DYNAMIC AND STATIC PARAMETERS OF THE AQUEOUS HOMOGENEOUS ARMOUR RESEARCH REACTOR

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

Terrell, C.W.; McElroy, W.N.

1959-06-01

A brief description of the aqueous homogeneous Armour Research Reactor is given. The negative reactivity coefficient resulting from a temperature increase was determined over a fuel temperature range of 37 to 150 deg F. Possession of an accurately calibrated rod and temperature coefficient permitted a direct measurement of the void coefficient. The reactor was taken to different power levels, and from the calibrated rod the total reduction in excess reactivity was obtained. During the power increase program additional U/sup 235/ and water were added to the core to determine the worth of U/sup 235/ and water. (W.D.M.)

Influence of nitrogen admixture to argon on the ion energy distribution in reactive high power pulsed magnetron sputtering of chromium

NASA Astrophysics Data System (ADS)

Breilmann, W.; Maszl, C.; Hecimovic, A.; von Keudell, A.

2017-04-01

Reactive high power impulse magnetron sputtering (HiPIMS) of metals is of paramount importance for the deposition of various oxides, nitrides and carbides. The addition of a reactive gas such as nitrogen to an argon HiPIMS plasma with a metal target allows the formation of the corresponding metal nitride on the substrate. The addition of a reactive gas introduces new dynamics into the plasma process, such as hysteresis, target poisoning and the rarefaction of two different plasma gases. We investigate the dynamics for the deposition of chromium nitride by a reactive HiPIMS plasma using energy- and time-resolved ion mass spectrometry, fast camera measurements and temporal and spatially resolved optical emission spectroscopy. It is shown that the addition of nitrogen to the argon plasma gas significantly changes the appearance of the localized ionization zones, the so-called spokes, in HiPIMS plasmas. In addition, a very strong modulation of the metal ion flux within each HiPIMS pulse is observed, with the metal ion flux being strongly suppressed and the nitrogen molecular ion flux being strongly enhanced in the high current phase of the pulse. This behavior is explained by a stronger return effect of the sputtered metal ions in the dense plasma above the racetrack. This is best observed in a pure nitrogen plasma, because the ionization zones are mostly confined, implying a very high local plasma density and consequently also an efficient scattering process.

Experiment investigation for dynamic behavior of hybrid fiber effects on reactive powder concrete

NASA Astrophysics Data System (ADS)

Wang, Liwen; Pang, Baojun; Yang, Zhenqi; Chi, Runqiang

2010-03-01

The influences of different hybrid fibers (steel fibers add polyvinyl-alcohol fibers) mixture rates for reactive power concrete's (RPC) dynamic mechanical behavior after high temperature burnt was investigated by the Split Hopkinson pressure bar (SHPB) device. A plumbic pulse shaper technique was applied in the experiment, PVDF stress gauge was used to monitor the stress uniformity state within the specimen. The strain rate was between 75~85s-1, base on the stressstrain curves and dynamic modes of concrete specimen, the hybrid fiber effect on the dynamic properties was determined. The results show, dynamic compression strength of specimens which mixed with steel fibers (1.0%,1.5%,2.0% vol. rate) and 0.1% PVA fibers is higher than normal reactive powder concrete (NRPC), but the toughness improves unconspicuous; while strength of the one which has both steel fiber (1.0%,1.5%,2.0% vol. rate) and 0.2%PVA fiber declines than NRPC but the toughness improves and the plastic behaviors strengthened, stress-strain curve has evident rising and plate portions. It can be deduced that the concrete with mixed two kinds of fibers has improved dynamic mechanical properties after high temperature burnt. By compounding previous literature results, the mechanism of the experimental results can be explained.

Reactive Power Compensation Method Considering Minimum Effective Reactive Power Reserve

NASA Astrophysics Data System (ADS)

Gong, Yiyu; Zhang, Kai; Pu, Zhang; Li, Xuenan; Zuo, Xianghong; Zhen, Jiao; Sudan, Teng

2017-05-01

According to the calculation model of minimum generator reactive power reserve of power system voltage stability under the premise of the guarantee, the reactive power management system with reactive power compensation combined generator, the formation of a multi-objective optimization problem, propose a reactive power reserve is considered the minimum generator reactive power compensation optimization method. This method through the improvement of the objective function and constraint conditions, when the system load growth, relying solely on reactive power generation system can not meet the requirement of safe operation, increase the reactive power reserve to solve the problem of minimum generator reactive power compensation in the case of load node.

Dynamics of heat-pipe reactors

NASA Technical Reports Server (NTRS)

Niederauer, G. F.

1971-01-01

A split-core heat pipe reactor, fueled with either U(233)C or U(235)C in a tungsten cermet and cooled by 7-Li-W heat pipes, was examined for the effects of the heat pipes on reactor while trying to safely absorb large reactivity inputs through inherent shutdown mechanisms. Limits on ramp reactivity inputs due to fuel melting temperature and heat pipe wall heat flux were mapped for the reactor in both startup and at-power operating modes.

A streamlined software environment for situated skills

NASA Technical Reports Server (NTRS)

Yu, Sophia T.; Slack, Marc G.; Miller, David P.

1994-01-01

This paper documents a powerful set of software tools used for developing situated skills. These situated skills form the reactive level of a three-tiered intelligent agent architecture. The architecture is designed to allow these skills to be manipulated by a task level engine which is monitoring the current situation and selecting skills necessary for the current task. The idea is to coordinate the dynamic activations and deactivations of these situated skills in order to configure the reactive layer for the task at hand. The heart of the skills environment is a data flow mechanism which pipelines the currently active skills for execution. A front end graphical interface serves as a debugging facility during skill development and testing. We are able to integrate skills developed in different languages into the skills environment. The power of the skills environment lies in the amount of time it saves for the programmer to develop code for the reactive layer of a robot.

Impact of wind generator infed on dynamic performance of a power system

NASA Astrophysics Data System (ADS)

Alam, Md. Ahsanul

Wind energy is one of the most prominent sources of electrical energy in the years to come. A tendency to increase the amount of electricity generation from wind turbine can be observed in many countries. One of the major concerns related to the high penetration level of the wind energy into the existing power grid is its influence on power system dynamic performance. In this thesis, the impact of wind generation system on power system dynamic performance is investigated through detailed dynamic modeling of the entire wind generator system considering all the relevant components. Nonlinear and linear models of a single machine as well as multimachine wind-AC system have been derived. For the dynamic model of integrated wind-AC system, a general transformation matrix is determined for the transformation of machine and network quantities to a common reference frame. Both time-domain and frequency domain analyses on single machine and multimachine systems have been carried out. The considered multimachine systems are---A 4 machine 12 bus system, and 10 machine 39 bus New England system. Through eigenvalue analysis, impact of asynchronous wind system on overall network damping has been quantified and modes responsible for the instability have been identified. Over with a number of simulation studies it is observed that for a induction generator based wind generation system, the fixed capacitor located at the generator terminal cannot normally cater for the reactive power demand during the transient disturbances like wind gust and fault on the system. For weak network connection, system instability may be initiated because of induction generator terminal voltage collapse under certain disturbance conditions. Incorporation of dynamic reactive power compensation scheme through either variable susceptance control or static compensator (STATCOM) is found to improve the dynamic performance significantly. Further improvement in transient profile has been brought in by supporting STATCOM with bulk energy storage devices. Two types of energy storage system (ESS) have been considered---battery energy storage system, and supercapacitor based energy storage system. A decoupled P -- Q control strategy has been implemented on STATCOM/ESS. It is observed that wind generators when supported by STATCOM/ESS can achieve significant withstand capability in the presence of grid fault of reasonable duration. It experiences almost negligible rotor speed variation, maintains constant terminal voltage, and resumes delivery of smoothed (almost transient free) power to the grid immediately after the fault is cleared. Keywords: Wind energy, induction generator, dynamic performance of wind generators, energy storage system, decoupled P -- Q control, multimachine system.

Using particle swarm optimization to enhance PI controller performances for active and reactive power control in wind energy conversion systems

NASA Astrophysics Data System (ADS)

Taleb, M.; Cherkaoui, M.; Hbib, M.

2018-05-01

Recently, renewable energy sources are impacting seriously power quality of the grids in term of frequency and voltage stability, due to their intermittence and less forecasting accuracy. Among these sources, wind energy conversion systems (WECS) received a great interest and especially the configuration with Doubly Fed Induction Generator. However, WECS strongly nonlinear, are making their control not easy by classical approaches such as a PI. In this paper, we continue deepen study of PI controller used in active and reactive power control of this kind of WECS. Particle Swarm Optimization (PSO) is suggested to improve its dynamic performances and its robustness against parameters variations. This work highlights the performances of PSO optimized PI control against classical PI tuned with poles compensation strategy. Simulations are carried out on MATLAB-SIMULINK software.

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.

Core Dynamics Analysis for Reactivity Insertion and Loss of Coolant Flow Tests Using the High Temperature Engineering Test Reactor

NASA Astrophysics Data System (ADS)

Takamatsu, Kuniyoshi; Nakagawa, Shigeaki; Takeda, Tetsuaki

Safety demonstration tests using the High Temperature Engineering Test Reactor (HTTR) are in progress to verify its inherent safety features and improve the safety technology and design methodology for High-temperature Gas-cooled Reactors (HTGRs). The reactivity insertion test is one of the safety demonstration tests for the HTTR. This test simulates the rapid increase in the reactor power by withdrawing the control rod without operating the reactor power control system. In addition, the loss of coolant flow tests has been conducted to simulate the rapid decrease in the reactor power by tripping one, two or all out of three gas circulators. The experimental results have revealed the inherent safety features of HTGRs, such as the negative reactivity feedback effect. The numerical analysis code, which was named-ACCORD-, was developed to analyze the reactor dynamics including the flow behavior in the HTTR core. We have modified this code to use a model with four parallel channels and twenty temperature coefficients. Furthermore, we added another analytical model of the core for calculating the heat conduction between the fuel channels and the core in the case of the loss of coolant flow tests. This paper describes the validation results for the newly developed code using the experimental results. Moreover, the effect of the model is formulated quantitatively with our proposed equation. Finally, the pre-analytical result of the loss of coolant flow test by tripping all gas circulators is also discussed.

Lifespan differences in nonlinear dynamics during rest and auditory oddball performance.

PubMed

Müller, Viktor; Lindenberger, Ulman

2012-07-01

Electroencephalographic recordings (EEG) were used to assess age-associated differences in nonlinear brain dynamics during both rest and auditory oddball performance in children aged 9.0-12.8 years, younger adults, and older adults. We computed nonlinear coupling dynamics and dimensional complexity, and also determined spectral alpha power as an indicator of cortical reactivity. During rest, both nonlinear coupling and spectral alpha power decreased with age, whereas dimensional complexity increased. In contrast, when attending to the deviant stimulus, nonlinear coupling increased with age, and complexity decreased. Correlational analyses showed that nonlinear measures assessed during auditory oddball performance were reliably related to an independently assessed measure of perceptual speed. We conclude that cortical dynamics during rest and stimulus processing undergo substantial reorganization from childhood to old age, and propose that lifespan age differences in nonlinear dynamics during stimulus processing reflect lifespan changes in the functional organization of neuronal cell assemblies. © 2012 Blackwell Publishing Ltd.

Three-Level 48-Pulse STATCOM with Pulse Width Modulation

NASA Astrophysics Data System (ADS)

Singh, Bhim; Srinivas, Kadagala Venkata

2016-03-01

In this paper, a new control strategy of a three-level 48-pulse static synchronous compensator (STATCOM) is proposed with a constant dc link voltage and pulse width modulation at fundamental frequency switching. The proposed STATCOM is realized using eight units of three-level voltage source converters (VSCs) to form a three-level 48-pulse STATCOM. The conduction angle of each three-level VSC is modulated to control the ac converter output voltage, which controls the reactive power of the STATCOM. A fuzzy logic controller is used to control the STATCOM. The dynamic performance of the STATCOM is studied for the control of the reference reactive power, the reference terminal voltage and under the switching of inductive and capacitive loads.

[Effects of Reactive Jump Training in Handball Players Regarding Jump Height and Power Development in the Triceps Surae Muscle].

PubMed

Rensing, N; Westermann, A; Möller, D; von Piekartz, H

2015-12-01

Studies have shown changes in the technical and physical demands in modern handball. The game has increased considerably in speed, power and dynamics. Jump training has, therefore, become ever more important in the training of the athletes. These developments contribute to the fact that handball is now one of the most injury-prone types of sport, with the lower extremities being most frequently affected. Reactive jump training is not only used in training by now, but also increasingly in injury prevention. The aim of this study was to investigate the effectiveness of reactive jump training with handball players. 21 regional league handball players were randomly divided into an intervention group (n = 12) and a control group (n = 9). The intervention group completed a six-week reactive jump training programme while the control group went through a non-specific training programme. Jump height (squat and counter movement jump), isokinetic and isometric maximum power as well as muscle activity served as measuring parameters. A comparison of the intervention and control groups revealed that the reactive jump training led to significant improvements in jump height. The isometric and isokinetic maximum power measurements and the electromyographic activities of the triceps surae muscle demonstrated an improvement in the values within the intervention group. However, this improvement was not significant compared with the control group. Likewise both jumps correlated with the muscle activity of the soleus muscle as shown by electromyography. A moderate correlation was noticed between the isokinetic maximum power measurement and the electromyographic activity of the soleus and gastrocnemius medialis muscles. Furthermore, the correlations of the isometric and isokinetic maximum power meas-urements resulted in a strong correlation coefficient. This study revealed a significant increase in jump height after reactive jump training. There was no significant difference in power development between the two groups. However, we were able to demonstrate correlations which would make it seem reasonable and interesting to investigate the question more closely. An interesting field of research could be the question of the effectiveness of reactive jump training in the areas of rehabilitation and injury prevention. © Georg Thieme Verlag KG Stuttgart · New York.

Core reactivity estimation in space reactors using recurrent dynamic networks

NASA Technical Reports Server (NTRS)

Parlos, Alexander G.; Tsai, Wei K.

1991-01-01

A recurrent multilayer perceptron network topology is used in the identification of nonlinear dynamic systems from only the input/output measurements. The identification is performed in the discrete time domain, with the learning algorithm being a modified form of the back propagation (BP) rule. The recurrent dynamic network (RDN) developed is applied for the total core reactivity prediction of a spacecraft reactor from only neutronic power level measurements. Results indicate that the RDN can reproduce the nonlinear response of the reactor while keeping the number of nodes roughly equal to the relative order of the system. As accuracy requirements are increased, the number of required nodes also increases, however, the order of the RDN necessary to obtain such results is still in the same order of magnitude as the order of the mathematical model of the system. It is believed that use of the recurrent MLP structure with a variety of different learning algorithms may prove useful in utilizing artificial neural networks for recognition, classification, and prediction of dynamic systems.

Local Voltage Control in Distribution Networks: A Game-Theoretic Perspective

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

Zhou, Xinyang; Tian, Jie; Chen, Lijun

Inverter-based voltage regulation is gaining importance to alleviate emerging reliability and power-quality concerns related to distribution systems with high penetration of photovoltaic (PV) systems. This paper seeks contribution in the domain of reactive power compensation by establishing stability of local Volt/VAr controllers. In lieu of the approximate linear surrogate used in the existing work, the paper establishes existence and uniqueness of an equilibrium point using nonlinear AC power flow model. Key to this end is to consider a nonlinear dynamical system with non-incremental local Volt/VAr control, cast the Volt/VAr dynamics as a game, and leverage the fixed-point theorem as wellmore » as pertinent contraction mapping argument. Numerical examples are provided to complement the analytical results.« less

Local Voltage Control in Distribution Networks: A Game-Theoretic Perspective: Preprint

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

Zhou, Xinyang; Tian, Jie; Chen, Lijun

Inverter-based voltage regulation is gaining importance to alleviate emerging reliability and power-quality concerns related to distribution systems with high penetration of photovoltaic (PV) systems. This paper seeks contribution in the domain of reactive power compensation by establishing stability of local Volt/VAr controllers. In lieu of the approximate linear surrogate used in the existing work, the paper establishes existence and uniqueness of an equilibrium point using nonlinear AC power flow model. Key to this end is to consider a nonlinear dynamical system with non-incremental local Volt/VAr control, cast the Volt/VAr dynamics as a game, and leverage the fixed-point theorem as wellmore » as pertinent contraction mapping argument. Numerical examples are provided to complement the analytical results.« less

The ReaxFF reactive force-field: Development, applications, and future directions

DOE PAGES

Senftle, Thomas; Hong, Sungwook; Islam, Md Mahbubul; ...

2016-03-04

The reactive force-field (ReaxFF) interatomic potential is a powerful computational tool for exploring, developing and optimizing material properties. Methods based on the principles of quantum mechanics (QM), while offering valuable theoretical guidance at the electronic level, are often too computationally intense for simulations that consider the full dynamic evolution of a system. Alternatively, empirical interatomic potentials that are based on classical principles require significantly fewer computational resources, which enables simulations to better describe dynamic processes over longer timeframes and on larger scales. Such methods, however, typically require a predefined connectivity between atoms, precluding simulations that involve reactive events. The ReaxFFmore » method was developed to help bridge this gap. Approaching the gap from the classical side, ReaxFF casts the empirical interatomic potential within a bond-order formalism, thus implicitly describing chemical bonding without expensive QM calculations. As a result, this article provides an overview of the development, application, and future directions of the ReaxFF method.« less

Dynamic Response Testing in an Electrically Heated Reactor Test Facility

NASA Astrophysics Data System (ADS)

Bragg-Sitton, Shannon M.; Morton, T. J.

2006-01-01

Non-nuclear testing can be a valuable tool in the development of a space nuclear power or propulsion system. In a non-nuclear test bed, electric heaters are used to simulate the heat from nuclear fuel. Standard testing allows one to fully assess thermal, heat transfer, and stress related attributes of a given system, but fails to demonstrate the dynamic response that would be present in an integrated, fueled reactor system. The integration of thermal hydraulic hardware tests with simulated neutronic response provides a bridge between electrically heated testing and fueled nuclear testing. By implementing a neutronic response model to simulate the dynamic response that would be expected in a fueled reactor system, one can better understand system integration issues, characterize integrated system response times and response characteristics, and assess potential design improvements at a relatively small fiscal investment. Initial system dynamic response testing was demonstrated on the integrated SAFE-100a heat pipe (HP) cooled, electrically heated reactor and heat exchanger hardware, utilizing a one-group solution to the point kinetics equations to simulate the expected neutronic response of the system. Reactivity feedback calculations were then based on a bulk reactivity feedback coefficient and measured average core temperature. This paper presents preliminary results from similar dynamic testing of a direct drive gas cooled reactor system (DDG), demonstrating the applicability of the testing methodology to any reactor type and demonstrating the variation in system response characteristics in different reactor concepts. Although the HP and DDG designs both utilize a fast spectrum reactor, the method of cooling the reactor differs significantly, leading to a variable system response that can be demonstrated and assessed in a non-nuclear test facility. Planned system upgrades to allow implementation of higher fidelity dynamic testing are also discussed. Proposed DDG testing will utilize a higher fidelity point kinetics model to control core power transients, and reactivity feedback will be based on localized feedback coefficients and several independent temperature measurements taken within the core block. This paper presents preliminary test results and discusses the methodology that will be implemented in follow-on DDG testing and the additional instrumentation required to implement high fidelity dynamic testing.

G T-Mohr Start-up Reactivity Insertion Transient Analysis Using Simulink

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

Fard, Mehdi Reisi; Blue, Thomas E.; Miller, Don W.

2006-07-01

As a part of a Department of Energy-Nuclear Engineering Research Initiative (NERI) Project, we at OSU are investigating SiC semiconductor detectors as neutron power monitors for Generation IV power reactors. As a part of this project, we are investigating the power monitoring requirements for a specific type of Generation IV reactor, namely the GT-MHR. To evaluate the power monitoring requirements for the GT-MHR that are most demanding for a SiC diode power monitor, we have developed a Simulink model to study the transient behavior of the GT-MHR. In this paper, we describe the application of the Simulink code to themore » analysis of a series of Start-up Reactivity Insertion Transients (SURITs). The SURIT is considered to be a limiting protectable accident in terms of establishing the dynamic range of a SiC power monitor because of the low count rate of the detector during the start-up and absence of the reactivity feedback mechanism at the beginning of transient. The SURIT is studied with the ultimate goal of identifying combinations of 1) reactor power scram setpoints and 2) cram initiation times (the time in which a scram must be initiated once the setpoint is exceeded) for which the GT-MHR core is protected in the event of a continuous withdrawal of a control rod bank from the core from low powers. The SURIT is initiated by withdrawing a rod bank when the reactor is cold (300 K) and sub-critical at the BOEC (Beginning of Equilibrium Cycle) condition. Various initial power levels have been considered corresponding to various degrees of sub-criticality and various source strengths. An envelope of response is determined to establish which initial powers correspond to the worst case SURIT. (authors)« less

A comprehensive approach to reactive power scheduling in restructured power systems

NASA Astrophysics Data System (ADS)

Shukla, Meera

Financial constraints, regulatory pressure, and need for more economical power transfers have increased the loading of interconnected transmission systems. As a consequence, power systems have been operated close to their maximum power transfer capability limits, making the system more vulnerable to voltage instability events. The problem of voltage collapse characterized by a severe local voltage depression is generally believed to be associated with inadequate VAr support at key buses. The goal of reactive power planning is to maintain a high level of voltage security, through installation of properly sized and located reactive sources and their optimal scheduling. In case of vertically-operated power systems, the reactive requirement of the system is normally satisfied by using all of its reactive sources. But in case of different scenarios of restructured power systems, one may consider a fixed amount of exchange of reactive power through tie lines. Reviewed literature suggests a need for optimal scheduling of reactive power generation for fixed inter area reactive power exchange. The present work proposed a novel approach for reactive power source placement and a novel approach for its scheduling. The VAr source placement technique was based on the property of system connectivity. This is followed by development of optimal reactive power dispatch formulation which facilitated fixed inter area tie line reactive power exchange. This formulation used a Line Flow-Based (LFB) model of power flow analysis. The formulation determined the generation schedule for fixed inter area tie line reactive power exchange. Different operating scenarios were studied to analyze the impact of VAr management approach for vertically operated and restructured power systems. The system loadability, losses, generation and the cost of generation were the performance measures to study the impact of VAr management strategy. The novel approach was demonstrated on IEEE 30 bus system.

Dynamic activation of Src induced by low-power laser irradiation in living cells mediated by reactive oxygen species

NASA Astrophysics Data System (ADS)

Zhang, Juntao; Gao, Xuejuan; Xing, Da; Liu, Lei

2007-11-01

Low-power laser irradiation (LPLI) leads to photochemical reaction and then activates intracellular several signaling pathway. Reactive oxygen species (ROS) are considered to be the primary messengers produced by LPLI. Here, we studied the signaling pathway mediated by ROS upon the stimulation of LPLI. Src tyrosine kinases are well-known targets of ROS and can be activated by oxidative events. Using a Src reporter based on fluorescence resonance energy transfer (FRET) technique, we visualized the dynamic Src activation in Hela cells immediately after LPLI. Moreover, Src activity was enhanced by increasing the duration of LPLI. In addition, our results suggested that ROS were key mediators of Src activation, as ROS scavenger, vitamin C decreased and exogenous H IIO II increased the activity of Src. Meanwhile, Gö6983 loading did not block the effect of LPLI. CCK-8 experiments proved that cell vitality was prominently improved by LPLI with all the doses we applied in our experiments ranging from 3 to 25J/cm2. The results indicated that LPLI/ROS/Src pathway may be involved in the LPLI biostimulation effects.

Dynamic behaviors of various volume rate steel-fiber reinforced reactive powder concrete after high temperature burnt

NASA Astrophysics Data System (ADS)

Pang, Baojun; Wang, Liwen; Yang, Zhenqi; Chi, Runqiang

2009-06-01

Dynamic strain-stress curves of reactive powder concrete under high strain rate (10/s-100/s) were determined by improved split Hopkinson pressure bar (SHPB) system. A plumbum pulse shaper was used to ensure the symmetrical stress in the specimens before fracture and avoid the fluctuation of test data due to input shaky stress pulse. A time modified method was induced for data processing in order to get accurate SHPB results. The results of experiment showed after high temperature burnt, different volume rate (0.0%, 0.5%, 1.0%, 1.5%) steel-fiber reinforced reactive power concrete had the same changing tendency of residual mechanics behaviors, e.g. after 400 centigrade burnt, the residual compression strength was about 70% of material strength without burnt under 100/s. After 800 centigrade burnt, the compression strength is about 30% under 100/s while the deformation ability increased. At meanwhile, steel fiber had improved the mechanism of reinforcing effect and toughening effect of concrete material after burnt. With increasing of steel fiber volume rate, dynamic residual behavior of samples was improved. Microcosmic characteristics and energy absorption were induced for explaining the experiment results.

Processus de modelisation et etude des orages geomagnetiques dans les reseaux electriques: Impact sur le reseau de transport d'Hydro-Quebec

NASA Astrophysics Data System (ADS)

Abdellaoui, Amr

This research project presents a complete modelling process of the effects of GIC on Hydro-Quebec power system network for system planning studies. The advantage of the presented method is that it enables planning engineers to simulate the effects of geomagnetic disturbances on the Hydro-Quebec System under different conditions and contingencies within reasonable calculation time frame. This modelling method of GIC in electric power systems has been applied to the Hydro-Quebec System. An equivalent HQ DC model has been achieved. A numerical calculation method of DC sources from a non-uniform geoelectric field has been developed and implemented on HQ DC model. Harmonics and increased reactive power losses of saturated transformers have been defined as a function of GIC through a binary search algorithm using a chosen HQ magnetization curve. The evolution in time of each transformer saturation according to its effective GIC has been evaluated using analytical formulas. The reactive power losses of saturated transformers have been modeled in PSS/E[1] HQ network as constant reactive current loads assigned to the corresponding transformer buses. Finally, time domain simulations have been performed with PSS/E taking into account transformer saturation times. This has been achieved by integrating HQ DC model results and analytical calculations results of transformer saturation times into an EMTP load model. An interface has been used to link EMTP load model to HQ PSS/E network. Different aspects of GIC effects on the Hydro-Quebec system have been studied, including the influence of uniform and non-uniform geoelectric fields, the comparison of reactive power losses of the 735kV HQ system with those of Montreal network, the risks to voltage levels and the importance of reactive power dynamic reserve. This dissertation presents a new GIC modelling approach for power systems for planning and operations purposes. This methodology could be further enhanced, particularly, the aspect regarding the transformer saturation times. Hence more research remains to be pursued in this area.

Adaptive Q–V Scheme for the Voltage Control of a DFIG-Based Wind Power Plant

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

Kim, Jinho; Seok, Jul-Ki; Muljadi, Eduard

Wind generators within a wind power plant (WPP) will produce different amounts of active power because of the wake effect, and therefore, they have different reactive power capabilities. This paper proposes an adaptive reactive power to the voltage (Q-V) scheme for the voltage control of a doubly fed induction generator (DFIG)-based WPP. In the proposed scheme, the WPP controller uses a voltage control mode and sends a voltage error signal to each DFIG. The DFIG controller also employs a voltage control mode utilizing the adaptive Q-V characteristics depending on the reactive power capability such that a DFIG with a largermore » reactive power capability will inject more reactive power to ensure fast voltage recovery. Test results indicate that the proposed scheme can recover the voltage within a short time, even for a grid fault with a small short-circuit ratio, by making use of the available reactive power of a WPP and differentiating the reactive power injection in proportion to the reactive power capability. This will, therefore, help to reduce the additional reactive power and ensure fast voltage recovery.« less

A study of the oxygen dynamics in a reactive Ar/O2 high power impulse magnetron sputtering discharge using an ionization region model

NASA Astrophysics Data System (ADS)

Lundin, D.; Gudmundsson, J. T.; Brenning, N.; Raadu, M. A.; Minea, T. M.

2017-05-01

The oxygen dynamics in a reactive Ar/O2 high power impulse magnetron sputtering discharge has been studied using a new reactive ionization region model. The aim has been to identify the dominating physical and chemical reactions in the plasma and on the surfaces of the reactor affecting the oxygen plasma chemistry. We explore the temporal evolution of the density of the ground state oxygen molecule O 2 ( X 1 Σg - ) , the singlet metastable oxygen molecules O 2 ( a 1 Δ g ) and O 2 ( b 1 Σ g ) , the oxygen atom in the ground state O(3P), the metastable oxygen atom O(1D), the positive ions O2 + and O+, and the negative ion O-. We furthermore investigate the reaction rates for the gain and loss of these species. The density of atomic oxygen increases significantly as we move from the metal mode to the transition mode, and finally into the compound (poisoned) mode. The main gain rate responsible for the increase is sputtering of atomic oxygen from the oxidized target. Both in the poisoned mode and in the transition mode, sputtering makes up more than 80% of the total gain rate for atomic oxygen. We also investigate the possibility of depositing stoichiometric TiO2 in the transition mode.

Abiotic/biotic coupling in the rhizosphere: a reactive transport modeling analysis

USGS Publications Warehouse

Lawrence, Corey R.; Steefel, Carl; Maher, Kate

2014-01-01

A new generation of models is needed to adequately simulate patterns of soil biogeochemical cycling in response changing global environmental drivers. For example, predicting the influence of climate change on soil organic matter storage and stability requires models capable of addressing complex biotic/abiotic interactions of rhizosphere and weathering processes. Reactive transport modeling provides a powerful framework simulating these interactions and the resulting influence on soil physical and chemical characteristics. Incorporation of organic reactions in an existing reactive transport model framework has yielded novel insights into soil weathering and development but much more work is required to adequately capture root and microbial dynamics in the rhizosphere. This endeavor provides many advantages over traditional soil biogeochemical models but also many challenges.

Secure provision of reactive power ancillary services in competitive electricity markets

NASA Astrophysics Data System (ADS)

El-Samahy, Ismael

The research work presented in this thesis discusses various complex issues associated with reactive power management and pricing in the context of new operating paradigms in deregulated power systems, proposing appropriate policy solutions. An integrated two-level framework for reactive power management is set forth, which is both suitable for a competitive market and ensures a secure and reliable operation of the associated power system. The framework is generic in nature and can be adopted for any electricity market structure. The proposed hierarchical reactive power market structure comprises two stages: procurement of reactive power resources on a seasonal basis, and real-time reactive power dispatch. The main objective of the proposed framework is to provide appropriate reactive power support from service providers at least cost, while ensuring a secure operation of the power system. The proposed procurement procedure is based on a two-step optimization model. First, the marginal benefits of reactive power supply from each provider, with respect to system security, are obtained by solving a loadability-maximization problem subject to transmission security constraints imposed by voltage and thermal limits. Second, the selected set of generators is determined by solving an optimal power flow (OPF)-based auction. This auction maximizes a societal advantage function comprising generators' offers and their corresponding marginal benefits with respect to system security, and considering all transmission system constraints. The proposed procedure yields the selected set of generators and zonal price components, which would form the basis for seasonal contracts between the system operator and the selected reactive power service providers. The main objective of the proposed reactive power dispatch model is to minimize the total payment burden on the Independent System Operator (ISO), which is associated with reactive power dispatch. The real power generation is decoupled and assumed to be fixed during the reactive power dispatch procedures; however, the effect of reactive power on real power is considered in the model by calculating the required reduction in real power output of a generator due to an increase in its reactive power supply. In this case, real power generation is allowed to be rescheduled, within given limits, from the already dispatched levels obtained from the energy market clearing process. The proposed dispatch model achieves the main objective of an ISO in a competitive electricity market, which is to provide the required reactive power support from generators at least cost while ensuring a secure operation of the power system. The proposed reactive power procurement and dispatch models capture both the technical and economic aspects of power system operation in competitive electricity markets; however, from an optimization point of view, these models represent non-convex mixed integer non-linear programming (MINLP) problems due to the presence of binary variables associated with the different regions of reactive power operation in a synchronous generator. Such MINLP optimization problems are difficult to solve, especially for an actual power system. A novel Generator Reactive Power Classification (GRPC) algorithm is proposed in this thesis to address this issue, with the advantage of iteratively solving the optimization models as a series of non-linear programming (NLP) sub-problems. The proposed reactive power procurement and dispatch models are implemented and tested on the CIGRE 32-bus system, with several case studies that represent different practical operating scenarios. The developed models are also compared with other approaches for reactive power provision, and the results demonstrate the robustness and effectiveness of the proposed model. The results clearly reveal the main features of the proposed models for optimal provision of reactive power ancillary service, in order to suit the requirements of an ISO under today's stressed system conditions in a competitive market environment.

Reactivating dynamics for the susceptible-infected-susceptible model: a simple method to simulate the absorbing phase

NASA Astrophysics Data System (ADS)

Macedo-Filho, A.; Alves, G. A.; Costa Filho, R. N.; Alves, T. F. A.

2018-04-01

We investigated the susceptible-infected-susceptible model on a square lattice in the presence of a conjugated field based on recently proposed reactivating dynamics. Reactivating dynamics consists of reactivating the infection by adding one infected site, chosen randomly when the infection dies out, avoiding the dynamics being trapped in the absorbing state. We show that the reactivating dynamics can be interpreted as the usual dynamics performed in the presence of an effective conjugated field, named the reactivating field. The reactivating field scales as the inverse of the lattice number of vertices n, which vanishes at the thermodynamic limit and does not affect any scaling properties including ones related to the conjugated field.

Reactive Power Pricing Model Considering the Randomness of Wind Power Output

NASA Astrophysics Data System (ADS)

Dai, Zhong; Wu, Zhou

2018-01-01

With the increase of wind power capacity integrated into grid, the influence of the randomness of wind power output on the reactive power distribution of grid is gradually highlighted. Meanwhile, the power market reform puts forward higher requirements for reasonable pricing of reactive power service. Based on it, the article combined the optimal power flow model considering wind power randomness with integrated cost allocation method to price reactive power. Meanwhile, considering the advantages and disadvantages of the present cost allocation method and marginal cost pricing, an integrated cost allocation method based on optimal power flow tracing is proposed. The model realized the optimal power flow distribution of reactive power with the minimal integrated cost and wind power integration, under the premise of guaranteeing the balance of reactive power pricing. Finally, through the analysis of multi-scenario calculation examples and the stochastic simulation of wind power outputs, the article compared the results of the model pricing and the marginal cost pricing, which proved that the model is accurate and effective.

77 FR 11109 - Reactive Power Resources; Notice of Technical Conference

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-24

... options for and cost of installing reactive power equipment at the time of interconnection as well as... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. AD12-10-000] Reactive Power... the need for reactive power capability among newly interconnecting asynchronous generators and raises...

Electrical engineering unit for the reactive power control of the load bus at the voltage instability

NASA Astrophysics Data System (ADS)

Kotenev, A. V.; Kotenev, V. I.; Kochetkov, V. V.; Elkin, D. A.

2018-01-01

For the purpose of reactive power control error reduction and decrease of the voltage sags in the electric power system caused by the asynchronous motors started the mathematical model of the load bus was developed. The model was built up of the sub-models of the following elements: a transformer, a transmission line, a synchronous and an asynchronous loads and a capacitor bank load, and represents the automatic reactive power control system taking into account electromagnetic processes of the asynchronous motors started and reactive power changing of the electric power system elements caused by the voltage fluctuation. The active power/time and reactive power/time characteristics based on the recommended procedure of the equivalent electric circuit parameters calculation were obtained. The derived automatic reactive power control system was shown to eliminate the voltage sags in the electric power system caused by the asynchronous motors started.

77 FR 21555 - Reactive Power Resources; Supplemental Notice of Technical Conference

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-10

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. AD12-10-000] Reactive Power... Commission (Commission) announced that a staff Technical Conference on Reactive Power Resources will be held... may register at the following Web page: https://www.ferc.gov/whats-new/registration/reactive-power-4...

77 FR 24949 - Reactive Power Resources; Supplemental Notice Requesting Comments

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-26

... storage resources; the design options for and cost of installing reactive power equipment at the time of... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. AD12-10-000] Reactive Power... the reactive power provisions of Order No. 661-A and examine what evidence could be developed under...

The effect of core configuration on temperature coefficient of reactivity in IRR-1

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

Bettan, M.; Silverman, I.; Shapira, M.

1997-08-01

Experiments designed to measure the effect of coolant moderator temperature on core reactivity in an HEU swimming pool type reactor were performed. The moderator temperature coefficient of reactivity ({alpha}{sub {omega}}) was obtained and found to be different in two core loadings. The measured {alpha}{sub {omega}} of one core loading was {minus}13 pcm/{degrees}C at the temperature range of 23-30{degrees}C. This value of {alpha}{sub {omega}} is comparable to the data published by the IAEA. The {alpha}{sub {omega}} measured in the second core loading was found to be {minus}8 pcm/{degrees}C at the same temperature range. Another phenomenon considered in this study is coremore » behavior during reactivity insertion transient. The results were compared to a core simulation using the Dynamic Simulator for Nuclear Power Plants. It was found that in the second core loading factors other than the moderator temperature influence the core reactivity more than expected. These effects proved to be extremely dependent on core configuration and may in certain core loadings render the reactor`s reactivity coefficient undesirable.« less

Link-state-estimation-based transmission power control in wireless body area networks.

PubMed

Kim, Seungku; Eom, Doo-Seop

2014-07-01

This paper presents a novel transmission power control protocol to extend the lifetime of sensor nodes and to increase the link reliability in wireless body area networks (WBANs). We first experimentally investigate the properties of the link states using the received signal strength indicator (RSSI). We then propose a practical transmission power control protocol based on both short- and long-term link-state estimations. Both the short- and long-term link-state estimations enable the transceiver to adapt the transmission power level and target the RSSI threshold range, respectively, to simultaneously satisfy the requirements of energy efficiency and link reliability. Finally, the performance of the proposed protocol is experimentally evaluated in two experimental scenarios-body posture change and dynamic body motion-and compared with the typical WBAN transmission power control protocols, a real-time reactive scheme, and a dynamic postural position inference mechanism. From the experimental results, it is found that the proposed protocol increases the lifetime of the sensor nodes by a maximum of 9.86% and enhances the link reliability by reducing the packet loss by a maximum of 3.02%.

Strategies for Voltage Control and Transient Stability Assessment

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

Hiskens, Ian A.

As wind generation grows, its influence on power system performance will becoming increasingly noticeable. Wind generation di ffers from traditional forms of generation in numerous ways though, motivating the need to reconsider the usual approaches to power system assessment and performance enhancement. The project has investigated the impact of wind generation on transient stability and voltage control, identifying and addressing issues at three distinct levels of the power system: 1) at the device level, the physical characteristics of wind turbine generators (WTGs) are quite unlike those of synchronous machines, 2) at the wind-farm level, the provision of reactive support ismore » achieved through coordination of numerous dissimilar devices, rather than straightforward generator control, and 3) from a systems perspective, the location of wind-farms on the sub-transmission network, coupled with the variability inherent in their power output, can cause complex voltage control issues. The project has sought to develop a thorough understanding of the dynamic behaviour of type-3 WTGs, and in particular the WECC generic model. The behaviour of such models is governed by interactions between the continuous dynamics of state variables and discrete events associated with limits. It was shown that these interactions can be quite complex, and may lead to switching deadlock that prevents continuation of the trajectory. Switching hysteresis was proposed for eliminating deadlock situations. Various type-3 WTG models include control blocks that duplicate integrators. It was shown that this leads to non-uniqueness in the conditions governing steady-state, and may result in pre- and post-disturbance equilibria not coinciding. It also gives rise to a zero eigenvalue in the linearized WTG model. In order to eliminate the anomalous behaviour revealed through this investigation, WECC has now released a new generic model for type-3 WTGs. Wind-farms typically incorporate a variety of voltage control equipment including tapchanging transformers, switched capacitors, SVCs, STATCOMs and the WTGs themselves. The project has considered the coordinated control of this equipment, and has addressed a range of issues that arise in wind-farm operation. The first concerns the ability of WTGs to meet reactive power requirements when voltage saturation in the collector network restricts the reactive power availability of individual generators. Secondly, dynamic interactions between voltage regulating devices have been investigated. It was found that under certain realistic conditions, tap-changing transformers may exhibit instability. In order to meet cost, maintenance, fault tolerance and other requirements, it is desirable for voltage control equipment to be treated as an integrated system rather than as independent devices. The resulting high-level scheduling of wind-farm reactive support has been investigated. In addressing this control problem, several forms of future information were considered, including exact future knowledge and stochastic predictions. Deterministic and Stochastic Dynamic Programming techniques were used in the development of control algorithms. The results demonstrated that while exact future knowledge is very useful, simple prediction methods yield little bene fit. The integration of inherently variable wind generation into weak grids, particularly subtransmission networks that are characterized by low X=R ratios, aff ects bus voltages, regulating devices and line flows. The meshed structure of these networks adds to the complexity, especially when wind generation is distributed across multiple nodes. A range of techniques have been considered for analyzing the impact of wind variability on weak grids. Sensitivity analysis, based on the power-flow Jacobian, was used to highlight sections of a system that are most severely a ffected by wind-power variations. A continuation power flow was used to determine parameter changes that reduce the impact of wind-power variability. It was also used to explore interactions between multiple wind-farms. Furthermore, these tools have been used to examine the impact of wind injection on transformer tap operation in subtransmission networks. The results of a tap operation simulation study show that voltage regulation at wind injection nodes increases tap change operations. The tradeo ff between local voltage regulation and tap change frequency is fundamentally important in optimizing the size of reactive compensation used for voltage regulation at wind injection nodes. Line congestion arising as a consequence of variable patterns of wind-power production has also been investigated. Two optimization problems have been formulated, based respectively on the DC and AC power flow models, for identifying vulnerable line segments. The DC optimization is computationally more e fficient, whereas the AC sensitivity-based optimization provides greater accuracy.« less

From ab Initio Potential Energy Surfaces to State-Resolved Reactivities: X + H 2O ↔ HX + OH [X = F, Cl, and O( 3P)] Reactions

DOE PAGES

Li, Jun; Jiang, Bin; Song, Hongwei; ...

2015-04-17

Here, we survey the recent advances in theoretical understanding of quantum state resolved dynamics, using the title reactions as examples. It is shown that the progress was made possible by major developments in two areas. First, an accurate analytical representation of many high-level ab initio points over a large configuration space can now be made with high fidelity and the necessary permutation symmetry. The resulting full-dimensional global potential energy surfaces enable dynamical calculations using either quasi-classical trajectory or more importantly quantum mechanical methods. The second advance is the development of accurate and efficient quantum dynamical methods, which are necessary formore » providing a reliable treatment of quantum effects in reaction dynamics such as tunneling, resonances, and zero-point energy. The powerful combination of the two advances has allowed us to achieve a quantitatively accurate characterization of the reaction dynamics, which unveiled rich dynamical features such as steric steering, strong mode specificity, and bond selectivity. The dependence of reactivity on reactant modes can be rationalized by the recently proposed sudden vector projection model, which attributes the mode specificity and bond selectivity to the coupling of reactant modes with the reaction coordinate at the relevant transition state. The deeper insights provided by these theoretical studies have advanced our understanding of reaction dynamics to a new level.« less

Time-Dependent Wave Packet Dynamics Calculations of Cross Sections for Ultracold Scattering of Molecules

NASA Astrophysics Data System (ADS)

Huang, Jiayu; Liu, Shu; Zhang, Dong H.; Krems, Roman V.

2018-04-01

Because the de Broglie wavelength of ultracold molecules is very large, the cross sections for collisions of molecules at ultracold temperatures are always computed by the time-independent quantum scattering approach. Here, we report the first accurate time-dependent wave packet dynamics calculation for reactive scattering of ultracold molecules. Wave packet dynamics calculations can be applied to molecular systems with more dimensions and provide real-time information on the process of bond rearrangement and/or energy exchange in molecular collisions. Our work thus makes possible the extension of rigorous quantum calculations of ultracold reaction properties to polyatomic molecules and adds a new powerful tool for the study of ultracold chemistry.

Time-Dependent Wave Packet Dynamics Calculations of Cross Sections for Ultracold Scattering of Molecules.

PubMed

Huang, Jiayu; Liu, Shu; Zhang, Dong H; Krems, Roman V

2018-04-06

Because the de Broglie wavelength of ultracold molecules is very large, the cross sections for collisions of molecules at ultracold temperatures are always computed by the time-independent quantum scattering approach. Here, we report the first accurate time-dependent wave packet dynamics calculation for reactive scattering of ultracold molecules. Wave packet dynamics calculations can be applied to molecular systems with more dimensions and provide real-time information on the process of bond rearrangement and/or energy exchange in molecular collisions. Our work thus makes possible the extension of rigorous quantum calculations of ultracold reaction properties to polyatomic molecules and adds a new powerful tool for the study of ultracold chemistry.

Spontaneous oscillations of cell voltage, power density, and anode exit CO concentration in a PEM fuel cell.

PubMed

Lu, Hui; Rihko-Struckmann, Liisa; Sundmacher, Kai

2011-10-28

The spontaneous oscillations of the cell voltage and output power density of a PEMFC (with PtRu/C anode) using CO-containing H(2) streams as anodic fuels have been observed during galvanostatic operating. It is ascribed to the dynamic coupling of the CO adsorption (poisoning) and the electrochemical CO oxidation (reactivating) processes in the anode chamber of the single PEMFC. Accompanying the cell voltage and power density oscillations, the discrete CO concentration oscillations at the anode outlet of the PEMFC were also detected, which directly confirms the electrochemical CO oxidation taking place in the anode chamber during galvanostatic operating. This journal is © the Owner Societies 2011

The voltage control for self-excited induction generator based on STATCOM

NASA Astrophysics Data System (ADS)

Yan, Dandan; Wang, Feifeng; Pan, Juntao; Long, Weijie

2018-05-01

The small independent induction generator can build up voltage under its remanent magnetizing and excitation capacitance, but it is prone to voltage sag and harmonic increment when running with load. Therefore, the controller for constant voltage is designed based on the natural coordinate system to adjust the static synchronous compensator (STATCOM), which provides two-way dynamic reactive power compensation for power generation system to achieve voltage stability and harmonic suppression. The control strategy is verified on Matlab/Sinmulik, and the results show that the STATCOM under the controller can effectively improve the load capacity and reliability of asynchronous generator.

The results of systems tests of the 500 kV busbar controllable shunting reactor in the Tavricheskaya substation

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

Gusev, S. I.; Karpov, V. N.; Kiselev, A. N.

2009-09-15

The results of systems tests of the 500 kV busbar magnetization-controllable shunting reactor (CSR), set up in the Tavricheskaya substation, including measurements of the quality of the electric power, the harmonic composition of the network currents of the reactor for different values of the reactive power consumed, the determination of the regulating characteristics of the reactor, the speed of response of the shunting reactor in the current and voltage stabilization modes, and also the operation of the reactor under dynamic conditions for different perturbations, are presented. The results obtained are analyzed.

Evaluation of Contribution for Voltage Control Ancillary Services Based on Social Surplus

NASA Astrophysics Data System (ADS)

Ueki, Yuji; Hara, Ryoichi; Kita, Hiroyuki; Hasegawa, Jun

Reactive power supply plays an important role in active power supply with adequate system voltages. Various pricing mechanism for reactive power supply have been developed and some of them are adopted in some power systems, however they are in a trial stage. The authors also focus on development of a pricing method for reactive power ancillary services. This problem involves two technical issues: rational estimation of the cost associated with reactive power supply and fair and transparent allocation of the estimated cost among the market participants. This paper proposes methods for evaluating the contribution of generators and demands.

Substation Reactive Power Regulation Strategy

NASA Astrophysics Data System (ADS)

Zhang, Junfeng; Zhang, Chunwang; Ma, Daqing

2018-01-01

With the increasing requirements on the power supply quality and reliability of distribution network, voltage and reactive power regulation of substations has become one of the indispensable ways to ensure voltage quality and reactive power balance and to improve the economy and reliability of distribution network. Therefore, it is a general concern of the current power workers and operators that what kind of flexible and effective control method should be used to adjust the on-load tap-changer (OLTC) transformer and shunt compensation capacitor in a substation to achieve reactive power balance in situ, improve voltage pass rate, increase power factor and reduce active power loss. In this paper, based on the traditional nine-zone diagram and combining with the characteristics of substation, a fuzzy variable-center nine-zone diagram control method is proposed and used to make a comprehensive regulation of substation voltage and reactive power. Through the calculation and simulation of the example, this method is proved to have satisfactorily reconciled the contradiction between reactive power and voltage in real-time control and achieved the basic goal of real-time control of the substation, providing a reference value to the practical application of the substation real-time control method.

Measured effects of wind turbine generation at the Block Island Power Company

NASA Technical Reports Server (NTRS)

Wilreker, V. F.; Smith, R. F.; Stiller, P. H.; Scot, G. W.; Shaltens, R. K.

1984-01-01

Data measurements made on the NASA MOD-OA 200-kw wind-turbine generator (WTG) installed on a utility grid form the basis for an overall performance analysis. Fuel displacement/-savings, dynamic interactions, and WTG excitation (reactive-power) control effects are studied. Continuous recording of a large number of electrical and mechanical variables on FM magnetic tape permit evaluation and correlation of phenomena over a bandwidth of at least 20 Hz. Because the wind-power penetration reached peaks of 60 percent, the impact of wind fluctuation and wind-turbine/diesel-utility interaction is evaluated in a worst-case scenario. The speed-governor dynamics of the diesel units exhibited an underdamped response, and the utility operation procedures were not altered to optimize overall WTG/utility performance. Primary findings over the data collection period are: a calculated 6.7-percent reduction in fuel consumption while generating 11 percent of the total electrical energy; acceptable system voltage and frequency fluctuations with WTG connected; and applicability of WTG excitation schemes using voltage, power, or VARS as the controlled variable.

Real Time Voltage and Current Phase Shift Analyzer for Power Saving Applications

PubMed Central

Krejcar, Ondrej; Frischer, Robert

2012-01-01

Nowadays, high importance is given to low energy devices (such as refrigerators, deep-freezers, washing machines, pumps, etc.) that are able to produce reactive power in power lines which can be optimized (reduced). Reactive power is the main component which overloads power lines and brings excessive thermal stress to conductors. If the reactive power is optimized, it can significantly lower the electricity consumption (from 10 to 30%—varies between countries). This paper will examine and discuss the development of a measuring device for analyzing reactive power. However, the main problem is the precise real time measurement of the input and output voltage and current. Such quality measurement is needed to allow adequate action intervention (feedback which reduces or fully compensates reactive power). Several other issues, such as the accuracy and measurement speed, must be examined while designing this device. The price and the size of the final product need to remain low as they are the two important parameters of this solution. PMID:23112662

Structural network heterogeneities and network dynamics: a possible dynamical mechanism for hippocampal memory reactivation.

NASA Astrophysics Data System (ADS)

Jablonski, Piotr; Poe, Gina; Zochowski, Michal

2007-03-01

The hippocampus has the capacity for reactivating recently acquired memories and it is hypothesized that one of the functions of sleep reactivation is the facilitation of consolidation of novel memory traces. The dynamic and network processes underlying such a reactivation remain, however, unknown. We show that such a reactivation characterized by local, self-sustained activity of a network region may be an inherent property of the recurrent excitatory-inhibitory network with a heterogeneous structure. The entry into the reactivation phase is mediated through a physiologically feasible regulation of global excitability and external input sources, while the reactivated component of the network is formed through induced network heterogeneities during learning. We show that structural changes needed for robust reactivation of a given network region are well within known physiological parameters.

Structural network heterogeneities and network dynamics: A possible dynamical mechanism for hippocampal memory reactivation

NASA Astrophysics Data System (ADS)

Jablonski, Piotr; Poe, Gina R.; Zochowski, Michal

2007-01-01

The hippocampus has the capacity for reactivating recently acquired memories and it is hypothesized that one of the functions of sleep reactivation is the facilitation of consolidation of novel memory traces. The dynamic and network processes underlying such a reactivation remain, however, unknown. We show that such a reactivation characterized by local, self-sustained activity of a network region may be an inherent property of the recurrent excitatory-inhibitory network with a heterogeneous structure. The entry into the reactivation phase is mediated through a physiologically feasible regulation of global excitability and external input sources, while the reactivated component of the network is formed through induced network heterogeneities during learning. We show that structural changes needed for robust reactivation of a given network region are well within known physiological parameters.

Thermal Decomposition of Condensed-Phase Nitromethane from Molecular Dynamics from ReaxFF Reactive Dynamics

DTIC Science & Technology

2011-05-04

pubs.acs.org/JPCB Thermal Decomposition of Condensed-Phase Nitromethane from Molecular Dynamics from ReaxFF Reactive Dynamics Si-ping Han,†,‡ Adri C. T. van...ABSTRACT: We studied the thermal decomposition and subsequent reaction of the energetic material nitromethane (CH3NO2) using molec- ular dynamics...with ReaxFF, a first principles-based reactive force field. We characterize the chemistry of liquid and solid nitromethane at high temperatures (2000

Wind turbine generator interaction with conventional diesel generators on Block Island, Rhode Island. Volume 1: Executive summary

NASA Technical Reports Server (NTRS)

Wilreker, V. F.; Stiller, P. H.; Scott, G. W.; Kruse, V. J.; Smith, R. F.

1984-01-01

Primary results are summarized for a three-part study involving the effects of connecting a MOD-OA wind turbine generator to an isolated diesel power system. The MOD-OA installation considered was the third of four experimental nominal 200 kW wind turbines connected to various utilities under the Federal Wind Energy Program and was characterized by the highest wind energy penetration levels of four sites. The study analyses address: fuel displacement, dynamic interaction, and three modes of reactive power control. These analyses all have as their basis the results of the data acquisition program conducted on Block Island, Rhode Island.

Mechanism study on mitochondrial fragmentation under oxidative stress caused by high-fluence low-power laser irradiation

NASA Astrophysics Data System (ADS)

Wu, Shengnan; Zhou, Feifan; Xing, Da

2012-03-01

Mitochondria are dynamic organelles that undergo continual fusion and fission to maintain their morphology and functions, but the mechanism involved is still not clear. Here, we investigated the effect of mitochondrial oxidative stress triggered by high-fluence low-power laser irradiation (HF-LPLI) on mitochondrial dynamics in human lung adenocarcinoma cells (ASTC-a-1). Upon HF-LPLI-triggered oxidative stress, mitochondria displayed a fragmented structure, which was abolished by exposure to dehydroascorbic acid (DHA), a reactive oxygen species scavenger, indicating that oxidative stress can induce mitochondrial fragmentation. Mitochondrial translocation of the profission protein dynamin-related protein 1 (Drp1) was observed following HF-LPLI, demonstrating apoptosis-related activation of Drp1. Notably, DHA pre-treatment prevented HF-LPLI-induced Drp1 activation. We conclude that mitochondrial oxidative stress through activation of Drp1 causes mitochondrial fragmentation.

The effect of reactive emotions expressed in response to another's anger on inferences of social power.

PubMed

Hareli, Shlomo; David, Shlomo

2017-06-01

Social perception of emotions is influenced by the context in which it occurs. One such context is a social interaction involving an exchange of emotions. The way parties to the interaction are perceived is shaped by the combination of emotions exchanged. This idea was examined by assessing the extent to which expressions of anger toward a target-which, in isolation, are perceived as signals of high social power-are influenced by the target's emotional reaction to it (i.e., reactive emotions). Three studies show that the angry person was perceived as having a higher level of social power when this anger was responded by fear or sadness than when it was responded by neutrality or anger. Study 1 indicated that reactive emotions have a stronger effect on perceived social power when emotions were incongruent with gender stereotypes. Study 2 indicated that these effects are a result of these emotions serving as reactive emotions rather than a benchmark against which the angry person's power is assessed. Study 3 showed that reactive emotions affect perceived social power by serving as signals of the level to which the high social power suggested by the first person's expression is confirmed by its target. Comparing effects of reactive emotions to anger with reactive emotions to sadness, showed that perceived social power of the expresser is determined by the nature of the expression, with some adjustment caused by the reactive emotions. This underscores the importance of social interaction as a context for the social perception of emotions. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Reactive power compensator

DOEpatents

El-Sharkawi, Mohamed A.; Venkata, Subrahmanyam S.; Chen, Mingliang; Andexler, George; Huang, Tony

1992-01-01

A system and method for determining and providing reactive power compensation for an inductive load. A reactive power compensator (50,50') monitors the voltage and current flowing through each of three distribution lines (52a, 52b, 52c), which are supplying three-phase power to one or more inductive loads. Using signals indicative of the current on each of these lines when the voltage waveform on the line crosses zero, the reactive power compensator determines a reactive power compensator capacitance that must be connected to the lines to maintain a desired VAR level, power factor, or line voltage. Alternatively, an operator can manually select a specific capacitance for connection to each line, or the capacitance can be selected based on a time schedule. The reactive power compensator produces control signals, which are coupled through optical fibers (102/106) to a switch driver (110, 110') to select specific compensation capacitors (112) for connections to each line. The switch driver develops triggering signals that are supplied to a plurality of series-connected solid state switches (350), which control charge current in one direction in respect to ground for each compensation capacitor. During each cycle, current flows from ground to charge the capacitors as the voltage on the line begins to go negative from its positive peak value. The triggering signals are applied to gate the solid state switches into a conducting state when the potential on the lines and on the capacitors reaches a negative peak value, thereby minimizing both the potential difference and across the charge current through the switches when they begin to conduct. Any harmonic distortion on the potential and current carried by the lines is filtered out from the current and potential signals used by the reactive power compensator so that it does not affect the determination of the required reactive compensation.

Reactive Power Compensator.

DOEpatents

El-Sharkawi, M.A.; Venkata, S.S.; Chen, M.; Andexler, G.; Huang, T.

1992-07-28

A system and method for determining and providing reactive power compensation for an inductive load. A reactive power compensator (50,50') monitors the voltage and current flowing through each of three distribution lines (52a, 52b, 52c), which are supplying three-phase power to one or more inductive loads. Using signals indicative of the current on each of these lines when the voltage waveform on the line crosses zero, the reactive power compensator determines a reactive power compensator capacitance that must be connected to the lines to maintain a desired VAR level, power factor, or line voltage. Alternatively, an operator can manually select a specific capacitance for connection to each line, or the capacitance can be selected based on a time schedule. The reactive power compensator produces control signals, which are coupled through optical fibers (102/106) to a switch driver (110, 110') to select specific compensation capacitors (112) for connections to each line. The switch driver develops triggering signals that are supplied to a plurality of series-connected solid state switches (350), which control charge current in one direction in respect to ground for each compensation capacitor. During each cycle, current flows from ground to charge the capacitors as the voltage on the line begins to go negative from its positive peak value. The triggering signals are applied to gate the solid state switches into a conducting state when the potential on the lines and on the capacitors reaches a negative peak value, thereby minimizing both the potential difference and across the charge current through the switches when they begin to conduct. Any harmonic distortion on the potential and current carried by the lines is filtered out from the current and potential signals used by the reactive power compensator so that it does not affect the determination of the required reactive compensation. 26 figs.

Stability analysis of offshore wind farm and marine current farm

NASA Astrophysics Data System (ADS)

Shawon, Mohammad Hasanuzzaman

Renewable energy has been playing an important role to meet power demand and 'Green Energy' market is getting bigger platform all over the world in the last few years. Due to massive increase in the prices of fossil fuels along with global warming issues, energy harvesting from renewable energy sources has received considerable interest, nowadays, where extensive researches are going on to ensure optimum use of renewable sources. In order to meet the increasing demand of electricity and power, integration of renewable energy is getting highest priorities around the world. Wind is one of the most top growing renewable energy resources and wind power market penetration is expected to reach 3.35 percent by 2013 from its present market of about 240 GW. A wind energy system is the most environmental friendly, cost effective and safe among all renewable energy resources available. Another promising form of renewable energy is ocean energy which covers 70 % of the earth. Ocean energy can be tapped from waves, tides and thermal elements. Offshore Wind farm (OWF) has already become very popular for large scale wind power integration with the onshore grid. Recently, marine current farm (MCF) is also showing good potential to become mainstream energy sources and already successfully commissioned in United Kingdom. However, squirrel cage induction generator (SCIG) has the stability problem similar to synchronous generator especially during fault location to restore the electromagnetic torque. Series dynamic braking resistor (SDBR) has been known as a useful mean to stabilize fixed speed wind generator system. On the other hand, doubly fed induction generator (DFIG) has the capability of coupling the control of active and reactive power and to provide necessary reactive power demand during grid fault conditions. Series dynamic braking resistor (SDBR) can also be employed with DFIG to limit the rotor over current. An integration of wind and tidal energy represents a new-trend for large electric energy production using offshore wind generators and marine current generators, respectively. Thus DFIG based offshore wind farm can be an economic solution to stabilize squirrel cage induction generator based marine current farm without installing any addition FACTS devices. This thesis first focuses on the stabilization of fixed speed IG based marine current farm using SDBR. Also stabilization of DFIG based variable speed wind farm utilizing SDBR is studied in this work. Finally a co-operative control strategy is proposed where DFIG is controlled in such a way that it can even provide necessary reactive power demand of induction generator, so that additional cost of FACTS devices can be avoided. In that way, the DFIGs of the offshore wind farm (OWF) will actively compensate the reactive power demand of adjacent IGs of the marine current farm (MCF) during grid fault. Detailed modeling and control scheme for the proposed system are demonstrated considering some realistic scenarios. The power system small signal stability analysis is also carried out by eigenvalue analysis for marine current generator topology, wind turbine generator topology and integrated topology. The relation between the modes and state variables are discussed in light of modal and sensitivity analyses. The results of theoretical analyses are verified by MATLAB/SIMULINK and laboratory standard power system simulator PSCAD/EMTDC.

Review of Reactive Power Dispatch Strategies for Loss Minimization in a DFIG-based Wind Farm

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

Zhang, Baohua; Hu, Weihao; Hou, Peng

This study reviews and compares the performance of reactive power dispatch strategies for the loss minimization of Doubly Fed Induction Generator (DFIG)-based Wind Farms (WFs). Twelve possible combinations of three WF level reactive power dispatch strategies and four Wind Turbine (WT) level reactive power control strategies are investigated. All of the combined strategies are formulated based on the comprehensive loss models of WFs, including the loss models of DFIGs, converters, filters, transformers, and cables of the collection system. Optimization problems are solved by a Modified Particle Swarm Optimization (MPSO) algorithm. The effectiveness of these strategies is evaluated by simulations onmore » a carefully designed WF under a series of cases with different wind speeds and reactive power requirements of the WF. The wind speed at each WT inside the WF is calculated using the Jensen wake model. The results show that the best reactive power dispatch strategy for loss minimization comes when the WF level strategy and WT level control are coordinated and the losses from each device in the WF are considered in the objective.« less

Review of Reactive Power Dispatch Strategies for Loss Minimization in a DFIG-based Wind Farm

DOE PAGES

Zhang, Baohua; Hu, Weihao; Hou, Peng; ...

2017-06-27

This study reviews and compares the performance of reactive power dispatch strategies for the loss minimization of Doubly Fed Induction Generator (DFIG)-based Wind Farms (WFs). Twelve possible combinations of three WF level reactive power dispatch strategies and four Wind Turbine (WT) level reactive power control strategies are investigated. All of the combined strategies are formulated based on the comprehensive loss models of WFs, including the loss models of DFIGs, converters, filters, transformers, and cables of the collection system. Optimization problems are solved by a Modified Particle Swarm Optimization (MPSO) algorithm. The effectiveness of these strategies is evaluated by simulations onmore » a carefully designed WF under a series of cases with different wind speeds and reactive power requirements of the WF. The wind speed at each WT inside the WF is calculated using the Jensen wake model. The results show that the best reactive power dispatch strategy for loss minimization comes when the WF level strategy and WT level control are coordinated and the losses from each device in the WF are considered in the objective.« less

Input Power Characteristics of a Three-Phase Thyristor Converter

DOT National Transportation Integrated Search

1973-10-01

A phase delay rectifier operating into a passive resistive load was instrumented in the laboratory. Techniques for accurate measurement of power, displacement reactive power, harmonic components, and distortion reactive power are presented. The chara...

A Multi-agent Based Cooperative Voltage and Reactive Power Control

NASA Astrophysics Data System (ADS)

Ishida, Masato; Nagata, Takeshi; Saiki, Hiroshi; Shimada, Ikuhiko; Hatano, Ryousuke

In order to maintain system voltage within the optimal range and prevent voltage instability phenomena before they occur, a variety of phase modifying equipment is installed in optimal locations throughout the power system network and a variety of methods of voltage reactive control are employed. The proposed system divided the traditional method to control voltage and reactive power into two sub problems; “voltage control” to adjust the secondary bus voltage of substations, and “reactive power control” to adjust the primary bus voltage. In this system, two types of agents are installed in substations in order to cooperate “voltage control” and “reactive power control”. In order to verify the performance of the proposed method, it has been applied to the model network system. The results confirm that our proposed method is able to control violent fluctuations in load.

Power quality improvement of a stand-alone power system subjected to various disturbances

NASA Astrophysics Data System (ADS)

Lone, Shameem Ahmad; Mufti, Mairaj Ud-Din

In wind-diesel stand-alone power systems, the disturbances like random nature of wind power, turbulent wind, sudden changes in load demand and the wind park disconnection effect continuously the system voltage and frequency. The satisfactory operation of such a system is not an easy task and the control design has to take in to account all these subtleties. For maintaining the power quality, generally, a short-term energy storage device is used. In this paper, the performance of a wind-diesel system associated with a superconducting magnetic energy storage (SMES) system is studied. The effect of installing SMES at wind park bus/load bus, on the system performance is investigated. To control the exchange of real and reactive powers between the SMES unit and the wind-diesel system, a control strategy based on fuzzy logic is proposed. The dynamic models of the hybrid power system for most common scenarios are developed and the results presented.

Brief analysis of Jiangsu grid security and stability based on multi-infeed DC index in power system

NASA Astrophysics Data System (ADS)

Zhang, Wenjia; Wang, Quanquan; Ge, Yi; Huang, Junhui; Chen, Zhengfang

2018-02-01

The impact of Multi-infeed HVDC has gradually increased to security and stability operating in Jiangsu power grid. In this paper, an appraisal method of Multi-infeed HVDC power grid security and stability is raised with Multi-Infeed Effective Short Circuit Ratio, Multi-Infeed Interaction Factor and Commutation Failure Immunity Index. These indices are adopted in security and stability simulating calculation of Jiangsu Multi-infeed HVDC system. The simulation results indicate that Jiangsu power grid is operating with a strong DC system. It has high level of power grid security and stability, and meet the safety running requirements. Jinpin-Suzhou DC system is located in the receiving end with huge capacity, which is easily leading to commutation failure of the transmission line. In order to resolve this problem, dynamic reactive power compensation can be applied in power grid near Jinpin-Suzhou DC system. Simulation result shows this method is feasible to commutation failure.

