a decision-making dashboard. A framework was developed which stratifies key components and advances the concept of contextualized biomarkers. The framework codifies how direct, indirect, composite, and contextualized composite data can drive innovation for the application of digital biomarkers in healthcare. The de novo framework implies consideration of physiological, behavioral, and environmental factors in the context of biomarker capture and analysis. Application in disease and wellness is highlighted, and incorporation in clinical feedback loops and closed-loop systems is illustrated. The study of contextualized biomarkers has the potential to offer rich and insightful data for clinical decision making. Moreover, advancement of the field will benefit from innovation at the intersection of medicine, engineering, and science. Technological developments in this dynamic field will thus fuel its logical evolution guided by inputs from patients, physicians, healthcare providers, end-payors, actuarists, medical device manufacturers, and drug companies.

Fuel injection system and method of operating the same for an engine

DOEpatents

Topinka, Jennifer Ann [Niskayuna, NY; DeLancey, James Peter [Corinth, NY; Primus, Roy James [Niskayuna, NY; Pintgen, Florian Peter [Niskayuna, NY

2011-02-15

A fuel injector is coupled to an engine. The fuel injector includes an injection opening configured to vary in cross-section between a open state and a fully closed state. The fuel injector is configured to provide a plurality of discrete commanded fuel injections into an engine cylinder by modulating the size of the injection opening without completely closing the opening to the fully closed state.

Replacing Arginine 33 for Alanine in the Hemophore HasA from Pseudomonas aeruginosa Causes Closure of the H32 Loop in the Apo-Protein

PubMed Central

Kumar, Ritesh; Qi, Yifei; Matsumura, Hirotoshi; Lovell, Scott; Yao, Huili; Battaile, Kevin P.; Im, Wonpil; Moënne-Loccoz, Pierre; Rivera, Mario

2017-01-01

Previous characterization of hemophores from Serratia marcescens (HasAs), Pseudomonas aeruginosa (HasAp) and Yersinia pestis (HasAyp) showed that hemin binds between two loops, where it is axially coordinated by H32 and Y75. The Y75 loop is structurally conserved in all three hemophores and harbors conserved ligand Y75. The other loop contains H32 in HasAs and HasAp, but a noncoordinating Q32 in HasAyp. The H32 loop in apo-HasAs and apo-HasAp is in an open conformation, which places H32 about 30 Å from the hemin-binding site. Hence, hemin binding onto the Y75 loop of HasAs or HasAp triggers a large relocation of the H32 loop from an open- to a closed-loop conformation and enables coordination of the hemin-iron by H32. In comparison, the Q32 loop in apo-HasAyp is in the closed conformation and hemin binding occurs with minimal reorganization and without coordinative interactions with the Q32 loop. Studies in crystallo and in solution have established that the open H32 loop in apo-HasAp and apo-HasAs is well structured and minimally affected by conformational dynamics. In this study we address the intriguing issue of the stability of the H32 loop in apo-HasAp and how hemin binding triggers its relocation. We address this question with a combination of NMR spectroscopy, X-ray crystallography, and molecular dynamics simulations and find that R33 is critical to the stability of the open H32 loop. Replacing R33 with A causes the H32 loop in R33A apo-HasAp to adopt a conformation similar to that of holo-HasAp. Finally, stopped-flow absorption and resonance Raman analyses of hemin binding to apo-R33A HasAp indicates that the closed H32 loop slows down the insertion of the heme inside the binding pocket, presumably as it obstructs access to the hydrophobic platform on the Y75 loop, but accelerate the completion of the heme iron coordination. PMID:27074415

Design validation and performance of closed loop gas recirculation system

NASA Astrophysics Data System (ADS)

Kalmani, S. D.; Joshi, A. V.; Majumder, G.; Mondal, N. K.; Shinde, R. R.

2016-11-01

A pilot experimental set up of the India Based Neutrino Observatory's ICAL detector has been operational for the last 4 years at TIFR, Mumbai. Twelve glass RPC detectors of size 2 × 2 m2, with a gas gap of 2 mm are under test in a closed loop gas recirculation system. These RPCs are continuously purged individually, with a gas mixture of R134a (C2H2F4), isobutane (iC4H10) and sulphur hexafluoride (SF6) at a steady rate of 360 ml/h to maintain about one volume change a day. To economize gas mixture consumption and to reduce the effluents from being released into the atmosphere, a closed loop system has been designed, fabricated and installed at TIFR. The pressure and flow rate in the loop is controlled by mass flow controllers and pressure transmitters. The performance and integrity of RPCs in the pilot experimental set up is being monitored to assess the effect of periodic fluctuation and transients in atmospheric pressure and temperature, room pressure variation, flow pulsations, uniformity of gas distribution and power failures. The capability of closed loop gas recirculation system to respond to these changes is also studied. The conclusions from the above experiment are presented. The validations of the first design considerations and subsequent modifications have provided improved guidelines for the future design of the engineering module gas system.

The scheme for evaluation of isotopic composition of fast reactor core in closed nuclear fuel cycle

NASA Astrophysics Data System (ADS)

Saldikov, I. S.; Ternovykh, M. Yu; Fomichenko, P. A.; Gerasimov, A. S.

2017-01-01

The PRORYV (i.e. «Breakthrough» in Russian) project is currently under development. Within the framework of this project, fast reactors BN-1200 and BREST-OD-300 should be built to, inter alia, demonstrate possibility of the closed nuclear fuel cycle technologies with plutonium as a main source of power. Russia has a large inventory of plutonium which was accumulated in the result of reprocessing of spent fuel of thermal power reactors and conversion of nuclear weapons. This kind of plutonium will be used for development of initial fuel assemblies for fast reactors. To solve the closed nuclear fuel modeling tasks REPRORYV code was developed. It simulates the mass flow for nuclides in the closed fuel cycle. This paper presents the results of modeling of a closed nuclear fuel cycle, nuclide flows considering the influence of the uncertainty on the outcome of neutron-physical characteristics of the reactor.

Bio-Inspired Controller on an FPGA Applied to Closed-Loop Diaphragmatic Stimulation

PubMed Central

Zbrzeski, Adeline; Bornat, Yannick; Hillen, Brian; Siu, Ricardo; Abbas, James; Jung, Ranu; Renaud, Sylvie

2016-01-01

Cervical spinal cord injury can disrupt connections between the brain respiratory network and the respiratory muscles which can lead to partial or complete loss of ventilatory control and require ventilatory assistance. Unlike current open-loop technology, a closed-loop diaphragmatic pacing system could overcome the drawbacks of manual titration as well as respond to changing ventilation requirements. We present an original bio-inspired assistive technology for real-time ventilation assistance, implemented in a digital configurable Field Programmable Gate Array (FPGA). The bio-inspired controller, which is a spiking neural network (SNN) inspired by the medullary respiratory network, is as robust as a classic controller while having a flexible, low-power and low-cost hardware design. The system was simulated in MATLAB with FPGA-specific constraints and tested with a computational model of rat breathing; the model reproduced experimentally collected respiratory data in eupneic animals. The open-loop version of the bio-inspired controller was implemented on the FPGA. Electrical test bench characterizations confirmed the system functionality. Open and closed-loop paradigm simulations were simulated to test the FPGA system real-time behavior using the rat computational model. The closed-loop system monitors breathing and changes in respiratory demands to drive diaphragmatic stimulation. The simulated results inform future acute animal experiments and constitute the first step toward the development of a neuromorphic, adaptive, compact, low-power, implantable device. The bio-inspired hardware design optimizes the FPGA resource and time costs while harnessing the computational power of spike-based neuromorphic hardware. Its real-time feature makes it suitable for in vivo applications. PMID:27378844

Estimation of joint stiffness with a compliant load.

PubMed

Ludvig, Daniel; Kearney, Robert E

2009-01-01

Joint stiffness defines the dynamic relationship between the position of the joint and the torque acting about it. It consists of two components: intrinsic and reflex stiffness. Many previous studies have investigated joint stiffness in an open-loop environment, because the current algorithm in use is an open-loop algorithm. This paper explores issues related to the estimation of joint stiffness when subjects interact with compliant loads. First, we show analytically how the bias in closed-loop estimates of joint stiffness depends on the properties of the load, the noise power, and length of the estimated impulse response functions (IRF). We then demonstrate with simulations that the open-loop analysis will fail completely for an elastic load but may succeed for an inertial load. We further show that the open-loop analysis can yield unbiased results with an inertial load and document IRF length, signal-to-noise ratio needed, and minimum inertia needed for the analysis to succeed. Thus, by using a load with a properly selected inertia, open-loop analysis can be used under closed-loop conditions.

Portable battery-free charger for radiation dosimeters

DOEpatents

Manning, Frank W.

1984-01-01

This invention is a novel portable charger for dosimeters of the electrometer type. The charger does not require batteries or piezoelectric crystals and is of rugged construction. In a preferred embodiment, the charge includes a housing which carries means for mounting a dosimeter to be charged. The housing also includes contact means for impressing a charging voltage across the mounted dosimeter. Also, the housing carries a trigger for operating a charging system mounted in the housing. The charging system includes a magnetic loop including a permanent magnet for establishing a magnetic field through the loop. A segment of the loop is coupled to the trigger for movement thereby to positions opening and closing the loop. A coil inductively coupled with the loop generates coil-generated voltage pulses when the trigger is operated to open and close the loop. The charging system includes an electrical circuit for impressing voltage pulses from the coil across a capacitor for integrating the pulses and applying the resulting integrated voltage across the above-mentioned contact means for charging the dosimeter.

High-Performance Computing Data Center Cooling System Energy Efficiency |

Science.gov Websites

approaches involve a cooling distribution unit (CDU) (2), which interfaces with the facility cooling loop and to the energy recovery water (ERW) loop (5), which is a closed-loop system. There are three heat rejection options for this IT load: When possible, heat energy from the energy recovery loop is transferred

Mobile satellite communications - Vehicle antenna technology update

NASA Technical Reports Server (NTRS)

Bell, D.; Naderi, F. M.

1986-01-01

This paper discusses options for vehicle antennas to be used in mobile satellite communications systems. Two types of antennas are identified. A non-steerable, azimuthally omnidirectional antenna with a modest gain of 3 to 5 dBi is suggested when a low cost is desired. Alternatively, mechanically or electronically steerable antennas with a higher gain of 10 to 12 dBi are suggested to alleviate power and spectrum scarcity associated with mobile satellite communications. For steerable antennas, both open-loop and closed-loop pointing schemes are discussed. Monopulse and sequential lobing are proposed for the mechanically steered and electronically steered antennas, respectively. This paper suggests a hybrid open-loop/closed-loop pointing technique as the best performer in the mobile satellite environment.

Hardware platforms for MEMS gyroscope tuning based on evolutionary computation using open-loop and closed -loop frequency response

NASA Technical Reports Server (NTRS)

Keymeulen, Didier; Ferguson, Michael I.; Fink, Wolfgang; Oks, Boris; Peay, Chris; Terrile, Richard; Cheng, Yen; Kim, Dennis; MacDonald, Eric; Foor, David

2005-01-01

We propose a tuning method for MEMS gyroscopes based on evolutionary computation to efficiently increase the sensitivity of MEMS gyroscopes through tuning. The tuning method was tested for the second generation JPL/Boeing Post-resonator MEMS gyroscope using the measurement of the frequency response of the MEMS device in open-loop operation. We also report on the development of a hardware platform for integrated tuning and closed loop operation of MEMS gyroscopes. The control of this device is implemented through a digital design on a Field Programmable Gate Array (FPGA). The hardware platform easily transitions to an embedded solution that allows for the miniaturization of the system to a single chip.

Cardinal features of involuntary force variability can arise from the closed-loop control of viscoelastic afferented muscles

PubMed Central

Laine, Christopher M.; Valero-Cuevas, Francisco J.

2018-01-01

Involuntary force variability below 15 Hz arises from, and is influenced by, many factors including descending neural drive, proprioceptive feedback, and mechanical properties of muscles and tendons. However, their potential interactions that give rise to the well-structured spectrum of involuntary force variability are not well understood due to a lack of experimental techniques. Here, we investigated the generation, modulation, and interactions among different sources of force variability using a physiologically-grounded closed-loop simulation of an afferented muscle model. The closed-loop simulation included a musculotendon model, muscle spindle, Golgi tendon organ (GTO), and a tracking controller which enabled target-guided force tracking. We demonstrate that closed-loop control of an afferented musculotendon suffices to replicate and explain surprisingly many cardinal features of involuntary force variability. Specifically, we present 1) a potential origin of low-frequency force variability associated with co-modulation of motor unit firing rates (i.e.,‘common drive’), 2) an in-depth characterization of how proprioceptive feedback pathways suffice to generate 5-12 Hz physiological tremor, and 3) evidence that modulation of those feedback pathways (i.e., presynaptic inhibition of Ia and Ib afferents, and spindle sensitivity via fusimotor drive) influence the full spectrum of force variability. These results highlight the previously underestimated importance of closed-loop neuromechanical interactions in explaining involuntary force variability during voluntary ‘isometric’ force control. Furthermore, these results provide the basis for a unifying theory that relates spinal circuitry to various manifestations of altered involuntary force variability in fatigue, aging and neurological disease. PMID:29309405

Cardinal features of involuntary force variability can arise from the closed-loop control of viscoelastic afferented muscles.

