Interactions of solid and liquid lithium with steady state hydrogen and helium plasmas

International Nuclear Information System (INIS)

Hirooka, Y.; Nishikawa, M.; Ohgaki, H.; Ohtsuka, Y.

2005-01-01

A variety of innovative Plasma-Facing Component (PFC) concepts, employing moving solid or liquid surfaces, have recently been proposed in order to resolve technical issues, associated with the applications of currently used PFCs in future steady state fusion devices. As the first step to evaluate the concept using flowing-liquids for PFCs, steady state hydrogen and helium plasma interactions with solid and standing liquid lithium have been investigated in the present work, using the H α and He-I spectroscopy at the ion bombarding energies up to 150eV and at the lithium temperatures between room temperature and 480 deg C. Data indicate that hydrogen recycling over liquid lithium is clearly reduced, relative to that over solid lithium, whereas helium recycling does not show the same trend. From the kinetic analysis of these recycling time constant data, the activation energies for the overall recycling processes have been evaluated to be 0.02±0.01eV, both for hydrogen and helium plasmas. Also, it has been found that the activation energy is nearly independent of ion bombarding energy. (author)

Steady state plasma operation in RF dominated regimes on EAST

Energy Technology Data Exchange (ETDEWEB)

Zhang, X. J.; Zhao, Y. P.; Gong, X. Z.; Hu, C. D.; Liu, F. K.; Hu, L. Q.; Wan, B. N., E-mail: bnwan@ipp.ac.cn; Li, J. G. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)

2015-12-10

Significant progress has recently been made on EAST in the 2014 campaign, including the enhanced CW H&CD system over 20MW heating power (LHCD, ICRH and NBI), more than 70 diagnostics, ITER-like W-monoblock on upper divertor, two inner cryo-pumps and RMP coils, enabling EAST to investigate long pulse H mode operation with dominant electron heating and low torque to address the critical issues for ITER. H-mode plasmas were achieved by new H&CD system or 4.6GHz LHCD alone for the first time. Long pulse high performance H mode has been obtained by LHCD alone up to 28s at H{sub 98}∼1.2 or by combing of ICRH and LHCD, no or small ELM was found in RF plasmas, which is essential for steady state operation in the future Tokamak. Plasma operation in low collision regimes were implemented by new 4.6GHz LHCD with core Te∼4.5keV. The non-inductive scenarios with high performance at high bootstrap current fraction have been demonstrated in RF dominated regimes for long pulse operation. Near full non-inductive CD discharges have been achieved. In addition, effective heating and decoupling method under multi-transmitter for ICRF system were developed in this campaign, etc. EAST could be in operation with over 30MW CW heating and current drive power (LHCD ICRH NBI and ECRH), enhanced diagnostic capabilities and full actively-cooled metal wall from 2015. It will therefore allow to access new confinement regimes and to extend these regimes towards to steady state operation.

Application of piezodetectors for diagnostics of pulsed and quasi-steady-state plasma streams

Energy Technology Data Exchange (ETDEWEB)

Bandura, A.N.; Chebotarev, V.V.; Garkusha, I.E.; Tereshin, V.I.; Ladygina, M.S. [NSC KIPT, Kharkov (Ukraine). Inst. of Plasma Physics

2006-04-15

The paper reports on studies of the plasma streams generated by two experimental devices: the quasi-steady-state plasma accelerator (QSPA) Kh-50 and the pulsed plasma gun PROSVET. The radial distributions of the plasma pressure for different times and varied distances from the accelerator output have been used for investigation of the plasma stream dynamics and study the plasma compression in the focus region for different operational regimes of plasma accelerators. In experiments for the application of pulsed plasma streams for surface modification of different industrial steels, optimal regimes of surface processing have been chosen on the basis of the plasma pressure measurements. Examples of application of the piezodetectors in simulation experiments on plasma surface interaction under high heat loads are presented.

Application of piezodetectors for diagnostics of pulsed and quasi-steady-state plasma streams

International Nuclear Information System (INIS)

Bandura, A.N.; Chebotarev, V.V.; Garkusha, I.E.; Tereshin, V.I.; Ladygina, M.S.

2006-01-01

The paper reports on studies of the plasma streams generated by two experimental devices: the quasi-steady-state plasma accelerator (QSPA) Kh-50 and the pulsed plasma gun PROSVET. The radial distributions of the plasma pressure for different times and varied distances from the accelerator output have been used for investigation of the plasma stream dynamics and study the plasma compression in the focus region for different operational regimes of plasma accelerators. In experiments for the application of pulsed plasma streams for surface modification of different industrial steels, optimal regimes of surface processing have been chosen on the basis of the plasma pressure measurements. Examples of application of the piezodetectors in simulation experiments on plasma surface interaction under high heat loads are presented

Current status and prospect of plasma control system for steady-state operation on QUEST

International Nuclear Information System (INIS)

Hasegawa, Makoto; Nakamura, Kazuo; Zushi, Hideki; Hanada, Kazuaki; Fujisawa, Akihide; Tokunaga, Kazutoshi; Idei, Hiroshi; Nagashima, Yoshihiko; Kawasaki, Shoji; Nakashima, Hisatoshi; Higashijima, Aki

2016-01-01

Highlights: • Overall configuration of plasma control system on QUEST are presented. • Multi core system and reflective memories are used for the real-time control. • Hall sensors are used for the identification of plasma current and its position. • Repetitive gas fueling with the feed-back control of Hα signal is implemented. - Abstract: The plasma control system (PCS) of QUEST is developed according to the progress of QUEST project. Since one of the critical goals of the project is to achieve the steady-state operation with high temperature vacuum vessel wall, the PCS is also required to have the capability to control the plasma for a long period. For the increase of the loads to processing power of the PCS, the PCS is decentralized with the use of reflective memories (RFMs). The PCS controls the plasma edge position with the real-time identification of plasma current and its position. This identification is done with not only flux loops but also hall sensors. The gas fueling method by piezo valve with monitoring the Hα signal filtered by a digital low-pass filter are proposed and suitable for the steady-state operation on QUEST. The present status and prospect of the PCS are presented with recent topics.

Current status and prospect of plasma control system for steady-state operation on QUEST

Energy Technology Data Exchange (ETDEWEB)

Hasegawa, Makoto, E-mail: hasegawa@triam.kyushu-u.ac.jp; Nakamura, Kazuo; Zushi, Hideki; Hanada, Kazuaki; Fujisawa, Akihide; Tokunaga, Kazutoshi; Idei, Hiroshi; Nagashima, Yoshihiko; Kawasaki, Shoji; Nakashima, Hisatoshi; Higashijima, Aki

2016-11-15

Highlights: • Overall configuration of plasma control system on QUEST are presented. • Multi core system and reflective memories are used for the real-time control. • Hall sensors are used for the identification of plasma current and its position. • Repetitive gas fueling with the feed-back control of Hα signal is implemented. - Abstract: The plasma control system (PCS) of QUEST is developed according to the progress of QUEST project. Since one of the critical goals of the project is to achieve the steady-state operation with high temperature vacuum vessel wall, the PCS is also required to have the capability to control the plasma for a long period. For the increase of the loads to processing power of the PCS, the PCS is decentralized with the use of reflective memories (RFMs). The PCS controls the plasma edge position with the real-time identification of plasma current and its position. This identification is done with not only flux loops but also hall sensors. The gas fueling method by piezo valve with monitoring the Hα signal filtered by a digital low-pass filter are proposed and suitable for the steady-state operation on QUEST. The present status and prospect of the PCS are presented with recent topics.

Application of quasi-steady-state plasma streams for simulation of ITER transient heat loads

International Nuclear Information System (INIS)

Bandura, A.N.; Chebotarev, V.V.; Garkusha, I.E.; Makhlaj, V.A.; Marchenko, A.K.; Solyakov, D.G.; Tereshin, V.I.; Trubchaninov, S.A.; Tsarenko, A.V.; Landman, I.

2004-01-01

The paper presents experimental investigations of energy characteristics of the plasma streams generated with quasi-steady-state plasma accelerator QSPA Kh-50 and adjustment of plasma parameters from the point of view its applicability for simulation of transient plasma heat loads expected for ITER disruptions and type I ELMs. Possibility of generation of high-power magnetized plasma streams with ion impact energy up to 0.6 keV, pulse length of 0.25 ms and heat loads varied in wide range from 0.5 to 30 MJ/m 2 has been demonstrated and some features of plasma interaction with tungsten targets in dependence on plasma heat loads are discussed. (author)

Exploration of one-dimensional plasma current density profile for K-DEMO steady-state operation

Energy Technology Data Exchange (ETDEWEB)

Kang, J.S. [Seoul National University, Seoul 151-742 (Korea, Republic of); Jung, L. [National Fusion Research Institute, Daejeon (Korea, Republic of); Byun, C.-S.; Na, D.H.; Na, Y.-S. [Seoul National University, Seoul 151-742 (Korea, Republic of); Hwang, Y.S., E-mail: yhwang@snu.ac.kr [Seoul National University, Seoul 151-742 (Korea, Republic of)

2016-11-01

Highlights: • One-dimensional current density and its optimization for the K-DEMO are explored. • Plasma current density profile is calculated with an integrated simulation code. • The impact of self and external heating profiles is considered self-consistently. • Current density is identified as a reference profile by minimizing heating power. - Abstract: Concept study for Korean demonstration fusion reactor (K-DEMO) is in progress, and basic design parameters are proposed by targeting high magnetic field operation with ITER-sized machine. High magnetic field operation is a favorable approach to enlarge relative plasma performance without increasing normalized beta or plasma current. Exploration of one-dimensional current density profile and its optimization process for the K-DEMO steady-state operation are reported in this paper. Numerical analysis is conducted with an integrated plasma simulation code package incorporating a transport code with equilibrium and current drive modules. Operation regimes are addressed with zero-dimensional system analysis. One-dimensional plasma current density profile is calculated based on equilibrium, bootstrap current analysis, and thermal transport analysis. The impact of self and external heating profiles on those parameters is considered self-consistently, where thermal power balance and 100% non-inductive current drive are the main constraints during the whole exploration procedure. Current and pressure profiles are identified as a reference steady-state profile by minimizing the external heating power with desired fusion power.

Design of an RF Antenna for a Large-Bore, High Power, Steady State Plasma Processing Chamber for Material Separation

International Nuclear Information System (INIS)

Rasmussen, D.A.; Freeman, R.L.

2001-01-01

The purpose of this Cooperative Research and Development Agreement (CRADA) between UT-Battelle, LLC, (Contractor), and Archimedes Technology Group, (Participant) is to evaluate the design of an RF antenna for a large-bore, high power, steady state plasma processing chamber for material separation. Criteria for optimization will be to maximize the power deposition in the plasma while operating at acceptable voltages and currents in the antenna structure. The project objectives are to evaluate the design of an RF antenna for a large-bore, high power, steady state plasma processing chamber for material separation. Criteria for optimization will be to maximize the power deposition in the plasma while operating at acceptable voltages and currents in the antenna structure

Theory of steady state plasma flow and confinement in a periodic magnetic field

International Nuclear Information System (INIS)

Brown, M.G.

1981-02-01

The steady flow of plasmas through spatially periodic magnetic fields is examined, and a theoretical model is developed for the case of axisymmetric geometry. The externally applied magnetic fields can be cusps or mirrors joined end to end; electrons are then localised by these fields because of their small Larmor radius, while the ions can traverse the magnetic mirrors. The properties of the model equations are studied and dimensionless parameters which appear are interpreted. Numerical methods used in steady flow applications are reviewed, and some techniques of solution for the model equations are discussed. A solution method involving numerical integration of time-dependent equations is described, which approaches the steady state asymptotically; results from this method are presented and compared with the results from perturbation theory. (author)

Steady state theta pinch concept for slow formation of FRC

International Nuclear Information System (INIS)

Hirano, K.

1987-05-01

A steady state high beta plasma flow through a channel along the magnetic field increasing downstream can be regarded as a ''steady state theta pinch'', because if we see the plasma riding on the flow we should observe very similar process taking place in a theta pinch. Anticipating to produce an FRC without using very high voltage technics such as the ones required in a conventional theta pinch, we have studied after the analogy a ''steady state reversed field theta pinch'' which is brought about by steady head-on collision of counter plasma streams along the channel as ejected from two identical co-axial plasma sources mounted at the both ends of the apparatus. The ideal Poisson and shock adiabatic flow models are employed for the analysis of the steady colliding process. It is demonstrated that an FRC involving large numbers of particles is produced only by the weak shock mode which is achieved in case energetic plasma flow is decelerated almost to be stagnated through Poisson adiabatic process before the streams are collided. (author)

Ignition phase and steady-state structures of a non-thermal air plasma

CERN Document Server

Lu Xin Pei

2003-01-01

An AC-driven, non-thermal, atmospheric pressure air plasma is generated within the gap separating a disc-shaped metal electrode and a water electrode. The ignition phase and the steady-state are studied by a high-speed CCD camera. It is found that the plasma always initiates at the surface of the water electrode. The plasma exhibits different structures depending on the polarity of the water electrode: when the water electrode plays the role of cathode, a relatively wide but visibly dim plasma column is generated. At the maximum driving voltage, the gas temperature is between 800 and 900 K, and the peak current is 67 mA; when the water electrode is anode, the plasma column narrows but increases its light emission. The gas temperature in this case is measured to be in the 1400-1500 K range, and the peak current is 81 mA.

Accuracy of the calculations of the ionization-state densities in a steady-state plasma

International Nuclear Information System (INIS)

Salzmann, D.

1980-01-01

A quantitative definition is given to the accuracy of the computation of the partial densities of the ionization states in a steady-state plasma when there is an inaccuracy in the rate coefficients used in the rate equation. It is found that the partial density of the most abundant ion species is almost independent of the exact form of the rate coefficients, but large errors may occur for the rare species. The effect of the variation of the total ion density on the partial densities is also calculated. For low-ion densities the partial ionization-state densities grow proportionally to the change of the total density, but at high densities there is an alteration of the charge-state distribution as well

Measurement of non-steady-state free fatty acid turnover

International Nuclear Information System (INIS)

Jensen, M.D.; Heiling, V.; Miles, J.M.

1990-01-01

The accuracy of non-steady-state equations for measuring changes in free fatty acid rate of appearance (Ra) is unknown. In the present study, endogenous lipolysis (traced with [ 14 C]-linoleate) was pharmacologically suppressed in six conscious mongrel dogs. A computer-responsive infusion pump was then used to deliver an intravenous oleic acid emulsion in both constant and linear gradient infusion modes. Both non-steady-state equations with various effective volumes of distribution (V) and steady-state equations were used to measure oleate Ra [( 14 C]oleate). Endogenous lipolysis did not change during the experiment. When oleate Ra increased in a linear gradient fashion, only non-steady-state equations with a large (150 ml/kg) V resulted in erroneous values (9% overestimate, P less than 0.05). In contrast, when oleate Ra decreased in a similar fashion, steady-state and standard non-steady-state equations (V = plasma volume = 50 ml/kg) overestimated total oleate Ra (18 and 7%, P less than 0.001 and P less than 0.05, respectively). Overall, non-steady-state equations with an effective V of 90 ml/kg (1.8 x plasma volume) allowed the most accurate estimates of oleate Ra

Characteristics of steady-state plasma flow in the tokamak limiter scrape-off layer

International Nuclear Information System (INIS)

Petrov, V.G.

1984-01-01

Steady state plasma flow in the scrape-off layer of a toroidal limiter is discussed. The force balance along the torus minor radius is taken into account, from which follows that the plasma pressure gradient is balanced by the ponderomotive force (1/c) j-vectorxB-vector, which arises in the presence of a current density component perpendicular to the magnetic field. The limiter has an important effect on the electric current flow in the scrape-off layer. It is shown that the electric potential and plasma density values differ from one side of the limiter to the other; this leads to plasma drift along the minor radius. The characteristic length of change in the plasma density is found to be of the order of the ion cyclotron radius calculated for a poloidal magnetic field. (author)

Implications of steady-state operation on divertor design

International Nuclear Information System (INIS)

Sevier, D.L.; Reis, E.E.; Baxi, C.B.; Silke, G.W.; Wong, C.P.C.; Hill, D.N.

1996-01-01

As fusion experiments progress towards long pulse or steady state operation, plasma facing components are undergoing a significant change in their design. This change represents the transition from inertially cooled pulsed systems to steady state designs of significant power handling capacity. A limited number of Plasma Facing Component (PFC) systems are in operation or planning to address this steady state challenge at low heat flux. However in most divertor designs components are required to operate at heat fluxes at 5 MW/m 2 or above. The need for data in this area has resulted in a significant amount of thermal/hydraulic and thermal fatigue testing being done on prototypical elements. Short pulse design solutions are not adequate for longer pulse experiments and the areas of thermal design, structural design, material selection, maintainability, and lifetime prediction are undergoing significant changes. A prudent engineering approach will guide us through the transitional phase of divertor design to steady-state power plant components. This paper reviews the design implications in this transition to steady state machines and the status of the community efforts to meet evolving design requirements. 54 refs., 5 figs., 2 tabs

Realizing steady-state tokamak operation for fusion energy

International Nuclear Information System (INIS)

Luce, T. C.

2011-01-01

Continuous operation of a tokamak for fusion energy has clear engineering advantages but requires conditions beyond those sufficient for a burning plasma. The fusion reactions and external sources must support both the pressure and the current equilibrium without inductive current drive, leading to demands on stability, confinement, current drive, and plasma-wall interactions that exceed those for pulsed tokamaks. These conditions have been met individually, and significant progress has been made in the past decade to realize scenarios where the required conditions are obtained simultaneously. Tokamaks are operated routinely without disruptions near pressure limits, as needed for steady-state operation. Fully noninductive sustainment with more than half of the current from intrinsic currents has been obtained for a resistive time with normalized pressure and confinement approaching those needed for steady-state conditions. One remaining challenge is handling the heat and particle fluxes expected in a steady-state tokamak without compromising the core plasma performance.

Initiation of arcing on tungsten surface exposed to steady state He plasmas

Science.gov (United States)

Kajita, Shin; Noiri, Yasuyuki; Ohno, Noriyasu

2015-09-01

Arcing was initiated in steady state helium plasmas by negatively biasing a tungsten electrode to around -500 V. On the tungsten electrode, nanostructures were grown by the plasma irradiation. In this study, we characterized the property of the initiated arcing by measuring the temporal evolutions of the electrode potential and the arc current. The ignition frequency and duration of arcing were presented from the potential measurements; the arc duration was in the range of changing the biasing voltage. The behavior of arc spots was observed with a fast framing camera. It was shown that the spots split frequently, and sometimes, they run on the surface independently. From the fluctuation of the arc current, the fractal feature of arcing was revealed.

Physical design of MW-class steady-state spherical tokamak, QUEST

International Nuclear Information System (INIS)

Hanada, K.; Sato, K.N.; Zushi, H.; Nakamura, K.; Sakamoto, M.; Idei, H.; Hasegawa, M.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Higashizono, Y.; Yoshida, N.; Takase, Y.; Ejiri, A.; Ogawa, Y.; Ono, Y.; Yoshida, Z.; Mitarai, O.; Maekawa, T.; Kishimoto, Y.; Ishiguro, M.; Yoshinaga, T.; Igami, H.; Hirooka, Y.; Komori, A.; Motojima, O.; Sudo, S.; Yamada, H.; Ando, A.; Asakura, Nobuyuki; Matsukawa, Makoto; Ishida, A.; Ohno, N.; Peng, M.

2008-10-01

QUEST (R=0.68 m, a=0.4 m) focuses on the steady state operation of the spherical tokamak (ST) by controlled PWI and electron Bernstain wave (EBW) current drive (CD). The QUEST project will be developed along two phases, phase I: steady state operation with plasma current, I p =20-30 kA on open divertor configuration and phase II: steady state operation with I p = 100 kA and β of 10% in short pulse on closed divertor configuration. Feasibility of the missions on QUEST was investigated and the suitable machine size of QUEST was decided based on the physical view of plasma parameters. Electron Bernstein wave (EBW) current drive are planned to establish the maintenance of plasma current in steady state. Mode conversion efficiency to EBW was calculated and the conversion of 95% will be expected. A new type antenna for QUEST has been fabricated to excite EBW effectively. The situation of heat and particle handling is challenging, and W and high temperature wall is adopted. The start-up scenario of plasma current was investigated based on the driven current by energetic electron and the most favorable magnetic configuration for start-up is proposed. (author)

Contour analysis of steady state tokamak reactor performance

International Nuclear Information System (INIS)

Devoto, R.S.; Fenstermacher, M.E.

1990-01-01

A new method of analysis for presenting the possible operating space for steady state, non-ignited tokamak reactors is proposed. The method uses contours of reactor performance and plasma characteristics, fusion power gain, wall neutron flux, current drive power, etc., plotted on a two-dimensional grid, the axes of which are the plasma current I p and the normalized beta, β n = β/(I p /aB 0 ), to show possible operating points. These steady state operating contour plots are called SOPCONS. This technique is illustrated in an application to a design for the International Thermonuclear Experimental Reactor (ITER) with neutral beam, lower hybrid and bootstrap current drive. The utility of the SOPCON plots for pointing out some of the non-intuitive considerations in steady state reactor design is shown. (author). Letter-to-the-editor. 16 refs, 3 figs, 1 tab

Steady State versus Pulsed Tokamak DEMO

Energy Technology Data Exchange (ETDEWEB)

Orsitto, F.P., E-mail: francesco.orsitto@enea.it [Associazione EURATOM-ENEA Unita Tecnica Fusione, Frascati (Italy); Todd, T. [CCFE/Fusion Association, Culham Science Centre, Abingdon (United Kingdom)

2012-09-15

Full text: The present report deals with a Review of problems for a Steady state(SS) DEMO, related argument is treated about the models and the present status of comparison between the characteristics of DEMO pulsed versus a Steady state device.The studied SS DEMO Models (SLIM CS, PPCS model C EU-DEMO, ARIES-RS) are analyzed from the point of view of the similarity scaling laws and critical issues for a steady state DEMO. A comparison between steady state and pulsed DEMO is therefore carried out: in this context a new set of parameters for a pulsed (6 - 8 hours pulse) DEMO is determined working below the density limit, peak temperature of 20 keV, and requiring a modest improvement in the confinement factor(H{sub IPBy2} = 1.1) with respect to the H-mode. Both parameters density and confinement parameter are lower than the DEMO models presently considered. The concept of partially non-inductive pulsed DEMO is introduced since a pulsed DEMO needs heating and current drive tools for plasma stability and burn control. The change of the main parameter design for a DEMO working at high plasma peak temperatures T{sub e} {approx} 35 keV is analyzed: in this range the reactivity increases linearly with temperature, and a device with smaller major radius (R = 7.5 m) is compatible with high temperature. Increasing temperature is beneficial for current drive efficiency and heat load on divertor, being the synchrotron radiation one of the relevant components of the plasma emission at high temperatures and current drive efficiency increases with temperature. Technology and engineering problems are examined including efficiency and availability R&D issues for a high temperature DEMO. Fatigue and creep-fatigue effects of pulsed operations on pulsed DEMO components are considered in outline to define the R&D needed for DEMO development. (author)

Progress and prospect of true steady state operation with RF

Directory of Open Access Journals (Sweden)

Jacquinot Jean

2017-01-01

Full Text Available Operation of fusion confinement experiments in full steady state is a major challenge for the development towards fusion energy. Critical to achieving this goal is the availability of actively cooled plasma facing components and auxiliary systems withstanding the very harsh plasma environment. Equally challenging are physics issues related to achieving plasma conditions and current drive efficiency required by reactor plasmas. RF heating and current drive systems have been key instruments for obtaining the progress made until today towards steady state. They hold all the records of long pulse plasma operation both in tokamaks and in stellarators. Nevertheless much progress remains to be made in particular for integrating all the requirements necessary for maintaining in steady state the density and plasma pressure conditions of a reactor. This is an important stated aim of ITER and of devices equipped with superconducting magnets. After considering the present state of the art, this review will address the key issues which remain to be solved both in physics and technology for reaching this goal. They constitute very active subjects of research which will require much dedicated experimentation in the new generation of superconducting devices which are now in operation or becoming close to it.

Magnetic Fusion Energy Plasma Interactive and High Heat Flux Components: Volume 5, Technical assessment of critical issues in the steady state operation of fusion confinement devices

Energy Technology Data Exchange (ETDEWEB)

1988-01-01

Critical issues for the steady state operation of plasma confinement devices exist in both the physics and technology fields of fusion research. Due to the wide range and number of these issues, this technical assessment has focused on the crucial issues associated with the plasma physics and the plasma interactive components. The document provides information on the problem areas that affect the design and operation of a steady state ETR or ITER type confinement device. It discusses both tokamaks and alternative concepts, and provides a survey of existing and planned confinement machines and laboratory facilities that can address the identified issues. A universal definition of steady state operation is difficult to obtain. From a physics point of view, steady state is generally achieved when the time derivatives approach zero and the operation time greatly exceeds the characteristic time constants of the device. Steady state operation for materials depends on whether thermal stress, creep, fatigue, radiation damage, or power removal are being discussed. For erosion issues, the fluence and availability of the machine for continuous operation are important, assuming that transient events such as disruptions do not limit the component lifetimes. The panel suggests, in general terms, that steady state requires plasma operation from 100 to 1000 seconds and an availability of more than a few percent, which is similar to the expectations for an ETR type device. The assessment of critical issues for steady state operation is divided into four sections: physics issues; technology issues; issues in alternative concepts; and devices and laboratory facilities that can address these problems.

Magnetic Fusion Energy Plasma Interactive and High Heat Flux Components: Volume 5, Technical assessment of critical issues in the steady state operation of fusion confinement devices

International Nuclear Information System (INIS)

1988-01-01

Critical issues for the steady state operation of plasma confinement devices exist in both the physics and technology fields of fusion research. Due to the wide range and number of these issues, this technical assessment has focused on the crucial issues associated with the plasma physics and the plasma interactive components. The document provides information on the problem areas that affect the design and operation of a steady state ETR or ITER type confinement device. It discusses both tokamaks and alternative concepts, and provides a survey of existing and planned confinement machines and laboratory facilities that can address the identified issues. A universal definition of steady state operation is difficult to obtain. From a physics point of view, steady state is generally achieved when the time derivatives approach zero and the operation time greatly exceeds the characteristic time constants of the device. Steady state operation for materials depends on whether thermal stress, creep, fatigue, radiation damage, or power removal are being discussed. For erosion issues, the fluence and availability of the machine for continuous operation are important, assuming that transient events such as disruptions do not limit the component lifetimes. The panel suggests, in general terms, that steady state requires plasma operation from 100 to 1000 seconds and an availability of more than a few percent, which is similar to the expectations for an ETR type device. The assessment of critical issues for steady state operation is divided into four sections: physics issues; technology issues; issues in alternative concepts; and devices and laboratory facilities that can address these problems

'Memory' and sustention of microdischarges in a steady-state DBD: volume plasma or surface charge?

International Nuclear Information System (INIS)

Akishev, Yuri; Aponin, Gregory; Balakirev, Anton; Grushin, Mikhail; Karalnik, Vladimir; Petryakov, Alexander; Trushkin, Nikolay

2011-01-01

The results of a numerical study on the spatio-temporal behavior of transient microdischarges (MDs) in a steady-state dielectric barrier discharge (DBD) excited by a sinusoidal voltage are presented. MDs have a spatial 'memory'-every subsequent MD appears at exactly the same location occupied by the MD at the preceding half-period (HP). In the majority of cases each MD appears at its location only once during every HP. For such a case, the memory effect is not attributed to the residual surface charge deposited by the preceding MD but determined by the residual MD plasma column shunting the gap right up to the beginning of the next HP. In contrast to good memory in space, each individual MD has a large scatter with time in its appearance within every HP, i.e. there is no 'memory' concerning the phase of an applied voltage. This MD jittering within the period is attributed to the stochastic nature of partial surface breakdowns around the bases of the MD plasma column. Numerical calculations show that surface breakdown provides an MD current splash at every HP. Hence, in the steady-state DBD, the volume plasma is responsible for the existence of MD spatial 'memory' (i.e. where the MD appears), and the deposited surface charge is responsible for MD jittering in time (i.e. when the MD appears).

Steady state neutral beam injector

International Nuclear Information System (INIS)

Mattoo, S.K.; Bandyopadhyay, M.; Baruah, U.K.; Bisai, N.; Chakbraborty, A.K.; Chakrapani, Ch.; Jana, M.R.; Bajpai, M.; Jaykumar, P.K.; Patel, D.; Patel, G.; Patel, P.J.; Prahlad, V.; Rao, N.V.M.; Rotti, C.; Singh, N.P.; Sridhar, B.

2000-01-01

Learning from operational reliability of neutral beam injectors in particular and various heating schemes including RF in general on TFTR, JET, JT-60, it has become clear that neutral beam injectors may find a greater role assigned to them for maintaining the plasma in steady state devices under construction. Many technological solutions, integrated in the present day generation of injectors have given rise to capability of producing multimegawatt power at many tens of kV. They have already operated for integrated time >10 5 S without deterioration in the performance. However, a new generation of injectors for steady state devices have to address to some basic issues. They stem from material erosion under particle bombardment, heat transfer > 10 MW/m 2 , frequent regeneration of cryopanels, inertial power supplies, data acquisition and control of large volume of data. Some of these engineering issues have been addressed to in the proposed neutral beam injector for SST-1 at our institute; the remaining shall have to wait for the inputs of the database generated from the actual experience with steady state injectors. (author)

A Novel Chronic Opioid Monitoring Tool to Assess Prescription Drug Steady State Levels in Oral Fluid.

Science.gov (United States)

Shaparin, Naum; Mehta, Neel; Kunkel, Frank; Stripp, Richard; Borg, Damon; Kolb, Elizabeth

2017-11-01

Interpretation limitations of urine drug testing and the invasiveness of blood toxicology have motivated the desire for the development of simpler methods to assess biologically active drug levels on an individualized patient basis. Oral fluid is a matrix well-suited for the challenge because collections are based on simple noninvasive procedures and drug concentrations better correlate to blood drug levels as oral fluid is a filtrate of the blood. Well-established pharmacokinetic models were utilized to generate oral fluid steady state concentration ranges to assess the interpretive value of the alternative matrix to monitor steady state plasma oxycodone levels. Paired oral fluid and plasma samples were collected from patients chronically prescribed oxycodone and quantitatively analyzed by liquid chromatography tandem mass spectrometry. Steady state plasma concentration ranges were calculated for each donor and converted to an equivalent range in oral fluid. Measured plasma and oral fluid oxycodone concentrations were compared with respective matrix-matched steady state ranges, using each plasma steady state classification as the control. A high degree of correlation was observed between matrices when classifying donors according to expected steady state oxycodone concentration. Agreement between plasma and oral fluid steady state classifications was observed in 75.6% of paired samples. This study supports novel application of basic pharmacokinetic knowledge to the pain management industry, simplifying and improving individualized drug monitoring and risk assessment through the use of oral fluid drug testing. Many benefits of established therapeutic drug monitoring in plasma can be realized in oral fluid for patients chronically prescribed oxycodone at steady state. © 2017 American Academy of Pain Medicine. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com

Hydrogen and helium recycling from stirred liquid lithium under steady state plasma bombardment

Energy Technology Data Exchange (ETDEWEB)

Hirooka, Yoshi, E-mail: hirooka.yoshihiko@nifs.ac.jp [National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292 (Japan); The Graduate School for Advanced Studies, 322-6 Oroshi, Toki, Gifu 509-5292 (Japan); Zhou, Haishan [The Graduate School for Advanced Studies, 322-6 Oroshi, Toki, Gifu 509-5292 (Japan); Ono, Masa [Princeton Plasma Physics Laboratory, PO Box 451, Princeton, NJ 08543 (United States)

2014-12-15

For improved core performance via edge plasma-wall boundary control, solid and liquid lithium has been used as a plasma-facing material in a number of confinement experiments over the past several decades. Unfortunately, it is unavoidable that lithium is saturated in the surface region with implanted hydrogenic species as well as oxygen-containing impurities. For steady state operation, a flowing liquid lithium divertor with forced convection would probably be required. In the present work, the effects of liquid stirring to simulate forced convection have been investigated on the behavior of hydrogen and helium recycling from molten lithium at temperatures up to ∼350 °C. Data indicate that liquid stirring reactivates hydrogen pumping via surface de-saturation and/or uncovering impurity films, but can also induce helium release via surface temperature change.

Feedback control of plasma density and heating power for steady state operation in LHD

Energy Technology Data Exchange (ETDEWEB)

Kamio, Shuji, E-mail: kamio@nifs.ac.jp; Kasahara, Hiroshi; Seki, Tetsuo; Saito, Kenji; Seki, Ryosuke; Nomura, Goro; Mutoh, Takashi

2015-12-15

Highlights: • We upgraded a control system for steady state operation in LHD. • This system contains gas fueling system and ICRF power control system. • Automatic power boost system is also attached for stable operation. • As a result, we achieved the long pulse up to 48 min in the electron density of more than 1 × 10{sup 19} m{sup −3}. - Abstract: For steady state operation, the feedback control of plasma density and heating power system was developed in the Large Helical Device (LHD). In order to achieve a record of the long pulse discharge, stable plasma density and heating power are needed. This system contains the radio frequency (RF) heating power control, interlocks, gas fueling, automatic RF phase control, ion cyclotron range of frequency (ICRF) antenna position control, and graphical user interface (GUI). Using the density control system, the electron density was controlled to the target density and using the RF heating power control system, the RF power injection could be stable. As a result of using this system, we achieved the long pulse up to 48 min in the electron density of more than 1 × 10{sup 19} m{sup −3}. Further, the ICRF hardware experienced no critical accidents during the 17th LHD experiment campaign in 2013.

Proceeding of A3 foresight program seminar on critical physics issues specific to steady state sustainment of high-performance plasmas 2014

International Nuclear Information System (INIS)

Morita, Shigeru; Hu Liqun; Oh, Yeong-Kook

2014-10-01

The A3 Foresight Program titled by 'Critical Physics Issues Specific to Steady State Sustainment of High-Performance Plasmas', based on the scientific collaboration among China, Japan and Korea in the field of plasma physics, has been started from August 2012 under the auspice of the Japan Society for the Promotion of Science (JSPS, Japan), the National Research Foundation of Korea (NRF, Korea) and the National Natural Science Foundation of China (NSFC, China). The main purpose of this project is to enhance joint experiments on three Asian advanced fully superconducting fusion devices (EAST in China, LHD in Japan and KSTAR in Korea) and other magnetic confinement devices to several key physics issues on steady state sustainment of high-performance plasmas. The fourth seminar on the A3 collaboration, as the fifth meeting of A3 program, took place in Kagoshima, Japan, 23-26 June 2014, which was hosted by National Institute for Fusion Science, to discuss achievement during past two years and to summarize intermediate report. New collaborative research was also encouraged as well as participation of young scientists. The topics include steady state sustainment of magnetic configuration, edge and divertor plasma control and confinement of alpha particles. This issue is the collection of 41 papers presented at the entitled meeting. All the 41 of the presented papers are indexed individually. (J.P.N.)

Steady states of a diode with counterstreaming electron and positron beams

Energy Technology Data Exchange (ETDEWEB)

Ender, A. Ya.; Kuznetsov, V. I., E-mail: victor.kuznetsov@mail.ioffe.ru; Gruzdev, A. A. [Russian Academy of Sciences, Ioffe Institute (Russian Federation)

2016-10-15

Steady states of a plasma layer with counterstreaming beams of oppositely charged particles moving without collisions in a self-consistent electric field are analyzed. The study is aimed at clarifying the mechanism of generation and reconstruction of pulsar radiation. Such a layer also models the processes occurring in Knudsen plasma diodes with counterstreaming electron and ion beams. The steady-state solutions are exhaustively classified. The existence of several solutions at the same external parameters is established.

Absorption kinetics and steady-state plasma concentrations of theophylline following therapeutic doses of two sustained-release preparations

DEFF Research Database (Denmark)

Andersen, O; Nielsen, M K; Eriksen, P B

1983-01-01

Ten healthy volunteers received two sustained-release preparations as a single and multiple dose regimen in an open crossover study. Plasma theophylline concentrations were measured by an enzyme immunoassay. The limited fluctuation of the theophylline levels at steady state, with twice daily...... formulation, whereas this was not the case for the other (r = 0.27 and 0.49). The daily dose necessary to keep the plasma concentration within the therapeutic range of 55-110 mumole/liter varied from 7.9 to 22.9 mg/kg. Only mild side effects were recorded, but they were not correlated to the plasma...... theophylline concentration....

Non-LTE population probabilities of the excited ionic levels in a steady state plasma

International Nuclear Information System (INIS)

Salzmann, D.

1982-01-01

A Complete-Staedy-State (CSS) model for the charge state distribution and the ionic levels population probabilities of ions in hot non-LTE plasmas is described. The following properties of this model are described: (i) it is shown that CSS covers LTE and Corona Equilibrium (CE) in the high and low electron density regimes respectively, (ii) an explicit expression is found for the low electron density asymptotic behaviour of the population probabilities, (iii) it is shown that at intermediate density regions the CSS model predicts results similar to that of the Quasi-Steady-State model, (iv) new validity limits are derived for LTE and CE, (v) the population distribution of the excited levels is revised, (vi) an analytical expression is found for the high electron density asymptotic behaviour of the population distribution, (vii) the influence of the radiation reabsorption in a spherically symmetric CSS plasma is briefly described, and (viii) the effect of the inaccuracies in the rate-coefficients on the results of CSS calculations is evaluated. (author)

Diffusion-driven steady states of the Z-pinch

International Nuclear Information System (INIS)

Lehnert, B.

1988-01-01

Steady states of a Z-pinch where no electric field is imposed along the pinch axis by external means are investigated. In this case, diffusion-driven states become possible when imposed volume sources of particles and heat drive a radial diffusion velocity that, in its turn, generates the electric plasma current. The particle sources can be from pellet injection or a neutral gas blanket, and the heat sources provided by thermonuclear reactions or auxiliary heating. The present analysis and associated kinetic considerations indicate that steady diffusion-driven operation should become possible for certain classes of plasma profiles, without running into singularity problems at the pinch axis. Such operation leads to higher axial currents in a Z-pinch without an axial magnetic field than in a tokamaklike case under similar plasma conditions. The technical difficulty in realizing a volume distribution of particle sinks introduces certain constraints on the plasma and current profiles. This fact has to be taken into account in a stability analysis. Neoclassical or anomalous diffusion will increase the diffusion velocity of the plasma but is not expected to affect the main physical features of the present results

Steady-state operation of spheromaks by inductive techniques

International Nuclear Information System (INIS)

Janos, A.

1984-04-01

A method to maintain a steady-state spheromak configuration inductively using the S-1 Spheromak device is described. The S-1 Spheromak formation apparatus can be utilized to inject magnetic helicity continuously (C.W., not pulsed or D.C.) into the spheromak configuration after equilibrium is achieved in the linked mode of operation. Oscillation of both poloidal- and toroidal-field currents in the flux core (psi-phi Pumping), with proper phasing, injects a net time-averaged helicity into the plasma. Steady-state maintenance relies on flux conversion, which has been earlier identified. Relevant experimental data from the operation of S-1 are described. Helicity flow has been measured and the proposed injection scheme simulated. In a reasonable time practical voltages and frequencies can inject an amount of helicity comparable to that in the initial plasma. Plasma currents can be maintained or increased. This pumping technique is similar to F-THETA Pumping of a Reversed-Field-Pinch but is applied to this inverse-pinch formation

Superconducting magnets and cryogenics for the steady state superconducting tokamak SST-1

International Nuclear Information System (INIS)

Saxena, Y.C.

2000-01-01

SST-1 is a steady state superconducting tokamak for studying the physics of the plasma processes in tokamak under steady state conditions and to learn technologies related to the steady state operation of the tokamak. SST-1 will have superconducting magnets made from NbTi based conductors operating at 4.5 K temperature. The design of the superconducting magnets and the cryogenic system of SST-1 tokamak are described. (author)

Progress towards Steady State on NSTX

International Nuclear Information System (INIS)

Gates, D.A.; Kessel, C.; Menard, J.; Taylor, G.; Wilson, J.R.

2005-01-01

In order to reduce recirculating power fraction to acceptable levels, the spherical torus concept relies on the simultaneous achievement of high toroidal β and high bootstrap fraction in steady state. In the last year, as a result of plasma control system improvements, the achievable plasma elongation on the National Spherical Torus Experiment (NSTX) has been raised from κ ∼ 2.1 to κ ∼ 2.6--approximately a 25% increase. This increase in elongation has lead to a doubling increase in the toroidal β for long-pulse discharges. The increase in β is associated with an increase in plasma current at nearly fixed poloidal β, which enables higher β t with nearly constant bootstrap fraction. As a result, for the first time in a spherical torus, a discharge with a plasma current of 1 MA has been sustained for 1 second. Data is presented from NSTX correlating the increase in performance with increased plasma shaping capability. In addition to improved shaping, H-modes induced during the current ramp phase of the plasma discharge have been used to reduce flux consumption during and to delay the onset of MHD instabilities. A modeled integrated scenario, which has 100% non-inductive current drive with very high toroidal β, will also be presented. The NSTX poloidal field coils are currently being modified to produce the plasma shape which is required for this scenario, which requires high triangularity ((delta) ∼ 0.8) at elevated elongation (κ ∼ 2.5). The other main requirement for steady state on NSTX is the ability to drive a fraction of the total plasma current with radio-frequency waves. The results of High Harmonic Fast Wave heating and current drive studies as well as electron Bernstein Wave emission studies will be presented

Steady state and transient thermal-hydraulic characterization of full-scale ITER divertor plasma facing components

International Nuclear Information System (INIS)

Tincani, A.; Malavasi, A.; Ricapito, I.; Riccardi, B.; Di Maio, P.A.; Vella, G.

2007-01-01

In the frame of the activities related to ITER divertor R and D, ENEA CR Brasimone was charged by EFDA (European Fusion Design Agreement) to investigate the thermal-hydraulic behaviour of the full-scale divertor plasma facing components, i.e. Inner Vertical Target, Dome Liner and Outer Vertical Target, both in steady state and during draining and drying transient. More in detail, for each PFC, the first phase of the work is the steady state hydraulic characterization which consists of: - measurements of pressure drops at different temperatures; - determination of the velocity distribution in the internal channels; - check the possible insurgence of cavitation. The subsequent phase of the thermal-hydraulic characterization foresees a testing campaign of draining and drying procedure by means of a suitable gas flow. The objective of this experimental procedure is to eliminate in the most efficient way the residual amount of water after gravity discharge. In order to accomplish this experimental campaign a significant modification of CEF1 loop has been designed and realized. This paper presents, first of all, the experimental set-up, the agreed test matrix and the achieved results for both steady state and transient tests. Moreover, the level of the implementation of a predictive hydraulic model, based on RELAP 5 code, as well as its results are described, discussed and compared with the experimental ones. (orig.)

On the optimization of a steady-state bootstrap-reactor

International Nuclear Information System (INIS)

Polevoy, A.R.; Martynov, A.A.; Medvedev, S.Yu.

1993-01-01

A commercial fusion tokamak-reactor may be economically acceptable only for low recirculating power fraction r 0 ≡ P CD /P α BS ≡I BS /I > 0.9 to sustain the steady-state operation mode for high plasma densities > 1.5 10 20 m -3 , fulfilled the divertor conditions. This paper presents the approximate expressions for the optimal set of reactor parameters for r BS /I∼1, based on the self-consistent plasma simulations by 1.5D ASTRA code. The linear MHD stability analysis for ideal n=1 kink and ballooning modes has been carried out to determine the conditions of stabilization for bootstrap steady state tokamak reactor BSSTR configurations. (author) 10 refs., 1 tab

Tore-Supra infrared thermography system, a real steady-state diagnostic

International Nuclear Information System (INIS)

Guilhem, D.; Bondil, J.L.; Bertrand, B.; Desgranges, C.; Lipa, M.; Messina, P.; Missirlian, M.; Portafaix, C.; Reichle, R.; Roche, H.; Saille, A.

2005-01-01

Tore-Supra Tokamak (I p = 1.5 MA, B t = 4 T) has been constructed with a steady-state magnetic field using super-conducting magnets and water-cooled plasma facing components (PFCs) for high-performance long pulse plasma discharges. When not actively cooled, plasma facing components can only accumulate a limited amount of energy since the temperature increases continuously during the discharge until radiation cooling equals the incoming heat flux. Such an environment is found in the JET Tokamak [JET Team, IAEA-CN-60/A1-3, Seville, 1994] and on TRIAM [M. Sakamoto, H. Nakashima, S. Kawasaki, A. Iyomasa, S.V. Kulkarni, M. Hasegawa, E. Jotaki, H. Zushi, K. Nakamura, K. Hanada, S. Itoh, Static and dynamic properties of wall recycling in TRIAM-1M, J. Nucl. Mater. 313-316 (2003) 519-523] [Y. Kamada, et al., Nucl. Fusion 3 (1999) 1845]. In Tore-Supra, the surface temperature of the actively cooled plasma facing components reach steady state within a second. We present here the Tore-Supra thermographic system, made of seven endoscope bodies equipped so far with eight infrared (IR) cameras. It has to be noted that this diagnostic is the first diagnostic to be actively cooled, as required for steady state. The main purpose of such a diagnostic is to prevent the plasma to damage the actively cooled plasma facing components (ACPFCs), which consist of the toroidal pumped limiter (TPL), 7 m 2 , and of five radio-frequency antennae, 1.5 m 2 each

Theory of minimum dissipation of energy for the steady state

International Nuclear Information System (INIS)

Chu, T.K.

1992-02-01

The magnetic configuration of an inductively driven steady-state plasma bounded by a surface (or two adjacent surfaces) on which B·n = 0 is force-free: ∇xB = 2αB, where α is a constant, in time and in space. α is the ratio of the Poynting flux to the magnetic helicity flux at the boundary. It is also the ratio of the dissipative rates of the magnetic energy to the magnetic helicity in the plasma. The spatial extent of the configuration is noninfinitesimal. This global constraint is a result of the requirement that, for a steady-state plasma, the rate of change of the vector potential, ∂A/∂t, is constant in time and uniform in space

Ideal MHD stability and performance of ITER steady-state scenarios with ITBs

Science.gov (United States)

Poli, F. M.; Kessel, C. E.; Chance, M. S.; Jardin, S. C.; Manickam, J.

2012-06-01

Non-inductive steady-state scenarios on ITER will need to operate with internal transport barriers (ITBs) in order to reach adequate fusion gain at typical currents of 9 MA. The large pressure gradients at the location of the internal barrier are conducive to the development of ideal MHD instabilities that may limit the plasma performance and may lead to plasma disruptions. Fully non-inductive scenario simulations with five combinations of heating and current drive sources are presented in this work, with plasma currents in the range 7-10 MA. For each configuration the linear, ideal MHD stability is analysed for variations of the Greenwald fraction and of the pressure peaking factor around the operating point, aiming at defining an operational space for stable, steady-state operations at optimized performance. It is shown that plasmas with lower hybrid heating and current drive maintain the minimum safety factor above 1.5, which is desirable in steady-state operations to avoid neoclassical tearing modes. Operating with moderate ITBs at 2/3 of the minor radius, these plasmas have a minimum safety factor above 2, are ideal MHD stable and reach Q ≳ 5 operating above the ideal no-wall limit.

Analysis of plasma equilibrium based on orbit-driven current density profile in steady-state plasma on QUEST

Energy Technology Data Exchange (ETDEWEB)

Nakamura, K., E-mail: nakamura@triam.kyushu-u.ac.jp [RIAM, Kyushu University, Kasuga 816-8580 (Japan); Alam, M.M. [IGSES, Kyushu University, Kasuga 816-8580 (Japan); Jiang, Y.Z. [Tsinghua University, Beijing 100084 (China); Mitarai, O. [Tokai University, Kumamoto 862-8652 (Japan); Kurihara, K.; Kawamata, Y.; Sueoka, M.; Takechi, M. [Japan Atomic Energy Agency, Naka 311-0193 (Japan); Hasegawa, M.; Tokunaga, K.; Araki, K.; Zushi, H.; Hanada, K.; Fujisawa, A.; Idei, H.; Nagashima, Y.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Nagata, T. [RIAM, Kyushu University, Kasuga 816-8580 (Japan); and others

2016-11-01

Highlights: • High energy particle guiding center orbit is calculated as a contour plot of conserved variable. • Current density profile is analyzed based on the orbit-driven current. • Plasma equilibrium is reconstructed by considering the hollow current profile. - Abstract: In the present RF-driven (ECCD) steady-state plasma on QUEST (B{sub t} = 0.25 T, R = 0.68 m, a = 0.40 m), plasma current seems to flow in the open magnetic surface outside of the closed magnetic surface in the low-field region according to plasma current fitting (PCF) method. We consider that the current in the open magnetic surface is due to orbit-driven current by high-energy particles in RF-driven plasma. So based on the analysis of current density profile based on the orbit-driven current, plasma equilibrium is to be calculated. We calculated high energy particles guiding center orbits as a contour plot of conserved variable in Hamiltonian formulation and considered particles initial position with different levels of energy and pitch angles that satisfy resonance condition. Then the profile of orbit-driven current is estimated by multiplying the particle density on the resonance surface and the velocity on the orbits. This analysis shows negative current near the magnetic axis and hollow current profile is expected even if pressure driven current is considered. Considering the hollow current profile shifted toward the low-field region, the equilibrium is fitted by J-EFIT coded by MATLAB.

Steady-state operation of magnetic fusion devices: Plasma control and plasma facing components. Report on the IAEA technical committee meeting held at Fukuoka, 25-29 October 1999

International Nuclear Information System (INIS)

Engelmann, F.

2000-01-01

An IAEA Technical Committee Meeting on Steady-State Operation of Magnetic Fusion Devices - Plasma Control and Plasma Facing Components was held at Fukuoka, Japan, from 25 to 29 October 1999. The meeting was the second IAEA Techical Committee Meeting on the subject, following the one held at Hefei, China, a year earlier. The meeting was attended by over 150 researchers from 10 countries

A monte carlo simulation model for the steady-state plasma in the scrape-off layer

International Nuclear Information System (INIS)

Wang, W.X.; Okamoto, M.; Nakajima, N.; Murakami, S.; Ohyabu, N.

1995-12-01

A new Monte Carlo simulation model for the scrape-off layer (SOL) plasma is proposed to investigate a feasibility of so-called 'high temperature divertor operation'. In the model, Coulomb collision effect is accurately described by a nonlinear Monte Carlo collision operator; a conductive heat flux into the SOL is effectively modelled via randomly exchanging the source particles and SOL particles; secondary electrons are included. The steady state of the SOL plasma, which satisfies particle and energy balances and the neutrality constraint, is determined in terms of total particle and heat fluxes across the separatrix, the edge plasma temperature, the secondary electron emission rate, and the SOL size. The model gives gross features of the SOL such as plasma temperatures and densities, the total sheath potential drop, and the sheath energy transmission factor. The simulations are performed for collisional SOL plasma to confirm the validity of the proposed model. It is found that the potential drop and the electron energy transmission factor are in close agreement with theoretical predictions. The present model can provide primarily useful information for collisionless SOL plasma which is difficult to be understood analytically. (author)

Materials for the plasma-facing components of steady state stellarators

International Nuclear Information System (INIS)

Bolt, H.; Boscary, J.; Greuner, H.; Grigull, P.; Maier, H.; Streibl, B.

2005-01-01

The specific advantage of current-free stellarators is their inherent capability for full steady-state operation. This will lead to long discharges and the corresponding stationary plasma exposure of the plasma-facing materials. Further to this, the absence of disruptions relaxes the requirements to the plasma-facing materials in terms of thermal shock stability, although ELM activity occurs also in stellarators and leads to fast transient surface loads on the ms-time scale. Another aspect regarding the plasma-material interactions in stellarators is the sensitivity to impurity accumulation in the core plasma. Thus, it is preferred to apply low-Z materials until operation scenarios are established which do not lead to this accumulation process. In the case of high-Z materials impurity accumulation will lead to a radiative plasma collapse. For the stellarator W7-X low-Z plasma-facing materials have been selected to protect the divertor and the wall surfaces. Due to the stationary operation, the plasma-facing materials have to be bonded or clamped to actively water-cooled substrates to remove the incident heat fluxes. The following materials have been selected to fulfil the operational requirements: 1. A three directionally carbon fibre reinforced carbon composite (CFC) with very high thermal conductivity bonded to a water cooled CuCrZr heat sink for the divertor which will be exposed to heat fluxes up to 10MW/m 2 . 2. Isotropic fine grain graphite tiles mechanically clamped to a CuCrZr heat sink which is brazed to a stainless steel cooling tube for the areas of moderate heat fluxes up to 0.5 MW/m 2 (baffles, inner wall). 3. Thick boron carbide coating on water cooled steel panels for the outer wall surfaces with low heat fluxes up to 0.2 MW/m 2 . This coating would be applied on most surfaces only after the initial operation. In the presentation the properties of these materials will be discussed with a view to the plasma-wall interaction in W7-X. In fusion reactors

Recent progresses on high performance steady-state plasmas in the superconducting tokamak TRIAM-1M

International Nuclear Information System (INIS)

Itoh, Satoshi; Sato, Kohnosuke; Nakamura, Kazuo

1999-01-01

The overview of TRIAM-1M experiments is described. The up-to-date issues for steady-state operation are presented through the experience of the achievement of super ultra long tokamak discharges (SULD) sustained by lower hybrid current drive (LHCD) over 2 hours. The importance of the control of an initial phase of plasma, the avoidance of the concentration of huge heat load, the wall conditioning, and abrupt stop of the long discharges are proposed as the indispensable issues for the achievement of the steady-state operation of tokamak. A high ion temperature (HIT) discharge fully sustained by 2.45 GHz LHCD with both high ion temperature and steep temperature gradient is successfully demonstrated for longer than 1 min in the limiter configuration. The HIT discharges can be obtained in the narrow window of density and position. Moreover, the avoidance of the concentration of heat load on a limiter is the key point for the achievement and its long sustainment. As the effective thermal insulation between the wall and the plasma is improved on the single null configuration, HIT discharges with peak ion temperature > 5keV and steeper gradient up to 85 keV/m can be achieved by the exquisite control of density and position. The plasmas with high κ ∼1.5 can be also demonstrated for longer than 1 min. The current profile is also well-controlled for about 2 orders in magnitude longer than the current diffusion time using combined LHCD. The serious damage to the material of the first wall caused by energetic neutral particles produced via charge exchange process is also described. As the neutral particles cannot be affected by magnetic field, this damage by neutral particles must be avoided by the new technique. (author)

Advanced control scenario of high-performance steady-state operation for JT-60 superconducting tokamak

International Nuclear Information System (INIS)

Tamai, H.; Kurita, G.; Matsukawa, M.; Urata, K.; Sakurai, S.; Tsuchiya, K.; Morioka, A.; Miura, Y.M.; Kizu, K.; Kamada, Y.; Sakasai, A.; Ishida, S.