Comparison of Virtual Oscillator and Droop Control

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

Johnson, Brian B; Rodriguez, Miguel; Sinha, Mohit

Virtual oscillator control (VOC) and droop control are distinct methods to ensure synchronization and power sharing of parallel inverters in islanded systems. VOC is a control strategy where the dynamics of a nonlinear oscillator are used to derive control states to modulate the switch terminals of an inverter. Since VOC is a time-domain controller that reacts to instantaneous measurements with no additional filters or computations, it provides a rapid response during transients and stabilizes volatile dynamics. In contrast, droop control regulates the inverter voltage in response to the measured average real and reactive power output. Given that real and reactivemore » power are phasor quantities that are not well-defined in real time, droop controllers typically use multiplicative operations in conjunction with low-pass filters on the current and voltage measurements to calculate such quantities. Since these filters must suppress low frequency ac harmonics, they typically have low cutoff frequencies that ultimately impede droop controller bandwidth. Although VOC and droop control can be engineered to produce similar steady-state characteristics, their dynamic performance can differ markedly. This paper presents an analytical framework to characterize and compare the dynamic response of VOC and droop control. The analysis is experimentally validated with three 120 V inverters rated at 1kW, demonstrating that for the same design specifications VOC is roughly 8 times faster and presents almost no overshoot after a transient.« less

Voronoi Diagram Based Optimization of Dynamic Reactive Power Sources

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

Huang, Weihong; Sun, Kai; Qi, Junjian

2015-01-01

Dynamic var sources can effectively mitigate fault-induced delayed voltage recovery (FIDVR) issues or even voltage collapse. This paper proposes a new approach to optimization of the sizes of dynamic var sources at candidate locations by a Voronoi diagram based algorithm. It first disperses sample points of potential solutions in a searching space, evaluates a cost function at each point by barycentric interpolation for the subspaces around the point, and then constructs a Voronoi diagram about cost function values over the entire space. Accordingly, the final optimal solution can be obtained. Case studies on the WSCC 9-bus system and NPCC 140-busmore » system have validated that the new approach can quickly identify the boundary of feasible solutions in searching space and converge to the global optimal solution.« less

Voltage control for a wind power plant based on the available reactive current of a DFIG and its impacts on the point of interconnection

DOE PAGES

Usman, Yasir; Kim, Jinho; Muljadi, Eduard; ...

2016-01-01

Wake effects cause wind turbine generators (WTGs) within a wind power plant (WPP) to produce different levels of active power and subsequent reactive power capabilities. Further, the impedance between a WTG and the point of interconnection (POI)-which depends on the distance between them-impacts the WPP's reactive power injection capability at the POI. This paper proposes a voltage control scheme for a WPP based on the available reactive current of the doubly-fed induction generators (DFIGs) and its impacts on the POI to improve the reactive power injection capability of the WPP. In this paper, a design strategy for modifying the gainmore » of DFIG controller is suggested and the comprehensive properties of these control gains are investigated. In the proposed scheme, the WPP controller, which operates in a voltage control mode, sends the command signal to the DFIGs based on the voltage difference at the POI. The DFIG controllers, which operate in a voltage control mode, employ a proportional controller with a limiter. The gain of the proportional controller is adjusted depending on the available reactive current of the DFIG and the series impedance between the DFIG and the POI. The performance of the proposed scheme is validated for various disturbances such as a reactive load connection and grid fault using an EMTP-RV simulator. Furthermore, simulation results demonstrate that the proposed scheme promptly recovers the POI voltage by injecting more reactive power after a disturbance than the conventional scheme.« less

Control circuit maintains unity power factor of reactive load

NASA Technical Reports Server (NTRS)

Kramer, M.; Martinage, L. H.

1966-01-01

Circuit including feedback control elements automatically corrects the power factor of a reactive load. It maintains power supply efficiency where negative load reactance changes and varies by providing corrective error signals to the control windings of a power supply transformer.

Hierarchical Control Scheme for Improving Transient Voltage Recovery of a DFIG-Based WPP

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

Kim, Jinho; Muljadi, Eduard; Kang, Yong Cheol

Modern grid codes require that wind power plants (WPPs) inject reactive power according to the voltage dip at a point of interconnection (POI). This requirement helps to support a POI voltage during a fault. However, if a fault is cleared, the POI and wind turbine generator (WTG) voltages are likely to exceed acceptable levels unless the WPP reduces the injected reactive power quickly. This might deteriorate the stability of a grid by allowing the disconnection of WTGs to avoid any damage. This paper proposes a hierarchical control scheme of a doubly-fed induction generator (DFIG)-based WPP. The proposed scheme aims tomore » improve the reactive power injecting capability during the fault and suppress the overvoltage after the fault clearance. To achieve the former, an adaptive reactive power-to-voltage scheme is implemented in each DFIG controller so that a DFIG with a larger reactive power capability will inject more reactive power. To achieve the latter, a washout filter is used to capture a high frequency component contained in the WPP voltage, which is used to remove the accumulated values in the proportional-integral controllers. Test results indicate that the scheme successfully supports the grid voltage during the fault, and recovers WPP voltages without exceeding the limit after the fault clearance.« less

Physiological and pathophysiological reactive oxygen species as probed by EPR spectroscopy: the underutilized research window on muscle ageing

PubMed Central

A. Abdel‐Rahman, Engy; Mahmoud, Ali M.; Khalifa, Abdulrahman M.

2016-01-01

Abstract Reactive oxygen and nitrogen species (ROS and RNS) play crucial roles in triggering, mediating and regulating physiological and pathophysiological signal transduction pathways within the cell. Within the cell, ROS efflux is firmly controlled both spatially and temporally, making the study of ROS dynamics a challenging task. Different approaches have been developed for ROS assessment; however, many of these assays are not capable of direct identification or determination of subcellular localization of different ROS. Here we highlight electron paramagnetic resonance (EPR) spectroscopy as a powerful technique that is uniquely capable of addressing questions on ROS dynamics in different biological specimens and cellular compartments. Due to their critical importance in muscle functions and dysfunction, we discuss in some detail spin trapping of various ROS and focus on EPR detection of nitric oxide before highlighting how EPR can be utilized to probe biophysical characteristics of the environment surrounding a given stable radical. Despite the demonstrated ability of EPR spectroscopy to provide unique information on the identity, quantity, dynamics and environment of radical species, its applications in the field of muscle physiology, fatiguing and ageing are disproportionately infrequent. While reviewing the limited examples of successful EPR applications in muscle biology we conclude that the field would greatly benefit from more studies exploring ROS sources and kinetics by spin trapping, protein dynamics by site‐directed spin labelling, and membrane dynamics and global redox changes by spin probing EPR approaches. PMID:26801204

Editorial

NASA Astrophysics Data System (ADS)

Bijeljic, Branko; Icardi, Matteo; Prodanović, Maša

2018-05-01

Substantial progress has been made over last few decades on understanding the physics of multiphase flow and reactive transport phenomena in subsurface porous media. Confluence of advances in experimental techniques (including micromodels, X-ray microtomography, Nuclear Magnetic Resonance (NMR)) as well as computational power have made it possible to observe static and dynamic multi-scale flow, transport and reactive processes, thus stimulating development of new generation of modelling tools from pore to field scale. One of the key challenges is to make experiment and models as complementary as possible, with continuously improving experimental methods in order to increase predictive capabilities of theoretical models across scales. This creates need to establish rigorous benchmark studies of flow, transport and reaction in porous media which can then serve as the basis for introducing more complex phenomena in future developments.

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

Smed, T.; Andersson, G.

In this paper, damping of slow oscillations with active and reactive power modulation of HVDC-links is analyzed with the aim of gaining a physical insight into the problem. The analysis shows that active power modulation is efficient when applied to a short mass-scaled electrical distance from one of the swinging machines, and reactive power modulation is most efficient when there exists a well-defined power flow direction and the modulation is made at a point close to the electrical midpoint between the swinging machines. It is shown that the intuitively appealing feedback signals frequency and derivative of the voltage are appropriatemore » for active and reactive power modulation, respectively. The impact of the constraints imposed by the HVDC equations are analyzed, and it is determined when the implicit reactive power modulation resulting from constant [gamma] control may be detrimental for the damping.« less

Formulation and experimental evaluation of closed-form control laws for the rapid maneuvering of reactor neutronic power

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

Bernard, J.A.

1989-09-01

This report describes both the theoretical development and the experimental evaluation of a novel, robust methodology for the time-optimal adjustment of a reactor's neutronic power under conditions of closed-loop digital control. Central to the approach are the MIT-SNL Period-Generated Minimum Time Control Laws' which determine the rate at which reactivity should be changed in order to cause a reactor's neutronic power to conform to a specified trajectory. Using these laws, reactor power can be safely raised by five to seven orders of magnitude in a few seconds. The MIT-SNL laws were developed to facilitate rapid increases of neutronic power onmore » spacecraft reactors operating in an SDI environment. However, these laws are generic and have other applications including the rapid recovery of research and test reactors subsequent to an unanticipated shutdown, power increases following the achievement of criticality on commercial reactors, power adjustments on commercial reactors so as to minimize thermal stress, and automated startups. The work reported here was performed by the Massachusetts Institute of Technology under contract to the Sandia National Laboratories. Support was also provided by the US Department of Energy's Division of University and Industry Programs. The work described in this report is significant in that a novel solution to the problem of time-optimal control of neutronic power was identified, in that a rigorous description of a reactor's dynamics was derived in that the rate of change of reactivity was recognized as the proper control signal, and in that extensive experimental trials were conducted of these newly developed concepts on actual nuclear reactors. 43 refs., 118 figs., 11 tabs.« less

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

Usman, Yasir; Kim, Jinho; Muljadi, Eduard

Wake effects cause wind turbine generators (WTGs) within a wind power plant (WPP) to produce different levels of active power and subsequent reactive power capabilities. Further, the impedance between a WTG and the point of interconnection (POI)-which depends on the distance between them-impacts the WPP's reactive power injection capability at the POI. This paper proposes a voltage control scheme for a WPP based on the available reactive current of the doubly-fed induction generators (DFIGs) and its impacts on the POI to improve the reactive power injection capability of the WPP. In this paper, a design strategy for modifying the gainmore » of DFIG controller is suggested and the comprehensive properties of these control gains are investigated. In the proposed scheme, the WPP controller, which operates in a voltage control mode, sends the command signal to the DFIGs based on the voltage difference at the POI. The DFIG controllers, which operate in a voltage control mode, employ a proportional controller with a limiter. The gain of the proportional controller is adjusted depending on the available reactive current of the DFIG and the series impedance between the DFIG and the POI. The performance of the proposed scheme is validated for various disturbances such as a reactive load connection and grid fault using an EMTP-RV simulator. Furthermore, simulation results demonstrate that the proposed scheme promptly recovers the POI voltage by injecting more reactive power after a disturbance than the conventional scheme.« less

Broadband and High power Reactive Jamming Resilient Wireless Communication

DTIC Science & Technology

2017-10-21

Broadband and High -power Reactive Jamming Resilient Wireless Communication The views, opinions and/or findings contained in this report are those of... available in extremely hostile environments, where FHSS and DSSS are completely defeated by a broadband and high -power reactive jammer. b. Wireless...SECURITY CLASSIFICATION OF: 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND SUBTITLE 13. SUPPLEMENTARY NOTES 12. DISTRIBUTION AVAILIBILITY STATEMENT 6. AUTHORS

Analysis and Research on the effect of the Operation of Small Hydropower in the Regional Power Grid

NASA Astrophysics Data System (ADS)

Ang, Fu; Guangde, Dong; Xiaojun, Zhu; Ruimiao, Wang; Shengyi, Zhu

2018-03-01

The analysis of reactive power balance and voltage of power network not only affects the system voltage quality, but also affects the economic operation of power grid. In the calculation of reactive power balance and voltage analysis in the past, the problem of low power and low system voltage has been the concern of people. When small hydropower stations in the wet period of low load, the analysis of reactive power surplus and high voltage for the system, if small hydropower unit the capability of running in phase is considered, it can effectively solve the system low operation voltage of the key point on the high side.

Voltage droop Coordinating Control applied in UPFC and STATCOM system

NASA Astrophysics Data System (ADS)

Junhui, Huang; Zhuyi, Peng; Chengjie, Ni; Yiqing, Xu; Jiliang, Xue

2018-04-01

When UPFC, unified power flow controller is applied with other FACTS into power grid, it is possible that the voltage controlled vibrates constantly to response to a sudden reactive power turbulent in grid if the parameters of these FACTS are not coordinating reasonably. Moreover, the reactive power generated by these equipment will intertwine unexpectedly. The article proposes a method named voltage-reactive power droop control to allow the reference voltage fluctuating around the rating voltage so that the vibration is reduced and the power distribution is improved. Finally, the article cite a electric-magnetic simulation by EMTDC models of east-China power grid to prove it effective when applied to improve the response characteristics to sudden turbulence in power grid.

Extremum Seeking Control of Smart Inverters for VAR Compensation

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

Arnold, Daniel; Negrete-Pincetic, Matias; Stewart, Emma

2015-09-04

Reactive power compensation is used by utilities to ensure customer voltages are within pre-defined tolerances and reduce system resistive losses. While much attention has been paid to model-based control algorithms for reactive power support and Volt Var Optimization (VVO), these strategies typically require relatively large communications capabilities and accurate models. In this work, a non-model-based control strategy for smart inverters is considered for VAR compensation. An Extremum Seeking control algorithm is applied to modulate the reactive power output of inverters based on real power information from the feeder substation, without an explicit feeder model. Simulation results using utility demand informationmore » confirm the ability of the control algorithm to inject VARs to minimize feeder head real power consumption. In addition, we show that the algorithm is capable of improving feeder voltage profiles and reducing reactive power supplied by the distribution substation.« less

A DFIG Islanding Detection Scheme Based on Reactive Power Infusion

NASA Astrophysics Data System (ADS)

Wang, M.; Liu, C.; He, G. Q.; Li, G. H.; Feng, K. H.; Sun, W. W.

2017-07-01

A lot of research has been done on photovoltaic (the “PV”) power system islanding detection in recent years. As a comparison, much less attention has been paid to islanding in wind turbines. Meanwhile, wind turbines can work in islanding conditions for quite a long period, which can be harmful to equipments and cause safety hazards. This paper presents and examines a double fed introduction generation (the “DFIG”) islanding detection scheme based on feedback of reactive power and frequency and uses a trigger signal of reactive power infusion which can be obtained by dividing the voltage total harmonic distortion (the "THD") by the voltage THD of last cycle to avoid the deterioration of power quality. This DFIG islanding detection scheme uses feedback of reactive power current loop to amplify the frequency differences in islanding and normal conditions. Simulation results show that the DFIG islanding detection scheme is effective.

Memory traces of long-range coordinated oscillations in the sleeping human brain.

PubMed

Piantoni, Giovanni; Van Der Werf, Ysbrand D; Jensen, Ole; Van Someren, Eus J W

2015-01-01

Cognition involves coordinated activity across distributed neuronal networks. Neuronal activity during learning triggers cortical plasticity that allows for reorganization of the neuronal network and integration of new information. Animal studies have shown post-learning reactivation of learning-elicited neuronal network activity during subsequent sleep, supporting consolidation of the reorganization. However, no previous studies, to our knowledge, have demonstrated reactivation of specific learning-elicited long-range functional connectivity during sleep in humans. We here show reactivation of learning-induced long-range synchronization of magnetoencephalography power fluctuations in human sleep. Visuomotor learning elicited a specific profile of long-range cortico-cortical synchronization of slow (0.1 Hz) fluctuations in beta band (12-30 Hz) power. The parieto-occipital part of this synchronization profile reappeared in delta band (1-3.5 Hz) power fluctuations during subsequent sleep, but not during the intervening wakefulness period. Individual differences in the reactivated synchronization predicted postsleep performance improvement. The presleep resting-state synchronization profile was not reactivated during sleep. The findings demonstrate reactivation of long-range coordination of neuronal activity in humans, more specifically of reactivation of coupling of infra-slow fluctuations in oscillatory power. The spatiotemporal profile of delta power fluctuations during sleep may subserve memory consolidation by echoing coordinated activation elicited by prior learning. © 2014 Wiley Periodicals, Inc.

Diffusional correlations among multiple active sites in a single enzyme.

PubMed

Echeverria, Carlos; Kapral, Raymond

2014-04-07

Simulations of the enzymatic dynamics of a model enzyme containing multiple substrate binding sites indicate the existence of diffusional correlations in the chemical reactivity of the active sites. A coarse-grain, particle-based, mesoscopic description of the system, comprising the enzyme, the substrate, the product and solvent, is constructed to study these effects. The reactive and non-reactive dynamics is followed using a hybrid scheme that combines molecular dynamics for the enzyme, substrate and product molecules with multiparticle collision dynamics for the solvent. It is found that the reactivity of an individual active site in the multiple-active-site enzyme is reduced substantially, and this effect is analyzed and attributed to diffusive competition for the substrate among the different active sites in the enzyme.

An improved AVC strategy applied in distributed wind power system

NASA Astrophysics Data System (ADS)

Zhao, Y. N.; Liu, Q. H.; Song, S. Y.; Mao, W.

2016-08-01

Traditional AVC strategy is mainly used in wind farm and only concerns about grid connection point, which is not suitable for distributed wind power system. Therefore, this paper comes up with an improved AVC strategy applied in distributed wind power system. The strategy takes all nodes of distribution network into consideration and chooses the node having the most serious voltage deviation as control point to calculate the reactive power reference. In addition, distribution principles can be divided into two conditions: when wind generators access to network on single node, the reactive power reference is distributed according to reactive power capacity; when wind generators access to network on multi-node, the reference is distributed according to sensitivity. Simulation results show the correctness and reliability of the strategy. Compared with traditional control strategy, the strategy described in this paper can make full use of generators reactive power output ability according to the distribution network voltage condition and improve the distribution network voltage level effectively.

Increasing the power of accelerated molecular dynamics methods and plans to exploit the coming exascale

NASA Astrophysics Data System (ADS)

Voter, Arthur

Many important materials processes take place on time scales that far exceed the roughly one microsecond accessible to molecular dynamics simulation. Typically, this long-time evolution is characterized by a succession of thermally activated infrequent events involving defects in the material. In the accelerated molecular dynamics (AMD) methodology, known characteristics of infrequent-event systems are exploited to make reactive events take place more frequently, in a dynamically correct way. For certain processes, this approach has been remarkably successful, offering a view of complex dynamical evolution on time scales of microseconds, milliseconds, and sometimes beyond. We have recently made advances in all three of the basic AMD methods (hyperdynamics, parallel replica dynamics, and temperature accelerated dynamics (TAD)), exploiting both algorithmic advances and novel parallelization approaches. I will describe these advances, present some examples of our latest results, and discuss what should be possible when exascale computing arrives in roughly five years. Funded by the U.S. Department of Energy, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, and by the Los Alamos Laboratory Directed Research and Development program.

Water reactive hydrogen fuel cell power system

DOEpatents

Wallace, Andrew P; Melack, John M; Lefenfeld, Michael

2014-01-21

A water reactive hydrogen fueled power system includes devices and methods to combine reactant fuel materials and aqueous solutions to generate hydrogen. The generated hydrogen is converted in a fuel cell to provide electricity. The water reactive hydrogen fueled power system includes a fuel cell, a water feed tray, and a fuel cartridge to generate power for portable power electronics. The removable fuel cartridge is encompassed by the water feed tray and fuel cell. The water feed tray is refillable with water by a user. The water is then transferred from the water feed tray into a fuel cartridge to generate hydrogen for the fuel cell which then produces power for the user.

Water reactive hydrogen fuel cell power system

DOEpatents

Wallace, Andrew P; Melack, John M; Lefenfeld, Michael

2014-11-25

A water reactive hydrogen fueled power system includes devices and methods to combine reactant fuel materials and aqueous solutions to generate hydrogen. The generated hydrogen is converted in a fuel cell to provide electricity. The water reactive hydrogen fueled power system includes a fuel cell, a water feed tray, and a fuel cartridge to generate power for portable power electronics. The removable fuel cartridge is encompassed by the water feed tray and fuel cell. The water feed tray is refillable with water by a user. The water is then transferred from the water feed tray into the fuel cartridge to generate hydrogen for the fuel cell which then produces power for the user.

Detonative propagation and accelerative expansion of the Crab Nebula shock front.

PubMed

Gao, Yang; Law, Chung K

2011-10-21

The accelerative expansion of the Crab Nebula's outer envelope is a mystery in dynamics, as a conventional expanding blast wave decelerates when bumping into the surrounding interstellar medium. Here we show that the strong relativistic pulsar wind bumping into its surrounding nebula induces energy-generating processes and initiates a detonation wave that propagates outward to form the current outer edge, namely, the shock front, of the nebula. The resulting detonation wave, with a reactive downstream, then provides the needed power to maintain propagation of the shock front. Furthermore, relaxation of the curvature-induced reduction of the propagation velocity from the initial state of formation to the asymptotic, planar state of Chapman-Jouguet propagation explains the observed accelerative expansion. Potential richness in incorporating reactive fronts in the description of various astronomical phenomena is expected. © 2011 American Physical Society

Physiological and pathophysiological reactive oxygen species as probed by EPR spectroscopy: the underutilized research window on muscle ageing.

PubMed

A Abdel-Rahman, Engy; Mahmoud, Ali M; Khalifa, Abdulrahman M; Ali, Sameh S

2016-08-15

Reactive oxygen and nitrogen species (ROS and RNS) play crucial roles in triggering, mediating and regulating physiological and pathophysiological signal transduction pathways within the cell. Within the cell, ROS efflux is firmly controlled both spatially and temporally, making the study of ROS dynamics a challenging task. Different approaches have been developed for ROS assessment; however, many of these assays are not capable of direct identification or determination of subcellular localization of different ROS. Here we highlight electron paramagnetic resonance (EPR) spectroscopy as a powerful technique that is uniquely capable of addressing questions on ROS dynamics in different biological specimens and cellular compartments. Due to their critical importance in muscle functions and dysfunction, we discuss in some detail spin trapping of various ROS and focus on EPR detection of nitric oxide before highlighting how EPR can be utilized to probe biophysical characteristics of the environment surrounding a given stable radical. Despite the demonstrated ability of EPR spectroscopy to provide unique information on the identity, quantity, dynamics and environment of radical species, its applications in the field of muscle physiology, fatiguing and ageing are disproportionately infrequent. While reviewing the limited examples of successful EPR applications in muscle biology we conclude that the field would greatly benefit from more studies exploring ROS sources and kinetics by spin trapping, protein dynamics by site-directed spin labelling, and membrane dynamics and global redox changes by spin probing EPR approaches. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

Contribution of concentrator photovoltaic installations to grid stability and power quality

NASA Astrophysics Data System (ADS)

del Toro García, Xavier; Roncero-Sánchez, Pedro; Torres, Alfonso Parreño; Vázquez, Javier

2012-10-01

Large-scale integration of Photovoltaic (PV) generation systems, including Concentrator Photovoltaic (CPV) technologies, will require the contribution and support of these technologies to the management and stability of the grid. New regulations and grid codes for PV installations in countries such as Spain have recently included dynamic voltage control support during faults. The PV installation must stay connected to the grid during voltage dips and inject reactive power in order to enhance the stability of the system. The existing PV inverter technologies based on the Voltage-Source Converter (VSC) are in general well suited to provide advanced grid-support characteristics. Nevertheless, new advanced control schemes and monitoring techniques will be necessary to meet the most demanding requirements.

High efficiency H6 single-phase transformerless grid-tied PV inverter with proposed modulation for reactive power generation

NASA Astrophysics Data System (ADS)

Almasoudi, Fahad M.; Alatawi, Khaled S.; Matin, Mohammad

2017-08-01

Implementation of transformerless inverters in PV grid-tied system offer great benefits such as high efficiency, light weight, low cost, etc. Most of the proposed transformerless inverters in literature are verified for only real power application. Currently, international standards such as VDE-AR-N 4105 has demanded that PV grid-tied inverters should have the ability of controlling a specific amount of reactive power. Generation of reactive power cannot be accomplished in single phase transformerless inverter topologies because the existing modulation techniques are not adopted for a freewheeling path in the negative power region. This paper enhances a previous high efficiency proposed H6 trnasformerless inverter with SiC MOSFETs and demonstrates new operating modes for the generation of reactive power. A proposed pulse width modulation (PWM) technique is applied to achieve bidirectional current flow through freewheeling state. A comparison of the proposed H6 transformerless inverter using SiC MOSFETs and Si MOSFTEs is presented in terms of power losses and efficiency. The results show that reactive power control is attained without adding any additional active devices or modification to the inverter structure. Also, the proposed modulation maintains a constant common mode voltage (CM) during every operating mode and has low leakage current. The performance of the proposed system verifies its effectiveness in the next generation PV system.

Sensitivity analysis of reactive ecological dynamics.

PubMed

Verdy, Ariane; Caswell, Hal

2008-08-01

Ecological systems with asymptotically stable equilibria may exhibit significant transient dynamics following perturbations. In some cases, these transient dynamics include the possibility of excursions away from the equilibrium before the eventual return; systems that exhibit such amplification of perturbations are called reactive. Reactivity is a common property of ecological systems, and the amplification can be large and long-lasting. The transient response of a reactive ecosystem depends on the parameters of the underlying model. To investigate this dependence, we develop sensitivity analyses for indices of transient dynamics (reactivity, the amplification envelope, and the optimal perturbation) in both continuous- and discrete-time models written in matrix form. The sensitivity calculations require expressions, some of them new, for the derivatives of equilibria, eigenvalues, singular values, and singular vectors, obtained using matrix calculus. Sensitivity analysis provides a quantitative framework for investigating the mechanisms leading to transient growth. We apply the methodology to a predator-prey model and a size-structured food web model. The results suggest predator-driven and prey-driven mechanisms for transient amplification resulting from multispecies interactions.

Algorithms of GPU-enabled reactive force field (ReaxFF) molecular dynamics.

PubMed

Zheng, Mo; Li, Xiaoxia; Guo, Li

2013-04-01

Reactive force field (ReaxFF), a recent and novel bond order potential, allows for reactive molecular dynamics (ReaxFF MD) simulations for modeling larger and more complex molecular systems involving chemical reactions when compared with computation intensive quantum mechanical methods. However, ReaxFF MD can be approximately 10-50 times slower than classical MD due to its explicit modeling of bond forming and breaking, the dynamic charge equilibration at each time-step, and its one order smaller time-step than the classical MD, all of which pose significant computational challenges in simulation capability to reach spatio-temporal scales of nanometers and nanoseconds. The very recent advances of graphics processing unit (GPU) provide not only highly favorable performance for GPU enabled MD programs compared with CPU implementations but also an opportunity to manage with the computing power and memory demanding nature imposed on computer hardware by ReaxFF MD. In this paper, we present the algorithms of GMD-Reax, the first GPU enabled ReaxFF MD program with significantly improved performance surpassing CPU implementations on desktop workstations. The performance of GMD-Reax has been benchmarked on a PC equipped with a NVIDIA C2050 GPU for coal pyrolysis simulation systems with atoms ranging from 1378 to 27,283. GMD-Reax achieved speedups as high as 12 times faster than Duin et al.'s FORTRAN codes in Lammps on 8 CPU cores and 6 times faster than the Lammps' C codes based on PuReMD in terms of the simulation time per time-step averaged over 100 steps. GMD-Reax could be used as a new and efficient computational tool for exploiting very complex molecular reactions via ReaxFF MD simulation on desktop workstations. Copyright © 2013 Elsevier Inc. All rights reserved.

Application of Improved APO Algorithm in Vulnerability Assessment and Reconstruction of Microgrid

NASA Astrophysics Data System (ADS)

Xie, Jili; Ma, Hailing

2018-01-01

Artificial Physics Optimization (APO) has good global search ability and can avoid the premature convergence phenomenon in PSO algorithm, which has good stability of fast convergence and robustness. On the basis of APO of the vector model, a reactive power optimization algorithm based on improved APO algorithm is proposed for the static structure and dynamic operation characteristics of microgrid. The simulation test is carried out through the IEEE 30-bus system and the result shows that the algorithm has better efficiency and accuracy compared with other optimization algorithms.

Power System Observation by using Synchronized Phasor Measurements as a Smart Device

NASA Astrophysics Data System (ADS)

Mitani, Yasunori

Phasor Measurement Unit (PMU) is an apparatus which detects the absolute value of phase angle in sinusoidal signal. When more than two units are located distantly apart from each other, and they are synchronized with GPS signal which tells us the information on exact time, it becomes ready to get phase differences between two distant places. Thus, PMU with GPS receiver is applied to the monitoring of AC power system dynamics and usually installed at substations of transmission lines. The states of power network are uniquely determined by the active and reactive power and the magnitude and phase angle of voltage in each node. Among these values the phase angle had not been easily obtained until the scheme of time synchronism with GPS appeared. In this report, the history of GPS and PMU, and the current status of the applications in power systems in the world are presented. In Japan we are developing a power system monitoring system with PMUs installed at University's campuses with 100V outlets, which is called Campus WAMS. This report also introduces some results from the Campus WAMS briefly.

Future Directions of Structural Mass Spectrometry using Hydroxyl Radical Footprinting

PubMed Central

Kiselar, Janna G.; Chance, Mark R.

2010-01-01

Hydroxyl radical protein footprinting coupled to mass spectrometry has been developed over the last decade and has matured to a powerful method for analyzing protein structure and dynamics. It has been successfully applied in the analysis of protein structure, protein folding, protein dynamics, and protein-protein and protein-DNA interactions. Using synchrotron radiolysis, exposures of proteins to a “white” x-ray beam for milliseconds provide sufficient oxidative modifications to surface amino acid side chains that can be easily detected and quantified by mass spectrometry. Thus, conformational changes in proteins or protein complexes can be examined using a time-resolved approach, which would be a valuable method for the study of macromolecular dynamics. In this review, we describe a new application of hydroxyl radical protein footprinting to probe the time evolution of the calcium-dependent conformational changes of gelsolin on the millisecond timescale. The data suggest a cooperative transition as multiple sites in different molecular sub-domains have similar rates of conformational change. These findings demonstrate that time-resolved protein footprinting is suitable for studies of protein dynamics that occur over periods ranging from milliseconds to seconds. In this review we also show how the structural resolution and sensitivity of the technology can be improved as well. The hydroxyl radical varies in its reactivity to different side chains by over two orders of magnitude, thus oxidation of amino acid side chains of lower reactivity are more rarely observed in such experiments. Here we demonstrate that selected reaction monitoring (SRM)-based method can be utilized for quantification of oxidized species, improving the signal to noise ratio. This expansion of the set of oxidized residues of lower reactivity will improve the overall structural resolution of the technique. This approach is also suggested as a basis for developing hypothesis driven structural mass spectrometry experiments. PMID:20812376

78 FR 63176 - Notice Announcing Workshop; Zero Rate Reactive Power Rate Schedules

Federal Register 2010, 2011, 2012, 2013, 2014

2013-10-23

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. AD14-1-000] Notice Announcing Workshop; Zero Rate Reactive Power Rate Schedules Concurrent with this notice, the Commission is issuing an order in Chehalis Power Generating, L.P., Docket No. ER05-1056-007 clarifying its policy...

Reactive Power Compensation Using an Energy Management System

DTIC Science & Technology

2014-09-01

bulk power grid or independent of the grid in islanded mode using various DG sources ( photovoltaic panels, fuel cells, gas generators, batteries...developed in order to forecast the system’s response to both capacitive and inductive power demands on the grid. The process was then confirmed in a...NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS Approved for public release; distribution is unlimited REACTIVE POWER

Dynamical footprint of cross-reactivity in a human autoimmune T-cell receptor

NASA Astrophysics Data System (ADS)

Kumar, Amit; Delogu, Francesco

2017-02-01

The present work focuses on the dynamical aspects of cross-reactivity between myelin based protein (MBP) self-peptide and two microbial peptides (UL15, PMM) for Hy.1B11 T-cell receptor (TCR). This same TCR was isolated from a patient suffering from multiple sclerosis (MS). The study aims at highlighting the chemical interactions underlying recognition mechanisms between TCR and the peptides presented by Major Histocompatibility Complex (MHC) proteins, which form a crucial component in adaptive immune response against foreign antigens. Since the ability of a TCR to recognize different peptide antigens presented by MHC depends on its cross-reactivity, we used molecular dynamics methods to obtain atomistic detail on TCR-peptide-MHC complexes. Our results show how the dynamical basis of Hy.1B11 TCR’s cross-reactivity is rooted in a similar bridging interaction pattern across the TCR-peptide-MHC interface. Our simulations confirm the importance of TCR CDR3α E98 residue interaction with MHC and a predominant role of P6 peptide residue in MHC binding affinity. Altogether, our study provides energetic and dynamical insights into factors governing peptide recognition by the cross-reactive Hy.1B11 TCR, found in MS patient.

Reaction-based small-molecule fluorescent probes for dynamic detection of ROS and transient redox changes in living cells and small animals.

PubMed

Lü, Rui

2017-09-01

Dynamic detection of transient redox changes in living cells and animals has broad implications for human health and disease diagnosis, because intracellular redox homeostasis regulated by reactive oxygen species (ROS) plays important role in cell functions, normal physiological functions and some serious human diseases (e.g., cancer, Alzheimer's disease, diabetes, etc.) usually have close relationship with the intracellular redox status. Small-molecule ROS-responsive fluorescent probes can act as powerful tools for dynamic detection of ROS and redox changes in living cells and animals through fluorescence imaging techniques; and great advances have been achieved recently in the design and synthesis of small-molecule ROS-responsive fluorescent probes. This article highlights up-to-date achievements in designing and using the reaction-based small-molecule fluorescent probes (with high sensitivity and selectivity to ROS and redox cycles) in the dynamic detection of ROS and transient redox changes in living cells and animals through fluorescence imaging. Copyright © 2017. Published by Elsevier Ltd.

Performance Evaluation of UPQC under Nonlinear Unbalanced Load Conditions Using Synchronous Reference Frame Based Control

NASA Astrophysics Data System (ADS)

Kota, Venkata Reddy; Vinnakoti, Sudheer

2017-12-01

Today, maintaining Power Quality (PQ) is very important in the growing competent world. With new equipments and devices, new challenges are also being put before power system operators. Unified Power Quality Conditioner (UPQC) is proposed to mitigate many power quality problems and to improve the performance of the power system. In this paper, an UPQC with Fuzzy Logic controller for capacitor voltage balancing is proposed in Synchronous Reference Frame (SRF) based control with Modified Phased Locked Loop (MPLL). The proposed controller with SRF-MPLL based control is tested under non-linear and unbalanced load conditions. The system is developed in Matlab/Simulink and its performance is analyzed under various conditions like non-linear, unbalanced load and polluted supply voltage including voltage sag/swells. Active and reactive power flow in the system, power factor and %THD of voltages and currents before and after compensation are also analyzed in this work. Results prove the applicability of the proposed scheme for power quality improvement. It is observed that the fuzzy controller gives better performance than PI controller with faster capacitor voltage balancing and also improves the dynamic performance of the system.

Reactive power planning under high penetration of wind energy using Benders decomposition

DOE PAGES

Xu, Yan; Wei, Yanli; Fang, Xin; ...

2015-11-05

This study addresses the optimal allocation of reactive power volt-ampere reactive (VAR) sources under the paradigm of high penetration of wind energy. Reactive power planning (RPP) in this particular condition involves a high level of uncertainty because of wind power characteristic. To properly model wind generation uncertainty, a multi-scenario framework optimal power flow that considers the voltage stability constraint under the worst wind scenario and transmission N 1 contingency is developed. The objective of RPP in this study is to minimise the total cost including the VAR investment cost and the expected generation cost. Therefore RPP under this condition ismore » modelled as a two-stage stochastic programming problem to optimise the VAR location and size in one stage, then to minimise the fuel cost in the other stage, and eventually, to find the global optimal RPP results iteratively. Benders decomposition is used to solve this model with an upper level problem (master problem) for VAR allocation optimisation and a lower problem (sub-problem) for generation cost minimisation. Impact of the potential reactive power support from doubly-fed induction generator (DFIG) is also analysed. Lastly, case studies on the IEEE 14-bus and 118-bus systems are provided to verify the proposed method.« less

Vehicle-to-Grid Automatic Load Sharing with Driver Preference in Micro-Grids

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

Wang, Yubo; Nazaripouya, Hamidreza; Chu, Chi-Cheng

Integration of Electrical Vehicles (EVs) with power grid not only brings new challenges for load management, but also opportunities for distributed storage and generation. This paper comprehensively models and analyzes distributed Vehicle-to-Grid (V2G) for automatic load sharing with driver preference. In a micro-grid with limited communications, V2G EVs need to decide load sharing based on their own power and voltage profile. A droop based controller taking into account driver preference is proposed in this paper to address the distributed control of EVs. Simulations are designed for three fundamental V2G automatic load sharing scenarios that include all system dynamics of suchmore » applications. Simulation results demonstrate that active power sharing is achieved proportionally among V2G EVs with consideration of driver preference. In additional, the results also verify the system stability and reactive power sharing analysis in system modelling, which sheds light on large scale V2G automatic load sharing in more complicated cases.« less

Comparison of Standard Wind Turbine Models with Vendor Models for Power System Stability Analysis: Preprint

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

Honrubia-Escribano, A.; Gomez Lazaro, E.; Jimenez-Buendia, F.

The International Electrotechnical Commission Standard 61400-27-1 was published in February 2015. This standard deals with the development of generic terms and parameters to specify the electrical characteristics of wind turbines. Generic models of very complex technological systems, such as wind turbines, are thus defined based on the four common configurations available in the market. Due to its recent publication, the comparison of the response of generic models with specific vendor models plays a key role in ensuring the widespread use of this standard. This paper compares the response of a specific Gamesa dynamic wind turbine model to the corresponding genericmore » IEC Type III wind turbine model response when the wind turbine is subjected to a three-phase voltage dip. This Type III model represents the doubly-fed induction generator wind turbine, which is not only one of the most commonly sold and installed technologies in the current market but also a complex variable-speed operation implementation. In fact, active and reactive power transients are observed due to the voltage reduction. Special attention is given to the reactive power injection provided by the wind turbine models because it is a requirement of current grid codes. Further, the boundaries of the generic models associated with transient events that cannot be represented exactly are included in the paper.« less

Electrolyte Structure near Electrode Interfaces in Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Lordi, Vincenzo; Ong, Mitchell; Verners, Osvalds; van Duin, Adri; Draeger, Erik; Pask, John

2014-03-01

The performance of lithium-ion secondary batteries (LIBs) is strongly tied to electrochemistry and ionic transport near the electrode-electrolyte interface. Changes in ion solvation near the interface affect ion conductivity and also are associated with the formation and evolution of solid-electrolyte interphase (SEI) layers, which impede transport but also passivate the interface. Thus, understanding these effects is critical to optimizing battery performance. Here we present molecular dynamics (MD) simulations of typical organic liquid LIB electrolytes in contact with graphite electrodes to understand differences in molecular structure and solvation near the interface compared to the bulk electrolyte. Results for different graphite terminations are presented. We compare the results of density-functional based MD to the empirical reactive forcefield ReaxFF and the non-reactive, non-polarizable COMPASS forcefield. Notable differences in the predictive power of each of these techniques are discussed. Prepared by LLNL under Contract DE-AC52-07NA27344.

Study of thermite mixture consolidated by the cold gas dynamic spray process

NASA Astrophysics Data System (ADS)

Bacciochini, A.; Maines, G.; Poupart, C.; Akbarnejad, H.; Radulescu, M.; Jodoin, B.; Zhang, F.; Lee, J. J.

2014-05-01

The present study focused on the cold gas dynamic spray process for manufacturing porosity free, finely structured energetic materials with high reactivity and structural integrity. The experiments have focused the reaction between the aluminium and metal oxide, such as Al-CuO system. The consolidation of the materials used the cold gas dynamic spray technique, where the particles are accelerated to high speeds and consolidated via plastic deformation upon impact. Reactive composites are formed in arbitrary shapes with close to zero porosity and without any reactions during the consolidation phase. Reactivity of mixtures has been investigated through flame propagation analysis on cold sprayed samples and compacted powder mixture. Deflagration tests showed the influence of porosity on the reactivity.

The READY program: Building a global potential energy surface and reactive dynamic simulations for the hydrogen combustion.

PubMed

Mogo, César; Brandão, João

2014-06-30

READY (REActive DYnamics) is a program for studying reactive dynamic systems using a global potential energy surface (PES) built from previously existing PESs corresponding to each of the most important elementary reactions present in the system. We present an application to the combustion dynamics of a mixture of hydrogen and oxygen using accurate PESs for all the systems involving up to four oxygen and hydrogen atoms. Results at the temperature of 4000 K and pressure of 2 atm are presented and compared with model based on rate constants. Drawbacks and advantages of this approach are discussed and future directions of research are pointed out. Copyright © 2014 Wiley Periodicals, Inc.

Real time implementation and control validation of the wind energy conversion system

NASA Astrophysics Data System (ADS)

Sattar, Adnan

The purpose of the thesis is to analyze dynamic and transient characteristics of wind energy conversion systems including the stability issues in real time environment using the Real Time Digital Simulator (RTDS). There are different power system simulation tools available in the market. Real time digital simulator (RTDS) is one of the powerful tools among those. RTDS simulator has a Graphical User Interface called RSCAD which contains detail component model library for both power system and control relevant analysis. The hardware is based upon the digital signal processors mounted in the racks. RTDS simulator has the advantage of interfacing the real world signals from the external devices, hence used to test the protection and control system equipments. Dynamic and transient characteristics of the fixed and variable speed wind turbine generating systems (WTGSs) are analyzed, in this thesis. Static Synchronous Compensator (STATCOM) as a flexible ac transmission system (FACTS) device is used to enhance the fault ride through (FRT) capability of the fixed speed wind farm. Two level voltage source converter based STATCOM is modeled in both VSC small time-step and VSC large time-step of RTDS. The simulation results of the RTDS model system are compared with the off-line EMTP software i.e. PSCAD/EMTDC. A new operational scheme for a MW class grid-connected variable speed wind turbine driven permanent magnet synchronous generator (VSWT-PMSG) is developed. VSWT-PMSG uses fully controlled frequency converters for the grid interfacing and thus have the ability to control the real and reactive powers simultaneously. Frequency converters are modeled in the VSC small time-step of the RTDS and three phase realistic grid is adopted with RSCAD simulation through the use of optical analogue digital converter (OADC) card of the RTDS. Steady state and LVRT characteristics are carried out to validate the proposed operational scheme. Simulation results show good agreement with real time simulation software and thus can be used to validate the controllers for the real time operation. Integration of the Battery Energy Storage System (BESS) with wind farm can smoothen its intermittent power fluctuations. The work also focuses on the real time implementation of the Sodium Sulfur (NaS) type BESS. BESS is integrated with the STATCOM. The main advantage of this system is that it can also provide the reactive power support to the system along with the real power exchange from BESS unit. BESS integrated with STATCOM is modeled in the VSC small time-step of the RTDS. The cascaded vector control scheme is used for the control of the STATCOM and suitable control is developed to control the charging/discharging of the NaS type BESS. Results are compared with Laboratory standard power system software PSCAD/EMTDC and the advantages of using RTDS in dynamic and transient characteristics analyses of wind farm are also demonstrated clearly.

Coherent diffractive imaging of time-evolving samples with improved temporal resolution

DOE PAGES

Ulvestad, A.; Tripathi, A.; Hruszkewycz, S. O.; ...

2016-05-19

Bragg coherent x-ray diffractive imaging is a powerful technique for investigating dynamic nanoscale processes in nanoparticles immersed in reactive, realistic environments. Its temporal resolution is limited, however, by the oversampling requirements of three-dimensional phase retrieval. Here, we show that incorporating the entire measurement time series, which is typically a continuous physical process, into phase retrieval allows the oversampling requirement at each time step to be reduced, leading to a subsequent improvement in the temporal resolution by a factor of 2-20 times. The increased time resolution will allow imaging of faster dynamics and of radiation-dose-sensitive samples. Furthermore, this approach, which wemore » call "chrono CDI," may find use in improving the time resolution in other imaging techniques.« less

Analyzing the Effect of Multi-fuel and Practical Constraints on Realistic Economic Load Dispatch using Novel Two-stage PSO

NASA Astrophysics Data System (ADS)

Chintalapudi, V. S.; Sirigiri, Sivanagaraju

2017-04-01

In power system restructuring, pricing the electrical power plays a vital role in cost allocation between suppliers and consumers. In optimal power dispatch problem, not only the cost of active power generation but also the costs of reactive power generated by the generators should be considered to increase the effectiveness of the problem. As the characteristics of reactive power cost curve are similar to that of active power cost curve, a nonconvex reactive power cost function is formulated. In this paper, a more realistic multi-fuel total cost objective is formulated by considering active and reactive power costs of generators. The formulated cost function is optimized by satisfying equality, in-equality and practical constraints using the proposed uniform distributed two-stage particle swarm optimization. The proposed algorithm is a combination of uniform distribution of control variables (to start the iterative process with good initial value) and two-stage initialization processes (to obtain best final value in less number of iterations) can enhance the effectiveness of convergence characteristics. Obtained results for the considered standard test functions and electrical systems indicate the effectiveness of the proposed algorithm and can obtain efficient solution when compared to existing methods. Hence, the proposed method is a promising method and can be easily applied to optimize the power system objectives.

Substantial difference in target surface chemistry between reactive dc and high power impulse magnetron sputtering

NASA Astrophysics Data System (ADS)

Greczynski, G.; Mráz, S.; Schneider, J. M.; Hultman, L.

2018-02-01

The nitride layer formed in the target race track during the deposition of stoichiometric TiN thin films is a factor 2.5 thicker for high power impulse magnetron sputtering (HIPIMS), compared to conventional dc processing (DCMS). The phenomenon is explained using x-ray photoelectron spectroscopy analysis of the as-operated Ti target surface chemistry supported by sputter depth profiles, dynamic Monte Carlo simulations employing the TRIDYN code, and plasma chemical investigations by ion mass spectrometry. The target chemistry and the thickness of the nitride layer are found to be determined by the implantation of nitrogen ions, predominantly N+ and N2+ for HIPIMS and DCMS, respectively. Knowledge of this method-inherent difference enables robust processing of high quality functional coatings.

Application of point kinetics equations to the design of a reactivity meter

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

Binney, S.E.; Bakir, A.J.M.

1988-01-01

The time-dependent reactivity of a nuclear reactor is obviously one of the most important reactor parameters that describes the state of the reactor. Although several different types of techniques exist to measure reactivity, only the kinetic method is described here. The paper illustrates the measured reactor power and calculated reactivity for a 70 cents step change in reactivity. These data were taken at 1-s time intervals. It is seen that the reactivity, initially at zero, rises rapidly to a predetermined value (determined by the reactivity change induced in the system) and then returns to zero as the reactor is reestablishedmore » in a critical situation by insertion of another control rod. It is concluded that the method of Tuttle has been adapted to produce a reliable, on-line calculation of reactivity from a time-dependent reactor power signal.« less

Reactive Power Compensating System.

DOEpatents

Williams, Timothy J.; El-Sharkawi, Mohamed A.; Venkata, Subrahmanyam S.

1985-01-04

The circuit was designed for the specific application of wind-driven induction generators. It has great potential for application in any situation where a varying reactive power load is present, such as with induction motors or generators, or for transmission network compensation.

78 FR 77670 - Zero Rate Reactive Power Rate Schedules; Notice Allowing Post-Workshop Comments

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-24

... staff-led workshop explored the mechanics of filing reactive power rate schedules for which there is no compensation.\\1\\ Interested persons are invited to file written comments focused on the mechanics of filing...

A Proposal for a Subcritical Reactivity Meter based on Gandini and Salvatores' point kinetics equations for Multiplying Subcritical Systems

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

Pinto, Leticia N.; Dos Santos, Adimir

2015-07-01

Multiplying Subcritical Systems were for a long time poorly studied and its theoretical description remains with plenty open questions. Great interest on such systems arose partly due to the improvement of hybrid concepts, such as the Accelerator-Driven Systems (ADS). Along with the need for new technologies to be developed, further study and understanding of subcritical systems are essential also in more practical situations, such as in the case of a PWR criticalization in their physical startup tests. Point kinetics equations are fundamental to continuously monitor the reactivity behavior to a possible variation of external sources intensity. In this case, quicklymore » and accurately predicting power transients and reactivity becomes crucial. It is known that conventional Reactivity Meters cannot operate in subcritical levels nor describe the dynamics of multiplying systems in these conditions, by the very structure of the classical kinetic equations. Several theoretical models have been proposed to characterize the kinetics of such systems with special regard to the reactivity, as the one developed by Gandini and Salvatores among others. This work presents a discussion about the derivation of point kinetics equations for subcritical systems and the importance of considering the external source. From the point of view of the Gandini and Salvatores' point kinetics model and based on the experimental results provided by Lee and dos Santos, it was possible to develop an innovative approach. This article proposes an algorithm that describes the subcritical reactivity with external source, contributing to the advancement of studies in the field. (authors)« less

Light induced kickoff of magnetic domain walls in Ising chains

NASA Astrophysics Data System (ADS)

Bogani, Lapo

2012-02-01

Controlling the speed at which systems evolve is a challenge shared by all disciplines, and otherwise unrelated areas use common theoretical frameworks towards this goal. A particularly widespread model is Glauber dynamics, which describes the time evolution of the Ising model and can be applied to any binary system. Here we show, using molecular nanowires under irradiation, that Glauber dynamics can be controlled by a novel domain-wall kickoff mechanism. Contrary to known processes, the kickoff has unambiguous fingerprints, slowing down the spin-flip attempt rate by several orders of magnitude, and following a scaling law. The required irradiation power is very low, a substantial improvement over present methods of magnetooptical switching: in our experimental demonstration we switched molecular nanowires with light, using powers thousands of times lower than in previous optical switching methods. This manipulation of stochastic dynamic processes is extremely clean, leading to fingerprint signatures and scaling laws. These observations can be used, in material science, to better study domain-wall displacements and solitons in discrete lattices. These results provide a new way to control and study stochastic dynamic processes. Being general for Glauber dynamics, they can be extended to different kinds of magnetic nanowires and to a myriad of fields, ranging from social evolution to neural networks and chemical reactivity. For nanoelectronics and molecular spintronics the kickoff affords external control of molecular spin-valves and a magnetic fingerprint in single molecule measurements. It can also be applied to the dynamics of mechanical switches and the related study of phasons and order-disorder transitions.

Investigation on application of genetic algorithms to optimal reactive power dispatch of power systems

NASA Astrophysics Data System (ADS)

Wu, Q. H.; Ma, J. T.

1993-09-01

A primary investigation into application of genetic algorithms in optimal reactive power dispatch and voltage control is presented. The application was achieved, based on (the United Kingdom) National Grid 48 bus network model, using a novel genetic search approach. Simulation results, compared with that obtained using nonlinear programming methods, are included to show the potential of applications of the genetic search methodology in power system economical and secure operations.

The Impact of Transformer Winding Connections of A Grid-Connected PV on Voltage Quality Improvement

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

Muljadi, Eduard; Tumbelaka, Hanny H.; Gao, Wenzhong

In this paper, the high-power PV plant is connected to the weak grid by means of a three-phase power transformer. The selection of transformer winding connection is critical especially when the PV inverter has a reactive power controller. In general, transformer winding connection can be arranged in star-star (with neutral earthed) or star-delta. The reactive power controller supports voltage regulation of the power system particularly under transient faults. Its control strategy is based on utilizing the grid currents to make a three-phase reactive unbalanced current with a small gain. The gain is determined by the system impedance. Simulation results exhibitmore » that the control strategy works very well particularly under disturbance conditions when the transformer winding connection is star-star with both neutrals grounded. The power quality in terms of the voltage quality is improved.« less

Optimal reactive planning with security constraints

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

Thomas, W.R.; Cheng, D.T.Y.; Dixon, A.M.

1995-12-31

The National Grid Company (NGC) of England and Wales has developed a computer program, SCORPION, to help system planners optimize the location and size of new reactive compensation plant on the transmission system. The reactive power requirements of the NGC system have risen as a result of increased power flows and the shorter timescale on which power stations are commissioned and withdrawn from service. In view of the high costs involved, it is important that reactive compensation be installed as economically as possible, without compromising security. Traditional methods based on iterative use of a load flow program are labor intensivemore » and subjective. SCORPION determines a near-optimal pattern of new reactive sources which are required to satisfy voltage constraints for normal and contingent states of operation of the transmission system. The algorithm processes the system states sequentially, instead of optimizing all of them simultaneously. This allows a large number of system states to be considered with an acceptable run time and computer memory requirement. Installed reactive sources are treated as continuous, rather than discrete, variables. However, the program has a restart facility which enables the user to add realistically sized reactive sources explicitly and thereby work towards a realizable solution to the planning problem.« less

Remote Monitoring of Near-Surface Soil Moisture Dynamics In Unstable Slopes Using a Low-Power Autonomous Resistivity Imaging System

NASA Astrophysics Data System (ADS)

Chambers, J. E.; Meldrum, P.; Gunn, D.; Wilkinson, P. B.; Uhlemann, S.; Swift, R. T.; Kuras, O.; Inauen, C.; Hutchinson, D.; Butler, S.

2016-12-01

ERT monitoring has been demonstrated in numerous studies as an effective means of imaging near surface processes for applications as diverse as permafrost studies and contaminated land assessment. A limiting factor in applying time-lapse ERT for long-term studies in remote locations has been the availability of cost-effective ERT measurement systems designed specifically for monitoring applications. Typically, monitoring is undertaken using repeated manual data collection, or by building conventional survey instruments into a monitoring setup. The latter often requires high power and is therefore difficult to operate remotely without access to mains electricity. We describe the development of a low-power resistivity imaging system designed specifically for remote monitoring, taking advantage of, e.g., solar power and data telemetry. Here, we present the results of two field deployments. The system has been installed on an active railway cutting to provide insights into the effect of vegetation on the moisture dynamics in unstable infrastructure slopes and to gather subsurface information for pro-active remediation measures. The system, comprising 255 electrodes, acquires 4596 reciprocal measurement pairs twice daily during standard operation. In case of severe weather events, the measurement schedule is reactively changed, to gather high temporal resolution data to image rainfall infiltration processes. The system has also been installed along a leaking and marginally stable canal embankment; a less favourable location for remote monitoring, with limited solar power and poor mobile reception. Nevertheless, the acquired data indicated the effectiveness of remedial actions on the canal. The ERT results showed that one leak was caused by the canal and fixed during remediation, while two other "leaks" were shown to be effects of groundwater dynamics. The availability of cost-effective, low-power ERT monitoring instrumentation, combined with an automated workflow of data processing and visualisation, has the potential to contribute to a step-change in the management and early warning of slope instability.

Study on improved Ip-iq APF control algorithm and its application in micro grid

NASA Astrophysics Data System (ADS)

Xie, Xifeng; Shi, Hua; Deng, Haiyingv

2018-01-01

In order to enhance the tracking velocity and accuracy of harmonic detection by ip-iq algorithm, a novel ip-iq control algorithm based on the Instantaneous reactive power theory is presented, the improved algorithm adds the lead correction link to adjust the zero point of the detection system, the Fuzzy Self-Tuning Adaptive PI control is introduced to dynamically adjust the DC-link Voltage, which meets the requirement of the harmonic compensation of the micro grid. Simulation and experimental results verify the proposed method is feasible and effective in micro grid.

Distributed cooperative control of AC microgrids

NASA Astrophysics Data System (ADS)

Bidram, Ali

In this dissertation, the comprehensive secondary control of electric power microgrids is of concern. Microgrid technical challenges are mainly realized through the hierarchical control structure, including primary, secondary, and tertiary control levels. Primary control level is locally implemented at each distributed generator (DG), while the secondary and tertiary control levels are conventionally implemented through a centralized control structure. The centralized structure requires a central controller which increases the reliability concerns by posing the single point of failure. In this dissertation, the distributed control structure using the distributed cooperative control of multi-agent systems is exploited to increase the secondary control reliability. The secondary control objectives are microgrid voltage and frequency, and distributed generators (DGs) active and reactive powers. Fully distributed control protocols are implemented through distributed communication networks. In the distributed control structure, each DG only requires its own information and the information of its neighbors on the communication network. The distributed structure obviates the requirements for a central controller and complex communication network which, in turn, improves the system reliability. Since the DG dynamics are nonlinear and non-identical, input-output feedback linearization is used to transform the nonlinear dynamics of DGs to linear dynamics. Proposed control frameworks cover the control of microgrids containing inverter-based DGs. Typical microgrid test systems are used to verify the effectiveness of the proposed control protocols.

Sloshing motion dynamics of a free surface in the draft tube cone of a Francis turbine operating in synchronous condenser mode

NASA Astrophysics Data System (ADS)

Vagnoni, Elena; Andolfatto, Loïc; Favrel, Arthur; Avellan, François

2016-11-01

The penetration of the electrical grid by intermittent renewable energy sources induces grid fluctuations which must be compensated in order to guarantee the stability of the grid. Hydropower plants can supply reactive power to ensure the grid stabilization by operating in condenser mode. In this operating mode, the turbine operates with the tail water depressed to let the runner spin in air to reduce the power consumption. Pressurized air is injected in the draft tube cone to maintain the water level below the runner and this induces air-water interaction phenomena which cause important power losses. Flow visualization and pressure fluctuation measurements are performed in a reduced scale physical model of a Francis turbine operating in condenser mode to investigate the dynamics of the air-water interaction in the draft tube cone which causes the sloshing motion of the free surface. An image post-processing method is developed, enabling a quantitative description of the sloshing motion. The latter depends on the Froude number. By increasing the value of the Froude number, the amplitude of the sloshing motion decreases, as well as the amplitude of the pressure fluctuations. The frequency of the sloshing motion corresponds to the first natural frequency of the water volume.

Reactive multi-particle collision dynamics with reactive boundary conditions

NASA Astrophysics Data System (ADS)

Sayyidmousavi, Alireza; Rohlf, Katrin

2018-07-01

In the present study, an off-lattice particle-based method called the reactive multi-particle collision (RMPC) dynamics is extended to model reaction-diffusion systems with reactive boundary conditions in which the a priori diffusion coefficient of the particles needs to be maintained throughout the simulation. To this end, the authors have made use of the so-called bath particles whose purpose is only to ensure proper diffusion of the main particles in the system. In order to model partial adsorption by a reactive boundary in the RMPC, the probability of a particle being adsorbed, once it hits the boundary, is calculated by drawing an analogy between the RMPC and Brownian Dynamics. The main advantages of the RMPC compared to other molecular based methods are less computational cost as well as conservation of mass, energy and momentum in the collision and free streaming steps. The proposed approach is tested on three reaction-diffusion systems and very good agreement with the solutions to their corresponding partial differential equations is observed.

The Dynamics of the Human Leukocyte Antigen Head Domain Modulates Its Recognition by the T-Cell Receptor.

PubMed

García-Guerrero, Estefanía; Pérez-Simón, José Antonio; Sánchez-Abarca, Luis Ignacio; Díaz-Moreno, Irene; De la Rosa, Miguel A; Díaz-Quintana, Antonio

2016-01-01

Generating the immune response requires the discrimination of peptides presented by the human leukocyte antigen complex (HLA) through the T-cell receptor (TCR). However, how a single amino acid substitution in the antigen bonded to HLA affects the response of T cells remains uncertain. Hence, we used molecular dynamics computations to analyze the molecular interactions between peptides, HLA and TCR. We compared immunologically reactive complexes with non-reactive and weakly reactive complexes. MD trajectories were produced to simulate the behavior of isolated components of the various p-HLA-TCR complexes. Analysis of the fluctuations showed that p-HLA binding barely restrains TCR motions, and mainly affects the CDR3 loops. Conversely, inactive p-HLA complexes displayed significant drop in their dynamics when compared with its free versus ternary forms (p-HLA-TCR). In agreement, the free non-reactive p-HLA complexes showed a lower amount of salt bridges than the responsive ones. This resulted in differences between the electrostatic potentials of reactive and inactive p-HLA species and larger vibrational entropies in non-elicitor complexes. Analysis of the ternary p-HLA-TCR complexes also revealed a larger number of salt bridges in the responsive complexes. To summarize, our computations indicate that the affinity of each p-HLA complex towards TCR is intimately linked to both, the dynamics of its free species and its ability to form specific intermolecular salt-bridges in the ternary complexes. Of outstanding interest is the emerging concept of antigen reactivity involving its interplay with the HLA head sidechain dynamics by rearranging its salt-bridges.

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

Dall'Anese, Emiliano

Past works that focused on addressing power-quality and reliability concerns related to renewable energy resources (RESs) operating with business-as-usual practices have looked at the design of Volt/VAr and Volt/Watt strategies to regulate real or reactive powers based on local voltage measurements, so that terminal voltages are within acceptable levels. These control strategies have the potential of operating at the same time scale of distribution-system dynamics, and can therefore mitigate disturbances precipitated fast time-varying loads and ambient conditions; however, they do not necessarily guarantee system-level optimality, and stability claims are mainly based on empirical evidences. On a different time scale, centralizedmore » and distributed optimal power flow (OPF) algorithms have been proposed to compute optimal steady-state inverter setpoints, so that power losses and voltage deviations are minimized and economic benefits to end-users providing ancillary services are maximized. However, traditional OPF schemes may offer decision making capabilities that do not match the dynamics of distribution systems. Particularly, during the time required to collect data from all the nodes of the network (e.g., loads), solve the OPF, and subsequently dispatch setpoints, the underlying load, ambient, and network conditions may have already changed; in this case, the DER output powers would be consistently regulated around outdated setpoints, leading to suboptimal system operation and violation of relevant electrical limits. The present work focuses on the synthesis of distributed RES-inverter controllers that leverage the opportunities for fast feedback offered by power-electronics interfaced RESs. The overarching objective is to bridge the temporal gap between long-term system optimization and real-time control, to enable seamless RES integration in large scale with stability and efficiency guarantees, while congruently pursuing system-level optimization objectives. The design of the control framework is based on suitable linear approximations of the AC power-flow equations as well as Lagrangian regularization methods. The proposed controllers enable an update of the power outputs at a time scale that is compatible with the underlying dynamics of loads and ambient conditions, and continuously drive the system operation towards OPF-based solutions.« less

Fires in Operating or Abandoned Coal Mines or Heaps of Reactive Materials and the Governing Transport and Reaction Processes

NASA Astrophysics Data System (ADS)

Wuttke, M. W.; Kessels, W.; Wessling, S.; Han, J.

2007-05-01

Spontaneous combustion is a world wide problem for technical operations in mining, waste disposal and power plant facilities. The principle driving the combustion is every where the same independent of the different reactive materials: Fresh air with the common oxygen content is getting in contact with the reactive material by human operations. The following reaction process produces heat at a usually low but constant rate. The reactive material in operating or abandoned coal mines, heaps of coal, waste or reactive minerals is most times strongly broken or fractured, such that the atmospheric oxygen can deeply penetrate into the porous or fractured media. Because the strongly broken or fractured medium with air filled pores and fractures is often combined with a low thermal conductivity of the bulk material the produced heat accumulates and the temperature increases with time. If the reactivity strongly increases with temperature, the temperature rise accelerates up to the "combustion temperature". Once the temperature is high enough the combustion process is determined by the oxygen transport to the combustion center rather than the chemical reactivity. Spontaneous combustion is thus a self- amplifying process where an initial small variation in the parameters and the starting conditions can create exploding combustion hot spots in an apparently homogenous material. The phenomenon will be discussed by various examples in the context of the German - Sino coal fire project. A temperature monitoring in hot fracture systems documents the strong influence of the weather conditions on the combustion process. Numerical calculations show the sensitivity of the combustion to the model geometries, the boundary conditions and mainly the permeability. The most used fire fighting operations like covering and water injection are discussed. A new method of using saltwater for fire fighting is presented and discussed. References: Kessels, W., Wessling, S., Li, X., and Wuttke, M. W. Numerical element distinction for reactive transport modeling regarding reaction rate. In Proceedings of MODFLOW and MORE 2006: Managing Groundwater Systems, May 21 - 24, 2006, Golden, CO USA (2006). Kessels, W., Wuttke, M. W., Wessling, S., and Li, X. Coal fires between self ignition and fire fighting: Numerical modeling and basic geophysical measurements. In ERSEC Ecological Book Series - 4 on Coal Fire Research (2007). Wessling, S., Litschke, T., Wiegand, J., Schlömer, S., and Kessels, W. Simulating dynamic subsurface coal fires and its applications. In ERSEC Ecological Book Series - 4 on Coal Fire Reserach (2007). Wessling, S., Kessels, W., Schmidt, M., and Krause, U. Investigating dynamic underground coal fires by means of numerical simulation. Geophys. J. Int. (submitted).

A Hierarchical Modeling for Reactive Power Optimization With Joint Transmission and Distribution Networks by Curve Fitting

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

Ding, Tao; Li, Cheng; Huang, Can

Here, in order to solve the reactive power optimization with joint transmission and distribution networks, a hierarchical modeling method is proposed in this paper. It allows the reactive power optimization of transmission and distribution networks to be performed separately, leading to a master–slave structure and improves traditional centralized modeling methods by alleviating the big data problem in a control center. Specifically, the transmission-distribution-network coordination issue of the hierarchical modeling method is investigated. First, a curve-fitting approach is developed to provide a cost function of the slave model for the master model, which reflects the impacts of each slave model. Second,more » the transmission and distribution networks are decoupled at feeder buses, and all the distribution networks are coordinated by the master reactive power optimization model to achieve the global optimality. Finally, numerical results on two test systems verify the effectiveness of the proposed hierarchical modeling and curve-fitting methods.« less

A Hierarchical Modeling for Reactive Power Optimization With Joint Transmission and Distribution Networks by Curve Fitting

DOE PAGES

Ding, Tao; Li, Cheng; Huang, Can; ...

2017-01-09

Here, in order to solve the reactive power optimization with joint transmission and distribution networks, a hierarchical modeling method is proposed in this paper. It allows the reactive power optimization of transmission and distribution networks to be performed separately, leading to a master–slave structure and improves traditional centralized modeling methods by alleviating the big data problem in a control center. Specifically, the transmission-distribution-network coordination issue of the hierarchical modeling method is investigated. First, a curve-fitting approach is developed to provide a cost function of the slave model for the master model, which reflects the impacts of each slave model. Second,more » the transmission and distribution networks are decoupled at feeder buses, and all the distribution networks are coordinated by the master reactive power optimization model to achieve the global optimality. Finally, numerical results on two test systems verify the effectiveness of the proposed hierarchical modeling and curve-fitting methods.« less

Large-scale neural networks and the lateralization of motivation and emotion.

PubMed

Tops, Mattie; Quirin, Markus; Boksem, Maarten A S; Koole, Sander L

2017-09-01

Several lines of research in animals and humans converge on the distinction between two basic large-scale brain networks of self-regulation, giving rise to predictive and reactive control systems (PARCS). Predictive (internally-driven) and reactive (externally-guided) control are supported by dorsal versus ventral corticolimbic systems, respectively. Based on extant empirical evidence, we demonstrate how the PARCS produce frontal laterality effects in emotion and motivation. In addition, we explain how this framework gives rise to individual differences in appraising and coping with challenges. PARCS theory integrates separate fields of research, such as research on the motivational correlates of affect, EEG frontal alpha power asymmetry and implicit affective priming effects on cardiovascular indicators of effort during cognitive task performance. Across these different paradigms, converging evidence points to a qualitative motivational division between, on the one hand, angry and happy emotions, and, on the other hand, sad and fearful emotions. PARCS suggests that those two pairs of emotions are associated with predictive and reactive control, respectively. PARCS theory may thus generate important new insights on the motivational and emotional dynamics that drive autonomic and homeostatic control processes. Copyright © 2017 Elsevier B.V. All rights reserved.

K 4R - Knowledge to the Power of RESTful, Resourceful and Reactive Rules

NASA Astrophysics Data System (ADS)

Amador, Ricardo

The Web of today clearly answers questions of the form "What is the representation of ...?". The Semantic Web (SW) of tomorrow aims at answering questions of the form "What is the meaning of ...?". It is our stance that in order to realize the full potential of the original concept proposed by Tim Berners-Lee et al. (in Scientific American, May 2001), the SW must also answer, in a meaningful way, questions of a dynamic and active nature, like "What to do if ...?" or "What to do when ...?". Moreover, SW questions of the form "What to do ...?" must be expressed and answered in a declarative, compositional and language agnostic way. It is our (hypo)thesis that formally established concepts, viz. the Web's REST architectural style, declarative SW representation of resources based on Description Logics (e.g., OWL-DL), and Reactive Rules (e.g., "on Event if Condition do Action" -ECA- rules), provide the proper theoretical foundations to achieve this goal. This paper describes our current research proposal, K 4R (pronounced, with an Italian flavor, "Che fare?"), towards achieving a declarative model for expressing (re)active behavior in and for the SW.