PubMed

Nagamori, Akira; Laine, Christopher M; Valero-Cuevas, Francisco J

2018-01-01

Involuntary force variability below 15 Hz arises from, and is influenced by, many factors including descending neural drive, proprioceptive feedback, and mechanical properties of muscles and tendons. However, their potential interactions that give rise to the well-structured spectrum of involuntary force variability are not well understood due to a lack of experimental techniques. Here, we investigated the generation, modulation, and interactions among different sources of force variability using a physiologically-grounded closed-loop simulation of an afferented muscle model. The closed-loop simulation included a musculotendon model, muscle spindle, Golgi tendon organ (GTO), and a tracking controller which enabled target-guided force tracking. We demonstrate that closed-loop control of an afferented musculotendon suffices to replicate and explain surprisingly many cardinal features of involuntary force variability. Specifically, we present 1) a potential origin of low-frequency force variability associated with co-modulation of motor unit firing rates (i.e.,'common drive'), 2) an in-depth characterization of how proprioceptive feedback pathways suffice to generate 5-12 Hz physiological tremor, and 3) evidence that modulation of those feedback pathways (i.e., presynaptic inhibition of Ia and Ib afferents, and spindle sensitivity via fusimotor drive) influence the full spectrum of force variability. These results highlight the previously underestimated importance of closed-loop neuromechanical interactions in explaining involuntary force variability during voluntary 'isometric' force control. Furthermore, these results provide the basis for a unifying theory that relates spinal circuitry to various manifestations of altered involuntary force variability in fatigue, aging and neurological disease.

Assisted closed-loop optimization of SSVEP-BCI efficiency

PubMed Central

Fernandez-Vargas, Jacobo; Pfaff, Hanns U.; Rodríguez, Francisco B.; Varona, Pablo

2012-01-01

We designed a novel assisted closed-loop optimization protocol to improve the efficiency of brain-computer interfaces (BCI) based on steady state visually evoked potentials (SSVEP). In traditional paradigms, the control over the BCI-performance completely depends on the subjects' ability to learn from the given feedback cues. By contrast, in the proposed protocol both the subject and the machine share information and control over the BCI goal. Generally, the innovative assistance consists in the delivery of online information together with the online adaptation of BCI stimuli properties. In our case, this adaptive optimization process is realized by (1) a closed-loop search for the best set of SSVEP flicker frequencies and (2) feedback of actual SSVEP magnitudes to both the subject and the machine. These closed-loop interactions between subject and machine are evaluated in real-time by continuous measurement of their efficiencies, which are used as online criteria to adapt the BCI control parameters. The proposed protocol aims to compensate for variability in possibly unknown subjects' state and trait dimensions. In a study with N = 18 subjects, we found significant evidence that our protocol outperformed classic SSVEP-BCI control paradigms. Evidence is presented that it takes indeed into account interindividual variabilities: e.g., under the new protocol, baseline resting state EEG measures predict subjects' BCI performances. This paper illustrates the promising potential of assisted closed-loop protocols in BCI systems. Probably their applicability might be expanded to innovative uses, e.g., as possible new diagnostic/therapeutic tools for clinical contexts and as new paradigms for basic research. PMID:23443214

Closed-loop control of epileptiform activities in a neural population model using a proportional-derivative controller

NASA Astrophysics Data System (ADS)

Wang, Jun-Song; Wang, Mei-Li; Li, Xiao-Li; Ernst, Niebur

2015-03-01

Epilepsy is believed to be caused by a lack of balance between excitation and inhibitation in the brain. A promising strategy for the control of the disease is closed-loop brain stimulation. How to determine the stimulation control parameters for effective and safe treatment protocols remains, however, an unsolved question. To constrain the complex dynamics of the biological brain, we use a neural population model (NPM). We propose that a proportional-derivative (PD) type closed-loop control can successfully suppress epileptiform activities. First, we determine the stability of root loci, which reveals that the dynamical mechanism underlying epilepsy in the NPM is the loss of homeostatic control caused by the lack of balance between excitation and inhibition. Then, we design a PD type closed-loop controller to stabilize the unstable NPM such that the homeostatic equilibriums are maintained; we show that epileptiform activities are successfully suppressed. A graphical approach is employed to determine the stabilizing region of the PD controller in the parameter space, providing a theoretical guideline for the selection of the PD control parameters. Furthermore, we establish the relationship between the control parameters and the model parameters in the form of stabilizing regions to help understand the mechanism of suppressing epileptiform activities in the NPM. Simulations show that the PD-type closed-loop control strategy can effectively suppress epileptiform activities in the NPM. Project supported by the National Natural Science Foundation of China (Grant Nos. 61473208, 61025019, and 91132722), ONR MURI N000141010278, and NIH grant R01EY016281.

Assisted closed-loop optimization of SSVEP-BCI efficiency.

PubMed

Fernandez-Vargas, Jacobo; Pfaff, Hanns U; Rodríguez, Francisco B; Varona, Pablo

2013-01-01

We designed a novel assisted closed-loop optimization protocol to improve the efficiency of brain-computer interfaces (BCI) based on steady state visually evoked potentials (SSVEP). In traditional paradigms, the control over the BCI-performance completely depends on the subjects' ability to learn from the given feedback cues. By contrast, in the proposed protocol both the subject and the machine share information and control over the BCI goal. Generally, the innovative assistance consists in the delivery of online information together with the online adaptation of BCI stimuli properties. In our case, this adaptive optimization process is realized by (1) a closed-loop search for the best set of SSVEP flicker frequencies and (2) feedback of actual SSVEP magnitudes to both the subject and the machine. These closed-loop interactions between subject and machine are evaluated in real-time by continuous measurement of their efficiencies, which are used as online criteria to adapt the BCI control parameters. The proposed protocol aims to compensate for variability in possibly unknown subjects' state and trait dimensions. In a study with N = 18 subjects, we found significant evidence that our protocol outperformed classic SSVEP-BCI control paradigms. Evidence is presented that it takes indeed into account interindividual variabilities: e.g., under the new protocol, baseline resting state EEG measures predict subjects' BCI performances. This paper illustrates the promising potential of assisted closed-loop protocols in BCI systems. Probably their applicability might be expanded to innovative uses, e.g., as possible new diagnostic/therapeutic tools for clinical contexts and as new paradigms for basic research.

Catalytic Steam and Partial Oxidation Reforming of Liquid Fuels for Application in Improving the Efficiency of Internal Combustion Engines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brookshear, Daniel William; Pihl, Josh A.; Szybist, James P.

Here, this study investigated the potential for catalytically reforming liquid fuels in a simulated exhaust gas recirculation (EGR) mixture loop for the purpose of generating reformate that could be used to increase stoichiometric combustion engine efficiency. The experiments were performed on a simulated exhaust flow reactor using a Rh/Al 2O 3 reformer catalyst, and the fuels evaluated included iso-octane, ethanol, and gasoline. Both steam reforming and partial oxidation reforming were examined as routes for the production of reformate. Steam reforming was determined to be an ineffective option for reforming in an EGR loop, because of the high exhaust temperatures (inmore » excess of 700 °C) required to produce adequate concentrations of reformate, regardless of fuel. However, partial oxidation reforming is capable of producing hydrogen concentrations as high as 10%–16%, depending on fuel and operating conditions in the simulated EGR gas mixture. Meanwhile, measurements of total fuel enthalpy retention were shown to have favorable energetics under a range of conditions, although a tradeoff between fuel enthalpy retention and reformate production was observed. Of the three fuels evaluated, iso-octane exhibited the best overall performance, followed by ethanol and then gasoline. Overall, it was found that partial oxidation reforming of liquid fuels in a simulated EGR mixture over the Rh/Al 2O 3 catalyst demonstrated sufficiently high reformate yields and favorable energetics to warrant further evaluation in the EGR system of a stoichiometric combustion engine.« less

Catalytic Steam and Partial Oxidation Reforming of Liquid Fuels for Application in Improving the Efficiency of Internal Combustion Engines

DOE PAGES

Brookshear, Daniel William; Pihl, Josh A.; Szybist, James P.

2018-02-07

Here, this study investigated the potential for catalytically reforming liquid fuels in a simulated exhaust gas recirculation (EGR) mixture loop for the purpose of generating reformate that could be used to increase stoichiometric combustion engine efficiency. The experiments were performed on a simulated exhaust flow reactor using a Rh/Al 2O 3 reformer catalyst, and the fuels evaluated included iso-octane, ethanol, and gasoline. Both steam reforming and partial oxidation reforming were examined as routes for the production of reformate. Steam reforming was determined to be an ineffective option for reforming in an EGR loop, because of the high exhaust temperatures (inmore » excess of 700 °C) required to produce adequate concentrations of reformate, regardless of fuel. However, partial oxidation reforming is capable of producing hydrogen concentrations as high as 10%–16%, depending on fuel and operating conditions in the simulated EGR gas mixture. Meanwhile, measurements of total fuel enthalpy retention were shown to have favorable energetics under a range of conditions, although a tradeoff between fuel enthalpy retention and reformate production was observed. Of the three fuels evaluated, iso-octane exhibited the best overall performance, followed by ethanol and then gasoline. Overall, it was found that partial oxidation reforming of liquid fuels in a simulated EGR mixture over the Rh/Al 2O 3 catalyst demonstrated sufficiently high reformate yields and favorable energetics to warrant further evaluation in the EGR system of a stoichiometric combustion engine.« less

Modeling of High Capacity Passive Cooling System

DTIC Science & Technology

2009-03-01

Pulsating Heat Pipes : Closed Loop Pulsating Heat Pipes , which is also known as Meandering Capillary Tube Heat Pipe or Closed Loop Oscillating Heat ... Pipe , has emerged in the recent years as a new electronics cooling technology. The Pulsating Heat Pipe is an innovating technology that has gained...horizontal orientation, the operating temperatures are lower. Pulsating heat pipes are capable of higher heat

Adams' Closed-Loop Concept of Learning and Motor Performance: It's Application in Behavioural Kinesiology and Patients Education in Rehabilitation.

ERIC Educational Resources Information Center

Olaogun, Matthew O. B.

1986-01-01

J. Adams' application of the closed-loop theory (involving feedback and correction) on human learning and motor performance is described. The theory's applicability to behavioral kinesiology (the science of human movement) is discussed in the context of physical therapy, stressing the importance of knowledge of results as a motivating factor.…

78 FR 53664 - Drawbridge Operation Regulations; Long Island, New York Inland Waterway From East Rockaway Inlet...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-30

... deviation the Loop Parkway and the Meadowbrook Parkway Bridges may remain in the closed position between 11... operation of the Loop Parkway Bridge, mile 0.7, across Long Creek, and the Meadowbrook Parkway Bridge, mile... remain in the closed position during this public event. DATES: This deviation is effective from 11 a.m...

Digital compensation techniques for the effects of time lag in closed-loop simulation using the 6 DOF motion system

NASA Technical Reports Server (NTRS)

Brown, R.

1982-01-01

Efforts are continued to develop digital filter compensation schemes for the correction of momentum gains observed in the closed loop simulation of the docking of two satellites using the 6 DOF motion system. Several filters that work well for small delays ( .100ms) and a non-preloaded probe are discussed.

Plasticity of 150-loop in influenza neuraminidase explored by Hamiltonian replica exchange molecular dynamics simulations.

PubMed

Han, Nanyu; Mu, Yuguang

2013-01-01

Neuraminidase (NA) of influenza is a key target for antiviral inhibitors, and the 150-cavity in group-1 NA provides new insight in treating this disease. However, NA of 2009 pandemic influenza (09N1) was found lacking this cavity in a crystal structure. To address the issue of flexibility of the 150-loop, Hamiltonian replica exchange molecular dynamics simulations were performed on different groups of NAs. Free energy landscape calculated based on the volume of 150-cavity indicates that 09N1 prefers open forms of 150-loop. The turn A (residues 147-150) of the 150-loop is discovered as the most dynamical motif which induces the inter-conversion of this loop among different conformations. In the turn A, the backbone dynamic of residue 149 is highly related with the shape of 150-loop, thus can function as a marker for the conformation of 150-loop. As a contrast, the closed conformation of 150-loop is more energetically favorable in N2, one of group-2 NAs. The D147-H150 salt bridge is found having no correlation with the conformation of 150-loop. Instead the intimate salt bridge interaction between the 150 and 430 loops in N2 variant contributes the stabilizing factor for the closed form of 150-loop. The clustering analysis elaborates the structural plasticity of the loop. This enhanced sampling simulation provides more information in further structural-based drug discovery on influenza virus.

Plasticity of 150-Loop in Influenza Neuraminidase Explored by Hamiltonian Replica Exchange Molecular Dynamics Simulations

PubMed Central

Han, Nanyu; Mu, Yuguang

2013-01-01

Neuraminidase (NA) of influenza is a key target for antiviral inhibitors, and the 150-cavity in group-1 NA provides new insight in treating this disease. However, NA of 2009 pandemic influenza (09N1) was found lacking this cavity in a crystal structure. To address the issue of flexibility of the 150-loop, Hamiltonian replica exchange molecular dynamics simulations were performed on different groups of NAs. Free energy landscape calculated based on the volume of 150-cavity indicates that 09N1 prefers open forms of 150-loop. The turn A (residues 147–150) of the 150-loop is discovered as the most dynamical motif which induces the inter-conversion of this loop among different conformations. In the turn A, the backbone dynamic of residue 149 is highly related with the shape of 150-loop, thus can function as a marker for the conformation of 150-loop. As a contrast, the closed conformation of 150-loop is more energetically favorable in N2, one of group-2 NAs. The D147-H150 salt bridge is found having no correlation with the conformation of 150-loop. Instead the intimate salt bridge interaction between the 150 and 430 loops in N2 variant contributes the stabilizing factor for the closed form of 150-loop. The clustering analysis elaborates the structural plasticity of the loop. This enhanced sampling simulation provides more information in further structural-based drug discovery on influenza virus. PMID:23593372

Closed-loop motor control using high-speed fiber optics

NASA Technical Reports Server (NTRS)

Dawson, Reginald (Inventor); Rodriquiz, Dagobert (Inventor)

1991-01-01

A closed-loop control system for controlling the operation of one or more servo motors or other controllable devices is described. The system employs a fiber optics link immune to electromagnetic interference, for transmission of control signals from a controller or controllers at a remote station to the power electronics located in proximity to the motors or other devices at the local station. At the remote station the electrical control signals are time-multiplexed, converted to a formatted serial bit stream, and converted to light signals for transmission over a single fiber of the fiber optics link. At the local station, the received optical signals are reconstructed as electrical control signals for the controlled motors or other devices. At the local station, an encoder sensor linked to the driven device generates encoded feedback signals which provide information as to a condition of the controlled device. The encoded signals are placed in a formatted serial bit stream, multiplexed, and transmitted as optical signals over a second fiber of the fiber optic link which closes the control loop of the closed-loop motor controller. The encoded optical signals received at the remote station are demultiplexed, reconstructed and coupled to the controller(s) as electrical feedback signals.