2004-01-01

Plasma control on high-β N steady-state operation for JT-60 superconducting modification is discussed. Accessibility to high-β N exceeding the free-boundary limit is investigated with the stabilising wall of reduced-activated ferritic steel and the active feedback control of the in-vessel non-axisymmetric field coils. Taking the merit of superconducting magnet, advanced plasma control for steady-state high performance operation could be expected. (authors)

The launching and propagation of drift waves in a steady-state plasma

International Nuclear Information System (INIS)

Sandeman, J.; Elliott, J.A.; Sutcliffe, M.; Rusbridge, M.G.

1992-01-01

The UMIST linear quadrupole GOLUX is a steady-state device in which hydrogen plasma is continuously injected axially, at one end, from an external duoplasmatron source. The electron temperature in the drift wave region is about 1 eV, and the density about 10 15 m -3 . Self-excited intrinsic drift modes are observed in the shared flux region of GOLUX, forming a broad band between 30 and 50 kHz. Drift waves may also be launched into the system, by passing an AC current through the plasma between the two flag antennae. These coherent launched waves present a powerful means of studying drift wave phenomena. We obtain information about the launched wave by detecting both density and potential fluctuations, using a small cylindrical Langmuir probe and lock-in amplifier techniques. Scanning the probe in the longitudinal (z) direction yields the spatial variation of amplitude and phase with respect to the launching signal; the ratio of the wave potential, extrapolated back to the probe, to the launching current gives the launching impedance, a measure of the effectiveness of the launching process. (author) 5 refs., 6 figs

Steady state operation of tokamaks. Proceedings of a technical committee meeting

International Nuclear Information System (INIS)

2000-10-01

The first IAEA Technical Committee Meeting (TCM) on Steady State Operation of Tokamaks was organized to discuss the operations of present long-pulse tokamaks (TRIAM-1M, TORE SUPRA, MT-7, HT-7M, HL-1M) and the plans for future steady-state tokamaks such as SST-1, CIEL, and HT-7U. This meeting, held from 13-15 October 1998, was hosted by the Academia Sinica Institute of Plasma Physics (ASIPP), Hefei, China. Participants from China, France, India, Japan, the Russian Federation, and the IAEA participated in the meeting. There were 18 individual presentations plus general discussions on many topics, including superconducting magnet systems, cryogenics, plasma position control, non-inductive current drive, auxiliary heating, plasma-wall interactions, high heat flux components, particle control, and data acquisition

Plasma flow reactor for steady state monitoring of physical and chemical processes at high temperatures.

Science.gov (United States)

Koroglu, Batikan; Mehl, Marco; Armstrong, Michael R; Crowhurst, Jonathan C; Weisz, David G; Zaug, Joseph M; Dai, Zurong; Radousky, Harry B; Chernov, Alex; Ramon, Erick; Stavrou, Elissaios; Knight, Kim; Fabris, Andrea L; Cappelli, Mark A; Rose, Timothy P

2017-09-01

We present the development of a steady state plasma flow reactor to investigate gas phase physical and chemical processes that occur at high temperature (1000 flow injector). We have modeled the system using computational fluid dynamics simulations that are bounded by measured temperatures. In situ line-of-sight optical emission and absorption spectroscopy have been used to determine the structures and concentrations of molecules formed during rapid cooling of reactants after they pass through the plasma. Emission spectroscopy also enables us to determine the temperatures at which these dynamic processes occur. A sample collection probe inserted from the open end of the reactor is used to collect condensed materials and analyze them ex situ using electron microscopy. The preliminary results of two separate investigations involving the condensation of metal oxides and chemical kinetics of high-temperature gas reactions are discussed.

Divertor modeling for the design of the National Centralized Tokamak with high beta steady-state plasmas

International Nuclear Information System (INIS)

Kawashima, H.; Sakurai, S.; Shimizu, K.; Takizuka, T.; Tamai, H.; Matsukawa, M.; Fujita, T.; Miura, Y.

2006-01-01

The modification of the JT-60U to a fully superconducting coil tokamak, National Centralized Tokamak (NCT) facility, has been programmed to accomplish the high beta steady-state plasma research. A 2D divertor simulation code, SOLDOR/NEUT2D, is applied to the construction of a database for optimum design of the divertor. A semi-closed divertor configuration with vertical target is adopted as the first conceptual divertor design on NCT. With an anticipated SOL power flux of 12 MW at the high beta steady-state operation, the peak heat load on the divertor target is evaluated to be ∼16 MW/m 2 . Effects of divertor geometry and intense gas puffing are demonstrated with a view to reduce the heat load. For the simulation of divertor pumping, we find that the pumping efficiency increases by a factor of 2∼3 by narrowing the divertor gap from 20 to 5 cm. An attractive feature in reducing the heat load and improving the particle controllability has been obtained for a new divertor design due to a recent progress in NCT design

Simulations of KSTAR high performance steady state operation scenarios

International Nuclear Information System (INIS)

Na, Yong-Su; Kessel, C.E.; Park, J.M.; Yi, Sumin; Kim, J.Y.; Becoulet, A.; Sips, A.C.C.

2009-01-01

We report the results of predictive modelling of high performance steady state operation scenarios in KSTAR. Firstly, the capabilities of steady state operation are investigated with time-dependent simulations using a free-boundary plasma equilibrium evolution code coupled with transport calculations. Secondly, the reproducibility of high performance steady state operation scenarios developed in the DIII-D tokamak, of similar size to that of KSTAR, is investigated using the experimental data taken from DIII-D. Finally, the capability of ITER-relevant steady state operation is investigated in KSTAR. It is found that KSTAR is able to establish high performance steady state operation scenarios; β N above 3, H 98 (y, 2) up to 2.0, f BS up to 0.76 and f NI equals 1.0. In this work, a realistic density profile is newly introduced for predictive simulations by employing the scaling law of a density peaking factor. The influence of the current ramp-up scenario and the transport model is discussed with respect to the fusion performance and non-inductive current drive fraction in the transport simulations. As observed in the experiments, both the heating and the plasma current waveforms in the current ramp-up phase produce a strong effect on the q-profile, the fusion performance and also on the non-inductive current drive fraction in the current flattop phase. A criterion in terms of q min is found to establish ITER-relevant steady state operation scenarios. This will provide a guideline for designing the current ramp-up phase in KSTAR. It is observed that the transport model also affects the predictive values of fusion performance as well as the non-inductive current drive fraction. The Weiland transport model predicts the highest fusion performance as well as non-inductive current drive fraction in KSTAR. In contrast, the GLF23 model exhibits the lowest ones. ITER-relevant advanced scenarios cannot be obtained with the GLF23 model in the conditions given in this work

MHD stability regimes for steady state and pulsed reactors

International Nuclear Information System (INIS)

Jardin, S.C.; Kessel, C.E.; Pomphrey, N.

1994-02-01

A tokamak reactor will operate at the maximum value of β≡2μ 0 /B 2 that is compatible with MHD stability. This value depends upon the plasma current and pressure profiles, the plasma shape and aspect ratio, and the location of nearby conducting structures. In addition, a steady state reactor will minimize its external current drive requirements and thus achieve its maximum economic benefit with a bootstrap fraction near one, I bs /I p ∼ 1, which constrains the product of the inverse aspect ratio and the plasma poloidal beta to be near unity, ε β p ∼ 1. An inductively driven pulsed reactor has different constraints set by the steady-state Ohm's law which relates the plasma temperature and density profiles to the parallel current density. We present the results obtained during the ARIES I, II/IV, and III and the PULSAR reactor studies where these quantities were optimized subject to different design philosophies. The ARIES-II/IV and ARIES-III designs are both in the second stability regime, but differ in requirements on the form of the profiles at the plasma edge, and in the location of the conducting wall. The relation between these, as well as new attractive MHD regimes not utilized in the ARIES or PULSAR studies is also discussed

Magnetohydrodynamic stability regimes for steady state and pulsed reactors

International Nuclear Information System (INIS)

Jardin, S.C.; Kessel, C.E.; Pomphrey, N.

1994-01-01

A tokamak reactor will operate at the maximum value of β≡2μ 0 left angle p right angle /B 2 that is compatible with magnetohydrodynamic (MHD) stability. This value depends on the plasma current and pressure profiles, the plasma shape and aspect ratio, and the location of nearby conducting structures. In addition, a steady state reactor will minimize its external current drive requirements and thus achieve its maximum economic benefit with a bootstrap fraction near unity, I BS /I P ∼1, which constrains the product of the inverse aspect ratio and the plasma poloidal β to be near unity, arepsilonβ P ∼1. An inductively driven pulsed reactor has different constraints set by the steady-state Ohm's law which relates the plasma temperature and density profiles to the parallel current density. We present the results obtained during ARIES I, II/IV, and III and PULSAR reactor studies where these quantities were optimized subject to different design philosophies. The ARIES-II/IV and ARIES-III designs are both in the second stability regime, but differ in requirements in the form of the profiles at the plasma edge, and in the location of the conducting wall. The relation between these, as well as new attractive MHD regimes not utilized in the ARIES or PULSAR studies, is also discussed. ((orig.))

Relaxed states of tokamak plasmas

International Nuclear Information System (INIS)

Kucinski, M.Y.; Okano, V.

1993-01-01

The relaxed states of tokamak plasmas are studied. It is assumed that the plasma relaxes to a quasi-steady state which is characterized by a minimum entropy production rate, compatible with a number of prescribed conditions and pressure balance. A poloidal current arises naturally due to the anisotropic resistivity. The minimum entropy production theory is applied, assuming the pressure equilibrium as fundamental constraint on the final state. (L.C.J.A.)

Steady state magnetic field configurations for the earth's magnetotail

International Nuclear Information System (INIS)

Hau, L.N.; Wolf, R.A.; Voigt, G.H.; Wu, C.C.

1989-01-01

The authors present a two-dimensional, force-balanced magnetic field model in which flux tubes have constant pVγ throughout an extended region of the nightside plasma sheet, between approximately 36 R E geocentric distance and the region of the inner edge of the plasma sheet. They have thus demonstrated the theoretical existence of a steady state magnetic field configuration that is force-balanced and also consistent with slow, lossless, adiabatic, earthward convection within the limit of the ideal MHD (isotropic pressure, perfect conductivity). The numerical solution was constructed for a two-dimensional magnetosphere with a rectangular magnetopause and nonflaring tail. The primary characteristics of the steady state convection solution are (1) a pressure maximum just tailward of the inner edge of the plasma sheet and (2) a deep, broad minimum in equatorial magnetic field strength B ze , also just tailward of the inner edge. The results are consistent with Erickson's (1985) convection time sequences, which exhibited analogous pressure peaks and B ze minima. Observations do not indicate the existence of a B ze minimum, on the average. They suggest that the configurations with such deep minima in B ze may be tearing-mode unstable, thus leading to substorm onset in the inner plasma sheet

Application of powerful quasi-steady-state plasma accelerators for simulation of ITER transient heat loads on divertor surfaces

Energy Technology Data Exchange (ETDEWEB)

Tereshin, V I [Institute of Plasma Physics of the NSC KIPT, Kharkov 61108 (Ukraine); Bandura, A N [Institute of Plasma Physics of the NSC KIPT, Kharkov 61108 (Ukraine); Byrka, O V [Institute of Plasma Physics of the NSC KIPT, Kharkov 61108 (Ukraine); Chebotarev, V V [Institute of Plasma Physics of the NSC KIPT, Kharkov 61108 (Ukraine); Garkusha, I E [Institute of Plasma Physics of the NSC KIPT, Kharkov 61108 (Ukraine); Landman, I [Forschungszentrum Karlsruhe, IHM, Karlsruhe 76021 (Germany); Makhlaj, V A [Institute of Plasma Physics of the NSC KIPT, Kharkov 61108 (Ukraine); Neklyudov, I M [Institute of Plasma Physics of the NSC KIPT, Kharkov 61108 (Ukraine); Solyakov, D G [Institute of Plasma Physics of the NSC KIPT, Kharkov 61108 (Ukraine); Tsarenko, A V [Institute of Plasma Physics of the NSC KIPT, Kharkov 61108 (Ukraine)

2007-05-15

The paper presents the investigations of high power plasma interaction with material surfaces under conditions simulating the ITER disruptions and type I ELMs. Different materials were exposed to plasma with repetitive pulses of 250 {mu}s duration, the ion energy of up to 0.6 keV, and the heat loads varying in the 0.5-25 MJ m{sup -2} range. The plasma energy transfer to the material surface versus impact load has been analysed. The fraction of plasma energy that is absorbed by the target surface is rapidly decreased with the achievement of the evaporation onset for exposed targets. The distributions of evaporated material in front of the target surface and the thickness of the shielding layer are found to be strongly dependent on the target atomic mass. The surface analysis of tungsten targets exposed to quasi-steady-state plasma accelerators plasma streams is presented together with measurements of the melting onset load and evaporation threshold, and also of erosion patterns with increasing heat load and the number of plasma pulses.

Recent QUEST experiments on non-inductive current drive and plasma-wall interaction towards steady state operation of spherical tokamak

International Nuclear Information System (INIS)

Hanada, K.; Zushi, H.; Idei, H.; Nakamura, K.; Nagashima, Y.; Hasegawa, M.; Fujisawa, A.; Higashijima, A.; Kawasaki, S.; Nakashima, H.; Ishiguro, M.; Tashima, S.; Kalinnikova, E.I.; Mitarai, O.; Maekawa, T.; Fukuyama, A.; Takase, Y.; Gao, X.; Liu, H.; Qian, J.; Ono, M.; Raman, R.; Peng, M.

2015-01-01

Full text of publication follows. Steady state operation (SSO) of magnetic fusion devices is one of the goals for fusion research. Development of non-inductive current drive and investigation of plasma-wall interaction (PWI) are issues to be resolved for SSO. Because of the very limited central solenoid (CS) flux in a spherical tokamak (ST), methods for non-inductive plasma current start-up and sustainment are necessary. Fully non-inductive plasma up to approximately 5 min was successfully demonstrated on the spherical tokamak QUEST. Furthermore, recharging of the center solenoid coil was also achieved in OH+RF plasmas with plasma current feedback using the CS. During the plasma start-up phase, precession motion of trapped electrons can drive some current, which plays an essential role in forming a closed flux surface. On QUEST, the main parts of the plasma facing components (PFCs) are covered by tungsten plates (W) or coated by W plasma spray and are actively cooled by water circulation. The increase in water temperature quantitatively provides the deposited power to each PFC. The power balance during long duration discharges has been studied for various types of magnetic configurations such as limiter, upper and lower single-null divertor discharges. As, the temperature of any PFCs reaches a steady-state condition during long pulse, the power balance can be obtained. It is found that the discharge duration of QUEST is significantly limited by particle imbalance shown by gradual increment of plasma and neutral density. The additional influx of neutrals was provided by recycling of hydrogen, which is still uncontrollable. A point model of particle balance was applied to a long-duration divertor discharge, and it was found that a small increment of particle-influx occurred around the end of the long duration discharge. A post-mortem analysis of surface-attaching specimen during an experimental campaign indicates that the increased amount of neutral influx could be

Full steady state LH scenarios in Tore Supra

International Nuclear Information System (INIS)

Kazarian-Vibert, F.; Litaudon, X.; Arslanbekov, R.; Hoang, G.T.; Moreau, D.; Peysson, Y.

1995-01-01

Lower Hybrid discharge have been realised in Tore Supra using feed-back control of the primary circuit voltage such that the loop voltage was maintained exactly to zero near the plasma surface. This new scenario allows the plasma current to float and quickly reach an equilibrium value determined by the current drive efficiency and Lower Hybrid power. Recent experimental results show that, with the new constant flux scenario the coupled plasma and primary currents reach a steady state in less than 10 s which is a good agreement with theoretical expectations. A complete analysis of this scenario is presented. (authors). 8 refs., 3 figs

Proceedings of A3 foresight program seminar on critical physics issues specific to steady state sustainment of high-performance plasmas

International Nuclear Information System (INIS)

Morita, Shigeru; Hu Liqun; Oh, Yeong-Kook

2013-06-01

The A3 Foresight Program titled by 'Critical Physics Issues Specific to Steady State Sustainment of High-Performance Plasmas', based on the scientific collaboration among China, Japan and Korea in the field of plasma physics, has been newly started from August 2012 under the auspice of the Japan Society for the Promotion of Science (JSPS, Japan), the National Research Foundation of Korea (NRF, Korea) and the National Natural Science Foundation of China (NSFC, China). A seminar on the A3 collaboration took place in Hotel Gozensui, Kushiro, Japan, 22-25 January 2013. This seminar was organized by National Institute for Fusion Science. One special talk and 36 oral talks were presented in the seminar including 13 Chinese, 14 Japanese and 9 Korean attendees. Steady state sustainment of high-performance plasmas is a crucial issue for realizing a nuclear fusion reactor. This seminar was motivated along the issues. Results on fusion experiments and theory obtained through A3 foresight program during recent two years were discussed and summarized. Possible direction of future collaboration and further encouragement of scientific activity of younger scientists were also discussed in this seminar with future experimental plans in three countries. This issue is the collection of 29 papers presented at the entitled meeting. All the 29 of the presented papers are indexed individually. (J.P.N.)

Recent results on steady state and confinement improvement research on JT-60U

International Nuclear Information System (INIS)

Ide, Shunsuke

2000-01-01

On the JT-60U tokamak, fusion plasma research for realization of a steady state tokamak reactor has been pursued. Towards that goal, confinement improved plasmas such as H-mode, high β p , reversed magnetic shear (RS) and latter two combined with H-mode edge pedestal have been developed and investigated intensively. A key issue to achieve non-inductive current drive relevant to a steady state fusion reactor is to increase the fraction of the bootstrap current and match the spatial profile to the optimum. In 1999, as the result of the optimization, the equivalent deuterium-tritium (D-T) fusion gain (Q DT eq ) of 0.5 was sustained for 0.8 s, which is roughly equal to the energy confinement time, in a RS plasma. In order to achieve a RS plasma in steady state two approach have been explored. One is to use external current driver such as lower hybrid current drive (LHCD), and by optimizing LHCD a quasi-steady RS discharge was obtained. The other approach is to utilize bootstrap current as much as possible, and with highly increased fraction of the bootstrap current, a confinement enhancement factor of 3.6 was maintained for 2.7 s in a RS plasma with H-mode edge. A heating and current drive system in the electron cyclotron range of frequency for localized heating and current drive has been installed on JT-60U, and in initial experiments a clear increase of the central electron temperature in a RS high density central region was confirmed only with injected power of 0.75 MW. (author)

Comparison of nevirapine plasma concentrations between lead-in and steady-state periods in Chinese HIV-infected patients.

Directory of Open Access Journals (Sweden)

Huijuan Kou

Full Text Available To investigate the potential of nevirapine 200 mg once-daily regimen and evaluate the influence of patient characteristics on nevirapine concentrations.This was a prospective, multicentre cohort study with 532 HIV-infected patients receiving nevirapine as a part of their initial antiretroviral therapy. Plasma samples were collected at trough or peak time at the end of week 2 (lead-in period and week 4, 12, 24, 36, and 48 (steady-state period, and nevirapine concentrations were determined using a validated HPLC method. Potential influencing factors associated with nevirapine concentrations were evaluated using univariate and multivariate logistic regression.A total of 2348 nevirapine plasma concentrations were collected, including 1510 trough and 838 peak values. The median nevirapine trough and peak concentration during the lead-in period were 4.26 µg/mL (IQR 3.05-5.61 and 5.07 µg/mL (IQR 3.92-6.44 respectively, which both exceeded the recommended thresholds of nevirapine plasma concentrations. Baseline hepatic function had a moderate effect on median nevirapine trough concentrations at week 2 (4.25 µg/mL v.s. 4.86 µg/mL, for ALT <1.5 × ULN and ≥ 1.5 × ULN, respectively, P = 0.045. No significant difference was observed in median nevirapine trough concentration between lead-in and steady-state periods in patients with baseline ALT and AST level ≥ 1.5 × ULN (P = 0.171, P = 0.769, which was different from the patients with ALT/AST level <1.5ULN. The median trough concentrations were significantly higher in HIV/HCV co-infected patients than those without HCV at week 48 (8.16 µg/mL v.s. 6.15 µg/mL, P = 0.004.The 200 mg once-daily regimen of nevirapine might be comparable to twice-daily in plasma pharmacokinetics in Chinese population. Hepatic function prior to nevirapine treatment and HIV/HCV coinfection were significantly associated with nevirapine concentrations.

Steady State Advanced Tokamak (SSAT): The mission and the machine

International Nuclear Information System (INIS)

Thomassen, K.; Goldston, R.; Nevins, B.; Neilson, H.; Shannon, T.; Montgomery, B.

1992-03-01

Extending the tokamak concept to the steady state regime and pursuing advances in tokamak physics are important and complementary steps for the magnetic fusion energy program. The required transition away from inductive current drive will provide exciting opportunities for advances in tokamak physics, as well as important impetus to drive advances in fusion technology. Recognizing this, the Fusion Policy Advisory Committee and the US National Energy Strategy identified the development of steady state tokamak physics and technology, and improvements in the tokamak concept, as vital elements in the magnetic fusion energy development plan. Both called for the construction of a steady state tokamak facility to address these plan elements. Advances in physics that produce better confinement and higher pressure limits are required for a similar unit size reactor. Regimes with largely self-driven plasma current are required to permit a steady-state tokamak reactor with acceptable recirculating power. Reliable techniques of disruption control will be needed to achieve the availability goals of an economic reactor. Thus the central role of this new tokamak facility is to point the way to a more attractive demonstration reactor (DEMO) than the present data base would support. To meet the challenges, we propose a new ''Steady State Advanced Tokamak'' (SSAT) facility that would develop and demonstrate optimized steady state tokamak operating mode. While other tokamaks in the world program employ superconducting toroidal field coils, SSAT would be the first major tokamak to operate with a fully superconducting coil set in the elongated, divertor geometry planned for ITER and DEMO

Measurement and Modelling of Tearing Mode Stability for Steady-State Plasmas in DIII-D

Energy Technology Data Exchange (ETDEWEB)

Turco, F; Luce, T; Ferron, J; Petty, C; Politzer, P; Turnbull, A; Brennan, D; Murakami, M; LoDestro, L; Pearlstein, L; Casper, T; Jayakumar, R; Holcomb, C

2009-06-23

High-beta, quasi-steady state scenarios represent a fundamental step towards the performance required for future fusion reactors. In DIII-D steady-state scenario discharges, the normalized beta {beta}{sub N} {triple_bond} {beta}(%) {center_dot} a(m) {center_dot} B{sub T}(T)/I{sub p}(MA) (where {beta} is the ratio of the plasma pressure to the magnetic field pressure, {alpha} the plasma minor radius, B{sub T} the toroidal magnetic field and I{sub p} the plasma current) exceeds the no-wall ideal kink beta limit. The performance of this scenario is limited by the onset of an n = 1 tearing mode, which appears on the resistive evolution time-scale (1-2 s) at constant pressure and causes both a loss of confinement and a radial redistribution of the current density from which the available current drive sources cannot recover. It is routinely observed that the injection of electron cyclotron current drive (ECCD), with a broad deposition localized around {rho} {approx} 0.35, can prevent the mode from appearing. It must be noted that this is not a case of a direct stabilization due to the interaction with the mode's rational surface. These variations of the scenario are illustrated in Fig. 1, where the total injected power [neutral beam injection (NBI) and ECCD], {beta}{sub N} and the n = 1 magnetic perturbation at the outer wall are shown. In case (a), the onset of the n = 1 mode is observed when the EC power is not present or if it is stopped before the end of the high {beta} phase, whereas in case (b) the difference is pointed out between broad and narrow current deposition (with the narrow deposition case becoming unstable). The current density profile evolution and the MHD modes of several sets of significant discharges with and without ECCD (at different locations) have been analyzed, using motional Stark effect (MSE) spectroscopy measurements for the former and edge magnetic probes measurements, toroidal rotation profiles and fast electron cyclotron emission

Measurement and Modelling of Tearing Mode Stability for Steady-State Plasmas in DIII-D

International Nuclear Information System (INIS)

Turco, F.; Luce, T.; Ferron, J.; Petty, C.; Politzer, P.; Turnbull, A.; Brennan, D.; Murakami, M.; LoDestro, L.; Pearlstein, L.; Casper, T.; Jayakumar, R.; Holcomb, C.

2009-01-01

High-beta, quasi-steady state scenarios represent a fundamental step towards the performance required for future fusion reactors. In DIII-D steady-state scenario discharges, the normalized beta β N (triple b ond) β(%) · a(m) · B T (T)/I p (MA) (where β is the ratio of the plasma pressure to the magnetic field pressure, α the plasma minor radius, B T the toroidal magnetic field and I p the plasma current) exceeds the no-wall ideal kink beta limit. The performance of this scenario is limited by the onset of an n = 1 tearing mode, which appears on the resistive evolution time-scale (1-2 s) at constant pressure and causes both a loss of confinement and a radial redistribution of the current density from which the available current drive sources cannot recover. It is routinely observed that the injection of electron cyclotron current drive (ECCD), with a broad deposition localized around ρ ∼ 0.35, can prevent the mode from appearing. It must be noted that this is not a case of a direct stabilization due to the interaction with the mode's rational surface. These variations of the scenario are illustrated in Fig. 1, where the total injected power (neutral beam injection (NBI) and ECCD), β N and the n = 1 magnetic perturbation at the outer wall are shown. In case (a), the onset of the n = 1 mode is observed when the EC power is not present or if it is stopped before the end of the high β phase, whereas in case (b) the difference is pointed out between broad and narrow current deposition (with the narrow deposition case becoming unstable). The current density profile evolution and the MHD modes of several sets of significant discharges with and without ECCD (at different locations) have been analyzed, using motional Stark effect (MSE) spectroscopy measurements for the former and edge magnetic probes measurements, toroidal rotation profiles and fast electron cyclotron emission (ECE) data for the latter. One equilibrium based on EFIT reconstruction (1) with kinetic

Technology and physics in the Tokamak Program: The need for an integrated, steady-state RandD tokamak experiment

International Nuclear Information System (INIS)

1988-05-01

The Steady-state Tokamak (STE) Experiment is a proposed superconducting-coil, hydrogen-plasma tokamak device intended to address the integrated non-nuclear issues of steady state, high-power tokamak physics and technology. Such a facility has been called for in the US program plan for the mid 1990's, and will play a unique role in the world-wide fusion effort. Information from STE on steady-state current drive, plasma control, and high power technology will contribute significantly to the operating capabilities of future steady-state devices. This paper reviews preliminary designs and expected technological contributions to the US and world fusion reactor research from each of the above mentioned reactor systems. This document is intended as a proposal and feasibility discussion and does not include exhaustive technical reviews. 12 figs., 3 tabs

Effects of Cytochrome P450 (CYP) 2C19 Genotypes on Steady-State Plasma Concentrations of Escitalopram and its Desmethyl Metabolite in Japanese Patients With Depression.

Science.gov (United States)

Tsuchimine, Shoko; Ochi, Shinichiro; Tajiri, Misuzu; Suzuki, Yutaro; Sugawara, Norio; Inoue, Yoshimasa; Yasui-Furukori, Norio

2018-06-01

Plasma concentrations of the S-enantiomer of citalopram were different between extensive and poor CYP2C19 metabolizers in healthy subjects and depressed patients. However, most studies applied dose-corrected concentrations. Thus, we studied the effects of polymorphisms of the CYP2C19 gene on raw plasma drug concentrations in Japanese patients with depression. Subjects in this study consisted of 412 depressed patients receiving 5, 10, 15, or 20 mg of escitalopram once a day. Plasma concentrations of escitalopram and desmethylescitalopram were quantified using HPLC. CYP2C19 genotypes were identified using polymerase chain reaction methods. There were no differences in the steady-state plasma concentrations of escitalopram or desmethylescitalopram in each dose group (5, 10, 15, or 20 mg of escitalopram) among CYP2C19 genotype groups. However, 1-way analysis of variance showed significant effects of CYP2C19 genotypes on the dose-adjusted plasma concentration of escitalopram but not in the dose-adjusted plasma concentration of desmethylescitalopram. Analysis of covariance including age, sex, and body weight showed significant effects of CYP2C19 genotypes on the dose-adjusted plasma concentration of escitalopram and the ratio of desmethylescitalopram to escitalopram. These findings suggest that the CYP2C19 variants are associated with steady-state plasma concentrations of escitalopram to some extent but are not associated with desmethylescitalopram.

A Review of Fusion and Tokamak Research Towards Steady-State Operation: A JAEA Contribution

Directory of Open Access Journals (Sweden)

Mitsuru Kikuchi

2010-11-01

Full Text Available Providing a historical overview of 50 years of fusion research, a review of the fundamentals and concepts of fusion and research efforts towards the implementation of a steady state tokamak reactor is presented. In 1990, a steady-state tokamak reactor (SSTR best utilizing the bootstrap current was developed. Since then, significant efforts have been made in major tokamaks, including JT-60U, exploring advanced regimes relevant to the steady state operation of tokamaks. In this paper, the fundamentals of fusion and plasma confinement, and the concepts and research on current drive and MHD stability of advanced tokamaks towards realization of a steady-state tokamak reactor are reviewed, with an emphasis on the contributions of the JAEA. Finally, a view of fusion energy utilization in the 21st century is introduced.

Progress on advanced tokamak and steady-state scenario development on DIII-D and NSTX

Energy Technology Data Exchange (ETDEWEB)

Doyle, E J [Department of Electrical Engineering and PSTI, University of California, Los Angeles, California 90095 (United States); Garofalo, A M [Columbia University, New York, New York 10027 (United States); Greenfield, C M [General Atomics, San Diego, California 92186-5608 (United States); Kaye, S M [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543-0451 (United States); Menard, J E [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543-0451 (United States); Murakami, M [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Sabbagh, S A [Columbia University, New York, New York 10027 (United States); Austin, M E [University of Texas-Austin, Austin, Texas 78712 (United States); Bell, R E [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543-0451 (United States); Burrell, K H [General Atomics, San Diego, California 92186-5608 (United States); Ferron, J R [General Atomics, San Diego, California 92186-5608 (United States); Gates, D A [Princeton Plasma Physics Lab., Princeton, New Jersey 08543-0451 (United States); Groebner, R J; Hyatt, A W; Luce, T C; Petty, C C; Wade, M R; Waltz, R E [General Atomics, San Diego, California 92186-5608 (United States); Jayakumar, R J [Lawrence Livermore National Lab., Livermore, California 94550 (United States); Kinsey, J E [Lehigh Univ., Bethlehem, Pennsylvania 18015 (United States); LeBlanc, B P [Princeton Plasma Physics Lab., Princeton, New Jersey 08543-0451 (United States); McKee, G R [Univ. of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Okabayashi, M [Princeton Plasma Physics Lab., Princeton, New Jersey 08543-0451 (United States); Peng, Y-K M [Oak Ridge National Lab., Oak Ridge, Tennessee 37831 (United States); Politzer, P A [General Atomics, San Diego, California 92186-5608 (United States); Rhodes, T L [Dept. of Electrical Engineering and PSTI, Univ. of California, Los Angeles, California 90095 (United States)

2006-12-15

Advanced tokamak (AT) research seeks to develop steady-state operating scenarios for ITER and other future devices from a demonstrated scientific basis. Normalized target parameters for steady-state operation on ITER are 100% non-inductive current operation with a bootstrap current fraction f{sub BS} {>=} 60%, q{sub 95} {approx} 4-5 and G {identical_to}{beta}{sub N}H{sub scaling}/q{sub 95}{sup 2} {>=}0.3. Progress in realizing such plasmas is considered in terms of the development of plasma control capabilities and scientific understanding, leading to improved AT performance. NSTX has demonstrated active resistive wall mode stabilization with low, ITER-relevant, rotation rates below the critical value required for passive stabilization. On DIII-D, experimental observations and GYRO simulations indicate that ion internal transport barrier (ITB) formation at rational-q surfaces is due to equilibrium zonal flows generating high local E ? B shear levels. In addition, stability modelling for DIII-D indicates a path to operation at {beta}{sub N} {>=} 4 with q{sub min} {>=} 2, using broad, hollow current profiles to increase the ideal wall stability limit. Both NSTX and DIII-D have optimized plasma performance and expanded AT operational limits. NSTX now has long-pulse, high performance discharges meeting the normalized targets for an spherical torus-based component test facility. DIII-D has developed sustained discharges combining high beta and ITBs, with performance approaching levels required for AT reactor concepts, e.g. {beta}{sub N} = 4, H{sub 89} = 2.5, with f{sub BS} > 60%. Most importantly, DIII-D has developed ITER steady-state demonstration discharges, simultaneously meeting the targets for steady-state Q {>=} 5 operation on ITER set out above, substantially increasing confidence in ITER meeting its steady-state performance objective.

On the minimum circulating power of steady state tokamaks

International Nuclear Information System (INIS)

Itoh, K.; Itoh, S.; Fukuyama, A.; Yagi, M.

1995-07-01

Circulating power for the sustenance and profile control of the steady state tokamak plasmas is discussed. The simultaneous fulfillment of the MHD stability at high beta value, the improved confinement and the stationary equilibrium requires the rotation drive as well as the current drive. In addition to the current drive efficiency, the efficiency for the rotation drive is investigated. The direct rotation drive by the external torque, such as the case of beam injection, is not efficient enough. The mechanism and the magnitude of the spontaneous plasma rotation are studied. (author)

Steady state drift vortices in plasmas with shear flow in equilibrium

DEFF Research Database (Denmark)

Chakrabarti, N.

1999-01-01

The Hasegawa-Mima equation in the presence of sheared poloidal flow is solved for two-dimensional steady state vortex. It is shown that when the phase velocity of the vortex is the same as the diamagnetic drift velocity, an exact solution in the form of counter-rotating vortices may appear...

Steady-state acceptor fluorescence anisotropy imaging under evanescent excitation for visualisation of FRET at the plasma membrane.

Directory of Open Access Journals (Sweden)

Viviane Devauges

Full Text Available We present a novel imaging system combining total internal reflection fluorescence (TIRF microscopy with measurement of steady-state acceptor fluorescence anisotropy in order to perform live cell Förster Resonance Energy Transfer (FRET imaging at the plasma membrane. We compare directly the imaging performance of fluorescence anisotropy resolved TIRF with epifluorescence illumination. The use of high numerical aperture objective for TIRF required correction for induced depolarization factors. This arrangement enabled visualisation of conformational changes of a Raichu-Cdc42 FRET biosensor by measurement of intramolecular FRET between eGFP and mRFP1. Higher activity of the probe was found at the cell plasma membrane compared to intracellularly. Imaging fluorescence anisotropy in TIRF allowed clear differentiation of the Raichu-Cdc42 biosensor from negative control mutants. Finally, inhibition of Cdc42 was imaged dynamically in live cells, where we show temporal changes of the activity of the Raichu-Cdc42 biosensor.

Economically attractive features of steady-state neoclassical reversed field pinch equilibrium with low aspect ratio

International Nuclear Information System (INIS)

Shiina, S.; Yagi, Y.; Sugimoto, H.; Ashida, H.; Hirano, Y.; Koguchi, H.; Sakakita, H.; Taguchi, M.; Nagamine, Y.; Osanai, Y.; Saito, K.; Watanabe, M.; Aizawa, M.

2005-01-01

Dominant plasma self-induced current equilibrium is achieved together with the high β for the steady-state neoclassical reversed field pinch (RFP) equilibrium with low aspect ratio by broadening the plasma pressure profile. The RF-driven current, when the safety factor is smaller than unity, is much less than the self-induced current, which dominates (96%) the toroidal current. This neoclassical RFP equilibrium has strong magnetic shear or a high-stability beta (β t = 63%) due to its hollow current profile. It is shown that the obtained equilibrium is close to the relaxed-equilibrium state with a minimum energy, and is also robust against microinstabilities. These attractive features allow the economical design of compact steady-state fusion power plants with low cost of electricity (COE). (author)

Dusty plasma phase in a steady state plasma device

International Nuclear Information System (INIS)

Liang Xiaoping; Zheng Jian; Ma Jinxiu; Liu Wangdong; Zhuang Ge; Xie Jinlin; Wang Congrong; Yu Changxuan

2000-01-01

A DC discharge dusty plasma device used for study of waves in dusty plasma is introduced. A dusty plasma column is produced with about 30 cm in length and about 8.4 cm in diameter. The electron saturation current of Langmuir probe is obviously decreasing while the dust grains are present in the plasma. The negative charge on dust grains is directly proportional to the rotation rate of the dispenser. And the dust grains carry up to 40% of the negative charges in the whole plasma

Status of fusion technology development in JAERI stressing steady-state operation for future reactors

International Nuclear Information System (INIS)

Matsuda, Shinzaburo

2000-01-01

This paper reports on the progress of the fusion reactor technologies developed at the Japan Atomic Energy Research Institute (JAERI) and expected to lead to a future steady state operation reactor. In particular, superconducting coil technology for plasma confinement, NBI and RF systems technology for plasma control and current drive, fueling and pumping systems technology for particle control, heat removal technology, and development of long life materials are highlighted as the important key elements for the future steady state operation. It will be discussed how these key technologies have already been developed by the ITER (International Thermonuclear Experimental Reactor) technology R and D as well as by the Japanese domestic program, and which technologies are planned for the near future

High-power and steady-state operation of ICRF heating in the large helical device

Energy Technology Data Exchange (ETDEWEB)

Mutoh, T., E-mail: mutoh@nifs.ac.jp; Seki, T.; Saito, K.; Kasahara, H.; Seki, R.; Kamio, S.; Kumazawa, R.; Kubo, S.; Shimozuma, T.; Yoshimura, Y.; Igami, H.; Takahashi, H.; Ii, T.; Makino, R.; Nagaoka, K.; Nomura, G. [National Institute for Fusion Science, 322-6, Oroshi-cho, Toki, Gifu, 509-5292 (Japan); Shinya, T. [The University of Tokyo, Kashiwa 2777-8561 (Japan)

2015-12-10

Recent progress in an ion cyclotron range of frequencies (ICRF) heating system and experiment results in a Large Helical Device (LHD) are reported. Three kinds of ICRF antenna pairs were installed in the LHD, and the operation power regimes were extended up to 4.5 MW; also, the steady-state operation was extended for more than 45 min in LHD at a MW power level. We studied ICRF heating physics in heliotron configuration using a Hand Shake type (HAS) antenna, Field Aligned Impedance Transforming (FAIT) antenna, and Poloidal Array (PA) antenna, and established the optimum minority-ion heating scenario in an LHD. The FAIT antenna having a novel impedance transformer inside the vacuum chamber could reduce the VSWR and successfully injected a higher power to plasma. We tested the PA antennas completely removing the Faraday-shield pipes to avoid breakdown and to increase the plasma coupling. The heating performance was almost the same as other antennas; however, the heating efficiency was degraded when the gap between the antenna and plasma surface was large. Using these three kinds of antennas, ICRF heating could contribute to raising the plasma beta with the second- and third-harmonic cyclotron heating mode, and also to raising the ion temperature as discharge cleaning tools. In 2014, steady-state operation plasma with a line-averaged electron density of 1.2 × 10{sup 19} m{sup −3}, ion and electron temperature of 2 keV, and plasma sustainment time of 48 min was achieved with ICH and ECH heating power of 1.2 MW for majority helium with minority hydrogen. In 2015, the higher-power steady-state operation with a heating power of up to 3 MW was tested with higher density of 3 × 10{sup 19} m{sup −3}.

S3C: EBT Steady-State Shooting code description and user's guide

International Nuclear Information System (INIS)

Downum, W.B.

1983-09-01

The Oak Ridge National Laboratory (ORNL) one-dimensional (1-D) Steady-State Shooting code (S3C) for ELMO Bumpy Torus (EBT) plasmas is described. Benchmark calculations finding the steady-state density and electron and ion temperature profiles for a known neutral density profile and known external energy sources are carried out. Good agreement is obtained with results from the ORNL Radially Resolved Time Dependent 1-D Transport code for an EBT-Q type reactor. The program logic is described, along with the physics models in each code block and the variable names used. Sample input and output files are listed, along with the main code

Proceedings of JSPS-CAS Core University Program seminar on production and steady state confinement of high performance plasmas in magnetic confinement systems

International Nuclear Information System (INIS)

Wan Baonian; Toi, Kazuo

2005-09-01

The JSPS-CAS Core University Program (CUP) seminar on 'Production and steady-state confinement of high performance plasmas in magnetic confinement systems' was held from 27 July to 29 July 2005 in Institute of Plasma Physics, the Chinese Academy of Sciences, Hefei, China. This seminar was organized in the framework of CUP in the field of plasma and nuclear fusion. About 50 persons including 20 Japanese attendees attended this seminar. Long time sustainment of high confinement and high beta plasmas is crucial for realization of an advanced nuclear fusion reactor. This seminar was motivated to summarize the results of CUP obtained in four years activities of CUP, and to extract crucial issues to be resolved near future, which must drive near and mid- term collaborations in the framework of CUP. The 32 of presented papers are indexed individually. (J.P.N.)

steady – state performance of induction and transfer state

African Journals Online (AJOL)

eobe

This paper presents paper presents paper presents the steady the steady the steady–state performance state performance state performance comparison comparison comparison between polyphase induction motor and polyphase between polyphase induction motor and polyphase. TF motor operating in. TF motor ...

Steady-state tokamak reactor with non-divertor impurity control: STARFIRE

International Nuclear Information System (INIS)

Baker, C.C.

1980-01-01

STARFIRE is a conceptual design study of a commercial tokamak fusion electric power plant. Particular emphasis has been placed on simplifying the reactor concept by developing design concepts to produce a steady-state tokamak with non-divertor impurity control and helium ash removal. The concepts of plasma current drive using lower hybrid rf waves and a limiter/vacuum system for reactor applications are described

Development of steady-state scenarios compatible with ITER-like wall conditions

Energy Technology Data Exchange (ETDEWEB)

Litaudon, X [Association Euratom-CEA, CEA/DSM/DRFC-Cadarache 13108, St Paul Durance (France); Arnoux, G [Association Euratom-CEA, CEA/DSM/DRFC-Cadarache 13108, St Paul Durance (France); Beurskens, M [Euratom/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom)] (and others)

2007-12-15

A key issue for steady-state tokamak operation is to determine the edge conditions that are compatible both with good core confinement and with the power handling and plasma exhaust capabilities of the plasma facing components (PFCs) and divertor systems. A quantitative response to this open question will provide a robust scientific basis for reliable extrapolation of present regimes to an ITER compatible steady-state scenario. In this context, the JET programme addressing steady-state operation is focused on the development of non-inductive, high confinement plasmas with the constraints imposed by the PFCs. A new beryllium main chamber wall and tungsten divertor together with an upgrade of the heating/fuelling capability are currently in preparation at JET. Operation at higher power with this ITER-like wall will impose new constraints on non-inductive scenarios. Recent experiments have focused on the preparation for this new phase of JET operation. In this paper, progress in the development of advanced tokamak (AT) scenarios at JET is reviewed keeping this long-term objective in mind. The approach has consisted of addressing various critical issues separately during the 2006-2007 campaigns with a view to full scenario integration when the JET upgrades are complete. Regimes with internal transport barriers (ITBs) have been developed at q{sub 95} {approx} 5 and high triangularity, {delta} (relevant to the ITER steady-state demonstration) by applying more than 30 MW of additional heating power reaching {beta}{sub N} {approx} 2 at B{sub o} {approx} 3.1 T. Operating at higher {delta} has allowed the edge pedestal and core densities to be increased pushing the ion temperature closer to that of the electrons. Although not yet fully integrated into a performance enhancing ITB scenario, Neon seeding has been successfully explored to increase the radiated power fraction (up to 60%), providing significant reduction of target tile power fluxes (and hence temperatures) and

US-Japan workshop on field-reversed configurations with steady-state high-temperature fusion plasmas and the 11th US-Japan workshop on compact toroids

International Nuclear Information System (INIS)

Barnes, D.C.; Fernandez, J.C.; Rej, D.J.

1990-05-01

The US-Japan Workshop on Field-Reversed Configurations with Steady-State High-Temperature Fusion Plasma and the 11th US-Japan Workshop on Compact Toroids were held at Los Alamos National Laboratory, Los Alamos, New Mexico on November 7--9, 1989. These proceedings contain the papers presented at the workshops as submitted by the authors. These papers have been indexed separately

US-Japan workshop on field-reversed configurations with steady-state high-temperature fusion plasmas and the 11th US-Japan workshop on compact toroids

Energy Technology Data Exchange (ETDEWEB)

Barnes, D.C.; Fernandez, J.C.; Rej, D.J. (comps.)

1990-05-01

The US-Japan Workshop on Field-Reversed Configurations with Steady-State High-Temperature Fusion Plasma and the 11th US-Japan Workshop on Compact Toroids were held at Los Alamos National Laboratory, Los Alamos, New Mexico on November 7--9, 1989. These proceedings contain the papers presented at the workshops as submitted by the authors. These papers have been indexed separately.

Paracetamol decreases steady-state exposure to lamotrigine by induction of glucuronidation in healthy subjects

DEFF Research Database (Denmark)

Gastrup, Sandra; Stage, Tore Bjerregaard; Fruekilde, Palle Bach Nielsen

2016-01-01

AIM: Patients receiving lamotrigine therapy frequently use paracetamol concomitantly. While one study suggests a possible, clinically relevant drug-drug interaction, practical recommendations of the concomitant use are inconsistent. We performed a systematic pharmacokinetic study in healthy...... volunteers to quantify the effect of 4-day treatment of paracetamol on the metabolism of steady-state lamotrigine. METHODS: Twelve healthy, male volunteers participated in an open-label, sequential interaction study. Lamotrigine was titrated to steady state (100 mg daily) over 36 days, and blood and urine...... sampling was performed in a non-randomised order with and without paracetamol (1 g four times daily). The primary endpoint was change in steady-state area under the plasma concentration-time curve of lamotrigine. Secondary endpoints were changes in total apparent oral clearance, renal clearance...

Steady-state and pre-steady-state kinetic analysis of halopropane conversion by a Rhodococcus haloalkane dehalogenase

NARCIS (Netherlands)

Bosma, T; Pikkemaat, MG; Kingma, Jacob; Dijk, J; Janssen, DB

2003-01-01

Haloalkane dehalogenase from Rhodococcus rhodochrous NCIMB 13064 (DhaA) catalyzes the hydrolysis of carbon-halogen bonds in a wide range of haloalkanes. We examined the steady-state and pre-steady-state kinetics of halopropane conversion by DhaA to illuminate mechanistic details of the

Pseudo Steady-State Free Precession for MR-Fingerprinting.

Science.gov (United States)

Assländer, Jakob; Glaser, Steffen J; Hennig, Jürgen

2017-03-01

This article discusses the signal behavior in the case the flip angle in steady-state free precession sequences is continuously varied as suggested for MR-fingerprinting sequences. Flip angle variations prevent the establishment of a steady state and introduce instabilities regarding to magnetic field inhomogeneities and intravoxel dephasing. We show how a pseudo steady state can be achieved, which restores the spin echo nature of steady-state free precession. Based on geometrical considerations, relationships between the flip angle, repetition and echo time are derived that suffice to the establishment of a pseudo steady state. The theory is tested with Bloch simulations as well as phantom and in vivo experiments. A typical steady-state free precession passband can be restored with the proposed conditions. The stability of the pseudo steady state is demonstrated by comparing the evolution of the signal of a single isochromat to one resulting from a spin ensemble. As confirmed by experiments, magnetization in a pseudo steady state can be described with fewer degrees of freedom compared to the original fingerprinting and the pseudo steady state results in more reliable parameter maps. The proposed conditions restore the spin-echo-like signal behavior typical for steady-state free precession in fingerprinting sequences, making this approach more robust to B 0 variations. Magn Reson Med 77:1151-1161, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Multimode optical fibers: steady state mode exciter.

Science.gov (United States)

Ikeda, M; Sugimura, A; Ikegami, T

1976-09-01

The steady state mode power distribution of the multimode graded index fiber was measured. A simple and effective steady state mode exciter was fabricated by an etching technique. Its insertion loss was 0.5 dB for an injection laser. Deviation in transmission characteristics of multimode graded index fibers can be avoided by using the steady state mode exciter.

LHCD current profile control experiments towards steady state improved confinement on JT-60U

International Nuclear Information System (INIS)

Ide, S.; Naito, O.; Oikawa, T.; Fujita, T.; Kondoh, T.; Seki, M.; Ushigusa, K.

2001-01-01

In JT-60U lower hybrid current drive (LHCD) experiments, a reversed magnetic shear configuration that was accompanied by the internal transport barriers was successfully maintained by means of LHCD almost in the full current drive quasi-steady state for 4.7 s. The normalized beta was kept near 1 and the neutron emission rate was almost steady as well indicating no accumulation of impurities into the plasma. Diagnostics data showed that all the profiles of the electron and ion temperatures, the electron density and the current profile were almost unchanged during the LHCD phase. Moreover, capability of LHCD in H-mode plasmas has been also investigated. It was found that the lower hybrid waves can be coupled to an H-mode edge plasma even with the plasma wall distance of about 14 cm. The maximum coupling distance was found to depend on the edge recycling. (author)

Internal transport barrier physics for steady state operation in tokamaks

Energy Technology Data Exchange (ETDEWEB)

Wakatani, Masahiro [Kyoto Univ., Graduate School of Engineering, Uji, Kyoto (Japan); Fukuda, Takeshi [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment; Connor, Jack W. [Culham Science Centre, EURATOM/UKAEA Association (United Kingdom); Garbet, Xavier [Culham Science Centre, EFDA-JET CSU (United Kingdom); Gormezano, Claude [Associazone EURATOM-ENEA sulla Fusione C.R. Frascati (Italy); Mukhovatov, Vladimir [ITER Naka Joint Work Site, ITER Physics Unit, Naka, Ibaraki (Japan)

2003-07-01

Experimental results for the ITB (Internal Transport Barrier) formation and sustainment are compiled in a unified manner to find common features of ITBs in tokamaks. Global scaling laws for threshold power to obtain the ITBs are discussed. Theoretical models for plasmas with ITBs are summarized from stability and transport point of view. Finally possibility to obtain steady-state ITBs will be discussed in addition to extrapolation to ITER. (author)

Study of impurity effects on CFETR steady-state scenario by self-consistent integrated modeling

Science.gov (United States)

Shi, Nan; Chan, Vincent S.; Jian, Xiang; Li, Guoqiang; Chen, Jiale; Gao, Xiang; Shi, Shengyu; Kong, Defeng; Liu, Xiaoju; Mao, Shifeng; Xu, Guoliang

2017-12-01

Impurity effects on fusion performance of China fusion engineering test reactor (CFETR) due to extrinsic seeding are investigated. An integrated 1.5D modeling workflow evolves plasma equilibrium and all transport channels to steady state. The one modeling framework for integrated tasks framework is used to couple the transport solver, MHD equilibrium solver, and source and sink calculations. A self-consistent impurity profile constructed using a steady-state background plasma, which satisfies quasi-neutrality and true steady state, is presented for the first time. Studies are performed based on an optimized fully non-inductive scenario with varying concentrations of Argon (Ar) seeding. It is found that fusion performance improves before dropping off with increasing {{Z}\\text{eff}} , while the confinement remains at high level. Further analysis of transport for these plasmas shows that low-k ion temperature gradient modes dominate the turbulence. The decrease in linear growth rate and resultant fluxes of all channels with increasing {{Z}\\text{eff}} can be traced to impurity profile change by transport. The improvement in confinement levels off at higher {{Z}\\text{eff}} . Over the regime of study there is a competition between the suppressed transport and increasing radiation that leads to a peak in the fusion performance at {{Z}\\text{eff}} (~2.78 for CFETR). Extrinsic impurity seeding to control divertor heat load will need to be optimized around this value for best fusion performance.

Preliminary design study of a steady state tokamak device

International Nuclear Information System (INIS)

Miya, Naoyuki; Nakajima, Shinji; Ushigusa, Kenkichi; and athors)

1992-09-01

Preliminary design study has been made for a steady tokamak with the plasma current of 10MA, as the next to the JT-60U experimental programs. The goal of the research program is the integrated study of steady state, high-power physics and technology. Present candidate design is to use superconducting TF and PF magnet systems and long pulse operation of 100's-1000's of sec with non inductive current drive mainly by 500keV negative ion beam injection of 60MW. Low activation material such as titanium alloy is chosen for the water tank type vacuum vessel, which is also the nuclear shield for the superconducting coils. The present preliminary design study shows that the device can meet the existing JT-60U facility capability. (author)

High Beta Steady State Research and Future Directions on JT-60U and JFT-2M

Science.gov (United States)

Ishida, Shinichi

2003-10-01

JT-60U and JFT-2M research is focused on high beta steady state operation towards economically and environmentally attractive reactors. In JT-60U, a high-βp H-mode plasma was sustained with βN 2.7 for 7.4 s in which neoclassical tearing modes (NTMs) limited the attainable β_N. Real-time tracking NTM stabilization system using ECCD demonstrated complete suppression of NTM leading to recovery of βN before onset of NTM. Performance in a fully non-inductive H-mode plasma was improved up to n_i(0) τE T_i(0) = 3.1 x 10^20 keV s m-3 using N-NBCD with βN 2.4, HH_y,2=1.2 and bootstrap fraction f_BS 0.5. ECH experiments extended the confinement enhancement for dominantly electron heated reversed shear plasmas up to HH_y,2 2 at T_e/Ti 1.25. A world record ECCD efficiency, 4.2 x 10^18 A/W/m^2, was achieved at Te 23 keV with a highly localized central current density. Innovative initiation and current build-up without center solenoid currents were established by LHCD/ECH and bootstrap current up to f_BS 0.9. In JFT-2M, the inside of the vacuum vessel wall was fully covered with low-activation ferritic steel plates to investigate their use in plasmas near fusion conditions. High βN plasmas were produced up to βN = 3.3 with an internal transport barrier (ITB) and a steady H-mode edge. A new H-mode regime with steady high recycling (HRS) and an ITB was exploited leading to βN H_89P 6.2 at n_e/nG 0.7. In 2003, JT-60U will be able to operate for the duration up to 65 s at 1 MA/2.7 T and the heating/current-drive duration up to 30 s at 17 MW to prolong high-βN and/or high-f_BS discharges with feedback controls. JFT-2M is planning to implement wall stabilization experiments in 2004 to pursue plasmas above the ideal no-wall limit using a ferritic wall. The modification of JT-60 to a fully superconducting tokamak is under discussion to explore high-β steady state operation in collision-less plasmas well above no-wall limit with ferritic wall in a steady state.

Steady-State Creep of Asphalt Concrete

Directory of Open Access Journals (Sweden)

Alibai Iskakbayev

2017-02-01

Full Text Available This paper reports the experimental investigation of the steady-state creep process for fine-grained asphalt concrete at a temperature of 20 ± 2 °С and under stress from 0.055 to 0.311 MPa under direct tension and was found to occur at a constant rate. The experimental results also determined the start, the end point, and the duration of the steady-state creep process. The dependence of these factors, in addition to the steady-state creep rate and viscosity of the asphalt concrete on stress is satisfactorily described by a power function. Furthermore, it showed that stress has a great impact on the specific characteristics of asphalt concrete: stress variation by one order causes their variation by 3–4.5 orders. The described relations are formulated for the steady-state of asphalt concrete in a complex stressed condition. The dependence is determined between stress intensity and strain rate intensity.