Tailoring non-equilibrium atmospheric pressure plasmas for healthcare technologies

NASA Astrophysics Data System (ADS)

Gans, Timo

2012-10-01

Non-equilibrium plasmas operated at ambient atmospheric pressure are very efficient sources for energy transport through reactive neutral particles (radicals and metastables), charged particles (ions and electrons), UV radiation, and electro-magnetic fields. This includes the unique opportunity to deliver short-lived highly reactive species such as atomic oxygen and atomic nitrogen. Reactive oxygen and nitrogen species can initiate a wide range of reactions in biochemical systems, both therapeutic and toxic. The toxicological implications are not clear, e.g. potential risks through DNA damage. It is anticipated that interactions with biological systems will be governed through synergies between two or more species. Suitable optimized plasma sources are improbable through empirical investigations. Quantifying the power dissipation and energy transport mechanisms through the different interfaces from the plasma regime to ambient air, towards the liquid interface and associated impact on the biological system through a new regime of liquid chemistry initiated by the synergy of delivering multiple energy carrying species, is crucial. The major challenge to overcome the obstacles of quantifying energy transport and controlling power dissipation has been the severe lack of suitable plasma sources and diagnostic techniques. Diagnostics and simulations of this plasma regime are very challenging; the highly pronounced collision dominated plasma dynamics at very small dimensions requires extraordinary high resolution - simultaneously in space (microns) and time (picoseconds). Numerical simulations are equally challenging due to the inherent multi-scale character with very rapid electron collisions on the one extreme and the transport of chemically stable species characterizing completely different domains. This presentation will discuss our recent progress actively combining both advance optical diagnostics and multi-scale computer simulations.

Molten uranium dioxide structure and dynamics

DOE PAGES

Skinner, L. B.; Parise, J. B.; Benmore, C. J.; ...

2014-11-21

Uranium dioxide (UO 2) is the major nuclear fuel component of fission power reactors. A key concern during severe accidents is the melting and leakage of radioactive UO 2 as it corrodes through its zirconium cladding and steel containment. Yet, the very high temperatures (>3140 kelvin) and chemical reactivity of molten UO 2 have prevented structural studies. In this work, we combine laser heating, sample levitation, and synchrotron x-rays to obtain pair distribution function measurements of hot solid and molten UO 2. The hot solid shows a substantial increase in oxygen disorder around the lambda transition (2670 K) but negligiblemore » U-O coordination change. On melting, the average U-O coordination drops from 8 to 6.7 ± 0.5. Molecular dynamics models refined to this structure predict higher U-U mobility than 8-coordinated melts.« less

Collinear Collision Chemistry: 1. A Simple Model for Inelastic and Reactive Collision Dynamics

ERIC Educational Resources Information Center

Mahan, Bruce H.

1974-01-01

Discusses a model for the collinear collision of an atom with a diatomic molecule on a simple potential surface. Indicates that the model can provide a framework for thinking about molecular collisions and reveal many factors which affect the dynamics of reactive and inelastic collisions. (CC)

Comparison of Virtual Oscillator and Droop Control: Preprint

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

Johnson, Brian B; Rodriguez, Miguel; Dhople, Sairaj

Virtual oscillator control and droop control are two techniques that can be used to ensure synchronization and power sharing of parallel inverters in islanded operation. VOC relies on the implementation of non-linear Van der Pol oscillator equations in the control system of the inverter, acting upon the time-domain instantaneous inverter current and terminal voltage. On the other hand, DC explicitly computes active and reactive power produced by the inverter and relies on limited bandwidth low-pass filters. Even though both methods can be engineered to produce the same steady-state characteristics, their dynamic performances are significantly different. This paper presents analytical andmore » experimental results that aim to compare both methods. It is shown that VOC is inherently faster and enables minimizing the circulating currents. The results are verified using three 120V, 1kW inverters.« less

A new model predictive control algorithm by reducing the computing time of cost function minimization for NPC inverter in three-phase power grids.

PubMed

Taheri, Asghar; Zhalebaghi, Mohammad Hadi

2017-11-01

This paper presents a new control strategy based on finite-control-set model-predictive control (FCS-MPC) for Neutral-point-clamped (NPC) three-level converters. Containing some advantages like fast dynamic response, easy inclusion of constraints and simple control loop, makes the FCS-MPC method attractive to use as a switching strategy for converters. However, the large amount of required calculations is a problem in the widespread of this method. In this way, to resolve this problem this paper presents a modified method that effectively reduces the computation load compare with conventional FCS-MPC method and at the same time does not affect on control performance. The proposed method can be used for exchanging power between electrical grid and DC resources by providing active and reactive power compensations. Experiments on three-level converter for three Power Factor Correction (PFC), inductive and capacitive compensation modes verify the good and comparable performance. The results have been simulated using MATLAB/SIMULINK software. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Improving Advanced Inverter Control Convergence in Distribution Power Flow

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

Nagarajan, Adarsh; Palmintier, Bryan; Ding, Fei

Simulation of modern distribution system powerflow increasingly requires capturing the impact of advanced PV inverter voltage regulation on powerflow. With Volt/var control, the inverter adjusts its reactive power flow as a function of the point of common coupling (PCC) voltage. Similarly, Volt/watt control curtails active power production as a function of PCC voltage. However, with larger systems and higher penetrations of PV, this active/reactive power flow itself can cause significant changes to the PCC voltage potentially introducing oscillations that slow the convergence of system simulations. Improper treatment of these advanced inverter functions could potentially lead to incorrect results. This papermore » explores a simple approach to speed such convergence by blending in the previous iteration's reactive power estimate to dampen these oscillations. Results with a single large (5MW) PV system and with multiple 500kW advanced inverters show dramatic improvements using this approach.« less

Development and Evaluation of a Reactive-Dispersive Plume Model: TexAQS II 2006 Case Study

NASA Astrophysics Data System (ADS)

Kim, Yong Hoon; Kim, Hyun Soo; Song, Chul Han

2015-04-01

We describe the development and evaluation of a reactive-dispersive plume model (RDPM) that combines a photo-chemistry model with a plume dilution driven by turbulent dispersion of a power-plant plume. The plume transport and turbulent dispersion are derived from a Gaussian plume model and the plume chemistry model uses 71 HxOy-NxOy-CH4 chemistry-related reactions and 184 NMHC-related reactions. Emissions from large-scale point sources have continuously increased due to the rapid industrial growth. To extensively understand and assess atmospheric impacts of the power-plant emissions, a general RDPM was applied to simultaneously simulate the dynamics and photo-chemistry of the Texas power-plant plumes. During the second Texas Air Quality Study 2006 (TexAQS II 2006) on 16 September 2006, pollutant concentrations were measured by NOAA WP-3D aircraft with successive transects across power-plant plumes in Texas, USA. The simulation performances of the RDPM were evaluated by a comparison study, using the observation data obtained from the measurements of a NOAA WP-3D flight during TexAQS II 2006 airborne field campaign. On 16 September, the WP-3D aircraft observed mainly meteorological parameters and particulate species concentrations, traversing the Monticello and Welsh power-plant plumes four times from transects A to D. In addition, some meteorological variables in an initial condition for model simulation were obtained from the Weather Research and Forecasting (WRF) model output for the specific objects. These power-plant plume cases were selected in this study, because a large number of nitrogen oxides and sulfur dioxide concentrations inside the power-plant plumes were measured without any interruption of other emission sources. For the Monticello and Welsh power-plant plumes, the model-predicted concentrations showed good agreements with the observed concentrations of ambient species (e.g., nitrogen oxides, ozone, sulfur dioxide, etc.) at the four transects. Based on these RDPM results, the power-plant plume chemistry and its possible impacts on atmospheric environments were also analyzed.

The effects of competition and implicit power motive on men's testosterone, emotion recognition, and aggression.

PubMed

Vongas, John G; Al Hajj, Raghid

2017-06-01

A contribution to a special issue on Hormones and Human Competition. We investigated the effects of competition on men's testosterone levels and assessed whether androgen reactivity was associated with subsequent emotion recognition and reactive and proactive aggression. We also explored whether personalized power (p Power) moderated these relationships. In Study 1, 84 males competed on a number tracing task and interpreted emotions from facial expressions. In Study 2, 72 males competed on the same task and were assessed on proactive and reactive aggression. In both studies, contrary to the biosocial model of status (Mazur, 1985), winners' testosterone levels decreased significantly while losers' levels increased, albeit not significantly. Personalized power moderated the effect of competition outcome on testosterone change in both studies. Using the aggregate sample, we found that the effect of decreased testosterone levels among winners (compared to losers) was significant for individuals low in p Power but not for those with medium or high p Power. Testosterone change was positively related to emotion recognition, but unrelated to either aggression subtype. The testosterone-mediated relationship between winning and losing and emotion recognition was moderated by p Power. In addition, p Power moderated the direct (i.e., non-testosterone mediated) path between competition outcome and emotion recognition and both types of aggression: high p-Power winners were more accurate at deciphering others' emotions than high p-Power losers. Finally, among high p-Power men, winners aggressed more proactively than losers, whereas losers aggressed more reactively than winners. Collectively, these studies highlight the importance of implicit power motivation in modulating hormonal, cognitive, and behavioral outcomes arising from human competition. Copyright © 2017 Elsevier Inc. All rights reserved.

Optimal reactive power planning for distribution systems considering intermittent wind power using Markov model and genetic algorithm

NASA Astrophysics Data System (ADS)

Li, Cheng

Wind farms, photovoltaic arrays, fuel cells, and micro-turbines are all considered to be Distributed Generation (DG). DG is defined as the generation of power which is dispersed throughout a utility's service territory and either connected to the utility's distribution system or isolated in a small grid. This thesis addresses modeling and economic issues pertaining to the optimal reactive power planning for distribution system with wind power generation (WPG) units. Wind farms are inclined to cause reverse power flows and voltage variations due to the random-like outputs of wind turbines. To deal with this kind of problem caused by wide spread usage of wind power generation, this thesis investigates voltage and reactive power controls in such a distribution system. Consequently static capacitors (SC) and transformer taps are introduced into the system and treated as controllers. For the purpose of getting optimum voltage and realizing reactive power control, the research proposes a proper coordination among the controllers like on-load tap changer (OLTC), feeder-switched capacitors. What's more, in order to simulate its uncertainty, the wind power generation is modeled by the Markov model. In that way, calculating the probabilities for all the scenarios is possible. Some outputs with consecutive and discrete values have been used for transition between successive time states and within state wind speeds. The thesis will describe the method to generate the wind speed time series from the transition probability matrix. After that, utilizing genetic algorithm, the optimal locations of SCs, the sizes of SCs and transformer taps are determined so as to minimize the cost or minimize the power loss, and more importantly improve voltage profiles. The applicability of the proposed method is verified through simulation on a 9-bus system and a 30-bus system respectively. At last, the simulation results indicate that as long as the available capacitors are able to sufficiently compensate the reactive power demand, the DG operation no longer imposes a significant effect on the voltage fluctuations in the distribution system. And the proposed approach is efficient, simple and straightforward.

Optimal Coordinated EV Charging with Reactive Power Support in Constrained Distribution Grids

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

Paudyal, Sumit; Ceylan, Oğuzhan; Bhattarai, Bishnu P.

Electric vehicle (EV) charging/discharging can take place in any P-Q quadrants, which means EVs could support reactive power to the grid while charging the battery. In controlled charging schemes, distribution system operator (DSO) coordinates with the charging of EV fleets to ensure grid’s operating constraints are not violated. In fact, this refers to DSO setting upper bounds on power limits for EV charging. In this work, we demonstrate that if EVs inject reactive power into the grid while charging, DSO could issue higher upper bounds on the active power limits for the EVs for the same set of grid constraints.more » We demonstrate the concept in an 33-node test feeder with 1,500 EVs. Case studies show that in constrained distribution grids in coordinated charging, average costs of EV charging could be reduced if the charging takes place in the fourth P-Q quadrant compared to charging with unity power factor.« less

Operational Characteristics of an Accelerator Driven Fissile Solution System

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

Kimpland, Robert Herbert

Operational characteristics represent the set of responses that a nuclear system exhibits during normal operation. Operators rely on this behavior to assess the status of the system and to predict the consequences of off-normal events. These characteristics largely refer to the relationship between power and system operating conditions. The static and dynamic behavior of a chain-reacting system, operating at sufficient power, is primarily governed by reactivity effects. The science of reactor physics has identified and evaluated a number of such effects, including Doppler broadening and shifts in the thermal neutron spectrum. Often these reactivity effects are quantified in the formmore » of feedback coefficients that serve as coupling coefficients relating the neutron population and the physical mechanisms that drive reactivity effects, such as fissile material temperature and density changes. The operational characteristics of such nuclear systems usually manifest themselves when perturbations between system power (neutron population) and system operating conditions arise. Successful operation of such systems requires the establishment of steady equilibrium conditions. However, prior to obtaining the desired equilibrium (steady-state) conditions, an approach from zero-power (startup) must occur. This operational regime may possess certain limiting system conditions that must be maintained to achieve effective startup. Once steady-state is achieved, a key characteristic of this operational regime is the level of stability that the system possesses. Finally, a third operational regime, shutdown, may also possess limiting conditions of operation that must be maintained. This report documents the operational characteristics of a “generic” Accelerator Driven Fissile Solution (ADFS) system during the various operational regimes of startup, steady-state operation, and shutdown. Typical time-dependent behavior for each operational regime will be illustrated, and key system parameters, such as response times, will be quantified. A generalized linear systems analysis of steady-state operations will be performed to evaluate the level of stability of ADFS systems. This information should provide a basic understanding of typical ADFS system operational behavior, and facilitate the development of monitoring procedures and operator aids.« less

A Gas-Surface Interaction Model based on Accelerated Reactive Molecular Dynamics for Hypersonic Conditions including Thermal Conduction

DTIC Science & Technology

2012-02-28

Interaction Model based on Accelerated Reactive Molecular Dynamics for Hypersonic conditions including Thermal Conduction FA9550-09-1-0157 Schwartzentruber...Dynamics for Hypersonic Conditions including Thermal Conduction Grant/Contract Number: FA9550-09-1-0157 Program Manager: Dr. John Schmisseur PI...through the boundary layer and may chemically react with the vehicle’s thermal protection system (TPS). Many TPS materials act as a catalyst for the

Application of Simulated Reactivity Feedback in Nonnuclear Testing of a Direct-Drive Gas-Cooled Reactor

NASA Technical Reports Server (NTRS)

Bragg-Sitton, S. M.; Webster, K. L.

2007-01-01

Nonnuclear testing can be a valuable tool in the development of an in-space nuclear power or propulsion system. In a nonnuclear test facility, electric heaters are used to simulate heat from nuclear fuel. Standard testing allows one to fully assess thermal, heat transfer, and stress related attributes of a given system but fails to demonstrate the dynamic response that would be present in an integrated, fueled reactor system. The integration of thermal hydraulic hardware tests with simulated neutronic response provides a bridge between electrically heated testing and full nuclear testing. By implementing a neutronic response model to simulate the dynamic response that would be expected in a fueled reactor system, one can better understand system integration issues, characterize integrated system response times and response and response characteristics, and assess potential design improvements with a relatively small fiscal investment. Initial system dynamic response testing was demonstrated on the integrated SAFE 100a heat pipe cooled, electrically heated reactor and heat exchanger hardware. This Technical Memorandum discusses the status of the planned dynamic test methodology for implementation in the direct-drive gas-cooled reactor testing and assesses the additional instrumentation needed to implement high-fidelity dynamic testing.

Index-based reactive power compensation scheme for voltage regulation

NASA Astrophysics Data System (ADS)

Dike, Damian Obioma

2008-10-01

Increasing demand for electrical power arising from deregulation and the restrictions posed to the construction of new transmission lines by environment, socioeconomic, and political issues had led to higher grid loading. Consequently, voltage instability has become a major concern, and reactive power support is vital to enhance transmission grid performance. Improved reactive power support to distressed grid is possible through the application of relatively unfamiliar emerging technologies of "Flexible AC Transmission Systems (FACTS)" devices and "Distributed Energy Resources (DERS)." In addition to these infrastructure issues, a lack of situational awareness by system operators can cause major power outages as evidenced by the August 14, 2003 widespread North American blackout. This and many other recent major outages have highlighted the inadequacies of existing power system indexes. In this work, a novel "Index-based reactive compensation scheme" appropriate for both on-line and off-line computation of grid status has been developed. A new voltage stability index (Ls-index) suitable for long transmission lines was developed, simulated, and compared to the existing two-machine modeled L-index. This showed the effect of long distance power wheeling amongst regional transmission organizations. The dissertation further provided models for index modulated voltage source converters (VSC) and index-based load flow analysis of both FACTS and microgrid interconnected power systems using the Newton-Raphson's load flow model incorporated with multi-FACTS devices. The developed package has been made user-friendly through the embodiment of interactive graphical user interface and implemented on the IEEE 14, 30, and 300 bus systems. The results showed reactive compensation has system wide-effect, provided readily accessible system status indicators, ensured seamless DERs interconnection through new islanding modes and enhanced VSC utilization. These outcomes may contribute to optimal utilization of compensation devices and available transfer capability as well as reduce system outages through better regulation of power operating voltages.

Antimicrobial Applications of Ambient--Air Plasmas

NASA Astrophysics Data System (ADS)

Pavlovich, Matthew John

The emerging field of plasma biotechology studies the applications of the plasma phase of matter to biological systems. "Ambient-condition" plasmas created at or near room temperature and atmospheric pressure are especially promising for biomedical applications because of their convenience, safety to patients, and compatibility with existing medical technology. Plasmas can be created from many different gases; plasma made from air contains a number of reactive oxygen and nitrogen species, or RONS, involved in various biological processes, including immune activity, signaling, and gene expression. Therefore, ambient-condition air plasma is of particular interest for biological applications. To understand and predict the effects of treating biological systems with ambient-air plasma, it is necessary to characterize and measure the chemical species that these plasmas produce. Understanding both gaseous chemistry and the chemistry in plasma-treated aqueous solution is important because many biological systems exist in aqueous media. Existing literature about ambient-air plasma hypothesizes the critical role of reactive oxygen and nitrogen species; a major aim of this dissertation is to better quantify RONS by produced ambient-air plasma and understand how RONS chemistry changes in response to different plasma processing conditions. Measurements imply that both gaseous and aqueous chemistry are highly sensitive to operating conditions. In particular, chemical species in air treated by plasma exist in either a low-power ozone-dominated mode or a high-power nitrogen oxide-dominated mode, with an unstable transition region at intermediate discharge power and treatment time. Ozone (O3) and nitrogen oxides (NO and NO2, or NOx) are mutually exclusive in this system and that the transition region corresponds to the transition from ozone- to nitrogen oxides-mode. Aqueous chemistry agrees well with to air plasma chemistry, and a similar transition in liquid-phase composition from ozone mode to nitrogen oxides mode occurs as the discharge power increases. One prominent example of plasma biotechnology is the use of plasma-derived reactive species as a novel disinfectant. Ambient-air plasma is an attractive means of disinfection because it is non-thermal, expends a small amount of power, and requires only air and electricity to operate. Both solid surfaces and liquid volumes can be effectively and efficiently decontaminated by the reactive oxygen and nitrogen species that plasma generates. Dry surfaces are decontaminated most effectively by the plasma operating in NOx mode and less effectively in ozone mode, with the weakest antibacterial effects in the transition region, and neutral reactive species are more influential in surface disinfection than charged particles. Aqueous bacterial inactivation correlates well with ozone concentration, suggesting that ozone is the dominant species for bacterial inactivation under the condition of a low-power discharge. Alternatively, air plasma operating in the higher-power, nitrogen oxides-rich mode can create a persistently antibacterial solution. Finally, when near-UV (UVA) treatment follows plasma treatment of bacterial suspension, the antimicrobial effect exceeds the effect predicted from the two treatments alone, and addition of nitrite to aqueous solution, followed by photolysis of nitrite by UVA photons, is hypothesized as the primary mechanism of synergy. The results presented in this dissertation underscore the dynamic nature of air plasma chemistry and the importance of careful chemical characterization of plasma devices intended for biological applications. The complexity of atmospheric pressure plasma devices, and their sensitivity to subtle differences in design and operation, can lead to different results with different mechanisms.

Implementing a Nuclear Power Plant Model for Evaluating Load-Following Capability on a Small Grid

NASA Astrophysics Data System (ADS)

Arda, Samet Egemen

A pressurized water reactor (PWR) nuclear power plant (NPP) model is introduced into Positive Sequence Load Flow (PSLF) software by General Electric in order to evaluate the load-following capability of NPPs. The nuclear steam supply system (NSSS) consists of a reactor core, hot and cold legs, plenums, and a U-tube steam generator. The physical systems listed above are represented by mathematical models utilizing a state variable lumped parameter approach. A steady-state control program for the reactor, and simple turbine and governor models are also developed. Adequacy of the isolated reactor core, the isolated steam generator, and the complete PWR models are tested in Matlab/Simulink and dynamic responses are compared with the test results obtained from the H. B. Robinson NPP. Test results illustrate that the developed models represents the dynamic features of real-physical systems and are capable of predicting responses due to small perturbations of external reactivity and steam valve opening. Subsequently, the NSSS representation is incorporated into PSLF and coupled with built-in excitation system and generator models. Different simulation cases are run when sudden loss of generation occurs in a small power system which includes hydroelectric and natural gas power plants besides the developed PWR NPP. The conclusion is that the NPP can respond to a disturbance in the power system without exceeding any design and safety limits if appropriate operational conditions, such as achieving the NPP turbine control by adjusting the speed of the steam valve, are met. In other words, the NPP can participate in the control of system frequency and improve the overall power system performance.

Design and implementation of a simple nuclear power plant simulator

NASA Astrophysics Data System (ADS)

Miller, William H.

1983-02-01

A simple PWR nuclear power plant simulator has been designed and implemented on a minicomputer system. The system is intended for students use in understanding the power operation of a nuclear power plant. A PDP-11 minicomputer calculates reactor parameters in real time, uses a graphics terminal to display the results and a keyboard and joystick for control functions. Plant parameters calculated by the model include the core reactivity (based upon control rod positions, soluble boron concentration and reactivity feedback effects), the total core power, the axial core power distribution, the temperature and pressure in the primary and secondary coolant loops, etc.

Optimal generator bidding strategies for power and ancillary services

NASA Astrophysics Data System (ADS)

Morinec, Allen G.

As the electric power industry transitions to a deregulated market, power transactions are made upon price rather than cost. Generator companies are interested in maximizing their profits rather than overall system efficiency. A method to equitably compensate generation providers for real power, and ancillary services such as reactive power and spinning reserve, will ensure a competitive market with an adequate number of suppliers. Optimizing the generation product mix during bidding is necessary to maximize a generator company's profits. The objective of this research work is to determine and formulate appropriate optimal bidding strategies for a generation company in both the energy and ancillary services markets. These strategies should incorporate the capability curves of their generators as constraints to define the optimal product mix and price offered in the day-ahead and real time spot markets. In order to achieve such a goal, a two-player model was composed to simulate market auctions for power generation. A dynamic game methodology was developed to identify Nash Equilibria and Mixed-Strategy Nash Equilibria solutions as optimal generation bidding strategies for two-player non-cooperative variable-sum matrix games with incomplete information. These games integrated the generation product mix of real power, reactive power, and spinning reserve with the generators's capability curves as constraints. The research includes simulations of market auctions, where strategies were tested for generators with different unit constraints, costs, types of competitors, strategies, and demand levels. Studies on the capability of large hydrogen cooled synchronous generators were utilized to derive useful equations that define the exact shape of the capability curve from the intersections of the arcs defined by the centers and radial vectors of the rotor, stator, and steady-state stability limits. The available reactive reserve and spinning reserve were calculated given a generator operating point in the P-Q plane. Four computer programs were developed to automatically perform the market auction simulations using the equal incremental cost rule. The software calculates the payoffs for the two competing competitors, dispatches six generators, and allocates ancillary services for 64 combinations of bidding strategies, three levels of system demand, and three different types of competitors. Matrix Game theory was utilized to calculate Nash Equilibrium solutions and mixed-strategy Nash solutions as the optimal generator bidding strategies. A method to incorporate ancillary services into the generation bidding strategy, to assure an adequate supply of ancillary services, and to allocate these necessary resources to the on-line units was devised. The optimal generator bid strategy in a power auction was shown to be the Nash Equilibrium solution found in two-player variable-sum matrix games.

Qualification of CASMO5 / SIMULATE-3K against the SPERT-III E-core cold start-up experiments

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

Grandi, G.; Moberg, L.

SIMULATE-3K is a three-dimensional kinetic code applicable to LWR Reactivity Initiated Accidents. S3K has been used to calculate several international recognized benchmarks. However, the feedback models in the benchmark exercises are different from the feedback models that SIMULATE-3K uses for LWR reactors. For this reason, it is worth comparing the SIMULATE-3K capabilities for Reactivity Initiated Accidents against kinetic experiments. The Special Power Excursion Reactor Test III was a pressurized-water, nuclear-research facility constructed to analyze the reactor kinetic behavior under initial conditions similar to those of commercial LWRs. The SPERT III E-core resembles a PWR in terms of fuel type, moderator,more » coolant flow rate, and system pressure. The initial test conditions (power, core flow, system pressure, core inlet temperature) are representative of cold start-up, hot start-up, hot standby, and hot full power. The qualification of S3K against the SPERT III E-core measurements is an ongoing work at Studsvik. In this paper, the results for the 30 cold start-up tests are presented. The results show good agreement with the experiments for the reactivity initiated accident main parameters: peak power, energy release and compensated reactivity. Predicted and measured peak powers differ at most by 13%. Measured and predicted reactivity compensations at the time of the peak power differ less than 0.01 $. Predicted and measured energy release differ at most by 13%. All differences are within the experimental uncertainty. (authors)« less

Inactivation of myeloma cancer cells by helium and argon plasma jets: The effect comparison and the key reactive species

NASA Astrophysics Data System (ADS)

Chen, Zeyu; Cui, Qingjie; Chen, Chen; Xu, Dehui; Liu, Dingxin; Chen, H. L.; Kong, Michael G.

2018-02-01

In plasma cancer therapy, the inactivation of cancer cells under plasma treatment is closely related to the reactive oxygen and nitrogen species (RONS) induced by plasmas. Quantitative study on the plasma-induced RONS that related to cancer cells apoptosis is critical for advancing the research of plasma cancer therapy. In this paper, the effects of several reactive species on the inactivation of LP-1 myeloma cancer cells are comparatively studied with variable working gas composition, surrounding gas composition, and discharge power. The results show that helium plasma jet has a higher cell inactivation efficiency than argon plasma jet under the same discharge power. By comparing the concentration of aqueous phase reactive species and the cell inactivation efficiency under different working gases and discharge powers, it is demonstrated that the inactivation efficiency of LP-1 myeloma cancer cells is strongly correlated with the concentration of peroxynitrite (ONOOH/ONOO-).

Why do electricity policy and competitive markets fail to use advanced PV systems to improve distribution power quality?

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

McHenry, Mark P.; Johnson, Jay; Hightower, Mike

The increasing pressure for network operators to meet distribution network power quality standards with increasing peak loads, renewable energy targets, and advances in automated distributed power electronics and communications is forcing policy-makers to understand new means to distribute costs and benefits within electricity markets. Discussions surrounding how distributed generation (DG) exhibits active voltage regulation and power factor/reactive power control and other power quality capabilities are complicated by uncertainties of baseline local distribution network power quality and to whom and how costs and benefits of improved electricity infrastructure will be allocated. DG providing ancillary services that dynamically respond to the networkmore » characteristics could lead to major network improvements. With proper market structures renewable energy systems could greatly improve power quality on distribution systems with nearly no additional cost to the grid operators. Renewable DG does have variability challenges, though this issue can be overcome with energy storage, forecasting, and advanced inverter functionality. This paper presents real data from a large-scale grid-connected PV array with large-scale storage and explores effective mitigation measures for PV system variability. As a result, we discuss useful inverter technical knowledge for policy-makers to mitigate ongoing inflation of electricity network tariff components by new DG interconnection requirements or electricity markets which value power quality and control.« less

Why do electricity policy and competitive markets fail to use advanced PV systems to improve distribution power quality?

DOE PAGES

McHenry, Mark P.; Johnson, Jay; Hightower, Mike

2016-01-01

The increasing pressure for network operators to meet distribution network power quality standards with increasing peak loads, renewable energy targets, and advances in automated distributed power electronics and communications is forcing policy-makers to understand new means to distribute costs and benefits within electricity markets. Discussions surrounding how distributed generation (DG) exhibits active voltage regulation and power factor/reactive power control and other power quality capabilities are complicated by uncertainties of baseline local distribution network power quality and to whom and how costs and benefits of improved electricity infrastructure will be allocated. DG providing ancillary services that dynamically respond to the networkmore » characteristics could lead to major network improvements. With proper market structures renewable energy systems could greatly improve power quality on distribution systems with nearly no additional cost to the grid operators. Renewable DG does have variability challenges, though this issue can be overcome with energy storage, forecasting, and advanced inverter functionality. This paper presents real data from a large-scale grid-connected PV array with large-scale storage and explores effective mitigation measures for PV system variability. As a result, we discuss useful inverter technical knowledge for policy-makers to mitigate ongoing inflation of electricity network tariff components by new DG interconnection requirements or electricity markets which value power quality and control.« less

Reactive power generation in high speed induction machines by continuously occurring space-transients

NASA Astrophysics Data System (ADS)

Laithwaite, E. R.; Kuznetsov, S. B.

1980-09-01

A new technique of continuously generating reactive power from the stator of a brushless induction machine is conceived and tested on a 10-kw linear machine and on 35 and 150 rotary cage motors. An auxiliary magnetic wave traveling at rotor speed is artificially created by the space-transient attributable to the asymmetrical stator winding. At least two distinct windings of different pole-pitch must be incorporated. This rotor wave drifts in and out of phase repeatedly with the stator MMF wave proper and the resulting modulation of the airgap flux is used to generate reactive VA apart from that required for magnetization or leakage flux. The VAR generation effect increases with machine size, and leading power factor operation of the entire machine is viable for large industrial motors and power system induction generators.

Reactive power compensating system

DOEpatents

Williams, Timothy J.; El-Sharkawi, Mohamed A.; Venkata, Subrahmanyam S.

1987-01-01

The reactive power of an induction machine is compensated by providing fixed capacitors on each phase line for the minimum compensation required, sensing the current on one line at the time its voltage crosses zero to determine the actual compensation required for each phase, and selecting switched capacitors on each line to provide the balance of the compensation required.

78 FR 72673 - Zero Rate Reactive Power Rate Schedules; Notice of Staff Workshop

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-03

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. AD14-1-000] Zero Rate Reactive Power Rate Schedules; Notice of Staff Workshop This notice establishes the location and date for... located at: https://www.ferc.gov/whats-new/registration/zero-rate-12-11-13-form.asp . The workshop will...

Tutorial: Reactive high power impulse magnetron sputtering (R-HiPIMS)

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

Anders, André

High Power Impulse Magnetron Sputtering (HiPIMS) is a coating technology that combines magnetron sputtering with pulsed power concepts. Furthermore, by applying power in pulses of high amplitude and a relatively low duty cycle, large fractions of sputtered atoms and near-target gases are ionized. In contrast to conventional magnetron sputtering, HiPIMS is characterized by self-sputtering or repeated gas recycling for high and low sputter yield materials, respectively, and both for most intermediate materials. The dense plasma in front of the target has the dual function of sustaining the discharge and providing plasma-assistance to film growth, affecting the microstructure of growing films.more » Many technologically interesting thin films are compound films, which are composed of one or more metals and a reactive gas, most often oxygen or nitrogen. When reactive gas is added, non-trivial consequences arise for the system because the target may become “poisoned,” i.e., a compound layer forms on the target surface affecting the sputtering yield and the yield of secondary electron emission and thereby all other parameters. It is emphasized that the target state depends not only on the reactive gas' partial pressure (balanced via gas flow and pumping) but also on the ion flux to the target, which can be controlled by pulse parameters. This is a critical technological opportunity for reactive HiPIMS (R-HiPIMS). The scope of this tutorial is focused on plasma processes and mechanisms of operation and only briefly touches upon film properties. It introduces R-HiPIMS in a systematic, step-by-step approach by covering sputtering, magnetron sputtering, reactive magnetron sputtering, pulsed reactive magnetron sputtering, HiPIMS, and finally R-HiPIMS. The tutorial is concluded by considering variations of R-HiPIMS known as modulated pulsed power magnetron sputtering and deep-oscillation magnetron sputtering and combinations of R-HiPIMS with superimposed dc magnetron sputtering.« less

Tutorial: Reactive high power impulse magnetron sputtering (R-HiPIMS)

DOE PAGES

Anders, André

2017-03-21

High Power Impulse Magnetron Sputtering (HiPIMS) is a coating technology that combines magnetron sputtering with pulsed power concepts. Furthermore, by applying power in pulses of high amplitude and a relatively low duty cycle, large fractions of sputtered atoms and near-target gases are ionized. In contrast to conventional magnetron sputtering, HiPIMS is characterized by self-sputtering or repeated gas recycling for high and low sputter yield materials, respectively, and both for most intermediate materials. The dense plasma in front of the target has the dual function of sustaining the discharge and providing plasma-assistance to film growth, affecting the microstructure of growing films.more » Many technologically interesting thin films are compound films, which are composed of one or more metals and a reactive gas, most often oxygen or nitrogen. When reactive gas is added, non-trivial consequences arise for the system because the target may become “poisoned,” i.e., a compound layer forms on the target surface affecting the sputtering yield and the yield of secondary electron emission and thereby all other parameters. It is emphasized that the target state depends not only on the reactive gas' partial pressure (balanced via gas flow and pumping) but also on the ion flux to the target, which can be controlled by pulse parameters. This is a critical technological opportunity for reactive HiPIMS (R-HiPIMS). The scope of this tutorial is focused on plasma processes and mechanisms of operation and only briefly touches upon film properties. It introduces R-HiPIMS in a systematic, step-by-step approach by covering sputtering, magnetron sputtering, reactive magnetron sputtering, pulsed reactive magnetron sputtering, HiPIMS, and finally R-HiPIMS. The tutorial is concluded by considering variations of R-HiPIMS known as modulated pulsed power magnetron sputtering and deep-oscillation magnetron sputtering and combinations of R-HiPIMS with superimposed dc magnetron sputtering.« less

Tutorial: Reactive high power impulse magnetron sputtering (R-HiPIMS)

NASA Astrophysics Data System (ADS)

Anders, André

2017-05-01

High Power Impulse Magnetron Sputtering (HiPIMS) is a coating technology that combines magnetron sputtering with pulsed power concepts. By applying power in pulses of high amplitude and a relatively low duty cycle, large fractions of sputtered atoms and near-target gases are ionized. In contrast to conventional magnetron sputtering, HiPIMS is characterized by self-sputtering or repeated gas recycling for high and low sputter yield materials, respectively, and both for most intermediate materials. The dense plasma in front of the target has the dual function of sustaining the discharge and providing plasma-assistance to film growth, affecting the microstructure of growing films. Many technologically interesting thin films are compound films, which are composed of one or more metals and a reactive gas, most often oxygen or nitrogen. When reactive gas is added, non-trivial consequences arise for the system because the target may become "poisoned," i.e., a compound layer forms on the target surface affecting the sputtering yield and the yield of secondary electron emission and thereby all other parameters. It is emphasized that the target state depends not only on the reactive gas' partial pressure (balanced via gas flow and pumping) but also on the ion flux to the target, which can be controlled by pulse parameters. This is a critical technological opportunity for reactive HiPIMS (R-HiPIMS). The scope of this tutorial is focused on plasma processes and mechanisms of operation and only briefly touches upon film properties. It introduces R-HiPIMS in a systematic, step-by-step approach by covering sputtering, magnetron sputtering, reactive magnetron sputtering, pulsed reactive magnetron sputtering, HiPIMS, and finally R-HiPIMS. The tutorial is concluded by considering variations of R-HiPIMS known as modulated pulsed power magnetron sputtering and deep-oscillation magnetron sputtering and combinations of R-HiPIMS with superimposed dc magnetron sputtering.

Chemically reactive species in liquids generated by atmospheric-pressure plasmas and their roles in plasma medicine

NASA Astrophysics Data System (ADS)

Hamaguchi, Satoshi

2013-07-01

Plasmas whose gas temperatures are close to room temperature may be generated in ambient air or a gas at atmospheric pressure with the use of low-frequency high voltage or low-power radio-frequency (RF) or microwave power applied to electrodes. Such plasmas can serve as a powerful source of free radicals and/or chemically reactive species that arise from atoms and molecules of the ambient gas. Recently use of such plasmas for medical purposes has attracted much attention as they can be implemented in possible medical devices that can cause blood coagulation, heal wounds, facilitate angiogenesis, sterilize surgical devices as well as living tissues without harming healthy cells, and selectively inactivate cancer cells. Especially of interest among reactive species generated by atmospheric-pressure plasmas (APP) are reactive oxygen species (ROS) and reactive nitrogen species (RNS) that are generated in liquid phase. Since most living tissues and cells are immersed in liquids (such as blood or culture media), reactive species generated by APPs in the gas phase are transported to the liquid phase and possibly converted to different types of reactive species therein before causing some influence on the tissues or cells. In this study, the rate equations are solved to evaluate concentrations of various reactive species in pure water that are originated by plasma reactions in atmosphere and possible effects of such species (including ROS/RNS) on living tissues and cells are discussed.

Use of DFIWG for Improvement of Voltage Stability Condition of a Power System

NASA Astrophysics Data System (ADS)

Hazarika, Durlav; Das, Ranjay

2017-12-01

This paper describes a method for improvement of voltage stability condition of a multi-bus power system by regulating reactive power generation at a Doubly Fed Induction Wind Generator (DFIWG). For this purpose, sensitivity relation between changes in voltage stability index at a bus with respect to change in reactive power generation of the DFIWG is derived. This relation is used to determine the required amount of change in rotor current of the DFIWG to improve the voltage stability index of the bus.

Control voltage and power fluctuations when connecting wind farms

NASA Astrophysics Data System (ADS)

Berinde, Ioan; Bǎlan, Horia; Oros Pop, Teodora Susana

2015-12-01

Voltage, frequency, active power and reactive power are very important parameters in terms of power quality. These parameters are followed when connecting any power plant, the more the connection of wind farms. Connecting wind farms to the electricity system must not cause interference outside the limits set by regulations. Modern solutions for fast and automatic voltage control and power fluctuations using electronic control systems of reactive power flows. FACTS (Flexible Alternating Current Transmision System) systems, established on the basis of power electronic circuits ensure control of electrical status quantities to achieve the necessary transfer of power to the power grid. FACTS devices can quickly control parameters and sizes of state power lines, such as impedance line voltages and phase angles of the voltages of the two ends of the line. Their use can lead to improvement in power system operation by increasing the transmission capacity of power lines, power flow control lines, improved static and transient stability reserve.

Method for generating a highly reactive plasma for exhaust gas after treatment and enhanced catalyst reactivity

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

Whealton, John H.; Hanson, Gregory R.; Storey, John M.

This patent application describes a method and apparatus of exhaust gas remediation that enhance the reactivity of the material catalysts found within catalytic converters of cars, trucks, and power stations.

Control of Solar Power Plants Connected Grid with Simple Calculation Method on Residential Homes

NASA Astrophysics Data System (ADS)

Kananda, Kiki; Nazir, Refdinal

2017-12-01

One of the most compatible renewable energy in all regions to apply is solar energy. Solar power plants can be built connected to existing or stand-alone power grids. In assisting the residential electricity in which there is a power grid, then a small scale solar energy power plants is very appropriate. However, the general constraint of solar energy power plants is still low in terms of efficiency. Therefore, this study will explain how to control the power of solar power plants more optimally, which is expected to reactive power to zero to raise efficiency. This is a continuation of previous research using Newton Rapshon control method. In this study we introduce a simple method by using ordinary mathematical calculations of solar-related equations. In this model, 10 PV modules type of ND T060M1 with a 60 Wp capacity are used. The calculations performed using MATLAB Simulink provide excellent value. For PCC voltage values obtained a stable quantity of approximately 220 V. At a maximum irradiation condition of 1000 W / m2, the reactive power value of Q solar generating system maximum 20.48 Var and maximum active power of 417.5 W. In the condition of lower irradiation, value of reactive power Q almost close to zero 0.77Var. This simple mathematical method can provide excellent quality control power values.

Controlling Heterogeneous Catalysis of Water Dissociation Using Cu-Ni Bimetallic Alloy Surfaces: A Quantum Dynamics Study.

PubMed

Ray, Dhiman; Ghosh, Smita; Tiwari, Ashwani Kumar

2018-06-07

Copper-Nickel bimetallic alloys are emerging heterogeneous catalysts for water dissociation which is the rate determining step of industrially important Water Gas Shift (WGS) reaction. Yet, the detailed quantum dynamics studies of water-surface scattering in literature are limited to pure metal surfaces. We present here, a three dimensional wave-packet dynamics study of water dissociation on Cu-Ni alloy surfaces, using a pseudo diatomic model of water on a London-Eyring-Polanyi-Sato (LEPS) potential energy surface in order to study the effect of initial vibration, rotation and orientation of water molecule on reactivity. For all the chosen surfaces reactivity increases significantly with vibrational excitation. In general, for lower vibrational states the reactivity increases with increasing rotational excitation but it decreases in higher vibrational states. Molecular orientation strongly affects reactivity by helping the molecule to align along the reaction path at higher vibrational states. For different alloys, the reaction probability follows the trend of barrier heights and the surfaces having all Ni atoms in the uppermost layer are much more reactive than the ones with Cu atoms. Hence the nature of the alloy surface and initial quantum state of the incoming molecule significantly influence the reactivity in surface catalyzed water dissociation.

Nanocarbon synthesis by high-temperature oxidation of nanoparticles

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

Nomura, Ken-ichi; Kalia, Rajiv K.; Li, Ying

High-temperature oxidation of silicon-carbide nanoparticles (nSiC) underlies a wide range of technologies from high-power electronic switches for efficient electrical grid and thermal protection of space vehicles to self-healing ceramic nanocomposites. Here, multimillion-atom reactive molecular dynamics simulations validated by ab initio quantum molecular dynamics simulations predict unexpected condensation of large graphene flakes during high-temperature oxidation of nSiC. Initial oxidation produces a molten silica shell that acts as an autocatalytic ‘nanoreactor’ by actively transporting oxygen reactants while protecting the nanocarbon product from harsh oxidizing environment. Percolation transition produces porous nanocarbon with fractal geometry, which consists of mostly sp 2 carbons with pentagonalmore » and heptagonal defects. Furthermore, this work suggests a simple synthetic pathway to high surface-area, low-density nanocarbon with numerous energy, biomedical and mechanical-metamaterial applications, including the reinforcement of self-healing composites.« less

Nanocarbon synthesis by high-temperature oxidation of nanoparticles

DOE PAGES

Nomura, Ken-ichi; Kalia, Rajiv K.; Li, Ying; ...

2016-04-20

High-temperature oxidation of silicon-carbide nanoparticles (nSiC) underlies a wide range of technologies from high-power electronic switches for efficient electrical grid and thermal protection of space vehicles to self-healing ceramic nanocomposites. Here, multimillion-atom reactive molecular dynamics simulations validated by ab initio quantum molecular dynamics simulations predict unexpected condensation of large graphene flakes during high-temperature oxidation of nSiC. Initial oxidation produces a molten silica shell that acts as an autocatalytic ‘nanoreactor’ by actively transporting oxygen reactants while protecting the nanocarbon product from harsh oxidizing environment. Percolation transition produces porous nanocarbon with fractal geometry, which consists of mostly sp 2 carbons with pentagonalmore » and heptagonal defects. Furthermore, this work suggests a simple synthetic pathway to high surface-area, low-density nanocarbon with numerous energy, biomedical and mechanical-metamaterial applications, including the reinforcement of self-healing composites.« less

Nanocarbon synthesis by high-temperature oxidation of nanoparticles

PubMed Central

Nomura, Ken-ichi; Kalia, Rajiv K.; Li, Ying; Nakano, Aiichiro; Rajak, Pankaj; Sheng, Chunyang; Shimamura, Kohei; Shimojo, Fuyuki; Vashishta, Priya

2016-01-01

High-temperature oxidation of silicon-carbide nanoparticles (nSiC) underlies a wide range of technologies from high-power electronic switches for efficient electrical grid and thermal protection of space vehicles to self-healing ceramic nanocomposites. Here, multimillion-atom reactive molecular dynamics simulations validated by ab initio quantum molecular dynamics simulations predict unexpected condensation of large graphene flakes during high-temperature oxidation of nSiC. Initial oxidation produces a molten silica shell that acts as an autocatalytic ‘nanoreactor’ by actively transporting oxygen reactants while protecting the nanocarbon product from harsh oxidizing environment. Percolation transition produces porous nanocarbon with fractal geometry, which consists of mostly sp2 carbons with pentagonal and heptagonal defects. This work suggests a simple synthetic pathway to high surface-area, low-density nanocarbon with numerous energy, biomedical and mechanical-metamaterial applications, including the reinforcement of self-healing composites. PMID:27095061

Wind turbine generator interaction with conventional diesel generators on Block Island, Rhode Island. Volume 2: Data analysis

NASA Technical Reports Server (NTRS)

Wilreker, V. F.; Stiller, P. H.; Scott, G. W.; Kruse, V. J.; Smith, R. F.

1984-01-01

Assessing the performance of a MOD-OA horizontal axis wind turbine connected to an isolated diesel utility, a comprehensive data measurement program was conducted on the Block Island Power Company installation on Block Island, Rhode Island. The detailed results of that program focusing on three principal areas of (1) fuel displacement (savings), (2) dynamic interaction between the diesel utility and the wind turbine, (3) effects of three models of wind turbine reactive power control are presented. The approximate two month duration of the data acquisition program conducted in the winter months (February into April 1982) revealed performance during periods of highest wind energy penetration and hence severity of operation. Even under such conditions fuel savings were significant resulting in a fuel reduction of 6.7% while the MOD-OA was generating 10.7% of the total electrical energy. Also, electrical disturbance and interactive effects were of an acceptable level.

Movable-molybdenum-reflector reactivity experiments for control studies of compact space power reactor concepts

NASA Technical Reports Server (NTRS)

Fox, T. A.

1973-01-01

An experimental reflector reactivity study was made with a compact cylindrical reactor using a uranyl fluoride - water fuel solution. The reactor was axially unreflected and radially reflected with segments of molybdenum. The reflector segments were displaced incrementally in both the axial and radial dimensions, and the shutdown of each configuration was measured by using the pulsed-neutron source technique. The reactivity effects for axial and radial displacement of reflector segments are tabulated separately and compared. The experiments provide data for control-system studies of compact-space-power-reactor concepts.

TLBO based Voltage Stable Environment Friendly Economic Dispatch Considering Real and Reactive Power Constraints

NASA Astrophysics Data System (ADS)

Verma, H. K.; Mafidar, P.

2013-09-01

In view of growing concern towards environment, power system engineers are forced to generate quality green energy. Hence the economic dispatch (ED) aims at the power generation to meet the load demand at minimum fuel cost with environmental and voltage constraints along with essential constraints on real and reactive power. The emission control which reduces the negative impact on environment is achieved by including the additional constraints in ED problem. Presently, the power system mostly operates near its stability limits, therefore with increased demand the system faces voltage problem. The bus voltages are brought within limit in the present work by placement of static var compensator (SVC) at weak bus which is identified from bus participation factor. The optimal size of SVC is determined by univariate search method. This paper presents the use of Teaching Learning based Optimization (TLBO) algorithm for voltage stable environment friendly ED problem with real and reactive power constraints. The computational effectiveness of TLBO is established through test results over particle swarm optimization (PSO) and Big Bang-Big Crunch (BB-BC) algorithms for the ED problem.

Reactive strategies in indirect reciprocity.

PubMed

Ohtsuki, Hisashi

2004-04-07

Evolution of reactive strategy of indirect reciprocity is discussed, where individuals interact with others through the one-shot Prisoner's Dilemma game, changing their partners in every round. We investigate all of the reactive strategies that are stochastic, including deterministic ones as special cases. First we study adaptive dynamics of reactive strategies by assuming monomorphic population. Results are very similar to the corresponding evolutionary dynamics of direct reciprocity. The discriminating strategy, which prescribes cooperation only with those who cooperated in the previous round, cannot be an outcome of the evolution. Next we examine the case where the population includes a diversity of strategies. We find that only the mean 'discriminatoriness' in the population is the parameter that affects the evolutionary dynamics. The discriminating strategy works as a promoter of cooperation there. However, it is again not the end point of the evolution. This is because retaliatory defection, which was prescribed by the discriminating strategy, is regarded as another defection toward the society. These results caution that we have to reconsider the role of retaliatory defection much more carefully.

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.

Characterization of Impact Initiation of Aluminum-Based Intermetallic-Forming Reactive Materials

DTIC Science & Technology

2011-12-01

compressed intermetallic-forming aluminum-based reactive materials upon impact initiation, consisting of equi-volumetric tantalum-aluminum, tungsten-aluminum...18 2.3.4 Dynamic Energy Release Characterization using Pig Test . . . . . . 21 2.3.5 Shock Compression of Reactive Powder Mixtures...is to evaluate the reaction initiation characteristics of quasi-statically compressed intermetallic-forming aluminum-based reactive materials upon

A miniaturized technique for assessing protein thermodynamics and function using fast determination of quantitative cysteine reactivity.

PubMed

Isom, Daniel G; Marguet, Philippe R; Oas, Terrence G; Hellinga, Homme W

2011-04-01

Protein thermodynamic stability is a fundamental physical characteristic that determines biological function. Furthermore, alteration of thermodynamic stability by macromolecular interactions or biochemical modifications is a powerful tool for assessing the relationship between protein structure, stability, and biological function. High-throughput approaches for quantifying protein stability are beginning to emerge that enable thermodynamic measurements on small amounts of material, in short periods of time, and using readily accessible instrumentation. Here we present such a method, fast quantitative cysteine reactivity, which exploits the linkage between protein stability, sidechain protection by protein structure, and structural dynamics to characterize the thermodynamic and kinetic properties of proteins. In this approach, the reaction of a protected cysteine and thiol-reactive fluorogenic indicator is monitored over a gradient of temperatures after a short incubation time. These labeling data can be used to determine the midpoint of thermal unfolding, measure the temperature dependence of protein stability, quantify ligand-binding affinity, and, under certain conditions, estimate folding rate constants. Here, we demonstrate the fQCR method by characterizing these thermodynamic and kinetic properties for variants of Staphylococcal nuclease and E. coli ribose-binding protein engineered to contain single, protected cysteines. These straightforward, information-rich experiments are likely to find applications in protein engineering and functional genomics. Copyright © 2010 Wiley-Liss, Inc.

Design, Specification, and Synthesis of Aircraft Electric Power Systems Control Logic

NASA Astrophysics Data System (ADS)

Xu, Huan

Cyber-physical systems integrate computation, networking, and physical processes. Substantial research challenges exist in the design and verification of such large-scale, distributed sensing, actuation, and control systems. Rapidly improving technology and recent advances in control theory, networked systems, and computer science give us the opportunity to drastically improve our approach to integrated flow of information and cooperative behavior. Current systems rely on text-based specifications and manual design. Using new technology advances, we can create easier, more efficient, and cheaper ways of developing these control systems. This thesis will focus on design considerations for system topologies, ways to formally and automatically specify requirements, and methods to synthesize reactive control protocols, all within the context of an aircraft electric power system as a representative application area. This thesis consists of three complementary parts: synthesis, specification, and design. The first section focuses on the synthesis of central and distributed reactive controllers for an aircraft elec- tric power system. This approach incorporates methodologies from computer science and control. The resulting controllers are correct by construction with respect to system requirements, which are formulated using the specification language of linear temporal logic (LTL). The second section addresses how to formally specify requirements and introduces a domain-specific language for electric power systems. A software tool automatically converts high-level requirements into LTL and synthesizes a controller. The final sections focus on design space exploration. A design methodology is proposed that uses mixed-integer linear programming to obtain candidate topologies, which are then used to synthesize controllers. The discrete-time control logic is then verified in real-time by two methods: hardware and simulation. Finally, the problem of partial observability and dynamic state estimation is explored. Given a set placement of sensors on an electric power system, measurements from these sensors can be used in conjunction with control logic to infer the state of the system.

Supramolecular reactivity in the gas phase: investigating the intrinsic properties of non-covalent complexes.

PubMed

Cera, Luca; Schalley, Christoph A

2014-03-21

The high vacuum inside a mass spectrometer offers unique conditions to broaden our view on the reactivity of supramolecules. Because dynamic exchange processes between complexes are efficiently suppressed, the intrinsic and intramolecular reactivity of the complexes of interest is observed. Besides this, the significantly higher strength of non-covalent interactions in the absence of competing solvent allows processes to occur that are unable to compete in solution. The present review highlights a series of examples illustrating different aspects of supramolecular gas-phase reactivity ranging from the dissociation and formation of covalent bonds in non-covalent complexes through the reactivity in the restricted inner phase of container molecules and step-by-step mechanistic studies of organocatalytic reaction cycles to cage contraction reactions, processes induced by electron capture, and finally dynamic molecular motion within non-covalent complexes as unravelled by hydrogen-deuterium exchange processes performed in the gas phase.

Application of a Virtual Reactivity Feedback Control Loop in Non-Nuclear Testing of a Fast Spectrum Reactor

NASA Technical Reports Server (NTRS)

Bragg-Sitton, Shannon M.; Forsbacka, Matthew

2004-01-01

For a compact, fast-spectrum reactor, reactivity feedback is dominated by core deformation at elevated temperature. Given the use of accurate deformation measurement techniques, it is possible to simulate nuclear feedback in non-nuclear electrically heated reactor tests. Implementation of simulated reactivity feedback in response to measured deflection is being tested at the NASA Marshall Space Flight Center Early Flight Fission Test Facility (EFF-TF). During tests of the SAFE-100 reactor prototype, core deflection was monitored using a high resolution camera. "virtual" reactivity feedback was accomplished by applying the results of Monte Carlo calculations (MCNPX) to core deflection measurements; the computational analysis was used to establish the reactivity worth of van'ous core deformations. The power delivered to the SAFE-100 prototype was then dusted accordingly via kinetics calculations, The work presented in this paper will demonstrate virtual reactivity feedback as core power was increased from 1 kilowatt(sub t), to 10 kilowatts(sub t), held approximately constant at 10 kilowatts (sub t), and then allowed to decrease based on the negative thermal reactivity coefficient.

Methods of computing steady-state voltage stability margins of power systems

DOEpatents

Chow, Joe Hong; Ghiocel, Scott Gordon

2018-03-20

In steady-state voltage stability analysis, as load increases toward a maximum, conventional Newton-Raphson power flow Jacobian matrix becomes increasingly ill-conditioned so power flow fails to converge before reaching maximum loading. A method to directly eliminate this singularity reformulates the power flow problem by introducing an AQ bus with specified bus angle and reactive power consumption of a load bus. For steady-state voltage stability analysis, the angle separation between the swing bus and AQ bus can be varied to control power transfer to the load, rather than specifying the load power itself. For an AQ bus, the power flow formulation is only made up of a reactive power equation, thus reducing the size of the Jacobian matrix by one. This reduced Jacobian matrix is nonsingular at the critical voltage point, eliminating a major difficulty in voltage stability analysis for power system operations.

A Calculation Method of Electric Distance and Subarea Division Application Based on Transmission Impedance

NASA Astrophysics Data System (ADS)

Fang, G. J.; Bao, H.

2017-12-01

The widely used method of calculating electric distances is sensitivity method. The sensitivity matrix is the result of linearization and based on the hypothesis that the active power and reactive power are decoupled, so it is inaccurate. In addition, it calculates the ratio of two partial derivatives as the relationship of two dependent variables, so there is no physical meaning. This paper presents a new method for calculating electrical distance, namely transmission impedance method. It forms power supply paths based on power flow tracing, then establishes generalized branches to calculate transmission impedances. In this paper, the target of power flow tracing is S instead of Q. Q itself has no direction and the grid delivers complex power so that S contains more electrical information than Q. By describing the power transmission relationship of the branch and drawing block diagrams in both forward and reverse directions, it can be found that the numerators of feedback parts of two block diagrams are all the transmission impedances. To ensure the distance is scalar, the absolute value of transmission impedance is defined as electrical distance. Dividing network according to the electric distances and comparing with the results of sensitivity method, it proves that the transmission impedance method can adapt to the dynamic change of system better and reach a reasonable subarea division scheme.

Control voltage and power fluctuations when connecting wind farms

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

Berinde, Ioan, E-mail: ioan-berinde@yahoo.com; Bălan, Horia, E-mail: hbalan@mail.utcluj.ro; Oros, Teodora Susana, E-mail: teodoraoros-87@yahoo.com

2015-12-23

Voltage, frequency, active power and reactive power are very important parameters in terms of power quality. These parameters are followed when connecting any power plant, the more the connection of wind farms. Connecting wind farms to the electricity system must not cause interference outside the limits set by regulations. Modern solutions for fast and automatic voltage control and power fluctuations using electronic control systems of reactive power flows. FACTS (Flexible Alternating Current Transmision System) systems, established on the basis of power electronic circuits ensure control of electrical status quantities to achieve the necessary transfer of power to the power grid.more » FACTS devices can quickly control parameters and sizes of state power lines, such as impedance line voltages and phase angles of the voltages of the two ends of the line. Their use can lead to improvement in power system operation by increasing the transmission capacity of power lines, power flow control lines, improved static and transient stability reserve.« less

New Approach to Optimize the Apfs Placement Based on Instantaneous Reactive Power Theory by Genetic Algorithm

NASA Astrophysics Data System (ADS)

Hashemi-Dezaki, Hamed; Mohammadalizadeh-Shabestary, Masoud; Askarian-Abyaneh, Hossein; Rezaei-Jegarluei, Mohammad

2014-01-01

In electrical distribution systems, a great amount of power are wasting across the lines, also nowadays power factors, voltage profiles and total harmonic distortions (THDs) of most loads are not as would be desired. So these important parameters of a system play highly important role in wasting money and energy, and besides both consumers and sources are suffering from a high rate of distortions and even instabilities. Active power filters (APFs) are innovative ideas for solving of this adversity which have recently used instantaneous reactive power theory. In this paper, a novel method is proposed to optimize the allocation of APFs. The introduced method is based on the instantaneous reactive power theory in vectorial representation. By use of this representation, it is possible to asses different compensation strategies. Also, APFs proper placement in the system plays a crucial role in either reducing the losses costs and power quality improvement. To optimize the APFs placement, a new objective function has been defined on the basis of five terms: total losses, power factor, voltage profile, THD and cost. Genetic algorithm has been used to solve the optimization problem. The results of applying this method to a distribution network illustrate the method advantages.

Settlement of reactive power compensation in the light of white certificates

NASA Astrophysics Data System (ADS)

Zajkowski, Konrad

2017-10-01

The article discusses the problem of the determination of savings on active energy as a result of a reactive power compensation. Statutory guidance on the required energy audit to obtain white certificates in the European Union was followed. The analysis was made on the basis of the Polish Law. The paper presents a detailed analytical method and an estimation method taking into account the impact on the line, the transformer and the generator. According to the relevant guidelines in the European Union, the reduction of CO2 emissions by calculating the saving of active power should be determined. The detailed method and an estimation method proposed for the determination of savings on active energy as a result of the reactive power compensation carried out possess some errors and inconvenience. The detailed method requires knowledge of the network topology and a determination of reactive power Q at each point of the network. The estimation method of analysis is easy in execution, especially if the consumer of energy is the main or the most significant purchaser of electricity in the network. Unfortunately, this latter method can be used only for activities that do not require high computational accuracy. The results obtained by this method are approximate values that can be used for the calculation of economic indicators. The estimation method is suitable for determining the number of white certificates when a power audit concerns a recipient of electricity, the structure of which is a large number of divisions scattered at many different locations in the power system.

Non-equilibrium dynamics due to moving deflagration front at RDX/HTPB interface

NASA Astrophysics Data System (ADS)

Chaudhuri, Santanu; Joshi, Kaushik; Lacevic, Naida

Reactive dissipative particle dynamics (DPD-RX), a promising tool in characterizing the sensitivity and performance of heterogeneous solid propellants like polymer bonded explosives (PSXs), requires further testing for non-equilibrium dynamics. It is important to understand detailed atomistic chemistry for developing coarse grain reactive models needed for the DPD-RX. In order to obtain insights into combustion chemistry of RDX/HTPB binder, we used reactive molecular dynamics (RMD) to obtain energy up-pumping and reaction mechanisms at RDX/HTPB interface when exposed to a self-sustaining deflagration front. Hot spots are ignited near and away from the heterogeneous interface using the thermal pulse. The results show that the hot spot near interface significantly delays the transition from ignition to deflagration. We will present the mechanical response and the combustion chemistry of HTPB when the propagating deflagration front hits the polymer binder. We will discuss our efforts to incorporate this RMD based chemistry into the DPD-RX which will enable us to perform such non-equilibrium dynamics simulations on large-length scale with microstructural heterogeneities. Funding from DTRA Grant Number HDTRA1-15-1-0034 is acknowledged.

SISGR: Physical Chemistry of Reaction Dynamics in Ionic Liquids

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

Blank, David

Room temperature ionic liquids (RTILs) are liquids made up of atomic and molecular ions. This is in contrast with more common liquids, such as water, that are made up of neutral molecules. The additional charges on the atoms and molecules can alter the properties of these liquids, for example they tend to have a very high vapor pressure and the ability to shield charge in electronic devices. For these and other reasons RTILs have recently been deployed in a number of applications that involve production of free electrons in the liquid, such as batteries, capacitors, nuclear power plants, and solarmore » cells. Electrons tend to be very reactive, and understanding their behaviour in these liquids is important for the future design of ionic liquids to be employed in these environments. This study investigated the behavior of electrons generated in RTILs by pulses of ultraviolet light, including how long they survive, and how reactive they are with the both the surrounding liquid and impurities in the liquid. The ionic liquid studied was one of the most commonly used, called N-alkyl-N-methyl-pyrrolidinium bistriflimide. What the study revealed was that the majority of the electrons initially created, about 96%, had a very short lifetime of less than one picosecond (10-12 second) due to a process called geminate recombination. The study also demonstrated that the electrons are very reactive at the moment they are detached from the molecules in the liquid by light, but that they relax very quickly and lose almost all of their reactivity in much less than one picosecond. The short lifetime and rapid loss of reactivity both serve as important mechanisms that protect the liquid from radiolytic damage.« less

13C ENDOR Spectroscopy of Lipoxygenase-Substrate Complexes Reveals the Structural Basis for C-H Activation by Tunneling.

PubMed

Horitani, Masaki; Offenbacher, Adam R; Carr, Cody A Marcus; Yu, Tao; Hoeke, Veronika; Cutsail, George E; Hammes-Schiffer, Sharon; Klinman, Judith P; Hoffman, Brian M

2017-02-08

In enzymatic C-H activation by hydrogen tunneling, reduced barrier width is important for efficient hydrogen wave function overlap during catalysis. For native enzymes displaying nonadiabatic tunneling, the dominant reactive hydrogen donor-acceptor distance (DAD) is typically ca. 2.7 Å, considerably shorter than normal van der Waals distances. Without a ground state substrate-bound structure for the prototypical nonadiabatic tunneling system, soybean lipoxygenase (SLO), it has remained unclear whether the requisite close tunneling distance occurs through an unusual ground state active site arrangement or by thermally sampling conformational substates. Herein, we introduce Mn 2+ as a spin-probe surrogate for the SLO Fe ion; X-ray diffraction shows Mn-SLO is structurally faithful to the native enzyme. 13 C ENDOR then reveals the locations of 13 C10 and reactive 13 C11 of linoleic acid relative to the metal; 1 H ENDOR and molecular dynamics simulations of the fully solvated SLO model using ENDOR-derived restraints give additional metrical information. The resulting three-dimensional representation of the SLO active site ground state contains a reactive (a) conformer with hydrogen DAD of ∼3.1 Å, approximately van der Waals contact, plus an inactive (b) conformer with even longer DAD, establishing that stochastic conformational sampling is required to achieve reactive tunneling geometries. Tunneling-impaired SLO variants show increased DADs and variations in substrate positioning and rigidity, confirming previous kinetic and theoretical predictions of such behavior. Overall, this investigation highlights the (i) predictive power of nonadiabatic quantum treatments of proton-coupled electron transfer in SLO and (ii) sensitivity of ENDOR probes to test, detect, and corroborate kinetically predicted trends in active site reactivity and to reveal unexpected features of active site architecture.

Muon reactivation in muon-catalyzed D-T fusion

NASA Astrophysics Data System (ADS)

Rafelski, H. E.; Müller, B.; Rafelski, J.; Trautmann, D.; Viollier, R. D.

We comprehensively reanalyze and search for the density dependence of the effective muon alpha sticking fraction ωsff observed experimentally in muon catalyzed deuterium-tritium fusion. In our work particular emphasis has been put on the density dependent dense hydrogen stopping power. The main technical details and improvements in this work are: The (αμ) + 2s and 2p states are treated independently and are assigned individual reaction rates. The essential muonic excitation rates have been recalculated taking into account finite nuclear mass effects. The stopping power for a charged projectile in liquid heavy hydrogen is modified to account for dynamic screening effects and a density dependent effective ionization potential. It is shown that the medium dependent stopping power for the (αμ) + ion is the crucial factor controlling the density dependence of the effective sticking fraction. It is also pointed out that the muonic helium K α X-ray yield and the sticking fraction at high density can not be simultaneously brought into agreement with the experimental results without invoking novel mechanisms suppressing Stark mixing in the (Heμ) L-shell.

Reaction-based small-molecule fluorescent probes for chemoselective bioimaging

PubMed Central

Chan, Jefferson; Dodani, Sheel C.; Chang, Christopher J.

2014-01-01

The dynamic chemical diversity of elements, ions and molecules that form the basis of life offers both a challenge and an opportunity for study. Small-molecule fluorescent probes can make use of selective, bioorthogonal chemistries to report on specific analytes in cells and in more complex biological specimens. These probes offer powerful reagents to interrogate the physiology and pathology of reactive chemical species in their native environments with minimal perturbation to living systems. This Review presents a survey of tools and tactics for using such probes to detect biologically important chemical analytes. We highlight design criteria for effective chemical tools for use in biological applications as well as gaps for future exploration. PMID:23174976

Dynamics of polymerization induced phase separation in reactive polymer blends

NASA Astrophysics Data System (ADS)

Lee, Jaehyung

Mechanisms and dynamics of phase decomposition following polymerization induced phase separation (PIPS) of reactive polymer blends have been investigated experimentally and theoretically. The phenomenon of PIPS is a non-equilibrium and non-linear dynamic process. The mechanism of PIPS has been thought to be a nucleation and growth (NG) type originally, however, newer results indicate spinodal decomposition (SD). In PIPS, the coexistence curve generally passes through the reaction temperature at off-critical compositions, thus phase separation has to be initiated first in the metastable region where nucleation occurs. When the system farther drifts from the metastable to unstable region, the NG structure transforms to the SD bicontinuous morphology. The crossover behavior of PIPS may be called nucleation initiated spinodal decomposition (NISD). The formation of newer domains between the existing ones is responsible for the early stage of PIPS. Since PIPS is non- equilibrium kinetic process, it would not be surprising to discern either or both structures. The phase separation dynamics of DGEBA/CTBN mixtures having various kinds of curing agents from low reactivity to high reactivity and various amount of curing agents were examined at various reaction temperatures. The phase separation behavior was monitored by a quantity of scattered light intensity experimentally and by a quantity of collective structure factor numerically. Prior to the study of phase separation dynamics, a preliminary investigation on the isothermal cure behavior of the mixtures were executed in order to determine reaction kinetics parameters. The cure behavior followed the overall second order reaction kinetics. Next, based on the knowledge obtained from the phase separation dynamics study of DGEBA/CTBN mixtures, the phase separation dynamics of various composition of DGEBA/R45EPI mixtures having MDA as a curing agent were investigated. The phase separation behavior was quite dependent upon the composition variation. R45EPI itself can react with itself or with DGEBA without curing, therefore three-component system was considered in this mixture. For the numerical studies of this three- component mixture, a system that is composed of a reactive component-1 that is miscible with its growing molecules and another reactive component-2 that is not miscible with its growing molecules was considered with crosslinking reaction kinetics of the each component.