Closed-loop and robust control of quantum systems.

PubMed

Chen, Chunlin; Wang, Lin-Cheng; Wang, Yuanlong

2013-01-01

For most practical quantum control systems, it is important and difficult to attain robustness and reliability due to unavoidable uncertainties in the system dynamics or models. Three kinds of typical approaches (e.g., closed-loop learning control, feedback control, and robust control) have been proved to be effective to solve these problems. This work presents a self-contained survey on the closed-loop and robust control of quantum systems, as well as a brief introduction to a selection of basic theories and methods in this research area, to provide interested readers with a general idea for further studies. In the area of closed-loop learning control of quantum systems, we survey and introduce such learning control methods as gradient-based methods, genetic algorithms (GA), and reinforcement learning (RL) methods from a unified point of view of exploring the quantum control landscapes. For the feedback control approach, the paper surveys three control strategies including Lyapunov control, measurement-based control, and coherent-feedback control. Then such topics in the field of quantum robust control as H(∞) control, sliding mode control, quantum risk-sensitive control, and quantum ensemble control are reviewed. The paper concludes with a perspective of future research directions that are likely to attract more attention.

A direct method for calculating instrument noise levels in side-by-side seismometer evaluations

USGS Publications Warehouse

Holcomb, L. Gary

1989-01-01

The subject of determining the inherent system noise levels present in modem broadband closed loop seismic sensors has been an evolving topic ever since closed loop systems became available. Closed loop systems are unique in that the system noise can not be determined via a blocked mass test as in older conventional open loop seismic sensors. Instead, most investigators have resorted to performing measurements on two or more systems operating in close proximity to one another and to analyzing the outputs of these systems with respect to one another to ascertain their relative noise levels.The analysis of side-by-side relative performance is inherently dependent on the accuracy of the mathematical modeling of the test configuration. This report presents a direct approach to extracting the system noise levels of two linear systems with a common coherent input signal. The mathematical solution to the problem is incredibly simple; however the practical application of the method encounters some difficulties. Examples of expected accuracies are presented as derived by simulating real systems performance using computer generated random noise. In addition, examples of the performance of the method when applied to real experimental test data are shown.

Closed-Loop Control System for Friction Stir Welding Retractable Pin Tool

NASA Technical Reports Server (NTRS)

Ding, R. Jeffrey; Romine, Peter L.; Munafo, Paul M. (Technical Monitor)

2001-01-01

NASA invention disclosure, NASA Case No. MFS-31413, entitled "System for Controlling the Stirring Pin of a Friction Stir Welding Apparatus", (Patent Pending) authored by Jeff Ding, Dr Peter Romine and Pete Oelgoetz, addresses the precision control of the friction stir welding process. The closed-loop control system automatically adjusts the spinning welding pin, real-time, to maintain a precise penetration ligament (i.e., distance between pin-tip and weld panel backside surface). A specific pin length can be maintained while welding constant thickness or tapered material thickness weld panels. The closed-loop control system provides operator data and information relative to the exact position of the welding pin inside the weld joint. This paper presents the closed-loop RPT control system that operates using the auto-feedback of force signals sensed by the tip and shoulder of the welding pin. Significance: The FSW process can be successfully used in a production environment only if there is a method or technique that informs the FSW operator the precise location of the welding pin inside the weld joint. This is essential for applications in aerospace, automotive, pressure vessel, commercial aircraft and other industries.

Closed-loop brain-machine-body interfaces for noninvasive rehabilitation of movement disorders.

PubMed

Broccard, Frédéric D; Mullen, Tim; Chi, Yu Mike; Peterson, David; Iversen, John R; Arnold, Mike; Kreutz-Delgado, Kenneth; Jung, Tzyy-Ping; Makeig, Scott; Poizner, Howard; Sejnowski, Terrence; Cauwenberghs, Gert

2014-08-01

Traditional approaches for neurological rehabilitation of patients affected with movement disorders, such as Parkinson's disease (PD), dystonia, and essential tremor (ET) consist mainly of oral medication, physical therapy, and botulinum toxin injections. Recently, the more invasive method of deep brain stimulation (DBS) showed significant improvement of the physical symptoms associated with these disorders. In the past several years, the adoption of feedback control theory helped DBS protocols to take into account the progressive and dynamic nature of these neurological movement disorders that had largely been ignored so far. As a result, a more efficient and effective management of PD cardinal symptoms has emerged. In this paper, we review closed-loop systems for rehabilitation of movement disorders, focusing on PD, for which several invasive and noninvasive methods have been developed during the last decade, reducing the complications and side effects associated with traditional rehabilitation approaches and paving the way for tailored individual therapeutics. We then present a novel, transformative, noninvasive closed-loop framework based on force neurofeedback and discuss several future developments of closed-loop systems that might bring us closer to individualized solutions for neurological rehabilitation of movement disorders.

Artificial Pancreas Device Systems for the Closed-Loop Control of Type 1 Diabetes

PubMed Central

Trevitt, Sara; Simpson, Sue; Wood, Annette

2015-01-01

Background: Closed-loop artificial pancreas device (APD) systems are externally worn medical devices that are being developed to enable people with type 1 diabetes to regulate their blood glucose levels in a more automated way. The innovative concept of this emerging technology is that hands-free, continuous, glycemic control can be achieved by using digital communication technology and advanced computer algorithms. Methods: A horizon scanning review of this field was conducted using online sources of intelligence to identify systems in development. The systems were classified into subtypes according to their level of automation, the hormonal and glycemic control approaches used, and their research setting. Results: Eighteen closed-loop APD systems were identified. All were being tested in clinical trials prior to potential commercialization. Six were being studied in the home setting, 5 in outpatient settings, and 7 in inpatient settings. It is estimated that 2 systems may become commercially available in the EU by the end of 2016, 1 during 2017, and 2 more in 2018. Conclusions: There are around 18 closed-loop APD systems progressing through early stages of clinical development. Only a few of these are currently in phase 3 trials and in settings that replicate real life. PMID:26589628

Closed-loop Brain-Machine-Body Interfaces for Noninvasive Rehabilitation of Movement Disorders

PubMed Central

Broccard, Frédéric D.; Mullen, Tim; Chi, Yu Mike; Peterson, David; Iversen, John R.; Arnold, Mike; Kreutz-Delgado, Kenneth; Jung, Tzyy-Ping; Makeig, Scott; Poizner, Howard; Sejnowski, Terrence; Cauwenberghs, Gert

2014-01-01

Traditional approaches for neurological rehabilitation of patients affected with movement disorders, such as Parkinson's disease (PD), dystonia, and essential tremor (ET) consist mainly of oral medication, physical therapy, and botulinum toxin injections. Recently, the more invasive method of deep brain stimulation (DBS) showed significant improvement of the physical symptoms associated with these disorders. In the past several years, the adoption of feedback control theory helped DBS protocols to take into account the progressive and dynamic nature of these neurological movement disorders that had largely been ignored so far. As a result, a more efficient and effective management of PD cardinal symptoms has emerged. In this paper, we review closed-loop systems for rehabilitation of movement disorders, focusing on PD, for which several invasive and noninvasive methods have been developed during the last decade, reducing the complications and side effects associated with traditional rehabilitation approaches and paving the way for tailored individual therapeutics. We then present a novel, transformative, noninvasive closed-loop framework based on force neurofeedback and discuss several future developments of closed-loop systems that might bring us closer to individualized solutions for neurological rehabilitation of movement disorders. PMID:24833254

Planetary Radio Interferometry and Doppler Experiment (PRIDE) technique: A test case of the Mars Express Phobos Flyby. II. Doppler tracking: Formulation of observed and computed values, and noise budget

NASA Astrophysics Data System (ADS)

Bocanegra-Bahamón, T. M.; Molera Calvés, G.; Gurvits, L. I.; Duev, D. A.; Pogrebenko, S. V.; Cimò, G.; Dirkx, D.; Rosenblatt, P.

2018-01-01

Context. Closed-loop Doppler data obtained by deep space tracking networks, such as the NASA Deep Space Network (DSN) and the ESA tracking station network (Estrack), are routinely used for navigation and science applications. By shadow tracking the spacecraft signal, Earth-based radio telescopes involved in the Planetary Radio Interferometry and Doppler Experiment (PRIDE) can provide open-loop Doppler tracking data only when the dedicated deep space tracking facilities are operating in closed-loop mode. Aims: We explain the data processing pipeline in detail and discuss the capabilities of the technique and its potential applications in planetary science. Methods: We provide the formulation of the observed and computed values of the Doppler data in PRIDE tracking of spacecraft and demonstrate the quality of the results using an experiment with the ESA Mars Express spacecraft as a test case. Results: We find that the Doppler residuals and the corresponding noise budget of the open-loop Doppler detections obtained with the PRIDE stations compare to the closed-loop Doppler detections obtained with dedicated deep space tracking facilities.

Closed-loop, pilot/vehicle analysis of the approach and landing task

NASA Technical Reports Server (NTRS)

Anderson, M. R.; Schmidt, D. K.

1986-01-01

In the case of approach and landing, it is universally accepted that the pilot uses more than one vehicle response, or output, to close his control loops. Therefore, to model this task, a multi-loop analysis technique is required. The analysis problem has been in obtaining reasonable analytic estimates of the describing functions representing the pilot's loop compensation. Once these pilot describing functions are obtained, appropriate performance and workload metrics must then be developed for the landing task. The optimal control approach provides a powerful technique for obtaining the necessary describing functions, once the appropriate task objective is defined in terms of a quadratic objective function. An approach is presented through the use of a simple, reasonable objective function and model-based metrics to evaluate loop performance and pilot workload. The results of an analysis of the LAHOS (Landing and Approach of Higher Order Systems) study performed by R.E. Smith is also presented.

Comparison between solar utilization of a closed microalgae-based bio-loop and that of a stand-alone photovoltaic system.

PubMed

Jin, Qiang; Chen, Lei; Li, Aimin; Liu, Fuqiang; Long, Chao; Shan, Aidang; Borthwick, Alistair G L

2015-05-01

This study compared the solar energy utilization of a closed microalgae-based bio-loop for energy efficient production of biogas with fertilizer recovery against that of a stand-alone photovoltaic (PV) system. The comparison was made from the perspective of broad life cycle assessment, simultaneously taking exergy to be the functional unit. The results indicated that the bio-loop was more environmentally competitive than an equivalent stand-alone PV system, but had higher economic cost due to high energy consumption during the operational phase. To fix the problem, a patented, interior pressurization scheduling method was used to operate the bio-loop, with microalgae and aerobic bacterial placed together in the same reactor. As a result, the overall environmental impact and total investment were respectively reduced by more than 75% and 84%, a vast improvement on the bio-loop. Copyright © 2014 Elsevier Ltd. All rights reserved.

Functional Loop Dynamics of the Streptavidin-Biotin Complex

PubMed Central

Song, Jianing; Li, Yongle; Ji, Changge; Zhang, John Z. H.

2015-01-01

Accelerated molecular dynamics (aMD) simulation is employed to study the functional dynamics of the flexible loop3-4 in the strong-binding streptavidin-biotin complex system. Conventional molecular (cMD) simulation is also performed for comparison. The present study reveals the following important properties of the loop dynamics: (1) The transition of loop3-4 from open to closed state is observed in 200 ns aMD simulation. (2) In the absence of biotin binding, the open-state streptavidin is more stable, which is consistent with experimental evidences. The free energy (ΔG) difference is about 5 kcal/mol between two states. But with biotin binding, the closed state is more stable due to electrostatic and hydrophobic interactions between the loop3-4 and biotin. (3) The closure of loop3-4 is concerted to the stable binding of biotin to streptavidin. When the loop3-4 is in its open-state, biotin moves out of the binding pocket, indicating that the interactions between the loop3-4 and biotin are essential in trapping biotin in the binding pocket. (4) In the tetrameric streptavidin system, the conformational change of the loop3-4 in each monomer is independent of each other. That is, there is no cooperative binding for biotin bound to the four subunits of the tetramer. PMID:25601277

PDCI Wide-Area Damping Control: PSLF Simulations of the 2016 Open and Closed Loop Test Plan

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilches Bernal, Felipe; Pierre, Brian Joseph; Elliott, Ryan Thomas

To demonstrate and validate the performance of the wide-are a damping control system, the project plans to conduct closed-loop tests on the PDCI in summer/fall 2016. A test plan details the open and closed loop tests to be conducted on the P DCI using the wide-area damping control system. To ensure the appropriate level of preparedness, simulations were performed in order to predict and evaluate any possible unsafe operations before hardware experiments are attempted. This report contains the result s from these simulations using the power system dynamics software PSLF (Power System Load Flow, trademark of GE). The simulations usemore » the WECC (Western Electricity Coordinating Council) 2016 light summer and heavy summer base cases.« less

A Survey on Security and Privacy in Emerging Sensor Networks: From Viewpoint of Close-Loop.

PubMed

Zhang, Lifu; Zhang, Heng

2016-03-26

Nowadays, as the next generation sensor networks, Cyber-Physical Systems (CPSs) refer to the complex networked systems that have both physical subsystems and cyber components, and the information flow between different subsystems and components is across a communication network, which forms a closed-loop. New generation sensor networks are found in a growing number of applications and have received increasing attention from many inter-disciplines. Opportunities and challenges in the design, analysis, verification and validation of sensor networks co-exists, among which security and privacy are two important ingredients. This paper presents a survey on some recent results in the security and privacy aspects of emerging sensor networks from the viewpoint of the closed-loop. This paper also discusses several future research directions under these two umbrellas.