Steady-state and time-dependent modelling of parallel transport in the scrape-off layer

DEFF Research Database (Denmark)

Havlickova, E.; Fundamenski, W.; Naulin, Volker

2011-01-01

The one-dimensional fluid code SOLF1D has been used for modelling of plasma transport in the scrape-off layer (SOL) along magnetic field lines, both in steady state and under transient conditions that arise due to plasma turbulence. The presented work summarizes results of SOLF1D with attention...... given to transient parallel transport which reveals two distinct time scales due to the transport mechanisms of convection and diffusion. Time-dependent modelling combined with the effect of ballooning shows propagation of particles along the magnetic field line with Mach number up to M ≈ 1...... temperature calculated in SOLF1D is compared with the approximative model used in the turbulence code ESEL both for steady-state and turbulent SOL. Dynamics of the parallel transport are investigated for a simple transient event simulating the propagation of particles and energy to the targets from a blob...

Scaling laws for steady-state fusion plasmas

Energy Technology Data Exchange (ETDEWEB)

Husseiny, A A [Carnegie-Mellon Univ., Pittsburgh, Pa. (USA)

1975-12-01

Experimental and semi-theoretical scaling laws are extrapolated to include the effect of fusion burn on the lifetime of plasma ions. Fractional burnups are also reconsidered on the same basis. The actual lifetime of fusion plasma ions and the estimated time necessary for feasible reactors, provide a correlation between the laboratory data and the hypothesis of reactor feasibility conditions. Based on these correlations criteria for the realization of self-heated plasmas are established.

Data system design considerations for a pseudo-steady-state device

International Nuclear Information System (INIS)

Wing, W.R.

1981-01-01

The Advanced Toroidal Facility is being designed to run in a steady state. This places stringent requirements on a data system, since it must provide steady-state support that is equivalent to the support users are accustomed to from pulsed experiments; i.e., enough capacity to reduce diagnostic data for live presentation. Parameters such as density, position, and temperature must be presented live (i.e., within 0.1 s). Quantities such as plasma shape or internal structure should be available with a minimum of delay. The traditional solution to providing such capabilities is to use distributed processing to off-load data acquisition from the analysis computers. However, this suffers in a real-time environment because of the necessity of moving large quantities of data from acquisition to analysis. We expect to solve the problem by using a pipelined design that will acquire data directly into shared memory, where any one of four CPU's (VAX 11/780's) can proceed with analysis

Steady State Turbulent Transport in Magnetic Fusion Plasmas

International Nuclear Information System (INIS)

Lee, W.W.; Ethier, S.; Kolesnikov, R.; Wang, W.X.; Tang, W.M.

2007-01-01

For more than a decade, the study of microturbulence, driven by ion temperature gradient (ITG) drift instabilities in tokamak devices, has been an active area of research in magnetic fusion science for both experimentalists and theorists alike. One of the important impetus for this avenue of research was the discovery of the radial streamers associated the ITG modes in the early nineties using a Particle-In-Cell (PIC) code. Since then, ITG simulations based on the codes with increasing realism have become possible with the dramatic increase in computing power. The notable examples were the demonstration of the importance of nonlinearly generated zonal flows in regulating ion thermal transport and the transition from Bohm to GyroBoham scaling with increased device size. In this paper, we will describe another interesting nonlinear physical process associated with the parallel acceleration of the ions, that is found to play an important role for the steady state turbulent transport. Its discovery is again through the use of the modern massively parallel supercomputers

Analysis of the steady-state operation of vacuum systems for fusion machines

International Nuclear Information System (INIS)

Roose, T.R.; Hoffman, M.A.; Carlson, G.A.

1975-01-01

A computer code named GASBAL was written to calculate the steady-state vacuum system performance of multi-chamber mirror machines as well as rather complex conventional multichamber vacuum systems. Application of the code, with some modifications, to the quasi-steady tokamak operating period should also be possible. Basically, GASBAL analyzes free molecular gas flow in a system consisting of a central chamber (the plasma chamber) connected by conductances to an arbitrary number of one- or two-chamber peripheral tanks. Each of the peripheral tanks may have vacuum pumping capability (pumping speed), sources of cold gas, and sources of energetic atoms. The central chamber may have actual vacuum pumping capability, as well as a plasma capable of ionizing injected atoms and impinging gas molecules and ''pumping'' them to a peripheral chamber. The GASBAL code was used in the preliminary design of a large mirror machine experiment--LLL's MX

Practical steady-state enzyme kinetics.

Science.gov (United States)

Lorsch, Jon R

2014-01-01

Enzymes are key components of most biological processes. Characterization of enzymes is therefore frequently required during the study of biological systems. Steady-state kinetics provides a simple and rapid means of assessing the substrate specificity of an enzyme. When combined with site-directed mutagenesis (see Site-Directed Mutagenesis), it can be used to probe the roles of particular amino acids in the enzyme in substrate recognition and catalysis. Effects of interaction partners and posttranslational modifications can also be assessed using steady-state kinetics. This overview explains the general principles of steady-state enzyme kinetics experiments in a practical, rather than theoretical, way. Any biochemistry textbook will have a section on the theory of Michaelis-Menten kinetics, including derivations of the relevant equations. No specific enzymatic assay is described here, although a method for monitoring product formation or substrate consumption over time (an assay) is required to perform the experiments described. © 2014 Elsevier Inc. All rights reserved.

Steady-State Performance of Kalman Filter for DPLL

Institute of Scientific and Technical Information of China (English)

QIAN Yi; CUI Xiaowei; LU Mingquan; FENG Zhenming

2009-01-01

For certain system models, the structure of the Kalman filter is equivalent to a second-order vari-able gain digital phase-locked loop (DPLL). To apply the knowledge of DPLLs to the design of Kalman filters, this paper studies the steady-state performance of Kalman filters for these system models. The results show that the steady-state Kalman gain has the same form as the DPLL gain. An approximate simple form for the steady-state Kalman gain is used to derive an expression for the equivalent loop bandwidth of the Kalman filter as a function of the process and observation noise variances. These results can be used to analyze the steady-state performance of a Kalman filter with DPLL theory or to design a Kalman filter model with the same steady-state performance as a given DPLL.

High-β steady-state advanced tokamak regimes for ITER and FIRE

International Nuclear Information System (INIS)

Meade, D.M.; Sauthoff, N.R.; Kessel, C.E.; Budny, R.V.; Gorelenkov, N.; Jardin, S.C.; Schmidt, J.A.; Navratil, G.A.; Bialek, J.; Ulrickson, M.A.; Rognlein, T.; Mandrekas, J.

2005-01-01

An attractive tokamak-based fusion power plant will require the development of high-β steady-state advanced tokamak regimes to produce a high-gain burning plasma with a large fraction of self-driven current and high fusion-power density. Both ITER and FIRE are being designed with the objective to address these issues by exploring and understanding burning plasma physics both in the conventional H-mode regime, and in advanced tokamak regimes with β N ∼ 3 - 4, and f bs ∼50-80%. ITER has employed conservative scenarios, as appropriate for its nuclear technology mission, while FIRE has employed more aggressive assumptions aimed at exploring the scenarios envisioned in the ARIES power-plant studies. The main characteristics of the advanced scenarios presently under study for ITER and FIRE are compared with advanced tokamak regimes envisioned for the European Power Plant Conceptual Study (PPCS-C), the US ARIES-RS Power Plant Study and the Japanese Advanced Steady-State Tokamak Reactor (ASSTR). The goal of the present work is to develop advanced tokamak scenarios that would fully exploit the capability of ITER and FIRE. This paper will summarize the status of the work and indicate critical areas where further R and D is needed. (author)

Feasibility study of steady state magnetic field measurement

International Nuclear Information System (INIS)

Kawahata, Kazuo; Fujita, Junji; Matsuura, Kiyokata; Sakata, Masataka; Fujiwaka, Setsuya; Matoba, Tohru.

1995-08-01

A rotating magnetic probe testing system has been designed and constructed for the purpose of establishing a technique of the plasma current measurement on a steady state tokamak. An air turbine is employed to drive the rotating magnetic coil from the viewpoint of avoiding the use of an electric motor in the vicinity of the tokamak device. The signal induced on the rotating probe is transmitted to the amplifier through a transformer coupling. A long term testing on mechanical as well as electrical characteristics has been carried out to find key technical issues on this system. A continuous operation for more than one week has successfully been achieved. (author)

Approach to the energetic coaxial gun of the steady-state mode operation

International Nuclear Information System (INIS)

Hirano, Kei-ichi

1993-01-01

Behaviors of a coaxial plasma gun operated in a steady-state mode have been studied. It is shown that the gun has potentialities to yield an energetic plasma beam, if a supersonic plasma flow is supplied instead of a neutral gas and if shorting out of the Hall potential is minimized on the surfaces of the electrodes. The former is necessary because a electromagnetic force chokes the subsonic flow appearing in the ionizing zone of the inlet gas. The latter is achieved if the electrodes are segmented into many insulated short elements along the axis. The required minimum number of the segmentation is estimated by the newly developed model based on the boundary layer concept. (author)

Steady-state cerebral glucose concentrations and transport in the human brain

OpenAIRE

Gruetter, R.; Ugurbil, K.; Seaquist, E. R.

1998-01-01

Understanding the mechanism of brain glucose transport across the blood- brain barrier is of importance to understanding brain energy metabolism. The specific kinetics of glucose transport nave been generally described using standard Michaelis-Menten kinetics. These models predict that the steady- state glucose concentration approaches an upper limit in the human brain when the plasma glucose level is well above the Michaelis-Menten constant for half-maximal transport, K(t). In experiments wh...

Control, data acquisition and remote participation for steady-state operation in LHD

International Nuclear Information System (INIS)

Sudo, S.; Nagayama, Y.; Emoto, M.; Nakanishi, H.; Chikaraishi, H.; Imazu, S.; Iwata, C.; Kogi, Y.; Kojima, M.; Komada, S.; Kubo, S.; Kumazawa, R.; Mase, A.; Miyazawa, J.; Mutoh, T.; Nakamura, Y.; Nonomura, M.; Ohsuna, M.; Saito, K.; Sakamoto, R.; Seki, T.; Shoji, M.; Tsuda, K.; Yoshida, M.

2006-01-01

Control, data acquisition, plasma monitoring and remote participation for steady state operation in the large helical device (LHD) are reviewed. By controlling the impedance matching of ICH, the plasma position and the electron density, high temperature plasma is confined for 1905s. The plasma parameters are monitored in real time. Data are continuously sampled by the YOKOGAWA WE7000 system and by the NATIONAL INSTRUMENTS CompactPCI system. Those data are managed by the object-oriented database system based on ObjectStore in distributed servers with mass storage. By using the multi protocol label switching-virtual private network (MPLS-VPN) technology, the local area network of LHD is expanded to the Japanese fusion community. This provides the remote participants with the same environment of the LHD control room

Control, data acquisition and remote participation for steady-state operation in LHD

Energy Technology Data Exchange (ETDEWEB)

Sudo, S. [National Institute of Natural Sciences, 322-6 Oroshi, Toki 509-5292 (Japan)]. E-mail: sudo@nifs.ac.jp; Nagayama, Y. [National Institute of Natural Sciences, 322-6 Oroshi, Toki 509-5292 (Japan); Emoto, M. [National Institute of Natural Sciences, 322-6 Oroshi, Toki 509-5292 (Japan); Nakanishi, H. [National Institute of Natural Sciences, 322-6 Oroshi, Toki 509-5292 (Japan); Chikaraishi, H. [National Institute of Natural Sciences, 322-6 Oroshi, Toki 509-5292 (Japan); Imazu, S. [National Institute of Natural Sciences, 322-6 Oroshi, Toki 509-5292 (Japan); Iwata, C. [National Institute of Natural Sciences, 322-6 Oroshi, Toki 509-5292 (Japan); Kogi, Y. [KASTEC, Kyushu University, Kasuga 816-8580 (Japan); Kojima, M. [National Institute of Natural Sciences, 322-6 Oroshi, Toki 509-5292 (Japan); Komada, S. [National Institute of Natural Sciences, 322-6 Oroshi, Toki 509-5292 (Japan); Kubo, S. [National Institute of Natural Sciences, 322-6 Oroshi, Toki 509-5292 (Japan); Kumazawa, R. [National Institute of Natural Sciences, 322-6 Oroshi, Toki 509-5292 (Japan); Mase, A. [KASTEC, Kyushu University, Kasuga 816-8580 (Japan); Miyazawa, J. [National Institute of Natural Sciences, 322-6 Oroshi, Toki 509-5292 (Japan); Mutoh, T. [National Institute of Natural Sciences, 322-6 Oroshi, Toki 509-5292 (Japan); Nakamura, Y. [National Institute of Natural Sciences, 322-6 Oroshi, Toki 509-5292 (Japan); Nonomura, M. [National Institute of Natural Sciences, 322-6 Oroshi, Toki 509-5292 (Japan); Ohsuna, M. [National Institute of Natural Sciences, 322-6 Oroshi, Toki 509-5292 (Japan); Saito, K. [National Institute of Natural Sciences, 322-6 Oroshi, Toki 509-5292 (Japan); Sakamoto, R.; Seki, T.; Shoji, M.; Tsuda, K.; Yoshida, M. [National Institute of Natural Sciences, 322-6 Oroshi, Toki 509-5292 (Japan)

2006-07-15

Control, data acquisition, plasma monitoring and remote participation for steady state operation in the large helical device (LHD) are reviewed. By controlling the impedance matching of ICH, the plasma position and the electron density, high temperature plasma is confined for 1905s. The plasma parameters are monitored in real time. Data are continuously sampled by the YOKOGAWA WE7000 system and by the NATIONAL INSTRUMENTS CompactPCI system. Those data are managed by the object-oriented database system based on ObjectStore in distributed servers with mass storage. By using the multi protocol label switching-virtual private network (MPLS-VPN) technology, the local area network of LHD is expanded to the Japanese fusion community. This provides the remote participants with the same environment of the LHD control room.

Current drive studies for the ARIES steady-state tokamak reactors

International Nuclear Information System (INIS)

Mau, T.K.; Ehst, D.A.; Mandrekas, J.

1994-01-01

Steady-state plasma operating scenarios are designed for three versions of the ARIES reactor, using non-inductive current drive techniques that have an established database. R.f. waves, including fast and lower hybrid waves, are the reference drivers for the D-T burning ARIES-I and ARIES-II/IV, while neutral beam injection is employed for ARIES-III which burns D- 3 He. Plasma equilibria with a high bootstrap-current component have been used, in order to minimize the recirculating power fraction and cost of electricity. To maintain plasma stability, the driven current profile has been aligned with that of equilibrium by proper choices of the plasma profiles and power launch parameters. Except for ARIES-III, the current-drive power requirements and the relevant technology developments are found to be quite reasonable. The wave-power spectrum and launch requirements are also considered achievable with a modest development effort. Issues such as an improved database for fast-wave current drive, lower-hybrid power coupling to the plasma edge, profile control in the plasma core, and access to the design point of operation remain to be addressed. ((orig.))

Steady-State Operation in Tore Supra

Science.gov (United States)

Hoang, G. T.; Tore Supra, Equipe

1999-11-01

The Tore Supra superconducting tokamak is devoted to steady-state operation. The CIEL (French acronym for internal component and limiter) project( LIPA, M., et al., Proc. of the 17th IEEE/NPSS Symp. on Fus. Engineering, San Diego, USA, 1997.) consists of a complete upgrade of the inner chamber of Tore Supra, planned to be installed during the year 2000. This project will allow physics scenarios with up to 24 MW of radio frequency heating and current drive (typically 8 - 10 MW of ICRF, 10 - 12 MW of LHCD and 2 MW of ECRF) in stationary plasmas up to 1000 s, with active particle control. This paper presents an overview of the experiments planned to explore the properties, such as the confinement and MHD stability, of various heating and current drive scenarios for long duration discharges. The expected performance for the CIEL phase is also reported.

Modular first wall concept for steady state operation

International Nuclear Information System (INIS)

Kotzlowski, H.E.

1981-01-01

On the basis of the limiter design proposed for ZEPHYR a first wall concept has been developed which can also be used as a large area limiter, heat shield or beam pump. Its specific feature is the thermal contact of the wall armour elements with the water-cooled base plates. The combination of radiation and contact cooling, compared with radiation only, helps to lower the steady state temperatures of the first wall by approximately 50 % and to reduce the cooling-time between discharges. Particulary the lower wall temperature give a larger margin for additional heating of the wall by plasma disruption or neutral beams until excessive erosion or damage of the armour takes place

Proceeding of A3 foresight program seminar on critical physics issues specific to steady state sustainment of high-performance plasmas 2015

International Nuclear Information System (INIS)

Hu Liqun; Morita, Shigeru; Oh, Yeong-Kook

2015-12-01

To enhance close collaborations among scientists in three Asian countries (China, Japan and Korea), A3 foresight program on Plasma Physics was launched from August 2012 under the auspice of JSPS (Japan), NRF (Korea) and NSFC (China). The main purpose of this project is to solve several key physics issues through joint experiments on three Asian advanced fully superconducting fusion devices (EAST in China, LHD in Japan and KSTAR in Korea) and other magnetic confinement devices to carry out multi-faceted and complementary physics researches. To summarize the progress and achievement in the second academic year under this A3 foresight program, the 6th workshop hosted by Institute of Plasma Physics, Chinese Academy of Sciences was held in Nanning during 6-9 January, 2015. The research collaboration carried out by young scientists was also encouraged with participation of graduated students. The three topics of steady state sustainment of magnetic configurations, edge and divertor plasma control and confinement of alpha particles are mainly discussed in addition to relevant studies in small devices. This issue is the collection of 41 papers presented at the entitled meeting. The 39 of the presented papers are indexed individually. (J.P.N.)

Steady-State Process Modelling

DEFF Research Database (Denmark)

Cameron, Ian; Gani, Rafiqul

2011-01-01

illustrate the “equation oriented” approach as well as the “sequential modular” approach to solving complex flowsheets for steady state applications. The applications include the Williams-Otto plant, the hydrodealkylation (HDA) of toluene, conversion of ethylene to ethanol and a bio-ethanol process....

Vacuum system problems of EBT: a steady-state fusion experiment

International Nuclear Information System (INIS)

Livesey, R.L.

1981-01-01

Many of the vacuum problems faced by EBT will soon be shared by other plasma devices as high-power microwave systems and long pulse lengths become more common. The solutions used on EBT (such as the raised lip with elastomer seal) are not unique; however, experience has shown that microwave-compatible designs must be carefully thought out. All details of the vacuum must be carefully thought out. All details of the vacuum must be carefully screened in advance to insure that microwaves do not leak into pumps or diagnostics where they can cause major damage. Sputter coating, which even now is noticeably present in most pulsed plasma systems, becomes much worse as systems approach steady state. And finally, radiation degradation of components which is presently a minor problem will become significant on high-power microwave-fed devices, such as EBT-P

Steady-State Ion Beam Modeling with MICHELLE

Science.gov (United States)

Petillo, John

2003-10-01

There is a need to efficiently model ion beam physics for ion implantation, chemical vapor deposition, and ion thrusters. Common to all is the need for three-dimensional (3D) simulation of volumetric ion sources, ion acceleration, and optics, with the ability to model charge exchange of the ion beam with a background neutral gas. The two pieces of physics stand out as significant are the modeling of the volumetric source and charge exchange. In the MICHELLE code, the method for modeling the plasma sheath in ion sources assumes that the electron distribution function is a Maxwellian function of electrostatic potential over electron temperature. Charge exchange is the process by which a neutral background gas with a "fast" charged particle streaming through exchanges its electron with the charged particle. An efficient method for capturing this is essential, and the model presented is based on semi-empirical collision cross section functions. This appears to be the first steady-state 3D algorithm of its type to contain multiple generations of charge exchange, work with multiple species and multiple charge state beam/source particles simultaneously, take into account the self-consistent space charge effects, and track the subsequent fast neutral particles. The solution used by MICHELLE is to combine finite element analysis with particle-in-cell (PIC) methods. The basic physics model is based on the equilibrium steady-state application of the electrostatic particle-in-cell (PIC) approximation employing a conformal computational mesh. The foundation stems from the same basic model introduced in codes such as EGUN. Here, Poisson's equation is used to self-consistently include the effects of space charge on the fields, and the relativistic Lorentz equation is used to integrate the particle trajectories through those fields. The presentation will consider the complexity of modeling ion thrusters.

Steady State Shift Damage Localization

DEFF Research Database (Denmark)

Sekjær, Claus; Bull, Thomas; Markvart, Morten Kusk

2017-01-01

The steady state shift damage localization (S3DL) method localizes structural deterioration, manifested as either a mass or stiffness perturbation, by interrogating the damage-induced change in the steady state vibration response with damage patterns cast from a theoretical model. Damage is, thus...... the required accuracy when examining complex structures, an extensive amount of degrees of freedom (DOF) must often be utilized. Since the interrogation matrix for each damage pattern depends on the size of the system matrices constituting the FE-model, the computational time quickly becomes of first......-order importance. The present paper investigates two sub-structuring approaches, in which the idea is to employ Craig-Bampton super-elements to reduce the amount of interrogation distributions while still providing an acceptable localization resolution. The first approach operates on a strict super-element level...

Quantum thermodynamics of nanoscale steady states far from equilibrium

Science.gov (United States)

Taniguchi, Nobuhiko

2018-04-01

We develop an exact quantum thermodynamic description for a noninteracting nanoscale steady state that couples strongly with multiple reservoirs. We demonstrate that there exists a steady-state extension of the thermodynamic function that correctly accounts for the multiterminal Landauer-Büttiker formula of quantum transport of charge, energy, or heat via the nonequilibrium thermodynamic relations. Its explicit form is obtained for a single bosonic or fermionic level in the wide-band limit, and corresponding thermodynamic forces (affinities) are identified. Nonlinear generalization of the Onsager reciprocity relations are derived. We suggest that the steady-state thermodynamic function is also capable of characterizing the heat current fluctuations of the critical transport where the thermal fluctuations dominate. Also, the suggested nonequilibrium steady-state thermodynamic relations seemingly persist for a spin-degenerate single level with local interaction.

Steady states in conformal theories

CERN Multimedia

CERN. Geneva

2015-01-01

A novel conjecture regarding the steady state behavior of conformal field theories placed between two heat baths will be presented. Some verification of the conjecture will be provided in the context of fluid dynamics and holography.

Differences between automatically detected and steady-state fractional flow reserve.

Science.gov (United States)

Härle, Tobias; Meyer, Sven; Vahldiek, Felix; Elsässer, Albrecht

2016-02-01

Measurement of fractional flow reserve (FFR) has become a standard diagnostic tool in the catheterization laboratory. FFR evaluation studies were based on pressure recordings during steady-state maximum hyperemia. Commercially available computer systems detect the lowest Pd/Pa ratio automatically, which might not always be measured during steady-state hyperemia. We sought to compare the automatically detected FFR and true steady-state FFR. Pressure measurement traces of 105 coronary lesions from 77 patients with intermediate coronary lesions or multivessel disease were reviewed. In all patients, hyperemia had been achieved by intravenous adenosine administration using a dosage of 140 µg/kg/min. In 42 lesions (40%) automatically detected FFR was lower than true steady-state FFR. Mean bias was 0.009 (standard deviation 0.015, limits of agreement -0.02, 0.037). In 4 lesions (3.8%) both methods lead to different treatment recommendations, in all 4 cases instantaneous wave-free ratio confirmed steady-state FFR. Automatically detected FFR was slightly lower than steady-state FFR in more than one-third of cases. Consequently, interpretation of automatically detected FFR values closely below the cutoff value requires special attention.

Steady state operation of the superconducting tokamak TRIAM-1M

International Nuclear Information System (INIS)

Hanada, K.; Itoh, S.; Sato, K.; Nakamura, K.; Zushi, H.; Sakamoto, M.; Jotaki, E.; Makino, K.

2000-01-01

A 2-hour limiter discharge in circular configuration was successfully maintained using both Hall generators to be free from the drift of integrator and position control by TV image to avoid the concentration of heat load. The property of wall saturation is discussed as the serious issue for steady state operation, which strongly depends on electron density. In the high density region, the discharges sometimes terminate due to uncontrollable increase in electron density caused by wall saturation. The plasmas with high k ∼1.5 can be demonstrated for longer than 1 min. The duration of discharge is limited by vertical displacement event (VDE). The avoidance of VDE is a crucial point to achieve long discharges with high k. A new technique to monitor the accurate magnetic field with high time resolution for a long time is required to achieve the longer discharge with high k. A high ion temperature (HIT) discharge characterized by high ion temperature up to 5 keV and by steep temperature gradient up to 85 keV/m is successfully sustained for longer than 30 sec by 2.45 GHz LHCD on single null divertor configuration. This indicates that the transport barrier of ion temperature can be maintained in steady state. (author)

Steady-State Diffusion of Water through Soft-Contact LensMaterials

Energy Technology Data Exchange (ETDEWEB)

Fornasiero, Francesco; Krull, Florian; Radke, Clayton J.; Prausnitz, JohnM.

2005-01-31

Water transport through soft contact lenses (SCL) is important for acceptable performance on the human eye. Chemical-potential gradient-driven diffusion rates of water through soft-contact-lens materials are measured with an evaporation-cell technique. Water is evaporated from the bottom surface of a lens membrane by impinging air at controlled flow rate and humidity. The resulting weight loss of a water reservoir covering the top surface of the contact-lens material is recorded as a function of time. New results are reported for a conventional hydrogel material (SofLens{trademark} One Day, hilafilcon A, water content at saturation W{sub 10} = 70 weight %) and a silicone hydrogel material (PureVision{trademark}, balafilcon A, W{sub 10} = 36 %), with and without surface oxygen plasma treatment. Also, previously reported data for a conventional HEMA-SCL (W{sub 10} = 38 %) hydrogel are reexamined and compared with those for SofLens{trademark} One Day and PureVision{trademark} hydrogels. Measured steady-state water fluxes are largest for SofLens{trademark} One Day, followed by PureVision{trademark} and HEMA. In some cases, the measured steady-state water fluxes increase with rising relative air humidity. This increase, due to an apparent mass-transfer resistance at the surface (trapping skinning), is associated with formation of a glassy skin at the air/membrane interface when the relative humidity is below 55-75%. Steady-state water-fluxes are interpreted through an extended Maxwell-Stefan diffusion model for a mixture of species starkly different in size. Thermodynamic nonideality is considered through Flory-Rehner polymer-solution theory. Shrinking/swelling is self-consistently modeled by conservation of the total polymer mass. Fitted Maxwell-Stefan diffusivities increase significantly with water concentration in the contact lens.

Steady-State Clozapine and Norclozapine Pharmacokinetics in Maori and European Patients.

Science.gov (United States)

Menkes, David B; Glue, Paul; Gale, Christopher; Lam, Frederic; Hung, Cheung-Tak; Hung, Noelyn

2018-01-01

Clozapine is the most effective drug for treatment-resistant schizophrenia, but its use is limited by toxicity. Because ethnicity has been reported to affect clozapine metabolism, we compared its steady state pharmacokinetics in New Zealand Maori and European patients. Clozapine and norclozapine steady state bioavailability was assessed over 24h under fasting and fed conditions in 12 Maori and 16 European patients treated for chronic psychotic illnesses with stable once-daily clozapine doses. Plasma clozapine and norclozapine concentrations were assessed using liquid chromatography with tandem mass spectrometry; pharmacokinetic parameters were calculated using standard non-compartmental methods, and compared using unpaired t-tests. Mean pharmacokinetic parameters (AUC, C max and C min ) for clozapine and norclozapine were virtually identical in Maori and European subjects, under both fed and fasted conditions. Clozapine bioavailability does not vary between Maori and European patients, and thus does not need to be considered in prescribing decisions. Additional studies are needed to identify if there are differences between Maori and European populations for drugs metabolized by other enzyme pathways. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

LANSCE steady state unperturbed thermal neutron fluxes at 100 μA

International Nuclear Information System (INIS)

Russell, G.J.

1989-01-01

The ''maximum'' unperturbed, steady state thermal neutron flux for LANSCE is calculated to be 2 /times/ 10 13 n/cm 2 -s for 100 μA of 800-MeV protons. This LANSCE neutron flux is a comparable entity to a steady state reactor thermal neutron flux. LANSCE perturbed steady state thermal neutron fluxes have also been calculated. Because LANSCE is a pulsed neutron source, much higher ''peak'' (in time) neutron fluxes can be generated than at a steady state reactor source. 5 refs., 5 figs

The steady-state pharmacokinetics of nevirapine during once daily and twice daily dosing in HIV-1-infected individuals

NARCIS (Netherlands)

van Heeswijk, R. P.; Veldkamp, A. I.; Mulder, J. W.; Meenhorst, P. L.; Wit, F. W.; Lange, J. M.; Danner, S. A.; Foudraine, N. A.; Kwakkelstein, M. O.; Reiss, P.; Beijnen, J. H.; Hoetelmans, R. M.

2000-01-01

OBJECTIVE: To investigate and to compare the steady-state plasma pharmacokinetics of nevirapine in a dosing regimen of 400 mg once daily versus 200 mg twice daily in HIV-1-infected individuals. DESIGN: Open-label, randomized, cross-over study. METHODS: Twenty HIV-1-infected individuals who already

Calculation analysis on steady state natural circulation characteristics

International Nuclear Information System (INIS)

Wang Fei; Nie Changhua; Huang Yanping

2005-01-01

The calculation results of single-phase steady state natural circulation characteristics by using Retran02 code have been presented, good agreement is achieved between the verified calculation result and the experimental data which were conducted at a test facility. Based on the calculation model, some sensibility analyses were made and much deeper understanding for single-phase steady state natural circulation characteristics was obtained. (author)

Selection of steady states in planar Darcy convection

International Nuclear Information System (INIS)

Tsybulin, V.G.; Karasoezen, B.; Ergenc, T.

2006-01-01

The planar natural convection of an incompressible fluid in a porous medium is considered. We study the selection of steady states under temperature perturbations on the boundary. A selection map is introduced in order to analyze the selection of a steady state from a continuous family of equilibria which exists under zero boundary conditions. The results of finite-difference modeling for a rectangular enclosure are presented

Steady-state oxygen-solubility in niobium

International Nuclear Information System (INIS)

Schulze, K.; Jehn, H.

1977-01-01

During annealing of niobium in oxygen in certain temperature and pressure ranges steady states are established between the absorption of molecular oxygen and the evaporation of volatile oxides. The oxygen concentration in the niobium-oxygen α-solid solution is a function of oxygen pressure and temperature and has been redetermined in the ranges 10 -5 - 10 -2 Pa O 2 and 2,070 - 2,470 K. It follows differing from former results the equation csub(o) = 9.1 x 10 -6 x sub(po2) x exp (502000/RT) with csub(o) in at.-ppm, sub(po2) in Pa, T in K, R = 8.31 J x mol -1 x K -1 . The existence of steady states is limited to a temperature range from 1870 to 2470 K and to oxygen concentrations below the solubility limit given by solidus and solvus lines in the T-c diagram. In the experiments high-purity niobium wires with a specific electrical ratio rho (273 K)/rho(4.2 K) > 5,000 have been gassed under isothermal-isobaric conditions until the steady state has been reached. The oxygen concentration has been determined analytically by vacuum fusion extraction with platinum-flux technique as well as by electrical residual resistivity measurements at 4.2 K. (orig.) [de

Steady-state entanglement activation in optomechanical cavities

Science.gov (United States)

Farace, Alessandro; Ciccarello, Francesco; Fazio, Rosario; Giovannetti, Vittorio

2014-02-01

Quantum discord, and related indicators, are raising a relentless interest as a novel paradigm of nonclassical correlations beyond entanglement. Here, we discover a discord-activated mechanism yielding steady-state entanglement production in a realistic continuous-variable setup. This comprises two coupled optomechanical cavities, where the optical modes (OMs) communicate through a fiber. We first use a simplified model to highlight the creation of steady-state discord between the OMs. We show next that such discord improves the level of stationary optomechanical entanglement attainable in the system, making it more robust against temperature and thermal noise.

Numerical method for three dimensional steady-state two-phase flow calculations

International Nuclear Information System (INIS)

Raymond, P.; Toumi, I.

1992-01-01

This paper presents the numerical scheme which was developed for the FLICA-4 computer code to calculate three dimensional steady state two phase flows. This computer code is devoted to steady state and transient thermal hydraulics analysis of nuclear reactor cores 1,3 . The first section briefly describes the FLICA-4 flow modelling. Then in order to introduce the numerical method for steady state computations, some details are given about the implicit numerical scheme based upon an approximate Riemann solver which was developed for calculation of flow transients. The third section deals with the numerical method for steady state computations, which is derived from this previous general scheme and its optimization. We give some numerical results for steady state calculations and comparisons on required CPU time and memory for various meshing and linear system solvers

Development of synchronous generator saturation model from steady-state operating data

Energy Technology Data Exchange (ETDEWEB)

Jadric, Martin; Despalatovic, Marin; Terzic, Bozo [FESB University of Split, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, Split (Croatia)

2010-11-15

A new method to estimate and model the saturated synchronous reactances of hydroturbine generators from operating data is presented. For the estimation process, measurements of only the generator steady-state variables are required. First, using a specific procedure, the field to armature turns ratio is estimated from measured steady-state variables at constant power generation and various excitation conditions. Subsequently, for each set of steady-state operating data, saturated synchronous reactances are identified. Fitting surfaces, defined as polynomial functions in two variables, are later used to model these saturated reactances. It is shown that the simpler polynomial functions may be used to model saturation at the steady-state than at the dynamic conditions. The developed steady-state model is validated with measurements performed on the 34 MVA hydroturbine generator. (author)

Steady-state kinetics of proguanil and its active metabolite, cycloguanil, in man.

Science.gov (United States)

Edstein, M D; Veenendaal, J R; Scott, H V; Rieckmann, K H

1988-01-01

The pharmacokinetics of proguanil and its active metabolite, cycloguanil, were determined at steady-state in 6 healthy male volunteers after daily administration of 2 Paludrine tablets (200 mg proguanil hydrochloride). A maximum plasma proguanil concentration of 130.3 +/- 16.0 ng/ml (mean +/- SD) was reached at 3.8 +/- 1.3 h while a maximum cycloguanil concentration of 52.0 +/- 15.2 ng/ml was obtained at 5.3 +/- 1.0 h after dosing. The elimination half-lives of proguanil and cycloguanil were 14.5 +/- 3.0 h and 11.7 +/- 3.1 h, respectively. The plasma clearance of proguanil was 1.43 +/- 0.33 l/h/kg and the apparent volume of distribution was 30.7 +/- 12.3 l/kg. Renal clearance of proguanil (0.33 +/- 0.19 l/h/kg) was about 23% of the plasma clearance and 35.6 +/- 9.6% of the oral dose was recovered as proguanil and cycloguanil.

Steady state and transient critical heat flux examinations

International Nuclear Information System (INIS)

Szabados, L.

1978-02-01

In steady state conditions within the P.W.R. parameter range the critical heat flux correlations based on local parameters reproduce the experimental data with less deviations than those based on system parameters. The transient experiments were restricted for the case of power transients. A data processing method for critical heat flux measurements has been developed and the applicability of quasi steady state calculation has been verified. (D.P.)

JET steady state ITB operation with active control of the pressure profile

Energy Technology Data Exchange (ETDEWEB)

Crisanti, F.; Litaudon, X.; Mailloux, J. [and others

2002-07-01

Stationary operations have been achieved at JET in ITBs scenarios, with the discharge time limited only by plant constraints. Full current drive was obtained, all over the high performance phase, with the current density profile frozen by using Lower Hybrid current drive. For the first time a feed-back control on the total pressure and on the electron temperature profile was implemented by using respectively the Neutral Beams and the Ion Cyclotron waves. Although impurity accumulation could be a problem in steady state ITBs, these experiments bring some elements to answer to it. Tokamak operation in enhanced confinement regimes, characterized by edge and/or Internal Transport Barriers (respectively known as H-mode and ITB), is attractive as it represents an important step towards the approach of ignition conditions. Moreover, the necessity of steady state operation in a Tokamak reactor, has led to the concept of the Advanced Tokamak, in which the current density profile is no longer tied to the plasma conductivity and is non inductively driven. Since the bootstrap current is a consequence of the pressure gradient, one of the primary goal of the Advanced Tokamak studies is to maximize the bootstrap fraction, with a proper alignment, both in H mode and in ITB regimes. However, for several reasons, it is difficult to envisage an operational situation in which the bootstrap fraction is close to 100%: for instance, there are few chances of pressure or/and current profile control to optimize the MHD stability. So far, various experiments have been performed with improved confinement regimes lasting up to tens of the confinement time and up to some current relaxation times. In some experiments a large non inductive plasma current (< 75%) was obtained with about 50% from bootstrap and 25% from Neutral Beam Injection (NBI); however, no full current drive operation was achieved and, moreover, with the available heating systems, no active feedback control of the current

Joint DIII-D/EAST research on the development of a high poloidal beta scenario for the steady state missions of ITER and CFETR

Science.gov (United States)

Garofalo, A. M.; Gong, X. Z.; Ding, S. Y.; Huang, J.; McClenaghan, J.; Pan, C. K.; Qian, J.; Ren, Q. L.; Staebler, G. M.; Chen, J.; Cui, L.; Grierson, B. A.; Hanson, J. M.; Holcomb, C. T.; Jian, X.; Li, G.; Li, M.; Pankin, A. Y.; Peysson, Y.; Zhai, X.; Bonoli, P.; Brower, D.; Ding, W. X.; Ferron, J. R.; Guo, W.; Lao, L. L.; Li, K.; Liu, H.; Lyv, B.; Xu, G.; Zang, Q.

2018-01-01

Experimental and modeling investigations on the DIII-D and EAST tokamaks show the attractive transport and stability properties of fully noninductive, high poloidal-beta (β P ) plasmas, and their suitability for steady-state operating scenarios in ITER and CFETR. A key feature of the high-β P regime is the large-radius (ρ > 0.6) internal transport barrier (ITB), often observed in all channels (ne, Te, Ti, rotation), and responsible for both excellent energy confinement quality and excellent stability properties. Experiments on DIII-D have shown that, with a large-radius ITB, very high β N and β P values (both ≥ 4) can be reached by taking advantage of the stabilizing effect of a nearby conducting wall. Synergistically, higher plasma pressure provides turbulence suppression by Shafranov shift, leading to ITB sustainment independent of the plasma rotation. Experiments on EAST have been used to assess the long pulse potential of the high-β P regime. Using RF-only heating and current drive, EAST achieved minute-long fully noninductive steady state H-mode operation with strike points on an ITER-like tungsten divertor. Improved confinement (relative to standard H-mode) and steady state ITB features are observed with a monotonic q-profile with q min ˜ 1.5. Separately, experiments have shown that increasing the density in plasmas driven by lower hybrid wave broadens the q-profile, a technique that could enable a large radius ITB. These experimental results have been used to validate MHD, current drive, and turbulent transport models, and to project the high-β P regime to a burning plasma. These projections suggest the Shafranov shift alone will not suffice to provide improved confinement (over standard H-mode) without rotation and rotation shear. However, increasing the negative magnetic shear (higher q on axis) provides a similar turbulence suppression mechanism to Shafranov shift, and can help devices such as ITER and CFETR achieve their steady-state fusion

The steady-state ECRH-system at Wendelstein7-X

International Nuclear Information System (INIS)

Laqua, H.P.; Erckmann, V.; Brakel, R.; Braune, H.; Maassberg, H.; Marushchenko, N.; Michel, G.; Turkin, Y.; Ullrich, S.; Dammertz, G.; Thumm, M.; Brand, P.; Gantenbein, G.; Kasparek, W.

2005-01-01

Electron Cyclotron Resonance Heating (ECRH) is the main heating system for the Wendelstein7-X (W7-X) stellarator and the only one for CW-operation in the first stage. The mission of W7-X, which is presently under construction at IPP-Greifswald, is to demonstrate the inherent steady state capability of stellarators at reactor relevant plasma parameters. A modular 10 MW ECRH plant at 140 GHz with 1 MW CW-capability power for each module is under construction to meet the scientific objectives. Simulations of different ECRH scenarios, which are foreseen for W7-X operation and base on ray- tracing calculations and confinement studies, will be presented. A steady state ECRH has specific requirements on the stellarator machine itself, on the ECRH-sources, transmissions elements and on the experimental environment. In particular all elements have to be sufficiently cooled, screened and armoured against microwaves. The commissioning of the ECRH plant is well under way, the strategy and status of the project will be reported. First full power, CW integral tests of one ECRH module have been performed. A large microwave stray radiation chamber for integrated in-vessel component tests had been brought into operation. A bi-axially movable, motor driven ECRH antenna mock-up was build and is tested for reliability now. A strategy for the commissioning and the first experimental campaign at W7-X has been developed. (author)

Surface wave propagation in steady ideal Hall-magnetohydrodynamic magnetic slabs

International Nuclear Information System (INIS)

Miteva, Rossitsa; Zhelyazkov, Ivan; Erdelyi, Robert

2003-01-01

This paper studies the dispersion characteristics of sausage and kink surface waves traveling along a plasma layer within the framework of Hall magnetohydrodynamics in steady state. While in a static plasma slab these waves are Alfven ones (their phase velocities are close to the Alfven speed in the layer); in a slab with steady flows they may become super Alfvenic waves. Moreover, there exist two types of waves: forward and backward ones bearing in mind that the flow velocity defines the positive (forward) direction. As a typical representative of a magnetic slab in steady state here is considered a solar wind flux rope with a finite β plasma flow (typically β∼1).The forward sausage surface mode exhibits an increased dispersion at small wave numbers while the forward kink waves become practically non-dispersive. Both backward propagating sausage and kink surface modes show an increased dispersion for large wave numbers

Properties of the electrostatically driven helical plasma state

Science.gov (United States)

Akçay, Cihan; Finn, John M.; Nebel, Richard A.; Barnes, Daniel C.; Martin, Neal

2018-02-01

A novel plasma state has been found [Akçay et al., Phys. Plasmas 24, 052503 (2017)] in the presence of a uniform applied axial magnetic field in periodic cylindrical geometry. This state is driven by external electrostatic fields provided by helical electrodes with a (m =1 ,n =1 ) (helical) symmetry where m and n represent the poloidal and axial harmonics. The resulting plasma is a function of the cylinder radius r safety factor q0(r ) just above the pitch of the electrodes m /n =1 in the interior, where the plasma is nearly force-free. However, at the edge the current density has a component perpendicular to the magnetic field B. This perpendicular current density drives nearly Alfvénic helical plasma flows, a notable feature of these states. This state is being studied for its possible application in DC electrical transformers. We present results on several issues of importance for these applications: the transient leading to the steady state; the twist and writhe of the field lines and their relation with the current density; the properties of the current density streamlines and length of the current density lines connected to the electrodes; the sensitivity to changes in the velocity boundary conditions; the effect of varying the radial resistivity profile; and the effects of a concentrated electrode potential.

The Markov process admits a consistent steady-state thermodynamic formalism

Science.gov (United States)

Peng, Liangrong; Zhu, Yi; Hong, Liu

2018-01-01

The search for a unified formulation for describing various non-equilibrium processes is a central task of modern non-equilibrium thermodynamics. In this paper, a novel steady-state thermodynamic formalism was established for general Markov processes described by the Chapman-Kolmogorov equation. Furthermore, corresponding formalisms of steady-state thermodynamics for the master equation and Fokker-Planck equation could be rigorously derived in mathematics. To be concrete, we proved that (1) in the limit of continuous time, the steady-state thermodynamic formalism for the Chapman-Kolmogorov equation fully agrees with that for the master equation; (2) a similar one-to-one correspondence could be established rigorously between the master equation and Fokker-Planck equation in the limit of large system size; (3) when a Markov process is restrained to one-step jump, the steady-state thermodynamic formalism for the Fokker-Planck equation with discrete state variables also goes to that for master equations, as the discretization step gets smaller and smaller. Our analysis indicated that general Markov processes admit a unified and self-consistent non-equilibrium steady-state thermodynamic formalism, regardless of underlying detailed models.

Individual differences in the radiosensitivity of hematopoietic progenitor cells detected in steady-state human peripheral blood

International Nuclear Information System (INIS)

Oriya, Asami; Takahashi, Kenji; Kashiwakura, Ikuo; Inanami, Osamu; Kuwabara, Mikinori; Miura, Toshiaki; Abe, Yoshinao

2008-01-01

The aim of this study is to evaluate the individual differences in radiosensitivity of lineage-committed myeloid hematopoietic progenitors, colony-forming cells (CFC), detected in steady-state human peripheral blood (PB). Mononuclear cells were prepared from the buffy-coat of 30 individuals PB, and were assayed for CFC by semi-solid culture supplemented with cytokines. X irradiation was performed in the range of 0.5-4 Gy at a dose rate of about 80 cGy/min. The mean number of hematopoietic progenitor cells is 5866±3408 in 1 ml of buffy-coat, suggesting that the erythroid progenitor cells are the major population. The total CFC radiosensitivity parameter D 0 and n value are 1.18±0.24 and 1.89±0.98, respectively. Using a linear regression analysis, a statistically significant correlation is observed between the D 0 value and the surviving fraction at 4 Gy (r=0.611 p 0 parameter and the level of antioxidants, plasma uric acid, plasma bilirubin, and intracellular glutathione. The present study demonstrates that there are large individual differences in the radiosensitivity of hematopoietic progenitor cells as detected in steady-state human PB. These differences demonstrate almost no correlation with plasma or intracellular antioxidants. The prediction of individual differences in radiosensitivity of CFC can only be measured by 4 Gy irradiation. (author)

Progress towards steady-state operation and real time control of internal transport barriers in JET

International Nuclear Information System (INIS)

Litaudon, X.

2002-01-01

In JET advanced tokamak research mainly focuses on plasmas with internal transport barriers (ITBs), generated by modifications of the current profile. The formerly developed optimised shear regime with low magnetic shear in the plasma center has been extended to deeply reversed magnetic shear configurations. ITBs occur at much lower access powers. The achievement of high fusion performance is reported in deeply reversed magnetic shear configuration. The generation of plasmas with wide ITBs in this configuration has allowed an extension of the accessible normalised toroidal beta at high magnetic field. We report on the successful sustainment and control of the electron and ion ITB in full current drive operation with a large fraction of bootstrap current. Progress towards the steady state capability of ITB plasmas includes techniques to avoid strong ELM activity and the newly developed real time control of the local ITB strength. Thanks to the real time control of the ITB characteristics the improved confinement state is maintained in a more reproducible and stable manner in quasi-stationary conditions. (author)

Microwave Production of Steady State Large Volume Air Plasmas

National Research Council Canada - National Science Library

Brandenburg, John

1999-01-01

...) and these plasmas persist for hundreds of milliseconds after power is turned off. These plasmas can be made in an inexpensive and easy to build apparatus based around a microwave oven operating at approximately 1kW and 2.45GHz...

A rad-hard, steady state, digital imaging bolometer system for ITER

International Nuclear Information System (INIS)

Wurden, G.A.

1995-01-01

The concept and design of a new type of bolometer system which can function with excellent spatial resolution and good time resolution in the next generation of long-pulse (or steady-state), harsh-neutron environment fusion plasmas, is outlined. It uses a cooled pinhole camera design, employing a robust, passive, segmented radiation absorber, cooled from the back-side. Infrared emission from the absorber's front surface is relayed by metal mirror optics to a shielded, high-resolution IR video camera with ± 0.01 C temperature resolution. It can make thousands of simultaneous ''pixel'' measurements at up to 50--60 Hz, without any signal wires through the vacuum interface

Solution of generalized control system equations at steady state

International Nuclear Information System (INIS)

Vilim, R.B.

1987-01-01

Although a number of reactor systems codes feature generalized control system models, none of the models offer a steady-state solution finder. Indeed, if a transient is to begin from steady-state conditions, the user must provide estimates for the control system initial conditions and run a null transient until the plant converges to steady state. Several such transients may have to be run before values for control system demand signals are found that produce the desired plant steady state. The intent of this paper is (a) to present the control system equations assumed in the SASSYS reactor systems code and to identify the appropriate set of initial conditions, (b) to describe the generalized block diagram approach used to represent these equations, and (c) to describe a solution method and algorithm for computing these initial conditions from the block diagram. The algorithm has been installed in the SASSYS code for use with the code's generalized control system model. The solution finder greatly enhances the effectiveness of the code and the efficiency of the user in running it

Steady-state spheromak reactor studies

International Nuclear Information System (INIS)

Krakowski, R.A.; Hagenson, R.L.

1985-01-01

After summarizing the essential elements of a gun-sustained spheromak, the potential for a steady-state is explored by means of a comprehensive physics/engineering/costing model. A range of cost-optimized reactor design points is presented, and the sensitivity of cost to key physics, engineering, and operational variables is reported

Steady state of tapped granular polygons

International Nuclear Information System (INIS)

Carlevaro, Carlos M; Pugnaloni, Luis A

2011-01-01

The steady state packing fraction of a tapped granular bed is studied for different grain shapes via a discrete element method. Grains are monosized regular polygons, from triangles to icosagons. Comparisons with disc packings show that the steady state packing fraction as a function of the tapping intensity presents the same general trends in polygon packings. However, better packing fractions are obtained, as expected, for shapes that can tessellate the plane (triangles, squares and hexagons). In addition, we find a sharp transition for packings of polygons with more than 13 vertices signaled by a discontinuity in the packing fraction at a particular tapping intensity. Density fluctuations for most shapes are consistent with recent experimental findings in disc packing; however, a peculiar behavior is found for triangles and squares

External heating and current drive source requirements towards steady-state operation in ITER

Science.gov (United States)

Poli, F. M.; Kessel, C. E.; Bonoli, P. T.; Batchelor, D. B.; Harvey, R. W.; Snyder, P. B.

2014-07-01

Steady state scenarios envisaged for ITER aim at optimizing the bootstrap current, while maintaining sufficient confinement and stability to provide the necessary fusion yield. Non-inductive scenarios will need to operate with internal transport barriers (ITBs) in order to reach adequate fusion gain at typical currents of 9 MA. However, the large pressure gradients associated with ITBs in regions of weak or negative magnetic shear can be conducive to ideal MHD instabilities, reducing the no-wall limit. The E × B flow shear from toroidal plasma rotation is expected to be low in ITER, with a major role in the ITB dynamics being played by magnetic geometry. Combinations of heating and current drive (H/CD) sources that sustain reversed magnetic shear profiles throughout the discharge are the focus of this work. Time-dependent transport simulations indicate that a combination of electron cyclotron (EC) and lower hybrid (LH) waves is a promising route towards steady state operation in ITER. The LH forms and sustains expanded barriers and the EC deposition at mid-radius freezes the bootstrap current profile stabilizing the barrier and leading to confinement levels 50% higher than typical H-mode energy confinement times. Using LH spectra with spectrum centred on parallel refractive index of 1.75-1.85, the performance of these plasma scenarios is close to the ITER target of 9 MA non-inductive current, global confinement gain H98 = 1.6 and fusion gain Q = 5.

Proceedings of the third meeting for A3 foresight program workshop on critical physics issues specific to steady state sustainment of high-performance plasmas

International Nuclear Information System (INIS)

Hu Liqun; Morita, Shigeru; Oh, Yeong-Kook

2013-12-01

To enhance close collaborations among scientists in three Asian countries (China, Japan and Korea), A3 foresight program on Plasma Physics was newly started from August 2012 under the auspice of JSPS (Japan), NRF (Korea) and NSFC (China). The main purpose of this project is to solve several key physics issues through joint experiments on three Asian advanced fully superconducting fusion devices (EAST in China, LHD in Japan and KSTAR in Korea) and other magnetic confinement devices to carry out multi-faceted and complementary physics researches. To summarize the progress and achievement in the first academic year under this A3 foresight program, this workshop was hosted by Institute of Plasma Physics, Chinese Academy of Sciences and held in Beijing during 19-24 May, 2013. Collaborated research and communication with other A3 programs and bilateral programs, as well as participation of young scientists were encouraged in this workshop. The topics include steady state sustainment of magnetic configurations, edge and divertor plasma control and confinement of alpha particles. This issue is the collection of 40 papers presented at the entitled meeting. All the 40 of the presented papers are indexed individually. (J.P.N.)

Progress Toward Steady State Tokamak Operation Exploiting the high bootstrap current fraction regime

Science.gov (United States)

Ren, Q.

2015-11-01

Recent DIII-D experiments have advanced the normalized fusion performance of the high bootstrap current fraction tokamak regime toward reactor-relevant steady state operation. The experiments, conducted by a joint team of researchers from the DIII-D and EAST tokamaks, developed a fully noninductive scenario that could be extended on EAST to a demonstration of long pulse steady-state tokamak operation. Fully noninductive plasmas with extremely high values of the poloidal beta, βp >= 4 , have been sustained at βT >= 2 % for long durations with excellent energy confinement quality (H98y,2 >= 1 . 5) and internal transport barriers (ITBs) generated at large minor radius (>= 0 . 6) in all channels (Te, Ti, ne, VTf). Large bootstrap fraction (fBS ~ 80 %) has been obtained with high βp. ITBs have been shown to be compatible with steady state operation. Because of the unusually large ITB radius, normalized pressure is not limited to low βN values by internal ITB-driven modes. βN up to ~4.3 has been obtained by optimizing the plasma-wall distance. The scenario is robust against several variations, including replacing some on-axis with off-axis neutral beam injection (NBI), adding electron cyclotron (EC) heating, and reducing the NBI torque by a factor of 2. This latter observation is particularly promising for extension of the scenario to EAST, where maximum power is obtained with balanced NBI injection, and to a reactor, expected to have low rotation. However, modeling of this regime has provided new challenges to state-of-the-art modeling capabilities: quasilinear models can dramatically underpredict the electron transport, and the Sauter bootstrap current can be insufficient. The analysis shows first-principle NEO is in good agreement with experiments for the bootstrap current calculation and ETG modes with a larger saturated amplitude or EM modes may provide the missing electron transport. Work supported in part by the US DOE under DE-FC02-04ER54698, DE-AC52-07NA

Steady-state propagation of interface corner crack

DEFF Research Database (Denmark)

Veluri, Badrinath; Jensen, Henrik Myhre

2013-01-01

Steady-state propagation of interface cracks close to three-dimensional corners has been analyzed. Attention was focused on modeling the shape of the interface crack front and calculating the critical stress for steady-state propagation of the crack. The crack propagation was investigated...... on the finite element method with iterative adjustment of the crack front to estimate the critical delamination stresses as a function of the fracture criterion and corner angles. The implication of the results on the delamination is discussed in terms of crack front profiles and the critical stresses...... for propagation and the angle of intersection of the crack front with the free edge....

Steady-state operation requirements of tokamak fusion reactor concepts

International Nuclear Information System (INIS)

Knobloch, A.F.