Adaptive accelerated ReaxFF reactive dynamics with validation from simulating hydrogen combustion.

PubMed

Cheng, Tao; Jaramillo-Botero, Andrés; Goddard, William A; Sun, Huai

2014-07-02

We develop here the methodology for dramatically accelerating the ReaxFF reactive force field based reactive molecular dynamics (RMD) simulations through use of the bond boost concept (BB), which we validate here for describing hydrogen combustion. The bond order, undercoordination, and overcoordination concepts of ReaxFF ensure that the BB correctly adapts to the instantaneous configurations in the reactive system to automatically identify the reactions appropriate to receive the bond boost. We refer to this as adaptive Accelerated ReaxFF Reactive Dynamics or aARRDyn. To validate the aARRDyn methodology, we determined the detailed sequence of reactions for hydrogen combustion with and without the BB. We validate that the kinetics and reaction mechanisms (that is the detailed sequences of reactive intermediates and their subsequent transformation to others) for H2 oxidation obtained from aARRDyn agrees well with the brute force reactive molecular dynamics (BF-RMD) at 2498 K. Using aARRDyn, we then extend our simulations to the whole range of combustion temperatures from ignition (798 K) to flame temperature (2998K), and demonstrate that, over this full temperature range, the reaction rates predicted by aARRDyn agree well with the BF-RMD values, extrapolated to lower temperatures. For the aARRDyn simulation at 798 K we find that the time period for half the H2 to form H2O product is ∼538 s, whereas the computational cost was just 1289 ps, a speed increase of ∼0.42 trillion (10(12)) over BF-RMD. In carrying out these RMD simulations we found that the ReaxFF-COH2008 version of the ReaxFF force field was not accurate for such intermediates as H3O. Consequently we reoptimized the fit to a quantum mechanics (QM) level, leading to the ReaxFF-OH2014 force field that was used in the simulations.

Probabilistic analysis on the failure of reactivity control for the PWR

NASA Astrophysics Data System (ADS)

Sony Tjahyani, D. T.; Deswandri; Sunaryo, G. R.

2018-02-01

The fundamental safety function of the power reactor is to control reactivity, to remove heat from the reactor, and to confine radioactive material. The safety analysis is used to ensure that each parameter is fulfilled during the design and is done by deterministic and probabilistic method. The analysis of reactivity control is important to be done because it will affect the other of fundamental safety functions. The purpose of this research is to determine the failure probability of the reactivity control and its failure contribution on a PWR design. The analysis is carried out by determining intermediate events, which cause the failure of reactivity control. Furthermore, the basic event is determined by deductive method using the fault tree analysis. The AP1000 is used as the object of research. The probability data of component failure or human error, which is used in the analysis, is collected from IAEA, Westinghouse, NRC and other published documents. The results show that there are six intermediate events, which can cause the failure of the reactivity control. These intermediate events are uncontrolled rod bank withdrawal at low power or full power, malfunction of boron dilution, misalignment of control rod withdrawal, malfunction of improper position of fuel assembly and ejection of control rod. The failure probability of reactivity control is 1.49E-03 per year. The causes of failures which are affected by human factor are boron dilution, misalignment of control rod withdrawal and malfunction of improper position for fuel assembly. Based on the assessment, it is concluded that the failure probability of reactivity control on the PWR is still within the IAEA criteria.

Modeling Intraindividual Dynamics Using Stochastic Differential Equations: Age Differences in Affect Regulation.

PubMed

Wood, Julie; Oravecz, Zita; Vogel, Nina; Benson, Lizbeth; Chow, Sy-Miin; Cole, Pamela; Conroy, David E; Pincus, Aaron L; Ram, Nilam

2017-12-15

Life-span theories of aging suggest improvements and decrements in individuals' ability to regulate affect. Dynamic process models, with intensive longitudinal data, provide new opportunities to articulate specific theories about individual differences in intraindividual dynamics. This paper illustrates a method for operationalizing affect dynamics using a multilevel stochastic differential equation (SDE) model, and examines how those dynamics differ with age and trait-level tendencies to deploy emotion regulation strategies (reappraisal and suppression). Univariate multilevel SDE models, estimated in a Bayesian framework, were fit to 21 days of ecological momentary assessments of affect valence and arousal (average 6.93/day, SD = 1.89) obtained from 150 adults (age 18-89 years)-specifically capturing temporal dynamics of individuals' core affect in terms of attractor point, reactivity to biopsychosocial (BPS) inputs, and attractor strength. Older age was associated with higher arousal attractor point and less BPS-related reactivity. Greater use of reappraisal was associated with lower valence attractor point. Intraindividual variability in regulation strategy use was associated with greater BPS-related reactivity and attractor strength, but in different ways for valence and arousal. The results highlight the utility of SDE models for studying affect dynamics and informing theoretical predictions about how intraindividual dynamics change over the life course. © The Author 2017. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

The mechanisms of plastic strain accommodation and post critical behavior of heterogeneous reactive composites subject to dynamic loading

NASA Astrophysics Data System (ADS)

Olney, Karl L.

The dynamic behavior of granular/porous and laminate reactive materials is of interest due to their practical applications; reactive structural components, reactive fragments, etc. The mesostructural properties control meso- and macro-scale dynamic behavior of these heterogeneous composites including the behavior during the post-critical stage of deformation. They heavily influence mechanisms of fragment generation and the in situ development of local hot spots, which act as sites of ignition in these materials. This dissertation concentrates on understanding the mechanisms of plastic strain accommodation in two representative reactive material systems with different heterogeneous mesostructrues: Aluminum-Tungsten granular/porous and Nickel-Aluminum laminate composites. The main focus is on the interpretation of results of the following dynamic experiments conducted at different strain and strain rates: drop weight tests, explosively expanded ring experiments, and explosively collapsed thick walled cylinder experiments. Due to the natural limitations in the evaluation of the mesoscale behavior of these materials experimentally and the large variation in the size scales between the mesostructural level and the sample, it is extremely difficult, if not impossible, to examine the mesoscale behavior in situ. Therefore, numerical simulations of the corresponding experiments are used as the main tool to explore material behavior at the mesoscale. Numerical models were developed to elucidate the mechanisms of plastic strain accommodation and post critical behavior in these heterogeneous composites subjected to dynamic loading. These simulations were able to reproduce the qualitative and quantitative features that were observable in the experiments and provided insight into the evolution of the mechanisms of plastic strain accommodation and post critical behavior in these materials with complex mesotructure. Additionally, these simulations provided a framework to examine the influence of various mesoscale properties such as the bonding of interfaces, the role of material properties, and the influence of mesoscale geometry. The results of this research are helpful in the design of material mesotructures conducive to the desirable behavior under dynamic loading.

A novel anti-theft security system for photovoltaic modules

NASA Astrophysics Data System (ADS)

Khan, Wasif Ali; Lim, Boon-Han; Lai, An-Chow; Chong, Kok-Keong

2017-04-01

Solar farms are considered as easy target for thieves because of insufficient protection measures. Existing anti-theft approaches are based on system level and are not very preventive and efficient because these can be bypassed with some technical knowledge. Additionally, it is difficult for security guards to tackle them as robbers come in a form of a gang equipped with heavy weapons. In this paper, a low power auto shut-off and non-destructive system is proposed for photovoltaic (PV) modules to achieve better level of security at module level. In proposed method, the power generation function of the PV module will be shut-off internally and cannot be re-activated by unauthorized personnel, in the case of theft. Hence, the PV module will not be functional even sold to new customers. The system comprises of a microcontroller, a low power position sensor, a controllable semiconductor switch and a wireless reactive-able system. The anti-theft system is developed to be laminated inside PV module and will be interconnected with solar cells so it becomes difficult for thieves to temper. The position of PV module is retrieved by position sensor and stored in a microcontroller as an initial reference value. Microcontroller uses this stored reference value to control power supply of PV module via power switch. The stored reference value can be altered using wireless circuitry by following authentication protocol. It makes the system non-destructive as anti-theft function can be reset again by authorized personnel, if it is recovered after theft or moved for maintenance purposes. The research component includes the design of a position sensing circuit, an auto shut-off circuit, a reactive-able wireless security protection algorithm and finally the integration of the multiple circuits.

Percutaneous Biopsy and Radiofrequency Ablation of Osteoid Osteoma with Excess Reactive New Bone Formation and Cortical Thickening Using a Battery-Powered Drill for Access: A Technical Note

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

Filippiadis, D., E-mail: dfilippiadis@yahoo.gr; Gkizas, C., E-mail: chgkizas@gmail.com; Kostantos, C., E-mail: drkarpen@yahoo.gr

PurposeTo report our experience with the use of a battery-powered drill in biopsy and radiofrequency ablation of osteoid osteoma with excess reactive new bone formation. The battery-powered drill enables obtaining the sample while drilling.Materials and MethodsDuring the last 18 months, 14 patients suffering from painful osteoid osteoma with excess reactive new bone formation underwent CT-guided biopsy and radiofrequency ablation. In order to assess and sample the nidus of the osteoid osteoma, a battery-powered drill was used. Biopsy was performed in all cases. Then, coaxially, a radiofrequency electrode was inserted and ablation was performed with osteoid osteoma protocol. Procedure time (i.e., drillingmore » including local anesthesia), amount of scans, technical and clinical success, and the results of biopsy are reported.ResultsAccess to the nidus through the excess reactive new bone formation was feasible in all cases. Median procedure time was 50.5 min. Histologic verification of osteoid osteoma was performed in all cases. Radiofrequency electrode was coaxially inserted within the nidus and ablation was successfully performed in all lesions. Median amount CT scans, performed to control correct positioning of the drill and precise electrode placement within the nidus was 11. There were no complications or material failure reported in our study.ConclusionsThe use of battery-powered drill facilitates access to the osteoid osteoma nidus in cases where excess reactive new bone formation is present. Biopsy needle can be used for channel creation during the access offering at the same time the possibility to extract bone samples.« less

Affect dynamics across the lifespan: with age, heart rate reacts less strongly, but recovers more slowly from unpleasant emotional situations.

PubMed

Wrzus, Cornelia; Müller, Viktor; Wagner, Gert G; Lindenberger, Ulman; Riediger, Michaela

2014-09-01

We propose that a comprehensive understanding of age differences in affective responses to emotional situations requires the distinction of 2 components of affect dynamics: reactivity, the deviation from a person's baseline, and recovery, the return to this baseline. The present study demonstrates the utility of this approach with a focus on age differences in responses of negative affect and heart rate to an unpleasant emotional situation in 92 participants aged 14 to 83. The emotional situation was elicited with a social-cognitive stress task. Participants' negative affect and heart rate were measured throughout the task. Results showed that heart rate reactivity decreased, but heart rate recovery time increased, with age. In contrast, no significant age differences were observed in either reactivity or recovery for negative affect. These findings confirm that reactivity to, and recovery from, unpleasant emotional situations are distinct components of affect dynamics. They underscore the multidirectional nature of age differences in affective processes. PsycINFO Database Record (c) 2014 APA, all rights reserved.

Applications of the Conceptual Density Functional Theory Indices to Organic Chemistry Reactivity.

PubMed

Domingo, Luis R; Ríos-Gutiérrez, Mar; Pérez, Patricia

2016-06-09

Theoretical reactivity indices based on the conceptual Density Functional Theory (DFT) have become a powerful tool for the semiquantitative study of organic reactivity. A large number of reactivity indices have been proposed in the literature. Herein, global quantities like the electronic chemical potential μ, the electrophilicity ω and the nucleophilicity N indices, and local condensed indices like the electrophilic P k + and nucleophilic P k - Parr functions, as the most relevant indices for the study of organic reactivity, are discussed.

Mood-Reactive Self-Esteem and Depression Vulnerability: Person-Specific Symptom Dynamics via Smart Phone Assessment.

PubMed

Clasen, Peter C; Fisher, Aaron J; Beevers, Christopher G

2015-01-01

Cognitive theories of depression suggest that mood-reactive self-esteem, a pattern of cognitive reactivity where low self-esteem is temporally dependent on levels of sadness, represents vulnerability for depression. Few studies have directly tested this hypothesis, particularly using intensive data collection methods (i.e., experience sampling) required to capture the temporal dynamics of sadness and self-esteem as they unfold naturally, over time. In this study we used participants' smartphones to collect multiple daily ratings of sadness and self-esteem over three weeks, in the real world. We then applied dynamic factor modeling to explore theoretically driven hypotheses about the temporal dependency of self-esteem on sadness (i.e., mood-reactive self-esteem) and its relationship to indices of depression vulnerability both contemporaneously (e.g., rumination, sad mood persistence) and prospectively (e.g., future symptomatology). In sum, individuals who demonstrated mood-reactive self-esteem reported higher levels of rumination at baseline, more persistent sad mood over three weeks, and increased depression symptoms at the end of three weeks above and beyond a trait-like index of self-esteem. The integration of smartphone assessment and person-specific analytics employed in this study offers an exiting new avenue to advance the study and treatment of depression.

Mood-Reactive Self-Esteem and Depression Vulnerability: Person-Specific Symptom Dynamics via Smart Phone Assessment

PubMed Central

Clasen, Peter C.; Fisher, Aaron J.; Beevers, Christopher G.

2015-01-01

Cognitive theories of depression suggest that mood-reactive self-esteem, a pattern of cognitive reactivity where low self-esteem is temporally dependent on levels of sadness, represents vulnerability for depression. Few studies have directly tested this hypothesis, particularly using intensive data collection methods (i.e., experience sampling) required to capture the temporal dynamics of sadness and self-esteem as they unfold naturally, over time. In this study we used participants’ smartphones to collect multiple daily ratings of sadness and self-esteem over three weeks, in the real world. We then applied dynamic factor modeling to explore theoretically driven hypotheses about the temporal dependency of self-esteem on sadness (i.e., mood-reactive self-esteem) and its relationship to indices of depression vulnerability both contemporaneously (e.g., rumination, sad mood persistence) and prospectively (e.g., future symptomatology). In sum, individuals who demonstrated mood-reactive self-esteem reported higher levels of rumination at baseline, more persistent sad mood over three weeks, and increased depression symptoms at the end of three weeks above and beyond a trait-like index of self-esteem. The integration of smartphone assessment and person-specific analytics employed in this study offers an exiting new avenue to advance the study and treatment of depression. PMID:26131724

Active and Reactive Power Optimal Dispatch Associated with Load and DG Uncertainties in Active Distribution Network

NASA Astrophysics Data System (ADS)

Gao, F.; Song, X. H.; Zhang, Y.; Li, J. F.; Zhao, S. S.; Ma, W. Q.; Jia, Z. Y.

2017-05-01

In order to reduce the adverse effects of uncertainty on optimal dispatch in active distribution network, an optimal dispatch model based on chance-constrained programming is proposed in this paper. In this model, the active and reactive power of DG can be dispatched at the aim of reducing the operating cost. The effect of operation strategy on the cost can be reflected in the objective which contains the cost of network loss, DG curtailment, DG reactive power ancillary service, and power quality compensation. At the same time, the probabilistic constraints can reflect the operation risk degree. Then the optimal dispatch model is simplified as a series of single stage model which can avoid large variable dimension and improve the convergence speed. And the single stage model is solved using a combination of particle swarm optimization (PSO) and point estimate method (PEM). Finally, the proposed optimal dispatch model and method is verified by the IEEE33 test system.

Research on Robust Control Strategies for VSC-HVDC

NASA Astrophysics Data System (ADS)

Zhu, Kaicheng; Bao, Hai

2018-01-01

In the control system of VSC-HVDC, the phase locked loop provides phase signals to voltage vector control and trigger pulses to generate the required reference phase. The PLL is a typical second-order system. When the system is in unstable state, it will oscillate, make the trigger angle shift, produce harmonic, and make active power and reactive power coupled. Thus, considering the external disturbances introduced by the PLL in VSC-HVDC control system, the parameter perturbations of the controller and the model uncertainties, a H∞ robust controller of mixed sensitivity optimization problem is designed by using the Hinf function provided by the robust control toolbox. Then, compare it with the proportional integral controller through the MATLAB simulation experiment. By contrast, when the H∞ robust controller is added, active and reactive power of the converter station can track the change of reference values more accurately and quickly, and reduce overshoot. When the step change of active and reactive power occurs, mutual influence is reduced and better independent regulation is achieved.

Modeling, analysis, control and design application guidelines of Doubly Fed Induction Generator (DFIG) for wind power applications

NASA Astrophysics Data System (ADS)

Masaud, Tarek

Double Fed Induction Generators (DFIG) has been widely used for the past two decades in large wind farms. However, there are many open-ended problems yet to be solved before they can be implemented in some specific applications. This dissertation deals with the general analysis, modeling, control and applications of the DFIG for large wind farm applications. A detailed "d-q" model of DFIG along with other applications is simulated using the MATLAB/Simulink platform. The simulation results have been discussed in detail in both sub-synchronous and super-synchronous mode of operation. An improved vector control strategy based on the rotor flux oriented vector control has been proposed to control the active power output of the DFIG. The new vector control strategy is compared with the stator flux oriented vector control which is commonly used. It is observed that the new improved vector control method provides a better active power tracking accuracy compare with the stator flux oriented vector control. The behavior of the DFIG -based wind farm under the various grid disturbances is also studied in this dissertation. The implementation of the Flexible AC Transmission System devices (FACTS) to overcome the voltage stability issue for such applications is investigated. The study includes the implementation of both a static synchronous compensator (STATCOM), and the static VAR compensator (SVC) as dynamic reactive power compensators at the point of common coupling to support DFIG-based wind farm during disturbances. Integrating FACTS protect the grid connected DFIG-based wind farm from going offline during and after the disturbances. It is found that the both devices improve the transient performance and therefore helps the wind turbine generator system to remain in service during grid faults. A comparison between the performance of the two devices in terms of the amount of reactive power injected, time response and the application cost has been discussed in this dissertation. Finally, the integration of the battery energy storage system (BESS) into a grid connected DFIG- based wind turbine as a proposed solution to smooth out the output power during wind speed variations is also addressed.

First-principles study of adsorption-desorption kinetics of aqueous V2+/V3+ redox species on graphite in a vanadium redox flow battery.

PubMed

Jiang, Zhen; Klyukin, Konstantin; Alexandrov, Vitaly

2017-06-14

Vanadium redox flow batteries (VRFBs) represent a promising solution to grid-scale energy storage, and understanding the reactivity of electrode materials is crucial for improving the power density of VRFBs. However, atomistic details about the interactions between vanadium ions and electrode surfaces in aqueous electrolytes are still lacking. Here, we examine the reactivity of the basal (0001) and edge (112[combining macron]0) graphite facets with water and aqueous V 2+ /V 3+ redox species at 300 K employing Car-Parrinello molecular dynamics (CPMD) coupled with metadynamics simulations. The results suggest that the edge surface is characterized by the formation of ketonic C[double bond, length as m-dash]O functional groups due to complete water dissociation into the H/O/H configuration with surface O atoms serving as active sites for adsorption of V 2+ /V 3+ species. The formation of V-O bonds at the surface should significantly improve the kinetics of electron transfer at the edge sites, which is not the case for the basal surface, in agreement with the experimentally hypothesized mechanism.

Cold atmospheric pressure plasma jets: Interaction with plasmid DNA and tailored electron heating using dual-frequency excitation

NASA Astrophysics Data System (ADS)

Niemi, K.; O'Neill, C.; Cox, L. J.; Waskoenig, J.; Hyland, W. B.; McMahon, S. J.; Reuter, S.; Currell, F. J.; Graham, W. G.; O'Connell, D.; Gans, T.

2012-05-01

Recent progress in plasma science and technology has enabled the development of a new generation of stable cold non-equilibrium plasmas operating at ambient atmospheric pressure. This opens horizons for new plasma technologies, in particular in the emerging field of plasma medicine. These non-equilibrium plasmas are very efficient sources for energy transport through reactive neutral particles (radicals and metastables), charged particles (ions and electrons), UV radiation, and electro-magnetic fields. The effect of a cold radio frequency-driven atmospheric pressure plasma jet on plasmid DNA has been investigated. The formation of double strand breaks correlates well with the atomic oxygen density. Taken with other measurements, this indicates that neutral components in the jet are effective in inducing double strand breaks. Plasma manipulation techniques for controlled energy delivery are highly desirable. Numerical simulations are employed for detailed investigations of the electron dynamics, which determines the generation of reactive species. New concepts based on nonlinear power dissipation promise superior strategies to control energy transport for tailored technological exploitations.

Molecular dynamics simulation of sodium aluminosilicate glass structures and glass surface-water reactions using the reactive force field (ReaxFF)

NASA Astrophysics Data System (ADS)

Dongol, R.; Wang, L.; Cormack, A. N.; Sundaram, S. K.

2018-05-01

Reactive potentials are increasingly used to study the properties of glasses and glass water reactions in a reactive molecular dynamics (MD) framework. In this study, we have simulated a ternary sodium aluminosilicate glass and investigated the initial stages of the glass surface-water reactions at 300 K using reactive force field (ReaxFF). On comparison of the simulated glass structures generated using ReaxFF and classical Buckingham potentials, our results show that the atomic density profiles calculated for the surface glass structures indicate a bond-angle distribution dependency. The atomic density profiles also show higher concentrations of non-bridging oxygens (NBOs) and sodium ions at the glass surface. Additionally, we present our results of formation of silanol species and the diffusion of water molecules at the glass surface using ReaxFF.

Ab initio molecular dynamics of the reactivity of vitamin C toward hydroxyl and HO₂/O⁻₂ radicals.

PubMed

Lespade, Laure

2017-11-21

Vitamin C is one of the most abundant exogenous antioxidants in the cell, and it is of the utmost importance to elucidate its mechanism of action against radicals. In this study, the reactivity of vitamin C toward OH and [Formula: see text] radicals in aqueous medium was analyzed by ab initio molecular dynamics using CPMD code. The simulations led to results similar to those of static studies or experiments for the pair of [Formula: see text] radicals but bring new insights for the reactivity with hydroxyl radical: the reaction takes place before the formation of an adduct and consists of two steps: first an electron is transferred to hydroxyl radical and then the ascorbyl radical loses a proton. Graphical Abstract Reactivity of vitamin C toward hydroxyl and [Formula: see text] radicals.

Quantification of air plasma chemistry for surface disinfection

NASA Astrophysics Data System (ADS)

Pavlovich, Matthew J.; Clark, Douglas S.; Graves, David B.

2014-12-01

Atmospheric-pressure air plasmas, created by a variety of discharges, are promising sources of reactive species for the emerging field of plasma biotechnology because of their convenience and ability to operate at ambient conditions. One biological application of ambient-air plasma is microbial disinfection, and the ability of air plasmas to decontaminate both solid surfaces and liquid volumes has been thoroughly established in the literature. However, the mechanism of disinfection and which reactive species most strongly correlate with antimicrobial effects are still not well understood. We describe quantitative gas-phase measurements of plasma chemistry via infrared spectroscopy in confined volumes, focusing on air plasma generated via surface micro-discharge (SMD). Previously, it has been shown that gaseous chemistry is highly sensitive to operating conditions, and the measurements we describe here extend those findings. We quantify the gaseous concentrations of ozone (O3) and nitrogen oxides (NO and NO2, or NOx) throughout the established ‘regimes’ for SMD air plasma chemistry: the low-power, ozone-dominated mode; the high-power, nitrogen oxides-dominated mode; and the intermediate, unstable transition region. The results presented here are in good agreement with previously published experimental studies of aqueous chemistry and parameterized models of gaseous chemistry. The principal finding of the present study is the correlation of bacterial inactivation on dry surfaces with gaseous chemistry across these time and power regimes. Bacterial decontamination is most effective in ‘NOx mode’ and less effective in ‘ozone mode’, with the weakest antibacterial effects in the transition region. Our results underscore the dynamic nature of air plasma chemistry and the importance of careful chemical characterization of plasma devices intended for biological applications.

Reactivity of hemodynamic responses and functional connectivity to different states of alpha synchrony: a concurrent EEG-fMRI study.

PubMed

Wu, Lei; Eichele, Tom; Calhoun, Vince D

2010-10-01

Concurrent EEG-fMRI studies have provided increasing details of the dynamics of intrinsic brain activity during the resting state. Here, we investigate a prominent effect in EEG during relaxed resting, i.e. the increase of the alpha power when the eyes are closed compared to when the eyes are open. This phenomenon is related to changes in thalamo-cortical and cortico-cortical synchronization. In order to investigate possible changes to EEG-fMRI coupling and fMRI functional connectivity during the two states we adopted a data-driven approach that fuses the multimodal data on the basis of parallel ICA decompositions of the fMRI data in the spatial domain and of the EEG data in the spectral domain. The power variation of a posterior alpha component was used as a reference function to deconvolve the hemodynamic responses from occipital, frontal, temporal, and subcortical fMRI components. Additionally, we computed the functional connectivity between these components. The results showed widespread alpha hemodynamic responses and high functional connectivity during eyes-closed (EC) rest, while eyes open (EO) resting abolished many of the hemodynamic responses and markedly decreased functional connectivity. These data suggest that generation of local hemodynamic responses is highly sensitive to state changes that do not involve changes of mental effort or awareness. They also indicate the localized power differences in posterior alpha between EO and EC in resting state data are accompanied by spatially widespread amplitude changes in hemodynamic responses and inter-regional functional connectivity, i.e. low frequency hemodynamic signals display an equivalent of alpha reactivity. Copyright 2010 Elsevier Inc. All rights reserved.

Environmental Controls and Eco-geomorphic Interactions of the Barchan-to-parabolic Dune Stabilisation and the Parabolic-to-barchan Dune Reactivation

NASA Astrophysics Data System (ADS)

Yan, Na; Baas, Andreas

2015-04-01

Parabolic dunes are one of a few common aeolian landforms which are highly controlled by eco-geomorphic interactions. Parabolic dunes, on the one hand, can be developed from highly mobile dune landforms, barchans for instance, in an ameliorated vegetation condition; or on the other hand, they can be reactivated and transformed back into mobile dunes due to vegetation deterioration. The fundamental mechanisms and eco-geomorphic interactions controlling both dune transformations remain poorly understood. To bridge the gap between complex processes involved in dune transformations on a relatively long temporal scale and real world monitoring records on a very limited temporal scale, this research has extended the DECAL model to incorporate 'dynamic' growth functions and the different 'growth' of perennial shrubs between growing and non-growing seasons, informed by field measurements and remote sensing analysis, to explore environmental controls and eco-geomorphic interactions of both types of dune transformation. A non-dimensional 'dune stabilising index' is proposed to capture the interactions between environmental controls (i.e. the capabilities of vegetation to withstand wind erosion and sand burial, the sandy substratum thickness, the height of the initial dune, and the sand transport potential), and establish the linkage between these controls and the geometry of a stabilising dune. An example demonstrates how to use the power-law relationship between the dune stabilising index and the normalised migration distance to assist in extrapolating the historical trajectories of transforming dunes. The modelling results also show that a slight increase in vegetation cover of an initial parabolic dune can significantly increase the reactivation threshold of climatic impact (both drought stress and wind strength) required to reactivate a stabilising parabolic dune into a barchan. Four eco-geomorphic interaction zones that govern a barchan-to-parabolic dune transformation and a parabolic-to-barchan dune transformation have been identified. These zones exhibit different characteristics and dynamics that are sensitive to changes in environmental forces, and can be potentially used as a proxy to monitor the mobility of a dune system.

A Three-Stage Enhanced Reactive Power and Voltage Optimization Method for High Penetration of Solar

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

Ke, Xinda; Huang, Renke; Vallem, Mallikarjuna R.

This paper presents a three-stage enhanced volt/var optimization method to stabilize voltage fluctuations in transmission networks by optimizing the usage of reactive power control devices. In contrast with existing volt/var optimization algorithms, the proposed method optimizes the voltage profiles of the system, while keeping the voltage and real power output of the generators as close to the original scheduling values as possible. This allows the method to accommodate realistic power system operation and market scenarios, in which the original generation dispatch schedule will not be affected. The proposed method was tested and validated on a modified IEEE 118-bus system withmore » photovoltaic data.« less

Mirrored continuum and molecular scale simulations of the ignition of high-pressure phases of RDX

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

Lee, Kibaek; Stewart, D. Scott, E-mail: santc@illinois.edu, E-mail: dss@illinois.edu; Joshi, Kaushik

2016-05-14

We present a mirrored atomistic and continuum framework that is used to describe the ignition of energetic materials, and a high-pressure phase of RDX in particular. The continuum formulation uses meaningful averages of thermodynamic properties obtained from the atomistic simulation and a simplification of enormously complex reaction kinetics. In particular, components are identified based on molecular weight bin averages and our methodology assumes that both the averaged atomistic and continuum simulations are represented on the same time and length scales. The atomistic simulations of thermally initiated ignition of RDX are performed using reactive molecular dynamics (RMD). The continuum model ismore » based on multi-component thermodynamics and uses a kinetics scheme that describes observed chemical changes of the averaged atomistic simulations. Thus the mirrored continuum simulations mimic the rapid change in pressure, temperature, and average molecular weight of species in the reactive mixture. This mirroring enables a new technique to simplify the chemistry obtained from reactive MD simulations while retaining the observed features and spatial and temporal scales from both the RMD and continuum model. The primary benefit of this approach is a potentially powerful, but familiar way to interpret the atomistic simulations and understand the chemical events and reaction rates. The approach is quite general and thus can provide a way to model chemistry based on atomistic simulations and extend the reach of those simulations.« less

Literature Survey on Operational Voltage Control and Reactive Power Management on Transmission and Sub-Transmission Networks

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

Elizondo, Marcelo A.; Samaan, Nader A.; Makarov, Yuri V.

Voltage and reactive power system control is generally performed following usual patterns of loads, based on off-line studies for daily and seasonal operations. This practice is currently challenged by the inclusion of distributed renewable generation, such as solar. There has been focus on resolving this problem at the distribution level; however, the transmission and sub-transmission levels have received less attention. This paper provides a literature review of proposed methods and solution approaches to coordinate and optimize voltage control and reactive power management, with an emphasis on applications at transmission and sub-transmission level. The conclusion drawn from the survey is thatmore » additional research is needed in the areas of optimizing switch shunt actions and coordinating all available resources to deal with uncertain patterns from increasing distributed renewable generation in the operational time frame. These topics are not deeply explored in the literature.« less

Modified artificial bee colony algorithm for reactive power optimization

NASA Astrophysics Data System (ADS)

Sulaiman, Noorazliza; Mohamad-Saleh, Junita; Abro, Abdul Ghani

2015-05-01

Bio-inspired algorithms (BIAs) implemented to solve various optimization problems have shown promising results which are very important in this severely complex real-world. Artificial Bee Colony (ABC) algorithm, a kind of BIAs has demonstrated tremendous results as compared to other optimization algorithms. This paper presents a new modified ABC algorithm referred to as JA-ABC3 with the aim to enhance convergence speed and avoid premature convergence. The proposed algorithm has been simulated on ten commonly used benchmarks functions. Its performance has also been compared with other existing ABC variants. To justify its robust applicability, the proposed algorithm has been tested to solve Reactive Power Optimization problem. The results have shown that the proposed algorithm has superior performance to other existing ABC variants e.g. GABC, BABC1, BABC2, BsfABC dan IABC in terms of convergence speed. Furthermore, the proposed algorithm has also demonstrated excellence performance in solving Reactive Power Optimization problem.

SELF-HEALING NANOMATERIALS: MULTIMILLION-ATOM REACTIVE MOLECULAR DYNAMICS SIMULATIONS

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

Hakamata, Tomoya; Shimamura, Kohei; Shimojo, Fuyuki

Organometal halide perovskites are attracting great attention as promising material for solar cells because of their high power conversion efficiency. The high performance has been attributed to the existence of free charge carriers and their large diffusion lengths, but the nature of carrier transport at the atomistic level remains elusive. Here, nonadiabatic quantum molecular dynamics simulations elucidate the mechanisms underlying the excellent free-carrier transport in CH 3NH 3PbI 3. Pb and I sublattices act as disjunct pathways for rapid and balanced transport of photoexcited electrons and holes, respectively, while minimizing efficiency-degrading charge recombination. On the other hand, CH 3NH 3more » sublattice quickly screens out electrostatic electron-hole attraction to generate free carriers within 1 ps. Together this nano-architecture lets photoexcited electrons and holes dissociate instantaneously and travel far away to be harvested before dissipated as heat. As a result, this work provides much needed structure-property relationships and time-resolved information that potentially lead to rational design of efficient solar cells.« less

An automated method to find transition states using chemical dynamics simulations.

PubMed

Martínez-Núñez, Emilio

2015-02-05

A procedure to automatically find the transition states (TSs) of a molecular system (MS) is proposed. It has two components: high-energy chemical dynamics simulations (CDS), and an algorithm that analyzes the geometries along the trajectories to find reactive pathways. Two levels of electronic structure calculations are involved: a low level (LL) is used to integrate the trajectories and also to optimize the TSs, and a higher level (HL) is used to reoptimize the structures. The method has been tested in three MSs: formaldehyde, formic acid (FA), and vinyl cyanide (VC), using MOPAC2012 and Gaussian09 to run the LL and HL calculations, respectively. Both the efficacy and efficiency of the method are very good, with around 15 TS structures optimized every 10 trajectories, which gives a total of 7, 12, and 83 TSs for formaldehyde, FA, and VC, respectively. The use of CDS makes it a powerful tool to unveil possible nonstatistical behavior of the system under study. © 2014 Wiley Periodicals, Inc.

Compensation for Harmonic Currents and Reactive Power in Wind Power Generation System using PWM Inverter

NASA Astrophysics Data System (ADS)

Shinohara, Katsuji; Shinhatsubo, Kurato; Iimori, Kenichi; Yamamoto, Kichiro; Saruban, Takamichi; Yamaemori, Takahiro

In recent year, consciousness of environmental problems is enhancing, and the price of the electric power purchased by an electric power company is established expensive for the power plant utilizing the natural energy. So, the introduction of the wind power generation is promoted in Japan. Generally, squirrel-cage induction machines are widely used as a generator in wind power generation system because of its small size, lightweight and low-cost. However, the induction machines do not have a source of excitation. Thus, it causes the inrush currents and the instantaneous voltage drop when the generator is directly connected to a power grid. To reduce the inrush currents, an AC power regulator is used. Wind power generations are frequently connected to and disconnected from the power grid. However, when the inrush currents are reduced, harmonic currents are caused by phase control of the AC power regulator. And the phase control of AC power regulator cannot control the power factor. Therefore, we propose the use of the AC power regulator to compensate for the harmonic currents and reactive power in the wind power generation system, and demonstrate the validity of its system by simulated and experimental results.

Effectiveness of reactive case detection for malaria elimination in three archetypical transmission settings: a modelling study.

PubMed

Gerardin, Jaline; Bever, Caitlin A; Bridenbecker, Daniel; Hamainza, Busiku; Silumbe, Kafula; Miller, John M; Eisele, Thomas P; Eckhoff, Philip A; Wenger, Edward A

2017-06-12

Reactive case detection could be a powerful tool in malaria elimination, as it selectively targets transmission pockets. However, field operations have yet to demonstrate under which conditions, if any, reactive case detection is best poised to push a region to elimination. This study uses mathematical modelling to assess how baseline transmission intensity and local interconnectedness affect the impact of reactive activities in the context of other possible intervention packages. Communities in Southern Province, Zambia, where elimination operations are currently underway, were used as representatives of three archetypes of malaria transmission: low-transmission, high household density; high-transmission, low household density; and high-transmission, high household density. Transmission at the spatially-connected household level was simulated with a dynamical model of malaria transmission, and local variation in vectorial capacity and intervention coverage were parameterized according to data collected from the area. Various potential intervention packages were imposed on each of the archetypical settings and the resulting likelihoods of elimination by the end of 2020 were compared. Simulations predict that success of elimination campaigns in both low- and high-transmission areas is strongly dependent on stemming the flow of imported infections, underscoring the need for regional-scale strategies capable of reducing transmission concurrently across many connected areas. In historically low-transmission areas, treatment of clinical malaria should form the cornerstone of elimination operations, as most malaria infections in these areas are symptomatic and onward transmission would be mitigated through health system strengthening; reactive case detection has minimal impact in these settings. In historically high-transmission areas, vector control and case management are crucial for limiting outbreak size, and the asymptomatic reservoir must be addressed through reactive case detection or mass drug campaigns. Reactive case detection is recommended only for settings where transmission has recently been reduced rather than all low-transmission settings. This is demonstrated in a modelling framework with strong out-of-sample accuracy across a range of transmission settings while including methodologies for understanding the most resource-effective allocations of health workers. This approach generalizes to providing a platform for planning rational scale-up of health systems based on locally-optimized impact according to simplified stratification.

Study of thermite mixtures consolidated by cold gas dynamic spray process

NASA Astrophysics Data System (ADS)

Bacciochini, Antoine; Maines, Geoffrey; Poupart, Christian; Radulescu, Matei; Jodoin, Bertrand; Lee, Julian

2013-06-01

The present study focused on the cold gas dynamic spray process for manufacturing finely structured energetic materials with high reactivity, vanishing porosity, as well as structural integrity and arbitrary shape. The experiments have focused the reaction between the aluminum and metal oxides, such as Al-CuO and Al-MoO3 systems. To increase the reactivity, an initial mechanical activation was achieved through interrupted ball milling. The consolidation of the materials used the supersonic cold gas spray technique, where the particles are accelerated to high speeds and consolidated via plastic deformation upon impact, forming activated nano-composites in arbitrary shapes with close to zero porosity. This technique permits to retain the feedstock powder micro-structure and prevents any reactions during the consolidation phase. Reactivity of mixtures has been investigated through flame propagation analysis on cold sprayed samples and compacted powder mixture. Deflagration tests showed the influence of porosity on the reactivity.

Modulation of inherent dynamical tendencies of the bisabolyl cation via preorganization in epi-isozizaene synthase.

PubMed

Pemberton, Ryan P; Ho, Krystina C; Tantillo, Dean J

2015-04-01

The relative importance of preorganization, selective transition state stabilization and inherent reactivity are assessed through quantum chemical and docking calculations for a sesquiterpene synthase ( epi -isozizaene synthase, EIZS). Inherent reactivity of the bisabolyl cation, both static and dynamic, appears to determine the pathway to product, although preorganization and selective binding of the final transition state structure in the multi-step carbocation cascade that forms epi -isozizaene appear to play important roles.

Neuro-Fuzzy Computational Technique to Control Load Frequency in Hydro-Thermal Interconnected Power System

NASA Astrophysics Data System (ADS)

Prakash, S.; Sinha, S. K.

2015-09-01

In this research work, two areas hydro-thermal power system connected through tie-lines is considered. The perturbation of frequencies at the areas and resulting tie line power flows arise due to unpredictable load variations that cause mismatch between the generated and demanded powers. Due to rising and falling power demand, the real and reactive power balance is harmed; hence frequency and voltage get deviated from nominal value. This necessitates designing of an accurate and fast controller to maintain the system parameters at nominal value. The main purpose of system generation control is to balance the system generation against the load and losses so that the desired frequency and power interchange between neighboring systems are maintained. The intelligent controllers like fuzzy logic, artificial neural network (ANN) and hybrid fuzzy neural network approaches are used for automatic generation control for the two area interconnected power systems. Area 1 consists of thermal reheat power plant whereas area 2 consists of hydro power plant with electric governor. Performance evaluation is carried out by using intelligent (ANFIS, ANN and fuzzy) control and conventional PI and PID control approaches. To enhance the performance of controller sliding surface i.e. variable structure control is included. The model of interconnected power system has been developed with all five types of said controllers and simulated using MATLAB/SIMULINK package. The performance of the intelligent controllers has been compared with the conventional PI and PID controllers for the interconnected power system. A comparison of ANFIS, ANN, Fuzzy and PI, PID based approaches shows the superiority of proposed ANFIS over ANN, fuzzy and PI, PID. Thus the hybrid fuzzy neural network controller has better dynamic response i.e., quick in operation, reduced error magnitude and minimized frequency transients.

Computational and analytical methods in nonlinear fluid dynamics

NASA Astrophysics Data System (ADS)

Walker, James

1993-09-01

The central focus of the program was on the application and development of modern analytical and computational methods to the solution of nonlinear problems in fluid dynamics and reactive gas dynamics. The research was carried out within the Division of Engineering Mathematics in the Department of Mechanical Engineering and Mechanics and principally involved Professors P.A. Blythe, E. Varley and J.D.A. Walker. In addition. the program involved various international collaborations. Professor Blythe completed work on reactive gas dynamics with Professor D. Crighton FRS of Cambridge University in the United Kingdom. Professor Walker and his students carried out joint work with Professor F.T. Smith, of University College London, on various problems in unsteady flow and turbulent boundary layers.

Measurement of the absorption cross sections of SiCl4, SiCl3, SiCl2 and Cl at H Lyman-α wavelength

NASA Astrophysics Data System (ADS)

Mével, R.; Catoire, L.; Fikri, M.; Roth, P.

2013-03-01

Atomic resonance absorption spectroscopy coupled with a shock tube is a powerful technique for studying high temperature dynamics of reactive systems. Presently, high temperature pyrolysis of SiCl4-Ar mixtures has been studied behind reflected shock waves. Using time-resolved absorption profiles at 121.6 nm and a detailed reaction model, the absorption cross sections of SiCl, SiCl, SiCl and Cl have been measured. Results agree well with available data for SiCl and constitute, to our knowledge, the first measurements for SiCl, SiCl and Cl at the Lyman-α wavelength. These data are relevant to silica particle production from SiCl-oxidant mixtures combustion synthesis.

Dynamics of defensive reactivity in patients with panic disorder and agoraphobia: implications for the etiology of panic disorder.

PubMed

Richter, Jan; Hamm, Alfons O; Pané-Farré, Christiane A; Gerlach, Alexander L; Gloster, Andrew T; Wittchen, Hans-Ulrich; Lang, Thomas; Alpers, Georg W; Helbig-Lang, Sylvia; Deckert, Jürgen; Fydrich, Thomas; Fehm, Lydia; Ströhle, Andreas; Kircher, Tilo; Arolt, Volker

2012-09-15

The learning perspective of panic disorder distinguishes between acute panic and anxious apprehension as distinct emotional states. Following animal models, these clinical entities reflect different stages of defensive reactivity depending upon the imminence of interoceptive or exteroceptive threat cues. The current study tested this model by investigating the dynamics of defensive reactivity in a large group of patients with panic disorder and agoraphobia (PD/AG). Three hundred forty-five PD/AG patients participated in a standardized behavioral avoidance test (being entrapped in a small, dark chamber for 10 minutes). Defense reactivity was assessed measuring avoidance and escape behavior, self-reports of anxiety and panic symptoms, autonomic arousal (heart rate and skin conductance), and potentiation of the startle reflex before and during exposure of the behavioral avoidance test. Panic disorder and agoraphobia patients differed substantially in their defensive reactivity. While 31.6% of the patients showed strong anxious apprehension during this task (as indexed by increased reports of anxiety, elevated physiological arousal, and startle potentiation), 20.9% of the patients escaped from the test chamber. Active escape was initiated at the peak of the autonomic surge accompanied by an inhibition of the startle response as predicted by the animal model. These physiological responses resembled the pattern observed during the 34 reported panic attacks. We found evidence that defensive reactivity in PD/AG patients is dynamically organized ranging from anxious apprehension to panic with increasing proximity of interoceptive threat. These data support the learning perspective of panic disorder. Copyright © 2012 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

Intelligent Distribution Voltage Control with Distributed Generation =

NASA Astrophysics Data System (ADS)

Castro Mendieta, Jose

In this thesis, three methods for the optimal participation of the reactive power of distributed generations (DGs) in unbalanced distributed network have been proposed, developed, and tested. These new methods were developed with the objectives of maintain voltage within permissible limits and reduce losses. The first method proposes an optimal participation of reactive power of all devices available in the network. The propose approach is validated by comparing the results with other methods reported in the literature. The proposed method was implemented using Simulink of Matlab and OpenDSS. Optimization techniques and the presentation of results are from Matlab. The co-simulation of Electric Power Research Institute's (EPRI) OpenDSS program solves a three-phase optimal power flow problem in the unbalanced IEEE 13 and 34-node test feeders. The results from this work showed a better loss reduction compared to the Coordinated Voltage Control (CVC) method. The second method aims to minimize the voltage variation on the pilot bus on distribution network using DGs. It uses Pareto and Fuzzy-PID logic to reduce the voltage variation. Results indicate that the proposed method reduces the voltage variation more than the other methods. Simulink of Matlab and OpenDSS is used in the development of the proposed approach. The performance of the method is evaluated on IEEE 13-node test feeder with one and three DGs. Variables and unbalanced loads are used, based on real consumption data, over a time window of 48 hours. The third method aims to minimize the reactive losses using DGs on distribution networks. This method analyzes the problem using the IEEE 13-node test feeder with three different loads and the IEEE 123-node test feeder with four DGs. The DGs can be fixed or variables. Results indicate that integration of DGs to optimize the reactive power of the network helps to maintain the voltage within the allowed limits and to reduce the reactive power losses. The thesis is presented in the form of the three articles. The first article is published in the journal Electrical Power and Energy System, the second is published in the international journal Energies and the third was submitted to the journal Electrical Power and Energy System. Two other articles have been published in conferences with reviewing committee. This work is based on six chapters, which are detailed in the various sections of the thesis.

Dynamics of confined reactive water in smectite clay-zeolite composites.

PubMed

Pitman, Michael C; van Duin, Adri C T

2012-02-15

The dynamics of water confined to mesoporous regions in minerals such as swelling clays and zeolites is fundamental to a wide range of resource management issues impacting many processes on a global scale, including radioactive waste containment, desalination, and enhanced oil recovery. Large-scale atomic models of freely diffusing multilayer smectite particles at low hydration confined in a silicalite cage are used to investigate water dynamics in the composite environment with the ReaxFF reactive force field over a temperature range of 300-647 K. The reactive capability of the force field enabled a range of relevant surface chemistry to emerge, including acid/base equilibria in the interlayer calcium hydrates and silanol formation on the edges of the clay and inner surface of the zeolite housing. After annealing, the resulting clay models exhibit both mono- and bilayer hydration structures. Clay surface hydration redistributed markedly and yielded to silicalite water loading. We find that the absolute rates and temperature dependence of water dynamics compare well to neutron scattering data and pulse field gradient measures from relevant samples of Ca-montmorillonite and silicalite, respectively. Within an atomistic, reactive context, our results distinguish water dynamics in the interlayer Ca(OH)(2)·nH(2)O environment from water flowing over the clay surface, and from water diffusing within silicalite. We find that the diffusion of water when complexed to Ca hydrates is considerably slower than freely diffusing water over the clay surface, and the reduced mobility is well described by a difference in the Arrhenius pre-exponential factor rather than a change in activation energy.

Cascaded H-bridge multilevel inverter for renewable energy generation

NASA Astrophysics Data System (ADS)

Pandey, Ravikant; Nath Tripathi, Ravi; Hanamoto, Tsuyoshi

2016-04-01

In this paper cascaded H-bridge multilevel inverter (CHBMLI) has been investigated for the application of renewable energy generation. Energy sources like solar, wind, hydro, biomass or combination of these can be manipulated to obtain alternative sources for renewable energy generation. These renewable energy sources have different electrical characteristics like DC or AC level so it is challenging to use generated power by connecting to grid or load directly. The renewable energy source require specific power electronics converter as an interface for conditioning generated power .The multilevel inverter can be utilized for renewable energy sources in two different modes, the power generation mode (stand-alone mode), and compensator mode (statcom). The performance of the multilevel inverter has been compared with two level inverter. In power generation mode CHBMLI supplies the active and reactive power required by the different loads. For operation in compensator mode the indirect current control based on synchronous reference frame theory (SRFT) ensures the grid operating in unity power factor and compensate harmonics and reactive power.

Analytic, empirical and delta method temperature derivatives of D-D and D-T fusion reactivity formulations, as a means of verification

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

Langenbrunner, James R.; Booker, Jane M.

We examine the derivatives with respect to temperature, for various deuterium-tritium (DT) and deuterium-deuterium (D-D) fusion-reactivity formulations. Langenbrunner and Makaruk [1] had studied this as a means of understanding the time and temperature domain of reaction history measured in dynamic fusion experiments. Presently, we consider the temperature derivative dependence of fusion reactivity as a means of exercising and verifying the consistency of the various reactivity formulations.

Chemical reactivity and spectroscopy explored from QM/MM molecular dynamics simulations using the LIO code

NASA Astrophysics Data System (ADS)

Marcolongo, Juan P.; Zeida, Ari; Semelak, Jonathan A.; Foglia, Nicolás O.; Morzan, Uriel N.; Estrin, Dario A.; González Lebrero, Mariano C.; Scherlis, Damián A.

2018-03-01

In this work we present the current advances in the development and the applications of LIO, a lab-made code designed for density functional theory calculations in graphical processing units (GPU), that can be coupled with different classical molecular dynamics engines. This code has been thoroughly optimized to perform efficient molecular dynamics simulations at the QM/MM DFT level, allowing for an exhaustive sampling of the configurational space. Selected examples are presented for the description of chemical reactivity in terms of free energy profiles, and also for the computation of optical properties, such as vibrational and electronic spectra in solvent and protein environments.

Photovoltaic Hosting Capacity of Feeders with Reactive Power Control and Tap Changers

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

Ceylan, Oğuzhan; Paudyal, Sumit; Bhattarai, Bishnu P.

This paper proposes an algorithm to determine photovoltaic (PV) hosting capacity of power distribution networks as a function of number of PV injection nodes, reactive power support from the PVs, and the sub-station load tap changers (LTCs). In the proposed method, several minute by minute simulations are run based on randomly chosen PV injection nodes, daily PV output profiles, and daily load profiles from a pool of high-resolution realistic data set. The simulation setup is built using OpenDSS and MATLAB. The performance of the proposed method is investigated in the IEEE 123-node distribution feeder for multiple scenarios. The case studiesmore » are performed particularly for one, two, five and ten PV injection nodes, and looking at the maximum voltage deviations. Case studies show that the PV hosting capacity of the 123-node feeder greatly differs with the number of PV injection nodes. We have also observed that the PV hosting capacity increases with reactive power support and higher tap position of sub-station LTC.« less

Network-Cognizant Voltage Droop Control for Distribution Grids

DOE PAGES

Baker, Kyri; Bernstein, Andrey; Dall'Anese, Emiliano; ...

2017-08-07

Our paper examines distribution systems with a high integration of distributed energy resources (DERs) and addresses the design of local control methods for real-time voltage regulation. Particularly, the paper focuses on proportional control strategies where the active and reactive output-powers of DERs are adjusted in response to (and proportionally to) local changes in voltage levels. The design of the voltage-active power and voltage-reactive power characteristics leverages suitable linear approximation of the AC power-flow equations and is network-cognizant; that is, the coefficients of the controllers embed information on the location of the DERs and forecasted non-controllable loads/injections and, consequently, on themore » effect of DER power adjustments on the overall voltage profile. We pursued a robust approach to cope with uncertainty in the forecasted non-controllable loads/power injections. Stability of the proposed local controllers is analytically assessed and numerically corroborated.« less

Network-Cognizant Voltage Droop Control for Distribution Grids

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

Baker, Kyri; Bernstein, Andrey; Dall'Anese, Emiliano

Our paper examines distribution systems with a high integration of distributed energy resources (DERs) and addresses the design of local control methods for real-time voltage regulation. Particularly, the paper focuses on proportional control strategies where the active and reactive output-powers of DERs are adjusted in response to (and proportionally to) local changes in voltage levels. The design of the voltage-active power and voltage-reactive power characteristics leverages suitable linear approximation of the AC power-flow equations and is network-cognizant; that is, the coefficients of the controllers embed information on the location of the DERs and forecasted non-controllable loads/injections and, consequently, on themore » effect of DER power adjustments on the overall voltage profile. We pursued a robust approach to cope with uncertainty in the forecasted non-controllable loads/power injections. Stability of the proposed local controllers is analytically assessed and numerically corroborated.« less

Assessment of the 3He pressure inside the CABRI transient rods - Development of a surrogate model based on measurements and complementary CFD calculations

NASA Astrophysics Data System (ADS)

Clamens, Olivier; Lecerf, Johann; Hudelot, Jean-Pascal; Duc, Bertrand; Cadiou, Thierry; Blaise, Patrick; Biard, Bruno

2018-01-01

CABRI is an experimental pulse reactor, funded by the French Nuclear Safety and Radioprotection Institute (IRSN) and operated by CEA at the Cadarache research center. It is designed to study fuel behavior under RIA conditions. In order to produce the power transients, reactivity is injected by depressurization of a neutron absorber (3He) situated in transient rods inside the reactor core. The shapes of power transients depend on the total amount of reactivity injected and on the injection speed. The injected reactivity can be calculated by conversion of the 3He gas density into units of reactivity. So, it is of upmost importance to properly master gas density evolution in transient rods during a power transient. The 3He depressurization was studied by CFD calculations and completed with measurements using pressure transducers. The CFD calculations show that the density evolution is slower than the pressure drop. Surrogate models were built based on CFD calculations and validated against preliminary tests in the CABRI transient system. Studies also show that it is harder to predict the depressurization during the power transients because of neutron/3He capture reactions that induce a gas heating. This phenomenon can be studied by a multiphysics approach based on reaction rate calculation thanks to Monte Carlo code and study the resulting heating effect with the validated CFD simulation.

Hexavalent chromium induces reactive oxygen species and impairs the antioxidant power of human erythrocytes and lymphocytes: Decreased metal reducing and free radical quenching ability of the cells.

PubMed

Husain, Nazim; Mahmood, Riaz

2017-08-01

The toxicity of hexavalent chromium [Cr(VI)] in biological systems is thought to be closely associated with the generation of free radicals and reactive oxygen species. These species are produced when Cr(VI) is reduced to its trivalent form in the cell. This process results in oxidative stress due to an imbalance between the detoxifying ability of the cell and the production of free radicals. We have studied the effect of potassium dichromate (K 2 Cr 2 O 7 ), a [Cr(VI)] compound, on the antioxidant power of human erythrocytes and lymphocytes under in vitro conditions. Incubation of erythrocytes and lymphocytes with different concentrations of K 2 Cr 2 O 7 resulted in a marked dose-dependent decrease in reduced glutathione and an increase in oxidized glutathione and reactive oxygen species levels. The antioxidant power of the cells was decreased, as determined by metal reducing and free radical quenching assays. These results show that [Cr(VI)] upregulates the generation of reactive oxygen species and, as a consequence, the cellular antioxidant defences are compromised. The resulting oxidative stress may contribute to Cr(VI)-induced cellular damage.

Analysis of Accidents at the Pakistan Research Reactor-1 Using Proposed Mixed-Fuel (HEU and LEU) Core

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

Bokhari, Ishtiaq H.

2004-12-15

The Pakistan Research Reactor-1 (PARR-1) was converted from highly enriched uranium (HEU) to low-enriched uranium (LEU) fuel in 1991. The reactor is running successfully, with an upgraded power level of 10 MW. To save money on the purchase of costly fresh LEU fuel elements, the use of less burnt HEU spent fuel elements along with the present LEU fuel elements is being considered. The proposal calls for the HEU fuel elements to be placed near the thermal column to gain the required excess reactivity. In the present study the safety analysis of a proposed mixed-fuel core has been carried outmore » at a calculated steady-state power level of 9.8 MW. Standard computer codes and correlations were employed to compute various parameters. Initiating events in reactivity-induced accidents involve various modes of reactivity insertion, namely, start-up accident, accidental drop of a fuel element on the core, flooding of a beam tube with water, and removal of an in-pile experiment during reactor operation. For each of these transients, time histories of reactor power, energy released, temperature, and reactivity were determined.« less

Startup of RAPID-L Lunar Base Reactor by Lithium Release Module

NASA Astrophysics Data System (ADS)

Kambe, Mitsuru

The 200 kWe uranium-nitride fueled lithium cooled fast reactor concept RAPID-L to be combined with thermoelectric power conversion system for lunar base power system is demonstrated. Unique challenges in reactivity control systems design have been attempted in RAPID-L concept. The reactor involves the following innovative reactivity control systems: Lithium Expansion Modules (LEM) for inherent reactivity feedback, Lithium Injection Modules (LIM) for inherent ultimate shutdown, and Lithium Release Modules (LRM) for automated reactor startup. All these systems adopt lithium-6 as a liquid poison instead of conventional B4C rods or Be reflectors. These systems are effective independent of the magnitude and direction of the gravity force. In 2006, however, the following design amendment has been made. 1) B4C poison rods were added to ensure criticality safety in unintended positive reactivity insertion by LRMs due to fire in the launch phase accident; because LRM freeze seal melts at 800°C which result in positive reactivity insertion. 2) Lower hot standby temperature of 200°C was adopted instead of conventional 800°C to reduce the external power at the startup. In this paper, development of the LRM orifice which dominates the startup transient of RAPID-L is discussed. An attention was focused how to achieve sufficiently small flow rate of 6Li in the orifice because it enables moderate positive reactivity insertion rate. The LRM orifice performance has been confirmed using 0.5 mm diameter SUS316 orifice/lithium flow test setup in the glove box.

Effect of working power and pressure on plasma properties during the deposition of TiN films in reactive magnetron sputtering plasma measured using Langmuir probe measurement

NASA Astrophysics Data System (ADS)

How, Soo Ren; Nayan, Nafarizal; Khairul Ahmad, Mohd; Fhong Soon, Chin; Zainizan Sahdan, Mohd; Lias, Jais; Shuhaimi Abu Bakar, Ahmad; Arshad, Mohd Khairuddin Md; Hashim, Uda; Yazid Ahmad, Mohd

2018-04-01

The ion, electron density and electron temperature during formation of TiN films in reactive magnetron sputtering system have been investigated for various settings of radio frequency (RF) power and working pressure by using Langmuir probe measurements. The RF power and working pressure able to affect the densities and plasma properties during the deposition process. In this work, a working pressure (100 and 20 mTorr) and RF power (100, 150 and 200 W) have been used for data acquisition of probe measurement. Fundamental of studied on sputter deposition is very important for improvement of film quality and deposition rate. Higher working pressure and RF power able to produce a higher ion density and reduction of electron temperature.

Development of a reactive-dispersive plume model

NASA Astrophysics Data System (ADS)

Kim, Hyun S.; Kim, Yong H.; Song, Chul H.

2017-04-01

A reactive-dispersive plume model (RDPM) was developed in this study. The RDPM can consider two main components of large-scale point source plume: i) turbulent dispersion and ii) photochemical reactions. In order to evaluate the simulation performance of newly developed RDPM, the comparisons between the model-predicted and observed mixing ratios were made using the TexAQS II 2006 (Texas Air Quality Study II 2006) power-plant experiment data. Statistical analyses show good correlation (0.61≤R≤0.92), and good agreement with the Index of Agreement (0.70≤R≤0.95). The chemical NOx lifetimes for two power-plant plumes (Monticello and Welsh power plants) were also estimated.

Compatibility of Space Nuclear Power Plant Materials in an Inert He/Xe Working Gas Containing Reactive Impurities

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

MM Hall

2006-01-31

A major materials selection and qualification issue identified in the Space Materials Plan is the potential for creating materials compatibility problems by combining dissimilar reactor core, Brayton Unit and other power conversion plant materials in a recirculating, inert He/Xe gas loop containing reactive impurity gases. Reported here are results of equilibrium thermochemical analyses that address the compatibility of space nuclear power plant (SNPP) materials in high temperature impure He gas environments. These studies provide early information regarding the constraints that exist for SNPP materials selection and provide guidance for establishing test objectives and environments for SNPP materials qualification testing.

Effects of microsolvation on a SN2 reaction: indirect atomistic dynamics and weakened suppression of reactivity.

PubMed

Yang, Li; Liu, Xu; Zhang, Jiaxu; Xie, Jing

2017-04-12

Systematic studies of microsolvation in the gas phase have enriched our knowledge of solvent effects. Here, the dynamics of a prototype S N 2 reaction of a hydrated fluoride ion with methyl iodide is uncovered employing direct dynamics simulations that show strikingly distinct features from those determined for an unsolvated system. An indirect scattering is found to prevail, which occurs dominantly by forming hydrated F - (H 2 O)-HCH 2 I and F - (H 2 O)-CH 3 I pre-reaction complexes at low energies, but proceeds through their water-free counterparts at higher energies. This finding is in strong contrast to a general evolution from indirect to direct dynamics with enhancing energy for the unsolvated substitution reactions, and this discrepancy is understood by the substantial steric hindrance introduced by a water molecule. As established in experiments, solvation suppresses the reactivity, whereas we find that this depression is remarkably frustrated upon raising the energy given that collision-induced dehydration essentially diminishes the water block for reactive collisions. The present study sheds light on how solute-solvent interactions affect the underlying dynamics at a deeper atomic level, thereby promoting our understanding of the fundamental solvent effects on chemical reactions in solution.

Security region-based small signal stability analysis of power systems with FSIG based wind farm

NASA Astrophysics Data System (ADS)

Qin, Chao; Zeng, Yuan; Yang, Yang; Cui, Xiaodan; Xu, Xialing; Li, Yong

2018-02-01

Based on the Security Region approach, the impact of fixed-speed induction generator based wind farm on the small signal stability of power systems is analyzed. Firstly, the key factors of wind farm on the small signal stability of power systems are analyzed and the parameter space for small signal stability region is formed. Secondly, the small signal stability region of power systems with wind power is established. Thirdly, the corresponding relation between the boundary of SSSR and the dominant oscillation mode is further studied. Results show that the integration of fixed-speed induction generator based wind farm will cause the low frequency oscillation stability of the power system deteriorate. When the output of wind power is high, the oscillation stability of the power system is mainly concerned with the inter-area oscillation mode caused by the integration of the wind farm. Both the active power output and the capacity of reactive power compensation of the wind farm have a significant influence on the SSSR. To improve the oscillation stability of power systems with wind power, it is suggested to reasonably set the reactive power compensation capacity for the wind farm through SSSR.

Dynamics of the O(3P) + CHD3(vCH = 0,1) reactions on an accurate ab initio potential energy surface

PubMed Central

Czakó, Gábor; Bowman, Joel M.

2012-01-01

Recent experimental and theoretical studies on the dynamics of the reactions of methane with F and Cl atoms have modified our understanding of mode-selective chemical reactivity. The O + methane reaction is also an important candidate to extend our knowledge on the rules of reactivity. Here, we report a unique full-dimensional ab initio potential energy surface for the O(3P) + methane reaction, which opens the door for accurate dynamics calculations using this surface. Quasiclassical trajectory calculations of the angular and vibrational distributions for the ground state and CH stretching excited O + CHD3(v1 = 0,1) → OH + CD3 reactions are in excellent agreement with the experiment. Our theory confirms what was proposed experimentally: The mechanistic origin of the vibrational enhancement is that the CH-stretching excitation enlarges the reactive cone of acceptance. PMID:22566657

Automated chemical kinetic modeling via hybrid reactive molecular dynamics and quantum chemistry simulations.

PubMed

Döntgen, Malte; Schmalz, Felix; Kopp, Wassja A; Kröger, Leif C; Leonhard, Kai

2018-06-13

An automated scheme for obtaining chemical kinetic models from scratch using reactive molecular dynamics and quantum chemistry simulations is presented. This methodology combines the phase space sampling of reactive molecular dynamics with the thermochemistry and kinetics prediction capabilities of quantum mechanics. This scheme provides the NASA polynomial and modified Arrhenius equation parameters for all species and reactions that are observed during the simulation and supplies them in the ChemKin format. The ab initio level of theory for predictions is easily exchangeable and the presently used G3MP2 level of theory is found to reliably reproduce hydrogen and methane oxidation thermochemistry and kinetics data. Chemical kinetic models obtained with this approach are ready-to-use for, e.g., ignition delay time simulations, as shown for hydrogen combustion. The presented extension of the ChemTraYzer approach can be used as a basis for methodologically advancing chemical kinetic modeling schemes and as a black-box approach to generate chemical kinetic models.

76 FR 26282 - Buckeye Power, Inc.; Notice of Filing

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-06

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. EL11-36-000] Buckeye Power...) (2010), Buckeye Power, Inc. (Buckeye) filed a petition for acceptance or approval of its monthly revenue requirement for its contribution to the supply of Reactive Power and Voltage Control from Generation Sources...

Split-core heat-pipe reactors for out-of-pile thermionic power systems.

NASA Technical Reports Server (NTRS)

Niederauer, G.; Lantz, E.; Breitweiser, R.

1971-01-01

Description of the concept of splitting a heat-pipe reactor for out-of-core thermionics into two identical halves and using the resulting center gap for reactivity control. Short Li-W reactor heat pipes penetrate the axial reflectors and form a heat exchanger with long heat pipes which wind through the shield to the thermionic diodes. With one reactor half anchored to the shield, the other is attached to a long arm with a pivot behind the shield and swings through a small arc for reactivity control. A safety shim prevents large reactivity inputs, and a fueled control arm drive shaft acts as a power stabilizer. Reactors fueled with U-235C and with U-233C have been studied.-

Applications of wind generation for power system frequency control, inter-area oscillations damping and parameter identification

NASA Astrophysics Data System (ADS)

Wilches-Bernal, Felipe

Power systems around the world are experiencing a continued increase in wind generation as part of their energy mix. Because of its power electronics interface, wind energy conversion systems interact differently with the grid than conventional generation. These facts are changing the traditional dynamics that regulate power system behavior and call for a re-examination of traditional problems encountered in power systems like frequency response, inter-area oscillations and parameter identification. To address this need, realistic models for wind generation are necessary. The dissertation implements such models in a MATLAB-based flexible environment suited for power system research. The dissertation continues with an analysis of the frequency response of a test power system dependent mainly on a mode referred to as the frequency regulation mode. Using this test system it is shown that its frequency regulation capability is reduced with wind penetration levels of 25% and above. A controller for wind generation to restore the frequency response of the system is then presented. The proposed controller requires the WTG to operate in a deloaded mode, a condition that is obtained through pitching the wind turbine blades. Time simulations at wind penetration levels of 25% and 50% are performed to demonstrate the effectiveness of the proposed controller. Next, the dissertation evaluates how the inter-area oscillation of a two-machine power system is affected by wind integration. The assessment is performed based on the positioning of the WTG, the level of wind penetration, and the loading condition of the system. It is determined that integrating wind reduces the damping of the inter-area mode of the system when performed in an area that imports power. For this worst-case scenario, the dissertation proposes two controllers for wind generation to improve the damping of the inter-area mode. The first controller uses frequency as feedback signal for the active power control of the WTG while the second controller manipulates the reactive power control of the WTG using the current magnitude as the feedback signal. Finally, the dissertation proposes a parameter identification method for identifying and verifying the reactive power control parameters of WTGs. Using voltage and current measurements of a wind unit as an input, the proposed method estimates an optimal set of parameters such that the output current of a standalone WTG model better approximates the measured signal. Because WTG are nonlinear systems, the identification method is solved by a Gauss-Newton iteration used to calculate the solution of a nonlinear least-squares problem. The effectiveness of the proposed method is illustrated using a set of simulated data and actual PMU recordings.