A classical model for closed-loop diagrams of binary liquid mixtures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schnitzler, J.v.; Prausnitz, J.M.

1994-03-01

A classical lattice model for closed-loop temperature-composition phase diagrams has been developed. It considers the effect of specific interactions, such as hydrogen bonding, between dissimilar components. This van Laar-type model includes a Flory-Huggins term for the excess entropy of mixing. It is applied to several liquid-liquid equilibria of nonelectrolytes, where the molecules of the two components differ in size. The model is able to represent the observed data semi-quantitatively, but in most cases it is not flexible enough to predict all parts of the closed loop quantitatively. The ability of the model to represent different binary systems is discussed. Finally,more » attention is given to a correction term, concerning the effect of concentration fluctuations near the upper critical solution temperature.« less

A low power flash-FPGA based brain implant micro-system of PID control.

PubMed

Lijuan Xia; Fattah, Nabeel; Soltan, Ahmed; Jackson, Andrew; Chester, Graeme; Degenaar, Patrick

2017-07-01

In this paper, we demonstrate that a low power flash FPGA based micro-system can provide a low power programmable interface for closed-loop brain implant inter- faces. The proposed micro-system receives recording local field potential (LFP) signals from an implanted probe, performs closed-loop control using a first order control system, then converts the signal into an optogenetic control stimulus pattern. Stimulus can be implemented through optoelectronic probes. The long term target is for both fundamental neuroscience applications and for clinical use in treating epilepsy. Utilizing our device, closed-loop processing consumes only 14nJ of power per PID cycle compared to 1.52μJ per cycle for a micro-controller implementation. Compared to an application specific digital integrated circuit, flash FPGA's are inherently programmable.

The early history of the closed loop fiber optic gyro and derivative sensors at McDonnell Douglas, Blue Road Research and Columbia Gorge Research

NASA Astrophysics Data System (ADS)

Udd, Eric

2016-05-01

On September 29, 1977 the first written disclosure of a closed loop fiber optic gyro was witnessed and signed off by four people at McDonnell Douglas Astronautics Company in Huntington Beach, California. Over the next ten years a breadboard demonstration unit, and several prototypes were built. In 1987 the fundamental patent for closed loop operation began a McDonnell Douglas worldwide licensing process. Internal fiber optic efforts were redirected to derivative sensors and inventions. This included development of acoustic, strain and distributed sensors as well as a Sagnac interferometer based secure fiber optic communication system and the new field of fiber optic smart structures. This paper provides an overview of these activities and transitions.

Feedforward control of a closed-loop piezoelectric translation stage for atomic force microscope.

PubMed

Li, Yang; Bechhoefer, John

2007-01-01

Simple feedforward ideas are shown to lead to a nearly tenfold increase in the effective bandwidth of a closed-loop piezoelectric positioning stage used in scanning probe microscopy. If the desired control signal is known in advance, the feedforward filter can be acausal: the information about the future can be used to make the output of the stage have almost no phase lag with respect to the input. This keeps in register the images assembled from right and left scans. We discuss the design constraints imposed by the need for the feedforward filter to work robustly under a variety of circumstances. Because the feedforward needs only to modify the input signal, it can be added to any piezoelectric stage, whether closed or open loop.

A modular, closed-loop platform for intracranial stimulation in people with neurological disorders.

PubMed

Sarma, Anish A; Crocker, Britni; Cash, Sydney S; Truccolo, Wilson

2016-08-01

Neuromodulation systems based on electrical stimulation can be used to investigate, probe, and potentially treat a range of neurological disorders. The effects of ongoing neural state and dynamics on stimulation response, and of stimulation parameters on neural state, have broad implications for the development of closed-loop neuro-modulation approaches. We describe the development of a modular, low-latency platform for pre-clinical, closed-loop neuromodulation studies with human participants. We illustrate the uses of the platform in a stimulation case study with a person with epilepsy undergoing neuro-monitoring prior to resective surgery. We demonstrate the efficacy of the system by tracking interictal epileptiform discharges in the local field potential to trigger intracranial electrical stimulation, and show that the response to stimulation depends on the neural state.

A closed-loop time-alignment system for baseband combining

NASA Technical Reports Server (NTRS)

Feria, Y.

1994-01-01

In baseband combining, the key element is the time alignment of the baseband signals. This article describes a closed-loop time-alignment system that estimates and adjusts the relative delay between two baseband signals received from two different antennas for the signals to be coherently combined. This system automatically determines which signal is advanced and delays it accordingly with a resolution of a sample period. The performance of the loop is analyzed, and the analysis is verified through simulation. The variance of the delay estimates and the signal-to-noise ratio degradation in the simulations agree with the theoretical calculations.

Closed-loop, pilot/vehicle analysis of the approach and landing task

NASA Technical Reports Server (NTRS)

Schmidt, D. K.; Anderson, M. R.

1985-01-01

Optimal-control-theoretic modeling and frequency-domain analysis is the methodology proposed to evaluate analytically the handling qualities of higher-order manually controlled dynamic systems. Fundamental to the methodology is evaluating the interplay between pilot workload and closed-loop pilot/vehicle performance and stability robustness. The model-based metric for pilot workload is the required pilot phase compensation. Pilot/vehicle performance and loop stability is then evaluated using frequency-domain techniques. When these techniques were applied to the flight-test data for thirty-two highly-augmented fighter configurations, strong correlation was obtained between the analytical and experimental results.

Frequency set on systems

NASA Astrophysics Data System (ADS)

Wilby, W. A.; Brett, A. R. H.

Frequency set on techniques used in ECM applications include repeater jammers, frequency memory loops (RF and optical), coherent digital RF memories, and closed loop VCO set on systems. Closed loop frequency set on systems using analog phase and frequency locking are considered to have a number of cost and performance advantages. Their performance is discussed in terms of frequency accuracy, bandwidth, locking time, stability, and simultaneous signals. Some experimental results are presented which show typical locking performance. Future ECM systems might require a response to very short pulses. Acoustooptic and fiber-optic pulse stretching techniques can be used to meet such requirements.

Integrated Testing of a Carbon Dioxide Removal Assembly and a Temperature-Swing Adsorption Compressor for Closed-Loop Air Revitalization

NASA Technical Reports Server (NTRS)

Knox, J. C.; Mulloth, Lila; Frederick, Kenneth; Affleck, Dave

2003-01-01

Accumulation and subsequent compression of carbon dioxide that is removed from space cabin are two important processes involved in a closed-loop air revitalization scheme of the International Space Station (ISS). The carbon dioxide removal assembly (CDRA) of ISS currently operates in an open loop mode without a compressor. This paper describes the integrated test results of a flight-like CDRA and a temperature-swing adsorption compressor (TSAC) for carbon dioxide removal and compression. The paper provides details of the TSAC operation at various CO2 loadings and corresponding performance of CDRA.

Structural features of the DNA hairpin d(ATCCTA-GTTA-TAGGAT): formation of a G-A base pair in the loop.

PubMed Central

van Dongen, M J; Mooren, M M; Willems, E F; van der Marel, G A; van Boom, J H; Wijmenga, S S; Hilbers, C W

1997-01-01

The three-dimensional structure of the hairpin formed by d(ATCCTA-GTTA-TAGGAT) has been determined by means of two-dimensional NMR studies, distance geometry and molecular dynamics calculations. The first and the last residues of the tetraloop of this hairpin form a sheared G-A base pair on top of the six Watson-Crick base pairs in the stem. The glycosidic torsion angles of the guanine and adenine residues in the G-A base pair reside in the anti and high- anti domain ( approximately -60 degrees ) respectively. Several dihedral angles in the loop adopt non-standard values to accommodate this base pair. The first and second residue in the loop are stacked in a more or less normal helical fashion; the fourth loop residue also stacks upon the stem, while the third residue is directed away from the loop region. The loop structure can be classified as a so-called type-I loop, in which the bases at the 5'-end of the loop stack in a continuous fashion. In this situation, loop stability is unlikely to depend heavily on the nature of the unpaired bases in the loop. Moreover, the present study indicates that the influence of the polarity of a closing A.T pair is much less significant than that of a closing C.G base pair. PMID:9092659

Dressed Wilson loops as dual condensates in response to magnetic and electric fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruckmann, Falk; Endroedi, Gergely

2011-10-01

We introduce dressed Wilson loops as a novel confinement observable. It consists of closed planar loops of arbitrary geometry but fixed area, and its expectation values decay with the latter. The construction of dressed Wilson loops is based on chiral condensates in response to magnetic and electric fields, thus linking different physical concepts. We present results for generalized condensates and dressed Wilson loops on dynamical lattice configurations and confirm the agreement with conventional Wilson loops in the limit of large probe mass. We comment on the renormalization of dressed Wilson loops.

A proof-of-principle simulation for closed-loop control based on preexisting experimental thalamic DBS-enhanced instrumental learning.

PubMed

Wang, Ching-Fu; Yang, Shih-Hung; Lin, Sheng-Huang; Chen, Po-Chuan; Lo, Yu-Chun; Pan, Han-Chi; Lai, Hsin-Yi; Liao, Lun-De; Lin, Hui-Ching; Chen, Hsu-Yan; Huang, Wei-Chen; Huang, Wun-Jhu; Chen, You-Yin

Deep brain stimulation (DBS) has been applied as an effective therapy for treating Parkinson's disease or essential tremor. Several open-loop DBS control strategies have been developed for clinical experiments, but they are limited by short battery life and inefficient therapy. Therefore, many closed-loop DBS control systems have been designed to tackle these problems by automatically adjusting the stimulation parameters via feedback from neural signals, which has been reported to reduce the power consumption. However, when the association between the biomarkers of the model and stimulation is unclear, it is difficult to develop an optimal control scheme for other DBS applications, i.e., DBS-enhanced instrumental learning. Furthermore, few studies have investigated the effect of closed-loop DBS control for cognition function, such as instrumental skill learning, and have been implemented in simulation environments. In this paper, we proposed a proof-of-principle design for a closed-loop DBS system, cognitive-enhancing DBS (ceDBS), which enhanced skill learning based on in vivo experimental data. The ceDBS acquired local field potential (LFP) signal from the thalamic central lateral (CL) nuclei of animals through a neural signal processing system. A strong coupling of the theta oscillation (4-7 Hz) and the learning period was found in the water reward-related lever-pressing learning task. Therefore, the theta-band power ratio, which was the averaged theta band to averaged total band (1-55 Hz) power ratio, could be used as a physiological marker for enhancement of instrumental skill learning. The on-line extraction of the theta-band power ratio was implemented on a field-programmable gate array (FPGA). An autoregressive with exogenous inputs (ARX)-based predictor was designed to construct a CL-thalamic DBS model and forecast the future physiological marker according to the past physiological marker and applied DBS. The prediction could further assist the design of a closed-loop DBS controller. A DBS controller based on a fuzzy expert system was devised to automatically control DBS according to the predicted physiological marker via a set of rules. The simulated experimental results demonstrate that the ceDBS based on the closed-loop control architecture not only reduced power consumption using the predictive physiological marker, but also achieved a desired level of physiological marker through the DBS controller. Copyright © 2017 Elsevier Inc. All rights reserved.

Multi-thermal observations of newly formed loops in a dynamic flare

NASA Technical Reports Server (NTRS)

Svestka, Zdenek F.; Fontenla, Juan M.; Machado, Marcos E.; Martin, Sara F.; Neidig, Donald F.

1987-01-01

The dynamic flare of November 6, 1980 (max at about 15:26 UT) developed a rich system of growing loops which could be followed in H-alpha for 1.5 hr. Throughout the flare, these loops, near the limb, were seen in emission against the disk. Theoretical computations of deviations from LTE populations for a hydrogen atom reveal that this requires electron densities in the loops close to, or in excess of 10 to the 12th/cu cm. From measured widths of higher Balmer lines the density at the tops of the loops was found to be 4 x 10 to the 12th/cu cm if no nonthermal motions were present, or 5 x 10 to the 11th/cu cm for a turbulent velocity of about 12 km/s. It is now general knowledge that flare loops are initially observed in X-rays and become visible in H-alpha only after cooling. For such a high density, a loop would cool through radiation from 10 to the 7th to 10 to the 4th K within a few minutes so that the dense H-alpha loops should have heights very close to the heights of the X-ray loops. This, however, contradicts the observations obtained by the HXIS and FCS instruments on board SMM which show the X-ray loops at much higher altitudes than the loops in H-alpha. Therefore, it is suggested that the density must have been significantly lower when the loops were formed, and that the flare loops were apparently both shrinking and increasing in density while cooling.

Design strategies for dynamic closed-loop optogenetic neurocontrol in vivo

NASA Astrophysics Data System (ADS)

Bolus, M. F.; Willats, A. A.; Whitmire, C. J.; Rozell, C. J.; Stanley, G. B.

2018-04-01

Objective. Controlling neural activity enables the possibility of manipulating sensory perception, cognitive processes, and body movement, in addition to providing a powerful framework for functionally disentangling the neural circuits that underlie these complex phenomena. Over the last decade, optogenetic stimulation has become an increasingly important and powerful tool for understanding neural circuit function, owing to the ability to target specific cell types and bidirectionally modulate neural activity. To date, most stimulation has been provided in open-loop or in an on/off closed-loop fashion, where previously-determined stimulation is triggered by an event. Here, we describe and demonstrate a design approach for precise optogenetic control of neuronal firing rate modulation using feedback to guide stimulation continuously. Approach. Using the rodent somatosensory thalamus as an experimental testbed for realizing desired time-varying patterns of firing rate modulation, we utilized a moving average exponential filter to estimate firing rate online from single-unit spiking measured extracellularly. This estimate of instantaneous rate served as feedback for a proportional integral (PI) controller, which was designed during the experiment based on a linear-nonlinear Poisson (LNP) model of the neuronal response to light. Main results. The LNP model fit during the experiment enabled robust closed-loop control, resulting in good tracking of sinusoidal and non-sinusoidal targets, and rejection of unmeasured disturbances. Closed-loop control also enabled manipulation of trial-to-trial variability. Significance. Because neuroscientists are faced with the challenge of dissecting the functions of circuit components, the ability to maintain control of a region of interest in spite of changes in ongoing neural activity will be important for disambiguating function within networks. Closed-loop stimulation strategies are ideal for control that is robust to such changes, and the employment of continuous feedback to adjust stimulation in real-time can improve the quality of data collected using optogenetic manipulation.