1991-06-01

In the last two decades tokamak conceptual reactor design studies have been deriving benefit from progressing plasma physics experiments, more depth in theory and increasing detail in technology and engineering. Recent full-scale reactor extrapolations such as the US ARIES-I and the EC Reference Reactor study provide information on rather advanced concepts that are called for when economic boundary conditions are imposed. The ITER international reactor design activity concentrated on defining the next step after the JET generation of experiments. For steady-state operation as required for any future commercial tokamak fusion power plants it is essential to have non-inductive current drive. The current drive power and other internal power requirements specific to magnetic confinement fusion have to be kept as low as possible in order to attain a competitive overall power conversion efficiency. A high plasma Q is primarily dependent on a high current drive efficiency. Since such conditions have not yet been attained in practice, the present situation and the degree of further development required are characterized. Such development and an appropriately designed next-step tokamak reactor make the gradual realization of high-Q operation appear feasible. (orig.)

Steady-state leaching of tritiated water from silica gel

DEFF Research Database (Denmark)

Das, H.A.; Hou, Xiaolin

2009-01-01

Aqueous leaching of tritium from silica gel, loaded by absorption of water vapor, makes part of reactor de-commissioning. It is found to follow the formulation of steady-state diffusion.......Aqueous leaching of tritium from silica gel, loaded by absorption of water vapor, makes part of reactor de-commissioning. It is found to follow the formulation of steady-state diffusion....

Modelling of arc jet plasma flow in transitional regime by Navier Stokes and state-to-state coupling

International Nuclear Information System (INIS)

Alexandrova, T.; Izrar, B.; Lino da Silva, M.; Dudeck, M.

2005-01-01

The combination of 2D Navier-Stokes and state-to-state approaches has been used to describe the air plasma flow in an arc-jet. The gas dynamic parameters were calculated in Navier-Stokes approximation in a steady state description without chemical reaction and vibrational exchanges. And then, the set of equations of vibrational level densities and atomic species densities was locally solved. Experimental validations have been performed

Quasi steady-state aerodynamic model development for race vehicle simulations

Science.gov (United States)

Mohrfeld-Halterman, J. A.; Uddin, M.

2016-01-01

Presented in this paper is a procedure to develop a high fidelity quasi steady-state aerodynamic model for use in race car vehicle dynamic simulations. Developed to fit quasi steady-state wind tunnel data, the aerodynamic model is regressed against three independent variables: front ground clearance, rear ride height, and yaw angle. An initial dual range model is presented and then further refined to reduce the model complexity while maintaining a high level of predictive accuracy. The model complexity reduction decreases the required amount of wind tunnel data thereby reducing wind tunnel testing time and cost. The quasi steady-state aerodynamic model for the pitch moment degree of freedom is systematically developed in this paper. This same procedure can be extended to the other five aerodynamic degrees of freedom to develop a complete six degree of freedom quasi steady-state aerodynamic model for any vehicle.

Anisotropic plasma with flows in tokamak: Steady state and stability

International Nuclear Information System (INIS)

Ilgisonis, V.I.

1996-01-01

An adequate description of equilibrium and stability of anisotropic plasma with macroscopic flows in tokamaks is presented. The Chew-Goldberger-Low (CGL) approximation is consistently used to analyze anisotropic plasma dynamics. The admissible structure of a stationary flow is found to be the same as in the ideal magnetohydrodynamics with isotropic pressure (MHD), which means an allowance for the same relabeling symmetry as in ideal MHD systems with toroidally nested magnetic surfaces. A generalization of the Grad-Shafranov equation for the case of anisotropic plasma with flows confined in the axisymmetric magnetic field is derived. A variational principle was obtained, which allows for a stability analysis of anisotropic pressure plasma with flows, and takes into account the conservation laws resulting from the relabeling symmetry. This principle covers the previous stability criteria for static CGL plasma and for ideal MHD flows in isotropic plasma as well. copyright 1996 American Institute of Physics

Assessing Quasi-Steady State in Evaporation of Sessile Drops by Diffusion Models

Science.gov (United States)

Martin, Cameron; Nguyen, Hoa; Kelly-Zion, Peter; Pursell, Chris

2017-11-01

The vapor distributions surrounding sessile drops of methanol are modeled as the solutions of the steady-state and transient diffusion equations using Matlab's PDE Toolbox. The goal is to determine how quickly the transient diffusive transport reaches its quasi-steady state as the droplet geometry is varied between a Weber's disc, a real droplet shape, and a spherical cap with matching thickness or contact angle. We assume that the only transport mechanism at work is diffusion. Quasi-steady state is defined using several metrics, such as differences between the transient and steady-state solutions, and change in the transient solution over time. Knowing the vapor distribution, the gradient is computed to evaluate the diffusive flux. The flux is integrated along the surface of a control volume surrounding the drop to obtain the net rate of diffusion out of the volume. Based on the differences between the transient and steady-state diffusive fluxes at the discrete points along the control-volume surface, the time to reach quasi-steady state evaporation is determined and is consistent with other proposed measurements. By varying the dimensions of the control volume, we can also assess what regimes have equivalent or different quasi-steady states for different droplet geometries. Petroleum Research Fund.

Existence of non-unique steady state solutions to the RMF current drive equations

Energy Technology Data Exchange (ETDEWEB)

Hugrass, W N [Flinders Univ. of South Australia, Bedford Park. School of Physical Sciences

1985-05-04

It is shown that the value of the d.c. current driven in a plasma cylinder by means of a rotating magnetic field (RMF) is not unique for R/delta >= 6 and eBsub(..omega..)/..nu..sub(ei)m approx.R/delta, where R is the radius of the plasma cylinder, delta is the classical skin depth, ..nu..sub(ei) is the electron-ion momentum transfer collision frequency, Bsub(..omega..) is the magnitude of the rotating magnetic field, e is the electron charge and m is the electron mass. This effect is predicted using three distinct approaches: (i) a steady state anaysis which ignores the second and higher harmonics of the fields and currents; (ii) a qualitative model which utilizes the analogy between the RMF current drive technique and the operation of the induction motor; (iii) a solution of the initial boundary value equations describing the RMF current drive in cylindrical plasmas.

Automatic plasma control in magnetic traps

International Nuclear Information System (INIS)

Samojlenko, Y.; Chuyanov, V.

1984-01-01

Hot plasma is essentially in thermodynamic non-steady state. Automatic plasma control basically means monitoring deviations from steady state and producing a suitable magnetic or electric field which brings the plasma back to its original state. Briefly described are two systems of automatic plasma control: control with a magnetic field using a negative impedance circuit, and control using an electric field. It appears that systems of automatic plasma stabilization will be an indispensable component of the fusion reactor and its possibilities will in many ways determine the reactor economy. (Ha)

Steady state and transient power handling in JET

International Nuclear Information System (INIS)

Matthews, G.F.

2002-01-01

Recent JET experiments and analysis have demonstrated the importance of edge collisionality for the physics of divertor power loading both during and between ELMs. Since collisionality decreases strongly with machine size, JET routinely operates in an ITER relevant regime which is difficult or impossible to access in smaller devices. This new understanding has enabled us to develop more physically justifiable scalings for static and transient power deposition in ITER and demonstrates a need for kinetic models when simulating edge behaviour in JET and ITER. Steady state power loading in ITER is likely to be within limits provided that the divertor plasma is kept in the high recycling or detached regime. Extrapolations of the typical type I ELMs found in JET to ITER highlight the importance of developing regimes characterised by small ELMs, if surface ablation is to be avoided. Disruptive power loads measured in the JET divertor appear far more benign than would be expected from current ITER assumptions. (author)

Fast-ion transport in qmin>2, high-β steady-state scenarios on DIII-D

International Nuclear Information System (INIS)

Holcomb, C. T.; Heidbrink, W. W.; Collins, C.; Ferron, J. R.; Van Zeeland, M. A.; Garofalo, A. M.; Bass, E. M.; Luce, T. C.; Pace, D. C.; Solomon, W. M.; Mueller, D.; Grierson, B.; Podesta, M.; Gong, X.; Ren, Q.; Park, J. M.; Kim, K.; Turco, F.

2015-01-01

Results from experiments on DIII-D [J. L. Luxon, Fusion Sci. Technol. 48, 828 (2005)] aimed at developing high β steady-state operating scenarios with high-q min confirm that fast-ion transport is a critical issue for advanced tokamak development using neutral beam injection current drive. In DIII-D, greater than 11 MW of neutral beam heating power is applied with the intent of maximizing β N and the noninductive current drive. However, in scenarios with q min >2 that target the typical range of q 95 = 5–7 used in next-step steady-state reactor models, Alfvén eigenmodes cause greater fast-ion transport than classical models predict. This enhanced transport reduces the absorbed neutral beam heating power and current drive and limits the achievable β N . In contrast, similar plasmas except with q min just above 1 have approximately classical fast-ion transport. Experiments that take q min >3 plasmas to higher β P with q 95 = 11–12 for testing long pulse operation exhibit regimes of better than expected thermal confinement. Compared to the standard high-q min scenario, the high β P cases have shorter slowing-down time and lower ∇β fast , and this reduces the drive for Alfvénic modes, yielding nearly classical fast-ion transport, high values of normalized confinement, β N , and noninductive current fraction. These results suggest DIII-D might obtain better performance in lower-q 95 , high-q min plasmas using broader neutral beam heating profiles and increased direct electron heating power to lower the drive for Alfvén eigenmodes

Progress towards Steady State at Low Aspect Ratio on the National Spherical Torus Experiment (NSTX)

International Nuclear Information System (INIS)

Gates, D.A.; Menard, J.; Maingi, R.; Kaye, S.; Sabbagh, S.A.; Diem, S.; Wilson, J.R.; Bell, M.G.; Bell, R.E.; Ferron, J.; Fredrickson, E.D.; Kessel, C.E.; LeBlanc, B.P.; Levinton, F.; Manickam, J.; Mueller, D.; Raman, R.; Stevenson, T.; Stutman, D.; Taylor, G.; Tritz, K.; Yu, H.

2007-01-01

Modifications to the plasma control capabilities and poloidal field coils of the National Spherical Torus Experiment (NSTX) have enabled a significant enhancement in shaping capability which has led to the transient achievement of a record shape factor (S (triple b ond) q 95 (I p /aB t )) of ∼ 41 (MA m -1 T -1 ) simultaneous with a record plasma elongation of κ (triple b ond) b/a ∼ 3. This result was obtained using isoflux control and real-time equilibrium reconstruction. Achieving high shape factor together with tolerable divertor loading is an important result for future ST burning plasma experiments as exemplified by studies for future ST reactor concepts, as well as neutron producing devices, which rely on achieving high shape factors in order to achieve steady state operation while maintaining MHD stability. Statistical evidence is presented which demonstrates the expected correlation between increased shaping and improved plasma performance.

A new perspective on steady-state cosmology: from Einstein to Hoyle

OpenAIRE

O'Raifeartaigh, Cormac; Mitton, Simon

2015-01-01

We recently reported the discovery of an unpublished manuscript by Albert Einstein in which he attempted a 'steady-state' model of the universe, i.e., a cosmic model in which the expanding universe remains essentially unchanged due to a continuous formation of matter from empty space. The manuscript was apparently written in early 1931, many years before the steady-state models of Fred Hoyle, Hermann Bondi and Thomas Gold. We compare Einstein’s steady-state cosmology with that of Hoyle, Bondi...

Identification of Plasma Parameters and Optimization of Magnetic Sensors in the Superconducting Steady-State Tokamak-1 Using Neural Networks

International Nuclear Information System (INIS)

Sengupta, A.; Ranjan, P.

2001-01-01

In this paper, we examine the possibility of using a multilayered feedforward neural network to extract tokamak plasma parameters from magnetic measurements as an improvement over the traditional methodology of function parametrization. It is also used to optimize the number and locations of the magnetic diagnostics designed for the tokamak. This work has been undertaken with the specific purpose of application of the neural network technique to the newly designed (and currently under fabrication) Superconducting Steady-State Tokamak-1 (SST-1). The magnetic measurements will be utilized to achieve real-time control of plasma shape, position, and some global profiles. A trained neural network is tested, and the results of parameter identification are compared with function parametrization. Both techniques appear well suited for the purpose, but a definite improvement with neural networks is observed. Although simulated measurements are used in this work, confidence regarding the network performance with actual experimental data is ensured by testing the network's noise tolerance with Gaussian noise of up to 10%. Finally, three possible methods of ranking the diagnostics in decreasing order of importance are suggested, and the neural network is used to optimize the number and locations of the magnetic sensors designed for SST-1. The results from the three methods are compared with one another and also with function parametrization. Magnetic probes within the plasma-facing side of the outboard limiter have been ranked high. Function parametrization and one of the neural network methods show a distinct tendency to favor the probes in the remote regions of the vacuum vessel, proving the importance of redundancy. Fault tolerance of the optimized network is tested. The results obtained should, in the long run, help in the decision regarding the final effective set of magnetic diagnostics to be used in SST-1 for reconstruction of the control parameters

Oscillatory processes in plasma

International Nuclear Information System (INIS)

Gallin, E.

1980-01-01

The oscillatory process play an important part in plasma evolution, In hot plasma in particular, the interactions between the oscillation modes are preponderant in relation to the binary collisions between particles. The nonlineary interactions between collective plasma oscillations can generate, in this case, a non-balanced steady state of plasma (steady turbulence). The paper elucidates some aspects of the oscillatory phenomena which contribute to the plasma state evolution, especially of hot plasma. A major part of the paper is devoted to the study of parametric instabilities in plasma and their role in increasing the temperature of plasma components (electrons, ions). Both parametric instabilities in plasma in the vicinity of thermodynamic balance and parametric processes is steady turbulent plasma are analysed - in relation to additional heating of hot plasma. An important result of the thesis refers to the drowing-up of a non-lineary interaction model between the oscillation modes in turbulent plasma, being responsible for the electromagnetic radiation in hot plasma. On the basis of the model suggested in the paper the existence of a low frequency radiative mode in hot plasma in a turbulent state, can be demonstrated. Its frequency could be even lower than plasma frequency in the field of long waves be even lower than plasma frequency in the field of long waves. Such a radiative mode was detected experimentally in focussed plasma installations. (author)

Waves and Instabilities in Steady-State High-Beta Plasmas

Science.gov (United States)

1976-07-01

us working on magnetospheric related problems. Several groups are now constructing identical devices including Y. Nishida of Utsunomiya University...and other satellites operate in the magnetospheric plasma environment at the geosynchronous orbit (%6.6 earth radii). Arc- related deterioration of the...carefully 16 - 3diagnosed device produces a plasma of density n 3 x 10 cm and temperature Te = Ti W 1.6eV. (3) Heat Flow Measurements in a Laser-Heated

Toroidal visco-resistive magnetohydrodynamic steady states contain vortices

International Nuclear Information System (INIS)

Bates, J.W.; Montgomery, D.C.

1998-01-01

Poloidal velocity fields seem to be a fundamental feature of resistive toroidal magnetohydrodynamic (MHD) steady states. They are a consequence of force balance in toroidal geometry, do not require any kind of instability, and disappear in the open-quotes straight cylinderclose quotes (infinite aspect ratio) limit. If a current density j results from an axisymmetric toroidal electric field that is irrotational inside a torus, it leads to a magnetic field B such that ∇x(jxB) is nonvanishing, so that the Lorentz force cannot be balanced by the gradient of any scalar pressure in the equation of motion. In a steady state, finite poloidal velocity fields and toroidal vorticity must exist. Their calculation is difficult, but explicit solutions can be found in the limit of low Reynolds number. Here, existing calculations are generalized to the more realistic case of no-slip boundary conditions on the velocity field and a circular toroidal cross section. The results of this paper strongly suggest that discussions of confined steady states in toroidal MHD must include flows from the outset. copyright 1998 American Institute of Physics

Transient and steady-state currents in epoxy resin

International Nuclear Information System (INIS)

Guillermin, Christophe; Rain, Pascal; Rowe, Stephen W

2006-01-01

Charging and discharging currents have been measured in a diglycidyl ether of bisphenol-A epoxy resin with and without silica fillers, below and above its glass transition temperature T g = 65 deg. C. Both transient and steady-state current densities have been analysed. The average applied fields ranged from 3 to 35 kV mm -1 with a sample thickness of 0.5 mm. Above T g , transient currents suggested a phenomenon of charge injection forming trapped space charges even at low fields. Steady-state currents confirmed that the behaviour was not Ohmic and suggested Schottky-type injection. Below T g , the current is not controlled by the metal-dielectric interface but by the conduction in the volume: the current is Ohmic at low fields and both transient and steady-state currents suggest a phenomenon of space-charge limited currents at high fields. The field threshold is similar in the filler-free and the filled resin. Values in the range 12-17 kV mm -1 have been measured

Transient and steady-state currents in epoxy resin

Energy Technology Data Exchange (ETDEWEB)

Guillermin, Christophe [Schneider Electric Industries S.A.S., 37 quai Paul-Louis Merlin, 38050 Grenoble Cedex 9 (France); Rain, Pascal [Laboratoire d' Electrostatique et de Materiaux Dielectriques (LEMD), CNRS, 25 avenue des Martyrs, 38042 Grenoble Cedex 9 (France); Rowe, Stephen W [Schneider Electric Industries S.A.S., 37 quai Paul-Louis Merlin, 38050 Grenoble Cedex 9 (France)

2006-02-07

Charging and discharging currents have been measured in a diglycidyl ether of bisphenol-A epoxy resin with and without silica fillers, below and above its glass transition temperature T{sub g} = 65 deg. C. Both transient and steady-state current densities have been analysed. The average applied fields ranged from 3 to 35 kV mm{sup -1} with a sample thickness of 0.5 mm. Above T{sub g}, transient currents suggested a phenomenon of charge injection forming trapped space charges even at low fields. Steady-state currents confirmed that the behaviour was not Ohmic and suggested Schottky-type injection. Below T{sub g}, the current is not controlled by the metal-dielectric interface but by the conduction in the volume: the current is Ohmic at low fields and both transient and steady-state currents suggest a phenomenon of space-charge limited currents at high fields. The field threshold is similar in the filler-free and the filled resin. Values in the range 12-17 kV mm{sup -1} have been measured.

Efficient steady-state solver for hierarchical quantum master equations

Science.gov (United States)

Zhang, Hou-Dao; Qiao, Qin; Xu, Rui-Xue; Zheng, Xiao; Yan, YiJing

2017-07-01

Steady states play pivotal roles in many equilibrium and non-equilibrium open system studies. Their accurate evaluations call for exact theories with rigorous treatment of system-bath interactions. Therein, the hierarchical equations-of-motion (HEOM) formalism is a nonperturbative and non-Markovian quantum dissipation theory, which can faithfully describe the dissipative dynamics and nonlinear response of open systems. Nevertheless, solving the steady states of open quantum systems via HEOM is often a challenging task, due to the vast number of dynamical quantities involved. In this work, we propose a self-consistent iteration approach that quickly solves the HEOM steady states. We demonstrate its high efficiency with accurate and fast evaluations of low-temperature thermal equilibrium of a model Fenna-Matthews-Olson pigment-protein complex. Numerically exact evaluation of thermal equilibrium Rényi entropies and stationary emission line shapes is presented with detailed discussion.

Heating and current drive requirements towards steady state operation in ITER

Energy Technology Data Exchange (ETDEWEB)

Poli, F. M.; Kessel, C. E.; Gorelenkova, M. [Princeton Plasma Physics Laboratory, Princeton, NJ 08543 (United States); Bonoli, P. T. [MIT Plasma Science and Fusion Center, Cambridge, MA 02139 (United States); Batchelor, D. B. [Oak Ridge National Laboratory, Oak Ridge, TN 37831-6169 (United States); Harvey, B.; Petrov, Y. [CompX, Box 2672, Del Mar, CA 92014 (United States)

2014-02-12

Steady state scenarios envisaged for ITER aim at optimizing the bootstrap current, while maintaining sufficient confinement and stability to provide the necessary fusion yield. Non-inductive scenarios will need to operate with Internal Transport Barriers (ITBs) in order to reach adequate fusion gain at typical currents of 9 MA. However, the large pressure gradients associated with ITBs in regions of weak or negative magnetic shear can be conducive to ideal MHD instabilities, reducing the no-wall limit. The E × B flow shear from toroidal plasma rotation is expected to be low in ITER, with a major role in the ITB dynamics being played by magnetic geometry. Combinations of H/CD sources that maintain weakly reversed magnetic shear profiles throughout the discharge are the focus of this work. Time-dependent transport simulations indicate that, with a trade-off of the EC equatorial and upper launcher, the formation and sustainment of quasi-steady state ITBs could be demonstrated in ITER with the baseline heating configuration. However, with proper constraints from peeling-ballooning theory on the pedestal width and height, the fusion gain and the maximum non-inductive current are below the ITER target. Upgrades of the heating and current drive system in ITER, like the use of Lower Hybrid current drive, could overcome these limitations, sustaining higher non-inductive current and confinement, more expanded ITBs which are ideal MHD stable.

Heating and current drive requirements towards steady state operation in ITER

Science.gov (United States)

Poli, F. M.; Bonoli, P. T.; Kessel, C. E.; Batchelor, D. B.; Gorelenkova, M.; Harvey, B.; Petrov, Y.

2014-02-01

Steady state scenarios envisaged for ITER aim at optimizing the bootstrap current, while maintaining sufficient confinement and stability to provide the necessary fusion yield. Non-inductive scenarios will need to operate with Internal Transport Barriers (ITBs) in order to reach adequate fusion gain at typical currents of 9 MA. However, the large pressure gradients associated with ITBs in regions of weak or negative magnetic shear can be conducive to ideal MHD instabilities, reducing the no-wall limit. The E × B flow shear from toroidal plasma rotation is expected to be low in ITER, with a major role in the ITB dynamics being played by magnetic geometry. Combinations of H/CD sources that maintain weakly reversed magnetic shear profiles throughout the discharge are the focus of this work. Time-dependent transport simulations indicate that, with a trade-off of the EC equatorial and upper launcher, the formation and sustainment of quasi-steady state ITBs could be demonstrated in ITER with the baseline heating configuration. However, with proper constraints from peeling-ballooning theory on the pedestal width and height, the fusion gain and the maximum non-inductive current are below the ITER target. Upgrades of the heating and current drive system in ITER, like the use of Lower Hybrid current drive, could overcome these limitations, sustaining higher non-inductive current and confinement, more expanded ITBs which are ideal MHD stable.

A steady-state axisymmetric toroidal system

International Nuclear Information System (INIS)

Hirano, K.

1984-01-01

Conditions for achieving a steady state in an axisymmetric toroidal system are studied with emphasis on a very-high-beta field-reversed configuration. The analysis is carried out for the electromotive force produced by the Ohkawa current that is induced by neutral-beam injection. It turns out that, since the perpendicular component of the current j-vectorsub(perpendicular) to the magnetic field can be generated automatically by the diamagnetic effect, only the parallel component j-vectorsub(parallel) must be driven by the electromotive force. The drive of j-vectorsub(parallel) generates shear in the field line so that the pure toroidal field on the magnetic axis is rotated towards the plasma boundary and matched to the external field lines. This matching condition determines the necessary amount of injection beam current and power. It is demonstrated that a very-high-beta field-reversed configuration requires only a small amount of current-driving beam power because almost all the toroidal current except that close to the magnetic axis is carried by the diamagnetic current due to high beta. A low-beta tokamak, on the other hand, needs very high current-driving power since most of the toroidal current is composed of j-vectorsub(parallel) which must be driven by the beam. (author)

Steady equilibrium of a cylindrically symmetric plasma sustained by fueling

International Nuclear Information System (INIS)

Tomita, Yukihiro; Momota, Hiromu

1993-01-01

By introducing a novel and natural method to obtain a steady equilibrium, it is shown that a pressure gradient produced by the particle injection or resultant diamagnetic current can sustain only an equilibrium of a diffused linear pinch. For an extremely elongated FRC where magnetic field vanishes at a certain point, a seed current is needed to sustain configuration in a steady state equilibrium. A directed flow of fusion produced protons forms a seed current and consequently it sustains a steady FRC equilibrium by fueling only once D- 3 He burning takes place. Effects of anomalous transports on the sustainment are discussed. (author)

Steady state flow evaluations for passive auxiliary feedwater system of APR

International Nuclear Information System (INIS)

Park, Jongha; Kim, Jaeyul; Seong, Hoje; Kang, Kyoungho

2012-01-01

This paper briefly introduces a methodology to evaluate steady state flow of APR+ Passive Auxiliary Feedwater System (PAFS). The PAFS is being developed as a safety grade passive system to completely replace the existing active Auxiliary Feedwater System (AFWS). Natural circulation cooling can be generally classified into the single-phase, two-phase, and boiling-condensation modes. The PAF is designed to be operated in a boiling-condensation natural circulation mode. The steady-state flow rate should be equal to the steady-state boiling/condensation rate determined by the steady-state energy and momentum balances in the PAFS. The determined steady-state flow rate can be used in the design optimization for the natural circulation loop of the PAFS through the steady-state momentum balance. Since the retarding force, which is to be balanced by the driving force in the natural circulation system design depends on the reliable evaluation of the success of a natural circulation system design depends on the reliable evaluation of the pressure loss coefficients. In PAFS, the core decay heat is released by natural circulation flow between the S G secondary side and the Passive Condensation Heat Exchanger (PCHX) that is immersed in the Passive Condensation Cooling Tank (PCCT). The PCCT is located on the top of Auxiliary building The driving force is determined by the difference between the S/G (heat Source) secondary water level and condensation liquid (heat sink) level. It will overcome retarding force at flowrate in the system, which is determined by vaporization and condensation of the steam which is generated at the S/G by the latent heat in system. In this study, the theoretical method to estimate the steady state flow rate in boiling-condensation natural circulation system is developed and compared with test results

Einstein's steady-state theory: an abandoned model of the cosmos

Science.gov (United States)

O'Raifeartaigh, Cormac; McCann, Brendan; Nahm, Werner; Mitton, Simon

2014-09-01

We present a translation and analysis of an unpublished manuscript by Albert Einstein in which he attempted to construct a `steady-state' model of the universe. The manuscript, which appears to have been written in early 1931, demonstrates that Einstein once explored a cosmic model in which the mean density of matter in an expanding universe is maintained constant by the continuous formation of matter from empty space. This model is very different to previously known Einsteinian models of the cosmos (both static and dynamic) but anticipates the later steady-state cosmology of Hoyle, Bondi and Gold in some ways. We find that Einstein's steady-state model contains a fundamental flaw and suggest that it was abandoned for this reason. We also suggest that he declined to explore a more sophisticated version because he found such theories rather contrived. The manuscript is of historical interest because it reveals that Einstein debated between steady-state and evolving models of the cosmos decades before a similar debate took place in the cosmological community.

Decomposition of toluene in a steady-state atmospheric-pressure glow discharge

International Nuclear Information System (INIS)

Trushkin, A. N.; Grushin, M. E.; Kochetov, I. V.; Trushkin, N. I.; Akishev, Yu. S.

2013-01-01

Results are presented from experimental studies of decomposition of toluene (C 6 H 5 CH 3 ) in a polluted air flow by means of a steady-state atmospheric pressure glow discharge at different water vapor contents in the working gas. The experimental results on the degree of C 6 H 5 CH 3 removal are compared with the results of computer simulations conducted in the framework of the developed kinetic model of plasma chemical decomposition of toluene in the N 2 : O 2 : H 2 O gas mixture. A substantial influence of the gas flow humidity on toluene decomposition in the atmospheric pressure glow discharge is demonstrated. The main mechanisms of the influence of humidity on C 6 H 5 CH 3 decomposition are determined. The existence of two stages in the process of toluene removal, which differ in their duration and the intensity of plasma chemical decomposition of C 6 H 5 CH 3 is established. Based on the results of computer simulations, the composition of the products of plasma chemical reactions at the output of the reactor is analyzed as a function of the specific energy deposition and gas flow humidity. The existence of a catalytic cycle in which hydroxyl radical OH acts a catalyst and which substantially accelerates the recombination of oxygen atoms and suppression of ozone generation when the plasma-forming gas contains water vapor is established.

Decomposition of toluene in a steady-state atmospheric-pressure glow discharge

Science.gov (United States)

Trushkin, A. N.; Grushin, M. E.; Kochetov, I. V.; Trushkin, N. I.; Akishev, Yu. S.

2013-02-01

Results are presented from experimental studies of decomposition of toluene (C6H5CH3) in a polluted air flow by means of a steady-state atmospheric pressure glow discharge at different water vapor contents in the working gas. The experimental results on the degree of C6H5CH3 removal are compared with the results of computer simulations conducted in the framework of the developed kinetic model of plasma chemical decomposition of toluene in the N2: O2: H2O gas mixture. A substantial influence of the gas flow humidity on toluene decomposition in the atmospheric pressure glow discharge is demonstrated. The main mechanisms of the influence of humidity on C6H5CH3 decomposition are determined. The existence of two stages in the process of toluene removal, which differ in their duration and the intensity of plasma chemical decomposition of C6H5CH3 is established. Based on the results of computer simulations, the composition of the products of plasma chemical reactions at the output of the reactor is analyzed as a function of the specific energy deposition and gas flow humidity. The existence of a catalytic cycle in which hydroxyl radical OH acts a catalyst and which substantially accelerates the recombination of oxygen atoms and suppression of ozone generation when the plasma-forming gas contains water vapor is established.

Method and apparatus for steady-state magnetic measurement of poloidal magnetic field near a tokamak plasma

Science.gov (United States)

Woolley, Robert D.

1998-01-01

A method and apparatus for the steady-state measurement of poloidal magnetic field near a tokamak plasma, where the tokamak is configured with respect to a cylindrical coordinate system having z, phi (toroidal), and r axes. The method is based on combining the two magnetic field principles of induction and torque. The apparatus includes a rotor assembly having a pair of inductive magnetic field pickup coils which are concentrically mounted, orthogonally oriented in the r and z directions, and coupled to remotely located electronics which include electronic integrators for determining magnetic field changes. The rotor assembly includes an axle oriented in the toroidal direction, with the axle mounted on pivot support brackets which in turn are mounted on a baseplate. First and second springs are located between the baseplate and the rotor assembly restricting rotation of the rotor assembly about its axle, the second spring providing a constant tensile preload in the first spring. A strain gauge is mounted on the first spring, and electronic means to continually monitor strain gauge resistance variations is provided. Electronic means for providing a known current pulse waveform to be periodically injected into each coil to create a time-varying torque on the rotor assembly in the toroidal direction causes mechanical strain variations proportional to the torque in the mounting means and springs so that strain gauge measurement of the variation provides periodic magnetic field measurements independent of the magnetic field measured by the electronic integrators.

Steady-state exhaust of helium ash in the W-shaped divertor of JT-60U

International Nuclear Information System (INIS)

Sakasai, A.; Takenaga, H.; Hosogane, N.

2001-01-01

By injecting a neutral beam of 60 keV helium (He) atoms as central fueling of helium into the ELMy H-mode plasmas, helium exhaust has been studied in the W-shaped pumped divertor on JT-60U. Efficient He exhaust was realized by He pumping using argon frosted cryopumps in the JT-60U new divertor. In steady state, good He exhaust capability (τ He */τ E =4 and high enrichment factor, where τ He * is a global particle confinement time of helium and τ E is the energy confinement time) was successfully demonstrated in attached ELMy H-mode plasmas. Good He exhaust capability was also obtained in detached ELMy H-mode plasmas, which was comparable to one in attached plasmas. This result of the helium exhaust is sufficient to support a detached divertor operation on ITER. After the divertor modification, helium exhaust in reversed shear plasmas has been investigated using He gas puff. Helium removal inside the internal transport barrier (ITB) is about two times as difficult as that outside the ITB in reversed shear discharges. (author)

Analysis of the steady state hydraulic behaviour of the ITER blanket cooling system

Energy Technology Data Exchange (ETDEWEB)

Di Maio, P.A., E-mail: pietroalessandro.dimaio@unipa.it [Dipartimento di Energia, Ingegneria dell’Informazione e Modelli Matematici, Università di Palermo, Viale delle Scienze, 90128 Palermo (Italy); Dell’Orco, G.; Furmanek, A. [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St Paul Lez Durance Cedex (France); Garitta, S. [Dipartimento di Energia, Ingegneria dell’Informazione e Modelli Matematici, Università di Palermo, Viale delle Scienze, 90128 Palermo (Italy); Merola, M.; Mitteau, R.; Raffray, R. [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St Paul Lez Durance Cedex (France); Spagnuolo, G.A.; Vallone, E. [Dipartimento di Energia, Ingegneria dell’Informazione e Modelli Matematici, Università di Palermo, Viale delle Scienze, 90128 Palermo (Italy)

2015-10-15

Highlights: • Nominal steady state hydraulic behaviour of ITER blanket standard sector cooling system has been investigated. • Numerical simulations have been run adopting a qualified thermal-hydraulic system code. • Hydraulic characteristic functions and coolant mass flow rates, velocities and pressure drops have been assessed. • Most of the considered circuits are able to effectively cool blanket modules, meeting ITER requirements. - Abstract: The blanket system is the ITER reactor component devoted to providing a physical boundary for plasma transients and contributing to thermal and nuclear shielding of vacuum vessel, magnets and external components. It is expected to be subjected to significant heat loads under nominal conditions and its cooling system has to ensure an adequate cooling, preventing any risk of critical heat flux occurrence while complying with pressure drop limits. At the University of Palermo a study has been performed, in cooperation with the ITER Organization, to investigate the steady state hydraulic behaviour of the ITER blanket standard sector cooling system. A theoretical–computational approach based on the finite volume method has been followed, adopting the RELAP5 system code. Finite volume models of the most critical blanket cooling circuits have been set-up, realistically simulating the coolant flow domain. The steady state hydraulic behaviour of each cooling circuit has been investigated, determining its hydraulic characteristic function and assessing the spatial distribution of coolant mass flow rates, velocities and pressure drops under reference nominal conditions. Results obtained have indicated that the investigated cooling circuits are able to provide an effective cooling to blanket modules, generally meeting ITER requirements in term of pressure drop and velocity distribution, except for a couple of circuits that are being revised.

Steady-state models in electrophoresis: from isotachophoresis to capillary zone electrophoresis

NARCIS (Netherlands)

Beckers, J.L.

1995-01-01

Although all electrophoretic techniques are closely allied and controlled by the same rules, we often distinguish between steady-state and dynamic models in the modeling of electrophoretic processes, whereby steady-state models are applied for isotachophoresis (ITP) and dynamic models are applied

Wave-driver options for low-aspect-ratio steady-state tokamak reactors

International Nuclear Information System (INIS)

Ehst, D.A.

1981-02-01

Low aspect ratio designs are proposed for steady-state tokamak reactors. Benefits stem from reduced major radius and lessened stresses in the toroidal field coils, resulting in possible cost savings in the tokamak construction. In addition, a low aspect ratio (A = 2.6) permits the application of a bundle divertor capable of diverting 3-T fields to a power reactor using STARFIRE technology. Such a low aspect ratio is possible with the elimination of poloidal field coils in the central hole of the tokamak, which implies a need for noninductive current drive. Several plasma waves are considered for this application, and it appears likely that a candidate can be found which reduces the electric power for current maintenance to an acceptable value

X-Ray Spectral Analysis of the Steady States of GRS1915+105

Science.gov (United States)

Peris, Charith S.; Remillard, Ronald A.; Steiner, James F.; Vrtilek, Saeqa D.; Varnière, Peggy; Rodriguez, Jerome; Pooley, Guy

2016-05-01

We report on the X-ray spectral behavior within the steady states of GRS1915+105. Our work is based on the full data set of the source obtained using the Proportional Counter Array (PCA) on the Rossi X-ray Timing Explorer (RXTE) and 15 GHz radio data obtained using the Ryle Telescope. The steady observations within the X-ray data set naturally separated into two regions in the color-color diagram and we refer to these regions as steady-soft and steady-hard. GRS1915+105 displays significant curvature in the coronal component in both the soft and hard data within the RXTE/PCA bandpass. A majority of the steady-soft observations displays a roughly constant inner disk radius ({R}{{in}}), while the steady-hard observations display an evolving disk truncation which is correlated to the mass accretion rate through the disk. The disk flux and coronal flux are strongly correlated in steady-hard observations and very weakly correlated in the steady-soft observations. Within the steady-hard observations, we observe two particular circumstances when there are correlations between the coronal X-ray flux and the radio flux with log slopes η ˜ 0.68+/- 0.35 and η ˜ 1.12+/- 0.13. They are consistent with the upper and lower tracks of Gallo et al. (2012), respectively. A comparison of the model parameters to the state definitions shows that almost all of the steady-soft observations match the criteria of either a thermal or steep power-law state, while a large portion of the steady-hard observations match the hard-state criteria when the disk fraction constraint is neglected.

Tungsten dust remobilization under steady-state and transient plasma conditions.

Czech Academy of Sciences Publication Activity Database

Ratynskaia, S.; Tolias, P.; De Angeli, M.; Weinzettl, Vladimír; Matějíček, Jiří; Bykov, I.; Rudakov, D.L.; Vignitchouk, L.; Thorén, E.; Riva, G.; Ripamonti, D.; Morgan, T.; Pánek, Radomír; De Temmerman, G.

2017-01-01

Roč. 12, August (2017), s. 569-574 ISSN 2352-1791. [PSI 2016 - 22nd International Conference on Plasma Surface Interactions in Controlled Fusion Devices/22./. Roma, 30.05.2016-03.06.2016] R&D Projects: GA ČR(CZ) GA14-12837S; GA MŠk(CZ) LM2015045 EU Projects: European Commission(XE) 633053 - EUROfusion Institutional support: RVO:61389021 Keywords : Tungsten * Dust * Remobilization * Tokamak Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) http://www.sciencedirect.com/science/article/pii/S2352179116301168

Effect of the poloidal current from the classical diffusion in the steady-state neo-classical transport

International Nuclear Information System (INIS)

Igna Junior, A.D.

1984-01-01

The relevant parameters of two steady-state models of a plasma column, in fusion regime, were analyzed for an ideal Tokamak. The neo-classical transport theory was considered in the banana regime and in the Pfirsch-Schlueter regime. The first model proposes a correction in the numerical coefficients of the transport equations. In the other one, a poloidal current from Pfirsch-Schlueter classical diffusion is considered aiming to satisfy the pressure balance. (M.C.K.) [pt

Plasma startup patterns in tokamak reactors

International Nuclear Information System (INIS)

Maki, Koichi; Tone, Tatsuzo.

1983-01-01

Plasma startup patterns are studied from the viewpoint of net power loss represented by the total power loss less the α-particle heating power. The existence is shown of a critical temperature of plasma at which the net power loss becomes independent of plasma density. Observations are made which indicate that the net power loss decreases with lowering plasma density in the range below the critical temperature and vice versa, whether governed by empirical or trapped-ion scaling laws. A startup pattern is presented which minimizes the net power loss during startup, and which prescribes that: (1) The plasma density should be kept as low as possible until the plasma is heated up to the critical temperature; (2) thereafter, the plasma density should be increased to its steady state value while retaining the critical temperature; and (3) finally, with the density kept constant, the temperature should be further raised to its steady state value. The net power loss at critical temperature represents the lower limit of heating power required to bring the plasma to steady state in tokamak reactors. (author)

Basin stability measure of different steady states in coupled oscillators

Science.gov (United States)

Rakshit, Sarbendu; Bera, Bidesh K.; Majhi, Soumen; Hens, Chittaranjan; Ghosh, Dibakar

2017-04-01

In this report, we investigate the stabilization of saddle fixed points in coupled oscillators where individual oscillators exhibit the saddle fixed points. The coupled oscillators may have two structurally different types of suppressed states, namely amplitude death and oscillation death. The stabilization of saddle equilibrium point refers to the amplitude death state where oscillations are ceased and all the oscillators converge to the single stable steady state via inverse pitchfork bifurcation. Due to multistability features of oscillation death states, linear stability theory fails to analyze the stability of such states analytically, so we quantify all the states by basin stability measurement which is an universal nonlocal nonlinear concept and it interplays with the volume of basins of attractions. We also observe multi-clustered oscillation death states in a random network and measure them using basin stability framework. To explore such phenomena we choose a network of coupled Duffing-Holmes and Lorenz oscillators which are interacting through mean-field coupling. We investigate how basin stability for different steady states depends on mean-field density and coupling strength. We also analytically derive stability conditions for different steady states and confirm by rigorous bifurcation analysis.

Molecular control of steady-state dendritic cell maturation and immune homeostasis.

Science.gov (United States)

Hammer, Gianna Elena; Ma, Averil

2013-01-01

Dendritic cells (DCs) are specialized sentinels responsible for coordinating adaptive immunity. This function is dependent upon coupled sensitivity to environmental signs of inflammation and infection to cellular maturation-the programmed alteration of DC phenotype and function to enhance immune cell activation. Although DCs are thus well equipped to respond to pathogens, maturation triggers are not unique to infection. Given that immune cells are exquisitely sensitive to the biological functions of DCs, we now appreciate that multiple layers of suppression are required to restrict the environmental sensitivity, cellular maturation, and even life span of DCs to prevent aberrant immune activation during the steady state. At the same time, steady-state DCs are not quiescent but rather perform key functions that support homeostasis of numerous cell types. Here we review these functions and molecular mechanisms of suppression that control steady-state DC maturation. Corruption of these steady-state operatives has diverse immunological consequences and pinpoints DCs as potent drivers of autoimmune and inflammatory disease.

The role of genetic variants in CYP2C8, LPIN1, PPARGC1A and PPARγ on the trough steady-state plasma concentrations of rosiglitazone and on glycosylated haemoglobin A1c in type 2 diabetes

DEFF Research Database (Denmark)

Stage, Tore B; Christensen, Mette M H; Feddersen, Søren

2013-01-01

OBJECTIVE: The aim of this study was to examine the effect of single nucleotide polymorphisms in CYP2C8, LPIN1, PPARGC1A and PPARγ on rosiglitazone's (i) trough steady-state plasma concentration (C(ss,min)), (ii) on glycosylated haemoglobin A1c (HbA1c) and (iii) the risk of developing adverse eve...

Dark Entangled Steady States of Interacting Rydberg Atoms

DEFF Research Database (Denmark)

Dasari, Durga; Mølmer, Klaus

2013-01-01

their short-lived excited states lead to rapid, dissipative formation of an entangled steady state. We show that for a wide range of physical parameters, this entangled state is formed on a time scale given by the strengths of coherent Raman and Rabi fields applied to the atoms, while it is only weakly...

Tailored parameter optimization methods for ordinary differential equation models with steady-state constraints.

Science.gov (United States)

Fiedler, Anna; Raeth, Sebastian; Theis, Fabian J; Hausser, Angelika; Hasenauer, Jan

2016-08-22

Ordinary differential equation (ODE) models are widely used to describe (bio-)chemical and biological processes. To enhance the predictive power of these models, their unknown parameters are estimated from experimental data. These experimental data are mostly collected in perturbation experiments, in which the processes are pushed out of steady state by applying a stimulus. The information that the initial condition is a steady state of the unperturbed process provides valuable information, as it restricts the dynamics of the process and thereby the parameters. However, implementing steady-state constraints in the optimization often results in convergence problems. In this manuscript, we propose two new methods for solving optimization problems with steady-state constraints. The first method exploits ideas from optimization algorithms on manifolds and introduces a retraction operator, essentially reducing the dimension of the optimization problem. The second method is based on the continuous analogue of the optimization problem. This continuous analogue is an ODE whose equilibrium points are the optima of the constrained optimization problem. This equivalence enables the use of adaptive numerical methods for solving optimization problems with steady-state constraints. Both methods are tailored to the problem structure and exploit the local geometry of the steady-state manifold and its stability properties. A parameterization of the steady-state manifold is not required. The efficiency and reliability of the proposed methods is evaluated using one toy example and two applications. The first application example uses published data while the second uses a novel dataset for Raf/MEK/ERK signaling. The proposed methods demonstrated better convergence properties than state-of-the-art methods employed in systems and computational biology. Furthermore, the average computation time per converged start is significantly lower. In addition to the theoretical results, the

A design of steady state fusion burner

International Nuclear Information System (INIS)

Hasegawa, Akira; Hatori, Tadatsugu; Itoh, Kimitaka; Ikuta, Takashi; Kodama, Yuji.

1975-01-01

We present a brief design of a steady state fusion burner in which a continuous burning of nuclear fuel may be achieved with output power of a gigawatt. The laser fusion is proposed to ignite the fuel. (auth.)

Steady State Dynamic Operating Behavior of Universal Motor

Directory of Open Access Journals (Sweden)

Muhammad Khan Burdi

2015-01-01

Full Text Available A detailed investigation of the universal motor is developed and used for various dynamic steady state and transient operating conditions of loads. In the investigation, output torque, motor speed, input current, input/output power and efficiency are computed, compared and analyzed for different loads. While this paper discusses the steady-state behavior of the universal motor, another companion paper, ?Transient dynamic behavior of universal motor?, will discuss its transient behavior in detail. A non-linear generalized electric machine model of the motor is considered for the analysis. This study was essential to investigate effect of output load on input current, power, speed and efficiency of the motor during operations. Previously such investigation is not known

Quasi-steady state natural convection in a tilted porous layer

Energy Technology Data Exchange (ETDEWEB)

Robillard, L.; Vasseur, P. (Ecole Polytechnique, Montreal, PQ (Canada))

1992-12-01

Natural convection in an inclined porous layer heated or cooled on one side, when its other walls are insulated, has several important engineering applications. These include solar power collection, regenerative heat exchangers, and high performance insulation for buildings and cold storage. Although the problem is basically an unsteady state one, it is known that if the heating (or cooling) process is maintained for a sufficiently long time, a quasi-steady state is approached. Quasi-steady state laminar natural convection in an inclined porous layer is studied analytically and numerically. On the basis of the Darcy-Oberbeck-Boussinesq equations, the problem is solved analytically in the limit of a thin porous layer heated on one side by a heat flux while the other boundaries are maintained adiabatic. For quasi-steady state, the flow and temperature fields overall heat transfer rates are obtained in terms of the controlling parameters and the onset of convection in a bottom heated horizantal system is predicted. It is also demonstrated for the case of a bottom-heated layer that for sufficiently small inclinations, multiple unicellular quasi-steady states exist, some of which are unstable. A numerical study of the same phenomenon, obtained by solving the complete set of governing equations, is conducted. Good agreement is found between the analytical predictions and the numerical simulation. 22 refs., 6 figs.

On Steady-State Tropical Cyclones

Science.gov (United States)

2014-01-01

Press: London. Marks FD, Black PG, Montgomery MT, Burpee RW. 2008. Structure of the eye and eyewall of Hurricane Hugo (1989). Mon. Weather Rev. 136: 1237... hurricanes ; tropical cyclones; typhoons; steady-state Received 18 April 2013; Revised 25 November 2013; Accepted 29 December 2013; Published online in Wiley...the concept of the ‘mature stage’ of a hurricane vortex. The definition of the ‘mature stage’ is commonly based on the time period in which the maximum

STEADY-STATE RELATIVISTIC STELLAR DYNAMICS AROUND A MASSIVE BLACK HOLE

Energy Technology Data Exchange (ETDEWEB)

Bar-Or, Ben; Alexander, Tal [Department of Particle Physics and Astrophysics, Weizmann Institute of Science, P.O. Box 26, Rehovot 76100 (Israel)

2016-04-01

A massive black hole (MBH) consumes stars whose orbits evolve into the small phase-space volume of unstable orbits, the “loss cone,” which take them into the MBH, or close enough to interact strongly with it. The resulting phenomena, e.g., tidal heating and disruption, binary capture and hyper-velocity star ejection, gravitational wave (GW) emission by inspiraling compact remnants, or hydrodynamical interactions with an accretion disk, can produce observable signatures and thereby reveal the MBH, affect its mass and spin evolution, test strong gravity, and probe stars and gas near the MBH. These continuous stellar loss and resupply processes shape the central stellar distribution. We investigate relativistic stellar dynamics near the loss cone of a non-spinning MBH in steady state, analytically and by Monte Carlo simulations of the diffusion of the orbital parameters. These take into account Newtonian mass precession due to enclosed stellar mass, in-plane precession due to general relativity, dissipation by GW, uncorrelated two-body relaxation, correlated resonant relaxation (RR), and adiabatic invariance due to secular precession, using a rigorously derived description of correlated post-Newtonian dynamics in the diffusion limit. We argue that general maximal entropy considerations strongly constrain the orbital diffusion in steady state, irrespective of the relaxation mechanism. We identify the exact phase-space separatrix between plunges and inspirals, and predict their steady-state rates. We derive the dependence of the rates on the mass of the MBH, show that the contribution of RR in steady state is small, and discuss special cases where unquenched RR in restricted volumes of phase-space may affect the steady state substantially.

Design optimization of JT-60SU for steady-state advanced operation

International Nuclear Information System (INIS)

Ushigusa, K.; Kurita, G.; Toyoshima, N.

2001-01-01

Design optimization of JT-60SU has been done for a steady-state advanced operation. A transport code simulation indicates that a fully non-inductive reversed shear plasmas with fractions of 70% of the bootstrap current and 30% of beam driven current can be sustained for more than 1,000s without any additional control. Investigations have been progressed on MHD stability, vertical positional stability and dynamics of the vertical displacement events. Significant progress has been achieved in the R and D of Nb 3 Al superconducting wires, low induced activation material (Fe-Cr-Mn steel). A design improvement has been made in TF coils to reduce a local stress on radial disk. Dynamic behaviors of the tokamak machine have been analyzed at emergency events such as an earthquake. (author)

40 CFR Appendix II to Part 1039 - Steady-State Duty Cycles

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Steady-State Duty Cycles II Appendix... Appendix II to Part 1039—Steady-State Duty Cycles (a) The following duty cycles apply for constant-speed engines: (1) The following duty cycle applies for discrete-mode testing: D2 mode number Engine speed...

Analysis of steady state creep of southeastern New Mexico bedded salt

International Nuclear Information System (INIS)

Herrmann, W.; Wawersik, W.R.; Lauson, H.S.

1980-03-01

Steady state creep rates have been obtained from a large suite of existing experimental creep data relating to bedded rock salt from the Salado formation of S.E. New Mexico. Experimental conditions covered an intermediate temperature range from 22 0 C to 200 0 C, and shear stresses from 1000 psi (7 MPa) to 6000 psi (31 MPa). An expression, based on a single diffusion controlled dislocation climb mechanism, has been found to fit the observed dependence of steady state creep rate on shear stress and temperature, yielding an activation energy of 12 kcal/mole (50 kJ/mole) and a stress exponent of 4.9. Multiple regression analysis revealed a dependence on stratigraphy, but no statistically significant dependence on pressure of specimen size. No consistent dilatancy or compaction associated with steady state creep was found, although some individual specimens dilated or compacted during creep. The steady state creep data were found to agree very well with creep data for both bedded and dome salt from a variety of other locations

Chlorine decay under steady and unsteady-state hydraulic conditions

DEFF Research Database (Denmark)

Stoianov, Ivan; Aisopou, Angeliki

2014-01-01

This paper describes a simulation framework for the scale-adaptive hydraulic and chlorine decay modelling under steady and unsteady-state flows. Bulk flow and pipe wall reaction coefficients are replaced with steady and unsteady-state reaction coefficients. An unsteady decay coefficient is defined...... which depends upon the absolute value of shear stress and the rate of change of shear stress for quasi-unsteady and unsteady-state flows. A preliminary experimental and analytical investigation was carried out in a water transmission main. The results were used to model monochloramine decay...... and these demonstrate that the dynamic hydraulic conditions have a significant impact on water quality deterioration and the rapid loss of disinfectant residual. © 2013 The Authors....

Steady-state heat transfer in an inverted U-tube steam generator

International Nuclear Information System (INIS)

Boucher, T.J.

1986-01-01

Experimental results are presented involving U-tube steam generator tube bundle local heat transfer and fluid conditions during steady-state, full-power operations performed at high temperatures and pressures with conditions typical of a pressurized water reactor (15.0 MPa primary pressure, 600 K hot-leg fluid temperatures, 6.2 MPa secondary pressure). The MOD-2C facility represents the state-of-the-art in measurement of tube local heat transfer data and average tube bundle secondary fluid density at several elevations, which allows an estimate of the axial heat transfer and void distributions during steady-state and transient operations. The method of heat transfer data reduction is presented and the heat flux, secondary convective heat transfer coefficient, and void fraction distributions are quantified for steady-state, full-power operations

40 CFR Appendix II to Part 1042 - Steady-State Duty Cycles

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Steady-State Duty Cycles II Appendix..., App. II Appendix II to Part 1042—Steady-State Duty Cycles (a) The following duty cycles apply as specified in § 1042.505(b)(1): (1) The following duty cycle applies for discrete-mode testing: E3 mode No...

Power exhaust and edge control in steady state Tore Supra plasma

International Nuclear Information System (INIS)

Mitteau, R.

2002-01-01

Tore Supra is operated since 2001 with a flat limiter which is designed for 10 MW/m 2 . The limiter is located in the bottom of the vacuum vessel. It was only partial in 2001, but it is now fully toroidal without poloidal leading edges. Part of the experimental campaign of 2001 was devoted to the physical as well as technological qualification of the limiter. For 4 MW injected, the limiter extracted 2.5 MW and heat flux densities reached 2.5 MW/m 2 . It is still modest compared to the design value, but nonetheless enables a comparison to the modelling as surface temperature increased locally to 400 deg C. Thermal steady state is reached in 5-8 seconds. The values of heat flux and the deposition pattern are in very good accordance with design simulations. The heat flux pattern is a combination of parallel and perpendicular flow components which are roughly of equal magnitude. Insights on the heat flux deposition pattern as well as on the tiles behaviour are given. Operation with such a large size high heat flux component sets renewed emphasis on issues such as feed back systems, active security, cooling parameter and in situ assessment of the elements. They are dealt with in the paper. (author)

Early insulin sensitivity after restrictive bariatric surgery, inconsistency between HOMA-IR and steady-state plasma glucose levels.

Science.gov (United States)

van Dielen, Francois M H; Nijhuis, Jeroen; Rensen, Sander S M; Schaper, Nicolaas C; Wiebolt, Janneke; Koks, Afra; Prakken, Fred J; Buurman, Wim A; Greve, Jan Willem M

2010-01-01

The low-grade inflammatory condition present in morbid obesity is thought to play a causative role in the pathophysiology of insulin resistance (IR). Bariatric surgery fails to improve this inflammatory condition during the first months after surgery. Considering the close relation between inflammation and IR, we conducted a study in which insulin sensitivity was measured during the first months after bariatric surgery. Different methods to measure IR shortly after bariatric surgery have given inconsistent data. For example, the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) levels have been reported to decrease rapidly after bariatric surgery, although clamp techniques have shown sustained insulin resistance. In the present study, we evaluated the use of steady-state plasma glucose (SSPG) levels to assess insulin sensitivity 2 months after bariatric surgery. Insulin sensitivity was measured using HOMA-IR and SSPG levels in 11 subjects before surgery and at 26% excess weight loss (approximately 2 months after restrictive bariatric surgery). The SSPG levels after 26% excess weight loss did not differ from the SSPG levels before surgery (14.3 +/- 5.4 versus 14.4 +/- 2.7 mmol/L). In contrast, the HOMA-IR values had decreased significantly (3.59 +/- 1.99 versus 2.09 +/- 1.02). During the first months after restrictive bariatric surgery, we observed a discrepancy between the HOMA-IR and SSPG levels. In contrast to the HOMA-IR values, the SSPG levels had not improved, which could be explained by the ongoing inflammatory state after bariatric surgery. These results suggest that during the first months after restrictive bariatric surgery, HOMA-IR might not be an adequate marker of insulin sensitivity. Copyright 2010 American Society for Metabolic and Bariatric Surgery. Published by Elsevier Inc. All rights reserved.