Instantaneous power control of a high speed permanent magnet synchronous generator based on a sliding mode observer and a phase locked loop

NASA Astrophysics Data System (ADS)

Duan, Jiandong; Fan, Shaogui; Wu, Fengjiang; Sun, Li; Wang, Guanglin

2018-06-01

This paper proposes an instantaneous power control method for high speed permanent magnet synchronous generators (PMSG), to realize the decoupled control of active power and reactive power, through vector control based on a sliding mode observer (SMO), and a phase locked loop (PLL). Consequently, the high speed PMSG has a high internal power factor, to ensure efficient operation. Vector control and accurate estimation of the instantaneous power require an accurate estimate of the rotor position. The SMO is able to estimate the back electromotive force (EMF). The rotor position and speed can be obtained using a combination of the PLL technique and the phase compensation method. This method has the advantages of robust operation, and being resistant to noise when estimating the position of the rotor. Using instantaneous power theory, the relationship between the output active power, reactive power, and stator current of the PMSG is deduced, and the power constraint condition is analysed for operation at the unit internal power factor. Finally, the accuracy of the rotor position detection, the instantaneous power detection, and the control methods are verified using simulations and experiments.

Dynamics of Reactive Microbial Hotspots in Concentration Gradient.

NASA Astrophysics Data System (ADS)

Hubert, A.; Farasin, J.; Tabuteau, H.; Dufresne, A.; Meheust, Y.; Le Borgne, T.

2017-12-01

In subsurface environments, bacteria play a major role in controlling the kinetics of a broad range of biogeochemical reactions. In such environments, nutrients fluxes and solute concentrations needed for bacteria metabolism may be highly variable in space and intermittent in time. This can lead to the formation of reactive hotspots where and when conditions are favorable to particular microorganisms, hence inducing biogeochemical reaction kinetics that differ significantly from those measured in homogeneous model environments. To investigate the impact of chemical gradients on the spatial structure and temporal dynamics of subsurface microorganism populations, we develop microfluidic cells allowing for a precise control of flow and chemical gradient conditions, as well as quantitative monitoring of the bacteria's spatial distribution and biofilm development. Using the non-motile Escherichia coli JW1908-1 strain and Gallionella capsiferriformans ES-2 as model organisms, we investigate the behavior and development of bacteria over a range of single and double concentration gradients in the concentrations of nutrients, electron donors and electron acceptors. We measure bacterial activity and population growth locally in precisely known hydrodynamic and chemical environments. This approach allows time-resolved monitoring of the location and intensity of reactive hotspots in micromodels as a function of the flow and chemical gradient conditions. We compare reactive microbial hotspot dynamics in our micromodels to classic growth laws and well-known growth parameters for the laboratory model bacteria Escherichia coli.We also discuss consequences for the formation and temporal dynamics of biofilms in the subsurface.

Modifying Memory: Selectively Enhancing and Updating Personal Memories for a Museum Tour by Reactivating Them

PubMed Central

St. Jacques, Peggy L.; Schacter, Daniel L.

2013-01-01

Memory can be modified when reactivated, but little is known about how the properties and extent of reactivation can selectively affect subsequent memory. We developed a novel museum paradigm to directly investigate reactivation-induced plasticity for personal memories. Participants reactivated memories triggered by photos taken from a camera they wore during a museum tour and made relatedness judgments on novel photos taken from a different tour of the same museum. Subsequent recognition memory for events at the museum was better for memories that were highly reactivated (i.e., the retrieval cues during reactivation matched the encoding experience) than for memories that were reactivated at a lower level (i.e., the retrieval cues during reactivation mismatched the encoding experience), but reactivation also increased false recognition of photographs depicting stops that were not experienced during the museum tour. Reactivation thus enables memories to be selectively enhanced and distorted via updating, thereby supporting the dynamic and flexible nature of memory. PMID:23406611

Design of specially adapted reactive coordinates to economically compute potential and kinetic energy operators including geometry relaxation

NASA Astrophysics Data System (ADS)

Thallmair, Sebastian; Roos, Matthias K.; de Vivie-Riedle, Regina

2016-06-01

Quantum dynamics simulations require prior knowledge of the potential energy surface as well as the kinetic energy operator. Typically, they are evaluated in a low-dimensional subspace of the full configuration space of the molecule as its dimensionality increases proportional to the number of atoms. This entails the challenge to find the most suitable subspace. We present an approach to design specially adapted reactive coordinates spanning this subspace. In addition to the essential geometric changes, these coordinates take into account the relaxation of the non-reactive coordinates without the necessity of performing geometry optimizations at each grid point. The method is demonstrated for an ultrafast photoinduced bond cleavage in a commonly used organic precursor for the generation of electrophiles. The potential energy surfaces for the reaction as well as the Wilson G-matrix as part of the kinetic energy operator are shown for a complex chemical reaction, both including the relaxation of the non-reactive coordinates on equal footing. A microscopic interpretation of the shape of the G-matrix elements allows to analyze the impact of the non-reactive coordinates on the kinetic energy operator. Additionally, we compare quantum dynamics simulations with and without the relaxation of the non-reactive coordinates included in the kinetic energy operator to demonstrate its influence.

The Everyday Emotional Experience of Adults with Major Depressive Disorder: Examining Emotional Instability, Inertia, and Reactivity

PubMed Central

Thompson, Renee J.; Mata, Jutta; Jaeggi, Susanne M.; Buschkuehl, Martin; Jonides, John; Gotlib, Ian H.

2013-01-01

Investigators have begun to examine the temporal dynamics of affect in individuals diagnosed with Major Depressive Disorder (MDD), focusing on instability, inertia, and reactivity of emotion. How these dynamics differ between individuals with MDD and healthy controls have not before been examined in a single study. In the present study, 53 adults with MDD and 53 healthy adults carried hand-held electronic devices for approximately seven days and were prompted randomly eight times per day to report their levels of current negative affect (NA), positive affect (PA), and the occurrence of significant events. In terms of NA, compared with healthy controls, depressed participants reported greater instability and greater reactivity to positive events, but comparable levels of inertia and reactivity to negative events. Neither average levels of NA nor NA reactivity to, frequency or intensity of, events accounted for the group difference in instability of NA. In terms of PA, the MDD and control groups did not differ significantly in their instability, inertia, or reactivity to positive or negative events. These findings highlight the importance of emotional instability in MDD, particularly with respect to NA, and contribute to a more nuanced understanding of the everyday emotional experiences of depressed individuals. PMID:22708886

Design of specially adapted reactive coordinates to economically compute potential and kinetic energy operators including geometry relaxation.

PubMed

Thallmair, Sebastian; Roos, Matthias K; de Vivie-Riedle, Regina

2016-06-21

Quantum dynamics simulations require prior knowledge of the potential energy surface as well as the kinetic energy operator. Typically, they are evaluated in a low-dimensional subspace of the full configuration space of the molecule as its dimensionality increases proportional to the number of atoms. This entails the challenge to find the most suitable subspace. We present an approach to design specially adapted reactive coordinates spanning this subspace. In addition to the essential geometric changes, these coordinates take into account the relaxation of the non-reactive coordinates without the necessity of performing geometry optimizations at each grid point. The method is demonstrated for an ultrafast photoinduced bond cleavage in a commonly used organic precursor for the generation of electrophiles. The potential energy surfaces for the reaction as well as the Wilson G-matrix as part of the kinetic energy operator are shown for a complex chemical reaction, both including the relaxation of the non-reactive coordinates on equal footing. A microscopic interpretation of the shape of the G-matrix elements allows to analyze the impact of the non-reactive coordinates on the kinetic energy operator. Additionally, we compare quantum dynamics simulations with and without the relaxation of the non-reactive coordinates included in the kinetic energy operator to demonstrate its influence.

Engine combustion control via fuel reactivity stratification

DOEpatents

Reitz, Rolf Deneys; Hanson, Reed M.; Splitter, Derek A.; Kokjohn, Sage L.

2015-07-14

A compression ignition engine uses two or more fuel charges having two or more reactivities to control the timing and duration of combustion. In a preferred implementation, a lower-reactivity fuel charge is injected or otherwise introduced into the combustion chamber, preferably sufficiently early that it becomes at least substantially homogeneously dispersed within the chamber before a subsequent injection is made. One or more subsequent injections of higher-reactivity fuel charges are then made, and these preferably distribute the higher-reactivity matter within the lower-reactivity chamber space such that combustion begins in the higher-reactivity regions, and with the lower-reactivity regions following thereafter. By appropriately choosing the reactivities of the charges, their relative amounts, and their timing, combustion can be tailored to achieve optimal power output (and thus fuel efficiency), at controlled temperatures (and thus controlled NOx), and with controlled equivalence ratios (and thus controlled soot).

Engine combustion control via fuel reactivity stratification

DOEpatents

Reitz, Rolf Deneys; Hanson, Reed M.; Splitter, Derek A.; Kokjohn, Sage L.

2016-06-28

A compression ignition engine uses two or more fuel charges having two or more reactivities to control the timing and duration of combustion. In a preferred implementation, a lower-reactivity fuel charge is injected or otherwise introduced into the combustion chamber, preferably sufficiently early that it becomes at least substantially homogeneously dispersed within the chamber before a subsequent injection is made. One or more subsequent injections of higher-reactivity fuel charges are then made, and these preferably distribute the higher-reactivity matter within the lower-reactivity chamber space such that combustion begins in the higher-reactivity regions, and with the lower-reactivity regions following thereafter. By appropriately choosing the reactivities of the charges, their relative amounts, and their timing, combustion can be tailored to achieve optimal power output (and thus fuel efficiency), at controlled temperatures (and thus controlled NOx), and with controlled equivalence ratios (and thus controlled soot).

Engine combustion control via fuel reactivity stratification

DOEpatents

Reitz, Rolf Deneys; Hanson, Reed M; Splitter, Derek A; Kokjohn, Sage L

2013-12-31

A compression ignition engine uses two or more fuel charges having two or more reactivities to control the timing and duration of combustion. In a preferred implementation, a lower-reactivity fuel charge is injected or otherwise introduced into the combustion chamber, preferably sufficiently early that it becomes at least substantially homogeneously dispersed within the chamber before a subsequent injection is made. One or more subsequent injections of higher-reactivity fuel charges are then made, and these preferably distribute the higher-reactivity matter within the lower-reactivity chamber space such that combustion begins in the higher-reactivity regions, and with the lower-reactivity regions following thereafter. By appropriately choose the reactivities of the charges, their relative amounts, and their timing, combustion can be tailored to achieve optimal power output (and thus fuel efficiency), at controlled temperatures (and thus controlled NOx), and with controlled equivalence ratios (and thus controlled soot).

Preliminary neutronic analysis of a cavity test reactor

NASA Technical Reports Server (NTRS)

Whitmarsh, C. L., Jr.

1973-01-01

A reference configuration was calculated for a cavity test reactor to be used for testing the gascore nuclear rocket concept. A thermal flux of 4.1 x 10 to the 14th power neutrons per square centimeter per second in the cavity was provided by a driver fuel loading of 6.4 kg of enriched uranium in MTR fuel elements. The reactor was moderated and cooled by heavy water and reflected with 25.4 cm of beryllium. Power generation of 41.3 MW in the driver fuel is rejected to a heat sink. Design effort was directed toward minimization of driver power while maintaining 2.7 MW in the cavity during a test run. Ancillary data on material reactivity worths, reactivity coefficients, flux spectra, and power distributions are reported.

Mobile detection system to evaluate reactive hyperemia using radionuclide plethysmography.

PubMed

Harel, François; Ngo, Quam; Finnerty, Vincent; Hernandez, Edgar; Khairy, Paul; Dupuis, Jocelyn

2007-08-01

We validated a novel mobile detection system to evaluate reactive hyperemia using the radionuclide plethysmography technique. Twenty-six subjects underwent simultaneously radionuclide plethysmography with strain gauge plethysmography. Strain gauge and radionuclide methods showed excellent reproducibility with intraclass correlation coefficients of 0.96 and 0.89 respectively. There was also a good correlation of flows between the two methods during reactive hyperemia (r = 0.87). We conclude that radionuclide plethysmography using this mobile detection system is a non-invasive alternative to assess forearm blood flow and its dynamic variations during reactive hyperemia.

Systems of mechanized and reactive droplets powered by multi-responsive surfactants

NASA Astrophysics Data System (ADS)

Yang, Zhijie; Wei, Jingjing; Sobolev, Yaroslav I.; Grzybowski, Bartosz A.

2018-01-01

Although ‘active’ surfactants, which are responsive to individual external stimuli such as temperature, electric or magnetic fields, light, redox processes or chemical agents, are well known, it would be interesting to combine several of these properties within one surfactant species. Such multi-responsive surfactants could provide ways of manipulating individual droplets and possibly assembling them into larger systems of dynamic reactors. Here we describe surfactants based on functionalized nanoparticle dimers that combine all of these and several other characteristics. These surfactants and therefore the droplets that they cover are simultaneously addressable by magnetic, optical and electric fields. As a result, the surfactant-covered droplets can be assembled into various hierarchical structures, including dynamic ones, in which light powers the rapid rotation of the droplets. Such rotating droplets can transfer mechanical torques to their non-nearest neighbours, thus acting like systems of mechanical gears. Furthermore, droplets of different types can be merged by applying electric fields and, owing to interfacial jamming, can form complex, non-spherical, ‘patchy’ structures with different surface regions covered with different surfactants. In systems of droplets that carry different chemicals, combinations of multiple stimuli can be used to control the orientations of the droplets, inter-droplet transport, mixing of contents and, ultimately, sequences of chemical reactions. Overall, the multi-responsive active surfactants that we describe provide an unprecedented level of flexibility with which liquid droplets can be manipulated, assembled and reacted.

Power oscillation suppression by robust SMES in power system with large wind power penetration

NASA Astrophysics Data System (ADS)

Ngamroo, Issarachai; Cuk Supriyadi, A. N.; Dechanupaprittha, Sanchai; Mitani, Yasunori

2009-01-01

The large penetration of wind farm into interconnected power systems may cause the severe problem of tie-line power oscillations. To suppress power oscillations, the superconducting magnetic energy storage (SMES) which is able to control active and reactive powers simultaneously, can be applied. On the other hand, several generating and loading conditions, variation of system parameters, etc., cause uncertainties in the system. The SMES controller designed without considering system uncertainties may fail to suppress power oscillations. To enhance the robustness of SMES controller against system uncertainties, this paper proposes a robust control design of SMES by taking system uncertainties into account. The inverse additive perturbation is applied to represent the unstructured system uncertainties and included in power system modeling. The configuration of active and reactive power controllers is the first-order lead-lag compensator with single input feedback. To tune the controller parameters, the optimization problem is formulated based on the enhancement of robust stability margin. The particle swarm optimization is used to solve the problem and achieve the controller parameters. Simulation studies in the six-area interconnected power system with wind farms confirm the robustness of the proposed SMES under various operating conditions.

A reactive, scalable, and transferable model for molecular energies from a neural network approach based on local information

NASA Astrophysics Data System (ADS)

Unke, Oliver T.; Meuwly, Markus

2018-06-01

Despite the ever-increasing computer power, accurate ab initio calculations for large systems (thousands to millions of atoms) remain infeasible. Instead, approximate empirical energy functions are used. Most current approaches are either transferable between different chemical systems, but not particularly accurate, or they are fine-tuned to a specific application. In this work, a data-driven method to construct a potential energy surface based on neural networks is presented. Since the total energy is decomposed into local atomic contributions, the evaluation is easily parallelizable and scales linearly with system size. With prediction errors below 0.5 kcal mol-1 for both unknown molecules and configurations, the method is accurate across chemical and configurational space, which is demonstrated by applying it to datasets from nonreactive and reactive molecular dynamics simulations and a diverse database of equilibrium structures. The possibility to use small molecules as reference data to predict larger structures is also explored. Since the descriptor only uses local information, high-level ab initio methods, which are computationally too expensive for large molecules, become feasible for generating the necessary reference data used to train the neural network.

Dynamic modeling of injection-induced fault reactivation and ground motion and impact on surface structures and human perception

DOE PAGES

Rutqvist, Jonny; Cappa, Frederic; Rinaldi, Antonio P.; ...

2014-12-31

We summarize recent modeling studies of injection-induced fault reactivation, seismicity, and its potential impact on surface structures and nuisance to the local human population. We used coupled multiphase fluid flow and geomechanical numerical modeling, dynamic wave propagation modeling, seismology theories, and empirical vibration criteria from mining and construction industries. We first simulated injection-induced fault reactivation, including dynamic fault slip, seismic source, wave propagation, and ground vibrations. From co-seismic average shear displacement and rupture area, we determined the moment magnitude to about M w = 3 for an injection-induced fault reactivation at a depth of about 1000 m. We then analyzedmore » the ground vibration results in terms of peak ground acceleration (PGA), peak ground velocity (PGV), and frequency content, with comparison to the U.S. Bureau of Mines’ vibration criteria for cosmetic damage to buildings, as well as human-perception vibration limits. For the considered synthetic M w = 3 event, our analysis showed that the short duration, high frequency ground motion may not cause any significant damage to surface structures, and would not cause, in this particular case, upward CO 2 leakage, but would certainly be felt by the local population.« less

Hierarchical Petascale Simulation Framework For Stress Corrosion Cracking

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

Grama, Ananth

2013-12-18

A number of major accomplishments resulted from the project. These include: • Data Structures, Algorithms, and Numerical Methods for Reactive Molecular Dynamics. We have developed a range of novel data structures, algorithms, and solvers (amortized ILU, Spike) for use with ReaxFF and charge equilibration. • Parallel Formulations of ReactiveMD (Purdue ReactiveMolecular Dynamics Package, PuReMD, PuReMD-GPU, and PG-PuReMD) for Messaging, GPU, and GPU Cluster Platforms. We have developed efficient serial, parallel (MPI), GPU (Cuda), and GPU Cluster (MPI/Cuda) implementations. Our implementations have been demonstrated to be significantly better than the state of the art, both in terms of performance and scalability.more » • Comprehensive Validation in the Context of Diverse Applications. We have demonstrated the use of our software in diverse systems, including silica-water, silicon-germanium nanorods, and as part of other projects, extended it to applications ranging from explosives (RDX) to lipid bilayers (biomembranes under oxidative stress). • Open Source Software Packages for Reactive Molecular Dynamics. All versions of our soft- ware have been released over the public domain. There are over 100 major research groups worldwide using our software. • Implementation into the Department of Energy LAMMPS Software Package. We have also integrated our software into the Department of Energy LAMMPS software package.« less

Results of the harmonics measurement program at the John F. Long photovoltaic house

NASA Astrophysics Data System (ADS)

Campen, G. L.

1982-03-01

Photovoltaic (PV) systems used in single-family dwellings require an inverter to act as an interface between the direct-current (dc) power output of the PV unit and the alternating-current (ac) power needed by house loads. A type of inverter known as line commutated injects harmonic currents on the ac side and requires large amounts of reactive power. Large numbers of such PV installations could lead to unacceptable levels of harmonic voltages on the utility system, and the need to increase the utility's deliver of reactive power could result in significant cost increases. The harmonics and power-factor effects are examined for a single PV installation using a line-commutated inverter. The magnitude and phase of various currents and voltages from the fundamental to the 13th harmonic were recorded both with and without the operation of the PV system.

A seven-degree-of-freedom, time-dependent quantum dynamics study on the energy efficiency in surmounting the central energy barrier of the OH + CH{sub 3} → O + CH{sub 4} reaction

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

Yan, Pengxiu; Wang, Yuping; Li, Yida

2015-04-28

A time-dependent, quantum reaction dynamics calculation with seven degrees of freedom was carried out to study the energy efficiency in surmounting the approximate center energy barrier of OH + CH{sub 3}. The calculation shows the OH vibration excitations greatly enhance the reactivity, whereas the vibrational excitations of CH{sub 3} and the rotational excitations hinder the reactivity. On the basis of equal amount of total energy, although this reaction has a slight early barrier, it is the OH vibrational energy that is the dominate force in promoting the reactivity, not the translational energy. The studies on both the forward O +more » CH{sub 4} and reverse OH + CH{sub 3} reactions demonstrate, for these central barrier reactions, a small change of the barrier location can significantly change the energy efficacy roles on the reactivity. The calculated rate constants agree with the experimental data.« less

Quantum Dynamics Study of the Potential Energy Minima Effect on Energy Efficiency for the F- + CH3Cl → FCH3 + Cl- Reaction.

PubMed

Li, Yida; Wang, Yuping; Wang, Dunyou

2017-04-13

The Polanyi rules on the energy efficiency on reactivity are summarized solely from the locations of barriers on the potential energy surfaces. Here, our quantum dynamics study for the F - + CH 3 Cl → FCH 3 + Cl - reaction shows that the two potential energy minima in the entrance channel on the potential energy surface play an essential role in energy efficiency on reactivity. The reactivity of this reaction is dominated by the low collision energies where two distinctive reaction mechanisms involve the two minima in the entrance channel. Overall, the Cl-CH 3 stretching motion and C-H 3 umbrella motion both are more efficient than the translational motion in promoting this reaction. Although this reaction has a negative energy barrier, our study shows that it is the minima in the entrance channel, together with the energy barrier relative to these minima, that determine the energy efficacy on reactivity.

Shock Response and Explosive Launch of Compacted Reactive Material

NASA Astrophysics Data System (ADS)

Molitoris, John; Gash, Alexander; Garza, Raul; Gagliardi, Franco; Tringe, Joseph; Batteux, Jan; Souers, P.; HEAF Team

2013-06-01

We have performed a series of experiments investigating the detailed dynamic response of compacted reactive material to shock and blast. Here a granular reactive formulation (Fe2O3/Al based thermite) was pressed into a solid cylinder of material and mated to a high-explosive charge of the same diameter. Detonation of the charge transmitted a shock wave to the thermite cylinder and imparted momentum launching it in the direction of the detonation. High-resolution time sequence radiography was used to image the dynamic response of the thermite. This technique allowed a detailed investigation of material deformation in addition to changes in the internal structure and indications of reactivity. The effect of variations in the initial density of the pressed thermite was also examined. We find that these pressed thermites behave much like solid metals during shock transit, then respond much differently. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Quantitative Understanding of SHAPE Mechanism from RNA Structure and Dynamics Analysis.

PubMed

Hurst, Travis; Xu, Xiaojun; Zhao, Peinan; Chen, Shi-Jie

2018-05-10

The selective 2'-hydroxyl acylation analyzed by primer extension (SHAPE) method probes RNA local structural and dynamic information at single nucleotide resolution. To gain quantitative insights into the relationship between nucleotide flexibility, RNA 3D structure, and SHAPE reactivity, we develop a 3D Structure-SHAPE Relationship model (3DSSR) to rebuild SHAPE profiles from 3D structures. The model starts from RNA structures and combines nucleotide interaction strength and conformational propensity, ligand (SHAPE reagent) accessibility, and base-pairing pattern through a composite function to quantify the correlation between SHAPE reactivity and nucleotide conformational stability. The 3DSSR model shows the relationship between SHAPE reactivity and RNA structure and energetics. Comparisons between the 3DSSR-predicted SHAPE profile and the experimental SHAPE data show correlation, suggesting that the extracted analytical function may have captured the key factors that determine the SHAPE reactivity profile. Furthermore, the theory offers an effective method to sieve RNA 3D models and exclude models that are incompatible with experimental SHAPE data.

Unscheduled load flow effect due to large variation in the distributed generation in a subtransmission network

NASA Astrophysics Data System (ADS)

Islam, Mujahidul

A sustainable energy delivery infrastructure implies the safe and reliable accommodation of large scale penetration of renewable sources in the power grid. In this dissertation it is assumed there will be no significant change in the power transmission and distribution structure currently in place; except in the operating strategy and regulatory policy. That is to say, with the same old structure, the path towards unveiling a high penetration of switching power converters in the power system will be challenging. Some of the dimensions of this challenge are power quality degradation, frequent false trips due to power system imbalance, and losses due to a large neutral current. The ultimate result is the reduced life of many power distribution components - transformers, switches and sophisticated loads. Numerous ancillary services are being developed and offered by the utility operators to mitigate these problems. These services will likely raise the system's operational cost, not only from the utility operators' end, but also reflected on the Independent System Operators and by the Regional Transmission Operators (RTO) due to an unforeseen backlash of frequent variation in the load-side generation or distributed generation. The North American transmission grid is an interconnected system similar to a large electrical circuit. This circuit was not planned but designed over 100 years. The natural laws of physics govern the power flow among loads and generators except where control mechanisms are installed. The control mechanism has not matured enough to withstand the high penetration of variable generators at uncontrolled distribution ends. Unlike a radial distribution system, mesh or loop networks can alleviate complex channels for real and reactive power flow. Significant variation in real power injection and absorption on the distribution side can emerge as a bias signal on the routing reactive power in some physical links or channels that are not distinguishable from the vast network. A path tracing methodology is developed to identify the power lines that are vulnerable to an unscheduled flow effect in the sub-transmission network. It is much harder to aggregate power system network sensitivity information or data from measuring load flow physically than to simulate in software. System dynamics is one of the key factors to determine an appropriate dynamic control mechanism at an optimum network location. Once a model of deterministic but variable power generator is used, the simulation can be meaningful in justifying this claim. The method used to model the variable generator is named the two-components phase distortion model. The model was validated from the high resolution data collected from three pilot photovoltaic sites in Florida - two in the city of St. Petersburg and one in the city of Tampa. The high resolution data was correlated with weather radar closest to the sites during the design stage of the model. Technically the deterministic model cannot replicate a stochastic model which is more realistically applicable for solar isolation and involves a Markov chain. The author justified the proposition based on the fact that for analysis of the response functions of different systems, the excitation function should be common for comparison. Moreover, there could be many possible simulation scenarios but fewer worst cases. Almost all commercial systems are protected against potential faults and contingencies to a certain extent. Hence, the proposed model for worst case studies was designed within a reasonable limit. The simulation includes steady state and transient mode using multiple software modules including MatlabRTM, PSCADRTM and Paladin Design BaseRTM. It is shown that by identifying vulnerable or sensitive branches in the network, the control mechanisms can be coordinated reliably. In the long run this can save money by preventing unscheduled power flow in the network and eventually stabilizing the energy market.

Balancing Power Absorption Against Structural Loads With Viscous Drag and Power-Takeoff Efficiency Considerations

DOE PAGES

Tom, Nathan; Yu, Yi-Hsiang; Wright, Alan; ...

2017-11-17

The focus of this paper is to balance power absorption against structural loading for a novel fixed-bottom oscillating surge wave energy converter in both regular and irregular wave environments. The power-to-load ratio will be evaluated using pseudospectral control (PSC) to determine the optimum power-takeoff (PTO) torque based on a multiterm objective function. This paper extends the pseudospectral optimal control problem to not just maximize the time-averaged absorbed power but also include measures for the surge-foundation force and PTO torque in the optimization. The objective function may now potentially include three competing terms that the optimizer must balance. Separate weighting factorsmore » are attached to the surge-foundation force and PTO control torque that can be used to tune the optimizer performance to emphasize either power absorption or load shedding. To correct the pitch equation of motion, derived from linear hydrodynamic theory, a quadratic-viscous-drag torque has been included in the system dynamics; however, to continue the use of quadratic programming solvers, an iteratively obtained linearized drag coefficient was utilized that provided good accuracy in the predicted pitch motion. Furthermore, the analysis considers the use of a nonideal PTO unit to more accurately evaluate controller performance. The PTO efficiency is not directly included in the objective function but rather the weighting factors are utilized to limit the PTO torque amplitudes, thereby reducing the losses resulting from the bidirectional energy flow through a nonideal PTO. Results from PSC show that shedding a portion of the available wave energy can lead to greater reductions in structural loads, peak-to-average power ratio, and reactive power requirement.« less

Development and Simulation of Increased Generation on a Secondary Circuit of a Microgrid

NASA Astrophysics Data System (ADS)

Reyes, Karina

As fossil fuels are depleted and their environmental impacts remain, other sources of energy must be considered to generate power. Renewable sources, for example, are emerging to play a major role in this regard. In parallel, electric vehicle (EV) charging is evolving as a major load demand. To meet reliability and resiliency goals demanded by the electricity market, interest in microgrids are growing as a distributed energy resource (DER). In this thesis, the effects of intermittent renewable power generation and random EV charging on secondary microgrid circuits are analyzed in the presence of a controllable battery in order to characterize and better understand the dynamics associated with intermittent power production and random load demands in the context of the microgrid paradigm. For two reasons, a secondary circuit on the University of California, Irvine (UCI) Microgrid serves as the case study. First, the secondary circuit (UC-9) is heavily loaded and an integral component of a highly characterized and metered microgrid. Second, a unique "next-generation" distributed energy resource has been deployed at the end of the circuit that integrates photovoltaic power generation, battery storage, and EV charging. In order to analyze this system and evaluate the impact of the DER on the secondary circuit, a model was developed to provide a real-time load flow analysis. The research develops a power management system applicable to similarly integrated systems. The model is verified by metered data obtained from a network of high resolution electric meters and estimated load data for the buildings that have unknown demand. An increase in voltage is observed when the amount of photovoltaic power generation is increased. To mitigate this effect, a constant power factor is set. Should the real power change dramatically, the reactive power is changed to mitigate voltage fluctuations.

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

Tom, Nathan; Yu, Yi-Hsiang; Wright, Alan

The focus of this paper is to balance power absorption against structural loading for a novel fixed-bottom oscillating surge wave energy converter in both regular and irregular wave environments. The power-to-load ratio will be evaluated using pseudospectral control (PSC) to determine the optimum power-takeoff (PTO) torque based on a multiterm objective function. This paper extends the pseudospectral optimal control problem to not just maximize the time-averaged absorbed power but also include measures for the surge-foundation force and PTO torque in the optimization. The objective function may now potentially include three competing terms that the optimizer must balance. Separate weighting factorsmore » are attached to the surge-foundation force and PTO control torque that can be used to tune the optimizer performance to emphasize either power absorption or load shedding. To correct the pitch equation of motion, derived from linear hydrodynamic theory, a quadratic-viscous-drag torque has been included in the system dynamics; however, to continue the use of quadratic programming solvers, an iteratively obtained linearized drag coefficient was utilized that provided good accuracy in the predicted pitch motion. Furthermore, the analysis considers the use of a nonideal PTO unit to more accurately evaluate controller performance. The PTO efficiency is not directly included in the objective function but rather the weighting factors are utilized to limit the PTO torque amplitudes, thereby reducing the losses resulting from the bidirectional energy flow through a nonideal PTO. Results from PSC show that shedding a portion of the available wave energy can lead to greater reductions in structural loads, peak-to-average power ratio, and reactive power requirement.« less

Gas dynamics of reactive gases in swirling-type furnace

NASA Astrophysics Data System (ADS)

Akhmetshina, A. I.; Pavlov, G. I.; Sabirzyanov, A. N.; Tikhonov, O. A.

2017-09-01

It is known from the literature that for the complete reaction of two gases (fuel and oxidizer), it is necessary to fulfill three basic conditions: the stoichiometric ratio of reactive gases, qualitative mixing and ensuring the cooling of combustion products without "quenching". Of the above-stated conditions it is more difficult to organize a qualitative mixture formation. This physical process requires additional expenditure of energy flow. In this work we present the results of experimental and theoretical studies of the gas dynamics of a reactive gas mixture in a swirling-type furnace. The design scheme of the furnace includes two reaction zones for combustible components: the first zone is the zone of generation of combustible gases which composition is constant; the second zone of the furnace - zone of a homogeneous combustion reaction.

Heat Pipe Reactor Dynamic Response Tests: SAFE-100 Reactor Core Prototype

NASA Technical Reports Server (NTRS)

Bragg-Sitton, Shannon M.

2005-01-01

The SAFE-I00a test article at the NASA Marshall Space Flight Center was used to simulate a variety of potential reactor transients; the SAFEl00a is a resistively heated, stainless-steel heat-pipe (HP)-reactor core segment, coupled to a gas-flow heat exchanger (HX). For these transients the core power was controlled by a point kinetics model with reactivity feedback based on core average temperature; the neutron generation time and the temperature feedback coefficient are provided as model inputs. This type of non-nuclear test is expected to provide reasonable approximation of reactor transient behavior because reactivity feedback is very simple in a compact fast reactor (simple, negative, and relatively monotonic temperature feedback, caused mostly by thermal expansion) and calculations show there are no significant reactivity effects associated with fluid in the HP (the worth of the entire inventory of Na in the core is .

Optimal Transmission Line Switching under Geomagnetic Disturbances

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

Lu, Mowen; Nagarajan, Harsha; Yamangil, Emre

Recently, there have been increasing concerns about how geomagnetic disturbances (GMDs) impact electrical power systems. Geomagnetically-induced currents (GICs) can saturate transformers, induce hot spot heating and increase reactive power losses. These effects can potentially cause catastrophic damage to transformers and severely impact the ability of a power system to deliver power. To address this problem, we develop a model of GIC impacts to power systems that includes 1) GIC thermal capacity of transformers as a function of normal Alternating Current (AC) and 2) reactive power losses as a function of GIC. We also use this model to derive an optimizationmore » problem that protects power systems from GIC impacts through line switching, generator dispatch, and load shedding. We then employ state-of-the-art convex relaxations of AC power flow equations to lower bound the objective. We demonstrate the approach on a modified RTS96 system and UIUC 150-bus system and show that line switching is an effective means to mitigate GIC impacts. We also provide a sensitivity analysis of decisions with respect to GMD direction.« less

Optimal Transmission Line Switching under Geomagnetic Disturbances

DOE PAGES

Lu, Mowen; Nagarajan, Harsha; Yamangil, Emre; ...

2017-10-11

Recently, there have been increasing concerns about how geomagnetic disturbances (GMDs) impact electrical power systems. Geomagnetically-induced currents (GICs) can saturate transformers, induce hot spot heating and increase reactive power losses. These effects can potentially cause catastrophic damage to transformers and severely impact the ability of a power system to deliver power. To address this problem, we develop a model of GIC impacts to power systems that includes 1) GIC thermal capacity of transformers as a function of normal Alternating Current (AC) and 2) reactive power losses as a function of GIC. We also use this model to derive an optimizationmore » problem that protects power systems from GIC impacts through line switching, generator dispatch, and load shedding. We then employ state-of-the-art convex relaxations of AC power flow equations to lower bound the objective. We demonstrate the approach on a modified RTS96 system and UIUC 150-bus system and show that line switching is an effective means to mitigate GIC impacts. We also provide a sensitivity analysis of decisions with respect to GMD direction.« less

Trends in Atmospheric Reactive Nitrogen for the Eastern United States

EPA Science Inventory

Reactive nitrogen can travel far from emission sources and impact sensitive ecosystems. From 2002-2006, policy actions have led to decreases in NO_x emissions from power plants and motor vehicles. In this study, atmospheric chemical transport modeling demonstrates tha...

Development of a three-dimensional transient code for reactivity-initiated events of BWRs (boiling water reactors) - Models and code verifications

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

Uematsu, Hitoshi; Yamamoto, Toru; Izutsu, Sadayuki

1990-06-01

A reactivity-initiated event is a design-basis accident for the safety analysis of boiling water reactors. It is defined as a rapid transient of reactor power caused by a reactivity insertion of over $1.0 due to a postulated drop or abnormal withdrawal of the control rod from the core. Strong space-dependent feedback effects are associated with the local power increase due to control rod movement. A realistic treatment of the core status in a transient by a code with a detailed core model is recommended in evaluating this event. A three-dimensional transient code, ARIES, has been developed to meet this need.more » The code simulates the event with three-dimensional neutronics, coupled with multichannel thermal hydraulics, based on a nonequilibrium separated flow model. The experimental data obtained in reactivity accident tests performed with the SPERT III-E core are used to verify the entire code, including thermal-hydraulic models.« less

77 FR 47059 - Southern Illinois Power Cooperative; Notice of Filing

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-07

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. EL12-92-000] Southern Illinois Power Cooperative; Notice of Filing Take notice that on July 30, 2012, Southern Illinois Power Cooperative filed a Proposed Revenue Requirement for reactive supply service under Midwest Independent...

The active control strategy on the output power for photovoltaic-storage systems based on extended PQ-QV-PV Node

NASA Astrophysics Data System (ADS)

Xu, Chen; Zhou, Bao-Rong; Zhai, Jian-Wei; Zhang, Yong-Jun; Yi, Ying-Qi

2017-05-01

In order to solve the problem of voltage exceeding specified limits and improve the penetration of photovoltaic in distribution network, we can make full use of the active power regulation ability of energy storage(ES) and the reactive power regulation ability of grid-connected photovoltaic inverter to provide support of active power and reactive power for distribution network. A strategy of actively controlling the output power for photovoltaic-storage system based on extended PQ-QV-PV node by analyzing the voltage regulating mechanism of point of commom coupling(PCC) of photovoltaic with energy storage(PVES) by controlling photovoltaic inverter and energy storage. The strategy set a small wave range of voltage to every photovoltaic by making the type of PCC convert among PQ, PV and QV. The simulation results indicate that the active control method can provide a better solution to the problem of voltage exceeding specified limits when photovoltaic is connectted to electric distribution network.

Non-equilibrium reaction and relaxation dynamics in a strongly interacting explicit solvent: F + CD3CN treated with a parallel multi-state EVB model

NASA Astrophysics Data System (ADS)

Glowacki, David R.; Orr-Ewing, Andrew J.; Harvey, Jeremy N.

2015-07-01

We describe a parallelized linear-scaling computational framework developed to implement arbitrarily large multi-state empirical valence bond (MS-EVB) calculations within CHARMM and TINKER. Forces are obtained using the Hellmann-Feynman relationship, giving continuous gradients, and good energy conservation. Utilizing multi-dimensional Gaussian coupling elements fit to explicitly correlated coupled cluster theory, we built a 64-state MS-EVB model designed to study the F + CD3CN → DF + CD2CN reaction in CD3CN solvent (recently reported in Dunning et al. [Science 347(6221), 530 (2015)]). This approach allows us to build a reactive potential energy surface whose balanced accuracy and efficiency considerably surpass what we could achieve otherwise. We ran molecular dynamics simulations to examine a range of observables which follow in the wake of the reactive event: energy deposition in the nascent reaction products, vibrational relaxation rates of excited DF in CD3CN solvent, equilibrium power spectra of DF in CD3CN, and time dependent spectral shifts associated with relaxation of the nascent DF. Many of our results are in good agreement with time-resolved experimental observations, providing evidence for the accuracy of our MS-EVB framework in treating both the solute and solute/solvent interactions. The simulations provide additional insight into the dynamics at sub-picosecond time scales that are difficult to resolve experimentally. In particular, the simulations show that (immediately following deuterium abstraction) the nascent DF finds itself in a non-equilibrium regime in two different respects: (1) it is highly vibrationally excited, with ˜23 kcal mol-1 localized in the stretch and (2) its post-reaction solvation environment, in which it is not yet hydrogen-bonded to CD3CN solvent molecules, is intermediate between the non-interacting gas-phase limit and the solution-phase equilibrium limit. Vibrational relaxation of the nascent DF results in a spectral blue shift, while relaxation of the post-reaction solvation environment results in a red shift. These two competing effects mean that the post-reaction relaxation profile is distinct from what is observed when Franck-Condon vibrational excitation of DF occurs within a microsolvation environment initially at equilibrium. Our conclusions, along with the theoretical and parallel software framework presented in this paper, should be more broadly applicable to a range of complex reactive systems.

Observation of a periodic runaway in the reactive Ar/O{sub 2} high power impulse magnetron sputtering discharge

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

Shayestehaminzadeh, Seyedmohammad, E-mail: ses30@hi.is, E-mail: shayesteh@mch.rwth-aachen.de; Arnalds, Unnar B.; Magnusson, Rögnvaldur L.

2015-11-15

This paper reports the observation of a periodic runaway of plasma to a higher density for the reactive discharge of the target material (Ti) with moderate sputter yield. Variable emission of secondary electrons, for the alternating transition of the target from metal mode to oxide mode, is understood to be the main reason for the runaway occurring periodically. Increasing the pulsing frequency can bring the target back to a metal (or suboxide) mode, and eliminate the periodic transition of the target. Therefore, a pulsing frequency interval is defined for the reactive Ar/O{sub 2} discharge in order to sustain the plasmamore » in a runaway-free mode without exceeding the maximum power that the magnetron can tolerate.« less

How does tunneling contribute to counterintuitive H-abstraction reactivity of nonheme Fe(IV)O oxidants with alkanes?

PubMed

Mandal, Debasish; Ramanan, Rajeev; Usharani, Dandamudi; Janardanan, Deepa; Wang, Binju; Shaik, Sason

2015-01-21

This article addresses the intriguing hydrogen-abstraction (H-abstraction) and oxygen-transfer (O-transfer) reactivity of a series of nonheme [Fe(IV)(O)(TMC)(Lax)](z+) complexes, with a tetramethyl cyclam ligand and a variable axial ligand (Lax), toward three substrates: 1,4-cyclohexadiene, 9,10-dihydroanthracene, and triphenyl phosphine. Experimentally, O-transfer-reactivity follows the relative electrophilicity of the complexes, whereas the corresponding H-abstraction-reactivity generally increases as the axial ligand becomes a better electron donor, hence exhibiting an antielectrophilic trend. Our theoretical results show that the antielectrophilic trend in H-abstraction is affected by tunneling contributions. Room-temperature tunneling increases with increase of the electron donation power of the axial-ligand, and this reverses the natural electrophilic trend, as revealed through calculations without tunneling, and leads to the observed antielectrophilic trend. By contrast, O-transfer-reactivity, not being subject to tunneling, retains an electrophilic-dependent reactivity trend, as revealed experimentally and computationally. Tunneling-corrected kinetic-isotope effect (KIE) calculations matched the experimental KIE values only if all of the H-abstraction reactions proceeded on the quintet state (S = 2) surface. As such, the present results corroborate the initially predicted two-state reactivity (TSR) scenario for these reactions. The increase of tunneling with the electron-releasing power of the axial ligand, and the reversal of the "natural" reactivity pattern, support the "tunneling control" hypothesis (Schreiner et al., ref 19). Should these predictions be corroborated, the entire field of C-H bond activation in bioinorganic chemistry would lay open to reinvestigation.

Synthesizing Virtual Oscillators to Control Islanded Inverters

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

Johnson, Brian B.; Sinha, Mohit; Ainsworth, Nathan G.

Virtual oscillator control (VOC) is a decentralized control strategy for islanded microgrids where inverters are regulated to emulate the dynamics of weakly nonlinear oscillators. Compared to droop control, which is only well defined in sinusoidal steady state, VOC is a time-domain controller that enables interconnected inverters to stabilize arbitrary initial conditions to a synchronized sinusoidal limit cycle. However, the nonlinear oscillators that are elemental to VOC cannot be designed with conventional linear-control design methods. We address this challenge by applying averaging- and perturbation-based nonlinear analysis methods to extract the sinusoidal steady-state and harmonic behavior of such oscillators. The averaged modelsmore » reveal conclusive links between real- and reactive-power outputs and the terminal-voltage dynamics. Similarly, the perturbation methods aid in quantifying higher order harmonics. The resultant models are then leveraged to formulate a design procedure for VOC such that the inverter satisfies standard ac performance specifications related to voltage regulation, frequency regulation, dynamic response, and harmonic content. Experimental results for a single-phase 750 VA, 120 V laboratory prototype demonstrate the validity of the design approach. They also demonstrate that droop laws are, in fact, embedded within the equilibria of the nonlinear-oscillator dynamics. This establishes the backward compatibility of VOC in that, while acting on time-domain waveforms, it subsumes droop control in sinusoidal steady state.« less

Proactive and Reactive Transmission Power Control for Energy-Efficient On-Body Communications

PubMed Central

Vallejo, Mónica; Recas, Joaquín.; Ayala, José L.

2015-01-01

In wireless body sensor network (WBSNs), the human body has an important effect on the performance of the communication due to the temporal variations caused and the attenuation and fluctuation of the path loss. This fact suggests that the transmission power must adapt to the current state of the link in a way that it ensures a balance between energy consumption and packet loss. In this paper, we validate our two transmission power level policies (reactive and predictive approaches) using the Castalia simulator. The integration of our experimental measurements in the simulator allows us to easily evaluate complex scenarios, avoiding the difficulties associated with a practical realization. Our results show that both schemes perform satisfactorily, providing overall energy savings of 24% and 22% for a case of study, as compared to the maximum transmission power mode. PMID:25769049

76 FR 5799 - Prairie Power, Inc.; Notice of Filing

Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-02

.... (Midwest ISO) Schedule 2, for reactive supply and voltage control service from certain of its owned... and Midwest ISO requirements for the provision of reactive supply and voltage control under Schedule 2 of the Midwest ISO Open Access Transmission, Energy, and Operating Reserve Markets Tariff, including...

77 FR 47062 - Kentucky Municipal Power Agency; Notice of Filing

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2012-08-07

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. EL12-94-000] Kentucky Municipal Power Agency; Notice of Filing Take notice that on July 30, 2012, Kentucky Municipal Power Agency filed a Proposed Revenue Requirement for reactive supply service under Midwest Independent Transmission...

77 FR 47060 - Indiana Municipal Power Agency; Notice of Filing

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2012-08-07

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. EL12-97-000] Indiana Municipal Power Agency; Notice of Filing Take notice that on July 30, 2012, Indiana Municipal Power Agency filed a Proposed Revenue Requirement for reactive supply service under Midwest Independent Transmission...

77 FR 61595 - Southern Illinois Power Cooperative; Notice of Filing

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2012-10-10

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. EL13-4-000] Southern Illinois Power Cooperative; Notice of Filing Take notice that on October 1, 2012, Southern Illinois Power Cooperative filed its Revised and Superseding Proposed Revenue Requirement for reactive supply service under...

77 FR 61596 - American Municipal Power, Inc.; Notice of Filing

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2012-10-10

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. EL13-1-000] American Municipal Power, Inc.; Notice of Filing Take notice that on October 1, 2012, American Municipal Power, Inc. filed its Revised and Superseding Proposed Revenue Requirement for reactive supply service under Midwest...

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2012-10-10

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. EL13-3-000] Kentucky Municipal Power Agency; Notice of Filing Take notice that on October 1, 2012, Kentucky Municipal Power Agency filed its Revised and Superseding Proposed Revenue Requirement for reactive supply service under...

77 FR 61594 - Prairie Power, Inc.; Notice of Filing

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2012-10-10

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. EL13-8-000] Prairie Power, Inc.; Notice of Filing Take notice that on October 1, 2012, Prairie Power, Inc. filed its Revised and Superseding Proposed Revenue Requirement for reactive supply service under Midwest Independent Transmission...

77 FR 47061 - Prairie Power, Inc.; Notice of Filing

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-07

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. EL12-90-000] Prairie Power, Inc.; Notice of Filing Take notice that on July 30, 2012, Prairie Power, Inc. filed a Proposed Revenue Requirement for reactive supply service under Midwest Independent Transmission System Operator, Inc. Tariff...

77 FR 47061 - American Municipal Power, Inc.; Notice of Filing

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2012-08-07

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. EL12-91-000] American Municipal Power, Inc.; Notice of Filing Take notice that on July 30, 2012, American Municipal Power, Inc. filed a Proposed Revenue Requirement for reactive supply service under Midwest Independent Transmission...

77 FR 61595 - Northern Illinois Municipal Power; Notice of Filing

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2012-10-10

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. EL13-5-000] Northern Illinois Municipal Power; Notice of Filing October 2, 2012. Take notice that on October 1, 2012, Northern Illinois Municipal Power filed its Revised and Superseding Proposed Revenue Requirement for reactive supply...

77 FR 61594 - Indiana Municipal Power Agency; Notice of Filing

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-10

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. EL13-7-000] Indiana Municipal Power Agency; Notice of Filing Take notice that on October 1, 2012, Indiana Municipal Power Agency filed its Revised and Superseding Proposed Revenue Requirement for reactive supply service under Midwest...

Characterization of high power impulse magnetron sputtering discharges

NASA Astrophysics Data System (ADS)

Hala, Matej

Paper I: In the first paper, we present a new approach in the characterization of the high power pulsed magnetron sputtering (HiPIMS) discharge evolution—time- and species-resolved plasma imaging—employing a set of band-pass optical interference filters suitable for the isolation of the emission originating from different species populating the plasma. We demonstrate that the introduction of such filters can be used to distinguish different phases of the discharge, and to visualize numerous plasma effects including background gas excitations during the discharge ignition, gas shock waves, and expansion of metal-rich plasmas. In particular, the application of this technique is shown on the diagnostics of the 200 µs long non-reactive HiPIMS discharges using a Cr target. Paper II: In order to gain further information about the dynamics of reactive HiPIMS discharges, both fast plasma imaging and time- and space-resolved optical emission spectroscopy (OES) are used for a systematic investigation of the 200 µs long HiPIMS pulses operated in Ar, N2 and N 2/Ar mixtures and at various pressures. It is observed that the dense metal plasma created next to the target propagates in the reactor at a speed ranging from 0.7 to 3.5 km s-1, depending on the working gas composition and the pressure. In fact, it increases with higher N 2 concentration and with lower pressure. The visible form of the propagating plasma wave changes from a hemispherical shape in Ar to a drop-like shape extending far from the target with increasing N2 concentration, owing to the significant emission from molecular N2. Interestingly, the evidence of the target self-sputtering is found for all investigated conditions, including pure N2 atmosphere. Paper III: Here, we report on the time- and species-resolved plasma imaging analysis of the dynamics of the 200 µs long HiPIMS discharges above a Cr target ignited in pure O2. It is shown that the discharge emission is dominated solely by neutral and ionized oxygen, since the monitored discharge is operated above a fully poisoned (oxidized) target from which only a minimum of Cr is sputtered. No signs of self-sputtering have been detected, in contrast to the discharges in Ar, N2 and N2/Ar mixtures previously investigated. Paper IV: In the fourth paper, we study different power management approaches in HiPIMS and MPPMS and their effects on the pulsed discharge evolution, plasma composition, and metal ionization estimated by OES. It is shown that HiPIMS is the only technique that enables the discharge operation in self-sputtering mode within the investigated range of applied powers, resulting in a significantly higher ionization of the sputtered metal than that reached with MPPMS. In contrast to HiPIMS, MPPMS provides a higher versatility in adjusting the pulse shape and pulse length. This feature can be particularly beneficial, for instance, in the discharge ignition. Nb coatings prepared by HiPIMS and MPPMS have very similar deposition rates that are lower than in DCMS. All films prepared at p = 1Pa possess a dense columnar structure. Coatings deposited by the two high power pulsed discharges exhibit higher compressive stress and larger out-of-plane lattice spacing than those prepared by DC sputtering under comparable conditions. At higher pressure, p = 2Pa, DCMS-grown films show a tensile stress due to a porous microstructure, while films prepared by HiPIMS and MPPMS are dense and in compression, most probably due to the substantial ion bombardment. Paper V: In the last paper, we analyze the behavior of the HiPIMS, MPPMS and DCMS discharges in reactive O2/Ar gas mixtures and evaluate the characteristics of the fabricated NbOx films. We demonstrate that the surface metal oxides can be effectively sputter-eroded from the target during both HiPIMS and MPPMS pulses, and that sputtering from a partially oxide-free target is possible even at high oxygen concentrations. This results in a hysteresisfree deposition process which allows one to prepare optically transparent b2O5 coatings at a high growth rate without the need of feedback control commonly used in reactive DCMS. Nb2O 5 coatings prepared by both reactive high power pulsed discharges exhibited a high index of refraction, a low extinction coefficient, a near-zero internal stress, and high hardness and Young's modulus. The HiPIMS-deposited coatings showed the highest deposition rate and the highest index of refraction. The latter observation was related to the higher film density. In comparison, MPPMS exhibited the highest power-normalized deposition rate among the three investigated deposition techniques, possibly due to the longer period that is available for the gradual target cleaning. (Abstract shortened by UMI.).

Transient Simulation of the Multi-SERTTA Experiment with MAMMOTH

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

Ortensi, Javier; Baker, Benjamin; Wang, Yaqi

This work details the MAMMOTH reactor physics simulations of the Static Environment Rodlet Transient Test Apparatus (SERTTA) conducted at Idaho National Laboratory in FY-2017. TREAT static-environment experiment vehicles are being developed to enable transient testing of Pressurized Water Reactor (PWR) type fuel specimens, including fuel concepts with enhanced accident tolerance (Accident Tolerant Fuels, ATF). The MAMMOTH simulations include point reactor kinetics as well as spatial dynamics for a temperature-limited transient. The strongly coupled multi-physics solutions of the neutron flux and temperature fields are second order accurate both in the spatial and temporal domains. MAMMOTH produces pellet stack powers that are within 1.5% of the Monte Carlo reference solutions. Some discrepancies between the MCNP model used in the design of the flux collars and the Serpent/MAMMOTH models lead to higher power and energy deposition values in Multi-SERTTA unit 1. The TREAT core results compare well with the safety case computed with point reactor kinetics in RELAP5-3D. The reactor period is 44 msec, which corresponds to a reactivity insertion of 2.685% delta k/kmore » $. The peak core power in the spatial dynamics simulation is 431 MW, which the point kinetics model over-predicts by 12%. The pulse width at half the maximum power is 0.177 sec. Subtle transient effects are apparent at the beginning insertion in the experimental samples due to the control rod removal. Additional difference due to transient effects are observed in the sample powers and enthalpy. The time dependence of the power coupling factor (PCF) is calculated for the various fuel stacks of the Multi-SERTTA vehicle. Sample temperatures in excess of 3100 K, the melting point UO$$_2$$, are computed with the adiabatic heat transfer model. The planned shaped-transient might introduce additional effects that cannot be predicted with PRK models. Future modeling will be focused on the shaped-transient by improving the control rod models in MAMMOTH and adding the BISON thermo-elastic models and thermal-fluids heat transfer.« less

Reactive astrocytes and therapeutic potential in focal ischemic stroke

PubMed Central

Choudhury, Gourav Roy; Ding, Shinghua

2015-01-01

Astrocytes are specialized and the most abundant cell type in the central nervous system (CNS). They play important roles in the physiology of the brain. Astrocytes are also critically involved in many CNS disorders including focal ischemic stroke, the leading cause of brain injury and death in patients. One of the prominent pathological features of a focal ischemic stroke is reactive astrogliosis and glial scar formation. Reactive astrogliosis is accompanied with changes in morphology, proliferation and gene expression in the reactive astrocytes. This study provides an overview of the most recent advances in astrocytic Ca2+ signaling, spatial and temporal dynamics of the morphology and proliferation of reactive astrocytes as well as signaling pathways involved in the reactive astrogliosis after ischemic stroke based on results from experimental studies performed in various animal models. This review also discusses the therapeutic potential of reactive astrocytes in a focal ischemic stroke. As reactive astrocytes exhibit high plasticity, we suggest that modulation of local reactive astrocytes is a promising strategy for cell-based stroke therapy. PMID:25982835

A multipath routing protocol based on clustering and ant colony optimization for wireless sensor networks.

PubMed

Yang, Jing; Xu, Mai; Zhao, Wei; Xu, Baoguo

2010-01-01

For monitoring burst events in a kind of reactive wireless sensor networks (WSNs), a multipath routing protocol (MRP) based on dynamic clustering and ant colony optimization (ACO) is proposed. Such an approach can maximize the network lifetime and reduce the energy consumption. An important attribute of WSNs is their limited power supply, and therefore some metrics (such as energy consumption of communication among nodes, residual energy, path length) were considered as very important criteria while designing routing in the MRP. Firstly, a cluster head (CH) is selected among nodes located in the event area according to some parameters, such as residual energy. Secondly, an improved ACO algorithm is applied in the search for multiple paths between the CH and sink node. Finally, the CH dynamically chooses a route to transmit data with a probability that depends on many path metrics, such as energy consumption. The simulation results show that MRP can prolong the network lifetime, as well as balance of energy consumption among nodes and reduce the average energy consumption effectively.

Recent Advances and Applications in Synchrotron X-Ray Protein Footprinting for Protein Structure and Dynamics Elucidation.

PubMed

Gupta, Sayan; Feng, Jun; Chance, Mark; Ralston, Corie

2016-01-01

Synchrotron X-ray Footprinting is a powerful in situ hydroxyl radical labeling method for analysis of protein structure, interactions, folding and conformation change in solution. In this method, water is ionized by high flux density broad band synchrotron X-rays to produce a steady-state concentration of hydroxyl radicals, which then react with solvent accessible side-chains. The resulting stable modification products are analyzed by liquid chromatography coupled to mass spectrometry. A comparative reactivity rate between known and unknown states of a protein provides local as well as global information on structural changes, which is then used to develop structural models for protein function and dynamics. In this review we describe the XF-MS method, its unique capabilities and its recent technical advances at the Advanced Light Source. We provide a comparison of other hydroxyl radical and mass spectrometry based methods with XFMS. We also discuss some of the latest developments in its usage for studying bound water, transmembrane proteins and photosynthetic protein components, and the synergy of the method with other synchrotron based structural biology methods.

Force Field Accelerated Density Functional Theory Molecular Dynamics for Simulation of Reactive Systems at Extreme Conditions

NASA Astrophysics Data System (ADS)

Lindsey, Rebecca; Goldman, Nir; Fried, Laurence

2017-06-01

Atomistic modeling of chemistry at extreme conditions remains a challenge, despite continuing advances in computing resources and simulation tools. While first principles methods provide a powerful predictive tool, the time and length scales associated with chemistry at extreme conditions (ns and μm, respectively) largely preclude extension of such models to molecular dynamics. In this work, we develop a simulation approach that retains the accuracy of density functional theory (DFT) while decreasing computational effort by several orders of magnitude. We generate n-body descriptions for atomic interactions by mapping forces arising from short density functional theory (DFT) trajectories on to simple Chebyshev polynomial series. We examine the importance of including greater than 2-body interactions, model transferability to different state points, and discuss approaches to ensure smooth and reasonable model shape outside of the distance domain sampled by the DFT training set. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Demonstration of Essential Reliability Services by a 300-MW Solar Photovoltaic Power Plant

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

Loutan, Clyde; Klauer, Peter; Chowdhury, Sirajul

The California Independent System Operator (CAISO), First Solar, and the National Renewable Energy Laboratory (NREL) conducted a demonstration project on a large utility-scale photovoltaic (PV) power plant in California to test its ability to provide essential ancillary services to the electric grid. With increasing shares of solar- and wind-generated energy on the electric grid, traditional generation resources equipped with automatic governor control (AGC) and automatic voltage regulation controls -- specifically, fossil thermal -- are being displaced. The deployment of utility-scale, grid-friendly PV power plants that incorporate advanced capabilities to support grid stability and reliability is essential for the large-scale integrationmore » of PV generation into the electric power grid, among other technical requirements. A typical PV power plant consists of multiple power electronic inverters and can contribute to grid stability and reliability through sophisticated 'grid-friendly' controls. In this way, PV power plants can be used to mitigate the impact of variability on the grid, a role typically reserved for conventional generators. In August 2016, testing was completed on First Solar's 300-MW PV power plant, and a large amount of test data was produced and analyzed that demonstrates the ability of PV power plants to use grid-friendly controls to provide essential reliability services. These data showed how the development of advanced power controls can enable PV to become a provider of a wide range of grid services, including spinning reserves, load following, voltage support, ramping, frequency response, variability smoothing, and frequency regulation to power quality. Specifically, the tests conducted included various forms of active power control such as AGC and frequency regulation; droop response; and reactive power, voltage, and power factor controls. This project demonstrated that advanced power electronics and solar generation can be controlled to contribute to system-wide reliability. It was shown that the First Solar plant can provide essential reliability services related to different forms of active and reactive power controls, including plant participation in AGC, primary frequency control, ramp rate control, and voltage regulation. For AGC participation in particular, by comparing the PV plant testing results to the typical performance of individual conventional technologies, we showed that regulation accuracy by the PV plant is 24-30 points better than fast gas turbine technologies. The plant's ability to provide volt-ampere reactive control during periods of extremely low power generation was demonstrated as well. The project team developed a pioneering demonstration concept and test plan to show how various types of active and reactive power controls can leverage PV generation's value from being a simple variable energy resource to a resource that provides a wide range of ancillary services. With this project's approach to a holistic demonstration on an actual, large, utility-scale, operational PV power plant and dissemination of the obtained results, the team sought to close some gaps in perspectives that exist among various stakeholders in California and nationwide by providing real test data.« less

Prediction of the Chapman-Jouguet chemical equilibrium state in a detonation wave from first principles based reactive molecular dynamics.

PubMed

Guo, Dezhou; Zybin, Sergey V; An, Qi; Goddard, William A; Huang, Fenglei

2016-01-21

The combustion or detonation of reacting materials at high temperature and pressure can be characterized by the Chapman-Jouguet (CJ) state that describes the chemical equilibrium of the products at the end of the reaction zone of the detonation wave for sustained detonation. This provides the critical properties and product kinetics for input to macroscale continuum simulations of energetic materials. We propose the ReaxFF Reactive Dynamics to CJ point protocol (Rx2CJ) for predicting the CJ state parameters, providing the means to predict the performance of new materials prior to synthesis and characterization, allowing the simulation based design to be done in silico. Our Rx2CJ method is based on atomistic reactive molecular dynamics (RMD) using the QM-derived ReaxFF force field. We validate this method here by predicting the CJ point and detonation products for three typical energetic materials. We find good agreement between the predicted and experimental detonation velocities, indicating that this method can reliably predict the CJ state using modest levels of computation.

Computational Study of Nonadiabatic Effects in Atom-Molecule Reactive Scattering.

DTIC Science & Technology

1982-11-15

a similar interpretation to those in Fig. 4-a, with the rotational effects most evident in the reactant tube (due to the mixing of the two open rotor ...AD-A125 135 COMPUTATIONAL STUDY OF NONRDIABATIC EFFECTS IN 1/2 ATOM-MOLECULE REACTIVE SCATTERING(U) CHEMICAL DYNAMICS CORP COLUMBUS OH B C GARRETT...COMPUTATIONAL STUDY OF NONADIABATIC EFFECTS [ Z IN ATOM-MOLECULE REACTIVE SCATTERING C:) TO AIR FORCE OFFICE OF SCIENTIFIC RESEARCHk CONTRACT NO. F49620-81

Design of specially adapted reactive coordinates to economically compute potential and kinetic energy operators including geometry relaxation

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

Thallmair, Sebastian; Lehrstuhl für BioMolekulare Optik, Ludwig-Maximilians-Universität München, D-80538 München; Roos, Matthias K.

Quantum dynamics simulations require prior knowledge of the potential energy surface as well as the kinetic energy operator. Typically, they are evaluated in a low-dimensional subspace of the full configuration space of the molecule as its dimensionality increases proportional to the number of atoms. This entails the challenge to find the most suitable subspace. We present an approach to design specially adapted reactive coordinates spanning this subspace. In addition to the essential geometric changes, these coordinates take into account the relaxation of the non-reactive coordinates without the necessity of performing geometry optimizations at each grid point. The method is demonstratedmore » for an ultrafast photoinduced bond cleavage in a commonly used organic precursor for the generation of electrophiles. The potential energy surfaces for the reaction as well as the Wilson G-matrix as part of the kinetic energy operator are shown for a complex chemical reaction, both including the relaxation of the non-reactive coordinates on equal footing. A microscopic interpretation of the shape of the G-matrix elements allows to analyze the impact of the non-reactive coordinates on the kinetic energy operator. Additionally, we compare quantum dynamics simulations with and without the relaxation of the non-reactive coordinates included in the kinetic energy operator to demonstrate its influence.« less

Cellular homeostasis in fungi: impact on the aging process.

PubMed

Scheckhuber, Christian Q; Hamann, Andrea; Brust, Diana; Osiewacz, Heinz D

2012-01-01

Cellular quality control pathways are needed for maintaining the biological function of organisms. If these pathways become compromised, the results are usually highly detrimental. Functional impairments of cell components can lead to diseases and in extreme cases to organismal death. Dysfunction of cells can be induced by a number of toxic by-products that are formed during metabolic activity, like reactive oxygen and nitrogen species, for example. A key source of reactive oxygen species (ROS) are the organelles of oxidative phosphorylation, mitochondria. Therefore mitochondrial function is also directly affected by ROS, especially if there is a compromised ROS-scavenging capacity. Biological systems therefore depend on several lines of defence to counteract the toxic effects of ROS and other damaging agents. The first level is active at the molecular level and consists of various proteases that bind and degrade abnormally modified and / or aggregated mitochondrial proteins. The second level is concerned with maintaining the quality of whole mitochondria. Among the pathways of this level are mitochondrial dynamics and autophagy (mitophagy). Mitochondrial dynamics describes the time-dependent fusion and fission of mitochondria. It is argued that this kind of organellar dynamics has the power to restore the function of impaired organelles by content mixing with intact organelles. If the first and second lines of defence against damage fail and mitochondria become damaged too severely, there is the option to remove affected cells before they can elicit more damage to their surrounding environment by apoptosis. This form of programmed cell death is strictly regulated by a complex network of interacting components and can be divided into mitochondria-dependent and mitochondria-independent modes of action. In this review we give an overview on various biological quality control systems in fungi (yeasts and filamentous fungi) with an emphasis on autophagy (mitophagy) and apoptosis and how these pathways allow fungal organisms to maintain a balanced cellular homeostasis.

78 FR 34370 - East Kentucky Power Cooperative, Inc.; Notice of Filing

Federal Register 2010, 2011, 2012, 2013, 2014

2013-06-07

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket Nos. EL13-68-000] East Kentucky Power Cooperative, Inc.; Notice of Filing Take notice that on May 30, 2013, East Kentucky Power Cooperative, Inc. filed its proposed revenue requirements for reactive supply and voltage control from...

78 FR 78347 - Combined Notice of Filings #1

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-26

..., 2013 Triennial Market Power Analysis of SGOC Southwest MBR Sellers for the Southwest Region. Filed Date... Numbers: ER14-630-000. Applicants: AlphaGen Power LLC. Description: Market-based rate application to be... Notice of succession-- Reactive Power Tariff to be effective 3/1/2014. Filed Date: 12/16/13. Accession...

76 FR 21722 - Combined Notice of Filings #1

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-18

... Notice of Cancellation of Reactive Power Rate Schedule. Filed Date: 04/07/2011. Accession Number...)(2)(iii): Revisions to the Tariff and OA re Emerg. Load Response Program ``Reporting'' to be... Reactive Rate Schedule Notice of Succession to be effective 3/9/2011. Filed Date: 04/07/2011. Accession...

Remediation of Explosives Contaminated Groundwater With Zero-Valent Iron

DTIC Science & Technology

2011-10-01

1947. Howson, P.E., Mackenzie, P.D. and Horney, D.P., 1996. Enhanced reactive metal wall for dehalogenation of hydrocarbons. Tertiary Enhanced...reactive metal wall for dehalogenation of hydrocarbons, United States. Hundal, L.S., Singh, J., Bier, E.L., Shea, P.J., Comfort, S.D. and Power, W.L

76 FR 72203 - Voltage Coordination on High Voltage Grids; Notice of Reliability Workshop Agenda

Federal Register 2010, 2011, 2012, 2013, 2014

2011-11-22

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. AD12-5-000] Voltage... currently coordinate the dispatch of reactive resources to support forecasted loads, generation and... reactive power needs of the distribution system or loads are coordinated or optimized. Panelists: Khaled...

Influence of reactive gas admixture on transition metal cluster nucleation in a gas aggregation cluster source

NASA Astrophysics Data System (ADS)

Peter, Tilo; Polonskyi, Oleksandr; Gojdka, Björn; Mohammad Ahadi, Amir; Strunskus, Thomas; Zaporojtchenko, Vladimir; Biederman, Hynek; Faupel, Franz

2012-12-01

We quantitatively assessed the influence of reactive gases on the formation processes of transition metal clusters in a gas aggregation cluster source. A cluster source based on a 2 in. magnetron is used to study the production rate of titanium and cobalt clusters. Argon served as working gas for the DC magnetron discharge, and a small amount of reactive gas (oxygen and nitrogen) is added to promote reactive cluster formation. We found that the cluster production rate depends strongly on the reactive gas concentration for very small amounts of reactive gas (less than 0.1% of total working gas), and no cluster formation takes place in the absence of reactive species. The influence of discharge power, reactive gas concentration, and working gas pressure are investigated using a quartz micro balance in a time resolved manner. The strong influence of reactive gas is explained by a more efficient formation of nucleation seeds for metal-oxide or nitride than for pure metal.