First Results from a Hardware-in-the-Loop Demonstration of Closed-Loop Autonomous Formation Flying

NASA Technical Reports Server (NTRS)

Gill, E.; Naasz, Bo; Ebinuma, T.

2003-01-01

A closed-loop system for the demonstration of autonomous satellite formation flying technologies using hardware-in-the-loop has been developed. Making use of a GPS signal simulator with a dual radio frequency outlet, the system includes two GPS space receivers as well as a powerful onboard navigation processor dedicated to the GPS-based guidance, navigation, and control of a satellite formation in real-time. The closed-loop system allows realistic simulations of autonomous formation flying scenarios, enabling research in the fields of tracking and orbit control strategies for a wide range of applications. The autonomous closed-loop formation acquisition and keeping strategy is based on Lyapunov's direct control method as applied to the standard set of Keplerian elements. This approach not only assures global and asymptotic stability of the control but also maintains valuable physical insight into the applied control vectors. Furthermore, the approach can account for system uncertainties and effectively avoids a computationally expensive solution of the two point boundary problem, which renders the concept particularly attractive for implementation in onboard processors. A guidance law has been developed which strictly separates the relative from the absolute motion, thus avoiding the numerical integration of a target trajectory in the onboard processor. Moreover, upon using precise kinematic relative GPS solutions, a dynamical modeling or filtering is avoided which provides for an efficient implementation of the process on an onboard processor. A sample formation flying scenario has been created aiming at the autonomous transition of a Low Earth Orbit satellite formation from an initial along-track separation of 800 m to a target distance of 100 m. Assuming a low-thrust actuator which may be accommodated on a small satellite, a typical control accuracy of less than 5 m has been achieved which proves the applicability of autonomous formation flying techniques to formations of satellites as close as 50 m.

Automatic control of finite element models for temperature-controlled radiofrequency ablation

PubMed Central

Haemmerich, Dieter; Webster, John G

2005-01-01

Background The finite element method (FEM) has been used to simulate cardiac and hepatic radiofrequency (RF) ablation. The FEM allows modeling of complex geometries that cannot be solved by analytical methods or finite difference models. In both hepatic and cardiac RF ablation a common control mode is temperature-controlled mode. Commercial FEM packages don't support automating temperature control. Most researchers manually control the applied power by trial and error to keep the tip temperature of the electrodes constant. Methods We implemented a PI controller in a control program written in C++. The program checks the tip temperature after each step and controls the applied voltage to keep temperature constant. We created a closed loop system consisting of a FEM model and the software controlling the applied voltage. The control parameters for the controller were optimized using a closed loop system simulation. Results We present results of a temperature controlled 3-D FEM model of a RITA model 30 electrode. The control software effectively controlled applied voltage in the FEM model to obtain, and keep electrodes at target temperature of 100°C. The closed loop system simulation output closely correlated with the FEM model, and allowed us to optimize control parameters. Discussion The closed loop control of the FEM model allowed us to implement temperature controlled RF ablation with minimal user input. PMID:16018811

Maximized Gust Loads of a Closed-Loop, Nonlinear Aeroelastic System Using Nonlinear Systems Theory

NASA Technical Reports Server (NTRS)

Silva, Walter A.

1999-01-01

The problem of computing the maximized gust load for a nonlinear, closed-loop aeroelastic aircraft is discusses. The Volterra theory of nonlinear systems is applied in order to define a linearized system that provides a bounds on the response of the nonlinear system of interest. The method is applied to a simplified model of an Airbus A310.

CLOSED-LOOP TREATMENT OF ELECTROLYTIC AND ELECTROLESS NICKEL RINSE WATER BY POINT-OF-USE ION EXCHANGE: A CASE STUDY.

EPA Science Inventory

Closed-Loop Treatment of Electrolytic and Electroless Nickel Rinse Water by Point-Of-Use Ion Exchange: A Case Study.

Dave Szlag1, Joe Leonhardt2, Albert Foster1, Mike Goss1 and Paul Bolger1.
1 U.S. EPA, National Risk Management Research Laboratory, 26 W. M. L. King D...

ACOSS Six (Active Control of Space Structures)

DTIC Science & Technology

1981-10-01

modes, specially useful simpler conditions for ensuring closed-loop asymptotic stability are also derived. In addition, conditions for robustness of...in this initial study of FOCL stability and robustness . Such a condition is strong but not unreasonable nor unrealistic. Many useful simple in- sights...smallest possible feedback gains) and many interesting numerical results on closed-loop stability and robustness of the modal-dashpot designs. The

Joint angle sensors for closed-loop control

NASA Astrophysics Data System (ADS)

Ko, Wen H.; Miao, Chih-Lei

In order to substitute braces that have built-in goniometers and to provide feedback signals for closed loop control of lower extremity Functional Neuromuscular System in paraplegics, a stretchable capacitive sensor was developed to accurately detect angular movement in joints. Promising clinical evaluations on the knee joints of a paraplegic and a volunteer were done. The evaluations show great promise for the possibility of implantation applications.

Interplanetary travel: Is gravity needed to close the loop

NASA Technical Reports Server (NTRS)

Vernikos-Danellis, Joan

1988-01-01

Evidence has been accumulating from spaceflight and ground simulation studies suggesting that the normal relationship between neuroendocrine driving mechanisms and their respective target organs may become uncoupled; and that the sensitivity of the various components of the closed-loop systems may be altered. Changes in the regulation of the pituitary-adrenal system and the angioten-sinaldosterone system is discussed in support of this thesis.

F-14 modeling study

NASA Technical Reports Server (NTRS)

Levison, W. H.; Baron, S.

1984-01-01

Preliminary results in the application of a closed loop pilot/simulator model to the analysis of some simulator fidelity issues are discussed in the context of an air to air target tracking task. The closed loop model is described briefly. Then, problem simplifications that are employed to reduce computational costs are discussed. Finally, model results showing sensitivity of performance to various assumptions concerning the simulator and/or the pilot are presented.

Fort Knox, KY Containment Berm Unit Installation

DTIC Science & Technology

2013-02-01

There is interest from the range community in establishing a sustainable, closed loop small arms firing range (SAFR) bullet impact system or Containment... system . The metals from the bullets will be retained, stabilized, in the berm material with the addition of proper amendments. Following sufficient...replaced or placed back in the connex. This provides a closed loop containment system for sustainable range training purposes. The Containment Berm

[Research on the Clinical Alarm Management Mechanism Based on Closed-loop Control Theory].

PubMed

Lin, Zhongkuan; Zheng, Kun; Shen, Yunming; Wu, Yunyun

2018-05-30

This paper proposes a clinical alarm management system based on the theory of the closed loop control. The alarm management mechanism can be divided into the expected standard, improving execution rule, rule execution, medical devices with alarm functions, results analysis strategy and the output link. And, we make relevant application and discussion. Results showed that the mechanism can be operable and effective.

Assurance of Learning and the MFT: Closing the Loops with an Online Review

ERIC Educational Resources Information Center

Middleton, Karen L.; Loveland, Karen A.

2014-01-01

The authors describe the four stages of the closing the loop process undertaken by a college of business (COB) over a 6-year period. The COB developed and offered an online, noncredit review course to help students prepare for the Major Field Test in Business (MFT). Early results demonstrated the efficacy of the course as student scores rose from…

Stabilization of a system with saturating, non-monotone hysteresis and frequency dependent power losses by a PD controller

NASA Astrophysics Data System (ADS)

Ekanayake, D. B.; Iyer, R. V.

2015-02-01

We prove the closed loop stability of a PD controller for certain systems with saturating, non-monotone hysteresis and frequency dependent power losses. Most controllers use inverse compensators to cancel out actuator hysteresis nonlinearity. We show that we can achieve stability of the closed-loop system without an explicit inverse computation (using least squares minimization or otherwise).

Performance of an Ambulatory Dry-EEG Device for Auditory Closed-Loop Stimulation of Sleep Slow Oscillations in the Home Environment

PubMed Central

Debellemaniere, Eden; Chambon, Stanislas; Pinaud, Clemence; Thorey, Valentin; Dehaene, David; Léger, Damien; Chennaoui, Mounir; Arnal, Pierrick J.; Galtier, Mathieu N.

2018-01-01

Recent research has shown that auditory closed-loop stimulation can enhance sleep slow oscillations (SO) to improve N3 sleep quality and cognition. Previous studies have been conducted in lab environments. The present study aimed to validate and assess the performance of a novel ambulatory wireless dry-EEG device (WDD), for auditory closed-loop stimulation of SO during N3 sleep at home. The performance of the WDD to detect N3 sleep automatically and to send auditory closed-loop stimulation on SO were tested on 20 young healthy subjects who slept with both the WDD and a miniaturized polysomnography (part 1) in both stimulated and sham nights within a double blind, randomized and crossover design. The effects of auditory closed-loop stimulation on delta power increase were assessed after one and 10 nights of stimulation on an observational pilot study in the home environment including 90 middle-aged subjects (part 2).The first part, aimed at assessing the quality of the WDD as compared to a polysomnograph, showed that the sensitivity and specificity to automatically detect N3 sleep in real-time were 0.70 and 0.90, respectively. The stimulation accuracy of the SO ascending-phase targeting was 45 ± 52°. The second part of the study, conducted in the home environment, showed that the stimulation protocol induced an increase of 43.9% of delta power in the 4 s window following the first stimulation (including evoked potentials and SO entrainment effect). The increase of SO response to auditory stimulation remained at the same level after 10 consecutive nights. The WDD shows good performances to automatically detect in real-time N3 sleep and to send auditory closed-loop stimulation on SO accurately. These stimulation increased the SO amplitude during N3 sleep without any adaptation effect after 10 consecutive nights. This tool provides new perspectives to figure out novel sleep EEG biomarkers in longitudinal studies and can be interesting to conduct broad studies on the effects of auditory stimulation during sleep. PMID:29568267

Phase III integrated water recovery testing at MSFC - Partially closed hygiene loop and open potable loop results and lessons learned

NASA Technical Reports Server (NTRS)

Bagdigian, R. M.; Traweek, M. S.; Griffith, G. K.; Griffin, M. R.

1991-01-01

A series of tests has been conducted at the NASA Marshall Space Flight Center (MSFC) to evaluate the performance of a predevelopment water recovery system. Potable, hygiene, and urine reclamation subsystems were integrated with end-use equipment items and successfully operated in open and partially closed-loop modes, with man-in-the-loop, for a total of 28 days. Several significant subsystem physical anomalies were encountered during testing. Reclaimed potable and hygiene water generally met the current Space Station Freedom (SSF) water quality specifications for inorganic and microbiological constituents, but exceeded the maximum allowable concentrations for Total Organic Carbon (TOC). This paper summarizes the test objectives, system design, test activities/protocols, significant results/anomalies, and major lessons learned.

A hybrid solution approach for a multi-objective closed-loop logistics network under uncertainty

NASA Astrophysics Data System (ADS)

Mehrbod, Mehrdad; Tu, Nan; Miao, Lixin

2015-06-01

The design of closed-loop logistics (forward and reverse logistics) has attracted growing attention with the stringent pressures of customer expectations, environmental concerns and economic factors. This paper considers a multi-product, multi-period and multi-objective closed-loop logistics network model with regard to facility expansion as a facility location-allocation problem, which more closely approximates real-world conditions. A multi-objective mixed integer nonlinear programming formulation is linearized by defining new variables and adding new constraints to the model. By considering the aforementioned model under uncertainty, this paper develops a hybrid solution approach by combining an interactive fuzzy goal programming approach and robust counterpart optimization based on three well-known robust counterpart optimization formulations. Finally, this paper compares the results of the three formulations using different test scenarios and parameter-sensitive analysis in terms of the quality of the final solution, CPU time, the level of conservatism, the degree of closeness to the ideal solution, the degree of balance involved in developing a compromise solution, and satisfaction degree.

Amplification of Reynolds number dependent processes by wave distortion. [acoustic instability of liquid propellant rocket engines

NASA Technical Reports Server (NTRS)

Ventrice, M. B.; Fang, J. C.; Purdy, K. R.

1975-01-01

A system using a hot-wire transducer as an analog of a liquid droplet of propellant was employed to investigate the ingredients of the acoustic instability of liquid-propellant rocket engines. It was assumed that the combustion process was vaporization-limited and that the combustion chamber was acoustically similar to a closed-closed right-circular cylinder. Before studying the hot-wire closed-loop system (the analog system), a microphone closed-loop system, which used the response of a microphone as the source of a linear feedback exciting signal, was investigated to establish the characteristics of self-sustenance of acoustic fields. Self-sustained acoustic fields were found to occur only at resonant frequencies of the chamber. In the hot-wire closed-loop system, the response of hot-wire anemometer was used as the source of the feedback exciting signal. The self-sustained acoustic fields which developed in the system were always found to be harmonically distorted and to have as their fundamental frquency a resonant frequency for which there also existed a second resonant frequency which was approximately twice the fundamental frequency.

A 16-Channel CMOS Chopper-Stabilized Analog Front-End ECoG Acquisition Circuit for a Closed-Loop Epileptic Seizure Control System.