Emergence of advance waves in a steady-state universe

Energy Technology Data Exchange (ETDEWEB)

Hobart, R.H.

1979-10-01

In standard Wheeler-Feynman electrodynamics advanced waves from any source are absolutely canceled by the advanced waves from the absorber responding to that source. The present work shows this cancellation fails over cosmic distances in a steady-state universe. A test of the view proposed earlier, in a paper which assumed failure of cancellation ad hoc, that zero-point fluctuations of the electromagnetic field are such emergent advanced waves, is posed. The view entails anomalous slowing of spontaneous transition rates at longer emission wavelengths; available data go against this, furnishing additional argument against the suspect assumption that the universe is steady-state.

Emergence of advance waves in a steady-state universe

International Nuclear Information System (INIS)

Hobart, R.H.

1979-01-01

In standard Wheeler-Feynman electrodynamics advanced waves from any source are absolutely canceled by the advanced waves from the absorber responding to that source. The present work shows this cancellation fails over cosmic distances in a steady-state universe. A test of the view proposed earlier, in a paper which assumed failure of cancellation ad hoc, that zero-point fluctuations of the electromagnetic field are such emergent advanced waves, is posed. The view entails anomalous slowing of spontaneous transition rates at longer emission wavelengths; available data go against this, furnishing additional argument against the suspect assumption that the universe is steady-state

Mechanism for multiplicity of steady states with distinct cell concentration in continuous culture of mammalian cells.

Science.gov (United States)

Yongky, Andrew; Lee, Jongchan; Le, Tung; Mulukutla, Bhanu Chandra; Daoutidis, Prodromos; Hu, Wei-Shou

2015-07-01

Continuous culture for the production of biopharmaceutical proteins offers the possibility of steady state operations and thus more consistent product quality and increased productivity. Under some conditions, multiplicity of steady states has been observed in continuous cultures of mammalian cells, wherein with the same dilution rate and feed nutrient composition, steady states with very different cell and product concentrations may be reached. At those different steady states, cells may exhibit a high glycolysis flux with high lactate production and low cell concentration, or a low glycolysis flux with low lactate and high cell concentration. These different steady states, with different cell concentration, also have different productivity. Developing a mechanistic understanding of the occurrence of steady state multiplicity and devising a strategy to steer the culture toward the desired steady state is critical. We establish a multi-scale kinetic model that integrates a mechanistic intracellular metabolic model and cell growth model in a continuous bioreactor. We show that steady state multiplicity exists in a range of dilution rate in continuous culture as a result of the bistable behavior in glycolysis. The insights from the model were used to devise strategies to guide the culture to the desired steady state in the multiple steady state region. The model provides a guideline principle in the design of continuous culture processes of mammalian cells. © 2015 Wiley Periodicals, Inc.

Recent developments towards steady state physics and technology of tokamaks in Cadarache

International Nuclear Information System (INIS)

Jacquinot, J.G.

2002-01-01

Recently, Tore Supra has undergone a total change of internal components in order to upgrade the heat extraction capability to 25 MW for 1000 s, and address long pulse operation of a tokamak at a level of power density owing through the separatrix relevant for next step. The present paper will both give an overview of the experimental results obtained during the last campaigns and highlight the related technology developments: industrial realisation and tests with plasma of about 600 actively cooled plasma limiter components, new experimental results concerning heating and current drive systems (ECRH, ICRH, LHCD), injection of matter for long pulses (supersonic injection, high repetition rate pellet injection), stability and control of high confinement steady-state discharges sustained by the LH wave, theoretical and experimental investigations of electron heat transport. Highlights of technology developments directly applicable to ITER are also presented. Finally, a brief account is given of the European studies for validating Cadarache as a possible site for ITER, concluding that all ITER technical site requests are fully met. (author)

Customized Steady-State Constraints for Parameter Estimation in Non-Linear Ordinary Differential Equation Models.

Science.gov (United States)

Rosenblatt, Marcus; Timmer, Jens; Kaschek, Daniel

2016-01-01

Ordinary differential equation models have become a wide-spread approach to analyze dynamical systems and understand underlying mechanisms. Model parameters are often unknown and have to be estimated from experimental data, e.g., by maximum-likelihood estimation. In particular, models of biological systems contain a large number of parameters. To reduce the dimensionality of the parameter space, steady-state information is incorporated in the parameter estimation process. For non-linear models, analytical steady-state calculation typically leads to higher-order polynomial equations for which no closed-form solutions can be obtained. This can be circumvented by solving the steady-state equations for kinetic parameters, which results in a linear equation system with comparatively simple solutions. At the same time multiplicity of steady-state solutions is avoided, which otherwise is problematic for optimization. When solved for kinetic parameters, however, steady-state constraints tend to become negative for particular model specifications, thus, generating new types of optimization problems. Here, we present an algorithm based on graph theory that derives non-negative, analytical steady-state expressions by stepwise removal of cyclic dependencies between dynamical variables. The algorithm avoids multiple steady-state solutions by construction. We show that our method is applicable to most common classes of biochemical reaction networks containing inhibition terms, mass-action and Hill-type kinetic equations. Comparing the performance of parameter estimation for different analytical and numerical methods of incorporating steady-state information, we show that our approach is especially well-tailored to guarantee a high success rate of optimization.

Diagnostics development for steady state operation of the stellarator wendelstein 7-x

Energy Technology Data Exchange (ETDEWEB)

Burhenn, R.; Baldzuhn, J.; Dreier, H.; Endler, M.; Jimenez-Gomez, R.; Grosser, K.; Hartfuss, H.J.; Hildebrandt, D.; Hirsch, M.; Koenig, R.; Kornejew, P.; Krychowiak, M.; Laqua, H.P.; Laux, M.; Oosterbeek, J.W.; Pasch, E.; Schneider, W.; Thomsen, H.; Weller, A.; Werner, A.; Wolf, R.; Zhang, D. [Max-Planck-Institute fuer Plasmaphysik, EURATOM Association, D-17491, Greifswald (Germany); Biel, W. [Institut fuer Energieforschung - Plasmaphysik, Forschungszentrum Juelich GmbH, EURATOM Association, Trilateral Euregio Cluster, D-52425 Juelich (Germany)

2011-03-15

The gain in experience with long-pulse operation under fusion relevant plasma conditions is an important step towards successful sustainment of future steady state reactor plasmas. The stellarator Wendelstein 7-X (W7-X) [1], presently being under construction, is already equipped with a superconducting coil system and principally capable of quasi-continuous operation. Like other long pulse devices, W7-X is faced with new enhanced technical requirements which have to be met by plasma facing components as well as the diagnostic systems in general. Water-cooled windows were qualified up to 60 kW/m{sup 2} thermal load, and shutters against evaporation of sensitive elements outside the attended time of the diagnostic as well as for baseline control had been developed. Shielding of in-vessel components against damage by absorption of microwave stray radiation originating from the heating systems appears to be one of the most challenging tasks. Experiments using a microwave test chamber identify critical materials and approved the necessity for careful shielding of both, sensitive diagnostics and cables. Spectroscopic systems for monitoring the impurity content and divertor load as well as for robust density measurement are presented (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Characterization of electron states in dense plasmas and its use in atomic kinetics modeling

International Nuclear Information System (INIS)

Fisher, D.V.; Maron, Y.

2003-01-01

We describe a self-consistent statistical approach to account for plasma density effects in collisional-radiative kinetics. The approach is based on the characterization of three distinct types of electron states, namely, bound, collectivized, and free, and on the formalism of the effective statistical weights (ESW) of the bound states. The present approach accounts for individual and collective effects of the surrounding electrons and ions on atomic (ionic) electron states. High-accuracy expressions for the ESWs of bound states have been derived. The notions of ionization stage population, free electron density, and rate coefficient are redefined in accordance with the present characterization scheme. The modified expressions for the probabilities of electron-impact induced transitions as well as spontaneous and induced radiative transitions are then obtained. The influence of collectivized states on a dense plasma ionization composition is demonstrated to be strong. Examples of calculated ESWs and populations of ionic quantum states for steady state and transient plasmas are given

Overview of JT-60U progress towards steady-state advanced tokamak

International Nuclear Information System (INIS)

Ide, S.

2005-01-01

Recent experimental results on steady state advanced tokamak (AT) research on JT-60U are presented with emphasis on longer time scale in comparison with characteristics time scales in plasmas. Towards this, modification on control in operation, heating and diagnostics systems have been done. As the results, ∼ 60 s I p flat top and an ∼ 30 s H-mode are obtained. The long pulse modification has opened a door into a new domain for JT-60U. The high normalized beta (β N ) of 2.3 is maintained for 22.3 s and 2.5 for 16.5 s in a high β p H-mode plasma. A standard ELMy H-mode plasma is also extended and change in wall recycling in such a longer time scale has been unveiled. Development and investigation of plasmas relevant to AT operation has been continued in former 15 s discharges as well in which higherNB power (≤ 10 s) is available. Higher β N ∼ 3 is maintained for 6.2 s in high β p H-mode plasmas. High bootstrap current fraction (f BS ) of ∼ 75% is sustained for 7.4 s in an RS plasma. On NTM suppression by localized ECCD, ECRF injection preceding the mode saturation is found to be more effective to suppress the mode with less power compared to the injection after the mode saturated. The domain of the NTM suppression experiments is extended to the high β N regime, and effectiveness of m/n=3/2 mode suppression by ECCD is demonstrated at β N ∼ 2.5-3. Genuine center-solenoid less tokamak plasma start up is demonstrated. In a current hole region, it is shown that no scheme drives a current in any direction. Detailed measurement in both spatial and energy spaces of energetic ions showed dynamic change in the energetic ion profile at collective instabilities. Impact of toroidal plasma rotation on ELM behaviors is clarified in grassy ELM and QH domains. (author)

Steady-state Operational Characteristics of Ghana Research ...

African Journals Online (AJOL)

Steady state operational characteristics of the 30 kW tank-in-pool type reactor named Ghana Research Reactor-1 were investigated after a successful on-site zero power critical experiments. The steadystate operational character-istics determined were the thermal neutron fluxes, maximum period of operation at nominal ...

Evidence for forcing-dependent steady states in a turbulent swirling flow.

Science.gov (United States)

Saint-Michel, B; Dubrulle, B; Marié, L; Ravelet, F; Daviaud, F

2013-12-06

We study the influence on steady turbulent states of the forcing in a von Karman flow, at constant impeller speed, or at constant torque. We find that the different forcing conditions change the nature of the stability of the steady states and reveal dynamical regimes that bear similarities to low-dimensional systems. We suggest that this forcing dependence may be applicable to other turbulent systems.

Constructive interference in steady-state/FIESTA-C clinical applications in neuroimaging

International Nuclear Information System (INIS)

Kulkami, Makarand

2011-01-01

Full text: High spatial resolution is one of the major problems in neuroimaging, par ticularly in cranial and spinal nerve imaging. Constructive interference in steady-state/fast imaging employing steady-state acquisition with phase cycling is a robust sequence in imaging the cranial and spinal nerve patholo gies. This pictorial review is a concise article about the applications of this sequence in neuroimaging with clinical examples.

Optimal control of transitions between nonequilibrium steady states.

Directory of Open Access Journals (Sweden)

Patrick R Zulkowski

Full Text Available Biological systems fundamentally exist out of equilibrium in order to preserve organized structures and processes. Many changing cellular conditions can be represented as transitions between nonequilibrium steady states, and organisms have an interest in optimizing such transitions. Using the Hatano-Sasa Y-value, we extend a recently developed geometrical framework for determining optimal protocols so that it can be applied to systems driven from nonequilibrium steady states. We calculate and numerically verify optimal protocols for a colloidal particle dragged through solution by a translating optical trap with two controllable parameters. We offer experimental predictions, specifically that optimal protocols are significantly less costly than naive ones. Optimal protocols similar to these may ultimately point to design principles for biological energy transduction systems and guide the design of artificial molecular machines.

The non-local Fisher–KPP equation: travelling waves and steady states

International Nuclear Information System (INIS)

Berestycki, Henri; Nadin, Grégoire; Perthame, Benoit; Ryzhik, Lenya

2009-01-01

We consider the Fisher–KPP equation with a non-local saturation effect defined through an interaction kernel φ(x) and investigate the possible differences with the standard Fisher–KPP equation. Our first concern is the existence of steady states. We prove that if the Fourier transform φ-circumflex(ξ) is positive or if the length σ of the non-local interaction is short enough, then the only steady states are u ≡ 0 and u ≡ 1. Next, we study existence of the travelling waves. We prove that this equation admits travelling wave solutions that connect u = 0 to an unknown positive steady state u ∞ (x), for all speeds c ≥ c * . The travelling wave connects to the standard state u ∞ (x) ≡ 1 under the aforementioned conditions: φ-circumflex(ξ) > 0 or σ is sufficiently small. However, the wave is not monotonic for σ large

Current drive efficiency requirements for an attractive steady-state reactor

Energy Technology Data Exchange (ETDEWEB)

Tonon, G

1994-12-31

The expected values of the figure of merit and the electrical efficiency of various non-inductive current drive methods are considered. The main experimental results achieved today with neutral beams and radiofrequency systems are summarized. Taking into account the simplified energy flow diagram of a steady state reactor, the figure of merit and the electrical efficiency values which are necessary in order to envisage an attractive steady-state reactor are determined. These values are compared to the theoretical predictions. (author). 16 refs., 11 figs., 2 tabs.

Current drive efficiency requirements for an attractive steady-state reactor

International Nuclear Information System (INIS)

Tonon, G.

1994-01-01

The expected values of the figure of merit and the electrical efficiency of various non-inductive current drive methods are considered. The main experimental results achieved today with neutral beams and radiofrequency systems are summarized. Taking into account the simplified energy flow diagram of a steady state reactor, the figure of merit and the electrical efficiency values which are necessary in order to envisage an attractive steady-state reactor are determined. These values are compared to the theoretical predictions. (author). 16 refs., 11 figs., 2 tabs

Joint DIII-D/EAST Experiments Toward Steady State AT Demonstration

Science.gov (United States)

Garofalo, A. M.; Meneghini, O.; Staebler, G. M.; van Zeeland, M. A.; Gong, X.; Ding, S.; Qian, J.; Ren, Q.; Xu, G.; Grierson, B. A.; Solomon, W. M.; Holcomb, C. T.

2015-11-01

Joint DIII-D/EAST experiments on fully noninductive operation at high poloidal beta have demonstrated several attractive features of this regime for a steady-state fusion reactor. Very large bootstrap fraction (>80 %) is desirable because it reduces the demands on external noninductive current drive. High bootstrap fraction with an H-mode edge results in a broad current profile and internal transport barriers (ITBs) at large minor radius, leading to high normalized energy confinement and high MHD stability limits. The ITB radius expands with higher normalized beta, further improving both stability and confinement. Electron density ITB and large Shafranov shift lead to low AE activity in the plasma core and low anomalous fast ion losses. Both the ITB and the current profile show remarkable robustness against perturbations, without external control. Supported by US DOE under DE-FC02-04ER54698, DE-AC02-09CH11466 & DE-AC52-07NA27344 & by NMCFSP under contracts 2015GB102000 and 2015GB110001.

Hydrogen and helium recycling from a JxB-force convected liquid metal Ga{sub 67}In{sub 20.5}Sn{sub 12.5} under steady state plasma bombardment

Energy Technology Data Exchange (ETDEWEB)

Hirooka, Yoshi, E-mail: hirooka.yoshihiko@nifs.ac.jp [National institute for Fusion Science, Oroshi, Toki, Gifu 509-5292 (Japan); Graduate University for Advanced Studies, Oroshi, Toki, Gifu 509-5292 (Japan); Bi, Hailin [Graduate University for Advanced Studies, Oroshi, Toki, Gifu 509-5292 (Japan); Shimada, Michiya [Japan Atomic Energy Agency, Rokkasho, Kamikita, Aomori 039-3212 (Japan); Ono, Masa [Princeton Plasma Physics Laboratory, Princeton, NJ 08543 (United States)

2017-04-15

A series of first-of-a-kind laboratory-scale experiments on the JxB-force convected liquid metal divertor concept have been carried out in the temperature range from room temperature to ∼200 °C, employing a eutectic alloy: Ga{sub 67}In{sub 20.5}Sn{sub 12.5}, the melting point of which is 10.5 °C. The electrical current conducted through the alloy is set at about 70A and the magnetic field is set at about 700 G. It has reproducibly been observed that hydrogen as well as helium particle recycling is noticeably reduced under steady state plasma bombardment when the liquid is convected by the JxB force.

Burn cycle requirements comparison of pulsed and steady-state tokamak reactors

International Nuclear Information System (INIS)

Brooks, J.N.; Ehst, D.A.

1983-12-01

Burn cycle parameters and energy transfer system requirements were analyzed for an 8-m commercial tokamak reactor using four types of cycles: conventional, hybrid, internal transformer, and steady state. Not surprisingly, steady state is the best burn mode if it can be achieved. The hybrid cycle is a promising alternative to the conventional. In contrast, the internal transformer cycle does not appear attractive for the size tokamak in question

40 CFR 1033.515 - Discrete-mode steady-state emission tests of locomotives and locomotive engines.

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Discrete-mode steady-state emission... Procedures § 1033.515 Discrete-mode steady-state emission tests of locomotives and locomotive engines. This... a warm-up followed by a sequence of nominally steady-state discrete test modes, as described in...

Possibility of Q>5 stable, steady-state operation in ITER with moderate βN and H-factor

International Nuclear Information System (INIS)

Polevoi, A.R.; Mukhovatov, V.S.; Shimada, M.; Medvedev, S.Yu.; Ivanov, A.A.; Poshekhonov, Yu.Yu.; Pustovitov, V.D.; Chu, M.S.

2003-01-01

A possibility of steady state stable operation in ITER with Q>5 and moderate requirements for plasma confinement is investigated. It is shown that there is some parametrical space for such operation where the ideal kink modes could be stabilised by the first wall. It is found that operational space where the ideal kink modes can be stabilised by the conducting wall could be noticeably extended by a relatively small reduction of the pressure peaking factor. The resistive wall mode stabilisation in ITER is discussed. (author)

Influence of longitudinal position on the evolution of steady-state signal in cardiac cine balanced steady-state free precession imaging.

Science.gov (United States)

Spear, Tyler J; Stromp, Tori A; Leung, Steve W; Vandsburger, Moriel H

2017-11-01

Emerging quantitative cardiac magnetic resonance imaging (CMRI) techniques use cine balanced steady-state free precession (bSSFP) to measure myocardial signal intensity and probe underlying physiological parameters. This correlation assumes that steady-state is maintained uniformly throughout the heart in space and time. To determine the effects of longitudinal cardiac motion and initial slice position on signal deviation in cine bSSFP imaging by comparing two-dimensional (2D) and three-dimensional (3D) acquisitions. Nine healthy volunteers completed cardiac MRI on a 1.5-T scanner. Short axis images were taken at six slice locations using both 2D and 3D cine bSSFP. 3D acquisitions spanned two slices above and below selected slice locations. Changes in myocardial signal intensity were measured across the cardiac cycle and compared to longitudinal shortening. For 2D cine bSSFP, 46% ± 9% of all frames and 84% ± 13% of end-diastolic frames remained within 10% of initial signal intensity. For 3D cine bSSFP the proportions increased to 87% ± 8% and 97% ± 5%. There was no correlation between longitudinal shortening and peak changes in myocardial signal. The initial slice position significantly impacted peak changes in signal intensity for 2D sequences ( P  cine bSSFP that is only restored at the center of a 3D excitation volume. During diastole, a transient steady-state is established similar to that achieved with 3D cine bSSFP regardless of slice location.

Experiments on steady state particle control in Tore Supra and DIII-D

International Nuclear Information System (INIS)

Mioduszewski, P.K.; Hogan, J.T.; Owen, L.W.; Maingi, R.; Lee, D.K.; Hillis, D.L.; Klepper, C.C.; Menon, M.M.; Thomas, C.E.; Uckan, T.; Wade, M.R.; Chatelier, M.; Grisolia, C.; Ghendrih, P.; Grosman, A.; Hutter, T.; Loarer, T.; Pegourie, B.; Mahdavi, M.A.; Schaffer, M.

1995-01-01

Particle control is playing an increasingly important role in tokamak plasma performance. The present paper discusses particle control of hydogen/deuterium by wall pumping on graphite or carbonized surfaces, as well as by external exhaust with pumped limiters and pumped divertors. Wall pumping is ultimately a transient effect and by itself not suitable for steady state particle exhaust. Therefore, external exhaust techniques with pumped divertors and limiters are being developed. How wall pumping phenomena interact and correlate with these inherently steady state, external exhaust techniques, is not well known to date. In the present paper, the processes involved in wall pumping and in external pumping are investigated in an attempt to evaluate the effect of external exhaust on wall pumping. Some of the key elements of this analysis are: (1) charge-exchange fluxes to the wall play a crucial role in the core-wall particle dynamics, (2) the recycling fluxes of thermal molecules have a high probability of ionization in the scrape-off layer, (3) thermal particles originating from the wall, which are ionized within the scrape-off layer, can be directly exhausted, thus providing a direct path between wall and exhaust which can be used to control the wall inventory. This way, the wall can be kept in a continuous pumping state in the sense that it continuously absorbs energetic particles and releases thermal molecules which are then removed by the external exhaust mechanism. While most of the ingredients of this analysis have been observed individually before, the present evaluation is an attempt to correlate effects of wall recycling and external exhaust. ((orig.))

The ITER divertor cassette. Steady state characterisation and draining and drying transient hydraulic analyses

International Nuclear Information System (INIS)

Pietro Alessandro Di Maio; Valerio Tomarchio; Giuseppe Vella; Irene Zammuto; Giovanni Dell'Orco

2005-01-01

gas bubbles. Due to the complex flow scheme of the hydraulic circuit, a pure theoretical study does not appears sufficient to address all the above mentioned items and an experimental validation of the models is mandatory. In addition to that, the assembly of the PFCs onto the cassette body as well as their integration by welding the coolant connections of the PFCs, also represent a critical step to be investigated. In order to investigate the aforementioned critical issues a theoretical and experimental research activity has been launched by the ENEA-Brasimone labs, in cooperation with the Department of Nuclear Engineering of the University of Palermo, with the specific aim of investigating the thermal-hydraulic behaviour of the whole divertor cassette both in steady state and operational or accidental transient conditions. The theoretical study, based on a computational approach, has been carried out with the RELAP5 code and the results obtained are herewith presented and critically discussed. In particular, the paper presents steady state and transient theoretical analyses intended to characterise the steady state behaviour of the cassette, determining flow distribution, pressure drop and CHF margin for each cooling channels, and to investigate the cassette behaviour during the draining and drying procedure, respectively. (authors)

Performance of tungsten-based materials and components under ITER and DEMO relevant steady-state thermal loads

Energy Technology Data Exchange (ETDEWEB)

Ritz, Guillaume Henri

2011-07-01

In nuclear fusion devices the surfaces directly facing the plasma are irradiated with high energy fluxes. The most intense loads are deposited on the divertor located at the bottom of the plasma chamber, which has to withstand continuous heat loads with a power density of several MW . m{sup -2} as well as transient events. These are much shorter (in the millisecond and sub-millisecond regime) but deposit a higher power densities of a few GW . m{sup -2}. The search for materials that can survive to those severe loading conditions led to the choice of tungsten which possesses advantageous attributes such as a high melting point, high thermal conductivity, low thermal expansion and an acceptable activation rate. These properties made it an attractive and promising candidate as armor material for divertors of future fusion devices such as ITER and DEMO. For the DEMO divertor, conceptual studies on helium-cooled tungsten plasma-facing components were performed. The concept was realized and tested under DEMO specific cyclic thermal loads. The examination of the plasma-facing components by microstructural analyses before and after thermal loading enabled to determine the mechanisms for components failure. Among others, it clearly showed the impact of the tungsten grade and the thermal stress induced crack formation on the performance of the armor material and in general of the plasma-facing component under high heat loads. A tungsten qualification program was launched to study the behaviour of various tungsten grades, in particular the crack formation, under fusion relevant steady-state thermal loads. In total, seven commercially available materials from two industrial suppliers were investigated. As the material's thermal response is strongly related to its microstructure, this program comprised different material geometries and manufacturing technologies. It also included the utilization of an actively cooled specimen holder which has been designed to perform

Performance of tungsten-based materials and components under ITER and DEMO relevant steady-state thermal loads

International Nuclear Information System (INIS)

Ritz, Guillaume Henri

2011-01-01

In nuclear fusion devices the surfaces directly facing the plasma are irradiated with high energy fluxes. The most intense loads are deposited on the divertor located at the bottom of the plasma chamber, which has to withstand continuous heat loads with a power density of several MW . m -2 as well as transient events. These are much shorter (in the millisecond and sub-millisecond regime) but deposit a higher power densities of a few GW . m -2 . The search for materials that can survive to those severe loading conditions led to the choice of tungsten which possesses advantageous attributes such as a high melting point, high thermal conductivity, low thermal expansion and an acceptable activation rate. These properties made it an attractive and promising candidate as armor material for divertors of future fusion devices such as ITER and DEMO. For the DEMO divertor, conceptual studies on helium-cooled tungsten plasma-facing components were performed. The concept was realized and tested under DEMO specific cyclic thermal loads. The examination of the plasma-facing components by microstructural analyses before and after thermal loading enabled to determine the mechanisms for components failure. Among others, it clearly showed the impact of the tungsten grade and the thermal stress induced crack formation on the performance of the armor material and in general of the plasma-facing component under high heat loads. A tungsten qualification program was launched to study the behaviour of various tungsten grades, in particular the crack formation, under fusion relevant steady-state thermal loads. In total, seven commercially available materials from two industrial suppliers were investigated. As the material's thermal response is strongly related to its microstructure, this program comprised different material geometries and manufacturing technologies. It also included the utilization of an actively cooled specimen holder which has been designed to perform sophisticated

Steady-state spheromak

International Nuclear Information System (INIS)

Jarboe, T.R.

1982-01-01

A major effort is being made in the national program to make the operation of axisymmetric, toroidal confinement systems steady state by the application of expensive rf current drive. Described here is a method by which such a confinement system, the spheromak, can be refluxed indefinitely through the application of dc power. As a step towards dc sustainment we have operated the present CTX source in the slow source mode with a longer power application time (approx. 0.1 ms) and successfully generated long-lived spheromaks. If the erosion of the electrodes can be controlled as well as it is with MPD arcs then dc operation should be very clean. If only a small fraction (approx. 10% for an experiment) of the poloidal flux of the spheromak connects to the source then the dc sustainment can be very efficient. The amount of connecting flux that is necessary for sustainment needs to be determined experimentally

The Steady State Calculation for SMART with MIDAS/SMR

International Nuclear Information System (INIS)

Park, Jong Hwa; Kim, Dong Ha; Chung, Young Jong; Park, Sun Hee; Cho, Seong Won

2010-01-01

KAERI is developing a new concept of reactor that all the main components such as the steam generator, the coolant pumps and the pressurizer are located inside the reactor vessel. Before the severe accident sequences are estimated, it is prerequisite that MIDAS code predicts the steady state conditions properly. But MIDAS code does not include the heat transfer model for the helical tube. Therefore, the heat transfer models for the helical tube from TASS/SMR-S were implemented into MIDAS code. To estimate the validity of the implemented heat transfer correlations for the helical tube and the input data, the steady state was recalculated with MIDAS/SMR based on design level 2 and compared with the design values

Computation of tokamak equilibria with steady flow

International Nuclear Information System (INIS)

Kerner, W.; Tokuda, Shinji

1987-08-01

The equations for ideal MHD equilibria with stationary flow are reexamined and addressed as numerically applied to tokamak configurations with a free plasma boundary. Both the isothermal (purely toroidal flow) and the poloidal flow cases are treated. Experiment-relevant states with steady flow (so far only in the toroidal direction) are computed by the modified SELENE40 code. (author)

Steady-state creep of discontinuous fibre composites

International Nuclear Information System (INIS)

Boecker Pedersen, O.

1975-07-01

A review is given of the relevant literature on creep of composites, including a presentation of existing models for the steady-state creep of composites containing aligned discontinuous fibres where creep of the matrix and fibres is assumed to follow a power law. A model is suggested for predicting the composite creep law from a matrix creep law given in a general form, in the case where the fibres do not creep. The composite creep law predicted by this model is compared with those predicted by previous models, when these are extended to comprise a general matrix creep law. Experimentally, pure copper and composites consisting of aligned discontinuous tungsten fibres in a copper matrix were creep tested at a temperature of 500 deg C. The results indicate a relatively low stress sensitivity of the steady-state creep-rate for pure copper and relatively high stress sensitivity for the composites. This may be explained by the creep models based upon a general matrix creep law. A quantitative prediction shows promising agreement with the present experimental results. (author)

Steady state statistical correlations predict bistability in reaction motifs.

Science.gov (United States)

Chakravarty, Suchana; Barik, Debashis

2017-03-28

Various cellular decision making processes are regulated by bistable switches that take graded input signals and convert them to binary all-or-none responses. Traditionally, a bistable switch generated by a positive feedback loop is characterized either by a hysteretic signal response curve with two distinct signaling thresholds or by characterizing the bimodality of the response distribution in the bistable region. To identify the intrinsic bistability of a feedback regulated network, here we propose that bistability can be determined by correlating higher order moments and cumulants (≥2) of the joint steady state distributions of two components connected in a positive feedback loop. We performed stochastic simulations of four feedback regulated models with intrinsic bistability and we show that for a bistable switch with variation of the signal dose, the steady state variance vs. covariance adopts a signatory cusp-shaped curve. Further, we find that the (n + 1)th order cross-cumulant vs. nth order cross-cumulant adopts a closed loop structure for at least n = 3. We also propose that our method is capable of identifying systems without intrinsic bistability even though the system may show bimodality in the marginal response distribution. The proposed method can be used to analyze single cell protein data measured at steady state from experiments such as flow cytometry.

Understanding void fraction in steady state and dynamic environments

International Nuclear Information System (INIS)

Chexal, B.; Maulbetsch, J.; Harrison, J.; Petersen, C.; Jensen, P.; Horowitz, J.

1997-01-01

Understanding void fraction behavior in steady-state and dynamic environments is important to accurately predict the thermal-hydraulic behavior of two-phase or two-component systems. The Chexal-Lellouche (C-L) void fraction mode described herein covers the full range of pressures, flows, void fractions, and fluid types (steam-water, air-water, and refrigerants). A drift flux model formulation is used which covers the complete range of concurrent and countercurrent flows. The (1996) model revises the earlier C-L void fraction correlation, improves the capability of the model in countercurrent flow based on the incorporation of additional data, and improves the characteristics of the correlation that are important in transient programs. The model has been qualified with data from a number of steady state two-phase and two-component tests, and has been incorporated into the transient analysis code RELAP5 and RETRAN-3D and evaluated with a variety of transient and steady state tests. A 'plug-in' module for the void fraction correlation has been developed and implemented in RELAP5 and RETRAN-3D. The module is available as source code for inclusion into other thermal-hydraulic programs and can be used in any program that utilizes the same interface variables

Extracting Steady State Components from Synchrophasor Data Using Kalman Filters

Directory of Open Access Journals (Sweden)

Farhan Mahmood

2016-04-01

Full Text Available Data from phasor measurement units (PMUs may be exploited to provide steady state information to the applications which require it. As PMU measurements may contain errors and missing data, the paper presents the application of a Kalman Filter technique for real-time data processing. PMU data captures the power system’s response at different time-scales, which are generated by different types of power system events; the presented Kalman Filter methods have been applied to extract the steady state components of PMU measurements that can be fed to steady state applications. Two KF-based methods have been proposed, i.e., a windowing-based KF method and “the modified KF”. Both methods are capable of reducing noise, compensating for missing data and filtering outliers from input PMU signals. A comparison of proposed methods has been carried out using the PMU data generated from a hardware-in-the-loop (HIL experimental setup. In addition, a performance analysis of the proposed methods is performed using an evaluation metric.

Ball lightning as a spherical plasma configuration of relevance to industrial plasma engineering

International Nuclear Information System (INIS)

Roth, J.R.

1992-01-01

One of the most interesting spherical plasma configurations found in nature is ball lightning, which has been extensively observed in atmospheric air, usually in association with thunderstorms. If the physical processes responsible for ball lightning were understood, this knowledge would have very interesting implications not only for fusion research, but also for industrial plasma engineering. The ability to create a steady-state atmospheric glow discharge would allow many surface modification and other plasma processing applications to be carried out under atmospheric conditions, rather than in expensive vacuum systems which enforce batch processing operations. The existence of ball lightning offers encouragement for the belief that a steady-state atmospheric glow discharge may be possible. Much progress has been made in theoretical attempts to understand ball lightning, perhaps the most comprehensive of which is the Koloc model. This and related models have not satisfactorily dealt with the long plasma lifetimes in the face of electron scattering at atmospheric density. This leads to an unsatisfactory aspect of the Koloc model, the requirement of a shell of relativistic electrons with very low Coulomb scattering cross sections. This last major conceptual roadblock in understanding ball lightning may have been removed by the recent suggestion of Witalis who pointed out that atmospheric gases, or their products, can exhibit the Ramsauer effect, extremely low electron scattering cross sections at low electron kinetic temperatures, on the order of one eV. This recent progress in ball lightning models has stimulated research aimed at producing a steady state glow discharge in air at atmospheric pressure. Such a glow discharge in argon with a few ppm of acetone has been reported by Kanda, et al. At the UTK Plasma Science Laboratory, the authors have generated at 2.8 liter plasma in a steady-state atmospheric pressure glow discharge in helium and other gases

Analysis of physical properties controlling steady-state infiltration rates on tropical savannah soils

International Nuclear Information System (INIS)

Mbagwu, J.S.C.

1993-10-01

A knowledge of physical properties influencing the steady-state infiltration rates (ic) of soils is needed for the hydrologic modelling of the infiltration process. In this study evidence is provided to show that effective porosity (Pe) (i.e. the proportion of macro pore spaces with equivalent radius of > 15 μm) and dry bulk density are the most important soil physical properties controlling the steady-state infiltration rates on a tropical savannah with varying land use histories. At a macro porosity value of ≤ 5.0% the steady-state infiltration rate is zero. Total porosity and the proportion of water-retaining pores explained only a small fraction of the variation in this property. Steady-state infiltration rates can also be estimated from either the saturated hydraulic conductivity (Ks) by the equation, i c = 31.1 + 1.06 (Ks), (R 2 = 0.8104, p ≤ 0.001) or the soil water transmissivity (A) by the equation, i c = 30.0 + 29.9(A), (R 2 = 0.8228, ρ ≤ 0.001). The Philip two-parameter model under predicted steady-state infiltration rates generally. Considering the ease of determination and reliability it is suggested that effective porosity be used to estimate the steady-state infiltration rates of these other soils with similar characteristics. The model is, i c 388.7(Pe) - 10.8(R 2 = 0.7265, p ≤ 0.001) where i c is in (cm/hr) and Pe in (cm 3 /cm 3 ). (author). 20 refs, 3 figs, 4 tabs

Full transmission modes and steady states in defect gratings,

NARCIS (Netherlands)

van Groesen, Embrecht W.C.; Sopaheluwakan, A.; Andonowati, A.; de Ridder, R.M; Altena, G; Geuzebroek, D.H.; Dekker, R

2003-01-01

For a symmetric grating structure with a defect, we show that a fully transmitted defect mode in the band gap can be obtained as a superposition of two steady states: an amplified and an attenuated defect state. Without scanning the whole band gap by transmission calculations, this simplifies the

Global gas balance and influence of atomic hydrogen irradiation on the wall inventory in steady-state operation of QUEST tokamak

Science.gov (United States)

Kuzmin, A.; Zushi, H.; Takagi, I.; Sharma, S. K.; Rusinov, A.; Inoue, Y.; Hirooka, Y.; Zhou, H.; Kobayashi, M.; Sakamoto, M.; Hanada, K.; Yoshida, N.; Nakamura, K.; Fujisawa, A.; Matsuoka, K.; Idei, H.; Nagashima, Y.; Hasegawa, M.; Onchi, T.; Banerjee, S.; Mishra, K.

2015-08-01

Hydrogen wall pumping is studied in steady state tokamak operation (SSTO) of QUEST with all metal plasma facing materials PFMs at 100 °C. The duration of SSTO is up to 820 s in fully non-inductive plasma. Global gas balance analysis shows that wall pumping at the apparent (retention-release) rate of 1-6 × 1018 H/s is dominant and 70-80% of injected H2 can be retained in PFMs. However, immediately after plasma termination the H2 release rate enhances to ∼1019 H/s. In order to understand a true retention process the direct measurement of retention flux has been carried out by permeation probes. The comparison between the evaluated wall retention and results from global analysis is discussed.

Bioaccumulation factors and the steady state assumption for cesium isotopes in aquatic foodwebs near nuclear facilities.

Science.gov (United States)

Rowan, D J

2013-07-01

Steady state approaches, such as transfer coefficients or bioaccumulation factors, are commonly used to model the bioaccumulation of (137)Cs in aquatic foodwebs from routine operations and releases from nuclear generating stations and other nuclear facilities. Routine releases from nuclear generating stations and facilities, however, often consist of pulses as liquid waste is stored, analyzed to ensure regulatory compliance and then released. The effect of repeated pulse releases on the steady state assumption inherent in the bioaccumulation factor approach has not been evaluated. In this study, I examine the steady state assumption for aquatic biota by analyzing data for two cesium isotopes in the same biota, one isotope in steady state (stable (133)Cs) from geologic sources and the other released in pulses ((137)Cs) from reactor operations. I also compare (137)Cs bioaccumulation factors for similar upstream populations from the same system exposed solely to weapon test (137)Cs, and assumed to be in steady state. The steady state assumption appears to be valid for small organisms at lower trophic levels (zooplankton, rainbow smelt and 0+ yellow perch) but not for older and larger fish at higher trophic levels (walleye). Attempts to account for previous exposure and retention through a biokinetics approach had a similar effect on steady state, upstream and non-steady state, downstream populations of walleye, but were ineffective in explaining the more or less constant deviation between fish with steady state exposures and non-steady state exposures of about 2-fold for all age classes of walleye. These results suggest that for large, piscivorous fish, repeated exposure to short duration, pulse releases leads to much higher (137)Cs BAFs than expected from (133)Cs BAFs for the same fish or (137)Cs BAFs for similar populations in the same system not impacted by reactor releases. These results suggest that the steady state approach should be used with caution in any

Feasibility study for improved steady-state initialization algorithms for the RELAP5 computer code

International Nuclear Information System (INIS)

Paulsen, M.P.; Peterson, C.E.; Katsma, K.R.

1993-04-01

A design for a new steady-state initialization method is presented that represents an improvement over the current method used in RELAP5. Current initialization methods for RELAP5 solve the transient fluidflow balance equations simulating a transient to achieve steady-state conditions. Because the transient solution is used, the initial conditions may change from the desired values requiring the use of controllers and long transient running times to obtain steady-state conditions for system problems. The new initialization method allows the user to fix thermal-hydraulic values in volumes and junctions where the conditions are best known and have the code compute the initial conditions in other areas of the system. The steady-state balance equations and solution methods are presented. The constitutive, component, and specialpurpose models are reviewed with respect to modifications required for the new steady-state initialization method. The requirements for user input are defined and the feasibility of the method is demonstrated with a testbed code by initializing some simple channel problems. The initialization of the sample problems using, the old and the new methods are compared

Time Reversibility, Correlation Decay and the Steady State Fluctuation Relation for Dissipation

Directory of Open Access Journals (Sweden)

Denis J. Evans

2013-04-01

Full Text Available Steady state fluctuation relations for nonequilibrium systems are under intense investigation because of their important practical implications in nanotechnology and biology. However the precise conditions under which they hold need clarification. Using the dissipation function, which is related to the entropy production of linear irreversible thermodynamics, we show time reversibility, ergodic consistency and a recently introduced form of correlation decay, called T-mixing, are sufficient conditions for steady state fluctuation relations to hold. Our results are not restricted to a particular model and show that the steady state fluctuation relation for the dissipation function holds near or far from equilibrium subject to these conditions. The dissipation function thus plays a comparable role in nonequilibrium systems to thermodynamic potentials in equilibrium systems.

Efficient decoding with steady-state Kalman filter in neural interface systems.

Science.gov (United States)

Malik, Wasim Q; Truccolo, Wilson; Brown, Emery N; Hochberg, Leigh R

2011-02-01

The Kalman filter is commonly used in neural interface systems to decode neural activity and estimate the desired movement kinematics. We analyze a low-complexity Kalman filter implementation in which the filter gain is approximated by its steady-state form, computed offline before real-time decoding commences. We evaluate its performance using human motor cortical spike train data obtained from an intracortical recording array as part of an ongoing pilot clinical trial. We demonstrate that the standard Kalman filter gain converges to within 95% of the steady-state filter gain in 1.5±0.5 s (mean ±s.d.). The difference in the intended movement velocity decoded by the two filters vanishes within 5 s, with a correlation coefficient of 0.99 between the two decoded velocities over the session length. We also find that the steady-state Kalman filter reduces the computational load (algorithm execution time) for decoding the firing rates of 25±3 single units by a factor of 7.0±0.9. We expect that the gain in computational efficiency will be much higher in systems with larger neural ensembles. The steady-state filter can thus provide substantial runtime efficiency at little cost in terms of estimation accuracy. This far more efficient neural decoding approach will facilitate the practical implementation of future large-dimensional, multisignal neural interface systems.

The quasi-steady state of the valley wind system

Directory of Open Access Journals (Sweden)

Juerg eSchmidli

2015-12-01

Full Text Available The quasi-steady-state limit of the diurnal valley wind system is investigated overidealized three-dimensional topography. Although this limit is rarely attained inreality due to ever-changing forcings, the investigation of this limit canprovide valuable insight, in particular on the mass and heat fluxes associatedwith the along-valley wind. We derive a scaling relation for the quasi-steady-state along-valleymass flux as a function of valley geometry, valley size, atmospheric stratification,and surface sensible heat flux forcing. The scaling relation is tested by comparisonwith the mass flux diagnosed from numerical simulations of the valleywind system. Good agreement is found. The results also provide insight into the relationbetween surface friction and the strength of the along-valley pressure gradient.

A Multidose Study to Examine the Effect of Food on Evacetrapib Exposure at Steady State

Science.gov (United States)

Zhang, Wei; Royalty, Jane; Cannady, Ellen A.; Downs, Delyn; Friedrich, Stuart; Suico, Jeffrey G.

2015-01-01

Purpose: To determine the effect of a high-fat meal on evacetrapib exposure at steady state in healthy participants. Methods: This was a randomized, 2-period, 2-sequence, open-label, crossover study. Patients were randomly assigned to 1 of the 2 treatment sequences in which they received evacetrapib 130 mg/d for 10 days following a 10-hour fast each day or following a high-fat breakfast each day. Plasma samples collected through 24 hours were analyzed for evacetrapib concentrations and pharmacokinetic parameter estimates including area under the concentration–time curve during a dosing interval (AUCτ), maximum observed concentration (Cmax), and time of Cmax (tmax) were calculated. Pharmacodynamic parameters, including cholesteryl ester transfer protein (CETP) activity, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), total cholesterol, and triglycerides, were also assessed. Results: A total of 34 males and 6 females, mean age 41.5 years and mean body mass index 26.6 kg/m2, were enrolled. Statistical analysis showed AUCτ was 44% higher (90% confidence interval [CI]: 29%-62%) and Cmax was 51% higher (90% CI: 28%-79%) in the fed state than in the fasted state, indicating an effect of food. Consistent with higher evacetrapib exposure, changes in HDL-C, LDL-C, and CETP activity appeared to be greater in the fed state than in the fasted state. There were no notable changes in total cholesterol or triglycerides following administration in the fed and fasted states. The 130-mg doses of evacetrapib were well tolerated with and without food. Conclusion: A high-fat meal increased evacetrapib mean exposure at steady state by 44% in healthy participants. PMID:25736283

Finite element modelling of creep process - steady state stresses and strains

Directory of Open Access Journals (Sweden)

Sedmak Aleksandar S.

2014-01-01

Full Text Available Finite element modelling of steady state creep process has been described. Using an analogy of visco-plastic problem with a described procedure, the finite element method has been used to calculate steady state stresses and strains in 2D problems. An example of application of such a procedure have been presented, using real life problem - cylindrical pipe with longitudinal crack at high temperature, under internal pressure, and estimating its residual life, based on the C*integral evaluation.

Plasma ignition and steady state simulations of the Linac4 H$^{-}$ ion source

CERN Document Server

Mattei, S; Yasumoto, M; Hatayama, A; Lettry, J; Grudiev, A

2014-01-01

The RF heating of the plasma in the Linac4 H- ion source has been simulated using an Particle-in-Cell Monte Carlo Collision method (PIC-MCC). This model is applied to investigate the plasma formation starting from an initial low electron density of 1012 m-3 and its stabilization at 1018 m-3. The plasma discharge at low electron density is driven by the capacitive coupling with the electric field generated by the antenna, and as the electron density increases the capacitive electric field is shielded by the plasma and induction drives the plasma heating process. Plasma properties such as e-/ion densities and energies, sheath formation and shielding effect are presented and provide insight to the plasma properties of the hydrogen plasma.

Multiple solutions of steady-state Poisson–Nernst–Planck equations with steric effects

International Nuclear Information System (INIS)

Lin, Tai-Chia; Eisenberg, Bob

2015-01-01

Experiments measuring currents through single protein channels show unstable currents. Channels switch between ‘open’ or ‘closed’ states in a spontaneous stochastic process called gating. Currents are either (nearly) zero or at a definite level, characteristic of each type of protein, independent of time, once the channel is open. The steady state Poisson–Nernst–Planck equations with steric effects (PNP-steric equations) describe steady current through the open channel quite well, in a wide variety of conditions. Here we study the existence of multiple solutions of steady state PNP-steric equations to see if they themselves, without modification or augmentation, can describe two levels of current. We prove that there are two steady state solutions of PNP-steric equations for (a) three types of ion species (two types of cations and one type of anion) with a positive constant permanent charge, and (b) four types of ion species (two types of cations and their counter-ions) with a constant permanent charge but no sign condition. The excess currents (due to steric effects) associated with these two steady state solutions are derived and expressed as two distinct formulas. Our results indicate that PNP-steric equations may become a useful model to study spontaneous gating of ion channels. Spontaneous gating is thought to involve small structural changes in the channel protein that perhaps produce large changes in the profiles of free energy that determine ion flow. Gating is known to be modulated by external structures. Both can be included in future extensions of our present analysis. (paper)

Plasma lenses for ultrashort multi-petawatt laser pulses

Energy Technology Data Exchange (ETDEWEB)

Palastro, J. P.; Gordon, D.; Hafizi, B.; Johnson, L. A.; Peñano, J.; Hubbard, R. F.; Helle, M.; Kaganovich, D. [Naval Research Laboratory, Washington DC 20375-5346 (United States)

2015-12-15

An ideal plasma lens can provide the focusing power of a small f-number, solid-state focusing optic at a fraction of the diameter. An ideal plasma lens, however, relies on a steady-state, linear laser pulse-plasma interaction. Ultrashort multi-petawatt (MPW) pulses possess broad bandwidths and extreme intensities, and, as a result, their interaction with the plasma lens is neither steady state nor linear. Here, we examine nonlinear and time-dependent modifications to plasma lens focusing, and show that these result in chromatic and phase aberrations and amplitude distortion. We find that a plasma lens can provide enhanced focusing for 30 fs pulses with peak power up to ∼1 PW. The performance degrades through the MPW regime, until finally a focusing penalty is incurred at ∼10 PW.

Dissipative dark matter halos: The steady state solution. II.

Science.gov (United States)

Foot, R.

2018-05-01

Within the mirror dark matter model and dissipative dark matter models in general, halos around galaxies with active star formation (including spirals and gas-rich dwarfs) are dynamical: they expand and contract in response to heating and cooling processes. Ordinary type II supernovae (SNe) can provide the dominant heat source, which is possible if kinetic mixing interaction exists with strength ɛ ˜10-9- 10-10 . Dissipative dark matter halos can be modeled as a fluid governed by Euler's equations. Around sufficiently isolated and unperturbed galaxies the halo can relax to a steady state configuration, where heating and cooling rates locally balance and hydrostatic equilibrium prevails. These steady state conditions can be solved to derive the physical properties, including the halo density and temperature profiles, for model galaxies. Here, we consider idealized spherically symmetric galaxies within the mirror dark particle model, as in our earlier paper [Phys. Rev. D 97, 043012 (2018), 10.1103/PhysRevD.97.043012], but we assume that the local halo heating in the SN vicinity dominates over radiative sources. With this assumption, physically interesting steady state solutions arise which we compute for a representative range of model galaxies. The end result is a rather simple description of the dark matter halo around idealized spherically symmetric systems, characterized in principle by only one parameter, with physical properties that closely resemble the empirical properties of disk galaxies.

40 CFR 86.1363-2007 - Steady-state testing with a discrete-mode cycle.

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 19 2010-07-01 2010-07-01 false Steady-state testing with a discrete-mode cycle. 86.1363-2007 Section 86.1363-2007 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Exhaust Test Procedures § 86.1363-2007 Steady-state testing with a discrete-mode cycle. This section...

Herd-Level Modeling and Steady-State Livestock Productivity ...

African Journals Online (AJOL)

... an outline of the scope for applications and addresses the prospects for refinement and model extensions. The algorithms for use in development of steady state derivations include transition of matrices in a Markov Chain approach, continuous differential equations and actuarial approach built on life and fecundity tables.

Principle of Entropy Maximization for Nonequilibrium Steady States

DEFF Research Database (Denmark)

Shapiro, Alexander; Stenby, Erling Halfdan

2002-01-01

The goal of this contribution is to find out to what extent the principle of entropy maximization, which serves as a basis for the equilibrium thermodynamics, may be generalized onto non-equilibrium steady states. We prove a theorem that, in the system of thermodynamic coordinates, where entropy...

Steady-state solidification of aqueous ammonium chloride

Science.gov (United States)

Peppin, S. S. L.; Huppert, Herbert E.; Worster, M. Grae

We report on a series of experiments in which a Hele-Shaw cell containing aqueous solutions of NH4Cl was translated at prescribed rates through a steady temperature gradient. The salt formed the primary solid phase of a mushy layer as the solution solidified, with the salt-depleted residual fluid driving buoyancy-driven convection and the development of chimneys in the mushy layer. Depending on the operating conditions, several morphological transitions occurred. A regime diagram is presented quantifying these transitions as a function of freezing rate and the initial concentration of the solution. In general, for a given concentration, increasing the freezing rate caused the steady-state system to change from a convecting mushy layer with chimneys to a non-convecting mushy layer below a relatively quiescent liquid, and then to a much thinner mushy layer separated from the liquid by a region of active secondary nucleation. At higher initial concentrations the second of these states did not occur. At lower concentrations, but still above the eutectic, the mushy layer disappeared. A simple mathematical model of the system is developed which compares well with the experimental measurements of the intermediate, non-convecting state and serves as a benchmark against which to understand some of the effects of convection. Movies are available with the online version of the paper.

Statistical steady states in turbulent droplet condensation

Science.gov (United States)

Bec, Jeremie; Krstulovic, Giorgio; Siewert, Christoph

2017-11-01

We investigate the general problem of turbulent condensation. Using direct numerical simulations we show that the fluctuations of the supersaturation field offer different conditions for the growth of droplets which evolve in time due to turbulent transport and mixing. This leads to propose a Lagrangian stochastic model consisting of a set of integro-differential equations for the joint evolution of the squared radius and the supersaturation along droplet trajectories. The model has two parameters fixed by the total amount of water and the thermodynamic properties, as well as the Lagrangian integral timescale of the turbulent supersaturation. The model reproduces very well the droplet size distributions obtained from direct numerical simulations and their time evolution. A noticeable result is that, after a stage where the squared radius simply diffuses, the system converges exponentially fast to a statistical steady state independent of the initial conditions. The main mechanism involved in this convergence is a loss of memory induced by a significant number of droplets undergoing a complete evaporation before growing again. The statistical steady state is characterised by an exponential tail in the droplet mass distribution.

ATC calculation with steady-state security constraints using Benders decomposition

International Nuclear Information System (INIS)

Shaaban, M.; Yan, Z.; Ni, Y.; Wu, F.; Li, W.; Liu, H.

2003-01-01

Available transfer capability (ATC) is an important indicator of the usable amount of transmission capacity accessible by assorted parties for commercial trading, ATC calculation is nontrivial when steady-state security constraints are included. In hie paper, Benders decomposition method is proposed to partition the AC problem with steady-state security constraints into a base case master problem and a series of subproblems relevant to various contingencies to include their impacts on ATC. The mathematical model is formulated and the two solution schemes are presented. Computer testing on the 4-bus system and IEEE 30-bus system shows the effectiveness of the proposed method and the solution schemes. (Author)

Global gas balance and influence of atomic hydrogen irradiation on the wall inventory in steady-state operation of QUEST tokamak

Energy Technology Data Exchange (ETDEWEB)

Kuzmin, A., E-mail: kuzmin@triam.kyushu-u.ac.jp [RIAM, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); Zushi, H. [RIAM, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); Takagi, I. [Graduate School of Engineering, Kyoto University (Japan); Sharma, S.K. [Institute for Plasma Research, Ahmadabad, Gujrat (India); Rusinov, A. [RIAM, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); Inoue, Y. [IGSES, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); Hirooka, Y. [National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292 (Japan); Zhou, H. [Graduate School for Advanced Studies, 322-6 Oroshi, Toki, Gifu 509-5292 (Japan); Kobayashi, M. [National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292 (Japan); Sakamoto, M. [Plasma Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577 (Japan); Hanada, K.; Yoshida, N.; Nakamura, K.; Fujisawa, A.; Matsuoka, K.; Idei, H.; Nagashima, Y.; Hasegawa, M.; Onchi, T. [RIAM, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); Banerjee, S. [IGSES, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); and others

2015-08-15

Hydrogen wall pumping is studied in steady state tokamak operation (SSTO) of QUEST with all metal plasma facing materials PFMs at 100 °C. The duration of SSTO is up to 820 s in fully non-inductive plasma. Global gas balance analysis shows that wall pumping at the apparent (retention–release) rate of 1–6 × 10{sup 18} H/s is dominant and 70–80% of injected H{sub 2} can be retained in PFMs. However, immediately after plasma termination the H{sub 2} release rate enhances to ∼10{sup 19} H/s. In order to understand a true retention process the direct measurement of retention flux has been carried out by permeation probes. The comparison between the evaluated wall retention and results from global analysis is discussed.