The Reactivation of Motion influences Size Categorization in a Visuo-Haptic Illusion.

PubMed

Rey, Amandine E; Dabic, Stephanie; Versace, Remy; Navarro, Jordan

2016-09-01

People simulate themselves moving when they view a picture, read a sentence, or simulate a situation that involves motion. The simulation of motion has often been studied in conceptual tasks such as language comprehension. However, most of these studies investigated the direct influence of motion simulation on tasks inducing motion. This article investigates whether a mo- tion induced by the reactivation of a dynamic picture can influence a task that did not require motion processing. In a first phase, a dynamic picture and a static picture were systematically presented with a vibrotactile stimulus (high or low frequency). The second phase of the experiment used a priming paradigm in which a vibrotactile stimulus was presented alone and followed by pictures of objects. Participants had to categorize objects as large or small relative to their typical size (simulated size). Results showed that when the target object was preceded by the vibrotactile stimulus previously associated with the dynamic picture, participants perceived all the objects as larger and categorized them more quickly when the objects were typically "large" and more slowly when the objects were typically "small." In light of embodied cognition theories, this bias in participants' perception is assumed to be caused by an induced forward motion. generated by the reactivated dynamic picture, which affects simulation of the size of the objects.

The combination of plyometric and balance training improves sprint and shuttle run performances more often than plyometric-only training with children.

PubMed

Chaouachi, Anis; Othman, Aymen Ben; Hammami, Raouf; Drinkwater, Eric J; Behm, David G

2014-02-01

Because balance is not fully developed in children and studies have shown functional improvements with balance only training studies, a combination of plyometric and balance activities might enhance static balance, dynamic balance, and power. The objective of this study was to compare the effectiveness of plyometric only (PLYO) with balance and plyometric (COMBINED) training on balance and power measures in children. Before and after an 8-week training period, testing assessed lower-body strength (1 repetition maximum leg press), power (horizontal and vertical jumps, triple hop for distance, reactive strength, and leg stiffness), running speed (10-m and 30-m sprint), static and dynamic balance (Standing Stork Test and Star Excursion Balance Test), and agility (shuttle run). Subjects were randomly divided into 2 training groups (PLYO [n = 14] and COMBINED [n = 14]) and a control group (n = 12). Results based on magnitude-based inferences and precision of estimation indicated that the COMBINED training group was considered likely to be superior to the PLYO group in leg stiffness (d = 0.69, 91% likely), 10-m sprint (d = 0.57, 84% likely), and shuttle run (d = 0.52, 80% likely). The difference between the groups was unclear in 8 of the 11 dependent variables. COMBINED training enhanced activities such as 10-m sprints and shuttle runs to a greater degree. COMBINED training could be an important consideration for reducing the high velocity impacts of PLYO training. This reduction in stretch-shortening cycle stress on neuromuscular system with the replacement of balance and landing exercises might help to alleviate the overtraining effects of excessive repetitive high load activities.

Enhancing the potential of enantioselective organocatalysis with light

NASA Astrophysics Data System (ADS)

Silvi, Mattia; Melchiorre, Paolo

2018-02-01

Organocatalysis—catalysis mediated by small chiral organic molecules—is a powerful technology for enantioselective synthesis, and has extensive applications in traditional ionic, two-electron-pair reactivity domains. Recently, organocatalysis has been successfully combined with photochemical reactivity to unlock previously inaccessible reaction pathways, thereby creating new synthetic opportunities. Here we describe the historical context, scientific reasoning and landmark discoveries that were essential in expanding the functions of organocatalysis to include one-electron-mediated chemistry and excited-state reactivity.

Dynamic analysis of gas-core reactor system

NASA Technical Reports Server (NTRS)

Turner, K. H., Jr.

1973-01-01

A heat transfer analysis was incorporated into a previously developed model CODYN to obtain a model of open-cycle gaseous core reactor dynamics which can predict the heat flux at the cavity wall. The resulting model was used to study the sensitivity of the model to the value of the reactivity coefficients and to determine the system response for twenty specified perturbations. In addition, the model was used to study the effectiveness of several control systems in controlling the reactor. It was concluded that control drums located in the moderator region capable of inserting reactivity quickly provided the best control.

Impact of Reactor Operating Parameters on Cask Reactivity in BWR Burnup Credit

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

Ilas, Germina; Betzler, Benjamin R; Ade, Brian J

This paper discusses the effect of reactor operating parameters used in fuel depletion calculations on spent fuel cask reactivity, with relevance for boiling-water reactor (BWR) burnup credit (BUC) applications. Assessments that used generic BWR fuel assembly and spent fuel cask configurations are presented. The considered operating parameters, which were independently varied in the depletion simulations for the assembly, included fuel temperature, bypass water density, specific power, and operating history. Different operating history scenarios were considered for the assembly depletion to determine the effect of relative power distribution during the irradiation cycles, as well as the downtime between cycles. Depletion, decay,more » and criticality simulations were performed using computer codes and associated nuclear data within the SCALE code system. Results quantifying the dependence of cask reactivity on the assembly depletion parameters are presented herein.« less

Optimization of the HyPer sensor for robust real-time detection of hydrogen peroxide in the rice blast fungus.

PubMed

Huang, Kun; Caplan, Jeff; Sweigard, James A; Czymmek, Kirk J; Donofrio, Nicole M

2017-02-01

Reactive oxygen species (ROS) production and breakdown have been studied in detail in plant-pathogenic fungi, including the rice blast fungus, Magnaporthe oryzae; however, the examination of the dynamic process of ROS production in real time has proven to be challenging. We resynthesized an existing ROS sensor, called HyPer, to exhibit optimized codon bias for fungi, specifically Neurospora crassa, and used a combination of microscopy and plate reader assays to determine whether this construct could detect changes in fungal ROS during the plant infection process. Using confocal microscopy, we were able to visualize fluctuating ROS levels during the formation of an appressorium on an artificial hydrophobic surface, as well as during infection on host leaves. Using the plate reader, we were able to ascertain measurements of hydrogen peroxide (H 2 O 2 ) levels in conidia as detected by the MoHyPer sensor. Overall, by the optimization of codon usage for N. crassa and related fungal genomes, the MoHyPer sensor can be used as a robust, dynamic and powerful tool to both monitor and quantify H 2 O 2 dynamics in real time during important stages of the plant infection process. © 2016 BSPP AND JOHN WILEY & SONS LTD.

First passage Brownian functional properties of snowmelt dynamics

NASA Astrophysics Data System (ADS)

Dubey, Ashutosh; Bandyopadhyay, Malay

2018-04-01

In this paper, we model snow-melt dynamics in terms of a Brownian motion (BM) with purely time dependent drift and difusion and examine its first passage properties by suggesting and examining several Brownian functionals which characterize the lifetime and reactivity of such stochastic processes. We introduce several probability distribution functions (PDFs) associated with such time dependent BMs. For instance, for a BM with initial starting point x0, we derive analytical expressions for : (i) the PDF P(tf|x0) of the first passage time tf which specify the lifetime of such stochastic process, (ii) the PDF P(A|x0) of the area A till the first passage time and it provides us numerous valuable information about the total fresh water availability during melting, (iii) the PDF P(M) associated with the maximum size M of the BM process before the first passage time, and (iv) the joint PDF P(M; tm) of the maximum size M and its occurrence time tm before the first passage time. These P(M) and P(M; tm) are useful in determining the time of maximum fresh water availability and in calculating the total maximum amount of available fresh water. These PDFs are examined for the power law time dependent drift and diffusion which matches quite well with the available data of snowmelt dynamics.

Event-related delta, theta, alpha and gamma correlates to auditory oddball processing during Vipassana meditation

PubMed Central

Delorme, Arnaud; Polich, John

2013-01-01

Long-term Vipassana meditators sat in meditation vs. a control (instructed mind wandering) states for 25 min, electroencephalography (EEG) was recorded and condition order counterbalanced. For the last 4 min, a three-stimulus auditory oddball series was presented during both meditation and control periods through headphones and no task imposed. Time-frequency analysis demonstrated that meditation relative to the control condition evinced decreased evoked delta (2–4 Hz) power to distracter stimuli concomitantly with a greater event-related reduction of late (500–900 ms) alpha-1 (8–10 Hz) activity, which indexed altered dynamics of attentional engagement to distracters. Additionally, standard stimuli were associated with increased early event-related alpha phase synchrony (inter-trial coherence) and evoked theta (4–8 Hz) phase synchrony, suggesting enhanced processing of the habituated standard background stimuli. Finally, during meditation, there was a greater differential early-evoked gamma power to the different stimulus classes. Correlation analysis indicated that this effect stemmed from a meditation state-related increase in early distracter-evoked gamma power and phase synchrony specific to longer-term expert practitioners. The findings suggest that Vipassana meditation evokes a brain state of enhanced perceptual clarity and decreased automated reactivity. PMID:22648958

Application of Static Var Compensator (SVC) With PI Controller for Grid Integration of Wind Farm Using Harmony Search

NASA Astrophysics Data System (ADS)

Keshta, H. E.; Ali, A. A.; Saied, E. M.; Bendary, F. M.

2016-10-01

Large-scale integration of wind turbine generators (WTGs) may have significant impacts on power system operation with respect to system frequency and bus voltages. This paper studies the effect of Static Var Compensator (SVC) connected to wind energy conversion system (WECS) on voltage profile and the power generated from the induction generator (IG) in wind farm. Also paper presents, a dynamic reactive power compensation using Static Var Compensator (SVC) at the a point of interconnection of wind farm while static compensation (Fixed Capacitor Bank) is unable to prevent voltage collapse. Moreover, this paper shows that using advanced optimization techniques based on artificial intelligence (AI) such as Harmony Search Algorithm (HS) and Self-Adaptive Global Harmony Search Algorithm (SGHS) instead of a Conventional Control Method to tune the parameters of PI controller for SVC and pitch angle. Also paper illustrates that the performance of the system with controllers based on AI is improved under different operating conditions. MATLAB/Simulink based simulation is utilized to demonstrate the application of SVC in wind farm integration. It is also carried out to investigate the enhancement in performance of the WECS achieved with a PI Controller tuned by Harmony Search Algorithm as compared to a Conventional Control Method.

Preparation of TiN films by reactive high-power pulsed sputtering Penning discharges

NASA Astrophysics Data System (ADS)

Kimura, Takashi; Yoshida, Ryo; Mishima, Toshihiko; Azuma, Kingo; Nakao, Setsuo

2018-06-01

Titanium nitride (TiN) films are prepared by reactive high-power pulsed sputtering Penning discharges at a total pressure of 0.7 Pa and an average power of 60 W, where the nitrogen fraction is varied up to 15%. The peak value of the instantaneous power ranges between 3 and 14 kW, and the peak power density ranges between 0.3 and 1.2 kW cm‑2. The hardness of TiN films is higher than 22 GPa at the nitrogen fractions lower than 10% and it reaches 31 GPa at a nitrogen fraction of 5%. The X-ray diffraction peak of TiN(111) texture is observed for all prepared films, showing the grain size of about 10 nm. In X-ray photoelectron spectroscopy, oxygen is mainly bonded to titanium, but the intensity of the TiN bond is dominant in the entire Ti 2p spectrum. The intensity ratio of N 1s to Ti 2p ranges between 0.85 and 0.95.

Cross-layer protocols optimized for real-time multimedia services in energy-constrained mobile ad hoc networks

NASA Astrophysics Data System (ADS)

Hortos, William S.

2003-07-01

Mobile ad hoc networking (MANET) supports self-organizing, mobile infrastructures and enables an autonomous network of mobile nodes that can operate without a wired backbone. Ad hoc networks are characterized by multihop, wireless connectivity via packet radios and by the need for efficient dynamic protocols. All routers are mobile and can establish connectivity with other nodes only when they are within transmission range. Importantly, ad hoc wireless nodes are resource-constrained, having limited processing, memory, and battery capacity. Delivery of high quality-ofservice (QoS), real-time multimedia services from Internet-based applications over a MANET is a challenge not yet achieved by proposed Internet Engineering Task Force (IETF) ad hoc network protocols in terms of standard performance metrics such as end-to-end throughput, packet error rate, and delay. In the distributed operations of route discovery and maintenance, strong interaction occurs across MANET protocol layers, in particular, the physical, media access control (MAC), network, and application layers. The QoS requirements are specified for the service classes by the application layer. The cross-layer design must also satisfy the battery-limited energy constraints, by minimizing the distributed power consumption at the nodes and of selected routes. Interactions across the layers are modeled in terms of the set of concatenated design parameters including associated energy costs. Functional dependencies of the QoS metrics are described in terms of the concatenated control parameters. New cross-layer designs are sought that optimize layer interdependencies to achieve the "best" QoS available in an energy-constrained, time-varying network. The protocol design, based on a reactive MANET protocol, adapts the provisioned QoS to dynamic network conditions and residual energy capacities. The cross-layer optimization is based on stochastic dynamic programming conditions derived from time-dependent models of MANET packet flows. Regulation of network behavior is modeled by the optimal control of the conditional rates of multivariate point processes (MVPPs); these rates depend on the concatenated control parameters through a change of probability measure. The MVPP models capture behavior of many service applications, e.g., voice, video and the self-similar behavior of Internet data sessions. Performance verification of the cross-layer protocols, derived from the dynamic programming conditions, can be achieved by embedding the conditions in a reactive routing protocol for MANETs, in a simulation environment, such as the wireless extension of ns-2. A canonical MANET scenario consists of a distributed collection of battery-powered laptops or hand-held terminals, capable of hosting multimedia applications. Simulation details and performance tradeoffs, not presented, remain for a sequel to the paper.

Mitigation of Power Quality Problems in Grid-Interactive Distributed Generation System

NASA Astrophysics Data System (ADS)

Bhende, C. N.; Kalam, A.; Malla, S. G.

2016-04-01

Having an inter-tie between low/medium voltage grid and distributed generation (DG), both exposes to power quality (PQ) problems created by each other. This paper addresses various PQ problems arise due to integration of DG with grid. The major PQ problems are due to unbalanced and non-linear load connected at DG, unbalanced voltage variations on transmission line and unbalanced grid voltages which severely affect the performance of the system. To mitigate the above mentioned PQ problems, a novel integrated control of distribution static shunt compensator (DSTATCOM) is presented in this paper. DSTATCOM control helps in reducing the unbalance factor of PCC voltage. It also eliminates harmonics from line currents and makes them balanced. Moreover, DSTATCOM supplies the reactive power required by the load locally and hence, grid need not to supply the reactive power. To show the efficacy of the proposed controller, several operating conditions are considered and verified through simulation using MATLAB/SIMULINK.

Dynamic Radioisotope Power System Development for Space Explorations

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

Qualls, A L

Dynamic power conversion offers the potential to produce radioisotope power systems (RPS) that generate higher power outputs and utilize the Pu-238 radioisotope more efficiently than Radioisotope Thermoelectric Generators (RTG). Additionally, dynamic systems also offer the potential of producing generators with significantly reduced power degradation over the course of deep space missions so that more power will be available at the end of the mission when it is needed for both powering the science and transmitting the results. The development of dynamic generators involves addressing technical issues not typically associated with traditional thermoelectric generators. Developing long-life, robust and reliable dynamic conversionmore » technology is challenging yet essential to building a suitable generator. Considerations include working within existing handling infrastructure where possible so that development costs can be kept low and integrating dynamic generators into spacecraft, which may be more complex than integration of static systems. Methods of interfacing to and controlling a dynamic generator must be considered and new potential failure modes must be taken into account. This paper will address some of the key issues of dynamic RPS design, development and adaption.Dynamic power conversion offers the potential to produce Radioisotope Power Systems (RPS) that generate higher power outputs and utilize the available heat source plutonium fuel more efficiently than Radioisotope Thermoelectric Generators. Additionally, dynamic systems offer the potential of producing generators with significantly reduced power degradation over the course of deep space missions so that more power would be available at the end of the mission, when it is needed most for both powering science instruments and transmitting the resulting data. The development of dynamic generators involves addressing technical issues not typically associated with traditional thermoelectric generators. Developing long-life, robust, and reliable dynamic conversion technology is challenging yet essential to building a suitable flight-ready generator. Considerations include working within existing hardware-handling infrastructure, where possible, so that development costs can be kept low, and integrating dynamic generators into spacecraft, which may be more complex than integration of static thermoelectric systems. Methods of interfacing to and controlling a dynamic generator must also be considered, and new potential failure modes must be taken into account. This paper will address some of the key issues of dynamic RPS design, development, and adaption.« less

A structurally driven analysis of thiol reactivity in mammalian albumins.

PubMed

Spiga, Ottavia; Summa, Domenico; Cirri, Simone; Bernini, Andrea; Venditti, Vincenzo; De Chiara, Matteo; Priora, Raffaella; Frosali, Simona; Margaritis, Antonios; Di Giuseppe, Danila; Di Simplicio, Paolo; Niccolai, Neri

2011-04-01

Understanding the structural basis of protein redox activity is still an open question. Hence, by using a structural genomics approach, different albumins have been chosen to correlate protein structural features with the corresponding reaction rates of thiol exchange between albumin and disulfide DTNB. Predicted structures of rat, porcine, and bovine albumins have been compared with the experimentally derived human albumin. High structural similarity among these four albumins can be observed, in spite of their markedly different reactivity with DTNB. Sequence alignments offered preliminary hints on the contributions of sequence-specific local environments modulating albumin reactivity. Molecular dynamics simulations performed on experimental and predicted albumin structures reveal that thiolation rates are influenced by hydrogen bonding pattern and stability of the acceptor C34 sulphur atom with donor groups of nearby residues. Atom depth evolution of albumin C34 thiol groups has been monitored during Molecular Dynamic trajectories. The most reactive albumins appeared also the ones presenting the C34 sulphur atom on the protein surface with the highest accessibility. High C34 sulphur atom reactivity in rat and porcine albumins seems to be determined by the presence of additional positively charged amino acid residues favoring both the C34 S⁻ form and the approach of DTNB. Copyright © 2011 Wiley Periodicals, Inc.

Evaporation-assisted high-power impulse magnetron sputtering: The deposition of tungsten oxide as a case study

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

Hemberg, Axel; Dauchot, Jean-Pierre; Snyders, Rony

2012-07-15

The deposition rate during the synthesis of tungsten trioxide thin films by reactive high-power impulse magnetron sputtering (HiPIMS) of a tungsten target increases, above the dc threshold, as a result of the appropriate combination of the target voltage, the pulse duration, and the amount of oxygen in the reactive atmosphere. This behavior is likely to be caused by the evaporation of the low melting point tungsten trioxide layer covering the metallic target in such working conditions. The HiPIMS process is therefore assisted by thermal evaporation of the target material.

Spinning reserve in Puerto Rico doesn`t spin. It`s a battery

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

Taylor, P.; Torres, W.; Akhil, A.

1995-04-01

A battery energy-storage facility is described which provides Puerto Rico Electric Power Authority 20 MW and 14.1 MWh for frequency control and instantaneous spinning reserve. A self-commuted power-conditioning system also enables black starts and provides reactive power for voltage control on transmission lines. 7 figs.

Highlighting the harmonic regime generated by electric locomotives equipped with DC motors

NASA Astrophysics Data System (ADS)

Baciu, I.; Cunţan, C. D.

2018-01-01

The paper presents the results of measurements made using the C.A. 8334 power quality analyzer on an electric locomotive equipped with DC motors. We carried out determinations of the current-voltage regime using a locomotive motor. The harmonic regime of the other motors being identical to the analysed one, we could easily deduce the effects caused by the entire locomotive. The data measured with the analyzer were firstly transferred into a computer system using the Qualistar software, followed by data processing in Excel, enabling therefore a graphical representation of the characteristic parameters of power quality. Based on the acquired data, we determined the power factor, as well as the active, reactive and apparent power. The measurements revealed high values of the current harmonics, fact that required some measures to be taken for reducing the values of these harmonics. For this, we ran a simulation using the PSCAD/EMTDC software, by introducing LC filters in tune with the harmonic frequencies. The result was a significant reduction in the harmonic regime, either in the harmonics values or the power factor and reactive power.

Enhanced power quality based single phase photovoltaic distributed generation system

NASA Astrophysics Data System (ADS)

Panda, Aurobinda; Pathak, M. K.; Srivastava, S. P.

2016-08-01

This article presents a novel control strategy for a 1-ϕ 2-level grid-tie photovoltaic (PV) inverter to enhance the power quality (PQ) of a PV distributed generation (PVDG) system. The objective is to obtain the maximum benefits from the grid-tie PV inverter by introducing current harmonics as well as reactive power compensation schemes in its control strategy, thereby controlling the PV inverter to achieve multiple functions in the PVDG system such as: (1) active power flow control between the PV inverter and the grid, (2) reactive power compensation, and (3) grid current harmonics compensation. A PQ enhancement controller (PQEC) has been designed to achieve the aforementioned objectives. The issue of underutilisation of the PV inverter in nighttime has also been addressed in this article and for the optimal use of the system; the PV inverter is used as a shunt active power filter in nighttime. A prototype model of the proposed system is developed in the laboratory, to validate the effectiveness of the control scheme, and is tested with the help of the dSPACE DS1104 platform.

A novel control strategy for enhancing the LVRT and voltage support capabilities of DFIG

NASA Astrophysics Data System (ADS)

Shen, Yangwu; Zhang, Bin; Liang, Liqing; Cui, Ting

2018-02-01

A novel integrated control strategy is proposed in this paper to enhance the low voltage ride through capacity for the double-fed induction generator by equipping an energy storage system. The energy storage system is installed into the DC-link capacitor of the DFIG and used to control the DC-link voltage during normal or transient operations. The energy storage device will absorb or compensate the power difference between the captured wind power and the power injected to the grid during the normal and transient period, and the grid side converter can be free from maintaining the voltage stability of the DC-link capacitor. Thus, the grid-side converter is changed to reactive power support while the rotor-side converter is used to control the maximum power production during normal operation. The grid-side converter and rotor-side converter will act as reactive power sources to further enhance the voltage support capability of double-fed induction generator during the transient period. Numerical Simulation are performed to validate the effectiveness of the proposed control designs.

Superconducting Magnetic Energy Storage (SMES) Program

NASA Astrophysics Data System (ADS)

Rogers, J. D.

1985-05-01

The 30 MJ, 10 MW superconducting magnetic energy storage (SMES) system was devised to interact in the Western US Power System as an alternate means to damp unstable oscillations at 0.35 Hz on the Pacific HVAC Interites. The operating limits of the 30 MJ SMES unit were established, and different means of controlling real and reactive power were tested. The unit can follow a sinusoidal power demand signal with an amplitude of up to 8.6 MW with the converter working in a 12 pulse mode. When the converter operates in the constant VAR mode, a time varying real power demand signal of up to 5 MW can be met. It was shown that the Pacific ac Interite has current and reactive power variations of the same frequency as the modulating frequency of the SMES device. The reliability of the SMES subsystems with a narrow band noise input was assessed. Parameters of the ac power system were determined. Converter short circuit tests, load tests under various control conditions, dc breaker tests for coil current interruption, and converter failure mode tests were conducted. The experimental operation of the SMES system is concluded.

Online Assessment of Voltage Stability in Power Systems with PMUs

NASA Astrophysics Data System (ADS)

Chitare, Prasad Bhagwat; Murthy Balijepalli, V. S. K.; Khaparde, S. A.

2013-05-01

Abstract: For the assessment of voltage instability which comprises the detection of voltage instability and identification of critical buses, two indices namely, system wide Qtax, and bus-specific qtax, are proposed. The Qtax, based on the sensitivity of the reactive power injections to the loading in the system provides early detection of impending voltage instability. The computed qtax indices identify the critcal buses among the load buses in the system. The identified critical buses provided optimal lacations for the corrective control actions for averting voltage instability. Additionally, for voltage stability monitoring, determining the poing of exhaustion of the reactive reserves in system is also crucial. This is addressed by proposed Q-Monitoring Index (QMI), which is the ratio of the reactive component of the source current to the sink current that flows through the adjacent transmission line. These proposed indices together can provide early indication to impending voltage instability. This has been illustrated on IEEE-39 bus system. The reactive support on identified critical buses results in maximum increase in the loadability of the system.

High heating rate decomposition dynamics of copper oxide by nanocalorimetry-coupled time-of-flight mass spectrometry

NASA Astrophysics Data System (ADS)

Yi, Feng; DeLisio, Jeffery B.; Nguyen, Nam; Zachariah, Michael R.; LaVan, David A.

2017-12-01

The thermodynamics and evolved gases were measured during the rapid decomposition of copper oxide (CuO) thin film at rates exceeding 100,000 K/s. CuO decomposes to release oxygen when heated and serves as an oxidizer in reactive composites and chemical looping combustion. Other instruments have shown either one or two decomposition steps during heating. We have confirmed that CuO decomposes by two steps at both slower and higher heating rates. The decomposition path influences the reaction course in reactive Al/CuO/Al composites, and full understanding is important in designing reactive mixtures and other new reactive materials.

How can the study of physiological reactivity contribute to our understanding of adversity and resilience processes in development?

PubMed

Obradović, Jelena

2012-05-01

The focus of this article is to present current progress in understanding the interplay among adversity, physiological sensitivity to context, and adaptive functioning, with an emphasis on implications and future directions for resilience researchers. It includes a review of current literature that demonstrates (a) links between various levels of adversity exposure and variability in physiological reactivity, (b) how the interplay between children's physiological reactivity and different sources of risk and adversity relates to variability in adaptive functioning, and (c) various approaches for capturing a more dynamic nature of physiological reactivity and related processes. Throughout, important conceptual and empirical issues are highlighted.

Carbon catalysis of reactions in the lithium SOCl2 and SO2 systems

NASA Technical Reports Server (NTRS)

Kilroy, W. P.

1981-01-01

Certain hazards associated with lithium batteries have delayed widespread acceptance of these power sources. The reactivity of ground lithium carbon mixtures was examined. The effect of carbon types on this reactivity was determined. The basic reaction involved mixtures of lithium and carbon with battery electrolyte. The various parameters that influenced this reactivity included: the nature and freshness of the carbon; the freshness, the purity, and the conductive salt of the electrolyte; and the effect of Teflon or moisture.

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

Ulvestad, Andrew; Sasikumar, Kiran; Kim, Jong Woo

Multielectron transfer processes are crucially important in energy and biological science but require favorable catalysts to achieve fast kinetics. Nanostructuring catalysts can dramatically improve their properties, which can be difficult to understand due to strain- and size-dependent thermodynamics, the influence of defects, and substrate-dependent activities. Here, we report three-dimensional (3D) imaging of single gold nanoparticles during catalysis of ascorbic acid decomposition using Bragg coherent diffractive imaging (BCDI). Local strains were measured in single nanoparticles and modeled using reactive molecular dynamics (RMD) simulations and finite element analysis (FEA) simulations. RMD reveals the pathway for local strain generation in the gold lattice:more » chemisorption of hydroxyl ions. FEA reveals that the RMD results are transferable to the nanocrystal sizes studied in the experiment. Our study probes the strain-activity connection and opens a powerful avenue for theoretical and experimental studies of nanocrystal catalysis.« less

Event-induced theta responses as a window on the dynamics of memory.

PubMed

Bastiaansen, Marcel; Hagoort, Peter

2003-01-01

An important, but often ignored distinction in the analysis of EEG signals is that between evoked activity and induced activity. Whereas evoked activity reflects the summation of transient post-synaptic potentials triggered by an event, induced activity, which is mainly oscillatory in nature, is thought to reflect changes in parameters controlling dynamic interactions within and between brain structures. We hypothesize that induced activity may yield information about the dynamics of cell assembly formation, activation and subsequent uncoupling, which may play a prominent role in different types of memory operations. We then describe a number of analysis tools that can be used to study the reactivity of induced rhythmic activity, both in terms of amplitude changes and of phase variability. We briefly discuss how alpha, gamma and theta rhythms are thought to be generated, paying special attention to the hypothesis that the theta rhythm reflects dynamic interactions between the hippocampal system and the neocortex. This hypothesis would imply that studying the reactivity of scalp-recorded theta may provide a window on the contribution of the hippocampus to memory functions. We review studies investigating the reactivity of scalp-recorded theta in paradigms engaging episodic memory, spatial memory and working memory. In addition, we review studies that relate theta reactivity to processes at the interface of memory and language. Despite many unknowns, the experimental evidence largely supports the hypothesis that theta activity plays a functional role in cell assembly formation, a process which may constitute the neural basis of memory formation and retrieval. The available data provide only highly indirect support for the hypothesis that scalp-recorded theta yields information about hippocampal functioning. It is concluded that studying induced rhythmic activity holds promise as an additional important way to study brain function.

Demonstration of Essential Reliability Services by Utility-Scale Solar

Science.gov Websites

control (AGC) * Primary frequency control * Active power ramp rate control * Voltage regulation and reactive power control. See a list of Questions and Answers from the webinar. Read the NREL technical

Method of measuring reactive acoustic power density in a fluid

DOEpatents

Wheatley, John C.; Swift, Gregory W.; Migliori, Albert

1985-01-01

A method for determining reactive acoustic power density level and its direction in a fluid using a single sensor is disclosed. In the preferred embodiment, an apparatus for conducting the method, which is termed a thermoacoustic couple, consists of a stack of thin, spaced apart polymeric plates, selected ones of which include multiple bimetallic thermocouple junctions positioned along opposite end edges thereof. The thermocouple junctions are connected in series in the nature of a thermopile, and are arranged so as to be responsive to small temperature differences between the opposite edges of the plates. The magnitude of the temperature difference, as represented by the magnitude of the electrical potential difference generated by the thermopile, is found to be directly related to the level of acoustic power density in the gas.

Method of measuring reactive acoustic power density in a fluid

DOEpatents

Wheatley, J.C.; Swift, G.W.; Migliori, A.

1985-09-03

A method for determining reactive acoustic power density level and its direction in a fluid using a single sensor is disclosed. In the preferred embodiment, an apparatus for conducting the method, which is termed a thermoacoustic couple, consists of a stack of thin, spaced apart polymeric plates, selected ones of which include multiple bimetallic thermocouple junctions positioned along opposite end edges thereof. The thermocouple junctions are connected in series in the nature of a thermopile, and are arranged so as to be responsive to small temperature differences between the opposite edges of the plates. The magnitude of the temperature difference, as represented by the magnitude of the electrical potential difference generated by the thermopile, is found to be directly related to the level of acoustic power density in the gas. 5 figs.

Fast-spectrum space-power-reactor concepts using boron control devices

NASA Technical Reports Server (NTRS)

Mayo, W.

1973-01-01

Several fast-spectrum space power reactor concepts that use boron carbide control devices were examined to determine the neutronic feasibility of the designs. The designs considered were (1) a 199-fuel-pin, 12-poison-reflector-control-drum reactor; (2) a 232-fuel-pin reactor with 12 reflector drums and three in-core control rods; (3) a 337-fuel-pin design with 12 incore control rods; and a 181-fuel-pin design with six drums closely coupled to the core to increase reactivity per drum. Adequate reactivity control and excess reactivity could be obtained for each concept, and the goals of 50,000 hours at 2.17 thermal megawatts with a lithium-7 coolant outlet temperature of 1222 K could be met without exceeding the 1-percent-clad-creep criterion. Heating rates in the boron carbide were calculated, but a heat transfer analysis was not done.

Dynamics of Electron Transfer for a Nonsuperexchange Coherent Mechanism. I

DTIC Science & Technology

1989-10-13

observation. In the treatment three collective nuclear coordinates are introduced, permitting independent reorganization energies for each reactive center... nuclear coordinates are introduced, permitting independent reorganization energies for each reactive center. With certain approximations, namely, equal...numerically. One rough but simple analytical result for the latter is also given. tPresent address: Departmento de Quimica , Facultad de Ciencias

Does Verbal Labeling Influence Age Differences in Proactive and Reactive Cognitive Control?

ERIC Educational Resources Information Center

Kray, Jutta; Schmitt, Hannah; Heintz, Sonja; Blaye, Agnès

2015-01-01

The main goal of this study was to examine whether different types of verbal labeling can influence age-related changes in the dynamic control of behavior by inducing either a proactive or reactive mode of control. Proactive control is characterized by a strong engagement in maintaining task-relevant information to be optimally prepared while…

Predictive performance modeling framework for a novel enclosed particle receiver configuration and application for thermochemical energy storage

DOE PAGES

Martinek, Janna; Wendelin, Timothy; Ma, Zhiwen

2018-04-05

Concentrating solar power (CSP) plants can provide dispatchable power with a thermal energy storage capability for increased renewable-energy grid penetration. Particle-based CSP systems permit higher temperatures, and thus, potentially higher solar-to-electric efficiency than state-of-the-art molten-salt heat-transfer systems. This paper describes a detailed numerical analysis framework for estimating the performance of a novel, geometrically complex, enclosed particle receiver design. The receiver configuration uses arrays of small tubular absorbers to collect and subsequently transfer solar energy to a flowing particulate medium. The enclosed nature of the receiver design renders it amenable to either an inert heat-transfer medium, or a reactive heat-transfer medium that requires a controllable ambient environment. The numerical analysis framework described in this study is demonstrated for the case of thermal reduction of CaCr 0.1Mn 0.9O 3-more » $$\\delta$$ for thermochemical energy storage. The modeling strategy consists of Monte Carlo ray tracing for absorbed solar-energy distributions from a surround heliostat field, computational fluid dynamics modeling of small-scale local tubular arrays, surrogate response surfaces that approximately capture simulated tubular array performance, a quasi-two-dimensional reduced-order description of counter-flow reactive solids and purge gas, and a radiative exchange model applied to embedded-cavity structures at the size scale of the full receiver. In this work we apply the numerical analysis strategy to a single receiver configuration, but the framework can be generically applicable to alternative enclosed designs. In conclusion, we assess sensitivity of receiver performance to surface optical properties, heat-transfer coefficients, solids outlet temperature, and purge-gas feed rates, and discuss the significance of model assumptions and results for future receiver development.« less

Predictive performance modeling framework for a novel enclosed particle receiver configuration and application for thermochemical energy storage

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

Martinek, Janna; Wendelin, Timothy; Ma, Zhiwen

Concentrating solar power (CSP) plants can provide dispatchable power with a thermal energy storage capability for increased renewable-energy grid penetration. Particle-based CSP systems permit higher temperatures, and thus, potentially higher solar-to-electric efficiency than state-of-the-art molten-salt heat-transfer systems. This paper describes a detailed numerical analysis framework for estimating the performance of a novel, geometrically complex, enclosed particle receiver design. The receiver configuration uses arrays of small tubular absorbers to collect and subsequently transfer solar energy to a flowing particulate medium. The enclosed nature of the receiver design renders it amenable to either an inert heat-transfer medium, or a reactive heat-transfer medium that requires a controllable ambient environment. The numerical analysis framework described in this study is demonstrated for the case of thermal reduction of CaCr 0.1Mn 0.9O 3-more » $$\\delta$$ for thermochemical energy storage. The modeling strategy consists of Monte Carlo ray tracing for absorbed solar-energy distributions from a surround heliostat field, computational fluid dynamics modeling of small-scale local tubular arrays, surrogate response surfaces that approximately capture simulated tubular array performance, a quasi-two-dimensional reduced-order description of counter-flow reactive solids and purge gas, and a radiative exchange model applied to embedded-cavity structures at the size scale of the full receiver. In this work we apply the numerical analysis strategy to a single receiver configuration, but the framework can be generically applicable to alternative enclosed designs. In conclusion, we assess sensitivity of receiver performance to surface optical properties, heat-transfer coefficients, solids outlet temperature, and purge-gas feed rates, and discuss the significance of model assumptions and results for future receiver development.« less

A novel transient rotor current control scheme of a doubly-fed induction generator equipped with superconducting magnetic energy storage for voltage and frequency support

NASA Astrophysics Data System (ADS)

Shen, Yang-Wu; Ke, De-Ping; Sun, Yuan-Zhang; Daniel, Kirschen; Wang, Yi-Shen; Hu, Yuan-Chao

2015-07-01

A novel transient rotor current control scheme is proposed in this paper for a doubly-fed induction generator (DFIG) equipped with a superconducting magnetic energy storage (SMES) device to enhance its transient voltage and frequency support capacity during grid faults. The SMES connected to the DC-link capacitor of the DFIG is controlled to regulate the transient dc-link voltage so that the whole capacity of the grid side converter (GSC) is dedicated to injecting reactive power to the grid for the transient voltage support. However, the rotor-side converter (RSC) has different control tasks for different periods of the grid fault. Firstly, for Period I, the RSC injects the demagnetizing current to ensure the controllability of the rotor voltage. Then, since the dc stator flux degenerates rapidly in Period II, the required demagnetizing current is low in Period II and the RSC uses the spare capacity to additionally generate the reactive (priority) and active current so that the transient voltage capability is corroborated and the DFIG also positively responds to the system frequency dynamic at the earliest time. Finally, a small amount of demagnetizing current is provided after the fault clearance. Most of the RSC capacity is used to inject the active current to further support the frequency recovery of the system. Simulations are carried out on a simple power system with a wind farm. Comparisons with other commonly used control methods are performed to validate the proposed control method. Project supported by the National Natural Science Foundation of China (Grant No. 51307124) and the Major Program of the National Natural Science Foundation of China (Grant No. 51190105).

76 FR 14965 - Combined Notice of Filings #1

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-18

...-000. Applicants: Troy Energy, LLC. Description: Troy Energy, LLC's Transfer of Reactive Power Revenue... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Combined Notice of Filings 1 Take notice...-2424-001. Applicants: Pinetree Power-Tamworth, Inc. Description: Second Supplemental Request for...

Forebody and base region real gas flow in severe planetary entry by a factored implicit numerical method. II - Equilibrium reactive gas

NASA Technical Reports Server (NTRS)

Davy, W. C.; Green, M. J.; Lombard, C. K.

1981-01-01

The factored-implicit, gas-dynamic algorithm has been adapted to the numerical simulation of equilibrium reactive flows. Changes required in the perfect gas version of the algorithm are developed, and the method of coupling gas-dynamic and chemistry variables is discussed. A flow-field solution that approximates a Jovian entry case was obtained by this method and compared with the same solution obtained by HYVIS, a computer program much used for the study of planetary entry. Comparison of surface pressure distribution and stagnation line shock-layer profiles indicates that the two solutions agree well.

Characterization of a Dynamic String Method for the Construction of Transition Pathways in Molecular Reactions

PubMed Central

Johnson, Margaret E.; Hummer, Gerhard

2012-01-01

We explore the theoretical foundation of different string methods used to find dominant reaction pathways in high-dimensional configuration spaces. Pathways are assessed by the amount of reactive flux they carry and by their orientation relative to the committor function. By examining the effects of transforming between different collective coordinates that span the same underlying space, we unmask artificial coordinate dependences in strings optimized to follow the free energy gradient. In contrast, strings optimized to follow the drift vector produce reaction pathways that are significantly less sensitive to reparameterizations of the collective coordinates. The differences in these paths arise because the drift vector depends on both the free energy gradient and the diffusion tensor of the coarse collective variables. Anisotropy and position dependence of diffusion tensors arise commonly in spaces of coarse variables, whose generally slow dynamics are obtained by nonlinear projections of the strongly coupled atomic motions. We show here that transition paths constructed to account for dynamics by following the drift vector will (to a close approximation) carry the maximum reactive flux both in systems with isotropic position dependent diffusion, and in systems with constant but anisotropic diffusion. We derive a simple method for calculating the committor function along paths that follow the reactive flux. Lastly, we provide guidance for the practical implementation of the dynamic string method. PMID:22616575

Coupled Modeling of Rhizosphere and Reactive Transport Processes

NASA Astrophysics Data System (ADS)

Roque-Malo, S.; Kumar, P.

2017-12-01

The rhizosphere, as a bio-diverse plant root-soil interface, hosts many hydrologic and biochemical processes, including nutrient cycling, hydraulic redistribution, and soil carbon dynamics among others. The biogeochemical function of root networks, including the facilitation of nutrient cycling through absorption and rhizodeposition, interaction with micro-organisms and fungi, contribution to biomass, etc., plays an important role in myriad Critical Zone processes. Despite this knowledge, the role of the rhizosphere on watershed-scale ecohydrologic functions in the Critical Zone has not been fully characterized, and specifically, the extensive capabilities of reactive transport models (RTMs) have not been applied to these hydrobiogeochemical dynamics. This study uniquely links rhizospheric processes with reactive transport modeling to couple soil biogeochemistry, biological processes, hydrologic flow, hydraulic redistribution, and vegetation dynamics. Key factors in the novel modeling approach are: (i) bi-directional effects of root-soil interaction, such as simultaneous root exudation and nutrient absorption; (ii) multi-state biomass fractions in soil (i.e. living, dormant, and dead biological and root materials); (iii) expression of three-dimensional fluxes to represent both vertical and lateral interconnected flows and processes; and (iv) the potential to include the influence of non-stationary external forcing and climatic factors. We anticipate that the resulting model will demonstrate the extensive effects of plant root dynamics on ecohydrologic functions at the watershed scale and will ultimately contribute to a better characterization of efflux from both agricultural and natural systems.

Fringe-controlled biodegradation under dynamic conditions: Quasi 2-D flow-through experiments and reactive-transport modeling

NASA Astrophysics Data System (ADS)

Eckert, Dominik; Kürzinger, Petra; Bauer, Robert; Griebler, Christian; Cirpka, Olaf A.

2015-01-01

Biodegradation in contaminated aquifers has been shown to be most pronounced at the fringe of contaminant plumes, where mixing of contaminated water and ambient groundwater, containing dissolved electron acceptors, stimulates microbial activity. While physical mixing of contaminant and electron acceptor by transverse dispersion has been shown to be the major bottleneck for biodegradation in steady-state plumes, so far little is known on the effect of flow and transport dynamics (caused, e.g., by a seasonally fluctuating groundwater table) on biodegradation in these systems. Towards this end we performed experiments in quasi-two-dimensional flow-through microcosms on aerobic toluene degradation by Pseudomonas putida F1. Plume dynamics were simulated by vertical alteration of the toluene plume position and experimental results were analyzed by reactive-transport modeling. We found that, even after disappearance of the toluene plume for two weeks, the majority of microorganisms stayed attached to the sediment and regained their full biodegradation potential within two days after reappearance of the toluene plume. Our results underline that besides microbial growth, also maintenance and dormancy are important processes that affect biodegradation performance under transient environmental conditions and therefore deserve increased consideration in future reactive-transport modeling.

Extended asymmetric hot region formation due to shockwave interactions following void collapse in shocked high explosive

NASA Astrophysics Data System (ADS)

Shan, Tzu-Ray; Wixom, Ryan R.; Thompson, Aidan P.

2016-08-01

In both continuum hydrodynamics simulations and also multimillion atom reactive molecular dynamics simulations of shockwave propagation in single crystal pentaerythritol tetranitrate (PETN) containing a cylindrical void, we observed the formation of an initial radially symmetric hot spot. By extending the simulation time to the nanosecond scale, however, we observed the transformation of the small symmetric hot spot into a longitudinally asymmetric hot region extending over a much larger volume. Performing reactive molecular dynamics shock simulations using the reactive force field (ReaxFF) as implemented in the LAMMPS molecular dynamics package, we showed that the longitudinally asymmetric hot region was formed by coalescence of the primary radially symmetric hot spot with a secondary triangular hot zone. We showed that the triangular hot zone coincided with a double-shocked region where the primary planar shockwave was overtaken by a secondary cylindrical shockwave. The secondary cylindrical shockwave originated in void collapse after the primary planar shockwave had passed over the void. A similar phenomenon was observed in continuum hydrodynamics shock simulations using the CTH hydrodynamics package. The formation and growth of extended asymmetric hot regions on nanosecond timescales has important implications for shock initiation thresholds in energetic materials.

Does reactivation trigger episodic memory change? A meta-analysis.

PubMed

Scully, Iiona D; Napper, Lucy E; Hupbach, Almut

2017-07-01

According to the reconsolidation hypothesis, long-term memories return to a plastic state upon their reactivation, leaving them vulnerable to interference effects and requiring re-storage processes or else these memories might be permanently lost. The present study used a meta-analytic approach to critically evaluate the evidence for reactivation-induced changes in human episodic memory. Results indicated that reactivation makes episodic memories susceptible to physiological and behavioral interference. When applied shortly after reactivation, interference manipulations altered the amount of information that could be retrieved from the original learning event. This effect was more pronounced for remote memories and memories of narrative structure. Additionally, new learning following reactivation reliably increased the number of intrusions from new information into the original memory. These findings support a dynamic view of long-term memory by showing that memories can be changed long after they were acquired. Copyright © 2016 Elsevier Inc. All rights reserved.

Nonlinear dynamics of skin blood flow response to mechanical and thermal stresses in the plantar foot of diabetics with peripheral neuropathy.

PubMed

Liao, Fuyuan; Jan, Yih-Kuen

2017-01-01

Diabetic foot ulcers (DFU) are a major complication in diabetics. Impaired microvascular reactivity is a major contributor to the development of DFU and has been traditionally quantified by time-domain or frequency-domain measures of skin blood flow (SBF). These measures, however, are unable to characterize the changes of nonlinear dynamics of SBF associated with diabetes and peripheral neuropathy. The objective of this study was to investigate altered nonlinear dynamics of skin blood flow in the plantar foot of diabetics with peripheral neuropathy. 18 type 2 diabetics with peripheral neuropathy and 8 healthy controls were recruited. SBF at the first metatarsal head in response to a loading pressure of 300 mmHg and a local heating was measured using laser Doppler flowmetry. A sample entropy approach was used to quantify the degree of regularity of SBF. Our results showed that the regularity degree of SBF in the diabetic foot underwent only small changes during post-occlusive reactive hyperemia and thermally induced biphasic response compared to non-diabetics. SBF of the diabetic foot has higher degree of irregularity during reactive hyperemia because of attenuated myogenic activity, and demonstrated higher regularity during the biphasic response largely due to significantly enhanced cardiac activities. This study suggests that the regularity degree of SBF at the first metatarsal head could be used to assess impaired microvascular reactivity and thus may be used to assess the risk for DFU in diabetics with peripheralneuropathy.

Fear of falling and postural reactivity in patients with glaucoma.

PubMed

Daga, Fábio B; Diniz-Filho, Alberto; Boer, Erwin R; Gracitelli, Carolina P B; Abe, Ricardo Y; Medeiros, Felipe A

2017-01-01

To investigate the relationship between postural metrics obtained by dynamic visual stimulation in a virtual reality environment and the presence of fear of falling in glaucoma patients. This cross-sectional study included 35 glaucoma patients and 26 controls that underwent evaluation of postural balance by a force platform during presentation of static and dynamic visual stimuli with head-mounted goggles (Oculus Rift). In dynamic condition, a peripheral translational stimulus was used to induce vection and assess postural reactivity. Standard deviations of torque moments (SDTM) were calculated as indicative of postural stability. Fear of falling was assessed by a standardized questionnaire. The relationship between a summary score of fear of falling and postural metrics was investigated using linear regression models, adjusting for potentially confounding factors. Subjects with glaucoma reported greater fear of falling compared to controls (-0.21 vs. 0.27; P = 0.039). In glaucoma patients, postural metrics during dynamic visual stimulus were more associated with fear of falling (R2 = 18.8%; P = 0.001) than static (R2 = 3.0%; P = 0.005) and dark field (R2 = 5.7%; P = 0.007) conditions. In the univariable model, fear of falling was not significantly associated with binocular standard perimetry mean sensitivity (P = 0.855). In the multivariable model, each 1 Nm larger SDTM in anteroposterior direction during dynamic stimulus was associated with a worsening of 0.42 units in the fear of falling questionnaire score (P = 0.001). In glaucoma patients, postural reactivity to a dynamic visual stimulus using a virtual reality environment was more strongly associated with fear of falling than visual field testing and traditional balance assessment.

Fear of falling and postural reactivity in patients with glaucoma

PubMed Central

Daga, Fábio B.; Diniz-Filho, Alberto; Boer, Erwin R.; Gracitelli, Carolina P. B.; Abe, Ricardo Y.; Medeiros, Felipe A.

2017-01-01

Purpose To investigate the relationship between postural metrics obtained by dynamic visual stimulation in a virtual reality environment and the presence of fear of falling in glaucoma patients. Methods This cross-sectional study included 35 glaucoma patients and 26 controls that underwent evaluation of postural balance by a force platform during presentation of static and dynamic visual stimuli with head-mounted goggles (Oculus Rift). In dynamic condition, a peripheral translational stimulus was used to induce vection and assess postural reactivity. Standard deviations of torque moments (SDTM) were calculated as indicative of postural stability. Fear of falling was assessed by a standardized questionnaire. The relationship between a summary score of fear of falling and postural metrics was investigated using linear regression models, adjusting for potentially confounding factors. Results Subjects with glaucoma reported greater fear of falling compared to controls (-0.21 vs. 0.27; P = 0.039). In glaucoma patients, postural metrics during dynamic visual stimulus were more associated with fear of falling (R2 = 18.8%; P = 0.001) than static (R2 = 3.0%; P = 0.005) and dark field (R2 = 5.7%; P = 0.007) conditions. In the univariable model, fear of falling was not significantly associated with binocular standard perimetry mean sensitivity (P = 0.855). In the multivariable model, each 1 Nm larger SDTM in anteroposterior direction during dynamic stimulus was associated with a worsening of 0.42 units in the fear of falling questionnaire score (P = 0.001). Conclusion In glaucoma patients, postural reactivity to a dynamic visual stimulus using a virtual reality environment was more strongly associated with fear of falling than visual field testing and traditional balance assessment. PMID:29211742

Digital slip frequency generator and method for determining the desired slip frequency

DOEpatents

Klein, Frederick F.

1989-01-01

The output frequency of an electric power generator is kept constant with variable rotor speed by automatic adjustment of the excitation slip frequency. The invention features a digital slip frequency generator which provides sine and cosine waveforms from a look-up table, which are combined with real and reactive power output of the power generator.

Molecular modeling studies of interfacial reactions in wet supercritical CO2.

NASA Astrophysics Data System (ADS)

Glezakou, V.; McGrail, B. P.; Windisch, C. F.; Schaef, H. T.; Martin, P.

2011-12-01

In the recent years, Carbon Capture and Sequestration (CCS) technologies have gained considerable momentum in a globally organized effort to mitigate greenhouse emissions and adverse climate change. Co-sequestration refers to the capture and geologic sequestration of carbon dioxide and minor contaminants (sulfur compounds, NOx, Hg, etc.) in subsurface formations. Cosequestration offers the potential to make carbon management more economically acceptable to industry relative to sequestration of pure CO2. This may be achieved through significant savings in plant (and retrofit) capital cost, operating cost, and energy savings as well by eliminating the need for one or more individual pollutant capture systems (such as SO2 scrubbers). The latter point is important because co-sequestration may result in a net positive impact to the environment through avoided loss of power generation capacity from parasitic loads and reduced fuel needs. This paper will discuss our research on modeling, imaging and characterization of cosequestration processes and reactivity at a fundamental level. Our work examines the interactions of CO2-rich fluids with metal and mineral surfaces, and how these are affected by the presence of other gas components (e.g. SO2, H2O or NOx) commonly present in the CO2 streams. We have found that reactivity is also affected by the composition of the surface or, less obviously, by the surface exposed, for example, (104) vs (100 )of carbonate minerals. We combine experimental techniques such as XRD and Raman spectroscopy, which can detect and follow reactive processes, with ab initio modeling methods based on density functional theory, to establish a reliable correspondence between theory and experiment with predictive capability. Analysis of our molecular dynamics simulations, reveals structural information and vibrational density of states that can directly compare with XRD measurements and vibrational spectroscopy. While reactivity in CO2-containing aqueous environments has been widely studied, the reverse, i.e. reactivity in water-bearing condensed media, is not true. Our simulations show that mechanistic details in these environments can be drastically different, and they are very important in elucidating molecular transformations relevant to CCS or carbon conversion.

Quantum Mechanics/Molecular Mechanics Free Energy Maps and Nonadiabatic Simulations for a Photochemical Reaction in DNA: Cyclobutane Thymine Dimer.

PubMed

Mendieta-Moreno, Jesús I; Trabada, Daniel G; Mendieta, Jesús; Lewis, James P; Gómez-Puertas, Paulino; Ortega, José

2016-11-03

The absorption of ultraviolet radiation by DNA may result in harmful genetic lesions that affect DNA replication and transcription, ultimately causing mutations, cancer, and/or cell death. We analyze the most abundant photochemical reaction in DNA, the cyclobutane thymine dimer, using hybrid quantum mechanics/molecular mechanics (QM/MM) techniques and QM/MM nonadiabatic molecular dynamics. We find that, due to its double helix structure, DNA presents a free energy barrier between nonreactive and reactive conformations leading to the photolesion. Moreover, our nonadiabatic simulations show that most of the photoexcited reactive conformations return to standard B-DNA conformations after an ultrafast nonradiative decay to the ground state. This work highlights the importance of dynamical effects (free energy, excited-state dynamics) for the study of photochemical reactions in biological systems.

Inferring Muscle-Tendon Unit Power from Ankle Joint Power during the Push-Off Phase of Human Walking: Insights from a Multiarticular EMG-Driven Model

PubMed Central

2016-01-01

Introduction Inverse dynamics joint kinetics are often used to infer contributions from underlying groups of muscle-tendon units (MTUs). However, such interpretations are confounded by multiarticular (multi-joint) musculature, which can cause inverse dynamics to over- or under-estimate net MTU power. Misestimation of MTU power could lead to incorrect scientific conclusions, or to empirical estimates that misguide musculoskeletal simulations, assistive device designs, or clinical interventions. The objective of this study was to investigate the degree to which ankle joint power overestimates net plantarflexor MTU power during the Push-off phase of walking, due to the behavior of the flexor digitorum and hallucis longus (FDHL)–multiarticular MTUs crossing the ankle and metatarsophalangeal (toe) joints. Methods We performed a gait analysis study on six healthy participants, recording ground reaction forces, kinematics, and electromyography (EMG). Empirical data were input into an EMG-driven musculoskeletal model to estimate ankle power. This model enabled us to parse contributions from mono- and multi-articular MTUs, and required only one scaling and one time delay factor for each subject and speed, which were solved for based on empirical data. Net plantarflexing MTU power was computed by the model and quantitatively compared to inverse dynamics ankle power. Results The EMG-driven model was able to reproduce inverse dynamics ankle power across a range of gait speeds (R2 ≥ 0.97), while also providing MTU-specific power estimates. We found that FDHL dynamics caused ankle power to slightly overestimate net plantarflexor MTU power, but only by ~2–7%. Conclusions During Push-off, FDHL MTU dynamics do not substantially confound the inference of net plantarflexor MTU power from inverse dynamics ankle power. However, other methodological limitations may cause inverse dynamics to overestimate net MTU power; for instance, due to rigid-body foot assumptions. Moving forward, the EMG-driven modeling approach presented could be applied to understand other tasks or larger multiarticular MTUs. PMID:27764110

Inferring Muscle-Tendon Unit Power from Ankle Joint Power during the Push-Off Phase of Human Walking: Insights from a Multiarticular EMG-Driven Model.

PubMed

Honert, Eric C; Zelik, Karl E

2016-01-01

Inverse dynamics joint kinetics are often used to infer contributions from underlying groups of muscle-tendon units (MTUs). However, such interpretations are confounded by multiarticular (multi-joint) musculature, which can cause inverse dynamics to over- or under-estimate net MTU power. Misestimation of MTU power could lead to incorrect scientific conclusions, or to empirical estimates that misguide musculoskeletal simulations, assistive device designs, or clinical interventions. The objective of this study was to investigate the degree to which ankle joint power overestimates net plantarflexor MTU power during the Push-off phase of walking, due to the behavior of the flexor digitorum and hallucis longus (FDHL)-multiarticular MTUs crossing the ankle and metatarsophalangeal (toe) joints. We performed a gait analysis study on six healthy participants, recording ground reaction forces, kinematics, and electromyography (EMG). Empirical data were input into an EMG-driven musculoskeletal model to estimate ankle power. This model enabled us to parse contributions from mono- and multi-articular MTUs, and required only one scaling and one time delay factor for each subject and speed, which were solved for based on empirical data. Net plantarflexing MTU power was computed by the model and quantitatively compared to inverse dynamics ankle power. The EMG-driven model was able to reproduce inverse dynamics ankle power across a range of gait speeds (R2 ≥ 0.97), while also providing MTU-specific power estimates. We found that FDHL dynamics caused ankle power to slightly overestimate net plantarflexor MTU power, but only by ~2-7%. During Push-off, FDHL MTU dynamics do not substantially confound the inference of net plantarflexor MTU power from inverse dynamics ankle power. However, other methodological limitations may cause inverse dynamics to overestimate net MTU power; for instance, due to rigid-body foot assumptions. Moving forward, the EMG-driven modeling approach presented could be applied to understand other tasks or larger multiarticular MTUs.

Cue-independent memory impairment by reactivation-coupled interference in human declarative memory.

PubMed

Zhu, Zijian; Wang, Yingying; Cao, Zhijun; Chen, Biqing; Cai, Huaqian; Wu, Yanhong; Rao, Yi

2016-10-01

Memory is a dynamic process. While memory becomes increasingly resistant to interference after consolidation, a brief reactivation renders it unstable again. Previous studies have shown that interference, when applied upon reactivation, impairs the consolidated memory, presumably by disrupting the reconsolidation of the memory. However, attempts have failed in disrupting human declarative memory, raising a question about whether declarative memory becomes unstable upon reactivation. Here, we used a double-cue/one-target paradigm, which associated the same target with two different cues in initial memory formation. Only one cue/target association was later reactivated and treated with behavioral interference. Our results showed, for the first time, that reactivation-coupled interference caused cue-independent memory impairment that generalized to other cues associated with the memory. Critically, such memory impairment appeared immediately after interference, before the reconsolidation process was completed, suggesting that common manipulations of reactivation-coupled interference procedures might disrupt other processes in addition to the reconsolidation process in human declarative memory. Copyright © 2016. Published by Elsevier B.V.

Combining a reactive potential with a harmonic approximation for molecular dynamics simulation of failure: construction of a reduced potential

NASA Astrophysics Data System (ADS)

Tejada, I. G.; Brochard, L.; Stoltz, G.; Legoll, F.; Lelièvre, T.; Cancès, E.

2015-01-01

Molecular dynamics is a simulation technique that can be used to study failure in solids, provided the inter-atomic potential energy is able to account for the complex mechanisms at failure. Reactive potentials fitted on ab initio results or on experimental values have the ability to adapt to any complex atomic arrangement and, therefore, are suited to simulate failure. But the complexity of these potentials, together with the size of the systems considered, make simulations computationally expensive. In order to improve the efficiency of numerical simulations, simpler harmonic potentials can be used instead of complex reactive potentials in the regions where the system is close to its ground state and a harmonic approximation reasonably fits the actual reactive potential. However the validity and precision of such an approach has not been investigated in detail yet. We present here a methodology for constructing a reduced potential and combining it with the reactive one. We also report some important features of crack propagation that may be affected by the coupling of reactive and reduced potentials. As an illustrative case, we model a crystalline two-dimensional material (graphene) with a reactive empirical bond-order potential (REBO) or with harmonic potentials made of bond and angle springs that are designed to reproduce the second order approximation of REBO in the ground state. We analyze the consistency of this approximation by comparing the mechanical behavior and the phonon spectra of systems modeled with these potentials. These tests reveal when the anharmonicity effects appear. As anharmonic effects originate from strain, stress or temperature, the latter quantities are the basis for establishing coupling criteria for on the fly substitution in large simulations.

The effect of micellization on the EPR spectra and reactivity of 2,2,4,4-tetramethylpiperidinoxyl (TEMPO) radicals.

PubMed

Aliaga, Carolina; Rezende, Marcos Caroli; Mena, Geraldine

2016-11-01

A series of 4-alkanoyloxy-2,2,6,6-tetramethylpiperidinoxyl radicals was prepared, and their reactivity in water vis-à-vis antioxidant Trolox was compared. Spectral (electron paramagnetic resonance) and dynamic-light-scattering measurements suggested the formation of micelles for the more hydrophobic members of the series. The observed increase in reactivity for the micelle-forming radicals reflected the increased local concentration of the radical fragment on the micellar interface. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Optimization of power systems with voltage security constraints

NASA Astrophysics Data System (ADS)

Rosehart, William Daniel

As open access market principles are applied to power systems, significant changes in their operation and control are occurring. In the new marketplace, power systems are operating under higher loading conditions as market influences demand greater attention to operating cost versus stability margins. Since stability continues to be a basic requirement in the operation of any power system, new tools are being considered to analyze the effect of stability on the operating cost of the system, so that system stability can be incorporated into the costs of operating the system. In this thesis, new optimal power flow (OPF) formulations are proposed based on multi-objective methodologies to optimize active and reactive power dispatch while maximizing voltage security in power systems. The effects of minimizing operating costs, minimizing reactive power generation and/or maximizing voltage stability margins are analyzed. Results obtained using the proposed Voltage Stability Constrained OPF formulations are compared and analyzed to suggest possible ways of costing voltage security in power systems. When considering voltage stability margins the importance of system modeling becomes critical, since it has been demonstrated, based on bifurcation analysis, that modeling can have a significant effect of the behavior of power systems, especially at high loading levels. Therefore, this thesis also examines the effects of detailed generator models and several exponential load models. Furthermore, because of its influence on voltage stability, a Static Var Compensator model is also incorporated into the optimization problems.

Measuring Memory Reactivation With Functional MRI: Implications for Psychological Theory.

PubMed

Levy, Benjamin J; Wagner, Anthony D

2013-01-01

Environmental cues often remind us of earlier experiences by triggering the reactivation of memories of events past. Recent evidence suggests that memory reactivation can be observed using functional MRI and that distributed pattern analyses can even provide evidence of reactivation on individual trials. The ability to measure memory reactivation offers unique and powerful leverage on theoretical issues of long-standing interest in cognitive psychology, providing a means to address questions that have proven difficult to answer with behavioral data alone. In this article, we consider three instances. First, reactivation measures can indicate whether memory-based inferences (i.e., generalization) arise through the encoding of integrated cross-event representations or through the flexible expression of separable event memories. Second, online measures of memory reactivation may inform theories of forgetting by providing information about when competing memories are reactivated during competitive retrieval situations. Finally, neural reactivation may provide a window onto the role of replay in memory consolidation. The ability to track memory reactivation, including at the individual trial level, provides unique leverage that is not afforded by behavioral measures and thus promises to shed light on such varied topics as generalization, integration, forgetting, and consolidation. © The Author(s) 2013.

Modulation of Active Site Electronic Structure by the Protein Matrix to Control [NiFe] Hydrogenase Reactivity

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

Smith, Dayle MA; Raugei, Simone; Squier, Thomas C.

2014-09-30

Control of the reactivity of the nickel center of the [NiFe] hydrogenase and other metalloproteins commonly involves outer coordination sphere ligands that act to modify the geometry and physical properties of the active site metal centers. We carried out a combined set of classical molecular dynamics and quantum/classical mechanics calculations to provide quantitative estimates of how dynamic fluctuations of the active site within the protein matrix modulate the electronic structure at the catalytic center. Specifically we focused on the dynamics of the inner and outer coordination spheres of the cysteinate-bound Ni–Fe cluster in the catalytically active Ni-C state. There aremore » correlated movements of the cysteinate ligands and the surrounding hydrogen-bonding network, which modulate the electron affinity at the active site and the proton affinity of a terminal cysteinate. On the basis of these findings, we hypothesize a coupling between protein dynamics and electron and proton transfer reactions critical to dihydrogen production.« less

Modulation of active site electronic structure by the protein matrix to control [NiFe] hydrogenase reactivity.

PubMed

Smith, Dayle M A; Raugei, Simone; Squier, Thomas C

2014-11-21

Control of the reactivity of the nickel center of the [NiFe] hydrogenase and other metalloproteins commonly involves outer coordination sphere ligands that act to modify the geometry and physical properties of the active site metal centers. We carried out a combined set of classical molecular dynamics and quantum/classical mechanics calculations to provide quantitative estimates of how dynamic fluctuations of the active site within the protein matrix modulate the electronic structure at the catalytic center. Specifically we focused on the dynamics of the inner and outer coordination spheres of the cysteinate-bound Ni-Fe cluster in the catalytically active Ni-C state. There are correlated movements of the cysteinate ligands and the surrounding hydrogen-bonding network, which modulate the electron affinity at the active site and the proton affinity of a terminal cysteinate. On the basis of these findings, we hypothesize a coupling between protein dynamics and electron and proton transfer reactions critical to dihydrogen production.

Reactive pathways of hydrogen and carbon removal from organosilicate glass low- κ films by F atoms

NASA Astrophysics Data System (ADS)

Voronina, Ekaterina N.; Mankelevich, Yuri A.; Rakhimova, Tatyana V.

2017-07-01

Direct molecular dynamic simulation on the base of the density functional theory (DFT) method is used to study some critical reactions of F atoms with organosilicate glass (OSG) low-κ films. Here static and dynamic DFT-based approaches are applied for a variety of reactive pathways of hydrogen and carbon removal in the form of volatile products (HF, CF2 and CF3 molecules) from initial SiCH3 surface groups. These reactions constitute an important part of the proposed multi-step mechanism of OSG films damage and etching by thermal F atoms. Two models (POSS and TMCTS macromolecules and their modifications) are used to illustrate the peculiarities and dynamics of the successive reactions of F atoms with the initial SiCH3 and appeared SiCHxFy (x + y ≤ 3) surface groups. Contribution to the Topical Issue "Dynamics of Molecular Systems (MOLEC 2016)", edited by Alberto Garcia-Vela, Luis Banares and Maria Luisa Senent.

The oxidizing power of illinois coal. II. The effects of extended time

USGS Publications Warehouse

Yohe, G.R.; Wilt, M.H.

1942-01-01

The oxidizing power exhibited by five Illinois coals has been shown to reach a maximum value and then decrease, suggesting that this "reactive oxygen" may play the role of an intermediate in the oxidative degradation of these coals.

Coordinated control of active and reactive power of distribution network with distributed PV cluster via model predictive control

NASA Astrophysics Data System (ADS)

Ji, Yu; Sheng, Wanxing; Jin, Wei; Wu, Ming; Liu, Haitao; Chen, Feng

2018-02-01

A coordinated optimal control method of active and reactive power of distribution network with distributed PV cluster based on model predictive control is proposed in this paper. The method divides the control process into long-time scale optimal control and short-time scale optimal control with multi-step optimization. The models are transformed into a second-order cone programming problem due to the non-convex and nonlinear of the optimal models which are hard to be solved. An improved IEEE 33-bus distribution network system is used to analyse the feasibility and the effectiveness of the proposed control method

Real-Time Load-Side Control of Electric Power Systems

NASA Astrophysics Data System (ADS)

Zhao, Changhong

Two trends are emerging from modern electric power systems: the growth of renewable (e.g., solar and wind) generation, and the integration of information technologies and advanced power electronics. The former introduces large, rapid, and random fluctuations in power supply, demand, frequency, and voltage, which become a major challenge for real-time operation of power systems. The latter creates a tremendous number of controllable intelligent endpoints such as smart buildings and appliances, electric vehicles, energy storage devices, and power electronic devices that can sense, compute, communicate, and actuate. Most of these endpoints are distributed on the load side of power systems, in contrast to traditional control resources such as centralized bulk generators. This thesis focuses on controlling power systems in real time, using these load side resources. Specifically, it studies two problems. (1) Distributed load-side frequency control: We establish a mathematical framework to design distributed frequency control algorithms for flexible electric loads. In this framework, we formulate a category of optimization problems, called optimal load control (OLC), to incorporate the goals of frequency control, such as balancing power supply and demand, restoring frequency to its nominal value, restoring inter-area power flows, etc., in a way that minimizes total disutility for the loads to participate in frequency control by deviating from their nominal power usage. By exploiting distributed algorithms to solve OLC and analyzing convergence of these algorithms, we design distributed load-side controllers and prove stability of closed-loop power systems governed by these controllers. This general framework is adapted and applied to different types of power systems described by different models, or to achieve different levels of control goals under different operation scenarios. We first consider a dynamically coherent power system which can be equivalently modeled with a single synchronous machine. We then extend our framework to a multi-machine power network, where we consider primary and secondary frequency controls, linear and nonlinear power flow models, and the interactions between generator dynamics and load control. (2) Two-timescale voltage control: The voltage of a power distribution system must be maintained closely around its nominal value in real time, even in the presence of highly volatile power supply or demand. For this purpose, we jointly control two types of reactive power sources: a capacitor operating at a slow timescale, and a power electronic device, such as a smart inverter or a D-STATCOM, operating at a fast timescale. Their control actions are solved from optimal power flow problems at two timescales. Specifically, the slow-timescale problem is a chance-constrained optimization, which minimizes power loss and regulates the voltage at the current time instant while limiting the probability of future voltage violations due to stochastic changes in power supply or demand. This control framework forms the basis of an optimal sizing problem, which determines the installation capacities of the control devices by minimizing the sum of power loss and capital cost. We develop computationally efficient heuristics to solve the optimal sizing problem and implement real-time control. Numerical experiments show that the proposed sizing and control schemes significantly improve the reliability of voltage control with a moderate increase in cost.