PubMed

Wu, Chung-Yu; Cheng, Cheng-Hsiang; Chen, Zhi-Xin

2018-06-01

In this paper, a 16-channel analog front-end (AFE) electrocorticography signal acquisition circuit for a closed-loop seizure control system is presented. It is composed of 16 input protection circuits, 16 auto-reset chopper-stabilized capacitive-coupled instrumentation amplifiers (AR-CSCCIA) with bandpass filters, 16 programmable transconductance gain amplifiers, a multiplexer, a transimpedance amplifier, and a 128-kS/s 10-bit delta-modulated successive-approximation-register analog-to-digital converter (SAR ADC). In closed-loop seizure control system applications, the stimulator shares the same electrode with the AFE amplifier for effective suppression of epileptic seizures. To prevent from overstress in MOS devices caused by high stimulation voltage, an input protection circuit with a high-voltage-tolerant switch is proposed for the AFE amplifier. Moreover, low input-referred noise is achieved by using the chopper modulation technique in the AR-CSCCIA. To reduce the undesired effects of chopper modulation, an improved offset reduction loop is proposed to reduce the output offset generated by input chopper mismatches. The digital ripple reduction loop is also used to reduce the chopper ripple. The fabricated AFE amplifier has 49.1-/59.4-/67.9-dB programmable gain and 2.02-μVrms input referred noise in a bandwidth of 0.59-117 Hz. The measured power consumption of the AFE amplifier is 3.26 μW per channel, and the noise efficiency factor is 3.36. The in vivo animal test has been successfully performed to verify the functions. It is shown that the proposed AFE acquisition circuit is suitable for implantable closed-loop seizure control systems.

The basic features of a closed fuel cycle without fast reactors

NASA Astrophysics Data System (ADS)

Bobrov, E. A.; Alekseev, P. N.; Teplov, P. S.

2017-01-01

In this paper the basic features of a closed fuel cycle with thermal reactors are considered. The three variants of multiple Pu and U recycling in VVER reactors was investigated. The comparison of MOX and REMIX fuel approaches for closed fuel cycle with thermal reactors is presented. All variants make possible to recycle several times the total amount of Pu and U obtained from spent fuel. The reported study was funded by RFBR according to the research project № 16-38-00021

IN-PILE CORROSION TEST LOOPS FOR AQUEOUS HOMOGENEOUS REACTOR SOLUTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Savage, H.C.; Jenks, G.H.; Bohlmann, E.G.

1960-12-21

An in-pile corrosion test loop is described which is used to study the effect of reactor radiation on the corrosion of materials of construction and the chemical stability of fuel solutions of interest to the Aqueous Homogeneous Reactor Program at ORNL. Aqueous solutions of uranyl sulfate are circulated in the loop by means of a 5-gpm canned-rotor pump, and the pump loop is designed for operation at temperatures to 300 ts C and pressures to 2000 psia while exposed to reactor radiation in beam-hole facilities of the LITR and ORR. Operation of the first loop in-pile was begun in Octobermore » 1954, and since that time 17 other in-pile loop experiments were completed. Design criteria of the pump loop and its associated auxiliary equipment and instrumentation are described. In-pile operating procedures, safety features, and operating experience are presented. A cost summary of the design, fabrication, and installation of the loop and experimental facillties is also included. (auth)« less

General view of a Space Shuttle Main Engine (SSME) mounted ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

General view of a Space Shuttle Main Engine (SSME) mounted on an SSME engine handler, taken in the SSME Processing Facility at Kennedy Space Center. The most prominent features of the engine assembly in this view are the Low-Pressure Fuel Turbopump Discharge Duct looping diagonally across the top of the assembly and connecting to the High-Pressure Fuel Turbopump, the Low-Pressure Oxidizer Turbopump (LPOTP) located center right of the assembly and the LPOTP Discharge Duct looping around from the pump to the underside of the engine assembly in this view. - Space Transportation System, Space Shuttle Main Engine, Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

In silico preclinical trials: a proof of concept in closed-loop control of type 1 diabetes.

PubMed

Kovatchev, Boris P; Breton, Marc; Man, Chiara Dalla; Cobelli, Claudio

2009-01-01

Arguably, a minimally invasive system using subcutaneous (s.c.) continuous glucose monitoring (CGM) and s.c. insulin delivery via insulin pump would be a most feasible step to closed-loop control in type 1 diabetes mellitus (T1DM). Consequently, diabetes technology is focusing on developing an artificial pancreas using control algorithms to link CGM with s.c. insulin delivery. The future development of the artificial pancreas will be greatly accelerated by employing mathematical modeling and computer simulation. Realistic computer simulation is capable of providing invaluable information about the safety and the limitations of closed-loop control algorithms, guiding clinical studies, and out-ruling ineffective control scenarios in a cost-effective manner. Thus computer simulation testing of closed-loop control algorithms is regarded as a prerequisite to clinical trials of the artificial pancreas. In this paper, we present a system for in silico testing of control algorithms that has three principal components: (1) a large cohort of n=300 simulated "subjects" (n=100 adults, 100 adolescents, and 100 children) based on real individuals' data and spanning the observed variability of key metabolic parameters in the general population of people with T1DM; (2) a simulator of CGM sensor errors representative of Freestyle Navigator™, Guardian RT, or Dexcom™ STS™, 7-day sensor; and (3) a simulator of discrete s.c. insulin delivery via OmniPod Insulin Management System or Deltec Cozmo(®) insulin pump. The system has been shown to represent adequate glucose fluctuations in T1DM observed during meal challenges, and has been accepted by the Food and Drug Administration as a substitute to animal trials in the preclinical testing of closed-loop control strategies. © Diabetes Technology Society

Feasibility of overnight closed-loop control based on hourly blood glucose measurements.

PubMed

Patte, Caroline; Pleus, Stefan; Galley, Paul; Weinert, Stefan; Haug, Cornelia; Freckmann, Guido

2012-07-01

Safe and effective closed-loop control (artificial pancreas) is the ultimate goal of insulin delivery. In this study, we examined the performance of a closed-loop control algorithm used for the overnight time period to safely achieve a narrow target range of blood glucose (BG) concentrations prior to breakfast. The primary goal was to compare the quality of algorithm control during repeated overnight experiments. Twenty-three subjects with type 1 diabetes performed 2 overnight experiments on each of three visits at the study site, resulting in 138 overnight experiments. On the first evening, the subject's insulin therapy was applied; on the second, the insulin was delivered by an algorithm based on subcutaneous continuous glucose measurements (including meal control) until midnight. Overnight closed-loop control was applied between midnight and 6 a.m. based on hourly venous BG measurements during the first and second nights. The number of BG values within the target range (90-150 mg/dl) increased from 52.9% (219 out of 414 measurements) during the first nights to 72.2% (299 out of 414 measurements) during the second nights (p < .001, χ²-test). The occurrence of hypoglycemia interventions was reduced from 14 oral glucose interventions, the latest occurring at 2:36 a.m. during the first nights, to 1 intervention occurring at 1:02 a.m. during the second nights (p < .001, χ²-test). Overnight controller performance improved when optimized initial control was given; this was suggested by the better metabolic control during the second night. Adequate controller run-in time seems to be important for achieving good overnight control. In addition, the findings demonstrate that hourly BG data are sufficient for the closed-loop control algorithm tested to achieve appropriate glycemic control. © 2012 Diabetes Technology Society.

Design of a Closed-Loop, Bidirectional Brain Machine Interface System With Energy Efficient Neural Feature Extraction and PID Control.

PubMed

Liu, Xilin; Zhang, Milin; Richardson, Andrew G; Lucas, Timothy H; Van der Spiegel, Jan

2017-08-01

This paper presents a bidirectional brain machine interface (BMI) microsystem designed for closed-loop neuroscience research, especially experiments in freely behaving animals. The system-on-chip (SoC) consists of 16-channel neural recording front-ends, neural feature extraction units, 16-channel programmable neural stimulator back-ends, in-channel programmable closed-loop controllers, global analog-digital converters (ADC), and peripheral circuits. The proposed neural feature extraction units includes 1) an ultra low-power neural energy extraction unit enabling a 64-step natural logarithmic domain frequency tuning, and 2) a current-mode action potential (AP) detection unit with time-amplitude window discriminator. A programmable proportional-integral-derivative (PID) controller has been integrated in each channel enabling a various of closed-loop operations. The implemented ADCs include a 10-bit voltage-mode successive approximation register (SAR) ADC for the digitization of the neural feature outputs and/or local field potential (LFP) outputs, and an 8-bit current-mode SAR ADC for the digitization of the action potential outputs. The multi-mode stimulator can be programmed to perform monopolar or bipolar, symmetrical or asymmetrical charge balanced stimulation with a maximum current of 4 mA in an arbitrary channel configuration. The chip has been fabricated in 0.18 μ m CMOS technology, occupying a silicon area of 3.7 mm 2 . The chip dissipates 56 μW/ch on average. General purpose low-power microcontroller with Bluetooth module are integrated in the system to provide wireless link and SoC configuration. Methods, circuit techniques and system topology proposed in this work can be used in a wide range of relevant neurophysiology research, especially closed-loop BMI experiments.

Closed-Loop System Identification Experience for Flight Control Law and Flying Qualities Evaluation of a High Performance Fighter Aircraft

NASA Technical Reports Server (NTRS)

Murphy, Patrick C.

1996-01-01

This paper highlights some of the results and issues associated with estimating models to evaluate control law design methods and design criteria for advanced high performance aircraft. Experimental fighter aircraft such as the NASA-High Alpha Research Vehicle (HARV) have the capability to maneuver at very high angles of attack where nonlinear aerodynamics often predominate. HARV is an experimental F/A-18, configured with thrust vectoring and conformal actuated nose strakes. Identifying closed-loop models for this type of aircraft can be made difficult by nonlinearities and high order characteristics of the system. In this paper, only lateral-directional axes are considered since the lateral-directional control law was specifically designed to produce classical airplane responses normally expected with low-order, rigid-body systems. Evaluation of the control design methodology was made using low-order equivalent systems determined from flight and simulation. This allowed comparison of the closed-loop rigid-body dynamics achieved in flight with that designed in simulation. In flight, the On Board Excitation System was used to apply optimal inputs to lateral stick and pedals at five angles at attack : 5, 20, 30, 45, and 60 degrees. Data analysis and closed-loop model identification were done using frequency domain maximum likelihood. The structure of identified models was a linear state-space model reflecting classical 4th-order airplane dynamics. Input time delays associated with the high-order controller and aircraft system were accounted for in data preprocessing. A comparison of flight estimated models with small perturbation linear design models highlighted nonlinearities in the system and indicated that the closed-loop rigid-body dynamics were sensitive to input amplitudes at 20 and 30 degrees angle of attack.

Closed-Loop System Identification Experience for Flight Control Law and Flying Qualities Evaluation of a High Performance Fighter Aircraft

NASA Technical Reports Server (NTRS)

Murphy, Patrick C.

1999-01-01

This paper highlights some of the results and issues associated with estimating models to evaluate control law design methods and design criteria for advanced high performance aircraft. Experimental fighter aircraft such as the NASA High Alpha Research Vehicle (HARV) have the capability to maneuver at very high angles of attack where nonlinear aerodynamics often predominate. HARV is an experimental F/A-18, configured with thrust vectoring and conformal actuated nose strakes. Identifying closed-loop models for this type of aircraft can be made difficult by nonlinearities and high-order characteristics of the system. In this paper only lateral-directional axes are considered since the lateral-directional control law was specifically designed to produce classical airplane responses normally expected with low-order, rigid-body systems. Evaluation of the control design methodology was made using low-order equivalent systems determined from flight and simulation. This allowed comparison of the closed-loop rigid-body dynamics achieved in flight with that designed in simulation. In flight, the On Board Excitation System was used to apply optimal inputs to lateral stick and pedals at five angles of attack: 5, 20, 30, 45, and 60 degrees. Data analysis and closed-loop model identification were done using frequency domain maximum likelihood. The structure of the identified models was a linear state-space model reflecting classical 4th-order airplane dynamics. Input time delays associated with the high-order controller and aircraft system were accounted for in data preprocessing. A comparison of flight estimated models with small perturbation linear design models highlighted nonlinearities in the system and indicated that the estimated closed-loop rigid-body dynamics were sensitive to input amplitudes at 20 and 30 degrees angle of attack.

Hypnosis closed loop TCI systems in outpatient surgery.

PubMed

Ramos-Luengo, A; Asensio-Merino, F

Determine the influence of general anaesthesia with closed-loop systems in the results of outpatient varicose vein surgery. Retrospective observational study including data from 270 outpatients between 2014 and 2015. The patients were divided into 2 groups according to the type of general anaesthesia used. The CL Group included patients who received propofol in closed-loop guided by BIS and remifentanil using TCI, and the C Group received non-closed-loop anaesthesia. Age, sex, surgical time, discharge time and failure of outpatient surgery were recorded. Quantitative data were checked for normal distribution by the method of Kolmogorov-Smirnov-Lilliefors. Differences between groups were analysed by a Student-t-test or Mann-Whitney-Wilcoxon test, depending on their distribution. Categorical data were analysed by a Chi-squared test. We used Kaplan-Meier estimator and the effect size (calculated by Cohen's d) to study the discharge time. Statistical analysis was performed using R 3.2.3 binary for Mac OS X 10.9. There were no significant differences in age, sex and surgical time and failure of outpatient surgery. Discharge time was different in both groups: 200 (100) vs. 180 (82.5) minutes, C Group and CL Group, respectively (data are median and interquartile rank); P=.005. The use of closed-loop devices for the hypnotic component of anaesthesia hastens discharge time. However, for this effect to be clinically significant, some improvements still need to be made in our outpatient surgery units. Copyright © 2016 Sociedad Española de Anestesiología, Reanimación y Terapéutica del Dolor. Publicado por Elsevier España, S.L.U. All rights reserved.

A novel system for automated propofol sedation: hybrid sedation system (HSS).