Global gas balance and influence of atomic hydrogen irradiation on the wall inventory in steady-state operation of QUEST tokamak

International Nuclear Information System (INIS)

Kuzmin, A.; Zushi, H.; Takagi, I.; Sharma, S.K.; Rusinov, A.; Inoue, Y.; Hirooka, Y.; Zhou, H.; Kobayashi, M.; Sakamoto, M.; Hanada, K.; Yoshida, N.; Nakamura, K.; Fujisawa, A.; Matsuoka, K.; Idei, H.; Nagashima, Y.; Hasegawa, M.; Onchi, T.; Banerjee, S.

2015-01-01

Hydrogen wall pumping is studied in steady state tokamak operation (SSTO) of QUEST with all metal plasma facing materials PFMs at 100 °C. The duration of SSTO is up to 820 s in fully non-inductive plasma. Global gas balance analysis shows that wall pumping at the apparent (retention–release) rate of 1–6 × 10 18 H/s is dominant and 70–80% of injected H 2 can be retained in PFMs. However, immediately after plasma termination the H 2 release rate enhances to ∼10 19 H/s. In order to understand a true retention process the direct measurement of retention flux has been carried out by permeation probes. The comparison between the evaluated wall retention and results from global analysis is discussed

Effect of Food on the Steady-State Pharmacokinetics of Tenofovir and Emtricitabine plus Efavirenz in Ugandan Adults

Directory of Open Access Journals (Sweden)

Mohammed Lamorde

2012-01-01

Full Text Available We investigated the effect of food on the steady-state pharmacokinetics of a proprietary fixed-dose combination (FDC tablet containing tenofovir disoproxil fumarate (TDF/emtricitabine/efavirenz. Fifteen Ugandan HIV-1 patients at steady-state dosing with TDF/emtricitabine/efavirenz were admitted for 24-hour intensive pharmacokinetic sampling after dosing in the fasting state. Blood sampling was repeated seven days later with TDF/emtricitabine/efavirenz administered with food (19 g fat. Drug concentrations in plasma were determined by liquid chromatography and tandem mass spectrometry. Geometric mean ratios (GMRs and confidence intervals (CIs of parameters were calculated (reference, fasting. For efavirenz, GMRs (90% CIs for Cmax, AUC0-24, and C24 were 1.47 (1.24–1.75, 1.13 (1.03–1.23, and 1.01 (0.91–1.11, respectively. Corresponding GMRs were 1.04 (0.84–1.27, 1.19 (1.10–1.29, and 0.99 (0.82–1.19 for tenofovir, 0.83 (0.76–0.92, 0.87 (0.78–0.97, and 0.91 (0.73–1.14 for emtricitabine. Stable patients may take the FDC without meal restrictions. The FDC should be taken without food by patients experiencing central nervous system toxicities.

How should we understand non-equilibrium many-body steady states?

Science.gov (United States)

Maghrebi, Mohammad; Gorshkov, Alexey

: Many-body systems with both coherent dynamics and dissipation constitute a rich class of models which are nevertheless much less explored than their dissipationless counterparts. The advent of numerous experimental platforms that simulate such dynamics poses an immediate challenge to systematically understand and classify these models. In particular, nontrivial many-body states emerge as steady states under non-equilibrium dynamics. In this talk, I use a field-theoretic approach based on the Keldysh formalism to study nonequilibrium phases and phase transitions in such models. I show that an effective temperature generically emerges as a result of dissipation, and the universal behavior including the dynamics near the steady state is described by a thermodynamic universality class. In the end, I will also discuss possibilities that go beyond the paradigm of an effective thermodynamic behavior.

An implicit steady-state initialization package for the RELAP5 computer code

International Nuclear Information System (INIS)

Paulsen, M.P.; Peterson, C.E.; Odar, F.

1995-08-01

A direct steady-state initialization (DSSI) method has been developed and implemented in the RELAP5 hydrodynamic analysis program. It provides a means for users to specify a small set of initial conditions which are then propagated through the remainder of the system. The DSSI scheme utilizes the steady-state form of the RELAP5 balance equations for nonequilibrium two-phase flow. It also employs the RELAP5 component models and constitutive model packages for wall-to-phase and interphase momentum and heat exchange. A fully implicit solution of the linearized hydrodynamic equations is implemented. An implicit coupling scheme is used to augment the standard steady-state heat conduction solution for steam generator use. It solves the primary-side tube region energy equations, heat conduction equations, wall heat flux boundary conditions, and overall energy balance equation as a coupled system of equations and improves convergence. The DSSI method for initializing RELAP5 problems to steady-state conditions has been compared with the transient solution scheme using a suite of test problems including; adiabatic single-phase liquid and vapor flow through channels with and without healing and area changes; a heated two-phase test bundle representative of BWR core conditions; and a single-loop PWR model

Major progress on tore supra toward steady state operation of tokamaks

International Nuclear Information System (INIS)

Saoutic, Y.

2003-01-01

During winter 2000-2001, a major upgrade of the internal components of Tore Supra has been completed that increased the heat extraction capability to 25 MW in steady state. Operating Tore Supra in this new configuration has produced a wealth of new results. The highlights of the 2002 long duration discharges campaign are: 4 minutes 25 seconds long discharges with an integrated energy of 0.75 GJ, which is three time higher than the old Tore Supra world record; recharge of the primary transformer by Lower Hybrid Current Drive (LHCD) for about 1 minute; 4 minutes long LHCD pulses; 1 minute long Ion Cyclotron Resonant Heating (ICRH) pulse (0.11 GJ of ICRH injected energy). Beyond the quantitative step, significant qualitative progress in the steady state nature of the discharge has been accomplished: contrary to the situation in the old Tore Supra configuration, the plasma density is perfectly controlled by active pumping over the overall shot duration. The duration of Tore Supra discharges is sufficient to allow the complete diffusion of the resistive current. Surprising new physics is revealed in such discharges when approaching zero loop voltage. Slow central electron temperature oscillations have been observed in a variety of situations. Such oscillations are not likely to be linked to any MHD instabilities and probably results from an interplay between current profile shape, LHCD power deposition and transport. Analysis of the temperature gradient in the core region shows a very interesting behaviour and the normalised temperature gradient length is compared to the critical thresholds. Finally, the performance of heating and current drive systems and the observations made of the interior of Tore Supra after the long duration discharges campaign are reported. (author)

Computational multiple steady states for enzymatic esterification of ethanol and oleic acid in an isothermal CSTR.

Science.gov (United States)

Ho, Pang-Yen; Chuang, Guo-Syong; Chao, An-Chong; Li, Hsing-Ya

2005-05-01

The capacity of complex biochemical reaction networks (consisting of 11 coupled non-linear ordinary differential equations) to show multiple steady states, was investigated. The system involved esterification of ethanol and oleic acid by lipase in an isothermal continuous stirred tank reactor (CSTR). The Deficiency One Algorithm and the Subnetwork Analysis were applied to determine the steady state multiplicity. A set of rate constants and two corresponding steady states are computed. The phenomena of bistability, hysteresis and bifurcation are discussed. Moreover, the capacity of steady state multiplicity is extended to the family of the studied reaction networks.

A quaternionic map for the steady states of the Heisenberg spin-chain

Energy Technology Data Exchange (ETDEWEB)

Mehta, Mitaxi P., E-mail: mitaxi.mehta@ahduni.edu.in [IICT, Ahmedabad University, Opp. IIM, Navrangpura, Ahmedabad (India); Dutta, Souvik; Tiwari, Shubhanshu [BITS-Pilani, K.K. Birla Goa campus, Goa (India)

2014-01-17

We show that the steady states of the classical Heisenberg XXX spin-chain in an external magnetic field can be found by iterations of a quaternionic map. A restricted model, e.g., the xy spin-chain is known to have spatially chaotic steady states and the phase space occupied by these chaotic states is known to go through discrete changes as the field strength is varied. The same phenomenon is studied for the xxx spin-chain. It is seen that in this model the phase space volume varies smoothly with the external field.

A quaternionic map for the steady states of the Heisenberg spin-chain

International Nuclear Information System (INIS)

Mehta, Mitaxi P.; Dutta, Souvik; Tiwari, Shubhanshu

2014-01-01

We show that the steady states of the classical Heisenberg XXX spin-chain in an external magnetic field can be found by iterations of a quaternionic map. A restricted model, e.g., the xy spin-chain is known to have spatially chaotic steady states and the phase space occupied by these chaotic states is known to go through discrete changes as the field strength is varied. The same phenomenon is studied for the xxx spin-chain. It is seen that in this model the phase space volume varies smoothly with the external field.

Steady state analysis of Boolean molecular network models via model reduction and computational algebra.

Science.gov (United States)

Veliz-Cuba, Alan; Aguilar, Boris; Hinkelmann, Franziska; Laubenbacher, Reinhard

2014-06-26

A key problem in the analysis of mathematical models of molecular networks is the determination of their steady states. The present paper addresses this problem for Boolean network models, an increasingly popular modeling paradigm for networks lacking detailed kinetic information. For small models, the problem can be solved by exhaustive enumeration of all state transitions. But for larger models this is not feasible, since the size of the phase space grows exponentially with the dimension of the network. The dimension of published models is growing to over 100, so that efficient methods for steady state determination are essential. Several methods have been proposed for large networks, some of them heuristic. While these methods represent a substantial improvement in scalability over exhaustive enumeration, the problem for large networks is still unsolved in general. This paper presents an algorithm that consists of two main parts. The first is a graph theoretic reduction of the wiring diagram of the network, while preserving all information about steady states. The second part formulates the determination of all steady states of a Boolean network as a problem of finding all solutions to a system of polynomial equations over the finite number system with two elements. This problem can be solved with existing computer algebra software. This algorithm compares favorably with several existing algorithms for steady state determination. One advantage is that it is not heuristic or reliant on sampling, but rather determines algorithmically and exactly all steady states of a Boolean network. The code for the algorithm, as well as the test suite of benchmark networks, is available upon request from the corresponding author. The algorithm presented in this paper reliably determines all steady states of sparse Boolean networks with up to 1000 nodes. The algorithm is effective at analyzing virtually all published models even those of moderate connectivity. The problem for

Quasi-steady state, low current behaviour of a magnetized coaxial plasma source

International Nuclear Information System (INIS)

Gray, Travis K; Mayo, Robert M; Bourham, Mohamed A

2005-01-01

The Coaxial Plasma Source-1 facility (Mayo R M et al 1995 Plasma Sources Sci. Technol. 4 47) was modified from a short pulse, high current (SPHC) pulse forming network (PFN) with very low inductance (∼200 nH) to a large inductance ladder circuit. This modification allows for a longer, flat top gun current pulse that eliminates the under-damped, sinusoidal behaviour of the gun current with consequent interruptions in plasma parameters. The new PFN was designed to produce a current waveform for a much longer period (∼1 ms). As a consequence of increasing the pulse length, the magnitude of the gun current was reduced as no additional energy storage was added to the PFN. The characterization of the electrical and plasma behaviour of the experiment operated with the long pulse, low current (LPLC) PFN is presented. The gun currents produced by the LPLC PFN are approximately one-fifth in magnitude of the gun currents produced by the SPHC PFN. Axial plasma parameters were measured near the muzzle of the plasma source, and electron densities were found to range from 1 x 10 19 m -3 to 7 x 10 19 m -3 depending upon the axial location. These values are approximately 1-2 orders of magnitude less than the electron densities produced by the SPHC PFN at the same locations. Electron temperatures range from 30 to 60 eV at these locations and are very similar to those produced by the SPHC PFN. A resistive MHD model was applied as an order estimate of the plasma resistivity and demonstrates reasonable agreement with measured values of the magnetized coaxial gun resistance

Quasi-steady state, low current behaviour of a magnetized coaxial plasma source

Energy Technology Data Exchange (ETDEWEB)

Gray, Travis K; Mayo, Robert M; Bourham, Mohamed A [Department of Nuclear Engineering, North Carolina State University, Raleigh, NC 27695-7909 (United States)

2005-11-15

The Coaxial Plasma Source-1 facility (Mayo R M et al 1995 Plasma Sources Sci. Technol. 4 47) was modified from a short pulse, high current (SPHC) pulse forming network (PFN) with very low inductance ({approx}200 nH) to a large inductance ladder circuit. This modification allows for a longer, flat top gun current pulse that eliminates the under-damped, sinusoidal behaviour of the gun current with consequent interruptions in plasma parameters. The new PFN was designed to produce a current waveform for a much longer period ({approx}1 ms). As a consequence of increasing the pulse length, the magnitude of the gun current was reduced as no additional energy storage was added to the PFN. The characterization of the electrical and plasma behaviour of the experiment operated with the long pulse, low current (LPLC) PFN is presented. The gun currents produced by the LPLC PFN are approximately one-fifth in magnitude of the gun currents produced by the SPHC PFN. Axial plasma parameters were measured near the muzzle of the plasma source, and electron densities were found to range from 1 x 10{sup 19} m{sup -3} to 7 x 10{sup 19} m{sup -3} depending upon the axial location. These values are approximately 1-2 orders of magnitude less than the electron densities produced by the SPHC PFN at the same locations. Electron temperatures range from 30 to 60 eV at these locations and are very similar to those produced by the SPHC PFN. A resistive MHD model was applied as an order estimate of the plasma resistivity and demonstrates reasonable agreement with measured values of the magnetized coaxial gun resistance.

Steady-state pharmacokinetics and pharmacodynamics of cysteamine bitartrate in paediatric nephropathic cystinosis patients.

Science.gov (United States)

Belldina, Eric B; Huang, Mei Y; Schneider, Jerry A; Brundage, Richard C; Tracy, Timothy S

2003-11-01

Cysteamine is used to reduce tissue cystine content in patients suffering from nephropathic cystinosis. The objectives of the current study were to investigate pharmacokinetics and pharmacodynamics of cysteamine bitartrate in children and young adults with nephropathic cystinosis. Cysteamine bitartrate was administered to 11 cystinosis patients at their regular dose level in a single-dose, open-label, steady-state study. Blood samples were collected and analysed for plasma cysteamine and white blood cell cystine content and pharmacokinetic and pharmacodynamic parameters estimated by NONMEM analysis using a linked pharmacokinetic-pharmacodynamic model. Cysteamine was rapidly cleared from the plasma (mean CL/F = 32.3 ml min(-1) kg(-1), range = 17.3-52.2), appeared to be extensively distributed (mean Vss/F = 15.1 l, range 2.7-32.3) and exhibited a mean Tmax of 1.4 h. White blood cell cystine content post-dosing was significantly decreased compared with pre- and post-dose values (average decrement approximately 47%). A counter-clockwise hysteresis was noted in all patients, suggestive of a lag time (mean Tlag = 0.44 h, range 0.22-0.92) between drug concentration and effect. The results of this study establish that cysteamine is rapidly cleared from the plasma but that an every 6 h dosing interval adequately maintains white blood cell cystine content below the target of 1 nmol cystine per mg protein.

Steady state ion acceleration by a circularly polarized laser pulse

International Nuclear Information System (INIS)

Zhang Xiaomei; Shen Baifei; Cang Yu; Li Xuemei; Jin Zhangying; Wang Fengchao

2007-01-01

The steady state ion acceleration at the front of a cold solid target by a circularly polarized flat-top laser pulse is studied with one-dimensional particle-in-cell (PIC) simulation. A model that ions are reflected by a steady laser-driven piston is used by comparing with the electrostatic shock acceleration. A stable profile with a double-flat-top structure in phase space forms after ions enter the undisturbed region of the target with a constant velocity

Poiseuille flow of soft glasses in narrow channels: from quiescence to steady state.

Science.gov (United States)

Chaudhuri, Pinaki; Horbach, Jürgen

2014-10-01

Using numerical simulations, the onset of Poiseuille flow in a confined soft glass is investigated. Starting from the quiescent state, steady flow sets in at a time scale which increases with a decrease in applied forcing. At this onset time scale, a rapid transition occurs via the simultaneous fluidization of regions having different local stresses. In the absence of steady flow at long times, creep is observed even in regions where the local stress is larger than the bulk yielding threshold. Finally, we show that the time scale to attain steady flow depends strongly on the history of the initial state.

Mass transport and the bootstrap current from Ohm's law in steady-state tokamaks

International Nuclear Information System (INIS)

Kim, J.-S.; Greene, J.M.

1989-01-01

The consequences of mass conservation and Ohm's law are examined for steady state Tokamaks. In a Tokamak, magnetofluid-dynamic waves rapidly equilibrate pressure and toroidal field along magnetic surfaces. As a result, the detailed current distribution is determined by the flux surface averaged poloidal and toroidal currents. The electrons that carry the plasma current are impeded in their motion by interactions with ions, which is resistivity and its generalizations, and by interactions with electrons, which is viscosity and its generalizations. The important viscous terms arise from the interaction between trapped and untrapped electrons, and so viscosity acts by impeding poloidal current. properly chosen, the results of neoclassical theory are The neoclassical viscous coefficient is here regarded as less likely than Spitzer conductivity to be experimentally relevant in a turbulent Tokamak. Thus, the toroidal Ohm's law is regarded as being more reliable than the poloidal Ohm's law. A combination of toroidal and poloidal Ohm's law, namely the component parallel to the magnetic field, eliminates the influence of plasma fueling, and directly relates the bootstrap current and the pressure gradient. The latter is the usual relation, but, since i

Steady-state bifurcations of the three-dimensional Kolmogorov problem

Directory of Open Access Journals (Sweden)

Zhi-Min Chen

2000-08-01

Full Text Available This paper studies the spatially periodic incompressible fluid motion in $mathbb R^3$ excited by the external force $k^2(sin kz, 0,0$ with $kgeq 2$ an integer. This driving force gives rise to the existence of the unidirectional basic steady flow $u_0=(sin kz,0, 0$ for any Reynolds number. It is shown in Theorem 1.1 that there exist a number of critical Reynolds numbers such that $u_0$ bifurcates into either 4 or 8 or 16 different steady states, when the Reynolds number increases across each of such numbers.

Fabrication and Characterization of Ultrathin-ring Electrodes for Pseudo-steady-state Amperometric Detection.

Science.gov (United States)

Kitazumi, Yuki; Hamamoto, Katsumi; Noda, Tatsuo; Shirai, Osamu; Kano, Kenji

2015-01-01

The fabrication of ultrathin-ring electrodes with a diameter of 2 mm and a thickness of 100 nm is established. The ultrathin-ring electrodes provide a large density of pseudo-steady-state currents, and realize pseudo-steady-state amperometry under quiescent conditions without a Faraday cage. Under the limiting current conditions, the current response at the ultrathin-ring electrode can be well explained by the theory of the microband electrode response. Cyclic voltammograms at the ultrathin-ring electrode show sigmoidal characteristics with some hysteresis. Numerical simulation reveals that the hysteresis can be ascribed to the time-dependence of pseudo-steady-state current. The performance of amperometry with the ultrathin-ring electrode has been verified in its application to redox enzyme kinetic measurements.

Existence and instability of steady states for a triangular cross-diffusion system: A computer-assisted proof

Science.gov (United States)

Breden, Maxime; Castelli, Roberto

2018-05-01

In this paper, we present and apply a computer-assisted method to study steady states of a triangular cross-diffusion system. Our approach consist in an a posteriori validation procedure, that is based on using a fixed point argument around a numerically computed solution, in the spirit of the Newton-Kantorovich theorem. It allows to prove the existence of various non homogeneous steady states for different parameter values. In some situations, we obtain as many as 13 coexisting steady states. We also apply the a posteriori validation procedure to study the linear stability of the obtained steady states, proving that many of them are in fact unstable.

Steady-state heat transfer in an inverted U-tube steam generator

International Nuclear Information System (INIS)

Boucher, T.J.

1987-01-01

Experimental results are presented involving U-tube steam generator tube bundle local heat transfer and fluid conditions during stead-state, full-power operations performed at high temperatures and pressures with conditions typical of a pressurized water reactor (15.0 MPa primary pressure, 600 K steam generator inlet plenum fluid temperatures, 6.2 MPa secondary pressure). The Semiscale (MOD-2C facility represents the state-of-the-art in measurement of tube local heat transfer data and average tube bundle secondary fluid density at several elevations, which allows an estimate of the axial heat transfer and void distributions during steady-state and transient operations. The method of heat transfer data reduction is presented and the heat flux, secondary convective heat transfer coefficient, and void fraction distributions are quantified for steady-state, full-power operations

An accelerator based steady state neutron source

International Nuclear Information System (INIS)

Burke, R.J.; Johnson, D.L.

1985-01-01

Using high current, c.w. linear accelerator technology, a spallation neutron source can achieve much higher average intensities than existing or proposed pulsed spallation sources. With about 100 mA of 300 MeV protons or deuterons, the Accelerator Based Neutron Research Facility (ABNR) would initially achieve the 10 16 n/cm 2 .s thermal flux goal of the advanced steady state neutron source, and upgrading could provide higher steady state fluxes. The relatively low ion energy compared to other spallation sources has an important impact on R and D requirements as well as capital cost, for which a range of $300-450M is estimated by comparison to other accelerator-based neutron source facilities. The source is similar to a reactor source in most respects. It has some higher energy neutrons but fewer gamma rays, and the moderator region is free of many of the design constraints of a reactor, which helps to implement sources for various neutron energy spectra, many beam tubes, etc. With the development of multi-beam concept and the basis for currents greater than 100 mA that is assumed in the R and D plan, the ABNR would serve many additional uses, such as fusion materials development, production of proton-rich isotopes, and other energy and defense program needs

Very low frequency oscillations of heat load and recycling flux in steady-state tokamak discharge in TRIAM-1M

International Nuclear Information System (INIS)

Zushi, H.; Sakamoto, M.; Hanada, K.; Iyomasa, A.; Nakamura, K.; Sato, K.N.; Idei, H.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Hasegawa, M.; Matsuo, Y.; Kuramoto, K.; Sugata, T.; Maezono, N.; Hoshika, H.; Sasaki, K.

2004-01-01

Plasma wall interaction (PWI) driven relaxation oscillations are investigated in the steady state discharge for 5 hours. The oscillation frequency was about 10 -3 Hz and each perturbation lasted for about 300 s. The heat load, recycling flux and impurity influx were varied from a few % to several tens of %. The largest variation of 70% was seen on the Mo XIII (molybdenum), although the influx of Mo I was only 20 %. Although the input rf power is kept constant during the discharge, the coupling between the rf and plasma was increased by about 10%. The current drive efficiency is decreased by 24 % in spite of current ramp. The toroidal and poloidal profiles of the recycling flux were also changed. During the last relaxation phase, the plasma was finally terminated. The current reduction (> 4 kA) was not recovered by intense local perturbation of the recycling superposed on the relaxation oscillation. (authors)

Reliable and Efficient Procedure for Steady-State Analysis of Nonautonomous and Autonomous Systems

Directory of Open Access Journals (Sweden)

J. Dobes

2012-04-01

Full Text Available The majority of contemporary design tools do not still contain steady-state algorithms, especially for the autonomous systems. This is mainly caused by insufficient accuracy of the algorithm for numerical integration, but also by unreliable steady-state algorithms themselves. Therefore, in the paper, a very stable and efficient procedure for the numerical integration of nonlinear differential-algebraic systems is defined first. Afterwards, two improved methods are defined for finding the steady state, which use this integration algorithm in their iteration loops. The first is based on the idea of extrapolation, and the second utilizes nonstandard time-domain sensitivity analysis. The two steady-state algorithms are compared by analyses of a rectifier and a C-class amplifier, and the extrapolation algorithm is primarily selected as a more reliable alternative. Finally, the method based on the extrapolation naturally cooperating with the algorithm for solving the differential-algebraic systems is thoroughly tested on various electronic circuits: Van der Pol and Colpitts oscillators, fragment of a large bipolar logical circuit, feedback and distributed microwave oscillators, and power amplifier. The results confirm that the extrapolation method is faster than a classical plain numerical integration, especially for larger circuits with complicated transients.

Steady-state hydrodynamic instabilities of active liquid crystals: hybrid lattice Boltzmann simulations.

Science.gov (United States)

Marenduzzo, D; Orlandini, E; Cates, M E; Yeomans, J M

2007-09-01

We report hybrid lattice Boltzmann (HLB) simulations of the hydrodynamics of an active nematic liquid crystal sandwiched between confining walls with various anchoring conditions. We confirm the existence of a transition between a passive phase and an active phase, in which there is spontaneous flow in the steady state. This transition is attained for sufficiently "extensile" rods, in the case of flow-aligning liquid crystals, and for sufficiently "contractile" ones for flow-tumbling materials. In a quasi-one-dimensional geometry, deep in the active phase of flow-aligning materials, our simulations give evidence of hysteresis and history-dependent steady states, as well as of spontaneous banded flow. Flow-tumbling materials, in contrast, rearrange themselves so that only the two boundary layers flow in steady state. Two-dimensional simulations, with periodic boundary conditions, show additional instabilities, with the spontaneous flow appearing as patterns made up of "convection rolls." These results demonstrate a remarkable richness (including dependence on anchoring conditions) in the steady-state phase behavior of active materials, even in the absence of external forcing; they have no counterpart for passive nematics. Our HLB methodology, which combines lattice Boltzmann for momentum transport with a finite difference scheme for the order parameter dynamics, offers a robust and efficient method for probing the complex hydrodynamic behavior of active nematics.

Pre-steady-state Kinetics for Hydrolysis of Insoluble Cellulose by Cellobiohydrolase Cel7A

DEFF Research Database (Denmark)

Cruys-Bagger, Nicolaj; Olsen, Jens Elmerdahl; Præstgaard, Eigil

2012-01-01

The transient kinetic behavior of enzyme reactions prior to the establishment of steady state is a major source of mechanistic information, yet this approach has not been utilized for cellulases acting on their natural substrate, insoluble cellulose. Here, we elucidate the pre-steady-state regime...... for the exo-acting cellulase Cel7A using amperometric biosensors and an explicit model for processive hydrolysis of cellulose. This analysis allows the identification of a pseudo-steady-state period and quantification of a processivity number as well as rate constants for the formation of a threaded enzyme...... to unveil fundamental reasons for the distinctive variability in hydrolytic activity found in different cellulase-substrate systems....

Numerical analysis on the ion species ratios in a steady state hydrogen plasma

International Nuclear Information System (INIS)

Fukumasa, Osamu; Saeki, Setsuo; Osaki, Katashi; Sakiyama, Satoshi; Itatani, Ryohei.

1984-07-01

Ion species ratios in a hydrogen plasma are calculated systematically as a function of plasma parameters, i.e. the electron density, the electron temperature, the pressure of hydrogen gas and the plasma volume. Furthermore, in the present analysis, the recombination factor for hydrogen atoms at the wall surface of a vacuum vessel is treated as another plasma parameter. The most significant point is that ion species ratios depend strongly not only on plasma parameters, but also on the recombination factor. The proton ratio increases with decreasing value of the recombination factor. Primary electrons also play an important role for ion species ratios, and the presence of primary electrons causes the proton ratio to decrease. (author)

Combined Steady-State and Dynamic Heat Exchanger Experiment

Science.gov (United States)

Luyben, William L.; Tuzla, Kemal; Bader, Paul N.

2009-01-01

This paper describes a heat-transfer experiment that combines steady-state analysis and dynamic control. A process-water stream is circulated through two tube-in-shell heat exchangers in series. In the first, the process water is heated by steam. In the second, it is cooled by cooling water. The equipment is pilot-plant size: heat-transfer areas…

Steady-state equations of even flux and scattering

International Nuclear Information System (INIS)

Verwaerde, D.

1985-11-01

Some mathematical properties of steady-state equation of even flux are shown in variational formalism. This theoretical frame allows to study the existence of a solution and its asymptotical behavior in opaque media (i.e. the relation with scattering equation). At last it allows to qualify the convergence velocity of resolution iterative processes used practically [fr

Hydrodynamics of stratified epithelium: Steady state and linearized dynamics

Science.gov (United States)

Yeh, Wei-Ting; Chen, Hsuan-Yi

2016-05-01

A theoretical model for stratified epithelium is presented. The viscoelastic properties of the tissue are assumed to be dependent on the spatial distribution of proliferative and differentiated cells. Based on this assumption, a hydrodynamic description of tissue dynamics at the long-wavelength, long-time limit is developed, and the analysis reveals important insights into the dynamics of an epithelium close to its steady state. When the proliferative cells occupy a thin region close to the basal membrane, the relaxation rate towards the steady state is enhanced by cell division and cell apoptosis. On the other hand, when the region where proliferative cells reside becomes sufficiently thick, a flow induced by cell apoptosis close to the apical surface enhances small perturbations. This destabilizing mechanism is general for continuous self-renewal multilayered tissues; it could be related to the origin of certain tissue morphology, tumor growth, and the development pattern.

Exact steady state manifold of a boundary driven spin-1 Lai–Sutherland chain

International Nuclear Information System (INIS)

Ilievski, Enej; Prosen, Tomaž

2014-01-01

We present an explicit construction of a family of steady state density matrices for an open integrable spin-1 chain with bilinear and biquadratic interactions, also known as the Lai–Sutherland model, driven far from equilibrium by means of two oppositely polarizing Markovian dissipation channels localized at the boundary. The steady state solution exhibits n+1 fold degeneracy, for a chain of length n, due to existence of (strong) Liouvillian U(1) symmetry. The latter can be exploited to introduce a chemical potential and define a grand canonical nonequilibrium steady state ensemble. The matrix product form of the solution entails an infinitely-dimensional representation of a non-trivial Lie algebra (semidirect product of sl 2 and a non-nilpotent radical) and hints to a novel Yang–Baxter integrability structure

Exact steady state manifold of a boundary driven spin-1 Lai–Sutherland chain

Energy Technology Data Exchange (ETDEWEB)

Ilievski, Enej; Prosen, Tomaž

2014-05-15

We present an explicit construction of a family of steady state density matrices for an open integrable spin-1 chain with bilinear and biquadratic interactions, also known as the Lai–Sutherland model, driven far from equilibrium by means of two oppositely polarizing Markovian dissipation channels localized at the boundary. The steady state solution exhibits n+1 fold degeneracy, for a chain of length n, due to existence of (strong) Liouvillian U(1) symmetry. The latter can be exploited to introduce a chemical potential and define a grand canonical nonequilibrium steady state ensemble. The matrix product form of the solution entails an infinitely-dimensional representation of a non-trivial Lie algebra (semidirect product of sl{sub 2} and a non-nilpotent radical) and hints to a novel Yang–Baxter integrability structure.

Integration of steady-state and temporal gene expression data for the inference of gene regulatory networks.

Science.gov (United States)

Wang, Yi Kan; Hurley, Daniel G; Schnell, Santiago; Print, Cristin G; Crampin, Edmund J

2013-01-01

We develop a new regression algorithm, cMIKANA, for inference of gene regulatory networks from combinations of steady-state and time-series gene expression data. Using simulated gene expression datasets to assess the accuracy of reconstructing gene regulatory networks, we show that steady-state and time-series data sets can successfully be combined to identify gene regulatory interactions using the new algorithm. Inferring gene networks from combined data sets was found to be advantageous when using noisy measurements collected with either lower sampling rates or a limited number of experimental replicates. We illustrate our method by applying it to a microarray gene expression dataset from human umbilical vein endothelial cells (HUVECs) which combines time series data from treatment with growth factor TNF and steady state data from siRNA knockdown treatments. Our results suggest that the combination of steady-state and time-series datasets may provide better prediction of RNA-to-RNA interactions, and may also reveal biological features that cannot be identified from dynamic or steady state information alone. Finally, we consider the experimental design of genomics experiments for gene regulatory network inference and show that network inference can be improved by incorporating steady-state measurements with time-series data.

Recent advancement in research and planning toward high beta steady state operation in KSTAR

International Nuclear Information System (INIS)

Park, Hyeon Keo; Hong, S.; Humphreys, D.

2015-01-01

The goal of Korean Superconducting Tokamak Advanced Research (KSTAR) research is to explore stable improved confinement regimes and technical challenge for superconducting tokamak operation and thus, to establish the basis for predictable high beta steady state tokamak plasma operation. To fulfil the goal, the current KSTAR research program is composed of three elements: 1) Exploration of anticipated engineering and technology for a stable long pulse operation of high beta plasmas including Edge Localized Mode (ELM) control with the low n (=1, 2) Resonant Magnetic Perturbation (RMP) using in-vessel control coils and innovative non-inductive current drives. The achieved long pulse operation up to ∼50s and fully non-inductive current drive will be combined in the future. Study of efficient heat exhaust will be combined with an innovative divertor design/operation. 2) Exploration of the operation boundary through establishment of true stability limits of the harmful MagnetoHydroDynamic (MHD) instabilities and confinement of the tokamak plasmas in KSTAR, making use of the lowest error field and magnetic ripple simultaneously achieved among all tokamaks ever built. The intrinsic machine error field has a long history of research as the source of MHD instabilities and magnetic ripple is known to be a cause of energy loss in the plasma. The achieved high beta discharges at β N ∼4 and stable discharges at q 95 (∼2) will be further improved. 3) Validation of theoretical modeling of MHD instabilities and turbulence toward predictive capability of stable high beta plasmas. In support of these research goals, the state of the art diagnostic systems, such as Electron Cyclotron Emission Imaging (ECEI) system in addition to accurate profile diagnostics, are deployed not only to provide precise 2D/3D information of the MHD instabilities and turbulence but also to challenge unresolved physics problems such as the nature of ELMs, ELM-crash dynamics and the role of the core

Steady-state dynamo and current drive in a nonuniform bounded plasma

International Nuclear Information System (INIS)

Mett, R.R.; Taylor, J.B.

1991-03-01

Current drive due to helicity injection and dynamo effect are examined in an inhomogeneous bounded plasma. Averaged over a magnetic surface, there is in general no dynamo effect independent of resistivity -- contrary to the results found previously for an unbounded plasma. The dynamo field is calculated explicitly for an incompressible visco-resistive fluid in the plane-slab model. In accord with our general conclusion, outside the Alfven resonant layer it is proportional to the resistivity. Within the resonant layer there is a contribution which is enhanced, relative to its value outside the layer, by a factor (ωa 2 /(η + ν)), where ω is the wave frequency, a the plasma radius, η the magnetic diffusivity, and ν the kinematic viscosity. However, this contribution vanishes when integrated across the layer. The average field in the layer is enhanced by factor (ωa 2 /(η + ν)) 2/3 and is proportional to the shear in the magnetic field and the cube root of the gradient of the Alfven speed. These results are interpreted in terms of helicity balance, and reconciled with the infinite medium calculations. 15 refs

Algorithm for determining two-periodic steady-states in AC machines directly in time domain

Directory of Open Access Journals (Sweden)

Sobczyk Tadeusz J.

2016-09-01

Full Text Available This paper describes an algorithm for finding steady states in AC machines for the cases of their two-periodic nature. The algorithm enables to specify the steady-state solution identified directly in time domain despite of the fact that two-periodic waveforms are not repeated in any finite time interval. The basis for such an algorithm is a discrete differential operator that specifies the temporary values of the derivative of the two-periodic function in the selected set of points on the basis of the values of that function in the same set of points. It allows to develop algebraic equations defining the steady state solution reached in a chosen point set for the nonlinear differential equations describing the AC machines when electrical and mechanical equations should be solved together. That set of those values allows determining the steady state solution at any time instant up to infinity. The algorithm described in this paper is competitive with respect to the one known in literature an approach based on the harmonic balance method operated in frequency domain.

Analysis on the steady-state coherent synchrotron radiation with strong shielding

International Nuclear Information System (INIS)

Li, R.; Bohn, C.L.; Bisognano, J.J.

1997-01-01

There are several papers concerning shielding of coherent synchrotron radiation (CSR) emitted by a Gaussian line charge on a circular orbit centered between two parallel conducting plates. Previous asymptotic analyses in the frequency domain show that shielded steady-state CSR mainly arises from harmonics in the bunch frequency exceeding the threshold harmonic for satisfying the boundary conditions at the plates. In this paper the authors extend the frequency-domain analysis into the regime of strong shielding, in which the threshold harmonic exceeds the characteristic frequency of the bunch. The result is then compared to the shielded steady-state CSR power obtained using image charges

Steady-state entanglement and thermalization of coupled qubits in two common heat baths

Science.gov (United States)

Hu, Li-Zhen; Man, Zhong-Xiao; Xia, Yun-Jie

2018-03-01

In this work, we study the steady-state entanglement and thermalization of two coupled qubits embedded in two common baths with different temperatures. The common bath is relevant when the two qubits are difficult to be isolated to only contact with their local baths. With the quantum master equation constructed in the eigenstate representation of the coupled qubits, we have demonstrated the variations of steady-state entanglement with respect to various parameters of the qubits' system in both equilibrium and nonequilibrium cases of the baths. The coupling strength and energy detuning of the qubits as well as the temperature gradient of the baths are found to be beneficial to the enhancement of the entanglement. We note a dark state of the qubits that is free from time-evolution and its initial population can greatly influence the steady-state entanglement. By virtues of effective temperatures, we also study the thermalization of the coupled qubits and their variations with energy detuning.

A displacement based FE formulation for steady state problems

NARCIS (Netherlands)

Yu, Y.

2005-01-01

In this thesis a new displacement based formulation is developed for elasto-plastic deformations in steady state problems. In this formulation the displacements are the primary variables, which is in contrast to the more common formulations in terms of the velocities as the primary variables. In a

Importance sampling large deviations in nonequilibrium steady states. I

Science.gov (United States)

Ray, Ushnish; Chan, Garnet Kin-Lic; Limmer, David T.

2018-03-01

Large deviation functions contain information on the stability and response of systems driven into nonequilibrium steady states and in such a way are similar to free energies for systems at equilibrium. As with equilibrium free energies, evaluating large deviation functions numerically for all but the simplest systems is difficult because by construction they depend on exponentially rare events. In this first paper of a series, we evaluate different trajectory-based sampling methods capable of computing large deviation functions of time integrated observables within nonequilibrium steady states. We illustrate some convergence criteria and best practices using a number of different models, including a biased Brownian walker, a driven lattice gas, and a model of self-assembly. We show how two popular methods for sampling trajectory ensembles, transition path sampling and diffusion Monte Carlo, suffer from exponentially diverging correlations in trajectory space as a function of the bias parameter when estimating large deviation functions. Improving the efficiencies of these algorithms requires introducing guiding functions for the trajectories.

Importance sampling large deviations in nonequilibrium steady states. I.

Science.gov (United States)

Ray, Ushnish; Chan, Garnet Kin-Lic; Limmer, David T

2018-03-28

Large deviation functions contain information on the stability and response of systems driven into nonequilibrium steady states and in such a way are similar to free energies for systems at equilibrium. As with equilibrium free energies, evaluating large deviation functions numerically for all but the simplest systems is difficult because by construction they depend on exponentially rare events. In this first paper of a series, we evaluate different trajectory-based sampling methods capable of computing large deviation functions of time integrated observables within nonequilibrium steady states. We illustrate some convergence criteria and best practices using a number of different models, including a biased Brownian walker, a driven lattice gas, and a model of self-assembly. We show how two popular methods for sampling trajectory ensembles, transition path sampling and diffusion Monte Carlo, suffer from exponentially diverging correlations in trajectory space as a function of the bias parameter when estimating large deviation functions. Improving the efficiencies of these algorithms requires introducing guiding functions for the trajectories.

Very low frequency oscillations of heat load and recycling flux in steady-state tokamak discharge in TRIAM-1M

Energy Technology Data Exchange (ETDEWEB)

Zushi, H.; Sakamoto, M.; Hanada, K.; Iyomasa, A.; Nakamura, K.; Sato, K.N.; Idei, H.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Hasegawa, M. [Kyushu Univ., Research Institute for Applied Mechanics (Japan); Matsuo, Y.; Kuramoto, K.; Sugata, T.; Maezono, N.; Hoshika, H.; Sasaki, K. [Kyushu Univ., Interdisciplinary Graduate School of Engineering Sciences (Japan)

2004-07-01

Plasma wall interaction (PWI) driven relaxation oscillations are investigated in the steady state discharge for 5 hours. The oscillation frequency was about 10{sup -3} Hz and each perturbation lasted for about 300 s. The heat load, recycling flux and impurity influx were varied from a few % to several tens of %. The largest variation of 70% was seen on the Mo XIII (molybdenum), although the influx of Mo I was only 20 %. Although the input rf power is kept constant during the discharge, the coupling between the rf and plasma was increased by about 10%. The current drive efficiency is decreased by 24 % in spite of current ramp. The toroidal and poloidal profiles of the recycling flux were also changed. During the last relaxation phase, the plasma was finally terminated. The current reduction (> 4 kA) was not recovered by intense local perturbation of the recycling superposed on the relaxation oscillation. (authors)

Pharmacokinetics of methadone during maintenance therapy: Pulse labeling with deuterated methadone in the steady state

International Nuclear Information System (INIS)

Aenggard, E.; Nilsson, M.I.; Holmstrand, J.; Gunne, L.M.; Uppsala Univ.; Karolinsky Institutet, Stockholm

1979-01-01

A technique is presented for study of steady state kinetics of methadone using pulse labeling with deuterated methadone (d 3 ) and mass fragmentography to measure both unlabeled and labeled methadone in blood. Seven subjects maintained on methadone for at least 10 months were admitted to a closed metabolic ward. The daily dose of unlabeled methadone (d 0 ) was substituted by one dose of methadone-d 3 and plasma levels of methadone-d 0 and methadone-d 3 were followed for 48 h using a precise (SD +- 5%) and sensitive (30 pmol/ml) mass fragmentographic technique. Plasma half-lives (tsub(1/2)) for both methadone-d 0 and methadone-d 3 were calculated from samples obtained 8-24 h following the dose of methadone-d 3 . The tsub(1/2) of oral methadone-d 3 was shorter (22 +- 2 h) than that of methadone-d 0 (52 +- 20 h). The same pattern was observed after intravenous administration. The results indicate multiple pools of methadone in the body. (orig.) 891 AJ/orig. 892 MKO [de

A novel multivariate STeady-state index during general ANesthesia (STAN).

Science.gov (United States)

Castro, Ana; de Almeida, Fernando Gomes; Amorim, Pedro; Nunes, Catarina S

2017-08-01

The assessment of the adequacy of general anesthesia for surgery, namely the nociception/anti-nociception balance, has received wide attention from the scientific community. Monitoring systems based on the frontal EEG/EMG, or autonomic state reactions (e.g. heart rate and blood pressure) have been developed aiming to objectively assess this balance. In this study a new multivariate indicator of patients' steady-state during anesthesia (STAN) is proposed, based on wavelet analysis of signals linked to noxious activation. A clinical protocol was designed to analyze precise noxious stimuli (laryngoscopy/intubation, tetanic, and incision), under three different analgesic doses; patients were randomized to receive either remifentanil 2.0, 3.0 or 4.0 ng/ml. ECG, PPG, BP, BIS, EMG and [Formula: see text] were continuously recorded. ECG, PPG and BP were processed to extract beat-to-beat information, and [Formula: see text] curve used to estimate the respiration rate. A combined steady-state index based on wavelet analysis of these variables, was applied and compared between the three study groups and stimuli (Wilcoxon signed ranks, Kruskal-Wallis and Mann-Whitney tests). Following institutional approval and signing the informed consent thirty four patients were enrolled in this study (3 excluded due to signal loss during data collection). The BIS index of the EEG, frontal EMG, heart rate, BP, and PPG wave amplitude changed in response to different noxious stimuli. Laryngoscopy/intubation was the stimulus with the more pronounced response [Formula: see text]. These variables were used in the construction of the combined index STAN; STAN responded adequately to noxious stimuli, with a more pronounced response to laryngoscopy/intubation (18.5-43.1 %, [Formula: see text]), and the attenuation provided by the analgesic, detecting steady-state periods in the different physiological signals analyzed (approximately 50 % of the total study time). A new multivariate approach for

A Data Filter for Identifying Steady-State Operating Points in Engine Flight Data for Condition Monitoring Applications

Science.gov (United States)

Simon, Donald L.; Litt, Jonathan S.

2010-01-01

This paper presents an algorithm that automatically identifies and extracts steady-state engine operating points from engine flight data. It calculates the mean and standard deviation of select parameters contained in the incoming flight data stream. If the standard deviation of the data falls below defined constraints, the engine is assumed to be at a steady-state operating point, and the mean measurement data at that point are archived for subsequent condition monitoring purposes. The fundamental design of the steady-state data filter is completely generic and applicable for any dynamic system. Additional domain-specific logic constraints are applied to reduce data outliers and variance within the collected steady-state data. The filter is designed for on-line real-time processing of streaming data as opposed to post-processing of the data in batch mode. Results of applying the steady-state data filter to recorded helicopter engine flight data are shown, demonstrating its utility for engine condition monitoring applications.

Hot ion plasma production in HIP-1 using water-cooled hollow cathodes

Science.gov (United States)

Reinmann, J. J.; Lauver, M. R.; Patch, R. W.; Layman, R. W.; Snyder, A.

1975-01-01

A steady-state ExB plasma was formed by applying a strong radially inward dc electric field near the mirror throats. Most of the results were for hydrogen, but deuterium and helium plasmas were also studied. Three water-cooled hollow cathodes were operated in the hot-ion plasma mode with the following results: (1) thermally emitting cathodes were not required to achieve the hot-ion mode; (2) steady-state operation (several minutes) was attained; (3) input powers greater than 40 kW were achieved; (4) cathode outside diameters were increased from 1.2 cm (uncooled) to 4.4 cm (water-cooled); (5) steady-state hydrogen plasma with ion temperatures from 185 to 770 eV and electron temperatures from 5 to 21 eV were produced. Scaling relations were empirically obtained for discharge current, ion temperature, electron temperature, and relative ion density as a function of hydrogen gas feed rate, magnetic field, and cathode voltage. Neutrons were produced from deuterium plasma, but it was not established whether thay came from the plasma volume or from the electrode surfaces.

Comparison of pulsed three-dimensional CEST acquisition schemes at 7 tesla : steady state versus pseudosteady state

NARCIS (Netherlands)

Khlebnikov, Vitaly; Geades, Nicolas; Klomp, DWJ; Hoogduin, Hans; Gowland, Penny; Mougin, Olivier

PURPOSE: To compare two pulsed, volumetric chemical exchange saturation transfer (CEST) acquisition schemes: steady state (SS) and pseudosteady state (PS) for the same brain coverage, spatial/spectral resolution and scan time. METHODS: Both schemes were optimized for maximum sensitivity to amide

Steady-state and dynamic models for particle engulfment during solidification

Science.gov (United States)

Tao, Yutao; Yeckel, Andrew; Derby, Jeffrey J.

2016-06-01

Steady-state and dynamic models are developed to study the physical mechanisms that determine the pushing or engulfment of a solid particle at a moving solid-liquid interface. The mathematical model formulation rigorously accounts for energy and momentum conservation, while faithfully representing the interfacial phenomena affecting solidification phase change and particle motion. A numerical solution approach is developed using the Galerkin finite element method and elliptic mesh generation in an arbitrary Lagrangian-Eulerian implementation, thus allowing for a rigorous representation of forces and dynamics previously inaccessible by approaches using analytical approximations. We demonstrate that this model accurately computes the solidification interface shape while simultaneously resolving thin fluid layers around the particle that arise from premelting during particle engulfment. We reinterpret the significance of premelting via the definition an unambiguous critical velocity for engulfment from steady-state analysis and bifurcation theory. We also explore the complicated transient behaviors that underlie the steady states of this system and posit the significance of dynamical behavior on engulfment events for many systems. We critically examine the onset of engulfment by comparing our computational predictions to those obtained using the analytical model of Rempel and Worster [29]. We assert that, while the accurate calculation of van der Waals repulsive forces remains an open issue, the computational model developed here provides a clear benefit over prior models for computing particle drag forces and other phenomena needed for the faithful simulation of particle engulfment.

Three-dimensional stellarator equilibrium as an ohmic steady state

International Nuclear Information System (INIS)

Park, W.; Monticello, D.A.; Strauss, H.; Manickam, J.

1985-07-01

A stable three-dimensional stellarator equilibrium can be obtained numerically by a time-dependent relaxation method using small values of dissipation. The final state is an ohmic steady state which approaches an ohmic equilibrium in the limit of small dissipation coefficients. We describe a method to speed up the relaxation process and a method to implement the B vector . del p = 0 condition. These methods are applied to obtain three-dimensional heliac equilibria using the reduced heliac equations

Comparison of Steady-State SVC Models in Load Flow Calculations

DEFF Research Database (Denmark)

Chen, Peiyuan; Chen, Zhe; Bak-Jensen, Birgitte

2008-01-01

This paper compares in a load flow calculation three existing steady-state models of static var compensator (SVC), i.e. the generator-fixed susceptance model, the total susceptance model and the firing angle model. The comparison is made in terms of the voltage at the SVC regulated bus, equivalent...... SVC susceptance at the fundamental frequency and the load flow convergence rate both when SVC is operating within and on the limits. The latter two models give inaccurate results of the equivalent SVC susceptance as compared to the generator model due to the assumption of constant voltage when the SVC...... is operating within the limits. This may underestimate or overestimate the SVC regulating capability. Two modified models are proposed to improve the SVC regulated voltage according to its steady-state characteristic. The simulation results of the two modified models show the improved accuracy...

Rapid mixing and short storage timescale in the magma dynamics of a steady-state volcano

Science.gov (United States)

Petrone, Chiara Maria; Braschi, Eleonora; Francalanci, Lorella; Casalini, Martina; Tommasini, Simone

2018-06-01

Steady-state volcanic activity implies equilibrium between the rate of magma replenishment and eruption of compositionally homogeneous magmas, lasting for tens to thousands of years in an open conduit system. The Present-day activity of Stromboli volcano (Aeolian Islands, Southern Italy) has long been recognised as typical of a steady-state volcano, with a shallow magmatic reservoir (highly porphyritic or hp-magma) continuously refilled by more mafic magma (with low phenocryst content or lp-magma) at a constant rate and accompanied by mixing, crystallisation and eruption. Our aim is to clarify the timescale and dynamics of the plumbing system at the establishment of the Present-day steady-state activity (volcanoes.

High resolution Thomson scattering system for steady-state linear plasma sources

Science.gov (United States)

Lee, K. Y.; Lee, K. I.; Kim, J. H.; Lho, T.

2018-01-01

The high resolution Thomson scattering system with 63 points along a 25 mm line measures the radial electron temperature (Te) and its density (ne) in an argon plasma. By using a DC arc source with lanthanum hexaboride (LaB6) electrode, plasmas with electron temperature of over 5 eV and densities of 1.5 × 1019 m-3 have been measured. The system uses a frequency doubled (532 nm) Nd:YAG laser with 0.25 J/pulse at 20 Hz. The scattered light is collected and sent to a triple-grating spectrometer via optical-fibers, where images are recorded by an intensified charge coupled device (ICCD) camera. Although excellent in stray-light reduction, a disadvantage comes with its relatively low optical transmission and in sampling a tiny scattering volume. Thus requires accumulating multitude of images. In order to improve photon statistics, pixel binning in the ICCD camera as well as enlarging the intermediate slit-width inside the triple-grating spectrometer has been exploited. In addition, the ICCD camera capture images at 40 Hz while the laser is at 20 Hz. This operation mode allows us to alternate between background and scattering shot images. By image subtraction, influences from the plasma background are effectively taken out. Maximum likelihood estimation that uses a parameter sweep finds best fitting parameters Te and ne with the incoherent scattering spectrum.

Comparing Non-Steady State Emissions under Start-Up and Shut-Down Operating Conditions with Steady State Emissions for Several Industrial Sectors: A Literature Review

Directory of Open Access Journals (Sweden)

Juwairia Obaid

2017-02-01

Full Text Available This study investigates the emissions of various industrial facilities under start-up, shut-down, and normal operations. The industries that have been investigated include power and/or heat generation, energy-from-waste generation, nuclear power generation, sulphuric acid production, ethylene production, petrochemical production, and waste incineration. The study investigated multiple facilities worldwide for each of these industrial categories. The different potential contaminants characteristic of each industry type have been investigated and the emissions of these contaminants under non-steady state have been compared to the steady state emissions. Where available, trends have been developed to identify the circumstances, i.e., the industrial sector and contaminant, under which the assessment and consideration of emissions from start-up and shut-down events is necessary for each industry. These trends differ by industrial sector and contaminant. For example, the study shows that sulphur dioxide (SO2 emissions should be assessed for the start-up operations of sulphuric acid production plants, but may not need to be assessed for the start-up operations of a conventional power generation facility. The trends developed as part of this research paper will help air permit applicants to effectively allocate their resources when assessing emissions related to non-steady state operations. Additionally, it will ensure that emissions are assessed for the worst-case scenario. This is especially important when emissions under start-up and shut-down operations have the potential to exceed enforceable emission limits. Thus, assessing emissions for the worst-case scenario can help in preventing the emissions from adversely impacting public health and the environment.

On the generation of steady currents in a plasma cylinder using RF waves

International Nuclear Information System (INIS)

Hugrass, W.N.

1980-10-01

The generation of a steady current in a resistive plasma cylinder by means of a travelling wave magnetic field has been studied using the resistive MHD equations. The nonlinear initial-boundary value problem has been solved using a semi-Lagrangian two dimensional algorithm. The numerical code has been used to simulate the Synchromak experiment of Nagoya University. Hollow d.c. current profiles, similar to the experimental data, have been obtained. A simple analytical argument, of a more general nature, shows that classical resistive diffusion cannot lead to a more uniform current distribution

Development of repetitive railgun pellet accelerator and steady-state pellet supply system

International Nuclear Information System (INIS)

Oda, Y.; Onozuka, M.; Azuma, K.; Kasai, S.; Hasegawa, K.

1995-01-01

A railgun system for repetitive high-speed pellet acceleration and steady-state pellet supply system has been developed and investigated. Using a 2m-long railgun system, the hydrogen pellet was accelerated to 2.6km/sec by the supplied energy of 1.7kJ. It is expected that the hydrogen pellet can be accelerated to 3km/sec using the present pneumatic pellet accelerator and a 2m-long augment railgun. Screw-driven hydrogen-isotope filament extruding system has been fabricated and will be tested to examine its applicability to the steady-state extrusion of the solid hydrogen-isotope filament

Development of repetitive railgun pellet accelerator and steady-state pellet supply system

Energy Technology Data Exchange (ETDEWEB)

Oda, Y.; Onozuka, M.; Azuma, K. [Mitsubishi Heavy Industries, Ltd., Kobe (Japan); Kasai, S.; Hasegawa, K. [Japan Atomic Energy Research Inst., Naka (Japan)

1995-12-31

A railgun system for repetitive high-speed pellet acceleration and steady-state pellet supply system has been developed and investigated. Using a 2m-long railgun system, the hydrogen pellet was accelerated to 2.6km/sec by the supplied energy of 1.7kJ. It is expected that the hydrogen pellet can be accelerated to 3km/sec using the present pneumatic pellet accelerator and a 2m-long augment railgun. Screw-driven hydrogen-isotope filament extruding system has been fabricated and will be tested to examine its applicability to the steady-state extrusion of the solid hydrogen-isotope filament.