Mitigating Space Weather Impacts on the Power Grid in Real-Time: Applying 3-D EarthScope Magnetotelluric Data to Forecasting Reactive Power Loss in Power Transformers

NASA Astrophysics Data System (ADS)

Schultz, A.; Bonner, L. R., IV

2017-12-01

Current efforts to assess risk to the power grid from geomagnetic disturbances (GMDs) that result in geomagnetically induced currents (GICs) seek to identify potential "hotspots," based on statistical models of GMD storm scenarios and power distribution grounding models that assume that the electrical conductivity of the Earth's crust and mantle varies only with depth. The NSF-supported EarthScope Magnetotelluric (MT) Program operated by Oregon State University has mapped 3-D ground electrical conductivity structure across more than half of the continental US. MT data, the naturally occurring time variations in the Earth's vector electric and magnetic fields at ground level, are used to determine the MT impedance tensor for each site (the ratio of horizontal vector electric and magnetic fields at ground level expressed as a complex-valued frequency domain quantity). The impedance provides information on the 3-D electrical conductivity structure of the Earth's crust and mantle. We demonstrate that use of 3-D ground conductivity information significantly improves the fidelity of GIC predictions over existing 1-D approaches. We project real-time magnetic field data streams from US Geological Survey magnetic observatories into a set of linear filters that employ the impedance data and that generate estimates of ground level electric fields at the locations of MT stations. The resulting ground electric fields are projected to and integrated along the path of power transmission lines. This serves as inputs to power flow models that represent the power transmission grid, yielding a time-varying set of quasi-real-time estimates of reactive power loss at the power transformers that are critical infrastructure for power distribution. We demonstrate that peak reactive power loss and hence peak risk for transformer damage from GICs does not necessarily occur during peak GMD storm times, but rather depends on the time-evolution of the polarization of the GMD's inducing fields and the complex ground (3-D) electric field response, and the resulting alignment of the ground electric fields with the power transmission line paths. This is informing our efforts to provide a set of real-time tools for power grid operators to use in mitigating damage from space weather events.

Best Practices for Operando Battery Experiments: Influences of X-ray Experiment Design on Observed Electrochemical Reactivity

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

Borkiewicz, O. J.; Wiaderek, Kamila M.; Chupas, Peter J.

Dynamic properties and multiscale complexities governing electrochemical energy storage in batteries are most ideally interrogated under simulated operating conditions within an electrochemical cell. We assess how electrochemical reactivity can be impacted by experiment design, including the X-ray measurements or by common features or adaptations of electrochemical cells that enable X-ray measurements.

A ReaxFF-based molecular dynamics study of the mechanisms of interactions between reactive oxygen plasma species and the Candida albicans cell wall

NASA Astrophysics Data System (ADS)

Zhao, T.; Shi, L.; Zhang, Y. T.; Zou, L.; Zhang, L.

2017-10-01

Atmospheric pressure non-equilibrium plasmas have attracted significant attention and have been widely used to inactivate pathogens, yet the mechanisms underlying the interactions between plasma-generated species and bio-organisms have not been elucidated clearly. In this paper, reactive molecular dynamics simulations are employed to investigate the mechanisms of interactions between reactive oxygen plasma species (O, OH, and O2) and β-1,6-glucan (a model for the C. albicans cell wall) from a microscopic point of view. Our simulations show that O and OH species can break structurally important C-C and C-O bonds, while O2 molecules exhibit only weak, non-bonded interactions with β-1,6-glucan. Hydrogen abstraction from hydroxyl or CH groups occurs first in all bond cleavage mechanisms. This is followed by a cascade of bond cleavage and double bond formation events. These lead to the destruction of the fungal cell wall. O and OH have similar effects related to their bond cleavage mechanisms. Our simulation results provide fundamental insights into the mechanisms underlying the interactions between reactive oxygen plasma species and the fungal cell wall of C. albicans at the atomic level.

The Dynamics of Memory: Context-Dependent Updating

ERIC Educational Resources Information Center

Hupbach, Almut; Hardt, Oliver; Gomez, Rebecca; Nadel, Lynn

2008-01-01

Understanding the dynamics of memory change is one of the current challenges facing cognitive neuroscience. Recent animal work on memory reconsolidation shows that memories can be altered long after acquisition. When reactivated, memories can be modified and require a restabilization (reconsolidation) process. We recently extended this finding to…

Guest Editorial Modeling and Advanced Control of Wind Turbines/Wind Farms

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

Hu, J.; Hou, Y.; Zhu, Z.

2017-09-01

The papers in this special section brings together papers focused on the recent advancements and breakthroughs in the technology of modeling and enhanced active/reactive power control of wind power conversion systems, ranging from components of wind turbines to wind farms.

An easy method for the determination of active concentrations of cholinesterase reactivators in blood samples: Application to the efficacy assessment of non quaternary reactivators compared to HI-6 and pralidoxime in VX-poisoned mice.

PubMed

Calas, André-Guilhem; Dias, José; Rousseau, Catherine; Arboléas, Mélanie; Touvrey-Loiodice, Mélanie; Mercey, Guillaume; Jean, Ludovic; Renard, Pierre-Yves; Nachon, Florian

2017-04-01

Organophosphorus nerve agents, like VX, are highly toxic due to their strong inhibition potency against acetylcholinesterase (AChE). AChE inhibited by VX can be reactivated using powerful nucleophilic molecules, most commonly oximes, which are one major component of the emergency treatment in case of nerve agent intoxication. We present here a comparative in vivo study on Swiss mice of four reactivators: HI-6, pralidoxime and two uncharged derivatives of 3-hydroxy-2-pyridinaldoxime that should more easily cross the blood-brain barrier and display a significant central nervous system activity. The reactivability kinetic profile of the oximes is established following intraperitoneal injection in healthy mice, using an original and fast enzymatic method based on the reactivation potential of oxime-containing plasma samples. HI-6 displays the highest reactivation potential whatever the conditions, followed by pralidoxime and the two non quaternary reactivators at the dose of 50 mg/kg bw. But these three last reactivators display equivalent reactivation potential at the same dose of 100 μmol/kg bw. Maximal reactivation potential closely correlates to surviving test results of VX intoxicated mice. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Reactive but not predictive locomotor adaptability is impaired in young Parkinson's disease patients.

PubMed

Moreno Catalá, María; Woitalla, Dirk; Arampatzis, Adamantios

2016-07-01

Gait and balance disorders are common in Parkinson's disease (PD) and major contributors to increased falling risk. Predictive and reactive adjustments can improve recovery performance after gait perturbations. However, these mechanisms have not been investigated in young-onset PD. We aimed to investigate the effect of gait perturbations on dynamic stability control as well as predictive and reactive adaptability to repeated gait perturbations in young PD patients. Fifteen healthy controls and twenty-five young patients (48±5yrs.) walked on a walkway. By means of a covered exchangeable element, the floor surface condition was altered to induce gait perturbations. The experimental protocol included a baseline on a hard surface, an unexpected trial on a soft surface and an adaptation phase with 5 soft trials to quantify the reactive adaptation. After the first and sixth soft trials, the surface was changed to hard, to examine after-effects and, thus, predictive motor control. Dynamic stability was assessed using the 'extrapolated center of mass' concept. Patients' unperturbed walking was less stable than controls' and this persisted in the perturbed trials. Both groups demonstrated after-effects directly after the first perturbation, showing similar predictive responses. However, PD patients did not improve their reactive behavior after repeated perturbations while controls showed clear locomotor adaptation. Our data suggest that more unstable gait patterns and a less effective reactive adaptation to perturbed walking may be a disease-related characteristic in young PD patients. These deficits were related to reduced ability to increase the base of support. Copyright © 2016 Elsevier B.V. All rights reserved.

On the dynamic nature of the engram: evidence for circuit-level reorganization of object memory traces following reactivation.

PubMed

Winters, Boyer D; Tucci, Mark C; Jacklin, Derek L; Reid, James M; Newsome, James

2011-11-30

Research has implicated the perirhinal cortex (PRh) in several aspects of object recognition memory. The specific role of the hippocampus (HPC) remains controversial, but its involvement in object recognition may pertain to processing contextual information in relation to objects rather than object representation per se. Here we investigated the roles of the PRh and HPC in object memory reconsolidation using the spontaneous object recognition task for rats. Intra-PRh infusions of the protein synthesis inhibitor anisomycin immediately following memory reactivation prevented object memory reconsolidation. Similar deficits were observed when a novel object or a salient contextual change was introduced during the reactivation phase. Intra-HPC infusions of anisomycin, however, blocked object memory reconsolidation only when a contextual change was introduced during reactivation. Moreover, disrupting functional interaction between the HPC and PRh by infusing anisomycin unilaterally into each structure in opposite hemispheres also impaired reconsolidation when reactivation was done in an altered context. These results show for the first time that the PRh is critical for reconsolidation of object memory traces and provide insight into the dynamic process of object memory storage; the selective requirement for hippocampal involvement following reactivation in an altered context suggests a substantial circuit level object trace reorganization whereby an initially PRh-dependent object memory becomes reliant on both the HPC and PRh and their interaction. Such trace reorganization may play a central role in reconsolidation-mediated memory updating and could represent an important aspect of lingering consolidation processes proposed to underlie long-term memory modulation and stabilization.

The Effect of Verbal Reminders on Memory Reactivation in 2-, 3-, and 4-Year-Old Children

ERIC Educational Resources Information Center

Imuta, Kana; Scarf, Damian; Hayne, Harlene

2013-01-01

For adults, verbal reminders provide a powerful key to unlock our memories. For example, a simple question, such as "Do you remember your wedding day?" can reactivate rich memories of the past, allowing us to recall experiences that may have occurred days, weeks, and even decades earlier. The ability to use another person's language to…

Enantioselective conjugate additions of α-amino radicals via cooperative photoredox and Lewis acid catalysis.

PubMed

Ruiz Espelt, Laura; McPherson, Iain S; Wiensch, Eric M; Yoon, Tehshik P

2015-02-25

We report the highly enantioselective addition of photogenerated α-amino radicals to Michael acceptors. This method features a dual-catalyst protocol that combines transition metal photoredox catalysis with chiral Lewis acid catalysis. The combination of these two powerful modes of catalysis provides an effective, general strategy to generate and control the reactivity of photogenerated reactive intermediates.

Reactive transport in a partially molten system with binary solid solution

NASA Astrophysics Data System (ADS)

Jordan, J.; Hesse, M. A.

2017-12-01

Melt extraction from the Earth's mantle through high-porosity channels is required to explain the composition of the oceanic crust. Feedbacks from reactive melt transport are thought to localize melt into a network of high-porosity channels. Recent studies invoke lithological heterogeneities in the Earth's mantle to seed the localization of partial melts. Therefore, it is necessary to understand the reaction fronts that form as melt flows across the lithological interface of a heterogeneity and the background mantle. Simplified melting models of such systems aide in the interpretation and formulation of larger scale mantle models. Motivated by the aforementioned facts, we present a chromatographic analysis of reactive melt transport across lithological boundaries, using theory for hyperbolic conservation laws. This is an extension of well-known linear trace element chromatography to the coupling of major elements and energy transport. Our analysis allows the prediction of the feedbacks that arise in reactive melt transport due to melting, freezing, dissolution and precipitation for frontal reactions. This study considers the simplified case of a rigid, partially molten porous medium with binary solid solution. As melt traverses a lithological contact-modeled as a Riemann problem-a rich set of features arise, including a reacted zone between an advancing reaction front and partial chemical preservation of the initial contact. Reactive instabilities observed in this study originate at the lithological interface rather than along a chemical gradient as in most studies of mantle dynamics. We present a regime diagram that predicts where reaction fronts become unstable, thereby allowing melt localization into high-porosity channels through reactive instabilities. After constructing the regime diagram, we test the one-dimensional hyperbolic theory against two-dimensional numerical experiments. The one-dimensional hyperbolic theory is sufficient for predicting the qualitative behavior of reactive melt transport simulations conducted in two-dimensions. The theoretical framework presented can be extended to more complex and realistic phase behavior, and is therefore a useful tool for understanding nonlinear feedbacks in reactive melt transport problems relevant to mantle dynamics.

Preliminary design study of small long life boiling water reactor (BWR) with tight lattice thorium nitride fuel

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

Trianti, Nuri, E-mail: nuri.trianti@gmail.com, E-mail: szaki@fi.itba.c.id; Su'ud, Zaki, E-mail: nuri.trianti@gmail.com, E-mail: szaki@fi.itba.c.id; Arif, Idam, E-mail: nuri.trianti@gmail.com, E-mail: szaki@fi.itba.c.id

2014-09-30

Neutronic performance of small long-life boiling water reactors (BWR) with thorium nitride based fuel has been performed. A recent study conducted on BWR in tight lattice environments (with a lower moderator percentage) produces small power reactor which has some specifications, i.e. 10 years operation time, power density of 19.1 watt/cc and maximum excess reactivity of about 4%. This excess reactivity value is smaller than standard reactivity of conventional BWR. The use of hexagonal geometry on the fuel cell of BWR provides a substantial effect on the criticality of the reactor to obtain a longer operating time. Supported by a tightmore » concept lattice where the volume fraction of the fuel is greater than the moderator and fuel, Thorium Nitride give good results for fuel cell design on small long life BWR. The excess reactivity of the reactor can be reduced with the addition of gadolinium as burnable poisons. Therefore the hexagonal tight lattice fuel cell design of small long life BWR that has a criticality more than 20 years of operating time has been obtained.« less

Focal vibration of quadriceps muscle enhances leg power and decreases knee joint laxity in female volleyball players.

PubMed

Brunetti, O; Botti, F M; Roscini, M; Brunetti, A; Panichi, R; Filippi, G M; Biscarini, A; Pettorossi, V E

2012-12-01

This double-blind randomized controlled study aims at determining the effect of repeated muscle vibration (rMV) on explosive and reactive leg power and on knee laxity of female volleyball players. Eighteen voluntary volleyball athletes, belonging to the same senior regional level team (age=22.7 ± 3 years, height=180.3 ± 5 cm, mass= 64 ± 4 kg) were assigned to three groups (N.=6) for vibration on contracted quadriceps (VC), vibration on relaxed muscle (VR), and sham vibration (NV), respectively. Intervention consisted in 3 rMV sessions performed in 3 consecutive days. In each session, 100 Hz, 300-500 μm amplitude vibratory stimuli were bilaterally delivered to the quadriceps in three consecutive 10-minutes applications. Explosive and reactive leg power and knee joint laxity were evaluated 1 day before, and 1, 30, and 240 days after intervention. In VC group, explosive and reactive leg power increased respectively by ~16% and ~9% at 1 day, by ~19% and ~11% at 30 days and by ~26% and ~13% at 240 days, concomitantly knee laxity decreased by ~6%, ~15% and ~18% at the same times. These changes were significantly larger than in the other groups, in which leg power increment and knee joint laxity reduction remained close to ~3%, ~5% and ~10% at 1, 30 and 240 days, respectively. Combined bilateral voluntary contraction and rMV of the quadriceps muscles is a short-lasting, non-invasive technique that can significantly and persistently improve muscle performance and knee laxity in volleyball women players.

A transaction assessment method for allocation of transmission services

NASA Astrophysics Data System (ADS)

Banunarayanan, Venkatasubramaniam

The purpose of this research is to develop transaction assessment methods for allocating transmission services that are provided by an area/utility to power transactions. Transmission services are the services needed to deliver, or provide the capacity to deliver, real and reactive power from one or more supply points to one or more delivery points. As the number of transactions increase rapidly in the emerging deregulated environment, accurate quantification of the transmission services an area/utility provides to accommodate a transaction is becoming important, because then appropriate pricing schemes can be developed to compensate for the parties that provide these services. The Allocation methods developed are based on the "Fair Resource Allocation Principle" and they determine for each transaction the following: the flowpath of the transaction (both real and reactive power components), generator reactive power support from each area/utility, real power loss support from each area/utility. Further, allocation methods for distributing the cost of relieving congestion on transmission lines caused by transactions are also developed. The main feature of the proposed methods is representation of actual usage of the transmission services by the transactions. The proposed method is tested extensively on a variety of systems. The allocation methods developed in this thesis for allocation of transmission services to transactions is not only useful in studying the impact of transactions on a transmission system in a multi-transaction case, but they are indeed necessary to meet the criteria set forth by FERC with regard to pricing based on actual usage. The "consistency" of the proposed allocation methods has also been investigated and tested.

Distributed Storage Inverter and Legacy Generator Integration Plus Renewables Solution for Microgrids

DTIC Science & Technology

2015-07-01

Reactive kVAR Kilo Watts kW Lithium Ion Li Ion Lithium-Titanate Oxide nLTO Natural gas NG Performance Objectives PO Photovoltaic PV Power ...cloud covered) periods. The demonstration features a large (relative to the overall system power requirements) photovoltaic solar array, whose inverter...microgrid with less expensive power storage instead of large scale energy storage and that the renewable energy with small-scale power storage can

Google-Earth Based Visualizations for Environmental Flows and Pollutant Dispersion in Urban Areas

PubMed Central

Liu, Daoming; Kenjeres, Sasa

2017-01-01

In the present study, we address the development and application of an efficient tool for conversion of results obtained by an integrated computational fluid dynamics (CFD) and computational reaction dynamics (CRD) approach and their visualization in the Google Earth. We focus on results typical for environmental fluid mechanics studies at a city scale that include characteristic wind flow patterns and dispersion of reactive scalars. This is achieved by developing a code based on the Java language, which converts the typical four-dimensional structure (spatial and temporal dependency) of data results in the Keyhole Markup Language (KML) format. The visualization techniques most often used are revisited and implemented into the conversion tool. The potential of the tool is demonstrated in a case study of smog formation due to an intense traffic emission in Rotterdam (The Netherlands). It is shown that the Google Earth can provide a computationally efficient and user-friendly means of data representation. This feature can be very useful for visualization of pollution at street levels, which is of great importance for the city residents. Various meteorological and traffic emissions can be easily visualized and analyzed, providing a powerful, user-friendly tool for traffic regulations and urban climate adaptations. PMID:28257078

Theoretical and computational studies of non-equilibrium and non-statistical dynamics in the gas phase, in the condensed phase and at interfaces.

PubMed

Spezia, Riccardo; Martínez-Nuñez, Emilio; Vazquez, Saulo; Hase, William L

2017-04-28

In this Introduction, we show the basic problems of non-statistical and non-equilibrium phenomena related to the papers collected in this themed issue. Over the past few years, significant advances in both computing power and development of theories have allowed the study of larger systems, increasing the time length of simulations and improving the quality of potential energy surfaces. In particular, the possibility of using quantum chemistry to calculate energies and forces 'on the fly' has paved the way to directly study chemical reactions. This has provided a valuable tool to explore molecular mechanisms at given temperatures and energies and to see whether these reactive trajectories follow statistical laws and/or minimum energy pathways. This themed issue collects different aspects of the problem and gives an overview of recent works and developments in different contexts, from the gas phase to the condensed phase to excited states.This article is part of the themed issue 'Theoretical and computational studies of non-equilibrium and non-statistical dynamics in the gas phase, in the condensed phase and at interfaces'. © 2017 The Author(s).

Coupling crystal plasticity and phase-field damage to simulate β-HMX-based polymer-bonded explosive under shock load

NASA Astrophysics Data System (ADS)

Grilli, Nicolo; Dandekar, Akshay; Koslowski, Marisol

2017-06-01

The development of high explosive materials requires constitutive models that are able to predict the influence of microstructure and loading conditions on shock sensitivity. In this work a model at the continuum-scale for the polymer-bonded explosive constituted of β-HMX particles embedded in a Sylgard matrix is developed. It includes a Murnaghan equation of state, a crystal plasticity model, based on power-law slip rate and hardening, and a phase field damage model based on crack regularization. The temperature increase due to chemical reactions is introduced by a heat source term, which is validated using results from reactive molecular dynamics simulations. An initial damage field representing pre-existing voids and cracks is used in the simulations to understand the effect of these inhomogeneities on the damage propagation and shock sensitivity. We show the predictions of the crystal plasticity model and the effect of the HMX crystal orientation on the shock initiation and on the dissipated plastic work and damage propagation. The simulation results are validated with ultra-fast dynamic transmission electron microscopy experiments and x-ray experiments carried out at Purdue University. Membership Pending.

Micromachined low frequency rocking accelerometer with capacitive pickoff

DOEpatents

Lee, Abraham P.; Simon, Jonathon N.; McConaghy, Charles F.

2001-01-01

A micro electro mechanical sensor that uses capacitive readout electronics. The sensor involves a micromachined low frequency rocking accelerometer with capacitive pickoff fabricated by deep reactive ion etching. The accelerometer includes a central silicon proof mass, is suspended by a thin polysilicon tether, and has a moving electrode (capacitor plate or interdigitated fingers) located at each end the proof mass. During movement (acceleration), the tethered mass moves relative to the surrounding packaging, for example, and this defection is measured capacitively by a plate capacitor or interdigitated finger capacitor, having the cooperating fixed electrode (capacitor plate or interdigitated fingers) positioned on the packaging, for example. The micromachined rocking accelerometer has a low frequency (<500 Hz), high sensitivity (.mu.G), with minimal power usage. The capacitors are connected to a power supply (battery) and to sensor interface electronics, which may include an analog to digital (A/D) converter, logic, RF communication link, antenna, etc. The sensor (accelerometer) may be, for example, packaged along with the interface electronics and a communication system in a 2".times.2".times.2" cube. The proof mass may be asymmetric or symmetric. Additional actuating capacitive plates may be used for feedback control which gives a greater dynamic range.

Power output and carrier dynamics studies of perovskite solar cells under working conditions.

PubMed

Yu, Man; Wang, Hao-Yi; Hao, Ming-Yang; Qin, Yujun; Fu, Li-Min; Zhang, Jian-Ping; Ai, Xi-Cheng

2017-08-02

Perovskite solar cells have emerged as promising photovoltaic systems with superb power conversion efficiency. For the practical application of perovskite devices, the greatest concerns are the power output density and the related dynamics under working conditions. In this study, the working conditions of planar and mesoscopic perovskite solar cells are simulated and the power output density evolutions with the working voltage are highlighted. The planar device exhibits higher capability of outputting power than the mesoscopic one. The transient photoelectric conversion dynamics are investigated under the open circuit, short circuit and working conditions. It is found that the power output and dynamic processes are correlated intrinsically, which suggests that the power output is the competitive result of the charge carrier recombination and transport. The present work offers a unique view to elucidating the relationship between the power output and the charge carrier dynamics for perovskite solar cells in a comprehensive manner, which would be beneficial to their future practical applications.

Taking Ockham's razor to enzyme dynamics and catalysis.

PubMed

Glowacki, David R; Harvey, Jeremy N; Mulholland, Adrian J

2012-01-29

The role of protein dynamics in enzyme catalysis is a matter of intense current debate. Enzyme-catalysed reactions that involve significant quantum tunnelling can give rise to experimental kinetic isotope effects with complex temperature dependences, and it has been suggested that standard statistical rate theories, such as transition-state theory, are inadequate for their explanation. Here we introduce aspects of transition-state theory relevant to the study of enzyme reactivity, taking cues from chemical kinetics and dynamics studies of small molecules in the gas phase and in solution--where breakdowns of statistical theories have received significant attention and their origins are relatively better understood. We discuss recent theoretical approaches to understanding enzyme activity and then show how experimental observations for a number of enzymes may be reproduced using a transition-state-theory framework with physically reasonable parameters. Essential to this simple model is the inclusion of multiple conformations with different reactivity.

Dynamic optical imaging of vascular and metabolic reactivity in rheumatoid joints.

PubMed

Lasker, Joseph M; Fong, Christopher J; Ginat, Daniel T; Dwyer, Edward; Hielscher, Andreas H

2007-01-01

Dynamic optical imaging is increasingly applied to clinically relevant areas such as brain and cancer imaging. In this approach, some external stimulus is applied and changes in relevant physiological parameters (e.g., oxy- or deoxyhemoglobin concentrations) are determined. The advantage of this approach is that the prestimulus state can be used as a reference or baseline against which the changes can be calibrated. Here we present the first application of this method to the problem of characterizing joint diseases, especially effects of rheumatoid arthritis (RA) in the proximal interphalangeal finger joints. Using a dual-wavelength tomographic imaging system together with previously implemented model-based iterative image reconstruction schemes, we have performed initial dynamic imaging case studies on a limited number of healthy volunteers and patients diagnosed with RA. Focusing on three cases studies, we illustrated our major finds. These studies support our hypothesis that differences in the vascular reactivity exist between affected and unaffected joints.

DFT-derived reactive potentials for the simulation of activated processes: the case of CdTe and CdTe:S.

PubMed

Hu, Xiao Liang; Ciaglia, Riccardo; Pietrucci, Fabio; Gallet, Grégoire A; Andreoni, Wanda

2014-06-19

We introduce a new ab initio derived reactive potential for the simulation of CdTe within density functional theory (DFT) and apply it to calculate both static and dynamical properties of a number of systems (bulk solid, defective structures, liquid, surfaces) at finite temperature. In particular, we also consider cases with low sulfur concentration (CdTe:S). The analysis of DFT and classical molecular dynamics (MD) simulations performed with the same protocol leads to stringent performance tests and to a detailed comparison of the two schemes. Metadynamics techniques are used to empower both Car-Parrinello and classical molecular dynamics for the simulation of activated processes. For the latter, we consider surface reconstruction and sulfur diffusion in the bulk. The same procedures are applied using previously proposed force fields for CdTe and CdTeS materials, thus allowing for a detailed comparison of the various schemes.

Communication: State-to-state dynamics of the Cl + H2O → HCl + OH reaction: Energy flow into reaction coordinate and transition-state control of product energy disposal.

PubMed

Zhao, Bin; Sun, Zhigang; Guo, Hua

2015-06-28

Quantum state-to-state dynamics of a prototypical four-atom reaction, namely, Cl + H2O → HCl + OH, is investigated for the first time in full dimensionality using a transition-state wave packet method. The state-to-state reactivity and its dependence on the reactant internal excitations are analyzed and found to share many similarities both energetically and dynamically with the H + H2O → H2 + OH reaction. The strong enhancement of reactivity by the H2O stretching vibrational excitations in both reactions is attributed to the favorable energy flow into the reaction coordinate near the transition state. On the other hand, the insensitivity of the product state distributions with regard to reactant internal excitation stems apparently from the transition-state control of product energy disposal.

Effects of a Supervised versus an Unsupervised Combined Balance and Strength Training Program on Balance and Muscle Power in Healthy Older Adults: A Randomized Controlled Trial.

PubMed

Lacroix, André; Kressig, Reto W; Muehlbauer, Thomas; Gschwind, Yves J; Pfenninger, Barbara; Bruegger, Othmar; Granacher, Urs

2016-01-01

Losses in lower extremity muscle strength/power, muscle mass and deficits in static and particularly dynamic balance due to aging are associated with impaired functional performance and an increased fall risk. It has been shown that the combination of balance and strength training (BST) mitigates these age-related deficits. However, it is unresolved whether supervised versus unsupervised BST is equally effective in improving muscle power and balance in older adults. This study examined the impact of a 12-week BST program followed by 12 weeks of detraining on measures of balance and muscle power in healthy older adults enrolled in supervised (SUP) or unsupervised (UNSUP) training. Sixty-six older adults (men: 25, women: 41; age 73 ± 4 years) were randomly assigned to a SUP group (2/week supervised training, 1/week unsupervised training; n = 22), an UNSUP group (3/week unsupervised training; n = 22) or a passive control group (CON; n = 22). Static (i.e., Romberg Test) and dynamic (i.e., 10-meter walk test) steady-state, proactive (i.e., Timed Up and Go Test, Functional Reach Test), and reactive balance (e.g., Push and Release Test), as well as lower extremity muscle power (i.e., Chair Stand Test; Stair Ascent and Descent Test) were tested before and after the active training phase as well as after detraining. Adherence rates to training were 92% for SUP and 97% for UNSUP. BST resulted in significant group × time interactions. Post hoc analyses showed, among others, significant training-related improvements for the Romberg Test, stride velocity, Timed Up and Go Test, and Chair Stand Test in favor of the SUP group. Following detraining, significantly enhanced performances (compared to baseline) were still present in 13 variables for the SUP group and in 10 variables for the UNSUP group. Twelve weeks of BST proved to be safe (no training-related injuries) and feasible (high attendance rates of >90%). Deficits of balance and lower extremity muscle power can be mitigated by BST in healthy older adults. Additionally, supervised as compared to unsupervised BST was more effective. Thus, it is recommended to counteract intrinsic fall risk factors by applying supervised BST programs for older adults. © 2015 The Author(s) Published by S. Karger AG, Basel.

A MATLAB-based finite-element visualization of quantum reactive scattering. I. Collinear atom-diatom reactions

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

Warehime, Mick; Alexander, Millard H., E-mail: mha@umd.edu

We restate the application of the finite element method to collinear triatomic reactive scattering dynamics with a novel treatment of the scattering boundary conditions. The method provides directly the reactive scattering wave function and, subsequently, the probability current density field. Visualizing these quantities provides additional insight into the quantum dynamics of simple chemical reactions beyond simplistic one-dimensional models. Application is made here to a symmetric reaction (H+H{sub 2}), a heavy-light-light reaction (F+H{sub 2}), and a heavy-light-heavy reaction (F+HCl). To accompany this article, we have written a MATLAB code which is fast, simple enough to be accessible to a wide audience,more » as well as generally applicable to any problem that can be mapped onto a collinear atom-diatom reaction. The code and user's manual are available for download from http://www2.chem.umd.edu/groups/alexander/FEM.« less

Plyometrics: A Legitimate Form of Power Training?

ERIC Educational Resources Information Center

Duda, Marty

1988-01-01

Plyometric exercises or drills combine speed and strength to produce an explosive-reactive movement or increased power. Some world-class athletes have used plyometric-training in sports such as high-jumping, hurdles, football, baseball, and hockey. The method is still considered experimental. Sample exercises are described. (JL)

Nanoklystron: A Monolithic Tube Approach to THz Power Generation

NASA Technical Reports Server (NTRS)

Siegel, Peter H.; Fung, Andy; Manohara, Harish; Xu, Jimmy; Chang, Baohe

2001-01-01

The authors propose a new approach to THz power generation: the nanoklystron. Utilizing silicon micromachining techniques, the design and fabrication concept of a monolithic THz vacuum-tube reflex-klystron source is described. The nanoklystron employs a separately fabricated cathode structure composed of densely packed carbon nanotube field emitters and an add-in repeller. The nanotube cathode is expected to increase the current density, extend the cathode life and decrease the required oscillation voltage to values below 100 V. The excitation cavity is based on ridged-waveguide and differs from the conventional cylindrical re-entrant structures found in lower frequency klystrons. A quasi-static field analysis of the cavity and output coupling structure show excellent control of the quality factor and desired field distribution. Output power is expected to occur through an iris coupled matched rectangular waveguide and integrated pyramidal feed horn. The entire circuit is designed so as to be formed monolithically from two thermocompression bonded silicon wafers processed using deep reactive ion etching (DRIE) techniques. To expedite prototyping, a 600 GHz mechanically machined structure has been designed and is in fabrication. A complete numeric analysis of the nanoklystron circuit, including the electron beam dynamics has just gotten underway. Separate evaluation of the nanotube cathodes is also ongoing. The authors will describe the progress to date as well as plans for the immediate implementation and testing of nanoklystron prototypes at 640 and 1250 GHz.

Differential blood flow responses to CO2 in human internal and external carotid and vertebral arteries

PubMed Central

Sato, Kohei; Sadamoto, Tomoko; Hirasawa, Ai; Oue, Anna; Subudhi, Andrew W; Miyazawa, Taiki; Ogoh, Shigehiko

2012-01-01

Arterial CO2 serves as a mediator of cerebral blood flow (CBF), and its relative influence on the regulation of CBF is defined as cerebral CO2 reactivity. Our previous studies have demonstrated that there are differences in CBF responses to physiological stimuli (i.e. dynamic exercise and orthostatic stress) between arteries in humans. These findings suggest that dynamic CBF regulation and cerebral CO2 reactivity may be different in the anterior and posterior cerebral circulation. The aim of this study was to identify cerebral CO2 reactivity by measuring blood flow and examine potential differences in CO2 reactivity between the internal carotid artery (ICA), external carotid artery (ECA) and vertebral artery (VA). In 10 healthy young subjects, we evaluated the ICA, ECA, and VA blood flow responses by duplex ultrasonography (Vivid-e, GE Healthcare), and mean blood flow velocity in middle cerebral artery (MCA) and basilar artery (BA) by transcranial Doppler (Vivid-7, GE healthcare) during two levels of hypercapnia (3% and 6% CO2), normocapnia and hypocapnia to estimate CO2 reactivity. To characterize cerebrovascular reactivity to CO2, we used both exponential and linear regression analysis between CBF and estimated partial pressure of arterial CO2, calculated by end-tidal partial pressure of CO2. CO2 reactivity in VA was significantly lower than in ICA (coefficient of exponential regression 0.021 ± 0.008 vs. 0.030 ± 0.008; slope of linear regression 2.11 ± 0.84 vs. 3.18 ± 1.09% mmHg−1: VA vs. ICA, P < 0.01). Lower CO2 reactivity in the posterior cerebral circulation was persistent in distal intracranial arteries (exponent 0.023 ± 0.006 vs. 0.037 ± 0.009; linear 2.29 ± 0.56 vs. 3.31 ± 0.87% mmHg−1: BA vs. MCA). In contrast, CO2 reactivity in ECA was markedly lower than in the intra-cerebral circulation (exponent 0.006 ± 0.007; linear 0.63 ± 0.64% mmHg−1, P < 0.01). These findings indicate that vertebro-basilar circulation has lower CO2 reactivity than internal carotid circulation, and that CO2 reactivity of the external carotid circulation is markedly diminished compared to that of the cerebral circulation, which may explain different CBF responses to physiological stress. PMID:22526884

Dynamic remedial action scheme using online transient stability analysis

NASA Astrophysics Data System (ADS)

Shrestha, Arun

Economic pressure and environmental factors have forced the modern power systems to operate closer to their stability limits. However, maintaining transient stability is a fundamental requirement for the operation of interconnected power systems. In North America, power systems are planned and operated to withstand the loss of any single or multiple elements without violating North American Electric Reliability Corporation (NERC) system performance criteria. For a contingency resulting in the loss of multiple elements (Category C), emergency transient stability controls may be necessary to stabilize the power system. Emergency control is designed to sense abnormal conditions and subsequently take pre-determined remedial actions to prevent instability. Commonly known as either Remedial Action Schemes (RAS) or as Special/System Protection Schemes (SPS), these emergency control approaches have been extensively adopted by utilities. RAS are designed to address specific problems, e.g. to increase power transfer, to provide reactive support, to address generator instability, to limit thermal overloads, etc. Possible remedial actions include generator tripping, load shedding, capacitor and reactor switching, static VAR control, etc. Among various RAS types, generation shedding is the most effective and widely used emergency control means for maintaining system stability. In this dissertation, an optimal power flow (OPF)-based generation-shedding RAS is proposed. This scheme uses online transient stability calculation and generator cost function to determine appropriate remedial actions. For transient stability calculation, SIngle Machine Equivalent (SIME) technique is used, which reduces the multimachine power system model to a One-Machine Infinite Bus (OMIB) equivalent and identifies critical machines. Unlike conventional RAS, which are designed using offline simulations, online stability calculations make the proposed RAS dynamic and adapting to any power system configuration and operating state. The generation-shedding cost is calculated using pre-RAS and post-RAS OPF costs. The criteria for selecting generators to trip is based on the minimum cost rather than minimum amount of generation to shed. For an unstable Category C contingency, the RAS control action that results in stable system with minimum generation shedding cost is selected among possible candidate solutions. The RAS control actions update whenever there is a change in operating condition, system configuration, or cost functions. The effectiveness of the proposed technique is demonstrated by simulations on the IEEE 9-bus system, the IEEE 39-bus system, and IEEE 145-bus system. This dissertation also proposes an improved, yet relatively simple, technique for solving Transient Stability-Constrained Optimal Power Flow (TSC-OPF) problem. Using the SIME method, the sets of dynamic and transient stability constraints are reduced to a single stability constraint, decreasing the overall size of the optimization problem. The transient stability constraint is formulated using the critical machines' power at the initial time step, rather than using the machine rotor angles. This avoids the addition of machine steady state stator algebraic equations in the conventional OPF algorithm. A systematic approach to reach an optimal solution is developed by exploring the quasi-linear behavior of critical machine power and stability margin. The proposed method shifts critical machines active power based on generator costs using an OPF algorithm. Moreover, the transient stability limit is based on stability margin, and not on a heuristically set limit on OMIB rotor angle. As a result, the proposed TSC-OPF solution is more economical and transparent. The proposed technique enables the use of fast and robust commercial OPF tool and time-domain simulation software for solving large scale TSC-OPF problem, which makes the proposed method also suitable for real-time application.

Analysis of economic benefit of wind power based on system dynamics

NASA Astrophysics Data System (ADS)

Zhao, Weibo; Han, Yaru; Niu, Dongxiao

2018-04-01

The scale of renewable power generation, such as wind power, has increased gradually in recent years. Considering that the economic benefits of wind farms are affected by many dynamic factors. The dynamic simulation model of wind power economic benefit system is established based on the system dynamics method. By comparing the economic benefits of wind farms under different setting scenarios through this model, the impact of different factors on the economic benefits of wind farms can be reflected.

The hydrophilic-to-hydrophobic transition in glassy silica is driven by the atomic topology of its surface

NASA Astrophysics Data System (ADS)

Yu, Yingtian; Krishnan, N. M. Anoop; Smedskjaer, Morten M.; Sant, Gaurav; Bauchy, Mathieu

2018-02-01

The surface reactivity and hydrophilicity of silicate materials are key properties for various industrial applications. However, the structural origin of their affinity for water remains unclear. Here, based on reactive molecular dynamics simulations of a series of artificial glassy silica surfaces annealed at various temperatures and subsequently exposed to water, we show that silica exhibits a hydrophilic-to-hydrophobic transition driven by its silanol surface density. By applying topological constraint theory, we show that the surface reactivity and hydrophilic/hydrophobic character of silica are controlled by the atomic topology of its surface. This suggests that novel silicate materials with tailored reactivity and hydrophilicity could be developed through the topological nanoengineering of their surface.

Fringe-controlled biodegradation under dynamic conditions: quasi 2-D flow-through experiments and reactive-transport modeling.

PubMed

Eckert, Dominik; Kürzinger, Petra; Bauer, Robert; Griebler, Christian; Cirpka, Olaf A

2015-01-01

Biodegradation in contaminated aquifers has been shown to be most pronounced at the fringe of contaminant plumes, where mixing of contaminated water and ambient groundwater, containing dissolved electron acceptors, stimulates microbial activity. While physical mixing of contaminant and electron acceptor by transverse dispersion has been shown to be the major bottleneck for biodegradation in steady-state plumes, so far little is known on the effect of flow and transport dynamics (caused, e.g., by a seasonally fluctuating groundwater table) on biodegradation in these systems. Towards this end we performed experiments in quasi-two-dimensional flow-through microcosms on aerobic toluene degradation by Pseudomonas putida F1. Plume dynamics were simulated by vertical alteration of the toluene plume position and experimental results were analyzed by reactive-transport modeling. We found that, even after disappearance of the toluene plume for two weeks, the majority of microorganisms stayed attached to the sediment and regained their full biodegradation potential within two days after reappearance of the toluene plume. Our results underline that besides microbial growth, also maintenance and dormancy are important processes that affect biodegradation performance under transient environmental conditions and therefore deserve increased consideration in future reactive-transport modeling. Copyright © 2014 Elsevier B.V. All rights reserved.

Lattice Boltzmann simulation of CO2 reactive transport in network fractured media

NASA Astrophysics Data System (ADS)

Tian, Zhiwei; Wang, Junye

2017-08-01

Carbon dioxide (CO2) geological sequestration plays an important role in mitigating CO2 emissions for climate change. Understanding interactions of the injected CO2 with network fractures and hydrocarbons is key for optimizing and controlling CO2 geological sequestration and evaluating its risks to ground water. However, there is a well-known, difficult process in simulating the dynamic interaction of fracture-matrix, such as dynamic change of matrix porosity, unsaturated processes in rock matrix, and effect of rock mineral properties. In this paper, we develop an explicit model of the fracture-matrix interactions using multilayer bounce-back treatment as a first attempt to simulate CO2 reactive transport in network fractured media through coupling the Dardis's LBM porous model for a new interface treatment. Two kinds of typical fracture networks in porous media are simulated: straight cross network fractures and interleaving network fractures. The reaction rate and porosity distribution are illustrated and well-matched patterns are found. The species concentration distribution and evolution with time steps are also analyzed and compared with different transport properties. The results demonstrate the capability of this model to investigate the complex processes of CO2 geological injection and reactive transport in network fractured media, such as dynamic change of matrix porosity.

Extended asymmetric hot region formation due to shockwave interactions following void collapse in shocked high explosive

DOE PAGES

Shan, Tzu -Ray; Wixom, Ryan R.; Thompson, Aidan P.

2016-08-01

In both continuum hydrodynamics simulations and also multimillion atom reactive molecular dynamics simulations of shockwave propagation in single crystal pentaerythritol tetranitrate (PETN) containing a cylindrical void, we observed the formation of an initial radially symmetric hot spot. By extending the simulation time to the nanosecond scale, however, we observed the transformation of the small symmetric hot spot into a longitudinally asymmetric hot region extending over a much larger volume. Performing reactive molecular dynamics shock simulations using the reactive force field (ReaxFF) as implemented in the LAMMPS molecular dynamics package, we showed that the longitudinally asymmetric hot region was formed bymore » coalescence of the primary radially symmetric hot spot with a secondary triangular hot zone. We showed that the triangular hot zone coincided with a double-shocked region where the primary planar shockwave was overtaken by a secondary cylindrical shockwave. The secondary cylindrical shockwave originated in void collapse after the primary planar shockwave had passed over the void. A similar phenomenon was observed in continuum hydrodynamics shock simulations using the CTH hydrodynamics package. Furthermore, the formation and growth of extended asymmetric hot regions on nanosecond timescales has important implications for shock initiation thresholds in energetic materials.« less

Extended asymmetric hot region formation due to shockwave interactions following void collapse in shocked high explosive

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

Shan, Tzu -Ray; Wixom, Ryan R.; Thompson, Aidan P.

In both continuum hydrodynamics simulations and also multimillion atom reactive molecular dynamics simulations of shockwave propagation in single crystal pentaerythritol tetranitrate (PETN) containing a cylindrical void, we observed the formation of an initial radially symmetric hot spot. By extending the simulation time to the nanosecond scale, however, we observed the transformation of the small symmetric hot spot into a longitudinally asymmetric hot region extending over a much larger volume. Performing reactive molecular dynamics shock simulations using the reactive force field (ReaxFF) as implemented in the LAMMPS molecular dynamics package, we showed that the longitudinally asymmetric hot region was formed bymore » coalescence of the primary radially symmetric hot spot with a secondary triangular hot zone. We showed that the triangular hot zone coincided with a double-shocked region where the primary planar shockwave was overtaken by a secondary cylindrical shockwave. The secondary cylindrical shockwave originated in void collapse after the primary planar shockwave had passed over the void. A similar phenomenon was observed in continuum hydrodynamics shock simulations using the CTH hydrodynamics package. Furthermore, the formation and growth of extended asymmetric hot regions on nanosecond timescales has important implications for shock initiation thresholds in energetic materials.« less

ReaxFF based molecular dynamics simulations of ignition front propagation in hydrocarbon/oxygen mixtures under high temperature and pressure conditions.

PubMed

Ashraf, Chowdhury; Jain, Abhishek; Xuan, Yuan; van Duin, Adri C T

2017-02-15

In this paper, we present the first atomistic-scale based method for calculating ignition front propagation speed and hypothesize that this quantity is related to laminar flame speed. This method is based on atomistic-level molecular dynamics (MD) simulations with the ReaxFF reactive force field. Results reported in this study are for supercritical (P = 55 MPa and T u = 1800 K) combustion of hydrocarbons as elevated pressure and temperature are required to accelerate the dynamics for reactive MD simulations. These simulations are performed for different types of hydrocarbons, including alkyne, alkane, and aromatic, and are able to successfully reproduce the experimental trend of reactivity of these hydrocarbons. Moreover, our results indicate that the ignition front propagation speed under supercritical conditions has a strong dependence on equivalence ratio, similar to experimentally measured flame speeds at lower temperatures and pressures which supports our hypothesis that ignition front speed is a related quantity to laminar flame speed. In addition, comparisons between results obtained from ReaxFF simulation and continuum simulations performed under similar conditions show good qualitative, and reasonable quantitative agreement. This demonstrates that ReaxFF based MD-simulations are a promising tool to study flame speed/ignition front speed in supercritical hydrocarbon combustion.

Network-Cognizant Design of Decentralized Volt/VAR Controllers

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

Baker, Kyri A; Bernstein, Andrey; Zhao, Changhong

This paper considers the problem of designing decentralized Volt/VAR controllers for distributed energy resources (DERs). The voltage-reactive power characteristics of individual DERs are obtained by solving a convex optimization problem, where given performance objectives (e.g., minimization of the voltage deviations from a given profile) are specified and stability constraints are enforced. The resultant Volt/VAR characteristics are network-cognizant, in the sense that they embed information on the location of the DERs and, consequently, on the effect of reactive-power adjustments on the voltages throughout the feeder. Bounds on the maximum voltage deviation incurred by the controllers are analytically established. Numerical results aremore » reported to corroborate the technical findings.« less

Solar pv fed stand-alone excitation system of a synchronous machine for reactive power generation

NASA Astrophysics Data System (ADS)

Sudhakar, N.; Jain, Siddhartha; Jyotheeswara Reddy, K.

2017-11-01

This paper presents a model of a stand-alone solar energy conversion system based on synchronous machine working as a synchronous condenser in overexcited state. The proposed model consists of a Synchronous Condenser, a DC/DC boost converter whose output is fed to the field of the SC. The boost converter is supplied by the modelled solar panel and a day time variable irradiance is fed to the panel during the simulation time. The model also has one alternate source of rechargeable batteries for the time when irradiance falls below a threshold value. Also the excess power produced when there is ample irradiance is divided in two parts and one is fed to the boost converter while other is utilized to recharge the batteries. A simulation is done in MATLAB-SIMULINK and the obtained results show the utility of such modelling for supplying reactive power is feasible.

Proliferative reactive gliosis is compatible with glial metabolic support and neuronal function

PubMed Central

2011-01-01

Background The response of mammalian glial cells to chronic degeneration and trauma is hypothesized to be incompatible with support of neuronal function in the central nervous system (CNS) and retina. To test this hypothesis, we developed an inducible model of proliferative reactive gliosis in the absence of degenerative stimuli by genetically inactivating the cyclin-dependent kinase inhibitor p27Kip1 (p27 or Cdkn1b) in the adult mouse and determined the outcome on retinal structure and function. Results p27-deficient Müller glia reentered the cell cycle, underwent aberrant migration, and enhanced their expression of intermediate filament proteins, all of which are characteristics of Müller glia in a reactive state. Surprisingly, neuroglial interactions, retinal electrophysiology, and visual acuity were normal. Conclusion The benign outcome of proliferative reactive Müller gliosis suggests that reactive glia display context-dependent, graded and dynamic phenotypes and that reactivity in itself is not necessarily detrimental to neuronal function. PMID:21985191

Enantioselective Conjugate Additions of α-Amino Radicals via Cooperative Photoredox and Lewis Acid Catalysis

PubMed Central

Espelt, Laura Ruiz; McPherson, Iain S.; Wiensch, Eric M.; Yoon, Tehshik P.

2015-01-01

We report the highly enantioselective addition of photogenerated α-amino radicals to Michael acceptors. This method features a dual-catalyst protocol that combines transition metal photoredox catalysis with chiral Lewis acid catalysis. The combination of these two powerful modes of catalysis provides an effective, general strategy to generate and control the reactivity of photogenerated reactive intermediates. PMID:25668687

Cancer vaccine enhanced, non-tumor-reactive CD8(+) T cells exhibit a distinct molecular program associated with "division arrest anergy".

PubMed

Beyer, Marc; Karbach, Julia; Mallmann, Michael R; Zander, Thomas; Eggle, Daniela; Classen, Sabine; Debey-Pascher, Svenja; Famulok, Michael; Jäger, Elke; Schultze, Joachim L

2009-05-15

Immune-mediated tumor rejection relies on fully functional T-cell responses and neutralization of an adverse tumor microenvironment. In clinical trials, we detected peptide-specific but non-tumor-reactive and therefore not fully functional CD8(+) T cells post-vaccination against tumor antigens. Understanding the molecular mechanisms behind nontumor reactivity will be a prerequisite to overcome this CD8(+) T-cell deviation. We report that these non-tumor-reactive CD8(+) T cells are characterized by a molecular program associated with hallmarks of "division arrest anergy." Non-tumor-reactive CD8(+) T cells are characterized by coexpression of CD7, CD25, and CD69 as well as elevated levels of lck(p505) and p27(kip1). In vivo quantification revealed high prevalence of non-tumor-reactive CD8(+) T cells with increased levels during cancer vaccination. Furthermore, their presence was associated with a trend toward shorter survival. Dynamics and frequencies of non-target-reactive CD8(+) T cells need to be further addressed in context of therapeutic vaccine development in cancer, chronic infections, and autoimmune diseases.

MERCURY EMISSIONS FROM GASOLINE AND DIESEL POWERED ON-ROAD VEHICLES

EPA Science Inventory

Measurements of elemental gaseous mercury (Hg0), divalent reactive gaseous mercury (RGM), and particulate phase mercury (Hg(p)) were made from 14 gasoline and 2 diesel powered in-use light-duty vehicles on a chassis dynamometer. All vehicles were tested under both cold and hot st...

Dynamics and reactivity of trapped electrons on supported ice crystallites.

PubMed

Stähler, Julia; Gahl, Cornelius; Wolf, Martin

2012-01-17

The solvation dynamics and reactivity of localized excess electrons in aqueous environments have attracted great attention in many areas of physics, chemistry, and biology. This manifold attraction results from the importance of water as a solvent in nature as well as from the key role of low-energy electrons in many chemical reactions. One prominent example is the electron-induced dissociation of chlorofluorocarbons (CFCs). Low-energy electrons are also critical in the radiation chemistry that occurs in nuclear reactors. Excess electrons in an aqueous environment are localized and stabilized by the local rearrangement of the surrounding water dipoles. Such solvated or hydrated electrons are known to play an important role in systems such as biochemical reactions and atmospheric chemistry. Despite numerous studies over many years, little is known about the microscopic details of these electron-induced chemical processes, and interest in the fundamental processes involved in the reactivity of trapped electrons continues. In this Account, we present a surface science study of the dynamics and reactivity of such localized low-energy electrons at D(2)O crystallites that are supported by a Ru(001) single crystal metal surface. This approach enables us to investigate the generation and relaxation dynamics as well as dissociative electron attachment (DEA) reaction of excess electrons under well-defined conditions. They are generated by photoexcitation in the metal template and transferred to trapping sites at the vacuum interface of crystalline D(2)O islands. In these traps, the electrons are effectively decoupled from the electronic states of the metal template, leading to extraordinarily long excited state lifetimes on the order of minutes. Using these long-lived, low-energy electrons, we study the DEA to CFCl(3) that is coadsorbed at very low concentrations (∼10(12) cm(-2)). Using rate equations and direct measurement of the change of surface dipole moment, we estimated the electron surface density for DEA, yielding cross sections that are orders of magnitude higher than the electron density measured in the gas phase.

Deducing multiple interfacial dynamics during polymeric foaming.

PubMed

Chandan, Mohammed Rehaan; Naskar, Nilanjon; Das, Anuja; Mukherjee, Rabibrata; Harikrishnan, Gopalakrishna Pillai

2018-06-15

Several interfacial phenomena are active during polymeric foaming, the dynamics of which significantly influence terminal stability, cell structure and in turn the thermo-mechanical properties of temporally evolved foam. Understanding these dynamics is important in achieving desired foam properties. Here, we introduce a method to simultaneously portray the time evolution of bubble growth, lamella thinning and Plateau border drainage, occurring during reactive polymeric foaming. In this method, we initially conduct bulk and surface shear rheology under polymerizing and non-foaming conditions. In a subsequent step, foaming experiments were conducted in a rheometer. The microscopic structural dimensions pertaining to the terminal values of the dynamics of each interfacial phenomena are then measured using a combination of scanning electron microscopy, optical microscopy and imaging ellipsometry, after the foaming is over. The measured surface and bulk rheological parameters are incorporated in time evolution equations that are derived from mass and momentum transport occurring when a model viscoelastic fluid is foamed by gas dispersion. Analytical and numerical solutions to these equations portray the dynamics. We demonstrate this method for a series of reactive polyurethane foams generated from different chemical sources. The effectiveness of our method is in simultaneously obtaining these dynamics that are difficult to directly monitor due to short active durations over multiple length scales.

Advanced and innovative wind energy concept development: Dynamic inducer system

NASA Astrophysics Data System (ADS)

Lissaman, P. B. S.; Zalay, A. D.; Hibbs, B. H.

1981-05-01

The performance benefits of the dynamic inducer tip vane system was demonstrated Tow-tests conducted on a three-bladed, 3.6-meter diameter rotor show that a dynamic inducer can achieve a power coefficient (based pon power blade swept area) of 0.5, which exceeds that of a plain rotor by about 35%. Wind tunnel tests conducted on a one-third scale model of the dynamic inducer achieved a power coefficient of 0.62 which exceeded that of a plain rotor by about 70%. The dynamic inducer substantially improves the performance of conventional rotors and indications are that higher power coefficients can be achieved through additional aerodynamic optimization.

Effects of rhythmic stimulus presentation on oscillatory brain activity: the physiology of cueing in Parkinson’s disease

PubMed Central

te Woerd, Erik S.; Oostenveld, Robert; Bloem, Bastiaan R.; de Lange, Floris P.; Praamstra, Peter

2015-01-01

The basal ganglia play an important role in beat perception and patients with Parkinson’s disease (PD) are impaired in perception of beat-based rhythms. Rhythmic cues are nonetheless beneficial in gait rehabilitation, raising the question how rhythm improves movement in PD. We addressed this question with magnetoencephalography recordings during a choice response task with rhythmic and non-rhythmic modes of stimulus presentation. Analyses focused on (i) entrainment of slow oscillations, (ii) the depth of beta power modulation, and (iii) whether a gain in modulation depth of beta power, due to rhythmicity, is of predictive or reactive nature. The results show weaker phase synchronisation of slow oscillations and a relative shift from predictive to reactive movement-related beta suppression in PD. Nonetheless, rhythmic stimulus presentation increased beta modulation depth to the same extent in patients and controls. Critically, this gain selectively increased the predictive and not reactive movement-related beta power suppression. Operation of a predictive mechanism, induced by rhythmic stimulation, was corroborated by a sensory gating effect in the sensorimotor cortex. The predictive mode of cue utilisation points to facilitation of basal ganglia-premotor interactions, contrasting with the popular view that rhythmic stimulation confers a special advantage in PD, based on recruitment of alternative pathways. PMID:26509117

Grassroots Leadership: Encounters with Power Dynamics and Oppression

ERIC Educational Resources Information Center

Kezar, Adrianna

2011-01-01

This article focuses on the nature of power dynamics that faculty and staff grassroots leaders encounter as they attempt to create change. I identified five distinctive types of power dynamics--"oppression," "silencing," "controlling," "inertia," and "micro-aggressions" from the most overt to more subtle and covert forms. Staff experience multiple…

Association of balance, strength, and power measures in young adults.

PubMed

Muehlbauer, Thomas; Gollhofer, Albert; Granacher, Urs

2013-03-01

The purpose of this study was to investigate the relationship between variables of static/dynamic balance, isometric strength, and power. Twenty-seven young healthy adults (mean age: 23 ± 4 years) performed measurements of static (unperturbed)/dynamic (perturbed) balance, isometric strength (i.e., maximal isometric torque [MIT]; rate of torque development [RTD] of the plantar flexor), and power (i.e., countermovement jump [CMJ] height and power). No significant associations were found between variables of static and dynamic balance (r = -0.090 to +0.329, p > 0.05) and between measures of static/dynamic balance and isometric strength (r = +0.041 to +0.387, p > 0.05) and static/dynamic balance and power (r = -0.076 to +0.218, p > 0.05). Significant positive correlations (r) were detected between variables of power and isometric strength ranging from +0.458 to +0.689 (p < 0.05). Furthermore, simple regression analyses revealed that a 10% increase in mean CMJ height (4.1 cm) was associated with 22.9 N·m and 128.4 N·m·s better MIT and RTD, respectively. The nonsignificant correlation between static and dynamic balance measures and between static/dynamic balance, isometric strength, and power variables implies that these capacities may be independent of each other and may have to be tested and trained complementarily.

Combustion Dynamics of Biocidal Metal-Based Energetic Components in Turbulent Reactive Flows

DTIC Science & Technology

2015-11-01

imperative for successful design of respective metalized energetic systems. This predictive ability must rely on accurate models describing...powders was reported to vary from 900 to 1200 K, depending on milling conditions (Zhang et al. 2010a). Another reactive material designed to...the Conference of the American Physical Society Topical Group on Shock Compression of Condensed Matter, 845 II; Baltimore, MD), pp. 972-975. Fuchs

Comparison of the oxime-induced reactivation of rhesus monkey, swine and guinea pig erythrocyte acetylcholinesterase following inhibition by sarin or paraoxon, using a perfusion model for the real-time determination of membrane-bound acetylcholinesterase activity.

PubMed

Herkert, Nadja M; Lallement, Guy; Clarençon, Didier; Thiermann, Horst; Worek, Franz

2009-04-28

Recently, a dynamically working in vitro model with real-time determination of membrane-bound human acetylcholinesterase (AChE) activity was shown to be a versatile model to investigate oxime-induced reactivation kinetics of organophosphate- (OP) inhibited enzyme. In this assay, AChE was immobilized on particle filters which were perfused with acetylthiocholine, Ellman's reagent and phosphate buffer. Subsequently, AChE activity was continuously analyzed in a flow-through detector. Now, it was an intriguing question whether this model could be used with erythrocyte AChE from other species in order to investigate kinetic interactions in the absence of annoying side reactions. Rhesus monkey, swine and guinea pig erythrocytes were a stable and highly reproducible enzyme source. Then, the model was applied to the reactivation of sarin- and paraoxon-inhibited AChE by obidoxime or HI 6 and it could be shown that the derived reactivation rate constants were in good agreement to previous results obtained from experiments with a static model. Hence, this dynamic model offers the possibility to investigate highly reproducible interactions between AChE, OP and oximes with human and animal AChE.

Ozone reactivity and free radical scavenging behavior of phenolic secondary metabolites in lichens exposed to chronic oxidant air pollution from Mexico City.

PubMed

Valencia-Islas, N; Zambrano, A; Rojas, J L

2007-08-01

Lichen secondary metabolites putatively protect lichens from a variety of environmental stress factors, but it is unknown whether these substances respond to air pollution. To assess such a possibility, the three major phenolics of two epiphytic lichen species with contrasting tolerance to chronic air pollution from Mexico City were studied by combining experimental reactivity data and measured field contents. The antioxidant activity and antiradical power of boninic (BO), 2-O-methylsekikaic (MA), and usnic (US) acids, isolated from the tolerant Ramalina asahinae and salazinic acid (SA), atranorin (AT), and chloroatranorin (CA), from the sensitive Parmotrema stuppeum, were determined in vitro by kinetic experiments with ozone and the free radical diphenyl picryl hidrazyl (DPPH*), respectively. In addition, the field contents of these phenolics in the lichens, and the potential antioxidant capacity (PAC) they provide, were compared among three forested sites exposed to urban emissions and a similar, relatively clean site. The six phenolics had antioxidant activity and antiradical power according to these trends: CA > AT > US > SA > or = BO > or = MA for O(3); and CA > AT > US > MA > SA = BO for DPPH*. The three most reactive phenolics are cortical compounds, located in the lichen portion most exposed to the surrounding environment. In contrast, the less reactive SA, BO, and MA are medullary. Such reactivity patterns indicate that some phenolics may provide antioxidative protection at the air-lichen interface. The higher antioxidant power of CA and AT may be due to the reactive hydroxyl groups at positions 2 and 4 of ring A, instead of the less reactive methoxyl at the same positions in both BO and MA. In the field comparisons, total quantified phenolics were significantly higher near Mexico City for both lichens, except for the tolerant R. asahinae at one site. Nevertheless, only the latter species had significantly increased PAC values at all sites near the city. This result is explained by species-dependent changes in individual phenolics. At the polluted sites, R. asahinae had consistently higher contents of its most reactive phenolic, US, with values approximately twice that of the control site. In contrast, P. stuppeum only increased its less reactive SA (26-35%), but this was counteracted by CA and, to a lesser extent, AT degradation. Thus, the substantial increase in US at the polluted sites appears to be associated with the current ecological success of R. asahinae near the city. On the other hand, the inability of P. stuppeum to overcome degradation of its most reactive phenolic (CA) at the same sites seems to partially explain the declining status of this lichen. These results provide evidence for a protective mechanism in lichens against air pollution based on secondary metabolites, which may eventually determine which species survive in forests stressed by oxidative air pollution.

Multiscale Reactive Molecular Dynamics

DTIC Science & Technology

2012-08-15

biology cannot be described without considering electronic and nuclear-level dynamics and their coupling to slower, cooperative motions of the system ...coupling to slower, cooperative motions of the system . These inherently multiscale problems require computationally efficient and accurate methods to...condensed phase systems with computational efficiency orders of magnitudes greater than currently possible with ab initio simulation methods, thus

Impact of sleep loss before learning on cortical dynamics during memory retrieval.

PubMed

Alberca-Reina, E; Cantero, J L; Atienza, M

2015-12-01

Evidence shows that sleep loss before learning decreases activation of the hippocampus during encoding and promotes forgetting. But it remains to be determined which neural systems are functionally affected during memory retrieval after one night of recovery sleep. To investigate this issue, we evaluated memory for pairs of famous people's faces with the same or different profession (i.e., semantically congruent or incongruent faces) after one night of undisturbed sleep in subjects who either underwent 4hours of acute sleep restriction (ASR, N=20) or who slept 8hours the pre-training night (controls, N=20). EEG recordings were collected during the recognition memory task in both groups, and the cortical sources generating this activity localized by applying a spatial beamforming filter in the frequency domain. Even though sleep restriction did not affect accuracy of memory performance, controls showed a much larger decrease of alpha power relative to a baseline period when compared to sleep-deprived subjects. These group differences affected a widespread frontotemporoparietal network involved in retrieval of episodic/semantic memories. Regression analyses further revealed that associative memory in the ASR group was negatively correlated with alpha power in the occipital regions, whereas the benefit of congruency in the same group was positively correlated with delta power in the left lateral prefrontal cortex. Retrieval-related decreases of alpha power have been associated with the reactivation of material-specific memory representations, whereas increases of delta power have been related to inhibition of interferences that may affect the performance of the task. We can therefore draw the conclusion that a few hours of sleep loss in the pre-training night, though insufficient to change the memory performance, is sufficient to alter the processes involved in retrieving and manipulating episodic and semantic information. Copyright © 2015 Elsevier Inc. All rights reserved.

A global plasma model for reactive deposition of compound films by modulated pulsed power magnetron sputtering discharges

NASA Astrophysics Data System (ADS)

Zheng, B. C.; Wu, Z. L.; Wu, B.; Li, Y. G.; Lei, M. K.

2017-05-01

A spatially averaged, time-dependent global plasma model has been developed to describe the reactive deposition of a TiAlSiN thin film by modulated pulsed power magnetron sputtering (MPPMS) discharges in Ar/N2 mixture gas, based on the particle balance and the energy balance in the ionization region, and considering the formation and erosion of the compound at the target surface. The modeling results show that, with increasing the N2 partial pressure from 0% to 40% at a constant working pressure of 0.3 Pa, the electron temperature during the strongly ionized period increases from 4 to 7 eV and the effective power transfer coefficient, which represents the power fraction that effectively heats the electrons and maintains the discharge, increases from about 4% to 7%; with increasing the working pressure from 0.1 to 0.7 Pa at a constant N2 partial pressure of 25%, the electron temperature decreases from 10 to 4 eV and the effective power transfer coefficient decreases from 8% to 5%. Using the modeled plasma parameters to evaluate the kinetic energy of arriving ions, the ion-to-neutral flux ratio of deposited species, and the substrate heating, the variations of process parameters that increase these values lead to an enhanced adatom mobility at the target surface and an increased input energy to the substrate, corresponding to the experimental observation of surface roughness reduction, the microstructure transition from the columnar structure to the dense featureless structure, and the enhancement of phase separation. At higher N2 partial pressure or lower working pressure, the modeling results demonstrate an increase in electron temperature, which shifts the discharge balance of Ti species from Ti+ to Ti2+ and results in a higher return fraction of Ti species, corresponding to the higher Al/Ti ratio of deposited films at these conditions. The modeling results are well correlated with the experimental observation of the composition variation and the microstructure transition of deposited TiAlSiN compound films, demonstrating the applicability of this approach in understanding the characteristics of reactive MPPMS discharges as well as the composition and microstructure of deposited compound films. The model for reactive MPPMS discharges has no special limitations and is applicable to high power impulse magnetron sputtering discharges as well.

Electroencephalographic markers of robot-aided therapy in stroke patients for the evaluation of upper limb rehabilitation.