PubMed

Zaouter, Cedrick; Taddei, Riccardo; Wehbe, Mohamad; Arbeid, Erik; Cyr, Shantale; Giunta, Francesco; Hemmerling, Thomas M

2017-04-01

Closed-loop systems for propofol have been demonstrated to be safe and reliable for general anesthesia. However, no study has been conducted using a closed-loop system specifically designed for sedation in patients under spinal anesthesia. We developed an automatic anesthesia sedation system that allows for closed-loop delivery of propofol for sedation integrating a decision support system, called the hybrid sedation system (HSS). The objective of this study is to compare this system with standard practice. One hundred fifty patients were enrolled and randomly assigned to two groups: HSS-Group (N = 75), in which propofol was administered using a closed-loop system; Control Group (N = 75), in which propofol was delivered manually. The clinical performance of the propofol sedation control is defined as efficacy to maintain bispectral index (BIS) near 65. The clinical control was called 'Excellent', 'Good', 'Poor' and 'Inadequate' with BIS values within 10 %, from 11 to 20 %, 21 to 30 %, or greater than 30 % of the BIS target of 65, respectively. The controller performance was evaluated using Varvel's parameters. Data are presented as mean ± standard deviation, groups were compared using t test or Chi square test, P < 0.05. Clinical performance of sedation showed 'Excellent' control in the HSS-group for a significantly longer period of time (49 vs. 26 % in the control group, P < 0.0001). 'Poor' and 'Inadequate' sedation was significantly shorter in the HSS Group compared to the Control Group (11 and 10 % vs. 20 and 18 %, respectively, P < 0.0001). The novel, closed-loop system for propofol sedation showed better maintenance of the target BIS value compared to manual administration.

Design and Operation of an Electrochemical Methanol Concentration Sensor for Direct Methanol Fuel Cell Systems

NASA Technical Reports Server (NTRS)

Narayanan, S. R.; Valdez, T. I.; Chun, W.

2000-01-01

The development of a 150-Watt packaged power source based on liquid feed direct methanol fuel cells is being pursued currently at the Jet propulsion Laboratory for defense applications. In our studies we find that the concentration of methanol in the fuel circulation loop affects the electrical performance and efficiency the direct methanol fuel cell systems significantly. The practical operation of direct methanol fuel cell systems, therefore, requires accurate monitoring and control of methanol concentration. The present paper reports on the principle and demonstration of an in-house developed electrochemical sensor suitable for direct methanol fuel cell systems.

Characterization of electrical noise limits in ultra-stable laser systems.

PubMed

Zhang, J; Shi, X H; Zeng, X Y; Lü, X L; Deng, K; Lu, Z H

2016-12-01

We demonstrate thermal noise limited and shot noise limited performance of ultra-stable diode laser systems. The measured heterodyne beat linewidth between such two independent diode lasers reaches 0.74 Hz. The frequency instability of one single laser approaches 1.0 × 10 -15 for averaging time between 0.3 s and 10 s, which is close to the thermal noise limit of the reference cavity. Taking advantage of these two ultra-stable laser systems, we systematically investigate the ultimate electrical noise contributions, and derive expressions for the closed-loop spectral density of laser frequency noise. The measured power spectral density of the beat frequency is compared with the theoretically calculated closed-loop spectral density of the laser frequency noise, and they agree very well. It illustrates the power and generality of the derived closed-loop spectral density formula of the laser frequency noise. Our result demonstrates that a 10 -17 level locking in a wide frequency range is feasible with careful design.

Neural network controller development and implementation for spark ignition engines with high EGR levels.

PubMed

Vance, Jonathan Blake; Singh, Atmika; Kaul, Brian C; Jagannathan, Sarangapani; Drallmeier, James A

2007-07-01

Past research has shown substantial reductions in the oxides of nitrogen (NOx) concentrations by using 10%-25% exhaust gas recirculation (EGR) in spark ignition (SI) engines (see Dudek and Sain, 1989). However, under high EGR levels, the engine exhibits strong cyclic dispersion in heat release which may lead to instability and unsatisfactory performance preventing commercial engines to operate with high EGR levels. A neural network (NN)-based output feedback controller is developed to reduce cyclic variation in the heat release under high levels of EGR even when the engine dynamics are unknown by using fuel as the control input. A separate control loop was designed for controlling EGR levels. The stability analysis of the closed-loop system is given and the boundedness of the control input is demonstrated by relaxing separation principle, persistency of excitation condition, certainty equivalence principle, and linear in the unknown parameter assumptions. Online training is used for the adaptive NN and no offline training phase is needed. This online learning feature and model-free approach is used to demonstrate the applicability of the controller on a different engine with minimal effort. Simulation results demonstrate that the cyclic dispersion is reduced significantly using the proposed controller when implemented on an engine model that has been validated experimentally. For a single cylinder research engine fitted with a modern four-valve head (Ricardo engine), experimental results at 15% EGR indicate that cyclic dispersion was reduced 33% by the controller, an improvement of fuel efficiency by 2%, and a 90% drop in NOx from stoichiometric operation without EGR was observed. Moreover, unburned hydrocarbons (uHC) drop by 6% due to NN control as compared to the uncontrolled scenario due to the drop in cyclic dispersion. Similar performance was observed with the controller on a different engine.

Closed-Loop Analysis of Soft Decisions for Serial Links

NASA Technical Reports Server (NTRS)

Lansdowne, Chatwin A.; Steele, Glen F.; Zucha, Joan P.; Schlesinger, Adam M.

2013-01-01

We describe the benefit of using closed-loop measurements for a radio receiver paired with a counterpart transmitter. We show that real-time analysis of the soft decision output of a receiver can provide rich and relevant insight far beyond the traditional hard-decision bit error rate (BER) test statistic. We describe a Soft Decision Analyzer (SDA) implementation for closed-loop measurements on single- or dual- (orthogonal) channel serial data communication links. The analyzer has been used to identify, quantify, and prioritize contributors to implementation loss in live-time during the development of software defined radios. This test technique gains importance as modern receivers are providing soft decision symbol synchronization as radio links are challenged to push more data and more protocol overhead through noisier channels, and software-defined radios (SDRs) use error-correction codes that approach Shannon's theoretical limit of performance.

A Survey on Security and Privacy in Emerging Sensor Networks: From Viewpoint of Close-Loop

PubMed Central

Zhang, Lifu; Zhang, Heng

2016-01-01

Nowadays, as the next generation sensor networks, Cyber-Physical Systems (CPSs) refer to the complex networked systems that have both physical subsystems and cyber components, and the information flow between different subsystems and components is across a communication network, which forms a closed-loop. New generation sensor networks are found in a growing number of applications and have received increasing attention from many inter-disciplines. Opportunities and challenges in the design, analysis, verification and validation of sensor networks co-exists, among which security and privacy are two important ingredients. This paper presents a survey on some recent results in the security and privacy aspects of emerging sensor networks from the viewpoint of the closed-loop. This paper also discusses several future research directions under these two umbrellas. PMID:27023559

Mathematical model development and simulation of heat pump fruit dryer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Achariyaviriya, S.; Soponronnarit, S.; Terdyothin, A.

2000-01-01

A mathematical model of a heat pump fruit dryer was developed to study the performance of heat pump dryers. Using the moisture content of papaya glace drying, the refrigerant temperature at the evaporator and condenser and the performance, was verified. It was found that the simulated results using closed loop heat pump dryer were close to the experimental results. The criteria for evaluating the performance were specific moisture extraction rate and drying rate. The results showed that ambient conditions affected significantly on the performance of the open loop dryer and the partially closed loop dryer. Also, the fraction of evaporatormore » bypass air affected markedly the performance of all heat pump dryers. In addition, it was found that specific air flow rate and drying air temperature affected significantly the performance of all heat pump dryers.« less

Study on digital closed-loop system of silicon resonant micro-sensor

NASA Astrophysics Data System (ADS)

Xu, Yefeng; He, Mengke

2008-10-01

Designing a micro, high reliability weak signal extracting system is a critical problem need to be solved in the application of silicon resonant micro-sensor. The closed-loop testing system based on FPGA uses software to replace hardware circuit which dramatically decrease the system's mass and power consumption and make the system more compact, both correlation theory and frequency scanning scheme are used in extracting weak signal, the adaptive frequency scanning arithmetic ensures the system real-time. The error model was analyzed to show the solution to enhance the system's measurement precision. The experiment results show that the closed-loop testing system based on FPGA has the personality of low power consumption, high precision, high-speed, real-time etc, and also the system is suitable for different kinds of Silicon Resonant Micro-sensor.

A synopsis of test results and knowledge gained from the Phase-0 CSI evolutionary model

NASA Technical Reports Server (NTRS)

Belvin, W. Keith; Elliott, Kenny B.; Horta, Lucas G.

1993-01-01

The Phase-0 CSI Evolutionary Model (CEM) is a testbed for the study of space platform global line-of-sight (LOS) pointing. Now that the tests have been completed, a summary of hardware and closed-loop test experiences is necessary to insure a timely dissemination of the knowledge gained. The testbed is described and modeling experiences are presented followed by a summary of the research performed by various investigators. Some early lessons on implementing the closed-loop controllers are described with particular emphasis on real-time computing requirements. A summary of closed-loop studies and a synopsis of test results are presented. Plans for evolving the CEM from phase 0 to phases 1 and 2 are also described. Subsequently, a summary of knowledge gained from the design and testing of the Phase-0 CEM is made.

Decentralized Sliding Mode Observer Based Dual Closed-Loop Fault Tolerant Control for Reconfigurable Manipulator against Actuator Failure.

PubMed

Zhao, Bo; Li, Chenghao; Liu, Derong; Li, Yuanchun

2015-01-01

This paper considers a decentralized fault tolerant control (DFTC) scheme for reconfigurable manipulators. With the appearance of norm-bounded failure, a dual closed-loop trajectory tracking control algorithm is proposed on the basis of the Lyapunov stability theory. Characterized by the modularization property, the actuator failure is estimated by the proposed decentralized sliding mode observer (DSMO). Moreover, the actuator failure can be treated in view of the local joint information, so its control performance degradation is independent of other normal joints. In addition, the presented DFTC scheme is significantly simplified in terms of the structure of the controller due to its dual closed-loop architecture, and its feasibility is highly reflected in the control of reconfigurable manipulators. Finally, the effectiveness of the proposed DFTC scheme is demonstrated using simulations.

Decentralized Sliding Mode Observer Based Dual Closed-Loop Fault Tolerant Control for Reconfigurable Manipulator against Actuator Failure

PubMed Central

Zhao, Bo; Li, Yuanchun

2015-01-01

This paper considers a decentralized fault tolerant control (DFTC) scheme for reconfigurable manipulators. With the appearance of norm-bounded failure, a dual closed-loop trajectory tracking control algorithm is proposed on the basis of the Lyapunov stability theory. Characterized by the modularization property, the actuator failure is estimated by the proposed decentralized sliding mode observer (DSMO). Moreover, the actuator failure can be treated in view of the local joint information, so its control performance degradation is independent of other normal joints. In addition, the presented DFTC scheme is significantly simplified in terms of the structure of the controller due to its dual closed-loop architecture, and its feasibility is highly reflected in the control of reconfigurable manipulators. Finally, the effectiveness of the proposed DFTC scheme is demonstrated using simulations. PMID:26181826

Robust Control Design via Linear Programming

NASA Technical Reports Server (NTRS)

Keel, L. H.; Bhattacharyya, S. P.

1998-01-01

This paper deals with the problem of synthesizing or designing a feedback controller of fixed dynamic order. The closed loop specifications considered here are given in terms of a target performance vector representing a desired set of closed loop transfer functions connecting various signals. In general these point targets are unattainable with a fixed order controller. By enlarging the target from a fixed point set to an interval set the solvability conditions with a fixed order controller are relaxed and a solution is more easily enabled. Results from the parametric robust control literature can be used to design the interval target family so that the performance deterioration is acceptable, even when plant uncertainty is present. It is shown that it is possible to devise a computationally simple linear programming approach that attempts to meet the desired closed loop specifications.

Smart lighting using a liquid crystal modulator

NASA Astrophysics Data System (ADS)

Baril, Alexandre; Thibault, Simon; Galstian, Tigran

2017-08-01

Now that LEDs have massively invaded the illumination market, a clear trend has emerged for more efficient and targeted lighting. The project described here is at the leading edge of the trend and aims at developing an evaluation board to test smart lighting applications. This is made possible thanks to a new liquid crystal light modulator recently developed for broadening LED light beams. The modulator is controlled by electrical signals and is characterized by a linear working zone. This feature allows the implementation of a closed loop control with a sensor feedback. This project shows that the use of computer vision is a promising opportunity for cheap closed loop control. The developed evaluation board integrates the liquid crystal modulator, a webcam, a LED light source and all the required electronics to implement a closed loop control with a computer vision algorithm.

Novel sensors to enable closed-loop active clearance control in gas turbine engines

NASA Astrophysics Data System (ADS)

Geisheimer, Jonathan; Holst, Tom

2014-06-01

Active clearance control within the turbine section of gas turbine engines presents and opportunity within aerospace and industrial applications to improve operating efficiencies and the life of downstream components. Open loop clearance control is currently employed during the development of all new large core aerospace engines; however, the ability to measure the gap between the blades and the case and close down the clearance further presents as opportunity to gain even greater efficiencies. The turbine area is one of the harshest environments for long term placement of a sensor in addition to the extreme accuracy requirements required to enable closed loop clearance control. This paper gives an overview of the challenges of clearance measurements within the turbine as well as discusses the latest developments of a microwave sensor designed for this application.