Local wettability reversal during steady-state two-phase flow in porous media.

Science.gov (United States)

Sinha, Santanu; Grøva, Morten; Ødegården, Torgeir Bryge; Skjetne, Erik; Hansen, Alex

2011-09-01

We study the effect of local wettability reversal on remobilizing immobile fluid clusters in steady-state two-phase flow in porous media. We consider a two-dimensional network model for a porous medium and introduce a wettability alteration mechanism. A qualitative change in the steady-state flow patterns, destabilizing the percolating and trapped clusters, is observed as the system wettability is varied. When capillary forces are strong, a finite wettability alteration is necessary to move the system from a single-phase to a two-phase flow regime. When both phases are mobile, we find a linear relationship between fractional flow and wettability alteration.

An equation oriented approach to steady state flowsheeting of methanol synthesis loop

International Nuclear Information System (INIS)

Fathikalajahi, J.; Baniadam, M.; Rahimpour, M.R.

2008-01-01

An equation-oriented approach was developed for steady state flowsheeting of a commercial methanol plant. The loop consists of fixed bed reactor, flash separator, preheater, coolers, and compressor. For steady sate flowsheeting of the plant mathematical model of reactor and other units are needed. Reactor used in loop is a Lurgi type and its configuration is rather complex. Previously reactor and flash separator are modeled as two important units of plant. The model is based on mass and energy balances in each equipment and utilizing some auxiliary equations such as rate of reaction and thermodynamics model for activity coefficients of liquid. In order to validate the mathematical model for the synthesis loop, some simulation data were performed using operating conditions and characteristics of the commercial plant. The good agreement between the steady state simulation results and the plant data shows the validity of the model

Coagulation profile of children with sickle cell anemia in steady state ...

African Journals Online (AJOL)

Background: Sickle cell anemia is associated with a hypercoagulable state that may lead to alterations in a coagulation profile. Measurements of coagulation factors are known to have some predictive value for clinical outcome. Objectives: To determine the coagulation profile of children with SCA in steady state and crisis ...

Cycle kinetics, steady state thermodynamics and motors-a paradigm for living matter physics

International Nuclear Information System (INIS)

Qian, Hong

2005-01-01

An integration of the stochastic mathematical models for motor proteins with Hill's steady state thermodynamics yields a rather comprehensive theory for molecular motors as open systems in the nonequilibrium steady state. This theory, a natural extension of Gibbs' approach to isothermal molecular systems in equilibrium, is compared with other existing theories with dissipative structures and dynamics. The theory of molecular motors might be considered as an archetype for studying more complex open biological systems such as biochemical reaction networks inside living cells

Determination of the Steady State Leakage Current in Structures with Ferroelectric Ceramic Films

Science.gov (United States)

Podgornyi, Yu. V.; Vorotilov, K. A.; Sigov, A. S.

2018-03-01

Steady state leakage currents have been investigated in capacitor structures with ferroelectric solgel films of lead zirconate titanate (PZT) formed on silicon substrates with a lower Pt electrode. It is established that Pt/PZT/Hg structures, regardless of the PZT film thickness, are characterized by the presence of a rectifying contact similar to p-n junction. The steady state leakage current in the forward direction increases with a decrease in the film thickness and is determined by the ferroelectric bulk conductivity.

steady and dynamic states analysis of induction motor: fea approach

African Journals Online (AJOL)

HOD

The flux levels at these loading conditions were also monitored. Key words: Three phase Induction Motor, Steady state and Dynamic Response, Flux Levels, FEA, Loading conditions. 1. INTRODUCTION ..... Boston: Computational Mechanics Publications;. New York: ... for Electrical Engineers, Cambridge University. Press ...

Post-CHF heat transfer during steady-state and transient conditions

International Nuclear Information System (INIS)

Fung, K.K.

1978-06-01

This review extends previous reviews of steady-state post-CHF literature by Groeneveld, Gardiner, and Fung by including more recent data. A review of the literature on transient post-CHF data is also included by extending the work of Yadigaroglu

Distraction task rather than focal attention modulates gamma activity associated with auditory steady-state responses (ASSRs)

DEFF Research Database (Denmark)

Griskova-Bulanova, Inga; Ruksenas, Osvaldas; Dapsys, Kastytis

2011-01-01

To explore the modulation of auditory steady-state response (ASSR) by experimental tasks, differing in attentional focus and arousal level.......To explore the modulation of auditory steady-state response (ASSR) by experimental tasks, differing in attentional focus and arousal level....

Steady state solution of the Poisson-Nernst-Planck equations

International Nuclear Information System (INIS)

Golovnev, A.; Trimper, S.

2010-01-01

The exact steady state solution of the Poisson-Nernst-Planck equations (PNP) is given in terms of Jacobi elliptic functions. A more tractable approximate solution is derived which can be used to compare the results with experimental observations in binary electrolytes. The breakdown of the PNP for high concentration and high applied voltage is discussed.

Spatial variability of steady-state infiltration into a two-layer soil system on burned hillslopes

Science.gov (United States)

Kinner, D.A.; Moody, J.A.

2010-01-01

Rainfall-runoff simulations were conducted to estimate the characteristics of the steady-state infiltration rate into 1-m2 north- and south-facing hillslope plots burned by a wildfire in October 2003. Soil profiles in the plots consisted of a two-layer system composed of an ash on top of sandy mineral soil. Multiple rainfall rates (18.4-51.2 mm h-1) were used during 14 short-duration (30 min) and 2 long-duration simulations (2-4 h). Steady state was reached in 7-26 min. Observed spatially-averaged steady-state infiltration rates ranged from 18.2 to 23.8 mm h-1 for north-facing and from 17.9 to 36.0 mm h-1 for south-facing plots. Three different theoretical spatial distribution models of steady-state infiltration rate were fit to the measurements of rainfall rate and steady-state discharge to provided estimates of the spatial average (19.2-22.2 mm h-1) and the coefficient of variation (0.11-0.40) of infiltration rates, overland flow contributing area (74-90% of the plot area), and infiltration threshold (19.0-26 mm h-1). Tensiometer measurements indicated a downward moving pressure wave and suggest that infiltration-excess overland flow is the runoff process on these burned hillslope with a two-layer system. Moreover, the results indicate that the ash layer is wettable, may restrict water flow into the underlying layer, and increase the infiltration threshold; whereas, the underlying mineral soil, though coarser, limits the infiltration rate. These results of the spatial variability of steady-state infiltration can be used to develop physically-based rainfall-runoff models for burned areas with a two-layer soil system. ?? 2010 Elsevier B.V.

MARS input data for steady-state calculation of ATLAS

International Nuclear Information System (INIS)

Park, Hyun Sik; Euh, D. J.; Choi, K. Y.; Kwon, T. S.; Jeong, J. J.; Baek, W. P.

2004-12-01

An integral effect test loop for Pressurized Water Reactors (PWRs), the ATLAS (Advanced Thermal-hydraulic Test Loop for Accident Simulation), is under construction by Thermal-Hydraulics Safety Research Division in Korea Atomic Energy Research Institute (KAERI). This report includes calculation sheets of the input for the best-estimate system analysis code, the MARS code, based on the ongoing design features of ATLAS. The ATLAS facility has been designed to have the length scale of 1/2 and area scale of 1/144 compared with the reference plant, APR1400. The contents of this report are divided into three parts: (1) core and reactor vessel, (2) steam generator and steam line, and (3) primary piping, pressurizer and reactor coolant pump. The steady-state analysis for the ATLAS facility will be performed based on these calculation sheets, and its results will be applied to the detailed design of ATLAS. Additionally, the calculation results will contribute to getting optimum test conditions and preliminary operational test conditions for the steady-state and transient experiments

Steady-state pharmacokinetics of pravastatin in children with familial hypercholesterolaemia

NARCIS (Netherlands)

Wiersma, Heleen E.; Wiegman, Albert; Koopmans, Richard P.; Bakker, Henk D.; Kastelein, John J. P.; van Boxtel, Chris J.

2004-01-01

Objective: To determine pharmacokinetic data for pravastatin in children, since current data are insufficient in this age group. Subjects and methods: A 2-week, multiple-dose, steady-state pharmacokinetic study was carried out with pravastatin 20mg daily in 24 children with familial

Optimising performance in steady state for a supermarket refrigeration system

DEFF Research Database (Denmark)

Green, Torben; Kinnaert, Michel; Razavi-Far, Roozbeh

2012-01-01

Using a supermarket refrigeration system as an illustrative example, the paper postulates that by appropriately utilising knowledge of plant operation, the plant wide performance can be optimised based on a small set of variables. Focusing on steady state operations, the total system performance...

Iterative Observer-based Estimation Algorithms for Steady-State Elliptic Partial Differential Equation Systems

KAUST Repository

Majeed, Muhammad Usman

2017-07-19

Steady-state elliptic partial differential equations (PDEs) are frequently used to model a diverse range of physical phenomena. The source and boundary data estimation problems for such PDE systems are of prime interest in various engineering disciplines including biomedical engineering, mechanics of materials and earth sciences. Almost all existing solution strategies for such problems can be broadly classified as optimization-based techniques, which are computationally heavy especially when the problems are formulated on higher dimensional space domains. However, in this dissertation, feedback based state estimation algorithms, known as state observers, are developed to solve such steady-state problems using one of the space variables as time-like. In this regard, first, an iterative observer algorithm is developed that sweeps over regular-shaped domains and solves boundary estimation problems for steady-state Laplace equation. It is well-known that source and boundary estimation problems for the elliptic PDEs are highly sensitive to noise in the data. For this, an optimal iterative observer algorithm, which is a robust counterpart of the iterative observer, is presented to tackle the ill-posedness due to noise. The iterative observer algorithm and the optimal iterative algorithm are then used to solve source localization and estimation problems for Poisson equation for noise-free and noisy data cases respectively. Next, a divide and conquer approach is developed for three-dimensional domains with two congruent parallel surfaces to solve the boundary and the source data estimation problems for the steady-state Laplace and Poisson kind of systems respectively. Theoretical results are shown using a functional analysis framework, and consistent numerical simulation results are presented for several test cases using finite difference discretization schemes.

Theoretical analysis of steady state operating forces in control valves

Directory of Open Access Journals (Sweden)

Basavaraj Hubballi

2018-01-01

Full Text Available The controlling components, such as valves are used to regulate controlled fluid power. It is not always possible to calculate valve forces accurately, and with some types of valves even the existence of certain types of forces cannot be predicted with certainty. In many cases, however, the analysis can be made fairly completely and accurately. The assumption of steady state conditions is valid for the valve alone, but transient effects in the rest of the system may be large. These effects are particularly important with regard to the instability of valves, where the system may react on the valve in such a way as to make it squeal or oscillate, sometimes with large amplitude. The origin of the steady state flow force understood from a brief qualitative explanation. The following paper will summarize much of what is known about valve forces in the spool type controlling element.

Cathodic Vacuum Arc Plasma of Thallium

International Nuclear Information System (INIS)

Yushkov, Georgy Yu.; Anders, Andre

2006-01-01

Thallium arc plasma was investigated in a vacuum arc ion source. As expected from previous consideration of cathode materials in the Periodic Table of the Elements, thallium plasma shows lead-like behavior. Its mean ion charge state exceeds 2.0 immediately after arc triggering, reaches the predicted 1.60 and 1.45 after about 100 microsec and 150 microsec, respectively. The most likely ion velocity is initially8000 m/s and decays to 6500 m/s and 6200 m/s after 100 microsec and 150microsec, respectively. Both ion charge states and ion velocities decay further towards steady state values, which are not reached within the 300microsec pulses used here. It is argued that the exceptionally high vapor pressure and charge exchange reactions are associated with the establishment of steady state ion values

Is steady-state capitalism viable? A review of the issues and an answer in the affirmative.

Science.gov (United States)

Lawn, Philip

2011-02-01

Most ecological economists believe that the transition to a steady-state economy is necessary to ensure ecological sustainability and to maximize a nation's economic welfare. While some observers agree with the necessity of the steady-state economy, they are nonetheless critical of the suggestion made by ecological economists-in particular, Herman Daly-that a steady-state economy is compatible with a capitalist system. First, they believe that steady-state capitalism is based on the untenable assumption that growth is an optional rather than in-built element of capitalism. Second, they argue that capitalist notions of efficient resource allocation are too restrictive to facilitate the transition to an "ecological" or steady-state economy. I believe these observers are outright wrong with their first criticism and, because they misunderstand Daly's vision of a steady-state economy, are misplaced with their second criticism. The nature of a capitalist system depends upon the institutional framework that supports and shapes it. Hence, a capitalist system can exist in a wide variety of forms. Unfortunately, many observers fail to recognize that the current "growth imperative" is the result of capitalist systems everywhere being institutionally designed to grow. They need not be designed this way to survive and thrive. Indeed, because continued growth is both existentially undesirable and ecologically unsustainable, redesigning capitalist systems through the introduction of Daly-like institutions would prove to be capitalism's savior. What's more, it would constitute humankind's best hope of achieving sustainable development. © 2011 New York Academy of Sciences.

Stabilizing the border steady-state solution of two interacting ...

African Journals Online (AJOL)

In this paper, we have successfully developed a feedback control which has been used to stabilize an unstable steady-state solution (0, 3.3534). This convergence has occurred when the values of the final time are 190, 200, 210 and 220 which corresponds to the scenario when the value of the step length of our simulation ...

Coherent control of long-distance steady-state entanglement in lossy resonator arrays

Science.gov (United States)

Angelakis, D. G.; Dai, L.; Kwek, L. C.

2010-07-01

We show that coherent control of the steady-state long-distance entanglement between pairs of cavity-atom systems in an array of lossy and driven coupled resonators is possible. The cavities are doped with atoms and are connected through waveguides, other cavities or fibers depending on the implementation. We find that the steady-state entanglement can be coherently controlled through the tuning of the phase difference between the driving fields. It can also be surprisingly high in spite of the pumps being classical fields. For some implementations where the connecting element can be a fiber, long-distance steady-state quantum correlations can be established. Furthermore, the maximal of entanglement for any pair is achieved when their corresponding direct coupling is much smaller than their individual couplings to the third party. This effect is reminiscent of the establishment of coherence between otherwise uncoupled atomic levels using classical coherent fields. We suggest a method to measure this entanglement by analyzing the correlations of the emitted photons from the array and also analyze the above results for a range of values of the system parameters, different network geometries and possible implementation technologies.

Producing a steady-state population inversion

International Nuclear Information System (INIS)

Richards, R.K.; Griffin, D.C.

1986-03-01

An observed steady-state transition at 17.5 nm is identified as the 2p 5 3s3p 4 S/sub 3/2/ → 2p 6 3p 2 P/sub 3/2/ transition in Na-like aluminum. The upper level is populated by electron inner shell ionization of metastable Mg-like aluminum. From the emission intensity, the rate coefficient for populating the upper level is calculated to be approximately 5 x 10 -10 ) cm 3 /sec. Since the upper level is quasimetastable with a lifetime 22 times longer than the lower level, it may be possible to produce a population inversion, if a competing process to populate the lower level can be reduced

The Effects of High Intensity Interval Training vs Steady State Training on Aerobic and Anaerobic Capacity.

Science.gov (United States)

Foster, Carl; Farland, Courtney V; Guidotti, Flavia; Harbin, Michelle; Roberts, Brianna; Schuette, Jeff; Tuuri, Andrew; Doberstein, Scott T; Porcari, John P

2015-12-01

High intensity interval training (HIIT) has become an increasingly popular form of exercise due to its potentially large effects on exercise capacity and small time requirement. This study compared the effects of two HIIT protocols vs steady-state training on aerobic and anaerobic capacity following 8-weeks of training. Fifty-five untrained college-aged subjects were randomly assigned to three training groups (3x weekly). Steady-state (n = 19) exercised (cycle ergometer) 20 minutes at 90% of ventilatory threshold (VT). Tabata (n = 21) completed eight intervals of 20s at 170% VO2max/10s rest. Meyer (n = 15) completed 13 sets of 30s (20 min) @ 100% PVO2 max/ 60s recovery, average PO = 90% VT. Each subject did 24 training sessions during 8 weeks. There were significant (p Tabata protocol was significantly less enjoyable (p HIIT protocols are time efficient, they are not superior to conventional exercise training in sedentary young adults. Key pointsSteady state training equivalent to HIIT in untrained studentsMild interval training presents very similar physiologic challenge compared to steady state trainingHIIT (particularly very high intensity variants were less enjoyable than steady state or mild interval trainingEnjoyment of training decreases across the course of an 8 week experimental training program.

TPSS plasma engineering studies: profile effects and plasma power balance

International Nuclear Information System (INIS)

Borowski, S.K.; Strickler, D.J.

1985-01-01

A computationally fast profile-averaged, steady-state plasma model has been developed to allow studies of radial effects in ignited and driven tokamak systems. This code was used to search for the smallest size tokamak consistent with power balance calculations

Iterative Observer-based Estimation Algorithms for Steady-State Elliptic Partial Differential Equation Systems

KAUST Repository

Majeed, Muhammad Usman

2017-01-01

the problems are formulated on higher dimensional space domains. However, in this dissertation, feedback based state estimation algorithms, known as state observers, are developed to solve such steady-state problems using one of the space variables as time

Analysis of steady state and transient two-phase flows in downwardly inclined lines

International Nuclear Information System (INIS)

Crawford, T.J.

1983-01-01

A study of steady-state and transient two-phase flows in downwardly inclined lines is described. Steady-state flow patterns maps are presented using Freon-113 as the working fluid to provide new high density vapors. These flow maps with high density vapor serve to significantly extend the investigations of steady-state downward two-phase flow patterns. Physical models developed which successfully predicted the onset or location of various flow pattern transitions. A new simplified criterion that would be useful to designers and experimenters is offered for the onset of dispersed flow. A new empirical holdup correlation and a new bubble diameter/flow rate correlation are also proposed. Flow transients in vertical downward lines were studied to investigate the possible formation of intermediate or spurious flow patterns that would not be seen at steady-state conditions. Void fraction behavior during the transients was modeled by using the dynamic slip equation from the transient analysis code RETRAN. Physical models of interfacial area were developed and compared with models and data from literature. There was satisfactory agreement between the models of the present study and the literature models and data. The concentration parameter of the drift flux model was evaluated for vertical downward flow. These new values of the flow dependent parameter were different from those previously proposed in the literature for use in upward flows, and made the drift flux model suitable for use in upward or downward flow lines

Steady-state ozone concentrations in radiation induced noble gas-oxygen discharges

International Nuclear Information System (INIS)

Elsayed-Ali, H.E.; Miley, G.H.

1985-01-01

Measurements of steady-state ozone concentrations in continuous radiation induced noble gas-O/sub 2/ and noble gas-o/sub 2/-SF/sub 6/ mixtures has been accomplished. The discharges were created through the bombardment of the gases with energetic particles from the boron-10 (n,α) lithium-7 nuclear reaction. Three noble gases were studied, He, Ne, and Ar at partial pressures of few hundred Torr. The dose rates studied were in the order of 10/sup 15/ eV . cm/sup -3/ . s/sup -1/. The experimental apparatus and procedure were previously described. The experimentally observed steady-state ozone concentrations in noble gas-O/sub 2/ discharges were about an order of magnitude lower than that observed for oxygen radiolysis at similar dose rates. These results were physically explained by an enhanced role of negative ionic reactions with ozone causing its destruction. In noble gas-O/sub 2/-SF/sub 6/ mixtures, the steady-state ozone concentrations were found to be significantly higher (3-6 times) than that without the SF/sub 6/ addition. This observation was contrary to only a small increase observed after SF/sub 6/ addition to a few hundred Torr oxygen and is explained by an enhanced rate of electron dissociative attachment of ozone in noble gas-O/sub 2/ discharges

Transient and Steady-State Responses of an Asymmetric Nonlinear Oscillator

Directory of Open Access Journals (Sweden)

Alex Elías-Zúñiga

2013-01-01

oscillator that describes the motion of a damped, forced system supported symmetrically by simple shear springs on a smooth inclined bearing surface. We also use the percentage overshoot value to study the influence of damping and nonlinearity on the transient and steady-state oscillatory amplitudes.

Capitalist Diversity and De-growth Trajectories to Steady-state Economies

DEFF Research Database (Denmark)

Buch-Hansen, Hubert

2014-01-01

Growth-critical scholarship has done much to both expose the environmentally unsustainable nature of the capitalist growth-economies of the overdeveloped part of the world and to develop an alternative vision of a degrowth transition leading to a steady-state economy. However, this scholarship fa...

Restitution slope is principally determined by steady-state action potential duration.

Science.gov (United States)

Shattock, Michael J; Park, Kyung Chan; Yang, Hsiang-Yu; Lee, Angela W C; Niederer, Steven; MacLeod, Kenneth T; Winter, James

2017-06-01

The steepness of the action potential duration (APD) restitution curve and local tissue refractoriness are both thought to play important roles in arrhythmogenesis. Despite this, there has been little recognition of the apparent association between steady-state APD and the slope of the restitution curve. The objective of this study was to test the hypothesis that restitution slope is determined by APD and to examine the relationship between restitution slope, refractoriness and susceptibility to VF. Experiments were conducted in isolated hearts and ventricular myocytes from adult guinea pigs and rabbits. Restitution curves were measured under control conditions and following intervention to prolong (clofilium, veratridine, bretylium, low [Ca]e, chronic transverse aortic constriction) or shorten (catecholamines, rapid pacing) ventricular APD. Despite markedly differing mechanisms of action, all interventions that prolonged the action potential led to a steepening of the restitution curve (and vice versa). Normalizing the restitution curve as a % of steady-state APD abolished the difference in restitution curves with all interventions. Effects on restitution were preserved when APD was modulated by current injection in myocytes pre-treated with the calcium chelator BAPTA-AM - to abolish the intracellular calcium transient. The non-linear relation between APD and the rate of repolarization of the action potential is shown to underpin the common influence of APD on the slope of the restitution curve. Susceptibility to VF was found to parallel changes in APD/refractoriness, rather than restitution slope. Steady-state APD is the principal determinant of the slope of the ventricular electrical restitution curve. In the absence of post-repolarization refractoriness, factors that prolong the action potential would be expected to steepen the restitution curve. However, concomitant changes in tissue refractoriness act to reduce susceptibility to sustained VF. Dependence on

A simulation study on burning profile tailoring of steady state, high bootstrap current tokamaks

International Nuclear Information System (INIS)

Nakamura, Y.; Takei, N.; Tobita, K.; Sakamoto, Y.; Fujita, T.; Fukuyama, A.; Jardin, S.C.

2007-01-01

From the aspect of fusion burn control in steady state DEMO plant, the significant challenges are to maintain its high power burning state of ∝3-5 GW without burning instability, hitherto well-known as ''thermal stability'', and also to keep its desired burning profile relevant with internal transport barrier (ITB) that generates high bootstrap current. The paper presents a simulation modeling of the burning stability coupled with the self-ignited fusion burn and the structure-formation of the ITB. A self-consistent simulation, including a model for improved core energy confinement, has pointed out that in the high power fusion DEMO plant there is a close, nonlinear interplay between the fusion burnup and the current source of non-inductive, ITB-generated bootstrap current. Consequently, as much distinct from usual plasma controls under simulated burning conditions with lower power (<<1 GW), the selfignited fusion burn at a high power burning state of ∝3-5 GW becomes so strongly selforganized that any of external means except fuelling can not provide the effective control of the stable fusion burn.It is also demonstrated that externally applied, inductive current perturbations can be used to control both the location and strength of ITB in a fully noninductive tokamak discharge. We find that ITB structures formed with broad noninductive current sources such as LHCD are more readily controlled than those formed by localized sources such as ECCD. The physics of the inductive current is well known. Consequently, we believe that the controllability of the ITB is generic, and does not depend on the details of the transport model (as long as they can form an ITB for sufficiently reversed magnetic shear q-profile). Through this external control of the magnetic shear profile, we can maintain the ITB strength that is otherwise prone to deteriorate when the bootstrap current increases. These distinguishing capabilities of inductive current perturbation provide steady

Dynamic fluid connectivity during steady-state multiphase flow in a sandstone.

Science.gov (United States)

Reynolds, Catriona A; Menke, Hannah; Andrew, Matthew; Blunt, Martin J; Krevor, Samuel

2017-08-01

The current conceptual picture of steady-state multiphase Darcy flow in porous media is that the fluid phases organize into separate flow pathways with stable interfaces. Here we demonstrate a previously unobserved type of steady-state flow behavior, which we term "dynamic connectivity," using fast pore-scale X-ray imaging. We image the flow of N 2 and brine through a permeable sandstone at subsurface reservoir conditions, and low capillary numbers, and at constant fluid saturation. At any instant, the network of pores filled with the nonwetting phase is not necessarily connected. Flow occurs along pathways that periodically reconnect, like cars controlled by traffic lights. This behavior is consistent with an energy balance, where some of the energy of the injected fluids is sporadically converted to create new interfaces.

Steady State and Transient Analysis of Induction Motor Driving a ...

African Journals Online (AJOL)

The importance of using a digital computer in studying the performance of Induction machine under steady and transient states is presented with computer results which show the transient behaviour of 3-phase machine during balanced and unbalanced conditions. The computer simulation for these operating conditions is ...

Plasma state. The universe's fire

International Nuclear Information System (INIS)

Lehner, Th.

2004-01-01

The plasma is the fourth state of matter, obtained at a very high temperature by the separation of the electrons from their nuclei. Plasma represents 99% of the visible mass of our present day universe and was the unique state of matter at its very beginning. Plasmas are present in the core of stars and in the interstellar environment. More closer to us, they are responsible of spectacular phenomena, like aurora borealis, lightning, comet queues etc.. This book makes a review of the different types of plasmas (electromagnetic, Earth's plasmas, spatial plasmas, solar plasmas, astrophysical plasmas). One chapter presents the thermonuclear fusion as future energy source. Another one treats of the chaos and turbulence inside plasmas. Some applications of plasmas are reviewed: MHD and ionic propulsion systems, MHD energy conversion and MHD generators, thermo-ionic converters, solid-state plasmas, particle accelerators, coherent radiation sources, 'Zeta' machines, X-ray lasers, isotopic separation, non-neutral plasmas and charged beams, free-electrons lasers, electrons and positrons plasmas, industrial applications (etching and cleaning, manufacturing of solar cells, flat screens, industrial reactors, waste treatment, cold plasma-assisted sterilization, effluents decontamination etc.). A last chapter makes an overview of the modern research in plasma physics. (J.S.)

Comparative steady-state pharmacokinetic study of an extended-release formulation of itopride and its immediate-release reference formulation in healthy volunteers.

Science.gov (United States)

Yoon, Seonghae; Lee, Howard; Kim, Tae-Eun; Lee, SeungHwan; Chee, Dong-Hyun; Cho, Joo-Youn; Yu, Kyung-Sang; Jang, In-Jin

2014-01-01

This study was conducted to compare the oral bioavailability of an itopride extended-release (ER) formulation with that of the reference immediate-release (IR) formulation in the fasting state. The effect of food on the bioavailability of itopride ER was also assessed. A single-center, open-label, randomized, multiple-dose, three-treatment, three-sequence, crossover study was performed in 24 healthy male subjects, aged 22-48 years, who randomly received one of the following treatments for 4 days in each period: itopride 150 mg ER once daily under fasting or fed conditions, or itopride 50 mg IR three times daily in the fasting state. Steady-state pharmacokinetic parameters of itopride, including peak plasma concentration (Cmax) and area under the plasma concentration versus time curve over 24 hours after dosing (AUC(0-24h)), were determined by noncompartmental analysis. The geometric mean ratio of the pharmacokinetic parameters was derived using an analysis of variance model. A total of 24 healthy Korean subjects participated, 23 of whom completed the study. The geometric mean ratio and its 90% confidence interval of once-daily ER itopride versus IR itopride three times a day for AUC(0-24h) were contained within the conventional bioequivalence range of 0.80-1.25 (0.94 [0.88-1.01]), although Cmax was reached more slowly and was lower for itopride ER than for the IR formulation. Food delayed the time taken to reach Cmax for itopride ER, but AUC(0-24h) was not affected. There were no serious adverse events and both formulations were generally well tolerated. At steady state, once-daily itopride ER at 150 mg has a bioavailability comparable with that of itopride IR at 50 mg given three times a day under fasting conditions. Food delayed the absorption of itopride ER, with no marked change in its oral bioavailability.

Steady-state evoked potentials possibilities for mental-state estimation

Science.gov (United States)

Junker, Andrew M.; Schnurer, John H.; Ingle, David F.; Downey, Craig W.

1988-01-01

The use of the human steady-state evoked potential (SSEP) as a possible measure of mental-state estimation is explored. A method for evoking a visual response to a sum-of-ten sine waves is presented. This approach provides simultaneous multiple frequency measurements of the human EEG to the evoking stimulus in terms of describing functions (gain and phase) and remnant spectra. Ways in which these quantities vary with the addition of performance tasks (manual tracking, grammatical reasoning, and decision making) are presented. Models of the describing function measures can be formulated using systems engineering technology. Relationships between model parameters and performance scores during manual tracking are discussed. Problems of unresponsiveness and lack of repeatability of subject responses are addressed in terms of a need for loop closure of the SSEP. A technique to achieve loop closure using a lock-in amplifier approach is presented. Results of a study designed to test the effectiveness of using feedback to consciously connect humans to their evoked response are presented. Findings indicate that conscious control of EEG is possible. Implications of these results in terms of secondary tasks for mental-state estimation and brain actuated control are addressed.

Design of plasma facing components for the SST-1 tokamak

International Nuclear Information System (INIS)

Jacob, S.; Chenna Reddy, D.; Choudhury, P.; Khirwadkar, S.; Pragash, R.; Santra, P.; Saxena, Y.C.; Sinha, P.

2000-01-01

Steady state Superconducting Tokamak, SST-1, is a medium sized tokamak with major and minor radii of 1.10 m and 0.20 m respectively. Elongated plasma operation with double null poloidal divertor is planned with a maximum input power of 1 MW. The Plasma Facing Components (PFC) like Divertors and Baffles, Poloidal limiters and Passive stabilizers form the first material boundary around the plasma and hence receive high heat and particle fluxes. The PFC design should ensure efficient heat and particle removal during steady state tokamak operation. A closed divertor geometry is adopted to ensure high neutral pressure in the divertor region (and hence high recycling) and less impurity influx into the core plasma. A set of poloidal limiters are provided to assist break down, current ramp-up and current ramp down phases and for the protection of the in-vessel components. Two pairs of Passive stabilizers, one on the inboard and the other on the outboard side of the plasma, are provided to slow down the vertical instability growth rates of the shaped plasma column. All PFCs are actively cooled to keep the plasma facing surface temperature within the design limits. The PFCs have been shaped/profiled so that maximum steady state heat flux on the surface is less than 1 MW/m 2 . (author)

Radial profiles of hard X-ray emission during steady state current drive in the TRIAM-1M tokamak

International Nuclear Information System (INIS)

Nakamura, Y.; Takabatake, Y.; Jotaki, E.; Moriyama, S.; Nagao, A.; Nakamura, K.; Hiraki, N.; Itoh, S.

1990-01-01

The hard X-ray emission from the TRIAM-1M tokamak plasma during steady state lower hybrid current drive with a discharge duration of a few minutes was measured with sodium iodide scintillation spectrometers. The radial profiles of the X-ray emission were also measured and indicate that, in the low density regime (n e =(1-3)x10 12 cm -3 ), the current carrying high energy electrons are mainly in the inner region of the plasma column and their radial profile remains unchanged during current drive. On the other hand, high density discharges (n e =(3-6)x10 12 cm -3 ) are always accompanied by an abrupt drop of the plasma current, and the X-ray emission profile changes from peaked to broad. This change can be attributed to the conditions of wave accessibility. As the electron density increases, the accessibility of the plasma to lower hybrid waves with low values of the parallel wave number n parallel is significantly reduced and high energy electrons resonating with the waves are produced at the plasma periphery. Interaction of these electrons with the limiters causes an increase of the electron density in this region; waves with low n parallel then become completely excluded from the inner part of the plasma column. This interpretation is supported by measurements of the density profile and impurity radiation, and has been confirmed in an investigation of discharges with additional gas puffing. (author). 17 refs, 21 figs

STEADY-STATE HADRONIC GAMMA-RAY EMISSION FROM 100-MYR-OLD FERMI BUBBLES

Energy Technology Data Exchange (ETDEWEB)

Crocker, Roland M.; Bicknell, Geoffrey V.; Sutherland, Ralph S. [Research School of Astronomy and Astrophysics, Australian National University, Canberra (Australia); Carretti, Ettore; Hill, Alex S. [CSIRO Astronomy and Space Science, Marsfield, N.S.W. (Australia)

2014-08-20

Fermi Bubbles are enigmatic γ-ray features of the Galactic bulge. Both putative activity (within few × Myr) connected to the Galactic center super-massive black hole and, alternatively, nuclear star formation have been claimed as the energizing source of the Bubbles. Likewise, both inverse-Compton emission by non-thermal electrons (''leptonic'' models) and collisions between non-thermal protons and gas (''hadronic'' models) have been advanced as the process supplying the Bubbles' γ-ray emission. An issue for any steady state hadronic model is that the very low density of the Bubbles' plasma seems to require that they accumulate protons over a multi-gigayear timescale, much longer than other natural timescales occurring in the problem. Here we present a mechanism wherein the timescale for generating the Bubbles' γ-ray emission via hadronic processes is ∼few × 10{sup 8} yr. Our model invokes the collapse of the Bubbles' thermally unstable plasma, leading to an accumulation of cosmic rays and magnetic field into localized, warm (∼10{sup 4} K), and likely filamentary condensations of higher-density gas. Under the condition that these filaments are supported by non-thermal pressure, the hadronic emission from the Bubbles is L {sub γ} ≅ 2 × 10{sup 37} erg s{sup –1} M-dot {sub in}/(0.1 M{sub ⊙} yr{sup –1} ) T{sub FB}{sup 2}/(3.5×10{sup 7} K){sup 2} M {sub fil}/M {sub pls}, equal to their observed luminosity (normalizing to the star-formation-driven mass flux into the Bubbles and their measured plasma temperature and adopting the further result that the mass in the filaments, M {sub fil} is approximately equal to the that of the Bubbles' plasma, M {sub pls})

The total quasi-steady-state approximation for complex enzyme reactions

DEFF Research Database (Denmark)

Pedersen, Morten Gram; Bersani, A. M.; Bersani, E.

2008-01-01

) approximation (or standard quasi-steady-state approximation (sQSSA)), which is valid when the enzyme concentration is sufficiently small. This condition is usually fulfilled for in vitro experiments, but often breaks down in vivo. The total QSSA (tQSSA), which is valid for a broader range of parameters covering...

Comparing Interval Management Control Laws for Steady-State Errors and String Stability

Science.gov (United States)

Weitz, Lesley A.; Swieringa, Kurt A.

2018-01-01

Interval Management (IM) is a future airborne spacing concept that leverages avionics to provide speed guidance to an aircraft to achieve and maintain a specified spacing interval from another aircraft. The design of a speed control law to achieve the spacing goal is a key aspect in the research and development of the IM concept. In this paper, two control laws that are used in much of the contemporary IM research are analyzed and compared to characterize steady-state errors and string stability. Numerical results are used to illustrate how the choice of control laws gains impacts the size of steady-state errors and string performance and the potential trade-offs between those performance characteristics.

Magnetic sensor for steady state tokamak

Energy Technology Data Exchange (ETDEWEB)

Neyatani, Yuzuru; Mori, Katsuharu; Oguri, Shigeru; Kikuchi, Mitsuru [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment

1996-06-01

A new type of magnetic sensor has been developed for the measurement of steady state magnetic fields without DC-drift such as integration circuit. The electromagnetic force induced to the current which leads to the sensor was used for the measurement. For the high frequency component which exceeds higher than the vibration frequency of sensor, pick-up coil was used through the high pass filter. From the results using tokamak discharges, this sensor can measure the magnetic field in the tokamak discharge. During {approx}2 hours measurement, no DC drift was observed. The sensor can respond {approx}10ms of fast change of magnetic field during disruptions. We confirm the extension of measured range to control the current which leads to the sensor. (author).

Blood flow patterns during incremental and steady-state aerobic exercise.

Science.gov (United States)

Coovert, Daniel; Evans, LeVisa D; Jarrett, Steven; Lima, Carla; Lima, Natalia; Gurovich, Alvaro N

2017-05-30

Endothelial shear stress (ESS) is a physiological stimulus for vascular homeostasis, highly dependent on blood flow patterns. Exercise-induced ESS might be beneficial on vascular health. However, it is unclear what type of ESS aerobic exercise (AX) produces. The aims of this study are to characterize exercise-induced blood flow patterns during incremental and steady-state AX. We expect blood flow pattern during exercise will be intensity-dependent and bidirectional. Six college-aged students (2 males and 4 females) were recruited to perform 2 exercise tests on cycleergometer. First, an 8-12-min incremental test (Test 1) where oxygen uptake (VO2), heart rate (HR), blood pressure (BP), and blood lactate (La) were measured at rest and after each 2-min step. Then, at least 48-hr. after the first test, a 3-step steady state exercise test (Test 2) was performed measuring VO2, HR, BP, and La. The three steps were performed at the following exercise intensities according to La: 0-2 mmol/L, 2-4 mmol/L, and 4-6 mmol/L. During both tests, blood flow patterns were determined by high-definition ultrasound and Doppler on the brachial artery. These measurements allowed to determine blood flow velocities and directions during exercise. On Test 1 VO2, HR, BP, La, and antegrade blood flow velocity significantly increased in an intensity-dependent manner (repeated measures ANOVA, pflow velocity did not significantly change during Test 1. On Test 2 all the previous variables significantly increased in an intensity-dependent manner (repeated measures ANOVA, pflow patterns during incremental and steady-state exercises include both antegrade and retrograde blood flows.

Concept study of the Steady State Tokamak Reactor (SSTR)

International Nuclear Information System (INIS)

1991-06-01

The Steady State Tokamak Reactor (SSTR) concept has been proposed as a realistic fusion power reactor to be built in the near future. An overall concept of SSTR is introduced which is based on a small extension of the present day physics and technologies. The major feature of SSTR is the maximum utilization of a bootstrap current in order to reduce the power required for the steady state operation. This requirement leads to the choice of moderate current (12 MA), and high βp (2.0) for the device, which are achieved by selecting high aspect ratio (A=4) and high toroidal magnetic field (16.5 T). A negative-ion-based neutral beam injection system is used both for heating and central current drive. Notable engineering features of SSTR are: the use of a uniform vacuum vessel and periodical replacements of the first wall and blanket layers and significant reduction of the electromagnetic force with the use of functionally gradient material. It is shown that a tokamak machine comparable to ITER in size can become a power reactor capable of generating about 1 GW of electricity with a plant efficiency of ∼30%. (author)

Steady-state pattern electroretinogram and short-duration transient visual evoked potentials in glaucomatous and healthy eyes.

Science.gov (United States)

Amarasekera, Dilru C; Resende, Arthur F; Waisbourd, Michael; Puri, Sanjeev; Moster, Marlene R; Hark, Lisa A; Katz, L Jay; Fudemberg, Scott J; Mantravadi, Anand V

2018-01-01

This study evaluates two rapid electrophysiological glaucoma diagnostic tests that may add a functional perspective to glaucoma diagnosis. This study aimed to determine the ability of two office-based electrophysiological diagnostic tests, steady-state pattern electroretinogram and short-duration transient visual evoked potentials, to discern between glaucomatous and healthy eyes. This is a cross-sectional study in a hospital setting. Forty-one patients with glaucoma and 41 healthy volunteers participated in the study. Steady-state pattern electroretinogram and short-duration transient visual evoked potential testing was conducted in glaucomatous and healthy eyes. A 64-bar-size stimulus with both a low-contrast and high-contrast setting was used to compare steady-state pattern electroretinogram parameters in both groups. A low-contrast and high-contrast checkerboard stimulus was used to measure short-duration transient visual evoked potential parameters in both groups. Steady-state pattern electroretinogram parameters compared were MagnitudeD, MagnitudeD/Magnitude ratio, and the signal-to-noise ratio. Short-duration transient visual evoked potential parameters compared were amplitude and latency. MagnitudeD was significantly lower in glaucoma patients when using a low-contrast (P = 0.001) and high-contrast (P state pattern electroretinogram stimulus. MagnitudeD/Magnitude ratio and SNR were significantly lower in the glaucoma group when using a high-contrast 64-bar-size stimulus (P state pattern electroretinogram was effectively able to discern between glaucomatous and healthy eyes. Steady-state pattern electroretinogram may thus have a role as a clinically useful electrophysiological diagnostic tool. © 2017 Royal Australian and New Zealand College of Ophthalmologists.

Real time control of fully non-inductive operation in Tore Supra leading to 6 minutes, 1 giga-joule plasma discharges

International Nuclear Information System (INIS)

Van Houtte, D.; Martin, G.; Becoulet, A.; Saoutic, B.

2004-01-01

The experimental programme of Tore Supra (a = 0.72 m, R = 2.4 m, I p T < 4.5 T) has been devoted in 2003 to study simultaneously heat removal capability and particle exhaust in steady-state fully non-inductive current drive discharges. This required both advanced technology integration and steady-state real time plasma control. In particular, an improvement of the plasma position within a few millimetre range, and new real time cross controls between radio frequency (RF) power and various actuators built around a shared memory network, have allowed Tore Supra to access a powerful steady-state regime with an improved safety level for the actively cooled plasma facing components. Feedback controlled fully non-inductive plasma discharges have been sustained in a steady-state regime up to 6 minutes with a new world record of injected-extracted energy exceeding 1 GJ. Advanced tools, experimental results and brief physics analysis of these discharges are presented and discussed. (authors)

Real time control of fully non-inductive operation in Tore Supra leading to 6 minutes, 1 giga-joule plasma discharges

Energy Technology Data Exchange (ETDEWEB)

Van Houtte, D.; Martin, G.; Becoulet, A.; Saoutic, B

2004-07-01

The experimental programme of Tore Supra (a = 0.72 m, R = 2.4 m, I{sub p} < 1.7 MA, B{sub T} < 4.5 T) has been devoted in 2003 to study simultaneously heat removal capability and particle exhaust in steady-state fully non-inductive current drive discharges. This required both advanced technology integration and steady-state real time plasma control. In particular, an improvement of the plasma position within a few millimetre range, and new real time cross controls between radio frequency (RF) power and various actuators built around a shared memory network, have allowed Tore Supra to access a powerful steady-state regime with an improved safety level for the actively cooled plasma facing components. Feedback controlled fully non-inductive plasma discharges have been sustained in a steady-state regime up to 6 minutes with a new world record of injected-extracted energy exceeding 1 GJ. Advanced tools, experimental results and brief physics analysis of these discharges are presented and discussed. (authors)

Steady-state free precession with myocardial tagging: CSPAMM in a single breathhold.

Science.gov (United States)

Zwanenburg, Jaco J M; Kuijer, Joost P A; Marcus, J Tim; Heethaar, Robert M

2003-04-01

A method is presented that combines steady-state free precession (SSFP) cine imaging with myocardial tagging. Before the tagging preparation at each ECG-R wave, the steady-state magnetization is stored as longitudinal magnetization by an alpha/2 flip-back pulse. Imaging is continued immediately after tagging preparation, using linearly increasing startup angles (LISA) with a rampup over 10 pulses. Interleaved segmented k-space ordering is used to prevent artifacts from the increasing signal during the LISA rampup. First, this LISA-SSFP method was evaluated regarding ghost artifacts from the steady-state interruption by comparing LISA with an alpha/2 startup method. Next, LISA-SSFP was compared with spoiled gradient echo (SGRE) imaging, regarding tag contrast-to-noise ratio and tag persistence. The measurements were performed in phantoms and in six subjects applying breathhold cine imaging with tagging (temporal resolution 51 ms). The results show that ghost artifacts are negligible for the LISA method. Compared to the SGRE reference, LISA-SSFP was two times faster, with a slightly better tag contrast-to-noise. Additionally, the tags persisted 126 ms longer with LISA-SSFP than with SGRE imaging. The high efficiency of LISA-SSFP enables the acquisition of complementary tagged (CSPAMM) images in a single breathhold. Copyright 2003 Wiley-Liss, Inc.

Steady-State Characterization of Bacteriorhodopsin-D85N Photocycle

Science.gov (United States)

Timucin, Dogan A.; Downie, John D.; Norvig, Peter (Technical Monitor)

1999-01-01

An operational characterization of the photocycle of the genetic mutant D85N of bacteriorhodopsin, BR-D85N, is presented. Steady-state bleach spectra and pump-probe absorbance data are obtained with thick hydrated films containing BR-D85N embedded in a gelatin host. Simple two- and three-state models are used to analyze the photocycle dynamics and extract relevant information such as pure-state absorption spectra, photochemical-transition quantum efficiencies, and thermal lifetimes of dominant states appearing in the photocycle, the knowledge of which should aid in the analysis of optical recording and retrieval of data in films incorporating this photochromic material. The remarkable characteristics of this material and their implications from the viewpoint of optical data storage and processing are discussed.

Study of heat and synchrotron radiation transport in fusion tokamak plasmas. Application to the modelling of steady state and fast burn termination scenarios for the international experimental fusion reactor ITER

International Nuclear Information System (INIS)

Villar Colome, J.

1997-12-01

The aim of this thesis is to give a global scope of the problem of energy transport within a thermonuclear plasma in the context of its power balance and the implications when modelling ITER operating scenarios. This is made in two phases. First, by furnishing new elements to the existing models of heat and synchrotron radiation transport in a thermonuclear plasma. Second, by applying the improved models to plasma engineering studies of ITER operating scenarios. The scenarios modelled are the steady state operating point and the transient that appears to have the biggest technological implications: the fast burn termination. The conduction-convection losses are modelled through the energy confinement time. This parameter is empirically obtained from the existing experimental data, since the underlying mechanisms are not well understood. In chapter 2 an expression for the energy confinement time is semi-analytically deduced from the Rebut-Lallia-Watkins local transport model. The current estimates of the synchrotron radiation losses are made with expressions of the dimensionless transparency factor deduced from a 0-dimensional cylindrical model proposed by Trubnikov in 1979. In chapter 3 realistic hypothesis for the cases of cylindrical and toroidal geometry are included in the model to deduce compact explicit expressions for the fast numerical computation of the synchrotron radiation losses. Numerical applications are provided for the cylindrical case. The results are checked against the existing models. In chapter 4, the nominal operating point of ITER and its thermal stability is studied by means of a 0-dimensional burn model of the thermonuclear plasma in ignition. This model is deduced by the elements furnished by the plasma particle and power balance. Possible heat overloading on the plasma facing components may provoke severe structural damage, implying potential safety problems related to tritium inventory and metal activation. In chapter 5, the assessment

Study of heat and synchrotron radiation transport in fusion tokamak plasmas. Application to the modelling of steady state and fast burn termination scenarios for the international experimental fusion reactor ITER

Energy Technology Data Exchange (ETDEWEB)

Villar Colome, J. [Association Euratom-CEA, Centre d`Etudes de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee]|[Universitat Polytechnica de Catalunya (Spain)

1997-12-01

The aim of this thesis is to give a global scope of the problem of energy transport within a thermonuclear plasma in the context of its power balance and the implications when modelling ITER operating scenarios. This is made in two phases. First, by furnishing new elements to the existing models of heat and synchrotron radiation transport in a thermonuclear plasma. Second, by applying the improved models to plasma engineering studies of ITER operating scenarios. The scenarios modelled are the steady state operating point and the transient that appears to have the biggest technological implications: the fast burn termination. The conduction-convection losses are modelled through the energy confinement time. This parameter is empirically obtained from the existing experimental data, since the underlying mechanisms are not well understood. In chapter 2 an expression for the energy confinement time is semi-analytically deduced from the Rebut-Lallia-Watkins local transport model. The current estimates of the synchrotron radiation losses are made with expressions of the dimensionless transparency factor deduced from a 0-dimensional cylindrical model proposed by Trubnikov in 1979. In chapter 3 realistic hypothesis for the cases of cylindrical and toroidal geometry are included in the model to deduce compact explicit expressions for the fast numerical computation of the synchrotron radiation losses. Numerical applications are provided for the cylindrical case. The results are checked against the existing models. In chapter 4, the nominal operating point of ITER and its thermal stability is studied by means of a 0-dimensional burn model of the thermonuclear plasma in ignition. This model is deduced by the elements furnished by the plasma particle and power balance. Possible heat overloading on the plasma facing components may provoke severe structural damage, implying potential safety problems related to tritium inventory and metal activation. In chapter 5, the assessment

Minimal gain marching schemes: searching for unstable steady-states with unsteady solvers

Science.gov (United States)

de S. Teixeira, Renan; S. de B. Alves, Leonardo

2017-12-01

Reference solutions are important in several applications. They are used as base states in linear stability analyses as well as initial conditions and reference states for sponge zones in numerical simulations, just to name a few examples. Their accuracy is also paramount in both fields, leading to more reliable analyses and efficient simulations, respectively. Hence, steady-states usually make the best reference solutions. Unfortunately, standard marching schemes utilized for accurate unsteady simulations almost never reach steady-states of unstable flows. Steady governing equations could be solved instead, by employing Newton-type methods often coupled with continuation techniques. However, such iterative approaches do require large computational resources and very good initial guesses to converge. These difficulties motivated the development of a technique known as selective frequency damping (SFD) (Åkervik et al. in Phys Fluids 18(6):068102, 2006). It adds a source term to the unsteady governing equations that filters out the unstable frequencies, allowing a steady-state to be reached. This approach does not require a good initial condition and works well for self-excited flows, where a single nonzero excitation frequency is selected by either absolute or global instability mechanisms. On the other hand, it seems unable to damp stationary disturbances. Furthermore, flows with a broad unstable frequency spectrum might require the use of multiple filters, which delays convergence significantly. Both scenarios appear in convectively, absolutely or globally unstable flows. An alternative approach is proposed in the present paper. It modifies the coefficients of a marching scheme in such a way that makes the absolute value of its linear gain smaller than one within the required unstable frequency spectra, allowing the respective disturbance amplitudes to decay given enough time. These ideas are applied here to implicit multi-step schemes. A few chosen test cases

The behaviour of population in a plasma interacting with an atomic gas

International Nuclear Information System (INIS)

Furukane, Utaro; Oda, Toshiatsu.

1983-01-01

The processes leading to the population inversion are investigated in a recombining hydrogen plasma which is interacting with a cool and dense neutral hydrogen gas by using the rate equations on the basis of the CR model and the energy equation for electrons ions and neutral parlicles. The quasi-steady state approximation are used only for the levels higher than a certain level which is not the first excited level. The calculations have shown that the quasi-steady state cannot be realized while intense energy-flows due to the collisional processes exist between different kinds of the particles such as the electrons and the ions in the plasma and the population inversion is realized only in the quasi-steady state following the transient phase. The effects of the initial conditions of the hydrogen plasma and the introduced neutral hydrogen gas on the overpopulation density are also discussed. (author)

Steady-state pulses and superradiance in short-wavelength, swept-gain amplifiers

International Nuclear Information System (INIS)

Bonifacio, R.; Hopf, F.A.; Meystre, P.; Scully, M.O.

1975-01-01

The steady-state behavior of amplifiers in which the excitation is swept at the speed of light is discussed in the semiclassical approximation. In the present work the case where the decay time of the population is comparable to that of the polarization is examined. Pulse propagation is shown to obey a generalized sine-Gordon equation which contains the effects of atomic relaxations. The analytical expression of the steady-state pulses (SSP) gives two threshold conditions. In the region of limited gain the SSP is a broad pulse with small area which can be obtained by small signal theory. In the second region of high gain the SSP is the superradiant π pulse. Its pulse power is not limited as in usual superradiant theory because, as is shown, for a swept excitation the cooperation-length limit does not exist

Ion-acoustic double layers in the presence of plasma source

International Nuclear Information System (INIS)

Okuda, H.; Ashour-Abdalla, M.

1981-11-01

Steady-state plasma turbulence and formation of negative potential spikes and double layers in the presence of ion acoustic instabilities have been studied by means of one-dimensional particle simulations in which velocities of a small fraction of electrons are replaced by the initial drifting Maxwellian at a constant rate. A steady state is found where negative potential spikes appear randomly in space and time giving rise to an anomalous resistivity much greater than previously found. Comparisons of the simulation results with laboratory and space plasmas are discussed

Ion acoustic double layers in the presence of plasma source

International Nuclear Information System (INIS)

Okuda, H.; Ashour-Abdalla, M.

1982-01-01

Steady-state plasma turbulence and the formation of negative potential spikes and double layers in the presence of ion acoustic instabilities have been studied by means of one-dimensional particle simulations in which the velocities of a small fraction of electrons are replaced by the initial drifting Maxwellian at a constant rate. A steady state is found where negative potential spikes appear randomly in space and time giving rise to an anomalous resistivity much greater than previously found. Comparisons of the simulation results with laboratory and space plasmas are discussed

Navier-Stokes Predictions of Dynamic Stability Derivatives: Evaluation of Steady-State Methods

National Research Council Canada - National Science Library

DeSpirito, James; Silton, Sidra I; Weinacht, Paul

2008-01-01

The prediction of the dynamic stability derivatives-roll-damping, Magnus, and pitch-damping moments-were evaluated for three spin-stabilized projectiles using steady-state computational fluid dynamic (CFD) calculations...

Diffusion in coronas around clinopyroxene: modelling with local equilibrium and steady state, and a non-steady-state modification to account for zoned actinolite-hornblende

Science.gov (United States)

Ashworth, J. R.; Birdi, J. J.; Emmett, T. F.

1992-01-01

Retrograde coronas of Caledonian age, between clinopyroxene and plagioclase in the Jotun Nappe Complex, Norway, illustrate the effects of diffusion kinetics on mineral distributions among layers and on the compositions of hornblende-actinolite. One corona type comprises a symplectite of epidote + quartz adjacent to plagioclase, and a less well-organized intergrowth of amphibole + quartz replacing clinopyroxene. The observed mineral proportions imply an open-system reaction, but the similarity of Al/Si ratios in reactant plagioclase and product symplectite indicates approximate conservation of Al2O3 and SiO2. The largest inferred open-system flux is a loss of CaO, mostly derived from consumption of clinopyroxene. The approximate layer structure, Pl|Ep + Qtz|Hbl + Qtz|Act±Hbl + Qtz|Cpx, is modelled using the theory of steady-state diffusion-controlled growth with local equilibrium. To obtain a solution, it is necessary to use a reactant plagioclase composition which takes into account aluminous (epidote) inclusions. The results indicate that, in terms of Onsager diffusion coefficients L ii , Ca is more mobile than AL ( L CaCa/ L AlAl≳3.) (where ≳ means greater than or approximately equal to). This behaviour of Ca is comparable with that of Mg in previously studied coronas around olivine. Si is non-diffusing in the present modelling, because of silica saturation. Oxidation of some Fe2+ to Fe3+ occurs within the corona. Mg diffuses towards its source (clinopyroxene) to maintain local equilibrium. Other coronas consist of two layers, hornblende adjacent to plagioclase and zoned amphibole + quartz adjacent to clinopyroxene. In the zoned layer, actinolitic hornblende forms relict patches, separated from quartz blebs by more aluminous hornblende. A preliminary steady-state, local-equilibrium model of grain-boundary diffusion explains the formation of low-Al and high-Al layers as due to Al immobility. Zoning and replacement are qualitatively explained in terms of

Single-dose and steady-state pharmacokinetics of tenofovir disoproxil fumarate in human immunodeficiency virus-infected children.