PubMed

Sale, Patrizio; Infarinato, Francesco; Del Percio, Claudio; Lizio, Roberta; Babiloni, Claudio; Foti, Calogero; Franceschini, Marco

2015-12-01

Stroke is the leading cause of permanent disability in developed countries; its effects may include sensory, motor, and cognitive impairment as well as a reduced ability to perform self-care and participate in social and community activities. A number of studies have shown that the use of robotic systems in upper limb motor rehabilitation programs provides safe and intensive treatment to patients with motor impairments because of a neurological injury. Furthermore, robot-aided therapy was shown to be well accepted and tolerated by all patients; however, it is not known whether a specific robot-aided rehabilitation can induce beneficial cortical plasticity in stroke patients. Here, we present a procedure to study neural underpinning of robot-aided upper limb rehabilitation in stroke patients. Neurophysiological recordings use the following: (a) 10-20 system electroencephalographic (EEG) electrode montage; (b) bipolar vertical and horizontal electrooculographies; and (c) bipolar electromyography from the operating upper limb. Behavior monitoring includes the following: (a) clinical data and (b) kinematic and dynamic of the operant upper limb movements. Experimental conditions include the following: (a) resting state eyes closed and eyes open, and (b) robotic rehabilitation task (maximum 80 s each block to reach 4-min EEG data; interblock pause of 1 min). The data collection is performed before and after a program of 30 daily rehabilitation sessions. EEG markers include the following: (a) EEG power density in the eyes-closed condition; (b) reactivity of EEG power density to eyes opening; and (c) reactivity of EEG power density to robotic rehabilitation task. The above procedure was tested on a subacute patient (29 poststroke days) and on a chronic patient (21 poststroke months). After the rehabilitation program, we observed (a) improved clinical condition; (b) improved performance during the robotic task; (c) reduced delta rhythms (1-4 Hz) and increased alpha rhythms (8-12 Hz) during the resting state eyes-closed condition; (d) increased alpha desynchronization to eyes opening; and (e) decreased alpha desynchronization during the robotic rehabilitation task. We conclude that the present procedure is suitable for evaluation of the neural underpinning of robot-aided upper limb rehabilitation.

Differential Evolution Based IDWNN Controller for Fault Ride-Through of Grid-Connected Doubly Fed Induction Wind Generators

PubMed Central

Manonmani, N.; Subbiah, V.; Sivakumar, L.

2015-01-01

The key objective of wind turbine development is to ensure that output power is continuously increased. It is authenticated that wind turbines (WTs) supply the necessary reactive power to the grid at the time of fault and after fault to aid the flowing grid voltage. At this juncture, this paper introduces a novel heuristic based controller module employing differential evolution and neural network architecture to improve the low-voltage ride-through rate of grid-connected wind turbines, which are connected along with doubly fed induction generators (DFIGs). The traditional crowbar-based systems were basically applied to secure the rotor-side converter during the occurrence of grid faults. This traditional controller is found not to satisfy the desired requirement, since DFIG during the connection of crowbar acts like a squirrel cage module and absorbs the reactive power from the grid. This limitation is taken care of in this paper by introducing heuristic controllers that remove the usage of crowbar and ensure that wind turbines supply necessary reactive power to the grid during faults. The controller is designed in this paper to enhance the DFIG converter during the grid fault and this controller takes care of the ride-through fault without employing any other hardware modules. The paper introduces a double wavelet neural network controller which is appropriately tuned employing differential evolution. To validate the proposed controller module, a case study of wind farm with 1.5 MW wind turbines connected to a 25 kV distribution system exporting power to a 120 kV grid through a 30 km 25 kV feeder is carried out by simulation. PMID:26516636

Differential Evolution Based IDWNN Controller for Fault Ride-Through of Grid-Connected Doubly Fed Induction Wind Generators.

PubMed

Manonmani, N; Subbiah, V; Sivakumar, L

2015-01-01

The key objective of wind turbine development is to ensure that output power is continuously increased. It is authenticated that wind turbines (WTs) supply the necessary reactive power to the grid at the time of fault and after fault to aid the flowing grid voltage. At this juncture, this paper introduces a novel heuristic based controller module employing differential evolution and neural network architecture to improve the low-voltage ride-through rate of grid-connected wind turbines, which are connected along with doubly fed induction generators (DFIGs). The traditional crowbar-based systems were basically applied to secure the rotor-side converter during the occurrence of grid faults. This traditional controller is found not to satisfy the desired requirement, since DFIG during the connection of crowbar acts like a squirrel cage module and absorbs the reactive power from the grid. This limitation is taken care of in this paper by introducing heuristic controllers that remove the usage of crowbar and ensure that wind turbines supply necessary reactive power to the grid during faults. The controller is designed in this paper to enhance the DFIG converter during the grid fault and this controller takes care of the ride-through fault without employing any other hardware modules. The paper introduces a double wavelet neural network controller which is appropriately tuned employing differential evolution. To validate the proposed controller module, a case study of wind farm with 1.5 MW wind turbines connected to a 25 kV distribution system exporting power to a 120 kV grid through a 30 km 25 kV feeder is carried out by simulation.

Investigation of plasma dynamics during the growth of amorphous titanium dioxide thin films

NASA Astrophysics Data System (ADS)

Kim, Jin-Soo; Jee, Hyeok; Yu, Young-Hun; Seo, Hye-Won

2018-06-01

We have grown amorphous titanium dioxide thin films by reactive DC sputtering method using a different argon/oxygen partial pressure at a room temperature. The plasma dynamics of the process, reactive and sputtered gas particles was investigated via optical emission spectroscopy. We then studied the correlations between the plasma states and the structural/optical properties of the films. The growth rate and morphology of the titanium dioxide thin films turned out to be contingent with the population and the energy profile of Ar, O, and TiO plasma. In particular, the films grown under energetic TiO plasma have shown a direct band-to-band transition with an optical energy band gap up to ∼4.2 eV.

Ion-mobility study of two functionalized pentacene structural isomers using a modified electrospray/triple quadrupole mass spectrometer

NASA Astrophysics Data System (ADS)

Prada, Svitlana V.; Bohme, Diethard K.; Baranov, Vladimir I.

2007-03-01

We report ion-mobility measurements with a modified triple quadrupole mass spectrometer fitted with an ion molecule reactor (IMR) designed to investigate ion molecule reactivity in organic mass spectrometry. Functionalized pentacene ions, which are generally unreactive were chosen for study to decouple drift/diffusion effects from reactivity (including clustering). The IMR is equipped with a variable axial electrostatic drift field (ADF) and is able to trap ions. These capabilities were successfully employed in the measurement of ion mobilities in different modes of IMR operation. Theoretical modeling of the drift dynamics and the special localization of the large ion packet was successfully implemented. The contribution of the quadrupole RF field to the drift dynamics also was taken into consideration.

Decentralized Optimal Dispatch of Photovoltaic Inverters in Residential Distribution Systems

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

Dall'Anese, Emiliano; Dhople, Sairaj V.; Johnson, Brian B.

Summary form only given. Decentralized methods for computing optimal real and reactive power setpoints for residential photovoltaic (PV) inverters are developed in this paper. It is known that conventional PV inverter controllers, which are designed to extract maximum power at unity power factor, cannot address secondary performance objectives such as voltage regulation and network loss minimization. Optimal power flow techniques can be utilized to select which inverters will provide ancillary services, and to compute their optimal real and reactive power setpoints according to well-defined performance criteria and economic objectives. Leveraging advances in sparsity-promoting regularization techniques and semidefinite relaxation, this papermore » shows how such problems can be solved with reduced computational burden and optimality guarantees. To enable large-scale implementation, a novel algorithmic framework is introduced - based on the so-called alternating direction method of multipliers - by which optimal power flow-type problems in this setting can be systematically decomposed into sub-problems that can be solved in a decentralized fashion by the utility and customer-owned PV systems with limited exchanges of information. Since the computational burden is shared among multiple devices and the requirement of all-to-all communication can be circumvented, the proposed optimization approach scales favorably to large distribution networks.« less

A Solar Dynamic Power Option for Space Solar Power

NASA Technical Reports Server (NTRS)

Mason, Lee S.

1999-01-01

A study was performed to determine the potential performance and related technology requirements of Solar Dynamic power systems for a Space Solar Power satellite. Space Solar Power is a concept where solar energy is collected in orbit and beamed to Earth receiving stations to supplement terrestrial electric power service. Solar Dynamic systems offer the benefits of high solar-to-electric efficiency, long life with minimal performance degradation, and high power scalability. System analyses indicate that with moderate component development, SD systems can exhibit excellent mass and deployed area characteristics. Using the analyses as a guide, a technology roadmap was -enerated which identifies the component advances necessary to make SD power generation a competitive option for the SSP mission.

A self-sensing magnetorheological damper with power generation

NASA Astrophysics Data System (ADS)

Chen, Chao; Liao, Wei-Hsin

2012-02-01

Magnetorheological (MR) dampers are promising for semi-active vibration control of various dynamic systems. In the current MR damper systems, a separate power supply and dynamic sensor are required. To enable the MR damper to be self-powered and self-sensing in the future, in this paper we propose and investigate a self-sensing MR damper with power generation, which integrates energy harvesting, dynamic sensing and MR damping technologies into one device. This MR damper has self-contained power generation and velocity sensing capabilities, and is applicable to various dynamic systems. It combines the advantages of energy harvesting—reusing wasted energy, MR damping—controllable damping force, and sensing—providing dynamic information for controlling system dynamics. This multifunctional integration would bring great benefits such as energy saving, size and weight reduction, lower cost, high reliability, and less maintenance for the MR damper systems. In this paper, a prototype of the self-sensing MR damper with power generation was designed, fabricated, and tested. Theoretical analyses and experimental studies on power generation were performed. A velocity-sensing method was proposed and experimentally validated. The magnetic-field interference among three functions was prevented by a combined magnetic-field isolation method. Modeling, analysis, and experimental results on damping forces are also presented.

Reactivity Coefficient Calculation for AP1000 Reactor Using the NODAL3 Code

NASA Astrophysics Data System (ADS)

Pinem, Surian; Malem Sembiring, Tagor; Tukiran; Deswandri; Sunaryo, Geni Rina

2018-02-01

The reactivity coefficient is a very important parameter for inherent safety and stability of nuclear reactors operation. To provide the safety analysis of the reactor, the calculation of changes in reactivity caused by temperature is necessary because it is related to the reactor operation. In this paper, the temperature reactivity coefficients of fuel and moderator of the AP1000 core are calculated, as well as the moderator density and boron concentration. All of these coefficients are calculated at the hot full power condition (HFP). All neutron diffusion constant as a function of temperature, water density and boron concentration were generated by the SRAC2006 code. The core calculations for determination of the reactivity coefficient parameter are done by using NODAL3 code. The calculation results show that the fuel temperature, moderator temperature and boron reactivity coefficients are in the range between -2.613 pcm/°C to -4.657pcm/°C, -1.00518 pcm/°C to 1.00649 pcm/°C and -9.11361 pcm/ppm to -8.0751 pcm/ppm, respectively. For the water density reactivity coefficients, the positive reactivity occurs at the water temperature less than 190 °C. The calculation results show that the reactivity coefficients are accurate because the results have a very good agreement with the design value.

Ab Initio Reactive Computer Aided Molecular Design

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

Martínez, Todd J.

Few would dispute that theoretical chemistry tools can now provide keen insights into chemical phenomena. Yet the holy grail of efficient and reliable prediction of complex reactivity has remained elusive. Fortunately, recent advances in electronic structure theory based on the concepts of both element- and rank-sparsity, coupled with the emergence of new highly parallel computer architectures, have led to a significant increase in the time and length scales which can be simulated using first principles molecular dynamics. This then opens the possibility of new discovery-based approaches to chemical reactivity, such as the recently proposed ab initio nanoreactor. Here, we arguemore » that due to these and other recent advances, the holy grail of computational discovery for complex chemical reactivity is rapidly coming within our reach.« less

Ab Initio Reactive Computer Aided Molecular Design

DOE PAGES

Martínez, Todd J.

2017-03-21

Few would dispute that theoretical chemistry tools can now provide keen insights into chemical phenomena. Yet the holy grail of efficient and reliable prediction of complex reactivity has remained elusive. Fortunately, recent advances in electronic structure theory based on the concepts of both element- and rank-sparsity, coupled with the emergence of new highly parallel computer architectures, have led to a significant increase in the time and length scales which can be simulated using first principles molecular dynamics. This then opens the possibility of new discovery-based approaches to chemical reactivity, such as the recently proposed ab initio nanoreactor. Here, we arguemore » that due to these and other recent advances, the holy grail of computational discovery for complex chemical reactivity is rapidly coming within our reach.« less

RTDS-Based Design and Simulation of Distributed P-Q Power Resources in Smart Grid

NASA Astrophysics Data System (ADS)

Taylor, Zachariah David

In this Thesis, we propose to utilize a battery system together with its power electronics interfaces and bidirectional charger as a distributed P-Q resource in power distribution networks. First, we present an optimization-based approach to operate such distributed P-Q resources based on the characteristics of the battery and charger system as well as the features and needs of the power distribution network. Then, we use the RTDS Simulator, which is an industry-standard simulation tool of power systems, to develop two RTDS-based design approaches. The first design is based on an ideal four-quadrant distributed P-Q power resource. The second design is based on a detailed four-quadrant distributed P-Q power resource that is developed using power electronics components. The hardware and power electronics circuitry as well as the control units are explained for the second design. After that, given the two-RTDS designs, we conducted extensive RTDS simulations to assess the performance of the designed distributed P-Q Power Resource in an IEEE 13 bus test system. We observed that the proposed design can noticeably improve the operational performance of the power distribution grid in at least four key aspects: reducing power loss, active power peak load shaving at substation, reactive power peak load shaving at substation, and voltage regulation. We examine these performance measures across three design cases: Case 1: There is no P-Q Power Resource available on the power distribution network. Case 2: The installed P-Q Power Resource only supports active power, i.e., it only utilizes its battery component. Case 3: The installed P-Q Power Resource supports both active and reactive power, i.e., it utilizes both its battery component and its power electronics charger component. In the end, we present insightful interpretations on the simulation results and suggest some future works.

Implementation of New Reactivity Measurement System and New Reactor Noise Analysis Equipment in a VVER-440 Nuclear Power Plant

NASA Astrophysics Data System (ADS)

Vegh, János; Kiss, Sándor; Lipcsei, Sándor; Horvath, Csaba; Pos, István; Kiss, Gábor

2010-10-01

The paper deals with two recently developed, high-precision nuclear measurement systems installed at the VVER-440 units of the Hungarian Paks NPP. Both developments were motivated by the reactor power increase to 108%, and by the planned plant service time extension. The first part describes the RMR start-up reactivity measurement system with advanced services. High-precision picoampere meters were installed at each reactor unit and measured ionization chamber current signals are handled by a portable computer providing data acquisition and online reactivity calculation service. Detailed offline evaluation and analysis of reactor start-up measurements can be performed on the portable unit, too. The second part of the paper describes a new reactor noise diagnostics system using state-of-the-art data acquisition hardware and signal processing methods. Details of the new reactor noise measurement evaluation software are also outlined. Noise diagnostics at Paks NPP is a standard tool for core anomaly detection and for long-term noise trend monitoring. Regular application of these systems is illustrated by real plant data, e.g., results of standard reactivity measurements during a reactor startup session are given. Noise applications are also illustrated by real plant measurements; results of core anomaly detection are presented.

76 FR 66220 - Automatic Underfrequency Load Shedding and Load Shedding Plans Reliability Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-26

..., EPRI Power Systems Dynamics Tutorial, Chapter 4 at page 4-78 (2009), available at http://www.epri.com.... Power systems consist of static components (e.g., transformers and transmission lines) and dynamic... decisions on simulations, both static and dynamic, using area power system models to meet requirements in...

Ensemble Kalman Filter for Dynamic State Estimation of Power Grids Stochastically Driven by Time-correlated Mechanical Input Power

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

Rosenthal, William Steven; Tartakovsky, Alex; Huang, Zhenyu

State and parameter estimation of power transmission networks is important for monitoring power grid operating conditions and analyzing transient stability. Wind power generation depends on fluctuating input power levels, which are correlated in time and contribute to uncertainty in turbine dynamical models. The ensemble Kalman filter (EnKF), a standard state estimation technique, uses a deterministic forecast and does not explicitly model time-correlated noise in parameters such as mechanical input power. However, this uncertainty affects the probability of fault-induced transient instability and increased prediction bias. Here a novel approach is to model input power noise with time-correlated stochastic fluctuations, and integratemore » them with the network dynamics during the forecast. While the EnKF has been used to calibrate constant parameters in turbine dynamical models, the calibration of a statistical model for a time-correlated parameter has not been investigated. In this study, twin experiments on a standard transmission network test case are used to validate our time-correlated noise model framework for state estimation of unsteady operating conditions and transient stability analysis, and a methodology is proposed for the inference of the mechanical input power time-correlation length parameter using time-series data from PMUs monitoring power dynamics at generator buses.« less

Ensemble Kalman Filter for Dynamic State Estimation of Power Grids Stochastically Driven by Time-correlated Mechanical Input Power

DOE PAGES

Rosenthal, William Steven; Tartakovsky, Alex; Huang, Zhenyu

2017-10-31

State and parameter estimation of power transmission networks is important for monitoring power grid operating conditions and analyzing transient stability. Wind power generation depends on fluctuating input power levels, which are correlated in time and contribute to uncertainty in turbine dynamical models. The ensemble Kalman filter (EnKF), a standard state estimation technique, uses a deterministic forecast and does not explicitly model time-correlated noise in parameters such as mechanical input power. However, this uncertainty affects the probability of fault-induced transient instability and increased prediction bias. Here a novel approach is to model input power noise with time-correlated stochastic fluctuations, and integratemore » them with the network dynamics during the forecast. While the EnKF has been used to calibrate constant parameters in turbine dynamical models, the calibration of a statistical model for a time-correlated parameter has not been investigated. In this study, twin experiments on a standard transmission network test case are used to validate our time-correlated noise model framework for state estimation of unsteady operating conditions and transient stability analysis, and a methodology is proposed for the inference of the mechanical input power time-correlation length parameter using time-series data from PMUs monitoring power dynamics at generator buses.« less

Ear canal dynamic motion as a source of power for in-ear devices

NASA Astrophysics Data System (ADS)

Delnavaz, Aidin; Voix, Jérémie

2013-02-01

Ear canal deformation caused by temporomandibular joint (jaw joint) activity, also known as "ear canal dynamic motion," is introduced in this paper as a candidate source of power to possibly recharge hearing aid batteries. The geometrical deformation of the ear canal is quantified in 3D by laser scanning of different custom ear moulds. An experimental setup is proposed to measure the amount of power potentially available from this source. The results show that 9 mW of power is available from a 15 mm3 dynamic change in the ear canal volume. Finally, the dynamic motion and power capability of the ear canal are investigated in a group of 12 subjects.

Optimization Scheduling Model for Wind-thermal Power System Considering the Dynamic penalty factor

NASA Astrophysics Data System (ADS)

PENG, Siyu; LUO, Jianchun; WANG, Yunyu; YANG, Jun; RAN, Hong; PENG, Xiaodong; HUANG, Ming; LIU, Wanyu

2018-03-01

In this paper, a new dynamic economic dispatch model for power system is presented.Objective function of the proposed model presents a major novelty in the dynamic economic dispatch including wind farm: introduced the “Dynamic penalty factor”, This factor could be computed by using fuzzy logic considering both the variable nature of active wind power and power demand, and it could change the wind curtailment cost according to the different state of the power system. Case studies were carried out on the IEEE30 system. Results show that the proposed optimization model could mitigate the wind curtailment and the total cost effectively, demonstrate the validity and effectiveness of the proposed model.

Mathematical Modeling Analysis of Operation Strategy after External Transmission Line Series Compensation

NASA Astrophysics Data System (ADS)

Feng, Peilei; Xu, Tianqi; Liu, Xiaoxin; Jan, Lisheng; Dai, Xiaozhong; Cai, Pengcheng

2018-01-01

Nujiang power grid is at the end of the Yunnan power grid, which is the side of power supply. Due to the regional restrictions and the lag of economic development and other factors, the structure of the power grid in Nujiang is relatively weak, and the voltage of the regional power grid is more prominent. Based on analysis on voltage exceeding limits of Nujiang different power grid, combined with the operating characteristics of regional power grid and reactive power compensation measures, this paper proposes measures for adjustment of Nujiang grid voltage, and analyses the result of adjustment of voltage exceeding limits, which can effectively improve the voltage and power quality.

Gasification and combustion technologies of agro-residues and their application to rural electric power systems in India

NASA Astrophysics Data System (ADS)

Bharadwaj, Anshu

Biomass based power generation has the potential to add up to 20,000 MW of distributed capacity in India close to the rural load centers. However, the present production of biomass-based electricity is modest, contributing a mere 300 MW of installed capacity. In this thesis, we shall examine some of the scientific, technological and policy issues concerned with the generation and commercial viability of biomass-based electric power. We first consider the present status of biomass-based power in India and make an attempt to understand the reasons for low utilization. Our analysis suggests that the small-scale biomass power plants (<100 kW) when used for village electrification have a low Plant Load Factor (PLF) that adversely affects their economic viability. Medium Scale units (0.5 MW--5 MW) do not appear attractive because of the costs involved in the biomass transportation. There is thus a merit in considering power plants that use biomass available in large quantities in agro-processing centers such as rice or sugar mills where power plants of capacities in excess of 5 MW are possible without biomass transportation. We then simulate a biomass gasification combustion cycle using a naturally aspirated spark ignition engine since it can run totally on biomass gas. The gasifier and engine are modeled using the chemical equilibrium approach. The simulation is used to study the impact of fuel moisture and the performance of different biomass feedstock. Biomass power plants when used for decentralized power generation; close to the rural load centers can solve some of the problems of rural power supply: provide voltage support, reactive power and peak shaving. We consider an innovative option of setting up a rural electricity micro-grid using a decentralized biomass power plant and selected a rural feeder in Tumkur district, Karnataka for three-phase AC load flow studies. Our results suggest that this option significantly reduces the distribution losses and improves the voltage profiles. We examine a few innovative policy options for making a rural micro-grid economically viable and also a pricing mechanism for reactive power and wheeling. We next consider co-firing biomass and coal in utility boilers as an attractive option for biomass utilization because of low capital costs; high efficiency of utility boilers; lower CO2 emissions (per kWh) and also lower NOx and SO2. However, efficiency derating of the boilers caused by unburnt carbon in the fly ash is a major concern of the utilities. We develop a computational fluid dynamics (CFD) based model to understand the impact of co-firing on utility boilers. A detailed biomass devolatilization sub-model is also developed to study the importance of intra-particle heat and mass transport. Finally, we conduct an experimental study of the pyrolysis of rice husk. We conducted single particle experiments in a Confocal Scanning Laser Microscope (CSLM) at the Department of Material Science and Engineering, Carnegie Mellon University coupled with Scanning Electron Microscope (SEM) analysis of partially and fully combusted particles. Our results seem to indicate that the role of silica fibers is not merely to act as geometric shields for the carbon atoms. Instead there appears to be a strong and thermally resistant inter-molecular bonding that prevents carbon conversion. Therefore, it may not be possible to achieve full carbon conversion.

Conversion of evanescent Lamb waves into propagating waves via a narrow aperture edge.

PubMed

Yan, Xiang; Yuan, Fuh-Gwo

2015-06-01

This paper presents a quantitative study of conversion of evanescent Lamb waves into propagating in isotropic plates. The conversion is substantiated by prescribing time-harmonic Lamb displacements/tractions through a narrow aperture at an edge of a semi-infinite plate. Complex-valued dispersion and group velocity curves are employed to characterize the conversion process. The amplitude coefficient of the propagating Lamb modes converted from evanescent is quantified based on the complex reciprocity theorem via a finite element analysis. The power flow generated into the plate can be separated into radiative and reactive parts made on the basis of propagating and evanescent Lamb waves, where propagating Lamb waves are theoretically proved to radiate pure real power flow, and evanescent Lamb waves carry reactive pure imaginary power flow. The propagating power conversion efficiency is then defined to quantitatively describe the conversion. The conversion efficiency is strongly frequency dependent and can be significant. With the converted propagating waves from evanescent, sensors at far-field can recapture some localized damage information that is generally possessed in evanescent waves and may have potential application in structural health monitoring.

System-level power optimization for real-time distributed embedded systems

NASA Astrophysics Data System (ADS)

Luo, Jiong

Power optimization is one of the crucial design considerations for modern electronic systems. In this thesis, we present several system-level power optimization techniques for real-time distributed embedded systems, based on dynamic voltage scaling, dynamic power management, and management of peak power and variance of the power profile. Dynamic voltage scaling has been widely acknowledged as an important and powerful technique to trade off dynamic power consumption and delay. Efficient dynamic voltage scaling requires effective variable-voltage scheduling mechanisms that can adjust voltages and clock frequencies adaptively based on workloads and timing constraints. For this purpose, we propose static variable-voltage scheduling algorithms utilizing criticalpath driven timing analysis for the case when tasks are assumed to have uniform switching activities, as well as energy-gradient driven slack allocation for a more general scenario. The proposed techniques can achieve closeto-optimal power savings with very low computational complexity, without violating any real-time constraints. We also present algorithms for power-efficient joint scheduling of multi-rate periodic task graphs along with soft aperiodic tasks. The power issue is addressed through both dynamic voltage scaling and power management. Periodic task graphs are scheduled statically. Flexibility is introduced into the static schedule to allow the on-line scheduler to make local changes to PE schedules through resource reclaiming and slack stealing, without interfering with the validity of the global schedule. We provide a unified framework in which the response times of aperiodic tasks and power consumption are dynamically optimized simultaneously. Interconnection network fabrics point to a new generation of power-efficient and scalable interconnection architectures for distributed embedded systems. As the system bandwidth continues to increase, interconnection networks become power/energy limited as well. Variable-frequency links have been designed by circuit designers for both parallel and serial links, which can adaptively regulate the supply voltage of transceivers to a desired link frequency, to exploit the variations in bandwidth requirement for power savings. We propose solutions for simultaneous dynamic voltage scaling of processors and links. The proposed solution considers real-time scheduling, flow control, and packet routing jointly. It can trade off the power consumption on processors and communication links via efficient slack allocation, and lead to more power savings than dynamic voltage scaling on processors alone. For battery-operated systems, the battery lifespan is an important concern. Due to the effects of discharge rate and battery recovery, the discharge pattern of batteries has an impact on the battery lifespan. Battery models indicate that even under the same average power consumption, reducing peak power current and variance in the power profile can increase the battery efficiency and thereby prolong battery lifetime. To take advantage of these effects, we propose battery-driven scheduling techniques for embedded applications, to reduce the peak power and the variance in the power profile of the overall system under real-time constraints. The proposed scheduling algorithms are also beneficial in addressing reliability and signal integrity concerns by effectively controlling peak power and variance of the power profile.

Modeling and simulation of CANDU reactor and its regulating system

NASA Astrophysics Data System (ADS)

Javidnia, Hooman

Analytical computer codes are indispensable tools in design, optimization, and control of nuclear power plants. Numerous codes have been developed to perform different types of analyses related to the nuclear power plants. A large number of these codes are designed to perform safety analyses. In the context of safety analyses, the control system is often neglected. Although there are good reasons for such a decision, that does not mean that the study of control systems in the nuclear power plants should be neglected altogether. In this thesis, a proof of concept code is developed as a tool that can be used in the design. optimization. and operation stages of the control system. The main objective in the design of this computer code is providing a tool that is easy to use by its target audience and is capable of producing high fidelity results that can be trusted to design the control system and optimize its performance. Since the overall plant control system covers a very wide range of processes, in this thesis the focus has been on one particular module of the the overall plant control system, namely, the reactor regulating system. The center of the reactor regulating system is the CANDU reactor. A nodal model for the reactor is used to represent the spatial neutronic kinetics of the core. The nodal model produces better results compared to the point kinetics model which is often used in the design and analysis of control system for nuclear reactors. The model can capture the spatial effects to some extent. although it is not as detailed as the finite difference methods. The criteria for choosing a nodal model of the core are: (1) the model should provide more detail than point kinetics and capture spatial effects, (2) it should not be too complex or overly detailed to slow down the simulation and provide details that are extraneous or unnecessary for a control engineer. Other than the reactor itself, there are auxiliary models that describe dynamics of different phenomena related to the transfer of the energy from the core. The main function of the reactor regulating system is to control the power of the reactor. This is achieved by using a set of detectors. reactivity devices. and digital control algorithms. Three main reactivity devices that are activated during short-term or intermediate-term transients are modeled in this thesis. The main elements of the digital control system are implemented in accordance to the program specifications for the actual control system in CANDU reactors. The simulation results are validated against requirements of the reactor regulating system. actual plant data. and pre-validated data from other computer codes. The validation process shows that the simulation results can be trusted in making engineering decisions regarding the reactor regulating system and prediction of the system performance in response to upset conditions or disturbances. KEYWORDS: CANDU reactors. reactor regulating system. nodal model. spatial kinetics. reactivity devices. simulation.

Dynamic analysis of a pumped-storage hydropower plant with random power load

NASA Astrophysics Data System (ADS)

Zhang, Hao; Chen, Diyi; Xu, Beibei; Patelli, Edoardo; Tolo, Silvia

2018-02-01

This paper analyzes the dynamic response of a pumped-storage hydropower plant in generating mode. Considering the elastic water column effects in the penstock, a linearized reduced order dynamic model of the pumped-storage hydropower plant is used in this paper. As the power load is always random, a set of random generator electric power output is introduced to research the dynamic behaviors of the pumped-storage hydropower plant. Then, the influences of the PI gains on the dynamic characteristics of the pumped-storage hydropower plant with the random power load are analyzed. In addition, the effects of initial power load and PI parameters on the stability of the pumped-storage hydropower plant are studied in depth. All of the above results will provide theoretical guidance for the study and analysis of the pumped-storage hydropower plant.

Photovoltaic power conditioning subsystem: State of the art and development opportunities

NASA Technical Reports Server (NTRS)

Krauthamer, S.; Bahrami, K.; Das, R.; Macie, T.; Rippel, W.

1984-01-01

Photovoltaic systems, the state of the art of power conditioning subsystem components, and the design and operational interaction between photovoltaic systems and host utilities are detailed in this document. Major technical issues relating to the design and development of power conditioning systems for photovoltaic application are considered; these include: (1) standards, guidelines, and specifications; (2) cost effective hardware design; (3) impact of advanced components on power conditioning development; (4) protection and safety; (5) quality of power; (6) system efficiency; and (7) system integration with the host utility. Theories of harmonic distortion and reactive power flow are discussed, and information about power conditioner hardware and manufacturers is provided.

Dynamics of Space Vehicles and Space Research

DTIC Science & Technology

1989-09-08

dynamics is used for study of longitudinal vibrations of RN, in which participates housing, power - supply system and engine installation. In American...scientific research of G. S. Narimanov. Research of the dynamics of solid bodies with the liquid filling, simulating RN and KA with ZhRD in the powered ...solid body. Page 9. Specifically, then he posed the problem about the review of the conceptual basis of research of rocket dynamics in the powered

Thermal analysis of a reactive generalized Couette flow of power law fluids between concentric cylindrical pipes

NASA Astrophysics Data System (ADS)

Makinde, O. D.

2014-12-01

In this paper, the steady generalized axial Couette flow of Ostwald-de Waele power law reactive fluids between concentric cylindrical pipes is investigated. It is assumed that the outer cylinder is stationary and exchanges heat with the ambient surrounding following Newton's law of cooling, while the inner cylinder with isothermal surface is set in motion in the axial direction. The model nonlinear differential equations for the momentum and energy balance are obtained and tackled numerically using the shooting method coupled with the Runge-Kutta-Fehlberg integration technique. The effects of various embedded thermophysical parameters on the velocity and temperature fields including skin friction, Nusselt number and thermal criticality conditions are presented graphically and discussed quantitatively.

The Influence of Submarine Groundwater Discharge on Nearshore Marine Dissolved Organic Carbon Reactivity, Concentration Dynamics, and Offshore Export

NASA Astrophysics Data System (ADS)

Goodridge, B.

2017-12-01

Dissolved organic carbon (DOC) is the largest pool of reduced carbon in the oceans, with a reservoir equivalent to atmospheric CO2. In nearshore marine regions, DOC sources include primary production, terrestrial DOC delivered by river discharge, and/or terrestrial and marine DOC delivered via submarine groundwater discharge (SGD). While the importance of SGD to coastal carbon cycling has been implicated, the actual influence of this process on nearshore carbon dynamics and offshore export has not been explicitly identified. This study, conducted at a predominantly marine-influenced intertidal beach-nearshore ocean system along the Santa Barbara, California coastline, aimed to address this knowledge gap. I coupled dark, temperature-controlled laboratory incubations, radioisotopic (Rn-222) SGD estimates, and a DOC box model to identify the influence of pore water mixing with seawater on nearshore DOC reactivity, concentration dynamics, and offshore export. Even with a relatively low volumetric contribution, SGD pore water mixing altered nearshore DOC reactivity, and elevated the nearshore DOC concentration by 0.9 to 5.6 µmol L-1 over nearshore seawater residence times ranging from 1 to 6 days. These elevated DOC concentrations were equivalent to 1.2 to 7.5% of the mean offshore DOC concentration taken during the summer months in the Santa Barbara Channel, when the coastal water column is highly thermally stratified. Despite the challenge of assessing carbon dynamics in physically and biogeochemically complex nearshore marine regions, this study demonstrates the need for future investigations to assess and account for SGD as a non-trivial component of coastal marine carbon cycles.

The Effect of Astaxanthin and Regular Training on Dynamic Pattern of Oxidative Stress on Male under Strenuous Exercise

NASA Astrophysics Data System (ADS)

Sylviana, N.; Gunawan, H.; Lesmana, R.; Purba, A.; Akbar, I. B.

2017-03-01

Strenuous physical activity will induced higher Reactive Oxygen Species (ROS) level in human body that can be measured by serum Malondialdehyde (MDA) level. Malondialdehyde is product of lipid peroxidation process that define as oxidative damage of lipid biomolecule by reactivity of reactive oxygen species. Still, the dynamic pattern of Malondialdehyde (MDA) level under strenuous exercise is not fully understood. Potent antioxidant such as Astaxanthin and training may be altered the level of MDA. Thus, purpose of this study is to understand effect of astaxanthin to MDA dynamic pattern on training male after strenuous physical activity. It was a double blind, experimental study, conducted on thirty young male age, divided into untrained and trained groups. Supplement Astaxanthin was given to 15 subject as well as placebo for one week after supplementation, Subjects were tested with anaerobic strenuous physical activity. The values were analyzed with ANOVA test followed by Duncan test showed that in every groups, mean of MDA before test was similar, start increase significantly after tested, begin decrease at 6th hour post test and back to baseline at 24th hour post-test ( p<0.05), except for group of untrained male with placebo still increase twice from baseline. The lowest mean of MDA was found on group of trained male with Astaxanthin supplementation and the highest was found on group of untrained male with placebo (p<0.05). These findings support that Astaxanthin and training might has positive effect to oxidative stress condition without altered its dynamic pattern in male after strenuous physical activity

NemR Is a Bleach-sensing Transcription Factor*

PubMed Central

Gray, Michael J.; Wholey, Wei-Yun; Parker, Benjamin W.; Kim, Minwook; Jakob, Ursula

2013-01-01

Hypochlorous acid (HOCl), the active component of household bleach, also functions as a powerful antimicrobial during the innate immune response. Despite its widespread use, surprisingly little is known about how cells sense or respond to HOCl. We now demonstrate that Escherichia coli NemR is a redox-regulated transcriptional repressor, which uses the oxidation status of HOCl-sensitive cysteine residues to respond to bleach and related reactive chlorine species. NemR controls bleach-mediated expression of two enzymes required for detoxification of reactive electrophiles: glyoxalase I and N-ethylmaleimide reductase. Both enzymes contribute to bacterial bleach survival. These results provide evidence that bleach resistance relies on the capacity of organisms to specifically sense reactive chlorine species and respond with the up-regulation of enzymes dedicated to detoxification of methylglyoxal and other reactive electrophiles. PMID:23536188

Passive Safety Features Evaluation of KIPT Neutron Source Facility

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

Zhong, Zhaopeng; Gohar, Yousry

2016-06-01

Argonne National Laboratory (ANL) of the United States and Kharkov Institute of Physics and Technology (KIPT) of Ukraine have cooperated on the development, design, and construction of a neutron source facility. The facility was constructed at Kharkov, Ukraine and its commissioning process is underway. It will be used to conduct basic and applied nuclear research, produce medical isotopes, and train young nuclear specialists. The facility has an electron accelerator-driven subcritical assembly. The electron beam power is 100 kW using 100 MeV electrons. Tungsten or natural uranium is the target material for generating neutrons driving the subcritical assembly. The subcritical assemblymore » is composed of WWR-M2 - Russian fuel assemblies with U-235 enrichment of 19.7 wt%, surrounded by beryllium reflector assembles and graphite blocks. The subcritical assembly is seated in a water tank, which is a part of the primary cooling loop. During normal operation, the water coolant operates at room temperature and the total facility power is ~300 KW. The passive safety features of the facility are discussed in in this study. Monte Carlo computer code MCNPX was utilized in the analyses with ENDF/B-VII.0 nuclear data libraries. Negative reactivity temperature feedback was consistently observed, which is important for the facility safety performance. Due to the design of WWR-M2 fuel assemblies, slight water temperature increase and the corresponding water density decrease produce large reactivity drop, which offset the reactivity gain by mistakenly loading an additional fuel assembly. The increase of fuel temperature also causes sufficiently large reactivity decrease. This enhances the facility safety performance because fuel temperature increase provides prompt negative reactivity feedback. The reactivity variation due to an empty fuel position filled by water during the fuel loading process is examined. Also, the loading mistakes of removing beryllium reflector assemblies and replacing them with dummy assemblies were analyzed. In all these circumstances, the reactivity change results do not cause any safety concerns.« less

A Dynamic Model for Induced Reactivation of Latent Virus

DTIC Science & Technology

2005-12-04

with human herpesvirus-6 in EBV -negative infectious mononucleosis , Journal of Medical Virology 71 (4), 569-577, 2003. [35] Wu FY, Ahn JH, Alcendor DJ...model that describes the reactivation of latent herpes virus by metabolic end products of anaerobic bacteria. Herpes viruses are double-stranded DNA ...cells that may be different from the types of cells targeted for primary infection. Latent virus persists in the cell nucleus as episomal DNA until it

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

Rutqvist, Jonny; Cappa, Frederic; Rinaldi, Antonio P.

We summarize recent modeling studies of injection-induced fault reactivation, seismicity, and its potential impact on surface structures and nuisance to the local human population. We used coupled multiphase fluid flow and geomechanical numerical modeling, dynamic wave propagation modeling, seismology theories, and empirical vibration criteria from mining and construction industries. We first simulated injection-induced fault reactivation, including dynamic fault slip, seismic source, wave propagation, and ground vibrations. From co-seismic average shear displacement and rupture area, we determined the moment magnitude to about M w = 3 for an injection-induced fault reactivation at a depth of about 1000 m. We then analyzedmore » the ground vibration results in terms of peak ground acceleration (PGA), peak ground velocity (PGV), and frequency content, with comparison to the U.S. Bureau of Mines’ vibration criteria for cosmetic damage to buildings, as well as human-perception vibration limits. For the considered synthetic M w = 3 event, our analysis showed that the short duration, high frequency ground motion may not cause any significant damage to surface structures, and would not cause, in this particular case, upward CO 2 leakage, but would certainly be felt by the local population.« less

Emergence of chaos in a spatially confined reactive system

NASA Astrophysics Data System (ADS)

Voorsluijs, Valérie; De Decker, Yannick

2016-11-01

In spatially restricted media, interactions between particles and local fluctuations of density can lead to important deviations of the dynamics from the unconfined, deterministic picture. In this context, we investigated how molecular crowding can affect the emergence of chaos in small reactive systems. We developed to this end an amended version of the Willamowski-Rössler model, where we account for the impenetrability of the reactive species. We analyzed the deterministic kinetics of this model and studied it with spatially-extended stochastic simulations in which the mobility of particles is included explicitly. We show that homogeneous fluctuations can lead to a destruction of chaos through a fluctuation-induced collision between chaotic trajectories and absorbing states. However, an interplay between the size of the system and the mobility of particles can counterbalance this effect so that chaos can indeed be found when particles diffuse slowly. This unexpected effect can be traced back to the emergence of spatial correlations which strongly affect the dynamics. The mobility of particles effectively acts as a new bifurcation parameter, enabling the system to switch from stationary states to absorbing states, oscillations or chaos.

PyGlobal: A toolkit for automated compilation of DFT-based descriptors.

PubMed

Nath, Shilpa R; Kurup, Sudheer S; Joshi, Kaustubh A

2016-06-15

Density Functional Theory (DFT)-based Global reactivity descriptor calculations have emerged as powerful tools for studying the reactivity, selectivity, and stability of chemical and biological systems. A Python-based module, PyGlobal has been developed for systematically parsing a typical Gaussian outfile and extracting the relevant energies of the HOMO and LUMO. Corresponding global reactivity descriptors are further calculated and the data is saved into a spreadsheet compatible with applications like Microsoft Excel and LibreOffice. The efficiency of the module has been accounted by measuring the time interval for randomly selected Gaussian outfiles for 1000 molecules. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Plasma & reactive ion etching to prepare ohmic contacts

DOEpatents

Gessert, Timothy A.

2002-01-01

A method of making a low-resistance electrical contact between a metal and a layer of p-type CdTe surface by plasma etching and reactive ion etching comprising: a) placing a CdS/CdTe layer into a chamber and evacuating said chamber; b) backfilling the chamber with Argon or a reactive gas to a pressure sufficient for plasma ignition; and c) generating plasma ignition by energizing a cathode which is connected to a power supply to enable the plasma to interact argon ions alone or in the presence of a radio-frequency DC self-bias voltage with the p-CdTe surface.

Simulation of Power Collection Dynamics for Simply Supported Power Rail

DOT National Transportation Integrated Search

1972-11-01

The mathematical model of a sprung mass moving along a simply supported beam is used to analyze the dynamics of a power-collection system. A computer simulation of one-dimensional motion is used to demonstrate the phenomenon of collector-power rail i...

Evolutionary growth for Space Station Freedom electrical power system

NASA Technical Reports Server (NTRS)

Marshall, Matthew Fisk; Mclallin, Kerry; Zernic, Mike

1989-01-01

Over an operational lifetime of at least 30 yr, Space Station Freedom will encounter increased Space Station user requirements and advancing technologies. The Space Station electrical power system is designed with the flexibility to accommodate these emerging technologies and expert systems and is being designed with the necessary software hooks and hardware scars to accommodate increased growth demand. The electrical power system is planned to grow from the initial 75 kW up to 300 kW. The Phase 1 station will utilize photovoltaic arrays to produce the electrical power; however, for growth to 300 kW, solar dynamic power modules will be utilized. Pairs of 25 kW solar dynamic power modules will be added to the station to reach the power growth level. The addition of solar dynamic power in the growth phase places constraints in the initial Space Station systems such as guidance, navigation, and control, external thermal, truss structural stiffness, computational capabilities and storage, which must be planned-in, in order to facilitate the addition of the solar dynamic modules.

Performance of U3Si2 Fuel in a Reactivity Insertion Accident

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

Cheng, Lap Y.; Cuadra, Arantxa; Todosow, Michael

In this study we examined the performance of the U3Si2 fuel cladded with Zircaloy (Zr) in a reactivity insertion accident (RIA) in a PWR core. The power excursion as a result of a $1 reactivity insertion was calculated by a TRACE PWR plant model using point-kinetics, for alternative cores with UO2 and U3Si2 fuel assemblies. The point-kinetics parameters (feedback coefficients, prompt-neutron lifetime and group constants for six delayed-neutron groups) were obtained from beginning-of-cycle equilibrium full core calculations with PARCS. In the PARCS core calculations, the few-group parameters were developed utilizing the TRITON/NEWT tools in the SCALE package. In order tomore » assess the fuel response in finer detail (e.g. the maximum fuel temperature) the power shape and thermal boundary conditions from the TRACE/PARCS calculations were used to drive a BISON model of a fuel pin with U3Si2 and UO2 respectively. For a $1 reactivity transient both TRACE and BISON predicted a higher maximum fuel temperature for the UO2 fuel than the U3Si2 fuel. Furthermore, BISON is noted to calculate a narrower gap and a higher gap heat transfer coefficient than TRACE. This resulted in BISON predicting consistently lower fuel temperatures than TRACE. This study also provides a systematic comparison between TRACE and BISON using consistent transient boundary conditions. The TRACE analysis of the RIA only reflects the core-wide response in power. A refinement to the analysis would be to predict the local peaking in a three-dimensional core as a result of control rod ejection.« less

Performance evaluation of a dynamic telepathology system (Panoptiq™) in the morphologic assessment of peripheral blood film abnormalities.

PubMed

Goswami, R; Pi, D; Pal, J; Cheng, K; Hudoba De Badyn, M

2015-06-01

The study evaluated the performance of a dynamic imaging telepathology system (Panoptiq(™) ) as a diagnostic aid to the identification of peripheral blood film (PBF) abnormalities. The study assumed a laboratory personnel working in a clinical laboratory were operating the telepathology system to seek diagnostic opinion from an external consulting hematopathologist. The study examined 100 blood films, encompassing 23 different hematological diseases, reactive or normal cases. The study revealed that with real-time image transmission in live scanning mode of operation, the telepathology system was able to aid reviewers in achieving excellent accuracy, that is correct interpretation of morphologic abnormalities obtained in 83/84 of the hematologic diseases and 12/12 of the reactive/normal conditions (Sensitivity: 0.99; Specificity: 1.00). In contrast, when only saved static images in digital capture mode of operation were reviewed remotely, interpretative omissions occurred in 8/84 of the hematologic diseases and 0/12 of the reactive/normal conditions (Sensitivity: 0.91; Specificity: 1.00). It is hypothesized that real-time operator-reviewer communication during live scanning played an important role in the identification of key morphologic abnormalities for review. Our study showed the Panoptiq system can be adopted reliably as a dynamic telepathology tool in aiding community laboratories in the triage of PBF cases for external diagnostic consultation. © 2014 John Wiley & Sons Ltd.

Avalanching strain dynamics during the hydriding phase transformation in individual palladium nanoparticles

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

Ulvestad, A.; Welland, M. J.; Collins, S. S. E.

2015-12-11

Phase transitions in reactive environments are crucially important in energy and information storage, catalysis and sensors. Nanostructuring active particles can yield faster charging/ discharging kinetics, increased lifespan and record catalytic activities. However, establishing the causal link between structure and function is challenging for nanoparticles, as ensemble measurements convolve intrinsic single-particle properties with sample diversity. Here we study the hydriding phase transformation in individual palladium nanocubes in situ using coherent X-ray diffractive imaging. The phase transformation dynamics, which involve the nucleation and propagation of a hydrogen-rich region, are dependent on absolute time (aging) and involve intermittent dynamics (avalanching). A hydrogen-rich surfacemore » layer dominates the crystal strain in the hydrogen-poor phase, while strain inversion occurs at the cube corners in the hydrogen-rich phase. A three-dimensional phase-field model is used to interpret the experimental results. In conclusion, our experimental and theoretical approach provides a general framework for designing and optimizing phase transformations for single nanocrystals in reactive environments.« less

Avalanching strain dynamics during the hydriding phase transformation in individual palladium nanoparticles

NASA Astrophysics Data System (ADS)

Ulvestad, A.; Welland, M. J.; Collins, S. S. E.; Harder, R.; Maxey, E.; Wingert, J.; Singer, A.; Hy, S.; Mulvaney, P.; Zapol, P.; Shpyrko, O. G.

2015-12-01

Phase transitions in reactive environments are crucially important in energy and information storage, catalysis and sensors. Nanostructuring active particles can yield faster charging/discharging kinetics, increased lifespan and record catalytic activities. However, establishing the causal link between structure and function is challenging for nanoparticles, as ensemble measurements convolve intrinsic single-particle properties with sample diversity. Here we study the hydriding phase transformation in individual palladium nanocubes in situ using coherent X-ray diffractive imaging. The phase transformation dynamics, which involve the nucleation and propagation of a hydrogen-rich region, are dependent on absolute time (aging) and involve intermittent dynamics (avalanching). A hydrogen-rich surface layer dominates the crystal strain in the hydrogen-poor phase, while strain inversion occurs at the cube corners in the hydrogen-rich phase. A three-dimensional phase-field model is used to interpret the experimental results. Our experimental and theoretical approach provides a general framework for designing and optimizing phase transformations for single nanocrystals in reactive environments.

Avalanching strain dynamics during the hydriding phase transformation in individual palladium nanoparticles

PubMed Central

Ulvestad, A.; Welland, M. J.; Collins, S. S. E.; Harder, R.; Maxey, E.; Wingert, J.; Singer, A.; Hy, S.; Mulvaney, P.; Zapol, P.; Shpyrko, O. G.

2015-01-01

Phase transitions in reactive environments are crucially important in energy and information storage, catalysis and sensors. Nanostructuring active particles can yield faster charging/discharging kinetics, increased lifespan and record catalytic activities. However, establishing the causal link between structure and function is challenging for nanoparticles, as ensemble measurements convolve intrinsic single-particle properties with sample diversity. Here we study the hydriding phase transformation in individual palladium nanocubes in situ using coherent X-ray diffractive imaging. The phase transformation dynamics, which involve the nucleation and propagation of a hydrogen-rich region, are dependent on absolute time (aging) and involve intermittent dynamics (avalanching). A hydrogen-rich surface layer dominates the crystal strain in the hydrogen-poor phase, while strain inversion occurs at the cube corners in the hydrogen-rich phase. A three-dimensional phase-field model is used to interpret the experimental results. Our experimental and theoretical approach provides a general framework for designing and optimizing phase transformations for single nanocrystals in reactive environments. PMID:26655832

New activity pattern in human interactive dynamics

NASA Astrophysics Data System (ADS)

Formentin, Marco; Lovison, Alberto; Maritan, Amos; Zanzotto, Giovanni

2015-09-01

We investigate the response function of human agents as demonstrated by written correspondence, uncovering a new pattern for how the reactive dynamics of individuals is distributed across the set of each agent’s contacts. In long-term empirical data on email, we find that the set of response times considered separately for the messages to each different correspondent of a given writer, generate a family of heavy-tailed distributions, which have largely the same features for all agents, and whose characteristic times grow exponentially with the rank of each correspondent. We furthermore show that this new behavioral pattern emerges robustly by considering weighted moving averages of the priority-conditioned response-time probabilities generated by a basic prioritization model. Our findings clarify how the range of priorities in the inputs from one’s environment underpin and shape the dynamics of agents embedded in a net of reactive relations. These newly revealed activity patterns might be universal, being present in other general interactive environments, and constrain future models of communication and interaction networks, affecting their architecture and evolution.

Neural mechanisms of reactivation-induced updating that enhance and distort memory

PubMed Central

St. Jacques, Peggy L.; Olm, Christopher; Schacter, Daniel L.

2013-01-01

We remember a considerable number of personal experiences because we are frequently reminded of them, a process known as memory reactivation. Although memory reactivation helps to stabilize and update memories, reactivation may also introduce distortions if novel information becomes incorporated with memory. Here we used functional magnetic resonance imaging (fMRI) to investigate the neural mechanisms mediating reactivation-induced updating in memory for events experienced during a museum tour. During scanning, participants were shown target photographs to reactivate memories from the museum tour followed by a novel lure photograph from an alternate tour. Later, participants were presented with target and lure photographs and asked to determine whether the photographs showed a stop they visited during the tour. We used a subsequent memory analysis to examine neural recruitment during reactivation that was associated with later true and false memories. We predicted that the quality of reactivation, as determined by online ratings of subjective recollection, would increase subsequent true memories but also facilitate incorporation of the lure photograph, thereby increasing subsequent false memories. The fMRI results revealed that the quality of reactivation modulated subsequent true and false memories via recruitment of left posterior parahippocampal, bilateral retrosplenial, and bilateral posterior inferior parietal cortices. However, the timing of neural recruitment and the way in which memories were reactivated contributed to differences in whether memory reactivation led to distortions or not. These data reveal the neural mechanisms recruited during memory reactivation that modify how memories will be subsequently retrieved, supporting the flexible and dynamic aspects of memory. PMID:24191059

Neural mechanisms of reactivation-induced updating that enhance and distort memory.

PubMed

St Jacques, Peggy L; Olm, Christopher; Schacter, Daniel L

2013-12-03

We remember a considerable number of personal experiences because we are frequently reminded of them, a process known as memory reactivation. Although memory reactivation helps to stabilize and update memories, reactivation may also introduce distortions if novel information becomes incorporated with memory. Here we used functional magnetic resonance imaging (fMRI) to investigate the neural mechanisms mediating reactivation-induced updating in memory for events experienced during a museum tour. During scanning, participants were shown target photographs to reactivate memories from the museum tour followed by a novel lure photograph from an alternate tour. Later, participants were presented with target and lure photographs and asked to determine whether the photographs showed a stop they visited during the tour. We used a subsequent memory analysis to examine neural recruitment during reactivation that was associated with later true and false memories. We predicted that the quality of reactivation, as determined by online ratings of subjective recollection, would increase subsequent true memories but also facilitate incorporation of the lure photograph, thereby increasing subsequent false memories. The fMRI results revealed that the quality of reactivation modulated subsequent true and false memories via recruitment of left posterior parahippocampal, bilateral retrosplenial, and bilateral posterior inferior parietal cortices. However, the timing of neural recruitment and the way in which memories were reactivated contributed to differences in whether memory reactivation led to distortions or not. These data reveal the neural mechanisms recruited during memory reactivation that modify how memories will be subsequently retrieved, supporting the flexible and dynamic aspects of memory.

Initial Comparison of Direct and Legacy Modeling Approaches for Radial Core Expansion Analysis

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

Shemon, Emily R.

2016-10-10

Radial core expansion in sodium-cooled fast reactors provides an important reactivity feedback effect. As the reactor power increases due to normal start up conditions or accident scenarios, the core and surrounding materials heat up, causing both grid plate expansion and bowing of the assembly ducts. When the core restraint system is designed correctly, the resulting structural deformations introduce negative reactivity which decreases the reactor power. Historically, an indirect procedure has been used to estimate the reactivity feedback due to structural deformation which relies upon perturbation theory and coupling legacy physics codes with limited geometry capabilities. With advancements in modeling andmore » simulation, radial core expansion phenomena can now be modeled directly, providing an assessment of the accuracy of the reactivity feedback coefficients generated by indirect legacy methods. Recently a new capability was added to the PROTEUS-SN unstructured geometry neutron transport solver to analyze deformed meshes quickly and directly. By supplying the deformed mesh in addition to the base configuration input files, PROTEUS-SN automatically processes material adjustments including calculation of region densities to conserve mass, calculation of isotopic densities according to material models (for example, sodium density as a function of temperature), and subsequent re-homogenization of materials. To verify the new capability of directly simulating deformed meshes, PROTEUS-SN was used to compute reactivity feedback for a series of contrived yet representative deformed configurations for the Advanced Burner Test Reactor design. The indirect legacy procedure was also performed to generate reactivity feedback coefficients for the same deformed configurations. Interestingly, the legacy procedure consistently overestimated reactivity feedbacks by 35% compared to direct simulations by PROTEUS-SN. This overestimation indicates that the legacy procedures are in fact not conservative and could be overestimating reactivity feedback effects that are closely tied to reactor safety. We conclude that there is indeed value in performing direct simulation of deformed meshes despite the increased computational expense. PROTEUS-SN is already part of the SHARP multi-physics toolkit where both thermal hydraulics and structural mechanical feedback modeling can be applied but this is the first comparison of direct simulation to legacy techniques for radial core expansion.« less

Reactivation or reinfection in adult tuberculosis: Is that the question?

PubMed

Cardona, Pere-Joan

2016-12-01

Looking at the chapter on "natural history" in any tuberculosis (TB) reference book, there is a kind of certainty regarding TB in adults. That is the concept of "post-primary" TB described as the reactivation of dormant bacilli hidden in an old lesion developed during infancy due to a type of local immunosuppression. Intriguingly, this concept involves at least two major uncertainties: how can dormant bacilli remain for such a long period, almost a lifetime, in an old lesion, taking into account granuloma dynamism; and what sort of local immunosuppression is the one that facilitates reactivation? The controversy between reactivation and exogenous reinfection as the cause of active TB started very soon in TB research. Interestingly, this "balance" was disturbed in the 1960s when the "Unitary Concept" became very successful in supporting the reactivation dogma. The "Unitary Concept" was mainly based on the data of tuberculin surveillance during the pre-antibiotic era as well as the data obtained from experimental modelling in animals. At the same time, the "Three-risks model" appeared to explain the relationship between the risk of infection and TB incidence, granting reinfection a key role in adult TB together with primary infection. This role was reinforced by the studies of recurrence based on molecular epidemiology, and a better knowledge of the immune response, granuloma dynamics, and lung physiology. Now it is a matter of taking it into account when designing new prophylactic and therapeutic strategies and also reflecting it in text books to better illustrate to our students. Copyright © 2016 Asian-African Society for Mycobacteriology. Published by Elsevier Ltd. All rights reserved.

Power Systems for Future Missions: Appendices A-L

NASA Technical Reports Server (NTRS)

Gill, S. P.; Frye, P. E.; Littman, Franklin D.; Meisl, C. J.

1994-01-01

Selection of power system technology for space applications is typically based on mass, readiness of a particular technology to meet specific mission requirements, and life cycle costs (LCC). The LCC is typically used as a discriminator between competing technologies for a single mission application. All other future applications for a given technology are usually ignored. As a result, development cost of a technology becomes a dominant factor in the LCC comparison. Therefore, it is common for technologies such as DIPS and LMR-CBC to be potentially applicable to a wide range of missions and still lose out in the initial LCC comparison due to high development costs. This collection of appendices (A through L) contains the following power systems technology plans: CBC DIPS Technology Roadmap; PEM PFC Technology Roadmap; NAS Battery Technology Roadmap; PV/RFC Power System Technology Roadmap; PV/NAS Battery Technology Roadmap; Thermionic Reactor Power System Technology Roadmap; SP-100 Power System Technology Roadmap; Dynamic SP-100 Power System Technology Roadmap; Near-Term Solar Dynamic Power System Technology Roadmap; Advanced Solar Dynamic Power System Technology Roadmap; Advanced Stirling Cycle Dynamic Isotope Power System Technology Roadmap; and the ESPPRS (Evolutionary Space Power and Propulsion Requirements System) User's Guide.

Who's in Control? Teachers from Five Countries Share Perspectives on Power Dynamics in the Learning Environment

ERIC Educational Resources Information Center

Lovorn, Michael; Sunal, Cynthia Szymanski; Christensen, Lois McFadyen; Sunal, Dennis W.; Shwery, Craig

2012-01-01

This article explores perspectives and strands of thought among teachers from five countries about power dynamics in learning environments, perspectives on power of dominant cultures and impacts of power on concepts of citizenship and social justice. Discourses revealed teachers have some understanding of how power impacts teaching and learning,…

Physical interface dynamics alter how robotic exosuits augment human movement: implications for optimizing wearable assistive devices.

PubMed

Yandell, Matthew B; Quinlivan, Brendan T; Popov, Dmitry; Walsh, Conor; Zelik, Karl E

2017-05-18

Wearable assistive devices have demonstrated the potential to improve mobility outcomes for individuals with disabilities, and to augment healthy human performance; however, these benefits depend on how effectively power is transmitted from the device to the human user. Quantifying and understanding this power transmission is challenging due to complex human-device interface dynamics that occur as biological tissues and physical interface materials deform and displace under load, absorbing and returning power. Here we introduce a new methodology for quickly estimating interface power dynamics during movement tasks using common motion capture and force measurements, and then apply this method to quantify how a soft robotic ankle exosuit interacts with and transfers power to the human body during walking. We partition exosuit end-effector power (i.e., power output from the device) into power that augments ankle plantarflexion (termed augmentation power) vs. power that goes into deformation and motion of interface materials and underlying soft tissues (termed interface power). We provide empirical evidence of how human-exosuit interfaces absorb and return energy, reshaping exosuit-to-human power flow and resulting in three key consequences: (i) During exosuit loading (as applied forces increased), about 55% of exosuit end-effector power was absorbed into the interfaces. (ii) However, during subsequent exosuit unloading (as applied forces decreased) most of the absorbed interface power was returned viscoelastically. Consequently, the majority (about 75%) of exosuit end-effector work over each stride contributed to augmenting ankle plantarflexion. (iii) Ankle augmentation power (and work) was delayed relative to exosuit end-effector power, due to these interface energy absorption and return dynamics. Our findings elucidate the complexities of human-exosuit interface dynamics during transmission of power from assistive devices to the human body, and provide insight into improving the design and control of wearable robots. We conclude that in order to optimize the performance of wearable assistive devices it is important, throughout design and evaluation phases, to account for human-device interface dynamics that affect power transmission and thus human augmentation benefits.

Chemical dynamics between wells across a time-dependent barrier: Self-similarity in the Lagrangian descriptor and reactive basins.

PubMed

Junginger, Andrej; Duvenbeck, Lennart; Feldmaier, Matthias; Main, Jörg; Wunner, Günter; Hernandez, Rigoberto

2017-08-14

In chemical or physical reaction dynamics, it is essential to distinguish precisely between reactants and products for all times. This task is especially demanding in time-dependent or driven systems because therein the dividing surface (DS) between these states often exhibits a nontrivial time-dependence. The so-called transition state (TS) trajectory has been seen to define a DS which is free of recrossings in a large number of one-dimensional reactions across time-dependent barriers and thus, allows one to determine exact reaction rates. A fundamental challenge to applying this method is the construction of the TS trajectory itself. The minimization of Lagrangian descriptors (LDs) provides a general and powerful scheme to obtain that trajectory even when perturbation theory fails. Both approaches encounter possible breakdowns when the overall potential is bounded, admitting the possibility of returns to the barrier long after the trajectories have reached the product or reactant wells. Such global dynamics cannot be captured by perturbation theory. Meanwhile, in the LD-DS approach, it leads to the emergence of additional local minima which make it difficult to extract the optimal branch associated with the desired TS trajectory. In this work, we illustrate this behavior for a time-dependent double-well potential revealing a self-similar structure of the LD, and we demonstrate how the reflections and side-minima can be addressed by an appropriate modification of the LD associated with the direct rate across the barrier.

Reactivity effects in VVER-1000 of the third unit of the kalinin nuclear power plant at physical start-up. Computations in ShIPR intellectual code system with library of two-group cross sections generated by UNK code

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

Zizin, M. N.; Zimin, V. G.; Zizina, S. N., E-mail: zizin@adis.vver.kiae.ru

2010-12-15

The ShIPR intellectual code system for mathematical simulation of nuclear reactors includes a set of computing modules implementing the preparation of macro cross sections on the basis of the two-group library of neutron-physics cross sections obtained for the SKETCH-N nodal code. This library is created by using the UNK code for 3D diffusion computation of first VVER-1000 fuel loadings. Computation of neutron fields in the ShIPR system is performed using the DP3 code in the two-group diffusion approximation in 3D triangular geometry. The efficiency of all groups of control rods for the first fuel loading of the third unit ofmore » the Kalinin Nuclear Power Plant is computed. The temperature, barometric, and density effects of reactivity as well as the reactivity coefficient due to the concentration of boric acid in the reactor were computed additionally. Results of computations are compared with the experiment.« less

Reactivity effects in VVER-1000 of the third unit of the kalinin nuclear power plant at physical start-up. Computations in ShIPR intellectual code system with library of two-group cross sections generated by UNK code

NASA Astrophysics Data System (ADS)

Zizin, M. N.; Zimin, V. G.; Zizina, S. N.; Kryakvin, L. V.; Pitilimov, V. A.; Tereshonok, V. A.

2010-12-01

The ShIPR intellectual code system for mathematical simulation of nuclear reactors includes a set of computing modules implementing the preparation of macro cross sections on the basis of the two-group library of neutron-physics cross sections obtained for the SKETCH-N nodal code. This library is created by using the UNK code for 3D diffusion computation of first VVER-1000 fuel loadings. Computation of neutron fields in the ShIPR system is performed using the DP3 code in the two-group diffusion approximation in 3D triangular geometry. The efficiency of all groups of control rods for the first fuel loading of the third unit of the Kalinin Nuclear Power Plant is computed. The temperature, barometric, and density effects of reactivity as well as the reactivity coefficient due to the concentration of boric acid in the reactor were computed additionally. Results of computations are compared with the experiment.

Generation of reactive species in atmospheric pressure dielectric barrier discharge with liquid water

NASA Astrophysics Data System (ADS)

Zelong, ZHANG; Jie, SHEN; Cheng, CHENG; Zimu, XU; Weidong, XIA

2018-04-01

Atmospheric pressure helium/water dielectric barrier discharge (DBD) plasma is used to investigate the generation of reactive species in a gas-liquid interface and in a liquid. The emission intensity of the reactive species is measured by optical emission spectroscopy (OES) with different discharge powers at the gas-liquid interface. Spectrophotometry is used to analyze the reactive species induced by the plasma in the liquid. The concentration of OH radicals reaches 2.2 μm after 3 min of discharge treatment. In addition, the concentration of primary long-lived reactive species such as H2O2, {{{{NO}}}3}- and O3 are measured based on plasma treatment time. After 5 min of discharge treatment, the concentration of H2O2, {{{{NO}}}3}-, and O3 increased from 0 mg · L-1 to 96 mg · L-1, 19.5 mg · L-1, and 3.5 mg · L-1, respectively. The water treated by plasma still contained a considerable concentration of reactive species after 6 h of storage. The results will contribute to optimizing the DBD plasma system for biological decontamination.

NHS-Esters As Versatile Reactivity-Based Probes for Mapping Proteome-Wide Ligandable Hotspots.

PubMed

Ward, Carl C; Kleinman, Jordan I; Nomura, Daniel K

2017-06-16

Most of the proteome is considered undruggable, oftentimes hindering translational efforts for drug discovery. Identifying previously unknown druggable hotspots in proteins would enable strategies for pharmacologically interrogating these sites with small molecules. Activity-based protein profiling (ABPP) has arisen as a powerful chemoproteomic strategy that uses reactivity-based chemical probes to map reactive, functional, and ligandable hotspots in complex proteomes, which has enabled inhibitor discovery against various therapeutic protein targets. Here, we report an alkyne-functionalized N-hydroxysuccinimide-ester (NHS-ester) as a versatile reactivity-based probe for mapping the reactivity of a wide range of nucleophilic ligandable hotspots, including lysines, serines, threonines, and tyrosines, encompassing active sites, allosteric sites, post-translational modification sites, protein interaction sites, and previously uncharacterized potential binding sites. Surprisingly, we also show that fragment-based NHS-ester ligands can be made to confer selectivity for specific lysine hotspots on specific targets including Dpyd, Aldh2, and Gstt1. We thus put forth NHS-esters as promising reactivity-based probes and chemical scaffolds for covalent ligand discovery.

Effects of anodic potential and chloride ion on overall reactivity in electrochemical reactors designed for solar-powered wastewater treatment.

PubMed

Cho, Kangwoo; Qu, Yan; Kwon, Daejung; Zhang, Hao; Cid, Clément A; Aryanfar, Asghar; Hoffmann, Michael R

2014-02-18

We have investigated electrochemical treatment of real domestic wastewater coupled with simultaneous production of molecular H2 as useful byproduct. The electrolysis cells employ multilayer semiconductor anodes with electroactive bismuth-doped TiO2 functionalities and stainless steel cathodes. DC-powered laboratory-scale electrolysis experiments were performed under static anodic potentials (+2.2 or +3.0 V NHE) using domestic wastewater samples, with added chloride ion in variable concentrations. Greater than 95% reductions in chemical oxygen demand (COD) and ammonium ion were achieved within 6 h. In addition, we experimentally determined a decreasing overall reactivity of reactive chlorine species toward COD with an increasing chloride ion concentration under chlorine radicals (Cl·, Cl2(-)·) generation at +3.0 V NHE. The current efficiency for COD removal was 12% with the lowest specific energy consumption of 96 kWh kgCOD(-1) at the cell voltage of near 4 V in 50 mM chloride. The current efficiency and energy efficiency for H2 generation were calculated to range from 34 to 84% and 14 to 26%, respectively. The hydrogen comprised 35 to 60% by volume of evolved gases. The efficacy of our electrolysis cell was further demonstrated by a 20 L prototype reactor totally powered by a photovoltaic (PV) panel, which was shown to eliminate COD and total coliform bacteria in less than 4 h of treatment.