Second International Workshop on Grid Simulator Testing of Wind Turbine

Science.gov Websites

, Clemson University, USA Update on the FSU-CAPS Megawatt Scale Power Hardware in the Loop Laboratory Loop Based Anti-Islanding Testing of PV Converters-Michael Steurer, Florida State University, USA Closed-Loop Control of Modern Test Benches Advanced Control Techniques for Dynamic Testing of Wind

Electrolyser and fuel cells, key elements for energy and life support

NASA Astrophysics Data System (ADS)

Bockstahler, Klaus; Funke, Helmut; Lucas, Joachim

Both, Electrolyser and Fuel Cells are key elements for regenerative energy and life support systems. Electrolyser technology is originally intended for oxygen production in manned space habitats and in submarines, through splitting water into hydrogen and oxygen. Fuel cells serve for energy production through the reaction, triggered in the presence of an electrolyte, between a fuel and an oxidant. Now combining both technologies i.e. electrolyser and fuel cell makes it a Regenerative Fuel Cell System (RFCS). In charge mode, i.e. with energy supplied e.g. by solar cells, the electrolyser splits water into hydrogen and oxygen being stored in tanks. In discharge mode, when power is needed but no energy is available, the stored gases are converted in the fuel cell to generate electricity under the formation of water that is stored in tanks. Rerouting the water to the electrolyser makes it a closed-loop i.e. regenerative process. Different electrolyser and fuel cell technologies are being evolved. At Astrium emphasis is put on the development of an RFCS comprised of Fixed Alkaline Electrolyser (FAE) and Fuel Cell (AFC) as such technology offers a high electrical efficiency and thus reduced system weight, which is important in space applications. With increasing power demand and increasing discharge time an RFCS proves to be superior to batteries. Since the early technology development multiple design refinements were done at Astrium, funded by the European Space Agency ESA and the German National Agency DLR as well as based on company internal R and T funding. Today a complete RFCS energy system breadboard is established and the operational behavior of the system is being tested. In parallel the electrolyser itself is subject to design refinement and testing in terms of oxygen production in manned space habitats. In addition essential features and components for process monitoring and control are being developed. The present results and achievements and the dedicated experience gained from testing will be presented, complemented by an outlook on next development steps preparatory to the application of electrolyser and fuel cell technology in human and robotic exploration building blocks.

Stabilization and analytical tuning rule of double-loop control scheme for unstable dead-time process

NASA Astrophysics Data System (ADS)

Ugon, B.; Nandong, J.; Zang, Z.

2017-06-01

The presence of unstable dead-time systems in process plants often leads to a daunting challenge in the design of standard PID controllers, which are not only intended to provide close-loop stability but also to give good performance-robustness overall. In this paper, we conduct stability analysis on a double-loop control scheme based on the Routh-Hurwitz stability criteria. We propose to use this unstable double-loop control scheme which employs two P/PID controllers to control first-order or second-order unstable dead-time processes typically found in process industries. Based on the Routh-Hurwitz stability necessary and sufficient criteria, we establish several stability regions which enclose within them the P/PID parameter values that guarantee close-loop stability of the double-loop control scheme. A systematic tuning rule is developed for the purpose of obtaining the optimal P/PID parameter values within the established regions. The effectiveness of the proposed tuning rule is demonstrated using several numerical examples and the result are compared with some well-established tuning methods reported in the literature.

Dismantling of Loop-Type Channel Equipment of MR Reactor in NRC 'Kurchatov Institute' - 13040

DOE Office of Scientific and Technical Information (OSTI.GOV)

Volkov, Victor; Danilovich, Alexey; Zverkov, Yuri

2013-07-01

In 2009 the project of decommissioning of MR and RTF reactors was developed and approved by the Expert Authority of the Russian Federation (Gosexpertiza). The main objective of the decommissioning works identified in this project: - complete dismantling of reactor equipment and systems; - decontamination of reactor premises and site in accordance with the established sanitary and hygienic standards. At the preparatory stage (2008-2010) of the project the following works were executed: loop-type channels' dismantling in the storage pool; experimental fuel assemblies' removal from spent fuel repositories in the central hall; spent fuel assembly removal from the liquid-metal-cooled loop-type channelmore » of the reactor core and its placement into the SNF repository; and reconstruction of engineering support systems to the extent necessary for reactor decommissioning. The project assumes three main phases of dismantling and decontamination: - dismantling of equipment/pipelines of cooling circuits and loop-type channels, and auxiliary reactor equipment (2011-2012); - dismantling of equipment in underground reactor premises and of both MR and RTF in-vessel devices (2013-2014); - decontamination of reactor premises; rehabilitation of the reactor site; final radiation survey of reactor premises, loop-type channels and site; and issuance of the regulatory authorities' de-registration statement (2015). In 2011 the decommissioning license for the two reactors was received and direct MR decommissioning activities started. MR primary pipelines and loop-type facilities situated in the underground reactor hall were dismantled. Works were also launched to dismantle the loop-type channels' equipment in underground reactor premises; reactor buildings were reconstructed to allow removal of dismantled equipment; and the MR/RTF decommissioning sequence was identified. In autumn 2011 - spring 2012 results of dismantling activities performed are: - equipment from underground rooms (No. 66, 66A, 66B, 72, 64, 63) - as well as from water and gas loop corridors - was dismantled, with the total radwaste weight of 53 tons and the total removed activity of 5,0 x 10{sup 10} Bq; - loop-type channel equipment from underground reactor hall premises was dismantled; - 93 loop-type channels were characterized, chopped and removed, with radwaste of 2.6 x 10{sup 13} Bq ({sup 60}Co) and 1.5 x 10{sup 13} Bq ({sup 137}Cs) total activity removed from the reactor pool, fragmented and packaged. Some of this waste was placed into the high-level waste (HLW) repository of the Center. Dismantling works were executed with application of remotely operated mechanisms, which promoted decrease of radiation impact on the personnel. The average individual dose for the personnel was 1.9 mSv/year in 2011, and the collective dose is estimated as 0.0605 man x Sv/year. (authors)« less

Cleanup of a jet fuel spill

NASA Astrophysics Data System (ADS)

Fesko, Steve

1996-11-01

Eaton operates a corporate aircraft hanger facility in Battle Creek, Michigan. Tests showed that two underground storage tanks leaked. Investigation confirmed this release discharged several hundred gallons of Jet A kerosene into the soil and groundwater. The oil moved downward approximately 30 feet and spread laterally onto the water table. Test results showed kerosene in the adsorbed, free and dissolved states. Eaton researched and investigated three clean-up options. They included pump and treat, dig and haul and bioremediation. Jet fuel is composed of readily biodegradable hydrocarbon chains. This fact coupled with the depth to groundwater and geologic setting made bioremediation the low cost and most effective alternative. A recovery well was installed at the leading edge of the dissolved contamination. A pump moved water from this well into a nutrient addition system. Nutrients added included nitrogen, phosphorous and potassium. Additionally, air was sparged into the water. The water was discharged into an infiltration gallery installed when the underground storage tanks were removed. Water circulated between the pump and the infiltration basin in a closed loop fashion. This oxygenated, nutrient rich water actively and aggressively treated the soils between the bottom of the gallery and the top of the groundwater and the groundwater. The system began operating in August of 1993 and reduced jet fuel to below detection levels. In August of 1995 The State of Michigan issued a clean closure declaration to the site.

Experimental Verification of AUV (Autonomous Underwater Vehicle) Performance.

DTIC Science & Technology

1988-03-01

7 3 First Order Plant Model 10 4 Closed Loop System Block Diagram 11 5 RLP[Kpz=l,U=0.5] 13 6 RLP[Kpz=I,U=I] 147 RLP[Kpz=0.5,U-0.5] 15 8 RLP[Kpz=0.5,U...circuit. The control circuit would then generate a radio control signal to maneuver the vehicle. 6 *’%4 MUMNT -. %Am -W’ This takes the man out of the loop ...angle, the constant Ky is 0.14i_" IN’ ft-lbf/rad. Estimated values of J and B were determined. The closed loop transfer function Go could then be

Clearing the Air: New Approaches to Life Support in Outer Space

NASA Technical Reports Server (NTRS)

Knox, J.; Howard, D.

2008-01-01

This article reports on research into atmospheric revitalization systems for long-term space travel and the use ofCOMSOL Multiphysics to understand how structured sorbents can be used to improve the performance of adsorption processes via thermal management. We are developing the next generation of atmosphere revitalization systems, which will reach for new levels of resource conservation via a high percentage of loop closure. For example, a high percentage of carbon dioxide, exhaled by crew, can be converted via reaction to drinking water, closing the loop from human metabolic waste to supply. Adsorption processes play a lead role in these new/closed loop systems.

On-off closed-loop control of vagus nerve stimulation for the adaptation of heart rate.

PubMed

Ugalde, Hector Romero; Le Rolle, Virginie; Bel, Alain; Bonnet, Jean-Luc; Andreu, David; Mabo, Philippe; Carrault, Guy; Hernández, Alfredo I

2014-01-01

Vagus nerve stimulation (VNS) is a potential therapeutic approach in a number of clinical applications. Although VNS is commonly delivered in an open-loop approach, it is now recognized that closed-loop approaches may be necessary to optimize the therapy and minimize side effects of neuro-stimulation devices. In this paper, we describe a prototype system for real-time control of the instantaneous heart rate, working synchronously with the heart period. As a first step, an on-off control method has been integrated. The system is evaluated on one sheep with induced heart failure, showing the interest of the proposed approach.

Stability of multiloop LQ regulators with nonlinearities. I - Regions of attraction. II - Regions of ultimate boundedness

NASA Technical Reports Server (NTRS)

Joshi, S. M.

1986-01-01

An investigation is conducted for the closed loop stability of linear time-invariant systems controlled by linear quadratic (LQ) regulators, in cases where nonlinearities exist in the control channels lying outside the stability sector in regions away from the origin. The estimate of the region of attraction thus obtained furnishes methods for the selection of performance function weights for more robust LQ designs. Attention is then given to the closed loop stability of linear time-invariant systems controlled by the LQ regulators when the nonlinearities in the loops escape the stability sector in a bounded region containing the origin.

Visualizing Active-Site Dynamics in Single Crystals of HePTP: Opening of the WPD Loop Involves Coordinated Movement of the E Loop

DOE Office of Scientific and Technical Information (OSTI.GOV)

D Critton; L Tautz; R Page

2011-12-31

Phosphotyrosine hydrolysis by protein tyrosine phosphatases (PTPs) involves substrate binding by the PTP loop and closure over the active site by the WPD loop. The E loop, located immediately adjacent to the PTP and WPD loops, is conserved among human PTPs in both sequence and structure, yet the role of this loop in substrate binding and catalysis is comparatively unexplored. Hematopoietic PTP (HePTP) is a member of the kinase interaction motif (KIM) PTP family. Compared to other PTPs, KIM-PTPs have E loops that are unique in both sequence and structure. In order to understand the role of the E loopmore » in the transition between the closed state and the open state of HePTP, we identified a novel crystal form of HePTP that allowed the closed-state-to-open-state transition to be observed within a single crystal form. These structures, which include the first structure of the HePTP open state, show that the WPD loop adopts an 'atypically open' conformation and, importantly, that ligands can be exchanged at the active site, which is critical for HePTP inhibitor development. These structures also show that tetrahedral oxyanions bind at a novel secondary site and function to coordinate the PTP, WPD, and E loops. Finally, using both structural and kinetic data, we reveal a novel role for E-loop residue Lys182 in enhancing HePTP catalytic activity through its interaction with Asp236 of the WPD loop, providing the first evidence for the coordinated dynamics of the WPD and E loops in the catalytic cycle, which, as we show, is relevant to multiple PTP families.« less

Design and Control of a Closed-Loop Brushless Torque Activator

DTIC Science & Technology

1990-05-01

AD-A270 760 Technical Report 1244 Design and Control of a Closed-Loop Brushless Torque Activator Michael Dean Levi MIT Artificial Intelligence... Brushless N00014-86-K-0685 Torque Actuator 6. AUTHOR(S) Michael Dean Levin 7. PERFORMING ORGANIZATION NAME(S) AND ADORESS(ES) B. PERFORMING...200 words) This’report explores the design and control issues associated with a brushless actuator capable of achieving extremely high torque

Closed-loop air cooling system for a turbine engine

DOEpatents

North, William Edward

2000-01-01

Method and apparatus are disclosed for providing a closed-loop air cooling system for a turbine engine. The method and apparatus provide for bleeding pressurized air from a gas turbine engine compressor for use in cooling the turbine components. The compressed air is cascaded through the various stages of the turbine. At each stage a portion of the compressed air is returned to the compressor where useful work is recovered.

Automatic temperature adjustment apparatus

DOEpatents

Chaplin, James E.

1985-01-01

An apparatus for increasing the efficiency of a conventional central space heating system is disclosed. The temperature of a fluid heating medium is adjusted based on a measurement of the external temperature, and a system parameter. The system parameter is periodically modified based on a closed loop process that monitors the operation of the heating system. This closed loop process provides a heating medium temperature value that is very near the optimum for energy efficiency.

Closed-Loop and Robust Control of Quantum Systems

PubMed Central

Wang, Lin-Cheng

2013-01-01

For most practical quantum control systems, it is important and difficult to attain robustness and reliability due to unavoidable uncertainties in the system dynamics or models. Three kinds of typical approaches (e.g., closed-loop learning control, feedback control, and robust control) have been proved to be effective to solve these problems. This work presents a self-contained survey on the closed-loop and robust control of quantum systems, as well as a brief introduction to a selection of basic theories and methods in this research area, to provide interested readers with a general idea for further studies. In the area of closed-loop learning control of quantum systems, we survey and introduce such learning control methods as gradient-based methods, genetic algorithms (GA), and reinforcement learning (RL) methods from a unified point of view of exploring the quantum control landscapes. For the feedback control approach, the paper surveys three control strategies including Lyapunov control, measurement-based control, and coherent-feedback control. Then such topics in the field of quantum robust control as H ∞ control, sliding mode control, quantum risk-sensitive control, and quantum ensemble control are reviewed. The paper concludes with a perspective of future research directions that are likely to attract more attention. PMID:23997680