Science.gov (United States)

Hazra, Rohan; Balis, Frank M; Tullio, Antonella N; DeCarlo, Ellen; Worrell, Carol J; Steinberg, Seth M; Flaherty, John F; Yale, Kitty; Poblenz, Marianne; Kearney, Brian P; Zhong, Lijie; Coakley, Dion F; Blanche, Stephane; Bresson, Jean Louis; Zuckerman, Judith A; Zeichner, Steven L

2004-01-01

Tenofovir disoproxil fumarate (DF) is a potent nucleotide analog reverse transcriptase inhibitor approved for the treatment of human immunodeficiency virus (HIV)-infected adults. The single-dose and steady-state pharmacokinetics of tenofovir were evaluated following administration of tenofovir DF in treatment-experienced HIV-infected children requiring a change in antiretroviral therapy. Using increments of tenofovir DF 75-mg tablets, the target dose was 175 mg/m(2); the median administered dose was 208 mg/m(2). Single-dose pharmacokinetics were evaluated in 18 subjects, and the geometric mean area under the concentration-time curve from 0 h to infinity (AUC(0- infinity )) was 2,150 ng. h/ml and the geometric mean maximum concentration (C(max)) was 266 ng/ml. Subsequently, other antiretrovirals were added to each patient's regimen based upon treatment history and baseline viral resistance results. Steady-state pharmacokinetics were evaluated in 16 subjects at week 4. The steady-state, geometric mean AUC for the 24-h dosing interval was 2,920 ng. h/ml and was significantly higher than the AUC(0- infinity ) after the first dose (P = 0.0004). The geometric mean C(max) at steady state was 302 ng/ml. Tenofovir DF was generally very well tolerated. Steady-state tenofovir exposures in children receiving tenofovir DF-containing combination antiretroviral therapy approached values seen in HIV-infected adults (AUC, approximately 3,000 ng. h/ml; C(max), approximately 300 ng/ml) treated with tenofovir DF at 300 mg.

Pre-steady state transients in the Drosophila alcohol dehydrogenase catalyzed reaction: isotope effects and stereospecificity

International Nuclear Information System (INIS)

Place, A.R.; Eccleston, J.F.

1987-01-01

The alcohol dehydrogenase (ADH) isolated from Drosophila is unique among alcohol metabolizing enzymes by not requiring metals for catalysis, by showing 4-pro-S (B-sided) hydride transfer stereospecificity, and by possessing a greater catalytic turnover rate for secondary alcohols than for primary alcohols. They have extended their studies on the kinetic mechanism for this enzyme by examining the pre-steady state transients of ternary complex interconversion using stopped-flow fluorescence methods. When enzyme and a 30-fold molar excess of NADH is mixed with excess acetadehyde, methyl ethyl ketone (MEK), or cyclohexanone a rapid (> 100 s -1 ) transient is observe before the steady-state. The rates are insensitive to isotope substitution. With the substrate MEK, the rate and amplitude suggests a single turnover of the enzyme. Similar pre-steady state transients are observed when enzyme and a 50-fold molar excess of NAD + is mixed with ethanol, 2-propanol, and cyclohexanol. The rates show a hyperbolic concentration dependence and a deuterium isotope effect. With d 6 -deuteroethanol the transient no longer occurs in the pre-steady state. When the optical isomers of secondary alcohols are used as substrates, transients are observed only in the R-(-) isomers for all chain lengths. With 2-S(+)-heptanol and 2-S(+)-octanol no transients occur

Steady-State pharmacokinetics and tolerability of trans-resveratrol 2000 mg twice daily with food, quercetin and alcohol (ethanol) in healthy human subjects.

Science.gov (United States)

la Porte, Charles; Voduc, Nha; Zhang, Guijun; Seguin, Isabelle; Tardiff, Danielle; Singhal, Neera; Cameron, D William

2010-07-01

Trans-resveratrol is a polyphenol, which is found in red wine and has cancer chemo-preventive properties and disease-preventive properties. The pharmacokinetics of trans-resveratrol have been investigated in single-dose studies and in studies with relatively low dosages. The present study aimed to investigate the steady-state pharmacokinetics and tolerability of trans-resveratrol 2000 mg twice daily with food, quercetin and alcohol (ethanol). This was a two-period, open-label, single-arm, within-subject control study in eight healthy subjects. The steady-state 12-hour pharmacokinetics of trans-resveratrol 2000 mg twice daily were studied with a standard breakfast, a high-fat breakfast, quercetin 500 mg twice daily and 5% alcohol 100 mL. Trans-resveratrol plasma concentrations were determined using liquid chromatography with tandem mass spectrometry. The mean (SD) area under the plasma concentration-time curve from 0 to 12 hours (AUC(12)) and maximum plasma concentration (C(max)) of trans-resveratrol were 3558 (2195) ng * h/mL and 1274 (790) ng/mL, respectively, after the standard breakfast. The high-fat breakfast significantly decreased the AUC(12) and C(max) by 45% and 46%, respectively, when compared with the standard breakfast. Quercetin 500 mg twice daily or 5% alcohol 100 mL did not influence trans-resveratrol pharmacokinetics. Diarrhoea was reported in six of the eight subjects. Significant but not clinically relevant changes from baseline were observed in serum potassium and total bilirubin levels. Trans-resveratrol 2000 mg twice daily resulted in adequate exposure and was well tolerated by healthy subjects, although diarrhoea was frequently observed. In order to maximize trans-resveratrol exposure, it should be taken with a standard breakfast and not with a high-fat meal. Furthermore, combined intake with quercetin or alcohol did not influence trans-resveratrol exposure.

Differential equation methods for simulation of GFP kinetics in non-steady state experiments.

Science.gov (United States)

Phair, Robert D

2018-03-15

Genetically encoded fluorescent proteins, combined with fluorescence microscopy, are widely used in cell biology to collect kinetic data on intracellular trafficking. Methods for extraction of quantitative information from these data are based on the mathematics of diffusion and tracer kinetics. Current methods, although useful and powerful, depend on the assumption that the cellular system being studied is in a steady state, that is, the assumption that all the molecular concentrations and fluxes are constant for the duration of the experiment. Here, we derive new tracer kinetic analytical methods for non-steady state biological systems by constructing mechanistic nonlinear differential equation models of the underlying cell biological processes and linking them to a separate set of differential equations governing the kinetics of the fluorescent tracer. Linking the two sets of equations is based on a new application of the fundamental tracer principle of indistinguishability and, unlike current methods, supports correct dependence of tracer kinetics on cellular dynamics. This approach thus provides a general mathematical framework for applications of GFP fluorescence microscopy (including photobleaching [FRAP, FLIP] and photoactivation to frequently encountered experimental protocols involving physiological or pharmacological perturbations (e.g., growth factors, neurotransmitters, acute knockouts, inhibitors, hormones, cytokines, and metabolites) that initiate mechanistically informative intracellular transients. When a new steady state is achieved, these methods automatically reduce to classical steady state tracer kinetic analysis. © 2018 Phair. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

40 CFR 1039.505 - How do I test engines using steady-state duty cycles, including ramped-modal testing?

Science.gov (United States)

2010-07-01

...-state duty cycles, including ramped-modal testing? 1039.505 Section 1039.505 Protection of Environment... duty cycles, including ramped-modal testing? This section describes how to test engines under steady-state conditions. In some cases, we allow you to choose the appropriate steady-state duty cycle for an...

Effects of governing parameters on steady-state inter-wrapper flow in an LMFBR

International Nuclear Information System (INIS)

Moriya, Shoichi

2001-01-01

Hydraulic experiments were performed using a 1/8th scale rectangular model, based on a Japanese demonstration fast breeder reactor design, in order to study fundamental characteristics of interwrapper flows occurring under steady state conditions in an LMFBR. The steady state interwrapper flow of which direction was downward in the center region and upward in the peripheral region of a core barrel was observed because of the radial static pressure gradient in the upper part of the core barrel, produced by a core blockage effect resulting from an above core structure with a perforated skirt. Thermal stratification phenomena were moreover observed in the interwrapper region, created by the hot steady state interwrapper flow from an upper plenum and the cold leakage flow through the separated plate of the core barrel. The thermal interface was generated in higher part of the core barrel when the core blockage effect was smaller and Richardson number and the leakage flow rate ratio were larger. Significant temperature fluctuations occurred in the peripheral region of the core barrel, when the difference between the interface elevations in the center and peripheral regions of the core barrel was enough large. (author)

Modeling of the blood rheology in steady-state shear flows

International Nuclear Information System (INIS)

Apostolidis, Alex J.; Beris, Antony N.

2014-01-01

We undertake here a systematic study of the rheology of blood in steady-state shear flows. As blood is a complex fluid, the first question that we try to answer is whether, even in steady-state shear flows, we can model it as a rheologically simple fluid, i.e., we can describe its behavior through a constitutive model that involves only local kinematic quantities. Having answered that question positively, we then probe as to which non-Newtonian model best fits available shear stress vs shear-rate literature data. We show that under physiological conditions blood is typically viscoplastic, i.e., it exhibits a yield stress that acts as a minimum threshold for flow. We further show that the Casson model emerges naturally as the best approximation, at least for low and moderate shear-rates. We then develop systematically a parametric dependence of the rheological parameters entering the Casson model on key physiological quantities, such as the red blood cell volume fraction (hematocrit). For the yield stress, we base our description on its critical, percolation-originated nature. Thus, we first determine onset conditions, i.e., the critical threshold value that the hematocrit has to have in order for yield stress to appear. It is shown that this is a function of the concentration of a key red blood cell binding protein, fibrinogen. Then, we establish a parametric dependence as a function of the fibrinogen and the square of the difference of the hematocrit from its critical onset value. Similarly, we provide an expression for the Casson viscosity, in terms of the hematocrit and the temperature. A successful validation of the proposed formula is performed against additional experimental literature data. The proposed expression is anticipated to be useful not only for steady-state blood flow modeling but also as providing the starting point for transient shear, or more general flow modeling

Steady state magnetic field configurations for the earth's magnetotail

Science.gov (United States)

Hau, L.-N.; Wolf, R. A.; Voigt, G.-H.; Wu, C. C.

1989-01-01

A two-dimensional, force-balance magnetic field model is presented. The theoretical existence of a steady state magnetic field configuration that is force-balanced and consistent with slow, lossless, adiabatic, earthward convection within the limit of the ideal MHD is demonstrated. A numerical solution is obtained for a two-dimensional magnetosphere with a rectangular magnetopause and nonflaring tail. The results are consistent with the convection time sequences reported by Erickson (1985).

Radioactivity computation of steady-state and pulsed fusion reactors operation

International Nuclear Information System (INIS)

Attaya, H.

1994-06-01

Different mathematical methods are used to calculate the nuclear transmutation in steady-state and pulsed neutron irradiation. These methods are the Schuer decomposition, the eigenvector decomposition, and the Pade approximation of the matrix exponential function. In the case of the linear decay chain approximation, a simple algorithm is used to evaluate the transition matrices

A steady state model for anaerobic digestion of sewage sludges ...

African Journals Online (AJOL)

A steady state model for anaerobic digestion of sewage sludge is developed that comprises three sequential parts – a kinetic part from which the % COD removal and ... and a carbonate system weak acid/base chemistry part from which the digester pH is calculated from the partial pressure of CO2 and alkalinity generated.

Natural equilibria in steady-state neutron diffusion with temperature feedback

International Nuclear Information System (INIS)

Pounders, J. M.; Ingram, R.

2013-01-01

The critical diffusion equation with feedback is investigated within the context of steady-state multiphysics. It is proposed that for critical configurations there is no need to include the multiplication factor k in the formulation of the diffusion equation. This is notable because exclusion of k from the coupled system of equations precludes the mathematically tenuous notion of a nonlinear eigenvalue problem. On the other hand, it is shown that if the factor k is retained in the diffusion equation, as is currently common practice, then the resulting problem is equivalent to the constrained minimization of a functional representing the critical equilibrium of neutron and temperature distributions. The unconstrained solution corresponding to k = 1 represents the natural equilibrium of a critical system at steady-state. Computational methods for solving the constrained problem (with k) are briefly reviewed from the literature and a method for the unconstrained problem (without k) is outlined. A numerical example is studied to examine the effects of the constraint in the nonlinear system. (authors)

Adaptively locating unknown steady states: Formalism and basin of attraction

International Nuclear Information System (INIS)

Wu, Yu; Lin, Wei

2011-01-01

The adaptive technique, which includes both dynamical estimators and coupling gains, has been recently verified to be practical for locating the unknown steady states numerically. This Letter, in the light of the center manifold theory for dynamical systems and the matrix spectrum principle, establishes an analytical formalism of this adaptive technique and reveals a connection between this technique and the original adaptive controller which includes only the dynamical estimator. More interestingly, in study of the well-known Lorenz system, the selections of the estimator parameters and initial values are found to be crucial to the successful application of the adaptive technique. Some Milnor-like basins of attraction with fractal structures are found quantitatively. All the results obtained in the Letter can be further extended to more general dynamical systems of higher dimensions. -- Highlights: → Establishing a new and rigorous formalism for the adaptive stabilization technique. → Showing a close connection between the adaptive technique and the original controller. → Providing feasible algorithms for simultaneous stabilization of multiple steady states. → Finding Milnor-like basins of attraction with fractal structures in adaptive control.

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

Science.gov (United States)

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.

Steady-state and transient heat transfer through fins of complex geometry

Directory of Open Access Journals (Sweden)

Taler Dawid

2014-06-01

Full Text Available Various methods for steady-state and transient analysis of temperature distribution and efficiency of continuous-plate fins are presented. For a constant heat transfer coefficient over the fin surface, the plate fin can be divided into imaginary rectangular or hexangular fins. At first approximate methods for determining the steady-state fin efficiency like the method of equivalent circular fin and the sector method are discussed. When the fin geometry is complex, thus transient temperature distribution and fin efficiency can be determined using numerical methods. A numerical method for transient analysis of fins with complex geometry is developed. Transient temperature distributions in continuous fins attached to oval tubes is computed using the finite volume - finite element methods. The developed method can be used in the transient analysis of compact heat exchangers to calculate correctly the heat flow rate transferred from the finned tubes to the fluid.

Operational characteristics of the high flux plasma generator magnum-PSI

NARCIS (Netherlands)

Van Eck, H.J.N.; Abrams, T.; Van Den Berg, M.A.; Brons, S.D.N.; Van Eden, G.G.; Jaworski, M.A.; Kaita, R.; Van Der Meiden, H.J.; Morgan, T.W.; van de Pol, Marc J.; Scholten, J.; Smeets, P.H.M.; De Temmerman, G.; De Vries, P.C.; Zeijlmans Van Emmichoven, P.A.

2014-01-01

In Magnum-PSI (MAgnetized plasma Generator and NUMerical modeling for Plasma Surface Interactions), the high density, low temperature plasma of a wall stabilized dc cascaded arc is confined to a magnetized plasma beam by a quasi-steady state axial magnetic field up to 1.3 T. It aims at conditions

Works preparatory to long-pulse/steady-state experiments in LHD

International Nuclear Information System (INIS)

Noda, Nobuaki; Sato, Motoyasu; Shimozuma, Takashi

1998-01-01

A steady state discharge for more than 1 hour with 3 MW heating power is a goal in the early stage of the LHD project. All the coils are superconducting, the vacuum vessel and the divertor plates are cooled by water, and a long pulse operation in heating devices (ECH, ICRF, NBI) is available. One of the concerns for this operation is an impact of residual microwave power upon rubber gaskets and windows, because the gaskets and/or the windows could be damaged by absorbing the microwave power. In order to avoid an unexpected catastrophe during the experiments due to the microwave effect, a series of tests has been carried out for several types of gate valves and windows with 84 GHz microwave incidence. The results suggest that (1) a gap in a SS flange as narrow as 0.2 mm in front of the gaskets is sufficient to prevent the power penetrating into the gasket region, (2) a fused quartz window absorbs much less power than a kovar-seal window does, (3) a mesh of 100 wires/inch is effective to reduce the power flow to the windows or the gate valves. A simplified detector for the microwave is developed in order to measure the residual power distribution outside a plasma in the vacuum vessel. (author)

SUPERENERGY-2: a multiassembly, steady-state computer code for LMFBR core thermal-hydraulic analysis

Energy Technology Data Exchange (ETDEWEB)

Basehore, K.L.; Todreas, N.E.

1980-08-01

Core thermal-hydraulic design and performance analyses for Liquid Metal Fast Breeder Reactors (LMFBRs) require repeated detailed multiassembly calculations to determine radial temperature profiles and subchannel outlet temperatures for various core configurations and subassembly structural analyses. At steady-state, detailed core-wide temperature profiles are required for core restraint calculations and subassembly structural analysis. In addition, sodium outlet temperatures are routinely needed for each reactor operating cycle. The SUPERENERGY-2 thermal-hydraulic code was designed specifically to meet these designer needs. It is applicable only to steady-state, forced-convection flow in LMFBR core geometries.

Transient and steady-state analyses of an electrically heated Topaz-II Thermionic Fuel Element

International Nuclear Information System (INIS)

El-Genk, M.S.; Xue, H.

1992-01-01

Transient and steady-state analyses of electrically heated, Thermionic Fuel Elements (TFEs) for Topaz-II space power system are performed. The calculated emitter and collector temperatures, load electric power and conversion efficiency are in good agreement with reported data. In this paper the effects or Cs pressure, thermal power input, and load resistance on the steady-state performance of the TFE are also investigated. In addition, the thermal response of the ZrH moderator during a startup transient and following a change in the thermal power input is examined

SUPERENERGY-2: a multiassembly, steady-state computer code for LMFBR core thermal-hydraulic analysis

International Nuclear Information System (INIS)

Basehore, K.L.; Todreas, N.E.

1980-08-01

Core thermal-hydraulic design and performance analyses for Liquid Metal Fast Breeder Reactors (LMFBRs) require repeated detailed multiassembly calculations to determine radial temperature profiles and subchannel outlet temperatures for various core configurations and subassembly structural analyses. At steady-state, detailed core-wide temperature profiles are required for core restraint calculations and subassembly structural analysis. In addition, sodium outlet temperatures are routinely needed for each reactor operating cycle. The SUPERENERGY-2 thermal-hydraulic code was designed specifically to meet these designer needs. It is applicable only to steady-state, forced-convection flow in LMFBR core geometries

40 CFR 1048.505 - How do I test engines using steady-state duty cycles, including ramped-modal testing?

Science.gov (United States)

2010-07-01

...-state duty cycles, including ramped-modal testing? 1048.505 Section 1048.505 Protection of Environment... SPARK-IGNITION ENGINES Test Procedures § 1048.505 How do I test engines using steady-state duty cycles... some cases, we allow you to choose the appropriate steady-state duty cycle for an engine. In these...

Dissipative dark matter halos: The steady state solution

Science.gov (United States)

Foot, R.

2018-02-01

Dissipative dark matter, where dark matter particle properties closely resemble familiar baryonic matter, is considered. Mirror dark matter, which arises from an isomorphic hidden sector, is a specific and theoretically constrained scenario. Other possibilities include models with more generic hidden sectors that contain massless dark photons [unbroken U (1 ) gauge interactions]. Such dark matter not only features dissipative cooling processes but also is assumed to have nontrivial heating sourced by ordinary supernovae (facilitated by the kinetic mixing interaction). The dynamics of dissipative dark matter halos around rotationally supported galaxies, influenced by heating as well as cooling processes, can be modeled by fluid equations. For a sufficiently isolated galaxy with a stable star formation rate, the dissipative dark matter halos are expected to evolve to a steady state configuration which is in hydrostatic equilibrium and where heating and cooling rates locally balance. Here, we take into account the major cooling and heating processes, and numerically solve for the steady state solution under the assumptions of spherical symmetry, negligible dark magnetic fields, and that supernova sourced energy is transported to the halo via dark radiation. For the parameters considered, and assumptions made, we were unable to find a physically realistic solution for the constrained case of mirror dark matter halos. Halo cooling generally exceeds heating at realistic halo mass densities. This problem can be rectified in more generic dissipative dark matter models, and we discuss a specific example in some detail.

Presheath profiles in simulated tokamak edge plasmas

International Nuclear Information System (INIS)

LaBombard, B.; Conn, R.W.; Hirooka, Y.; Lehmer, R.; Leung, W.K.; Nygren, R.E.; Ra, Y.; Tynan, G.

1988-04-01

The PISCES plasma surface interaction facility at UCLA generates plasmas with characteristics similar to those found in the edge plasmas of tokamaks. Steady state magnetized plasmas produced by this device are used to study plasma-wall interaction phenomena which are relevant to tokamak devices. We report here progress on some detailed investigations of the presheath region that extends from a wall surface into these /open quotes/simulated tokamak/close quotes/ edge plasma discharges along magnetic field lines

Stochastic pumping of non-equilibrium steady-states: how molecules adapt to a fluctuating environment.

Science.gov (United States)

Astumian, R D

2018-01-11

In the absence of input energy, a chemical reaction in a closed system ineluctably relaxes toward an equilibrium state governed by a Boltzmann distribution. The addition of a catalyst to the system provides a way for more rapid equilibration toward this distribution, but the catalyst can never, in and of itself, drive the system away from equilibrium. In the presence of external fluctuations, however, a macromolecular catalyst (e.g., an enzyme) can absorb energy and drive the formation of a steady state between reactant and product that is not determined solely by their relative energies. Due to the ubiquity of non-equilibrium steady states in living systems, the development of a theory for the effects of external fluctuations on chemical systems has been a longstanding focus of non-equilibrium thermodynamics. The theory of stochastic pumping has provided insight into how a non-equilibrium steady-state can be formed and maintained in the presence of dissipation and kinetic asymmetry. This effort has been greatly enhanced by a confluence of experimental and theoretical work on synthetic molecular machines designed explicitly to harness external energy to drive non-equilibrium transport and self-assembly.

Steady and dynamic states analysis of induction motor: FEA approach

African Journals Online (AJOL)

This paper deals with the steady and dynamic states analysis of induction motor using finite element analysis (FEA) approach. The motor has aluminum rotor bars and is designed for direct-on-line operation at 50 Hz. A study of the losses occurring in the motor performed at operating frequency of 50Hz showed that stator ...

Relaxed states with plasma flow

International Nuclear Information System (INIS)

Avinash, K.; Taylor, J.B.

1991-01-01

In the theory of relaxation, a turbulent plasma reaches a state of minimum energy subject to constant magnetic helicity. In this state the plasma velocity is zero. Attempts have been made by introducing a number of different constraints, to obtain relaxed states with plasma flow. It is shown that these alternative constraints depend on two self-helicities, one for ions, and one for electrons. However, whereas there are strong arguments for the effective invariance of the original magnetic-helicity, these arguments do not apply to the self-helicities. Consequently the existence of relaxed states with flow remains in doubt. (author)

A fission-fusion hybrid reactor in steady-state L-mode tokamak configuration with natural uranium

International Nuclear Information System (INIS)

Reed, Mark; Parker, Ronald R.; Forget, Benoit

2012-01-01

This work develops a conceptual design for a fusion-fission hybrid reactor operating in steady-state L-mode tokamak configuration with a subcritical natural or depleted uranium pebble bed blanket. A liquid lithium-lead alloy breeds enough tritium to replenish that consumed by the D-T fusion reaction. The fission blanket augments the fusion power such that the fusion core itself need not have a high power gain, thus allowing for fully non-inductive (steady-state) low confinement mode (L-mode) operation at relatively small physical dimensions. A neutron transport Monte Carlo code models the natural uranium fission blanket. Maximizing the fission power gain while breeding sufficient tritium allows for the selection of an optimal set of blanket parameters, which yields a maximum prudent fission power gain of approximately 7. A 0-D tokamak model suffices to analyze approximate tokamak operating conditions. This fission blanket would allow the fusion component of a hybrid reactor with the same dimensions as ITER to operate in steady-state L-mode very comfortably with a fusion power gain of 6.7 and a thermal fusion power of 2.1 GW. Taking this further can determine the approximate minimum scale for a steady-state L-mode tokamak hybrid reactor, which is a major radius of 5.2 m and an aspect ratio of 2.8. This minimum scale device operates barely within the steady-state L-mode realm with a thermal fusion power of 1.7 GW. Basic thermal hydraulic analysis demonstrates that pressurized helium could cool the pebble bed fission blanket with a flow rate below 10 m/s. The Brayton cycle thermal efficiency is 41%. This reactor, dubbed the Steady-state L-mode non-Enriched Uranium Tokamak Hybrid (SLEUTH), with its very fast neutron spectrum, could be superior to pure fission reactors in terms of breeding fissile fuel and transmuting deleterious fission products. It would likely function best as a prolific plutonium breeder, and the plutonium it produces could actually be more

Steady-state response of periodically supported structures to a moving load

NARCIS (Netherlands)

Metrikine, A.V.; Wolfert, A.R.M.; Vrouwenvelder, A.C.W.M.

1999-01-01

Steady-state vibrations of periodically supported structures under a moving load are analytically investigated. The following three structures are considered: an overhead power line for a train, a long suspended bridge and a railway track. The study is based on the application of so-called

Steady State Stokes Flow Interpolation for Fluid Control

DEFF Research Database (Denmark)

Bhatacharya, Haimasree; Nielsen, Michael Bang; Bridson, Robert

2012-01-01

— suffer from a common problem. They fail to capture the rotational components of the velocity field, although extrapolation in the normal direction does consider the tangential component. We address this problem by casting the interpolation as a steady state Stokes flow. This type of flow captures......Fluid control methods often require surface velocities interpolated throughout the interior of a shape to use the velocity as a feedback force or as a boundary condition. Prior methods for interpolation in computer graphics — velocity extrapolation in the normal direction and potential flow...

Vulcan: A steady-state tokamak for reactor-relevant plasma–material interaction science

International Nuclear Information System (INIS)

Olynyk, G.M.; Hartwig, Z.S.; Whyte, D.G.; Barnard, H.S.; Bonoli, P.T.; Bromberg, L.; Garrett, M.L.; Haakonsen, C.B.; Mumgaard, R.T.; Podpaly, Y.A.

2012-01-01

Highlights: ► A new scaling for obtaining reactor similarity in the divertor of scaled tokamaks. ► Conceptual design for a tokamak (“Vulcan”) to implement this new scaling. ► Demountable superconducting coils and compact neutron shielding. ► Helium-cooled high-temperature vacuum vessel and first wall. ► High-field-side lower hybrid current drive for non-inductive operation. - Abstract: An economically viable magnetic-confinement fusion reactor will require steady-state operation and high areal power density for sufficient energy output, and elevated wall/blanket temperatures for efficient energy conversion. These three requirements frame, and couple to, the challenge of plasma–material interaction (PMI) for fusion energy sciences. Present and planned tokamaks are not designed to simultaneously meet these criteria. A new and expanded set of dimensionless figures of merit for PMI have been developed. The key feature of the scaling is that the power flux across the last closed flux surface P/S ≃ 1 MW m −2 is to be held constant, while scaling the core volume-averaged density weakly with major radius, n ∼ R −2/7 . While complete similarity is not possible, this new “P/S” or “PMI” scaling provides similarity for the most critical reactor PMI issues, compatible with sufficient current drive efficiency for non-inductive steady-state core scenarios. A conceptual design is developed for Vulcan, a compact steady-state deuterium main-ion tokamak which implements the P/S scaling rules. A zero-dimensional core analysis is used to determine R = 1.2 m, with a conventional reactor aspect ratio R/a = 4.0, as the minimum feasible size for Vulcan. Scoping studies of innovative fusion technologies to support the Vulcan PMI mission were carried out for three critical areas: a high-temperature, helium-cooled vacuum vessel and divertor design; a demountable superconducting toroidal field magnet system; and a steady-state lower hybrid current drive system

Overview of time synchronization system of steady state superconducting tokamak SST-1

Energy Technology Data Exchange (ETDEWEB)

Kumar, A., E-mail: aveg@ipr.res.in; Masand, H.; Dhongde, J.; Patel, K.; Mahajan, K.; Gulati, H.; Bhandarkar, M.; Chudasama, H.; Pradhan, S.

2016-11-15

The Steady State Superconducting Tokamak (SST-1) consists of many distributed and heterogeneous plant/experiment systems viz. Water-Cooling, Power Supplies, Cryogenics, Vacuum, Magnets, Auxiliary-Heating sources, Diagnostics, Front End Electronics (FEE) & Data Acquisition systems, having their own data acquisition & control systems and control & monitor by Central Control System (CCS) during the machine operation. With distributed computing and interdependent systems, it is essential that all the data/event acquired must be with disciplined & precise time-base, so as to make the co-relation of the data/event from various plant and experiment systems easy. Hence it is important to have accurate and precise Time Synchronization in place. The two systems fulfill the requirement of the time synchronization in SST-1. The VME based Timing System (TS) provides synchronization amongst various experiment systems during the plasma discharges and works as discharge control system (DCS) while the GPS based Time Synchronization System (TSS) caters the requirement of synchronization during the continuous operation of various plant systems by feeding a central clock to all the plant systems. This paper presents the Time Synchronization System of SST-1, the results of the integrated testing and engineering validation with various SST-1 subsystems.

Pre-conceptual design activities for the materials plasma exposure experiment

International Nuclear Information System (INIS)

Lumsdaine, Arnold; Rapp, Juergen; Varma, Venugopal; Bjorholm, Thomas; Bradley, Craig; Caughman, John; Duckworth, Robert; Goulding, Richard; Graves, Van; Giuliano, Dominic; Lessard, Timothy; McGinnis, Dean; Meitner, Steven

2016-01-01

Highlights: • The development of long-pulse nuclear fusion devices requires testing plasma facing components at reactor relevant conditions. • The pre-conceptual design of a proposed linear plasma facility is presented. • Engineering considerations for multiple systems—plasma source and heating, magnet, vacuum, water cooling, and target, are presented. - Abstract: The development of next step fusion facilities such as DEMO or a Fusion Nuclear Science Facility (FNSF) requires first closing technology gaps in some critical areas. Understanding the material-plasma interface is necessary to enable the development of divertors for long-pulse plasma facilities. A pre-conceptual design for a proposed steady-state linear plasma device, the Materials Plasma Exposure Experiment (MPEX), is underway. A helicon plasma source along with ion cyclotron and electron Bernstein wave heating systems will produce ITER divertor relevant plasma conditions with steady-state parallel heat fluxes of up to 40 MW/m"2 with ion fluxes up to 10"2"4/m"2 s on target. Current plans are for the device to use superconducting magnets to produce 1–2 T fields. As a steady-state device, active cooling will be required for components that interact with the plasma (targets, limiters, etc.), as well as for other plasma facing components (transport regions, vacuum tanks, diagnostic ports). Design concepts for the vacuum system, the cooling system, and the plasma heating systems have been completed. The device will include the capability for handling samples that have been neutron irradiated in order to consider the multivariate effects of neutrons, plasma, and high heat-flux on the microstructure of divertor candidate materials. A vacuum cask, which can be disconnected from the high field environment in order to perform in-vacuo diagnosis of the surface evolution is also planned for the facility.

Pre-conceptual design activities for the materials plasma exposure experiment

Energy Technology Data Exchange (ETDEWEB)

Lumsdaine, Arnold, E-mail: lumsdainea@ornl.gov; Rapp, Juergen; Varma, Venugopal; Bjorholm, Thomas; Bradley, Craig; Caughman, John; Duckworth, Robert; Goulding, Richard; Graves, Van; Giuliano, Dominic; Lessard, Timothy; McGinnis, Dean; Meitner, Steven

2016-11-01

Highlights: • The development of long-pulse nuclear fusion devices requires testing plasma facing components at reactor relevant conditions. • The pre-conceptual design of a proposed linear plasma facility is presented. • Engineering considerations for multiple systems—plasma source and heating, magnet, vacuum, water cooling, and target, are presented. - Abstract: The development of next step fusion facilities such as DEMO or a Fusion Nuclear Science Facility (FNSF) requires first closing technology gaps in some critical areas. Understanding the material-plasma interface is necessary to enable the development of divertors for long-pulse plasma facilities. A pre-conceptual design for a proposed steady-state linear plasma device, the Materials Plasma Exposure Experiment (MPEX), is underway. A helicon plasma source along with ion cyclotron and electron Bernstein wave heating systems will produce ITER divertor relevant plasma conditions with steady-state parallel heat fluxes of up to 40 MW/m{sup 2} with ion fluxes up to 10{sup 24}/m{sup 2} s on target. Current plans are for the device to use superconducting magnets to produce 1–2 T fields. As a steady-state device, active cooling will be required for components that interact with the plasma (targets, limiters, etc.), as well as for other plasma facing components (transport regions, vacuum tanks, diagnostic ports). Design concepts for the vacuum system, the cooling system, and the plasma heating systems have been completed. The device will include the capability for handling samples that have been neutron irradiated in order to consider the multivariate effects of neutrons, plasma, and high heat-flux on the microstructure of divertor candidate materials. A vacuum cask, which can be disconnected from the high field environment in order to perform in-vacuo diagnosis of the surface evolution is also planned for the facility.

An expression of excess work during the transition between nonequilibrium steady states

International Nuclear Information System (INIS)

Yuge, Tatsuro

2014-01-01

Excess work is a nondiverging part of the work during the transition between nonequilibrium steady states (NESSs). It is a central quantity in steady-state thermodynamics (SST), which is a candidate for nonequilibrium thermodynamics theory. We derive an expression of excess work during quasistatic transitions between NESSs by using the macroscopic linear response relation of the NESS. This expression is a line integral of a vector potential in the space of control parameters. We show a relationship between the vector potential and the response function of the NESS, and thus obtain a relationship between the SST and a macroscopic quantity. We also connect the macroscopic formulation to microscopic physics through a microscopic expression of the nonequilibrium response function, which gives a result that is consistent with previous studies. (paper)

Development of repetitive railgun pellet accelerator and steady-state solid hydrogen extruder

International Nuclear Information System (INIS)

Oda, Y.; Azuma, K.; Onozuka, M.; Kasai, S.; Hasegawa, K.

1995-01-01

Development of a railgun pellet accelerator and a steady-state solid hydrogen extruder has been conducted. A railgun accelerator has been investigated for a high-speed repetitive pellet acceleration. The final objective is to develop a railgun system that can achieve a 5km/s speed-class repetitive (2Hz) pellet injection. Improvement in the acceleration efficiency showed a pellet velocity of more than 2km/s using augment rails and a ceramic insulator applied to a 1m-long railgun. The other investigation focused on the development of a steady-state solid hydrogen extruder for continuous pellet injection. Screw-driven extruding system has been chosen to extrude the solid hydrogen filament continuously. Theoretical considerations suggest that temperature control of the system is important in future research. (orig.)

Development of repetitive railgun pellet accelerator and steady-state solid hydrogen extruder

Energy Technology Data Exchange (ETDEWEB)

Oda, Y. [Mitsubishi Heavy Industries Ltd., Kobe (Japan); Azuma, K. [Mitsubishi Heavy Industries Ltd., Kobe (Japan); Onozuka, M. [Mitsubishi Heavy Industries Ltd., Kobe (Japan); Kasai, S. [Japan Atomic Energy Research Inst., Ibaraki (Japan); Hasegawa, K. [Japan Atomic Energy Research Inst., Ibaraki (Japan)

1995-12-31

Development of a railgun pellet accelerator and a steady-state solid hydrogen extruder has been conducted. A railgun accelerator has been investigated for a high-speed repetitive pellet acceleration. The final objective is to develop a railgun system that can achieve a 5km/s speed-class repetitive (2Hz) pellet injection. Improvement in the acceleration efficiency showed a pellet velocity of more than 2km/s using augment rails and a ceramic insulator applied to a 1m-long railgun. The other investigation focused on the development of a steady-state solid hydrogen extruder for continuous pellet injection. Screw-driven extruding system has been chosen to extrude the solid hydrogen filament continuously. Theoretical considerations suggest that temperature control of the system is important in future research. (orig.).

Characterizing steady states of genome-scale metabolic networks in continuous cell cultures.

Directory of Open Access Journals (Sweden)

Jorge Fernandez-de-Cossio-Diaz

2017-11-01

Full Text Available In the continuous mode of cell culture, a constant flow carrying fresh media replaces culture fluid, cells, nutrients and secreted metabolites. Here we present a model for continuous cell culture coupling intra-cellular metabolism to extracellular variables describing the state of the bioreactor, taking into account the growth capacity of the cell and the impact of toxic byproduct accumulation. We provide a method to determine the steady states of this system that is tractable for metabolic networks of arbitrary complexity. We demonstrate our approach in a toy model first, and then in a genome-scale metabolic network of the Chinese hamster ovary cell line, obtaining results that are in qualitative agreement with experimental observations. We derive a number of consequences from the model that are independent of parameter values. The ratio between cell density and dilution rate is an ideal control parameter to fix a steady state with desired metabolic properties. This conclusion is robust even in the presence of multi-stability, which is explained in our model by a negative feedback loop due to toxic byproduct accumulation. A complex landscape of steady states emerges from our simulations, including multiple metabolic switches, which also explain why cell-line and media benchmarks carried out in batch culture cannot be extrapolated to perfusion. On the other hand, we predict invariance laws between continuous cell cultures with different parameters. A practical consequence is that the chemostat is an ideal experimental model for large-scale high-density perfusion cultures, where the complex landscape of metabolic transitions is faithfully reproduced.

On the generation of steady currents in a plasma cylinder using m=0 radio-frequency waves

International Nuclear Information System (INIS)

Hugrass, W.N.

1981-01-01

The generation of a steady current in a resistive plasma cylinder by means of a travelling-wave magnetic field has been studied by using the resistive MHD equations. The non-linear initial-boundary value problem has been solved numerically. Hollow DC current profiles, similar to the experimental data obtained by other workers, have been found. A simple analytical argument, of a more general nature, shows that classical resistive diffusion cannot lead to a more uniform current distribution. (author)

Study of the general plasma characteristics of a high power multifilament ion source

International Nuclear Information System (INIS)

Schoenberg, K.F.

1979-09-01

A general assessment of the steady state and time dependent plasma properties which characterize a high power multifilament ion source is presented. Steady state measurements, obtained via a pulsed electrostatic probe data acquisition system, are described. Fluctuation measurements, obtained via a broadband digital spectral analysis system, are also given

Reactor kinetics - pulse and steady state

Energy Technology Data Exchange (ETDEWEB)

Estes, B F; Morris, F M [Sandia Laboratories (United States)

1974-07-01

An analytical model has been developed which couples the nuclear and thermal characteristics of the Annular Core Pulse Reactor (ACPR) into a solution which describes both the neutron kinetics of the reactor and the temperature behavior of a fuel-moderator element. The model describes both pulse and steady state operations. This paper describes the important aspects of the reactor, the fuel- moderator elements, the neutron kinetic equations of the reactor, and the time-temperature behavior of a fuel-moderator element that is being subjected to the maximum power density in the core. The parameters which are utilized in the equations are divided into two classes, those that can be measured directly and those that are assumed to be known (each is described briefly). Some of the solutions which demonstrate the versatility of the analytical model are described. (author)

Plasma concentrations of midazolam during continuous subcutaneous administration in palliative care.

Science.gov (United States)

Bleasel, M D; Peterson, G M; Dunne, P F

1994-01-01

We have investigated the steady-state plasma concentrations of midazolam during continuous subcutaneous administration in palliative care. Using a sensitive gas chromatography with electron capture detector assay, plasma concentrations of midazolam were measured in 11 patients (median age 68 years; range 47-82 years; six females) receiving the drug by continuous subcutaneous infusion (median rate 20 mg/day; range 10-60 mg/day). While not significant, the infusion rate tended to decrease with increasing age of the patient (Spearman's p = -0.51; p = 0.11). The steady-state plasma concentration range was 10-147 ng/ml, with a median of 30 ng/ml. Infusion rates and plasma concentrations of midazolam were correlated (Spearman's p = 0.71; p < 0.05). No other significant relationships were found between plasma concentrations and the variables of age, sex and liver function.

Maximum Entropy Production Is Not a Steady State Attractor for 2D Fluid Convection

Directory of Open Access Journals (Sweden)

Stuart Bartlett

2016-12-01

Full Text Available Multiple authors have claimed that the natural convection of a fluid is a process that exhibits maximum entropy production (MEP. However, almost all such investigations were limited to fixed temperature boundary conditions (BCs. It was found that under those conditions, the system tends to maximize its heat flux, and hence it was concluded that the MEP state is a dynamical attractor. However, since entropy production varies with heat flux and difference of inverse temperature, it is essential that any complete investigation of entropy production allows for variations in heat flux and temperature difference. Only then can we legitimately assess whether the MEP state is the most attractive. Our previous work made use of negative feedback BCs to explore this possibility. We found that the steady state of the system was far from the MEP state. For any system, entropy production can only be maximized subject to a finite set of physical and material constraints. In the case of our previous work, it was possible that the adopted set of fluid parameters were constraining the system in such a way that it was entirely prevented from reaching the MEP state. Hence, in the present work, we used a different set of boundary parameters, such that the steady states of the system were in the local vicinity of the MEP state. If MEP was indeed an attractor, relaxing those constraints of our previous work should have caused a discrete perturbation to the surface of steady state heat flux values near the value corresponding to MEP. We found no such perturbation, and hence no discernible attraction to the MEP state. Furthermore, systems with fixed flux BCs actually minimize their entropy production (relative to the alternative stable state, that of pure diffusive heat transport. This leads us to conclude that the principle of MEP is not an accurate indicator of which stable steady state a convective system will adopt. However, for all BCs considered, the quotient of

Rheological behavior of semi-solid 7075 aluminum alloy at steady state

Directory of Open Access Journals (Sweden)

Li Yageng

2014-03-01

Full Text Available The further application of semi-solid processing lies in the in-depth fundamental study like rheological behavior. In this research, the apparent viscosity of the semi-solid slurry of 7075 alloy was measured using a Couette type viscometer. The effects of solid fraction and shearing rate on the apparent viscosity of this alloy were investigated under different processing conditions. It can be seen that the apparent viscosity increases with an increase in the solid fraction from 10% to 50% (temperature 620 篊 to 630 篊 at steady state. When the solid fraction was fixed, the apparent viscosity can be decreased by altering the shearing rate from 61.235 s-1 to 489.88 s-1 at steady state. An empirical equation that shows the effects of solid fraction and shearing rate on the apparent viscosity is fitted. The microstructure of quenched samples was examined to understand the alloy抯 rheological behavior.

Steady State Thermo-Hydrodynamic Analysis of Two-Axial groove and Multilobe Hydrodynamic Bearings

Directory of Open Access Journals (Sweden)

C. Bhagat

2014-12-01

Full Text Available Steady state thermo-hydrodynamic analysis of two axial groove and multi lobe oil journal bearings is performed in this paper. To study the steady state thermo-hydrodynamic characteristics Reynolds equation is solved simultaneously along with the energy equation and heat conduction equation in bush and shaft. The effect of groove geometry, cavitation in the fluid film, the recirculation of lubricant, shaft speed has also been taken into account. Film temperature in case of three-lobe bearing is found to be high as compared to other studied bearing configurations. The data obtained from this analysis can be used conveniently in the design of such bearings, which are presented in dimensionless form.

Stability of periodic steady-state solutions to a non-isentropic Euler-Poisson system

Science.gov (United States)

Liu, Cunming; Peng, Yue-Jun

2017-06-01

We study the stability of periodic smooth solutions near non-constant steady-states for a non-isentropic Euler-Poisson system without temperature damping term. The system arises in the theory of semiconductors for which the doping profile is a given smooth function. In this stability problem, there are no special restrictions on the size of the doping profile, but only on the size of the perturbation. We prove that small perturbations of periodic steady-states are exponentially stable for large time. For this purpose, we introduce new variables and choose a non-diagonal symmetrizer of the full Euler equations to recover dissipation estimates. This also allows to make the proof of the stability result very simple and concise.

Influence of operating conditions upon the dynamic steady-state performance of a switched reluctance motor

International Nuclear Information System (INIS)

Faiz, J.; Shafagh, E.

1999-01-01

In order to obtain more accurate predicted dynamic steady-state performance with shorter computation time, an available mathematical model is modified and presented. Using this modified model, performance of a typical switched reluctance motor under a wide range of variations of operating conditions is obtained and discussed. These include variations of speed, voltage, load and switching angle. The static test characteristics of the motor are carefully measured and measured flux-linkage data are then used to predict the steady-state performance

Kinematic Cosmology & a new ``Steady State'' Model of Continued Creation

Science.gov (United States)

Wegener, Mogens

2006-03-01

Only a new "steady state" model justifies the observations of fully mature galaxies at ever increasing distances. The basic idea behind the world model presented here, which is a synthesis of the cosmologies of Parmenides and Herakleitos, is that the invariant structure of the infinite contents of a universe in flux may be depicted as a finite hyperbolic pseudo-sphere.

Influence of non-steady state during isoglycemic hyperinsulinemic clamp in hypertension. A LIFE substudy

DEFF Research Database (Denmark)

Olsen, M H; Andersen, U B; Wachtell, K

1999-01-01

We wanted to investigate whether time to steady state was reached within 2 h of insulin infusion during isoglycemic hyperinsulinemic clamp, comparing the glucose uptake index (M/IG) with Bergman's insulin sensitivity index (Sip). We performed a 2-h oral glucose tolerance test and a 3-h isoglycemic....... Because the 2-h M/IG correlated strongly with the 3-h Sip with relatively narrow limits of agreement, it is a good measure of insulin sensitivity. However, a 2-h clamp results in lower insulin sensitivity values in elderly, hypertensive patients due to the fact that steady state is not reached...

Lower bounds for ballistic current and noise in non-equilibrium quantum steady states

Directory of Open Access Journals (Sweden)

Benjamin Doyon

2015-03-01

Full Text Available Let an infinite, homogeneous, many-body quantum system be unitarily evolved for a long time from a state where two halves are independently thermalized. One says that a non-equilibrium steady state emerges if there are nonzero steady currents in the central region. In particular, their presence is a signature of ballistic transport. We analyze the consequences of the current observable being a conserved density; near equilibrium this is known to give rise to linear wave propagation and a nonzero Drude peak. Using the Lieb–Robinson bound, we derive, under a certain regularity condition, a lower bound for the non-equilibrium steady-state current determined by equilibrium averages. This shows and quantifies the presence of ballistic transport far from equilibrium. The inequality suggests the definition of “nonlinear sound velocities”, which specialize to the sound velocity near equilibrium in non-integrable models, and “generalized sound velocities”, which encode generalized Gibbs thermalization in integrable models. These are bounded by the Lieb–Robinson velocity. The inequality also gives rise to a bound on the energy current noise in the case of pure energy transport. We show that the inequality is satisfied in many models where exact results are available, and that it is saturated at one-dimensional criticality.

History independence of steady state in simultaneous two-phase flow through two-dimensional porous media.

Science.gov (United States)

Erpelding, Marion; Sinha, Santanu; Tallakstad, Ken Tore; Hansen, Alex; Flekkøy, Eirik Grude; Måløy, Knut Jørgen

2013-11-01

It is well known that the transient behavior during drainage or imbibition in multiphase flow in porous media strongly depends on the history and initial condition of the system. However, when the steady-state regime is reached and both drainage and imbibition take place at the pore level, the influence of the evolution history and initial preparation is an open question. Here, we present an extensive experimental and numerical work investigating the history dependence of simultaneous steady-state two-phase flow through porous media. Our experimental system consists of a Hele-Shaw cell filled with glass beads which we model numerically by a network of disordered pores transporting two immiscible fluids. From measurements of global pressure evolution, histograms of saturation, and cluster-size distributions, we find that when both phases are flowing through the porous medium, the steady state does not depend on the initial preparation of the system or on the way it has been reached.

Do's and don'ts in Fourier analysis of steady-state potentials.

Science.gov (United States)

Bach, M; Meigen, T

1999-01-01

Fourier analysis is a powerful tool in signal analysis that can be very fruitfully applied to steady-state evoked potentials (flicker ERG, pattern ERG, VEP, etc.). However, there are some inherent assumptions in the underlying discrete Fourier transform (DFT) that are not necessarily fulfilled in typical electrophysiological recording and analysis conditions. Furthermore, engineering software-packages may be ill-suited and/or may not fully exploit the information of steady-state recordings. Specifically: * In the case of steady-state stimulation we know more about the stimulus than in standard textbook situations (exact frequency, phase stability), so 'windowing' and calculation of the 'periodogram' are not necessary. * It is mandatory to choose an integer relationship between sampling rate and frame rate when employing a raster-based CRT stimulator. * The analysis interval must comprise an exact integer number (e.g., 10) of stimulus periods. * The choice of the number of stimulus periods per analysis interval needs a wise compromise: A high number increases the frequency resolution, but makes artifact removal difficult; a low number 'spills' noise into the response frequency. * There is no need to feel tied to a power-of-two number of data points as required by standard FFT, 'resampling' is an easy and efficient alternative. * Proper estimates of noise-corrected Fourier magnitude and statistical significance can be calculated that take into account the non-linear superposition of signal and noise. These aspects are developed in an intuitive approach with examples using both simulations and recordings. Proper use of Fourier analysis of our electrophysiological records will reduce recording time and/or increase the reliability of physiologic or pathologic interpretations.

The non-steady state oceanic CO2 signal: its importance, magnitude and a novel way to detect it

Directory of Open Access Journals (Sweden)

B. I. McNeil

2013-04-01

Full Text Available The role of the ocean has been pivotal in modulating rising atmospheric CO2 levels since the industrial revolution, sequestering nearly half of all fossil-fuel derived CO2 emissions. Net oceanic uptake of CO2 has roughly doubled between the 1960s (~1 Pg C yr−1 and 2000s (~2 Pg C yr−1, with expectations that it will continue to absorb even more CO2 with rising future atmospheric CO2 levels. However, recent CO2 observational analyses along with numerous model predictions suggest the rate of oceanic CO2 uptake is already slowing, largely as a result of a natural decadal-scale outgassing signal. This recent CO2 outgassing signal represents a significant shift in our understanding of the oceans role in modulating atmospheric CO2. Current tracer-based estimates for the ocean storage of anthropogenic CO2 assume the ocean circulation and biology is in steady state, thereby missing the new and potentially important "non-steady state" CO2 outgassing signal. By combining data-based techniques that assume the ocean is in a steady state, with techniques that constrain the net oceanic CO2 uptake signal, we show how to extract the non-steady state CO2 signal from observations. Over the entire industrial era, the non-steady state CO2 outgassing signal (~13 ± 10 Pg C is estimated to represent about 9% of the total net CO2 inventory change (~142 Pg C. However, between 1989 and 2007, the non-steady state CO2 outgassing signal (~6.3 Pg C has likely increased to be ~18% of net oceanic CO2 storage over that period (~36 Pg C. The present uncertainty of our data-based techniques for oceanic CO2 uptake limit our capacity to quantify the non-steady state CO2 signal, however with more data and better certainty estimates across a range of diverse methods, this important and growing CO2 signal could be better constrained in the future.

Active control of divertor heat and particle fluxes in EAST towards advanced steady state operations

Energy Technology Data Exchange (ETDEWEB)

Wang, L., E-mail: lwang@ipp.ac.cn [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Dalian University of Technology, Dalian 116024 (China); Guo, H.Y. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); General Atomics, P. O. Box 85608, San Diego, CA 92186 (United States); Li, J.; Wan, B.N.; Gong, X.Z.; Zhang, X.D.; Hu, J.S. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Liang, Y. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Association EURATOM-FZJ, D-52425 Jülich (Germany); Xu, G.S. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Zou, X.L. [CEA, IRFM, F-13108 Saint-Paul-lez-Durance (France); Loarte, A. [ITER Organization, Route de Vinon sur Verdon, 13115 St Paul Lez Durance (France); Maingi, R.; Menard, J.E. [Princeton Plasma Physics Laboratory, Princeton, NJ 08543 (United States); Luo, G.N.; Gao, X.; Hu, L.Q.; Gan, K.F.; Liu, S.C.; Wang, H.Q.; Chen, R. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); and others

2015-08-15

Significant progress has been made in EAST towards advanced steady state operations by active control of divertor heat and particle fluxes. Many innovative techniques have been developed to mitigate transient ELM and stationary heat fluxes on the divertor target plates. It has been found that lower hybrid current drive (LHCD) can lead to edge plasma ergodization, striation of the stationary heat flux and lower ELM transient heat and particle fluxes. With multi-pulse supersonic molecular beam injection (SMBI) to quantitatively regulate the divertor particle flux, the divertor power footprint pattern can be actively modified. H-modes have been extended over 30 s in EAST with the divertor peak heat flux and the target temperature being controlled well below 2 MW/m{sup 2} and 250 °C, respectively, by integrating these new methods, coupled with advanced lithium wall conditioning and internal divertor pumping, along with an edge coherent mode to provide continuous particle and power exhaust.

Quasi-steady state thermal performances of a solar air heater with ...

African Journals Online (AJOL)

Quasi-steady state thermal performance of a solar air heater with a combined absorber is studied. The whole energy balance equations related to the system were articulated as a linear system of temperature equations. Solutions to this linear system were assessed from program based on an iterative process. The mean ...

Steady-state transport equation resolution by particle methods, and numerical results

International Nuclear Information System (INIS)

Mercier, B.

1985-10-01

A method to solve steady-state transport equation has been given. Principles of the method are given. The method is studied in two different cases; estimations given by the theory are compared to numerical results. Results got in 1-D (spherical geometry) and in 2-D (axisymmetric geometry) are given [fr

Plasma electron losses in a multidipole plasma

International Nuclear Information System (INIS)

Haworth, M.D.

1983-01-01

The magnitude of the plasma electron cusp losses in a multidipole plasma device is determined by using a plasma electron heating technique. This method consists of suddenly generating approximately monoenergetic test electrons inside the multidipole plasma, which is in a steady-state equilibrium prior to the introduction of the test electrons. The Coulomb collisions between the test electrons and the plasma electrons result in heating the plasma electrons. The experimentally measured time evolution of the plasma electron temperature is compared with that predicted by a kinetic-theory model which calculates the time evolution of the test electron and the plasma electron distribution functions. The analytical solution of the plasma electron heating rate when the test electrons are first introduced into the plasma predicts that there is no dependence on ion mass. Experimental results in helium, neon, argon, and krypton multidipole plasmas confirm this prediction. The time-evolved solution of the kinetic equations must be solved numerically, and these results (when coupled with the experimental heating results) show that the plasma electron cusp-loss width is on the order of an electron Larmor radius

Steady-State-Preserving Simulation of Genetic Regulatory Systems